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A high-resolution benthic stable-isotope record for the South Atlantic: Implications for orbital-scale changes in Late Paleocene–Early Eocene climate and carbon cycling
Supplementary resource (1)
Data
January 2014
... Since the discovery of the PETM, numerous studies have reported similar but less pronounced paired negative shifts in δ 13 C and δ 18 O during the late Paleocene and early Eocene in both outcrop sections (e.g., Agnini et al., 2009;Coccioni et al., 2012;Galeotti et al., 2010;Slotnick et al., 2015) and within deep sea sediment cores (e.g., Cramer et al., 2003;Kirtland Turner et al., 2014;Lauretano et al., 2015;Littler et al., 2014;Stap et al., 2010;Westerhold et al., 2007;Westerhold et al., 2017;Zachos et al., 2010). These hyperthermals have been labeled from A to L (Cramer et al., 2003) and M to W (Lauretano et al., 2016), and can also be recognized as peaks in X-Ray fluorescence (XRF)-derived iron intensity data caused by carbonate dissolution (e.g., Röhl et al., 2000Röhl et al., , 2007Westerhold, Röhl, Donner, & Zachos, 2018;Zachos et al., 2010). ...
... Currently, our best astronomically-calibrated Paleogene age models are restricted to low-and mid-latitude sites such as Demerara Rise (ODP Leg 207; equatorial Atlantic Ocean), Walvis Ridge (ODP Leg 208; mid-latitude South Atlantic Ocean), and Shatsky Rise (ODP Leg 198; subtropical Pacific Ocean) (e.g., Barnet et al., 2019;Littler et al., 2014;Röhl et al., 2007;Westerhold et al., 2017;Westerhold, Röhl, Donner, & Zachos, 2018;Westerhold et al., 2020;Zachos et al., 2010). In comparison, higher latitude early Paleogene age models are scarce, although do exist for Maud Rise in the Atlantic sector of the Southern Ocean (ODP Sites 689 and 690; Bains et al., 1999;Cramer et al., 2003;Kennett & Stott, 1991;Röhl et al., 2007;Thomas et al., 1990), for the Kerguelen Plateau (ODP Sites 738 and 1135; Jiang & Wise, 2009) and the Mantelle Basin (International Ocean Discovery Program (IODP) Site U1514; Vahlenkamp et al., 2020) in the southern Indian Ocean, and for the Campbell Plateau in the South Pacific Ocean (Deep Sea Drilling Program (DSDP) 277; Hollis, 1997;Hollis et al., 2015;Shepherd et al., 2021). ...
... As described for many other late Paleocene to early Eocene sections worldwide, the U1553 record exhibits a pronounced cyclicity (e.g., Kirtland Turner et al., 2014;Littler et al., 2014;Vahlenkamp et al., 2020;Westerhold et al., 2017;Zachos et al., 2010). Therefore, we plotted the eccentricity according to Laskar et al. (2011) and added a bandpass filter to highlight the long eccentricity cycle of 405 kyr (Figure 6a). ...
The late Paleocene to early Eocene interval is characterized by a series of carbon perturbations that caused transient warming (hyperthermal) events, of which the Paleocene‐Eocene Thermal Maximum (PETM) was the largest. These hyperthermals can be recognized in the pelagic sedimentary record as paired negative δ¹³C and δ¹⁸O excursions, in addition to decreased calcium carbonate and increased iron content caused by carbonate dissolution. However, current data are predominantly sourced from the equatorial‐to subequatorial regions. Here we present a new high‐latitude late Paleocene—early Eocene record, recovered during International Ocean Discovery Program (IODP) Expedition 378 on the Campbell Plateau off New Zealand, in the southwest Pacific Ocean. To construct an age model, we correlated our chemostratigraphic and biostratigraphic data to existing astronomically‐tuned age models from Walvis Ridge (South Atlantic Ocean) and Demerara Rise (equatorial Atlantic Ocean). Our results indicate that the Site U1553 composite section spans ∼7 million years of the latest Paleocene to early Eocene (50.5–57.5 Ma), and preserves many of the early Eocene hyperthermals; including a PETM interval that is more expanded than elsewhere in this region. However, construction of the age model also revealed discrepancies between the chemostratigraphic and biostratigraphic tie points used for correlation. This is likely due to latitudinal diachroneity in the calcareous nannofossil biostratigraphic datums, which are primarily based on low‐to mid‐latitude assemblages. Therefore, our study highlights the need to establish a revised calcareous nannofossil biozonation that is more appropriate for high‐latitude age models.
... High-resolution paleoclimate records across the Cenozoic Era show that global climate and carbon cycling are closely connected on astronomical timescales on the order of 10 4 -10 6 years (e.g., Barnet et al., 2019;Mix et al., 1995;Pälike et al., 2006;Peterson et al., 2014;Sigman & Boyle, 2000;Wang et al., 2010;Westerhold et al., 2018;Zachos et al., 2001). In particular, during the early ice-free Cenozoic, benthic foraminiferal oxygen and carbon isotopes (δ 18 O and δ 13 C) show a strongly coherent astronomical influence (Cramer et al., 2003;Littler et al., 2014;Westerhold et al., 2011;Zachos et al., 2010), suggesting tightly coupled carbon cycle-climate dynamics. Multiple records reveal periodic, astronomically paced negative δ 13 C excursions with a magnitude of 0.3-1.0‰ ...
... Variations in global climate and the carbon cycle during the early ice-free Cenozoic, including "hyperthermals," are predominately paced by short and long eccentricity cycles (Barnet et al., 2019;Lauretano et al., 2015;Littler et al., 2014;Westerhold et al., 2011Westerhold et al., , 2018Zachos et al., 2001). While eccentricity is the only astronomical parameter that alters Earth's annual global mean solar energy insolation, the total variability is small (∼0.5 W m 2 ) (Laskar et al., 2004). ...
... In comparison to benthic high-resolution paleoclimate records throughout the Cenozoic (Barnet et al., 2019;Beddow et al., 2016;Holbourn et al., 2013;Littler et al., 2014;Pälike et al., 2006;Tian et al., 2018;Westerhold et al., 2018), our simulations show minor variability in δ 13 C on astronomical timescales (the maximum variability in simulated δ 13 C cycles is less than 0.15‰ in ASYM). This model-data discrepancy is especially pronounced as we are evaluating modeled water column δ 13 C and not considering the impact of bioturbation on the range of preserved cycles. ...
Astronomical cycles are strongly expressed in marine geological records, providing important insights into Earth system dynamics and an invaluable means of constructing age models. However, how various astronomical periods are filtered by the Earth system and the mechanisms by which carbon reservoirs and climate components respond, particularly in absence of dynamic ice sheets, is unclear. Using an Earth system model that includes feedbacks between climate, ocean circulation, and inorganic (carbonate) carbon cycling relevant to geological timescales, we systematically explore the impact of astronomically‐modulated insolation forcing and its expression in model variables most comparable to key paleoceanographic proxies (temperature, the δ¹³C of inorganic carbon, and sedimentary carbonate content). Temperature predominately responds to obliquity and is little influenced by the modeled carbon cycle feedbacks. In contrast, the cycling of nutrients and carbon in the ocean generates significant precession power in atmospheric CO2, benthic ocean δ¹³C, and sedimentary wt% CaCO3, while inclusion of marine sedimentary and weathering processes shifts power to the long eccentricity period. Our simulations produce reduced pCO2 and dissolved inorganic carbon δ¹³C at long eccentricity maxima and, contrary to early Cenozoic marine records, CaCO3 preservation in the model is enhanced during eccentricity modulated warmth. Additionally, the magnitude of δ¹³C variability simulated in our model underestimates marine proxy records. These model‐data discrepancies hint at the possibility that the Paleogene silicate weathering feedback was weaker than modeled here and that additional organic carbon cycle feedbacks are necessary to explain the full response of the Earth system to astronomical forcing.
... Notably, eccentricity signals could have been amplified relative to shorter-term climate forcing owing to long residence time of carbon in the ocean (Ao et al., 2021;Pälike et al., 2006;Zhang et al., 2023a), favoring preservation of eccentricity-scale changes but not shorter precession scale changes. Numerous early Eocene sedimentary records indicate a primary coupling of eccentricity forcing, climate and the carbon cycle (e.g., Barnet et al., 2019;Lauretano et al., 2018;Littler et al., 2014;Sexton et al., 2011;Zachos et al., 2010). Periodic variations in eccentricity could modify seasonal contrasts (seasonality). ...
... Periodic variations in eccentricity could modify seasonal contrasts (seasonality). High eccentricity conditions are conducive for the formation of seasonally uneven rainfall on the continents, forming "monsoon-like" climate state (Littler et al., 2014;Zachos et al., 2010). This could promote intense but relatively short-wet seasons and prolonged seasons, which is less beneficial for the storage of biogenic carbon from wetlands and peat (Littler et al., 2014;Zachos et al., 2010). ...
... High eccentricity conditions are conducive for the formation of seasonally uneven rainfall on the continents, forming "monsoon-like" climate state (Littler et al., 2014;Zachos et al., 2010). This could promote intense but relatively short-wet seasons and prolonged seasons, which is less beneficial for the storage of biogenic carbon from wetlands and peat (Littler et al., 2014;Zachos et al., 2010). This could possibly result in the release of 12 C-enriched carbon to ocean-atmosphere system from wetlands and peat, thus amplifying warming. ...
The Early Eocene Climatic Optimum (EECO) may be a potentially useful analog for future global warming under high CO2 concentrations. However, a paucity of orbital‐scale terrestrial records limits our understanding of how the hydrological cycle responded during this protracted (∼4 Myr) interval of global warmth. In this study, we combine zircon U‐Pb dating and cyclostratigraphy to establish a high‐resolution astronomical timescale spanning the EECO (∼52.9 Ma to ∼49.9 Ma) through a >1 km fluviolacustrine succession from the Gonjo Basin, Southeast Tibet. Our results suggest that hydroclimate variability in the region during this interval was strongly controlled by eccentricity forcing (∼405 Kyr, ∼135–100 Kyr, and possibly ∼200 Kyr cycles). The dominance of eccentricity forcing in our record is consistent with coeval marine records, and indicates that modulation of low‐latitude summer insolation through nonlinear interactions with the global carbon cycle likely controlled hydroclimate and paleolake level in the Gonjo basin during the EECO. Our study offers new perspectives for the forcing mechanisms of terrestrial hydroclimate changes of East Asia in response to subtle changes in insolation during the EECO.
... It was characterized by progressive, albeit non-linear, climatic cooling, interrupted by the discrete episodes of dramatic warming and perturbations in the global carbon cycle, accompanied by significant biotic turnovers. The multiple studies of δ 13 C and δ 18 O fluctuations in the oceanic sites and inland sections revealed a series of different scale transient events (Kennett and Stott, 1991;Zachos et al., 2001;Bralower et al., 2002;Cramer et al., 2003;Westerhold et al., 2011Westerhold et al., , 2014Westerhold et al., , 2015Coccioni et al., 2012aCoccioni et al., , 2012bLittler et al., 2014;Barnet et al., 2019, ect.), which serve as reliable levels for interbasinal correlation. ...
... The widely known Mid-Paleocene Biotic Event (MPBE), or Early Late Paleocene Event (ELPE) occurs in the lower NP6 or CP5 zone in many World areas (Bralower et al., 2002;Petrizzo, 2005;Bernaola et al., 2009;Schmitz et al., 2011;Littler et al., 2014; Hyland et al., 2015;Coccioni et al., 2019). At Kheu section, the minor C isotope excursion (CIE) is detected in the topmost NP5 or CP4 zone (see Fig. 10a) that can be caused by later LO of Heliotrochus (Heliolithus) kleinpellii in the Caucasian basin. ...
... Similarly to Zumaia section (Schmitz et al., 2011), the negative δ 13 C values at Kheu section correspond to the clayrich interval characterized by reduced nannofossil total abundance. Immediately above the MPBE, δ 13 C turns to long-term positive values corresponding to Paleocene Carbon Isotope Maximum (PCIM; Shackleton, 1986;Westerhold et al., 2011;Littler et al., 2014;Barnet et al., 2020;Hollis et al., 2021), which ranges NP6-NP8, CP5-CP7 or CNP8-CNP10 zones. δ 18 O shows gentle negative trend enhanced by dramatic negative excursions in the middle of CNP9 zone and at the top of PCIM. ...
A continuous outcrop of the neritic sediments ranging from the Cretaceous/Paleogene to
Eocene/Oligocene boundary is exposed along the Kheu R., Kabardino-Balkaria Republic, southern Russia.
High calcareous nannofossil abundance and species diversity in Kheu section make possible the application
of various standard calcareous nannofossil zonations for the investigated interval. This provides a direct correlation of the biohorizons used as zonal markers in these zonations and recognition of the stage boundaries
in this complete succession, which represents the reference Paleogene section of the NE Peri-Tethys. The
carbon and oxygen isotope records revealed a series of excursions correlated to peculiar Paleogene paleoecological events on the basis of nannofossil biostratigraphy. The continuous Maastrichtian/Danian transition displays ca. 1 m thick interval containing only scarce Cretaceous survivors between the highest occurrence (HO)
of the most Cretaceous nannofossil taxa and the lowest occurrence (LO) of the Paleogene taxa; this interval
is characterized by prominent positive δ13C and δ18O excursions. The Late Danian Event (LDE) is identified
as minor δ13C and δ18O excursions in the upper Danian. The base of Selandian stage is defined by the
2nd radiation of fasciculiths, followed by negative δ13C and δ18O shifts corresponding to the Danian/Selandian Transition Event. Mid-Paleocene Biotic Event (MPBE), A, B1/B2, C1/C2 and D1/D2 events are pronounced in the upper Paleocene C and O isotope record. Wide expansion of Discoasterales (Fasciculithus,
Heliotrochus, Heliolithus, Discoaster), served as a basis for nannofossil zonations, is featured for this time span.
The base of Ypresian (lower Eocene) corresponds to the onset of the carbon isotope excursion (CIE) documented at the base of the TOC-rich bed. This 0.6 m thick sapropelitic bed corresponds to the Paleocene–
Eocene Thermal Maximum (PETM) and contains specific nannofossil assemblage known as “excursion
taxa”. The high sedimentation rate and completeness of the early Eocene sedimentary succession allowed to
record the evolution of Tribrachiatus bramlettei–T. digitalis–T. contortus–T. orthostylus lineage spanning the
interval of NP10–NP12 zones. Multiple δ13C and δ18O excursions, occurred in the lower Ypresian sediments,
correspond to the early Eocene hyperthermals E1/E2, F1, F2, G, ETM2, I1/I2 and J. The intercalations of
a series of TOC-rich layers in the interval ranging the upper NP12 to lower NP13 zones correspond to ETM3
and individual episodes (L-T) of the Early Eocene Climatic optimum (EECO). Long-term cooling trend in
the Caucasian basin begins in the uppermost Ypresian (upper NP13 zone). The middle Eocene δ18O record
demonstrates a succession of negative excursions occurred against the background of relatively high values.
The hyperthermal C21r–H6 is recognized at the base of Lutetian stage defined by the LO of Blackites inflatus.
Two later excursions of this time interval corresponding to the Late Lutetian Event (LLE) and Middle
Eocene Climatic Optimum (MECO) occur in the enriched in TOC Kuma Fm. (late Lutetian to Bartonian)
and fall at the levels with highest TOC concentrations. Nannoplankton assemblages are widely dominated
by eurytopic reticulofenestrids during both events, while Chiasmolithus and Discoaster become oppressed
that can indicate lower salinity caused by enhanced humidity. The base of Priabonian is defined by the LO
of Chiasmolithus oamaruensis and the base of Cribrocentrum erbae acme. These bioevents are preceded by
the negative δ13C excursion and very positive δ18O values, possibly correlated to the Priabonian Oxygen
Maximum (PrOM). The relatively warm Priabonian time, characterized by recovery of Chiasmolithus, Discoaster and Sphenolithus, gives way to a new cooling phase known as Late Eocene Event (LEE). The base
of Clausicoccus subdistichus acme, approximated to the base of Oligocene, falls at the level ca. 0.5 m below
the facial change corresponding to the large-scale sea-level fall and, thus, slightly precedes the accumulation of low-calcareous oil-bearing Oligocene-lower Miocene Maikop Fm. The prominent positive δ13C
and δ18O excursions occur at the base of this formation.
... A series of global warming events (~10 4 -10 5 yrs. duration), termed early Eocene hyperthermals, occurred during the early Eocene (Ypresian; ~56 to 47.8 Ma) following the Paleocene-Eocene Thermal Maximum (PETM) (Abels et al., 2012;Cui and Schubert, 2017;Harper et al., 2020;Jiang et al., 2021;Leon-Rodriguez and Dickens, 2010;Littler et al., 2014;Nicolo et al., 2007;Slotnick et al., 2012;Stap et al., 2010). These hyperthermal events are characterized by higher global temperatures, fundamental perturbations to the global carbon cycle (i.e., negative carbon isotope excursions), and other environmental effects (e. g., dissolution of CaCO 3 in deep-sea sediments and enhanced chemical weathering on the continent). ...
... This is because these nannofossil taxa have been reported to occur only during the PETM and ETM2 because of their adaptation to the rapidly and severely changing surface-water environment (Jiang and Wise Jr, 2006;Kahn and Aubry, 2004;Lei et al., 2016;Raffi and De Bernardi, 2008;Self-Trail et al., 2012). As a result, the geochemical features observed in Unit 2 are consistent with the characteristics of the I1/I2 event (e.g., ~53.6 Ma) (Abels et al., 2012;Cui and Schubert, 2017;Harper et al., 2020;Jiang et al., 2021;Leon-Rodriguez and Dickens, 2010;Littler et al., 2014;Stap et al., 2010), which led to the suggestion that at least one of the early Eocene hyperthermals may have been recorded in the southeastern Neo-Tethys region. Due to the uncertainty of the age based on biostratigraphy at the study site, we are unable to specify whether the hyperthermal event recorded is I1 or I2. ...
... I1/I2 hyperthermal events are prominent global warming events just before the long period of the early Eocene climatic optimum (EECO), but has a smaller degree of warming compared to the PETM and ETM2 (Cramer et al., 2003;Nicolo et al., 2007;Lauretano et al., 2015;Cui and Schubert, 2017). At present, the I1/I2 events have been documented in multiple pelagichemipelagic sequences, such as the DSDP (Deep Sea Drilling Project) Site 577 and ODP (Ocean Drilling Program) Site 1209 at Shatsky Rise in the central Pacific (Cramer et al., 2003;Westerhold et al., 2018), DSDP Site 550 and ODP Site 1051 in the northern Atlantic (Cramer et al., 2003), ODP Site 1258 at Demerara Rise in the western equatorial Atlantic (D'Onofrio et al., 2020;Sexton et al., 2006), ODP Sites 1262 and 1263 at Walvis Ridge in the south Atlantic (Lauretano et al., 2015;Littler et al., 2014;Zachos et al., 2010), ODP Site 1215 near Hawaii in the central Pacific (Leon-Rodriguez and Dickens, 2010), Terche and Possagno sections in Southern Alps in Italy (D'Onofrio et al., 2016;Galeotti et al., 2019), Contessa section in the central Italy (Francescone et al., 2019;Galeotti et al., 2010). A few I1/I2 records are found in shallow marine sequences, including Mead and Dee Stream in New Zealand (Nicolo et al., 2007;Slotnick et al., 2012), and Galala platform in the Egyptian shelf (Höntzsch et al., 2011). ...
The early Eocene is thought to be the warmest period of the Cenozoic Era, with global temperatures ~10 ℃ higher than today. Few studies have focused on the paleoclimatic history of the early Eocene southeastern Neo- Tethys Ocean despite its tectonic significance. Here, we report new geochemical data that reveal the paleoclimate conditions of the early Eocene (~ 53.7 to 52.6 Ma) from the Qumiba section in the Tingri region of the southern Tibetan Plateau, China, which likely represents the youngest marine strata in the southeastern Neo- Tethys Ocean. The studied Qumiba section consists of the Enba and Zhaguo Formations characterized by silty marls, mudstones and thin layers of lithic sandstones. The paleoclimate and paleoenvironment history of the Qumiba section is reconstructed using stable carbon and oxygen isotopes of marine carbonates (δ13Ccarb and δ18Ocarb), major, trace and rare earth elements. At least one early Eocene hyperthermal event (I1 or I2; ~53.6 Ma) has been recorded in the Qumiba section supported by abrupt negative excursions in δ13Ccarb in Unit 2. This is further supported by enhanced chemical weathering (e.g., chemical index of alteration), which can be attributed to increased temperature and precipitation. The continued negative δ13Ccarb excursions in Unit 3 may have been caused by the release of 13C-depleted carbon from volcanic activities. The volcanic inputs may have increased nutrient availability and promoted marine primary productivity (e.g., higher enrichment factors of P, Ba, Ni and Cu). Furthermore, the basin may have experienced bottom water anoxia as suggested by the redox- sensitive proxies (e.g., higher enrichment factors of U and V and Ce/Ce*) during this period (Unit 3). Our findings support warming-induced changes in paleoenvironmental conditions in the southeastern Neo-Tethys Ocean during the early Eocene.
... Early Eocene Ypresian times saw the warmest sustained global temperatures of the past 80 Myr (Zachos et al. 2001). This time interval was also punctuated by short-term global perturbations of the carbon-cycle, which caused abrupt hyperthermal events (Zachos et al. 2001, Cramer et al. 2003, Lourens et al. 2005, Galeotti et al. 2010, Littler et al. 2014, Lauretano et al. 2015, Lauretano et al. 2016, Westerhold et al. 2018. Thus, Ypresian sedimentary successions provide reliable records of the behaviour of the Earth's climate under extreme atmospheric pCO 2 concentrations, which can be used as past analogues of today's greenhouse effect and global warming (Burke et al. 2018, Westerhold et al. 2020. ...
... Despite this limitation, great advances have been made in the construction of the Ypresian ATS using climate sensitive proxy records from oceanic deep marine sediment cores (Cramer et al. 2003, Lourens et al. 2005, Westerhold et al. Westerhold et al. 2007, Westerhold et al. 2012, Westerhold et al. 2017, Littler et al. 2014, Lauretano et al. 2016. In particular, the study by Westerhold et al. (2017) provided a coherent orbital tuning between Ypresian records from the Atlantic Ocean and the La10b orbital solution at short eccentricity level, which allowed the calculation of absolute ages for biostratigraphic events, magnetic polarity reversals and hyperthermal events. ...
... Most of the Ypresian astronomical calibrations published to date are based on proxy records from Atlantic ODP cores (Zachos et al. 2004, Lourens et al. 2005, Westerhold et al. 2007, Westerhold et al. 2012, Westerhold et al. 2017, Littler et al. 2014, Lauretano et al. 2016, Zeebe and Lourens 2019. Although many oceanic successions are known to be condensed or discontinuous due to low sedimentation rates, thereby hampering high-resolution chronological studies, this is not the case of the earliest Eocene, which is fully recorded in Walvis Ridge records (Westerhold et al. 2007, Westerhold et al. 2017. ...
The early Eocene paleoclimate record provides one of the best analogues for today’s global warming. In order to reconstruct the evolution of the early Eocene paleoclimate, and understand how environmental feedback mechanisms acted on it, an accurate time framework is necessary. In this regard, the astronomically calibrated time scale (ATS) provides the highest possible resolution, but models beyond 40–50 Ma are not fully resolved and actual geological data are incomplete. With the aim of filling this gap, the expanded lower Ypresian Arnakatxa section studied herein offered a potentially valuable orbitally paced geological record. This outcrop displays a well-defined arrangement of strata in couplets and bundles. The spectral analyses of colour data series showed the dominance of two main periodicities, which were related to orbital forcing on sedimentation by precession (20 ky) and short (100 ky) eccentricity cycles. Despite not being represented in the spectrograms, the influence of long (405 ky) eccentricity on sedimentation was also deduced. Moreover, the disruption of the orbital signal in the upper half of the Arnakatxa section correlates with a very long (2.4 Myr) eccentricity node centred at ~54.6 Ma, which could also have caused the amplification of the orbital signal related to obliquity (41 ky). Taking everything into account, the cyclostratigraphic analyses carried out in Arnakatxa resulted in a precessional scale orbital chronology for the time interval between 55.805 and 54.435 Ma (duration of 1.37 Myr). Thus, the Arnakatxa succession could be reliably correlated with Atlantic ODP records, which are the main reference for Ypresian astrochronology, at precessional scale. Furthermore, the results from Arnakatxa also help to identify the astronomical solutions that better match actual geological data, contributing to the construction of a definitive Ypresian ATS. In this regard, the Arnakatxa results are not a good fit for solutions La10a, La10d, La11 and ZB18a, but match well with the previously thought to be less reliable solutions La10b and La10c.
... The PCIM appears to have been the result of relatively cool greenhouse conditions between ~63 and ~59 Ma, which facilitated carbon accumulation in reservoirs such as peat bogs, permafrost, and methane hydrates, leading to a positive shift in residual oceanic 13 C (51, 52). The largescale burial of carbon likely also led to the drawdown of atmospheric CO 2 , which agrees with benthic 18 O evidence for concurrent global cooling (53,54). The 57.99 ± 0.54 Ma age of the Hiawatha impact is presently indistinguishable from (i) a ~58-Ma negative step in benthic 13 C values, (ii) a subsequent large positive step in benthic 13 C values (of ~1‰), known as the peak-PCIM event, and (iii) the initiation of a long-term warming trend when 13 C values began a long-term decline, likely reflecting less favorable conditions for sequestration of organic carbon matter in the oceans or on land (Fig. 6) (53). ...
... The largescale burial of carbon likely also led to the drawdown of atmospheric CO 2 , which agrees with benthic 18 O evidence for concurrent global cooling (53,54). The 57.99 ± 0.54 Ma age of the Hiawatha impact is presently indistinguishable from (i) a ~58-Ma negative step in benthic 13 C values, (ii) a subsequent large positive step in benthic 13 C values (of ~1‰), known as the peak-PCIM event, and (iii) the initiation of a long-term warming trend when 13 C values began a long-term decline, likely reflecting less favorable conditions for sequestration of organic carbon matter in the oceans or on land (Fig. 6) (53). However, in the absence of a known ejecta layer, the Hiawatha impact cannot yet be correlated with any of these events. ...
... However, in the absence of a known ejecta layer, the Hiawatha impact cannot yet be correlated with any of these events. Negative and positive steps in benthic 13 C values often reflect sudden shifts in the proportion of carbon removed from the system through carbonate or organic matter burial, reflecting contractions and expansions, respectively, of sedimentary reservoirs such as peat bogs, permafrost, and marine organic matter (53). However, changes in organic burial fluxes appear to occur too slowly to adequately explain very sharp steps in 13 C, such as the positive excursion of the peak-PCIM event (53). ...
The ~31-km-wide Hiawatha structure, located beneath Hiawatha Glacier in northwestern Greenland, has been proposed as an impact structure that may have formed after the Pleistocene inception of the Greenland Ice Sheet. To date the structure, we conducted 40 Ar/ 39 Ar analyses on glaciofluvial sand and U-Pb analyses on zircon separated from glaciofluvial pebbles of impact melt rock, all sampled immediately downstream of Hiawatha Glacier. Unshocked zircon in the impact melt rocks dates to ~1915 million years (Ma), consistent with felsic intrusions found in local bedrock. The 40 Ar/ 39 Ar data indicate Late Paleocene resetting and shocked zircon dates to 57.99 ± 0.54 Ma, which we interpret as the impact age. Consequently, the Hiawatha impact structure far predates Pleistocene glaciation and is unrelated to either the Paleocene-Eocene Thermal Maximum or flood basalt volcanism in east Greenland. However, it was contemporaneous with the Paleocene Carbon Isotope Maximum, although the impact's exact paleoenvironmental and climatic significance awaits further investigation.
... benthic foraminiferal oxygen and carbon isotopes (δ 18 O and δ 13 C) show a strongly coherent astronomical influence (Cramer et al., 2003;Littler et al., 2014;Turner, 2014;Westerhold et al., 2011;Zachos et al., 2010), suggesting tightly coupled carbon cycle-climate dynamics. Multiple records reveal periodic, astronomically paced negative δ 13 C excursions with a magnitude of 0.3‰-1.0‰ ...
... Variations in global climate and the carbon cycle during the early, ice-free Cenozoic, including "hyperthermals," are predominately paced by short and long eccentricity cycles (Barnet et al., 2019;Lauretano et al., 2015;Littler et al., 2014;Turner, 2014;Westerhold et al., 2011Westerhold et al., , 2018Zachos et al., 2001). While eccentricity is the only astronomical parameter that alters Earth's annual global mean solar energy insolation, the total variability is small (∼0.5 Wm −2 ) (Laskar et al., 2004). ...
... In comparison to benthic high-resolution paleoclimate records throughout the Cenozoic (Barnet et al., 2019;Beddow et al., 2016;Holbourn et al., 2013;Littler et al., 2014;Pälike et al., 2006;Tian et al., 2018;Westerhold et al., 2018), our simulations show minor variability in δ 13 C on astronomical timescales (the maximum variability in simulated δ 13 C cycles is less than 0.2‰ in ASYM). This model-data discrepancy is especially pronounced as we are evaluating modeled water column δ 13 C and not considering the impact of bioturbation on the range of preserved cycles. ...
Astronomical cycles are strongly expressed in marine geological records, providing important insights into Earth system dynamics and an invaluable means of constructing age models. However, how various astronomical periods are filtered by the Earth system and the mechanisms by which carbon reservoirs and climate components respond, particularly in absence of dynamic ice sheets, is unclear. Using an Earth system model that includes feedbacks between climate, ocean circulation, and inorganic (carbonate) carbon cycling relevant to geological timescales, we systematically explore the impact of astronomically-modulated insolation forcing and its expression in model variables most comparable to key paleoceanographic proxies (temperature, the δ13C of inorganic carbon, and sedimentary carbonate content). Temperature predominately responds to short and long eccentricity and is little influenced by the modeled carbon cycle feedbacks. In contrast, the cycling of nutrients and carbon in the ocean generates significant precession power in atmospheric CO2, benthic ocean δ13C, and sedimentary wt% CaCO3, while inclusion of marine sedimentary and weathering processes shifts power to the long eccentricity period. Our simulations produce reduced pCO2 and DIC δ13C at long eccentricity maxima and, contrary to early Cenozoic marine records, CaCO3 preservation in the model is enhanced during eccentricity modulated warmth. Additionally, the magnitude of δ13C variability simulated in our model underestimates marine proxy records. These model-data discrepancies hint at the possibility that the Paleogene silicate weathering feedback was weaker than modeled here and that additional organic carbon cycle feedbacks are necessary to explain the full response of the Earth system to astronomical forcing.
... Waipawa deposition also coincides with a marked decrease in the coarse fraction in foraminiferal residues from sites 1209 and 1262 (Fig. 1, 13b). This represents a marked decrease in the abundance of planktic foraminifera and is attributed to carbonate dissolution (Littler et al., 2014). Although short-lived dissolution episodes have been linked to the PETM and 435 other early Eocene hyperthermals (Zachos et al, 2005;Alexander et al., 2015), the longer duration of this episode and its association with positive shifts in both δ 13 C and δ 18 O suggest a link to climatic cooling and carbon burial as outlined by Hilting et al. (2008). ...
... Cooling on land is also indicated by temperature reconstructions based on pollen assemblages at Site 1172 (Contreras et al., 2014). Correlation with the POIM in the deep-sea isotope record Littler et al., 2014, Barnet et al., 2019 further suggests that the positive δ 13 C excursion in Waipawa organofacies (Fig. 13c-f) is linked in some way to 445 climatic cooling. Although the large 8‰ excursion in bulk OM (Fig. 13c) is inferred to be partly a result of lignin degradation, excursions of 2.5‰ in HMW n-alkanes and fatty acids (Fig. 13d) and 4‰ in MMW and LMW n-alkanes and fatty acids, as well as in pristane (Fig. 13e, f) are clear indications of major perturbations in the terrestrial and marine environments. ...
... When correlated to deep sea benthic isotope records (Westerhold et al., , 2020Littler et al., 2014;Barnet et al., 2019), Waipawa organofacies deposition is found to coincide with a minimum in deep-sea temperatures and the onset of the 2.2 ...
Late Paleocene deposition of an organic-rich sedimentary facies on the continental shelf and slope of New Zealand and eastern Australia has been linked to short-lived climatic cooling and terrestrial denudation following sea-level fall. Recent studies have confirmed that the organic matter in this facies, termed Waipawa organofacies, is primarily of terrestrial origin, with a minor marine component. It is also unusually enriched in δ13C. In this study we aim to determine the cause or causes of this enrichment. For Waipawa organofacies and its bounding facies in the Taylor White section, Hawkes Bay, paired palynofacies and δ13C analysis of density fractions indicate that the heaviest δ13C values are associated with degraded phytoclasts (woody plant matter) and that the 13C enrichment is partly due to lignin degradation. Compound specific δ13C analyses of samples from the Taylor White and mid-Waipara (Canterbury) sections confirms this relationship but also reveal a residual 13C enrichment of ~ 2.5 ‰ in higher plant biomarkers (n-alkanes and n-alkanoic acids) and 3–4 ‰ in the subordinate marine component, which we interpret as indicating a significant drawdown of atmospheric CO2. Refined age control for Waipawa organofacies indicates that deposition occurred between 59.2 and 58.4 Ma, which coincides with a Paleocene oxygen isotope maximum (POIM) and the onset of the Paleocene carbon isotope maximum (PCIM). This timing suggests that this depositional event was related to global cooling and carbon burial. This relationship is further supported by published TEX86-based sea surface temperatures that indicate a pronounced regional cooling during deposition. We suggest that reduced greenhouse gas emissions from volcanism and accelerated carbon burial related to several tectonic factors and positive feedbacks resulted in short-lived global cooling, growth of ephemeral ice sheets, and a global fall in sea level. Accompanying erosion and carbonate dissolution in deep sea sediment archives may have hidden the evidence of this "hypothermal" event until now.
... Volcanic activity occurred across the North Atlantic region during the end of the Palaeocene and the early Eocene (Roberts et al., 1984;Steinberger et al., 2018;Svensen et al., 2004), with the intrusion of approximately 6.6 × 10 6 km 3 of magma (Saunders, 2016). Massive explosive eruptions also resulted in tephra deposition across much of north-western Europe and the North Atlantic Ocean, with PETM-age tephra found as far as Austria, c.1,900 km away from the source area (Egger and Brückl, 2006;Larsen et al., 2003;Stokke et al., 2020a) (Fig. 1). Importantly, coupled sea surface pH reconstructions and carbon isotope modelling indicate that the 3,000 Pg to >10,000 Pg of carbon emissions was required to initiate the PETM most likely derived from a volcanic source (Gutjahr et al., 2017). ...
... (b) Indicative age of each of the sections studied, based on nannofossil and magnetostratigraphy, adapted from Stokke et al. (2020b). Also shown is the age of Danish tephras from the Fur formation, and oxygen and carbon isotope curves for the interval (Littler et al., 2014), indicating the excursions that characterise the PETM and other hyperthermal events. (For interpretation of the colours in the figure(s), the reader is referred to the web version of this article.) ...
... We investigated the potential impact of C auth formation in PETM-age tephra deposits from the island of Fur, Denmark (Supplementary Figure 1), the Rockall Plateau (Deep Sea Drilling Project (DSDP) Leg 81, Holes 553A and 555), and a hydrothermal vent complex in the Vøring Basin offshore Norway (core 6607/12-1) (Fig. 1). The Rockall tephra layers were deposited immediately above basaltic lavas formed during the main phase (phase 2) of NAIP activity (see Methods) during the Paleogene (Roberts et al., 1984), the same activity that led to the deposition of the Fur tephras, which are preserved across Denmark (Larsen et al., 2003) and broadly coeval with hydrothermal vent formation (Frieling et al., 2016;Svensen et al., 2003) (Fig. 1). ...
The Palaeocene-Eocene Thermal Maximum (PETM) was a period of intense global warming that began ~55.9 million years ago and lasted about 170,000 years. Various mechanisms have been proposed to cause this warming, including the emplacement of the North Atlantic Igneous Province (NAIP). Equally, many mechanisms have been invoked to explain sequestration of carbon from the ocean-atmosphere system necessary to promote the recovery to more temperate conditions. Here we propose that an important path for carbon sequestration was tied to NAIP volcanism through the precipitation of calcium carbonate (CaCO3) cements within the tephra layers. These cements formed after the deposition and burial of tephra over a wide area of the North Atlantic Ocean during the late Palaeocene and early Eocene. We find strong evidence that authigenic CaCO3 cements formed shortly after tephra deposition. Monte Carlo simulations suggest that this process may have been responsible for a quarter of the carbon sequestered during the PETM recovery phase, providing a major, but previously unconsidered sink of isotopically-light carbon, and one
41 which may have persisted into the Eocene.
... This trend, coupled with a long-term decrease of δ 18 O values in marine carbonates by~1‰, is associated with some of the highest global temperatures and pCO 2 concentrations recorded during the Cenozoic (Westerhold et al., 2020;Zachos et al., 2001). Prior to the onset of this drastic warming episode, the mid to late Paleocene benthic δ 13 C carb record shows the most positive values of the Cenozoic; commonly referred to as the Paleocene Carbon Isotope Maximum (PCIM), it appears as a broad peak centered at ∼58-57.5 Ma (Littler et al., 2014). Such positive δ 13 C carb values have been interpreted to result from a~4 Myr global cooling event (Littler et al., 2014;Westerhold et al., 2020). ...
... Prior to the onset of this drastic warming episode, the mid to late Paleocene benthic δ 13 C carb record shows the most positive values of the Cenozoic; commonly referred to as the Paleocene Carbon Isotope Maximum (PCIM), it appears as a broad peak centered at ∼58-57.5 Ma (Littler et al., 2014). Such positive δ 13 C carb values have been interpreted to result from a~4 Myr global cooling event (Littler et al., 2014;Westerhold et al., 2020). Importantly, because of their ubiquity, the afore-mentioned negative CIEs and long-term rise and fall in δ 13 C carb compositions spanning the Late Cretaceous to early Paleogene have been used to correlate rock sequences worldwide (e.g., Aubry et al., 2007;Westerhold et al., 2020Westerhold et al., , 2011. ...
The Late Cretaceous–early Paleogene interva is globally associated with transient to long-term changes in the stable carbon isotopic composition of marine carbonates δ13Ccarb). Based on biostratigraphic reconstruction, this critical period of Earth's history is thought to coincide with the deposition of world heritage Paleocene phosphate deposits (phosphorites) in northwestern Morocco. However, the detailed stratigraphy of the Gantour basin, one of the most important Moroccan phosphate deposits, has not yet been constrained. For instance, the former
“Montian” Stage has been used to tentatively approximate the Danian, whereas the succeeding Selandian Stage remains to be identified. Here, we develop a detailed organic carbon isotopic (δ13Corg) curve from phosphorus-rich horizons of the western Gantour sedimentary sequence in an attempt to constrain their stratigraphic placement and depositional age model. Upsection, these strata host long-term negative and positive δ13Corg trends that tend to correlate with global δ13Ccarb records of the Cretaceous–Paleogene and mid-Thanetian transitional boundaries. The data support the presence of Danian and Selandian rocks in the Gantour basin, which are succeeded by strata containing characteristic signatures of the well-known Cenozoic δ13C maximum at 58–57.5 Ma (the Paleocene Carbon Isotope Maximum). Our results shift the previously proposed Cretaceous–Paleogene transition in the Gantour basin further down into the older sediment C2M layer without interfering with recorded massive biological turnover in faunal diversity and abundance. Moreover, the refined stratigraphy suggests that the deposition of the Gantour phosphorites spanned ~8.5 Myr. Our results confirm the utility of δ13Corg chemostratigraphy for dating and correlating phosphate-bearing deposits of the Tethyan province. They have important implications for deciphering Paleocene phosphogenesis, the co-evolution of associated vertebrate groups, and for prospecting phosphorus-rich mineral deposits
... Greenhouse conditions prevailed during the early Paleogene, with a general global warming trend culminating in the Early Eocene Climatic Optimum (EECO, ~53-49 Ma, Westerhold et al., 2020). Temperatures gradually decreased during the middle through late Eocene towards the cooler 'icehouse' conditions of the Oligocene, with the major Antarctic icesheet developing during the earliest Oligocene Oi glaciation (e.g., Zachos et al., 2008;Littler et al., 2014;Bornemann et al., 2016;Barnet et al., 2019). Later in the Oligocene, climate temporarily returned to somewhat warmer conditions similar to those in the late Eocene (e.g., O'Brien et al., 2020). ...
... Since the recognition of these multiple negative CIEs combined with warming (Thomas and Zachos, 2000;Cramer et al., 2003), numerous studies have looked into their origin, tempo and similarities with the largest hyperthermal event, the PETM (e.g., Lourens et al., 2005;Nicolo et al., 2007;Sluijs et al., 2009;Leon-Rodriguez and Dickens, 2010;Stap et al., 2010;Zachos et al., 2010;Littler et al., 2014;Lauretano et al., 2015;Barnet et al., 2019;Westerhold et al., 2020). Other studies have dealt with the biotic consequences of such warming events (including typical and atypical hyperthermals) and their impact on the ecosystems (e.g., Bernaola et al., 2007;Agnini et al., 2009;D'haenens et al., 2012;Payros et al., 2012;Sprong et al., 2012;Boscolo-Galazzo et al., 2013Jennions et al., 2015;Alegret et al., 2016;Frontalini et al., 2016;Deprez et al., 2017;Thomas et al., 2018;Rivero-Cuesta et al., 2019, but generally these studies focus on a specific event, type of biota, and/or exclusively one or few locations. ...
Long-term climatic trends of the Paleogene were interrupted by global perturbations of the carbon cycle, commonly associated with warming of surface and bottom waters and ecosystem disturbance. Most of these perturbations occurred in the Paleocene - Eocene greenhouse climate, but others were superimposed on the transition of greenhouse-to- icehouse conditions during the middle to late Eocene.
Here we analyze deep-sea benthic foraminifera to focus on the impact of Paleogene warming events on ocean bottom water ecosystems. We compare changes in assemblage diversity (Fisher-α index) across nine warming events at 16 locations (ocean drilling sites and land sections; 25 case studies) by applying the Epps-Singleton and Fligner-Killeen non-parametric statistical tests. Generally, diversity decreased whereas the coefficient of variation increased during warming events, but not all changes were statistically significant. The declines in diversity may have been due to adaptation to stressed conditions, whereas the higher coefficients of variation may have been caused by unstable environmental conditions. The most severe events, the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) and Eocene Thermal Maximum 2 (ETM2, ~53.7 Ma), had a higher impact on bottom water ecosystems, as shown in major drops in diversity. Regression analysis of data for ODP Sites 1262 and 1263 (SE Atlantic) shows that only up to 62% of the variability of benthic foraminiferal diversity at these sites depends on δ¹³C and δ¹⁸O values, indicating that changes in diversity were not exclusively determined by the magnitude of the events as defined by the magnitude of changes in carbon isotope excursion and temperature. No major changes in diversity were identified during middle Eocene warming events, and post-event diversity became significantly more stable, suggesting that the overall cooler middle Eocene conditions supported higher faunal diversity and stability of benthic foraminiferal assemblages.
... As highlighted in several works (Dickens 2003, Sexton et al. 2011, Kirtland Turner et al. 2014, the reason for this lies in the rapid cycling of carbon between various Earth surface reservoirs and a highly dynamic global carbon cycle during this time. Starting with the biostratigraphy at Core RH-323, the bulk carbonate δ 13 C record at this location was correlated to the high-resolution benthic foraminifera δ 13 C records of Ocean Drilling Program (ODP) Sites 1262 and 1263 from Walvis Ridge in the southeast Atlantic Ocean (Littler et al. 2014, Lauretano et al. 2015, Lauretano et al. 2018 and 1209 from Shatsky Rise in the Pacific Ocean , Westerhold et al. 2018. This is best realized through six horizons (tie-points) in Core RH-323 (Table 1, Fig. 7). ...
... The dashed green line connects the two low-confidence tie-points in the upper part of the core. Benthic foraminifera isotope data is fromMcCarren et al. (2008),Stap et al. (2010),Westerhold et al. (2011Westerhold et al. ( , 2018,Littler et al. (2014),Lauretano et al. (2015Lauretano et al. ( , 2016. b) Right-top panel shows the linear regression analysis between RH-323 bulk carbonate δ 13 C and open ocean benthic foraminifer δ 13 C from Walvis ridge (Blue; R 2 = 0.86; P < 0.001; y = 0.31 + 0.87 x; n = 92) and Shatsky Rise (Red; R 2 = 0.87; P < 0.001; y = 0.01 + 0.83 x; n = 116) based on this carbon isotope stratigraphic correlation (see Discussion 5.2). ...
... It has been proposed that the absence of these top trophic predators left ecological niches that remained empty or unoccupied until the later Paleogene [14]. The appearance of both S. secans and the earliest carnivorans around 60 Ma, 6-7 My after the K-Pg event, may not have been coincidental: their ages are broadly coincident with a global warming event, the Early Late Paleocene Event (ELPE) [15,16] and ELPE, which triggered faunal turnover [15] , [17]. Estimates of ecosystem recovery from K-Pg event required 100 years to 10 My both terrestrial and marine ecosystems [18][19][20][21][22]. ...
... It has been proposed that the absence of these top trophic predators left ecological niches that remained empty or unoccupied until the later Paleogene [14]. The appearance of both S. secans and the earliest carnivorans around 60 Ma, 6-7 My after the K-Pg event, may not have been coincidental: their ages are broadly coincident with a global warming event, the Early Late Paleocene Event (ELPE) [15,16] and ELPE, which triggered faunal turnover [15] , [17]. Estimates of ecosystem recovery from K-Pg event required 100 years to 10 My both terrestrial and marine ecosystems [18][19][20][21][22]. ...
Vertebrates evolved tooth replacement over 400 million years ago. Over 200 million years later, the combination of vertical tooth replacement with thecodont implantation (teeth in bone sockets) has been considered a key morphological innovation in mammal evolution. We discovered that an extinct fish taxon, Serrasalmimus secans, that shows this same innovation in a lineage (Serrasalmimidae) that survived the end Cretaceous mass extinction. Carnassial teeth are known in both mammals and pycnodont fish, but these teeth do not share the same tissues nor developmental processes. Therefore, a serrasalmimid pycnodont fish independently acquired mammal-like tooth replacement and implantation, thus showing that fishes and mammals evolved convergent carnassial dental morphologies at about the same time, around 60 Ma, in separate ecosystems.
... A significant body of research has been dedicated to investigating the long-term environmental and climatic changes within marine systems following the end-Cretaceous mass extinction. For instance, orbitally forcing of carbon cycles was proposed to interpret the climatic conditions and mechanisms in deep sea (e.g., Coccioni et al., 2012;Hollis et al., 2012;Littler et al., 2014;Zeebe et al., 2017;Barnet et al., 2018;Barnet et al., 2019;Gilabert et al., 2021b), and other hypotheses of carbon cycle and surface sea temperature (SST) were used to reconstruct the paleoclimate in surface sea system (e.g., Keller and Lindinger, 1989;Eldrett et al., 2021). ...
... The main cause of this mass extinction was the Chicxulub bolide impact (e.g., Alvarez et al., 1980;Alvarez, 1987;Hull, 2010;Hull et al., 2020), and additional effects of Deccan Traps volcanism are also debated (e.g., Keller et al., 2008Keller et al., , 2020Font et al., 2011Font et al., , 2016Font et al., , 2018. The early Paleogene time interval, specifically, was a time of environmental recovery in the aftermath of the K-Pg event, and recorded a series of perturbations of the global carbon cycle that were associated with global warming, known as hyperthermal events (e.g., Thomas and Zachos, 2000;Cramer et al., 2003;Littler et al., 2014;Barnet et al., 2019). ...
The Cerro Azul Section provides a continuous record of the Cretaceous-Paleogene (K-Pg) transition in a shallow marine context of the South Atlantic Ocean in the Neuquén Basin. Ostracod assemblages were severely affected by environmental changes across the event. Excellent ostracod preservation at the Cerro Azul Section allows to infer paleoecological preferences of four Danian species based on carbon and oxygen stable isotopes. The studied species were Paracypris bertelsae Ceolin and Whatley, 2015, Cytherella spp., Togoina argentinensis and Henryhowella (Wichmannella) meridionalis (Bertels, 1974). To assess the reliability of ostracod δ13C and δ18O values as paleoenvironmental proxies, we pre-characterized valves with micro x-ray microdiffraction (μXRD) and microRaman (μRaman spectroscopy). Togoina argentinensis and Henryhowella (Wichmannella) meridionalis present in their major calcitic compositions, with small differences of crystallinity within intervals of environmental stress, but no authigenic phases formed during diagenesis. δ13C and δ18O values depict clear interspecific differences between smooth specimens and ornamented specimens. These differences in stable isotope values were likely controlled by microhabitat preferences, which would be comparable with patterns described for benthic foraminifera as well as paleonutrients variations, suing Ba/Ti and P/Ti ratios.
... Optimum (EECO) 13 . While changes in mean temperature conditions during the PETM and EECO have been reconstructed at a relatively high resolution at the poles and mid-latitude locations 14 , changes in precipitation are not well understood 15 . ...
As the world warms, the Earth system moves towards a climate state without societal precedent ¹ . This challenges predictions of the future, as climate models need to be tested and calibrated with real-world data from high carbon dioxide climates ² . Despite the many advances in climate modeling, predictions of precipitation have particularly high uncertainties ³ . Earth history provides an opportunity to observe how the Earth system responded to high greenhouse gas emissions, enabling us to better predict how it may do so in the future. Here, we compile global proxy data from the Early Paleogene (66 − 49 Ma), a period with a warm climate overprinted by multiple rapid global warming events ⁴ , and suggested as a possible analogue for future worst-case scenarios 1, 2 . We show surprising results in the timing and duration of dramatic shifts in the hydrologic cycle occurring well prior to maximum temperatures and persisting well beyond. We provide a glimpse of an extremely warm Earth with ever-wet or monsoonal conditions in the northern and southern polar regions, and sustained aridity interrupted by extreme rainfall events at mid-latitudes. Our results indicate inconsistencies between proxy data and state-of-the-art paleoclimate models that are commonly used to predict and understand future climate change. Our focus on precipitation intermittency and intensity provides new data on long-term precipitation trends in high greenhouse gas climates to help address large uncertainties in future precipitation trends.
... All of the samples used in this study were derived from the Paleogene succession in northern Denmark (Fig. 2). Pleistocene glaciotectonism provides valuable onshore outcrops (Heilmann-Clausen et al., 1985;King, 2016) in relation to the GTS2020 geological timescale (Speijer et al., 2020) and global oxygen and carbon isotope curves (Cramer et al., 2009;Littler et al., 2014). PETM: Paleocene-Eocene Thermal Maximum; ETM2: Eocene Thermal Maximum 2. (c) A view of Stolleklint Beach from the north, with the outcropping strata labelled . ...
There is a temporal correlation between the peak activity of the North Atlantic Igneous Province (NAIP) and the Paleocene–Eocene Thermal Maximum (PETM), suggesting that the NAIP may have initiated and/or prolonged this extreme warming event. However, corroborating a causal relationship is hampered by a scarcity of expanded sedimentary records that contain both climatic and volcanic proxies. One locality hosting such a record is the island of Fur in Denmark, where an expanded pre- to post-PETM succession containing hundreds of NAIP ash layers is exceptionally well preserved. We compiled a range of environmental proxies, including mercury (Hg) anomalies, paleotemperature proxies, and lithium (Li) and osmium (Os) isotopes, to trace NAIP activity, hydrological changes, weathering, and seawater connectivity across this interval. Volcanic proxies suggest that NAIP activity was elevated before the PETM and appears to have peaked during the body of the δ13C excursion but decreased considerably during the PETM recovery. This suggests that the acme in NAIP activity, dominated by flood basalt volcanism and thermogenic degassing from contact metamorphism, was likely confined to just ∼ 200 kyr (ca. 56.0–55.8 Ma). The hundreds of thick (> 1 cm) basaltic ashes in the post-PETM strata likely represent a change from effusive to explosive activity, rather than an increase in NAIP activity. Detrital δ7Li values and clay abundances suggest that volcanic ash production increased the basaltic reactive surface area, likely enhancing silicate weathering and atmospheric carbon sequestration in the early Eocene. Signals in lipid biomarkers and Os isotopes, traditionally used to trace paleotemperature and weathering changes, are used here to track seaway connectivity. These proxies indicate that the North Sea was rapidly cut off from the North Atlantic in under 12 kyr during the PETM recovery due to NAIP thermal uplift. Our findings reinforce the hypothesis that the emplacement of the NAIP had a profound and complex impact on Paleocene–Eocene climate, both directly through volcanic and thermogenic degassing and indirectly by driving regional uplift and changing seaway connectivity.
... The chemical composition of foraminiferal shell (hereafter referred as test) is used as proxy for the interpretation of palaeoecological and palaeoclimatic conditions such as temperature, carbon saturation, salinity, palaeocirculation, oxygen concentration and hydrodynamics during their life time (e.g. Thomas 2007;Boscolo Galazzo et al. 2014;Littler et al. 2014;Nwojiji et al. 2014;Pälike et al. 2014;and Arreguín-Rodríguez et al. 2016). The physiological makeup of foraminifera plays a huge role in the surviving strategies they adopt while alive and has been demonstrated in the fossil and modern species records to have a close relationship with environmental parameters (Keating-Bitonti and Payne 2017). ...
Benthic foraminiferal turnover during the Palaeocene–Eocene Thermal Maximum (PETM) has been extensively studied but numerous questions remained unresolved, question such as why some foraminiferal species went into extinction at a particular location but survive in another or why some species survive in extremely low oxygen environment. Because foraminiferal community interaction with the environment is driven by biological traits instead of taxonomic composition, this study has adopted trait-based approach to provide insight into the life strategies of foraminifera that enables them to survive in extreme environmental conditions. The result from this study shows that traits such as test composition, perforation, ornamentation and living habits play an important role in the ecological functioning and adaptability of foraminifera in the environment. The faunal assemblage in the studied site is dominantly cosmopolitan taxa suggesting the environment was perturbed during the PETM. Foraminiferal composition is characterised by faunal turnover indicated in extensive mortalities and extinction of both planktonic and benthic fauna. The ordination (non-metric dimensional scaling) of faunal composition also indicated ecological disturbance. The planktonic community was relatively stable before and after PETM but experienced a high level of ecological perturbation during the carbon isotopic excursion (CIE). The benthic community showed higher evidence of perturbation as the fauna assemblage ordination indicated that ecological stress started before the PETM with the disarray of samples in the ordination diagram. Only the recovery interval experienced some level of ecological stability. The environmental disturbance noticed in the fauna composition reflected on the trait. Benthic foraminiferal traits indicated instability throughout the studied section. The evidence of environmental disturbance in the benthic community suggests that the source of the light carbon that caused the PETM may have originated beneath sea floor in the Atlantic Ocean.
... The chemical composition of foraminiferal shell (hereafter referred as test) is used as proxy for the interpretation of palaeoecological and palaeoclimatic conditions such as temperature, carbon saturation, salinity, palaeocirculation, oxygen concentration and hydrodynamics during their life time (e.g. Thomas 2007;Boscolo Galazzo et al. 2014;Littler et al. 2014;Nwojiji et al. 2014;Pälike et al. 2014;and Arreguín-Rodríguez et al. 2016). The physiological makeup of foraminifera plays a huge role in the surviving strategies they adopt while alive and has been demonstrated in the fossil and modern species records to have a close relationship with environmental parameters (Keating-Bitonti and Payne 2017). ...
Benthic foraminiferal turnover during the Palaeocene–Eocene Thermal Maximum (PETM) has been extensively studied but
numerous questions remained unresolved, question such as why some foraminiferal species went into extinction at a particular
location but survive in another or why some species survive in extremely low oxygen environment. Because foraminiferal
community interaction with the environment is driven by biological traits instead of taxonomic composition, this study has
adopted trait-based approach to provide insight into the life strategies of foraminifera that enables them to survive in extreme
environmental conditions. The result from this study shows that traits such as test composition, perforation, ornamentation
and living habits play an important role in the ecological functioning and adaptability of foraminifera in the environment.
The faunal assemblage in the studied site is dominantly cosmopolitan taxa suggesting the environment was perturbed during
the PETM. Foraminiferal composition is characterised by faunal turnover indicated in extensive mortalities and extinction
of both planktonic and benthic fauna. The ordination (non-metric dimensional scaling) of faunal composition also indicated
ecological disturbance. The planktonic community was relatively stable before and after PETM but experienced a high level
of ecological perturbation during the carbon isotopic excursion (CIE). The benthic community showed higher evidence of
perturbation as the fauna assemblage ordination indicated that ecological stress started before the PETM with the disarray
of samples in the ordination diagram. Only the recovery interval experienced some level of ecological stability. The environmental
disturbance noticed in the fauna composition reflected on the trait. Benthic foraminiferal traits indicated instability
throughout the studied section. The evidence of environmental disturbance in the benthic community suggests that the source
of the light carbon that caused the PETM may have originated beneath sea floor in the Atlantic Ocean.
... The Early Eocene is punctuated by a series of transient phases of carbon input and global warming, termed hyperthermals (e.g., Thomas and Zachos, 2000;Cramer et al., 2003;Littler et al., 2014). The well-studied Paleocene-Eocene Thermal Maximum (PETM) may represent the closest approximation to modern day warming in the geologic record (Zachos et al., 45 2008). ...
Eocene transient global warming events (hyperthermals) can provide insight into a future, warmer world. While much research has focused on the Paleocene-Eocene Thermal Maximum (PETM), hyperthermals of smaller magnitude can be used to characterize climatic responses over different magnitudes of forcing. This study identifies two events, Eocene Thermal Maximum 2 (ETM2 and H2) for the first time in a shallow marine setting along the United States Atlantic margin in the Salisbury Embayment of Maryland, based on magnetostratigraphy, calcareous nannofossil and dinocyst biostratigraphy, and recognition of negative stable carbon isotope excursions (CIEs) in biogenic calcite. We assess local environmental change in the Salisbury Embayment utilizing clay mineralogy, marine palynology, δ18O of biogenic calcite, and biomarker paleothermometry (TEX86). Paleo-temperature proxies show broad agreement between surface water and bottom water temperature changes. However, the timing of warming does not correspond to the CIE of ETM2 as expected from other records, and the highest values are observed during H2, suggesting factors other than pCO2 forcing influenced temperature changes in the region. The ETM2 interval exhibits a shift in clay mineralogy from smectite-dominated facies to illite-rich facies, suggesting hydroclimatic changes but with a rather dampened weathering response relative to that of the PETM in the same region. Organic walled dinoflagellate cyst assemblages show large fluctuations throughout the studied section, none of which seem systematically related to ETM2. These observations are contrary to the typical tight correspondence between climate change and assemblages across the PETM, regionally and globally, and ETM2 in the Arctic Ocean. The data do indicate very warm and (seasonally) stratified conditions, likely salinity-driven, across H2. The absence of evidence for strong perturbations in local hydrology and nutrient supply during ETM2 and H2, compared to the PETM, is consistent with the less extreme forcing and the warmer pre-event baseline, as well as the non-linear response in hydroclimates to greenhouse forcing.
... These data are uniquely poised to: 1) assess changes in environmental conditions across the PETM and in the earliest Eocene; 2) interrogate how the style and magnitude of NAIP activity varied concurrently; and 3) evaluate how these regional signals relate to global changes through comparison to existing PETM localities worldwide. -Clausen et al., 1985;King, 2016) in relation to the GTS2020 geological timescale (Speijer et al., 2020) and global oxygen and carbon isotope curves (Cramer et al., 2009;Littler et al., 2014). PETM = Paleocene-Eocene Thermal Maximum; 235 ETM2 = Eocene Thermal Maximum 2. C) A view of Stolleklint Beach from the north, with the outcropping strata labelled . ...
There is a temporal correlation between the peak activity of the North Atlantic Igneous Province (NAIP) and the Paleocene–Eocene Thermal Maximum (PETM), suggesting that the NAIP may have initiated and/or prolonged this extreme warming event. However, corroborating a causal relationship is hampered by a scarcity of expanded sedimentary records that contain both climatic and volcanic proxies. One locality hosting such a record is Fur Island in Denmark, where an expanded pre- to post-PETM succession containing hundreds of NAIP ash layers is exceptionally well preserved. We compiled a range of environmental proxies, including mercury (Hg) anomalies, paleotemperature proxies, and lithium (Li) and osmium (Os) isotopes, to trace NAIP activity, hydrological changes, weathering, and seawater connectivity across this interval. Volcanic proxies suggest that NAIP activity was elevated before the PETM and appears to have peaked during the body of the δ13C excursion, but decreased considerably during the PETM recovery. This suggests that the acme in NAIP activity, dominated by flood basalt volcanism and thermogenic degassing from contact metamorphism, was likely confined to just ~200 kyr (ca. 56.0–55.8 Ma). The hundreds of thick basaltic ashes in the post-PETM strata likely represent a change from effusive to explosive activity, rather than an increase in NAIP activity. Detrital δ7Li values and clay abundances suggest that volcanic ash production increased basaltic reactive surface area, likely enhancing silicate weathering and atmospheric carbon sequestration in the early Eocene. Signals in lipid biomarkers and Os isotopes, traditionally used to trace paleotemperature and weathering changes, are used here to track seaway connectivity. These proxies indicate that the North Sea was rapidly cut off from the North Atlantic in under 12 kyr during the PETM recovery due to NAIP thermal uplift. Our findings reinforce the hypothesis that the emplacement of the NAIP had a profound and complex impact on Paleocene–Eocene climate, both directly through volcanic and thermogenic degassing, and indirectly by driving regional uplift and changing seaway connectivity.
... Hence reduced variations in Earth's obliquity from ∼58 to ∼48 Ma should also have affected Earth's climate across this time interval (aka the late Paleocene-early Eocene; LPEE). Remarkably, a nearly ubiquitous phenomenon in long-term geologic records across the LPEE is a very weak or absent obliquity signal (e.g., Lourens et al. 2005;Westerhold et al. 2007;Littler et al. 2014;Zeebe et al. 2017;Barnet et al. 2019). We do not rule out that other factors such as the greenhouse climate at the time, the absence of large ice sheets, etc. may have contributed to a weak expression of obliquity (high-latitude) forcing as well. ...
The dynamical evolution of the solar system is chaotic with a Lyapunov time of only ∼5 Myr for the inner planets. Due to the chaos it is fundamentally impossible to accurately predict the solar system’s orbital evolution beyond ∼50 Myr based on present astronomical observations. We have recently developed a method to overcome the problem by using the geologic record to constrain astronomical solutions in the past. Our resulting optimal astronomical solution (called ZB18a) shows exceptional agreement with the geologic record to ∼58 Ma (Myr ago) and a characteristic resonance transition around 50 Ma. Here we show that ZB18a and integration of Earth’s and Mars’ spin vector based on ZB18a yield reduced variations in Earth’s and Mars’ orbital inclination and Earth’s obliquity (axial tilt) from ∼58 to ∼48 Ma—the latter being consistent with paleoclimate records. The changes in the obliquities have important implications for the climate histories of Earth and Mars. We provide a detailed analysis of solar system frequencies ( g and s modes) and show that the shifts in the variation in Earth’s and Mars’ orbital inclination and obliquity around 48 Ma are associated with the resonance transition and caused by changes in the contributions to the superposition of s modes, plus g – s mode interactions in the inner solar system. The g – s mode interactions and the resonance transition (consistent with geologic data) are unequivocal manifestations of chaos. Dynamical chaos in the solar system hence not only affects its orbital properties but also the long-term evolution of planetary climate through eccentricity and the link between inclination and axial tilt.
... Hence reduced variations in Earth's obliquity from ∼58 to ∼48 Ma should also have affected Earth's climate across this time interval (aka the late Paleocene -early Eocene, LPEE). Remarkably, a nearly ubiquitous phenomenon in long-term geologic records across the LPEE is a very weak or absent obliquity signal (e.g., Lourens et al. 2005;Westerhold et al. 2007;Littler et al. 2014;Zeebe et al. 2017;Barnet et al. 2019). We do not rule out that other factors such as the greenhouse climate at the time, the absence of large ice sheets, etc. may have contributed to a weak expression of obliquity (high-latitude) forcing as well. ...
The dynamical evolution of the solar system is chaotic with a Lyapunov time of only $\sim$5 Myr for the inner planets. Due to the chaos it is fundamentally impossible to accurately predict the solar system's orbital evolution beyond $\sim$50 Myr based on present astronomical observations. We have recently developed a method to overcome the problem by using the geologic record to constrain astronomical solutions in the past. Our resulting optimal astronomical solution (called ZB18a) shows exceptional agreement with the geologic record to $\sim$58 Ma (Myr ago) and a characteristic resonance transition around 50 Ma. Here we show that ZB18a and integration of Earth's and Mars' spin vector based on ZB18a yield reduced variations in Earth's and Mars' orbital inclination and Earth's obliquity (axial tilt) from $\sim$58 to $\sim$48 Ma -- the latter being consistent with paleoclimate records. The changes in the obliquities have important implications for the climate histories of Earth and Mars. We provide a detailed analysis of solar system frequencies ($g$- and $s$-modes) and show that the shifts in the variation in Earth's and Mars' orbital inclination and obliquity around 48 Ma are associated with the resonance transition and caused by changes in the contributions to the superposition of $s$-modes, plus $g$-$s$-mode interactions in the inner solar system. The $g$-$s$-mode interactions and the resonance transition (consistent with geologic data) are unequivocal manifestations of chaos. Dynamical chaos in the solar system hence not only affects its orbital properties, but also the long-term evolution of planetary climate through eccentricity and the link between inclination and axial tilt.
... Our record would support the increasing evidence that this POE is a global event. The lower excursion in SBZ3 would be time equivalent to P4a andP4b (Scheibner & Speijer, 2009) potentially linking it to the Early Late Paleocene Event (ELPE) at 59.2 Ma (Jehle et al., 2015;Littler et al., 2014). The ELPE (also termed mid-Paleocene biotic event, MPBE) has been described from several localities around the world including the Pacific, Atlantic, Southern Ocean, and several sections in the Tethys (see Coccioni et al., 2019 and references therein). ...
The Paleocene‐Eocene Thermal Maximum (PETM) is associated with major extinctions in the deep ocean, and significant paleogeographic and ecological changes in surface ocean and terrestrial environments. However, the impact of the associated environmental change on shelf biota is less well understood. Here, we present a new PETM record of a low paleolatitude shallow‐marine carbonate platform from Meghalaya, NE India (eastern Tethys). The biotic assemblage was distinctly different to other Tethyan PETM records dominated by larger benthic foraminifera and calcareous algae both in the Paleocene and Eocene. A change in taxa and forms indicating deeper waters with a concurrent decrease in abundance of shallow water algae suggests a sea‐level rise during the onset of the PETM. The record is lacking the ecological change from corals to larger foraminiferal assemblages and the Lockhartia dominance, characteristic of several other sections in the Tethys. Comparison with a global circulation model (GCM) indicates high regional temperatures in the Thanetian which may have excluded corals from the region. Furthermore, the regional circulation pattern is isolating the site from the wider Paratethys. Our study highlights the need for a diverse global perspective on shallow‐marine response to the PETM and the strength of coupling data to global climate models for interpretation.
... Massive coal deposits associated with paralic and delta systems of the paleo-Mississippi, Brazos, Colorado, and Rio Grande Rivers form the largest lignite producing region in the United States ( Fig. 1; EIA, 2017). They contribute to a peak in global terrestrial organic matter deposition and Paleocene carbon isotope maximum (Dyni, 2003;Kurtz et al., 2003;Littler et al., 2014). Source beds for a petroleum system extending from the coastal plain into deep water containing terrestrial and marine organic matter were deposited in deltaic to submarine fan environments of the Wilcox Gp (McDade, 1992;McDade et al., 1993;Hood et al., 2002;Ferworn et al., 2003;Holguin-Quinones et al., 2005). ...
We suggest these biotic and organic geochemical responses reflect connection to the Global Ocean during the PETM, with ventilation reduced but not eliminated by increases in salinity stratification due to runoff and reductions in deeper water entry into the GoM at gateways.
... As a potential ancient analogue to the present-day anthropogenicforced climate change, the early Eocene hothouse period and hyperthermals have become a focal point of research during the last decades (Dickens et al., 1995;Lourens et al., 2005). Most studies dealing with early Paleogene hyperthermals focused on the age, duration, and mechanism of carbon emissions, and on the consequences on biotic evolution (Nicolo et al., 2007;Westerhold et al., 2007Westerhold et al., , 2018Littler et al., 2014;Lauretano et al., 2015;Cui and Schubert, 2017;Li et al., 2020a;Li et al., 2020b;Jiang et al., 2021a;Jiang et al., 2021b). More recently, an increasing number of studies have been dedicated to the sedimentological changes associated with the early Paleogene hyperthermals. ...
Early Paleogene hyperthermal episodes including the Paleocene-Eocene Thermal Maximum (PETM) have long been viewed as analogues of the Anthropocene global warming. Few studies, however, have analyzed the environmental consequences of such climatic anomalies in deep-water turbidite-rich successions. This integrated sedimentological, biostratigraphic, and stable-isotope study of the Paleogene Pabdeh Formation, deposited along the Arabian continental margin of southwestern Iran, allowed us to document the geological response of hyperthermal events in deep Neo-Tethyan Ocean. The late Thanetian event (Pre-Onset Excursion or long-term late Paleocene climatic perturbation), the Early Eocene Climate Optimum, and the Middle Eocene Thermal Maximum were successfully identified within the Pabdeh Formation. The PETM event could not be documented because the Paleocene/Eocene boundary corresponds to a prolonged non-depositional hiatus marked by a glauco-phosphorite interval. Based on high-resolution microfacies analysis, three different processes in a carbonate slope to basin-margin environment were distinguished including pelagic settling, upwelling-condensation-reworking, and storm-induced turbiditic deposition. Detailed sedimentological analysis revealed an anomalous abundance of storm-induced proximal to distal turbidites represented by packstones with deep-water and reworked shallow-water bioclasts occurring during the hyperthermal intervals. A close causal link between climate warming and tropical storms during the early Paleogene hyperthermal events is thus envisaged. As a principal mechanism, we propose that rapid warming in response to massive carbon release triggered pronounced sedimentological changes along low-latitude tropical margins, leading to generation of storm-induced calciturbidite and re-deposition in the deep sea during hothouse stages.
... If we consider the lack of a deep-sea isotopic expression of the POE event at face value, it suggests that the duration and mass of carbon release was insufficient to alter the deepocean reservoir. The lack of a deep-sea POE event is consistent with a lack of a negative excursion before the CIE in deep-sea benthic records or indirect evidence for deep-sea acidification as seafloor carbonate dissolution before the main CIE (46). While chemical erosion associated with the CIE might have erased evidence of a precursor event in carbonate-rich pelagic sections, models show that erosion was limited in sites with higher clay fluxes and more likely bioturbation contributed to the lack of a short-lived excursion being preserved (47). ...
The Paleocene-Eocene Thermal Maximum (PETM) is recognized by a major negative carbon isotope (δ13C) excursion (CIE) signifying an injection of isotopically light carbon into exogenic reservoirs, the mass, source, and tempo of which continue to be debated. Evidence of a transient precursor carbon release(s) has been identified in a few localities, although it remains equivocal whether there is a global signal. Here, we present foraminiferal δ13C records from a marine continental margin section, which reveal a 1.0 to 1.5‰ negative pre-onset excursion (POE), and concomitant rise in sea surface temperature of at least 2°C and a decline in ocean pH. The recovery of both δ13C and pH before the CIE onset and apparent absence of a POE in deep-sea records suggests a rapid (< ocean mixing time scales) carbon release, followed by recovery driven by deep-sea mixing. Carbon released during the POE is therefore likely more similar to ongoing anthropogenic emissions in mass and rate than the main CIE.
... Massive coal deposits associated with paralic and delta systems of the paleo-Mississippi, Brazos, Colorado, and Rio Grande Rivers form the largest lignite producing region in the United States ( Fig. 1; EIA, 2017). They contribute to a peak in global terrestrial organic matter deposition and Paleocene carbon isotope maximum (Dyni, 2003;Kurtz et al., 2003;Littler et al., 2014). Source beds for a petroleum system extending from the coastal plain into deep water containing terrestrial and marine organic matter were deposited in deltaic to submarine fan environments of the Wilcox Gp (McDade, 1992;McDade et al., 1993;Hood et al., 2002;Ferworn et al., 2003;Holguin-Quinones et al., 2005). ...
Deposition of the Paleocene-Eocene Wilcox Group (Gp) in the northern Gulf of Mexico (GoM) occurred during dramatic global climate and regional tectonic change. Key drivers impacting the GoM over this time were 1) significantly enhanced runoff and sediment supply from the developing Laramide hinterland, 2) intense global warming culminating in the Paleocene–Eocene Thermal Maximum (PETM) at ∼56 Ma, and 3) proposed Paleogene restriction of the GoM as Cuba docked with Yucatan-Bahamas-Florida. In this paper, we investigate biological and organic geochemical responses to these drivers across the PETM and identify spatial variations in productivity, oxygenation, and ultimately, ventilation. The PETM has been identified by calcareous nannofossil marker taxa and/or excursion taxa from the genera Rhomboaster and Discoaster that exclusively existed during the event. A calcareous nannofossil transition from cool eutrophic to warm oligotrophic assemblages occurs across the PETM broadly over the GoM suggesting that surface water nutrient supply decreased due to slowing circulation or increased sequestration of nutrients along the margins. Associated radiolarian bursts indicate additional factors, such as eustacy and runoff, may have modulated nutrient supply. Benthic habitats were impacted as agglutinated foraminifera, which were dominant in the Paleocene, disappeared at the PETM over submarine fan environments while calcareous benthic forams remained largely absent until the late Eocene. Deoxygenation may have contributed to benthic ecosystem decline as marine kerogen enrichment is noted broadly in the middle Wilcox and PETM. Total organic carbon is generally <3% except in more isolated marginal settings suggesting that deep-basin dysoxia co-existed with a variably enhanced oxygen minimum. We suggest these biotic and organic geochemical responses reflect connection to the Global Ocean during the PETM, with ventilation reduced but not eliminated by increases in salinity stratification due to runoff and reductions in deeper water entry into the GoM at gateways.
... They have found that a large number of thermal events occurred at 55-47 Ma, including Eocene Thermal Maximum 2 (ETM2), H1, H2, I1, I2, ETM3 and EECO. In addition, the EECO period was composed of multiple hyperthermal events, such as L, M, N, O, P, Q, R, S, T, U, V, W, C22nH3, C22nH4, C22nH5, C21rH1, C21rH2, C21rH3, C21rH4, C21rH4, C21rH5, C21nH1 and C21nH2 (Lourens et al., 2005;Galeotti et al., 2010;Littler et al., 2014;Lauretano et al., 2015Lauretano et al., , 2016Westerhold et al., 2017Westerhold et al., , 2018Hu et al., 2020). These global hyperthermal events altered the palaeoclimate, sedimentary patterns and sedimentary records during the impacted periods (Zachos et al., 2008). ...
Frequent hyperthermal events during the Eocene (55-47 Ma), primarily characterised by carbon isotope excursions (CIEs), have been identified from marine records worldwide. However, only a few excursions have been recognised and described in continental deposits, thereby limiting the understanding of the effect of global warming on terrestrial systems. Thick, dark, organic-rich mudstone containing complete astronomical age information was deposited during the Palaeogene in the Fushun Basin. Based on U-Pb zircon dating and Milankovitch cycle analysis, the astronomical time scale (ATS) of the Fushun Basin was established. Based on the high-resolution chronostratigraphic framework, combined with the negative migration characteristics of organic carbon isotopes (δ 13 C TOC), three hyperthermal events were identified: Eocene Thermal Maximum 2 (ETM2), Eocene Thermal Maximum (ETM3) and long-term Early Eocene Climatic Optimum (EECO). In particular, several periods of short-term hyperthermal events were identified in the EECO period: L, M, N, O, P, Q, R, S, T, U, V, W, C22nH3, C22nH4, C22nH5, C21rH1, C21rH2, C21rH3, C21rH4, C21rH5, C21nH1 and C21nH2. The records of sea and land hyperthermal events show that the records corresponding to land basins are timelier and more sensitive.
... High-quality, multiple-hole Cenozoic sedimentary successions from the Atlantic (ODP Legs 171B, 207, and 208 and Integrated Ocean Drilling Program Expedition 342) and Pacific (ODP Legs 198 and 199 and Integrated Ocean Drilling Program Expeditions 320 and 321) drill sites yielded high-resolution geochemical records that also led to the development of astronomically calibrated age models (e.g., Röhl et al., 2007;Westerhold et al., 2011Westerhold et al., , 2018Westerhold et al., , 2020Littler et al., 2014;Lauretano et al., 2016;Barnet et al., 2019). Expedition 378 will contribute a unique section that includes crucial time intervals for the South Pacific area and will be integrated into the global chronostratigraphy. ...
... High-quality, multiple-hole Cenozoic sedimentary successions from the Atlantic (ODP Legs 171B, 207, and 208 and Integrated Ocean Drilling Program Expedition 342) and Pacific (ODP Legs 198 and 199 and Integrated Ocean Drilling Program Expeditions 320 and 321) yielded high-resolution geochemical records that also led to the development of astronomically calibrated age models (e.g., Röhl et al., 2007;Westerhold et al., 2011Westerhold et al., , 2018Littler et al., 2014;Lauretano et al., 2016;Barnet et al., 2019;Westerhold et al., 2020;De Vleeschouwer et al., 2020;Tierney et al., 2020). Expedition 378 will contribute a unique section that includes crucial time intervals for the South Pacific area that will be integrated into the global chronostratigraphy. ...
... However, in some fluvial settings, these cycles are rarely influenced by base-level changes at orbital timescales, and instead, they are driven by orbital climate change controlling water discharge and sediment load (Noorbergen et al., 2018(Noorbergen et al., , 2020. With its ability to incur climatic variability over 10⁴-10⁵ year timescales, orbital forcing has been demonstrated in extensive marine and lacustrine sedimentary archives (Abels et al., 2010;Huang and Hinnov, 2019;Kuiper et al., 2008;Littler, 2014;Lourens et al., 2005), with proxies like stable carbon isotope (δ¹³C) and oxygen isotope (δ¹⁸O) ratios of deep-sea foraminifera (Kocken et al., 2019). However, it is challenging to be proven in the fluvial realm that is subjected to fragmentary sedimentation and stratigraphic incompleteness (Fielding and Webb, 1996;Hilgen et al., 2015). ...
Alluvial stratigraphy is influenced by both allogenic and autogenic factors, which are difficult to be distinguished from each other because they operate at overlapping spatial and temporal scales. Moreover, it remains uncertain whether autogenic dynamics can result in sedimentary cyclicity that resembles allogenically-driven stratigraphic products. In order to undertake this challenge and address the uncertainty, we first test what sedimentary processes can produce the alluvial cyclicity observed in outcrops by designing comparable scenarios in the process-based numerical modelling. In the meantime, we systematically characterize floodplain aggradation cycles by tracing them in a UAV-based photogrammetric model. Moreover, we comprehensively describe channelized sandstone bodies in the field and the UAV model to reconstruct the paleogeography. Lastly, we configure the stratigraphic relationships between floodplain aggradation cycles and sandstone bodies of different river styles, based on which we identify the link between alluvial stratigraphy and orbital forcing.
... mundulus ( Figure 3) in order to assess preservation. Samples were imaged from intervals of both high and low percentage coarse fraction, which in other sites has been related to variable carbonate preservation (e.g., Littler et al., 2014). Analysis was carried out at the University of Exeter, Penryn Campus on a TESCAN VEGA3 GMU SEM. ...
The geological history of the South Asian monsoon (SAM) before the Pleistocene is not well-constrained, primarily due to a lack of available continuous sediment archives. Previous studies have noted an intensification of SAM precipitation and atmospheric circulation during the middle Miocene (∼14 Ma), but no records are available to test how the monsoon changed prior to this. In order to improve our understanding of monsoonal evolution, geochemical and sedimentological data were generated for the Oligocene–early Miocene (30–20 Ma) from Indian National Gas Hydrate Expedition 01 Site NGHP-01-01A in the eastern Arabian Sea, at 2674 m water depth. We find the initial glaciation phase (23.7–23.0 Ma) of the Oligocene–Miocene transition (OMT) to be associated with an increase in water column ventilation and water mass mixing, suggesting an increase in winter monsoon type atmospheric circulation, possibly driven by a relative southward shift of the intertropical convergence zone. During the latter part of the OMT, or ‘deglaciation’ phase (23.0–22.7 Ma), a long-term decrease in Mn (suggestive of deoxygenation), increase in Ti/Ca and dissolution of the biogenic carbonate fraction suggest an intensification of a proto-summer SAM system, characterised by the formation of an oxygen minimum zone in the eastern Arabian Sea and a relative increase of terrigenous material delivered by runoff to the site. With no evidence at this site for an active SAM prior to the OMT we suggest that changes in orbital parameters, as well as possibly changing Tethyan/Himalayan tectonics, caused this step change in the proto-monsoon system at this intermediate-depth site.
... Beyond rapid rises in ocean temperature, these "hyperthermals" (Thomas, 1998) share several key characteristics, most notably negative carbon isotope (δ 13 C) excursions (CIEs) and evidence for dissolution of deep-sea carbonate (e.g., Zachos et al., 2005;Leon-Rodriguez and Dickens, 2010). Several hyperthermals have been identified, beside the widely studied Paleocene Eocene Thermal Maximum (PETM, ~56 Ma), including the H-1 or ETM2 (~54 Ma), I-1 (~ 53.6 Ma), J (~53 Ma) and K/X or ETM3 events (~ 52.8 Ma) (Cramer et al., 2003;Lourens et al., 2005;Nicolo et al., 2007;Agnini et al., 2009;Stap et al., 2009Stap et al., , 2010aStap et al., , 2010bZachos et al., 2010;Coccioni et al., 2012;D'Onofrio et al., 2014D'Onofrio et al., , 2016Kirtland-Turner et al., 2014;Littler et al., 2014;Lauretano et al., 2015), with the J event initiating the EECO according to Slotnick et al. (2012Slotnick et al. ( , 2015, Lauretano et al. (2016) and Luciani et al. (2016). ...
Coiling direction is a basic characteristic of trochospiral planktic foraminifera. Modifications in the coiling direction within ancient planktic foraminiferal populations may reflect important changes in evolution or environment, yet they remain scarcely discussed. Here we investigate fluctuations in the coiling direction within Morozovella assemblages from sections that span the interval of peak Cenozoic warmth, the Early Eocene Climatic Optimum (EECO; ~53–49 million years ago, Ma), at Atlantic Ocean Drilling Program (ODP) sites 1051, 1258 and 1263. The surface-dwelling genus Morozovella is of particular interest because it dominated tropical-subtropical early Paleogene assemblages then suffered an abrupt and permanent decline in abundance and taxonomic diversity at the start of the EECO. At all ODP sites, morozovellids display a dominant dextral coiling preference during the interval preceding the EECO. However, all the Morozovella species at all sites modify their coiling from preferentially dextral to sinistral coiling within the EECO <200 kyr after the K/X event (~52.8 Ma), providing a new biostratigraphic tool for correlation. We also document that before the major shift in morozovellid coiling, transient excursions to higher abundances of sinistral tests occurred in conjunction with negative carbon isotope excursions. Significantly, carbon isotope data reveal that sinistral morphotypes belonging to the same morphospecies typically have lower δ¹³C values. The dominance of sinistral morphotypes, at the expense of dextral forms within the EECO, coupled with the lower δ¹³C signatures of the former, suggests that the sinistral forms were less dependent on their photosymbiotic partnerships and thus able to adapt more readily to paleoceanographic change at the EECO. The observed sinistral and dextral coiling of morozovellids can be a genetically heritable characteristic that lies within cryptic speciation across multiple morphologically defined species. Alternatively the coiling changes were exclusively ecophenotypic responses whereby different species were able to preferentially adopt sinistral coiling in reaction to the changed conditions in the mixed-layer during the EECO. Previous interpretations of coiling flips in planktic foraminifera in the early Eocene, especially including morozovellids, have favoured a genetic explanation rather than an ecological response. Our present data cannot validate or disprove this idea, but should stimulate renewed thought on the matter.
... The relative abundance of the >63 µm fraction in pelagic sediments, which constitutes the coarse fraction (CF, same as defined in 4.1) has been commonly used as a proxy for carbonate dissolution in paleoceanography (e.g., Bassinot et al., 1994;Kelly et al., 2010). It generally co-varies with lysoclinal depth changes, which control the preservation of planktic foraminifers in pelagic sediments (Broecker and Clark, 1999;Kelly et al., 2005;Littler et al., 2014) due to their higher vulnerability to carbonate dissolution (e.g., Nguyen et al., 2009). Because benthic foraminifers constitute only a minor fraction of pelagic carbonate sediments (e.g., Rothwell, 2016), carbonate dissolution events cause a net decrease in CF abundance owing to fragmentation and consequent dissolution of the predominant planktic foraminiferal fraction (Berger et al., 1982;Bhattacharya & Dickens, 2020;Chiu & Broecker, 2008;Colosimo et al., 2006;Hancock & Dickens, 2005;Luciani et al., 2017). ...
Carbon isotope (δ¹³C) records from marine sediments and sedimentary rocks have been extensively used in Cenozoic chemostratigraphy. The early Paleogene interval in particular has received exceptional attention because negative carbon isotope excursions (CIEs) documented in the sedimentary record, for example, at the Paleocene Eocene Thermal Maximum (PETM), ca ∼56 Ma, are believed to reflect significant global carbon cycle perturbations during the warmest interval of the Cenozoic era. However, while bulk carbonate δ¹³C values exhibit robust correlations across widely separated marine sedimentary basins, their absolute values and magnitude of CIEs vary spatially, especially over time intervals characterized by major deviations in global carbon cycling. Moreover, bulk carbonates in open‐marine environments are an ensemble of different components, each with a distinct isotope composition. Consequently, a comprehensive interpretation of the bulk‐δ¹³C record requires an understanding of co‐evolution of these components. In this study, we dissect sediments, from the late Paleocene‐early Eocene interval, at ODP Site 1209 (Shatsky Rise, Pacific Ocean) to investigate how a temporally varying bulk carbonate ensemble influences the overall carbon isotope record. A set of 45 samples were examined for δ¹³C and δ¹⁸O compositions, as bulk and individual size fractions. We find a significant increase in coarse‐fraction abundance across the PETM, driven by a changing community structure of calcifiers, modulating the size of the CIE at Site 1209 and thus making it distinct from those recorded at other open‐marine sites. These results highlight the importance of biogeography in the marine stable isotope record, especially when isotope excursions are driven by climate‐ and/or carbon cycle changes. In addition, community composition changes will alter the interpretation of weight percent coarse fraction as proxy for carbonate dissolution.
We investigate early Eocene hyperthermals by complementing foraminiferal and bulk carbonate isotopes with benthic foraminiferal assemblages from three marine coreholes located along a paleoshelf transect on the New Jersey coastal plain (ODP 174AX Bass River, Double Trouble, and Ancora). Distinct negative δ13C and δ18O excursions likely correspond to the globally documented ETM-2, H2, I1, I2, and J events. Foraminiferal stable isotope data at Bass River reveal greater warming in benthic and thermocline communities compared to the surface dwellers during these excursion events. During the largest excursion event (ETM-2), thermocline-dwelling Subbotina not only experienced greater overall warming, but also recorded lower δ18O values than Morozovella (–5.1‰ vs. –4.3‰). This suggests either greater warming in the thermocline, habitat depth restructuring, or possibly a change in calcification season. We also demonstrate a potential biotic threshold, providing the first comprehensive evaluation of the sensitivity of shallow-marine taxa in response to these transient warming events.
We investigate early Eocene hyperthermals by complementing foraminiferal and bulk carbonate isotopes with benthic foraminiferal assemblages from three marine coreholes located along a paleoshelf transect on the New Jersey coastal plain (ODP 174AX Bass River, Double Trouble, and Ancora). Distinct negative δ13C and δ18O excursions likely correspond to the globally documented ETM-2, H2, I1, I2, and J events. Foraminiferal stable isotope data at Bass River reveal greater warming in benthic and thermocline communities compared to the surface dwellers during these excursion events. During the largest excursion event (ETM-2), thermocline-dwelling Subbotina not only experienced greater overall warming, but also recorded lower δ18O values than Morozovella (–5.1‰ vs. –4.3‰). This suggests either greater warming in the thermocline, habitat depth restructuring, or possibly a change in calcification season. We also demonstrate a potential biotic threshold, providing the first comprehensive evaluation of the sensitivity of shallow-marine taxa in response to these transient warming events.
Eocene transient global warming events (hyperthermals) can provide insight into a future warmer world. While much research has focused on the Paleocene–Eocene Thermal Maximum (PETM), hyperthermals of a smaller magnitude can be used to characterize climatic responses over different magnitudes of forcing. This study identifies two events, namely the Eocene Thermal Maximum 2 (ETM2 and H2), in shallow marine sediments of the Eocene-aged Salisbury Embayment of Maryland, based on magnetostratigraphy, calcareous nannofossil, and dinocyst biostratigraphy, as well as the recognition of negative stable carbon isotope excursions (CIEs) in biogenic calcite. We assess local environmental change in the Salisbury Embayment, utilizing clay mineralogy, marine palynology, δ18O of biogenic calcite, and biomarker paleothermometry (TEX86). Paleotemperature proxies show broad agreement between surface water and bottom water temperature changes. However, the timing of the warming does not correspond to the CIE of the ETM2 as expected from other records, and the highest values are observed during H2, suggesting factors in addition to pCO2 forcing have influenced temperature changes in the region. The ETM2 interval exhibits a shift in clay mineralogy from smectite-dominated facies to illite-rich facies, suggesting hydroclimatic changes but with a rather dampened weathering response relative to that of the PETM in the same region. Organic walled dinoflagellate cyst assemblages show large fluctuations throughout the studied section, none of which seem systematically related to CIE warming. These observations are contrary to the typical tight correspondence between climate change and assemblages across the PETM, regionally and globally, and ETM2 in the Arctic Ocean. The data do indicate very warm and (seasonally) stratified conditions, likely salinity-driven, across H2. The absence of evidence for strong perturbations in local hydrology and nutrient supply during ETM2 and H2, compared to the PETM, is consistent with the less extreme forcing and the warmer pre-event baseline, as well as the non-linear response in hydroclimates to greenhouse forcing.
Carbon releases into the climate system produce global warming and ocean acidification events that can be reversed eventually by carbon sequestration. However, the underlying controls on the timescales of carbon removal, and their dependence on the amplitude of the initial perturbation, are poorly understood. Here, we assess a series of late Paleocene-early Eocene (LPEE) carbon cycle perturbations (∼56-52 Ma) of different amplitudes to constrain carbon removal timescales. Carbon isotope excursions (CIEs) and sedimentation patterns for the largest event, the Paleocene-Eocene Thermal Maximum (PETM), allow identification of a light carbon injection that appeared ∼85 kyr after the PETM onset. This CIE may have been triggered by orbital forcing of long (∼400 kyr) and short (∼100 kyr) eccentricity maxima. The various LPEE light carbon injections were followed by exponential carbon removal trends with half-life (t1/2) estimates of ∼6-26 kyr. These values are smaller than background estimates for the modern carbon cycle (t1/2 > 100 kyr), which reveals accelerated light carbon sequestration. We find that one estimated t1/2 period coincided temporally with ocean acidification recovery in different locations with contrasting paleo-water depths. This pattern indicates enhanced chemical weathering following LPEE CIEs; however, chemical weathering timescales are an order of magnitude longer than the observed t1/2 estimates. This reveals that several carbon processes were optimized during LPEE CIE recovery. Similar t1/2 estimates are obtained for light carbon injections of different sizes, which suggests that carbon removal was optimized to conditions induced by the initial perturbation. Temperature controls on oxygen solubility may have accelerated the oceanic biological pump in proportion to each LPEE carbon injection. This process may have caused accelerated carbon sequestration during LPEE CIE recovery and produced the short carbon removal timescales identified by t1/2 estimates of LPEE carbon cycle perturbations.
Paleocene−Eocene hyperthermal events are a current research focus in the fields of sedimentology and paleoclimatology. The Fushun Basin in northeast China contains continuous continental Eocene fine-grained rocks, and a series of Eocene hyperthermal events in the Fushun Basin have been identified. Because of the high cost of high-precision isotope data testing, it is necessary to find new and alternative paleoclimate parameters. In this study, Eocene coal and oil shale-bearing layers in the Fushun Basin are used as research objects. The high-precision data of magnetic susceptibility, color reflectance, rock composition, and cluster analyses are used to conduct a vertical comparison in the same category and compare that analysis with the identified Eocene hyperthermal events in the Fushun Basin. The preliminary results show that high-frequency-dependent susceptibility, high color reflectance a* (redness)/L* (lightness) values, and high kaolinite content in the study area have good correspondence with global hyperthermal events and can be used as effective parameters for the identification of continental basin hyperthermal events. The detailed magnetic susceptibility and color reflectance data also reveal that the Eocene strata in the Fushun Basin recorded the Late Lutetian Thermal Maximum (LLTM) and 13 short-term hyperthermal events during the Early Eocene Climatic Optimum (EECO). These results indicate that the parameters of rock physical properties can be used to study the evolution of the paleoclimate in geological history, and it has universal practicability in continental and marine fine-grained sedimentary rocks.
Late Paleocene deposition of an organic-rich sedimentary facies on the continental shelf and slope of New Zealand and eastern Australia has
been linked to short-lived climatic cooling and terrestrial denudation
following sea level fall. Recent studies confirm that the organic matter in
this facies, termed “Waipawa organofacies”, is primarily of terrestrial origin, with a minor marine component. It is also unusually enriched in 13C. In this study we address the cause of this enrichment. For Waipawa organofacies
and its bounding facies in the Taylor White section, Hawke's Bay, paired
palynofacies and carbon isotope analysis of heavy liquid-separated density
fractions indicate that the heaviest δ13C values are associated
with degraded phytoclasts (woody plant matter) and that the 13C
enrichment may be partly due to lignin degradation. Compound-specific stable carbon isotope analyses of samples from the Taylor White and mid-Waipara (Canterbury) sections display similar trends and further reveal a residual 13C enrichment of ∼ 2.5 ‰ in higher
plant biomarkers (long chain n-alkanes and fatty acids) and a ∼ 2 ‰–5 ‰ change in subordinate marine biomarkers. Using the relationship between atmospheric CO2 and C3 plant tissue δ13C values, we determine that the 3 ‰ increase in terrestrial δ13C may represent a ∼ 35 % decrease in atmospheric CO2.
Refined age control for Waipawa organofacies indicates that deposition
occurred between 59.2 and 58.5 Ma, which coincides with an interval of
carbonate dissolution in the deep sea that is associated with a Paleocene
oxygen isotope maximum (POIM, 59.7–58.1 Ma) and the onset of the Paleocene carbon isotope maximum (PCIM, 59.3–57.4 Ma). This association suggests that Waipawa deposition occurred during a time of cool climatic conditions and increased carbon burial. This relationship is further supported by published
TEX86-based sea surface temperatures that indicate a pronounced
regional cooling during deposition. We suggest that reduced greenhouse gas
emissions from volcanism and accelerated carbon burial, due to tectonic
factors, resulted in short-lived global cooling, growth of ephemeral ice
sheets and a global fall in sea level. Accompanying erosion and carbonate
dissolution in deep-sea sediment archives may have hidden the evidence of
this “hypothermal” event until now.
Here, we compare the ocean overturning circulation of the early Eocene (47–56 Ma) in eight coupled climate model simulations from the Deep‐Time Model Intercomparison Project (DeepMIP) and investigate the causes of the observed inter‐model spread. The most common global meridional overturning circulation (MOC) feature of these simulations is the anticlockwise bottom cell, fed by sinking in the Southern Ocean. In the North Pacific, one model (GFDL) displays strong deepwater formation and one model (CESM) shows weak deepwater formation, while in the Atlantic two models show signs of weak intermediate water formation (MIROC and NorESM). The location of the Southern Ocean deepwater formation sites varies among models and relates to small differences in model geometry of the Southern Ocean gateways. Globally, convection occurs in the basins with smallest local freshwater gain from the atmosphere. The global MOC is insensitive to atmospheric CO2 concentrations from 1× (i.e., 280 ppm) to 3× (840 ppm) pre‐industrial levels. Only two models have simulations with higher CO2 (i.e., CESM and GFDL) and these show divergent responses, with a collapsed and active MOC, respectively, possibly due to differences in spin‐up conditions. Combining the multiple model results with available proxy data on abyssal ocean circulation highlights that strong Southern Hemisphere‐driven overturning is the most likely feature of the early Eocene. In the North Atlantic, unlike the present day, neither model results nor proxy data suggest deepwater formation in the open ocean during the early Eocene, while the evidence for deepwater formation in the North Pacific remains inconclusive.
The Paleocene–Eocene Thermal Maximum (PETM; ∼ 55.9 Ma) was a
period of rapid and sustained global warming associated with significant
carbon emissions. It coincided with the North Atlantic opening and
emplacement of the North Atlantic Igneous Province (NAIP), suggesting a
possible causal relationship. Only a very limited number of PETM studies
exist from the North Sea, despite its ideal position for tracking the impact
of both changing climate and NAIP activity. Here we present
sedimentological, mineralogical, and geochemical proxy data from Denmark in
the eastern North Sea, exploring the environmental response to the PETM. An
increase in the chemical index of alteration and a kaolinite content up to
50 % of the clay fraction indicate an influx of terrestrial input shortly
after the PETM onset and during the recovery, likely due to an intensified
hydrological cycle. The volcanically derived zeolite and smectite minerals
comprise up to 36 % and 90 % of the bulk and clay mineralogy
respectively, highlighting the NAIP's importance as a sediment source for the
North Sea and in increasing the rate of silicate weathering during the PETM.
X-Ray fluorescence element core scans also reveal possible hitherto unknown
NAIP ash deposition both prior to and during the PETM. Geochemical proxies
show that an anoxic to sulfidic environment persisted during the PETM,
particularly in the upper half of the PETM body with high concentrations of
molybdenum (MoEF > 30), uranium (UEF up to 5), sulfur
(∼ 4 wt %), and pyrite (∼ 7 % of bulk). At
the same time, export productivity and organic-matter burial reached its
maximum intensity. These new records reveal that negative feedback
mechanisms including silicate weathering and organic carbon sequestration
rapidly began to counteract the carbon cycle perturbations and temperature
increase and remained active throughout the PETM. This study highlights the
importance of shelf sections in tracking the environmental response to the
PETM climatic changes and as carbon sinks driving the PETM recovery.
The Eocene continental sequence investigated in this study belongs to the Salta Group; it was deposited in an intracontinental rift, the Salta Basin (NW Argentina) that evolved from the Lower Cretaceous to middle Paleogene. The Salta Group contains the Maíz Gordo and Lumbrera Fms, spans the Paleocene-early Eocene, and shows excellent exposures in the region of the Valles Calchaquíes. This research is focused on the continental facies of the Lumbrera Fm, which correspond to the early Eocene. We studied the mineralogy of the fine-grained beds of the Lumbrera Fm in five locations (Valle Encantado, Tonco, Tin Tin, Luracatao, and Obelisco) by X-ray diffraction and scanning electron microscopy in order to examine the vertical variations in clay mineralogy and their relations with global paleoclimatic changes registered during the Eocene. The microtexture of the authigenic smectite-type clays (Sm to I/Sm R0) suggests that they mainly originated by crystallization from glassy volcanic materials. The high reactivity of the glass precludes the use of smectite-type-clay formation as an indicator of specific paleoclimatic conditions in the studied sediments. In contrast, the formation of kaolinite in sections with very low smectite proportions and a strong degree of weathering in crystalline silicates reflects intense weathering conditions and is a useful paleoclimatic proxy in terrestrial sediments. Significant variations in kaolinite/muscovite ratios at the base and in an intermediate bed in the Lumbrera Fm at Valle Encantado suggest the presence of cyclic hyperthermals through the Ypresian stage that may be tentatively correlated with the Eocene Thermal Maxima 2 and 3, which are the largest events that have been identified at a global scale in early Eocene marine sediments.
Environmental and biotic responses to early Eocene hyperthermal events in the southwest Pacific are critical for global paleoclimate reconstructions during Cenozoic greenhouse intervals, but detailed multidisciplinary studies are generally missing from this time and location. Eocene carbonate sediments were recovered during International Ocean Discovery Program Expedition 371 at Site U1510 on southern Lord Howe Rise in the Tasman Sea. Part of the Early Eocene Climatic Optimum (EECO; 53.26–49.14 Ma) and superimposed hyperthermal events have been identified based on refined calcareous nannofossil biostratigraphic data and carbon stable isotope records on bulk sediment and benthic foraminifera. Four negative carbon isotope excursions (CIEs) associated with negative oxygen isotope excursions are recognized within the EECO. Comparison with a global compilation of sites indicates these CIEs correlate to the K event (Eocene Thermal Maximum 3), and tentatively to the S, T, and U events. Sediments with a high carbonate content throughout the EECO provide an excellent opportunity to examine these CIEs, as carbonate dissolution often impacts correlative records elsewhere. Benthic foraminifera and calcareous nannoplankton taxa indicative of warm waters are most abundant during the K event, the most prominent hyperthermal of the EECO. Eutrophication of surface waters during the K event did not lead to increased trophic conditions at the seafloor, whereas a coupled response is observed during smaller hyperthermals. The biotic turnover sheds new light on the paleoenvironmental consequences of hyperthermal events.
Thirty years after oxygen isotope records frommicrofossils deposited in ocean sediments confirmed the hypothesis that variations in the Earth’s orbital geometry control the ice ages1, fundamental questions remain over the response of the Antarctic ice sheets to orbital cycles2. Furthermore, an understanding of the behaviour of the marinebased West Antarctic ice sheet (WAIS) during the ‘warmerthan- present’ early-Pliocene epoch ( ~5–3Myr ago) is needed to better constrain the possible range of ice-sheet behaviour in the context of future global warming3. Here we present a marine glacial record from the upper 600mof the AND-1B sediment core recovered from beneath the northwest part of the Ross ice shelf by the ANDRILL programme and demonstrate well-dated, ~40-kyr cyclic variations in ice-sheet extent linked to cycles in insolation influenced by changes in the Earth’s axial tilt (obliquity) during the Pliocene. Our data provide direct evidence for orbitally induced oscillations in the WAIS, which periodically collapsed, resulting in a switch from grounded ice, or ice shelves, to open waters in the Ross embayment when planetary temperatures were up to ~3 C warmer than today4 and atmospheric CO2 concentration was as high as ~400 p.p.m.v. (refs 5, 6). The evidence is consistent with a new ice-sheet/ice-shelf model7 that simulates fluctuations in Antarctic ice volume of up to +7min equivalent sea level associated with the loss of the WAIS and up to+3min equivalent sea level from the EastAntarctic ice sheet, in response to ocean-inducedmelting paced by obliquity.During interglacial times, diatomaceous sediments indicate high surface-water productivity, minimal summer sea ice and air temperatures above freezing, suggesting an additional influence of surface melt 8 under conditions of elevated CO2.
Changes in ocean circulation have been proposed as a trigger mechanism for the large coupled climate and carbon cycle perturbations at the Paleocene-Eocene Thermal Maximum (PETM, ca. 55 Ma). An abrupt warming of oceanic intermediate waters could have initiated the thermal destabilization of sediment-hosted methane gas hydrates and potentially triggered sediment slumps and slides. In an ensemble of fully coupled atmosphere-ocean general circulation model (AOGCM) simulations of the late Paleocene and early Eocene, we identify such a circulation-driven enhanced intermediate-water warming. Critically, we find an approximate twofold amplification of Atlantic intermediate-water warming when CO2 levels are doubled from 2x to 4x preindustrial CO2 compared to when they are doubled from 1x to 2x. This warming is largely focused on the equatorial and South Atlantic and is driven by a significant reduction in deep-water formation from the Southern Ocean. This scenario is consistent with altered PETM circulation patterns inferred from benthic carbon isotope data and the intensity of deep-sea carbonate dissolution in the South Atlantic. The linkage between intermediate-water warming and gas hydrate destabilization could provide an important feedback in the establishment of peak PETM warmth.
[1] Oxygen and carbon isotope records are important tools used to reconstruct past ocean and climate conditions, with those of benthic foraminifera providing information on the deep oceans. Reconstructions are complicated by interspecies isotopic offsets that result from microhabitat preferences (carbonate precipitation in isotopically distinct environments) and vital effects (species-specific metabolic variation in isotopic fractionation). We provide correction factors for early Cenozoic benthic foraminifera commonly used for isotopic measurements (Cibicidoides spp., Nuttallides truempyi, Oridorsalis spp., Stensioina beccariiformis, Hanzawaia ammophila, and Bulimina spp.), showing that most yield reliable isotopic proxies of environmental change. The statistical methods and larger data sets used in this study provide more robust correction factors than do previous studies. Interspecies isotopic offsets appear to have changed through the Cenozoic, either (1) as a result of evolutionary changes or (2) as an artifact of different statistical methods and data set sizes used to determine the offsets in different studies. Regardless of the reason, the assumption that isotopic offsets have remained constant through the Cenozoic has introduced an ∼1–2°C uncertainty into deep sea paleotemperature calculations. In addition, we compare multiple species isotopic data from a western North Atlantic section that includes the Paleocene-Eocene thermal maximum to determine the most reliable isotopic indicator for this event. We propose that Oridorsalis spp. was the most reliable deepwater isotopic recorder at this location because it was best able to withstand the harsh water conditions that existed at this time; it may be the best recorder at other locations and for other extreme events also.
The Re-Os and major element geochemistry of an expanded gray shale
sequence from the Central Basin in Spitsbergen, Svalbard Archipelago
(Norway) over the Paleocene Eocene Thermal Maximum (PETM) is presented.
The data suggest that a significant volcanic episode, as indicated
primarily by a large drop in 187Os/188Os, occurred
just prior to or coincident with the onset of the PETM. The distinct
geochemistry of the inferred ash component is consistent with the
geochemistry of contemporaneous ashes previously sampled in Denmark, and
persists in the sedimentary record for ˜8 ka. Based on the
substantial size of the 187Os/188Os decrease
(Δ187Os/188Os ˜-0.23), the volcanic
event must have involved widespread ash deposition in the local
catchment. The terrestrially deposited ash weathered rapidly, shifting
the 187Os/188Os of the basin water column to
<0.5. Temporally, the volcanic event coincides with (or predates by a
few thousand years) the onset of the PETM, suggesting northwest European
shelf volcanism as the trigger for the PETM. As the planet warmed, both
dissolved and detrital indicators of weathering indicate a <10 ka
pulse of more weathered material to the basin, shifting authigenic
187Os/188Os to more radiogenic values and
depositing clastic materials with higher Chemical Index of Alteration
and lower Na/Ti. Persistently anoxic sedimentary pore fluids,
interpreted to reflect bottom water anoxia, initiated close to the onset
of the PETM. Anoxic, mainly euxinic, conditions persisted for ˜50
ka, ending abruptly ˜55.77 Ma. Anoxia appears related to enhanced
high-latitude hydrological cycling and consequent basinal stratification
during the PETM.
We propose that Plio-Pleistocene East African climate is forced by both
high latitude climate changes and local orbital forcing, but is
independent of glacial-interglacial cycles. Paleo-records show that the
late Cenozoic climate of East African is punctuated by episodes of
short, alternating periods of extreme wetness and aridity, superimposed
on a long-term drying trend. The periods of extreme climate variability
are characterised by the precession-forced appearance and disappearance
of large, deep lakes in the East African Rift Valley, paralleled by low
and high wind-driven dust loads reaching the adjacent ocean basins. Over
the last 3 million years such periods only occur at the times of major
global climatic transitions, such as the Onset of Northern Hemisphere
Glaciation (2.7-2.5 Ma), intensification of the Walker circulation
(1.9-1.7 Ma) and the Mid- Pleistocene Revolution (1-0.7 Ma). High
latitude forcing in both Hemispheres is required to compress the Inter-
Tropical Convergence Zone so that East Africa becomes locally sensitive
to precessional forcing, resulting in rapid shifts from wet to dry
conditions. Between 0.5 Ma and 5.0 Ma the periods of highly variable
East African climate, oscillating from very dry to very wet, occupied
less than a third of the total time. In contrast, 12 out of the 15
hominin species i.e., four fifths, first appeared in one of these
extreme `wet-dry' periods. We suggest that ephemeral lakes, expanding
and contracting on precessional timescales, would have evoked a wide-
spread, regional-scale, rapid, and extreme environmental variability,
required by the Variability Selection Hypothesis of human evolution.
Marine sediment records from the Oligocene and Miocene reveal clear 400,000-year climate cycles related to variations in orbital eccentricity. These cycles are also observed in the Plio-Pleistocene records of the global carbon cycle. However, they are absent from the Late Pleistocene ice-age record over the past 1.5 million years. Here we present a simulation of global ice volume over the past 5 million years with a coupled system of four three-dimensional ice-sheet models. Our simulation shows that the 400,000-year long eccentricity cycles of Antarctica vary coherently with δ(13)C data during the Pleistocene, suggesting that they drove the long-term carbon cycle changes throughout the past 35 million years. The 400,000-year response of Antarctica was eventually suppressed by the dominant 100,000-year glacial cycles of the large ice sheets in the Northern Hemisphere.
[1] The late Paleocene to the early Eocene (∼58–52 Ma) was marked by significant changes in global climate and carbon cycling. The evidence for these changes includes stable isotope records that reveal prominent decreases in δ18O and δ13C, suggesting a rise in Earth's surface temperature (∼4°C) and a drop in net carbon output from the ocean and atmosphere. Concurrently, deep-sea carbonate records at several sites indicate a deepening of the calcite compensation depth (CCD). Here we investigate possible causes (e.g., increased volcanic degassing or decreased net organic burial) for these observations, but from a new perspective. The basic model employed is a modified version of GEOCARB III. However, we have coupled this well-known geochemical model to LOSCAR (Long-term Ocean-atmosphere Sediment CArbon cycle Reservoir model), which enables simulation of seawater carbonate chemistry, the CCD, and ocean δ13C. We have also added a capacitor, in this case represented by gas hydrates, that can store and release13C-depleted carbon to and from the shallow geosphere over millions of years. We further consider accurate input data (e.g., δ13C of carbonate) on a currently accepted timescale that spans an interval much longer than the perturbation. Several different scenarios are investigated with the goal of consistency amongst inferred changes in temperature, the CCD, and surface ocean and deep ocean δ13C. The results strongly suggest that a decrease in net organic carbon burial drove carbon cycle changes during the late Paleocene and early Eocene, although an increase in volcanic activity might have contributed. Importantly, a drop in net organic carbon burial may represent increased oxidation of previously deposited organic carbon, such as stored in peat or gas hydrates. The model successfully recreates trends in Earth surface warming, as inferred from δ18O records, the CCD, and δ13C. At the moment, however, our coupled modeling effort cannot reproduce the magnitude of change in all these records collectively. Similar problems have arisen in simulations of short-term hyperthermal events during the early Paleogene (Paleocene-Eocene Thermal Maximum), suggesting one or more basic issues with data interpretation or geochemical modeling remain.
A new 55 m.y. global compilation of benthic foraminifera delta C-13 and delta O-18 for the middle to Late Cretaceous shows that there was widespread formation of bottom waters with temperatures >20 degrees C during the Cretaceous greenhouse world. These bottom waters filled the silled North Atlantic and probably originated as thermocline or intermediate waters in the tropical oceans. Carbon burial during the Cretaceous oceanic anoxic events produced a positive delta C-13 shift in global carbon reservoirs, but this is not particularly large, especially by comparison with the remarkable Late Paleocene carbon maximum. The interbasin delta C-13 gradient was unusually large during the Cretaceous hot greenhouse, probably because the North Atlantic sills prevented the free exchange of waters in the deep basin. The hot greenhouse ended when the Equatorial Atlantic Gateway opened sufficiently to flood the deep North Atlantic with relatively cool polar waters formed in the Southern Ocean.
Cultured planktonic foraminifera, Orbulina universa (symbiotic) and Globigerina bulloides (nonsymbiotic), are used to reexamine temperature:δ18O relationships at 15°–25°C. Relationships for both species can be described by linear equations. Equations for O. universa grown under low light (LL) and high light (HL) share a slope of −4.80 (0.21‰ °C−1) with a HL-LL offset of −0.33‰ due to symbiont photosynthetic activity. The effect of [CO32−] on O. universa is −0.002‰ µmol−1 kg−1 and is insensitive to temperature. For G. bulloides, ontogenetic effects produce size-related trends in temperature:δ18O, whereby larger shells are enriched in 18O relative to smaller specimens. The O. universa temperature:δ18O relationships are more accurate than previously published equations for describing plankton tow data. Our equations do not explain planktonic core top data with the same precision but provide a good fit to benthic Cibicidoides data below 10°C. Temperature:δ18O relationships for G. bulloides provide good agreement with field data for this species from the northeast Pacific.
A remarkable oxygen and carbon isotope excursion occurred in Antarctic
waters near the end of the Palaeocene (~57.33 Myr ago), indicating rapid
global warming and oceanographic changes that caused one of the largest
deep-sea benthic extinctions of the past 90 million years. In contrast,
the oceanic plankton were largely unaffected, implying a decoupling of
the deep and shallow ecosystems. The data suggest that for a few
thousand years, ocean circulation underwent fundamental changes
producing a transient state that, although brief, had long-term effects
on environmental and biotic evolution.
A series of transient global warming events occurred during the late
Palaeocene and early Eocene, about 59 to 50 million years ago. The
events, although variable in magnitude, were apparently paced by orbital
cycles and linked to massive perturbations of the global carbon cycle.
However, a causal link between orbital changes in insolation and the
carbon cycle has yet to be established for this time period. Here we
present a series of coupled climate model simulations that demonstrate
that orbitally induced changes in ocean circulation and intermediate
water temperature can trigger the destabilization of methane hydrates.
We then use a simple threshold model to show that progressive global
warming over millions of years, in combination with the increasing
tendency of the ocean to remain in a more stagnant state, can explain
the decreasing magnitude and increasing frequency of hyperthermal events
throughout the early Eocene. Our work shows that nonlinear interactions
between climate and the carbon cycle can modulate the effect of orbital
variations, in this case producing transient global warming events with
varying timing and magnitude.
Enormous amounts of 13C-depleted carbon rapidly entered the exogenic carbon cycle during the onset of the Paleocene-Eocene thermal maximum (PETM), as attested to by a prominent negative carbon isotope (delta13C) excursion and deep-sea carbonate dissolution. A widely cited explanation for this carbon input has been thermal dissociation of gas hydrate on continental slopes, followed by release of CH4 from the seafloor and its subsequent oxidation to CO2 in the ocean or atmosphere. Increasingly, papers have argued against this mechanism, but without fully considering existing ideas and available data. Moreover, other explanations have been presented as plausible alternatives, even though they conflict with geological observations, they raise major conceptual problems, or both. Methane release from gas hydrates remains a congruous explanation for the delta13C excursion across the PETM, although it requires an unconventional framework for global carbon and sulfur cycling, and it lacks proof. These issues are addressed here in the hope that they will prompt appropriate discussions regarding the extraordinary carbon injection at the start of the PETM and during other events in Earth's history.
The Paleocene-Eocene thermal maximum (PETM) is one of the best known examples of a transient climate perturbation, associated with a brief, but intense, interval of global warming and a massive perturbation of the global carbon cycle from injection of isotopically light carbon into the ocean-atmosphere system. One key to quantifying the mass of carbon released, identifying the source(s), and understanding the ultimate fate of this carbon is to develop high-resolution age models. Two independent strategies have been employed, cycle stratigraphy and analysis of extraterrestrial helium (HeET), both of which were first tested on Ocean Drilling Program (ODP) Site 690. These two methods are in agreement for the onset of the PETM and initial recovery, or the clay layer (``main body''), but seem to differ in the final recovery phase of the event above the clay layer, where the carbonate contents rise and carbon isotope values return toward background values. Here we present a state-of-the-art age model for the PETM derived from a new orbital chronology developed with cycle stratigraphic records from sites drilled during ODP Leg 208 (Walvis Ridge, Southeastern Atlantic) integrated with published records from Site 690 (Weddell Sea, Southern Ocean, ODP Leg 113). During Leg 208, five Paleocene-Eocene (P-E) boundary sections (Sites 1262 to 1267) were recovered in multiple holes over a depth transect of more than 2200 m at the Walvis Ridge, yielding the first stratigraphically complete P-E deep-sea sequence with moderate to relatively high sedimentation rates (1 to 3 cm/ka, where ``a'' is years). A detailed chronology was developed with nondestructive X-ray fluorescence (XRF) core scanning records on the scale of precession cycles, with a total duration of the PETM now estimated to be ~170 ka. The revised cycle stratigraphic record confirms original estimates for the duration of the onset and initial recovery but suggests a new duration for the final recovery that is intermediate to the previous estimates by cycle stratigraphy and HeET.
The carbonate saturation profile of the oceans shoaled markedly during a transient global warming event known as the Paleocene-Eocene thermal maximum (PETM) (circa 55 Ma). The rapid release of large quantities of carbon into the ocean-atmosphere system is believed to have triggered this intense episode of dissolution along with a negative carbon isotope excursion (CIE). The brevity (120–220 kyr) of the PETM reflects the rapid enhancement of negative feedback mechanisms within Earth's exogenic carbon cycle that served the dual function of buffering ocean pH and reducing atmospheric greenhouse gas levels. Detailed study of the PETM stratigraphy from Ocean Drilling Program Site 690 (Weddell Sea) reveals that the CIE recovery period, which postdates the CIE onset by ∼80 kyr, is represented by an expanded (∼2.5 m thick) interval containing a unique planktic foraminiferal assemblage strongly diluted by coccolithophore carbonate. Collectively, the micropaleontological and sedimentological changes preserved within the CIE recovery interval reflect a transient state when ocean-atmosphere chemistry fostered prolific coccolithophore blooms that suppressed the local lysocline to relatively deeper depths. A prominent peak in the abundance of the clay mineral kaolinite is associated with the CIE recovery interval, indicating that continental weathering/runoff intensified at this time as well (Robert and Kennett, 1994). Such parallel stratigraphic changes are generally consonant with the hypothesis that enhanced continental weathering/runoff and carbonate precipitation helped sequester carbon during the PETM recovery period (e.g., Dickens et al., 1997; Zachos et al., 2005).
Benthic foraminiferal oxygen isotopic (δ18O) and carbon isotopic (δ13C) trends, constructed from compilations of data series from multiple ocean sites, provide one of the primary means of reconstructing changes in the ocean interior. These records are also widely used as a general climate indicator for comparison with local and more specific marine and terrestrial climate proxy records. We present new benthic foraminiferal δ18O and δ13C compilations for individual ocean basins that provide a robust estimate of benthic foraminiferal stable isotopic variations to ∼80 Ma and tentatively to ∼110 Ma. First-order variations in interbasinal isotopic gradients delineate transitions from interior ocean heterogeneity during the Late Cretaceous (>∼65 Ma) to early Paleogene (35–65 Ma) homogeneity and a return to heterogeneity in the late Paleogene–early Neogene (35–0 Ma). We propose that these transitions reflect alterations in a first-order characteristic of ocean circulation: the ability of winds to make water in the deep ocean circulate. We document the initiation of large interbasinal δ18O gradients in the early Oligocene and link the variations in interbasinal δ18O gradients from the middle Eocene to Oligocene with the increasing influence of wind-driven mixing due to the gradual tectonic opening of Southern Ocean passages and initiation and strengthening of the Antarctic Circumpolar Current. The role of wind-driven upwelling, possibly associated with a Tethyan Circumequatorial Current, in controlling Late Cretaceous interior ocean heterogeneity should be the subject of further research.
The Palaeocene-Eocene Thermal Maximum (about 55Myrago) represents a
possible analogue for the future and thus may provide insight into
climate system sensitivity and feedbacks. The key feature of this event
is the release of a large mass of 13C-depleted carbon into
the carbon reservoirs at the Earth's surface, although the source
remains an open issue. Concurrently, global surface temperatures rose by
5-9∘C within a few thousand years. Here we use published
palaeorecords of deep-sea carbonate dissolution and stable carbon
isotope composition along with a carbon cycle model to constrain the
initial carbon pulse to a magnitude of 3,000PgC or less, with an
isotopic composition lighter than -50‰. As a result, atmospheric
carbon dioxide concentrations increased during the main event by less
than about 70% compared with pre-event levels. At accepted values for
the climate sensitivity to a doubling of the atmospheric CO2
concentration, this rise in CO2 can explain only between 1
and 3.5∘C of the warming inferred from proxy records. We
conclude that in addition to direct CO2 forcing, other
processes and/or feedbacks that are hitherto unknown must have caused a
substantial portion of the warming during the Palaeocene-Eocene Thermal
Maximum. Once these processes have been identified, their potential
effect on future climate change needs to be taken into account.
The late Cretaceous and Paleogene paleoclimate reveals a rather complex history of gradual as well as rapid warming and cooling transitions and events. In particular, the early Paleogene is thought to contain unique and critical records of greenhouse conditions that could provide valuable insights into past as well as future greenhouse worlds. The Zachos et al. (2001) benthic isotope compilation includes data from more than 40 DSDP and ODP sites, from which the Paleocene interval is a combined record of mainly Atlantic Ocean, S Ocean, and Indian Ocean sites. Detailed insight into the Paleocene climate record was hampered until the first continuous and complete records covering the entire early Paleogene have been retrieved from the equatorial Pacific (ODP Leg 198, Shatsky Rise) and the South Atlantic (ODP Leg 208, Walvis Ridge). Here we present the first complete high-resolution benthic foraminiferal stable isotope record from a single Pacific site (ODP Site 1209) covering the entire Paleocene (magnetic polarity chrons C24r to C30n). The record provides unprecedented insight into the sensitivity of climate system and carbon cycle to orbital and other forcing over the entire Paleocene including detailed characteristics of the early Late Paleocene Biotic event (ELPE), the Chron 27n event and the K/Pg boundary. The pronounced beat of the global carbon cycle in the Paleocene as recorded in the d13C record is related to the long (405 kyr) eccentricity cycle. In addition, we show that the Chron 27n event at 61.7 Ma is characterized by a clear negative excursion in d13C and d18O associated with a decreased in carbonate content. The abrupt warming of 2°C in the deep equatorial Pacific supports the hypothesis that this event may represent an early Paleocene hyperthermal.
Ar-39Ar incremental heating experiments were performed on volcanic rocks recovered by drilling during Ocean Drilling Program Leg 152, southeast Greenland Margin (63°N), and Deep Sea Drilling Project Leg 81, southwest Rockall Plateau (56°N). Both of these legs drilled into thick sections of submerged lava flows, known as seaward-dipping reflector sequences, that are part of the Tertiary North Atlantic Volcanic Province (NAVP). Results show that subaerial volcanism began at the southeast Greenland Margin as early as 61-62 Ma with the eruption of continentally contaminated lavas. After an apparent hia- tus, volcanism continued with the subaerial eruption of noncontaminated, mid-ocean-ridge basalt (MORB) -like lavas. A sill or flow was emplaced at 52 Ma into the sediments overlying the basement lavas at the most seaward site (918). The MORB-like lavas of the Rockall Plateau gave poor results, although the data suggest that they erupted at 57 -58 Ma and may be contempo- raneous with the compositionally similar oceanic lavas of Leg 152. Compiled ages from the NAVP indicate that most of the lavas were erupted in two distinct magmatic episodes. The first occurred prior to 60 Ma with volcanism at the southeast Greenland Margin, in West Greenland, and the northwest British Isles. This early stage of widespread volcanism most likely records the arrival of the Iceland mantle plume. The second phase of magmatism began about 57 Ma with voluminous basaltic eruptions centralized along the eventual line of continental separa- tion. Magmatism at this stage was associated with continental breakup and asthenospheric upwelling with probable thermal input from the mantle plume.
A pulse of intense carbonate dissolution occurred during the early late Paleocene at 58.4 Ma. A prominent 5- to 25-cm-thick dark brown clay-rich calcareous nannofossil ooze was found on Shatsky Rise at Sites 1209, 1210, 1211, and 1212 during Ocean Drilling Program Leg 198. The layer corresponds to the lower part of planktonic foraminiferal Zone P4 and coincides with the evolutionary first occurrence of the nannolith Heliolithus kleinpellii, an important component of late Paleocene assemblages and a marker for the base of Zone CPS. The clay-rich layer contains common crystals of phillipsite, fish teeth, and phosphatic micronodules and corresponds to a prominent peak in magnetic susceptibility that probably reflects these high amounts of detrital and authigenic materials. Detailed quantitative analysis of planktonic foraminiferal assemblages across the clay-rich nannofossil ooze layer shows that fundamental changes in faunal composition occurred before, during, and after deposition of the clay-rich ooze. Planktonic foraminifers in the clay-rich layer are characterized by a low-diversity, largely dissolved assemblage dominated by representatives of the genus Igorina (mainly Igorina tadjikistanensis and Igorina pusilla). Conversely, Igorina albeari, morozovellids, acarininids, globanomalinids, subbotinids, and chiloguembelinids are common below the clay-rich layer, almost disappear within it, and reappear in low abundances above the clay-rich layer. These changes in faunal compositions are likely a response to a change in carbonate saturation that caused increased dissolution on the seafloor owing to the shoaling of the lysocline and the carbonate compensation depth.
A detailed, quantitative analysis of planktonic foraminiferal composition and shell fragmentation is presented for samples from Ocean Drilling Program Site 1209 (Leg 198, Shatsky Rise, Pacific Ocean) in a stratigraphic interval from the Paleocene/Eocene boundary, which is characterized by enhanced carbonate dissolution, to the base of the middle Eocene where no distinct dissolution layers are recorded. The aims are to evaluate whether the composition of the fossil Paleogene assemblage is representative of the original assemblage and to what extent it is influenced by carbonate dissolution. By comparing the absolute abundances of whole specimens and fragments of the three most common Paleogene genera (Morozovella, Acarinina and Subbotina), it is demonstrated that the percentage of foraminiferal fragments, identified to genus, is helpful in interpreting the paleoenvironment of fossil planktonic foraminiferal assem-blages affected by marked carbonate dissolution. In addition, the absolute abundance of whole specimens and fragments of the three Paleogene genera collected at the Paleocene/Eocene boundary and in the Eocene reveal that, contrary to earlier suggestions, the spinose, asymbiotic, deep-dweller Subbotina is less resistant to dissolution than the muricate, symbiont-bearing, surface-dwellers Morozovella and Acarinina. Distinguishing between primary and taphonomic signals in Paleogene planktonic foraminiferal assemblages will be an important challenge to overcome in order to better constrain paleoecologic and paleoclimatic signals of global significance.
Variations in the efficiency of the biological pumping of carbon from the surface to the deep ocean have been invoked to explain changes in atmospheric pCO(2) and thus climate on a variety of timescales. We compiled published Paleocene and Eocene foraminiferal carbon isotope data and adjusted them to a uniform timescale to investigate changes in the biological pump in the early Cenozoic. Eight basinal time series were binned into 0.01 Ma increments and five water column depth horizons. The carbon isotope data reveal remarkably coherent trends in surface, thermocline, and deep water carbon isotope values through the Paleocene and Eocene. These data were used to drive a three-box ocean carbon isotope model to estimate long-term relationships among changes in atmospheric pCO(2), organic and inorganic carbon burial, and biological pumping. Our model results provide evidence for two different modes of organic carbon cycling. During the Paleocene and earliest Eocene, atmospheric pCO(2) drawdown was driven externally by terrestrial organic carbon burial. After the earliest Eocene, variations in atmospheric pCO(2) resulting from imbalances in organic carbon cycling appear to have been driven by variations in the biological pump. A temporary decline in biological pump efficiency at similar to 50 Ma may have led to increased atmospheric pCO(2), increased weathering and nutrient delivery to the oceans, and enhanced organic carbon burial. Thus, a biological-pump-driven increase in atmospheric pCO(2) created a counterintuitive inverse relationship between organic carbon burial and atmospheric pCO(2), with no indication of the burial event in the surface water carbon isotope record.
16. 1997. The North Atlantic Igneous Province. In: (eds) , . 100, .
A Macintosh computer program that can perform many time-series analysis
procedures is now available on the Internet free of charge. Although
AnalySeries was originally designed for paleoclimatic time series, it
can be useful for most fields of Earth sciences. The program's graphical
user interface allows easy access even for people unfamiliar with
computer calculations. Previous versions of the program are already used
by hundreds of scientists worldwide.
During the Paleocene-Eocene Thermal Maximum (PETM), ∼â̂ 56 Mya, thousands of petagrams of carbon were released into the ocean-atmosphere system with attendant changes in the carbon cycle, climate, ocean chemistry, and marine and continental ecosystems. The period of carbon release is thought to have lasted <20 ka, the duration of the whole event was ∼ 200 ka, and the global temperature increase was 5-8°C. Terrestrial and marine organisms experienced large shifts in geographic ranges, rapid evolution, and changes in trophic ecology, but few groups suffered major extinctions with the exception of benthic foraminifera. The PETM provides valuable insights into the carbon cycle, climate system, and biotic responses to environmental change that are relevant to long-term future global changes.
Carbon-isotope stratigraphy has proven to be a powerful tool in the global correlation of Cretaceous successions. Here we present new, high-resolution carbon-isotope records for the Global Boundary Stratotype Section and Point (GSSP) of the Maastrichtian stage at Tercis les Bains (France), the Bottaccione and Contessa sections at Gubbio (Italy), and the coastal sections at Norfolk (UK) to provide a global δ13C correlation between shelf-sea and oceanic sites. The new δ13C records are correlated with δ13C-stratigraphies of the boreal chalk sea (Trunch borehole, Norfolk, UK, Lägerdorf-Kronsmoor-Hemmoor section, northern Germany, Stevns-1 core, Denmark), the tropical Pacific (ODP Hole 1210B, Shatsky Rise) and the South Atlantic and Southern Ocean (DSDP Hole 525A, ODP Hole 690C) by using an assembled Gubbio δ13C record as a reference curve. The global correlation allows the identification of significant high-frequency δ13C variations that occur superimposed on prominent Campanian - Maastrichtian events, namely the Late Campanian Event (LCE), the Campanian - Maastrichtian Boundary Event (CMBE), the mid-Maastrichtian Event (MME), and the Cretaceous-Paleogene transition (KPgE). The carbon-isotope events are correlated with the geomagnetic polarity scale recalculated using the astronomical 40Ar/39Ar calibration of the Fish Canyon sanidine. This technique allows the evaluation of the relative timing of base occurrences of stratigraphic index fossils such as ammonites, planktonic foraminifera and calcareous nannofossils. Furthermore, the Campanian - Maastrichtian boundary, as defined in the stratotype at Tercis, can be precisely positioned relative to carbon-isotope stratigraphy and the geomagnetic polarity timescale. The average value for the age of the Campanian - Maastrichtian boundary is 72.1 ± 0.1 Ma, estimated by three independent approaches that utilize the Fish Canyon sanidine calibration and Option 2 of the Maastrichtian astronomical timescale. The CMBE covers a time span of 2.5 Myr and reflects changes in the global carbon cycle probably related to tectonic process rather than to glacio-eustasy. The duration of the high-frequency δ13C variations instead coincides with the frequency band of long eccentricity, indicative of orbital forcing of changes in climate and the global carbon cycle.
Abrupt periods of global warming between 57 and 50 million years
ago--known as the Early Palaeogene hyperthermal events--were associated
with the repeated injection of massive amounts of carbon into the
atmosphere. The release of methane from the sea floor following the
dissociation of gas hydrates is often invoked as a source. However,
seafloor temperatures before the events were at least 4-7°C higher
than today, which would have limited the area of sea floor suitable for
hosting gas hydrates. Palaeogene gas hydrate reservoirs may therefore
not have been sufficient to provide a significant fraction of the carbon
released. Here we use numerical simulations of gas hydrate accumulation
at Palaeogene seafloor temperatures to show that near-present-day values
of gas hydrates could have been hosted in the Palaeogene. Our
simulations show that warmer temperatures during the Palaeogene would
have enhanced the amount of organic carbon reaching the sea floor as
well as the rate of methanogenesis. We find that under plausible
temperature and pressure conditions, the abundance of gas hydrates would
be similar or higher in the Palaeogene than at present. We conclude that
methane hydrates could have been an important source of carbon during
the Palaeogene hyperthermal events.
Holes 1209A and 1211A on Southern High, Shatsky Rise contain expanded , nearly continuous records of carbonate-rich sediment deposited in deep water of the equatorial Pacific Ocean during the Paleocene and Eocene. In this study, we document intervals of carbonate dissolution in these records by examining temporal changes in four parameters: carbonate content, coarse size fraction (>38 µm), benthic foraminiferal abundance, and planktonic foraminiferal fragmentation ratio. Carbonate content is not a sensitive indicator of carbonate dissolution in the studied sections, although rare intervals of low carbonate may reflect times of relatively high dissolution. The proportion of coarse size fraction does not accurately record carbonate dissolution either because the relative abundance of nannofossils largely determines the grain-size distribution. Benthic abundance and fragmentation co-vary (r 2 = 0.77) and are probably the best indicators for carbonate dissolution. For both holes, records of these parameters indicate two episodes of prominent dissolution. The first of these occurs in the upper Paleocene (~59–58 Ma) and the second in the middle to upper Eocene (~45–33.7 Ma). Other intervals of enhanced carbonate dissolution are located in the upper Paleocene (~56 Ma) and in the upper lower Eocene (~51 Ma). Enhanced preservation of planktonic foraminiferal assemblages marks the start of both the Paleocene and Eocene epochs.
Palaeogene and Cretaceous palaeoceanography has been the focus of intense international intereste in the last few years, spurred by deep ocean drilling at Blake Nose in the North Atlantic as well as the need to use past climate change as input for modelling future climate change. This book brings together a number of review papers that describe ancient oceans and unique events in the Earth's climatic history and evolution of biota. The papers show evidence of exceptional global warmth such as the late Palaeocene Thermal Maximum and Cretaceous anoxic events. Geochemical records and modelling will make the reader aware the these periods were forced by greenhouse gases. This information is essential for understanding the response of the ocean-climate system to the current input of fossil fuels. In this sense the book contributes to the understanding of fundamental aspects of Earth's climate, the carbon cycle and marine ecosystems. A number of papers describe mass wasting deposits resulting from the energy released by the bolide impact at the Cretaceous-Tertiary boundary as well as the geochemistry of the boundary itself. Additional papers covers aspects of cyclostratigraphy and biostratigraphy of Palaeogene and Cretaceous records.
Oxygen and carbon isotope measurements have been made in picked planktonic and benthonic foraminifers from the five sites drilled on Leg 74, covering the whole Cenozoic. For the Neogene, the coverage gives good information on the development of the vertical temperature structure of Atlantic deep water. For the Paleogene, vertical gradients were weak and it is possible to combine data from different sites to obtain a very detailed record of both the temperature and carbon isotope history of Atlantic deep waters.-Authors
Samples collected from a depth transect of eight sites during Ocean Drilling Program Leg 198 to Shatsky Rise contain a remarkable sedimentary record of surface and deepwater circulation in the tropical Pacific over the past 120 m.y. In addition, basement sills recovered provide valuable constraints on the age and origin of the volcanic foundations of the rise. The sediments recovered contain evidence of the long-term transition from greenhouse to icehouse climate state and of several abrupt climate change events. Shatsky Rise cores contain an exceptional record of an Oceanic Anoxic Event (OAE1a) in the early Aptian (120 Ma), with some of the highest organic carbon contents measured in pelagic sediments. These strata contain exceptionally preserved organic compounds including the oldest known alkenones. Organic geochemistry suggests that bacterial activity played a significant role in sequestering organic carbon. Stable isotope data from Upper Cretaceous and Paleogene sediments reveal several abrupt switches in the sources of intermediate waters bathing Shatsky Rise. Neodymium isotopes also show evidence for these changes and help to identify source regions in the North Pacific, Southern Ocean, and, possibly, Tethys. Strong evidence exists in Shatsky cores for the mid-Maastrichtian (∼69 Ma) global extinction of inoceramids, a long-ranging, widespread group of bottom-dwelling clams. Stable and neodymium isotopes combined with biotic data show changes in intermediate water sources at this time as well as significant changes in surface water oceanography. Shatsky Rise sites contain high-quality records of the Cretaceous/Tertiary boundary event. Detailed nannofossil assemblage studies demonstrate that the survivor taxa are those that were adapted to unstable environmental conditions of shelves, including taxa that have cyst stages. The Paleogene sedimentary record from Shatsky Rise is strongly cyclic with variations in the amount of dissolution. Superimposed on this record are "hyperthermal" episodes including the Paleocene/Eocene Thermal Maximum (PETM; ∼55.0 Ma) and events in the early late Paleocene (∼58.4 Ma) and early Eocene (52.7 Ma). The PETM on Shatsky Rise contains evidence for 5°C warming of tropical sea-surface temperatures, major reorganization of benthic and planktonic communities, and pronounced short-term shoaling of the lysocline. Oxygen isotope and Mg/Ca data demonstrate warming of surface and intermediate waters (possibly combined with decreasing salinity) during the early Eocene and help constrain the timing of the acceleration of Antarctic glaciation during the middle Eocene. Recovery of basaltic sills provides valuable age and geochemical constraints for interpreting the origin of Shatsky Rise. Radiometric ages confirm previous suggestions that this large igneous province was emplaced rapidly. Isotope geochemistry shows a mid-ocean-ridge basalt signature that argues against a mantle plume origin. However, alternative origins are difficult to prove unequivocally.
Holes 1209A and 1211A on Southern High, Shatsky Rise contain expanded, nearly continuous records of carbonate-rich sediment deposited in deep water of the equatorial Pacific Ocean during the Paleocene and Eocene. In this study, we document intervals of carbonate dissolution in these records by examining temporal changes in four parameters: carbonate content, coarse size fraction (>38 μm), benthic foraminiferal abundance, and planktonic foraminiferal fragmentation ratio. Carbonate content is not a sensitive indicator of carbonate dissolution in the studied sections, although rare intervals of low carbonate may reflect times of relatively high dissolution. The proportion of coarse size fraction does not accurately record carbonate dissolution either because the relative abundance of nannofossils largely determines the grain-size distribution. Benthic abundance and fragmentation covary (r 2 = 0.77) and are probably the best indicators for carbonate dissolution. For both holes, records of these parameters indicate two episodes of prominent dissolution. The first of these occurs in the upper Paleocene (∼59-58 Ma) and the second in the middle to upper Eocene (∼45-33.7 Ma). Other intervals of enhanced carbonate dissolution are located in the upper Paleocene (∼56 Ma) and in the upper lower Eocene (∼51 Ma). Enhanced preservation of planktonic foraminiferal assemblages marks the start of both the Paleocene and Eocene epochs.
Natural gas hydrate is found worldwide in sediments of outer continental margins of all oceans and in polar areas with continuous permafrost. There are currently 77 localities identified globally where geophysical, geochemical and/or geological evidence indicates the presence of gas hydrate. Details concerning individual gas-hydrate occurrences are compiled at a new world-wide-web (www) site (http://walrus.wr.usgs.gov/globalhydrate). This site has been created to facilitate global gas-hydrate research by providing information on each of the localities where there is evidence for gas hydrate. Also considered are the implications of gas hydrate as a potential (1) energy resource, (2) factor in global climate change, and (3) geohazard.
The Palaeocene/Eocene thermal maximum, ~55 million years ago, was a brief period of widespread, extreme climatic warming, that was associated with massive atmospheric greenhouse gas input. Although aspects of the resulting environmental changes are well documented at low latitudes, no data were available to quantify simultaneous changes in the Arctic region. Here we identify the Palaeocene/Eocene thermal maximum in a marine sedimentary sequence obtained during the Arctic Coring Expedition. We show that sea surface temperatures near the North Pole increased from 18°C to over 23°C during this event. Such warm values imply the absence of ice and thus exclude the influence of ice-albedo feedbacks on this Arctic warming. At the same time, sea level rose while anoxic and euxinic conditions developed in the ocean's bottom waters and photic zone, respectively. Increasing temperature and sea level match expectations based on palaeoclimate model simulations, but the absolute polar temperatures that we derive before, during and after the event are more than 10°C warmer than those model-predicted. This suggests that higher-than-modern greenhouse gas concentrations must have operated in conjunction with other feedback mechanisms—perhaps polar stratospheric clouds or hurricane-induced ocean mixing – to amplify early Palaeogene polar temperatures.
Unusual cordierite-bearing peraluminous dacites, produced by melting of organic-rich sediments by intrusion of basaltic magma, are found within the North Atlantic Volcanic Province (NAVP). Calculations suggest that formation of the dacites, radiometric dated at 55.9 ± 0.3 Ma and possibly widespread, could have released an average of ∼4,500 Gt (range from 3,000 to 6,000 Gt) of carbon as methane, with a δ13C of about −35‰. Published model results suggest that such a methane release could explain the negative δ13C excursion in the oceans and atmosphere, the extreme global warming, and the marked dissolution of carbonates in the deep oceans that accompanied the concurrent Paleocene–Eocene Thermal Maximum (PETM). Outgassing from melting of sediments and formation of dacites, possibly in conjunction with methane produced in contact metamorphic aureoles and by methane hydrate release, provides a novel way of explaining the PETM and its timing.
Lysocline reconstructions play an important role in scenarios purporting to explain the lowered atmospheric CO2 content of glacial time. These reconstructions are based on indicators such as the CaCO3 content, the percent of coarse fraction, the ratio of fragments to whole foraminifera shells, the ratio of solution-susceptible to solution-resistant species, and the ratio of coarse to fine CaCO3. All assume that changes with time in the composition of the input material do not bias the result. However, as the composition of the input material does depend on climate, none of these indicators provides an absolute measure of the extent of dissolution. In this paper we evaluate the reliability of the ratio of >63 mum CaCO3 to total CaCO3 as a dissolution indicator. We present here results that suggest that in today's tropics this ratio appears to be determined solely by CO3= ion concentration and water depth (i.e., the saturation state of bottom waters). This finding offers the possibility that the size fraction index can be used to reconstruct CO3= ion concentrations for the late Quaternary ocean to an accuracy of +/-5 mumol kg-1.
High-resolution stable carbon isotope records for upper Paleocene-lower Eocene sections at Ocean Drilling Program Sites 1051 and 690 and Deep Sea Drilling Project Sites 550 and 577 show numerous rapid (40-60 kyr duration) negative excursions of up to 10/00. We demonstrate that these transient decreases are the expected result of nonlinear insolation forcing of the carbon cycle in the context of a long carbon residence time. The transients occur at maxima in Earth's orbital eccentricity, which result in high-amplitude variations in insolation due to forcing by climatic precession. The construction of accurate orbital chronologies for geologic sections older than ~35 Ma relies on identifying a high-fidelity recorder of variations in Earth's orbital eccentricity. We use the carbon isotope records as such a recorder, establishing a robust orbitally tuned chronology for latest Paleocene-earliest Eocene events. Moreover, the transient decreases provide a means of precise correlation among the four sites that is independent of magnetostratigraphic and biostratigraphic data at the
We have compiled deep water benthic δ13C data from the Paleocene portions of several DSDP and ODP holes and present it using the new timescale of Berggren et al. (1995). Our data show that the north Atlantic hole DSDP 384 was the most positive site for δ13C in the late Cretaceous and the earliest Paleocene, suggesting that the sub-tropical north Atlantic was an important locus of deep water production during these intervals. Salinity and temperatue comparisons do not support unequivocal deep water production by halothermal means in this region so we prefer to avoid the term Warm Saline Deep Water (WSDW) and employ instead the more neutral term 'palaeo-North Atlantic Deep Water' (palaeo-NADW). During K/T boundary time, the southern ocean apparently became the major producer of deep waters. Based on δ13C comparisons both the North Atlantic and Southern Ocean were deep water producers during the early Paleocene to the late Paleocene interval. In the latest Paleocene (during the 'Paleocene carbon isotope maximum') Southern Ocean δ13C was most positive, supporting a Southern Ocean deep water source. The earliest Eocene ocean was characterized by deep water production in the high southern latitudes with well developed interbasinal δ13C gradients. δ18O data show an overall decrease from the late Cretaceous into the Early Eocene interrupted by an increase between 64 and 57 Ma. This is interpreted as an overall warming trend with a superimposed, previously undocumented, cooling phase in the early to late Paleocene.
The Paleocene-Eocene thermal maximum (PETM) ca. 55.5 Ma was a
geologically brief interval characterized by massive influx of
isotopically light carbon, extreme changes in global climate, and
profound variations in Earth system processes. An outstanding issue is
whether it was an isolated event, or the most prominent example of a
recurring phenomenon. Recent studies of condensed deep-sea sections
support the latter, but this finding remains uncertain. Here we present
and discuss lithologic and carbon isotope records across two lower
Eocene outcrops on South Island, New Zealand. The PETM manifests as a
marl-rich horizon with a significant negative carbon isotope excursion
(CIE). Above, in sediment deposited between 54 and 53 Ma, are four
horizons with similar though less pronounced expressions. Marl beds of
all five horizons represent increased terrigenous sedimentation,
presumably linked to an accelerated hydrological cycle. Five
corresponding clay-rich horizons and CIEs are found in deep-sea records,
although the lithologic variations represent carbonate dissolution
rather than siliciclastic dilution. The presence of five intervals with
similar systemic responses in different environments suggests a
mechanism that repeatedly injected large masses of 13
C-depleted carbon during the early Eocene.
Possible sources of carbon that may have caused global warmingat the Paleocene-Eocene boundary are constrained using an intermediatecomplexity Earth-system model configured with early Eocene paleogeography.We find that 6800 Pg C (13C of -22) is the smallest pulsemodeled here to reasonably reproduce observations of the extentof seafloor CaCO3 dissolution. This pulse could not have beensolely the result of methane hydrate destabilization, suggestingthat additional sources of CO2 such as volcanic CO2, the oxidationof sedimentary organic carbon, or thermogenic methane must alsohave contributed. Observed contrasts in dissolution intensitybetween Atlantic and Pacific sites are reproduced in the modelby reducing bioturbation in the Atlantic during the event, simulatinga potential consequence of the spread of low-oxygen bottom waters.
Deep-sea sediment Ba*(Ba/Al2O3(sample)×15%-Ba(aluminosilicate)) records show increasing values synchronous with the evolution of the late Paleocene global delta13C maximum, reflecting an increase in marine surface primary production and biogenic barite formation at this time. At two oligotrophic locations, Deep Sea Drilling Project (DSDP) Sites 384 and 527 in the North and South Atlantic, respectively, Ba* increases from 160-360 ppm in the early Paleocene to 1100-3000 ppm during the delta13C maximum. At equatorial DSDP Site 577, positioned within or near the high-productivity zone, Ba* increases from ~15,500ppm in the early Paleocene to ~25,400ppm in conjunction with late Paleocene maximum delta13C values. Linear fitted correlation plots of sediment Ba* content versus surface water delta13C in all three regions support barite originating in the euphotic zone. The early to late Paleocene relative increase in Ba* illustrates how burial rates of Corg (relative to Al2O3) accelerated by a factor of ~1.8 and ~6.0 in the eutrophic and oligotrophic areas, respectively. A tentative estimate, weighing our result for the entire ocean, suggests that accumulation rates of organic carbon increased by a factor of 2 during the late Paleocene delta13C maximum.
The present study is a compilation of published data on coal facies studies in Canada based on coal petrological and other methods. The geological age of the coals range from the Devonian coal deposits in Arctic Canada to coals of Tertiary age in the Western Canada Sedimentary Basin, intermontane British Columbia and Arctic Canada. In terms of rank, the coal deposits studied range from lignite to low volatile bituminous.Coal petrological methods include maceral and microlithotype analyses, frequently integrated with data from palynological and geochemical analyses. Most recently, a number of studies have applied sequence stratigraphic concepts to the coal-bearing strata including the interpretation of coal petrological data in the context of this concept.
Ocean Drilling Program (ODP) Leg 198 was designed to obtain high-quality and high-resolution records of the environments of the Cretaceous to Paleogene Pacific Ocean. These new records should improve our understanding of the behavior of Earth's climate during greenhouse intervals. A key aspect of the cruise was to drill sites along depth and latitudinal transects in order to provide additional dimensions to reconstruction of the paleoenvironment through time. Sites 1209 to 1212 were drilled on the Southern High in a range of water depths spanning more than 500 m. A prominent 5 to 25 cm-thick, clay-rich nannofossil ooze layer has been found at Sites 1209 to 1212 in lower upper Paleocene sediments. An age of about 58.4 Ma was assigned to this layer based on the first occurrence (FO) of the nannofossil Heliolithus kleinpellii (marker for the base of Zone CP5), which lies just below the clay-rich layer. This age assignment is in agreement with the planktonic foraminiferal assemblage that belongs to the P4 Globanomalina pseudomenardi Zone. Detailed analysis were performed on samples from selected holes (1209A, 1210A, 11211B and 1212B; water depth from 2387 m to 2907 m) and for a range of depth below sea floor spanning more than 150 m. The clay-rich ooze shows changes in thickness and color. In Holes 1209A, 1210A and 1211B this horizon occurs between 124.80 mbsf (meters below sea floor) and 211.70 mbsf and is characterized by a dark-brown color. In Hole 1212B the clay-rich layer occurs at 88.30 mbsf, and the sediments are considerably lighter than the equivalent interval elsewhere. Moreover, the thickness of the clay-rich layer decreases with the increasing water depth; it is 23 cm-thick in the shallower Hole 1209A compared to 11 cm in the deeper Hole 1211B. The clay-rich layer also contains common crystals of phillipsite, fish teeth, and phosphatic micronodules, and corresponds to a prominent peak in magnetic susceptibility that probably reflects the higher amount of terrigenous material as Fe-Mn coating of grains. The onset of the event coincides with the beginning of the sharp increase in magnetic susceptibility, but precedes the occurrence of phillipsite. The magnetic susceptibility and the amount of phillipsite show a close relationship: phillipsite can be found throughout the interval characterized by high magnetic susceptibility values. The top of the event is marked by the disappearance of phillipsite and decreasing magnetic susceptibility. The detailed quantitative analysis of the planktonic foraminiferal assemblage across the clay-rich nannofossil ooze layer shows fundamental changes in faunal populations occurring before, during and after the deposition of the clay-rich ooze. Planktonic foraminifera in the clay-rich layer are characterized by a low-diversity, largely dissolved assemblage, dominated by representatives of the genus Igorina (mainly I. tadjikistanensis and I. pusilla). Conversely, I. albeari, morozovellids, acarininids, globanomalinids, subbotinids, and chiloguembelinids show the opposite trend: they are quite common below the clay-rich layer, almost disappear within it, and reappear in low abundance above the clay-rich layer. These changes likely are a response to major changes in surface water conditions or possibly increased dissolution on the sea floor The foraminiferal assemblage data has been combined with measurements of major chemical elements and bulk stable isotopes to understand the oceanographic conditions that gave rise to this mid-Paleocene event as well as the detailed evolutionary relationships of the key taxa.
