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The last global extinction (Mid-Pleistocene) of deep sea benthic foraminifera (Chrysalogoniidae, Ellipsoidinidae, Glandulonodosariidae, Plectofrondiculariidae, Pleurostomellidae, Stilostomellidae), their Late Cretaceous-Cenozoic history and taxonomy
Abstract
Part 1. The Last Global Extinction in the Deep Sea
During the Last Global Extinction (LGE) c. 20% (30 genera, 105 species) of cosmopolitan, mainly deep-sea (600–4000 m), benthic foraminiferal species (excluding unilocular taxa), belonging to seven families, became extinct. During this late Pliocene–middle Pleistocene interval (3.6–0.13 Ma), five families (Chrysalogoniidae, Glandulonodosariidae, Stilostomellidae, Ellipsoidinidae, Pleurostomellidae) were wiped out and one more (Plectofrondiculariidae) was almost wiped out with just one species surviving to the present. Most (76 of 105 species) of these extinctions occurred during the mid-Pleistocene Climate Transition (MPT, 1.2–0.55 Ma) at an extinction rate of 25% myr-1 of the deep-sea benthic foraminifera, compared with a background rate through the Cenozoic of c. 2% myr-1.
Most species in the families Chrysalogoniidae, Stilostomellidae, Ellipsoidinidae and Pleurostomellidae had equal levels of abundance throughout their middle bathyal–middle abyssal depth ranges. The Glandulonodosariidae mostly lived at middle bathyal to uppermost abyssal depths and the Plectofrondiculariidae at bathyal to outer shelf depths. These Extinction Group (Ext. Gp) families comprised 30–70% of the deep-sea benthic foraminiferal fauna in the middle to late Eocene. Major declines in their relative abundance and species richness at abyssal depths began in the late Oligocene–Miocene in the Southern Ocean, in the late Miocene in the deep Indian Ocean, in the early Pliocene in the West Pacific, then globally in the late Pliocene at upper abyssal (2300–3000 m) depths and all depths in the Mediterranean Sea. At bathyal depths (900–2200 m) declines and extinctions were largely confined to the Pleistocene. These declines occurred in pulses mostly coinciding with glacial episodes of expansion of polar ice sheets, initially in Antarctica but during the MPT in the Arctic.
The LGE preferentially impacted species with specific morphologies (elongate, cylindrical, often uniserial tests) and apertural types (e.g., small rounded, dentate, cribrate, or lunate slit). The precise functions of these are not known but the apertural modifications could be related to having a specific food source whose pulsed decline in abundance in the plankton resulted in the LGE. Data on δ13C analyses suggest that Ext. Gp species lived infaunally. Strong positive correlation of Ext. Gp abundance in the Pliocene–MPT with foraminiferal proxies for sustained and pulsed organic carbon flux supports the hypothesis that the Ext. Gp favoured enhanced food supply with consequent lower oxygen concentrations.
Decreased bottom temperature, increased bottom water ventilation or carbonate corrosiveness, increased interspecific competition and predation, or increased or more wildly fluctuating food supply are all rejected as unlikely to be the causes of the LGE. We hypothesise that the cause may have been the progressive decline or demise of the specific phytoplankton source of the detritus that the Ext. Gp fed upon, during global cooling and later increasingly cold glacials of the MPT with lowered atmospheric CO2.
The LGE and regional highest occurrence levels of Ext. Gp species have considerable biostratigraphic value in providing rapid age assessments of Quaternary oceanic sediment where planktic foraminiferal age datums are rare.
Part 2. Late Cretaceous–Cenozoic History of the Extinction Group
The absolute abundance and flux of the Ext. Gp were generally greater at bathyal than at deeper abyssal depths and in more eutrophic rather than oligotrophic regions. Peak Ext. Gp fluxes, relative abundance and species richness occurred between the middle Eocene and early Miocene but some short abundance peaks in the Pliocene–MPT were associated with brief periods of locally high productivity.
The oldest Ext. Gp species originated in the Jurassic and eight more appeared in the Early Cretaceous. The peak of Ext. Gp species originations (2.7% myr-1) was Late Cretaceous, except in the Glandulonodosariidae (Paleocene) and Plectofrondiculariidae (middle to late Eocene). A secondary peak of originations (2% myr-1) occurred in the late Eocene across all Ext. Gp families. More than 80% of Ext. Gp species originated during the Cretaceous–Eocene (Greenhouse World) compared with c. 30% of modern deep-sea benthic foraminifera. The Cretaceous–Cenozoic Ext. Gp species had an even spread of species durations between five and 85 myrs (except plectofrondiculariids), with mean species durations of 50 myrs (Pleurostomellidae), 47 myrs (Glandulonodosariidae), 46 myrs (Stilostomellidae), 44 myrs (Ellipsoidinidae), 41 myrs (Chrysalogoniidae) and 20 myrs (Plectofrondiculariidae). Cenozoic Ext. Gp faunas are dominated by mostly long-lived species of just three genera – Strictocostella, Siphonodosaria and Pleurostomella.
The Ext. Gp was largely unaffected by the K/Pg or PETM extinction events. The late Eocene–Oligocene cooling was the first interval where the Ext. Gp showed an above background level of faunal change or instability and species turnover (1% myr-1, esp. Ellipsoidinidae, Plectofrondiculariidae, Glandulonodosariidae). After an early Miocene decline, extinctions began accelerating in the middle to late Miocene (1% myr-1) concurrent with progressive cooling of mid and high latitude climate and surface waters. During the Middle Miocene Climate Transition, Ext. Gp relative abundance declined and some local changes in assemblage composition occurred, but there was no pulse in global species turnover. The rate of extinctions accelerated further in the Pliocene (3% myr-1, dominantly stilostomellids), accompanied by significant changes in the composition of the dominant and overall Ext. Gp fauna as they became less diverse. With one exception, the remaining 40% of the total Cretaceous–Cenozoic diversity of the Ext. Gp disappeared during the Pleistocene, mainly during the MPT.
Part 3. Taxonomy of the Extinction Group
Two hundred and fifty-three species from 38 genera in the Extinction Group families (Chrysalogoniidae, Glandulonodosariidae, Plectofrondiculariidae, Stilostomellidae, Ellipsoidinidae, Pleurostomellidae, Nodosariidae in part), are reviewed and illustrated, together with eight additional species that became extinct or declined dramatically during the Last Global Extinction. Twelve genera and 26 species are described as new (Anastomosa n.gen., A. boomgaarti n.sp., A. loeblichi n.sp., Cribroconica n.gen., Epelistoma n.gen., E. morgansi n.sp., Lotostomoides n.gen., L. jorisseni n.sp., L. schwageri n.sp., Scallopostoma n.gen., Glandulonodosaria colomi n.sp., G. lutzei n.sp., Fingerina n.gen., Grigelis schoenfeldi n.sp., Mucronina hornibrooki n.sp., M. resigae n.sp., Plectolingulina n.gen., Carchariostomoides n.gen., Caveastomella n.gen., C. caralpae n.sp., C. weinholzi n.sp., Siphonodosaria campana n.sp., S. kaihoi n.sp., S. robertsoni n.sp., Stilostomella? guptai n.sp., Strictocostella srinivasani n.sp., S. strongi n.sp., Toddostomella n.gen., Unidens n.gen., U. ishizakii n.sp., Ellipsoglandulina keyzeri n.sp., Ellipsoidella tappanae n.sp., Laterohiatus n.gen., Nodosarella kohli n.sp., N. nomurai n.sp., N. schroederadamsae n.sp., Obesopleurostomella n.gen., O. boltovskoyi n.sp., Ossaggittia n.gen., O. thomasae n.sp.). Three-hundred and seventy-three species and 20 genera are suppressed as subjective junior synonyms.
... Ma) (Srinivasan & Sharma, 1980). The fauna contains many species that became extinct during the Last Global Extinction in the deep sea during the Mid-Pleistocene Transition, and many of these (e.g., Anastomosa gomphiformis, Chrysalogonium rude, C. polystomum, Epelistoma crassitesta, Siphonodosaria insecta, S. tauricornis, Siphouvigerina hispida) are characteristic of lower bathyal to mid abyssal (1000-4000 m) depths (Hayward et al., 2012). ...
... Neogene fossil fauna described world-wide. It comprises a mix of cosmopolitan species that became extinct during the Last Global extinction (27 species), mostly during the Mid-Pleistocene Climate Transition (Hayward et al., 2012) and most of the remainder are cosmopolitan benthic taxa (50 species) that are still extant. Schwager (1866) and the Novara Expedition predated and therefore has primacy over the deepwater foraminifera described from around the world by Brady (1879aBrady ( , b, 1881Brady ( , 1884 from the Challenger Expedition (1872-1876). ...
... Many of these latter species are still recognised as valid in New Zealand where many may be endemic. Global taxonomic reviews in the future may show that some of these species were more FIGURE 17. Illustrations of foraminiferal species described from samples collected by Hochstetter that have been designated the type species of new genera [specimen images (not types) from Hayward et al., 1997Hayward et al., , 2012. Scale bars 5 100 mm. ...
Ferdinand Hochstetter was the geologist on the Austrian trans-global Novara Expedition (1857–1859). During these travels he collected sedimentary rock samples from three places that he recognised in the field to have rich foraminiferal faunas and on his return to Austria they were studied by three foraminiferal specialists. Conrad Schwager (1866) described 97 new species (79 currently accepted) from a Pliocene lower bathyal-abyssal fauna from Car Nicobar, India. This was the earliest description of cosmopolitan, deep-water Neogene foraminiferal species and thus includes descriptions of many species widely recognised today such as Lobatula wuellerstorfi, Cibicidoides cicatricosus, Neogloboquadrina conglomerata, Pyrgo murrhina and many of the more common elongate taxa that became extinct during the Last Global extinction in the Mid Pleistocene Climate Transition. Felix Karrer (1864) and Guido Stache (1864) described 19 foraminiferal species (16 currently accepted) from the early Miocene and 126 species (50 currently accepted) from the Oligocene of the North Island of New Zealand, respectively. Among the species described from Hochstetter’s collections are the type species of 15 genera that are accepted today. Three species have been named hochstetteri from these localities. Because of their significance, all these new species from New Zealand and India were revised and typified in monographs by Hornibrook (1971) and Srinivasan & Sharma (1980), respectively.
... In some cases, environmental biozonations described for Holocene deposits in the Colombian Caribbean region (Parada-Ruffinatti, 1996;Fiorini, 2015) and Central America, the Gulf of Mexico, and the eastern Pacific regions (Smith, 1964;Finger, 1990Finger, , 2013Sen Gupta et al., 2009) were used for additional information. We also used the paleobathymetric information reported by Hayward (2004) and Hayward et al. (2012). Since downslope redeposition is very likely in continental margins, particularly in tectonically active areas, we followed the methodological proposal of Van Morkhoven et al. (1986), Coates et al. (2004), and Hayward (2004), who recommend using approximations to the upper-depth limits and giving preference to the deeper associations. ...
... Only a few specimens of Anomalinoides globulosus, Cibicidoides mundulus, Cibicidoides spp., Dentalina spp., Globocassidulina subglobosa, Lenticulina spp., Neugeborina longiscata, Nothia spp., Pyrgo spp., and Siphonodosaria spp. were recovered (Fig. 6), which indicates middle to lower bathyal depths (600-2000 m;Van Morkhoven et al., 1986;Katz and Miller, 1993;Hayward et al., 2012;Holbourn et al., 2013;Murray, 2013;Fiorini, 2015). ...
A controversy has developed in recent years regarding the timing of the closure of the Central American Seaway. This tectonic event significantly impacted oceanic circulation between the tropical Pacific and Atlantic oceans and resulted in the formation of a land bridge connecting the South and North American continents. The long-held view of a Pliocene age (ca. 3 Ma) for the closure of the Central American Seaway has been challenged by the proposal that the Panamá Arc collided with South America during the Middle Miocene (15−13 Ma) as a deep oceanic gap between them closed along the Uramita suture zone. However, direct geologic evidence from this suture zone to support either interpretation has been lacking. Here, we report on a comprehensive study of three stratigraphic transects across the Uramita suture zone, using a host of methodologies including sedimentological, ichnological, micropaleontological, U-Pb detrital geochronological, and provenance analyses. Our data reveal that lower offshore to slope conditions prevailed in the Central American Seaway along the suture zone during the latest Early to earliest Middle Miocene (16.4−15.1 Ma) and that oceanic conditions there ceased to exist between the Middle and Late Miocene. These results agree with the Middle Miocene age proposed for the Central American Seaway closure along the tectonic boundary. However, other deeper portions of the Central American Seaway persisted in western Colombia, which challenges the notion of a Central American Seaway confined to the suture zone between the Panamá Arc and South American Plate during the Middle Miocene.
... Absent a detailed and well constrained biochronostratigraphy of the Miocene sections in Quebada Perdida, it remains uncertain if the shark teeth were collected from basal Tunga strata or as reworked Tunga bioclasts from basal Chilcatay beds. Ranges of diagnostic benthic foraminifers found in the Tunga and Chilcatay formations calibrated to the Gradstein et al. (2020) geologic time scale based on species ranges derived from cosmopolitan (van Morkhoven et al. 1986;Hayward et al. 2012;Holbourn et al. 2013), Pacific (Kleinpell 1938;Mallory 1959;Dulanto 1960;Finger 1990;McDougall 2008) and Caribbean studies (Cushman 1918;Renz 1948;Araújo et al. 2018). The age range for the Tunga Formation is modified from the diatom age range (pale blue) to include an additional 100 000 years before and after (dark blue extensions) to accommodate basal and uppermost diatom-free sandstones. ...
The East Pisco Basin, occupying the coastal plain of Peru between 13°S and 16°S, is widely known for its extensive Eocene to Quaternary biosiliceous deposits and excellent preservation of fossil marine vertebrates. Biochronologic studies published over the past 35 years record a hiatus of about 13 million years (*32–19 Ma) separating the youngest Paleogene deposits (Otuma Formation) from the oldest Neogene deposits (Chilcatay Formation). We describe a newly identified Lower Miocene depositional sequence that lies below documented Chilcatay strata, rich in diatoms and benthic foraminifers, which we name the Tunga Formation. A low-latitude diatom assemblage from the Tunga Formation indicates an age of 21.6 to 20.5 Ma age, whereas an ash within basal Tunga strata yields an 206Pb/238U weighted mean age of 20.58 ± 0.13 Ma. Benthic foraminifer paleodepth analysis and the diatom assemblage of the Tunga Formation indicate deposition took place along the continental margin at upper bathyal depths under hypoxic conditions beneath highly productive waters, a scenario also supported by the presence of abundant clupeoid fish scales and dolomitized horizons. The Tunga Formation is characterized by a profound scarcity of cetacean fossils, unlike the cetacean-rich neritic sediments of the overlying Chilcatay Formation.
... Absent a detailed and well constrained biochronostratigraphy of the Miocene sections in Quebada Perdida, it remains uncertain if the shark teeth were collected from basal Tunga strata or as reworked Tunga bioclasts from basal Chilcatay beds. Ranges of diagnostic benthic foraminifers found in the Tunga and Chilcatay formations calibrated to the Gradstein et al. (2020) geologic time scale based on species ranges derived from cosmopolitan (van Morkhoven et al. 1986;Hayward et al. 2012;Holbourn et al. 2013), Pacific (Kleinpell 1938;Mallory 1959;Dulanto 1960;Finger 1990;McDougall 2008) and Caribbean studies (Cushman 1918;Renz 1948;Araújo et al. 2018). The age range for the Tunga Formation is modified from the diatom age range (pale blue) to include an additional 100 000 years before and after (dark blue extensions) to accommodate basal and uppermost diatom-free sandstones. ...
The East Pisco Basin, occupying the coastal plain of Peru between 13°S and 16°S, is widely known for its extensive Eocene to Quaternary biosiliceous deposits and excellent preservation of fossil marine vertebrates. Biochronologic studies published over the past 35 years record a hiatus of about 13 million years (*32-19 Ma) separating the youngest Paleogene deposits (Otuma Formation) from the oldest Neogene deposits (Chilcatay Formation). We describe a newly identified Lower Miocene depositional sequence that lies below documented Chilcatay strata, rich in diatoms and benthic foraminifers, which we name the Tunga Formation. A low-latitude diatom assemblage from the Tunga Formation indicates an age of 21.6 to 20.5 Ma age, whereas an ash within basal Tunga strata yields an 206 Pb/ 238 U weighted mean age of 20.58 ± 0.13 Ma. Benthic foraminifer paleodepth analysis and the diatom assemblage of the Tunga Formation indicate deposition took place along the continental margin at upper bathyal depths under hypoxic conditions beneath highly productive waters, a scenario also supported by the presence of abundant clupeoid fish scales and dolomitized horizons. The Tunga Formation is characterized by a profound scarcity of cetacean fossils, unlike the cetacean-rich neritic sediments of the overlying Chilcatay Formation.
... The planktic foraminifera index species from the core depths 470 cm to 90 cm all indicate the final depositonal age at those intervals to be in the middle Miocene, whereas if there were appreciable reworking of foraminifera, then taxa from the Oligocene or early Miocene would be found in the Langhian section. Furthermore, benthic foraminifera such as Stilostomella lepidula, Pyramidulina latejugata and Laevidentalina spp. that went extinct during the mid-Pleistocene extinction were extant during the Miocene (Hayward, 2002;O'Neill et al., 2007;Hayward et al., 2012). A similar Langhian assemblage was also recorded from northern Namibia (Bergh et al., 2018;Bergh and Compton, 2022b). ...
The sedimentary record of the western South African continental shelf is condensed compared to the continental slope and contains erosional unconformities, owing to periods of non deposition, eustatic sea-level fluctuations, episodic uplift and intensified continental aridity. Despite this, the sedimentary record of the continental shelf provides important information on the depositional history and palaeoenvironmental evolution of the region. A core retrieved from the western shelf of South Africa was analysed for its sedimentary composition, lithological variation, foraminiferal content and its relation to the palaeoenvironment of the region. Four depositional facies were identified along the core, namely quartzitic sand, sandy mud, and glauco phosphatic sand and a glaucophosphatic gravel. The basal facies consisting of quartzitic sand is interpreted to have been deposited between 15.90 and 14.60 Ma, corresponding to the timing of the Mid-Miocene Climatic Optimum (MMCO). The highly quartzitic nature of the sediments indicate a high terrestrial influence from fluvial sources. The overlying sandy mud facies was deposited between 14.60 and 13.90 Ma based on planktic foraminiferal biostratigraphy. Foraminiferal analyses of these two facies that were deposited in the Langhian stage of the middle Miocene point to subtropical sea surface conditions and mesotrophic benthic environments. Sea level was noticeably higher during the MMCO and part of the cooling period following the MMCO. An erosional surface that spans 10.77 Myr, equal to the late Miocene (13.90 Ma) to early Pliocene (3.13 Ma), marks the boundary between the two Langhian facies and the overlying two Pleistocene facies, consisting of coarser grained glauco-phosphatic gravelly sand units. The Pleistocene environment on the shelf is interpreted to contrast with the Langhian environment, where cooler, shallower conditions and a more eutrophic benthic environment was prevalent, during a time that Benguela upwelling intensified with higher frequency and higher amplitude sea level fluctuations. Palaeobathymetric interpretations indicate that middle Miocene sea-level in the region were up to 77 m higher than present day and 101 m lower in the Pleistocene, in-line with previous global studies. Glauco-phosphatic content that increase upcore also marks the shallowing of the environment under high productivity conditions.
... Nakkady [43] , LeRoy [44] ) and considered here to be related to the Midway-Type Fauna (MTF) of Berggren & Aubert [45] . Hay-ward et al. [46] noted the paleobathymetric distribution of Pleurostomella acuta in present-day depth ranges of sites in the lower bathyal to middle abyssal. ...
Rich and well preserved Argentinian taxa made it possible to correlate them with those previously identified species in the coeval sequence in different Tethyan North America, Europe and Middle East localities. This study deals with new information on paleontology and lineages of fourteen Argentinian Ypresian benthic foraminiferal species from the Punta Torcida Formation, lower-middle Eocene (Ypresian-lower Lutetian), Tierra del Fuego Island and Fuegian continental shelf, which belongs to twelve genera: Laevidentalina, Lagenoglandulina, Tollmannia, Tristix, Leticuzonaria, Palmula, Leroyia, Marginulina, Ramulina, Orthokarstenia, Rectuvigerina and Pleurostomella. Ten of the illustrated species are believed to be new: Laevidentalina jannoui, Lagenoglandulina argentinica, Tollmannia argentinica, Leticuzonaria argentinica, Palmula americana, Leroyia argentinica, Marginulina argentinica, Ramulina subornata, Ramulina morsii and Rectuvigerina argentinica sp. nov. The paleoenvironment of the Argentinian taxa would have been a shelf sea of normal salinity, where muds were deposited under low energy and low oxygen conditions, as is suggested by the dominance of infaunal morphotypes and excellent preservation of the tests, whereas intercalated sandstones reflect moderate energy and oxic conditions, bearing microfossil assemblages displaced from shallower settings.
... deep-sea diversity, faunal turnover, macroecological patterns, Mid-Brunhes Event, North Atlantic, Ostracoda involves large-scale changes in ice shelf development, sea ice volume, global ocean circulation and potentially marginal marine systems that are sensitive to changes in climate (Huang et al., 2018). From analyses of microfossils in deep-sea sediment cores, major faunal shifts and extinctions have recently been reported across the MBE in various places (Cronin et al., , 2017DeNinno et al., 2015;Hayward et al., 2007Hayward et al., , 2012Huang et al., 2018Huang et al., , 2019Polyak et al., 2013;Zarikian et al., 2022). If "Quaternary glaciation" plays a role in the deep Norwegian Sea biodiversity, a shift in the mode of glacial-interglacial climatic variability may affect it to a certain degree. ...
Aim
Within the intensively‐studied, well‐documented latitudinal diversity gradient, the deep‐sea biodiversity of the present‐day Norwegian Sea stands out with its notably low diversity, constituting a steep latitudinal diversity gradient in the North Atlantic. The reason behind this has long been a topic of debate and speculation. Most prominently, it is explained by the deep‐sea glacial disturbance hypothesis, which states that harsh environmental glacial conditions negatively impacted Norwegian Sea diversities, which have not yet fully recovered. Our aim is to empirically test this hypothesis. Specific research questions are: (1) Has deep‐sea biodiversity been lower during glacials than during interglacials? ( 2) Was there any faunal shift at the Mid‐Brunhes Event (MBE) when the mode of glacial–interglacial climatic change was altered?
Location
Norwegian Sea, deep sea (1819–2800 m), coring sites MD992277, PS1243, and M23352.
Time period
620.7–1.4 ka (Middle Pleistocene–Late Holocene).
Taxa studied
Ostracoda (Crustacea).
Methods
We empirically test the deep‐sea glacial disturbance hypothesis by investigating whether diversity in glacial periods is consistently lower than diversity in interglacial periods. Additionally, we apply comparative analyses to determine a potential faunal shift at the MBE, a Pleistocene event describing a fundamental shift in global climate.
Results
The deep Norwegian Sea diversity was not lower during glacial periods compared to interglacial periods. Holocene diversity was exceedingly lower than that of the last glacial period. Faunal composition changed substantially between pre‐ and post‐MBE.
Main conclusions
These results reject the glacial disturbance hypothesis, since the low glacial diversity is the important precondition here. The present‐day‐style deep Norwegian Sea ecosystem was established by the MBE, more specifically by MBE‐induced changes in global climate, which has led to more dynamic post‐MBE conditions. In a broader context, this implies that the MBE has played an important role in the establishment of the modern polar deep‐sea ecosystem and biodiversity in general.
... The approach taken here builds on the biofacies developed by and allows coeval foraminiferal assemblages along the East Pacific Margin to be compared. Assignment of species to a biofacies is based on overviews of Pacific benthic foraminifers, calcareous and agglutinated species by , Ingle & Keller (1980), and studies of cosmopolitan benthic foraminifers by Douglas (1981), Tjalsma & Lohmann (1983), Woodruff (1985), van Morkhoven et al. (1986), Kaminski & Gradstein (2005), and Hayward et al. (2012). Since foraminiferal assemblages can contain indigenous and transported species, the abundance of each biofacies was determined by the percent of benthic foraminiferal specimens with upper depth limits TABLE 1. Distribution and abundance of foraminifers and associated microfossils in the lower Coaledo Formation, North Simpson Beach Cove, South Simpson Beach Cove, and Bathers Cove, south of Coos Bay, Oregon. ...
The middle Eocene lower Coaledo Formation was interpreted as ten shoaling upward delta-margin cycles based on sediments and macrofauna. The strata, however, contains deep-water foraminifers. Explanations to resolve this anomaly included reworking, bathymetric range extension , or upward migration of water masses. Paleoecology analysis of foraminifers indicates that the few shelf species are poorly preserved whereas the well-preserved lower bathyal species dominate, and planktic organisms are present. Evidence for reworking, bathymetric range extension , or upward migration of water masses was not found in any of the cycles. The paleoecologic utility of hum-mocky cross-bedded sandstones is questioned as these features are controversial. In addition, there is no evidence of sea-level changes or tectonic activity to accommodate the bathymetric changes needed. Deposition of the lower Coaledo Formation on a submarine fan at lower bathyal depths eliminates the need to explain bathymetric anomalies or lack of tectonic movement.
... reworked from older sediments (Stilostomella) (Weinholz and Lutze, 1989;Hayward et al., 2012) or transported to the deep-sea from shallow-water environments, including symbiont-bearing larger foraminifera such as Sorites, Parasorites, Borelis, Peneroplis, Laevipeneroplis, Amphistegina, Heterostegina, Planostegina, Operculina, Neorotalia, Pararotalia, Gypsina, Sphaerogypsina (Murray, 1991(Murray, , 2006Hohenegger et al., 1999;Renema, 2006), and other typical shallow-marine taxa such as Acervulina, Ammonia, Cibicides refulgens, Cribrononion, Cymbaloporetta, Elphidium, Lobatula lobatula, Millettiana, Planorbulina, Planorbulinella, Tretomphaloides, and Tretomphalus (Banner et al., 1985;Murray, 1991Murray, , 2006Culver et al., 1996;Milker et al., 2009). The adjusted data sets were evaluated in terms of diversity, selected indicator taxa, and oxygen concentration. ...
The middle Eocene lower Coaledo Formation was interpreted as ten shoaling upward delta-margin cycles based on sediments and macrofauna. The strata, however, contains deep-water foraminifers. Explanations to resolve this anomaly included reworking, bathymetric range extension, or upward migration of water masses. Paleoecology analysis of foraminifers indicates that the few shelf species are poorly preserved whereas the well-preserved lower bathyal species dominate, and planktic organisms are present. Evidence for reworking, bathymetric range extension, or upward migration of water masses was not found in any of the cycles. The paleoecologic utility of hummocky cross-bedded sandstones is questioned as these features are controversial. In addition, there is no evidence of sea-level changes or tectonic activity to accommodate the bathymetric changes needed. Deposition of the lower Coaledo Formation on a submarine fan at lower bathyal depths eliminates the need to explain bathymetric anomalies or lack of tectonic movement.
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