No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Towards interactive global paleogeographic maps, new reconstructions at 60, 40 and 20 Ma
Abstract
Paleogeographic maps are essential tools for understanding Earth system dynamics. They provide boundary conditions for climate and geodynamic modelling, for analysing surface processes and biotic interactions. However, the temporal and spatial distribution of key features such as seaways and mountain belts that govern climate changes and biotic interchange differ between various paleogeographies that require regular updates with new data and models. We developed a reproducible and systematic approach to paleogeographic reconstruction and provide a set of worldwide Cenozoic paleogeographic maps at 60, 40 and 20 Ma. We followed a six-stage methodology that integrates an extensive review of geological data into a coherent plate tectonic model using the open source software GPlates. (1) We generated a global plate kinematic model, and reconstructed intensely-deformed plate boundaries using a review of structural, paleomagnetic and other geologic data in six key regions: the Andes, the North American Cordillera, the Scotia Arc, Africa, the Mediterranean region and the Tibetan-Himalayan collision zone. (2) We modified previously published paleobathymetry in several regions where continental and oceanic crust overlap due to differences in the plate models. (3) We then defined paleoshorelines using updated fossil and geologic databases to locate the terrestrial to marine transition. (4) We applied isostatic compensation in polar regions and global eustatic sea level adjustments. (5) Paleoelevations were estimated using a broad range of data including thermochronology and stable isotopes, combined with paleobotanical (mostly pollen and leaf physiognomy), structural and geomorphological data. We address ongoing controversies on the mechanisms and chronology of India-Asia collision by providing alternate reconstructions for each time slice. We finally discuss the implications of our reconstructions on the Cenozoic evolution of continental weatherability and review methodological limitations and potential improvements. Future addition of new data, tools and reconstructions can be accommodated through a dedicated interactive website tool (https://map.paleoenvironment.eu/) that enables users to interactively upload and download data and compare with other models, and generate their own plots. Our aim is to regularly update the models presented here with new data as they become available.
... Straume et al. (2020) presented the paleogeographic reconstruction for the early Miocene (~20 Ma), based on their paleobathymetric model and previous published paleotopographic data (e.g., Paxman et al., 2019). Poblete et al. (2021) also reconstructed the early Miocene paleogeography, based on previous paleoshoreline map (Golonka et al., 2006), paleobathymetric data (Müller et al., 2008a), and the collected geological data (e.g., paleoelevation data) from the literatures. ...
... The paleotopography of East Asia also differs among the reconstructions. The south-central Tibetan Plateau reached elevations of ~5000-8100 m in the reconstruction of Scotese and Wright (2018), whereas it reached elevations of ~3000-4000 m in the reconstructions of Straume et al. (2020) and Poblete et al. (2021). The uncertainties in the areal extent of the Paratethys or topography of the Tibetan Plateau affect simulations of precipitation, wind seasonality, and atmospheric dynamics in Asia (e.g., Zhang et al., 2007). ...
... On the east side of the Mediterranean, the western part of the India-Asia collision zone was submerged (0-1500 m deep). Compared with the two aforementioned reconstructions, in the reconstruction by Poblete et al. (2021) the Paratethys was the largest, retreated into the Carpathian (0-100 m deep)-Black Sea (0-2200 m deep)-Caspian Sea (0-1000 m deep) areas, and was disconnected from the Mediterranean. The central-eastern Mediterranean was 0-4000 m deep. ...
... Here, we thus simulate the ocean dynamics using the IPSL-CM5A2 model with a fixed pCO 2 and updated paleogeography of the early Miocene proposed by Poblete et al. (2021), which exhibits open connections between the Pacific, Atlantic and Artic oceanic basins through the Central American Seaway, the Fram Strait, the Greenland-Scotland Ridge and the Drake Passage. ...
... Three simulations were run in this study with a paleogeography corresponding to the early Miocene (∼20 Ma) from the study of Poblete et al. (2021) (Figure 1). In this paleogeography, most of the mountain belts are lower than today, there is a modern Antarctic ice-sheet and the Paratethys shallow sea covers part of Central and Eastern Europe with a connection to the Mediterranean Sea. ...
The Modern Ocean is characterized by the formation of deep‐water in the North Atlantic Ocean (i.e., NADW). This feature has been attributed to the modern geography, in which the Atlantic Ocean is a large basin extending from northern polar latitudes to the Southern Ocean, the latter enabling the connection of the otherwise isolated Atlantic with the Pacific and Indian Oceans. Sedimentary data date the establishment of the NADW between the beginning of the Eocene (∼49 Ma) and the beginning of the Miocene (∼23 Ma). The objective of this study is to quantify the impact of Miocene geography (∼20 Ma) on NADW using new simulations performed with the Earth System Model IPSL‐CM5A2. We specifically focus on the closure of the Eastern Tethys Seaway (ETS), dated between 22 and 14 Ma, which allowed the connection between the Atlantic and Indian Oceans, and on the Greenland Ice Sheet, whose earliest onset remains open to discussion but for which evidence suggest a possible existence as early as the Eocene. Our results show that the closure of the ETS does not appear to impact the establishment of NADW, because waters from the Indian Ocean do not reach the NADW formation zone when the seaway is open. Conversely, the existence of an ice sheet over Greenland strengthens the formation of NADW owing to topography induced changes in wind patterns over the North Atlantic, which in turn, results in a salinification of the North Atlantic and Nordic Seas, and in an increase in deep‐water formation.
... In this case, the South Atlantic Basin was still narrow but had sufficient fetch for southerly low-level winds and convection to occur over the Atlantic Ocean. We find the Northern Hemisphere overturning circulation persisting since the formation of the Northern Atlantic Basin (Poblete et al., 2021;Seton et al., 2012). Our study demonstrates that a Southern Hemisphere Hadley cell overturning circulation fully existed in the Miocene, but we hypothesize that this could have occurred earlier as the South Atlantic Basin gained a sufficient fetch (Poblete et al., 2021;Seton et al., 2012). ...
... We find the Northern Hemisphere overturning circulation persisting since the formation of the Northern Atlantic Basin (Poblete et al., 2021;Seton et al., 2012). Our study demonstrates that a Southern Hemisphere Hadley cell overturning circulation fully existed in the Miocene, but we hypothesize that this could have occurred earlier as the South Atlantic Basin gained a sufficient fetch (Poblete et al., 2021;Seton et al., 2012). ...
The widening of the South Atlantic Basin led to the reorganization of regional atmospheric and oceanic circulations. However, the response of the Atlantic Intertropical Convergence Zone (ITCZ), and South American and African monsoons across paleoclimate states, especially under constant paleogeographic and climatic changes, has not been well understood. Here we report on paleoclimate simulations of the Cenomanian (∼95 Ma), early Eocene (∼55 Ma), and middle Miocene (∼14 Ma) using the Community Earth System Model version 1.2 to understand how the migration of the South American and African continents to their modern‐day positions, uplift of the Andes and East African Rift Zone, and the decline of atmospheric CO2 changed the Atlantic ITCZ, and the South American and African monsoons and rainforests. Our work demonstrates that the South Atlantic widening developed the Atlantic ITCZ. The South Atlantic widening and Andean orogeny led to a stronger South American monsoon. We find the orogeny of the East African Rift Zone is the primary mechanism that strengthened the East African monsoon, whereas the West African monsoon became weaker through time as West Africa migrated toward the subtropics and CO2 levels fell below 500 ppm. We utilize the Köppen‐Geiger Climate Classification as an indicator for maximum rainforest extent. We find that during the Cenomanian and early Eocene, a Pan‐African rainforest existed, while the Amazon rainforest was restricted toward the northwestern corner of South America. During the middle Miocene, the Pan‐African rainforest was reduced to near its modern‐day size, while the Amazon rainforest expanded eastward.
... All our maps were crosschecked with the occurrences of terrestrial and marine fossils (www.paleobiodb.org) and the 60, 40 and 20 Ma maps underwent some refinements according to Poblete et al. (2021). ...
... The thick grey curve shows the average continental paleolatitude (weighted by area) while the blue curve corresponds to the percentage of exposed land (10 6 km 2 ). Our model covers the period from 520 to 70 Ma followed by a revision of the model from Golonka et al. (2006;digitized in Heine et al., 2015) and Poblete et al. (2021) after 70 Ma. (b) Exposed land in the southern and northern hemisphere belts between 40 and 50°(wet belts) as well as within ±10°. ...
The validity of sea level estimates based on stratigraphic correlations has been debated since the 1990s as relative sea level curves differ between sites due to local tectonics, different deposition rates and changes in dynamic topography. Here, we offer a new eustatic (global) sea level curve for the past 520 million years (Myrs) based on observations of global flooding. We use paleogeographic reconstructions to measure the area of today’s exposed land that was flooded in the past (modern-land flooding). We then apply the modern global hypsometric slope to reconstruct the sea level history. We find minimum sea levels (comparable to today’s level) towards the end of Pangea (210 Ma) and peak levels (∼280 m higher than today) at 80 Ma when Pangea was widely dispersed. A first-order “supercontinent” cycle of 250 million years (Myrs) is recognized but we also document a second-order cycle of 37 Myrs that was previously thought to be undetectable using the hypsometric method. The hypsometric slope is critical for reconstructing past sea levels, and steepening the hypsometric slope during Pangea assembly implies dramatically larger sea level fluctuations. Our new sea level curve shares strong similarities with stratigraphic constraints and correlates with seafloor production proxies throughout the Phanerozoic. Measurements of global flooding represent averages across great continental extents, making them less sensitive than stratigraphic analyses to regional-scale vertical land motion, such as from dynamic topography and hence more reliable for estimating eustatic sea level. This method can also help to identify local deviations caused by regional uplift or subsidence and serves to constrain geodynamic mechanisms for sea level change. Our new sea level reconstruction usefully tracks global variations in Phanerozoic eustatic sea level, but also opens opportunities to estimate such variations in deeper time.
... The central and eastern EES extent and area (ca. 8.5 × 10 6 km 2 ; Fig. 3a, b) were determined from a review of land-sea distribution data 17 over a 60 Ma paleogeographic reconstruction 34 . We used a broad range of wellestablished bulk density values (from 2.1 × 10 12 to 2.7 × 10 12 kg km-3) proposed for organic shales 35 . ...
... Continental shelves were previously recognized as potentially important carbon sinks, and have been estimated to sequester 2200-2900 Gt C org during the PETM 13 . However, these estimates were based on present-day shelf areas, and high Palaeocene sea level might have tripled the global shelf area 34 . We estimate a total shelf area of ca. ...
The Palaeocene-Eocene Thermal Maximum (ca. 56 million years ago) offers a primary analogue for future global warming and carbon cycle recovery. Yet, where and how massive carbon emissions were mitigated during this climate warming event remains largely unknown. Here we show that organic carbon burial in the vast epicontinental seaways that extended over Eurasia provided a major carbon sink during the Palaeocene-Eocene Thermal Maximum. We coupled new and existing stratigraphic analyses to a detailed paleogeographic framework and using spatiotemporal interpolation calculated ca. 720-1300 Gt organic carbon excess burial, focused in the eastern parts of the Eurasian epicontinental seaways. A much larger amount (2160-3900 Gt C, and when accounting for the increase in inundated shelf area 7400-10300 Gt C) could have been sequestered in similar environments globally. With the disappearance of most epicontinental seas since the Oligocene-Miocene, an effective negative carbon cycle feedback also disappeared making the modern carbon cycle critically dependent on the slower silicate weathering feedback.
... The Australian continent was shifted southwards to account for its northward migration throughout the Cenozoic 59 and the Sunda shelf was partly emerged 60 . The EM palaeogeography was taken from the recent study by Poblete et al. 38 . Most of the mountain belts have lower elevation compared with the LM palaeogeography to account for major phases of uplift recorded during the late Neogene. ...
... 84 ). The EM palaeogeographic reconstructions 38 are also available on the Paleoenvironment map website (https:// map.paleoenvironment.eu). The repository also contains palaeogeography grids used for the simulations. ...
In the modern northern Indian Ocean, biological productivity is intimately
linked to near-surface oceanographic dynamics forced by the South Asian, or
Indian, monsoon. In the late Pleistocene, this strong seasonal signal is
transferred to the sedimentary record in the form of strong variance in the
precession band (19–23 kyr), because precession dominates low-latitude
insolation variations and drives seasonal contrast in oceanographic
conditions. In addition, internal climate system feedbacks (e.g. ice-sheet
albedo, carbon cycle, topography) play a key role in monsoon variability.
Little is known about orbital-scale monsoon variability in the
pre-Pleistocene, when atmospheric CO2 levels and global temperatures
were higher. In addition, many questions remain open regarding the timing of the initiation and intensification of the South Asian monsoon during the
Miocene, an interval of significant global climate change that culminated in bipolar glaciation. Here, we present new high-resolution (<1 kyr)
records of export productivity and sediment accumulation from International
Ocean Discovery Program Site U1443 in the southernmost part of the Bay of Bengal
spanning the late Miocene (9 to 5 million years ago). Underpinned by a new
orbitally tuned benthic isotope stratigraphy, we use X-ray
fluorescence-derived biogenic barium variations to discern productivity
trends and rhythms. Results show strong eccentricity-modulated
precession-band productivity variations throughout the late Miocene,
interpreted to reflect insolation forcing of summer monsoon wind strength in the equatorial Indian Ocean. On long timescales, our data support the
interpretation that South Asian monsoon winds were already established by 9 Ma in the equatorial sector of the Indian Ocean, with no apparent
intensification over the latest Miocene.
... The Australian continent was shifted southwards to account for its northward migration throughout the Cenozoic 59 and the Sunda shelf was partly emerged 60 . The EM palaeogeography was taken from the recent study by Poblete et al. 38 . Most of the mountain belts have lower elevation compared with the LM palaeogeography to account for major phases of uplift recorded during the late Neogene. ...
... 84 ). The EM palaeogeographic reconstructions 38 are also available on the Paleoenvironment map website (https:// map.paleoenvironment.eu). The repository also contains palaeogeography grids used for the simulations. ...
The drivers of the evolution of the South Asian Monsoon remain widely debated. An intensification of monsoonal rainfall recorded in terrestrial and marine sediment archives from the earliest Miocene (23–20 million years ago (Ma)) is generally attributed to Himalayan uplift. However, Indian Ocean palaeorecords place the onset of a strong monsoon around 13 Ma, linked to strengthening of the southwesterly winds of the Somali Jet that also force Arabian Sea upwelling. Here we reconcile these divergent records using Earth system model simulations to evaluate the interactions between palaeogeography and ocean–atmosphere dynamics. We show that factors forcing the South Asian Monsoon circulation versus rainfall are decoupled and diachronous. Himalayan and Tibetan Plateau topography predominantly controlled early Miocene rainfall patterns, with limited impact on ocean–atmosphere circulation. The uplift of the East African and Middle Eastern topography played a pivotal role in the establishment of the modern Somali Jet structure above the western Indian Ocean, while strong upwelling initiated as a direct consequence of the emergence of the Arabian Peninsula and the onset of modern-like atmospheric circulation. Our results emphasize that although elevated rainfall seasonality was probably a persistent feature since the India–Asia collision in the Paleogene, modern-like monsoonal atmospheric circulation only emerged in the late Neogene. A modern-like South Asian Monsoon only appeared when East African and Middle Eastern uplift led to the establishment of the Somali Jet around 13 million years ago, according to Earth system modelling using a range of regional palaeogeographies.
... Five simulations were carried out to reconstruct the evolution of temperature seasonality from the middle Eocene to the early Oligocene (Table 1). The applied 40 Ma paleogeography framework is the map developed by Poblete et al. (2021) and already used in Tardif et al. (2020) and Toumoulin et al. (2020) (Fig. 1). The orbital parameters were set to preindustrial values and the solar constant was reduced accordingly to its Eocene value (1360.19 ...
... Paleocoordinates for every locality were reconstructed using the online service of Gplates (https://www.gplates.org/, last access: 16 February 2022), according to the 40 Ma paleogeography used for the paleoclimate models (Poblete et al., 2021) that essentially follows the plate tectonic reconstruction model of Matthews et al. (2016) with some modifications. ...
At the junction of greenhouse and icehouse climate states, the
Eocene–Oligocene Transition (EOT) is a key moment in Cenozoic climate
history. While it is associated with severe extinctions and biodiversity
turnovers on land, the role of terrestrial climate evolution remains poorly
resolved, especially the associated changes in seasonality. Some
paleobotanical and geochemical continental records in parts of the Northern
Hemisphere suggest the EOT is associated with a marked cooling in winter,
leading to the development of more pronounced seasons (i.e., an increase in the
mean annual range of temperature, MATR). However, the MATR increase has been
barely studied by climate models and large uncertainties remain on its
origin, geographical extent and impact. In order to better understand and
describe temperature seasonality changes between the middle Eocene and the
early Oligocene, we use the Earth system model IPSL-CM5A2 and a set of
simulations reconstructing the EOT through three major climate forcings:
pCO2 decrease (1120, 840 and 560 ppm), the Antarctic ice-sheet (AIS)
formation and the associated sea-level decrease. Our simulations suggest
that pCO2 lowering alone is not sufficient to explain the seasonality
evolution described by the data through the EOT but rather that the
combined effects of pCO2, AIS formation and increased continentality
provide the best data–model agreement. pCO2 decrease induces a zonal
pattern with alternating increasing and decreasing seasonality bands
particularly strong in the northern high latitudes (up to 8 ∘C
MATR increase) due to sea-ice and surface albedo feedback. Conversely, the
onset of the AIS is responsible for a more constant surface albedo yearly,
which leads to a strong decrease in seasonality in the southern midlatitudes to
high latitudes (>40∘ S). Finally, continental areas
that emerged due to the sea-level lowering cause the largest increase in
seasonality and explain most of the global heterogeneity in MATR changes
(ΔMATR) patterns. The ΔMATR patterns we reconstruct are
generally consistent with the variability of the EOT biotic crisis intensity
across the Northern Hemisphere and provide insights on their underlying
mechanisms.
... Paleogeographic maps for the Eocene (Figs. 1 and 5) were reconstructed with Gplates software for the paleo-position of Balkanatolian terranes and fossil sites, using the global plate rotation model provided by Poblete et al. (2021) and incorporating the high-resolution model of van Hinsbergen et al. (2020) for the Mediterranean domain, with fixed Eurasia. Paleo-shorelines are from Barrier et al. (2018) for the central and eastern Mediterranean domain and from Kováč et al. (2016) for the western Mediterranean domain, which were adapted to our plate rotation model using Gplates and QGIS software. ...
... Faunal exchanges between Europe and Asia through higher latitudes, such as evidenced by Mennecart et al. (2021) for some artiodactyls, were likely limited to taxa adapted to temperate or colder, drier environments; these high latitude bridges are yet inadequate for taxa adapted to wetter and warmer environments, such as anthracotheriids and possibly some rhinocerotoids (Böhme et al., 2013). The Turgaï Strait, which connected the Arctic Sea to the Paratethys and is frequently proposed as the main biogeographic barrier between Europe and East Asia (Fig. 1), completely receded by 37 Ma, well before the Oi-1 glaciation, and experienced earlier events of closure during the Eocene (Kaya et al., 2019;Poblete et al., 2021). If highlatitude dispersals barely occurred earlier in the Eocene when the climate was milder, they are less likely to have occurred after the transition into the Oligocene icehouse and the aridification of central Asia (Barbolini et al., 2020). ...
The Grande Coupure corresponds to a major episode of faunal turnover in western Europe around the Eocene-Oligocene boundary that is generally attributed to the influx of multiple clades of Asian mammals. However, Asian mammal clades begin to appear in the fossil record of southeastern Europe during the middle Eocene, 5–10 million years prior to the Grande Coupure. How and when these Asian mammal clades colonized southeastern Europe remains poorly understood, partly because the fossil record of mammals from nearby Anatolia is characterized by marked endemism and very limited exchanges with Asia during most of the Eocene. We resolve this apparent paradox by reviewing the age of existing paleontological sites from the Balkans to the Caucasus and documenting the oldest Asian perissodactyls found so far in central Anatolia, which date to the lower or middle Priabonian, 37.8 to 35 million years ago, on the basis of geochronological, magnetostratigraphic and biostratigraphic data. We show that the Eocene distribution of mammals across Eurasia supports a previously unrecognized biogeographic province, designated here as Balkanatolia, spanning the eastern and central segment of the Neotethyan margin. Isolated from mainland Eurasia during the early and middle Eocene, Balkanatolia formed a low-topography archipelago where endemic and anachronistic mammals thrived. We show that the Eocene fossil record supports Balkanatolia having been colonized by Asian ungulates and rodents by the late Bartonian (mammalian Paleogene biohorizon MP16), following the establishment of a continuous terrestrial dispersal corridor across the central segment of the Neotethyan margin. This colonization event was facilitated by a drop in global eustatic sea level and a tectonically-driven sea retreat in eastern Anatolia and the Lesser Caucasus during the late middle Eocene. These paleogeographic changes instigated the demise of Balkanatolia as a distinct biogeographic province and paved the way for the dispersal of Asian endemic clades before and during the Grande Coupure in western Europe.
... All our maps were crosschecked with the occurrences of terrestrial and marine fossils (www.paleobiodb.org) and the 60, 40 and 20 Ma maps underwent some refinements according to Poblete et al. (2021). ...
... The thick grey curve shows the average continental paleolatitude (weighted by area) while the blue curve corresponds to the percentage of exposed land (10 6 km 2 ). Our model covers the period from 520 to 70 Ma followed by a revision of the model from Golonka et al. (2006;digitized in Heine et al., 2015) and Poblete et al. (2021) after 70 Ma. (b) Exposed land in the southern and northern hemisphere belts between 40 and 50°(wet belts) as well as within ±10°. ...
Long-term carbon cycle models are critical for understanding the levels and underlying controls of atmospheric CO2 over geological time-scales. We have refined the implementation of two important boundary conditions in carbon cycle models, namely consumption by silicate weathering and carbon degassing. Through the construction of continental flooding maps for the past 520 million years (Myrs), we have estimated exposed land area relative to the present-day (fA), and the fraction of exposed land area undergoing silicate weathering (fAW-fA). The latter is based on the amount of exposed land within the tropics (±10°) plus the northern/southern wet belts (±40-50°) relative to today, which are the prime regions for silicate weathering. We also evaluated climate gradients and potential weatherability by examining the distribution of climate-sensitive indicators. This is particularly important during and after Pangea formation, when we reduce fAW-fA during times when arid equatorial regions were present. We also estimated carbon degassing for the past 410 Myrs using the subduction flux from full-plate models as a proxy. We further used the subduction flux to scale and normalize the arc-related zircon age distribution (arc-activity), allowing us to estimate carbon degassing in much deeper time. The effect of these refined modelling parameters for weathering and degassing was then tested in the GEOCARBSULFvolc model, and the results are compared to other carbon cycle models and CO2 proxies. The use of arc-activity as a proxy for carbon degassing brings Mesozoic model estimates closer to CO2 proxy values but our models are highly sensitive to the definition of fAW-fA. Considering only variations in the land availability to weathering that occur in tropical latitudes (corrected for arid regions) and the use of our new degassing estimates leads to notably higher CO2 levels in the Mesozoic, and a better fit with the CO2 proxies.
... After reaching maximum temperatures during the Early Eocene Climate Optimum (~53-52 Mya), gradual cooling from greenhouse to icehouse conditions reached a threshold at the Eocene-Oligocene Transition (~34 Mya; Zachos et al., 2001), having dramatic impacts around the globe, including ice expansion in Antarctica, increased aridity of continent interiors, a reduction in sea surface temperatures at high latitudes, and changes in the atmospheric and oceanic circulation (Zachos & Kump, 2005;Dupont-Nivet et al., 2007;Liu et al., 2009). The entire region where our study focused in Argentina was below sea level, as a product of the Atlantic Ocean marine transgression, after which, during the Middle Miocene to Pliocene, this region began to emerge (Poblete et al., 2021). Hernandez et al. (2005) described one high craton occupying the north of the Chaco and Formosa Argentinian provinces during the marine transgression. ...
The genus Caiman is one of the most taxonomically conflicted among crocodilians. Caiman crocodilus has four subspecies: Caiman crocodilus crocodilus, Caiman crocodilus fuscus, Caiman crocodilus chiapasius and Caiman crocodilus apaporiensis, but some studies recognize Caiman yacare as a subspecies of C. crocodilus or as a C. crocodilus–C. yacare complex. In Argentina, Caiman latirostris and C. yacare are present and included in sustainable use programmes, although they have hardly been studied at the genetic level. The present study had two main objectives: (1) to study the genetic diversity, structure and phylogeny of C. yacare and C. latirostris in Argentina; and (2) to perform a phylogenetic analysis of the genus Caiman throughout its entire distribution. The results show high haplotype diversity for both species but low nucleotide diversity for C. latirostris. Phylogenetic analysis shows a clear separation between both species but, surprisingly, a well-differentiated clade belonging to the Chaco region was observed. The phylogenetic analysis exhibited clades made up of the sequences of each Caiman species, with some inconsistencies: in the clade of C. crocodilus, one sequence of C. yacare is included, and one clade is observed including sequences from C. c. fuscus and C. c. chiapasius. These data indicate the need to undertake interdisciplinary studies to clarify the taxonomic status of these crocodilian species.
... This tectonic event locally changed the organic carbon burial and reduced southward heat transport, cooling the Southern Ocean and the land masses around it (Eagles et al., 2006). The second hypothesis consists of a global decline in atmospheric CO 2 (e.g., De Conto and Pollard, 2003) that may be related to the rapid increase in Cenozoic orography (Barbeau et al., 2009;Poblete et al., 2021), the contribution of arc volcanism (Sternai et al., 2020), or an increase of terrestrial and marine organic carbon burial (Galy et al., 2015). Regardless of the responsible mechanism, the rocks that document the onset of this glacial event are exceptionally well exposed in northeast King George Island (Figure 14; e.g., Warny et al., 2015); specifically in Polonez Cove (Figure 14; e.g., Birkenmajer, 1980;Warny et al., 2019a) and on the Melville Peninsula (Figure 13, e.g., Bikenmajer, 2001;Warny et al., 2015). ...
Over the last few decades, numerous geological studies have been carried out in the South Shetland Islands, which have greatly contributed to a better understanding of its geological evolution. However, few attempts have been conducted to correlate the geological units throughout this archipelago. We present herein a review of the literature available in the South Shetland Islands, which we use to propose a lithostratigraphical correlation that constitutes a coherent stratigraphy for the main Mesozoic and Cenozoic rocks of the South Shetland Islands along with a new geological map. The lithostratigraphical correlation shows that the geological and environmental evolution comprises three main stages: 1) deep marine sedimentation from ∼164 to 140 Ma, 2) subaerial volcanism and sedimentation with a proliferation of plants and fauna from ∼140 to 35 Ma and 3) glacial and interglacial deposits from ∼35 Ma. The lithostratigraphical correlation also shows a broad geographical trend of decreasing age of volcanism from southwest to northeast, which has been previously suggested. However, this spatial age trend is disrupted by the presence of Eocene magmatism in Livingston Island, located in the centre of the archipelago. We suggest that the migration of volcanism occurred from the Late Cretaceous until the early Eocene. Subsequently, enhanced magmatic activity took place from the mid-Eocene until the Miocene, which we associate with processes related with the waning of subduction. Constraining the protolith age of the metamorphic complex of Smith Island remains challenging, yet holds key implications for the tectonic and accretionary evolution of the Antarctic Peninsula. The rocks recording the glaciation of this sector of Antarctica are well exposed in the northern South Shetland Islands and hold critical information for understanding the timings and processes that lead to the greenhouse to icehouse transition at the end of the Eocene. Finally, contemporaneous rocks to the breakup of Antarctic Peninsula from Patagonia that led to the opening of the Drake Passage and the development of the Scotia Sea are exposed in the centre and north of the South Shetland archipelago. Better constraints on the age and tectonic settings on these units may lead to further understanding the paleobiogeographical evolution of the region, which may have played an important role for speciation as a land bridge between South America and Antarctica. The dataset containing the geological map and associated information is shared as a shapefile or KML file.
... During the Paleogene (c. 55 to 33 Ma), the Proto-Amazon-Orinoco river basin (Proto-Amazon basin, hereafter) drained the Sub-Andean Foreland basin, including much of northern South America and the northern La Plata region ( Fig. 1 A [18][19][20]. Third, tectonic reactivation and uplift of Serra do Mar and Serra da Mantiqueira ranges in southeastern Brazil during the Early Miocene (c. 23 to 16 Ma) re-routed some rivers from the La Plata basin directly to the Atlantic ( Fig. 1D; 21,[22][23][24], isolating many terrestrial and aquatic species in the coastal basins of the Atlantic Forest. ...
Landscape dynamics are widely thought to govern the tempo and mode of continental radiations, yet the effects of river network rearrangements on dispersal and lineage diversification remain poorly understood. We integrated an unprecedented occurrence dataset of 4,967 species with a newly compiled, time-calibrated phylogeny of South American freshwater fishes-the most species-rich continental vertebrate fauna on Earth-to track the evolutionary processes associated with hydrogeographic events over 100 Ma. Net lineage diversification was heterogeneous through time, across space, and among clades. Five abrupt shifts in net diversification rates occurred during the Paleogene and Miocene (between 30 and 7 Ma) in association with major landscape evolution events. Net diversification accelerated from the Miocene to the Recent (c. 20 to 0 Ma), with Western Amazonia having the highest rates of in situ diversification, which led to it being an important source of species dispersing to other regions. All regional biotic interchanges were associated with documented hydrogeographic events and the formation of biogeographic corridors, including the Early Miocene (c. 23 to 16 Ma) uplift of the Serra do Mar and Serra da Mantiqueira and the Late Miocene (c. 10 Ma) uplift of the Northern Andes and associated formation of the modern transcontinental Amazon River. The combination of high diversification rates and extensive biotic interchange associated with Western Amazonia yielded its extraordinary contemporary richness and phylogenetic endemism. Our results support the hypothesis that landscape dynamics, which shaped the history of drainage basin connections, strongly affected the assembly and diversification of basin-wide fish faunas.
... In the past two decades, several Eocene paleogeographic maps have been produced, such as those of Sewall et al. (2000), Bice and Marotzke (2001), Markwick (2007), Herold et al. (2014), Scotese (2014), He et al. (2019), and Poblete et al. (2021). These maps show large differences in the topography of East Asia, particularly the mountains in Southern China, including the Gangdese Mountains, the Nanling Mountains, and the Zhe-Min Highlands. ...
Inconsistencies in the Eocene climates of East Asia have been revealed in both geological studies and simulations. Several earlier reconstructions showed an arid zonal band in mid‐latitude China, but others showed a humid climate in the same region. Moreover, previous Eocene modeling studies have demonstrated that climate models can simulate both scenarios in China. Therefore, it is essential to investigate the cause of this model spread. We conducted a series of experiments using Norwegian Earth System Model 1‐F and examined the impact of mountains in Southern China on the simulated Eocene climate. These mountains, including the Gangdese and Southeast Mountains, are located along the main path of water vapor transport to East Asia. Our results reveal that the Southeast Mountains play the dominant role in controlling the simulated precipitation in Eastern China during the Eocene. When the heights of the Southeast Mountains exceed ∼2,000 m, an arid zonal band appears in mid‐latitude China, whereas humid climates appear in Eastern China when the elevation of the Southeast Mountains is relatively low.
... These paleoclimatic conditions were marked by >800 mm mean annual precipitation, >140 mm mean precipitation in the warmest month, >4 mm precipitation in the coldest month, >10°C mean annual temperature, >23°C mean temperature in the warmest month, and >0°C mean temperature in the coldest month (16). Temporal and spatial distributions of carbonate 18 O and 13 C across Asia support the notion that, during the Oligocene, regional moisture in the Lanzhou Basin was predominantly transported by the Asian summer monsoon from the western Pacific and Northern Indian Oceans, with a smaller additional winter moisture transport by the westerlies from the shallow proto-Paratethys Sea (25), which was located to the west of the Tibetan Plateau (Fig. 1A) (26). Thus, the high-resolution Rb/Sr and lf records from the Lanzhou Basin, which reflect regional pedogenesis and magnetic mineral transport, were predominantly controlled by changes in summer monsoon precipitation on orbital time scales. ...
Constraining monsoon variability and dynamics in the warm unipolar icehouse world of the Late Oligocene can provide important clues to future climate responses to global warming. Here, we present a ~4-thousand year (ka) resolution rubidium-to-strontium ratio and magnetic susceptibility records between 28.1 and 24.1 million years ago from a distal alluvial sedimentary sequence in the Lanzhou Basin (China) on the northeastern Tibetan Plateau margin. These Asian monsoon precipitation records exhibit prominent short (~110-ka) and long (405-ka) eccentricity cycles throughout the Late Oligocene, with a weak expression of obliquity (41-ka) and precession (19-ka and 23-ka) cycles. We conclude that a combination of eccentricity-modulated low-latitude summer insolation and glacial-interglacial Antarctic Ice Sheet fluctuations drove the eccentricity-paced precipitation variability on the northeastern Tibetan Plateau in the Late Oligocene high CO 2 world by governing regional temperatures, water vapor loading in the western Pacific and Indian Oceans, and the Asian monsoon intensity and displacement.
... Although some studies inferred that paleoseawater likely originated from the northwest (e.g., the proto-Paratethys Sea; Wang et al. 49 ), this recharge model cannot explain the observation that late Cretaceous marine deposits were absent between the Qiangtang and the Simao-Khorat Basins 47 . Rather, the pronounced southward thickening trends of the evaporite marker intervals 50 , together with the terrestrial palaeogeographic reconstruction of East Asia spanning the late Cretaceous-early Palaeogene transition (e.g., Poblete et al. 51 ) likely argue for a transgression of the Neo-Tethyan Ocean from the south or southwest (e.g., refs. 48,50 ). ...
The establishment of continental-scale drainage systems on Earth is largely controlled by topography related to plate boundary deformation and buoyant mantle. Drainage patterns of the great rivers in Asia are thought to be highly dynamic during the Cenozoic collision of India and Eurasia, but the drainage pattern and landscape evolution prior to the development of high topography in eastern Tibet remain largely unknown. Here we report the results of petro-stratigraphy, heavy-mineral analysis, and detrital zircon U-Pb dating from late Cretaceous–early Palaeogene sedimentary basin strata along the present-day eastern margin of the Tibetan Plateau. Similarities in the provenance signatures among basins indicate that a continental-scale fluvial system once drained southward into the Neo-Tethyan Ocean. These results challenge existing models of drainage networks that flowed toward the East Asian marginal seas and require revisions to inference of palaeo-topography during the Late Cretaceous. The presence of a continent-scale river may have provided a stable long-term base level which, in turn, facilitated the development of an extensive low-relief landscape that is preserved atop interfluves above the deeply incised canyons of eastern Tibet.
... For instance, the sensitivity of 18 O w to regional, global, and topographic variations in paleotemperature, environmental conditions of an air mass prior to orographic ascent, evapotranspiration, water vapor recycling, and changes in vapor source has been shown to introduce uncertainties in stable-isotopebased elevation reconstructions (e.g., Mulch, 2016;Botsyun et al., 2020, Botsyun andEhlers 2021). In particular, isotopic changes over continental Europe could be related to a variety of factors such as declining pCO 2 levels (Pagani et al., 1999), variable ocean circulation and sea surface temperatures (Flower and Kennett, 1994;Wright et al., 1992), sea-level fluctuations (Foster and Rohling, 2013), paleogeographic changes (Herold et al., 2008;Poblete et al., 2021), and other processes affecting 18 O w (Botsyun et al., 2019;Poulsen et al., 2007;Risi et al., 2008;Roe et al., 2016;Sewall and Fricke, 2013;Sturm et al., 2010). We thus compare our newly refined near-sea-level 18 O estimate with paleoclimate simulations from the isotope-enabled ECHAM5-wiso atmospheric general circulation model (iGCM), which predicts changes in 18 O of precipitation. ...
Reconstructing Oligocene–Miocene paleoelevation
contributes to our understanding of the evolutionary history of the European
Alps and sheds light on geodynamic and Earth surface processes involved in
the development of Alpine topography. Despite being one of the most
intensively explored mountain ranges worldwide, constraints on the elevation
history of the European Alps remain scarce. Here we present stable and
clumped isotope measurements to provide a new paleoelevation estimate for
the mid-Miocene (∼14.5 Ma) European Central Alps. We apply
stable isotope δ–δ paleoaltimetry to near-sea-level
pedogenic carbonate oxygen isotope (δ18O) records from the
Northern Alpine Foreland Basin (Swiss Molasse Basin) and high-Alpine
phyllosilicate hydrogen isotope (δD) records from the Simplon Fault
Zone (Swiss Alps). We further explore Miocene paleoclimate and
paleoenvironmental conditions in the Swiss Molasse Basin through carbonate
stable (δ18O, δ13C) and clumped (Δ47)
isotope data from three foreland basin sections in different alluvial
megafan settings (proximal, mid-fan, and distal). Combined pedogenic
carbonate δ18O values and Δ47 temperatures
(30±5 ∘C) yield a near-sea-level precipitation
δ18Ow value of -5.8±1.2 ‰ and, in
conjunction with the high-Alpine phyllosilicate δD value of -14.6±0.3 ‰, suggest that the region surrounding the
Simplon Fault Zone attained surface elevations of >4000 m no
later than the mid-Miocene. Our near-sea-level δ18Ow
estimate is supported by paleoclimate (iGCM ECHAM5-wiso) modeled δ18O values, which vary between −4.2 ‰ and −7.6 ‰ for
the Northern Alpine Foreland Basin.
Plate tectonic and paleogeographic maps are presented for nine time intervals during the Ordovician: early Tremadocian (485 Ma), late Tremadocian (480 Ma), early Floian (475 Ma), earliest Dapingian (470 Ma), early Darriwilian (465 Ma), late Darriwilian (460 Ma), middle Sandbian (455 Ma), middle Katian (450 Ma), and early Hirnantian (445 Ma). The maps show the location of active plate boundaries (i.e., subduction zones, mid-ocean rifts, transform faults, island arcs, and collision zones) and the age of the ocean floor. During the Ordovician there were six continental plates: Gondwana, Laurentia, Baltica, Cathaysia, Avalonia, and Cuyania; six oceanic plates: Iapetus, Ran, Kipchak, and Panthallasa (1-3); as well as several poorly constrained back-arc basins: Zealandia, Alexander, and Farwell. Paleogeographic maps illustrate the ancient distribution of mountains, land, shallow seas, and deep ocean basins. A plate tectonic model was used to predict the changing age of the ocean floor and hence the changing volume of the ocean basins and the resulting degree of continental flooding. Sea level was high during the early Ordovician, fell during the middle Ordovician, and rose again during the late Ordovician. A precipitous fall in sea level occurred at the end of the Ordovician during the short-lived Hirnantian Ice Age.
Supplementary material at https://doi.org/10.6084/m9.figshare.c.6381072
The extant tropical tribe Hybocephalini is a morphologically highly derived group of the subfamily Pselaphinae (Coleoptera: Staphylinidae), which is characterized most notably by the modified squamous setae that cover various parts of the body. Ten genera and 69 extant species have been found in the Afrotropical and Oriental regions, with one species found in northern Australia. Prior to this study the evolutionary history of the tribe has been remained elusive due to the dearth of known fossils. Here, we describe the first fossil representative of Hybocephalini, Europharinodes schaufussi Yin & Cai gen. et sp. nov. , based on an adult male preserved in Baltic amber ( ca 45.0–38.0 Ma). Using X-ray microtomography, the anatomy including the endoskeletal structures of the head, the full pattern of foveation, and the aedeagus of the beetle were reconstructed. Europharinodes shares most derived traits that are congruent with extant members of Hybocephalini, but it also possesses plesiomorphic and autapomorphic characters unknown in living relatives. In order to constrain the phylogenetic placement of Europharinodes , we created an updated morphological character matrix to explore relationships among this genus and related groups. A monophyletic Hybocephalini was recovered by maximum likelihood and parsimony analyses, with Europharinodes being well-resolved as sister to all modern relatives in the likelihood tree. The fossil thus sheds new light on the morphological evolution of Hybocephalini and suggests a broader palaeodistribution of the tribe during the middle Eocene. The disjunct distribution of an Eocene Baltic amber species and an extant Afrotropical-Oriental distribution of the tribe is probably relictual, and was shaped by global cooling during the Eocene–Oligocene transition.
L'Éocène (56 - 33,9 Ma) est une époque charnière dans l’évolution du climat au cours du Phanérozoïque. Elle est caractérisée par des changements de géographie importants, des évènements de réchauffements climatiques extrêmes, mais aussi, après près de 260 Ma de températures globalement plus élevées par un long refroidissement, initiant l’englacement à l'échelle continentale de l'Antarctique à la limite Éocène-Oligocène (~ 33,5 Ma). Cette thèse s'intéresse à la fois aux causes et aux conséquences de cette détérioration du climat. Une première partie analyse tout d’abord, les répercussions de l’ouverture du passage de Drake sur le système océanique (circulation globale et températures). Nos résultats, en accord avec de précédentes études de géochimie (notamment isotopes de l’oxygène, du carbone et du néodyme) indiquent la mise en place d’un proto-courant circumpolaire antarctique et d’une réorganisation de la circulation profonde dès les premiers stades d’ouverture du passage (100 m de profondeur), et la mise en place d’une différenciation thermique au sein de l’Atlantique avec des eaux plus froides dans l’hémisphère Sud. Nous montrons par ailleurs que, bien qu’il ne soit pas directement responsable de la progression de la calotte de glace Antarctique, cet évènement pourrait avoir participé à la mise en place de conditions climatiques y étant favorables. Une deuxième partie s'intéresse plus particulièrement à la Transition Éocène-Oligocène (EOT, ~ 34 Ma) à travers les répercussions de la baisse de la pCO2, de l'englacement de l'Antarctique et, de la chute du niveau marin associée, sur les systèmes océanique et continental. Une place importante est dédiée à la modélisation des changements de saisonnalité annuelle des températures. Cette analyse permet de reconstruire la présence de zones de fort renforcement des saisons, lesquelles pourraient avoir contribué à expliquer une partie des renouvellements de la biodiversité au cours de l’EOT. Enfin, une troisième partie tend à évaluer l’impact de l’évolution des forçages climatiques évoqués dans les chapitres précédents sur la productivité primaire marine. Nous montrons qu’à travers son effet sur la distribution des nutriments, l’ouverture du passage de Drake favorise le développement de phytoplancton, lequel pourrait avoir joué un rôle dans la chute de la pCO2 au cours de l’Éocène.
The Eocene (56 - 33.9 Ma) is a key epoch in the evolution of the climate during the Phanerozoic. It is characterized by significant changes in geography, extreme climate warming events, but also, after nearly 260 Ma of globally higher temperatures by a long cooling, initiating the formation of continental-scale ice sheet on Antarctica at the Eocene-Oligocene boundary (~ 33.5 Ma). This thesis focuses both on the causes and consequences of this climate deterioration. A first part analyzes, the repercussions of the opening of the Drake Passage on the ocean system (global circulation and temperatures). Our results, in agreement with previous geochemical studies (notably isotopes of oxygen, carbon and neodymium) indicate the establishment of a proto-Antarctic Circumpolar Current and a reorganization of the deep circulation from the first stages of the passage’s opening (100 m deep), and the establishment of thermal differentiation within the Atlantic with colder waters in the Southern Hemisphere. We also show that, although it is not directly responsible for the progression of the Antarctic ice cap, this event may have contributed to the establishment of favorable climatic conditions. A second part focuses on the Eocene-Oligocene Transition (EOT, ~ 34 Ma) through the impact of declining pCO2 and, Antarctic Ice-sheet formation and the associated sea level drop, on ocean and continental systems. An important place is dedicated to the modelling of temperature seasonality changes. This analysis reconstructs the presence of strong seasonality strengthening zones, which could have contributed to explain part of the renewal of biodiversity across the EOT. Finally, a third part tends to evaluate the impact of the evolution of the climatic forcings evoked in the preceding chapters on marine primary productivity. We show that through its effect on the distribution of nutrients, the opening of the Drake Passage favors the development of phytoplankton, which may have played a role in the drop in pCO2 during the Eocene.
Orogens that form at convergent plate boundaries typically consist of accreted rock units that form a highly incomplete archive of subducted oceanic and continental lithosphere, as well as of deformed crust of the former upper plate. Reading the construction of orogenic architecture forms the key to decipher the paleogeographic distribution of oceans and continents and bathymetric and topographic features that existed thereon, such as igneous plateaus or seamounts, microcontinents or magmatic arcs. Current classification schemes of orogens divide between settings associated with termination of subduction (continent-continent collision, continent-ocean collision (obduction)) and with ongoing subduction (accretionary orogenesis), alongside intraplate orogens. Perceived diagnostic features for such classifications heavily hinge on dynamic interpretations linking downgoing plate paleogeography, particularly continental collision, to upper plate deformation, plate motion changes, or magmatism. Here, we show, however, that Mesozoic-Cenozoic orogens that undergo collision almost all defy these proposed diagnostic features and behave like accretionary orogens instead. To reconstruct paleogeography of subducted and upper plates, we therefore propose an alternative approach to navigating through orogenic architecture: subducted plate units comprise nappes (or melanges) with Ocean Plate Stratigraphy (OPS) and Continental Plate Stratigraphy (CPS) stripped from their now-subducted or otherwise underthrusted lower crustal and mantle lithospheric underpinnings. Upper plate paleogeography and deformation responds to the competition between absolute motion of the upper plate and the subducting slab. Our navigation approach through orogenic architecture contains no a priori dynamic interpretations that link downgoing plate paleogeography to deformation or magmatic responses in the upper plate and thus provide an independent basis for geodynamic analysis. From our analysis we identify ‘rules of orogenesis’ that link the rules of rigid plate tectonics with the reality of plate deformation. We illustrate the use of these rules with a thought experiment, in which we predict orogenic architecture that results from subducting the present-day Indian ocean and colliding the Somali, Madagascar, and Indian margins using a published continental drift scenario for a future supercontinent as basis. We illustrate that our inferred rules (of thumb) generate orogenic architecture comparable to elements of modern orogens, unlocking the well-known modern geography for interpreting paleogeography from orogens that formed since the birth of plate tectonics.
Reconstructing Oligocene-Miocene paleoelevation contributes to our understanding of the evolutionary history of the European Alps and sheds light on geodynamic and Earth’s surface processes involved in the development of Alpine topography. Despite being one of the most intensively explored mountain ranges worldwide, constraints on the elevation history of the European Alps, however, remain scarce. Here we present stable and clumped isotope geochemistry measurements to provide a new paleoelevation estimate for the mid-Miocene (~14.5 Ma) European Central Alps. We apply stable isotope δ-δ paleoaltimetry on near sea level pedogenic carbonate oxygen isotope (δ18O) records from the Northern Alpine Foreland Basin (Swiss Molasse Basin) and high-Alpine phyllosilicate hydrogen isotope (δD) records from the Simplon Fault Zone (Swiss Alps). We further explore Miocene paleoclimate and paleoenvironmental conditions in the Swiss Molasse Basin through carbonate stable (δ18O, δ13C) and clumped (Δ47) isotope data from three foreland basin sections in different alluvial megafan settings (proximal, mid-fan, and distal). Combined pedogenic carbonate δ18O values and Δ47 temperatures (30 ± 5 °C) yield a near sea level precipitation δ18Ow value of −5.8 ± 0.2 ‰ and in conjunction with the high-Alpine phyllosilicate δD record suggest that the region surrounding the SFZ attained surface elevations of > 4000 m no later than the mid-Miocene. Our near sea level δ18Ow estimate is supported by paleoclimate (iGCM Echam5-wiso) modeled δ18O values, which vary between −4.2 and −7.6 ‰ for the Northern Alpine Foreland Basin.
Plain Language Summary
The Tibetan plateau is Earth’s highest and largest plateau and has a protracted growth history closely related to Cenozoic convergence between India and Asia. Resolving its paleoelevation in the early Cenozoic is instructive to understand its growth history and Asian climate changes. Although paleoaltimetry studies have provided critical constraints for the southern Tibetan plateau during Paleogene, the paleoelevation of the northern Tibet remains enigmatic. The largest basin in the plateau is the Qaidam Basin, surrounded by high elevation thrust belts. We conducted flexural modeling of early Cenozoic strata from the Qaidam basin, which suggests higher topography in the north (0.4–1.5 km) and lower topography (0.4–1.0 km) in the south. This unique topographic relief in the northern Tibetan plateau suggests that very significant surface uplift (3–4 km) occurred along the southern margin of Qaidam basin in the late Cenozoic. These results of early topographic relief in northern Tibet support hypotheses of a Paleogene warmer and more humid climate in North Tibet. This study provides a new approach that provides an independent constraint on the Paleogene paleoelevation of northern Tibet, contributing to our understanding of the growth of the Tibetan plateau and Asian paleoclimate.
El Grupo Mapa Geológico de Colombia está adscrito a la Dirección de Geociencias Básicas del Servicio Geológico Colombiano (SGC) y su objetivo es realizar versiones periódicas y actualizadas de las 26 planchas del Atlas Geológico de Colombia (AGC). La primera edición de este atlas fue publicada en 2007; la segunda, en 2015; y esta, la tercera, se libera en 2020.
Esta tercera edición del AGC se actualizó con los mapas geológicos a escala 1:100 000 publicados por el SGC, con los datos de los artículos científicos publicados en revistas indexadas desde noviembre de 2014 hasta diciembre de 2019 y con los capítulos de los cuatro volúmenes de la obra The Geology of Colombia. Las unidades cronoestratigráficas, fallas y pliegues del mapa se ajustaron con la imagen de relieve sombreado de Colombia a escala 1:100 000 creada para este fin.
Las unidades representadas en el mapa son unidades cronoestratigráficas y fueron agrupadas de acuerdo a la edad y la litología de los materiales. Para la edad se utilizó como referencia la Carta Cronoestratigráfica Internacional 2020 y para la división litológica se diferenciaron las rocas y los depósitos. Las rocas se representaron según su clasificación principal: ígneas, metamórficas y sedimentarias; también, se consideraron las rocas volcanoclásticas como un tipo adicional. Los depósitos se dividieron en paludal, aluvial, volcanoclástico, morrénico, de terraza, de abanico, de caída de ceniza, de dunas y de costas. Las rocas ígneas se clasificaron por ambiente de formación en volcánicas, hipoabisales y plutónicas; estas a su vez se subdividieron por composición en ultramáficas, máficas, intermedias y félsicas. Las rocas metamórficas se separaron por grado de metamorfismo en muy bajo, bajo, medio y alto grado; y se diferenciaron las de alta presión y, por su importancia económica, los mármoles. Las rocas sedimentarias y volcanoclásticas se agruparon según su ambiente de formación. Las primeras se clasificaron en continental, transicional, continental–transicional, continental–transicional–marino, transicional–marino y marino, mientras que las segundas, en continental, continental–transicional y marino.
En el AGC 2020 las unidades cronoestratigráficas, fallas y pliegues del mapa se ajustaron con la imagen de relieve sombreado de Colombia a escala 1:100 000 creada para este fin. Los usuarios pueden consultar el mapa en diversos formatos: SIG (File Geodatabase, MXD, style), PDF y TIFF.
The early and late Eocene have both been the subject of many modelling studies, but few have focused on the middle Eocene. The latter still holds many challenges for climate modellers but is also key to understanding the events leading towards the conditions needed for Antarctic glaciation at the Eocene–Oligocene transition. Here, we present the results of CMIP5-like coupled climate simulations using the Community Earth System Model (CESM) version 1. Using a new detailed 38 Ma geography reconstruction and higher model resolution compared to most previous modelling studies and sufficiently long equilibration times, these simulations will help to further understand the middle to late Eocene climate. At realistic levels of atmospheric greenhouse gases, the model is able to show overall good agreement with proxy records and capture the important aspects of a warm greenhouse climate during the Eocene.
With a quadrupling of pre-industrial concentrations of both CO2 and CH4 (i.e. 1120 ppm and ∼2700 ppb, respectively, or 4 × PIC; pre-industrial carbon), sea surface temperatures correspond well to the available late middle Eocene (42–38 Ma; ∼ Bartonian) proxies. Being generally cooler, the simulated climate under 2 × PIC forcing is a good analogue for that of the late Eocene (38–34 Ma; ∼ Priabonian). Terrestrial temperature proxies, although their geographical coverage is sparse, also indicate that the results presented here are in agreement with the available information.
Our simulated middle to late Eocene climate has a reduced Equator-to-pole temperature gradient and a more symmetric meridional heat distribution compared to the pre-industrial reference. The collective effects of geography, vegetation, and ice account for a global average 5–7 ∘C difference between pre-industrial and 38 Ma Eocene boundary conditions, with important contributions from cloud and water vapour feedbacks. This helps to explain Eocene warmth in general, without the need for greenhouse gas levels much higher than indicated by proxy estimates (i.e. ∼500–1200 ppm CO2) or low-latitude regions becoming unreasonably warm. High-latitude warmth supports the idea of mostly ice-free polar regions, even at 2 × PIC, with Antarctica experiencing particularly warm summers. An overall wet climate is seen in the simulated Eocene climate, which has a strongly monsoonal character.
Equilibrium climate sensitivity is reduced (0.62 ∘C W−1 m2; 3.21 ∘C warming between 38 Ma 2 × PIC and 4 × PIC) compared to that of the present-day climate (0.80 ∘C W−1 m2; 3.17 ∘C per CO2 doubling). While the actual warming is similar, we see mainly a higher radiative forcing from the second PIC doubling. A more detailed analysis of energy fluxes shows that the regional radiative balance is mainly responsible for sustaining a low meridional temperature gradient in the Eocene climate, as well as the polar amplification seen towards even warmer conditions. These model results may be useful to reconsider the drivers of Eocene warmth and the Eocene–Oligocene transition (EOT) but can also be a base for more detailed comparisons to future proxy estimates.
The evolution of the Northern Hemisphere oceanic gateways has facilitated ocean circulation changes and may have influenced climatic variations in the Cenozoic time (66 Ma–0 Ma). However, the timing of these oceanic gateway events is poorly constrained and is often neglected in global paleobathymetric reconstructions. We have therefore re-evaluated the evolution of the Northern hemisphere oceanic gateways (i.e. the Fram Strait, Greenland–Scotland Ridge, the Central American Seaway, and the Tethys Seaway) and embedded their tectonic histories in a new global paleobathymetry and topography model for the Cenozoic time. Our new paleobathymetry model incorporates Northeast Atlantic paleobathymetric variations due to Iceland mantle plume activity, updated regional plate kinematics, and models for the oceanic lithospheric age, sediment thickness, and reconstructed oceanic plateaus and microcontinents. We also provide a global paleotopography model based on new and previously published regional models. In particular, the new model documents important bathymetric changes in the Northeast Atlantic and in the Tethys Seaway at Eocene–Oligocene transition (~34 Ma), the time of the first glaciations of Antarctica, believed to be triggered by the opening of the Southern Ocean gateways (i.e. the Drake Passage and the Tasman Gateway) and subsequent Antarctic Circumpolar Current initiation. Our new model can be used to test whether the Northern Hemisphere gateways could have also played an important role modulating ocean circulation and climate at that time. In addition, we provide a set of realistic global bathymetric and topographic reconstructions for the Cenozoic time at one million-year interval for further use in paleo-ocean circulation and climate models.
Understanding of the role of ocean circulation on climate during the Late Cretaceous is contingent on the ability to reconstruct its modes and evolution. Geochemical proxies used to infer modes of past circulation provide conflicting interpretations for the reorganization of the ocean circulation through the Late Cretaceous. Here, we present climate model simulations of the Cenomanian (100.5–93.9 Ma) and Maastrichtian (72.1–66.1 Ma) stages of the Cretaceous with the CCSM4 earth system model. We focus on intermediate (500–1500 m) and deep (> 1500 m) ocean circulation and show that while there is continuous deep-water production in the southwestern Pacific, major circulation changes occur between the Cenomanian and Maastrichtian. Opening of the Atlantic and Southern Ocean, in particular, drives a transition from a mostly zonal circulation to enhanced meridional exchange. Using additional experiments to test the effect of deepening of major ocean gateways in the Maastrichtian, we demonstrate that the geometry of these gateways likely had a considerable impact on ocean circulation. We further compare simulated circulation results with compilations of εNd records and show that simulated changes in Late Cretaceous ocean circulation are reasonably consistent with proxy-based inferences. In our simulations, consistency with the geologic history of major ocean gateways and absence of shift in areas of deep-water formation suggest that Late Cretaceous trends in εNd values in the Atlantic and southern Indian oceans were caused by the subsidence of volcanic provinces and opening of the Atlantic and Southern oceans rather than changes in deep-water formation areas and/or reversal of deep-water fluxes. However, the complexity in interpreting Late Cretaceous εNd values underscores the need for new records as well as specific εNd modeling to better discriminate between the various plausible theories of ocean circulation change during this period.
The Tajik basin archives the orogenic evolution of the Pamir hinterland.
Stratigraphic‐sedimentologic observations from Cretaceous‐Pliocene strata along its eastern margin describe the depositional environment and basin‐formation stages in reaction to hinterland exhumation and
basin inversion. During the Late Cretaceous‐Eocene (preorogenic stage: ~100–34 Ma), a shallow‐marine to terrestrial basin extended throughout Central Asia. An alluvial plain with influx of conglomerate bodies (Baljuvon Formation) indicates a first pulse of hinterland erosion and foreland‐basin formation in the late Oligocene‐early Miocene (synorogenic stage Ia: ~34–23 Ma). Further hinterland exhumation deposited massive alluvial conglomerates (Khingou Formation) in the early‐middle Miocene (synorogenic stage Ib: ~23–15 Ma). Westward thickening growth strata suggest transformation of the Tajik basin into the Tajik fold‐thrust belt in the middle‐late Miocene (synorogenic stage IIa: ~15–5 Ma). Increased water supply led to the formation of fluvial mega‐fans (Tavildara Formation). Latest Miocene‐Pliocene shortening
constructed basin morphology that blocked sediment bypass into the central basin from the east (Karanak Formation), triggering drainage‐system reorganization from transverse to longitudinal sediment transport
(synorogenic stage IIb: < ~5 Ma). Accelerated shortening (~27–20 Ma) and foreland‐directed collapse (~23–12 Ma) of Pamir‐plateau crust loaded the foreland and induced synorogenic stages Ia and Ib. Coupling
of Indian and Asian cratonic lithospheres and onset of northward and westward delamination/rollback of Asian lithosphere (i.e., lithosphere of the Tajik basin) beneath the Pamir at ~12–11 Ma transformed the
Tajik basin into the Tajik fold‐thrust belt (synorogenic stage IIa). The timing of the sedimentologically derived basin reconfiguration matches the thermochronologically derived onset of Tajik‐basin inversion at ~12 Ma.
Abstract. While the early Eocene has been considered in many modelling studies, detailed simulations of the middle and late Eocene climate are currently scarce. To get a better understanding of both Antarctic glaciation at the Eocene-Oligocene transition (~34 Ma) and late middle Eocene warmth, it is vital to have an adequate reconstruction of the middle-to-late Eocene climate. Results of higher (CMIP5-like) resolution coupled climate simulations are represented here using the Community Earth System Model (CESM) version 1. Two middle-to-late Eocene cases are considered with the same general boundary conditions but a different radiative forcing, using a new detailed 38 Ma geography reconstruction.
Under 4× pre-industrial concentrations (PIC) of both CO<sub>2</sub> (i.e. 1120 ppm) and CH<sub>4</sub> (~2700 ppb), equilibrium sea surface temperatures correspond well to the available late middle Eocene (42–38 Ma; ~Bartonian) proxies. Being generally cooler, the simulated climate under 2× PIC forcing is a good analog for that of the late Eocene (38–34 Ma; ~Priabonian). Terrestrial temperature proxies, although their geographical coverage is sparse, also indicate that the results presented here are realistic.
The reconstructed 38 Ma climate has a reduced equator-to-pole temperature gradient and a more symmetric meridional heat distribution compared to the pre-industrial reference. The collective effects of geography, vegetation and ice accounts for a global mean 5–7 °C difference between pre-industrial and 38 Ma Eocene boundary conditions, with important contributions from cloud and water vapour feedbacks. These simulations effectively show that a realistic middle-to-late Eocene climate can be reconstructed without the need for greenhouse gas concentrations much higher than proxy estimates (i.e. ~500–1200 ppm CO<sub>2</sub>).
Equilibrium climate sensitivity is reduced (0.62 °C/W m<sup>2</sup>; 3.2 °C warming between 38 Ma 2× PIC and 4× PIC) compared to that of the present-day climate (0.79 °C/W m<sup>2</sup>; 3.1 °C per CO<sub>2</sub> doubling). Despite very limited sea ice and snow cover in both 38Ma cases, the model still shows a factor ~2 polar amplification in response to a further increase of atmospheric greenhouse gas concentrations. High latitudes in the modelled Eocene climate are mainly kept warm by an altered radiative balance in combination with global changes in geography and the absence of polar ice sheets compared to the pre-industrial reference.
Previous studies of the central United States Cordillera have indicated that a high-elevation orogenic plateau, the Nevadaplano, was present in Late Cretaceous to early Paleogene time. The southern United States Cordillera and northern Mexican Cordillera share a similar geologic history and many of the same tectonic features (e.g., metamorphic core complexes) as the central United States Cordillera, raising the possibility that a similar plateau may have been present at lower latitudes. To test the hypothesis of an elevated plateau, we examined Laramide-age continental-arc geochemistry and employed an empirical relation between whole-rock La/Yb and Moho depth as a proxy for crustal thickness. Calculations of crustal thickness from individual data points range between 45 and 72 km, with an average of 57 ± 12 km (2σ) for the entire data set, which corresponds to 3 ± 1.8 km paleoelevation assuming simple Airy isostasy. These crustal thickness and paleoaltimetry estimates are similar to previous estimates for the Nevadaplano and are interpreted to suggest that an analogous high-elevation plateau may have been present in the southern United States Cordillera. This result raises questions about the mechanisms that thickened the crust, because shortening in the Sevier thrust belt is generally not thought to have extended into the southern United States Cordillera, south of ~35°N latitude.
Established theories ascribe much of the observed long-term Cenozoic climate cooling to atmospheric carbon consumption by erosion and weathering of tectonically uplifted terrains, but climatic effects due to changes in magmatism and carbon degassing are also involved. At timescales comparable to those of Milankovitch cycles, late Cenozoic building/melting of continental ice-sheets, erosion and sea level changes can affect magmatism, which provides an opportunity to explore possible feedbacks between climate and volcanic changes. Existing data show that extinction of Neo-Tethyan volcanic arcs is largely synchronous with phases of atmospheric carbon reduction, suggesting waning degassing as a possible contribution to climate cooling throughout the early to middle Cenozoic. In addition, the increase in atmospheric CO2 concentrations during the last deglaciation may be ascribed to enhanced volcanism and carbon emissions due to unloading of active magmatic provinces on continents. The deglacial rise in atmospheric CO2 points to a mutual feedback between climate and volcanism mediated by the redistribution of surface masses and carbon emissions. This may explain the progression to higher amplitude and increasingly asymmetric cycles of late Cenozoic climate oscillations. Unifying theories relating tectonic, erosional, climatic, and magmatic changes across timescales via the carbon cycle offers an opportunity for future research into the coupling between surface and deep Earth processes.
The modern physiography of central Turkey is dominated by the 1-km-high Central Anatolian Plateau and the Central Tauride mountains that form the southern plateau margin. These correspond to a Cretaceous–Eocene backarc extensional province and forearc fold-thrust belt, respectively. The extent to which the morphology of the Miocene plateau was inherited from the physiography of the Cretaceous–Eocene subduction zone that assembled the Anatolian crust has not been tested but is important if we are to isolate the signal of Miocene and younger subduction dynamics in the formation of the modern plateau margin. There is no known stratigraphic record of the post-Eocene pre-Miocene evolution of the Taurides. We therefore collected rock samples across the Taurides and used zircon (U-Th)/He (ZHe), apatite (U-Th)/He (AHe), and apatite fission-track (AFT) low-temperature thermochronometers to constrain cooling; we interpret these thermochronometers to signal erosional exhumation. We use inverse thermal modeling to aid interpretation of our results and find that: (1) thermochronometers across the Taurides were reset as a result of heating by the emplacement of the Antalya and Bozkır nappes; (2) AFT and ZHe Eocene cooling ages are related to structurally driven uplift and erosional exhumation on major thrust culminations; (3) dispersed AHe ages record low rates of Oligocene–early Miocene cooling and hence low rates of erosional exhumation; and (4) fast rates of cooling were determined for samples along the margin of the Köprüçay Basin. We interpret that early Miocene cooling is a signal of active erosion of the western Central Taurides at a time of marine sedimentation in the Mut Basin on the southern Central Taurides, and these differing histories may reflect evolution above the Antalya and Cyprus slabs. Our thermochronological data, the enigmatic development of the Antalya Basin, and thrusting within the basin may be explained as the surface expression of stepwise delamination of the Antalya slab from the Tauride hinterland to its current position below the Gulf of Antalya since early Miocene time over a distance of ~150 km.
Convergence between the Indian and Asian plates has reshaped large parts of Asia, changing regional climate and biodiversity, yet geodynamic models fundamentally diverge on how convergence was accommodated since the India–Asia collision. Here we report palaeomagnetic data from the Burma Terrane, which is at the eastern edge of the collision zone and is famous for its Cretaceous amber biota, to better determine the evolution of the India–Asia collision. The Burma Terrane was part of a Trans-Tethyan island arc and stood at a near-equatorial southern latitude at ~95 Ma, suggesting island endemism for the Burmese amber biota. The Burma Terrane underwent significant clockwise rotation between ~80 and 50 Ma, causing its subduction margin to become hyper-oblique. Subsequently, it was translated northward on the Indian Plate by an exceptional distance of at least 2,000 km along a dextral strike-slip fault system in the east. Our reconstructions are only compatible with geodynamic models involving an initial collision of India with a near-equatorial Trans-Tethyan subduction system at ~60 Ma, followed by a later collision with the Asian margin.
Late Cretaceous trench basin strata were deposited in the subduction zone that consumed Neo-Tethyan oceanic lithosphere along the southern margin of the proto–Tibetan Plateau. We conducted detrital zircon (DZ) U-Pb geochronology on six trench basin samples (n = 1716) collected near Dênggar, Tibet (~500 km west of Lhasa), to assess the provenance of these rocks and reconstruct Late Cretaceous sediment transport pathways. They contained DZ ages that point to a unique source around Lhasa city, north of the Late Cretaceous Gangdese magmatic arc. The modern Lhasa River catchment contains the requisite sources, and its main trunk transects the Gangdese magmatic arc, joining with the Yarlung River at a barbed junction at the India-Asia suture. We infer that the Lhasa River is an ancient feature that transported sediment to the subduction zone in Late Cretaceous time and persisted during India-Asia collision.
The basins and orogens of the Mediterranean region ultimately result from the opening of oceans during the early break-up of Pangea since the Triassic, and their subsequent destruction by subduction accommodating convergence between the African and Eurasian Plates since the Jurassic. The region has been the cradle for the development of geodynamic concepts that link crustal evolution to continental break-up, oceanic and continental subduction, and mantle dynamics in general. The development of such concepts requires a first-order understanding of the kinematic evolution of the region for which a multitude of reconstructions have previously been proposed. In this paper, we use advances made in kinematic restoration software in the last decade with a systematic reconstruction protocol for developing a more quantitative restoration of the Mediterranean region for the last 240 million years. This restoration is constructed for the first time with the GPlates plate reconstruction software and uses a systematic reconstruction protocol that limits input data to marine magnetic anomaly reconstructions of ocean basins, structural geological constraints quantifying timing, direction, and magnitude of tectonic motion, and tests and iterations against paleomagnetic data. This approach leads to a reconstruction that is reproducible, and updatable with future constraints. We first review constraints on the opening history of the Atlantic (and Red Sea) oceans and the Bay of Biscay. We then provide a comprehensive overview of the architecture of the Mediterranean orogens, from the Pyrenees and Betic-Rif orogen in the west to the Caucasus in the east and identify structural geological constraints on tectonic motions. We subsequently analyze a newly constructed database of some 2300 published paleomagnetic sites from the Mediterranean region and test the reconstruction against these constraints. We provide the reconstruction in the form of 12 maps being snapshots from 240 to 0 Ma, outline the main features in each time-slice, and identify differences from previous reconstructions, which are discussed in the final section.
Accurate models of past Antarctic ice sheet behaviour require realistic reconstructions of the evolution of bedrock topography. However, other than a preliminary attempt to reconstruct Antarctic topography at the Eocene–Oligocene boundary, the long-term evolution of Antarctica's subglacial topography throughout its glacial history has not previously been quantified. Here, we derive new reconstructions of Antarctic topography for four key time slices in Antarctica's climate and glacial history: the Eocene–Oligocene boundary (ca. 34 Ma), the Oligocene–Miocene boundary (ca. 23 Ma), the mid-Miocene climate transition (ca. 14 Ma), and the mid-Pliocene warm period (ca. 3.5 Ma). To reconstruct past topography, we consider a series of processes including ice sheet loading, volcanism, thermal subsidence, horizontal plate motion, erosion, sedimentation and flexural isostatic adjustment, and validate our models where possible using onshore and offshore geological constraints. Our reconstructions show that the land area of Antarctica situated above sea level was ~25% larger at the Eocene–Oligocene boundary than at the present-day. Offshore sediment records and terrestrial constraints indicate that the incision of deep subglacial topographic troughs around the margin of East Antarctica occurred predominantly in the Oligocene and early Miocene, whereas in West Antarctica erosion and sedimentation rates accelerated after the mid-Miocene. Changes to the topography after the mid-Pliocene were comparatively minor. Our new palaeotopography reconstructions provide a critical boundary condition for models seeking to understand past behaviour of the Antarctic Ice Sheet, and have implications for estimating changes in global ice volume, temperature, and sea level across major Cenozoic climate transitions.
A carbon cycle model constrained by weathering-sensitive isotopic tracers reveals that long-term cooling in the Neogene period reflects a change in how surface denudation is partitioned into weathering and erosion.
Plate kinematic reconstructions play an essential role in our understanding of global geodynamics, but become increasingly difficult to constrain back in geological time due to the subduction of oceanic lithosphere. Here, we attempt to kinematically reconstruct the Cretaceous and older plate tectonic history of the Caribbean Plate within the Mesozoic Panthalassa (paleo-Pacific) Ocean. To this end, we present new paleomagnetic data from Jurassic and Cretaceous oceanic sedimentary and volcanic Large Igneous Province-related rocks of the Nicoya Peninsula and Murciélago Islands of northwestern Costa Rica. We use these data, as well as constraints from marine magnetic anomalies to infer the age of the lithospheric basement, seismic tomography to locate deep-mantle plume generation zones, and general kinematic feasibility to test different reconstruction scenarios connecting the Caribbean Plate to the Farallon Plate as restored from Pacific spreading records. Our resulting reconstruction implies that the western Caribbean subduction zone initiated around 100 Ma, in an intra-oceanic setting, breaking up oceanic lithosphere of at least 70 Myr old.
The Himalayan-Tibetan orogen culminated during the Cenozoic India – Asia collision, but its geological framework and initial growth were fundamentally the result of multiple, previous ocean closure and intercontinental suturing events. As such, the Himalayan-Tibetan orogen provides an ideal laboratory to investigate geological signatures of the suturing process in general, and how the Earth’s highest and largest orogenic feature formed in specific. This paper synthesizes the Triassic through Cenozoic geology of the central Himalayan-Tibetan orogen and presents our tectonic interpretations in a time series of schematic lithosphere-scale cross-sections and paleogeographic maps. We suggest that north-dipping subducting slabs beneath Asian continental terranes associated with closure of the Paleo-, Meso-, and Neo-Tethys oceans experienced phases of southward trench retreat prior to intercontinental suturing. These trench retreat events created ophiolites in forearc extensional settings and/or a backarc oceanic basins between rifted segments of upper-plate continental margin arcs. This process may have occurred at least three times along the southern Asian margin during northward subduction of Neo-Tethys oceanic lithosphere: from ~174 to 156 Ma; 132 to 120 Ma; and 90 to 70 Ma. At most other times, the Tibetan terranes underwent Cordilleran-style or collisional contractional deformation. Geological records indicate that most of northern and central Tibet (the Hoh-Xil and Qiangtang terranes, respectively) were uplifted above sea level by Jurassic time, and southern Tibet (the Lhasa terrane) north of its forearc region has been above sea level since ~100 Ma. Stratigraphic evidence indicates that the northern Himalayan margin of India collided with an Asian-affinity subduction complex – forearc – arc system beginning at ~60 Ma. Both the Himalaya (composed of Indian crust) and Tibet show continuous geological records of orogenesis since ~60 Ma. As no evidence exists in the rock record for a younger suture, the simplest interpretation of the geology is that India – Asia collision initiated at ~60 Ma. Plate circuit, paleomagnetic, and structural reconstructions, however, suggest that the southern margin of Asia was too far north of India to have collided with it at that time. Seismic tomographic images are also suggestive of a second, more southerly Neo-Tethyan oceanic slab in the lower mantle where the northernmost margin of India may have been located at ~60 Ma. The geology of Tibet and the India – Asia suture zone permits an alternative collision scenario in which the continental margin arc along southern Asia (the Gangdese arc) was split by extension beginning at ~90 Ma, and along with its forearc to the south (the Xigaze forearc), rifted southward and opened a backarc ocean basin. The rifted arc collided with India at ~60 Ma whereas the hypothetical backarc ocean basin may not have been consumed until ~45 Ma. A compilation of igneous age data from Tibet shows that the most recent phase of Gangdese arc magmatism in the southern Lhasa terrane initiated at ~70 Ma, peaked at ~51 Ma, and terminated at ~38 Ma. Cenozoic potassic-adakitic magmatism initiated at ~45 Ma within a ~200-km-wide elliptical area within the northern Qiangtang terrane, after which it swept westward and southward with time across central Tibet until ~26 Ma. At 26-23 Ma, potassic-adakitic magmatism swept southward across the Lhasa terrane, a narrow (~20 km width), orogen-parallel basin developed at low elevation along the axis of the India – Asia suture zone (the Kailas basin), and Greater Himalayan Sequence rocks began extruding southward between the South Tibetan Detachment and Main Central Thrust. The Kailas basin was then uplifted to >4 km elevation by ~20 Ma, after which parts of the India – Asia suture zone and Gangdese arc experienced >6 km of exhumation (between ~20 and 16 Ma). Between ~16 and 12 Ma, slip along the South Tibetan Detachment terminated and east-west extension initiated in the northern Himalaya and Tibet. Potassic-adakitic magmatism in the Lhasa terrane shows a northward younging trend in the age of its termination, beginning at 20-18 Ma until volcanism ended at 8 Ma. We interpret the post-45 Ma geological evolution in the context of the subduction dynamics of Indian continental lithosphere and its interplay with delamination of Asian mantle lithosphere.
Global deep‐time plate motion models have traditionally followed a classical rigid plate approach, even though plate deformation is known to be significant. Here we present a global Mesozoic–Cenozoic deforming plate motion model that captures the progressive extension of all continental margins since the initiation of rifting within Pangea at ~240 Ma. The model also includes major failed continental rifts and compressional deformation along collision zones. The outlines and timing of regional deformation episodes are reconstructed from a wealth of published regional tectonic models and associated geological and geophysical data. We reconstruct absolute plate motions in a mantle reference frame with a joint global inversion using hot spot tracks for the last 80 million years and minimizing global trench migration velocities and net lithospheric rotation. In our optimized model, net rotation is consistently below 0.2°/Myr, and trench migration scatter is substantially reduced. Distributed plate deformation reaches a Mesozoic peak of 30 × 10⁶ km² in the Late Jurassic (~160–155 Ma), driven by a vast network of rift systems. After a mid‐Cretaceous drop in deformation, it reaches a high of 48 x 10⁶ km² in the Late Eocene (~35 Ma), driven by the progressive growth of plate collisions and the formation of new rift systems. About a third of the continental crustal area has been deformed since 240 Ma, partitioned roughly into 65% extension and 35% compression. This community plate model provides a framework for building detailed regional deforming plate networks and form a constraint for models of basin evolution and the plate‐mantle system.
The Eocene (~50‐45 Ma) major absolute plate motion change of the Pacific plate forming the Hawaii‐Emperor bend is thought to result from inception of Pacific plate subduction along one of its modern western trenches. Subduction is suggested to have started either spontaneously, or result from subduction of the Izanagi‐Pacific mid‐ocean ridge, or from subduction polarity reversal after collision of the Olyutorsky arc that was built on the Pacific plate with NE Asia. Here we provide a detailed plate‐kinematic reconstruction of back‐arc basins and accreted terranes in the northwest Pacific region, from Japan to the Bering Sea, since the Late Cretaceous. We present a new tectonic reconstruction of the intra‐oceanic Olyutorsky and Kronotsky arcs, which formed above two adjacent, oppositely‐dipping subduction zones at ~85 Ma within the north Pacific region, during another Pacific‐wide plate reorganization. We use our reconstruction to explain the formation of the submarine Shirshov and Bowers Ridges, and show that if marine magnetic anomalies reported from the Aleutian Basin represent magnetic polarity reversals, its crust most likely formed in an ~85‐60 Ma back‐arc basin behind the Olyutorsky arc. The Olyutorsky arc was then separated from the Pacific plate by a spreading ridge, so that the ~55‐50 Ma subduction polarity reversal that followed upon Olyutorsky‐NE Asia collision initiated subduction of a plate that was not the Pacific. Hence, this polarity reversal may not be a straightforward driver of the Eocene Pacific plate motion change, whose causes remain enigmatic.
The Late Paleogene surface height and paleoenvironment for the core area of the Qinghai-Tibetan Plateau (QTP) remain critically unresolved. Here, we report the discovery of the youngest well-preserved fossil palm leaves from Tibet. They were recovered from the Late Paleogene (Chattian), ca. 25.5 ± 0.5 million years, paleolake sediments within the Lunpola Basin (32.033°N, 89.767°E), central QTP at a present elevation of 4655 m. The anatomy of palms renders them intrinsically susceptible to freezing, imposing upper bounds on their latitudinal and altitudinal distribution. Combined with model-determined paleoterrestrial lapse rates, this shows that a high plateau cannot have existed in the core of Tibet in the Paleogene. Instead, a deep paleovalley, whose floor was <2.3 km above mean sea level bounded by (>4 km) high mountain systems, formed a topographically highly varied landscape. This finding challenges prevailing views on tectonic processes, monsoon dynamics, and the evolution of Asian biodiversity.
Ancient height of the Tibetan Plateau
The elevation of the Tibetan Plateau has a major impact on climate, affecting the monsoons and regional weather patterns. Although some isotope proxies have suggested a roughly equivalent height for the plateau as far back as the Eocene (∼40 million years ago), other lines of evidence suggest a lower elevation in the distant past. Botsyun et al. used a model to show that several previously overlooked factors contribute to the isotopic record from the Eocene (see the Perspective by van Hinsbergen and Boschman). The results harmonize the isotopic record with other proxies and argue for a Tibetan Plateau that was about 1000 meters lower than it is today.
Science , this issue p. eaaq1436 ; see also p. 928
Inorganic sediment is not the only solid-fraction component of river flows; flows may also carry significant amounts of large organic material (i.e., large wood), but the characteristics of these wood-laden flows (WLF) are not well understood yet. With the aim to shed light on these relatively unexamined phenomena, we collected home videos showing natural flows with wood as the main solid component. Analyses of these videos as well as the watersheds and streams where the videos were recorded allowed us to define for the first time WLF, describe the main characteristics of these flows and broaden the definition of wood transport regimes (adding a new regime called here hypercongested wood transport). According to our results, WLF may occur repeatedly, in a large range of catchment sizes, generally in steep, highly confined single thread channels in mountain areas. WLF are typically highly unsteady and the log motion is non-uniform, as described for other inorganic sediment-laden flows (e.g., debris flows). The conceptual integration of wood into our understanding of flow phenomena is illustrated by a novel classification defining the transition from clear water to hypercongested, wood and sediment-laden flows, according to the composition of the mixture (sediment, wood, and water). We define the relevant metrics for the quantification and modelling of WLF, including an exhaustive discussion of different modelling approaches (i.e., Voellmy, Bingham and Manning) and provide a first attempt to simulate WLF. We draw attention to WLF phenomena to encourage further field, theoretical, and experimental investigations that may contribute to a better understanding of flows river basins, leading to more accurate predictions, and better hazard mitigation and management strategies.
The Paleogene Lulehe Formation marks the onset of deposition in the Qaidam basin and preserves evidence of the initial topographic growth of northern Tibet. However, limited outcrops impede understanding of the sedimentary features of the Lulehe Formation as well as the tectonic relationship between the basin and surrounding topography. To fill this gap, we investigated core samples along the basin margin and conducted flexural modeling to estimate the topographic load of the Qilian Shan and Eastern Kunlun Shan during the deposition of the Lulehe Formation. Core samples reveal that the Lulehe Formation mainly consists of distal fluvial to marginal lacustrine deposits and proximal fluvial deposits along the southern margin of the basin while characterized by proximal alluvial fan deposits along the northern margin of the basin. Together with evidence for faulting shown on the seismic profiles, we infer that simultaneous deformation within the Qilian Shan and Altyn Tagh Shan during the Paleogene resulted in accumulation of coarse detrital deposits in the northwestern and northeastern Qaidam basin. The simultaneous deformation within the Altyn Tagh Shan and Qilian Shan since the Paleogene supports the idea that deformation in these two regions is kinematically linked. One- and two-load beam flexural modeling indicates that the topographic load generated by both the Eastern Kunlun Shan and the Qilian Shan is responsible for the subsidence of the Qaidam basin during deposition of the Lulehe Formation. Our results highlight the initial relative high topography in the northern Tibetan plateau during the early Cenozoic.
Geologic evidence across orogenic plateau margins helps to discriminate the relative contributions of orogenic, epeirogenic and/or climatic processes leading to growth and maintenance of orogenic plateaus and plateau margins. Here, we discuss the mode of formation of the southern margin of the Central Anatolian Plateau (SCAP), and evaluate its time of formation, using fieldwork in the onshore and seismic reflection data in the offshore. In the onshore, uplifted Miocene rocks in a dip‐slope topography show monocline flexure over >100 km, few‐km asymmetric folds verging south, and outcrop‐scale syn‐sedimentary reverse faults. On the Turkish shelf, vertical faults transect the basal latest Messinian of a ~10 km fold where on‐structure syntectonic wedges and synsedimentary unconformities indicate pre‐Pliocene uplift and erosion followed by Pliocene and younger deformation. Collectively, Miocene rocks delineate a flexural monocline at plateau margin scale, expressed along our on‐offshore sections as a kink‐band fold with a steep flank ~20–25 km long. In these reconstructed sections, we estimate a relative vertical displacement of ~3.8 km at rates of ~0.5 mm/y, and horizontal shortening values <1%. We use this evidence together with our observations of shortening at outcrop, basin, plateau‐margin and forearc system scales to infer that the SCAP forms as a monoclinal flexure to accommodate deep‐seated thickening and shortening since >5 Ma, and to contextualize the plateau margin as the forearc high of the Cyprus subduction system.
This article is protected by copyright. All rights reserved.
This chapter summarizes the available stratigraphic, petrographical and mineralogical evidence from sediments and sedimentary rocks on the evolution of the Himalayan belt and its associated foreland basin. The use of compositional signatures of modern sediments to unravel provenance changes and palaeodrainage evolution through time is hampered by a poor match with detrital modes of ancient strata markedly affected by selective chemical dissolution of unstable minerals during diagenesis. Only semi-quantitative diagnoses can thus be attempted. Volcanic detritus derived from Transhimalayan arcs since India–Asia collision onset at c. 60 Ma was deposited onto the Indian lower plate throughout the Protohimalayan stage, with the exception of the Tansen region of Nepal that is characterized by quartz-arenites yielding orogen-derived zircon grains. During the Eohimalayan stage, begun in the late Eocene when most sedimentation ceased in the Tethys Himalayan domain, low-rank metasedimentary detritus was overwhelming in the central foreland basin, where a widespread unconformity developed spanning locally as much as 20 myr. Volcanic detritus from Transhimalayan arcs remained significant in northern Pakistan. Arrival of higher-rank metamorphic detritus since the earliest Miocene, and the successive occurrence of garnet, staurolite, kyanite and finally sillimanite, characterized the Neohimalayan stage, when repeated compositional changes in the foreland-basin succession document the stepwise propagation of crustal deformation across the Indian Plate margin and widening of the thrust belt with exhumation of progressively more external tectonic units. The correspondence in time between the activity of major thrusts and petrofacies changes indicates a promising approach to accurately reconstruct the geological evolution of the coupled orogen–basin system. Conversely, a poor conceptual framework and the general reliance on ad hoc mechanisms to explain phenomena unpredicted by simplified models represent major factors limiting the robustness of palaeotectonic interpretations. Improved knowledge requires taking into full account the dynamic role played by still poorly understood subduction processes – rather than exclusively the effect of passive loading – as well as the role played by the presence of inherited structures on the downgoing Indian Plate, which control both lateral variability of orogenic deformation and the location of depocentres in the foreland basin.
Spatiotemporal patterns of deformation and exhumation in the central Andes are key parameters for reconstructing the kinematic history of the orogenic belt. Previous studies of the retroarc thrust belt document overall eastward propagation of deformation since the late Eocene, but the amount and timing of exhumation during the early phase of Andean orogeny remains largely unconstrained, particularly in the modern forearc region. In order to determine the timing and amount of exhumation prior to the late Eocene, we employed a multidating approach combining zircon U-Pb geochronology with apatite fission track and apatite (U-Th)/He thermochronology. We focus on the low-temperature cooling history of the Cordillera de Domeyko thrust belt and synorogenic deposits in the Salar de Atacama basin. Our results show Late Cretaceous to Oligocene cooling and exhumation in the Cordillera de Domeyko. The distribution of cooling ages in the forearc indicates three periods of exhumation: ~86–65, ~65–50, and 50–28 Ma. The amount of cooling was variable in space and time but requires total exhumation of ~2.5–3.3 km of rocks above major structures in the thrust belt. Regional unconformities in the Salar de Atacama basin correlate with periods of eastward migration of the orogenic front at ~65 Ma and ~50–40 Ma. Pulses of deformation at the front of the thrust belt alternated with periods of out-of-sequence hinterland deformation and exhumation. Overall, our data show that shortening in the central Andes commenced during the Late Cretaceous (as early as ~86 Ma) and that deformation (shortening) and exhumation were coupled in space and time.
We present a new algorithm for solving the common problem of flow trapped in closed depressions within digital elevation models, as encountered in many applications relying on flow routing. Unlike other approaches (e.g., the so-called Priority-Flood depression filling algorithm), this solution is based on the explicit computation of the flow paths both within and across the depressions through the construction of a graph connecting together all adjacent drainage basins. Although this represents many operations, a linear time-complexity can be reached for the whole computation, making it very efficient. Compared to the most optimized solutions proposed so far, we show that this algorithm of flow path enforcement yields the best performance when used in landscape evolution models. Besides its efficiency, our proposed method has also the advantage of letting the user choose among different strategies of flow path enforcement within the depressions (i.e., filling vs. carving). Furthermore, the computed graph of basins is a generic structure that has the potential to be reused for solving other problems as well. This sequential algorithm may be helpful for those who need to, e.g., process digital elevation models of moderate size on single computers or run batches of simulations as part of an inference study.
The Late Mesozoic-Cenozoic topographic and climate evolution of Central Asia remains highly debated. The final retreat of the proto-Paratethys Sea from the western Tarim Basin is thought to correspond in time with the onset of tectonic uplift in the Pamir, Tian Shan and Altai ranges, as well as with regional aridification. The oxygen and carbon isotope compositions of the sediment deposits in the various Central Asian basins have already been used to decipher both the topographic and climatic changes that occurred in that region during the Cenozoic, generally concentrating on one sedimentary section and/or on a limited time range and either using multiple-type samples including sandstone calcitic cements, marine carbonates, fossils, or paleosols. In order to get a homogeneous dataset, minimizing variations in the isotopic composition of the material depending on its type and/or depositional environment, we selected only calcareous paleosols sampled in several continuous sections covering a wide time range from the Late Jurassic to the Pliocene. Our sampling also covers a wide area encompassing the whole Tian Shan region, which allows detecting regional variations in the δ 18 O and δ 13 C values. We show that the influence of the distance to the proto-Paratethys Sea on the paleosol δ 18 O record was not significant. Besides local factors such as the occurrence of large lakes that can have a significant effect on the isotopic composition of the calcareous paleosols, the long-term evolution of both the δ 18 O and δ 13 C values possibly reflects the hypsometry of the river drainage systems that bring water to the basins. However, as it is commonly accepted that the δ 18 O of soil carbonates is controlled by the δ 18 O of in-situ precipitation, this last conclusion remains to be further investigated.
Tectonic plates subducting at trenches having strikes oblique to the absolute subducting plate
motion undergo trench-parallel slab motion through the mantle, recently defined as a form of “slab
dragging.” We investigate here long-term slab-dragging components of the Tonga-Kermadec subduction system driven by absolute Pacific plate motion. To this end we develop a kinematic restoration of Tonga-Kermadec Trench motion placed in a mantle reference frame and compare it to tomographically imaged slabs in the mantle. Estimating Tonga-Kermadec subduction initiation is challenging because another (New Caledonia) subduction zone existed during the Paleogene between the Australia and Pacific plates. We test partitioning of plate convergence across the Paleogene New Caledonia and Tonga-Kermadec subduction zones against resulting mantle structure and show that most, if not all, Tonga-Kermadec subduction occurred after ca. 30 Ma. Since then, Tonga-Kermadec subduction has accommodated 1,700 to 3,500 km of subduction along the southern and northern ends of the trench, respectively. When placed in a mantle reference frame, the predominantly westward directed subduction evolved while the Tonga-Kermadec Trench underwent ~1,200 km of northward absolute motion. We infer that the entire Tonga-Kermadec slab was laterally transported through the mantle over 1,200 km. Such slab dragging by the Pacific plate may explain observed deep-slab deformation and may also have significant effects on surface tectonics, both resulting from the resistance to slab dragging by the viscous mantle.
Studies of paleoclimatology, paleoceanography, paleobiology, and other studies of paleoenvironment require paleogeographic reconstructions that display the past distribution of land and sea, and of bathymetry and altimetry. Quantitative reconstructions of past positions of continents and oceans have been available for decades, and have become easy to access and develop with the advance of GPlates software. Quantitative estimates of bathymetry and especially altimetry and topography, however, are considerably more challenging to develop. First attempts towards a global, quantitative approach towards paleotopography reconstruction were made in recent years. However these models are largely based on present day topography and require extensive manual adjustment for local modification that is subjective and precludes reproducibility. In this project, we attempt to overcome this subjectivity, and develop a quantitative methodology to calculate paleogeography based on kinematic input parameters.
Our aim is to develop ‘Paleogeography.org’, a free, online paleogeography calculator. This project calculates oceanic bathymetry and continental altitude and topography from plate tectonic reconstructions for various geodynamic settings. The algorithms are based on simple and straightforward dynamic principles: bathymetry of the ocean floor is at first order inferred from its age, and altimetry is based on computing crustal thickness based on shortening or extension reconstructions, assuming isostacy. Distinctions are made between undisturbed ocean floor, oceanic plateaus, trenches, continental rifts and back-arc basins, oceanic and continental volcanic arcs, upper plate orogens (e.g., Andes, Tibet) vs accretionary orogens (Zagros, Himalaya, Apennines, Alps), etc. This allows to calculate a global geography for any given time slice for which underlying kinematic reconstructions are available. These reconstructions are subsequently tested against independent quantitative estimates of e.g., altimetry and bathymetry and iterated where necessary. This approach provides a reproducible, global estimate of paleogeography without input from paleobiological or paleoclimatic indicators, enabling an independent platform for paleo-environmental study. The iteration between prediction and observation, moreover, will provide novel constraints on 4D geodynamic processes.
Code is written mainly in Python, especially using pyGPlates. The calculator will be available as open source code for scientists and other professionals. They can use it to make reproducible paleogeographic reconstructions based on their own plate tectonic reconstructions or on specific moments in time. In addition the output makes appealing pictures of plate tectonic reconstructions for both scientists and a wider audience.
The evolution of continental crust in convergent margins can be explored in southernmost South America (54-56°S). Plutonic rocks of the Fuegian Batholith and the rear-arc satellite Ushuaia Pluton were emplaced within the magmatic arc and the Fuegian fold-and-thrust belt, respectively. They record subduction zone processes in two distinct tectonic settings during the evolution of the Rocas Verdes Basin. We report new U-Pb zircon geochronology, bulk rock chemistry, Sr-Nd isotope data, and EPMA and in-situ LA-ICP-MS analyses of amphibole from ‘hornblendites’ and gabbroic-granitoid suites in order to evaluate the origin and evolution of the magmatic plumbing systems in the upper plate of the subduction zone. Textural relationships and amphibole compositions in hornblendite indicate crystallization at lower crustal depths with pressures of 7-8 kbar in the Fuegian Batholith and of 5-6 kbar in the Ushuaia Pluton. Lower Cretaceous suites of hornblendite and calc-alkaline hornblende-gabbro, diorite and tonalite in the Fuegian Batholith have εNdt values ranging between +2 and +4. They were emplaced within an island arc coeval with mid-oceanic type spreading in the Rocas Verdes back-arc basin. Isotope ratios and amphibole compositions in hornblendite indicate crystallization from primitive and hydrous sub-alkaline basaltic melts with relatively low LREE/HREE and low alkali contents. The Late Cretaceous plutons in the fold-and-thrust belt were emplaced after the tectonic juxtaposition of Rocas Verdes ophiolitic complexes. The Ushuaia Pluton, consisting of clinopyroxene-hornblende cumulates, hornblende-gabbro, diorite and monzodiorite, was emplaced during the waning stage of Late Cretaceous magmatism. In this case hornblendite amphiboles show high contents of alkalis, LREE and incompatible elements with a strong crustal affinity (Th, Ba, Rb). The enriched incompatible trace element patterns indicate their derivation from K-rich transitional magmas formed in supra-subduction settings. Chemical variations in amphibole from hornblendites and spatially related plutonic rocks are evaluated in terms of fluid flux from the subducted slab and partial melting of the sub-arc mantle, ultimately controlled by the thermal state of the subducted slab and convergence rates.
The Southern Ocean is a key player in the climate, ocean and atmospheric system. As the only direct connection between all three major oceans since the opening of the Southern Ocean gateways, the development of the Southern Ocean and its relationship with the Antarctic cryosphere has influenced the climate of the entire planet. Although the depths of the ocean floor have been recognized as an important factor in climate and paleoclimate models, appropriate paleobathymetric models including a detailed analysis of the sediment cover are not available. Here, we utilize more than 40 years of seismic reflection data acquisition along the margins of Antarctica and its conjugate margins, along with multiple drilling campaigns by the International Ocean Discovery Program (IODP) and its predecessor programs. We combine and update the seismic stratigraphy across the regions of the Southern Ocean and calculate ocean-wide paleobathymetry grids via a backstripping method. We present a suite of high-resolution paleobathymetric grids from the Eocene-Oligocene Boundary to modern times. The grids reveal the development of the Southern Ocean from isolated basins to an interconnected ocean affected by the onset and vigor of an Antarctic Circumpolar Current, as well as the glacial sedimentation and erosion of the Antarctic continent. The ocean-wide comparison through time exposes patterns of ice sheet development such as switching of glacial outlets and the change from wet-based to dry-based ice sheets. Ocean currents and bottom-water production interact with the sedimentation along the continental shelf and slope and profit from the opening of the ocean gateways.
Over the last several decades a number of studies have attempted to reconstruct the rise of the Himalaya and Tibet since India-Asia collision began in the early Cenozoic, with rather contradictory results. Here, we evaluate the efforts at reconstructing the history of this major mountain-building event as archived in oxygen, carbon, and clumped isotope records from carbonates exposed on the southern Tibetan Plateau. We find that a number of potential isotopic records of paleoaltimetry from Tibet – using both conventional oxygen and clumped isotope systems–may have been reset during burial and heating. Without exception, the marine δ¹⁸O values of Cretaceous and Paleogene marine carbonates across the orogen have been reset from their primary values of 0 ± 4‰ (VPDB) to lower values between −5 and −20‰, most conspicuously in the Indo-Asian suture zone. For this and other reasons, we view isotopic records of paleoaltimetry from the suture zone and adjacent Gangdese arc with great caution, especially early Cenozoic basin sediments that have experienced similar burial and heating as the underlying marine limestones. Outside the suture zone/arc, marine carbonates retain the isotopic imprint of low-elevation, meteoric diagenesis, a result that supports paleoaltimetric reconstruction from these areas using younger non-marine carbonates. We are even more cautious about temperature reconstructions using clumped isotope analyses, which previous studies suggest are sensitive to resetting at moest burial temperatures. With a few possible exceptions, primary clumped isotope values have probably not withstood the elevated temperatures of the suture zone and magmatic arc, nor burial depths of >3 km in basins outside the suture. In light of susceptibility to alteration of oxygen isotopes in carbonates in orogenic belts, future paleoaltimetric reconstruction prior to the Miocene on the Tibetan Plateau should couple δ¹⁸O, Δ47, and Δ'¹⁷O analysis of carbonates with analysis of noncarbonate archives—such as silicates and organic matter— that are less susceptible to resetting.
Carbon, unlike oxygen, isotopic values from paleosol carbonate are well preserved from all periods, due to the very low C/O ratio of most altering fluids. Samples from within the suture zone yield a record of paleo-vegetation change covering much of the Cenozoic. Carbon isotopic values from paleosols have no analog among modern Tibetan soils and most resemble in appearance and chemical composition the vegetated soils in the lowlands of northern India today. Carbon isotopes from paleosols depict a major reduction in vegetation cover in the suture zone since 20 Ma, probably due to a combination of uplift of the suture zone and global cooling. Northward on the Lhasa and Qiantang terranes, the landscape was less vegetated in the Oligocene compared to the contemporaneous suture zone, but more vegetated and less arid than it is today.
Thick- and thin-skinned “hybrid” thrust belts are typically developed in areas where crustal shortening was preceded by extension and normal faulting. They have been recognized in many places within the Central Andean backarc regions of Perú, Argentina, and Bolivia. In contrast, these structures have not been broadly studied in forearc regions. To understand the geometry and kinematics of this style of tectonism in a forearc setting related to Andean-type subduction zones, we used field and industrial 2D seismic data to study the Potrerillos thrust and fold belt and the Salar de Pedernales Basin in northern Chile (26°S). Our results indicate that the structure in this region consists of a dominantly east-verging contracting system composed of large basement thrusts, Mesozoic inverted normal faults, and shallow thrust-related folds. Large basement thrust ramps and imbricated wedges represent the most prominent basement structures, which accommodated major crustal shortening. Reactivated and tectonically inverted Mesozoic extensional structures also constitute an important structural component, especially beneath the Salar de Pedernales Basin. These exhibit asymmetrical inverted anticlines with arrowhead shapes on the hanging walls of the inverted normal faults. The subsidiary shallow thrust-related folds commonly display fault bend and propagation folds that primarily accommodated the shortening of the Mesozoic and Cenozoic stratified deposits overlying the basement thrusts and cored anticlines. The age of the contraction in this region is poorly constrained; however, many of the oldest sequences accumulated in the top of the syn-rift sequences and related to synorogenic deposits, can be correlated with those identified in neighboring regions (e.g., Salar de Atacama, Salar de Punta Negra basins and Frontal Cordillera, among others), which have reported Upper Cretaceous ages. Based on this stratigraphic correlation we suggest that orogenesis may have begun in the Late Cretaceous with basin inversion, and then continued during the Cenozoic with basement thrusting.
The Cretaceous and Cenozoic fill of the continental margins of southern Africa (South‐East Atlantic and Agulhas Margins) contains a continuous record of sediment supplied from the South African Plateau for the past 134 million years. Estimates of solid sediment volumes deposited offshore were calculated from isopach maps and extrapolated vertical cross‐sections derived from a large amount of industrial geophysical data. Solid phase volumes and accumulation rates were calculated for six epochs: Lower Cretaceous (134‐113 Ma), Mid Cretaceous (113‐93.5 Ma), Upper Cretaceous (93.5‐81 Ma and 81‐66 Ma), Paleogene (66‐25 Ma), Neogene (25‐0 Ma). Our new compilation demonstrates the existence of two periods of elevated flux. The most important one occurs in the late Cretaceous (93.5 to 66 Ma) and was synchronous with an acceleration of onshore denudation as shown by thermochronometric data. After a period of extremely low accumulation rate, the second phase of elevated flux started in the Oligocene (~30‐25 Ma) until present‐day. From these observations we suggest that the main phase of uplift of the South African Plateau took place during the Upper Cretaceous. Two mechanisms, namely uplift caused by lithospheric delamination or by dynamic topography caused by the continent moving over the African Superplume, are viable explanations for our observations. The more recent and lower amplitude episode of enhanced accumulation rates is likely to correspond to a second period of uplift, potentially associated with the onset of uplift and extension along the East African Rift System.
The uplift and associated exhumation of the Tibetan Plateau has been widely considered a key control of Cenozoic global cooling. The south‐central parts of this plateau experienced rapid exhumation during the Cretaceous‐Paleocene periods. When and how the northern part was exhumed, however, remains controversial. The Hoh Xil Basin (HXB) is the largest late Cretaceous‐Cenozoic sedimentary basin in the northern part, and it preserves the archives of the exhumation history. We present detrital apatite and zircon (U‐Th)/He data from late Cretaceous‐Cenozoic sedimentary rocks of the western and eastern HXB. These data, combined with regional geological constraints and interpreted with inverse and forward model of sediment deposition and burial reheating, suggest that the occurrence of ~4‐2.7 km and ~4‐2.3 km of vertical exhumation initiated at approximately 30‐25 Ma and 40‐35 Ma in the eastern and western HXB, respectively. The initial differential exhumation of the eastern HXB and the western HXB might be controlled by the oblique subduction of the Qaidam block beneath the HXB. The initial exhumation timing in the northern Tibetan Plateau is younger than that in the south‐central parts. This reveals an episodic exhumation of the Tibetan Plateau compared to models of synchronous Miocene exhumation of the entire plateau and the early Eocene exhumation of the northern Tibetan Plateau shortly after the India‐Asia collision. One possible mechanism to account for outward growth is crustal shortening. A simple model of uplift and exhumation would predict a maximum of 0.8 km of surface uplift after upper crustal shortening during 30‐27 Ma, which is insufficient to explain the high elevations currently observed. One way to increase elevation without changing exhumation rates and to decouple uplift from upper crustal shortening is through the combined effects of continental subduction, mantle lithosphere removal and magmatic inflation.
The marine sedimentary record contains unique information about the history of erosion, uplift and climate of the adjacent continent. Inverting this record has been the purpose of many numerical studies. However, limited attention has been given to linking continental erosion to marine sediment transport and deposition in large-scale surface process evolution models. Here we present a new numerical method for marine sediment transport and deposition that is directly coupled to a landscape evolution algorithm solving for the continental fluvial and hillslope erosion equations using implicit and O(N) algorithms. The new method takes into account the sorting of grain sizes (e.g., silt and sand) in the marine domain using a non-linear multiple grain-size diffusion equation and assumes that the sediment flux exported from the continental domain is proportional to the bathymetric slope. Specific transport coefficients and compaction factors are assumed for the two different grain sizes to simulate the stratigraphic architecture. The resulting set of equations is solved using an efficient (O(N) and implicit) algorithm. It can thus be used to invert stratigraphic geometries using a Bayesian approach that requires a large number of simulations. This new method is used to invert the sedimentary geometry of a natural example, the Ogooué Delta (Gabon), over the last ∼5 Myr. The objective is to unravel the set of erosional histories of the adjacent continental domain compatible with the observed geometry of the offshore delta. For this, we use a Bayesian inversion scheme in which the misfit function is constructed by comparing four geometrical parameters between the natural and the simulated delta: the volume of sediments stored in the delta, the surface slope, the initial and the final shelf lengths. We find that the best-fit values of the transport coefficients for silt in the marine domain are in the range of 300−500 m²/yr, in agreement with previous studies on offshore diffusion. We also show that, in order to fit the sedimentary geometry, erosion rate on the continental domain must have increased by a factor of 6 to 8 since 5.3 Ma.
Combined research on the structural and stratigraphic evolution of the southeastern Austral Basin identifies three major depositional systems strongly influenced by the tectonic stages of the Fuegian Andes between the Late Cretaceous and the Miocene. During orogenic growth, a submarine ramp system characterized by oblique progradational clinoforms with transverse sediment dispersal, formed adjacent to the deformation front in the wedge-top or proximal foredeep. In moments when the tectonic load and flexural subsidence were reduced, this system was replaced by a progradational-aggradational system with oblique to sigmoidal clinoforms. This occurred during a short span in the middle Eocene, but especially and definitively after contractional deformation ceased in the early Miocene. The third depositional system was long lived, and comprised axial turbidite channel systems located at the clinoform bases, which re-routed sediment toward the deeper foredeep of the western Malvinas Basin. Distinct facies types develop in each depositional system, and their recognition allows evaluating sediment fairways in the foreland basin system.
In Central Asia, numerous fragments of planation surfaces are visible within the present day topography. However, their precise timing of formations is still poorly constrained and it is not clear if they are remnants of a single extensive planation surface or if they represent different planation episodes. By reconstructing the landscape evolution of the Tian Shan region and by analyzing the relations between the planation surfaces preserved within the eastern Tarim Basin and the sedimentary record, we demonstrate that the numerous erosional surfaces preserved within the Tian Shan Range represent different episodes of surfaces genesis. These erosion events span from the late Paleozoic to the Early Cenozoic. The widespread preservation of large fragments of these surfaces within the Tian Shan Range implies that this region did not undergo strong relief building during most of its Mesozoic evolution but was dominated by plains associated to small hills along episodically active discrete tectonic structures. Finally, the preservation of these surfaces within the active Tian 2 Shan Range implies a long-term, strong non-equilibrium state of the topography during its Cenozoic evolution. This was probably promoted by the arid to semi-arid climate prevailing since the Late Paleogene onset of relief building.
Controlling cooling
On million-year time scales, Earth's climate state is determined by sources and sinks of carbon to the ocean-atmosphere system. But which specific mechanisms are important in controlling the timing of glacial intervals? Macdonald et al. identify arc-continent collisions in the tropics as a primary control (see the Perspective by Hartmann). They compiled a database of Phanerozoic arc-continent collisions and the latitudinal distribution of ice sheets, showing that ice coverage was greatest when those collisions were most widespread, maximizing global weatherability.
Science , this issue p. 181 ; see also p. 126
The uplift of the Tibetan Plateau is an important geological event, but there is considerable controversy about its growth history. Different geological observations contribute to this controversial issue, while data from geochemistry, tectonics, and paleontology further fuel the debate. Vertebrate fossils have provided significant evidence for documenting the uplift of the Tibetan Plateau in the geologic past. The earliest fossil evidence recently collected from the Oligocene Dingqing Formation in central Tibet includes the climbing perch and cyprinine fish fossils whose modern close relatives are distributed in the tropical zone of Asia and Africa. These discoveries not only are significant for the phylogeny and zoogeography of fishes, but also imply that the hinterland of the Tibetan Plateau was a warm and humid lowland at ~26 Ma. The co-existing plant assemblage, which includes palms and golden rain trees among others, indicates that the warm and humid airs from the Indian Ocean could flow deeply into central Tibet, consistent with the inference from the fish fossils. Since that time, the geographical features and natural environments within the Tibetan Plateau have greatly changed. The Tibetan Plateau was consistently uplifted in the Early Miocene and reached an elevation of ~3000 m, which was demonstrated by fish, mammal, and plant fossils. The endemic schizothoracines (snow carps) originated from the Miocene when the Tibetan Plateau turned into a barrier for mammalian migrations between north and south sides. A series of fish and mammal fossils provided unequivocal evidence that the Tibetan Plateau uplifted close to its modern elevation in the Pliocene and developed a cryospheric environment. As a result, the plateau region became the origination center for the cold-adapted Quaternary Ice Age fauna.
The proto‐Paratethys Sea covered a vast area extending from the Mediterranean Tethys to the Tarim Basin in western China during Cretaceous and early Paleogene. Climate modelling and proxy studies suggest that Asian aridification has been governed by westerly moisture modulated by fluctuations of the proto‐Paratethys Sea. Transgressive and regressive episodes of the proto‐Paratethys Sea have been previously recognized but their timing, extent and depositional environments remain poorly constrained. This hampers understanding of their driving mechanisms (tectonic and/or eustatic) and their contribution to Asian aridification. Here, we present a new chronostratigraphic framework based on biostratigraphy and magnetostratigraphy as well as a detailed paleoenvironmental analysis for the Paleogene proto‐Paratethys Sea incursions in the Tajik and Tarim basins. This enables us to identify the major drivers of marine fluctuations and their potential consequences on Asian aridification. A major regional restriction event, marked by the exceptionally thick (≤ 400 m) shelf evaporites is assigned a Danian‐Selandian age (~63‐59 Ma) in the Aertashi Formation. This is followed by the largest recorded proto‐Paratethys sea incursion with a transgression estimated as early Thanetian (~59‐57 Ma) and a regression within the Ypresian (~53‐52 Ma), both within the Qimugen Formation. The transgression of the next incursion in the Kalatar and Wulagen formations is now constrained as early Lutetian (~47‐46 Ma), whereas its regression in the Bashibulake Formation is constrained as late Lutetian (~41 Ma) and is associated with a drastic increase in both tectonic subsidence and basin infilling. The age of the final and least pronounced sea incursion restricted to the westernmost margin of the Tarim Basin is assigned as Bartonian–Priabonian (~39.7‐36.7 Ma). We interpret the long‐term westward retreat of the proto‐Paratethys Sea starting at ~41 Ma to be associated with far‐field tectonic effects of the Indo‐Asia collision and Pamir/Tibetan plateau uplift. Short‐term eustatic sea level transgressions are superimposed on this long‐term regression and seem coeval with the transgression events in the other northern Peri‐Tethyan sedimentary provinces for the 1st and 2nd sea incursions. However, the 3rd sea incursion is interpreted as related to tectonism. The transgressive and regressive intervals of the proto‐Paratethys Sea correlate well with the reported humid and arid phases, respectively in the Qaidam and Xining basins, thus demonstrating the role of the proto‐Paratethys Sea as an important moisture source for the Asian interior and its regression as a contributor to Asian aridification. This article is protected by copyright. All rights reserved.
The topographic history of mountain belts reflects changes in lithospheric structure and rheology and exerts an influence on cli- mate. Although substantial progress has been made to constrain the growth history of the southern Tibetan Plateau, the timing and geodynamic drivers for surface uplift of the central plateau remain poorly constrained. Here, we used both carbonate clumped iso- tope geothermometry and modified stable isotope–based paleoaltimetry that considers proportional mixing of two major moisture sources to infer late Eocene paleoelevations of the Nangqian Basin in the east-central Tibetan Plateau. The mean clumped isotope temperature, T(Δ47), of minimally altered late Eocene lacustrine carbonates is 30.0 °C, and the reconstructed least-evaporated paleo- water δ18Omw value is –9.8‰. These two in- dependent approaches indicate that during late Eocene time, the Nangqian Basin floor was 2.7 (+0.6/–0.4) km above sea level, and the hypsometric mean elevation of surround- ing mountains was 3.0 ± 1.1 km above sea level. These estimates are 1.1–1.2 km lower than their modern counterparts. The mod- erate to high late Eocene paleoelevation of the Nangqian Basin suggests that Eocene upper-crustal shortening and thickening can explain most, but not all, of the surface uplift of the east-central Tibetan Plateau. The ad- ditional 1.1–1.2 km (at most) of post–late Eo- cene elevation increase to the present height may have been a result of either lower-crustal flow or slab detachment.
The motion of diverging tectonic plates is typically constrained by geophysical data from preserved ocean crust. However, constraining plate motions during continental rifting and the breakup process relies on balancing evidence from a diverse range of geological and geophysical observations, often subject to differing interpretations. Reconstructing the evolution of rifting and breakup between Australia and Antarctica epitomizes the challenges involved in creating detailed models of Pangea breakup. In this example, differing degrees of emphasis on and alternative interpretations of offshore geophysical data, in particular magnetic anomalies and seismic reflection profiles, and onshore geological data, lead to starkly contrasting views of how the continents were configured at the onset of Mesozoic rifting. Here, we critically review reconstructions of rifting and breakup in the light of all available geological and geophysical data, including magnetic anomalies, fracture zones, conjugate crustal domains, amounts of continental extension, continental geology, plate boundary locations, break-up ages and stratigraphy. We identify the most viable plate tectonic reconstructions both with and without the input of the oldest, more controversial magnetic anomaly interpretations, and discuss implications for reconstructions of other margin pairs. Our analysis highlights key discrepancies between reconstructions based solely on geological piercing points, and those based on a range of constraints. These insights provide a powerful framework for reducing the range of viable models for Australian-Antarctic rifting, and provide key lessons for future efforts aimed at constraining pre- and syn-rift plate tectonic reconstructions.
Atlas of 20 Tectonono-Sedimentary-Palinspastic maps from Late Permian to Pliocene (scale: 1/15 000 000)
AVAILABLE UPON REQUEST
The present Atlas is one of the end-products of the DARIUS Programme.
The DARIUS Programme (2009–14) was a multidisciplinary geological programme that comprised original scientific projects, executed by academic scientific teams involving more than 350 scientists representing 150 research institutions from 25 countries in Europe, the Middle East and western Central Asia. The DARIUS consortium was sponsored by major oil companies (BHP Billiton, BP, ENI, Maersk Oil, Petronas Carigali, Shell, Statoil, Total) and French research organizations (Centre National de la Recherche Scientifique-INSU, University Pierre & Marie Curie). The main objective of DARIUS was to characterize the tectonostratigraphic evolution of a vast domain around the central Tethys extending from the eastern Black Sea in the west to western Central Asia in the east, and to reconstruct the post-Late Palaeozoic geodynamic evolution of the domain. The priority
was to investigate the 6000 km long continuous orogenic belt extending from Crimea/Anatolia in the west to the western Tien Shan in the east, including the surrounding basins, through the collection of original data and the development of
regional syntheses.
way to refer:
Barrier E., Vrielynck, B., Brouillet J.F. & Brunet M.F. (Contributors : Angiolini L., Kaveh F., Plunder A., Poisson A., Pourteau A., Robertson A., Shekawat R., Sosson M. and Zanchi A.) 2018.- Paleotectonic Reconstruction of the Central Tethyan Realm. Tectonono-Sedimentary-Palinspastic maps from Late Permian to Pliocene. CCGM/CGMW, Paris, http://www.ccgm.org. Atlas of 20 maps (scale: 1/15 000 000).
The aim of this study is to constrain the post-rift deformations of the Atlantic passive margin of Namibia and South Africa using an extensive industrial 2D reflection seismic dataset calibrated by wells and onshore outcrops that have been revaluated in age (biostratigraphy) in order to discuss the evolution of the South African Plateau uplift. The first-order evolution of the margin is tectonically driven and can be divided into three principal phases. The first (131-93.5 Ma) comprises an overall retrogradational trend that results from a rate of accommodation , created by the thermal flexure of the margin, that is higher than the sediment supply. The second (93.5-66 Ma) comprises an overall aggradational-progradational trend that results from a relative increase in sediment supply due to an uplift and subsequent erosion of the margin and the inland domain. The third (66-0 Ma) is retrogradational again in response to a decrease in sediment supply induced by a relative stability of the margin and climate conditions. This study demonstrates that the present-day configuration of the margin is acquired during the Late Cretaceous (from 81 to 66 Ma) with a strike, long-wavelength and seaward tilt of the margin which could be related to the growth of the onshore main escarpment. We also characterize a regional Oligocene unconformity marked by a significant downward shift of the shoreline which suggests a moderate uplift of the inland domain and could be associated with a reactivation of the relic late Cretaceous relief.