Conference Agenda

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Session Overview
3.12-2 Past climates and environments inform our future
Wednesday, 06/Sept/2023:
4:00pm - 5:30pm

Session Chair: Cécile Blanchet, GFZ Potsdam
Session Chair: Stefanie Kaboth-Bahr, Free University Berlin
Location: Wiwi 104a


4:00pm - 4:15pm
Topics: 3.12 Past climates and environments inform our future

New insights into Early Cretaceous continental environments and climate based on lignite-bearing strata from central Mongolia

Fritz-Lukas Stoepke1, Ralf Littke2, Laura Zieger2, Hitoshi Hasegawa3, Niiden Ichinnorov4, Ulrich Heimhofer1

1Leibniz University Hannover, Germany; 2RWTH Aachen University, Germany; 3Kochi University, Japan; 4Mongolian Academy of Sciences, Mongolia

The late Early Cretaceous (121.4 to 100.5 Ma) was characterized by a gradual warming trend superimposed on an already warm greenhouse climate. Whereas the evolution of ocean temperatures during this time interval is relatively well constrained, information on the response of continental interiors to such climatic extremes is limited. Here we report new data from the continental Choir-Nyalga Basin of central Mongolia, which contains thick, lignite-rich successions (Khukhteeg Fm.) bearing an exceptionally well-preserved fossil flora of various pine and redwood species as well as representatives of extinct seed plant lineages. The continuous and often long-lasting accumulation of plant remains results in continental high-resolution archives documenting the palaeoecological conditions prevailing during bog growth.

In order to reconstruct the palaeoenvironmental conditions, a combined approach including brGDGT-based palaeothermometry, coal petrology and palynology is applied, complemented by geochemical measurements (TOC, TS, δ13Corg). Due to the limited biostratigraphic resolution of the continental Khukhteeg Fm., stratigraphic trends in δ13Corg will be applied for local and super-regional chemostratigraphic correlation. The carbon isotopic composition of the land plant-derived organic matter shows pronounced stratigraphic fluctuations and varies between -20.8 ‰ to -24.4 ‰ (average: -22.4 ‰). The brGDGT data represent the oldest analyses obtained from lignites so far. The new data indicate that the climatic conditions in central paleo-Asia (paleolatitude of ~38°N) during the late Early Cretaceous were characterised by high mean annual air temperatures (ranging between 8 ± 3°C and 10 ± 4°C).

4:15pm - 4:30pm
Topics: 3.12 Past climates and environments inform our future

New insights into hyperthermal events during the late Paleocene to early Eocene

Bryan Niederbockstruck1, Heather Jones1, Kazutaka Yasukawa2, Erika Tanaka3,4, Isabella Raffi5, Thomas Westerhold1, Ursula Röhl1

1MARUM - Center for Marine Environmental Sciences, University of Bremen, Germany; 2University of Tokyo; 3Kochi University; 4Chiba Institute of Technology; 5Dipartimento di Ingegneria e Geologia, Universita’ degli Studi “G. d’Annunzio” di Chieti-Pescara

The late Paleocene and early Eocene climate was punctuated by several warming events known as hyperthermals. These events reflect perturbations in the carbon cycle, identified by the negative carbon isotope excursions, including the prominent Paleocene-Eocene Thermal Maximum. Under the high carbon emission scenario of RCP8.5, the climate is predicted to most closely resemble early Eocene conditions within the next hundred years, making it a promising analog to study the possible long-term environmental changes that we have to face in the near future. High-resolution geochemical records from the Atlantic and Pacific provide astronomically calibrated age models of the early Paleogene. However, these sites are located in the equatorial- to subequatorial regions, so the high-latitude climate changes of the early Paleogene still remain elusive. IODP Expedition 378 recovered new Paleogene sediments at Site U1553 in the high-latitude Southwest Pacific.

Here, we present a novel late Paleocene to early Eocene age model spanning ~7 million years, which will be essential for future paleoceanographic studies of this site. To construct the age model, we used a combined chemostratigraphic and biostratigraphic approach. Our results show that the shape and pattern of the U1553 bulk sediment δ13C record generally match the orbitally-tuned records, which is reflective of a global trend. However, the nannofossil events at site U1553 exhibit a striking delay compared to lower latitude sites, suggesting that these commonly-used datums are not applicable at the high latitudes.

4:30pm - 4:45pm
Topics: 3.12 Past climates and environments inform our future

Environmental change at the Mid-Eocene Climate Optimum in Central Asia and potential relations with Eurasian paleoecological dispersals

Guillaume Dupont-Nivet1,2, Silke Voigt3, Alina Seufert3, Erwin Appel4, Saida Niglatova5, Nariman Jamikeshev1

1CNRS - université de rennes, France; 2GFZ Potsdam; 3Frankfurt university; 4Tuebingen university; 5Saptayev institute of geology, Kazakhstan

limatic optima and hyperthermals of the Paleogene period (66-34 Ma) open windows into the past to explore the Earth System under extreme conditions, beyond several tipping points. During this period Central Asia was intensely hot and arid and offered only a few corridors between Asian and European ecosystems that enabled significant dispersal events such as the "Grande Coupure". These events may have beentriggered by climatic and/or paleogeographical events including the fluctuations of the proto-Paratethysepicontinental sea and its progressive retreat. To date, it has been difficult to disentangle these various forcing factors.Sedimentary sections and associated climate tracers in this region and period are notoriously rare, and existing records suffer from poor age control that precludes robust correlations. We present here a high-resolution magnetostratigraphic dating of integrated environmental proxies from deposits of the Ili Basin, Kazakhstan, bearing rare Eocene mammal fossils. Preliminary results suggest the section encompasses a significantly wetter phase that can be precisely correlated to the Middle Eocene Climate Optimum, a globally recognized hyperthermal expressed by various extreme climate events from 40.5 to 40.1 Ma. In the studied Ili Basin record, Mammal fossils are reported to come precisely from this wet interval. This singular concentration of evidence suggests the MECO may have promoted Eurasian dispersal, however, further climate modelling and proxy data are required to identify potential controlling mechanisms.

4:45pm - 5:00pm
Topics: 3.12 Past climates and environments inform our future

Post-glacial climate amelioration recorded in the early Permian Aramac Coal Measures (Galilee Basin, Australia)

Alexander Thomas Wheeler1, Ulrich Heimhofer1, Joan Sharon Esterle2, Ralf Littke3, Laura Zieger3

1Institute for Geology, Leibniz University Hannover, Callinstraße 30, D-30167 Hannover, Germany; 2School of Earth and Environmental Sciences, The University of Queensland, QLD 4072, Australia; 3Energy and Mineral Resources Group (EMR), Institute of Geology and Geochemistry of Petroleum and Coal, Lochnerstr. 4-20, RWTH Aachen University, 52056 Aachen, Germany

The end of the Late Palaeozoic Ice Age (LPIA) was characterized by the development of widespread peat-forming mires across Gondwana concurrently with the evolution of the Glossopteris­-flora. The Aramac Coal Measures in the Galilee Basin of Australia represent some of the early phase of humic peat formation following the deglaciation in an ameliorating climate. This work aims to examine two boreholes using a multidisciplinary approach involving palynology, coal petrology, carbon isotope geochemistry and biomarkers to reconstruct the climate, environment and floras of this post-glacial period.

Palynostratigraphy suggests a late Artinskian to early Kungurian age for the Aramac Coal Measures separated from the overlying JK seams by an unconformity. Small-scale sedimentary dykes and cryostructured palaeosols suggest the peats would have formed under permafrost conditions. Palynological assemblages display a typical mix of early Permian elements and remnants of the Carboniferous floras with striate bisaccate pollen representing glossopterids, monosaccate pollen representing cordaitaleans, and spores representing herbaceous ferns, lycopsids and horsetails. Maceral analysis of the coals show high inertinite values, which, along with pristane/phytane ratios indicate an oxidative environment in which the peats were influenced by fire and/or fungi and bacteria. Stable carbon isotope values are typical for terrestrial environments (-22‰ to -26‰) but show an apparent cyclicity that may be related to climatic fluctuations following the end of the glaciation. This indicates the rise of the Glossopteris-flora was a gradual process which may have been influenced by warm and cool climatic phases well into the Permian.