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Extensive ice coverage largely prevents investigations of Antarctica’s unglaciated past. Knowledge about environmental and tectonic development before large-scale glaciation, however, is important for understanding the transition into the modern icehouse world. We report geochronological and sedimentological data from a drill core from the Amundsen Sea shelf, providing insights into tectonic and topographic conditions during the Eocene (~44 to 34 million years ago), shortly before major ice sheet buildup. Our findings reveal the Eocene as a transition period from >40 million years of relative tectonic quiescence toward reactivation of the West Antarctic Rift System, coinciding with incipient volcanism, rise of the Transantarctic Mountains, and renewed sedimentation under temperate climate conditions. The recovered sediments were deposited in a coastal-estuarine swamp environment at the outlet of a >1500-km-long transcontinental river system, draining from the rising Transantarctic Mountains into the Amundsen Sea. Much of West Antarctica hence lied above sea level, but low topographic relief combined with low elevation inhibited widespread ice sheet formation.

Polar research is an interdisciplinary and multi-faceted field of research ranging from history to geology and geophysics to social sciences and education. Thus, several different universities and institutions within Germany participate in polar research. The seminar series POLARSTUNDE, organized by the German Society for Polar Research (Deutsche Gesellschaft für Polarforschung) and the German National Committee of the Association of Polar Early Career Scientists (APECS Germany) regularly features different topics of German polar research. Although initially a "pandemic solution", the seminar series has established itself as a valuable and highly successful part of the German polar research landscape. The seminar series was held in German and was aimed at both scientists and the general public. This article addresses the first season of POLARSTUNDE and provides (1) comprehensive summaries of the talks and (2) insight into the planning and execution from an organizational point of view.

The first low‐temperature thermochronological data from Thurston Island, West Antarctica, provide insights into the poorly constrained thermo‐tectonic evolution of the paleo‐Pacific margin of Gondwana since the Late Paleozoic. Here we present the first apatite fission track (AFT) and apatite (U‐Th‐Sm)/He (AHe) data from Carboniferous to mid‐Cretaceous (meta‐) igneous rocks from the Thurston Island area. Thermal history modeling of AFT dates of 145–92 Ma and AHe dates of 112–71 Ma, in combination with kinematic indicators, geological information and thermobarometrical measurements, indicate a complex thermal history with at least six episodes of cooling and reheating. Thermal history models are interpreted to reflect Late Paleozoic to Early Mesozoic tectonic uplift of pre‐Jurassic arc sequences, prior to the formation of an extensional Jurassic–Early Cretaceous back‐arc basin up to 4.5 km deep, which was deepened during intrusion and rapid exhumation of rocks of the Late Jurassic granite suite. Overall Early to mid‐Cretaceous exhumation and basin inversion coincided with an episode of intensive magmatism and crustal thickening and was followed by exhumation during formation of the Zealandia‐West Antarctica rift and continental break‐up. Final exhumation since the Oligocene was likely triggered by activity of the West Antarctic rift system and by glacial erosion.

TheWest Antarctic Rift System is one of the largest continental rifts on Earth. Because theWest Antarctic Ice Sheet mostly covers it, its evolution is still poorly understood. Here we present the first low-temperature thermochronology data from eastern Marie Byrd Land, an area that stretches 1000 km along the rift system. Furthermore, we petrographically analysed glacially transported detritus deposited in the marine realm offshore Marie Byrd Land. Our data provide information about the subglacial geology, and the tectonic and morphologic history of the rift system. Dominant lithologies of coastal Marie Byrd Land are igneous rocks that intruded (presumably early Paleozoic) low-grade meta-sediments. No evidence was found for un-metamorphosed sedimentary rocks exposed beneath the ice. According to the thermochronology data, rifting occurred in two episodes. The earlier occurred between 100 and 60 Ma and led to widespread tectonic denudation and block faulting over large areas of Marie Byrd Land. The later started during the Early Oligocene and was confined to western Pine Island Bay area. This Oligocene structure may kinematically be linked to previously described rift structures reaching into Bellingshausen Sea and beneath Pine Island Glacier, which were also assumed to be of Cenozoic age. However, our data provide the first direct evidence for Cenozoic tectonic activity along the rift system outside the Ross Sea area. Furthermore, our data suggest that uplift of the Marie Byrd Land dome only started at �20 Ma; that is, nearly 10 Ma later than previously assumed. The Marie Byrd Land dome is the only extensive part of West Antarctica elevated above sea level. Since the formation of a continental ice sheet requires a significant area of emergent land, our data imply that initiation of extensive glaciation of this part of West Antarctica may only have started since the early Miocene.

Polar geoscientific research in Germany during the past decades has substantially contributed to the understanding of the geological structure and history of the polar regions, and of the complex feedback mechanisms operating both in Antarctica and in the Arctic. Important questions could be answered, new ones raised from the results obtained. This strategy paper describes the status quo of Germany‘s polar research in the light of its present social importance. On this basis, the key questions concerning the geological settings and the role of the polar regions in the global climate system are intro- duced, which have to be answered in order to better predict future changes and feedbacks in the Earth System. The results could provide significant support towards a sustainable development of the polar regions. Finally, the need for action for the national polar geoscientific research is outlined with a perspec- tive of 10 to 20 years, based upon the currently existing political and logistical boundary conditions.

Due to extensive glacial cover, the evolution or the West Antarctic Rift System (WARS) and the proto- Pacific margin of Gondwana are still poorly understood. Here we present the first low-temperature thermochronology data from eastern Marie Byrd Land and the Pine Island Bay area. The goal of our study is to decipher the long-term thermotectonic evolution of this area, infer its denudation history, and to provide estimates for paleotopography and potential links to the glaciation history. Our data show that during early and mid-Cretaceous subduction along the proto-Pacific margin, all of Marie Byrd Land and the Pine Island Bay area experienced rapid exhumation. This rapid exhumation continued for about 25 Myr after subduction stopped, presumably driven by tectonic denudation related to continental breakup between Zealandia and West Antarctica and rifting activity of the WARS. This late Cretaceous extension period was related to rapid topography reduction, as expressed by the formation of the West Antarctic erosion surface close to sea level, and was probably related to free-boundary gravitational collapse of the Gondwanide orogen. By ~60 Ma, rapid exhumation stopped, which we interpret as cessation of the first WARS rifting period. Cretaceous rapid exhumation was followed by very low exhumation rates throughout the Cenozoic, which we explain by tectonic quiescence and subdued topography. After ~30 Ma, and restricted to the western Pine Island Bay area, rapid exhumation resumed, presumably coeval with large-scale crustal tilting of the eastern Pine Island Bay area towards the Pine Island trough. We interpret this as indicating renewed activity of the WARS, (i) suggesting that Cenozoic rifting activity was much more localized than Cretaceous rifting, and (ii) corroborating previous assumptions that the WARS branches from the continental interior into the Amundsen Sea. Our structural model, based on the thermochronology data, kinematically links the rift branches reachi

Due to extensive glacial cover, the evolution or the West Antarctic Rift System (WARS) and the proto-Pacific margin of Gondwana are still poorly understood. Here we present the first low-temperature thermochronology data from eastern Marie Byrd Land and the Pine Island Bay area. The goal of our study is to decipher the long-term thermotectonic evolution of this area, infer its denudation history, and to provide estimates for paleotopography and potential links to the glaciation history. Our data show that during early and mid-Cretaceous subduction along the proto-Pacific margin, all of Marie Byrd Land and the Pine Island Bay area experienced rapid exhumation. This rapid exhumation continued for about 25 Myr after subduction stopped, presumably driven by tectonic denudation related to continental breakup between Zealandia and West Antarctica and rifting activity of the WARS. This late Cretaceous extension period was related to rapid topography reduction, as expressed by the formation of the West Antarctic erosion surface close to sea level, and was probably related to free-boundary gravitational collapse of the Gondwanide orogen. By ~60 Ma, rapid exhumation stopped, which we interpret as cessation of the first WARS rifting period. Cretaceous rapid exhumation was followed by very low exhumation rates throughout the Cenozoic, which we explain by tectonic quiescence and subdued topography. After ~30 Ma, and restricted to the western Pine Island Bay area, rapid exhumation resumed, presumably coeval with large-scale crustal tilting of the eastern Pine Island Bay area towards the Pine Island trough. We interpret this as indicating renewed activity of the WARS, (i) suggesting that Cenozoic rifting activity was much more localized than Cretaceous rifting, and (ii) corroborating previous assumptions that the WARS branches from the continental interior into the Amundsen Sea. Our structural model, based on the thermochronology data, kinematically links the rift branches reachin

East Antarctica formed by amalgamation of a number of cratons along distinct Ediacaran mobile belts. They include the ca. 600-500 Ma old East African-Antarctic Orogen (EAAO) and the Kuunga Orogen, which seem to converge in the region of Dronning Maud Land. In central Dronning Maud Land, the major Forster Magnetic Anomaly separates rocks with Grenville-age protolith ages (ca. 1130-1000 Ma) to the West from rocks with Early Neoproterozic protolith ages (ca. 1000-930 Ma) to the East. The Forster Magnetic Anomaly is therefore interpreted as a suture between these two provinces. New field work during three recent international expeditions, Geodynamic Evolution of East Antarctica (GEA) I to III, and first geoscientific results reveal a complex tectonic architecture between central Dronning Maud Land and Sør Rondane in eastern Dronning Maud Land. East of the Forster Magnetic Anomaly, the magnetic anomaly pattern changes significantly and typical Maud-type crust is apparently lacking. Particularly, the GEA II campaign targeted a range of previously unvisited nunataks between Sør Rondane and central Dronning Maud Land (from Blåklettane and Bergekongen in the East to Urna and Sørsteinen in the West). These nunataks are dominated by medium- to high-grade metasedimentary and metavolcanic rocks of possibly Neoproterozoic age, including abundant marble and graphite schists. Sør Rondane in eastern Dronning Maud Land, on the other hand, is dominated by two distinct blocks separated by the dextral Main Shear Zone. The northwestern block appears as part of the EAAO or the Kuunga Orogen, where new SHRIMP zircon data from metamorphic rims provide ages of ca. 560 Ma. The southeastern block is made up of a TTG terrane, which provides 12 new zircon crystallization ages ranging from 1000-930 Ma. The TTG terrane has predominantly oceanic affinities and the wide range of ages might indicate long-lasting accretionary tectonics. The TTG terrane shows in part limited tectonic overprint and coul

Rock samples from previously undescribed nunataks and moraines of the Steingarden area, southeasternmost central Dronning Maud Land, Antarctica, were petrographically studied. The nunatak rocks comprise banded felsic and mafic gneisses and amphibolites with some minor marbles. They underwent granulite-facies peak metamorphism. Moraine rocks, which were sourced from ice-covered occurrences in the south, comprise garnet-biotite gneisses, kyanite-staurolite-sillimanite gneisses, amphibolites, late-tectonic and post-tectonic igneous rocks as well as an assemblage of conspicuous dark graphite-bearing and pyrite-bearing schists with related vanadium-green muscovite bearing lithologies. The dark schists represent greenschist-facies to amphibolite-facies grade metamorphosed black-shale-type sediments. The nunatak rocks and parts of the moraine rocks are comparable to lithologies in central Dronning Maud Land. The dark graphite-bearing and pyritebearing schists and related vanadium-green muscovite bearing lithologies have higher-grade metamorphosed equivalents in central Sør Rondane. These rocks indicate the existence of a tectonic boundary south of Steingarden, which may represent the Pan-African suture between West and East Gondwana.

An integrated structural, petrological, and geochronological/ thermochronological study was undertaken to constrain the tectonic controls on the exhumation of the Voltri Massif high-pressure (HP) complex, located in the Ligurian portion of the Western Alps (Italy). Petrotextural analyses were performed to identify the pressure-temperature interval of (1) peak metamorphism (the D1-M1 stage) to eclogitic/blueschist facies conditions and (2) the main retrogressive event (the D2-M2 stage) to greenschist facies conditions. U-Pb SHRIMP dating on a zircon rim (33.8 ± 0.8 Ma) and titanite grains (29 ± 5 Ma), coupled with 40Ar-39Ar analyses on phengite (∼64 Ma to ∼34 Ma) placed temporal constraints on the exhumation path from the D1-M 1 to the D2-M2 stages at the Eocene-Oligocene boundary. Apatite fission track thermochronology, with older ages of 23.9 ± 4.9 Ma, confirms the existence of a regional, Late Oligocene to Miocene cooling/exhumation event for the Voltri Massif (the D3-M3 stage). The compilation of this pressure-temperature-deformation-time path supports a change in the exhumation history: (1) an initial stage, from the D1-M1 to the D2-M2, which was nearly isothermal with highly variable exhumation rates, and (2) a second stage, from D2-M2 to upper crustal levels, which was accomplished by cooling and moderate exhumation rates of ∼1-2 mm yr-1. This two-stage path can be reconciled with the dominant tectonic mechanisms responsible for exhumation of HP rocks in the Voltri Massif area. At the regional scale, this path is consistent with major geodynamic reorganization in the Mediterranean region at the Eocene-Oligocene time boundary, which involved a switch from synorogenic events during transpressive kinematics at the Alpine-Apennine plate boundaries, to postorogenic processes related to crustal thinning and opening of back-arc basins.

This research paper investigates the thermo-tectonic history of the north Mozambican basement subsequent to the Pan-African metamorphism. Six 40Ar/39Ar hornblende, three 40Ar/39Ar biotite and 25 titanite fission-track data place new constraints on the earliest timing of rifting in the central sector of Gondwana, and demonstrate a close linkage between the geometric rift configuration and the ductile metamorphic basement fabrics during the initial dispersal of the supercontinent. The 40Ar/39Ar hornblende and biotite ages range from c. 542 to 456 Ma and from c. 448 to 428 Ma, respectively. These data record slow basement cooling after the latest Pan-African metamorphism at rates of c. 7–11 °C Ma−1 between Early and Late Ordovician times. Locally, syn- to post-tectonic granitoid emplacements around 500–450 Ma delayed basement cooling to Late Ordovician–Early Silurian times. The titanite fission-track (TFT) ages fall into two age groups of c. 378–327 Ma and c. 284–219 Ma. The older TFT ages record very slow cooling from the Late Ordovician–Early Silurian to below 275±25 °C in the Late Devonian–Early Carboniferous at slow rates of less than 1 °C Ma−1. This slow cooling is related to decreasing denudation in association with the establishment of pre-Karoo peneplains in central Gondwana. The younger TFT ages record denudation due to rift flank uplift in the context of initial Gondwana disintegration in the Mozambican sector. Corresponding Early–Late Permian crustal extension proceeded obliquely to a NW–SE tensional palaeo-stress field and was associated with a brittle reactivation of easterly trending ductile basement fabrics. In total, up to ≤9–12 km of denudation is deduced from the TFT results since Permo-Carboniferous times.