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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.

Regional variations in the evolution of the Tibetan Plateau have important implications for our understanding of crustal deformation processes. There have been few studies of the evolution of the NW margin of the plateau and its transition to the Pamir Mountains to the west. We focus on this region with a multi-technique detrital study of two sedimentary sections in the Tarim Basin. Our provenance data show that an appreciable component of the detrital material in the sedimentary sections was derived from the Songpan-Ganzi–Tianshuihai composite terrane, with some contribution from the Karakoram and/or West Qiangtang. Given the proximity of the West Kunlun terrane to the sedimentary sections under study, and its long history of exhumation, this terrane in all likelihood also contributed to the studied successions. Our thermochronological data record phases of exhumation in the hinterland in the Triassic, Early Cretaceous and Oligo-Miocene. Similar to the Pamir Mountains, the Triassic and Oligo-Miocene periods of exhumation are attributed to the Cimmerian and Himalayan orogenies, respectively. The Early Cretaceous signal may reflect the distal effects of the Lhasa–Qiangtang collision. Coevality with deformation in the Pamir Mountains suggests a coupled geodynamic system, with retro-arc deformation associated with Neotethyan subduction in the west and terrane accretion in the east. Supplementary material: Detailed analytical method, sample information, petrographic, geochronological and low-temperature thermochronological data are available at https://doi.org/10.6084/m9.figshare.c.7040686

The Himalayan syntaxes, characterized by extreme rates of rock exhumation co-located with major trans-orogenic rivers, figure prominently in the debate on tectonic versus erosional forcing of exhumation. Both the mechanism and timing of rapid exhumation of the Namche Barwa massif in the eastern syntaxis remain controversial. It has been argued that coupling between crustal rock advection and surface erosion initiated in the late Miocene (8-10 Ma). Recent studies, in contrast, suggest a Quaternary onset of rapid exhumation linked to a purely tectonic mechanism. We report new multisystem detrital thermochronology data from the most proximal Neogene clastic sediments downstream of Namche Barwa and use a thermo-kinematic model constrained by new and published data to explore its exhumation history. Modeling results show that exhumation accelerated to ~4 km/m.y. at ~8 Ma and to ~9 km/m.y. after ~2 Ma. This three-stage history reconciles apparently contradictory evidence for early and late onset of rapid exhumation, and suggests efficient coupling between tectonics and erosion since the late Miocene. Quaternary acceleration of exhumation is consistent with river-profile evolution, and may be linked to a Quaternary river-capture event.

The mid-Cretaceous period was one of the warmest intervals of the past 140 million years, driven by atmospheric carbon dioxide levels of around 1,000 parts per million by volume. In the near absence of proximal geological records from south of the Antarctic Circle, it is disputed whether polar ice could exist under such environmental conditions. Here we use a sedimentary sequence recovered from the West Antarctic shelf—the southernmost Cretaceous record reported so far—and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82° S during the Turonian–Santonian age (92 to 83 million years ago). This record contains an intact 3-metre-long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores. A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1,120–1,680 parts per million by volume and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide.

The mid-Cretaceous period was one of the warmest intervals of the past 140 million years1,2,3,4,5, driven by atmospheric carbon dioxide levels of around 1,000 parts per million by volume6. In the near absence of proximal geological records from south of the Antarctic Circle, it is disputed whether polar ice could exist under such environmental conditions. Here we use a sedimentary sequence recovered from the West Antarctic shelf—the southernmost Cretaceous record reported so far—and show that a temperate lowland rainforest environment existed at a palaeolatitude of about 82° S during the Turonian–Santonian age (92 to 83 million years ago). This record contains an intact 3-metre-long network of in situ fossil roots embedded in a mudstone matrix containing diverse pollen and spores. A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric carbon dioxide concentrations of 1,120–1,680 parts per million by volume and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo under high levels of atmospheric carbon dioxide.

The mid-Cretaceous was one of the warmest intervals of the past 140 million years (Myr) driven by atmospheric CO2 levels around 1000 ppmv. In the near absence of proximal geological records from south of the Antarctic Circle, it remains disputed whether polar ice could exist under such environmental conditions. Here we present results from a unique sedimentary sequence recovered from the West Antarctic shelf. This by far southernmost Cretaceous record contains an intact ~3 m-long network of in-situ fossil roots. The roots are embedded in a mudstone matrix bearing diverse pollen and spores, indicative of a temperate lowland rainforest environment at a palaeolatitude of ~82°S during the Turonian–Santonian (92–83 Myr). A climate model simulation shows that the reconstructed temperate climate at this high latitude requires a combination of both atmospheric CO2 contents of 1120–1680 ppmv and a vegetated land surface without major Antarctic glaciation, highlighting the important cooling effect exerted by ice albedo in high-CO2 climate worlds.

West Antarctica hosts one of the largest continental rift systems on earth. Due to the extensive ice cover and the lack of exposed sedimentary rocks, little is known about the detailed geological and climatic evolution of West Antarc- tica. Here we present initial geochronologic, petrographic, stratigraphic, palynologic and clay mineralogy data of the first drill cores from the Amundsen Sea, off West Antarctica. The drilled succession revealed fine-grained, plant- bearing sediments of late Cretaceous age (∼93 to 85 Ma), deposited during continental stretching and breakup between West Antarctica and New Zealand. The Cretaceous deposits are separated by a peat layer from coarse- grained sandstones, which contain zircon and apatite yielding U-Pb ages of ca. 46-39 Ma. This implies a hiatus of at least 40 Myr between the fine-grained Cretaceous deposits and the overlying sandstones, which is in agreement with the absence of in-situ or reworked Paleocene to early/mid-Eocene palynomorphs. We tentatively interpret this hiatus as reflecting tectonic quiescence and slow downwearing, or non-deposition. This interpretation supports our previous thermochronological data from the onshore realm, which show that extension-related exhumation ceased at the end of the Cretaceous. We interpret renewed deposition during the upper Eocene to Oligocene to reflect renewed rapid exhumation along the West Antarctic Rift System and the rise of the Transantarctic Mountains. As well as the Eocene dates, the Eocene to Oligocene sandstones contain Cambro-Silurian, Permo-Triassic, Early Jurassic and Cretaceous apatite U-Pb age groups, which we interpret as derived from the Transantarctic Moun- tains (igneous and metamorphic rocks of the Cambro-Ordovician Ross Orogeny, and volcanic rocks related to the Early Jurassic Ferrar volcanic event) and Marie Byrd Land / West Antarctica (Permo-Triassic magmatic arc and widespread Cretaceous batholiths). Unusual for this kind of lithology, the sandstones’ apat

The Bengal Fan provides a Neogene record of Eastern and Central Himalaya exhumation. We provide the first detrital thermochronological study (apatite and rutile U-Pb, mica Ar-Ar, zircon fission track) of sediment samples collected during International Ocean Discovery Program (IODP) Expedition 354 to the mid-Bengal Fan. Our data from rutile and zircon fission-track thermochronometry show a shift in lag times over the interval 5.59-3.47 Ma. The oldest sample with a lag time of 6 m.y.) has a depositional age of 5.594.50 Ma, and the zircon and rutile populations then show a static peak until >12 Ma. This interval, from 5.59-4.50 Ma to >12 Ma, is most easily interpreted as recording passive erosion of the Greater Himalaya. However, single grains with lag times of

The Siwalik sedimentary rocks of the Himalayan foreland basin preserve a record of Himalayan orogenesis, paleo-drainage evolution, and erosion. This study focuses on the still poorly studied easternmost Himalaya Siwalik record located directly downstream of the Namche Barwa syntaxis. We use luminescence, palaeomagnetism, magnetostratigraphy, and apatite fission-track dating to constrain the depositional ages of three Siwalik sequences: the Sibo outcrop (Upper Siwalik sediments at ca. 200–800 ka), the Remi section (Middle and Upper Siwalik rocks at >0.8–<8.8±2.4 Ma), and the Siang section (Middle Siwalik rocks at <9.3±1.5 to <13.5±1.5 Ma). Cretaceous-Paleogene detrital zircon and apatite U-Pb ages, characteristic of the Transhimalayan Gangdese Batholiths that crop out northwest of the syntaxis, are present throughout the Sibo, Remi, and Siang successions, confirming the existence of a Yarlung-Brahmaputra connection since at least the Late Miocene. A ca. 500 Ma zircon population increases up section, most strikingly sometime between 3.6 to 6.6 Ma, at the expense of Transhimalayan grains. We consider the ca. 500 Ma population to be derived from the Tethyan or Greater Himalaya, and we interpret the up-section increase to reflect progressive exhumation of the Namche Barwa syntaxis. Early Cretaceous zircon and apatite U-Pb ages are rare in the Sibo, Remi, and Siang successions, but abundant in modern Siang River sediments. Zircons of this age range are characteristic of the Transhimalayan Bomi-Chayu batholiths, which crop out east of the syntaxis and are eroded by the Parlung River, a modern tributary of the Siang River. We interpret the difference in relative abundance of Early Cretaceous zircons between the modern and ancient sediments to reflect capture of the Parlung by the Siang after 800 ka.

The Lower Old Red Sandstone in southern Ireland is hosted in the Early Devonian Dingle Basin, which lies immediately south of the Iapetus Suture on the Dingle Peninsula, County Kerry. The basin developed as a post-Caledonian pull-apart structure prior to Acadian deformation, which in turn was followed by end-Carboniferous Variscan deformation. Detrital zircon U–Th–Pb geochronology is complemented by mica Ar–Ar and apatite U–Pb geochronology to gain a comprehensive understanding of the provenance of the Lower Devonian Lower Old Red Sandstone of the Dingle Basin and assess contributions of major tectonic components (e.g. Laurentia, Ganderia). Sedimentary rocks in the Lower Old Red Sandstone have similar detrital zircon age distributions, which are dominated by c. 1.2 Ga zircons as well as late Neoproterozoic grains. This indicates a dominant contribution of detritus of Laurentian affinity as well as contributions from westerly and southerly derived Ganderian detritus. Caledonian uplift of the area north of the Iapetus Suture would have facilitated a large contribution of (peri-)Laurentian material. The Upper Old Red Sandstone on the Dingle Peninsula has a distinctly different detrital zircon character including few late Neoproterozoic zircons and abundant zircons of c. 1.05 Ga age, indicating sediment derivation only from Laurentia and no recycling from the Lower Old Red Sandstone.