Volcanism and paleoenvironment of the pula maar complex: A pliocene terrestrial fossil site in Central Europe (Hungary) Publication date: 1 January 2020 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 537 Author(s): János Kovács, Károly Németh, Péter Szabó, László Kocsis, Gábor Kereszturi, Gábor Újvári, Torsten Vennemann Abstract We describe the Late Pliocene paleoenvironment and paleoclimate of the Pula fossil site of the western Pannonian Basin, Hungary, which occurs within a lacustrine succession deposited in a volcanic crater (maar). Radiometric dating of adjacent volcanic bodies hosting the fossil-bearing sedimentary assemblages gives an age of 4.25 ± 0.17 Ma (K–Ar). To date, five, articulated rhinoceros skeletons (Dihoplus sp.) have been recovered, and a few fragmentary remains of artiodactyls and freshwater fishes (Perca sp., Leuciscus sp. and Gobius sp.) are also present. An insect taphocoenosis comprises terrestrial groups that inhabited the former lake margins (Syrphidae, Heteroptera, Chalcidoidea, Tenebrionidae) as well as aquatic insects (Dytiscidae, Baetidae, and Chironomidae). Deciduous broad-leaved, woody plants prevailed in and around the Pula locality (Quercus, Ulmus, Zelkova, Acer, Salicaceae) and are associated with some rare floral elements (Ginkgo, Sassafras) and Buxus. Deposition at the lake bottom seems to have taken place in oxygen-depleted layers, and taphonomic evidence indicates that fossil material underwent minimal (if any) weathering. δ13C values of one rhinoceros tooth suggest that this mammal consumed mixed C3 plants in a wooded environment. The climatic conditions inferred from the reconstructed vegetation and stable oxygen isotope data from the tooth enamel support a Cf-type climate (Köppen classification) with a mean annual temperature of 10–13 °C with some dry periods during the year. Pula is comparable to other maar fossil sites of Pliocene age such as Camp dels Ninots, Spain, and Hajnáčka I, Slovakia.

Reconstruction on regional paleo-drainage evolution in the northern Junggar Basin, China during the last ~27 myr from provenance analyses and its implications for uplift of the Altai Mountains Publication date: 1 January 2020 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 537 Author(s): Chaopeng Li, Dewen Zheng, Jimin Sun, Jingxing Yu, Yan Ma, Huiping Zhang, Yizhou Wang, Jianzhang Pang, Youjuan Li, Yuqi Hao Abstract Tectonic activity and climate change are regarded as two important driving forces on the evolution of large-scale drainage. The evolution of the Irtysh River and Ulungu River, two large-scale drainage systems in the northern Junggar Basin, can provide a key constraint on the uplift of the Altai Mountains and Central Asian aridification. However, we know little about the evolution of these two large-scale rivers. This study presents new detrital zircon U–Pb data from the late Oligocene to late Miocene sedimentary sequences and modern river sediments to reconstruct Cenozoic paleo-drainage evolution in the northern Junggar Basin. The detrital zircon U–Pb results show a single major population at 460-360 Ma, which is mainly derived from the Altai Mountains, for late Oligocene and early Miocene sequences, but two populations at 460-360 Ma and 340-200 Ma, which are mainly from the Altai Mountains and East Junggar terrane, for middle and late Miocene sequences. Our provenance study argues that the Irtysh River and Ulungu River in their modern extent did not exist prior ~18 Ma when the Altai Mountains allowed southward-flowing rivers to transport sediments into the inner Junggar Basin directly. The provenance shift in northern Junggar Basin at 17–18 Ma represents the progressive drainage expansion of the Ulungu River, evolving from relatively small rivers confined to the eastern Junggar Basin to a near-modern large-scale drainage system, due to the rapid uplift in the East Junggar terrane and eastern Altai Mountains in early Miocene. After ~6 Ma, the Irtysh River experienced a progressive drainage expansion, captured the southward-flowing tributaries of the Ulungu River and formed modern drainage pattern. Our study supports the initiation of exhumation before late Oligocene and a local tectonic uplift in early Miocene in Altai Mountains, which imply a complex deformation process in the Central Asia.

Vegetation succession and climate change during the early pleistocene (2.2-1.8 Ma) in the Nihewan Basin, northern China Publication date: 1 January 2020 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 537 Author(s): Guoqiang Ding, Yuecong Li, Zhen Zhang, Wensheng Zhang, Yong Wang, Zhenqing Chi, Gaihui Shen, Baoshuo Fan Abstract The Nihewan Formation, northern China is ideal for studying environmental changes during the early Pleistocene. In conjunction with palaeomagnetic measurements, pollen and grain-size analyses were conducted on 120 samples from a ~24 m long section (2.2-1.8 Ma) of core NHA from the Nihewan Basin, in order to reconstruct past vegetation and climatic changes. The pollen assemblages were dominated by Pinus, indicating that the vegetation was primarily pine forest and that the climate was relatively warm and wet. From 2.15-1.92 Ma, deciduous broad-leaved tree pollen significantly increased to >10% of the total, showing that more broad-leaved trees grew in the study area during the warmest and wettest period in the study section. From 1.92-1.78 Ma (coeval with the Olduvai event), Pinus and broad-leaved tree pollen types decreased. The percentages of Picea (>20%), Artemisia and Chenopodiaceae increased, indicating that spruce forests expanded, the openness of the forested areas increased and the climate became cold and dry. The vegetation changes reconstructed during the Olduvai period indicates that the climate in the Nihewan Basin was cold and dry, relating to global cooling facilitated by the uplift of the Tibetan Plateau and the strengthening of the winter monsoon.

A long-term, high-latitude record of Eocene hydrological change in the Greenland region Publication date: 1 January 2020 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 537 Author(s): Gordon N. Inglis, Matthew J. Carmichael, Alexander Farnsworth, Daniel J. Lunt, Richard D. Pancost Abstract A range of proxy approaches have been used to reconstruct short-term changes to Earth's hydrological cycle during the early Eocene hyperthermals. However, little is known about the response of Earth's hydrological and biogeochemical systems to long-term Cenozoic cooling, which began following the Early Eocene Climatic Optimum (53.3 – 49.4 million years ago; Ma). Here, we use the molecular distribution and isotopic composition of terrestrial biomarkers preserved in marine sediments of ODP Site 913, East Greenland, to develop a long-term record of high-latitude hydrological change between 50 and 34 Ma. There is a marked decline in the concentration of conifer-derived diterpenoids and angiosperm-derived triterpenoids during the Eocene. As the input of wind-blown conifer pollen remains stable during this interval, this implies that decreasing di- and triterpenoid concentrations reflect declining influence of fluvial inputs – and perhaps terrestrial runoff – throughout the Eocene. Branched GDGTs and bacterial-derived hopanes indicate an increased input of soil- and kerogen-derived organic matter, respectively, after 38 Ma. This coincides with evidence for ice rafted debris and suggests input of organic matter via glacial processes. This also implies some continental glaciation occurred on East Greenland in the middle-to-late Eocene. Leaf wax hydrogen isotopes extending throughout this section – the first such long-term record from the Paleogene - indicate that precipitation δ2H was persistently higher than that of modern coastal Greenland, consistent with warmer ocean source waters and enhanced poleward moisture transport. Non-intuitively, however, this effect appears to have been smallest during the warmest part of the record, and higher δ2H values occur in the middle Eocene. Although interpretation of these hydrogen isotope trends is unclear, they clearly indicate – alongside the changes in biomarker abundances – a perturbed hydrological cycle through the Eocene in coastal Greenland. More long-term records are required to ascertain if this represents regional or global hydrological reorganisation.

Continuous simulations over the last 40 million years with a coupled Antarctic ice sheet-sediment model Publication date: 1 January 2020 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 537 Author(s): David Pollard, Robert M. DeConto Abstract Much of the knowledge of Antarctic Ice Sheet variations since its inception ~34 Ma derives from marine sediments on the continental shelf, deposited in glacimarine or sub-ice environments by advancing and retreating grounded ice, and observed today by seismic profiling and coring. Here we apply a 3-D coupled ice sheet and sediment model from 40 Ma to the present, with the goal of directly linking ice-sheet variations with the sediment record. The ice-sheet model uses vertically averaged ice dynamics and parameterized grounding-line flux. The sediment model includes quarrying of bedrock, sub-ice transport, and marine deposition. Atmospheric and oceanic forcing are determined by uniform shifts to modern climatology in proportion to records of atmospheric CO2, deep-sea-core δ18O, and orbital insolation variations. The model is run continuously over the last 40 Myr at coarse resolution (80 or 160 km), modeling post-Eocene ice, landscape evolution and off-shore sediment packages in a single self-consistent simulation. Strata and unconformities are tracked by recording times of deposition within the model sediment stacks, which can be compared directly with observed seismic profiles. The initial bedrock topography is initialized to 34 Ma geologic reconstructions, or an iterative procedure is used that yields independent estimates of paleo bedrock topography. Preliminary results are compared with recognized Cenozoic ice-sheet variations, modern sediment distributions and seismic profiles, and modern and paleo bedrock topographies.

Early growth dynamics of titanosaur sauropods inferred from bone histology Publication date: 1 January 2020 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 537 Author(s): Romina González, Ignacio A. Cerda, Leonardo S. Filippi, Leonardo Salgado Abstract Histological studies have proven to be a powerful tool for addressing sauropod paleobiology, with most focus on adult and subadult individuals. The aim of this study is to describe long bone histology (femur) in early juvenile titanosaur sauropods, to expand our knowledge about early stages of development. The material consists of two small femora of indeterminate titanosaurs from the Upper Cretaceous Bajo de la Carpa and Allen formations of Argentina. Both femora from juvenile specimens show predominant fibrolamellar bone tissue with plexiform vascularization pattern, suggesting a fast growth rate. Despite the early stage of development of the studied specimens, secondary remodelling is evident in one of them. In the other sample, a growth mark is observed, which suggests unexpected cyclical growth and a possible departure from the typical growth strategy of sauropod dinosaurs. In addition, we examine indeterminate long bones of titanosaur embryos from the Anacleto Formation of Argentina. The embryos shows poor development of cortical bone, high density of large simple canals and presence of Kastschenko's line suggest that these individuals died during an early stage of ossification. This study reveals that the early growth of at least some titanosaurs departs from the reported in neosauropod dinosaurs. Graphical abstract

Abrupt changes in Indian summer monsoon strength during the last ~900 years and their linkages to socio-economic conditions in the Indian subcontinent Publication date: 15 December 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 536 Author(s): Anil K. Gupta, Som Dutt, Hai Cheng, Raj K. Singh Abstract Abrupt shifts in Indian summer monsoon (ISM) precipitation largely affected regional hydrometeorology, accelerating socio-economic and cultural adaptations of agrarian economies in South Asia in the last millennium. Linking ISM variability to human history in the Indian subcontinent is still limited by the scarcity of high-resolution paleoclimatic data for the period encompassing the last 1000 years or earlier. We present a new high resolution oxygen isotope proxy record from the Wah Shikar cave, northeastern India and identified abrupt shifts in the ISM that had profound impact on human societies during the last ~900 yrs. The ISM was strong during the Medieval Climate Anomaly (MCA) and the Current Warm Period (CWP), and show multiple shifts during the Little Ice Age (LIA). The abrupt shifts in the ISM were more frequent during warm intervals, showing a secular trend with few exceptions during the cold periods. Intervals of prolonged summer monsoon weakening are correlated to the decline of major dynasties in India, possibly due to decrease in agriculture productivity, declining economy and societal crisis. Changes in atmospheric temperature due to volcanic eruptions and sun spot activity have played major role in the onset of the LIA and other prolonged weak intervals of the ISM during the last ~900 yrs.

Wind variability over the northern Indian Ocean during the past 4 million years – Insights from coarse aeolian dust (IODP exp. 359, site U1467, Maldives) Publication date: 15 December 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 536 Author(s): Sebastian Lindhorst, Christian Betzler, Dick Kroon Abstract The lithogenic fraction of carbonate drift sediments from IODP Exp. 359 Site U1467 (Maldives) provides a unique record of atmospheric dust transport over the northern Indian Ocean during the past 4 Myr. Grain-size data provide proxies for dust flux (controlled by source area aridity) as well as wind transport capacity (wind speed). Entrainment and long-range transport of dust in the medium to coarse silt size range is linked to the strength of the Arabian Shamal winds and the occurrence of convective storms which prolong dust transport. Dust flux and the size of dust particles increased between 4.0 and 3.3 Ma, corresponding to the closure of the Indonesian seaway and the intensification of the South Asian Monsoon. There is no clear trend in dust flux between 3.3 and 1.6 Ma, whereas wind transport capacity decreased. Between 1.6 Ma and the Recent, dust flux increased and shows higher variability, especially during the last 500 kyr. Transport capacity increased between 1.2 and 0.5 Ma and slightly decreased since then. Frequency analysis shows that dust transport varies on orbital timescales, with eccentricity control being the most prominent (400 kyr throughout the record, 100 kyr between 2.0 and 1.3 Ma, and since 1.0 Ma). Higher frequency cycles (obliquity and precession) are more pronounced in wind transport capacity than in the amount of dust. This indicates that the amount of coarse dust in sediments from the Maldives as a far-field site is more prone to changes in transport mechanisms than to changes in dust source-area aridity.

Palaeoecology of the archaeocyathan reefs from the lower Cambrian Harkless Formation, southern Nevada, western United States and carbon isotopic evidence for their demise Publication date: 15 December 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 536 Author(s): Sara B. Pruss, Emily F. Smith, Olivia Leadbetter, Rhiannon Z. Nolan, Melissa Hicks, David A. Fike Abstract Archaeocyath sponges, the first group of reef-building organisms, have a globally distributed albeit restricted stratigraphic occurrence. Archaeocyathan reefs are well known from the western United States, particularly in units like the Montenegro, Poleta, and Harkless formations of the White-Inyo ranges and Esmeralda County, Nevada. While it is recognized that these organisms disappear at some time above the last occurrence of their reefs in the Harkless Formation, the precise timing of their disappearance is unknown. Here, we show that the last archaeocyathan reefs in the upper Harkless Formation near Gold Point, Nevada, are overlain by 20–60 m of interbedded siltstone and carbonate that preserve a negative carbon isotopic excursion consistent with the AECE event (archaeocyath extinction carbon excursion). Point counts of reef thin sections and analysis of acid-insoluble residues of reef and reef-adjacent samples illustrate that these last reefs also harbor previously undescribed diversity and abundance of animals living in and among the reefs, including an array of small shelly fossil taxa. We confirm previous work that the reefs of the early Cambrian were ecologically diverse and functioned in many ways like reefs of the later Paleozoic, even just prior to their global demise in the late early Cambrian, and that the extinction of archaeocyaths is recorded in strata of the Harkless Formation.

Evolution of mid-Cretaceous radiolarians in response to oceanic anoxic events in the eastern Tethys (southern Tibet, China) Publication date: 15 December 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 536 Author(s): Tianyang Wang, Guobiao Li, Jonathan C. Aitchison, Lin Ding, Jiani Sheng Abstract Oceanic anoxic events (OAEs) are well-known from their widespread black shale and carbon isotopic excursions in the (western and eastern) Tethys and Atlantic Ocean. However, the weakest link in the studies of the OAEs is biological evolution. Sedimentological, biostratigraphical and geochemical data from Albian to Coniacian strata in southern Tibet recorded turnover events and fluctuations in diversity of the radiolarian fauna within the eastern Tethys during OAE 1d and OAE 2. Abundant radiolarian fossils were obtained from the Gyabula Formation, with 93 species from 43 genera identified and assigned to the mid to Upper Cretaceous Acaeniotyle umbilicata, Archaeospongoprunum tehamaensis, Crucella cachensis, Alievium superbum, and Dictyomitra formosa zones. The association of carbon isotopic excursions, black shale and radiolarian turnover indicates extensive changes in the ocean-climate system. Nutrients are made increasing available to the marine plankton through submarine volcanic activity and rising sea-level, which were a likely cause of radiolarian turnover at/or near the OAEs. Active submarine tectonism-volcanism leads to the expansion of the hypoxic zone and may cause many deeper dwelling forms to become extinct whereas most of the shallower dwelling radiolarians survive. Radiolarian evolution thus provides a useful record with which to seek understand relationships between climate, paleoceanographic processes and plankton evolution.