Diagenetic changes on bone histology of Quaternary mammals from a tropical cave deposit in southeastern Brazil Publication date: 1 January 2020 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 537 Author(s): Elver Luiz Mayer, Alex Hubbe, Jennifer Botha-Brink, Ana Maria Ribeiro, Paulo Miguel Haddad-Martim, Walter Neves Abstract Karst caves are suitable environments for the accumulation and preservation of fossils. Cave deposits are often complex and the environmental conditions within cave sites result from intricate interactions between various biological, physical and chemical factors. However, it is not fully understood how the complexity of the environmental conditions of caves influences bone diagenesis. The study of the initial stages of bone diagenesis depends to a large extent on understanding the changes in the bone histology. To contribute to this issue, we examine a set of postmortem changes affecting the bone histology of Quaternary mammals that accumulated naturally in Locus 2, a pitfall site in Cuvieri Cave, located in the tropical region of Brazil. Our analyses show that bones deposited in caves may be subject to a peculiar set of environmental conditions that in tropical regions may prevent the preservation of bone histological structure. The effect of diagenetic processes on the bones differs depending on the taphonomic stage of the bone and the diagenetic alterations appear to have influenced each other. The deposition of bioclasts following the entrapment of individuals in Locus 2 favours the proliferation of bacteria on bones and appears to be important in directing the diagenetic alteration. The hydrological regime of the cave, that is recharge with potential phases of higher humidity, also is important in directing the diagenetic alteration and further decreased the preservation potential of the bone microstructure. The formation of macroscopic and microscopic cracks related to bone weathering in caves shows that the taphonomic processes peculiar to these environments are poorly understood, highlighting the need for more research to be conducted on cave taphonomy.

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.

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

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.

Two long and pronounced cold periods 3,000–5,000 and 6,600–8,400 years B.P. in East Asia and the southward migration of the westerly jet Publication date: 1 January 2020 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 537 Author(s): Si Woong Bae, Kyung Eun Lee, Tae Soo Chang Abstract To reconstruct the variations in sea surface temperature (SST) during the Holocene, the alkenone unsaturation index of marine sediments from two deep-drilled cores and 81 different core-top surface sediments recovered from the Heuksan Mud Belt, located off the southwestern coast of the Korean Peninsula, was measured. First, comparison of the alkenone temperature estimates of 81 core-top sediments with in situ temperatures indicated that the alkenone temperatures corresponded to the average SST in April to October. The spatial distribution pattern of the core-top alkenone SST showed a north–south temperature gradient, which represented the in situ temperatures well. This indicated that the effects of the resuspension and lateral transport of sediments on the past temperature estimation might be insignificant. Based on the two deep-drilled cores, variations in the alkenone SST during the Holocene were reconstructed. In general, the alkenone SST decreased by less than 1 °C from the early to late Holocene. An interesting feature was the presence of two long and pronounced cold (approximately 2 °C) periods, which occurred at 3–5 kyr and 6.6–8.4 kyr B.P. These cold periods were also observed in other mid-latitude regions in East Asia, indicating that the cooling pattern was regional. The cold periods appeared to be associated with the southward migration of the westerly jet at that time. Investigations into the effects of local sea level changes and resultant changes in the tidal regime on changes in the SST during the Holocene period suggested that they were insignificant in the study area.

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.

Lower Sappington Formation palynofacies in Montana confirm upper famennian black shale paleoenvironments and sequences across western North America Publication date: 15 December 2019 Source: Palaeogeography, Palaeoclimatology, Palaeoecology, Volume 536 Author(s): Mercedes di Pasquo, George W. Grader, Marcelina Kondas, P. Ted Doughty, Paweł Filipiak, Beverly J. Rice, Peter E. Isaacson Abstract For the first time, Late Devonian palynofacies analyses of the Lower Sappington shale units U1A─D was carried out at Peak 9559 (Sacajawea) and Ainger Lake in the Bridger Range of Montana. Diagnostic spore species Apiculiretusispora verrucosa, Diducites mucronatus and D. versabilis allowed the correlation of our U1A-D with the European Late Famennian A. verrucosa-V. hystricosus Palynozone. The first appearance of Gorgonisphaeridium winslowiae in U1 is the oldest record before the inception of Retispora lepidophyta. Four palynofacies correlative with U1A-D and new findings of invertebrates and microfossils allow the interpretation of paleoenvironmental changes. Amorphous organic matter, marine phytoplankton and pyrite in black shales of U1A-B indicate anoxic bottom conditions occurred in offshore marine environments. An erosional fossiliferous phosphatic lag above these units confirms a regional SB. U1C black shales composed by AOM, marine and terrestrial phytoplankton, land–derived remains and pyrite reveal shallower, dysoxic-anoxic, brackish water environments. A thin layer at the base of Unit 1D yielded AOM and marine phytoplankton and low terrestrial input indicating dysoxic-anoxic conditions were maintained. The lack of organic matter and the presence of invertebrates and microfossils in a thin green fossiliferous mudstone supports the establishment of normal, oxygenated marine conditions maintained in the basal Middle Sappington Member (U2). These two thin units are not part of the underlying anoxic black shale (U1A-B) sequence as commonly was over-simplified. Instead, they are part of a transgressive interval with the basal Middle Sappington. A correlation of the U1 shale interval is established with the global multiphase Dasberg Event.

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.