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Unlike other mass extinctions of the Phanerozoic, the Late Ordovician mass extinction took place during an icehouse interval, accompanied by the glaciation of Gondwana. Ice sheets reached their maximum during the Hirnantian and global sea-level dropped substantially. Consequently, the shallow tropical shelf environments of Laurentia and Baltica became subaerially exposed or remaining submerged shelves were characterized by very shallow water-depths. Redox proxies suggest that most shallow shelf settings were well oxygenated to that time, while the global extent of anoxic environments increased, implying that deoxygenation was confined to the open ocean. We speculate that the burial rate of the nutrient phosphorus (P) on shelves was minimal during the Hirnantian glacial maximum (HGM) due to bypass of the shelves in respect to the incoming riverine dissolved load. Hence, a large excess of bioavailable P entering the open ocean would have stimulated phytoplankton production which lowered oxygen concentrations by aerobic respiration. In order to test this hypothesis, we determined reactive P (P react) contents in two low-latitude carbonate successions (Anticosti Island and Estonia) spanning the HGM. Moreover, we measured total organic carbon (C) concentrations and calculated C/P ratios to evaluate the burial efficiency of P. Samples from both sites are characterized by overall low P react contents. We observe a decreasing trend in P react towards the HGM, reaching a minimum during the initial transgression thereafter. C/P ratios suggest efficient P-burial throughout the study interval and, hence, P react contents are assumed to be a direct measure of primary productivity, P-availability, and P-burial. Using the P react concentrations, we modeled shelf P-burial fluxes with estimates for global shelf area and sedimentation rates. The model suggests that shelf P-burial fluxes around the HGM were approximately halved due to a reduced shelf area and minimum P react contents. With the assumption of a constant P-input to the ocean, the proposed scenario serves as a plausible explanation for the observed redox gradients. • we provide phosphorus (P) speciation data for Late Ordovician carbonate samples. • samples were collected from two far-distant sections representing shelf settings. • P-burial into shelf sediments was minimal during the Hirnantian glacial maximum. • large excess of bioavailable P entered the open ocean fueling primary productivity. • high organic matter sinking flux led to intense anoxia as suggested by U-isotopes. [ABSTRACT FROM AUTHOR]

The Ediacaran-Cambrian transition is recognized as a warm period. However, glaciations have been reported in many paleocontinents worldwide during this transition, including the Luoquan glaciation in Northern China. The type of glacier remains unclear, and there are still uncertainties regarding the differences and similarities between the Luoquan glaciation and other Ediacaran glaciations, which restrict global comparison of glaciation characteristics. Research on sedimentary characteristics and succession of eight sections of the Luoquan and Dongpo formations in western Henan Province in the southern North China Craton shows that from north to south, the Luoquan and Dongpo formations show three vertical facies associations spatially, indicating an obvious sedimentary environment evolution of subglacial-periglacial-glaciomarine-shallow marine, namely, from the subglacial lodgement to the periglacial outwash fan and permafrost, then to the proximal glaciomarine grounding-line fan and iceberg rainout to the distal glaciomarine ice-rafted deposits, and finally to the normal shallow sea. The spatial evolution of sedimentary environment indicates that the Luoquan glaciation in western Henan Province was a large ice sheet that extended from land to the sea and was not completely frozen but partially melted during warm periods, and temporary open-water conditions existed. Further comparison shows that although the number, frequency and global characteristics have not yet been determined, the global Ediacaran glaciations also show dynamic evolution characteristics from continental to marine glaciers, which is similar to the evolution mechanism of ice sheet during the snowball Earth, and also not indicative of hard snowball Earth pattern of complete ice cover. • Four facies associations of Luoquan glaciation in western Henan province on the southern margin of NCC are recognized. • The sedimentary evolution of Luoquan glaciation is from subglacial to periglacial, then to glaciomarine and shallow sea. • The Luoquan glaciation is a warm-based ice-sheet that extends from continent into the sea, rather than a mountain glacier. [ABSTRACT FROM AUTHOR]

Abstract During the Quaternary several glaciations occurred in the mountain regions around the Mediterranean and, in recent years, new ages have better constrained their timing. However, this is not the case for the Apuan Alps, a high-rainfall mountain chain adjacent to the Mediterranean Sea. Here, in spite of the widespread evidence for glaciers, the complete lack of geochronological information hinders our understanding of glaciation history. In this paper, we utilize speleothem ages to better constrain the timing of these glacial features. We re-examine 293 uranium‑thorium ages from 19 speleothems collected in five caves at different elevations. After a period of very low growth between 160 and 132 ka, the analysed speleothems grew almost continuously to ~75 ka, this period was followed by intermittent growth with lower deposition rate and presence of hiatuses until ~12.5/12 ka. This is consistent with an ice coverage persisting over the Apuan Alps, inhibiting or interrupting the growth of speleothems via the limited availability of groundwater and the scarcity/absence of soils. This interval is much greater than the time interval that has previously been attributed to the existence of glaciers on the Apuan Alps, which has been assumed to be restricted to Marine Isotope Stage (MIS) 2. Instead, ice cover probably also appeared in the Apuan Alps during MIS 4. The phase of restarting of growth, which may implies the definitive or substantial glacier melts seem to predate the Holocene. Highlights • Speleothem growth curves used to better constrain the timing of glacial features. • 293 U\Th ages from 19 speleothems collected in five caves at different elevations. • Glacial expansion in the Apuan Alps was not only limited to the MIS2. [ABSTRACT FROM AUTHOR]

The author examined the high-latitude Hirnantian diamictites of the Ghelli Formation and the early Silurian olive-gray shales of the Niur Formation exposed in the northeastern Alborz Mountains, Iran. These 404 m thick glacial deposits can be divided into three progradational-retrogradational cycles, each potentially controlled by the regional advance and retreat of the Hirnantian ice sheet. The glaciated source area was west of the study area, in the Arabian Shield region, where numerous tunnel valleys have been reported. Time calibration was performed based on a high-quality biostratigraphic control, mainly derived from the chitinozoan biozones Tanuchitina fistulosa , Acanthochitina barbata , Armoricochitina nigerica , Ancyrochitina merga , Tanuchitina elongata , Spinachitina oulebsiri , and Spinachitina fragili s. The land-derived miospores present in most chitinozoan assemblages, often abundant, seem associated with global sea-level changes during the Late Ordovician glaciation. The Ghelli Formation's high abundance of terrestrial miospores and low abundance of marine palynomorphs suggests its deposition in a shallow marine environment. Additionally, rhythmic bedded tidalites of claystone and sandstone indicate the growth of early land plants producing cryptospores on adjacent flooded areas. Based on marine palynomorphs (chitinozoans and acritarchs), the northeastern Alborz Mountains glacial deposits were dated as Hirnantian; the Niur Formation was assigned to the earliest Llandovery (Rhuddanian). Glacial deposits and marine palynomorphs suggest the presence of Hirnantian ice caps in the Alborz Mountains, at the margin of the Arabian Plate, and indicate the peripheral extension of the Late Ordovician ice sheet. Several biostrome beds forming pelmatozoan-bryozoan mud-mounds, mainly comprising bryozoans, echinoderms, tentaculites, and subordinate trilobites, were found in the glacial deposits of the Ghelli Formation, suggesting carbonate deposition during the Hirnantian. These carbonate beds are not related to the Boda warming event, which happened over the Gondwana landmass in the Katian interval; the glacial deposits of the Alborz Mountain Ranges are thus not correlated to those of the Gondwana paleocontinent. Climatic amelioration is more likely than local reduction of clastic input to be responsible for the biostrome beds in the Glacial Member of the Ghelli Formation, namely a short-lived episode of global warming during the Hirnantian interval (the Milankovitch cycles). Four new chitinozoan species, namely Armoricochitina persianense n. sp., Tanuchitina alborzensis n. sp., Spinachitina iranense n. sp., and Hyalochitina jajarmensis n. sp., are described and illustrated. Biometric data are also provided for the Iranian S . oulebsiri and A . nigerica . [ABSTRACT FROM AUTHOR]

Deciphering the variations of past glaciations over southeastern Tibet which holds the largest mass of contemporary temperate glaciers over Asia helps to advance our understanding of the ice-climate interactions and how glaciers may respond to future climate change. Using an ice sheet model forced by the reconstructed climatic change during the past 88 ka, we investigate the timing and extent of glaciations over southeastern Tibet and explore the potential influences of model parameters and horizontal resolution. Our results illustrate a long-term decreasing trend in the glacierized area during the past 88 ka, suggesting progressively restricted glaciations over southeastern Tibet. Apart from the long-term trend, there are multiple glacier advance events on millennial timescales. The maximum extent of glaciation occurs at late MIS 4 (∼58 ka) and early MIS 3 (∼51 ka), with the minimum glacier extent predicted in the late Holocene (∼4 ka). The evolution of glaciations during the past 88 ka is dominated by the change in air temperature in our simulations in which temperature and precipitation serve as the climatic forcing. Regarding modeling uncertainty, we show that the pattern of glacier evolution is independent of the values of model parameters and horizontal resolution used, but the amplitude of glacier extent is significantly affected, especially for model parameters. Compared with glacial geological evidence, the timing of the modeled widespread glaciations broadly matches with the ages of known moraines, but the mapped glacier bounds across specific mountain ranges are generally underestimated. The adoption of a spatially uniform climatic forcing and the related uncertainty may contribute to the model-data discrepancy. Our results aid in the establishment of a testable link between climate change and glacier response during the last glacial stage and have important implications for glacier behavior in the future. • A general long-term decreasing trend in glacier extent during the past 88 ka. • The maximum extent of glaciation occurs at late MIS 4 and early MIS 3. • The minimum glacier extent occurs in the late Holocene (∼4 ka). • Temperature change dominates the variations of glaciations. • The pattern of glacier evolution is independent of model parameters and resolution. [ABSTRACT FROM AUTHOR]

The Eltville Tephra (ET) is an important stratigraphic marker bed in the Western European loess stratigraphy at the boundary between the regional Last Glacial Maximum (LGM) in the sense of the maximum extent of glaciation of the Scandinavian ice sheet and a ‘terrestrial’ LGM with the highest degree of aridity and coldness. Stratigraphic marker beds such as tephra layers are commonly dated at more than one location, and often with more than one method. The sediments surrounding the ET were dated 87 times at 15 localities with different luminescence techniques yielding ages between 13.5 and 49.6 ka. Based on individual sections, the deposition of the ET was supposed to have taken place between 20 and 23 ka. This raises the question of whether a quantitative combination of individual ages can give a reproducible common age, including uncertainties. After screening the dataset and applying selection criteria, a Bayesian resampling approach is applied to obtain a common age consistent with a high percentage of observations from multiple localities. Four new luminescence ages bracketing the ET and two ages directly generated from the tephra horizon are presented and combined with all available data. The 1σ age range of the Bayesian age modelling yields a deposition age between 23.2 and 25.6 ka, which is in excellent agreement with two new luminescence ages from the tephra of 24.1 ± 1.9 ka (quartz) and 24.3 ± 1.8 ka (pIRIR 290 ) and a peak of volcanic minerals in the Dehner Maar core around 24.3 ka. This age is clearly older than previously suggested for the ET volcanic eruption, but fits better with stratigraphic and paleoenvironmental evidence. Therefore, the ET was deposited during phases of strong aeolian activity of the Greenland Stadial 3. Additionally, for the first time, a correlation can be made between the ET and tephra layers recognized in the Eifel Maar lake cores. [ABSTRACT FROM AUTHOR]

Millennial-scale variations in the Asian monsoon vapor transport are always associated with long-term changes in monsoon rainfall according to the conventional understanding. However, recent advances in monsoon studies suggested that regional monsoon rainfall has different responses to monsoon vapor transport. This paper presents a comparison between monsoonal vapor and precipitation records along the path of the Asian summer monsoon vapor transport. Pedogenic carbonate δ 18 O values in both surface sediment and Holocene eolian and lacustrine sediments from the Shiyang River drainage basin were used to investigate the variations of the Asian monsoon vapor transport. Meanwhile, Holocene lake-level changes of the terminal lake were reconstructed to reflect the monsoon precipitation variability. The results show that millennial-scale monsoon vapor transport is in accordance with low-latitude summer insolation, while the increasing summer monsoon rainfall during the early Holocene lags the monsoon water vapor transport. In addition, the relatively cold oceans left over from glacial periods and slow melting of ice sheets may temper the onset of the rainfall. These findings can provide insights into the interpretation of the asynchronous Holocene records from lakes and caves in East Asia. [ABSTRACT FROM AUTHOR]

Asian dust deposition in the northwestern Pacific is generally linked to high-latitude paleoclimate evolution during the Quaternary. However, whether low-latitude tropical Pacific processes, such as El Niño-Southern Oscillation (ENSO), influence Asian dust input into the northwestern Pacific remains uncertain. Here, we present clear periodic variations in potassium content (K (wt%)) and gamma-ray attenuation (GRA) bulk density, which are closely linked to the variations in Asian dust, in a sediment core recovered at Site U1438 in the Amami Sankaku Basin (ASB), northwestern Philippine Sea. Based on the shipboard age-depth model, we tuned the GRA to the mass accumulation rate curve on the Chinese Loess Plateau and the 8-kyr-lagged obliquity curve, and established the astronomical timescale. The K (wt%) content and GRA were higher during glacials and lower during interglacials, as driven by the variability in the Northern Hemisphere ice sheet (NHIS) during the Quaternary. In addition, strong long eccentricity 405-kyr cycles were observed in the dust records (K (wt%) content and GRA) during the early Pleistocene. The 405-kyr filter results showed that increased (decreased) Asian dust corresponded to the La Niña-like (El Niño-like) state, suggesting that Asian dust input into the northwestern Pacific was modulated by ENSO on 405-kyr cycles in the early Pleistocene. Our study illustrated the possible link between long eccentricity 405-kyr cycles in the Asian interior and low-latitude forcing, including potential modulation by ENSO. • K (wt%) and GRA from Site U1438 are related to input of Asian dust. • Dust signals were used to reconstruct the orbital chronological model. • Dust signals have clear 405-kyr cycles during the early Pleistocene. • Long eccentricity forcing Asian dust input into the northwestern Pacific. [ABSTRACT FROM AUTHOR]

Abstract: Detailed records of ice-sheet advances and retreats are reconstructed for the Hirnantian and Katian ages of the Late Ordovician using Nd isotopes (εNd) as a sea-level proxy in three study sections from the western margin of Laurentia: two shallow water platform sections located south and north of the paleo-equator, and one deep water section located in a continental slope-rise setting. When sea-level was high and paleo-shorelines had migrated eastward, the εNd value of seawater in the vicinity of each of the study sections shifted toward the εNd value of the eastern Panthalassa Ocean (~−4.0). By contrast, when sea-level was low and paleo-shorelines had migrated westward, the εNd value of seawater shifted toward the εNd value of the continental weathering flux from Laurentia (−8.5±0.2, 2σmean). These stratigraphic patterns of changing εNd values are interpreted to reflect the eustatic sea-level fluctuations that previous studies have documented in response to Gondwanan ice-sheet advances and retreats, thus linking the εNd sea-level proxy to Late Ordovician global-scale climate changes. The εNd profiles for the two platform sections yielded similar proxy sea-level curves with five cycles of oscillation recorded during the latest Katian and Hirnantian. Three additional cycles of late Katian sea-level change are recognized in the εNd profile of the deep water continental slope-rise section. The combination of εNd, δ13C and graptolite biostratigraphic data facilitates a precise interregional correlation of the Hirnantian Age and the paleoclimate changes that took place during this interval. The new correlations support previous findings that the Hirnantian ice age comprised two major glacial periods separated by a minor interglacial during the early part of the Metabolograptus persculptus Biozone. The younger glacial (confined to mid M. persculptus Biozone time) led to more extensive sea surface cooling than did the earlier one, and resulted in extensive eustatic sea-level drawdown and C-cycle changes. It records the strata most often recognized as HICE (the Hirnantian Carbon Isotope Excursion) in sedimentary successions worldwide, such as Anticosti Island, Scotland, Estonia, Siberia, and South China. The results of this study support and strengthen the view that glaciation predated the Hirnantian Age in the Late Ordovician, and that the records of small positive δ13C excursions in Katian successions from Baltica and eastern North America are themselves proxy indicators of glaciation frequency and eustatic sea-level changes. [Copyright &y& Elsevier]

Abstract: Ice-rafted grains of the central Arctic Ocean sediments provide a reliable proxy for Arctic palaeoenvironments and climatic conditions that prevailed at the time of their deposition. To understand ice involvement and implications for environmental advancement, it has proven necessary to ascertain whether these detrital grains were rafted on glacial ice or sea-ice. Surface microtexture identification allows grain differentiation based on the processes and conditions in its environmental provenance. Here, quartz sand grain surface microtextures are used to detect glacially crushed and reworked grains from the Lomonosov Ridge sediments obtained by the Integrated Ocean Drilling Program Expedition 302 (Arctic Coring Expedition). The data show that the most frequent distributions of glacial grains were deposited at the middle–late Miocene and during the Pliocene and early Pleistocene. Especially, the middle Miocene climatic cooling and the presence of glacial ice are well indicated at ~13.5Ma sediment grains. Earliest finding of the high frequency occurrence of glacigenic microtextures represents the age of ~56Ma. This first sedimentological evidence for the late Palaeocene glacial ice supports the existing hypothesis of ephemeral polar glaciations during times of marked global warmth. However, due to lack of uninterrupted sediment recovery and non-continuous nature of sampling, the glacially influenced samples recovered here should be treated as an estimate of the minimum frequency of glacier appearance in the Arctic. [Copyright &y& Elsevier]

Abstract: We present an integrated micropalaeontological study (using smaller and larger benthic foraminifera, planktonic foraminifera and calcareous nannofossils) of the late Oligocene from the Zarabanda section (western Tethys), in order to reconstruct the palaeoenvironmental turnover and to precisely establish the chronology of the palaeoclimatic events. Planktonic foraminifera show that the Zarabanda section is apparently continuous and spans the planktonic foraminiferal zones O5 (upper part), O6 and O7, and the calcareous nannofossil zones CP19b and CN1a (lower part). The quantitative analysis of smaller benthic foraminiferal assemblages enabled us to determine a middle–lower bathyal depth of deposition for most part of the section. The smaller benthic foraminifera show a bloom of neritic species, an increase in the percentages of cool‐water species, a decrease of the Planktonic/Benthic ratio, generic richness, heterogeneity and diversity all around a 10m thick succession of calcarenites, in the lower part of the planktonic foraminifera O6 Zone and the middle part of the calcareous nannofossil CP19b Zone. These changes coincide with the major turnover in the larger benthic foraminiferal assemblages; the last occurrence of Eulepidina dilatata and the first occurrence of Nephrolepidina morgani. These variations in the smaller and larger benthic foraminiferal assemblages may be associated with the major expansion of the Antarctic Ice Sheet at approximately 26.7Ma, which is known as the Oi‐2b global glaciation event. [Copyright &y& Elsevier]

Abstract: Cyclic sedimentary deposits characterize low-latitude late Paleozoic successions and preserve evidence of dynamic climate change on the Pangaean supercontinent. Although their orbitally paced glacioeustatic origins are widely accepted, their climatic signatures are open to interpretation. In this study, we utilize the GENESIS general circulation model (GCM) coupled to dynamic ice sheet and ecosystem components, to explore the response of low-latitude continental climate and high-latitude ice sheets to orbital and atmospheric pCO2 forcing. Our results suggest that atmospheric pCO2 concentration exerts the primary control over low-latitude continental climate and high-latitude glaciation. Our experiments constrain the atmospheric pCO2 window within which late Paleozoic climate was amenable to orbitally-driven glacial-interglacial fluctuations. The results suggest that both high-latitude ice-sheet accumulation and ablation and low-latitude climate change were paced by the eccentricity of Earth''s orbit. Periods of high eccentricity amplified precession-driven changes in insolation and promoted high-latitude ice sheet volume fluctuations as well as increased low-latitude precipitation variability. When eccentricity was low, the amplification of precessionally-driven insolation fluctuations was reduced, which promoted high-latitude continental ice sheet stability and less variable low-latitude precipitation. Based on these modeling results we discuss the implications of eccentricity paced precessional-scale climatic changes on low-latitude Pangaean depositional environments. [Copyright &y& Elsevier]

Abstract: Some researchers have suggested that Phanerozoic land-based ice sheets extended occasionally into the tropical realm. If true, the tropical ocean at those times must have been distinctly colder than at the Last Glacial Maximum (LGM) when northern hemisphere ice sheets did not extend below 38° latitude. Low-latitude ocean temperatures derived from oxygen isotopes of brachiopod shells test this hypothesis by comparing the temperature regime for Paleozoic and early Mesozoic low-latitude settings to the tropical temperature regime of the modern interstadial ocean, and to mean temperatures estimated for the tropical ocean at LGM. A running mean of pH-adjusted brachiopod habitat temperatures (BHTs) shows that Paleozoic low-latitude oceans were, on average, cool to cold relative to the modern interstadial tropical ocean. At times during Pennsylvanian, Serpukhovian, Tournaisian and Ordovician–Silurian glaciations, these tropical seas were indeed significantly colder on average than at the LGM. Ice-sheets within tropical latitudes can be reasonably predicted at those times. Abundant and diverse Paleozoic brachiopod communities reflect these cool tropical oceans, consistent with modern brachiopod ecological preference for colder waters. Amplified Paleozoic temperature oscillations suggest recurring global warming events which episodically drove these cold tropical oceans to temperatures significantly higher than the warmest modern tropical ocean. [Copyright &y& Elsevier]

Abstract: New field data demonstrate that during the Late Ordovician (Hirnantian) glaciation, an ice sheet expanding northwestwards over the Anti-Atlas range reached into the southern Meseta of northern Morocco. Its growth to a glacial maximum position resulted in extensive subglacial erosion and deformation including the development of soft-sediment striated surfaces and streamlined subglacial bedforms preserved between the High Atlas of Marrakech and Rehamna. These features imply that this ice mass extended >200 km further than previously thought, and increase its size by at least ca. 190, 000 km2 (comparable in area to the UK). Correlation between a measured section in the High Atlas of Marrakech and that of the southern Meseta identifies sedimentary evolution within an ice-contact system common to both. These findings imply that the West African Craton and northern Morocco were in full glaciological communication during the latest Ordovician. Palaeogeographic reconstruction shows that beyond the ice sheet, south and southeastward palaeoslopes persisted on the shelf. A palaeohigh beyond the main ice sheet was a major source for sand, feeding delta systems that grew along the shelf as far as the shelf break. This palaeohigh probably formed as a result of rift shoulder uplift and supported a satellite ice mass. In the eastern Meseta, a thick (350 m) underflow-dominated deep-marine fan was fed both from this shelf delta system and from glaciogenic debris derived from the main ice sheet. The occurrence of this unexpected deep-marine area in northern Morocco implies that continued northward advance of the ice sheet was hampered by a dramatic break in bathymetry. Two depositional units are recognised across the Meseta, containing four distinct sedimentary cycles, each recognised as a glacioeustatic response to the waxing and waning of ice masses elsewhere in West Gondwana. [Copyright &y& Elsevier]

New seismic–stratigraphic analysis of the Ross Sea continental shelf suggests that there were a at least five shelf-wide grounding events of the West Antarctic Ice Sheet (WAIS) during the middle Miocene. Although the number of WAIS grounding events generally matches the number of extreme δ18O enrichments and eustatic lowstands, these results do not support the long-standing assumption that West Antarctica was substantially ice-free. Instead, seismic–stratigraphic evidence from the Ross Sea shelf documents waxing and waning of a well-developed WAIS in the marine environment at least on the Pacific sector of the West Antarctic continental shelf. [Copyright &y& Elsevier]

Vegetation in East Africa is generally thought to have shifted from forests to more open grasslands and savannas as global climate cooled and high-latitude ice sheets expanded during the Plio-Pleistocene. Such a shift would have greatly influenced landscape resources, and potentially hominin evolution as well. Existing records of African vegetation spanning these time-scales are generally derived from offshore marine records that record continental-scale changes, or paleosol carbonate records that record very local vegetation changes during the short time intervals of soil carbonate formation. Here we present a new record of basin-scale vegetation change from the late Pliocene (~3.3–2.6 Ma) derived from a drill core from the Chemeron Formation, located in the Baringo Basin/Tugen Hills region of the Kenya Rift Valley. Specifically, we present a new record of the relative abundance of C 4 grasses and C 3 vegetation based on the carbon isotopic composition of leaf wax biomarkers (δ13C wax), which captures a signal of regional vegetation change. These data demonstrate that vegetation in the Baringo Basin varied greatly between C 3 forests and C 4 grasslands, and that vegetation exhibits both long-term (secular) trends and orbital-scale variations. The contribution of C 3 plants was lower than estimates based on low-resolution carbon isotope data from paleosol carbonates and organic matter in the basin. C 3 plants averaged ~53% of the vegetation during the late Pliocene, from ~3.3 to ~3.04 Ma, after which time δ13C wax indicates more open vegetation and ~41% C 3 plants. This transition may have been driven by changes in basin geomorphology, but also possibly occurred as part of larger-scale drying and expansion of C 4 vegetation in East Africa. In addition to this secular change, we observe high amplitude variability in the δ13C wax record including oscillations between ~80 and ~0% C 3 plants. These vegetation changes are correlated with changes in precipitation inferred from δ2H wax and lake level oscillations inferred from sedimentary facies, implying that high-amplitude, orbital-scale variations in precipitation drove significant changes in vegetation resources during the late Pliocene in the Baringo Basin. These variations have important implications for changes in terrestrial resources in light of the evolutionary innovations in the hominin fossil record related to changes in foraging strategies. • We present a record of δ13C wax from the BTB13 drill core in central Kenya 3.3–2.6 Ma. • Baringo Basin vegetation was highly variable in the Late Pliocene. • There was a shift at 3.04 Ma towards a more open grassland environment. • Strong vegetation oscillations, rather than long-term changes, may influence evolution. [ABSTRACT FROM AUTHOR]

Investigations of interstadials during early stages of glacial periods are of special interest, because they featured large-scale transformations of the climate system and the build-up of land-based ice sheets. Lacustrine sediment sequences are considered to be important natural archives that register past climate and environmental signals. Here, we present new multi-proxy data obtained from a palaeolake succession preserved in the inner-alpine terrace of Unterangerberg, Eastern Alps. These sediments formed during the second Early Würmian Interstadial, equivalent to Marine Isotope Stage (MIS) 5a, and were used to reconstruct changes in lake conditions and to infer past air temperatures. The sediment geochemical data and subfossil aquatic biota provide evidence of a cyclic lake–fen–lake development during this interstadial. The proxy records reveal stable lacustrine conditions with dense charophyte meadows and abundant aquatic fauna during the early part of the interstadial, a progressive shallowing of the lake resulting in the spreading out of fen vegetation in the middle part, and a transition from wetland to a renewed shallow lake stage towards the end of the interstadial. Chironomids were used to reconstruct mean July air temperatures, employing a combined Norwegian-Swiss chironomid temperature inference model. The reconstruction indicates a temperature close to present-day values of ca. 18 °C in the middle part of the record, while temperatures of ca. 13–14 °C are recorded for the lower and upper parts. The proxy data from this palaeolake provide evidence of heat and drought in the middle part of MIS 5a, supported by the chironomid-based temperature reconstruction. Our reconstruction shows a climate pattern broadly similar to that found in pollen-based estimates of mean July air temperatures from sites in the northern Alpine foreland and compares well to other European palaeoclimatic reconstructions of MIS 5a climate. • Palaeoenvironmental data from MIS 5a lacustrine deposits in the Alps are reported. • Proxy records provide evidence of cyclic lake–fen–lake development. • Quantitative estimates of summer temperatures are based on chironomid assemblages. • Cool conditions are inferred for the beginning and end of the interstadial sequence. • Hot and dry summers occurred in the middle part of MIS 5a. [ABSTRACT FROM AUTHOR]

The Cryogenian Period (~720–635 Ma) witnessed the most extensive and prolonged glaciation events in Earth history. Vast ice sheets of at least two global glaciations, the Sturtian (~720–660 Ma) and Marinoan (<654–635 Ma), advanced to sea level at low latitudes, a scenario that is at the heart of the general Snowball Earth hypothesis. This hypothesis is supported by results of recent work in geochronology and geochemistry, but certain parts of the glacial sedimentary records remained debated regarding ice sheet dynamics. Here we report findings from four sections of the Sturtian-age Tiesi'ao/Dongshanfeng Formation and related strata on the Yangtze Block in South China. Our work has documented the presence of four lithofacies: massive diamictite, crudely stratified diamictite, stratified to massive pebbly sandstone and dropstone-bearing laminated siltstone and our interpretation is that these rocks were deposited in proximal glacio-marine environments during five successive episodes of glacial advance and retreat. We have also identified an interval of deformation structures near the base of the Tiesi'ao/Dongshanfeng Formation that is characterized by upward increasing strain intensity, indicating that these structures were caused by overriding ice sheets. All the observations collectively suggest that the Sturtian ice sheets in South China were warm-based, rapidly moving, and sensitive to changes in climate. Further, our data suggest that the ice grounding line reached the slope area, implying a major drop in global sea level, enormous ice sheet thickness, or both during the Sturtian Glaciation. • Four lithofacies of Tiesi'ao/Dongshanfeng Formation (Cryogenian, South China) • The Tiesi'ao/Dongshanfeng Formation formed through five depositional stages. • The glacio-tectonic deformation near the base of the formation is observed for the first time. • A new glacio-tectonic deformation model is proposed. • Warm-based, productive and unstable ice sheets of Sturtian Snowball are inferred. [ABSTRACT FROM AUTHOR]

The timing of the final collision of Laurentia and Gondwana as well as the disappearance of the gateway between the Rheic and Tethyan oceans are quite controversial and poorly established. Accurate constraints on the gateway closure are vitally important for the understanding of global sea-level fluctuations, ocean circulation, regional and global environments, salinity and reorganization of the thermohaline circulation in the western Tethys, the Bashkirian glacial episode and the overall decline of atmospheric CO 2 concentrations. Here we present a new approach by applying warm-water benthic foraminifera (WWBF) data to precisely constrain the Rheic-Tethys gateway (RTG) closure, utilizing taxonomic and statistical methods. The link to the RTG closure and the profound biotic transformations in the oceans, sea-level, and expansion of the Gondwana ice sheet are discussed herein. The WWBF records in the studied regions constrain the timing of the RTG disappearance and support a linkage between the appearance of the Alleghenian Isthmus and the onset of the Bashkirian glaciation. Image 1 [ABSTRACT FROM AUTHOR]

The timing and geographic distribution of glaciers in high-latitude southern Gondwana during the Late Paleozoic Ice Age remain poorly constrained, ultimately precluding our ability to estimate ice volume and associated climate teleconnections and feedbacks during Earth's penultimate icehouse. Current aerial extents of glaciers, constrained by sedimentary flow directions, near exclusively infer paleo-glaciation to be highland-driven and may underestimate potential ice sources in continental regions from which ice sheets may have emanated. Here, we report new U-Pb ages and Hf isotope compositions of detrital zircons recovered from diamictites in two key mid- to high-latitude Gondwanan basins (Paraná, Brazil and Tepuel, Argentine Patagonia). The results indicate regional sediment sources for both basins during the early period of late Paleozoic glaciation evolving into more distal sources during the final deglaciation along southern and western Gondwana. Similar age sediment sourced from diamictites in the Congo Basin, that require an ice center in eastern Africa suggest the possibility of a large ice sheet in this area of Africa proximal to the Carboniferous-Permian boundary, which may have sourced sediments to the Paraná Basin. An inferred distal southern source of glacial sediment for the Tepuel Basin argues for the presence of an ice sheet(s) in the Ellsworth Block of Antarctica towards the end of the glaciation history in Patagonia. These findings indicate an evolution during the Late Paleozoic Ice Age from proximally to extrabasinally sourced sediment reflecting continental-scale glaciation and subsequent drainage from the Windhoek Highlands, Ellsworth Block and an east African source in west-central Gondwana. Coincidence with a long-term fall in atmospheric p CO 2 during the Pennsylvanian to a minimum across the Carboniferous-Permian boundary and a subsequent rise in the early Permian suggests a primary CO 2 -driver for deglaciation in the Paraná Basin. Additional boundary conditions including availability of moisture and paleogeography likely further contributed to the timing of nucleation, growth and demise of these Gondwanan glaciers. • Demise of LPIA associated with shifts in detrital zircon provenance related to glaciation. • Ice centers located in the Ellsworth Block of Antarctica, Windhoek Highlands of Namibia and east Africa. • Deglaciation driven by changes in p CO 2 for the Paraná Basin. [ABSTRACT FROM AUTHOR]