Marine Isotope Stage Research Articles

Seasonally dry tropical forests in the late Pleistocene of Mesopotamia, Argentina and their relationship to environmental changes during the Last Interglacial

ABSTRACTThe concept of seasonal forests groups structural types of vegetation that are related to climatic seasonality in the tropics of South America. Consequently, this determines the physiognomy of the vegetation, from semi‐deciduous to strongly deciduous. The strongest link between seasonally dry tropical forests (SDTFs) is their floristic composition, where Leguminosae and Anacardiaceae dominate the woody flora. The fossil records of the Neogene of northwestern Argentina reveal a list of species found in various locations and formations of the Miocene–Lower Pleistocene obtained from studies of pollen, woods (logs), cuticles, impressions of leaves and fruits. The analysis of sediments and woody structures from the Tapebicuá, Toropí/Yupoí and El Palmar Formations (Upper Pleistocene) of the Mesopotamia region allowed us to identify several pollen taxa and silicified wood fragments (mineralized). The woody and shrubby association whose current relatives characterize the SDTF is composed of the 16 fossil species described here belonging to seven families. In our samples, Anadenanthera colubrina and Myracrodruon balansae are the most significant members of the families Leguminosae and Anacardiaceae, which are dominant in the SDTF. The paleobotanical species described in this study confirm the extension of the SDTF to the province of Corrientes, coinciding with various climatic events (dry subtropical, semi‐desert and warm‐humid climate) that would have favored the development of these forests during the Pleistocene in this region. The absolute dates obtained for the Toropí/Yupoí and Tapebicuá Formations confirm their synchronicity and correlation to Marine Isotope Stage 5. The palynological analysis, the presence of Menendoxylon and the sedimentological data allow us to infer the existence of a seasonally dry humid paleoclimate in northeastern Argentina during the Late Pleistocene favorable to the development of the SDTF.

Paleoenvironmental characterisation of the Campos Basin slope (SE Brazil) in front of Cape São Tomé based on benthic foraminiferal biofacies succession since MIS 5

The distribution of benthic foraminifera and the assemblage dynamics were analysed on piston core GL-54 to understand the changes in paleoecology since Marine Isotopic Stage 5 (MIS 5). The core was drilled on the upper slope of the Campos Basin on the Rio de Janeiro (Brazil) coast. Benthic foraminifera biofacies, ecological indices, lithological facies, biostratigraphy, and isotopic analyses were undertaken to characterise the paleoenvironment in front of Cape of São Tomé. Two distinct biofacies were identified in the GL-54 sedimentary record since the Last Interglacial Period (MIS 5). These two biofacies point to seasonal organic matter and a well-oxygenated environment, however, Biofacies 2 can be differentiated from Biofacies 1 by the presence of significant bottom water currents. Biofacies 2 has the same species as Biofacies 1, except for Miliolinella subrotunda. Benthic foraminiferal species and biofacies from GL-54 were compared to the ones present in the upper portion of the GL-39 piston core, which was drilled from the middle slope of the same basin. Species such as Globocassidulina crassa, Islandiella norcrossi, Alabaminella weddellensis, Bolivina paula, M. subrotunda, Bulimina aculeata, Globocassidulina subglobosa, Rotorbinella lepida, and Uvigerina peregrina were found in both piston cores. The biofacies of both piston cores were correlated, pointing to similarities between the upper slope and the middle slope in the Campos Basin since MIS 5. In general, the upper and middle slopes of the Campos Basin are characterised as a well-oxygenated environment with variation in the deposition of organic matter. In addition to these environmental factors, there is evidence for a strong bottom current in MIS 2 at both sites, probably due to the displacement of Brazil Current and Intermediate Western Boundary Current.

Nonlinear comparative analysis of Greenland and Antarctica ice cores data.

We analyze the temperature time series of the EPICA Dome C ice cores in Antarctica and of the Greenland project, Summit, with durations of 800 000 and 248 000 years, respectively, with a recent mathematical tool defined through the Fourier phases of the series, known as the J-index. This data driven index can differentiate between purely random dynamics and dynamics with a deterministic component. It is sensitive to nonlinear components and robust to the presence of noise. Our J-index data analysis shows that both Greenland and Antarctica climatic fluctuations possess deterministic traits and suggests the presence of an underlying nonlinear dynamics. Furthermore, in both regions, it reveals the simultaneous occurrence of an important global event known as the "Pelukian transgression." For Antarctica, it also detects the marine isotopic stage 11. Additionally, our calculation of the time series Hurst exponents and our detrended fluctuation analysis show the presence of long-range persistent correlations for Antarctica and anti-persistent correlations for Greenland. For the latter case, our fractal dimension determinations are indicative of a more complex climatic dynamics in Greenland with respect to Antarctica. Our results are encouraging for further development of climate variability deterministic models for these regions.

An overview of Upper Pleistocene coastal deposits on Mallorca island

This review paper delves into the geological history of Mallorca, focusing on the Middle to Late Pleistocene period and its impact on the landscape and climate of the island. The Quaternary, particularly, the Last Interglacial, represents a relatively short timeframe on the global chronological scale, yet it is notable for its climatic instability and complex alternation of glacial and interglacial phases, leading to fluctuations in sea levels. During the last interglacial, millennial-scale fluctuations, known as Dansgaard–Oeschger and Heinrich events, occurred. Aeolianites are thought to have formed during periods of sparse vegetation cover and abundant sediment availability from the sea bed or platform (Heinrich events), while colluvial deposits and paleosols are believed to represent periods of reduced sediment supply and enhanced pedogenesis (Dansgaard–Oeschger events). These different deposits reflect climatic shifts and sea-level changes, offering insights into the environmental history of the island. Fossil evidence, including Strombus bubonius (currently known as Thetystrombus lauts) or “Senegalese hosts,” reveals past warm climatic fluctuations, particularly during the Last Interglacial. Myotragus balearicus exemplifies evolutionary adaptation and isolation on the island, offering a unique perspective on its paleontological legacy. The integration of stratigraphic characteristics and literature research on Optically Stimulated Luminescence (OSL) dating techniques provides a comprehensive temporal framework, spanning from Marine Isotope Stage 6 (MIS 6) to Marine Isotope Stage 2 (MIS 2), enabling the precise dating of geological events and a stratigraphic correlation.

Sedimentation record of a complete glacial-interglacial cycle: Down-slope deposits, contourites and plumites of the North Sea trough mouth fan

Trough mouth fans (TMFs) are major submarine depocentres that form in front of ice streams advancing onto the continental shelf, and they provide extensive records of past glaciations and ice-sheet dynamics. However, early research about TMFs was conducted using primarily 2D seismic data, which limits the insights on the deposit's geometries and internal structures and more recent studies using 3D data have focused on the general depositional history of TMFs. Here, we assess the spatial and temporal changes of the glacio-marine landforms and deposits throughout the last glacial-interglacial cycle (Marine Isotope Stage (MIS) 6 to 1, ∼130 ka to present) recorded in a >550 m thick progradational sequence. We use 3D reflection seismic data with significant vertical resolution (up to 2 m) imaging over 14000 km2 from the uppermost North Sea Fan (NSF) to document the seismic stratigraphy and sedimentary processes, by combining horizon picking and geomorphological analyses. The studied interval comprises five mappable units, four on the slope and one on the shelf, spanning from the modern seabed down to the top of the Tampen Slide (∼130 ka). Five different channel types (here included slide scars), as well as contourite and plumite packages are described based on their seismic facies, morphology, geometry, and stratigraphical position. We propose that contour currents are responsible for sediment delivery after the Tampen Slide deposition during the interglacial period before the onset of the Last Glacial Maximum, when high meltwater influx from the shelf produced turbidites. Sedimentation became debris-flow-dominated towards the end of the period of shelf-edge glaciation. The deglacial interval is characterized by the deposition of plumites on the slope. On the shelf, subglacial tills are deposited during both glacial and deglacial periods. We calculate an average sedimentation rate of <1 m/kyr during the interglacial (MIS 5-3), and around 50–65 m/kyr during the glacial and deglacial periods (MIS2-early MIS1). Thus, we document a change of two orders of magnitude in sedimentation rate during a glacial cycle on the slope of a glaciated margin.

Re-evaluating Marine Isotope Stage 5a paleo-sea-level trends from across the Florida Keys reef tract

Unraveling how Global Mean Sea Level (GMSL) fluctuated during past warm periods can improve our understanding of linkages between sea-level fluctuations, orbital forcing, and ice-sheet dynamics. Current estimates of GMSL for Marine Isotope Stages (MIS) 5a and 5c — two warm intervals following the relatively well-documented MIS 5e — contain meters of uncertainty and fewer data due to several challenges. These challenges include concealment of datable in-situ coral facies by MIS 1 deposits and inaccessibility due to submergence by modern sea level. We present a comprehensive dataset based on U–Th dating and stratigraphic correlation of 23 cores totaling over 170 m of recovered coral-reef deposits across the tectonically stable Florida Keys Reef Tract (FKRT). Following detailed facies descriptions, 34 in-situ, minimally altered aragonitic coral samples (≤2.7% calcite) below the Holocene-Pleistocene boundary were targeted for U–Th geochronology. Fourteen closed-system coral U–Th ages from MIS 5a include the commonly used sea-level indicator Acropora palmata, but also the massive coral taxa Pseudodiploria strigosa, Siderastrea siderea, Orbicella spp., and Porites astreoides. Dating yielded ages in the range of 88–81 ka (average 2σ uncertainty of less than 200 years). These ages suggest MIS 5a reef initiation at ∼88 ka BP, a peak near 83 ka with minimum elevations between −6.0 ± 0.5 and −5.6 ± 0.5 m MSL (2σ uncertainty and subsidence-corrected), and reef termination and sea-level fall by ∼81 ka BP. Notably, the range of peak MIS 5a relative sea-level estimates of −6.5 to −5.1 m MSL are more than 2 m shallower (higher) than previous estimates of −11 to −9 m. Our higher resolution regional sea-level reconstruction across four subregions of the Florida Keys reef tract aligns with changes in July insolation at 65° N: a trend that most other records, such as deep-sea sediments, do not have the accuracy and precision to resolve. Three massive coral samples from MIS 5c, consisting of Pseudodiploria clivosa, and Orbicella spp., yielded ages in the range of 104 to 99 ka (average 2σ uncertainty less than 200 years); however, because only one sample met the closed-system criteria, our ability to estimate MIS 5c sea level is relatively limited. More empirical estimates of sea-level from the MIS 5a and MIS 5c intervals based on numerical dating of reliable local sea-level constraints are critical for GMSL calculations and relating changes in sea-level amplitude and timing to global ice volume modeling and glacio-isostatic effects, all of which can improve predictions of future sea-level changes in coastal regions.

Climate and ice sheet dynamics in Patagonia throughout marine isotope stages 2 and 3

Abstract. During the Last Glacial Maximum (LGM, ∼ 23 000 to 19 000 years ago), the Patagonian Ice Sheet (PIS) covered the central chain of the Andes between ∼ 38 to 55° S. Existing paleoclimate evidence – mostly derived from glacial landforms – suggests that maximum ice sheet expansions in the Southern Hemisphere and Northern Hemisphere were not synchronized. However, large uncertainties still exist in the timing of the onset of regional deglaciation and its major drivers. Here we present an ensemble of numerical simulations of the PIS during the LGM. We assess the skill of paleoclimate model products in reproducing the range of atmospheric conditions needed to enable an ice sheet growth in concordance with geomorphological and geochronological evidence. The resulting best-fit climate product is then combined with records from southern South America offshore sediment cores and Antarctic ice cores to drive transient simulations throughout the last 70 ka using a glacial index approach. Our analysis suggests a strong dependence of the PIS geometry on near-surface air temperature forcing. Most ensemble members underestimate the ice cover in the northern part of Patagonia, while tending to expand beyond its constrained eastern boundaries. We largely attribute these discrepancies between the model-based ice geometries and geological evidence to the low resolution of paleoclimate models and their prescribed ice mask. In the southernmost sector, evidence suggests full glacial conditions during marine isotope stage 3 (MIS3, ∼ 59 400 to 27 800 years ago), followed by a warming trend towards MIS2 (∼ 27 800 to 14 700 years ago). However, in northern Patagonia, this deglacial trend is absent, indicating a relatively consistent signal throughout MIS3 and MIS2. Notably, Antarctic cores do not reflect a glacial history consistent with the geochronological observations. Therefore, investigations of the glacial history of the PIS should take into account southern midlatitude records to capture effectively its past climatic variability.

Taphonomic and zooarchaeological analysis of fauna from the Howiesons Poort and post-Howiesons Poort at Klasies River main site: Examining links between the environment and subsistence behaviour in Marine Isotope Stages 4 and 3

Marine Isotope Stages (MIS) 4 and 3 were significant periods encompassing some 50,000 years, including at least two techno-cultural entities: the Howiesons Poort (HP) and post-HP. Exploring subsistence and environmental changes during these periods may help us understand broader aspects of behavioural and occupational patterns over MIS 4 and 3. In this paper, we report on taphonomic analyses of a sample of early HP, late HP and post-HP fauna from Klasies River main site cave 1A. We use these and other faunal data to examine the links between subsistence behaviour and the environment during the HP and post-HP. The results of our analyses indicate that percussion marks are abundant in the HP, with percussion mark frequencies more prevalent in the later HP than the early HP indicating that humans were the primary accumulators of fauna in the HP. Other taphonomic data such as fracture patterns, burning and trampling marks also suggests that human activity was more prevalent in the HP than the post-HP. In contrast, in the post-HP, the prevalence of zoogenic marks on small mammal remains, and comparisons to actualistic assemblages indicate that carnivores probably contributed significantly to the post-HP assemblage. In all the samples investigated, crania dominate skeletal-part profiles. This could be a result of taphonomic bias, or it could indicate that foraging likely occurred relatively close to the site. Analyses of carcass-part utility show that marrow-extraction may have been a key subsistence strategy in the HP. In the post-HP, bone density-mediated attrition had a significant effect on fauna making it challenging to ascertain subsistence patterns, but preliminary analysis may also suggest marrow extraction in combination with other strategies.Post-depositional taphonomic marks such as manganese staining suggest that post-HP and late HP deposits were significantly more affected by moisture than the early HP deposits. Previous investigations of large mammal data point to more closed environments in the early HP, while our data indicate that the environment in the late HP and post-HP was largely similar. In comparing our data to previously analysed micromammal proxy data, we show that major environmental changes at KRM occurred after the shift to post-HP lithic technology. However, the taphonomic data suggests a close relationship between changing subsistence strategies and the MIS4/3 transition.

Earliest evidence of human occupations and technological complexity above the 45th North parallel in Western Europe. The site of Lunery-Rosieres la-Terre-des-Sablons (France, 1.1 Ma)

The site of LuneryRosieres la-Terre-des-Sablons (Lunery, Cher, France) comprises early evidence of human occupation in mid-latitudes in Western Europe. It demonstrates hominin presence in the Loire River Basin during the Early Pleistocene at the transition between an interglacial stage and the beginning of the following glacial stage. Three archaeological levels sandwiched and associated with two diamicton levels deposited on the downcutting river floor indicate repeated temporary occupations. Lithic material yields evidence of simple and more complex core technologies on local Jurassic siliceous rocks and Oligocene millstone. Hominins availed of natural stone morphologies to produce flakes with limited preparation. Some cores show centripetal management and a partially prepared striking platform. The mean ESR age of 1175 ka ± 98 ka obtained on fluvial sediments overlying the archaeological levels could correspond to the transition between marine isotopic stages (MIS) 37 and 36, during the normal Cobb Mountain subchron, and in particular at the beginning of MIS 36. The Lunery site shows that hominins were capable of adapting to early glacial environmental conditions and adopting appropriate strategies for settling in mid-latitude zones. These areas cannot be considered as inhospitable at that time as Lunery lies at some distance from the forming ice cap.

Patagonian dust, Agulhas Current, and Antarctic ice-rafted debris contributions to the South Atlantic Ocean over the past 150,000 years

Disentangling inputs of aeolian dust, ice-rafted debris (IRD), and eroded continental detritus delivered by ocean currents to marine sediments provide important insights into Earth System processes and climate. This study uses Sr-Nd-Pb isotope ratios of the continent-derived (lithogenic) fraction in deep-sea core TN057-6 from the subantarctic Southern Ocean southwest of Africa over the past 150,000 y to identify source regions and quantify their relative contributions and fluxes utilizing a mixing model set in a Bayesian framework. The data are compared with proxies from parallel core Ocean Drilling Program Site 1090 and newly presented data from potential South America aeolian dust source areas (PSAs), allowing for an integrated investigation into atmospheric, oceanic, and cryospheric dynamics. PSA inputs varied on glacial/interglacial timescales, with southern South American sources dominating up to 88% of the lithogenic fraction (mainly Patagonia, which provided up to 68%) during cold periods, while southern African sources were more important during interglacials. During the warmer Marine Isotope Stage (MIS) 3 of the last glacial period, lithogenic fluxes were twice that of colder MIS2 and MIS4 at times, and showed unique isotope ratios best explained by Antarctic-derived IRD, likely from the Weddell Sea. The IRD intrusions contributed up to 41% at times and followed Antarctic millennial warming events that raised temperatures, causing instability of icesheet margins. High IRD was synchronous with increased bioavailable iron, nutrient utilization, high biological productivity, and decreased atmospheric CO2. Overall, TN057-6 sediments record systematic Southern Hemisphere climate shifts and cryospheric changes that impacted biogeochemical cycling on both glacial/interglacial and subglacial timescales.

How old are the Mojave topographic dunes? The implications of new luminescence dating analyses from the Cady Mountains, Mojave Desert, southwest USA

The aeolian landforms of the Mojave Desert in the SW USA have been studied in detail over the last three decades, particularly in terms of their relationship to the region's topography and Pleistocene climate / sediment supply histories, as well as wider developments, such as the aeolian “sediment state” concept. In this context, the evolution of the Mojave River and its associated palaeolakes is thought to have been a key control on long-term sediment supply to aeolian systems, and luminescence dating chronologies for a range of (resulting) aeolian landforms have been related to these hydrological changes. Here we argue that at least some of these aeolian chronologies need to be re-assessed.We focus on luminescence chronologies for aeolian landforms within and marginal to the Cady Mountains, a mountain block adjacent to the Mojave River and palaeolake Manix, east of Barstow, California. We demonstrate that quartz in this locale exhibits several malign luminescence properties, and that low temperature K-feldspar infrared stimulated luminescence (IRSL) consistently exhibits high anomalous fading rates. Both contribute to age underestimation. We address these issues via post-infrared IRSL (pIRIR) and post-isothermal post-IR (pIt-IR) analyses of K-feldspars. The resulting ages span the last ~120 ka and imply phases of aeolian activity of a substantially greater antiquity than previously inferred. Notably, at one well-studied site – the Soldier Mountain sand ramp – the new ages suggest a landform dating not to Marine Isotope Stage (MIS) 1 or 2, as previously suggested, but more likely to MIS 5. The Cady Mountain record indicates that the only period of the last glacial cycle lacking evidence for aeolian sedimentation is ~40–9 ka, broadly consistent with expectations of increased regional humidity. These results also suggest that site topographic context may influence the age structure of aeolian deposits. In this instance, sand ramps consistently represent the oldest type of deposit (range ~ 40–120 ka), while early-mid Holocene dune accumulation is associated with sandsheets and valley-fill sands. Based on these findings, we argue that there is a need to critically re-assess the existing regional luminescence age database, and that there is potential to significantly revise our understanding of the region's aeolian system responses, and associated paleoenvironmental interpretations.

Sedimentary ancient DNA sequences reveal marine ecosystem shifts and indicator taxa for glacial-interglacial sea ice conditions

Sedimentary ancient DNA (sedaDNA) analysis is a promising new approach for reconstructing the impact of past climate and environmental changes on marine paleobiodiversity. By recovering, amplifying, and sequencing taxonomically informative sedaDNA fragments preserved in sediments, it is possible to assess the response of a broad range of eukaryote taxa, including non-fossilizing lineages, to past climate change. Here we present a unique marine derived sedaDNA metabarcoding record, spanning the penultimate glacial-interglacial transition across Marine Isotope Stages 6 to 5d (>135–107 ka) from an Eirik Drift core-site in the Labrador Sea. We identified a range of marine groups including dinoflagellates, diatoms, coccolithophores, chlorophytes, and copepods. There were representatives of primary/secondary producers, grazers, and parasites, which may represent remnants of complex ecosystems and ancient food webs. There were significant biodiversity shifts following the penultimate deglaciation and changing sea ice conditions throughout the Last Interglacial. These shifts reflected the striking increase in community richness during periods of seasonal sea ice and reduction under extensive perennial sea ice cover and open ocean. We identify two potential sedaDNA indicator taxa sequences associated with past seasonal sea ice which are most likely pico-eukaryote representatives of Micromonas and Pyramimonas, both green algae with known sea ice associations in modern ecosystems. Our work demonstrates the importance of high resolution marine sedaDNA metabarcoding for unravelling climate-ecosystem linkages and strengthens the potential of sedaDNA signals for past sea ice reconstructions through indicator sequences.

Hydrological Regime of Rivers in the Periglacial Zone of the East European Plain in the Late MIS 2

At the end of the Pleniglacial and the first half of the Late Glacial period, approximately between 18 and 14 ka BP, rivers of the central and southern parts of the East European Plain had channels up to 10 times as large as the present day channels of the same rivers. These ancient channels, called large meandering palaeochannels, are widespread in river floodplains and low terraces. The hydrological regime of these large rivers is of great interest in terms of the palaeoclimatology of the late Marine Isotope Stage 2 (MIS 2). In this study, we aimed at quantitative estimation of maximum flood discharges of rivers in the Dnepr, Don and Volga basins in the late MIS 2. To approach this, we used massive measurements of the morphometric characteristics of large palaeochannels on topographic maps and remote sensing data—palaeochannel width, meander wavelength and their relationships with river flow parameters. The runoff depth of the maximum flood, which corresponds to the maximum depth of daily snow thaw during the snowmelt period, was obtained for unit basins with an area of &lt;1000 km2. The mean value for the southern megaslope of the East European Plain was 44.2 mm/day (6 times the modern value), with 46 mm/day for the Volga River (5.5 times), 45 mm/day (6.3 times) for the Don River and 39 mm/day (8 times the modern value) for the Dnepr River basins. In general, the Dnepr basin was drier than the Don and Volga basins, which corresponds well to the modern distribution of humidity. At the same time, the westernmost part of the Dnepr River basin was relatively wet in the past, and the decrease in humidity from the past to the modern situation was greater there than in the eastern and central regions. The obtained results contradict the prevailing ideas, based mainly on climatic modeling and palynological data, that the climate of Europe was cold and dry during MIS 2. The reason is that palaeoclimatic reconstructions were made predominantly for the LGM epoch (23–20 ka BP). On the East European Plain, the interval 18–14 ka BP is rather poorly studied. Our results of paleoclimatological and palaeohydrological reconstructions showed that the Late Pleniglacial and the first half of the Late Glacial period was characterized by a dramatic increase in precipitation and river discharge relative to the present day.

Ursus spelaeus (Rosenmüller, 1794) during the MIS 3: new evidence from the Cioclovina Uscată Cave and radiocarbon age overview for the Carpathians*

ABSTRACT Ursus spelaeus, the Late Pleistocene a cave bear is known from numerous accumulations found in the fossil sector of caves situated in the Carpathian and Apuseni Mountains. In this study, we present new radiocarbon data along a profile of the Cioclovina Uscată Cave, which is situated in the South Carpathians. The data suggest that, during the entire Marine Isotope Stage 3 (MIS 3) interval, the cave was serving as a shelter for U. spelaeus, with the oldest dated bone indicating an age of > 47,710 and the youngest one, an age of 31,820 ± 400 years cal BP. Histogram plots of 110 radiocarbon data from different caves of the Carpathian and Apuseni Mountains as Cioclovina Uscată, Peștera (Cave) cu Oase, Peștera Muierii, or Peștera Urșilor, respectively, show a maximum expansion of the cave bear population between 50,000 and 40,000, a decline between 40,000 and 35,000 and a partial recovery from 35,000–30,000 years cal BP. Radiocarbon data of Homo sapiens remains, younger than 35,000 years cal BP, support the fact that H. sapiens accessed the same caves where the cave bear persisted to hibernate. Besides general cool conditions and restricted food sources, the presence of H. sapiens constituted an additional stress factor driving the cave bear to extinction.

Single-grain luminescence dating of Manas Lake paleoshorelines reveals late quaternary glacial meltwater forced lake level highstand in arid Central Asia

The spatiotemporal patterns of late Quaternary lake evolution, along with their responses to climatic changes and glacial meltwater in the westerlies-dominated Central Asia, remain unclear primarily due to the lack of well-dated records spanning across glacial and interglacial cycles. In this study, we investigated five well-preserved paleolake shoreline sequences, 15–27 m above the modern lake basin of the now-dry Manas Lake, a representative terminal lake in the Junggar Basin of arid Central Asia. Both single aliquot and single-grain K-feldspar post-infrared infrared stimulated luminescence (pIRIR) dating protocols were applied to 26 shoreline samples to reconstruct a lake level variation for Manas Lake over the past 90 kyr. The reliability of the K-feldspar pIRIR dating was tested through assessment of luminescence characteristics and comparison of single-grain and single-aliquot K-feldspar pIRIR Des. The results indicate that the highest water levels (∼25 m deep) occurred during late Marine Isotope Stage (MIS) 5 (∼80 ka) and MIS 3 (31–27 ka). A lake level 20 m above modern lake basin (a.m.l.b.) occurred from the last deglaciation to the early Holocene (14–10 ka) and again in the late Holocene (3.4–0.3 ka). The lake level changes of Manas Lake are decoupled from observed Westerlies precipitation changes over the past 90 kyr. This decoupling suggests enhanced glacial meltwater sourced from the high Tianshan Mountains, triggered by higher mean summer temperatures, worked together with Westerlies precipitation drove periods of lake level highstand in Manas Lake during late MIS 5, late MIS 3, and early Holocene periods.

Sustained North Atlantic warming drove anomalously intense MIS 11c interglacial

The Marine Isotope Stage (MIS) 11c interglacial and its preceding glacial termination represent an enigmatically intense climate response to relatively weak insolation forcing. So far, a lack of radiometric age control has confounded a detailed assessment of the insolation-climate relationship during this period. Here, we present 230Th-dated speleothem proxy data from northern Italy and compare them with palaeoclimate records from the North Atlantic region. We find that interglacial conditions started in subtropical to middle latitudes at 423.1 ± 1.3 thousand years (kyr) before present, during a first weak insolation maximum, whereas northern high latitudes remained glaciated (sea level ~ 40 m below present). Some 14.5 ± 2.8 kyr after this early subtropical onset, peak interglacial conditions were reached globally, with sea level 6–13 m above present, despite weak insolation forcing. We attribute this remarkably intense climate response to an exceptionally long (~15 kyr) episode of intense poleward heat flux transport prior to the MIS 11c optimum.

Landscape and paleoenvironmental change in stream valleys of the Central Great Plains, North America, during Marine Isotope Stage 3 (ca. 59–27 ka)

Recent studies of late Quaternary landscape evolution in stream valleys throughout the central Great Plains of North America have identified thick packages of MIS 3-age alluvium and colluvium beneath terraces, alluvial fans, and footslopes. Here, we review and build on these studies to highlight the geomorphic history of river systems in the Central Plains during MIS 3 and reconstruct the paleoclimatic conditions and vegetation communities that existed in the region at that time.A suite of 50 radiocarbon and optically stimulated luminescence ages indicate that late MIS 3 was a period of widespread landscape stability and soil development in the Central Plains. In general, river systems were actively aggrading during early MIS 3, but aggradation slowed after ca. 40 ka, allowing soils to develop until ca. 30–27 ka. In some river valleys, a second pulse of aggradation occurred shortly after that time followed by a period of landscape stability and pedogenesis during early MIS 2 (ca. 24–19 ka). Evidence for widespread landscape stability in stream valleys implies that high magnitude flooding was minimal. Atmospheric circulation patterns that favor these conditions include zonal airflow that inhibits incursions of moist, maritime air from the Gulf of Mexico.Paleoenvironmental conditions during late MIS 3 were reconstructed using the stable carbon, oxygen, and hydrogen isotopic composition of pedogenic phyllosilicates, carbonates, and organic matter. Estimated paleotemperatures ranged from 6 to 9 °C ± 3 °C and are approximately 4–7 °C lower than modern mean annual temperature. The estimated δ18O values of soil water from phyllosilicates range from −10.6‰ to −9.6‰. These estimates are lower (18O-depleted) by about 1.5–3‰ relative to modern meteoric δ18O values and we estimate that the δ18O of paleoprecipitation was likely 18O-depleted by up to 8.5‰ relative to modern values. Our estimated δ18O values for soil waters in the Central Plains during late MIS 3 can be explained by climatic conditions characterized by 1) cooler temperatures, 2) precipitation being sourced primarily from Pacific/Arctic air masses, 3) seasonal changes in precipitation patterns (i.e., predominantly winter precipitation), or 4) a combination of the above. δ13C values indicate the presence of a notable proportion of C4 vegetation in the Central Plains during late MIS 3. We suggest that C4 productivity was likely favored at that time by a low atmospheric CO2 environment that had sufficiently warm temperatures and effective precipitation during the growing season.

Pliocene–Pleistocene warm-water incursions and water mass changes on the Ross Sea continental shelf (Antarctica) based on foraminifera from IODP Expedition 374

Abstract. International Ocean Discovery Program (IODP) Expedition 374 sailed to the Ross Sea in 2018 to reconstruct paleoenvironments, track the history of key water masses, and assess model simulations that show warm-water incursions from the Southern Ocean led to the loss of marine-based Antarctic ice sheets during past interglacials. IODP Site U1523 (water depth 828 m) is located at the continental shelf break, northeast of Pennell Bank on the southeastern flank of Iselin Bank, where it lies beneath the Antarctic Slope Current (ASC). This site is sensitive to warm-water incursions from the Ross Sea Gyre and modified Circumpolar Deep Water (mCDW) today and during times of past warming climate. Multiple incursions of subpolar or temperate planktic foraminifera taxa occurred at Site U1523 after 3.8 Ma and prior to ∼ 1.82 Ma. Many of these warm-water taxa incursions likely represent interglacials of the latest Early Pliocene and Early Pleistocene, including Marine Isotope Stage (MIS) Gi7 to Gi3 (∼ 3.72–3.65 Ma), and Early Pleistocene MIS 91 or 90 (∼ 2.34–2.32 Ma) and MIS 77–67 (∼ 2.03–1.83 Ma) and suggest warmer-than-present conditions and less ice cover in the Ross Sea. However, a moderately resolved age model based on four key events prohibits us from precisely correlating with Marine Isotope Stages established by the LR04 Stack; therefore, these correlations are best estimates. Diatom-rich intervals during the latest Pliocene at Site U1523 include evidence of anomalously warm conditions based on the presence of subtropical and temperate planktic foraminiferal species in what likely correlates with interglacial MIS G17 (∼ 2.95 Ma), and a second interval that likely correlates with MIS KM3 (∼ 3.16 Ma) of the mid-Piacenzian Warm Period. Collectively, these multiple incursions of warmer-water planktic foraminifera provide evidence for polar amplification during super-interglacials of the Pliocene and Early Pleistocene. Higher abundances of planktic and benthic foraminifera during the Mid- to Late Pleistocene associated with interglacials of the MIS 37–31 interval (∼ 1.23–1.07 Ma), MIS 25 (∼ 0.95 Ma), MIS 15 (∼ 0.60 Ma), and MIS 6–5e transition (∼ 0.133–0.126 Ma) also indicate a reduced ice shelf and relatively warm conditions, including multiple warmer interglacials during the Mid-Pleistocene Transition (MPT). A decrease in sedimentation rate after ∼ 1.78 Ma is followed by a major change in benthic foraminiferal biofacies marked by a decrease in Globocassidulina subglobosa and a decrease in mud (&lt; 63 µm) after ∼ 1.5 Ma. Subsequent dominance of Trifarina earlandi biofacies beginning during MIS 15 (∼ 600 ka) indicate progressive strengthening of the Antarctic Slope Current along the shelf edge of the Ross Sea during the mid to Late Pleistocene. A sharp increase in foraminiferal fragmentation after the MPT (∼ 900 ka) and variable abundances of T. earlandi indicate higher productivity, a stronger but variable ASC during interglacials, and/or corrosive waters, suggesting changes in water masses entering (mCDW) and exiting (High Salinity Shelf Water or Dense Shelf Water) the Ross Sea since the MPT.

Temperature and palaeolake evolution during a Middle Pleistocene interglacial–glacial transition at the Palaeolithic locality of Schöningen, Germany

The Middle Pleistocene Reinsdorf sequence at the Lower Palaeolithic sites of Schöningen offers the opportunity to reconstruct a rarely well‐preserved post‐Holsteinian environmental transition from an interglacial into a glacial phase along with its highly dynamic interjacent climatic oscillations. Combining biological proxies, element composition and stable isotope ratios of two lakeshore sequences at excavation site 13 II, we demonstrate repeated variations in climate, hydrology and catchment vegetation cover. New ostracod‐based quantitative mean summer and winter air temperature reconstructions with the Mutual Ostracod Temperature Range (MOTR) method provide the first detailed information about the temperature evolution. The interglacial temperature maximum, probably corresponding to Marine Isotope Stage 9e, is followed by a first dry phase and, during the younger part of the Reinsdorf sequence, by a second dry period. Both were marked by lower precipitation/evaporation ratios, reduced vegetation cover in the catchment and increased surface inflows from springs. Temperature reconstructions of these two steppe (open woodland) phases yield very narrow ranges for mean January (−4–0 °C) and July (+17–19 or +17–21 °C) air temperatures, demonstrating that, while summers were similar to those of today, winters were at least 1 °C colder, hinting at a more pronounced continental climate. Precise temperature estimates for the interjacent woodland and steppe (woodland) phase are hindered by generally wider ranges produced by the MOTR method (January mean −4–3 °C, July mean +15–21 °C). The development of a more extensive vegetation cover, reducing surface runoff and erosion in favour of increased river and groundwater discharge, as indicated by a shift in microfossil and stable isotope records, suggests generally more humid climates with higher precipitation/evaporation ratios as well as reduced seasonal temperature variations.

A Mismatched Piece in a Cultural Middle Stone Age Puzzle: Traces of Human Activity Dated to 90 kya (MIS 5) at Sites EDAR 134 and 155 in the Eastern Sahara, Sudan

ABSTRACT This article presents the results of research carried out at two previously unreported Eastern Desert Atbara River project (EDAR) Middle Stone Age (MSA) sites—EDAR 134 and EDAR 155. Luminescence dating results indicate human activity in this area during the Marine Isotope Stage 5 period (MIS 5), approximately 90 kya. Discussion concerning the affiliation of both analyzed inventories will be provided, including another MSA site from the EDAR area, where an assemblage dated to MIS 6/5e does not have technological features known from other technocomplexes in the eastern Sahara region (EDAR 135). Microscopic analysis of traces of tool use for the EDAR 155 assemblage shows the high impact of post-depositional (aeolian) processes on the state of preservation of lithic material. Sites EDAR 134 and 155 provide evidence for hominin activity during the late Pleistocene within an area only episodically accessible, due to arid conditions prevailing in the Saharan deserts.