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We present a hydroclimate synthesis of the southern Great Basin over the last two glacial-interglacial cycles focused on paleolakes in Death Valley (core DV93-1), Searles Valley (core SLAPP-SRLS17), Owens Valley (core OL92), and the Devils Hole cave. There is close agreement between the occurrence of lakes in Death Valley and the height of the water table in the Devils Hole (50 km east of Death Valley) during the last 200 kyr. Death Valley and Devils Hole have adjacent, partly overlapping, drainage areas and most likely did over the last 200 kyr. When the water table in the Devils Hole was above the threshold level of ∼5 m higher than the modern, permanent lakes existed in Death Valley. At water table elevations less than 5 m above the modern, ephemeral lakes, saline pans, and mudflats occurred in Death Valley. The close temporal agreement between inferred paleoenvironments from the sediments in the Death Valley core and the paleowater table elevation in Devils Hole suggests a common forcing and provides insight into climate variability in the southwestern United States over the last 200 kyr. Owens Valley and Searles Valley, which derived inflow waters from the Sierra Nevada via the Owens River, contain paleohydrologic records which match those from Death Valley and the Devils Hole in terms of timing and direction of water availability over the last 200 kyr, indicating a similar paleohydrologic history for the entire southern Great Basin region. Near the end of Marine Oxygen Isotope Stage 6 (MIS 6), 140 ka - 130 ka, Lake Manly in Death Valley became shallow and hypersaline, and ultimately dried up at 127.1 ka ±4.3 ka. The transition from glacial to interglacial vegetation, which involved the loss of Juniperus pollen and an increase in Quercus (oak) pollen, occurred in Death Valley core DV93-1 at 131.3 ka ±4.0 ka. Following the glacial to interglacial pollen shift, a large alkaline lake formed in Death Valley. Similar conditions (freshwater, high productivity, and a mixed, deeply oxygenated water column indicated by biomarkers) existed in Searles Lake between 135.3 +2.7/ -2.9 ka and 130.1+2.7/ -2.6 ka, also following the juniper-oak pollen transition. Sr isotopes in calcite and sulfate minerals (gypsum, glauberite, thenardite), and the rare occurrence of the sodium carbonate mineral northupite with a low 87Sr/86Sr ratio in core DV93-1, together with organic geochemical proxies from Searles core SLAPP-SRLS17, all suggest that at this time, late MIS 6 Lake Manly in Death Valley received alkaline water via spillover from Searles Valley into Death Valley through Panamint Valley. The hydrologic connection between Searles Valley, Panamint Valley, and Death Valley at Termination II (130 ka) is documented here for this system of pluvial lakes for the first time. The Devils Hole water table decreased to +6.5 m at 140.8 ka ±3.2 ka, rose briefly to +8 m at 137.6 ka ±0.5 ka, and then dropped 8 m by 120.36 ka ±0.45 ka, when it reached an elevation similar to the modern. The pluvial lakes in Death Valley and Searles Valley may have coincided with the rise of the Devils Hole water table at ∼137.6 ka ±0.5 ka years ago, although the age models for core DV93-1 and core SLAPP-SLRS17 during the end of MIS 6 carry large uncertainties. • 200,000 year paleohydrologic synthesis of southern Great Basin: Death Valley, Searles Valley, Owens Valley, Devils Hole cave. • New data from Death Valley: U-Th dates (halite) and 87Sr/86Sr ratios (carbonates and sulfates). • Close agreement between Death Valley paleoenvironments and water table elevations in Devils Hole. • Searles Lake overflowed into Death Valley via Panamint Valley near the end of MIS 6. [ABSTRACT FROM AUTHOR]

Long-term hydroclimate records provide an opportunity to understand potential drivers of the past, and give context to modern and future climate warming. A wide variety of proxy data now allow for reconstruction of climate variables that were not previously possible. Here we present a multi-proxy dataset including n -alkane δ2H (δ2H n-alk) values from an open-basin lake in Estonia to reconstruct past hydroclimate conditions for the eastern Baltic region. We complement our sedimentary δ2H n-alk data with existing carbonate-based oxygen stable isotope (δ18O) data to derive deuterium (d -) excess. We present multiple isotopic records and reconstructed relative humidity (ΔRH) values over the Holocene, and link these with modern precipitation δ2H and δ18O values to guide the interpretation of the paleo-proxies. Fossil pollen and chironomid-based temperature reconstructions, as well as biogeochemical data provide additional information for inferring past environmental changes. Our results indicate that the middle Holocene in Estonia had on average 6 ± 3% higher RH values than the late Holocene. The δ18O and δ2H values were also higher during the middle Holocene, which we interpret as increased warm season precipitation. Our reconstructed d -excess values were relatively higher during the middle Holocene, indicating a more northerly or cold source water origin, in comparison to the late Holocene. In addition to the paleoclimatic significance, our results show how multiple quantitative proxies can be combined to characterize hydroclimate sensitivity to changes in relative humidity, temperature and moisture source. • Combined H and O isotope proxies permit d -excess and RH reconstructions. • Sedimentary biomarkers in the eastern Baltic region reflect Holocene hydroclimate. • Higher relative humidity and d-excess values recorded during the middle Holocene. • Relative humidity changes were modeled and quantified using n-alkane proxy. • Northerly moisture sources were dominant in Estonia during the late Holocene. [ABSTRACT FROM AUTHOR]

Understanding the Indian summer monsoon (ISM) variabilities under different climatic constraints on various timescales is crucial for socio-economic stabilization within the ongoing warming globe. However, aside from stalagmite records, very few terrestrial paleoclimate archives have been used to explore the last glacial ISM characteristic, which limits our understanding of the ISM natural behaviors and their underlying mechanisms on longer timescales. Here, we present a grain size end-member analysis for Tengchongbeihai wetland sediments from southwestern China to investigate the paleo-hydroclimate changes since the late MIS3. The overall low fine silt content before ∼19 cal ka BP resulted from weak catchment erosion indicating weak ISM during cold glacial while the increasing trend thereafter indicates the ISM strengthened during the last deglaciation and Holocene. Such an orbital ISM evolution resembles to the insolation gradient between 25°N and 25°S during the boreal summer periods, which implies that the transequatorial insolation difference could be an alternative explanation for the orbital scale low latitude hydroclimate changes. The remarkable peaks of coarse component around ∼9, 12, 19, 26, 32, 37 and 42 cal ka BP were related to significant water level descending indicating the millennial ISM collapse corresponding to the YD and Heinrich events. However, the absence of sawtooth feature as the NGRIP δ18O and the well correspondence to the Indian Ocean sea surface temperatures (SSTs) of the ISM collapses evidence the modulation of low latitude forcing on the North Atlantic climate effects on the millennial scale hydroclimate variabilities. • Millennial to orbital ISM changes over 46 ka was studied using a wetland sediment. • The trans-equatorial insolation gradient controlled orbital ISM evolution. • The millennial ISM fluctuations tele-connected to the North Atlantic instabilities. • Indian Ocean SSTs modulated the relation between ISM and North Atlantic climate. [ABSTRACT FROM AUTHOR]

Bat guano is an emergent paleoenvironmental archive and isotopic compositions of bat guano have been tied to climate, vegetation, and trophic processing in isolated studies. However, a comprehensive, multi-isotope assessment of bat guano has not been established, hindering the proliferation of guano-based paleoenvironmental research. In this study, we comprehensively examine isotopic compositions of a 12,000-year long bat guano core from Cave Springs Cave, Alabama as well as relevant isotopic data from other sources to improve our understanding of each isotope system (δ13C, δ15N, and δ2H), the source-to-sink components of guano isotope pathways, and the fractionation occurring along each multi-step isotopic pathway from sources (i.e., soil, atmosphere, rainfall) to guano formation. We find the δ13C values of guano from Cave Springs Cave primarily reflect local vegetation with a large shift that coincides with the onset of the Anthropocene (after 1950 C.E.). We also determine that the δ15N values of Cave Springs Cave guano were not associated with precipitation or any other climatic variable but instead reflect a change in bat diet and agricultural intensification during the past 600 years. Overall, this study adds to the existing body of bat guano research and supports bat guano as a reliable archive for paleoenvironmental reconstructions. [ABSTRACT FROM AUTHOR]

Reconstructing past climate seasonality is fundamental to understanding the nature of past climate changes. This is especially true in the Arctic, where climate is intensely seasonal and proxies that can distinguish climate conditions of multiple seasons in a single year are relatively rare. We propose that submerged aquatic mosses, which are abundant subfossils in some Arctic lake sediments and have distinctive seasonal growth morphologies, can be used to estimate past lake water oxygen isotope composition (δ18O lw) across multiple seasons. Aquatic mosses are abundant, well preserved, and grow continuously in Arctic lakes whenever light is available, with some species displaying unique seasonal morphologies influenced by water temperature. Although Greenland paleorecords suggest that aquatic moss oxygen isotope values (δ18O om) reflect the δ18O values of lake water, no modern calibration between δ18O om and δ18O lw exists in Greenland. We present a modern δ18O om vs. δ18O lw calibration using multiple moss species or morphotypes from eight lakes and ponds near Pituffik (Thule), northwest Greenland. We find strong linear relationships (r2 = 0.76-0.85) between the δ18O om and δ18O lw values of multiple species or morphotypes across the range of relatively low δ18O lw values at Pituffik, and our results indicate isotopic fractionations are similar to those found previously at lower latitudes. To assess the potential of mosses as archives of seasonal δ18O lw values, we analyzed δ18O om in season-specific segments of moss strands, with seasons identified based upon growth morphology. Moss inferred lake water δ18O values (δ18O lwom) are higher in autumn than spring or summer, likely due to increasing contributions of 18O enriched precipitation and the cumulative effects of lake water evaporation throughout the ice-free season. For moss subsampled throughout summer, δ18O lwom values generally increased through the season in parallel with observed δ18O lw values. Potential temperature dependent fractionation effects during biosynthesis, however, remain unconstrained and should be further addressed with future research. Overall, these findings suggest that aquatic mosses from lake sediments could be used to directly resolve climate seasonality of the past. • Aquatic moss strand δ18O values reflect lake water values through multiple seasons. • Summer subsampled moss strands show weekly to monthly evolution of lake water δ18O. • Aquatic moss vs. lake water δ18O calibrations are similar for species tested here. • Aquatic moss δ18O needs testing down core to evaluate past seasonal signals. • Temperature-dependent fractionation and pre-treatment effects need more research. [ABSTRACT FROM AUTHOR]

Holocene paleotemperature records from ice-free margins of Greenland suggest spatiotemporal heterogeneity in the timing of key climate transitions following retreat of the Greenland Ice Sheet. However, the paucity of high-resolution climate records from this region limits our understanding of the timing, spatial variation, and drivers of Holocene climate variability. Here, we present a middle to late Holocene climate reconstruction based on δ18O of aquatic invertebrate (chironomid and cladoceran) remains and sediment geochemistry from lake sediments to elucidate millennial to submillennial-scale drivers of climate in southwestern Greenland. We establish that our site, Arrowhead Lake, is a through-flowing basin with an integrated signal of annual meteoric water with no evidence of significant evaporative enrichment. Core sediment geochemistry captures the transition from minerogenic-dominated to organic-rich sediments ∼8 cal ka BP. Chitin-based δ18O measurements of both chironomid head capsules and ephippia exhibit similar temporal variability through the record, broadly decreasing from 8.2 cal ka BP to present, concurrent with decreasing summer insolation and regional Neoglacial cooling. A simplified assumption that temperature is the sole driver of changes in isotopes of precipitation yields an estimated average temperature change from the middle to late Holocene at Arrowhead Lake of 2.1–3.0 °C, comparable to existing estimates of middle to late Holocene temperature decline in western Greenland. Depleted δ18O values after 3.3 cal ka BP correspond to the onset of Neoglacial cooling and independent evidence for a slowdown of the West Greenland Current, and suggests that both temperature and sea-ice variability were important controls on isotopic variability at this site. Highly depleted isotopic values at 8.2 cal ka BP followed by high isotopic variability in the early part of the middle Holocene suggests that our record may capture regional 8.2 ka cooling. This new isotope record provides insight into climate influences during the middle and late Holocene along the western Greenland margin that are important for understanding how ongoing melt of the Greenland Ice Sheet and amplified warming in the Arctic may impact the climate system. • A new δ18O record offers insight into 8200 years of climate change in SW Greenland. • Data suggest ∼2.1–3.0 °C Neoglacial cooling, consistent with regional records. • Decreasing magnitude of temperature from north to south in western Greenland. • Highly depleted isotopic values are consistent with the 8.2 ka cooling. [ABSTRACT FROM AUTHOR]

In the piedmont of uplifting mountains, alluvial fan rivers undergo significant aggradation-degradation processes, which are usually attributed to climate change. An ongoing debate is whether this process requests the participation of glaciation. To address this debate, we need the knowledge of the quantitative relationship between the ratio of water to sediment flux (q w / q s) with the aggradation/degradation process. This study examined the aggradation and degradation processes in three alluvial rivers at the piedmont of the Qilian Shan (Shan referes to Mountain) and simulated the river processes by a one-dimensional numerical model based on the transport-limited principle. Along the studied piedmont rivers, field measurements show a magnitude of 120–200 m degradation and aggradation in the Late Pleistocene. Through simulation analysis, we explored how factors like the ratio of water to sediment flux (q w / q s), channel width, and sediment grain size influence river processes and longitudinal profiles, and found distinct morphologies in different processes, where aggradation is characterized by concave-up profiles, while degradation is characterized by convex-down profiles. Additionally, the water flux is inversely proportional to the time required for the river to reach a new equilibrium profile. The simulated degradation amplitude aligns closely with the measured data in the Qilian Shan, indicating that precipitation during the Last Glacial Maximum in the region amounted to approximately ∼32% of the Holocene precipitation. This supports the notion that changes in water flux or precipitation alone can induce significant piedmont deepening without the necessity of glaciation. • Built a model to quantify the link between water-sediment fluxes and river processes. • Simulated Qilian Shan piedmont river incision: ∼32% LGM precipitation vs. Holocene. • Precipitation alone can create deep canyons without requiring glaciation. [ABSTRACT FROM AUTHOR]

Mainland Southeast Asia experiences complex and variable hydroclimatic conditions, mainly due to its location at the intersection of Asian monsoon subsystems. Predicting future changes requires an in-depth understanding of paleoclimatic conditions that is currently hindered by a paucity of records in some regions. In this paper, we present the first speleothem stable isotope records from western Thailand detailing the Bølling-Allerød interstadial, Younger Dryas termination, and early- to mid-Holocene period. We find evidence of higher precipitation during the Bølling-Allerød (14,321–12,824 years before present (1950: BP)) compared to a Younger Dryas termination that starts 11,702–11,674 BP, has a rapid shift centered on 11,660–11,641 BP, and ends 11,603–11,589 BP. In addition, our records show Holocene monsoon intensity peaking at 8250 BP or before, a multi-millennia delay from the Northern Hemisphere summer insolation peak, followed by a trend to drier conditions until at least 750 BP. Assessment of the timing of the Younger Dryas termination in paleoclimate records across Southeast Asia reveals an earlier shift of the Indian Summer Monsoon to global climate shifts when compared to East Asian Summer Monsoon records. The causes of this are currently unknown. Some potentially important aspects include: an Indian Summer Monsoon influence on East Asian Summer Monsoon strength via the Indian Ocean Dipole climate pattern, the role of the Tibetan Plateau in monsoon dynamics, and exposure of the Sundaland shoreline. More high-resolution paleoclimate records, especially on the pathway of Indian Summer Monsoon to East Asian Summer Monsoon, are required for further discussion on the mechanisms controlling the differences between climate regimes. • We present two new speleothem stable isotope records from western Thailand. • Conditions trend wetter during the Bølling-Allerød. • Early and abrupt termination of the Younger Dryas (11,675–11,600 BP, ±73 years). • Change Point Analysis of records finds earlier rapid shift in Indian Summer Monsoon. • Distinct trend of increasing δ18O and δ13C values throughout Holocene. [ABSTRACT FROM AUTHOR]

The Southern Hemisphere Westerlies (SHW) are a vital part of the Southern Hemisphere's coupled ocean-atmosphere system and play an important role in the global climate system. The SHW affect the upwelling of carbon-rich deep water and exchange of CO 2 from the ocean to the atmosphere by driving the Antarctic Circumpolar Current. On seasonal to millennial timescales, changes in the strength and position of the SHW are associated with temperature and precipitation changes throughout the extratropical Southern Hemisphere. Understanding the behaviour of the SHW under different background climate states is important for anticipating its future behaviour and remains a subject of ongoing research. Terrestrial paleoclimate records from lake sediments are valuable for reconstructing past atmospheric change and records from the handful of sub-Antarctic islands provide the opportunity to develop datasets to document spatio-temporal patterns of long-term SHW behaviour. Here, we generate palynological, microcharcoal, and sedimentological reconstructions (including CT imagery, μXRF analysis, magnetic susceptibility, and loss-on-ignition) on lake sediments from the Kerguelen Islands (49°S) to constrain variability in Holocene vegetation, climate, and atmospheric circulation (SHW position). Due to the influence of the SHW on the Kerguelen Islands, the influx of long-distance transported (LDT) pollen and microcharcoal from southern Africa serve as proxies for the meridional position of the SHW. In contrast with the stable conditions that prevailed on the Kerguelen Islands over the past 8,600 cal yr BP, our findings reveal a highly dynamic Early Holocene period. Consistent with local palynological evidence of warmer conditions, a high influx of LDT pollen and charcoal from southern Africa suggest that the SHW core belt was located further south of the Kerguelen Islands during this time. Comparison against paleoclimate records from the surrounding region and beyond suggests that the inferred changes might be explained by changes to our planet's interhemispheric thermal gradient, triggered by North Atlantic cooling in response to melting of the last remnants of the Laurentide Ice Sheet. • We study Holocene vegetation and atmospheric circulation on the Kerguelen Islands. • Southern Hemisphere Westerlies position is based on long-distance pollen transport. • Wind belt shifts coincide with changes in local temperature and precipitation. • Durin the Early Holocene the core wind belt was positioned south of the Kerguelen. • From 8,600 cal yr BP the core wind belt shifted northward of the Kerguelen Islands. [ABSTRACT FROM AUTHOR]

Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are a type of bacterial membrane lipid that are ubiquitous and robust for inferring paleoclimate evolution in continental settings, especially for paleotemperature. They can be engineered to show differential responses to ambient conditions under different settings, making setting-specific brGDGTs-based calibrations, mostly being linear models, preferable for paleoclimate reconstructions. However, even such a cautious approach is challenging given the allochthonous inputs and changing sedimentary settings that were inevitable in the geological past. In this study, a method called Locally Weighted Weighted Average-Partial Least Squares Regression (LWWA-PLS) commonly used in pollen-based reconstructions was introduced to address this challenge. In the latest modern global brGDGTs dataset from all archives known to host brGDGTs (n = 3068), we found that the LWWA-PLS model had high credibility in predicting environmental parameters (temperature, precipitation and pH) and that the average accuracy in estimating the contribution of brGDGTs in a sample from different environments (soil, peat, and subaqueous) reached 81%. Based on brGDGTs in two lacustrine sediment cores exhibiting multiple deposition settings since 90 and 70 cal ka BP, the LWWA-PLS model was able to generate results comparable to those from pollen-derived paleorecords and better than those derived from linear models. This is especially true for the mean annual air temperature reconstruction. Moreover, the LWWA-PLS model successfully estimated the contribution of brGDGTs from different sources, which was generally consistent with the sedimentary facies of the two sequences. Overall, the LWWA-PLS model based on the global brGDGTs dataset is expected to advance the applicability of brGDGTs to complicated terrestrial environments. • Confirm the efficacy of LWWA-PLS model in the modern brGDGTs dataset. • Generate records comparable to the pollen derived-paleoclimate parameters. • Reduce the influence from the lithology transition on paleotemperatures. [ABSTRACT FROM AUTHOR]

The Mid Piacenzian Warm Interval (MPWI) has been identified as an analogue for future global warming because it had warmer temperatures and higher atmospheric CO 2 levels than today, while subsequent early Pleistocene cooling is more similar to modern climate. However, reconstructions of these intervals lack seasonal-scale temperature reconstructions. Seasonal sea surface temperature (SST) reconstructions from deep-time archives can potentially provide insight into the nature of the climate system on sub-annual scales during critical climate states. Here we compared seasonal variability in growth temperatures during the MPWI and subsequent early Pleistocene cooling to modern climate reconstructed from oxygen isotope ratios recorded by the bivalve Mercenaria. Modern shells were collected from the University of North Carolina's Marine Sanctuary. Fossil shells from the Mid-Atlantic Coastal Plain (North Carolina) were collected from the Duplin Formation (MPWI) and the Waccamaw Formation (early Pleistocene). Oxygen isotope ratios range from −1 to 2.4 ‰ during the MPWI, −1–2.4 ‰ during the early Pleistocene, and −2.2 to 2.3 ‰ in modern shells. Stable carbon isotope ratios ranged from −0.91 to 1.67 ‰ during the MPWI, 0.19–1.87 ‰ during the early Pleistocene, and −2.46 to 0.60 ‰ in modern shells. Average seasonal growth temperature variations for the MPWI (∼11 ± 3 °C) are reduced compared to modern instrument records (∼16 ± 3 °C), while the early Pleistocene (∼14 ± 2 °C) was more similar to today. Modern Mercenaria record dark increment formation during the summer while fossil Mercenaria record dark increment formation during the winter. We hypothesize that this difference is timing of dark increment formation may be due in part to differences in water depth (∼1m for modern shells and ∼20m for fossil shells) or a shift in the location of the boundary between biogeographic zones. A −1.6 ‰ shift in mean stable carbon isotope ratios between fossil (0.92 ± 0.66 ‰) and modern (−0.65 ± 0.44 ‰) shells has been observed and may be a result of the "Suess Effect" and/or influences of estuarine/freshwater relative to marine settings. • Growth temperatures derived from oxygen isotope ratios show the MPWI had warmer winters and reduced seasonal amplitude compared to the early Pleistocene and today. • Mercenaria from the early Pleistocene recorded cooler summers and winter growth temperatures compared to modern Mercenaria. • Modern and fossil Mercenaria shells exhibit differences in the seasonal timing of dark increment formation. [ABSTRACT FROM AUTHOR]

Paleoclimatic records of sub-annual to interannual resolution are valuable for the study of climatic forcing mechanisms but these records are rare in terrestrial settings. Here, we show that high-resolution stable carbon isotope data within shells of land snails (δ13C shell) living in a C 3 plant-dominated community can be an indicator of growing season precipitation (GSP) amount. We collected modern land snails along two wet-dry climate gradients from northern Iran and the Chinese Loess Plateau (CLP), where the precipitation is mainly distributed in the boreal winter and boreal summer seasons, respectively. Our results indicate a common pattern of δ13C shell values increasing with aridity, driven by water stress in the local plant community. In contrast, temperature has a weak and inverse effect on δ13C shell values in these two regions, suggesting that rainfall amount is the primary control on δ13C shell for this modern comparison. Furthermore, we present a δ13C shell record covering the middle Holocene to the middle Pleistocene from the CLP. This record suggests that most of the average δ13C shell values from interglacial paleosol layers are lower than those from the adjacent glacial loess strata, suggesting higher GSP. However, the reconstructed glacial-interglacial difference in GSP is smaller than that estimated by other proxy indicators. This is likely due to the dietary preference of land snails and/or the sparse nature of this dataset, which might not be sufficient to capture the glacial-interglacial history of rainfall on the CLP. Large datasets with good taxonomic control and high stratigraphic resolution will be required to better describe the glacial-interglacial differences. • We report δ13C shell values from Westerlies Asia and Monsoonal Asia. • δ13C shell in C 3 plant communities is an indicator of growth season rainfall. • Reconstructed GSP are higher during interglacial periods than glacial periods. • Large dataset with high stratigraphic resolution will be required in future work. [ABSTRACT FROM AUTHOR]

This study offers a new record of laminated ooze for paleoclimate, paleoceanography and paleoecology interpretation in the deep ocean, promoting search for other similar records in the West Pacific Ocean to improve understanding of Ethmodiscus rex ooze formation and relative paleoenvironmental change. The laminated diatomaceous ooze includes large quantities of fragmented E. rex in a box core retrieved from the Challenger Deep, Southern Mariana Trench. Radiocarbon dating of the ooze revealed the studied sediment to originate during an interval of ca. 23 400 to ca. 6620 cal. yr. BP, inserting a hiatus during ca. 19 800 - 16 800 cal. yr. BP. This is the first geochronology data to constrain the E. rex ooze time span across the Pleistocene/Holocene boundary, compared to previous studies in this West Pacific Ocean trench. In this study, the laminated diatomaceous E. rex ooze type, with increased abundance of fragmented E. rex valves is mainly documented during ca. 23 400 - 19 800 cal. yr. BP. within the Last Glacial Maximum stage, at ca. 12 900 - 11 500 cal. yr. BP. in the Younger Dryas stadial, and around 9000–7700 cal. yr. BP. in the Postglacial. These data show a response to the paleoclimatic conditions with late Pleistocene cold periods that triggered E. rex diatom bloom that strongly competed for nutrients in this principally oligotrophic region. These phenomena are likely to be linked with terrestrial nutrients input through the aeolian dust transfer by winter Monsoon and the silicon supply from Southern Ocean via thermohaline circulation. In the Postglacial, the E. rex bloom generated a high ooze accumulation rate in terms of higher flux deposition with a complicated formation mechanism. • Laminated diatomaceous ooze with fragmented E. rex described from Mariana Trench. • First geochronology data shows E. rex ooze also occurred in Holocene in this Trench. • Diatomaceous ooze was not only driven by glacial stage but also created in warm period. • High E. rex flux responses to the LGM, YD event, and early-mid Holocene transition. • This offers a new record of ooze for paleoclimate, -oceanography, -ecology in this Trench. [ABSTRACT FROM AUTHOR]

Glacial-marine sediments from the Antarctic continental margin provide a record of depositional environment, oceanographic variability and ice dynamics that is tapped with scientific ocean drilling. This study focuses on Ocean Drilling Program Core 693A-2R, a 9.7 m sediment core retrieved from near the continental margin of the Archean Grunehogna Craton in Dronning Maud Land (DML), East Antarctica. The results contribute to a better understanding of ice-shelf behavior in DML during the mid-Pleistocene transition (MPT), a well-known transition from 40-kyr to 100-kyr cycle periods. The age model, constructed based on Sr isotope stratigraphy and geomagnetic reversals, indicates that the core spans 1.20 to 0.65 Ma. The dynamic behavior of DML ice shelves with periodic iceberg calving is revealed by the glacial–interglacial variation in sedimentation patterns, with interglacials characterized by higher concentrations of ice-rafted debris (IRD) associated with enhanced paleoproductivity than glacial intervals. The responses of DML ice shelves to warm climates are represented by a prolonged interglacial period at 1.0–1.1 Ma (MIS 31–27) and significant interglacial expressions during MIS 19 and 17. The 40Ar/39Ar ages of individual ice-rafted hornblende grains are compared with the on-land geology of DML and neighboring regions to determine the provenances of IRD. Specifically, 40Ar/39Ar results record primarily late Neoproterozoic to Cambrian ages (600–400 Ma) with a predominant peak of 520–480 Ma. This Pan-African/Ross orogeny signature is very common in East Antarctica but is not found in the most proximal margin of the Grunehogna Craton, and is instead associated with the region of DML several hundred kilometers east of the deposition site. This indicates that significant discharges of icebergs occurred in the remote DML, which were then transported by the westward-flowing Antarctic Coastal Current to deposit IRD at the studied site during the MPT. This study establishes a confirmed MPT sedimentary sequence off DML, against which future MPT proxy records from the Weddell Sea embayment and other sectors in Antarctica can be compared and correlated, and provides a basis for more detailed analyses of the response of DML ice sheet to Pleistocene climate variations. • Records from ODP Core 693A-2R indicate DML ice shelf instability during the MPT. • An age model constructed by Sr isotope stratigraphy and geomagnetic reversals. • A multi-proxy study to identify and characterize glacial-interglacial sedimentation. • Ice-rafted debris has a predominantly distal source instead of a local origin. • DML ice responses to climate changes align with global glacial cycles. [ABSTRACT FROM AUTHOR]