Late MIS Research Articles

Authigenic greigite in late MIS 3 sediments: Implications for the Yellow Sea Cold Water Mass and Yellow Sea Warm Current evolution

Yellow Sea current conditions during the late Marine Isotope Stage 3 (late MIS3, 40–30 ka B.P.) highstand remain unknown. Here, environmental magnetism, geochemistry, particle size, and scanning electron microscope methods are employed to analyze core YS01A with a basal age of 40 kyr from the South Yellow Sea mud deposits. Greigite formed in marine sedimentary layers with thickness >7 m during early diagenesis. Greigite formation is related to the redox state and total organic content (TOC) availability, which are controlled, respectively, by the Yellow Sea Cold Water Mass (YSCWM) and the Yellow Sea Warm Current (YSWC). In MIS1 (7–0 ka B.P.), a strong YSWC brought greater TOC, and a strong YSCWM (thickness of 48 m) resulted in a strongly reducing low-oxygen environment. This led to massive magnetite dissolution and pyrite preservation. In late MIS3 (37–31 ka B.P.), the weak Kuroshio Current and East Asian Winter Monsoon (EAWM) resulted in a low-intensity YSWC that provided less TOC. A weak YSCWM (thickness of 35 m), caused by shallow water depths and a weak EAWM, contributed to a less reducing sedimentary environment. Thus, pyritization was interrupted and greigite was preserved. Greigite content can, thus, be used to trace the development of Yellow Sea currents. During a period of slow sea level rise at 41–37 ka B.P., minor greigite formed with most magnetite being preserved, which indicates that the environment started to become reducing. This can be interpreted as due to initial formation of a thin and weak YSCWM. During the 37–31 ka B.P. highstand, the greigite content increased, which suggests more reducing conditions related to establishment of a thicker and intensified YSCWM. In addition, the greigite content decreased progressively, which may have resulted from YSWC weakening. Our results suggest that greigite can be used as a simple tool to reflect current evolution in the Yellow Sea, which can give a better understanding of continental shelf environment change.

A marine isotope stage 13 Acheulian sequence from the Amanzi Springs Area 2 Deep Sounding excavation, Eastern Cape, South Africa

Renewed research at Amanzi Springs has increased resolution on the timing and technology of the Acheulian industry in South Africa. The archeology from the Area 1 spring eye has recently been dated to MIS 11 (∼404–390 ka), and analyses revealed significant technological variability when compared to other southern African Acheulian assemblages. We expand on these results in presenting new luminescence dating and technological analyses of Acheulian stone tools from three artifact-bearing surfaces exposed within the White Sands unit of the Deep Sounding excavation in the Area 2 spring eye. The two lowest surfaces (Surfaces 3 and 2) are sealed within the White Sands and dated between ∼534 to 496 ka and ∼496 to 481 ka (MIS 13), respectively. Surface 1 represents materials deflated onto an erosional surface that cut the upper part of the White Sands (∼481 ka; late MIS 13), which occurred before the deposition of younger Cutting 5 sediments (<408–<290 ka; MIS 11–8). Archaeological comparisons reveal that the older Surface 3 and 2 assemblages are predominated by unifacial and bifacial core reduction and relatively thick, cobble-reduced large cutting tools. In contrast, the younger Surface 1 assemblage is characterized by discoidal core reduction and thinner large cutting tools, mostly made from flake blanks. Typological similarities between the older Area 2 White Sands and younger Area 1 (404–390 ka; MIS 11) assemblages further suggest long-term continuity in site function. We hypothesize Amanzi Springs represent a workshop locality that Acheulian hominins repeatedly visited to access unique floral, faunal, and raw material resources from at least ∼534 to 390 ka.

Sea ice and productivity changes over the last glacial cycle in the Adélie Land region, East Antarctica, based on diatom assemblage variability

Abstract. Although diatoms can provide important palaeoenvironmental information about seasonal sea ice extent productivity, sea surface temperature, and ocean circulation variability, there are still relatively few studies analysing the last glacial cycle near the Antarctic continent. This study examines diatom assemblages over the last glacial cycle from core TAN1302-44, offshore Adélie Land, East Antarctica. Two distinct diatom assemblages were identified using principal component analysis (PC 1–PC 2). The PC 1 assemblage is characterised by Thalassiosira lentiginosa, Actinocyclus actinochilus, Eucampia antarctica, Azpeitia tabularis and Asteromphalus hyalinus and is associated with the interglacial, sedimentary Facies 1, suggesting that the MIS 5e and Holocene interglacials were characterised by seasonal sea ice environments with similar ocean temperature and circulation. The PC 2 assemblage is characterised by Fragilariopsis obliquecostata, Asteromphalus parvulus and Thalassiosira tumida and is associated with the glacial Facies 2. The variability of PC 2 indicates that, during the MIS 4–2 glacial and the last glaciation, there was an increase in the length of the sea ice season compared with that of the interglacial period, yet there was still no permanent sea ice cover. The initial increase of PC 2 at the start of the glaciation stage and then the gradual increase throughout late MIS 4–2 suggest that sea ice cover steadily increased, reaching a maximum towards the end of MIS 2. The increase in sea ice during glaciation and MIS 4–2 glacial is further supported by the increase in the Eucampia index (terminal/intercalary valve ratio), an additional proxy for sea ice, which coincides with increases in PC 2. Aside from the statistical results, the increase in the relative abundance of Thalassiothrix antarctica at 40 and 270 cm suggests that, during the last two deglacials, there was a period of enhanced nutrient delivery, which is inferred to reflect an increase in upwelling of Circumpolar Deep Water. Interestingly, the diatom data suggest that, during the last deglacial, the onset of increased Circumpolar Deep Water occurred after the loss of a prolonged sea ice season (decrease in PC 2) but before the ice sheet started to retreat (increase in IRD). Together, these results suggest the changes in sea ice season potentially influenced the ocean's thermohaline circulation and were important factors in driving the climate transitions. The results contribute to our understanding of the sea ice extent and ocean circulation changes proximal to East Antarctica over the last glacial cycle.

Vegetation and chemical weathering changes since the late MIS 3 in the mid-lower Yangtze River Valley: Evidence from pollen and geochemical records

The vegetation and chemical weathering history since the late Marine Isotope Stages 3 (MIS3) is still poorly studied in the Yangtze River Valley (YRV), central China, which hinders a better understanding of their relationship to climate and anthropogenic impacts. We here coupled pollen and geochemical proxy based on a fluvial sedimentary sequence from the YRV. The pollen data show that the past natural land-cover was dominated continuously by forest before 5 cal kyr BP, with arboreal pollen abundance larger than 60%. Nevertheless, the forest community underwent major changes in response to temperature fluctuations, from a evergreen and deciduous broadleaved mixed forest during the moderately warm late MIS 3, to a coniferous and broadleaved mixed forest during the cold MIS 2, and back to a evergreen and deciduous broadleaved mixed forest during the Holocene Thermal Maximum. Since ca. 5 cal kyr BP, the unprecedented increases in Poaceae and decreases in arboreal pollen abundances indicated that regional vegetation was strongly disturbed, along with the expansion of rice agriculture to the entire YRV. The geochemical data reveals more intense chemical weathering during the relatively cold periods (e.g., the LGM) than that during the relatively warm periods (e.g., the late MIS 3 and mid-Holocene), with a gradual weakening from the LGM to the early Holocene. The variations in chemical weathering were mainly controlled by regional precipitation changes. There was a “dipolar” mode of precipitation changes at millennial to orbital timescale between north China and the YRV during the last 30,000 years, which were predominantly regulated by the ENSO-like states in the tropical Pacific; an El Niño state resulted in more (less) precipitation in the YRV (northern China), while opposite condition occurred during a La Niña state. Severe deforestation by intense human activity also influenced the intensity of chemical weathering since ca. 5 cal kyr BP.

Modeling the timing and extent of glaciations over southeastern Tibet during the last glacial stage

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.

The peopling of the hinterland of the Tibetan Plateau during the late MIS 3

The peopling of the hinterland of the Tibetan Plateau during the late MIS 3

Paleoenvironment and human activity on the central Korean Peninsula during the late MIS 3 and MIS 2

AbstractLayers 12 and 13 of the Chongphadae Cave site located northwest of the central part of the Korean Peninsula include human fossils, fireplaces, a great number of lithic artefacts, and mammal remains. These layers represent new evidence for the paleoenvironment, human occupation, and activities in this region during the late MIS 3 and MIS 2, associated with global cold and dry climate, respectively. Most of lithic artefacts collected are flake tools. Raw material selection, lithic reduction technology, and lithic industry represent peculiar local characteristics. Our analysis of faunal assemblages also suggests that the Chongphadae region had a rich ecosystem capable of forming a diverse mammalian fauna including ungulates (mainly deer and horses) during this period. It is likely that the mosaic landscapes, including grasslands, forests, rivers, and wetlands, provided a favorable environment for humans, as well as mammals and plants, and the occupants of the site actively hunted and gathered in a relatively temperate environment. Our study suggests that the central Korean Peninsula was not severely affected by global dry and cold events such as LGM, although it was a somewhat humid and cold environment during the late MIS 3 and MIS 2. The central Korean Peninsula may have existed as an unknown refugium (or area of endemism) in northeastern Asia during this time.

After the blades: The late MIS3 flake-based technology at Shuidonggou Locality 2, North China.

Contrasting with the predominance of blade-based assemblages in the Eurasian Upper Paleolithic, the large-scale persistence of a core-and-flake technology remains one of the defining features of Late Pleistocene lithic technology in East Asia. In North China, Shuidonggou is an exceptional site where both technologies are documented, therefore, it is an important archaeological sequence to understand regional technological evolution during the Marine Isotopic Stage 3. Blade technology first occurred at Shuidonggou Locality 1 and 2 around 41 ka cal BP while core-and-flake assemblages were widespread in North China. However, systematic technological studies on assemblages postdating 34 ka cal BP have not been conducted to examine whether the blade technology appeared and disappeared over a short yet abrupt episode, or persists and integrates into other forms in the region. Here, we conducted qualitative and quantitative analyses to reconstruct lithic productions on the assemblages at Shuidonggou Locality 2, dated after 34 ka cal BP. Our results show that there is a total absence of laminar elements in stone artifacts dated to 34–28 ka cal BP at Shuidonggou. Instead, we observe a dominance of an expedient production of flakes in the younger assemblages, illustrating a rapid return to flake-based technology after a relatively brief episode of stone blade production. Combining archaeological, environmental, and genetic evidence, we suggest that this technological ‘reversal’ from blades back to core and flake technology reflect population dynamics and adaptive strategies at an ecological interface between East Asian winter and summer monsoon.

Multiple carbon cycle mechanisms associated with the glaciation of Marine Isotope Stage 4

Here we use high-precision carbon isotope data (δ13C-CO2) to show atmospheric CO2 during Marine Isotope Stage 4 (MIS 4, ~70.5-59 ka) was controlled by a succession of millennial-scale processes. Enriched δ13C-CO2 during peak glaciation suggests increased ocean carbon storage. Variations in δ13C-CO2 in early MIS 4 suggest multiple processes were active during CO2 drawdown, potentially including decreased land carbon and decreased Southern Ocean air-sea gas exchange superposed on increased ocean carbon storage. CO2 remained low during MIS 4 while δ13C-CO2 fluctuations suggest changes in Southern Ocean and North Atlantic air-sea gas exchange. A 7 ppm increase in CO2 at the onset of Dansgaard-Oeschger event 19 (72.1 ka) and 27 ppm increase in CO2 during late MIS 4 (Heinrich Stadial 6, ~63.5-60 ka) involved additions of isotopically light carbon to the atmosphere. The terrestrial biosphere and Southern Ocean air-sea gas exchange are possible sources, with the latter event also involving decreased ocean carbon storage.

Végétation interstadiaire de la fin du SIM 3 dans les sables éoliens landais à Saint‑Vincent‑de‑Paul, sud‑ouest de la France.

Végétation interstadiaire de la fin du SIM 3 dans les sables éoliens landais à Saint‑Vincent‑de‑Paul, sud‑ouest de la France.

New paleoecological perspectives on Late Pleistocene Neanderthals in northern Balkans: the rodent assemblages from Smolućka cave (Serbia)

During the Late Pleistocene, the Balkans came to be an important region with many isolated areas, enabling fauna, alongside Neanderthals, to thrive in the area. This work is focused on paleoenvironmental and paleoclimatic changes that occurred in the northern Balkan Peninsula with a special focus on fossil record from Smolućka cave aging from MIS 5 to MIS 3. Based on available data, an attempt has been made to establish a synthetic chronological context for the faunal assemblages recovered from Smolućka cave. Tentative attribution of layer 5 to MIS 5 relies on the interstadial pattern of our reconstructions, with favorable climate conditions for a large diversity of species and with mean annual temperature (MAT) reaching up to 3 °C higher than present values and abundant rainfall in the area. Cold conditions for MIS 4 are not present in Smolućka, although layer 4 (late MIS 5 or early MIS 4) shows somewhat dryer and cooler climate when compared with other layers. Layers 3z and 3 (MIS 3) are characterized by temperate and humid conditions together with a complex system of mosaic habitats with high environmental heterogeny but generally favorable conditions for a large diversity of life. Although still not fully chronologically constrained, Smolućka cave presents an interesting opportunity for future research, in the time period when only Neanderthals occupied the Balkans and thrived in local conditions. The transition between the Neanderthals and anatomically modern humans has not yet been established but can be expected in future research.

Landform mapping used to identify glaciations in the multi-glaciated landscape of Yorkshire, U.K

Landform mapping, coupled with luminescence dating, has confirmed two glaciations in the Vale of Pickering in northern England: a Late Devensian (MIS 2) glaciation and a Drenthe stage late Saalian (MIS 6) glaciation. In addition, mapping of strandlines around the margins of proglacial Lake Humber has suggested a parallel evolution for the Vales of York and Pickering with synchronous flooding in both regions during the Late Devensian. This mapping also confirms a lack of recognisable glacioisostatic rebound post-MIS 2, while a review of the literature indicates the spacing regularity of the strandlines, recorded during the drainage of Lake Humber, can be attributed to cyclical climate changes. In contrast, the penultimate glaciation that is represented by a North Sea glacial incursion into the Vale if Pickering as far as the Wykeham Moraine, records post-glacial rebound of up to 30m. It is also probable that a proglacial lake, which has been given a tentative late MIS 7 date, impounded in the Vale of York could be indicative of an MIS 8 or early Saalian glacial blockage of the Humber.

Testing a proposed new chronology for the Jasmund Glacitectonic Complex (SW Baltic Sea): No indication of incipient deformation during MIS 3

Weichselian advances of the Scandinavian Ice Sheet have generated several glacitectonically deformed structures in the southwestern Baltic Sea area. One example is the 100 km 2 large Jasmund Glacitectonic Complex (JGC), which was formed proglacially and consists of two subparallel-orientated sets of composite ridges that represent a northern and southern structural complex. The two-part morphological structure of the JGC suggests a formation by two ice advances, one approaching from NE and one from SE direction. So far, this divided structure has been assumed to have been formed by short-time ice-front oscillations during an MIS 2 ice advance. However, based on their recently published ice dynamic model for MIS 3 and the available age data from Jasmund, lüthgens et al. (2020) propose a chronological reinterpretation of the JGC development, according to which two distinct ice advances during early and late MIS 3 formed the JGC. In order to test this novel stratigraphical model for the JGC formation, five OSL samples were taken from fluvial and lacustrine deposits at a key section near Glowe (NW Jasmund). The investigated succession is divided into pre-kinematic sediments, deposited before the glacitectonic deformation, and post-kinematic sediments, deposited after the deformation. Our results show that the youngest dated pre-tectonic sediment has a burial age between ∼40 and 34 ka, which rules out a glacitectonic deformation during an early MIS 3 ice advance (∼60–50 ka). In addition, by reviewing the existing age data set, a development of the JGC during an early and late MIS 3 advance of the SIS must be rejected. Instead, our data confirm the genesis of the JGC during MIS 2.

Changing sea-surface and deep-water conditions in the southern Cape Verde Basin during the mid-Pleistocene to Holocene

Reconstruction of the Atlantic Meridional Overturning Circulation (AMOC) based on long-term records spanning multiple glacial-interglacial transitions is essential for understanding the interplay between ocean dynamics and global climate change. However, despite valuable previous studies, many uncertainties remain, especially regarding the distribution of glacial water masses in the Atlantic and the AMOC intensity. Such long-term reconstructions are highly constrained by sedimentary geochemical records. Here, we present isotope, geochemical, and micropaleontological records from the core ANS-33047 retrieved from the southern part of the Cape Verde Basin at a water depth of 4027 m. The data reflect the glacial–interglacial changes in surface and near-bottom conditions in the area over the last 513 kyr. Within the upper ocean layer, enhanced bioproductivity associated with northward ITCZ migration has been determined during MIS 13/12, early MIS 11, 9, 7, and MIS 1. A gradual deepening of the mixed layer is inferred from MIS 5 to the present. Stronger deep-water upwelling and shoaling of the mixed layer over the study site preceded these intervals. In the deep-water environment, we propose three different regimes within the interglacials: a “classical model” and “local productivity effect” associated with a stronger advection of paleo-NADW into the study area (MIS 11, 5, 1, warm early phases of MIS 9 and 7, MIS 13/12 boundary), as well as “amplified paleo-AABW influence” (late MIS 13 and 7). The bottom-water chemistry was affected by organic matter degradation coinciding with intervals of northward ITCZ migrations and enhanced surface bioproductivity. The most prominent signal of southern-sourced deep water was reconstructed during the late MIS 12, MIS 8, and at the MIS 10/9 boundary. During MIS 3 and sub-stage 12b, the study area was bathed by a mixture of paleo-NADW and paleo-AABW. A comparison of the carbon isotope records from the northeastern and southeastern equatorial Atlantic demonstrates a larger difference in the deep-water properties within glacials in contrast to interglacials. • ITCZ shifts northwards and bioproductivity is enhanced during interglacial intervals. • Increased surface bioproductivity affects δ 13 C composition of paleo-NADW. • Three deep-water regimes occurrs within interglacials. • Stronger meridional variability of deep-water circulation in cold climatic phases.

Last glacial fluctuations in the southwestern Massif Central, Aubrac (France): First direct chronology from cosmogenic 10Be and 26Al exposure dating

The chronology of the late Pleistocene glaciation in the Massif Central, France, is not well documented and there are divergent hypotheses regarding the timing of glacial events in this area. This study aims at reconstructing the chronology of late Pleistocene glacial fluctuations in the Aubrac Mountains. We present a new set of Be-10 and Al-26 exposure ages from twenty erratic boulders embedded in six glacial landforms. Glacial landforms were sampled to determine the timing of three glacial stades and the deglaciation of the Aubrac Mountains. These new data allowed us to constrain the timing of: (i) the Local Last Glacial Maximum, which is coeval with the early Marine Isotopic Stage 2 (MIS 2) (28–24 ka), and (ii) the Grandvals and Bouquincan stades, which are both coeval with the late MIS 2 (24–16 ka). Deglaciation occurred during Heinrich Stadial 1 (18–15.6 ka). This new direct glacial chronology is supported by regional paleoenvironmental proxies and it updates the chronostratigraphic framework available for the southwestern Massif Central. Western European atmospheric circulation changes (i.e., a southward shift in North Atlantic storm tracks and Mediterranean influences) during MIS 2 were identified as significant factors controlling glacier growth in the Aubrac Mountains as well as other glaciated mountains within the southwestern Massif Central, such as the Cantal, Margeride and Lozère mountains.

Subfossil Coleoptera from Eifel maar sediments as indicators of the environmental evolution in Central Europe over the last 60,000 years

A reconstruction of landscape and paleotemperatures is presented from a composite drill core from the Eifel maar lakes of Auel and Holzmaar, Germany. The compositecore is 112 m long and covers the last 60,000 years (Marine Isotope Stages MIS 3, 2, and 1) based on the new ELSA-20 stratigraphy. Findings are based on an analysis of arthropod remains, with moisture-dependent, riparian or (semi)aquatic Staphylinidae representing the majority of beetle sclerites in the assemblages, especially during cold intervals. Assemblages change corresponding to climate and vegetation, with a greater variety of taxa during the woodland phases (60,000–44,000 yr b2k, i.e. years before 2,000 CE) versus cold adapted taxa during late MIS 3 and early MIS 2 (28,500–23,500 yr b2k). Beetles that inhabit damp, moist or wet locations, as well as aquatic or riparian taxa are present throughout the record. The assemblage corresponding to a period of tundra-like vegetation (29,000–24,000 yr b2k), contained three taxa suitable for temperature calculation (Arpedium brachypterum, Bembidion fellmanni, and Boreaphilus henningianus), all of which are found only in cold phases (Greenland Stadial 2 and 4, and Heinrich Event 2). Paleotemperatures were reconstructed via the Mutual Climatic Range method giving the following results. Mean temperature for the early tundra phase (28,500–27,800 yr b2k) is −32 to −2 °C for the coldest month, and 6 to 9.5 °C for the warmest month. Mean temperature for the later tundra phase (27,000–24,000 yr b2k) is −30 to −20 °C for the coldest month and 6 to 9.5 °C for the warmest month. This shift indicates an increase in seasonality towards the Last Glacial Maximum. Paleotemperature calculations are in good agreement with other European records and indicate a major decline in median winter temperatures towards the Last Glacial Maximum, whereas the summer temperatures remained relatively stable throughout Europe, resulting in an increase in seasonality and continentality.

Climatic quantification and seasonality of the late MIS 3 in North China: A perspective from carbon and oxygen isotopes of fossil mammal teeth

Marine Isotope Stage 3 (MIS 3, at 60–25 ka B.P.) was a short interstadial within the Last Glacial period. A generally warm and wet climatic condition during the MIS 3 period has been suggested by many previous studies. Quantitative climatic reconstruction and studies of seasonality, however, have been seldom attempted given the scarcity of useful proxy indicators. A full understanding the climatic characteristics during this period is hampered by their absence. This is especially the case in the East Asian monsoon region in North China, which is very sensitive to climatic change. To help fill this knowledge gap, we have determined the stable carbon (δ13C) and oxygen isotope (δ18O) compositions of tooth enamel from fossil mammals (Bubalus sp [buffalo] and Cervus elaphus [red deer], dated at ∼33–31 ka B.P.) recovered from Longquan Cave in North China. We use these data to constrain ecology, local air temperature and precipitation amounts during the late MIS 3. The average δ13C (VPDB) of tooth enamel (−14.4‰ and −8.8‰, respectively for buffalo and red deer) indicate that C3 plants comprised the main diet of animals living in this area. Pollen assemblages demonstrated that vegetation mainly consisted of grasses and herbs (∼64%) with trees only accounting for about 26%. These results indicate a landscape of open steppe with sparsely distributed trees. The reconstructed climate derived from tooth enamel δ18O was relatively colder and drier than present-day condition, with mean annual air temperature ranging from 4 to 13 °C and mean annual precipitation ranging from 360 to 670 mm. Moreover, the inferred summer and winter half-year temperatures were respectively 8–24 °C and −2 to 5 °C, which represents either similar or weaker seasonality than at the present time. The inferred cold and dry climate suggested by our study contrasts with the warm and wet conditions previously reconstructed using proxy indicators from bulk soil samples in North China. In comparison to the long-term, time-averaged climatic condition reflected by those soil proxies, the stable isotope compositions of fossil more likely recorded climatic conditions at annual or seasonal time-scale. The inferred annual cold/dry climate at Luanchuan Cave suggested by our data may indicate a short climatic cooling event from Greenland Interstadial (GIS) 5 to its following stadial. Mean annual temperature fluctuated by ∼8 °C during this interstadial-stadial cycle.

Timing of late quaternary glaciations in the Yankti Kuti valley of the upper Kali Ganga catchment, Northern India

The Yankti Kuti valley which is located in the transitional climatic zone of the upper Kali Ganga catchment of northern India has witnessed multiple glacier advances since Marine Isotopic Stage 3 (MIS 3). The oldest glacial advance in the valley occurred during early MIS-3 and is dated to 52 ± 3 ka (52.8 ± 3 and 50.4 ± 3 ka), the second advance occurred during late MIS 3 and is dated to 35 ± 2 ka (36.4 ± 1.8 and 34.5 ± 2.2 ka). The termination of this stage occurred at ∼30.3 ± 2 ka and is reflected in the vertical shrinkage of the glacier. The third glacial advance which was more restricted is dated to the Last Glacial Maximum (LGM) 22 ± 1 ka (22.2 ± 1.1 and 21.4 ± 1.2 ka). Following this, a glacial advance is dated to 16.1 ± 1 ka corresponding to the Older Dryas cooling of the late glacial period. A subsequent minor re-advance is dated to 4.3 ± 2.0 ka (4.4 ± 0.4 and 4.2 ± 0.1 ka) and can be attributed to the globally identified 4.2 ka cooling (arid) event. The study is in accordance with earlier observations made from the monsoon-dominated central Himalayan region. It provides a robust chronology and climatic evidence indicating significant ice volume depicted by the moraine height during MIS 3, implying that the moisture-deficient valleys of semi-arid Himalayan regions respond sensitively to enhance precipitation. The study suggests a regional synchronicity of glacier response to climate variability since MIS 3 and was in accordance with the synoptic-scale, climatic perturbation triggered by the North Atlantic millennial-scale climate oscillations.

The Formation of Late Pleistocene and Holocene Sand Dunes on Kikaijima Island, Nansei Islands

Coastal sand dunes dating to the latter part of the late Pleistocene were constructed at substantially lower sea levels on Kikaijima Island. They are preserved because of large-magnitude uplifts ascertained from occurrences of outstanding late Pleistocene and Holocene coral terraces. In addition, because Holocene sand dunes occur close to those of Marine Oxygen Isotope Stage 3 (MIS 3), the island is ideal for examining the environments of the formation of sand dunes, which were constructed under different climatic and sea-level conditions. Distributional and depositional features of sand dunes are clarified, and their chronology is constructed on the basis of tephrochronology, 14C dating, and chronological relationships of the sand dunes with marine terraces of known age. The environments of sand-dune formation on Kikaijima are examined in relation to climatic and sea-level records within regional and global contexts. Nine tephra layers are recognized. These include two widespread tephras, Kikai-Akahoya tephra (K-Ah) and Aira-Tn tephra (AT). The other seven tephras, consisting of fine ash layers, are newly recognized and named Kikaijima-1 tephra (Kj-1) to Kikaijima-7 tephra (Kj-7), of which the upper six, lying between K-Ah and AT, are aged from 13,000 to 30,000 cal BP. Holocene sand dunes began to form at c. 8,000 cal BP before the culmination of maximum Holocene sea-level rise. This is earlier than dune formation on other coasts of the Japanese Islands, where formation was generally after the culmination of maximum Holocene sea-level rise. The earlier formation on Kikaijima Island is probably due to coastal emergence caused by the conspicuous uplifts of Kikaijima and the high production of calcareous beach sands sourced from coral and foraminiferal and other materials. Late Pleistocene sand dunes, predominantly distributed at the southwestern part of Kikaijima Island, were formed in MIS 3. These dunes consist of longitudinal and parallel dunes. The largest longitudinal dunes on the lowest MIS 3 terraces, at the northern area of the southwestern part of Kikaijima Island, were formed in late MIS 3, c. 40 to 32 ka, while small and parallel sand dunes on the upper MIS 3 terraces were formed in early MIS 3. The occurrence and chronology of the Holocene and late Pleistocene sand dunes suggest that their formation on Kikaijima Island is mainly related to the occurrence of coastal sandy beaches during sea-level high stands. Although Holocene sand dunes are related to Holocene high stand, those of MIS 3 are related to high stands during cycles of sea-level fluctuations in MIS 3. The longitudinal landform of the sand dunes recognized in the late MIS 3 suggests that the prevailing winds in MIS 3 were stronger than in the Holocene. This study provides critical data for constructing a chronological framework that integrates various aspects of palaeoenvironments, as well as human interactions and responses in southern Kyushu.

Glacier-Induced Alluvial Fan Development on the Northeast Tibetan Plateau Since the Late Pleistocene

The origin of alluvial fans at the drainage basin or the margins of the arid sedimentary basin on the northeastern Tibetan Plateau (NETP) has been a focus of debate among scientific communities. Extensive alluvial fans had developed in the mountain-basin systems of this region during the late Pleistocene. Based on geomorphic/stratigraphic studies and the optically stimulated luminescence (OSL) chronology, we investigated numerous alluvial sequences in the drainage basin of the coupled mountain-basin system on the NETP. Sedimentologic analyses showed that these alluvial sediments mainly comprise crudely meter and decimeter beds of fanglomerate and sandy lenticles, which occasionally contain boulders in the thinner layers. OSL dating results showed that the alluvial sediments were mainly developed during the late MIS 5, MIS 3, and Last Glaciation and Deglaciation (maximum aggradations), while little had occurred during the early Holocene. Comparing our ages and their probability density curves with those of glacial advances from the northeastern/eastern TP, the consistency of both records during different stages since the late Pleistocene suggested that the development of alluvial fans was driven by glacier activities, which yielded abundant outwash, feeding alluvial aggradations. Based on this finding, together with results of previous studies, we argued that the dynamics of alluvial geomorphic processes had a paleoclimatic origin rather than surface uplifts. Further studies indicated that the precipitation of glaciations originated from the ISM northward intrusion during the late MIS 5, MIS 3, and Holocene; however, it was mainly influenced by the westerlies during the Last Glaciation and Deglaciation. Therefore, the development of alluvial fans on the NETP represents coupling signals of the ISM and the westerlies on the interglacial–glacial cycle timescales. The coupling evolution of glacier activities and alluvial aggradations in the drainage basins of mountain-basin systems on the NETP provides a model for assessing the linkages between regional geomorphic processes and atmospheric circulations on hemispheric scales.