Glacial Advances Research Articles

Glacier fluctuations since the global Last Glacial Maximum in the eastern Tanggula Mountains, China

Distinct moraine complexes are well-preserved at the headwaters of the Requ River valley on the southern slope of Bujia Gangri, the largest center of modern glaciation in the eastern Tanggula Mountains in western China. Dating these moraines is an important step in understanding glacial history, palaeoclimate, and landscape evolution in this region. Surface exposure dating using 10Be was done on twenty-three rock samples from large granitic boulders embedded in moraine crests were collected from the Yongqu River valley and the Daxiong River valley, two glaciated valleys at the headwaters of the Requ River valley. The moraines (MW1 and ME1) closest to the current glaciers in the west (main) and east (hanging) valleys of the Yongqu River valley were dated to 203 ± 51 a (n = 4) and 162 ± 58 a (n = 3); the inner four end moraines (MW3–1) and outer ones (MW3–2) of the third moraine complex (MW3) in the main valley date to 16.8 ± 1.8 ka (n = 3) and 20.7 ± 1.3 ka (n = 2); end moraines (ME2) near the mouth of the east valley and a high lateral moraine (MEL) on its east side date to 18.9 ± 3.0 ka (n = 4); and a high lateral moraine in the Daxiong valley (MDXL) dates to 18.6 ± 1.3 ka (n = 3). The dating results indicate that these moraines were formed during the Little Ice Age (LIA), the Heinrich 1 (H1) event period, and the global Last Glacial Maximum (LGMG). These glacial events are synchronous with those across the Tibetan Plateau (TP) and its surrounding mountains. Combining the palaeoclimatic and palaeoenvironmental proxies in the TP and its surroundings, we infer that the cooling during the LIA, H1, and LGMG was a main control for these glacial advances.

Role of Different Moisture Sources in Driving the Western Himalayan Past-glacier Advances

The fragmented pattern and the rapidly declining preservation of older glacial features/evidences limits the precision, with which glacial chronologies can be established. The challenge is exacerbated by the scarcity of datable material and limitations of dating methods. Nevertheless, the preserved glacial landforms have been fairly utilized to establish glacial chronologies from different sectors of the Indian Himalayas. The existing Himalayan glacial chrono-stratigraphies have revealed that in a single valley, past glacial advances rarely surpass four stages. Thus, local and regional glacial chronologies must be synthesized to understand glacial dynamics and potential forcing factors. This research presents an overview of glacier responses to climate variations revealed by glacial chrono-stratigraphies in the western Indian Himalayan region over the Quaternary (late). The synthesis demonstrated that, although the glacial advances were sporadic, glaciers in western Himalayas generally advanced during the Marine isotope stage (MIS)-3/4, MIS-2, late glacial, Younger Dryas (YD) and Holocene periods. The Holocene has witnessed multiple glacial advances and the scatter is significant. While previous glacial research revealed that Himalayan glaciers were out of phase with the global last glacial maximum (gLGM), weak Indian Summer Monsoon (ISM) has been implicated (ISM was reduced by roughly 20%). Recent research, however, has shown that gLGM glaciation responded to the global cooling associated with the enhanced mid-latitude westerlies (MLW). Further, the magnitude of gLGM glacier advance varied along and across the Himalayas particularly the transitional valleys located between the ISM and MLW influence. It is also evident that both the ISM and MLW have governed the late Quaternary glacial advances in the western Himalayan region. However, the responses of glaciers to ISM changes are more prominent. The insights gained from this synthesis will help us understand the dynamics of glacier response to climate change, which will be valuable for future climate modelling.

Cave sediments in the Western Bauges karst: A record of Middle and Upper Pleistocene glacial advances in the French Alps

Previous studies point to a discrepancy in the timing of the maximum extent of the Alpine glaciation during the last glacial cycle (Würmian) in the Western Alps. Work carried out on the Lyon palaeoglacier lobe in France suggests that the glacial maximum occurred during Marine Isotope Stage (MIS) 4, while more recent studies on the Rhône palaeoglacier lobe in Switzerland provide evidence of a maximum during MIS 2. Here, we present new chronological data from the karst region of the Western Bauges (French Alps). Between 500 m and 1200 m a.s.l. several karst systems were in lateral position to the Isère palaeoglacier. This palaeoglacier invaded the Bauges limestone massif and the Chéran valley by a transfluence controlled by the Frêne pass at 980 m a.s.l. Allochthonous glacier-derived gravel and sand interbedded with speleothems are present in caves, providing terminus ante quem and post quem age constraints on the timing of several glacial advances. Other speleothems were submerged by rising water levels in the karst due to damming by the glacier. Finally, some speleothems show shatter marks caused by the impact of pebbles transported by highly turbulent meltwaters. 25 U/Th dates of speleothems cover MIS 9 to 1. For MIS 4 to 2, they allow, indirectly, to constrain the different glacial advances into the Bauges limestone massif and to re-evaluate the timing of the maximum Alpine glaciation during the Würmian in this part of the Western Alps. Although the new data and observations do not exclude the possibility of a maximum glacier advance during MIS 2, they argue for a maximum advance during MIS 4 and a local, smaller one during MIS 2.

Facies sedimentology and sequence stratigraphy of the carboniferous lower section of the Ansilta Formation, Calingasta-Uspallata Basin, NW Argentina

The Ansilta Formation is located 5 km southeast of the Astronomical Observatory El Leoncito near Barreal, San Juan Province, Argentina. It consists of glacimarine, nearshore, and fluvial systems deposited during the Late Paleozoic Ice Age along the eastern margin of the Calingasta-Uspallata Basin. Glacial environments are unique in that facies changes occur because of glacial ice margin fluctuations that may be independent from changes of eustatic sea-level. For this reason, an alternative conceptual framework outside of the traditional sequence stratigraphic approach is necessary to understand the genesis of these strata. The lower glacially influenced succession (0–427 m) records at least five glacial advances, where glacial dynamic signatures are interpreted using glacial sequence stratigraphy and glacial systems tracts (GST). The upper succession of the Ansilta Formation (427–700 m) consists of progradational shallow marine shelf, deltaic, and fluvial strata. This assemblage shows no direct evidence of ice contact deposition in the outcrop belt due to an absence of glacially shared diamictites and glacially modified clasts, representing a major deglaciation phase in western Argentina and is part of the stepped deglaciation across Gondwana that ended elsewhere during the late Permian.

Timing and extent of late Quaternary glaciations on Karlik Mountain, eastern Tianshan range, China

Glacial landforms formed by multiple glaciations are well-preserved in the valleys around Karlik Mountain in the easternmost Tianshan range, Central Asia. These landforms are direct imprints of palaeoglaciers and represent important archives of past climatic and environmental conditions. Dating these landforms contributes to understanding the spatiotemporal variations of past glaciers and provides key information for reconstructing the palaeoclimate and palaeoenvironment in Central Asia. In this study, thirty-two boulder and bedrock samples were collected from two glaciated valleys on the southern slope of Karlik Mountain for terrestrial in situ cosmogenic nuclides (TCN) 10Be surface exposure dating. Based on the geomorphic relationships and dating results, the innermost MS1 moraine complex was deposited during the Little Ice Age (LIA); the MS2 moraine complex was formed during the Lateglacial; the MS3 moraine complex was deposited during the global Last Glacial Maximum (LGMG); the MS4 moraine complex, which is the largest moraine complex, is marine oxygen isotope stage (MIS) 4 in ages; and the MS5 moraine complex, which is only preserved at the interfluve ridges, has a similar age to MS4. The age of MS4 demonstrates that the largest local last glacial maximum (LGML) occurred during the early part of the last glacial cycle rather than during the LGMG. The MS4 and MS5 glacial complexes imply that a large ice cap with outlet valley glaciers developed on the whole of Karlik Mountain during MIS 4. These ages, combined with previous landform mapping and dating on the northern slope of the mountain, show that glacial advances since MIS 4 in this mountainous area were restricted to the valleys, rather than large ice cap scale, which is consistent with moraine records in the other valleys across the Tianshan range. The pattern and nearly synchronous timing of palaeoglacier fluctuations during the last glaciation in arid Central Asia imply that the main determinant for glacier fluctuations in this region has been changes in precipitation brought by the westerlies during periods of low temperature.

Quaternary glaciations in western China: A review of the chronologies established by absolute dating

Quaternary glaciations in western China have been investigated over the last century with the emphasis on the Tibetan Plateau and its adjacent regions. Earlier studies were mainly based on field observation and interpretation of geomorphic landforms and processes to identify and define past glacial sequences. The advent of absolute dating techniques, such as optically stimulated luminescence dating and cosmogenic radionuclide exposure dating, has revolutionized glacial chronological research in recent decades. Glacial chronologies have been established across various mountains, providing evidence to reject the Tibetan ice sheet hypothesis. Glacial advances generally occurred synchronously in this region, but the detailed timing, extent, and form of past glaciers vary at different locations. This review presents recent progress and challenges on reconstructing the timing and extent of Quaternary glaciations in western China, seeking to promote further studies and a broader interest from the physical geography community in this critical region.

Glacial fluctuations during the Last Glacial Maximum and Lateglacial in the Zhuxi and Songlong valleys, eastern Nyainqêntanglha Range, southeastern Tibet

ABSTRACTThis study outlines the paleoglacial history and paleoclimatic conditions that were present during the Last Glacial Maximum (LGM) and Lateglacial (LG) in the Songlong and Zhuxi valleys in the eastern Nyainqêntanglha Range, southeastern Tibet. Two sets of moraines were identified at the valley mouths, and were dated using cosmogenic 10Be exposure and optically stimulated luminescence (OSL) dating. The ages suggest that two glaciations occurred at ~20–21 and ~14–16 ka, respectively, coinciding with the LGM and LG. Using glacier–climate modeling, temperature drops were calculated to have ranged from 6.3 to 7.8 °C during the LGM–LG, with precipitation being 40–60% of the present‐day value. The results in the modeled domain appear generally consistent with other climatic records from the Tibetan Plateau. Glacial advances in monsoon‐dominated southeastern Tibet during the LGM–LG were probably driven by low temperatures rather than by high precipitation, which was usually produced by an enhanced Indian Summer Monsoon during periods of climatic warming.

10Be age control of glaciation in the Beartooth Mountains, USA, from the latest Pleistocene through the Holocene

Abstract. Alpine glaciers in the western United States are often associated with late Holocene Little Ice Age (LIA) advances. Yet, recent studies have shown many of these glacial landforms are remnants of latest Pleistocene retreat with only the most cirque-proximal moraines preserving LIA activity. Additionally, the timing and magnitude of glacial advances during the Neoglacial–LIA interval remains uncertain, with presumed maximum extents occurring during the LIA driven by lower Northern Hemisphere insolation levels. Here we present 10Be surface exposure ages from a glacial valley in the Beartooth Mountains of Montana and Wyoming, United States. These new data constrain the presence of the glacier within 2–3 km of the cirque headwalls by the end of the Pleistocene with implications for large-scale retreat after the Last Glacial Maximum. Cirque moraines from two glaciers within the valley preserve a late Holocene readvance, with one reaching its maximum prior to 2.1±0.2 ka and the other 0.2±0.1 ka. Age variability among the moraines demonstrates that not all glaciers were at their largest during the LIA and presents the possibility of regional climate dynamics controlling glacial mass balance.

Modelled sensitivity of Monte San Lorenzo ice cap, Patagonian Andes, to past and present climate

Sparse measurements of glacier mass balance, velocity and ice thickness in Patagonia challenge our ability to understand glacier sensitivity to climate change and relate past glacier fluctuations to palaeoclimate change. Small ice caps, such as Monte San Lorenzo, have short response times and high climate sensitivity, making well-dated moraines in their glacier foregrounds an important tool for exploring glacier response to rapid changes in palaeoclimate. Here, the Parallel Ice Sheet Model (PISM) is used to model ice flow across a domain centred on the Monte San Lorenzo ice cap. Ice-flow parameters are calibrated to match present-day ice extent, velocity and thickness. Our aim is, firstly, to quantify present-day physical glacier properties, and ice cap dynamics and sensitivities, and secondarily, to evaluate the controls on the deglaciation of the ice cap within the context of the Southern Hemisphere palaeoclimate system during the Last Glacial-Interglacial Transition (LGIT). The simulated present-day ice cap shows high surface mass flux, with ablation at outlet glacier tongues up to 18 m w. e. a−1, accumulation at the highest elevations of up to 5.5 m w. e. a−1 and a simulated Equilibrium Line Altitude (ELA) of 1750–2000 m asl. The ice cap is more sensitive to changes in precipitation relative to changes in temperature. We provide envelopes with likely ranges of palaeotemperature and palaeoprecipitation for glacial advances to moraines formed during the Last Glacial-Interglacial Transition and Holocene. Our numerical model predicts that cooling and an increase in precipitation is required to force glacial advance to mapped moraine limits at 12.1 ka (2°C cooler, 50% more precipitation), 5.6 ka (0°C cooler, 50% more precipitation) and 0.2 ka (1°C cooler, 25% more precipitation). Our modelling results thus provide insights into the present-day mass balance, thermal regime and velocity of the ice cap, explores the sensitivities of this ice cap to various model and climatic parameters, and provide palaeoclimatic envelopes for readvances during the LGIT and Holocene in Patagonia.

Marine Oxygen Isotope Stage (MIS)‐6 Glacial Advances on the Tibetan Plateau More Extensive than during MIS‐2 due to More Abundant Precipitation

AbstractNumerous studies dated glacial deposits within the Himalayan‐Tibetan orogen. While most focus on young deposits, i.e., younger than the Last Glacial Maximum (LGM or Marine oxygen Isotope Stage (MIS)‐2, ∼20 ka), older moraines such as those from MIS‐6 (∼130–191 ka) are much harder to date and interpret due to the less well‐preserved nature of their surfaces and boulders, as well as their scattered and continuous age distribution due to long‐lived erosion since deposition. Here, we dated with 10Be, two imbricated moraines near Yadong in southern Tibet, as MIS‐2 and 6, showing that the most extensive, smooth surfaces were abandoned during MIS‐6. Compiling published data from 54 MIS‐6 moraines on the Tibetan Plateau reveals that they exist in most regions, dry or humid. They are particularly well‐preserved (sharp crests) in eastern and northern Tibet, while in southern and central Tibet, their crests are rounded to sub‐rounded. Because both MIS‐2 and 6 were equally cold, and because MIS‐6 moraines are much more extensive than those from the LGM, we conclude that MIS‐6 glacial advances were controlled by more abundant precipitation than during MIS‐2. This would be consistent with the peak in Asian monsoon during MIS‐6, revealed by sediments from the South China Sea.

Implications of glacial deposit ages for the timing and rate of active crustal faulting in the central Cascade arc, Oregon, USA

Abstract New cosmogenic 3He chronologies and geologic mapping of faulted glacial drift provide new constraints for the slip rates of active faulting in the central Cascade arc, Oregon, USA. The White Branch and Dilman Meadows fault zones cut deposits created by three distinct glacial advances, which provide timing, kinematics, and rate constraints for fault motion. New cosmogenic 3He data from landforms comprising the youngest and most widespread deposits have ages between 19.4 +10.1/–6.2 ka and 21.3 ± 4.9 ka; therefore, they were deposited during the last glacial maximum (LGM). A second, older outwash surface reveals an age of 74.2 ± 3.8 ka, which suggests glaciation possibly associated with marine isotope stage (MIS) 5b. Dip-slip displacement across fault scarps expressed by lidar data reveal similar magnitudes of extensional deformation for LGM and older glacial deposits on the White Branch fault zone, which implies a lack of earthquake ruptures between the oldest and LGM advances. In contrast, scarp profiles along the Dilman Meadows fault zone reveal progressive cumulative slip for surfaces of increasing age. Taken together, our measurements provide the first constraints on the rate of extensional faulting derived from Quaternary geochronology along the White Branch and Dilman Meadows faults, which total 0.1–0.4 mm/yr since ca. 75 ka and 0.6 ± 0.04 mm/yr since the LGM, respectively. The White Branch fault zone accommodates predominately fault-normal extension, whereas right-oblique slip characterizes the Dilman Meadows fault zone. Active deformation across the central Cascade Range thus reflects the combined effects of ongoing crustal block rotation and arc magmatism.

Seismic constraints for ice sheets along the northern margin of Beringia

Beringia today is a partly submerged Arctic region bordered by the Lena River in East Siberia and the Mackenzie River in North America. Whilst emergent at times of eustatic sea-level fall, the northern Beringian Margin was affected by the repeated growth and decay of regional ice sheets. The size and dynamism of these ice sheets are a subject of some debate that can be addressed using geophysical data, which reveal widespread evidence for glacial processes on the continental shelves. We use published and reprocessed 2D multichannel seismic reflection data from the northern margins of Beringia between 147° E to 149° W to investigate their glacially deposited sediments in detail. Deposition of up to 450 m of sediments caused the shelf break to migrate basinward by up to 13 km between 165° E and 161° W. On the Kucherov Terrace (175° E to 176° W) the data show evidence for erosion by grounded ice in water depths of 1200 m. Deposits in the Northwind Basin, between 165° W and 161° W, are separated by continuous reflections indicating at least 3–5 glacial advances. However, the continental slopes of the western East Siberian Sea and the Beaufort Sea lack the thick glacial deposits found in the intervening region. Overall, the volume of glacial deposited sediments along the margins of Beringia are significantly smaller than the reported amounts along the Norwegian and Greenland margins. Therefore, we suggest a less dynamic and fewer number of glaciations of Beringia compared to other glaciated margins during the Quaternary. • Evidence for multiple glacial advances along the northern rim of Beringia. • Erosion by ice sheets only to water depths of 1200 m. • Three main depocenters of glacial deposits along the Beringian margin.

Paleo-glacial reconstruction of the Thajwas glacier in the Kashmir Himalaya using 10Be cosmogenic radionuclide dating

Quantitative glacial chronologies of past glaciations are sparse in the Himalaya, and mostly absent in the Kashmir Himalaya. We used cosmogenic 10Be exposure dating, and geomorphological mapping to reconstruct glacial advances of the Thajwas Glacier (TG) in the Great Himalayan Range of the Kashmir Himalaya. From 10Be exposure dating of ten moraine boulders, four glacial stages with ages ∼20.77 ± 2.28 ka, ∼11.46 ± 1.69 ka, ∼9.12 ± 1.39 ka and ∼4.19 ± 0.78 ka, were identified. The reconstructed cosmogenic radionuclide ages confirmed the global Last Glacial Maximum (gLGM), Younger Dryas, Early Holocene, and Neoglaciation episodes. As per area and volume change analyses, the TG has lost 51.1 km2 of its area and a volume of 2.64 km3 during the last 20.77 ± 2.28 ka. Overall, the results suggested that the TG has lost 64% of area and 73% of volume from the Last glacial maximum to Neoglaciation and about 85.74% and 87.67% of area and volume, respectively, from Neoglaciation to the present day. The equilibrium line altitude of the TG fluctuated from 4238 m a.s.l present to 3365 m a.s.l during the gLGM (20.77 ± 2.28 ka). The significant cooling induced by a drop in mean ambient temperature resulted in a positive mass balance of the TG during the gLGM. Subsequently the melting accelerated due to the continuing rise of the global ambient temperature. Paleo-glacial history reconstruction of the Kashmir Himalaya, with its specific geomorphic and climatic setting, would help close the information gap about the chronology of past regional glacial episodes.

Cosmogenic nuclide dating of two stacked ice masses: Ong Valley, Antarctica

Abstract. We collected a debris-rich ice core from a buried ice mass in Ong Valley, located in the Transantarctic Mountains in Antarctica. We measured cosmogenic nuclide concentrations in quartz obtained from the ice core to determine the age of the buried ice mass and infer the processes responsible for the emplacement of the debris currently overlaying the ice. Such ice masses are valuable archives of paleoclimate proxies; however, the preservation of ice beyond 800 kyr is rare, and therefore much effort has been recently focused on finding ice that is older than 1 Myr. In Ong Valley, the large, buried ice mass has been previously dated at > 1.1 Ma. Here we provide a forward model that predicts the accumulation of the cosmic-ray-produced nuclides 10Be, 21Ne, and 26Al in quartz in the englacial and supraglacial debris and compare the model predictions to measured nuclide concentrations in order to further constrain the age. Large downcore variation in measured cosmogenic nuclide concentrations suggests that the englacial debris is sourced both from subglacially derived material and recycled paleo-surface debris that has experienced surface exposure prior to entrainment. We find that the upper section of the ice core is 2.95 + 0.18 / −0.22 Myr old. The average ice sublimation rate during this time period is 22.86 + 0.10 / −0.09 m Myr−1, and the surface erosion rate of the debris is 0.206 + 0.013 / −0.017 m Myr−1. Burial dating of the recycled paleo-surface debris suggests that the lower section of the ice core belongs to a separate, older ice mass which we estimate to be 4.3–5.1 Myr old. The ages of these two stacked, separate ice masses can be directly related to glacial advances of the Antarctic ice sheet and potentially coincide with two major global glaciations during the early and late Pliocene epoch when global temperatures and CO2 were higher than present. These ancient ice masses represent new opportunities for gathering ancient climate information.

Chronology of Glacial Advances and Deglaciation in the Encierro River Valley (29° Lat. S), Southern Atacama Desert, Based on Geomorphological Mapping and Cosmogenic 10Be Exposure Ages

The high mountain segments of the valleys of the southernmost Atacama Desert of Chile present Late Quaternary glacial landforms that developed in already incised valleys. Glacier advances and deglaciation have left a geomorphic imprint in the southernmost Atacama Desert. In this work, the glacial landforms of the Encierro River Valley (29.1°S–69.9°W) have been revisited and new detailed geomorphological mapping is provided. This work also includes new 10Be exposure ages from moraine boulders and one age from an ice-molded bedrock surface. The former glacier of the El Encierro valley extended 16 km down the valley during the last local glacial maximum recorded by a terminal moraine (ENC 1a) with an exposure age of ∼40 ka. Four inboard moraine arcs were deposited upstream in telescopic patterns (ENC 1b–d), whose exposure ages range between ∼25 and ∼33 ka (ENC 1d). Exposure ages between ∼17–24 ka on lateral moraines (ENC 1L) developed during the later ice recession of the ENC 1 drift. Thus, the ice mostly disappeared in the main valley before ∼18 ka, as is also supported by the exposure age obtained from an ice-molded bedrock surface. Seven kilometers up the valley from the ENC 1, the ENC 2a–d moraine arcs correspond to a small ice advance by ∼17–20 ka. The last glacial advance (ENC 2), which occurred after deglaciation of the last local glacial maximum (ENC 1), coincides with the start of the Heinrich Stadial Event 1 (HS1; 18–14.5 ka), which is thought to play a direct role in the last glacial termination in the Andes.

A model of ice-marginal sediment-landform development at Lake Tekapo, Southern Alps, New Zealand

ABSTRACT The extent of the Southern Alps icefield in New Zealand is well-constrained chronologically for the last glacial cycle. The sediment-landform imprint of this glacial system, however, offers insight into ice-marginal processes that chronological control cannot. We present the first detailed investigation of sediments along the southwestern shores of Lake Tekapo, South Island. We identify seven lithofacies, from which a five-stage palaeoglaciological reconstruction of depositional and glaciotectonic events is proposed: (i) ice-marginal advance and deposition of outwash gravels in lithofacies (LF) 1; (ii) ice-marginal recession and the development of an ice-contact lake, manifest in rhythmite deposition and iceberg rafting of dropstones (LF 2), followed by a depositional hiatus; (iii) ice-marginal recession recorded in ice-proximal aggradation of glaciofluvial hyperconcentrated flows (LFs 3, 4); (iv) ice-marginal advance documented by glaciotectonic disturbance and localized hydrofracturing, coeval with the deposition of delta foresets and a subglacial diamicton/till (LFs 5, 6); (v) final stages of ice-marginal recession and deposition of outwash gravels in LF 7. Two infrared stimulated luminescence ages were obtained from the glaciolacustrine sediments and, whilst the dating has some limitations, the sediments pre-date both the global and local Last Glacial Maximum. Overall, this sequence, consistent with sediment fills recorded elsewhere across South Island, suggests recurrence of processes from different glacial advances and the role of topographic constraints on maintaining lake positions.

The Last Glaciation in Valchiavenna (Italian Alps): maximum ice elevation data and recessional glacial deposits and landforms

This work presents the first extensive, 1:10,000-scale field survey data concerning glacial deposits and glacigenic landforms in the Valchiavenna territory, which has an area of 578 km2. Valchiavenna is an inner Alpine valley in Northern Italy between the Lepontine and Western Rhaetian Alps.A comprehensive 1:25,000 map of deposits and landforms from the last glaciation to the present is provided, describing i) glacial trimline evidence and associated features, such as moraine ridges, erratic boulders, ice- moulded bedrock surfaces and kame terraces; ii) glacial, ice-contact, lacustrine/peat and gravity-reworked till deposits; iii) other supraglacial, marginoglacial and subglacial landforms; and iv) erratics in glacial deposits. Establishing an absolute chronology of glacier dynamics was not the objective of this work. However, a relative chronology was inferred from sedimentological and geomorphological evidence: this allowed the description of the general behaviour of glaciers in the area during and after the Last Glacial Maximum (LGM).The palaeogeography at the LGM and the palaeo-ice-flow pattern were reconstructed on the basis of field data; this data confirmed that the valleys were almost completely filled by glacier ice, covering about 88% of the study area, with only the most elevated ridges and a few nunataks emerging above the ice surface, and allowed the identification of different source areas for the erratics found on opposite sides of the main valley.The observation of stratigraphical and geomorphological relationships between glacial deposits and landforms made it possible to propose a relative chronology of glacial advances and to outline the general glacial dynamics of the area. Both at the LGM and during the deglaciation after the LGM, the valley glacier inserted offshoots in tributary valleys, thus generally blocking the advance of local glaciers. With the gradual melting of the valley glacier during the deglaciation after the LGM, tributary glaciers could deposit tills on areas previously covered by valley glacier ice and at lower altitudes than the older lateral moraines. The main outcome of this work is a rich and homogeneous database of glacial deposits and glacigenic landforms that will be useful for further local and regional studies. It can guide the planning of geochronological dating and represents a fundamental step in the identification of glacial stadials and ice mass modelling. It can also support biogeography studies and the evaluation of the effects of climate change, slope dynamics modelling and hazard prediction.

New cosmogenic nuclide constraints on Late Glacial and Holocene glacier fluctuations in the sub-Antarctic Indian Ocean (Kerguelen Islands, 49°S)

Cosmogenic nuclide dating of glacial landforms on the Kerguelen Archipelago (49°S, 69°E) gives the opportunity to study multi-millennial glacier fluctuations within the sub-Antarctic sector of the Indian Ocean. We here dated such geomorphic features to provide time constraints over the last 17,000 years using in situ-produced 36Cl in three glacial valleys: Val Travers valley, Ampere Glacier valley and Arago Glacier valley. For the first time, a combination of in situ-produced 36Cl and 10Be dating and 26Al/10Be ratios analysis was performed in the quartz-bearing syenite boulders of the Arago Glacier site. In addition, a Bayesian approach was computed to obtain a better constraint on moraine dating. Glacial advances occurred during the Late Glacial at 16.0 ± 1.9 ka and at 12.9 ± 1.7 ka in Val Travers, and at 13.6 ± 1.8 ka in Arago Glacier valley, probably linked to the Heinrich Stadial 1 and/or Antarctic Cold Reversal events, respectively. This suggests that all glaciers at this latitude were broadly sensitive to the large-scale climatic signal of the Antarctic Cold Reversal. So far, no Early nor Mid-Holocene moraines have been found in the glacial valleys on Kerguelen, indicating that the glaciers had probably receded significantly during these periods. This is in agreement with previously determined 14C ages from peat bogs, which suggest extensive deglaciation during several millennia of the Holocene period. Samples from glacially-polished bedrock surfaces (ranging from ∼4.4 ka to ∼14 ka) at Ampere Glacier site also suggest that this valley was ice free for several millennia during the Holocene. Finally, glaciers seem to have re-advanced only during the Late Holocene, especially within the last millennium, at ∼1 ka, ∼ 430 yr and ∼300 yr. A comparison of this new dataset with the available 10Be ages from other southern mid-latitude regions during the Holocene allows the identification of three different glacier evolution patterns. We suspect that variations of Kerguelen glaciers, which are located in the Southern Indian Ocean, were controlled by the combined effects of sea surface temperature related to the variations of the Antarctic Polar Front and fluctuations of precipitation related to long-term variations of the Southern Annular Mode.

Glaciofluvial sequences recording the Birrfeld Glaciation (MIS 5d\u20132) in the Bern area, Swiss Plateau

In this paper, we document that glaciofluvial gravel sequences and glacial till deposits that are exposed in the Müntschemier and Finsterhennen gravel pits (Swiss Plateau west of Bern) record three glacial advances during the Birrfeld Glaciation, which corresponds to the last glacial cycle. Sedimentological logging shows that both gravel pits expose deposits of glaciofluvial braided river systems. These sediments are overlain by a till that was deposited during the Last Glacial Maximum (LGM). The results of the provenance analysis imply that the sediments were mainly supplied by the Valais Glacier, which originated in the Central Alps. A minor contribution of the material was supplied by the Saane Glacier with sources in the northern parts of the Alps. In addition, the morphometric analysis particularly of quartzite clasts in the till deposits indicate that while some clasts (the angular ones) were eroded and transported by the Valais Glacier from the Central Alps to the depositional site, the majority of the quartzite constituents (the rounded ones) were most likely reworked from the Molasse bedrock or older gravels. This implies that a large fraction of the sediments in the Müntschemier and Finsterhennen gravel pits could represent recycled material from older fluvial gravels and conglomerates that were then reworked by the glaciers as they advanced to the foreland. Based on the sedimentological data and considering published and new optically stimulated luminescence (OSL) chronological data, we propose a landscape evolution scenario where the first glacial advance occurred during Marine Isotope Stage (MIS) 5d. The second glacier advance followed during MIS 4, while the last one during the Last Glacial Maximum (LGM), which corresponds to the MIS 2. The MIS 5d advance is recorded by the lowest unit of the Müntschemier gravel pit and consists of a fining upward sequence made up of an alternation of gravel and sand beds. The MIS 4 advance is recorded by the unit beneath the LGM till at Müntschemier and by the lowermost layer in the Finsterhennen gravel pit. It comprises an alternation of gravel and sand beds, which coarsens and thickens upwards. The LGM advance, finally, resulted in the deposition of amalgamated gravel beds at Finsterhennen, which ended with the construction of a till that is encountered on the top of both gravel pits. Sediments related to the interstadial conditions between MIS 5a and MIS 5b and MIS 3 were not encountered, which suggests that the warmer periods were characterised by non-deposition and/or erosion, which possibly resulted in the observed sedimentary hiatus. Although the chronological results are still preliminary, the available information allows us to suggest that during the Birrfeld Glaciation, the Valais lobe advanced several times to the Swiss Plateau. In addition, the facies associations imply that the eastward expansion of the Valais lobe during the MIS 5d and MIS 4 were most likely shorter than during the LGM.

Global Last Glacial Maximum climate inferred from reconstructing the Eryehai Valley, Mount Taibai, Qinling Mountains, eastern China

Although numerous global Last Glacial Maximum (gLGM) dating-based paleoclimatic and paleoglacial reconstructions exist for the Tibetan Plateau, no such study is available for the mountains to the Tibetan Plateaus east. Mount Taibai lies east of the Tibetan Plateau, and is known to have experienced glaciation during the Quaternary. In this study, optically stimulated luminescence (OSL) dating was employed to determine the ages of two lateral moraines in the Eryehai Valley on Mount Taibai. The ages obtained were 22.1 ± 1.7–18.7 ± 1.1 ka and 25.8 ± 1.8–24.3 ± 1.5 ka, constrain the timing of the gLGM glaciation in the study area. Using GlaRe and equilibrium-line altitude (ELA) calculations, these two toolboxes, based on a Geographic Information System (GIS), were used to reconstructed the extent of the study areas paleoglacial surface and the ∆ELA. The glacial coverage and ELA for the gLGM in the Eryehai Valley on Mount Taibai were 0.17 km3 and 3351.5 ± 5 m above sea level (asl), respectively. This gLGM ELA is lower than the modern theoretical ELA (4816.5 m asl) by 1465 ± 5 m. From the sporopollen records of the Zoigê Basin in the northwestern Mount Taibai, the precipitation during the gLGM period was equivalent to 60–80% of the present, combined with this record, ∆ELA-based models of the precipitation–temperature relationship (P-T) and the temperature lapse rate (LR) model at the ELA indicate that this area was 7.0 –9.4 °C colder during the gLGM. Combined with other paleoclimatic proxies, a decrease in temperature emerges as the primary driver of glaciation during the gLGM on Mount Taibai. Paleoclimatic reconstructions of paleoglaciers on the Tibetan Plateau and its adjacent mountains also indicate that a drop in temperatures was the principal driver of glacial advances in these regions during the gLGM. Regions affected by the East Asian Monsoon, the Indian Monsoon and the Westerlies would have experienced a greater cooling during the gLGM, while regions blocked by high mountains, and therefore less affected by monsoons and westerly winds, would have seen less cooling.