Late Quaternary glacial and climate history of the Pamir Mountains derived from cosmogenic Be exposure ages

Moraines southwest of Lake Yashilkul, Pamir, Tajikistan, were dated using ¹⁰Be exposure ages of boulder surfaces. We found evidence for (1) an extensive glaciation ∼60,000 yr ago; (2) a less extensive glacial advance, which deposited a characteristic hummocky moraine lobe with exposure ages ranging from ∼11,000 to 47,000 yr, probably deposited at or before 47,000 yr ago; and (3) lateral moraines with exposure ages of ∼40,000 yr, 27,000 yr and 19,000 yr, respectively. Increasing aridity in the Pamir is most likely responsible for the progressively limited extent of the glaciers during the Late Pleistocene.     

Exposure ages from relict lateral moraines overridden by the Fennoscandian ice sheet

Lateral moraines constructed along west to east sloping outlet glaciers from mountain centred, pre-last glacial maximum (LGM) ice fields of limited extent remain largely preserved in the northern Swedish landscape despite overriding by continental ice sheets, most recently during the last glacial. From field evidence, including geomorphological relationships and a detailed weathering profile including a buried soil, we have identified seven such lateral moraines that were overridden by the expansion and growth of the Fennoscandian ice sheet. Cosmogenic ¹⁰Be and ²⁶Al exposure ages of 19 boulders from the crests of these moraines, combined with the field evidence, are correlated to episodes of moraine stabilisation, Pleistocene surface weathering, and glacial overriding. The last deglaciation event dominates the exposure ages, with ¹⁰Be and ²⁶Al data derived from 15 moraine boulders indicating regional deglaciation 9600 ± 200 yr ago. This is the most robust numerical age for the final deglaciation of the Fennoscandian ice sheet. The older apparent exposure ages of the remaining boulders (14,600-26,400 yr) can be explained by cosmogenic nuclide inheritance from previous exposure of the moraine crests during the last glacial cycle. Their potential exposure history, based on local glacial chronologies, indicates that the current moraine morphologies formed at the latest during marine oxygen isotope stage 5. Although numerous deglaciation ages were obtained, this study demonstrates that numerical ages need to be treated with caution and assessed in light of the geomorphological evidence indicating moraines are not necessarily formed by the event that dominates the cosmogenic nuclide data.     

Surface exposure dating of the Great Aletsch Glacier Egesen moraine system,western Swiss Alps,using the cosmogenic nuclide 10Be

Egesen moraines throughout the Alps mark a glacial advance that has been correlated with the Younger Dryas cold period. Using the surface exposure dating method, in particular the measurement of the cosmogenic nuclide ¹⁰Be in rock surfaces, we attained four ages for boulders on a prominent Egesen moraine of Great Aletsch Glacier, in the western Swiss Alps. The ¹⁰Be dates range from 10 460±1100 to 9040±1020 yr ago. Three ¹⁰Be dates between 9630±810 and 9040±1020 yr ago are based upon samples from the surfaces of granite boulders. Two ¹⁰Be dates, 10 460±1100 and 9910±970 yr ago, are based upon a sample from a quartz vein at the surface of a schist boulder. In consideration of the numerous factors that can influence apparently young ¹⁰Be dates and the scatter within the data, we interpret the weighted mean of four boulder ages, 9640±430 yr (including the weighted mean of two ¹⁰Be dates of the quartz vein), as a minimum age of deposition of the moraine. All ¹⁰Be dates from the Great Aletsch Glacier Egesen moraine are consistent with radiocarbon dates of nearby bog‐bottom organic sediments, which provide minimum ages of deglaciation from the moraine. The ¹⁰Be dates from boulders on the Great Aletsch Glacier Egesen moraine also are similar to ¹⁰Be dates from Egesen moraines of Vadret Lagrev Glacier on Julier Pass, in the eastern Swiss Alps. Both the morphology of the Great Aletsch Glacier Egesen moraine and the comparison with ¹⁰Be dates from the inner Vadret Lagrev Egesen moraine support the hypothesis that the climatic cooling that occurred during the Younger Dryas cold episode influenced the glacial advance that deposited the Great Aletsch Glacier Egesen moraine. Because of the large size and slow response time of Great Aletsch Glacier, we suggest that the Great Aletsch Glacier Egesen moraine was formed during the last glacial advance of the multiphased Egesen cold period, the Kromer stage, during the Preboreal chron. Copyright © 2004 John Wiley & Sons, Ltd.     

Palaeoglaciology of Bayan Har Shan,NE Tibetan Plateau: exposure ages reveal a missing LGM expansion

The Bayan Har Shan, a prominent upland area in the northeastern sector of the Tibetan Plateau, hosts an extensive glacial geological record. To reconstruct its palaeoglaciology we have determined ¹⁰Be exposure ages based on 67 samples from boulders, surface pebbles, and sediment sections in conjunction with studies of the glacial geology (remote sensing and field studies) and numerical glacier modelling. Exposure ages from moraines and glacial sediments in Bayan Har Shan range from 3 ka to 129 ka, with a large disparity in exposure ages for individual sites and within the recognised four morphostratigraphical groups. The exposure age disparity cannot be explained by differences in inheritance without using unrealistic assumptions but it can be explained by differences in post-depositional shielding which produces exposure ages younger than the deglaciation age. We present a palaeoglaciological time-slice reconstruction in which the most restricted glaciation, with glaciers less than 10 km long, occurred before 40–65 ka. More extensive glaciations occurred before 60–100 ka and 95–165 ka. Maximum glaciation is poorly constrained but probably even older. The Bayan Har Shan exposure age dataset indicates that glaciers on the northeastern Tibetan Plateau have remained surprisingly restricted for at least 40 ka, including the global last glacial maximum (LGM). This case of a missing LGM is further supported by high-resolution glacier modelling experiments.     

Holocene evolution of the Triftje- and the Oberseegletscher (Swiss Alps) constrained with <Superscript>10</Superscript>Be exposure and radiocarbon dating

To develop a more precise understanding of Alpine glacier fluctuations during the Holocene, the glacier forefields of the Triftjegletscher and the Oberseegletscher east of Zermatt in the Valais Alps, Switzerland, were investigated. A multidisciplinary approach of detailed geological and geomorphological field mapping combined with ¹⁰Be exposure and radiocarbon dating was applied. A total of twelve samples of boulders and bedrock were taken from both Little Ice Age (LIA) landforms, as documented by the Dufour map published in 1862, and from landforms outside of the LIA. The resulting ¹⁰Be ages range between 12590 ± 350 a and 420 ± 170 a. A piece of wood found embedded in the Little Ice Age moraine gave radiocarbon ages that range between 293 cal years BP up to modern (356–63 cal years before 2013). Based on these results, four tentative steps of the Holocene evolution could be distinguished. An early Holocene stage, which documents the decay of the Egesen stadial glaciers when the first parts of the study area became ice free. This was followed by a phase with no evidence of glacier advance. Then in the late Holocene, the glaciers advanced (at least) twice. An advance around 1200 a, as shown by several moraine ages, coincides with the Göschenen II cold phase. A more extensive readvance occurred during the LIA as shown on the historical maps and underpinned by one ¹⁰Be exposure age and the radiocarbon age. This later advance destroyed or overprinted the earlier landforms in most parts of the area.     

Cosmogenic nuclide chronology of pre-last glacial maximum moraines at Lago Buenos Aires, 46°S, Argentina

At Lago Buenos Aires, Argentina, ¹⁰Be, ²⁶Al, and ⁴⁰Ar/³⁹Ar ages range from 190,000 to 109,000 yr for two moraines deposited prior to the last glaciation, 23,000–16,000 yr ago. Two approaches, maximum boulder ages assuming no erosion, and the average age of all boulders and an erosion rate of 1.4 mm/10³ yr, both yield a common estimate age of 150,000–140,000 yr for the two moraines. The erosion rate estimate derives from ¹⁰Be and ²⁶Al concentrations in old erratics, deposited on moraines that are >760,000 yr old on the basis of interbedded ⁴⁰Ar/³⁹Ar dated lavas. The new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid-latitude Andes. The next five youngest moraines correspond to stage 2. There is no preserved record of a glacial advance during stage 4. The distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760,000 and >200,000 yr ago. The mid-latitude Patagonian glacial record, which is well preserved because of low erosion rates, indicates that during the last two glacial cycles major glaciations in the southern Andes have been in phase with growth and decay of Northern Hemisphere ice sheets, especially at the 100,000 yr periodicity. Thus, glacial maxima are global in nature and are ultimately paced by small changes in Northern Hemisphere insolation.     

Uplift rate and landscape development in southwest Fiordland, New Zealand, determined using Be and Al exposure dating of marine terraces

We demonstrate that cosmogenic nuclide surface exposure dating can be used to provide the first well-constrained age for a Fiordland bedrock surface that was created by coastal erosion and has since been uplifted. Tight clustering of ¹⁰Be and ²⁶Al apparent exposure ages between 102-119 kyr on a terrace with strandline at 65 ± 8 m gives a last interglacial age of terrace formation of 130-120 ka, and an uplift rate of 0.52 ± 0.08 mm/yr. Apparent exposure ages from a higher (92-130 m), more incised region of remnant coastal morphology fall in the range 53-111 kyr. The anomalously low ages and large variance demonstrate that weathering and fluvial or rockfall erosion rates are too extreme at the higher sites to determine an age of coastal erosion. Sea level samples have apparent exposure ages in the range 2-11 kyr, with an uncertainty of about 3 kyr. This is consistent with surface exposure during the present sea level high-stand, indicates minimal inheritance of ancient cosmogenic nuclides, and is in accord with geomorphic arguments. Mean ²⁶Al/¹⁰Be ratios of 6.6 for each sample set is consistent with the actively exhuming late Quaternary tectonic setting. Large boulders and gently convex rocky outcrops formed during coastal erosion preserve surfaces that are least modified during later uplift, and are hence the best sites for determining the age of coastal erosion.     

Cosmogenic Be dating of the Salpausselkä I Moraine in southwestern Finland

We determined in situ cosmogenic ¹⁰Be ages for nine boulders sampled on the Salpausselkä I (Ss I) Moraine. Previous dating of this moraine indicated that it formed during the Younger Dryas Stadial along the southern margin of the Scandinavian Ice Sheet in southern Finland. Our new exposure ages range from 10.9±1.0 to 13.5±1.2 ¹⁰Be ka, with an error-weighted mean age of 12.4±0.7 ¹⁰Be ka. Our results confirm four previous ¹⁰Be ages obtained 40 km northeast of our sample location. The combined data (n=13) indicate that retreat from the Ss I Moraine occurred at 12.5±0.7 ¹⁰Be ka, in excellent agreement with an age of 12.1 ka for retreat from the Ss I Moraine based on varve chronologies. These results identify the Ss I Moraine as among the best-dated margins associated with Late Quaternary ice sheets.     

Post‐Last Glacial Maximum glacier fluctuations in the southern Écrins massif (westernmost Alps): insights from 10Be cosmic ray exposure dating

Only a few chronological constraints on Lateglacial and Early Holocene glacier variability in the westernmost Alps have hitherto been obtained. In this paper, moraines of two palaeoglaciers in the southern Écrins massif were mapped. The chronology of the stabilization of selected moraines was established through the use of ¹⁰Be cosmic ray exposure (CRE) dating. The equilibrium line altitude (ELA) during moraine deposition was reconstructed assuming an accumulation area ratio (AAR) of 0.67. Ten pre‐Little Ice Age (LIA) ice‐marginal positions of the Rougnoux palaeoglacier were identified and seven of these have been dated. The ¹⁰Be CRE age of a boulder on the lowermost sampled moraine indicates that the landform may have been first formed during a period of stable glaciers at around 16.2±1.7 ka (kiloyears before AD 2017) or that the sampled boulder experienced pre‐exposure to secondary cosmic radiation. The moraine was re‐occupied or, alternatively, shaped somewhat before 12.2±0.6 ka when the ELA was lowered by 230 m relative to the LIA ELA. At least six periods of stable ice margins occurred thereafter when the ELA was 220–160 m lower than during the LIA. The innermost dated moraine stabilized at or before 10.9±0.7 ka. Three ¹⁰Be CRE ages from a moraine of the Prelles palaeoglacier indicate a period of stationary ice margins at or before 10.9±0.6 ka when the ELA was lowered by 160 m with respect to the end of the LIA. The presented ¹⁰Be CRE ages are in good agreement with those of moraines that have been attributed to the Egesen stadial. Assuming unchanged precipitation, summer temperature in the southern Écrins massif at ~12 ka must have been at least 2 °C lower relative to the LIA.     

Late Glacial ice advances in southeast Tibet

The sensitivity of Tibetan glacial systems to North Atlantic climate forcing is a major issue in palaeoclimatology. In this study, we present surface exposure ages of erratic boulders from a valley system in the Hengduan Mountains, southeastern Tibet, showing evidence of an ice advance during Heinrich event 1. Cosmogenic nuclide analyses (¹⁰Be and ²¹Ne) revealed consistent exposure ages, indicating no major periods of burial or pre-exposure. Erosion-corrected (3 mm/ka) ¹⁰Be exposure ages range from 13.4 to 16.3 ka. This is in agreement with recalculated exposure ages from the same valley system by [Tschudi, S., Schäfer, J.M., Zhao, Z., Wu, X., Ivy-Ochs, S., Kubik, P.W., Schlüchter, C., 2003. Glacial advances in Tibet during the Younger Dryas? Evidence from cosmogenic ¹⁰Be, ²⁶Al, and ²¹Ne. Journal of Asian Earth Sciences 22, 301–306.]. Thus this indicates that local glaciers advanced in the investigated area as a response to Heinrich event 1 cooling and that periglacial surface adjustments during the Younger Dryas overprinted the glacial morphology, leading to deceptively young exposure ages of certain erratic boulders.     

Last glacial maximum climate inferences from cosmogenic dating and glacier modeling of the western Uinta ice field, Uinta Mountains, Utah

During the last glacial maximum (LGM), the western Uinta Mountains of northeastern Utah were occupied by the Western Uinta Ice Field. Cosmogenic ¹⁰Be surface-exposure ages from the terminal moraine in the North Fork Provo Valley and paired ²⁶Al and ¹⁰Be ages from striated bedrock at Bald Mountain Pass set limits on the timing of the local LGM. Moraine boulder ages suggest that ice reached its maximum extent by 17.4 ± 0.5 ka (± 2σ). ¹⁰Be and ²⁶Al measurements on striated bedrock from Bald Mountain Pass, situated near the former center of the ice field, yield a mean ²⁶Al/¹⁰Be ratio of 5.7 ± 0.8 and a mean exposure age of 14.0 ± 0.5 ka, which places a minimum-limiting age on when the ice field melted completely. We also applied a mass/energy-balance and ice-flow model to investigate the LGM climate of the western Uinta Mountains. Results suggest that temperatures were likely 5 to 7°C cooler than present and precipitation was 2 to 3.5 times greater than modern, and the western-most glaciers in the range generally received more precipitation when expanding to their maximum extent than glaciers farther east. This scenario is consistent with the hypothesis that precipitation in the western Uintas was enhanced by pluvial Lake Bonneville during the last glaciation.     

Cosmogenic radionuclide dating indicates ice‐sheet configuration during MIS 2 on Nordaustlandet,Svalbard

Hormes, A., Akçar, N. & Kubik, P. W. 2011: Cosmogenic radionuclide dating indicates ice‐sheet configuration during MIS 2 on Nordaustlandet, Svalbard. Boreas, 10.1111/j.1502‐3885.2011.00215.x. ISSN 0300‐9483.0300‐9843 Glacial geological field surveys, aerial image interpretation and cosmogenic radionuclide (CRN) dating allowed us to reconstruct the ice‐sheet configuration on Nordaustlandet, the northernmost island of the European sector on the margin of the Arctic Ocean. The timing of deglaciation was investigated by determining the ²⁶Al and ¹⁰Be ages of glacially scoured bedrock, weathered periglacial blockfields and glacial erratic boulders. Only ¹⁰Be ages were useful for our interpretations, because of unresolved analytical problems with ²⁶Al. Fjords and lowlands on Nordaustlandet yielded Late Weichselian ¹⁰Be ages, indicating that actively erosive ice streams scoured the coastal fjord bathymetry during marine isotope stage (MIS) 2. In Murchisonfjorden, ground‐truthed air‐photograph interpretation and ¹⁰Be ages of boulders indicated a cold‐based glacier ice cover during MIS 2 on higher plateaus. ¹⁰Be ages and lithological studies of erratic boulders on higher and interior plateaus of Prins Oscars Land (>200–230 m a.s.l.) suggest that the Mid‐Weichselian glaciation (MIS 4) might have been more extensive than that during MIS 2.     

A glacial chronology for the Fish Creek drainage of Boulder Mountain, Utah, USA

Boulder Mountain, located in South Central Utah, is one of several mountain ranges on the Colorado Plateau that was glaciated during the late Pleistocene. Using ³He exposure-age dating (corrected for non-cosmogenic ³He with shielded samples), we determined ³He exposure-ages for boulders from the most well-preserved moraines in the Fish Creek drainage of Boulder Mountain. ³He exposure-ages indicate a last glacial maximum (LGM) advance ∼23,100 ± 1300 to 20,000 ± 1400 yr ago and a later and smaller advance ∼16,800 ± 500 to 15,200 ± 500 yr ago. This chronology is very similar to other cosmogenic glacial chronologies from the Western U.S. and suggests that the timing of glacial advance and retreat on the Colorado Plateau was generally in phase with the rest of the Western U.S. during the late Pleistocene.     

Chronology of glaciation and deglaciation during the Loch Lomond (Younger Dryas) Stade in the Scottish Highlands: implications of recalibrated 10Be exposure ages

Considerable uncertainty surrounds the timing of glacier advance and retreat during the Younger Dryas or Loch Lomond Stade (LLS) in the Scottish Highlands. Some studies favour ice advance until near the end of the stade (c. 11.7 ka), whereas others support the culmination of glacier advance in mid‐stade (c. 12.6–12.4 ka). Most published ¹⁰ Be exposure ages reported for boulders on moraines or deglacial sites post‐date the end of the LLS, and thus appear to favour the former view, but recalibration of 33 ¹⁰ Be ages using a locally derived ¹⁰ Be production rate and assuming rock surface erosion rates of zero to 1 mm ka^?1 produces exposure ages 130–980 years older than those originally reported. The recalibrated ages are filtered to exclude anomalous data, and then employed to generate aggregate probability density distributions for the timing of moraine deposition and deglaciation. The results suggest that the most probable age for the timing of the deposition of the sampled outermost moraines lies in the interval 12.4–12.1 ka or earlier. Deglacial ages obtained for sites inside Loch Lomond Stadial glacier limits imply that glaciers at some or all of the sampled sites were retreating prior to 12.1 ka. Use of aggregated data does not exclude the possibility of asynchronous glacier behaviour at different sites, but confirms that some glaciers reached their maximum limits and began to retreat several centuries before the rapid warming that terminated the LLS at 11.7–11.6 ka, consistent with the retrodictions of recent numerical modelling experiments and with geomorphological evidence for gradual oscillatory ice‐margin retreat under stadial conditions.     

Late Quaternary glaciation of the Tianshan, Central Asia, using cosmogenic Be surface exposure dating

Glacial deposits are present at the head of the Ürümqi River valley, Tianshan, Central Asia. ¹⁰Be surface exposure ages of 15 boulders from three sites along a 12 km valley transect range from 9 to 21 ka suggesting emplacement by glacial retreat and advance commencing at the global last glacial maximum (LGM) and most likely abating in the early Holocene. Although the age spread for a given locality is not small, perhaps indicating post-depositional reworking, maximum ages per site are either coeval with or are post-LGM and inconsistent with previous pre-LGM electron spin resonance ages.     

Late Pleistocene Glaciations in the Northwestern Sierra Nevada, California

Pleistocene fluvial landforms and riparian ecosystems in central California responded to climate changes in the Sierra Nevada, yet the glacial history of the western Sierra remains largely unknown. Three glacial stages in the northwestern Sierra Nevada are documented by field mapping and cosmogenic radionuclide surface-exposure (CRSE) ages. Two CRSE ages of erratic boulders on an isolated till above Bear Valley provide a limiting minimum age of 76,400±3800 ¹⁰Be yr. Another boulder age provides a limiting minimum age of 48,800±3200 ¹⁰Be yr for a broad-crested moraine ridge within Bear Valley. Three CRSE ages producing an average age of 18,600±1180 yr were drawn from two boulders near a sharp-crested bouldery lateral moraine that represents an extensive Tioga glaciation in Bear Valley. Nine CRSE ages from striated bedrock along a steep valley transect average 14,100±1500 yr and suggest rapid late-glacial ice retreat from lower Fordyce Canyon with no subsequent extensive glaciations. These ages are generally consistent with glacial and pluvial records in east-central California and Nevada.     

Cosmogenic Be inferred lake-level changes in Sumxi Co basin, Western Tibet

Most Tibetan lakes are surrounded by conspicuous regressive shorelines attesting to high-water levels in the past. Concentrations of the in situ produced cosmogenic radionuclide ¹⁰Be in bedrock from the three highest terraces surrounding Sumxi Co, situated in Western Kunlun, indicate that the highest lake-level appeared before 10,000–11,500 yr, and most likely between 11,000 and 12,800 yr. Younger ages for the two lower terraces imply regression of Sumxi Co during the early-mid Holocene. The concurrency of the highest lake-level with orbitally induced maximum northern hemisphere summer insolation suggests that the increase in water supply to Sumxi Co was most likely associated with increased recharge from melting glaciers. We conclude that the enhanced Indian monsoon during the early Holocene did not penetrate the Tibetan plateau and affect the northwestern part of Tibet significantly.     

Latest Pleistocene and Holocene glacier variations in the European Alps

In the Alps, climatic conditions reflected in glacier and rock glacier activity in the earliest Holocene show a strong affinity to conditions in the latest Pleistocene (Younger Dryas). Glacier advances in the Alps related to Younger Dryas cooling led to the deposition of Egesen stadial moraines. Egesen stadial moraines can be divided into three or in some cases even more phases (sub-stadials). Moraines of the earliest and most extended advance, the Egesen maximum, stabilized at 12.2 ± 1.0 ka based on ¹⁰Be exposure dating at the Schönferwall (Tyrol, Austria) and the Julier Pass-outer moraine (Switzerland). Final stabilization of moraines at the end of the Egesen stadial was at 11.3 ± 0.9 ka as shown by ¹⁰Be data from four sites across the Alps. From west to east the sites are Piano del Praiet (northwestern Italy), Grosser Aletschgletscher (central Switzerland), Julier Pass-inner moraine (eastern Switzerland), and Val Viola (northeastern Italy). There is excellent agreement of the ¹⁰Be ages from the four sites. In the earliest Holocene, glaciers in the northernmost mountain ranges advanced at around 10.8 ± 1.1 ka as shown by ¹⁰Be data from the Kartell site (northern Tyrol, Austria). In more sheltered, drier regions rock glacier activity dominated as shown, for example, at Julier Pass and Larstig valley (Tyrol, Austria). New ¹⁰Be dates presented here for two rock glaciers in Larstig valley indicate final stabilization no later than 10.5 ± 0.8 ka. Based on this data, we conclude the earliest Holocene (between 11.6 and about 10.5 ka) was still strongly affected by the cold climatic conditions of the Younger Dryas and the Preboreal oscillation, with the intervening warming phase having had the effect of rapid downwasting of Egesen glaciers. At or slightly before 10.5 ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate. Between about 10.5 ka and 3.3 ka conditions in the Alps were not conducive to significant glacier expansion except possibly during rare brief intervals. Past tree-line data from Kaunertal (Tyrol, Austria) in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the Swiss and Austrian Alps points to long periods during the Holocene when glaciers were smaller than they were during the late 20th century. Equilibrium line altitudes (ELA) were about 200 m higher than they are today and about 300 m higher in comparison to Little Ice Age (LIA) ELAs. The Larstig rock glacier site we dated with ¹⁰Be is the type area for a postulated mid-Holocene cold period called the Larstig oscillation (presumed age about 7.0 ka). Our data point to final stabilization of those rock glaciers in the earliest Holocene and not in the middle Holocene. The combined data indicate there was no time window in the middle Holocene long enough for rock glaciers of the size and at the elevation of the Larstig site to have formed. During the short infrequent cold oscillations between 10.5 and 3.3 ka small glaciers (less than several km²) may have advanced to close to their LIA dimensions. Overall, the cold periods were just too short for large glaciers to advance. After 3.3 ka, climate conditions became generally colder and warm periods were brief and less frequent. Large glaciers (for example Grosser Aletschgletscher) advanced markedly at 3.0–2.6 ka, around 600 AD and during the LIA. Glaciers in the Alps attained their LIA maximum extents in the 14th, 17th, and 19th centuries, with most reaching their greatest LIA extent in the final 1850/1860 AD advance.     

Lateglacial and early Holocene surface exposure ages of glacial boulders in the Taiwanese high mountain range

Glacial landforms and sediments mapped in three presently unglaciated mountain massifs, the Nanhuta Shan, the Hsueh Shan and the Yushan, support the concept of repeated, multi-stage glaciations in the Taiwanese high mountain range during the late Pleistocene. New results from surface exposure dating using in situ produced cosmogenic ¹⁰Be measured in samples taken from erratic and moraine boulders in Nanhuta Shan at altitudes between 3100 and 3500 m are presented here. The results confirm independent and previously reported Optically Stimulated Luminescence (OSL) ages and ¹⁰Be exposure ages from glacial deposits in the same area and suggest a Lateglacial and early Holocene glaciation, the so called Nanhuta glacier advance with two substages at about 12–15 ka and 9.5 ka BP. The respective equilibrium line altitudes (ELA) were calculated at 3340 m and 3440 m with corresponding ELA depressions of 610 ± 100 m and 510 ± 100 m relative to the present day (theoretical) ELA, which is estimated to be at about 3950 ± 100 m in Taiwan. Large-scale erosional landforms indicate a much wider glacier extent during an earlier stage, which is not dated in Nanhuta Shan so far. Luminescence dating from near Hsueh Shan suggests an age of marine isotope stage (MIS) 4 for this stage.     

Surface exposure dating reveals MIS-3 glacial maximum in the Khangai Mountains of Mongolia

This study presents results from geomorphological mapping and cosmogenic radionuclide dating (¹⁰Be) of moraine sequences at Otgon Tenger (3905 m), the highest peak in the Khangai Mountains (central Mongolia). Our findings indicate that glaciers reached their last maximum extent between 40 and 35 ka during Marine Oxygen Isotope Stage (MIS) 3. Large ice advances also occurred during MIS-2 (at ~ 23 and 17–16 ka), but these advances did not exceed the limits reached during MIS-3. The results indicate that climatic conditions during MIS-3, characterized by a cool-wet climate with a greater-than-today input from winter precipitation, generated the most favorable setting for glaciation in the study region. Yet, glacial accumulation also responded positively to the far colder and drier conditions of MIS-2, and again during the last glacial–interglacial transition when precipitation levels increased. Viewed in context of other Pleistocene glacial records from High Asia, the pattern of glaciation in central Mongolia shares some features with records from southern Central Asia and NE-Tibet (i.e. ice maxima during interstadial wet phases), while other features of the Mongolian record (i.e. major ice expansion during the MIS-2 insolation minimum) are more in tune with glacier responses known from Siberia and western Central Asia.