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The final deglaciation stages of the Laurentide Ice Sheet in northern Quebec–Labrador were marked by the incursion of the d'Iberville Sea into the coastal areas of Ungava Bay. Remote and field mapping of raised marine strandlines along the Ungava Peninsula east coast show that the maximum marine limit decreases from south (165 m) to north (100 m), reflecting differential uplift linked to an ice mass remnant located to the southwest of the bay. Reconstruction of the uppermost marine limit in two east–west transects extending into the Peninsula interior reveals distinct sea‐level stands with limited extents towards the west, indicating that the early stages of the marine incursion occurred in contact with the ice margin. The reconstruction also identifies the maximum eastward extent of ice‐dammed lakes that occupied the Arnaud River and Aux‐Feuilles River valleys. 10Be surface exposure dating of marine strandlines yielded consistent 10Be ages that indicate a rapid deglaciation of Ungava Bay between 8900 ± 200 a (north) and 7900 ± 200 a (south). These results provide constraints on the position of the Labrador Sector eastern and western ice margins during the late deglaciation, in addition to the timing of ice and meltwater discharges from the Ungava Bay region. [ABSTRACT FROM AUTHOR]

Geomorphological records of past ice sheet change offer the opportunity to examine their centennial‐scale response to changing boundary conditions, which are not adequately captured in the satellite record. Here, we present the first reconstruction of ice surface lowering at Byrd Glacier, the largest outlet glacier of the Transantarctic Mountains. Using surface exposure ages from glacial erratic cobbles collected in two vertical transects along the Lonewolf Nunataks, we find the initial emergence of this set of nunataks occurred at ~15 ka, with a rapid pulse of thinning at ~8 ka. We compare our glacier thinning profiles with modelled ice sheet thickness and grounding line histories from two model ensembles to identify key processes responsible for ice sheet change. All model runs from the two ensembles predict grounding line retreat and inland thinning to occur in one rapid step from Last Glacial Maximum to present, in line with marine geology records, our exposure age data and derived glacier thinning rates. Experiments best matching the glacial thickness constraints, reconstructed from the surface exposure data, have faster basal sliding (i.e., promote greater sliding rates resulting in thinner ice). However, experiments best matching the timing and rapid rate of ice thinning derived from the same surface exposure data have higher basal friction. This apparent change in the modelled basal sliding regime, from when the ice surface is at maximum thickness, to the rapid thinning at ~8 ka, occurs as the grounding line retreats towards the Byrd Glacier and Ross Ice Shelf forms during the Holocene. This past context has implications for the stability of the modern grounding line of Byrd Glacier, which is characterised by high basal melt rates at the terminus—a process that has the potential to propagate glacier thinning far inland, impacting the overall (in)stability of the Byrd Glacier and Ross Ice Shelf. [ABSTRACT FROM AUTHOR]

The mountains systems of Central Asia are primary targets to study late Pleistocene climate evolution given their location at the crossroads of several atmospheric circulation systems. The timing of glacier extent during this period remains understudied, especially in the Altai Mountains. Here, we have reconstructed glacier extent during three main Late Pleistocene stadials in the upper Kalguty basin (south‐eastern Russian Altai) based on field‐based geomorphic analysis. Additionally, surface exposure dating with 10Be and 26Al at a key site was used to infer a minimum‐limiting age for the outermost well‐preserved Pleistocene frontal moraine system and to date the inception of glacier withdrawal. According to our data, around 20.6 ± 1.8 ka Kalguty Glacier was still 200 m thick at the key site, 10 km upstream of the outermost moraine, and the site was totally deglaciated shortly after 20.4 ± 0.4 ka. These results point to a rapid retreat of this low‐gradient valley glacier after its probably MIS 2 maximum which was prior to 21 ka and probably prior to 22.5 ka. Two other glacier stages have been identified upvalley, characterized by a depression of the equilibrium‐line altitude of 420 and 314 m with respect to the Little Ice Age, thus corresponding to Lateglacial advances. Our glacier reconstruction further provides a geomorphological and geochronological background to put into context archaeological findings in this area. [ABSTRACT FROM AUTHOR]

Landslide deposits preserved in the geological record afford opportunities to better inform hillslope and seismic hazard and risk models, particularly in regions where observational records are short. In the Southern Alps of New Zealand, small coseismic landslides are frequent, but the geological record preserves several instances of more substantial (> 1 km3) but infrequent mass failures. With an estimated volume of 27 km3, the giant Green Lake Landslide represents one of the largest subaerial landslides on Earth. Previous work has suggested this deep-seated mass movement was most likely triggered by high-intensity seismic shaking, but that local structural weakness and/or glacial debuttressing may help to explain the anomalously large failure volume. Resolving the potential contribution of the latter is important given predictions concerning alpine deglaciation in the coming decades to centuries. Key to resolution are secure chronologies of landslide emplacement and past glacier change. Here we present in situ cosmogenic 10Be exposure ages from the Green Lake Landslide that suggest an emplacement age of 15.5 ± 0.7 ka. Recent work shows that glacial retreat in the region was underway by 19 ka, indicating that the Green Lake Landslide was emplaced 3–4 kyr after the onset of glacier retreat. Given the geometry of the former confining valley glacier, we expect that the deglaciation-landslide age gap is closer to the upper end of this estimate. If correct, this conclusion places greater weight on the roles of local geological structure and/or a great earthquake as factors contributing to the exceptionally large volume of this event. [ABSTRACT FROM AUTHOR]

A standing stone was found near Velmaio (Italy), on the valley floor of the Torrente Bévera. The analysis of its morphology and of traces on its surface on all faces showed that the block is not in an original position but was placed later in its vertical position. The standing stone is made of a dolomite breccia. The texture and, in particular, the lithological composition of the breccia corresponds to that of the Invorio Breccia known only from one locality some 30 km southwest of Velmaio. Surface exposure dating of the boulder surface with cosmogenic 36Cl gave an age of 89.72 ± 5.1 ka. The smooth surface of the standing stone and the absence of traces of quarrying and human transport suggest that the Velmaio boulder was exhumed from Pleistocene deposits. Original deposition of the boulder may have been during the Penultimate glaciation, occurring at around 140 ka. Based on typological correlation with recently discovered megalithism in Claro (Cantone Ticino, Switzerland), we may assume that the boulder was probably chosen because of its particular lithology, transported from the location of its original deposition as an erratic boulder to Velmaio and finally erected, as we suggest as a hypothesis, during the 3rd millennium BCE.

In situ 14C surface exposure dating is a powerful tool for understanding the Earth's surface processes during the late Quaternary. This study developed an in situ 14C extraction system that heats samples to 1650 °C to extract in situ 14C from quartz. The initial experiments showed a high blank level (1.80 × 107 14C atoms) and low extraction efficiency (5.36%). Each procedural step required a blank test to understand the cause of the high background, and the results identified several components of the extraction system as sources of 14C contamination. After improving the apparatus design, the new system showed a sufficiently low blank level (5.32 × 104 14C atoms). The extraction efficiency ranged from 111% to 127% with this system. These results show that the system is capable of extracting in situ 14C from quartz for surface exposure dating. [ABSTRACT FROM AUTHOR]

Pleistocene periglacial activity in eastern Australia was widespread and has been predicted to have extended along much of the east coast. This paper describes block deposits in the New England Tablelands, Australia, as far north as 30°S. These deposits are characterized by openwork blocks on slopes below the angle of repose. The deposits are positioned where frost cracking was significant and range in area up to 8 ha. Surface exposure dating using the cosmogenic nuclide 36Cl from four block deposits indicate all sites were active late during the last glacial cycle, with a concentration of activity between 15-30 ka. Modern temperature measurements from block deposits highlight the importance of local topography for promoting freezing. Periglacial deposits are likely to have been more extensive than previously recognized at these northern limits, and mean annual temperature more than 8°C colder than today. [ABSTRACT FROM AUTHOR]

A technique for parameterizing rock surfaces for luminescence surface exposure dating involves the use of known age rock surfaces which may host no surficial alterations or weathering rinds. However, exposure dated rock surfaces often host subsurface weathering rinds or foreign surficial components, which may impact the development of luminescence depth profiles in the rock material. To observe any effects of depth profile development and parameterizations of naturally altered rock surfaces, controlled exposure experiments were conducted on surface altered and surface non-altered luminescence saturated quartzite samples from the top and bottom portions of rock surface cores, collected from two erratic members of the Foothills Erratics Train, Alberta. Spatially resolved OSL laser scanning techniques were used to acquire two-dimensional OSL maps of the surface core samples for depth profile generation. Results produced varied intensities of depth profile data scatter and depth profile parameterizations between surface altered and non-altered samples. Several cores which exhibited surface alterations produced lower attenuation coefficients than comparable cores with no surface alterations, possibly from the effects of surface features and weathering rinds attenuating light intensity for OSL stimulation. These trends indicate samples hosting surface alterations such as weathering rinds, lichen cover, and staining may offer parameterizations which are inequivalent to rock surfaces with no surface altered components, and that depth dependent, multi-order parameterizations may be needed to adequately parameterize rock surfaces hosting surface altered features for exposure dating. • Spatially resolved OSL maps are produced from weathered and nonweathered quartzite surfaces. • Lower light attenuation values are generally fitted from weathered surface samples. • Weathering rinds, surface coverage may reduce OSL bleaching deeper into the subsurface. [ABSTRACT FROM AUTHOR]

Sub-Antarctic glacier chronologies can provide valuable information about the past variability of climate dynamics in the Southern Ocean region. The Kerguelen Archipelago (49°S) is advantageously located under the influence of the Southern Hemisphere's westerly wind belt, thus fluctuations of climate-sensitive glaciers on Kerguelen can provide a baseline for understanding the behavior of this atmospheric regime in response to climatic forcings. We present 17 36Cl exposure ages of moraine and erratic boulders to provide chronological constraints to paleoglacier extents of the Guynemer cirque glacier, located just north of the Cook Ice Cap. Erratic boulders show ice thinning in the Guynemer region started to occur in the Late Glacial by 13.5 ka and continued past 12.4 ka. Ice retreat was punctuated by the formation of two moraine stages, the outermost at 11.5 ± 0.4 ka followed by another at 10.4 ± 1.2 ka, which are indicative of Early Holocene glacier advances/standstills. A glacial advance occurred at 1.4 ± 0.3 ka, which corroborates other Late Holocene re-advances elsewhere on the archipelago. Finally, three undated moraine stages are found between 1.4 ka and the 1960s. The lack of moraines after 10.4 ka and through the Mid-Holocene suggests that the Guynemer glacier was significantly smaller during this extended period of the Holocene compared to its Early Holocene as well as its Late Holocene limits. The Guynemer glacier history provides unique evidence of Early Holocene moraines on Kerguelen, which have not been discovered thus far on the archipelago. Similar to glaciers in Patagonia, New Zealand and South Georgia, the Guynemer glacier was at its largest Holocene extent in the Early Holocene. However, while other southern mid-latitude glacier chronologies show progressively smaller glacial extents throughout the Mid- to Late Holocene, the Late Holocene re-advance of the Guynemer glacier, like other Kerguelen glaciers, likely exceeded its Mid-Holocene extent. • We present 17 new 36Cl surface exposure ages from the Kerguelen Archipelago. • 36Cl ages range from 13.5 ± 0.3 ka to 1.2 ± 0.2 ka. • First early Holocene-dated moraines on Kerguelen. • Glacial readvance occurred in late Holocene. • Holocene glacial evolution on Kerguelen differs from other sub-Antarctic glaciers. [ABSTRACT FROM AUTHOR]

We present a geomorphic map of the landforms created by the Patagonian Ice Sheet during the local Last Glacial Maximum and perhaps prior glaciations in southernmost Patagonia. Building on prior work, the new mapping focuses in unprecedented detail on the right lateral and frontal landforms formed by the Strait of Magellan ice lobe. We produced the map using aerial orthophotography, Sentinel-2 and SPOT satellite imagery, ALOS PALSAR digital elevation model and fieldwork to ground-truth preliminary interpretations. We delineate at least five glacial events defined by a sequence of moraine drifts and associated glaciofluvial features. In contrast to previous studies, we propose the Magellan ice lobe extended ∼65 km farther, to the Primera Angostura peninsula, during the local Last Glacial Maximum. Our study provides a new context to establish a precise glacial chronology of the Magellan ice lobe during the last glacial cycle in the middle-high latitudes of the Southern Hemisphere.

We present new chronological data and Equilibrium Line Altitude (ELA) information for palaeoglaciers in the Maritime Alps during the Last Glacial Maximum (LGM) and the early deglaciation. Three relatively small catchments were investigated to test if the response of small (1–10 km2) glaciers to LGM climatic forcing was distinguishable from that of larger glacial systems. Palaeoglacier geometries and ELAs were reconstructed using geomorphological evidence and toolboxes in a geographic information system. Chronological control was provided through 10Be surface exposure dating of erratic boulders located on frontal and lateral moraine ridges. Our data indicate two phases of glacier advance or stabilisation in the Maritime Alps, the first occurring at ca. 25 to 24 ka and the second at ca. 20.5 to 19 ka. This is consistent with ages that have been reported from larger outlet lobes along the south-western Alpine fringe, where the second LGM advance is usually preserved in the form of a recessional moraine. Within the uncertainty of the dating technique, there are no distinguishable differences between the responses of small and large Alpine glaciers to the LGM climate. The reconstructed ELAs for palaeoglaciers in the Maritime Alps indicate a considerable variability, which appears to be linked to differences in received solar radiation, from ca. 1600 m a.s.l. for north-facing cirque glaciers to almost 2000 m a.s.l. for glaciers with a southerly aspect. We argue that such influence of solar radiation needs to be considered when using ELAs for palaeoclimatic inferences at regional scales. The calculated ELAs are up to 450 m higher than those in the northern Apennines or the Corsican mountains, indicating a relatively dry LGM climate on the Italian side of the Maritime Alps. • Glaciers in the Maritime Alps advanced at 25 to 24 ka and at 20.5 to 19 ka. • Synchronous advances of small and large glaciers across the south-western Alps. • Catchment aspect and solar radiation had a crucial influence on palaeoglacier ELAs. • Regional glacier ELA of 1800 m a.s.l. indicates a relatively dry LGM climate. [ABSTRACT FROM AUTHOR]

Blue ice moraines are common supraglacial landforms in Antarctica and they are considered to record the ice volume fluctuations. In this study, we use photogrammetry and the analysis of multiple cosmogenic nuclides (10Be, 26Al, and in-situ 14C) in boulders on three blue ice moraines to explore the timing of ice volume fluctuations in the Sør Rondane Mountains, Queen Maud Land, and provide insights into the role of sediment sources in the reconstruction of their chronology. In the field, we observe that the blue ice moraines are composed of subglacially and supraglacially transported sediments. Cosmogenic 10Be and 26Al exposure ages of 14 surface samples, collected from boulders on three blue ice moraines, range from 15.4 ± 1.1 to 659.5 ± 33.9 ka. 26Al/10Be ratios vary between 3.53 ± 0.20 and 7.01 ± 0.32, and many of these ratios indicate complex exposure histories. In contrast, among nine in-situ 14C exposure ages, five vary between 4.2 ± 0.1 and 22.0 ± 1.3 ka, and four are saturated. We conclude that the accumulation of these blue ice moraines commenced before or during the global Last Glacial Maximum. Our results indicate that surficial sediment sources can yield exposure ages that are older than real exposure age, and exhibit a wider scatter. This can alter the reconstructed chronology of these landforms. The analysis of in-situ 14C has a high potential in tracking the pace of their evolution, especially since the Last Glacial Maximum.

We present a geomorphic map of the landforms created by the Patagonian Ice Sheet during the local Last Glacial Maximum and perhaps prior glaciations in southernmost Patagonia. Building on prior work, the new mapping focuses in unprecedented detail on the right lateral and frontal landforms formed by the Strait of Magellan ice lobe. We produced the map using aerial orthophotography, Sentinel-2 and SPOT satellite imagery, ALOS PALSAR digital elevation model and fieldwork to ground-truth preliminary interpretations. We delineate at least five glacial events defined by a sequence of moraine drifts and associated glaciofluvial features. In contrast to previous studies, we propose the Magellan ice lobe extended ∼65 km farther, to the Primera Angostura peninsula, during the local Last Glacial Maximum. Our study provides a new context to establish a precise glacial chronology of the Magellan ice lobe during the last glacial cycle in the middle-high latitudes of the Southern Hemisphere. [ABSTRACT FROM AUTHOR]

Surface exposure dating using cosmic-ray-produced nuclides has been applied to determine the age of thousands of landforms produced by alpine glaciers in mountain areas worldwide. These data are potentially an extensive, easily accessible, and globally distributed paleoclimate record. In particular, exposure-dated glacier chronologies are commonly applied to study the dynamics of massive, abrupt climate changes characteristic of the transition between the Last Glacial Maximum and the present interglacial climate. This article reviews developments in exposure dating from the perspective of whether this goal is achievable and concludes that (a) individual exposure-dated landforms cannot, in general, be associated with millennial-scale climate events at high confidence, but (b) dating uncertainties appear to be geographically and temporally unbiased, so the data set as a whole can be used to gain valuable insight into regional and global paleoclimate dynamics. Future applications of exposure-age chronologies of glacier change should move away from reliance on individual dated landforms and toward synoptic analysis of the global data set. ▪ Mountain glaciers worldwide leave a geologic record of their past advances and retreats, which reflect past climate changes. ▪ Geochemical dating methods based on cosmic-ray-produced nuclides have been used to date these deposits at thousands of sites worldwide. ▪ This data set is potentially an extensive, accessible, and globally distributed paleoclimate record. [ABSTRACT FROM AUTHOR]

Cosmogenic in situ 14C in quartz is rapidly becoming a widely used geochronological tool for studying earth surface processes over the last 30,000 years. The Lamont-Doherty Earth Observatory houses one of the longest continuously-operating cosmogenic in situ 14C laboratories; in this contribution, we provide an update on the status of the laboratory following Goehring et al. (2014). From 2010 to the present, our long-term average blank value is 119,000 ± 37,000 14C atoms, with no statistically significant trend over the last nine years. While our average measured 14C concentration of the CRONUS-A inter-laboratory comparison standard is in line with data published from other laboratories, we note a step increase between 2013 and 2015 that is still under investigation. Additionally, we report our first procedural blanks and CRONUS-A values analyzed on the gas source of the AixMICADAS at CEREGE, France. Many of the >75 samples analyzed at Lamont for in situ 14C from the Arctic, Antarctic, New Zealand, and the Alps have been paired with 10Be analyses contributing to the increasing density of burial dating data covering the last 20,000 years. Currently we are working on increasing sample throughput, streamlining the 14C extraction procedure, and considerably decreasing blank levels. [ABSTRACT FROM AUTHOR]

The investigation of periglacial and related landforms in South Norway is of great interest for exploring the timing of deglaciation and to assess their geomorphological connectivity to palaeoclimatic changes during the Late Pleistocene and the Holocene. The ice margins of the Scandinavian Ice Sheet during the Last Glacial Maximum (LGM) are reasonably well established. Palaeo-ice thickness can, however, only be estimated by modelling and remains uncertain over large parts of Norway due to sparse field based evidence. Because of the significant influence of the former horizontal and vertical ice-sheet extent on sea-level rise, atmospheric and oceanic circulation patterns, erosive properties of glaciers and ice sheets, englacial thermal boundaries, and deglaciation dynamics, it is crucial to improve the understanding of the topographic properties of the LGM ice sheet. Despite recent progress, there is a lack of terrestrial evidence in the form of numerical age data from South Norway. In this study two high-mountain regions and their surroundings in west (Dalsnibba, 1476 m a.s.l.) and east (Blåhø, 1617 m a.s.l.) South Norway were studied to reconstruct palaeoclimatic conditions and deglaciation patterns. Terrestrial cosmogenic nuclide (10Be) and Schmidt-hammer exposure-age dating (SHD) have been utilized to determine the surface exposure age of glacially transported boulders as well as of boulder-dominated glacial, periglacial, and paraglacial landforms and bedrock outcrops. By developing calibration curves at both study sites for the first time it was possible to obtain landform-age estimates from Schmidt hammer R-(rebound) values. In addition, the formation and stabilization of those landforms and the formative processes have provided indications about the Late Pleistocene and Holocene climate variability and its connectivity to landform development. [ABSTRACT FROM AUTHOR]

Accurate estimation of fault slip rate is fundamental to seismic hazard assessment. Previous work suggested a discrepancy between short-term geodetic and long-term geologic slip rates in the Mojave Desert section of the Eastern California Shear Zone (ECSZ). Understanding the origin of this discrepancy can improve understanding of earthquake hazard and fault evolution. We measured offsets in alluvial fans along the Calico Fault near Newberry Springs, California, and used several techniques to date the offset landforms and determine a slip rate. Our preferred slip rate estimate is 3.2 ± 0.4 mm/yr, representing an average over the last few hundred thousand years, faster than previous estimates. Seismic hazard associated with this fault may therefore be higher than previously assumed. We discuss possible biases in the various slip rate estimates and discuss possible reasons for the rate discrepancy. We suggest that the ECSZ discrepancy is an artefact of limited data, and represents a combination of faster slip on the Calico Fault, off-fault deformation, unmapped fault strands, and uncertainties in the geologic rates that have been underestimated. Assuming our new rate estimate is correct and a fair amount (40%) of off-fault deformation occurs on major ECSZ faults, the summed geologic rate estimate across the Mojave section of the ECSZ is 10.5 ± 3.1 mm/yr, which is equivalent within uncertainties to the geodetic rate estimate. [ABSTRACT FROM AUTHOR]

Terrestrial cosmogenic nuclide (TCN) exposure dating of boulders is frequently used for rockslide chronology. A well-recognized source of error that cannot be readily quantified is related to inheritance of TCN produced in the rock prior to failure. The effect of inheritance is not constant and will be greatest in the instance of a very recent shallow failure on a high-altitude surface with low event frequencies. We illustrate the effect by measuring 10Be concentrations in six boulders exposed for only 9 years before sampling, on a rock avalanche in Puerto Aysén, Chile. Their apparent exposure ages range from 216 ± 76 to 1755 ± 436 years. The mean apparent exposure age of a statistical cluster of three samples exceeds the real exposure time by 345 ± 36 years (3800%), implying that all sampled rock surfaces experienced pre-failure TCN production. A reconstructed pre-failure topography enables the analysis of possible pre-failure boulder positions and an estimate of the range of possible inherited concentrations along a 2D transect. Despite a maximum failure-mass thickness of 110 m, the boulders seem to have originated from depths shallower than 14 m. Because of the likelihood that large boulders, prioritized for TCN sampling, originate from relatively shallow pre-failure depths owing to surface-near transport with minor turbation, it is necessary to consider potentially inherited TCN concentrations and their effect on the age determination, especially in cases of young rockslides, where the commonly adjusted effects of boulder erosion and snow, ash, or vegetation shielding are negligible in comparison. [ABSTRACT FROM AUTHOR]

Abstract The Tibetan Plateau was formed by the collision between the Indian and Eurasian plates, and it continues to grow laterally while keeping its elevation constant. The mechanism of the lateral expansion at the northeastern margin of the plateau, however, is highly debated owing to the scarcity of tectonic research. We conducted tectonic geomorphological analyses in the Kumkol Basin, where lateral growth is ongoing. This basin encloses a large active anticlinorium, the Kumkol Anticlinorium (KA), which would provide a quantitative constraint on the lateral growth of the plateau if the tectonically deformed landforms were dated. Our geomorphological mapping revealed six terrace steps, designated T1 to T6 in descending order, along the Pitileke River. In situ cosmogenic radionuclide concentrations in subsurface and surface samples from T1, T2, T3, T4, and T6 showed their formation ages to be 252 ± 24 ka, 140–160 ka, 103 ± 23 ka, 98 ± 11 ka, and 0–23 ka, respectively. Thus, T1 formed during marine isotope stage (MIS) 8, T2 during MIS 6, and T3 and T4 during MIS 5. Our results are quantitative evidence that degradation–aggradation cycles in the basin are correlated with global climatic fluctuations. To estimate the geometry of faults contributing to the evolution of the anticlinorium, we used a dislocation fault model and the overall surface deformation across the KA. The results suggest that the KA has been produced principally by slip on a detachment fault at 15 to 10 km depth, which is within or just above the brittle–ductile transition zone. We then determined the maximum uplift rate to be ~1 mm/yr and the horizontal shortening rate to be 2.5–3.2 mm/yr from the formation ages of the terraces and their deformation. These results suggest that there is a large-scale detachment fault below a basement-involved fold-and-thrust belt and that the concentration of stress at the plateau margin likely facilitated the development of crustal-scale deformation underlying the Kumkol Basin, and this deformation then accelerated the lateral growth of the Tibetan Plateau. Graphical abstract Unlabelled Image Highlights • Geomorphological study revealed a large-scale active anticlinorium in Kumkol Basin. • Late Quaternary terraces are highly deformed by the activity of the anticlinorium. • The surface deformation was quantified by surface exposure dating of terraces. • The horizontal shortening rate of the Kumkol Basin was estimated at 2.5–3.2 mm/yr. • Crustal scale faulting facilitated the lateral growth of Tibet at its NE margin. [ABSTRACT FROM AUTHOR]

Highlights • Young faults often undetected but potentially crucial for seismic hazard assessments. • First geomorphic evidence for the Southern San Cayetano fault (SSCF). • 10Be dating of offset terraces records Holocene slip rate of 1.3 + 0.5 − 0.3 mm yr−1. • SSCF has major implications for seismic hazard in southern California. Abstract We present surface evidence and displacement rates for a young, active, low-angle (∼20°) reverse thrust fault in close proximity to major population centers in southern California (USA), the Southern San Cayetano fault (SSCF). Active faulting along the northern flank of the Santa Clara River Valley displaces young landforms, such as late Quaternary river terraces and alluvial fans. Geomorphic strain markers are examined using field mapping, high-resolution lidar topographic data, 10Be surface exposure dating, and subsurface well data to provide evidence for a young, active SSCF along the northern flank of the Santa Clara River Valley. Displacement rates for the SSCF are calculated over 103–104 yr timescales with maximum slip rates for the central SSCF of 1.9 + 1.0 − 0.5 mm yr−1 between ∼19–7 ka and minimum slip rates of 1.3 + 0.5 − 0.3 mm yr−1 since ∼7 ka. Uplift rates for the central SSCF have not varied significantly over the last ∼58 ka, with a maximum value of 1.7 + 0.9 − 0.6 mm yr−1 for the interval ∼58–19 ka, and a minimum value of 1.2 ± 0.3 mm yr−1 since ∼7 ka. The SSCF is interpreted as a young, active structure with onset of activity at some time after ∼58 ka. The geometry for the SSCF presented here, with a ∼20° north dip in the subsurface, is the first interpretation of the SSCF based on geological field data. Our new interpretation is significantly different from the previously proposed model-derived geometry, which dips more steeply at 45–60° and intersects the surface in the middle of the Santa Clara River Valley. We suggest that the SSCF may rupture in tandem with the main San Cayetano fault. Additionally, the SSCF could potentially act as a rupture pathway between the Ventura and San Cayetano faults in large-magnitude, multi-fault earthquakes in southern California. However, given structural complexities, including significant changes in dip and varying Holocene displacement rates along strike, further work is required to examine the possible mechanism, likelihood, and frequency of potential through-going ruptures between the Ventura and San Cayetano faults. Confirmation of the SSCF in a previously well-studied area, such as southern California, demonstrates that identification of young faults is critical for accurate seismic hazard assessment. We suggest that many young, active faults remain undetected in other structurally complex and tectonically active regions globally, and that significant seismic hazards can be overlooked. [ABSTRACT FROM AUTHOR]

We test the hypothesis that glacier systems, located in continental regions proximal to the Laurentide Ice Sheet (LIS), had local ice maxima considerably earlier than the LIS maximum and thus before the insolation minima at ∼21 ka. Ranges located in the northwest US exhibit earlier deglaciation timing between ∼23 and 22 ka, except for the Yellowstone region where younger time-transgressive ages complicate regional interpretations and the northern Montana ice cap where late glacial ages have recently been produced. Constraining the glacial history of more ice sheet-proximal alpine glaciers provides insight into whether the contrasting maximum-ice times in the northern Rocky Mountains were caused by regional climatic differences, such as anticyclonic wind patterns driven by the presence of the LIS. In the Pioneer Mountains of Montana, we measured in situ cosmogenic 10Be in 35 boulders on moraines marking the maximum Late Pleistocene positions of alpine glaciers from three valleys. The 10Be samples produced a range of ages, spanning pre Bull Lake to the last glaciation (i.e., Pinedale/Marine Isotope Stage (MIS) 2). We find an average exposure age for initial deglaciation of 18.2 ± 0.9 during the local Last Glacial Maximum, indicative of synchronous retreat in the Pioneer Mountains. The similarity of initial deglaciation timing of the Pioneer Mountain glaciers with the northwestern Yellowstone glacial system and northern MT ice cap suggests that topography more proximal to the LIS margin maintained full ice extent longer. Our findings, in context of previous work, suggest that in the case of the Pioneer Mountains their more proximal location to the ice margin may have delayed onset of deglaciation by greater exposure to local cooling from katabatic winds and/or additional moisture sourced from large ice-marginal glacial lakes, hence the lack of earlier deglacial ages like those found further to the west and east of the northern Rocky Mountain cordillera. [ABSTRACT FROM AUTHOR]

The thinning and final decay of the Scandinavian Ice Sheet in the Gudbrandsdalen area in central southern Norway is described, based on (1) cosmogenic 10Be surface exposure dating of 25 glacially transported boulders, (2) radiocarbon dating of plant remains in the basal strata in four lakes and (3) mapping of large ice-dammed lakes that formed at different elevations and at different times during the last deglacation. We complement the new chronology with previously published 10Be-ages from the same region. The dated samples are spread from mountain summits 1800 m a.s.l. to the valley floor at 250 m a.s.l. Our results suggest that the ice sheet surface remained well above 1800 m a.s.l. in northern Gudbrandsdalen throughout the Younger Dryas. During the Early Holocene the ice sheet thinned rapidly, at rates estimated to 1.7–5.8 m yr−1. The final phase of deglaciation involved formation of large ice-dammed lakes, most notably the Store Dølasjø which was formed after 10.4 ka BP and finally drained around 10.0 ka BP. The ice-marginal landforms that characterize the mountain region of northern Gudbrandsdalen, i.e., moraine ridges, lateral meltwater channels, as well as deposits and shorelines from ice-dammed lakes, thus collectively originate from a period of rapid ice sheet downwasting over ca. 1600 years. • Three independent methods used to reconstruct deglaciation in southern Norway. • Ice-dammed lakes, 10Be-dating of boulders and radiocarbon dated lake records. • Thinning rates for the Scandinavian Ice Sheet based on empirical data. • New reconstruction and dating of the Store Dølasjø ice-dammed lake. • Important constraints for ice sheet models and eustatic sea level budgets. [ABSTRACT FROM AUTHOR]

Providing quantitative constraints on late Pleistocene glacier fluctuations remains an important challenge for understanding glacier response to past and future climate changes. In most mountainous settings, paleo-glacier reconstructions are limited because they often lack precise temporal constraints. Different geochronological methods have been developed and applied to date specific geomorphological or sedimentological markers for paleo-glacier dynamics. Recently, OSL (Optically Stimulated Luminescence) surface exposure dating has been introduced and provides us with an opportunity to improve paleo-glacier reconstructions. This method is based on the sensitivity of the OSL signal from rock minerals to light, resulting in bleaching of the OSL signal within the upper first millimeters of the exposed rock surface, a process that depends on the exposure age, the rock type and the local setting (e.g. topographic shielding, bedrock orientation etc.). Here, we investigate the potential of OSL surface exposure along a vertical cross-section of polished bedrock surfaces with known post-LIA (Little Ice Age) exposure ages (from 3 to 137 years) along the Mer de Glace glacier (Mont Blanc massif, France). The infrared stimulated luminescence (IRSL) signals from rock slices exhibit increasingly deep bleaching profiles with elevation and thus exposure age, which is consistent with progressive glacier thinning since the LIA. Our results show that OSL surface exposure dating can be applied to periglacial environments, and is a promising tool for high-resolution reconstruction of ice extent fluctuations, both in space and time. [ABSTRACT FROM AUTHOR]

Reconstructing Quaternary landscape evolution today frequently builds upon cosmogenic-nuclide surface exposure dating. However, the study of complex surface exposure chronologies on the 10 2 –10 4 years’ timescale remains challenging with the commonly used long-lived radionuclides ( 10 Be, 26 Al, 36 Cl). In glacial settings, key points are the inheritance of nuclides accumulated in a rock surface during a previous exposure episode and (partial) shielding of a rock surface after the main deglaciation event, e.g. during phases of glacier readvance. Combining the short-lived in situ cosmogenic 14 C isotope with 10 Be dating provides a valuable approach to resolve and quantify complex exposure histories and burial episodes within Lateglacial and Holocene timescales. The first studies applying the in situ 14 C- 10 Be pair have demonstrated the great benefit from in situ 14 C analysis for unravelling complex glacier chronologies in various glacial environments worldwide. Moreover, emerging research on in situ 14 C in sedimentary systems highlights the capacity of combined in situ 14 C- 10 Be analysis to quantify sediment transfer times in fluvial catchments or to constrain changes in surface erosion rates. Nevertheless, further methodological advances are needed to obtain truly routine and widely available in situ 14 C analysis. Future development in analytical techniques has to focus on improving the analytical reproducibility, reducing the background level and determining more accurate muonic production rates. These improvements should allow extending the field of applications for combined in situ 14 C- 10 Be analysis in Earth surface sciences and open up a number of promising applications for dating young sedimentary deposits and the quantification of recent changes in surface erosion dynamics. [ABSTRACT FROM AUTHOR]

Terrestrial cosmogenic nuclide dating has been widely used to estimate the surface exposure age of bedrock and boulder surfaces associated with deglaciation and Holocene glacier variations, but the effect of inherited age has been rarely directly addressed. In this study, small clasts, embedded in flute surfaces on two cirque glacier forelands in Jotunheimen, southern Norway and deposited within the last ~60 years, were used to test whether such clasts have the modern surface exposure age expected in the absence of inheritance. Two different approaches were taken involving dating of (1) a single clast of cobble size from the proglacial area of Austanbotnbreen, and (2) 75 clasts mostly of pebble size from the proglacial area of Storbreen crushed and treated as a single sample. 10Be surface exposure ages were 99 ± 98 and 368 ± 90 years, respectively, with 95% confidence (±2σ). It is concluded that (1) these small glaciers have eroded and deposited rock fragments with a cosmogenic zero or near-zero concentration, (2) the likelihood of inherited cosmogenic nuclide concentrations in similar rock fragments deposited by larger warm-based glaciers and ice sheets should be small, and (3) combining a large number of small rock particles into one sample rather than using single large clasts of boulder size may provide a viable alternative to the commonly perceived need for five or more independent estimates of exposure age per site. [ABSTRACT FROM AUTHOR]

Surface exposure dating was applied to erosional shorelines associated with the Angliers lake level that marks an important stage of Lake Ojibway. The distribution of 15 10Be ages from five sites shows a main group (10 samples) of coherent 10Be ages yielding a mean age of 9.9±0.7 ka that assigns the development of this lake level to the early part of the Lake Ojibway history. A smaller group (3 samples) is part of a more scattered distribution of older 10Be ages (with 2 outliers) that points to an inheritance of cosmogenic isotopes from a previous exposure, revealing an apparent mean age of 15.8±0.9 ka that is incompatible with the Ojibway inundation and the regional deglaciation. Our results provide the first direct 10Be chronology on the sequence of lake levels in the Ojibway basin, which includes the lake stage presumably associated with the confluence and subsequent drainage of Lakes Agassiz and Ojibway. This study demonstrates the potential of this approach to date glacial lake shorelines and underlies the importance of obtaining additional chronological constraints on the Agassiz-Ojibway shoreline sequence to confidently assign a particular lake stage and/or lake-level drawdown to a specific time interval of the deglaciation. [ABSTRACT FROM PUBLISHER]

In this study, we document deglaciation in a sector of the southern–central Pyrenees (the Panticosa massif and the upper Gállego and Ossau valleys) using cosmic-ray exposure (CRE) dating methods, which were applied to samples from high altitude polished rock steps and rock glacier boulders. The obtained CRE dates show a coherent spatial distribution and confirm results previously obtained in this study area, thus demonstrating the reliability and robustness of the method. The results of analyses based on two distinct isotopes ( 10 Be and 36 Cl) are consistent, although the error is higher for results based on the 36 Cl isotope. The study provides evidence for ice extent in the High Gállego Valley during the Oldest Dryas, with glacial advance until the bottom of the valleys, although the main glacier tongues remained disconnected from each other. During this period, the extent of glacier advance was directly related to the elevation of the associated summits. The Younger Dryas glaciers were constrained to cirques or very short ice tongues, and dating of the polished rock steps indicates that the ice masses were present until the first millennium of the Holocene. The Brazato rock glacier developed at the beginning of the Holocene and remained active until the Holocene Thermal Optimum, because of the protective effect of large masses of blocks and boulders. [ABSTRACT FROM AUTHOR]

Alluvial fans and megafans hold a key position in the sediment routing system and are particularly sensitive to changes in geodynamic and climatic forcing, as well as autogenic fluvial processes. The Lannemezan megafan in the Northern Pyrenean foreland (SW France) was built during Miocene to Pliocene times and subsequently abandoned as the stream network deeply entrenched the foreland. We report new cosmogenic nuclide ( 10 Be, 26 Al) exposure dates for the abandoned fan surface and a series of alluvial terraces along the Neste and Garonne rivers. Our results show that abandonment of the fan occurred at or before ~ 300 ka, and we suggest that this abandonment is the result of the autogenic dynamics of the river system leading to the capture of the feeding Neste River by the Garonne. However, the incision episodes that produced the terrace levels are concomitant to major climatic shifts. Detailed analysis of stream network morphometry does not reveal knickpoints or patterns in the steepness index and chi-values that could be linked to either active tectonic features, base-level change or network reorganization. We therefore suggest that fan abandonment and long-term incision occurred through autogenic processes and that climate shifts may have modulated the incision, allowing for the formation and persistence of alluvial terraces. [ABSTRACT FROM AUTHOR]

Over the last three decades, theoretical and technical developments have considerably fostered and intensified the use of terrestrial (or in situ) cosmogenic nuclides as a geochronometer in a variety of environments at the Earth's surface for the Late Cenozoic. These dating methods, including both surface exposure and burial dating, also significantly benefited to fluvial geomorphology. They opened new dating horizons for different kinds of fluvial archives at distinct time scales and thereby provided new insights into previously unanswered questions. This contribution aims at providing a concise (but not exhaustive) overview of these dating applications in a variety of fluvial environments (e.g. river terraces, alluvial fans, in cave-deposited alluvium). Therefore, it briefly presents the fundamental principles of both surface exposure and burial dating, together with a clear statement of the main methodological issues arising from the use of these methods in fluvial contexts. For each dating applications, key information about sampling procedures in the field and representative case studies are also provided. [ABSTRACT FROM AUTHOR]

Southern Africa is located in a unique setting for investigating past cold climate geomorphology over glacial-interglacial timescales. It lies at the junction of three of the world's major oceans and is affected by subtropical and temperate circulation systems, therefore recording changes in Southern Hemisphere circulation patterns. Cold climate landforms are very sensitive to changes in climate and thus provide an opportunity to investigate past changes in this region. The proposed existence of glaciers in the high Eastern Cape Drakensberg mountains, together with possible rock glaciers, has led to the suggestion that temperatures in this region were as much as 10–17 °C lower than present. Such large temperature depressions are inconsistent with many other palaeoclimatic proxies in Southern Africa. This paper presents new field observations and cosmogenic nuclide exposure ages from putative cold climate landforms. We discuss alternative interpretations for the formation of the landforms and confirm that glaciers were absent in the Eastern Cape Drakensberg during the last glaciation. However, we find widespread evidence for periglacial activity down to an elevation of ~ 1700 m asl, as illustrated by extensive solifluction deposits, blockstreams, and stone garlands. These periglacial deposits suggest that the climate was significantly colder (~ 6 °C) during the Last Glacial Maximum, in keeping with other climate proxy records from the region, but not cold enough to initiate or sustain glaciers or rock glaciers. [ABSTRACT FROM AUTHOR]

Despite elevated summer insolation forcing during the early Holocene, global ice sheets retained nearly half of their volume from the Last Glacial Maximum, as indicated by deglacial records of global mean sea level (GMSL). Partitioning the GMSL rise among potential sources requires accurate dating of ice-sheet extent to estimate ice-sheet volume. Here, we date the final retreat of the Laurentide Ice Sheet with 10 Be surface exposure ages for the Labrador Dome, the largest of the remnant Laurentide ice domes during the Holocene. We show that the Labrador Dome deposited moraines during North Atlantic cold events at ∼10.3 ka, 9.3 ka and 8.2 ka, suggesting that these regional climate events helped stabilize the retreating Labrador Dome in the early Holocene. After Hudson Bay became seasonally ice free at ∼8.2 ka, the majority of Laurentide ice-sheet melted abruptly within a few centuries. We demonstrate through high-resolution regional climate model simulations that the thermal properties of a seasonally ice-free Hudson Bay would have increased Laurentide ice-sheet ablation and thus contributed to the subsequent rapid Labrador Dome retreat. Finally, our new 10 Be chronology indicates full Laurentide ice-sheet had completely deglaciated by 6.7 ± 0.4 ka, which re quires that Antarctic ice sheets contributed 3.6–6.5 m to GMSL rise since 6.3–7.1 ka. [ABSTRACT FROM AUTHOR]