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Glacial strata are excellent stratigraphic markers in Paleozoic basins worldwide. The eastern Parnaíba Basin in northern Brazil is a highly favorable setting for studying episodes related to the Ordovician-Silurian glaciation. Previous studies in this region led to the recognition of unequivocally glaciogenic sediments associated with pre- and postglacial deposits, favoring the understanding of lower Paleozoic events that occurred in West Gondwana. Outcrop-based facies and stratigraphic analyses of the ~170 m-thick siliciclastic succession of the Serra Grande Group indicate fluvial, glacial, and coastal depositional systems. Seventeen sedimentary facies are grouped into seven facies associations (FAs): FA1, interpreted as intermediary sheet braided plain deposits that consist of tabular cross-bedded coarse-grained sandstones and conglomerates; FA2-FA4, which correspond to subaqueous glacial deposits comprising massive to stratified diamictites, cross-laminated sandstones, diamictites and organic matter-rich black shales with dumpstone and dropstone structures; FA5-FA6, constituting organic matter-rich black shales, fine- to medium-grained sandstones with sigmoidal cross-bedding and occurrences of the ichnotaxon Arthrophycus interpreted as delta front deposits; and FA7, composed of medium- to coarse-grained pebbly sandstones interpreted as channelized braided plain deposits. This interpretation partially confirms the previous paleoenvironmental interpretation discounting the presence of subaerial alluvial fan and outwash plain deposits for this unit. The sequence stratigraphy of the Serra Grande Group is refined mainly using the coherent interpretation of the key surfaces and comparing the systems tracts with the global sea-level curve, providing a more robust third-order sequential evolutionary model that includes three depositional sequences. The Middle Ordovician sheet braided deposits are the lowstand sediments of Sequence 1 truncated by an extensive unconformity that possibly removed the transgressive and highstand strata. This unconformity generated by glacial dynamics represents 23 Myr during the Late Ordovician to early Silurian. The second sequence started with the advance of ice sheets in marginal areas of the basin, causing the deposition of ablation diamicton during the lowstand. The postglacial transgression is marked by ice-rafted debris from icebergs deposited onto organic matter-rich mud in the shoreface-offshore zone. The maximum flooding during the middle to late Silurian was succeeded by the highstand phase marked by the progradation of deltaic deposits. Biological activity is marked by the presence of polychaetes that reworked the marine seafloor. The Early Devonian featured extensive sea-level fall and renewed continental drainage with the formation of a braided plain marking a lowstand phase of Sequence 3. These new interpretations allow the global correlation of the Serra Grande Group and provide an improved understanding of the role of ice sheets and postglacial transgressions that affected West Gondwana during the Ordovician-Silurian periods. [ABSTRACT FROM AUTHOR]

• The well-preserved micro-macro scale subglacial forms and erosional landscapes are widely presented on the surface of the residual Mesoproterozoic quartzite basement rocks in North China. • A continental ice sheet gradually advanced from highland in the north to shallow sea in the south during Luoquan glacial period in North China. • An icehouse environment of Proterozoic-Phanerozoic transition period in global greenhouse background is indicated. Diamictites of late Ediacaran to early Cambrian age (ca. 551–518 Ma) are widespread across Southeast–Central Asia, with the Luoquan Formation particularly well preserved along the southern margin of the North China craton. A basal unconformity, comprising striations and p-forms interpreted to have been produced subglacially, was cut into Mesoproterozoic basement. Integrating new observations on the basal unconformity with the stratigraphy and sedimentology of the Luoquan Formation, an unequivocal glacial origin is demonstrated. The succession evolves from massive or stratified diamictite at the base to laminated fine-siltstone with dropstones upward, and is capped by siltstone with or without dropstones on the top. These lithological combinations represent a glacial sedimentary succession deposited recording progressive retreat of the ice margin. Based on multiple palaeoflow measurements, data from 7 new measured sections, and facies analysis, a new paleogeographic model is proposed. This model envisages the expansion of a large continental ice sheet from north to south at the southern flank of the North China Craton (NCC). [ABSTRACT FROM AUTHOR]

The geologic record of mountain glaciation is one of the most sensitive archives of terrestrial climate change during the late Quaternary Period. Pleistocene glacial deposits are exceptionally well preserved in the Great Basin of North America where they are found in close proximity to shoreline deposits of coeval paleo-lakes, representing a unique opportunity to investigate paleoclimate change using both hydrologic systems. Mountain glaciers advanced across much of the Wasatch Range, Utah during the same general time interval when Lake Bonneville expanded in the adjacent Bonneville Basin. Here we present a range-wide Latest Pleistocene glacial history for the Wasatch Range based on 22 new and 41 recalculated cosmogenic 10Be surface exposure ages, and reconstruct glaciers and climate for the Last Glacial Maximum (LGM) and Lateglacial periods. Our results indicate three distinct, range-wide phases of glaciation in the Wasatch including the Pinedale 1 (ca. 21–20 ka), Pinedale 2 (ca. 17.5 ka) and Pinedale 3 (ca. 15 ka). Our modeling results indicate that the Pinedale 1 advance, near the end of the global LGM, was primarily driven by decreased annual temperatures with little to no change in precipitation as compared to modern. Wasatch glaciers appear to have reoccupied near maximum positions after the end of the LGM during the Pinedale 2, responding to increased precipitation in concert with rising lake levels across Western North America, and then retreated from ice-distal positions near ca. 17.5 ka. Wasatch glaciers occupied recessional positions at approximately half their maximum lengths during Pinedale 3 until ca. 15 ka, followed by rapid (i.e. several millennia) deglaciation. Our glacial chronologies establish that Wasatch glaciers responded synchronously across the range to global and regional climate forcings during the Latest Pleistocene. The new Wasatch glacial chronology, combined with global glacial chronologies and paleoclimate proxies from Western North America, suggest glacier change was driven by a combination of long-term global temperature forcing as well as regional to local modifications in precipitation. • Paleoclimate modeling and glacial mapping for the Latest Pleistocene in the Wasatch. • 22 new and 41 recalculated cosmogenic exposure ages. • Three range-wide glacial stadia at ca. 21–20 ka, ca. 17.5 ka, and ca. 15 ka. • Modeling suggests −9 to −11.5 °C depression (relative to modern) during LGM. • Modeling shows increase in precipitation (200% of modern) during Lateglacial. [ABSTRACT FROM AUTHOR]

We present PATICE, a GIS database of Patagonian glacial geomorphology and recalibrated chronological data. PATICE includes 58,823 landforms and 1,669 geochronological ages, and extends from 38°S to 55°S in southern South America. We use these data to generate new empirical reconstructions of the Patagonian Ice Sheet (PIS) and subsequent ice masses and ice-dammed palaeolakes at 35 ka, 30 ka, 25 ka, 20 ka, 15 ka, 13 ka (synchronous with the Antarctic Cold Reversal), 10 ka, 5 ka, 0.2 ka and 2011 AD. At 35 ka, the PIS covered of 492.6 x103 km2, had a sea level equivalent of ~1,496 mm, was 350 km wide and 2090 km long, and was grounded on the Pacific continental shelf edge. Outlet glacier lobes remained topographically confined and the largest generated the suites of subglacial streamlined bedforms characteristic of ice streams. The PIS reached its maximum extent by 33 – 28 ka from 38°S to 48°S, and earlier, around 47 ka from 48°S southwards. Net retreat from maximum positions began by 25 ka, with ice-marginal stabilisation then at 21 – 18 ka, which was then followed by rapid, irreversible deglaciation. By 15 ka, the PIS had separated into disparate ice masses, draining into large ice-dammed lakes along the eastern margin, which strongly influenced rates of recession. Glacial readvances or stabilisations occurred at least at 14 – 13 ka, 11 ka, 6 – 5 ka, 2 – 1 ka, and 0.5 – 0.2 ka. We suggest that 20th century glacial recession (% a-1) is occurring faster than at any time documented during the Holocene. Unlabelled Image [ABSTRACT FROM AUTHOR]

Glaciovolcanism produces distinctive features that are useful paleoclimate proxies for the distribution of past ice sheets and glacier extent. The Copahue volcano located in the Andean Southern Volcanic Zone, Argentina-Chile, is an active composite volcano known to have glaciovolcanic features such as lava bodies with glassy margins and anomalous cooling fractures. However, the emplacement conditions of these products and the influence of Pleistocene glaciations on the evolution of the Copahue volcano remains poorly understood. In this contribution, we propose a model for glaciovolcanic evolution of the Copahue volcano based on the analysis, interpretation, and mapping of its products. Ten lithofacies are described on the eastern flank of Copahue volcano exhibiting several examples of glaciovolcanism. The evolution of the Copahue volcano can be divided into two main sequences: the Ancient Sequence (S1) and the Young Sequence (S2), separated by a major erosive phase. The S1 (early-middle Pleistocene-late Pleistocene) consists of an initial subaerial effusive stage followed by a major glaciovolcanic stage, during which a thick ice cap existed and the edifice grew beneath an englacial lake with the eventual formation of a lava-fed delta. The S2 (late Pleistocene-Present) is defined by mainly effusive activity during periods of glacial advance and retreat recorded by an alternation of unconfined subaerial lavas and ice-confined lavas. The evolution of the Copahue volcano therefore indicates two glaciations in the Copahue-Caviahue area during the late Pleistocene, in contrast to a single glaciation. Based on the glacial history in the area we associate the first glaciation with the end of Marine Isotope Stage 3 (57–29 ka) and/or the Last Glacial Maximum period (26.5–19.0 ka), and the second less-extensive glacial period with the Antarctic Cold Reversal (14.5–12.9 ka). • Copahue volcano comprises abundant and diverse glaciovolcanic deposits. • The edifice comprises two eruptive sequences separated by a major phase of erosion. • Glaciovolcanic indicators include pillow lavas, pillow breccias, fractured glassy lavas and overthickened lavas. • Unique syn-eruptive volcaniclastic deposits record meltwater drainage events. • The lithofacies constrain ice conditions and suggest two late Pleistocene glaciations. [ABSTRACT FROM AUTHOR]

• Both massive diamictite and sandstone/mudstone deposits are observed in the Nantuo Formation. • Two ice advance-retreat sedimentary cycles were identified in the Nantuo Formation. • During the Nantuo glaciation, climate, sea level and sedimentary environment evolution may be closely related. • The Marinoan glaciation may be characterized by episodic evolution rather than monotonous ice-covered evolution. Detailed sedimentological investigations of the Cryogenian glacial deposits are critical for constraining the true nature of the Sturtian and Marinoan glaciations. The entire succession of the Nantuo Formation, which corresponds to the Marinoan glaciation, is well developed in South China. Here a detailed lithological and sedimentological analysis of two cores of the Nantuo Formation in Guizhou, South China, is presented in which two continuous ice advance–retreat cycles are identified. The base consists of a massive diamictite lithofacies that is representative of glacier-dominated subaqueous debris flow deposits. These proximal glaciomarine deposits are overlain by a gravel-free sandy mudstone lithofacies that is lacking in diamictites, which implies distal glaciomarine deposits. This ice advance–retreat sedimentary cycle is overlain by a weakly laminated diamictite lithofacies, which represents subaqueous debris flow deposits that formed during the second episode of ice advance. These proximal glaciomarine deposits are overlain by an interbedded sandstone–mudstone lithofacies, which is indicative of distal glaciomarine deposits that formed during another episode of ice retreat. These sedimentary cycles imply that the climate switched twice from relatively warm to extremely cold and back during the Marinoan glaciation. The global sea-level and sedimentary environments fluctuated in response to these climate changes. This co-evolution of the climate, sea-level, and sedimentary environments, which is represented by the lithofacies and sedimentary sequence of the Nantuo Formation, as well as the corresponding strata of other sections worldwide, suggests that the Marinoan glaciation is characterized by a progressive and dynamic course. [ABSTRACT FROM AUTHOR]

Increasing air temperature and declining winter snowfalls are resulting in rapid glacier recession and the expansion of proglacial margins in Alpine regions. Such margins include substantial debris accumulations (e.g. frontal/lateral moraine ridges; till-covered and steep valley sidewalls) which may be unstable due to glacial debuttressing. Rainfall, snowmelt and ice melt out may then cause mass movements. Here, we quantify the decadal-scale erosion and deposition patterns and changes in connectivity for two valley sidewall geomorphological systems following retreat of the Glacier d'Otemma, Switzerland. We apply archival digital photogrammetric methods to the period 1964 to 2009 to determine high resolution digital elevation models. These were differenced to calculate patterns of erosion and deposition and to quantify the evolution of sediment connectivity. We found that gully headward erosion (rates between ca. −10.6 mm/year and −1002.1 mm/year) was the main geomorphological process during glacier thinning but increasing depositional rates downslope of the gullies (ca. +21.3 to +298.5 mm/year) were recorded in the following years associated with significant alluvial fan growth at the slope base. While gullying enhanced connectivity by removing glacially conditioned sediment transfer buffers, so connecting side-slopes to upstream sediment sinks (the upslope contributing area between 1964 and 2009 increased by +73.8% and +195.1% in each subsystem), alluvial fans reduced the rates of sediment transfer to the rapidly enlarging glacial forefields. The detail of these responses is conditioned by three generic processes: (1) the wider geomorphic setting – here, the presence of a moraine bastion as a primary part of the sediment cascade strongly influenced gully morphology evolution and the likely length of the paraglacial period length; (2) the thickness of sediment left by the retreating glacier which controlled the influence of bedrock topographic buffers on connectivity; and (3) the extent to which diffusive drainage systems develop in response to the deposition at the hillslope base, which tend to disconnect sediment flux. Post-glacially, gully development has a self-limiting effect on sediment connectivity in that while gullying increases sediment connectivity, the eroded sediment leads to deposition on the alluvial plain that reduces sediment connectivity. • One of the first multi-decadal scale records concerning geomorphological processes and connectivity glacial debuttressing. • Connectivity develops in response to glacial recession and thinning by gully headward erosion. • Connectivity impacts morphodynamics, and vice-versa. • Paraglacial geomorphological festures may extent the paraglacial period through secondary reworking of sediment. • Gullying process increases the vertical connectivity (basin scale) but it may cause local dis-connection (within the gully network). [ABSTRACT FROM AUTHOR]

Driven by climate change, periods of dominating glacial and fluvial erosion have both sculpted mountain ranges during the Quaternary. To understand the evolution of mountain landforms, there is considerable interest in knowing which erosion agent leads to more incision, how glacial thermal regime impacts erosion and landscape development, and whether glacial erosion can result in increased relief. To investigate the relative efficiency of glacial and fluvial erosion, and the influence of glacial thermal regime on topography, we compare two different mountain ranges–the Qionglai Shan (monsoonal temperate glaciation) and Lenglongling (subcontinental glaciation) in western China. We use a 1-D model to construct presumptive fluvial longitudinal profiles if glaciation had not occurred, and compare these with the actual glacial profiles to obtain relative incision rates of fluvial and glacial erosion. Results demonstrate that glacial incision is smaller than fluvial incision in Lenglongling and larger than fluvial incision in the Qionglai Shan, which may be influenced by different tectonics and glacier types. Topographic analysis of glacial and fluvial valleys with similar drainage areas show that glacial erosion results in valley widening, local valley relief increase induced by isostatic uplift, and slope gradient increase in Lenglongling. However, there is no local valley relief and slope increase observed in the Qionglai Shan, which may reflect slope process responses to threshold hillslope limiting the height above valley bottoms. • Different relative efficiency of glacial and fluvial incision on the Tibetan Plateau. • Relief increase is influenced by isostatic uplift and threshold hillslope angles. • Tectonic uplift and glacier types control incision rate variations for rivers and glaciers. [ABSTRACT FROM AUTHOR]

At least seven late Pliocene tills cap plateaus (mesetas) south of Lago Viedma, just east of the Andes in Argentine Patagonia. Chronologic constraints on the tills are provided by 40Ar/39Ar ages and magnetic polarities on associated basalt flows and sediments. The tills were deposited by piedmont glaciers that reached at least 80 km east of the crest of the Andes and flowed on a low-relief surface sloping gently downward in that direction. The oldest of the tills is about 3.6 Ma old. Glacial deposits dating to the Pliocene-Pleistocene transition are present at least 40 km beyond the east limit of the Pliocene tills at Lago Viedma, and tills of similar age occur at Condor Cliff in the Río Santa Cruz valley to the southeast. A sequence of at least seven Early Pleistocene (2.1–1.1 Ma) tills is present between basalt flows in the Cerro del Fraile meseta south of Lago Argentino. The glaciers that deposited these Early Pleistocene tills reached far beyond the Marine Isotope Stage 2 limit in the Río Santa Cruz valley. Based on positions, extents, and ages of the un-deformed, basalt-capped mesetas flanking Lago Viedma, we conclude that the topography in this area was profoundly changed during the Pleistocene – the low to moderate relief Pliocene surface was deeply incised by glaciers that became increasingly confined to, and flowed within, troughs. The valley floors today are up to 1350 m below the late Pliocene surface. • The Patagonian Ice Sheet advanced over the western Argentine steppe many times during the late Pliocene. • The steppe east of the southern Andes during the late Pliocene was an elevated surface of low to moderate relief. • The late Pliocene steppe was elevated and slightly tilted during the Quaternary, but not otherwise deformed. • Pleistocene glaciers deeply incised the Pliocene land surface, forming the deep valleys of the present landscape. [ABSTRACT FROM AUTHOR]

During the Last Glacial Maximum (LGM), ice streams of the last British-Irish Ice Sheet (BIIS) controlled ice discharge from various dispersal centres. Deglaciation was characterised by shifts in ice-divide location and changes in internal ice-sheet dynamics, resulting in substantial flow switches and significant ice-stream reconfiguration, and hence modification of their landform signatures. We present new geomorphological mapping and 11 10Be cosmogenic nuclide ages from Northern England (Stainmore Gap, Eden Valley and Vale of York), that constrain regional dynamic ice-stream retreat following the LGM. We identify complex decoupling of competing ice lobes, characterised by early retreat of the North Sea Lobe and a minor re-advance of Stainmore ice prior to ∼20 ka. This was followed by rapid recession of the central Stainmore Gap, which was ice-free by 19.8 ± 0.7 to 18.0 ± 0.5 ka, contemporaneous with the recession of the Tyne Gap Ice Stream. In the southern Vale of Eden, Crossby Ravensworth Fell became exposed between 19.2 and 20.3 ka. The northwards ice-flow reversal in the Vale of Eden was associated with the development of ice domes across the northern Pennines, Howgill Fells and the Lake District. This shift in dispersal centres and ice divide migration likely triggered the rapid collapse of eastward ice stream corridors. The central sector of the BIIS rapidly collapsed back up into upland dispersal centres between 20 and 17.5 ka. This work highlights the role internal factors, such as topography, in driving ice-divide migration and flow switches during externally and climatically forced ice-sheet thinning. • We present data constraining ice dynamics during and after the LGM in the central British-Irish Ice Sheet. • These new data reveal 1561 moraines and 677 new meltwater channels that relate to 108 ice-marginal positions. • We identify the decoupling of the Vale of York and North Sea Lobe ice streams in the Vale of Mowbray prior to 20 ka. • The Stainmore corridor became ice free by 19.8 ka – 18.0 ka. By 17 ka, ice had retreated back into upland ice-dispersal centres. • During thinning, local ice domes became more important, forcing an ice-flow reversal. • Ice now flowed north through the Vale of Eden towards the Solway Lowlands. [ABSTRACT FROM AUTHOR]

To investigate the ability of the onset of Quaternary glaciations to drive an acceleration in erosion rates we compare short timescale (103–104 yr) erosion rates using the in situ terrestrial cosmogenic nuclide (TCN) 10Be to longer time scale exhumation rates (106–107 yr) using the apatite (U Th)/He method in the Presidential and Carter ranges of the White Mountains in New Hampshire, USA. Our results are generally consistent with but refine previous studies using similar techniques. Resulting (U Th)/He ages and thermal modeling from Mt. Washington in the Presidential Range (n = 4, 91.7 to 117.3 Ma) suggest that exhumation rates from the Late Cretaceous to the present were slow, <0.01–0.02 mm yr−1. Be-10 analyses of high elevation bedrock and talus from the Presidential Range (n = 4; 1.5–1.8 km above mean sea level [amsl]; 18–130 ka) and Carter Range (n = 4; 1.0–1.4 km amsl; 14–22 ka) yield exposure ages that dominantly predate the retreat of the last glacial maximum ice sheet (13.9 ka) and indicate inheritance or inefficient glacial erosion of peaks. A non-linear positive relationship between exposure age and elevation suggests a component of elevation dependent polythermal basal ice conditions. A comparison of 10Be concentrations measured in modern fluvial sand and flood deposits in the region (n = 14; 5–19 × 104 atoms g−1 SiO 2) to till (n = 5; ~2–7 × 104 atoms g−1 SiO 2), colluvium (n = 2; 2–7 × 104 atoms g−1 SiO 2), bedrock, and talus suggests that the modern day sediment budget continues to be dominantly sourced from remobilized glacial sediment rather than postglacial weathering. As such, late Cenozoic glaciation and postglacial processes modified existing topography at lower elevations but did not significantly accelerate exhumation rates in the higher elevation regions of White Mountains of New Hampshire. These results refute the idea of a global acceleration in erosion rates resulting from late Cenozoic climatic cooling and glaciation as a result of frozen-based minimally erosive ice cover in conjunction with low rates of tectonic uplift. • Slow background Cenozoic exhumation rates of ≤0.01 mm yr−1 at Mt. Washington. • Insignificant late-Wisconsin glacial exhumation in the White Mountains, NH. • Slow rock uplift and cold-based ice prevent accelerated erosion during glaciation. [ABSTRACT FROM AUTHOR]

The location, longevity, and geographic extent of late Paleozoic ice centers in west-central Gondwana remain ambiguous. Paleovalleys on the Rio Grande do Sul Shield of southernmost Brazil have previously been interpreted as fjords carved by outlet glaciers that originated in Africa and emptied into the Paraná Basin (Brazil). In this study, the sedimentology, stratigraphy, and provenance of sediments infilling two such paleovalleys (the Mariana Pimentel and Leão paleovalleys) were examined in order to test the hypothesis that an ice center over present day Namibia drained across southernmost Brazil during the Carboniferous and Permian. Contrary to previous findings, the facies assemblage from within the paleovalleys is inconsistent with a fjord setting and no clear evidence for glaciation was observed. The facies show a transition from a non-glacial lacustrine/estuarine environment, to a fluvial-dominated setting, and finally to a restricted marine/estuarine environment. Detrital zircon results present a single population of Neoproterozoic ages (c. 800–550 Ma) from the paleovalley fill that matches the ages of underlying igneous and metamorphic basement (Dom Feliciano Belt) and is incongruent with African sources that contain abundant older (Mesoproterozoic, Paleoproterozoic, and Archean) zircons. Furthermore, results suggest that the formation of the paleovalleys and the deposition of their fill were controlled by the reactivation of Neoproterozoic basement structures during the Carboniferous and Permian. The lack of evidence for glaciation in these paleovalleys highlights the need for detailed studies of supposed late Paleozoic glacial deposits. These results are supportive of the hypothesis that well-established glacial sediments on the Rio Grande do Sul Shield (southern margin of the Paraná Basin) may be the product of a separate lobe extending north across Uruguay, rather than a single, massive ice sheet draining west from Africa. • Paleovalleys on the southernmost margin of Paraná Basin are not paleofjords. • The Mariana Pimentel and Leão paleovalleys likely have a tectonic origin. • Sediments from paleovalleys do not have an African provenance. • Separate ice centers are likely for eastern and southern margins of Paraná Basin. [ABSTRACT FROM AUTHOR]

The timing and geographic distribution of glaciers in high-latitude southern Gondwana during the Late Paleozoic Ice Age remain poorly constrained, ultimately precluding our ability to estimate ice volume and associated climate teleconnections and feedbacks during Earth's penultimate icehouse. Current aerial extents of glaciers, constrained by sedimentary flow directions, near exclusively infer paleo-glaciation to be highland-driven and may underestimate potential ice sources in continental regions from which ice sheets may have emanated. Here, we report new U-Pb ages and Hf isotope compositions of detrital zircons recovered from diamictites in two key mid- to high-latitude Gondwanan basins (Paraná, Brazil and Tepuel, Argentine Patagonia). The results indicate regional sediment sources for both basins during the early period of late Paleozoic glaciation evolving into more distal sources during the final deglaciation along southern and western Gondwana. Similar age sediment sourced from diamictites in the Congo Basin, that require an ice center in eastern Africa suggest the possibility of a large ice sheet in this area of Africa proximal to the Carboniferous-Permian boundary, which may have sourced sediments to the Paraná Basin. An inferred distal southern source of glacial sediment for the Tepuel Basin argues for the presence of an ice sheet(s) in the Ellsworth Block of Antarctica towards the end of the glaciation history in Patagonia. These findings indicate an evolution during the Late Paleozoic Ice Age from proximally to extrabasinally sourced sediment reflecting continental-scale glaciation and subsequent drainage from the Windhoek Highlands, Ellsworth Block and an east African source in west-central Gondwana. Coincidence with a long-term fall in atmospheric p CO 2 during the Pennsylvanian to a minimum across the Carboniferous-Permian boundary and a subsequent rise in the early Permian suggests a primary CO 2 -driver for deglaciation in the Paraná Basin. Additional boundary conditions including availability of moisture and paleogeography likely further contributed to the timing of nucleation, growth and demise of these Gondwanan glaciers. • Demise of LPIA associated with shifts in detrital zircon provenance related to glaciation. • Ice centers located in the Ellsworth Block of Antarctica, Windhoek Highlands of Namibia and east Africa. • Deglaciation driven by changes in p CO 2 for the Paraná Basin. [ABSTRACT FROM AUTHOR]

The Yangtze Plain (floodplains in the middle and lower reaches of the Yangtze River) is a region with numerous lakes, including the three largest freshwater lakes in China, i.e. Poyang Lake (PYL), Dongting Lake (DTL), and Taihu Lake (THL). The formation mechanism of these lakes offers insights into the ongoing debate concerning the interaction between tectonic activity, climate, sea-level, human impact, and Earth-surface processes. Previous studies have usually focused on individual lakes, so there remains no over-arching and consistent framework for lake formation in the region as a whole. Here we review published sedimentary and chronological records on the above three lakes and propose that sea-level change has determined their formation. During the last glacial maximum (LGM; ca 30–20 ka), with a sea-level >120 m lower than present, a landscape of incised valleys and interfluves prevailed over the entire Yangtze Plain, including the DTL area, which is >1400 km upstream from the modern river mouth, and there was no large lake on the plain. The lakes emerged in the Holocene, although more precise ages await further investigations. The glacial sea-level lowstand, with concomitant headward incision, was responsible for the extensive deeply incised landscape of the LGM, whereas the Holocene high sea-level, with resultant infilling of the incised valleys, accounted for the formation of lakes. This sea-level forcing hypothesis suggests a more far-reaching influence of sea-level change on the Yangtze Plain, and a closer relationship between Earth-surface processes and glacial–interglacial cycles (global climate) than is commonly believed. According to our newly hypothesized climate-controlled geomorphological (CCG) model, it is very likely that similar lake-forming processes could have occurred multiple times during earlier glacial–interglacial cycles, and that this pattern might also have occurred in many other river systems in the eastern coastal areas of China, as well as in other similar river plains worldwide, thus having an important role in shaping modern coastal-plain landscapes. Further work is required to test this CCG model. • We propose a model that sea level controlled the land surface processes and lake formation in Yangtze Plain. • During glacial period deep-cut landscape prevailed in the plain due to sea level lowering and concomitant headward incision. • Sea level rise after LGM raised Yangtze water level which filled up the incised valleys and depressions to form lakes. • Influence of sea level change on land surface at orbital timescales could be felt >1400 km upstream from the coast. [ABSTRACT FROM AUTHOR]

We defined the bathymetry of Shelikof Strait and the western Gulf of Alaska (WGOA) from the edges of the land masses down to about 7000 m deep in the Aleutian Trench. This map was produced by combining soundings from historical National Ocean Service (NOS) smooth sheets (2.7 million soundings); shallow multibeam and LIDAR (light detection and ranging) data sets from the NOS and others (subsampled to 2.6 million soundings); and deep multibeam (subsampled to 3.3 million soundings), single-beam, and underway files from fisheries research cruises (9.1 million soundings). These legacy smooth sheet data, some over a century old, were the best descriptor of much of the shallower and inshore areas, but they are superseded by the newer multibeam and LIDAR, where available. Much of the offshore area is only mapped by non-hydrographic single-beam and underway files. We combined these disparate data sets by proofing them against their source files, where possible, in an attempt to preserve seafloor features for research purposes. We also attempted to minimize bathymetric data errors so that they would not create artificial seafloor features that might impact such analyses. The main result of the bathymetry compilation is that we observe abundant features related to glaciation of the shelf of Alaska during the Last Glacial Maximum including abundant end moraines, some medial moraines, glacial lineations, eskers, iceberg ploughmarks, and two types of pockmarks. We developed an integrated onshore–offshore geomorphic map of the region that includes glacial flow directions, moraines, and iceberg ploughmarks to better define the form and flow of former ice masses. [ABSTRACT FROM AUTHOR]

• Present stratigraphic synthesis and δ13C carb data from the pre-Sturtian Ugab Subgroup. • Two distinct late Tonian negative carbon isotope anomalies in northwestern Namibia. • Correlation with Ethiopia suggests little truncation beneath Sturtian glacial deposits. The Islay carbon isotope anomaly is a late Tonian negative δ13C excursion that has been documented in marine carbonates globally. It has in the past been thought to be causally linked to the onset of Cryogenian glaciation ca. 717 Ma. However, recent work suggests that this anomaly is instead closer to ca. 739–735 Ma and that it may be one of two distinct late Tonian carbon isotope anomalies. Here we present the litho- and chemo-stratigraphy of the late Tonian Ugab Subgroup of the Otavi/Swakop Group in northwestern Namibia. Carbon isotope data from two separate outcrop belts, the Summas Mountains and the Vrede Domes, indicate that the Ugab Subgroup strata exposed in the former inlier are older than those of the latter, with only approximately 100 m of stratigraphic overlap. We use detailed measured sections to develop a sequence stratigraphic framework for the Ugab Subgroup in each outcrop belt, and correlate strata across the two exposures to construct a composite carbonate δ13C record for the late Tonian in Namibia. This carbon isotope profile of the Ugab Subgroup shows two separate pre-Sturtian negative anomalies, consistent with findings in northern Canada, Svalbard, Scotland, and Ethiopia. Our results are an important contribution to the pre-Cryogenian carbon isotope record, as these data may serve as the first definitive documentation of both anomalies within a single basin. [ABSTRACT FROM AUTHOR]

• Neoproterozoic cap carbonates are discovered on the western margin of North China Craton. • The Zhengmuguan Formation in North China may provide evidence for mid-late Ediacaran glaciation. • High spatial resolution of major, trace and rare earth elements and carbon analysis are used for the interpretation of depositional environments. The late Neoproterozoic Era was characterized by dramatic transitions in climate, including Snowball Earth glaciation, and in the increasing oxygenation state of the atmosphere and oceans. However, late Neoproterozoic glacial deposits are poorly documented in North China. To better understand the Neoproterozoic glacial events in North China, we investigated five sections along a north-south transect across the Helan Mountains capturing a transition from shelf margin to intrashelf basin. This effort revealed an excellent exposure of Neoproterozoic diamictite and associated carbonate succession (Zhengmuguan Formation) on the western shelf margin of North China. Sedimentary features in the diamictite indicate that it might be a glacial sequence partially influenced by sediment gravity flows, with values for the Chemical Index of Alternation (CIA) consistent with cold, arid depositional environment. The overlying carbonate succession is sporadic, with exposures confined mostly to southern areas that disappear to the north. Identification of the Zhengmuguan sequence as a cap carbonate is based on the occurrence of distinctive attributes that are widely found in typical Neoproterozoic cap carbonates around the world. The ∼1.6-m-thick cap carbonate consists of a lower thinly laminated dolomite and an upper thick-bedded dolomite, directly overlying the top of the Zhengmuguan glacial diamictite. Based on field and petrographic observations and high-resolution geochemical analyses of major, trace, and rare earth elements; organic carbon isotopes (δ13C org); and total organic carbon (TOC), we are able to interpret the depositional environments and the possible origin of the cap carbonate. The occurrence of late Ediacaran fossils in the overlying Tuerkeng Formation imply that the Zhengmuguan Formation is mid-late Ediacaran and thus may represent a mid-late Ediacaran glaciation. Our petrographic and geochemical results suggest the Zhengmuguan cap carbonate was initially deposited via glacial meltwater with significant inputs from continental weathering subsequently overprinted by upwelling anoxic deep seawaters along a continental margin. In summary, our data from a poorly known mid-late Ediacaran cap carbonate capture a high-resolution record of shifting climatic and oceanographic conditions of at least regional importance. The uncertainties of these interpretations are high, but the potential importance of these findings justifies the need to publish the data and our conclusions—along with the unavoidable caveats that come with any poorly dated frontier section. [ABSTRACT FROM AUTHOR]

Recent climatic warming has resulted in rapid retreat of glacier margins in the northern hemisphere exposing landforms which record changes in glacier extent and behaviour through their sedimentology and geomorphology. These modern glacial systems can be used as analogues for paleoglacial deposits, such as those found throughout Europe, Canada and the northern USA. Large ice sheets that covered land masses in the northern hemisphere during the Quaternary are known to have hosted fast-flowing ice streams that controlled ice dynamics and behaviour. However, the former positions of these ice steams are difficult to determine in paleoglacial deposits. This study focuses on documentation of sedimentological and geomorphological characteristics of the proglacial fields of western Slettjökull and Öldufellsjökull, northern outlet glaciers of the Mýrdalsjökull Ice Cap in southern Iceland. These glaciers were selected as they have both experienced periodic episodes of fast ice flow and rapid marginal advance (surges) during the last century. It is believed that surging ice margins can be used as analogues for rapidly moving paleoice streams common within the Laurentide and Scandinavian Ice Sheets during the last glaciation. A combination of landsystem analysis, whereby landforms are classified into genetically related landform-sediment assemblages, and architectural element analysis (AEA), a hierarchal method of examining sedimentary deposits, is applied in this study. This methodology allows a detailed model of the process-form relationship of landforms and sediments exposed in front of the retreating glaciers to be created. Initial mapping of the proglacial fields of Sléttjökull and Öldufellsjökull was completed using high resolution digital elevation models (DEM) obtained from the Icelandic Meteorological Office to investigate the types, scale and distribution of glacial landforms. These maps were ground checked in the field using a portable geographic information systems (GIS) unit. Sedimentological data were collected from exposures along river banks and terraces to identify the sediment types associated with different landform types. An unmanned aerial vehicle (UAV) was also used to collect high resolution imagery of the proglacial fields, focusing in particular on areas impacted by the most recent surge events. Field and remotely sensed data were combined into a GIS to examine the spatial relationship between the various landforms and their associated sediments. The proglacial fields of these two outlet glaciers show overall similarities in the distribution and morphology of landsystems tracts connected with end moraine development. However, the proglacial field of Sléttjökull has a larger sandur proximal to the glacier margin and a greater amount of glaciofluvial sediment compared with Öldufellsjökull. The areas of the proglacial fields impacted by surges that occurred in the 20th century show a distribution of landforms that is similar to that described from other surge-type glaciers, including hummocky terrain and kettle holes. However, these proglacial fields lack the prominent glaciotectonized end moraine frequently reported at surge-type glaciers. The model developed for these proglacial fields may be utilized to help identify areas affected by fast-flowing ice and the position of former ice streams in previously glaciated regions. [ABSTRACT FROM AUTHOR]

Marine Isotope Stage 2 (MIS 2) is the latest glacial period and includes the Last Glacial Maximum, which is known as the period when global ice volume reached its maximum and global temperature lower than today. An advantage of MIS 2 is the availability of radiocarbon dating to make it possible to compare sea-level data with other paleoclimatic proxies. However, the number and accuracy of sea-level records during MIS 2 is currently lacking. Here we present the history of MIS 2 sea-level and ice-sheet change as recorded in the Bonaparte Gulf, northwestern Australia, by reconstructing relative sea level and then modeling glacial isostatic adjustment. The isostatically-corrected global sea-level history indicates that sea-level plateaued around 23 cal kyr BP prior reaching its minimum (~19 cal kyr BP). These large changes in ice volume over such a short time indicates that the continental ice sheets never reached their isostatic equilibrium during the Last Glacial Maximum. [ABSTRACT FROM AUTHOR]

The maximal extent of the Laurentide Ice Sheet (LIS) on eastern Baffin Island during the Last Glacial Maximum (LGM; about 20 000 years ago) has been widely debated during the last decades as different palaeo-glaciological models have been proposed. Spatial and temporal variability of ice sheets extension during Quaternary glaciations complicate the establishment of a reliable reconstruction of the ice margin. Furthermore, the lack of geophysical data in most of the fjords, and seaward, makes it difficult to reconcile the proposed terrestrial and marine glacial margins. Here we use high-resolution swath bathymetry imagery, combined with acoustic stratigraphy data and sediment cores collected during various oceanographic expeditions, focusing on the ice dynamics in the area of Clyde Inlet since the LGM. Our data reveal possible positions of the maximal extent of the LIS near the continental shelf edge. The deglaciation on the shelf was rather slow and episodic, as indicated by the presence of grounding-zone wedges, recessional moraines, as well as time-transgressive glacial lineations. Ice retreat in the fjord occurred more rapidly, most likely due to increased water depths. However, the presence of multiple moraine systems reveals periods of ice-margin stabilizations. This study provides additional information to the terrestrial data and, thus, helps improve the models of glacial dynamics in the northeastern sector of the LIS. [ABSTRACT FROM AUTHOR]

A complex ice stream network occupied the European Alps during the last glacial maximum (LGM, MIS 2, Würmian Pleniglacial) with large valley glaciers extending as piedmont lobes into the northern and southern forelands. A completely different situation is reported for the easternmost Alps, where only a patchy pattern of isolated glaciers, confined to minor valleys, localized cirques and small plateaus could develop. Although the Alpine LGM glaciation was intensively studied, data sets vary considerably in the easternmost Alps (e.g concerning the numbers of local glaciers as well as extents) and systematic analyses of the glacial record are missing for the entire region. Consequently, equilibrium line altitudes (ELAs) and ELA depressions (ΔELAs) for these paleo glaciers remain unknown as well, though such data can be extremly useful to provide information on the variance of atmospheric circulation patterns over glacial to interglacial timescales. Characterized by relatively simple geometries and obviously rather simple source area relations (compared to the ice-stream network in the central Alps), they are most suitable for paleo-glacier reconstruction and ELA modelling – and can provide a robust dataset on ELA depression variabilities during the LGM. Such analysis is hardly possible for the ice-stream network occupying most of the central Alps at the same time.To fill this gap, we provide a new GIS-dataset of the LGM glaciation at the Eastern Alps based on the principal work of van Husen (1987), a number of case studies, geological maps, and the analyses of multiple orthophoto and DEM data. First systematic analyses on ELAs and ELA depressions of these low elevated isolated glaciers highlight the highly variable glacier response across the Eastern Alps to topographic and climatic forcing. [ABSTRACT FROM AUTHOR]

Located between Melville Peninsula and northwestern Baffin Island (69.9247° N, 84.5121° W), the Fury and Hecla Strait region plays a key role in the understanding of the postglacial evolution of the Canadian Arctic. The absence of paleolimnological data in the region as well as the strategic position of the strait itself, given its location at the junction of the Atlantic Ocean currents coming from Foxe Basin and those of the Pacific Ocean through the Gulf of Boothia, make it a prominent region for Quaternary research. Although some studies have suggested a timing for the regional deglaciation, results remain extrapolated and do not provide high-resolution data for the region. This project aims to analyze sediment cores of lakes located on the southern shore of the Fury and Hecla Strait, in the Canadian Arctic, in order to reconstruct past climates and landscapes since the end of the last glacial period. A multi-proxy approach based on physical, chemical and biological core parameters, allowed high-resolution paleoenvironmental reconstructions of the region, including natural climate fluctuations, past extreme climate events and major landscape changes induced by glacial retreat, marine inundation and glacial isostatic readjustment.Various radiometric dating methods (210Pb, 137Cs and 14C) were used to establish a chronology for the reconstructed changes, pointing towards a glacio-marine phase that lasted from 8250 cal. BP, at its latest, to 6675 cal. BP, followed by a gradual transition towards freshwater conditions and the establishment of a lacustrine phase at 6125 cal. BP. An extreme event, marked by major geochemical and sedimentological shifts, also appears to have happened at 3950 cal. BP, but the nature of this abrupt change remains unknown. The results were also correlated with regional temperature data from previous studies to explore the relationship between diatom assemblage changes and environmental fluctuations. This study is crucial to respond to many unsolved questions in oceanography, biogeography, genetics or even anthropology, by providing a high-resolution chronology of geophysical changes, namely regional deglaciation and the opening of the strait. Furthermore, it improves our understanding of paleoenvironmental variability in the Foxe Basin throughout the Holocene, including climatic and physico-chemical shifts, enabling us to predict ecosystem responses to future global change. [ABSTRACT FROM AUTHOR]

Although it is well documented that the late Paleozoic experienced one of the most severe ice ages of Earth's history, the exact timing and frequency of glaciations is still debated. This is in part due to the difficulty of accurately dating glacial deposits that are often barren, with no faunal recovery, and riddled with stratigraphic hiatuses. In order to circumvent these limitations, one alternative way to reconstruct the evolution of grounded ice volume during the Early Carboniferous is to use far-field reconstruction of eustatic sea-level fluctuations.In this study, we report on a detailed sedimentological investigation of Early Carboniferous strata from Western Libya. In the Late Paleozoic, this region was part of the Saharan platform, on the Northern margin of Gondwana, that formed a widespread, extremely low-angle, tectonically stable ramp. During the Early Carboniferous, extensive and thick exposures of siliciclastic-dominated sediments were deposited along a N-S orientated outcrop belt, parallel to depositional dip.A total of 4800m of sedimentary section was logged over a ca. 400km-long transect. Fieldwork observations and integrated subsurface data allow establishment of a detailed sequence stratigraphic framework. During the Tournaisian, Visean and Early Serpukhovian, six lowstand system tracts are identified, composed of incised valleys filled with fully amalgamated fluvial sandstones, capped by open marine packages. These incised valleys can reach a thickness of 50m. Given that they are embedded within shoreface to offshore marine deposits, total sea-level fluctuations of at least 70-80m can be estimated from these deposits. Due to the stable tectonic nature of the Saharan Platform during the Early Carboniferous, glacio-eustasy is the most-likely explanation for the origin of the observed scale of sea-level fluctuations, pointing at the onset of incipient Late Paleozoic glaciation during the earliest Visean. This is compatible with published evidence of Visean glacial deposits in Southern Sahara and South America, further inland on the Gondwanan margins. Ice sheet retreat is probably the mechanism responsible for contribution of the large volume of coarse continental clastics that initially fill the valleys exclusively with fluvial facies, preserved by the followed rapid transgression associated with ice melt.In line with paleotemperature reconstruction, our study indicate that the Late Paleozoic Ice Age has started prior to what is generally depicted in the literature. The location of the study area, on a stable passive margin, provides confidence in the mechanism controlling the incision, and the results provide improved resolution that offers an insight into the scale and frequency of glacial cycles in the Visean. [ABSTRACT FROM AUTHOR]

Glacial cirque landforms are the result of glacier erosion on mountain ridges and they are repeatedly activated on every glaciation. Cirque distribution is largely determined by climatic patterns during periods of glacier initiation, whilst their dimensions are largely determined by glacial erosion over tens of thousands of years (continued in successive glacial cycles), which is likely maximised during the onset and termination of periods of glaciation (Barr and Spagnolo 2015). Glacial cirque morphometry has been widely used in revealing glaciation climatic patterns (Barr et al. 2017).In this contribution, the ACME GIS toolbox for ArcGIS (Spagnolo et al. 2017) was used to calculate glacial cirque morphometry in manually mapped glacial cirques N and NW of the Iberian Peninsula. Given that several mountain areas in N and NW of Iberian Peninsula are below the regional Late Quaternary ELA, only areas were Quaternary glaciation has been identified and described were used. A total of 445 cirques were mapped. A 5 m. pixelsize national DEM provided the surface data. The amount of cirque population makes us confident enough to dismiss the influence of topography, lithology or geological structure on the statistically relevant results.Results show an unsurprising NW-SE cirque floor altitude increase pattern, which is concomitant to Quaternary ELA distribution. Cirque orientation shows a N-NE preference, which we interpret as temperature-driven, confirming that glaciation was marginal during a long period of the Quaternary. Cirque depth and shape shows larger, deeper and rounder cirques located in mountain ranges well above the ELA, where cirques have been active for longer. Glacial cirque morphometry has proved to be valuable as palaeoenvironmental tool only if a large population of cirques is considered. The study area for this contribution -the entire Cantabrian Range- and the amount of cirques mapped, can be seen as a minimum thresholds for achieving reliable conclusions. Therefore, only through the use of automatic calculation methods, these studies can be performed in a cost-effective way. I would like to stress the possibilities that ACME has for morphometric analysis on glacial and non-glacial landforms, such as cirques, drumlin, esker, landslides or meanders. Also, I would like to point to automatic or semi-automatic mapping tools as the way forward in the geomorphological mapping research field. [ABSTRACT FROM AUTHOR]

We present a geomorphological assessment of the extent and dynamics of glaciation in the Wicklow Mountains, Ireland, during the Last Glacial Interglacial Transition (LGIT; ~ 20 – 11 ka BP). Previous research has established the existence of a local ice cap, confluent with regional ice at the Last Glacial Maximum (LGM; ~ 25 ka BP). However, there has been little consideration of ice retreat in response to climate amelioration during the LGIT. Here, we investigate ice dynamics during and after the transition from an ice cap to topographically restricted mountain glaciation. The geomorphological record indicates that initial ice cap recession was characterised by rapid retreat and large-scale disintegration, with ice masses only stabilising once topographically constrained within valleys. Following fragmentation of the LGM ice cap, three distinct landsystems were established in the Wicklow Mountains: (1) the large north-eastern sector of the region hosted a mountain icefield with multiple outlet glaciers; (2) a small plateau icefield existed in the central sector, with several outlet glaciers; and (3) several individual valley glaciers persisted in the south-western sector. Each of these landsystems document sustained retreat and subsequent stabilisation during the LGIT, prior to the Younger Dryas. Two-dimensional reconstructions of ice dynamics indicate variations in recession patterns throughout the region. Based on our ice margin reconstructions and the limited published dates for the region, we suggest that following the retreat of regional ice after the LGM, the local ice cap was relatively stable until the start of the LGIT (~20 ka BP). After this, ice experienced sustained thinning and ice margin retreat until ~ 17 ka BP. By this point, ice was topographically restricted and the three aforementioned landsystems established. A period of ice margin stabilisation occurred before further persistent retreat until ~ 15 ka BP, by which time ice had retreated into the upper reaches of valleys. It is likely that the plateau icefield and most of the mountain icefield had disappeared by ~15 ka BP, when the outlet glaciers of both landsystems had detached from their central accumulation areas and experienced sustained retreat. Following this, some small cirque glaciers experienced minor readvance before ice recession continued. The geomorphological record indicates that it is likely that glacial ice disappeared in the Wicklow Mountains during this period but was re-established, in a small number of cirques, during the Younger Dryas. [ABSTRACT FROM AUTHOR]

High-latitude trough mouth fans are high-resolution paleoclimate and ice-sheet monitors, and allow a continuous reconstruction of climate and sedimentary processes active during glacial-interglacial cycles. The North Sea Fan is located on the northern North Sea margin and is built-up by c. 40,000 km3 of sediments dominated by the erosional products of the Norwegian Channel Ice Stream. The aims of this contribution are (i) to characterize the sediments deposited in the North Sea Fan, and (ii) to do a three-dimensional reconstruction of the processes involved into the formation of the North Sea Fan. We use 16,000 km2 of high-resolution processed 3D seismic data collected in 2017 and 2018 from the proximal North Sea Fan. These data allow us to image the shallow subsurface in a resolution of 8 m vertically and 20 m horizontally. Fifteen horizons have been picked with an in-line spacing of 150 m, followed by gridding, horizon attribute extraction, sediment volume calculations, and seismic geomorphological interpretation. Our results show that six sediment packages containing stacked glacigenic debris flows (GDFs) have been deposited at the upper slope of the North Sea Fan. The GDF package related to the last glaciation has a thickness of up to 400 m and is characterized by a homogenous seismic facies intercalated by five continuous high-amplitude reflections, which separate the package into six sub-units. The structure maps of these reflections show multiple sharp, SE-NW-oriented channels with well-developed levees and densely-spaced pockmarks. The GDF deposits have been removed from the upper slope by four megaslides, which are identified as deformed sequences bound by smooth lower and irregular upper surfaces. Negative-amplitude, continuous reflections at the base of the megaslides fade out uphill of the slide headwalls. The topography shaped by these megaslides is infilled by glacimarine deposits identified as low-amplitude, continuous reflections. Continuous reflections with mounded geometries, interpreted as contourites, characterize the deepest part of the fan. The GDF packages show that the Norwegian Channel Ice Stream reached the shelf edge during six marine isotope stages, and that the ice stream oscillated six times during the last glaciation. The up to 400 m thick GDF package related to the last glaciation has been deposited within 4 kyr, which correlates to a sedimentation rate of up to 100 m/kyr, and a sediment flux of 1500 km3/kyr for the study area. Channels identified at multiple levels within the GDF package indicate that the sediment delivery from the Norwegian Channel Ice Stream to the slope was continuous and did not occur in pulses of several decades. Channel-fed levees and debris lobes characterize the paleo-seafloor between the channels. The circular depressions, interpreted as pockmarks, indicate fluid escape events in some intra-channel areas during the deposition of the GDFs. Negative, high-amplitude reflections below the GDFs and megaslides indicate gas-charged sandy bases and show a strong correlation between pre-conditioned glacimarine glide planes and megaslide occurrence. Contourites at the base of the fan indicate different oceanic processes dominating the early Quaternary deposition. [ABSTRACT FROM AUTHOR]

Mars' present climate is extremely cold and arid. Until recently, it was widely thought that debris-covered glaciers in Mars' mid-latitudes have been pervasively cold-based since their formation 10s–100s Myr ago. However, we recently discovered eskers associated with ~110–150 Myr old glaciers in the Phlegra Montes [1] and NW Tempe Terra [2] regions of Mars' northern mid-latitudes. Eskers are sinuous ridges comprising sediments deposited in glacial meltwater conduits. Therefore, eskers associated with existing mid-latitude glaciers on Mars indicate that localised wet-based glaciation did occur during Mars' most recent geological period. Eskers are important tools for reconstructing the nature, extent, and dynamics of wet-based glaciation on Earth, and have similar potential for Mars.We used 1–2 m/pixel resolution digital elevation models derived from 25–50 cm/pixel High Resolution Imaging Science Experiment stereo-pair images to measure the planform and 3D morphometries of the Phlegra Montes and NW Tempe Terra eskers, and compare them with the morphometries of Quaternary-aged eskers in Canada [3] and SW Finland [4]. We found that the Martian eskers have remarkably similar lengths, sinuosities and heights to terrestrial eskers, but that the Martian eskers are typically wider and have lower side slopes. Large width-height ratios of the Martian eskers are consistent with our previous measurements of ancient (~3.5 Ga) eskers close to Mars' south pole [5], and may arise from differences in either: esker degradation state, or fundamental glacio-hydrological controls on esker formation between Mars and Earth. Portions of the two Martian eskers with comparable crest morphologies (e.g., sharp- or round-crested) have similar width-height relationships, suggesting that glacio-hydrological processes may exert controls upon the observed relationships between esker morphology and morphometry.Our morphometric analyses also reveal that the Martian esker in NW Tempe Terra has a 'stacked' morphology: the crest of a wide, round-crested underlying ridge is superposed by a narrow, sharp- to multi-crested ridge. Based on morpho-sedimentary relationships observed along terrestrial eskers [6], we interpret this transition to represent waning sediment supply and meltwater discharge towards the end of the esker-forming drainage episode(s). Direct sedimentary insights into Martian eskers are not yet possible so we emphasise that such inferences should be rigorously grounded in observations of analogous landforms on Earth.This work was funded by STFC grant ST/N50421X/1.References: [1] Gallagher, C., and Balme, M.R., (2015), Earth. Planet. Sci. Lett. 431, 96-109, [2] Butcher, F.E.G., et al. (2017), J. Geophys. Res. Planets. 122(12), 2445-2468, [3] Storrar, R.D., et al. (2014) Quat. Sci. Rev. 105, 1-25, [4] Storrar, R.D., and Jones, A., Unpublished, [5] Butcher, F.E.G., et al. (2016), Icarus 275, 65-84, [6] Burke, M.J., et al. (2010) Geol. Soc. Am. Bull. 122, 1637-1645. [ABSTRACT FROM AUTHOR]

The high-altitudinal plateaus of Jotunheimen in central South Norway, the mountain region home of Norway's highest summits, create a unique and diverse natural environment. The specific gross morphology of Jotunheimen facilitates the occurrence of a variety of periglacial landforms ranging considerably in both dimension and age. The regional distribution of permafrost is one of the major controlling factors for the altitudinal distribution of these periglacial landforms. The largest individual features of patterned ground, undisputed the regionally most dominant periglacial landforms, are situated on terrain currently underlain by permafrost. They visually appear to be quite relict, despite the occurrence of permafrost, and the exact timing of their formation remains unknown. This example points to additional factors significantly influencing the periglacial landform assemblage, like topography, ground moisture availability, and the local deglaciation history. The lack of a regional overview regarding periglacial landforms in Jotunheimen exacerbates the need for a profound investigation of their altitudinal zonation and potential causal links to climate, permafrost, (de-)glaciation, and other factors.The compilation of a regional overview based on aerial imagery and a literature review aims, therefore, to reveal further insight into the controlling factors for and mechanisms of periglacial landform development in Jotunheimen. This shall be achieved by creating an altitudinal zonation for periglacial features and highlighting causal links between their spatial/altitudinal distribution and possible influencing factors. In an outlook to future studies this attempt may also provide more detailed information on the regional basal properties of the former Scandinavian ice sheet, the regional/local deglaciation patterns for the Jotunheimen region, and about the exact chronology of formation of the periglacial landforms studied. [ABSTRACT FROM AUTHOR]

Aim of the research: In general, marine terraces are covered by later non-marine deposits and difficult to obtain former shoreline using disturbed terrace surfaces. Precise determination of the former shoreline could be obtained from geological analysis of marine terrace deposits. Numbers of tight drilling have done to establish new method for terrace analysis.Study area and geology: Japan Sea side margin of the Shakotan Peninsula and the southern region, Hokkaido, Japan. MIS5e Marine Terrace deposits which are mainly composed of well sorted shore sand and gravels associated with volcanic ash, Toya (erupted about 115,000 years ago) in the upper most part of the deposits. The terrace deposits (1 to 4m) are covered by thick talus deposits (5 to 30m) formed by periglacial process.Method of terrace analysis: 7 sections across the MIS5e Terrace were selected. 4 to 8 tight drilling in individual sections, total numbers of 32(total length 456m) drilling have done. Buried wave-cut bench and sea cliff are reconstructed by distribution of the terrace deposits and the precise site of former shoreline was obtained.Results: Obtained altitudes of the former shoreline from the 7 sections are about the same 25m. Our research proofed that the MIS5e terrace surface is not inclined in the study area and the previous study was misinterpreted by the cover of talus deposits. In some areas, we were recognized three peat layers from drilling cores. The deposition rate obtained from the depth of some peat layer and the 14C dating value is approximately 0.3mm / yr. Events in the last glacial period were recorded. [ABSTRACT FROM AUTHOR]

Loess deposits cover 10% of the world continental surface and larger parts in Eurasia but are really limited in Mediterranean areas. In the Iberian Peninsula it has been described mainly in the central Tagus basin and in the Eastern Ebro basin besides other minor outcrops (Andalucia, la Mancha, Girona). These loess deposits have a great potential for climate interpretation that can illustrate environmental changes during the glacial cycles and record past global atmospheric mineral dust dynamics and palaeoenvironmental changes in the Mediterranean. The contribution of this work is to identify with more detail the distribution of loess in the Eastern Ebro basin to the boundary with the Prelitoral Catalan System, as a first step to locate their source areas and to understand their formation conditions and pedogenesis. The spatial distribution of loess outcrops is highly discontinuous over a surface of 2500 km2, and therefore it may be considered as the largest loess region in the Iberian Peninsula. These loess deposits overly the Tertiary sediments and the Quaternary terraces of the Central Ebro Valley and the Eastern Móra d'Ebre basin. Representative profiles with primary loess have been determined for the macromorphological characterization of the deposit. Samples were obtained for physico-chemical, particle-size, micromorphological analyses and OSL dating. From several possible source areas, samples were collected from terrace T2 of the Ebro River and from nearby tributaries (Cinca, Segre). Samples were also taken from Tertiary materials for textural analysis, grain-size distribution and heavy mineral analysis, to be compared with loess samples. The studied deposits are very sandy, formed by homogeneous silt and fine sands, are very porous and they form highly stable slopes. The particlse are composed of quartz (40-50%), calcite (30-40%) and other minerals as feldspars, biotites and muscovites besides accessory minerals. These sediments are carbonated (around 38% calcite) and contain very little organic matter (<0.05%). To the West of the area some outrcops contain gypsum (up to 28%). The relatively coarse grain size, mineralogy, distribution and depth indicate that the potential source areas are not very far, with a W-NW wind direction. They are probably found at alluvial valleys of the Central basin or at Chiprana endorheic basins and surrondings, where deflaction areas are found. The age of the deposits can be classified into two groups. Most of them were formed between 17-34 ky, which correspond to the cold Heinrich phases 1, 2 and 3 of the last Maximum (LGM). In a few cases older outcrops, with ages older than 115 ky, were probably deposited at the end of the penultimate glacial period and underwent pedogenesis during the Eemian warmer period. [ABSTRACT FROM AUTHOR]

The waterways and the portages connecting them played a huge role in the settlement and economic development of forest landscapes of the vast territory of the Center and the North of the Russian Plain. Since VIII - XI centuries, water transport and trade routes have been formed: "The Great Volga Route", "From the Varangians to the Greeks", Severodvinsk way and others.It was possible to move from one river basin to another in forest areas on the interfluves only by the shortest paths between the upper reaches of the rivers - the places of the transitions - portages, where boats, ships and cargoes were moved on dry land. The main signs of the direction to the portages on the forested difficult terrain were large boulders or their clusters, and with the adoption of Christianity, so-called "portage" crosses.The landscape analysis of the location of the portage pathways in the northern part of the Russian plain showed that most of them were confined to the nodal sections of the network of troughs of the glacial water flow in the marginal regions of the Quaternary glaciation. Currently, these areas are also the main watersheds of almost all the river systems of the Russian Plain. The portages were laid along small troughs of the runoff of glacial waters ("through valleys" or "inter-basin overflows"), occupied by residual lakes or upland bogs. These hollows connected the larger troughs of the runoff, in which, in the late glacial period, the upper reaches of the rivers were actually laid.Stone crosses were set as landmarks on waterways on key portages. These original traffic signs were created from granite, sandstone, limestone and other local materials with an average height of 1 to 2 m. One of the most famous crosses of the chronicles: Ignach cross (set no later than in 1238), which was on the watershed section of the "Seregersk waterway" on the Novgorod land. In 2003, a memorial sign was erected on its place on the territory of the Valdai National Park. The Sterzhensk cross on the Tver land (dated 1133) was established as a pointer to the confluence of the river Volga into the lake Sterzh. Today, the Sterzhensk cross is located in the Tver regional natural history museum. The portage crosses of the IX – X centuries are in the expositions of local history museums in the town of Ostashkov (Tver region) and in the town of Polotsk (Belarus). A unique stone landmark cross is kept in the Church of Mary Magdalene in the village of Parichi of the Svetlogorsk district in the Gomel region (Belarus). There are crosses that were preserved in their historical places of origin: for example, the portage cross at the Malskoye lake, which is 4 km from the town of Izborsk (Pskov region, Russia). At present, these monuments are reliable witnesses to the development of ancient waterways and are valuable objects of the natural and cultural heritage.The work is performed under the project of Russian Foundation for Basic Research № 19-05-00233, № 18-311-00222 [ABSTRACT FROM AUTHOR]

Producing three-dimensional palaeoglaciological reconstructions of discrete ice masses hasbeen the focus of many glacial geomorphological studies in the Scottish Highlands over thepast 15 years or so. Despite this, understanding of the extent, style and timing of Quaternaryglacier fluctuations in Scotland remains incomplete. This is exemplified by the enigmatic andcontentious Gaick (or Gaick Plateau), a dissected upland plateau in the Central Grampians.Previous studies of the glacial sediment-landform assemblages in this area have resulted inwidely-differing and conflicting interpretations, although the 'generally-accepted&#x2019;model is one of extensive plateau icefield glaciation during the Younger Dryas(∼12.9–11.7 ka). We present the results of renewed, systematic geomorphological andsedimentological investigations in the Gaick. Using a glacial landsystems approach,morphostratigraphic principles and 'glacierisation threshold&#x2019; analysis, we establish thatthe area experienced only spatially-restricted plateau icefield glaciation during theYounger Dryas. This contrasts starkly with the widely-held view that the Gaick wascovered by an extensive plateau icefield during the Younger Dryas. We use thegeomorphological evidence, together with surface profile modelling, to produce athree-dimensional reconstruction of a ∼42 km2 Younger Dryas plateau icefield. Thisnewly-reconstructed icefield is then used to derive palaeoclimatic variables for theYounger Dryas and assess regional climate trends across Scotland during that period. [ABSTRACT FROM AUTHOR]

Located in Asia where Russia, China, Mongolia, and Kazakhstan share a border, the Altai Mountains are composed by high ranges peaking at 4,506 m (Belukha), still glaciated large plateaus and deep valleys. With more than 1000 km², the Altai glaciers represent 50 % of the glaciated area of North Asia. Although because of repeated occurrences of glacial megafloods during the Pleistocene have been intensively studied in Russian Altai, the chronology and extent of its glaciations are poorly understood compared to other Central Asian regions.In relation with archaeological researches developed by the Russian-French team ARTEMIR, we investigated the upper Kalguty basin located in the south-eastern part of the Ukok Plateau, Russian Altai. Along the border with Mongolia, the elevation of this very dry area (100 mm/a) ranges from 2300 to 3500 m. Although current glacier area is < 0.25 km², many glacial landforms allow reconstructing past glaciations in the upper Kalguty basin. A detailed geomorphological study was carried out on the field in July 2015, and rock samples were taken on scoured bedrock and erratic boulders at one key site for surface exposure dating using in situ-produced cosmogenic nuclides.The maximal extent of the Kalguty valley glacier in the upper basin occurred shortly before 20.9 ka. As evidenced by moraines and kame terraces located higher on one valley side, larger and earlier, but not dated, glaciations occurred prior to the ~21 ka Kalguty Glacier advance. On the other hand, three morainic complexes testify to smaller advances corresponding to a reduced Kalguty glacier and two smaller valley glaciers. Reconstructed ELAs of these former glaciers were used to infer their Late Glacial extents ages and the corresponding regional palaeoclimatic conditions. The results regarding the chronology and extent of the Kalguty Basin glaciations since the LGM are discussed by relating them to other regional studies in the Altai Mountains and Central Asia. [ABSTRACT FROM AUTHOR]

Last Glacial Maximum reconstructions of former glacier in the European Alps shows large ice expansion on the northern side of the Alps, with wide piedmont lobes spreading over lowlands (synthese in Ehlers et al., 2011). The general chronological outline of the LGM in the Alps suggests a fairly synchronous glacial maximum around 26-20 ka (marine isotope stage 2; Wirsig et al., 2016), in line with global data from the Northern Hemisphere. However, a long lasting debate persists in French Alps regarding the timing of the Late Pleistocene maximum ice lobe extent in the Lyon area, varying from MIS 2 to MIS 4 based on indirect and contradictory radiocarbon ages (Mandier et al., 2003) and field constraints (Monjuvent and Nicoud, 1988). This debate was further rekindled by recent alpine ice modelling studies (Becker et al., 2016; Seguinot et al., 2018).A clear and robust chronological constrain of the Lyon glacial lobe extent is now critical as it would have major implication in terms of our understanding of past atmospheric circulation patterns. Traditional dating techniques such as radiocarbon and cosmogenic nuclides exposure are challenging in this area due to the scarcity of organic material incorporated within glacial deposits and the huge scarcity of in-place moraine boulders. In these circumstances, Optically Stimulated Luminescence (OSL) techniques, which allow the dating of buried sedimentary material, offer a promising alternative. In this study, we propose a new chronological reconstruction of the Lyon Lobe maximum extent during the Late Pleistocene. This chronology is based on new OSL data measured from fluvio-glacial deposits located in presently dry valleys only active during the Late Pleistocene maximum extent of the Lyon Lobe. Our preliminary results suggest that in fact, two major phases of glacial advance of similar extent occurred during the Last Glacial cycle, around the MIS 2 and around the MIS 4. These results not only bring a fresh contribution to the debate of the local paleoglacial history in the French Western Alps but may also have significant implications in terms of Late Pleistocene glaciations pattern and paleoclimate evolution in the Alps. [ABSTRACT FROM AUTHOR]

Research on mountain glaciations has a long history and in the light of current global change, they are increasingly recognised as highly important palaeoclimatic archives for the immediate and more distant geological past. One of the most important leaps forward with the investigation of mountain glaciations during the past 2 decades was substantial improvement achieved within the field of numerical age dating techniques, in particular progress of surface exposure dating using cosmogenic radionuclides (CRN). This development has definitely given the entire research field new momentum. Unfortunately, this methodological progress is in many cases not matched by the recommended necessary level of precautions regarding the interpretative steps with the reconstruction of Holocene glacier chronologies. Improved precision and accuracy with numerical dating techniques comes often with an increasing lack of attention with the geomorphological analysis of the dated landforms. With recent studies it has subsequently become more popular to outline moraines primarily based on individual CRN boulder age clusters without detailed geomorphological mapping or examination. Such an attempt has also been conducted on Holocene glacier forelands in Aoraki/Mt.Cook National Park where a substantial number of CRN boulders ages have been employed to identify and label numerous "moraines". Subsequently, arithmetic means of CRN ages for these apparent "moraines" were linked to individual glacier advances and palaeoclimatically interpreted accordingly. A sound geomorphological analysis of the studied glacier foreland does, however, reveal that this procedure is actually erroneous. Among the problems identified are (a) inclusion of hugely overprinted moraine remnants that lack proper characterisation, (b) wrong subdivision of moraine segments belonging to one defined individual moraines, and (c) mismatching of apparent CRN ages for moraine segments that morphologically need to correspond for any meaningful reconstruction of former marginal positions. A revision of this particular glacier chronology provides major implications for any subsequent palaeoclimatic interpretation as the number of reliably documented neoglacial events decrease from 9 to 5.The value of geomorphological analysis in the context of investigating mountain glaciations is, however, not primarily restricted to chronological approaches. It may also provide assistance with the conceptual context for mechanisms of deglaciation patterns or long-term landscape evolution. In the upper Waimakariri River catchment following a Late Glacial readvance dated to c. 17.5 ka ago, a lake dammed by the related moraine system and debris-covered dead ice should have existed for many centuries before it subsequently drained. That lake would naturally have influenced both the immediate deglaciation mechanism and landform evolution post-LGM. Despite introduced during the 1950s, the concept of this particular palaeo-lake has never been exposed to any detailed geomorphological analysis yet. Whereas the existence of a post-LGM palaeo-lake itself remains out of question, the proposed link to glacier retreat following a Late Glacial re-advance is unrealistic in light of a logical time sequence for individual elements of the local landform assemblage. The lake needs to be younger and postdate Deglaciation in this section of the Waimakariri River.Summarising, detailed geomorphological analysis is indispensable with any attempt to investigate mountain glaciations. [ABSTRACT FROM AUTHOR]