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A new [sup.10]Be data set from a small glacial catchment in the Pyrenees confirms almost full glacier extent during Marine Isotope Stage (MIS) 2, extends the oldest cosmogenic exposure ages of moraines in this mountain range to MIS 5, and constrains paleoclimate reconstructions in the Mediterranean region. It also illustrates the advantageous conditions for the long-term preservation of terminal moraines provided by small, low-gradient glacier catchments that did not merge with compound ice masses even during glacial maxima. These small, gently sloping, and isolated glacier catchments are proposed as priority targets for terrestrial cosmogenic nuclide dating of peak Pleistocene glacier advances, providing scope for greater accuracy in interregional paleoclimatic correlations. doi: 10.1130/G31164.1

We present ground-penetrating radar (GPR) profiles that reveal the sedimentary architecture of an esker deposited during a surge-associated outburst flood at the Bering Glacier, Alaska. The wide, up-flow end of the esker contains a transition from large backset beds to large foreset beds interpreted to reflect composite macroform development in an enlarged part of the conduit. By contrast, the narrow, down-flow portion of the esker is dominated by plane beds interpreted to have been deposited where the conduit was constricted and the flow was faster. A previously studied outburst esker at Skeioararjokull, Iceland has a similar morphology and stratigraphic architecture. This suggests that outburst floods generate distinct depositional signatures in eskers, both in terms of morphology and sedimentary architecture. Identification of these distinct signatures in ancient eskers will help assess the paleohydraulic conditions under which ancient eskers formed and, by extension, the nature of meltwater drainage systems beneath the Laurentide and Eurasian ice sheets. doi: 10.1130/B30008.1

Time was, saying something moved 'at a glacier's pace' meant it was grindingly slow. No longer. Glaciers don't move like that anymore. Since, the early 1990s, glaciers in Greenland have [...]

Well-preserved submarine landforms from the continental shelf and fjords of northwesternmost Svalbard provide an example of ice-sheet deposition in an inter-ice-stream setting. EM1002 swath-bathymetric imagery covering 1280 [km.sup.2] was examined. At the shelf edge, a distinctive and continuous belt of hummocky topography represents the grounding zone of a slow-moving Late Weichselian ice sheet. Active ice on the outer shelf is inferred from subtle lineations orientated parallel to flow. Low-amplitude transverse moraines crosscut the lineations, suggesting ice retreat across the outer shelf with brief stillstands. On the middle and inner shelf, large moraine ridges indicate multiple stillstands during deglaciation. There are arcuate moraine ridges at fjord mouths. Streamlined crag-and-tail landforms are preserved from when active full-glacial ice flowed out of the fjords. Clusters of smaller transverse ridges indicate slow retreat of grounded ice through the fjords. Holocene sedimentation is by rainout from sediment-rich meltwater, producing smooth basin fill. Small slides from the fjord walls are common. Little Ice Age glacier readvance produced another set of terminal moraines and smaller retreat moraines in the innermost fjords. A schematic model of this inter-ice-stream glacial landform assemblage summarizes the geomorphic record. It is compared with a model derived from several Svalbard cross-shelf troughs occupied by fast-flowing Late Weichselian ice streams. In general, the seafloor morphology of continental margins affected by ice streams is dominated by streamlined, subglacially produced landforms oriented in the former ice-flow direction, interrupted by major grounding-zone wedges formed during temporary halts in ice retreat. By contrast, between ice streams, shelf and fjord morphology records submarine landforms of various dimensions oriented mainly transverse to ice flow, produced at slowly retreating, grounded icesheet margins. There is little evidence for channeled subglacial water flow in the form of eskers and ice-contact fans on the Svalbard margin, implying that basal water is drained or advected mainly within soft subglacial sediments.

An active microbial assemblage cycles sulfur in a sulfate-rich, ancient marine brine beneath Taylor Glacier, an outlet glacier of the East Antarctic Ice Sheet, with Fe(lll) serving as the terminal electron acceptor. Isotopic measurements of sulfate, water, carbonate, and ferrous iron and functional gene analyses of adenosine 5'-phosphosulfate reductase imply that a microbial consortium facilitates a catalytic sulfur cycle. These metabolic pathways result from a limited organic carbon supply because of the absence of contemporary photosynthesis, yielding a subglacial ferrous brine that is anoxic but not sulfidic. Coupled biogeochemical processes below the glacier enable subglacial microbes to grow in extended isolation, demonstrating how analogous organic-starved systems, such as Neoproterozoic oceans, accumulated Fe(II) despite the presence of an active sulfur cycle.

Author(s): Tanguy Bertrand [1]; Franois Forget (corresponding author) [1] Pluto has a variety of surface frosts and landforms as well as a complex atmosphere [1]. There is ongoing geological activity [...]

This article discusses the terminological and disciplinary problems associated with the point of view that ice is a rock, resulting from a dynamic development of earth sciences which have begun the research into other planets as well. Such a position necessitates a revision of the definitions of the hydrosphere, atmosphere and lithosphere. It is the state that determines which particular sphere ice belongs to. Water is understood to be a triphase substance. As a result permafrost should now include the 'cold' layer of polythermal glaciers. Rock glaciers are features that integrate glacial and periglacial permafrost. This facilitates the research into the interaction between the glacial and the periglacial environment by recognizing the leading role of the isotherm 0 [degrees]C as the physical feature integrating these fields. Keywords: ice; glacier; permafrost; terminology

This paper describes a method for estimating the volume change of mountain glaciers using the Shuttle Radar Topography Mission (SRTM) C-band data (2000) and a digital elevation model (DEM) generated from topographic maps. This approach was developed with SRTM data and topographic maps of 1 : 25 000 scale (1977) from the Akshiirak glaciers (Tien Shan, Central Asia). The DEM for 1977 was generated using 10-m contour lines from 18 map sheets covering the Akshiirak massif and surrounding area. The nominal vertical accuracy of the maps is 3.3 m. The standard deviation of the differences between the map-derived DEM and the SRTM data on glacier-free areas of less than 25[degrees] is 6.3 m. A single localized region in the western periphery of the study area with systematic error in the SRTM data from -20 to 12 m on a 30-km spatial scale was found and excluded from the error analysis. Assuming a 10-m map error on the upper snow-covered glacier areas, the estimated root-mean-square error of the glacier surface change is 8.2 m. From 1977 to 1999, the average glacier surface thinning is 15.1 m, and the estimated volume loss is 6.15 [km.sup.3]. The rate of the Akshiirak glacier volume loss has increased by 2.7 times, compared with historical data from 1943 to 1977. The SRTM data show an opportunity for quantifying climatic and dynamic surface elevation changes in mountain glaciers. Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry and SRTM data could also be used for the estimation of short-term surface changes of mountain glaciers. Index Terms--Error analysis, glaciers, remote sensing, terrain mapping, volume measurement.

Detailed sedimentological analyses of diamicton sequences in two areas of the Pindus Mountains, Greece, indicate multiple episodes of glacier advance and retreat during cold stages of the Middle-Pleistocene. These glacial sequences represent some of the most southerly in Europe and are important archives of regional and global climate change. The Pindus glaciers were relatively small by world standards and would have been highly responsive to changes in air temperature and precipitation. On Mount Tymphi, at least three phases of glacier advance are recorded within deposits assigned to the Skamnellian Stage (MIS 12). Further north on Mount Smolikas, a thick multiple diamicton sequence records evidence for multiple glacier advances during both the Skamnellian Stage and the Vlasian Stage (MIS 6). These records highlight the dynamic nature of glacier behaviour in the Mediterranean mountains during the Middle Pleistocene and provide new evidence for unstable cold stage climates.

Alpine glaciers are efficient agents of erosion and capable of significantly modifying topography. Despite recent advances in theoretical and field studies that quantify glacial erosion processes, few studies have documented glacial erosion rates over long (>[10.sup.6] yr) or large (more than tens of kilometers) scales. We use apatite (U-Th)/He (AHe) and apatite fission track (AFT) cooling ages to address the late Miocene to Holocene erosion history across two 60-km-long transects of the heavily glaciated southern Coast Mountains, British Columbia. Observed AHe cooling ages from equal elevation samples range between 1.5 and 8 Ma and suggest that thick alpine glaciers resulted in a 16 km shift of the highest point in the topography in the past 1.5-4.0 m.y. We evaluated temporal and spatial variations in erosion rates using a three-dimensional thermal-kinematic model that predicted AHe and AFT ages at the surface for different erosion histories. Comparison of model predicted and observed cooling ages suggests an increase in erosion rates of as much as 300% over the past 1.5-7 m.y., coincident with the onset of glaciation of this range. Keywords: glacial erosion, apatite (U-Th)/He, numerical modeling, Coast Mountains, paleotopography.

Space is used as a proxy for time in determining the role of glaciation in shaping valley cross profiles in the Two Thumb Range (Southern Alps), New Zealand. The range is undergoing rapid tectonic transport and uplift as it is advected toward the Alpine fault. Repeated cycles of glacial erosion during the Quaternary have fashioned U-shaped valleys in the north of the range, close to the Main Divide, while valleys in the less glaciated south of the range have rounded divides and convex fluvial cross profiles. Tectonic transport and uplift rates, coupled with an offshore oxygen isotope [[delta].sup.18]O) record and glacialgeological reconstructions, allow time constraints to be applied to valley development along the range. Valley width and depth measurements and power-law equations were used to quantify the shape of cross-profile transects in 37 valleys. Valleys evolved into a characteristic U-shaped cross profile formed over [greater than or equal to] 400 k.y. of glacial occupancy. This, regardless of other models of glacial flattening of valley long profiles, suggests that alpine glaciation excavates greater volumes of rock, indicating that glaciers are a more effective erosional agent than fluvial activity in alpine mountain belts. Keywords: glacial valleys, morphology, landscape evolution.

The Dorrel Rock intrusive complex in Marie Byrd Land, West Antarctica, consists of a coarse-grained gabbro cut by fine-grained benmoreite and trachyte dikes, all exposed in a single nunatak. It is the only exposed plutonic body related to late Cenozoic volcanism in this part of the West Antarctic rift system. Our [sup.40]Ar-[sup.39]Ar age determinations indicate emplacement of the gabbro took place ca. 34 Ma, followed by dike injection at ca. 33.5 Ma. Marie Byrd Land volcanoes are all younger than ca. 27-29 Ma, and lie on a low-relief Late Cretaceous erosion surface that has been disrupted by block faulting and dome uplitt since late Oligocene time. The erosion surface and overlying volcanoes are well preserved, but in contrast, we estimate that at least 3 km of overburden has been eroded away to expose the gabbro. This anomaly is most easily explained if most of the exhumation took place during a period of rapid erosion between ca. 34 Ma and 27-29 Ma and was followed by a pronounced decrease in erosion rate in the late Oligocene. Temporal anomalies in the degree of dissection of volcanic edifices, together with evidence from hydrovolcanic deposits, suggest there was an ice cap in Marie Byrd Land in the late Oligocene and that inland (200+ km) volcanoes were being actively eroded by glaciers until ca. 15 Ma. This is consistent with seismic and stratigraphic work in the Ross Sea, which documents at least two expansions of the West Antarctic Ice Sheet in the early mid-Miocene. We find that rates of glacial erosion in Marie Byrd Land increase significantly with nearness to the coast, and in nonresistant rock. Thus, the observation that inland volcanoes younger than ca. 15Ma show no effects of glacial erosion, except for one with a basal section of weak tuffs, suggests that a transition from warm-based to cold-based glaciers took place around 15 Ma. These findings are similar to many of those reported from well-studied McMurdo Sound and Ross Sea localities, so they provide a wider regional picture of middle to late Cenozoic climatic and surficial geologic events in Antarctica. Keywords: erosion anomalies, erosion rate, glacial erosion, volcanic morphology, West Antarctic Ice Sheet.

Quebrada de las Lajas, near San Juan, Argentina, preserves an early Pennsylvanian deglacial-postglacial succession in a highly confined paleofjord setting. The sedimentary succession records four distinct stages in the evolution of the valley fill. Stage 1 is represented by the deposits of subglacial diamictites, ice-contact deltas, and related deepwater lacustrine environments, including several subaqueous channels. Stage 2 records a glacio-eustatic marine transgression, and a slow-down of the clastic supply into the paleofjord. Stage 3 records a sandy, confined turbidite environment. Stage 4 consists of a coarse-grained delta, which represents a significant rejuvenation of the sedimentary system in the paleofjord. The transition from stage 1 to stage 2 was abrupt and basin-wide, and has proven to be a good regional correlation marker. In this paleovalley, the glacioeustatic rise probably caused floating and consequent rapid melting of the valley glacier. This resulted in a paleovalley-wide turbidite event that is up to 5 m thick and indicates an overall waning character. The rapid sediment emplacement in this event and resulting loading of the paleovalley sediments may have helped cause widespread mass-transport events at the stage 1-2 boundary. All stages show evidence of mass-transport--related deposits, but stage 1 records the most widespread mass transport, with a large spectrum of processes represented, including coherently slumped material, rafted blocks, and completely mixed debris-flow deposits. These mass-transport deposits range from a few meters to over 50 m thick, and up to hundreds of meters wide and long. Most of the large mass-transport deposits in the lower part of the fjord fill occurred at the transition to stage 2, implicating a rise in relative sea level as a possible trigger for the slope failures. Additionally, stage 3 deposits were affected by several thrust-sense dislocations that have large offsets relative to the scale of the sedimentary succession (tens to over 50 m vertically and hundreds of meters laterally); strata associated with the dislocations exhibit growth, indicating very early movement, and they are interpreted as the frontal ramp zones of mass-transport deposits. The abundance and size of mass-transport deposits in stages 1 and 3 helped control sediment pathways throughout the paleofjord. Keywords: mass transport, deglaciation, fjord, climate change, Carboniferous, Argentina.

[1] Paleoseismological investigations, brittle fault analysis, and paleostrain calculations combined with the interpretation of satellite imagery and flood wave modeling were used to investigate the seismic and associated glacial hazard potential in Eastern Lunana, a remote area in NW Bhutan. Seismically induced liquefaction features, cracked pebbles, and a surface rupture of about 6.8 km length constrain the occurrence of M [greater than or equal to] 6 earthquakes within this high-altitude periglacial environment, which are the strongest earthquakes ever been reported for the Kingdom of Bhutan. Seismicity occurs along conjugate sets of faults trending NE-SW to NNW-SSE by strike-slip and normal faulting mechanism indicating E-W extension and N-S shortening. The strain field for these conjugate sets of active faults is consistent with widespread observations of young E-W expansion throughout southern Tibet and the north Himalaya. We expect, however, that N-S trending active strike-slip faults may even reach much farther to the south, at least into southern Bhutan. Numerous glacial lakes exist in the investigation area, and today more than 100 x [10.sup.6] [m.sup.3] of water are stored in moraine-dammed and supraglacial lakes which are crosscut by active faults. Strong earthquakes may trigger glacial lake outburst floods, and the impact of such flash floods may be worst 80 km downstream where the valley is broad and densely populated. Consequently, tectonic models of active deformation have to be closely linked with glacial hazard evaluation and require rethinking and modification. Citation: Meyer, M. C., G. Wiesmayr, M. Brauner, H. Hausler, and D. Wangda (2006), Active tectonics in Eastern Lunana (NW Bhutan): Implications for the seismic and glacial hazard potential of the Bhutan Himalaya, Tectonics, 25, TC3001, doi:10.1029/ 2005TC001858.

There is growing consensus that development of a semipermanent ice sheet on Antarctica began at or near the Eocene-Oligocene (E-O) boundary. Beyond ice-rafted debris in oceanic settings, however, direct evidence for a substantial ice sheet at this time has been limited and thus far restricted to East Antarctica. It is unclear where glacier ice first accumulated and how extensive it was on the Antarctic continent in the earliest Oligocene. Sediments at the top of the Eocene marine shelf section on Seymour Island, Antarctic Peninsula, include glacial marine deposits and a lodgment till with clasts derived from a variety of rock units on the peninsula. Dinoflagellate biostratigraphy and strontium isotope stratigraphy indicate an age at or very close to the E-O boundary. Glacier ice extending to sea level in the northern peninsula at this time suggests the presence of a regionally extensive West Antarctica ice sheet, and thus an even more dramatic response to the forcing factors that facilitated high-latitude ice expansion in the earliest Oligocene. Keywords: Oligocene, glaciation, Antarctica, till, stratigraphy.

Evidence from high-sedimentation-rate South Atlantic deep-sea cores indicates that global and Southern Ocean carbon budget shifts preceded thermohaline circulation changes during the last ice age initiation and termination and that these were preceded by ice-sheet growth and retreat, respectively. No consistent lead-lag relationships are observed during abrupt millennial warming events during the last ice age, allowing for the possibility that ocean circulation triggered some millenial climate changes. At the major glacial-interglacial transitions, the global carbon budget and thermohaline ocean circulation responded sequentially to the climate changes that forced the growth and decline of continental ice sheets., Records of past global climate preserve evidence of large-scale changes in temperature and ice volume at glacial-interglacial boundaries. Although the timing of ice ages is broadly driven by Milankovich orbital [...]

Cosmogenic nuclide surface-exposure dating reveals that glaciers in southern South America (46[degrees]S) advanced ca. 8.5 and 6.2 ka, likely as a result of a northward migration of the Southern Westerlies that caused an increase in precipitation and/or a decrease in temperature at this latitude. The older advance precedes the currently accepted initiation of Holocene glacial activity in southern South America by ~3000 yr. Both of these advances are temporally synchronous with Holocene climate oscillations that occurred in Greenland and the rest of the world. If there are causal links between these events, then rapid climate changes appear to be either externally forced (e.g., solar variability) or are rapidly propagated around the globe (e.g., atmospheric processes). Keywords: cosmogenic elements, exposure age, paleoclimatology, glacial geology, Chile, Patagonia.

Brine springs discharging from Devonian carbonates of the Western Canada Sedimentary Basin have distinct water chemistry from brines in laterally equivalent units deeper in the basin. Stable isotope data suggest that the brine springs originated as Pleistocene meltwater. These waters are interpreted to originate as an influx of subglacial meltwater related to a reversal of the basin-scale flow system, caused by the overriding ice sheet. Esker distribution shows a notable relationship between shield and sedimentary rocks. An integrated sedimentary basin/ice sheet model supports the interpretation that high permeability carbonate units acted as preferential subglacial drains that in turn affected esker development. The fluid flow history of the Western Canada Sedimentary Basin is characterized by back-and-forth movement through geological time in response to changing boundary conditions. Modern-day flow systems may not then be indicative of historic movement of economic fluids through the basin. Keywords: Subglacial recharge, hydrogeology, Western Canada Sedimentary Basin, eskers.

A late Palaeoproterozoic unconformity surface developed on low-dipping sandstone in the Kimberley region, northwestern Australia, exhibits numerous linear, parallel grooves 10-50 mm deep, 40-80 mm wide and tens of metres long, and other erosional forms including sichelwannen. These features are interpreted as Nye channels and sculpted forms eroded by subglacial meltwaters. Sandstone-filled cracks exposed at the unconformity are viewed as periglacial frost fissures. An overlying conglomerate facies 1-15 m thick at the base of the c. 1800 Ma King Leopold Sandstone, Kimberley Basin succession, contains poorly sorted, pebble to boulder conglomerate and is interpreted as glaciofluvial in origin. The orientation of the Nye channels and sculpted forms and the palaeocurrent direction for the glaciofluvial deposits indicate westward ice flow. The conformably following, locally glauconitic quartzarenitc of the King Leopold Sandstone probably accumulated in an epeiric sea, implying that glaciation reached close to sea level. Transgression in northwestern and central Australia at c. 1800 Ma may have been partly glacio-eustatic. Glaciation was initiated to the east of the Kimberley Basin, evidently in the Halls Creek Orogen, during a major phase of continental collision in Australia and worldwide supercontinental assembly. Recognition of the King Leopold glaciation, which occurred in low palaeolatitudes ( Keywords: Western Australia, Palaeoproterozoic, Kimberley Basin, subglacial environment, glaciofluvial sedimentation.