The Middle and Late Pleistocence evolution and the Bear Island Trough Mouth Fan

The evolution of a submarine fan, the Bear Island Trough Mouth Fan, is outlined using high-resolution seismic data. Eight seismic units are identified. The identified units comprise sediments of Middle and Late Pleistocene age. They were probably deposited during eight glacial advances of the Barents Sea Ice Sheet to the shelf break. The units are dominated by a chaotic seismic signature on the upper fan and a mounded seismic facies further downslope. The mounded signature is inferred to reflect large submarine debris flow deposits, probably generated by oversteepening of the upper slope. Unlike many other passive margin fans, glacigenic sediments derived from an ice sheet at the shelf break were the primary sediment input. During interstadials and interglacials the sedimentation rate was reduced markedly. Three large sliding events also influenced the Middle and Late Pleistocene fan growth.     

Late Cenozoic evolution of the western Barents Sea-Svalbard continental margin

Seven regionally correlatable reflectors, named R7 (oldest) to R1, have been identified in the Upper Cenozoic sedimentary succession along the western continental margin of Svalbard and the Barents Sea. Regional seismic profiles have been used to correlate between submarine fans that comprise major depocentres in this region. Glacial sediment thicknesses reach up to 3 seconds two-way time, corresponding to 3.5–4 km. Despite limited chronostratigraphic control, ages have been assigned to the major sequence boundaries based on ties both to exploration wells and to shallow boreholes, and by paleoenvironmental interpretations and correlations with other regions. Lateral and vertical variations in seismic facies, between stratified and chaotic with slump structures, have major implications for the interpretation of the depositional regime along the margin. The main phases of erosion and deposition at different segments of the margin are discussed in the paper, which also provides a regional seismic stratigraphic framework for two complementary papers in the present volume. Reflector R7 marks the onset of extensive continental shelf glaciations, but whereas the outer Svalbard shelf has been heavily and frequently glaciated since R7 time, this did not occur, or occurred to a much less extent, until R5 time in the southern Barents Sea. The present study provides the background for a quantification of the late Cenozoic glacial erosion of Svalbard and the Barents Sea. The rates of erosion and deposition exhibit large temporal and spatial variations reflecting the importance of glacial processes in the Late Cenozoic development of this nearly 1000 km long margin.     

Climatic versus tectonic factors in the formation of the glaciolacustrine succession (Be chatów outcrop, central Poland)

Pleistocene glaciolacustrine sediments of the Kleszczów Graben (the Be chatów outcrop, central Poland) record the origin, development, and decay of a glacial lake formed in the area of a subsiding basin during the advance of the Elsterian ice sheet. The sediments represent a transition from glaciofluvial to glaciolacustrine facies at the bottom part, and from glaciolacustrine to glacial facies at the top. The glaciolacustrine facies represent a few environments inside the lake basin, from the marginal sub-aqueous slope through the bottom part to the sub-aqueous fan. The contact of the glaciolacustrine facies and the overlying glacial till is erosional, and implies that a considerable part of the shallow-water lake facies was eroded.The lake existed for not longer than 600 years, but its development proceeded under the conditions of the Kleszczów Graben subsidence and the approach of the Elsterian ice sheet. Both factors influenced the sedimentation processes. The tectonic and climatic factors were recognised on the basis of facies analysis of lithofacies associations, and of their vertical and lateral changes.     

Soil investigations, offshore mid Norway: A case study of glacial influence on geotechnical properties

Fine-grained glaciomarine and glacial deposits on the outer Mid Norwegian continental shelf show complex variations in shear strength and degree of consolidation. At the Smørbukk Sør field (approx. 65°N, 7°E) about 80 m of variably overconsolidated clayey till is found on top of normally- or possibly underconsolidated glaciomarine and marine sediments. A high gas content is found below 60 m, and the porewater in the rather soft sediments in the lower part of the borehole may have been partly trapped by gas hydrates when the overlying hard till was deposited. The variations in geotechnical properties of the 80 m thick till section are suggested to result mainly from compaction below grounded ice during the last glaciation, and we interpret the strength variations in the till to reflect shifts between freeze of sediment porewater onto the base of the ice causing highly overconsolidated intervals, and thermal equilibrium or melting at the ice sole resulting in intervals of softer till.A large ridge northwest of Smørbukk (Skjoldryggen) is probably partly formed by ice push during ice flow oscillations at the same time as the described till at Smørbukk was deposited. This ridge retarded the ice flow and hence the frictional heating at the end of surges, creating pulses of net freezing base ice and consolidation of the substratum. The described process has possibly affected a wide area up-ice of Skjoldryggen, and may be common in areas with a complex glacial history and a fine-grained substratum.     

Accumulation of particulate organic carbon at the Eurasian continental margin during late Quaternary times: controlling mechanisms and paleoenvironmental significance

Data on the amount and composition of organic carbon were determined in sediment cores from the Kara and Laptev Sea continental margin, representing oxygen isotope stages 1–6. The characterization of organic matter is based on hydrogen index (HI) values, n-alkanes and maceral composition, indicating the predominance of terrigenous organic matter through space and time. The variations in the amount and composition of organic carbon are mainly influenced by changes in fluvial sediment supply, Atlantic water inflow, and continental ice sheets. During oxygen isotope stage (OIS) 6, high organic carbon contents in sediments from the Laptev Sea and western East Siberian Sea continental margin were probably caused by the increased glacial erosion and further transport in the eastward-flowing boundary current along the continental margin. During OIS 5 and early OIS 3, some increased amounts of marine organic matter were preserved in sediments east of the Lomonosov Ridge, suggesting an influence of nutrient-rich Pacific waters. During OIS 2, terrigenous organic carbon supply was increased along the Barents and western Kara Sea continental margin caused by extended continental ice sheets in the Barents Sea (Svalbard to Franz Josef Land) area and increased glacial erosion. Along the Laptev Sea continental margin, on the other hand, the supply of terrigenous (organic) matter was significantly reduced due to the lack of major ice sheets and reduced river discharge. Towards the Holocene, the amount of total organic carbon (TOC) increased along the Kara and Laptev Sea continental margin, reaching average values of up to 0.5 g C cm⁻² ky⁻¹. Between about 8 and 10 ka (9 and 11 Cal ka), i.e., during times when the inner shallow Kara and Laptev seas became largely flooded for the first time after the Last Glacial Maximum, maximum supply of terrigenous organic carbon occurred, which is related to an increase in coastal erosion and Siberian river discharge. During the last 8000 years, the increased amount of marine organic carbon preserved in the sediments from the Kara and Laptev Sea continental margin is interpreted as a result of the intensification of Atlantic water inflow along the Eurasian continental margin.     

Late Cenozoic depositional history of the western Svalbard continental shelf, controlled by subsidence and climate

Based on a grid of high resolution, single channel seismic lines, this paper addresses the Late Cenozoic evolution of the western Svalbard continental shelf. The seismic structure of the shelf includes at least 16 erosional unconformities, each representing a glacial advance. The evolution during the last approximately one million years has been divided into six main erosional and depositional phases. Differential margin subsidence around a hinge zone is an important controlling mechanism for the accumulation of the sedimentary wedge at the outer shelf. The most significant depositional change appears to be related to a general climatic shift, globally recorded to be centred around 1 Ma. At this level, corresponding to the Upper Regional Unconformity (URU) on the shelf, the depositional regime changed from net erosion to net deposition and shelf aggradation. Of major significance is probably a shift from thick, eroding glaciers with steep ice profiles, to low profile fast flowing ice streams maintained by an increased amount of interglacial and interstadial sediments. The relationship between climatic fluctuations, glacial dynamics and depositional regime is discussed.     

Stratigraphy, mineralogy, and origin of layered deposits inside Terby crater, Mars

The 174 km diameter Terby impact crater (28.0°S-74.1°E) located on the northern rim of the Hellas basin displays anomalous inner morphology, including a flat floor and light-toned layered deposits. An analysis of these deposits was performed using multiple datasets from Mars Global Surveyor, Mars Odyssey, Mars Express and Mars Reconnaissance Orbiter missions, with visible images for interpretation, near-infrared data for mineralogical mapping, and topography for geometry. The geometry of layered deposits was consistent with that of sediments that settled mainly in a sub-aqueous environment, during the Noachian period as determined by crater counts. To the north, the thickest sediments displayed sequences for fan deltas, as identified by 100 m to 1 km long clinoforms, as defined by horizontal beds passing to foreset beds dipping by 6-10° toward the center of the Terby crater. The identification of distinct sub-aqueous fan sequences, separated by unconformities and local wedges, showed the accumulation of sediments from prograding/onlapping depositional sequences, due to lake level and sediment supply variations. The mineralogy of several layers with hydrated minerals, including Fe/Mg phyllosilicates, supports this type of sedimentary environment. The volume of fan sediments was estimated as >5000 km³ (a large amount considering classical martian fan deltas such as Eberswalde (6 km³)) and requires sustained liquid water activity. Such a large sedimentary deposition in Terby crater is characteristic of the Noachian/Phyllosian period during which the environment favored the formation of phyllosilicates. The latter were detected by spectral data in the layered deposits of Terby crater in three distinct layer sequences. During the Hesperian period, the sediments experienced strong erosion, possibly enhanced by more acidic conditions, forming the current morphology with three mesas and closed depressions. Small fluvial valleys and alluvial fans formed subsequently, attesting to late fluvial processes dated as late Early to early Late Hesperian. After this late fluvial episode, the Terby impact crater was submitted to aeolian processes and permanent cold conditions with viscous flow features. Therefore, the Terby crater displays, in a single location, geologic features that characterize the three main periods of time on Mars, with the presence of one of the thickest sub-aqueous fan deposits reported on Mars. The filling of Terby impact crater is thus one potential “reference geologic cross-section” for Mars stratigraphy.     

Ice-rich terrain in Gusev Crater, Mars?

The morphology of materials on the floor of Gusev Crater (14° S, 175° W), Mars, imply a history of volcanism and subsequent removal of an ice-rich deposit. Fluid lava flows observed in the western portion of Gusev Crater paradoxically terminate in a steep, thick (<60 m) flow front adjacent to hummocky terrain. The hummocky terrain is morphologically similar to deglaciated terrain on Earth, generated when glacial debris are left behind after the glacier has retreated. We propose the following scenario for the floor of Gusev Crater. First, ice-rich material was deposited adjacent to Thira Crater. Second, fluid lavas were emplaced and ponded against the ice-rich deposits. At some later time, the ice within the deposit sublimated, leaving hummocky terrain. Current age estimates for the Gusev flows are Hesperian, suggesting that the ice removal occurred in the upper Hesperian or more recently. If this hypothesis is correct, quench features (glassy rinds, columnar jointing) should be observed at the lava flow margin; the hummocky deposit should be poorly sorted, angular debris.     

Cenozoic sediment distribution and tectonic movements in the Faroe region

A complex history of Cenozoic vertical movements in the Faroe region has been revealed from interpretation of geophysical and geological data, mainly offshore reflection seismic data, side-scan images, shallow cores, and onshore mapping. The history comprises several phases of tectonic disturbances observed at different scales. On the eastern margin of the Faroe Platform a late Eocene–early Oligocene phase of doming of the Faroe Platform has caused a postdepositional tilting of Eocene strata along the southern margin of the platform; a mid-Miocene phase of compressional tectonics is evidenced on seismic transects as gentle anticlines and associated reverse faults; and possible Pliocene uplift of the Faroe Islands is indicated by a progradational wedge of sediments deposited on the eastern Faroe Platform. At the continental margin/slope north of the Faroe Platform, reflection seismic data imaging the postbasalt sedimentary strata indicate three distinct tectonic events phases in the Eocene–Oligocene, Miocene and Pliocene, respectively. In contrast to the Faroe Platform the Faroe–Shetland Channel was characterised by more or less continuous subsidence dominated throughout the Cenozoic. During the Eocene, sediments deposited in the Faroe–Shetland Channel was mostly derived from a source area on the British shelf.     

Climatic implications of correlated Upper Pleistocene glacial and fluvial deposits on the Cinca and Gállego Rivers (NE Spain) based on OSL dating and soil stratigraphy

We correlate Upper Pleistocene glacial and fluvial deposits of the Cinca and Gállego River valleys (south central Pyrenees and Ebro basin, Spain) using geomorphic position, luminescence dates, and time-related trends in soil development. The ages obtained from glacial deposits indicate glacial periods at 85 ± 5 ka, 64 ± 11 ka, and 36 ± 3 ka (from glacial till) and 20 ± 3 ka (from loess). The fluvial drainage system, fed by glaciers in the headwaters, developed extensive terrace systems in the Cinca River valley at 178 ± 21 ka, 97 ± 16 ka, 61 ± 4 ka, 47 ± 4 ka, and 11 ± 1 ka, and in the Gállego River valley at 151 ± 11 ka, 68 ± 7 ka, and 45 ± 3 ka. The times of maximum geomorphic activity related to cold phases coincide with Late Pleistocene marine isotope stages and Heinrich events. The maximum extent of glaciers during the last glacial occurred at 64 ± 11 ka, and the terraces correlated with this glacial phase are the most extensive in both the Cinca (61 ± 4 ka) and Gállego (68 ± 7 ka) valleys, indicating a strong increase in fluvial discharge and availability of sediments related to the transition to deglaciation. The global Last Glacial Maximum is scarcely represented in the south central Pyrenees owing to dominantly dry conditions at that time. Precipitation must be controlled by the position of the Iberian Peninsula with respect to the North Atlantic atmospheric circulation system. The glacial systems and the associated fluvial dynamic seem sensitive to 1) global climate changes controlled by insolation, 2) North Atlantic thermohaline circulation influenced by freshwater pulses into the North Atlantic, and 3) anomalies in atmospheric circulation in the North Atlantic controlling precipitation on the Iberian Peninsula. Our scenario of glacial and fluvial evolution during the Late Pleistocene in northern Spain could be extrapolated to other glaciated mountainous areas in southern Europe.     

The Ascraeus Mons fan-shaped deposit: Volcano-ice interactions and the climatic implications of cold-based tropical mountain glaciation

Amazonian-aged fan-shaped deposits extending to the northwest of each of the Tharsis Montes in the Tharsis region on Mars have been interpreted to have originated from mass-wasting, volcanic, tectonic and/or glacial processes. We use new data from MRO, MGS, and Odyssey to characterize these deposits. Building on recent evidence for cold-based glacial activity at Pavonis Mons and Arsia Mons, we interpret the smaller Ascraeus fan-shaped deposit to be of glacial origin. Our geomorphological assessment reveals a number of characteristics indicative of glacial growth and retreat, including: (1) a ridged facies, interpreted to be composed of drop moraines emplaced during episodic glacial advance and retreat, (2) a knobby facies, interpreted to represent vertical downwasting of the ice sheet, and (3) complex ridges showing a cusp-like structure. We also see evidence of volcano-ice interactions in the form of: (1) an arcuate inward-facing scarp, interpreted to have formed by the chilling of lava flows against the glacial margin, (2) a plateau feature, interpreted to represent a subglacial eruption, and (3) knobby facies superimposed on flat-topped flows with leveed channels, interpreted to be subglacial inflated lava flows that subsequently drained and are covered by glacial till. We discuss the formation mechanisms of these morphologies during cold-based glacial activity and concurrent volcanism. On the basis of a Mid- to Late-Amazonian age (250-380 Ma) established from crater size-frequency distribution data, we explore the climatic implications of recent glaciation at low latitudes on Mars. GCM results show that increased insolation to the poles at high obliquities (>45°) forces sublimation of polar ice, which is transported to lower latitudes and deposited on the flanks of the Tharsis Montes. We assess how local orographic effects, the mass balance of the glacier, and the position of equilibrium line altitudes, all played a role in producing the observed geomorphologies. In doing so, we outline a glacial history for the evolution of the Ascraeus Mons fan-shaped deposit and compare its initiation, growth and demise with those of Arsia Mons and Pavonis Mons.     

Denudation and uplift history of the Jameson Land basin, East Greenland—constrained from maturity and apatite fission track data

The Jameson Land basin in East Greenland comprises a well exposed succession of Upper Paleozoic–Mesozoic sediments. During Middle Devonian–Early Permian rifting, 13 km of continental clastics were deposited. In latest Paleozoic to Mesozoic times, 4 km of sediments accumulated during regional subsidence. In the Early Paleocene, during North Atlantic break-up, the basin was covered by a thick volcanic pile. Subsequently, uplift and erosion took place over the whole region. The volcanic cover was completely removed from Jameson Land and erosion cut deeply into the underlying sediments. To assess the exploration potential of Jameson Land, a basin modelling study with 21 1D pseudo-wells was carried out based on all seismic and surface data available. In addition to the calculation of hydrocarbon generation in space and time, the basin modelling provided an opportunity to study the magnitude and timing of uplift and erosion. Basin modelling constrained by apatite fission track data has made it possible to determine a consistent uplift and erosion history of the area. Tectonic backstripping based on a simple Airy type isostatic model has been used to separate the tectonic uplift from the actual uplift. The combined basin modelling and backstripping study has led to the following conclusions: (1) the thickness of the Cretaceous succession varied from 1.3 km in the south to 0.3 km in the north; (2) the volcanic rocks formed a wedge with a thickness of >2 km in the south thinning to <0.1 km in the north; (3) the subsequent erosion of 2–3 km is in response to tectonic uplift with a magnitude of 1 km, and the calculated tectonic uplift shows increasing values to the north. The erosion rate generally accelerated from Late Paleocene up to the present time.     

Evidence for ocean water invasion into the Chicxulub crater at the Cretaceous/Tertiary boundary

Abstract The possibility of ocean water invasion into the Chicxulub crater following the impact at the Cretaceous/Tertiary boundary was investigated based on examination of an impactite between approximately 794.63 and 894.94 m in the Yaxcopoil‐1 (Yax‐1) core. The presence of cross lamination in the uppermost part of the impactite suggests the influence of an ocean current at least during the sedimentation of this interval. Abundant occurrence of nannofossils of late Campanian to early Maastrichtian age in the matrices of samples from the upper part of the impactite suggests that the carbonate sediments deposited on the inner rim margin and outside the crater were eroded and transported into the crater most likely by ocean water that invaded the crater after its formation. The maximum grain size of limestone lithics and vesicular melt fragments, and grain and bulk chemical compositions show a cyclic variation in the upper part of the impactite. The upward fining grain size and the absence of erosional contact at the base of each cycle suggest that the sediments were derived from resuspension of units elsewhere in the crater, most likely by high energy currents association with ocean water invasion.     

Evidence for ocean water invasion into the Chicxulub crater at the Cretaceous/Tertiary boundary

Abstract— The possibility of ocean water invasion into the Chicxulub crater following the impact at the Cretaceous/Tertiary boundary was investigated based on examination of an impactite between approximately 794.63 and 894.94 m in the Yaxcopoil‐1 (Yax‐1) core. The presence of cross lamination in the uppermost part of the impactite suggests the influence of an ocean current at least during the sedimentation of this interval. Abundant occurrence of nannofossils of late Campanian to early Maastrichtian age in the matrices of samples from the upper part of the impactite suggests that the carbonate sediments deposited on the inner rim margin and outside the crater were eroded and transported into the crater most likely by ocean water that invaded the crater after its formation. The maximum grain size of limestone lithics and vesicular melt fragments, and grain and bulk chemical compositions show a cyclic variation in the upper part of the impactite. The upward fining grain size and the absence of erosional contact at the base of each cycle suggest that the sediments were derived from resuspension of units elsewhere in the crater, most likely by high energy currents association with ocean water invasion.     

Cenozoic uplift of Fennoscandia inferred from a study of the mid-Norwegian margin

Studies of the mid-Norwegian margin reveal that the Fennoscandian continental uplift represents a flexural intraplate deformation event separated in time and space from the regional syn-rift uplift associated with crustal breakup at the Plaeocene-Eocene transition. In the area 64–68°N, the uplift occurred from late Oligocene through Pliocene. During Late Pliocene and Pleistocene times the tectonic uplift was amplified by isostatic rebound in response to the Northern Hemisphere glaciation. The tectonic uplift component reaches 1 km in the northern part of the study area decreasing to the south. The shelf stratigraphy and sediment composition record the combined effects of tectonic uplift, eustatic sea level changes and Neogene climatic deterioration. The coeval uplift and climatic change may suggest causal relations. The resulting depositional model has three stages: (1) late Miocene ( 10.5-5.5 m.y.) increased continental erosion and deposition of prograding wedges most of which were later removed; (2) early-middle Pliocene (5.5-2.6 m.y.) development of extensive local ice-sheets reaching the coastline and deposition of the prominent, oldest Pliocene wedges; (3) Northern Hemisphere glaciation (2.6-0.01 m.y.) resulting in the younger wedges farther west covered by Quaternary deposits. The model is consistent with the development of landforms on the adjacent mainland. Both the tectonic and isostatic components of the Fennoscandian uplift appear to vary in magnitude along the uplift axis, however separation of the syn-rift plate boundary related uplift and the intraplate event support the Neogene age of the main Fennoscandian uplift. We document a correspondence between structural and physiographic margin segmentation and uplift magnitude and suggest that the intraplate deformation has a thermal origin. A hot-cold asthenosphere boundary beneath the Caledonide-Baltic Shield transition combined with pre-Tertiary relief at the base of the lithosphere might induce small-scale convection and preferential volume expansion beneath the observed elongate uplift.     

Deglaciation chronology of the Scandinavian Ice Sheet from the Lake Onega Basin to the Salpausselkä End Moraines

Several long sediment cores (max. 12 m) from various parts (up to 150 km apart) of Lake Onega, Russian Karelia, have been studied for lithology, varve chronology and palaeomagnetism. The two longest varve records from the central basin contain 1300 varves. These indicate the length of the deglaciation period from these localities to the north of Lake Onega, where the drainage of glacial meltwaters was directed towards the White Sea and the deposition of varves in the Onega basin terminated. An estimate of the duration of deglaciation of the whole Onega basin is 1500 years. Natural remanent magnetization (NRM) is strong and stable in these sediments and accurately records changes in the Earth's magnetic field. A distinct change in the magnetic field, when the declination shifted from east to west by at least 60° in 350 varve years, is clearly identifiable in all cores. This palaeomagnetic feature was used for core to core correlation together with other variations in magnetic parameters and widely distributed lithological marker horizons. On the basis of the correlations between the cores and calibration of AMS radiocarbon dates from varves obtained from the northern archipelago of Lake Onega, the age of the westerly declination peak is dated to 13 090 cal. BP and accordingly the deglaciation of the Onega basin took place between 14 250 and 12 750±100 cal. BP. The westerly declination peak was also recognized earlier by Bakhmutov and Zagniy in the Helylä varved clay sequence near Sortavala on the northern shore of Lake Ladoga. Helylä is situated outside the Salpausselkä end moraines and the accumulation of varved clays continued there 1500 years after the declination peak, up until the drainage of the Baltic Ice Lake, which more or less coincides with the ice margin retreat from Salpausselkä II end moraine and the termination of the Younger Dryas event. The date thus arrived at for this event is 11 590±100 cal. BP, close to the recent results from Greenland ice cores and from varved lake sediments and tree rings from Central Europe. It is further suggested that the formation of the major Younger Dryas end moraines, the Finnish Salpausselkä I and Salpausselkä II and their correlatives in Russian Karelia, took place between 12 250 and 11 590 calendar years ago, clearly earlier than earlier estimated through correlation with the Swedish varve chronology.     

Towards a 4D topographic view of the Norwegian sea margin

The present-day topography/bathymetry of the Norwegian mainland and passive margin is a product of complex interactions between large-scale tectonomagmatic and climatic processes that can be traced back in time to the Late Silurian Caledonian Orogeny. The isostatic balance of the crust and lithosphere was clearly influenced by orogenic thickening during the Caledonian Orogeny, but was soon affected by post-orogenic collapse including overprinting of the mountain root, and was subsequently affected by a number of discrete extensional events eventually leading to continental break-up in Early Eocene time. In the mid-Jurassic the land areas experienced deep erosion in the warm and humid climate, forming a regional paleic surface. Rift episodes in the Late Jurassic and Early Cretaceous, with differential uplift along major fault zones, led to more pronounced topographic contrasts during the Cretaceous, and thick sequences of clastic sediments accumulated in the subsiding basins on the shelf. Following renewed extension in the Late Cretaceous, a new paleic surface developed in the Paleocene. Following break-up the margin has largely subsided thermally, but several Cenozoic shortening events have generated positive contraction structures. On the western side of the on-shore drainage divide, deeper erosion took place along pre-existing weakness zones, creating the template of the present day valleys and fjords. In the Neogene the mainland and large portions of the Barents Sea were uplifted. It appears that this uplift permitted ice caps to nucleate and accumulate during the Late Pliocene northern hemisphere climatic deterioration. The Late Pliocene to Pleistocene glacial erosion caused huge sediment aprons to be shed on to the Norwegian Sea and Barents Sea margins. Upon removal of the ice load the landmass adjusted isostatically, and this still continues today.     

Formation of a terraced fan deposit in Coprates Catena, Mars

We have studied a terraced fan deposit with unique characteristics located within a trough of Coprates Catena. The fan has an average length of 6.8 km, and is approximately 44 km² in area and 18 km³ in volume. The fan's broad contributing valley is approximately 35 km long and it noticeably increases in depth about 12.8 km before it intersects the trough, where a rounded knickpoint marks the transition between flat-floored upstream and V-shaped downstream cross-sections. A 14-km-long channel with no apparent source enters the contributing valley from the south. A much smaller sinuous channel has incised along a smaller V-shaped valley in the uppermost eastern portion of the fan deposit. We explored several possible origins for the terraced fan, including mass wasting, volcanic flow, alluvial fan, and delta. We propose that water sourced from volcanic melting of ice eroded and transported material along the contributing valley. This material was then deposited as a delta in a lake within the trough. The concentric terraces are most likely the result of shoreline or ice cover erosion during drops in lake level. A light-toned layered deposit to the east of the fan deposit along the floor of the trough may represent a sedimentary unit formed during the terminal stages of the lake. Although other terraced fans have been identified on Mars, the Coprates Catena fan is unique because it has many more terraces and its surface was incised by a channel and associated valley. The identification of several other valleys to the east suggests that volcanic melting of volatiles during the Hesperian Period created favorable conditions for water flow along the plains in this region.     

Simulation of the Eurasian ice sheet dynamics during the last glaciation

The Eurasian Weichselian glaciation is studied with the SICOPOLIS ice-sheet model and UKMO PMIP climate anomaly forcings. A set of sensitivity tests are completed, including runs in cold-ice mode, different positive-degree-day (PDD) factors and modified climatic data-sets. The model set-up with present-day climatology modified by a glacial index brings forth an areally correct Last Glacial Maximum (LGM) extent in the western areas, but the ice-sheet volume is too small compared to reconstructions from rebound rates. Applying modified climate data results in similar extent as indicated by the Quaternary Environment of the Eurasian North (QUEEN) Late Weichselian ice-sheet reconstruction. The simulation results display freshwater fluxes from melting and calving in phase with Heinrich events H3 at 27, H2 at 22, and H1 at 14 ka ago. These peaks correspond to fast flow areas, with main activity at 27 and 22 ka ago in the Nordic Channel area and later in the Bear Island and Storfjorden region. The activity of these areas seems to be shifting from south to north from LGM to the Holocene. The freshwater pulse at 19–18.5 ka could correspond to Dansgaard–Oeschger oscillation, as well as ice volume flux peaks around 18–17 ka ago on the western margin of the ice sheet.