The morphological characteristics of glacial deposits during the Last Glaciation, taking the Parlung Zangbo River Basin as an example

Moraine morphology is a valuable indicator of climate change. The glacial deposits of ten valleys were selected in the Parlung Zangbo River Basin, southeastern Tibetan Plateau, to study the glacial characteristics of the Last Glaciation and the climate change processes as revealed by these moraines. Investigation revealed that a huge moraine ridge was formed by ancient glacier in the Marine Isotope Stage 2 （MIS2）, and this main moraine ridge indicates the longest sustained and stable climate. There are at least two smaller moraine ridges that are external extensions of or located at the bottom of the main moraine ridge, indicating that the climate of the glacial stage before MIS2 was severer but the duration was relatively shorter. This distribution may reflect the climate of MIS4 or MIS3b. The glacial valleys show multi-channel, small-scale moraine ridges between the contemporary glacial tongue and the main moraine ridge. Some of these multi-channel mo- raine ridges might be recessional moraine, indicating the significant glacial advance during the Younger Dryas or the Heinrich event. The moraine ridges of the Neoglaciation and the Little Ice Age are near the ends of the contemporary glaciers. Using high-precision system dating, we can fairly well reconstruct the pattern of climate change by studying the shape, extent, and scale characteristics of glacial deposits in southeastern Tibet. This is valuable research to understand the relationship between regional and global climate change.     

Moraine Formation at an Advancing Temperate Glacier: Brigsdalsbreen, Western Norway

Owing to increased winter balances especially since AD 1988/89, almost all valley outlet glaciers of Jostedalsbreen in western Norway are experiencing the largest advance since that of the early 18th century, the regional "Little Ice Age" maximum. Brigsdalsbreen advanced 441 m between 1987 and 1997. By the end of this period, the glacier had reached the outlet of the proglacial lake Brigsdalsvatnet, ploughing into unfrozen, fine-grained, water-soaked glaciolimnic sediments from the lake bottom and forming frontal moraines. These moraines are characterised by a lack of internal structures and preferred fabric. Owing to the strong advance, the moraine morphology is constantly changing, leaving only temporary moraine ridges.
Observations made along the glacier front suggest that the formation of these moraines can best be described as "bulldozed moraines", since the term push moraine, commonly associated with advancing glaciers, should be restricted to permafront environments. Different processes involved in moraine formation at frontal and lateral glacier margins result from variations in proglacial sediment properties, microrelief and glacier dynamics. Among these processes, large boulders left in the proglacial areas are pushed forward, forming pressure ridges on the distal side. Some of the largest boulders ( c . 80–120 m³) are overturned or rotated by the glacier.     

The most extensive Holocene advance in the Stauning Alper, East Greenland, occurred in the Little Ice Age

We present glacial geologic and chronologic data concerning the Holocene ice extent in the Stauning Alper of East Greenland. The retreat of ice from the late-glacial position back into the mountains was accomplished by at least 11 000 cal years B.P. The only recorded advance after this time occurred during the past few centuries (the Little Ice Age). Therefore, we postulate that the Little Ice Age event represents the maximum Holocene ice extent in this part of East Greenland.     

Glacial history, Holocene shoreline displacement and palaeoclimate based on radiocarbon ages in the area of Bockfjorden, north-western Spitsbergen, Svalbard

Age determinations of bivalve shells indicate that Bockfjorden, a fjord in north-western Spitsbergen, Svalbard, was deglaciated shortly before 10 Kya, and that the upper marine limit in this area, with an altitude of about 50 m a.s.l., has the same age. During most of the Holocene, the glaciers in Bockfjorden were less extensive than they are today. Their maximum Holocene extension occurred during the Little Ice Age. The initial shoreline emergence after the deglaciation was rapid, and former shorelines younger than 8.5 Ky are below the present sea level. A mid-Holocene transgression of the sea is traced as well as a transgression during the last thousand years.     

Proglacial Sediment—Landform Associations of a Polythermal Glacier: Storglaciären, Northern Sweden

Mapping and laboratory analysis of the sediment—landform associations in the proglacial area of polythermal Storglaciären, Tarfala, northern Sweden, reveal six distinct lithofacies. Sandy gravel, silty gravel, massive sand and silty sand are interpreted as glaciofluvial in origin. A variable, pervasively deformed to massive clast‐rich sandy diamicton is interpreted as the product of an actively deforming subglacial till layer. Massive block gravels, comprising two distinctive moraine ridges, reflect supraglacial sedimentation and ice‐marginal and subglacial reworking of heterogeneous proglacial sediments during the Little Ice Age and an earlier more extensive advance. Visual estimation of the relative abundance of these lithofacies suggests that the sandy gravel lithofacies is of the most volumetric importance, followed by the diamicton and block gravels. Sedimentological analysis suggests that the role of a deforming basal till layer has been the dominant factor controlling glacier flow throughout the Little Ice Age, punctuated by shorter (warmer and wetter climatic) periods where high water pressures may have played a more important role. These results contribute to the database that facilitates discrimination of past glacier thermal regimes and dynamics in areas that are no longer glacierized, as well as older glaciations in the geological record.     

Transient impacts of Little Ice Age glacier expansion on sedimentation processes at glacier-dammed Iceberg Lake, southcentral Alaska

Iceberg Lake, a glacier-dammed proglacial lake in southern Alaska, contains a 1,500+ year varve record complicated by a history of episodic lake-level changes associated with fluctuations in ice-dam thickness and position. To better understand the basinwide glaciolacustrine response to late Holocene climate variability, we collected five cores from two areas in the lake, including a previously unexamined deepwater area distal from inlet streams. Based on eight AMS ¹⁴C dates, and correlations among our cores and previously documented outcrops, we describe ~1,000?years of stratigraphy from each area. Deposition at both areas was dominated by fine-grained varves, but cores from the distal area uniquely contain coarser deposits, including rhythmites and graded sand beds, that we attribute to deposition of a subaqueous outwash fan-delta between ~1250 and 1650 AD. We attribute this event to thickening of the impounding glacier and consequent incursion of the glacier margin, and an associated lateral moraine, into the lake. This result suggests an early onset of the Little Ice Age (LIA) glacial advance in this region. Changes in basinwide circulation and sedimentation associated with this event probably caused minor thickening of varves used previously to reconstruct summer temperatures, reducing sensitivity of that record to early LIA cooling. The basinwide impact of this event illustrates the potentially significant spatial and temporal variability of lacustrine sedimentary processes in dynamic glacial landscapes.     

The Retreat of Tien Shan Glaciers (Kyrgyzstan) Since the Little Ice Age Estimated from Aerial Photographs, Lichenometric and Historical Data

The retreat of 293 glaciers in the Tien Shan Mountains (Kyrgyz Republic) from their maximum extent during the Little Ice Age (LIA) is estimated using aerial photographs from 1980 to 1985 and maps at a scale of 1:25000, constructed during period 1956–1990. Two indices of changes are used: the linear distance from the glacier terminus to its Little Ice Age moraine and the difference in absolute elevation of the terminus and the moraine. Historical information about the front positions of glaciers in the 1880s to the 1930s was used as an indirect control of remote sensing data. The age of moraines in key regions was estimated by lichenometry. On average, Tien Shan glaciers have retreated by 989 ± 540 m since the LIA maximum. Their front elevations (dh) rose by 151 ± 105 m. These changes are similar to changes observed in the Alps and western Norway, Pamir‐Alay and Koryak plateau, but greater than in east Siberia over the same interval. Differences between four regions in Tien Shan (northern, western, inner, central) are generally small, though in the northern Tien Shan the glacier retreat and frontal rise are more prominent (1065 ± 479 m and 215 ± 140 m, respectively).     

THE LANDFORMS AND PATTERN OF DEGLACIATION IN THE STRAIT OF MAGELLAN AND BAHÍA INÚTIL, SOUTHERNMOST SOUTH AMERICA

ABSTRACT. We report the results of glacial geomorphological mapping of the Strait of Magellan and Bahía Inútil, southernmost South America. Our aims are to determine the pattern and process of deglaciation during the last glacial–interglacial transition, and to provide a firm geomorphological basis for the interpretation of radiocarbon, cosmogenic isotope and amino acid dates for the timing of deglaciation. The area is important because it lies in a southerly location, providing a link between Antarctica and southern mid‐latitudes, and also lies in the zone of the southern westerlies which are a key element in regional climate change. Our mapping shows that it is possible to make a clear weathering and morphological distinction between last glaciation and older landforms and sediments. Within the last glacial deposits we have identified a number of former glacier limits. The key to delineating many of these limits is continuous meltwater channels that run for several kilometres along the outer edge of discontinuous moraine belts. There are four distinct belts of moraines within the deposits of the last glaciation in the central part of the Strait of Magellan. There are two closely spaced major limits (Band C) at the north end of the Strait that reach Punta Arenas airport on the west side, and Península Juan Mazia on the east side. A third limit (D) terminates south of Punta Arenas on the west side, and passes close to Porvenir on the east. In Bahía Inútil there is a more complex pattern with a prominent outer limit (C) and a series of four equally prominent limits (D₁ to D₄) on both sides of the bay. South of these limits, there is a fourth group of moraine limits (E) on both coasts of the northern end of Isla Dawson, reflecting the last fluctuations of the Magellan glacier before final deglaciation of the southern end of the Strait. There are a number of drumlins within the outer moraine limits. The drumlins are draped by small, younger moraines showing that they have been overridden by subsequent advance(s). The coastlines of the study area are cut by a number of shorelines which record the presence of ice‐dammed lakes in the Strait of Magellan and Bahía Inútil during the later stages of deglaciation. We conclude that there are four main readvances or stillstands that marked the transition from the Last Glacial Maximum to the onset of the Holocene.     

THE 'LITTLE ICE AGE': RE-EVALUATION OF AN EVOLVING CONCEPT

ABSTRACT. This review focuses on the development of the ‘Little Ice Age’ as a glaciological and climatic concept, and evaluates its current usefulness in the light of new data on the glacier and climatic variations of the last millennium and of the Holocene. ‘Little Ice Age’ glacierization occurred over about 650 years and can be defined most precisely in the European Alps (c. AD 1300–1950) when extended glaciers were larger than before or since. ‘Little Ice Age’ climate is defined as a shorter time interval of about 330 years (c. AD 1570–1900) when Northern Hemisphere summer temperatures (land areas north of 20°N) fell significantly below the AD 1961–1990 mean. This climatic definition overlaps the times when the Alpine glaciers attained their latest two highstands (AD 1650 and 1850). It is emphasized, however, that ‘Little Ice Age’ glacierization was highly dependent on winter precipitation and that ‘Little Ice Age’ climate was not simply a matter of summer temperatures. Both the glacier‐centred and the climate‐centred concepts necessarily encompass considerable spatial and temporal variability, which are investigated using maps of mean summer temperature variations over the Northern Hemisphere at 30‐year intervals from AD 1571 to 1900. ‘Little Ice Age’‐type events occurred earlier in the Holocene as exemplified by at least seven glacier expansion episodes that have been identified in southern Norway. Such events provide a broader context and renewed relevance for the ‘Little Ice Age’, which may be viewed as a ‘modern analogue’ for the earlier events; and the likelihood that similar events will occur in the future has implications for climatic change in the twenty‐first century. It is concluded that the concept of a ‘Little Ice Age’ will remain useful only by (1) continuing to incorporate the temporal and spatial complexities of glacier and climatic variations as they become better known, and (2) by reflecting improved understanding of the Earth‐atmosphere‐ocean system and its forcing factors through the interaction of palaeoclimatic reconstruction with climate modelling.     

ESTABLISHING LICHENOMETRIC AGES FOR NINETEENTH- AND TWENTIETH-CENTURY GLACIER FLUCTUATIONS ON SOUTH GEORGIA (SOUTH ATLANTIC)

Glaciers in small mountain cirques on South Georgia respond rapidly and sensitively to changes in South Atlantic climate. The timing and rate of their deglaciation can be used to examine the impact that nineteenth- and twentieth-century climate change has had on the glacial dynamics and terrestrial ecosystems of South Georgia. As part of a reconnaissance study in Prince Olav Harbour (POH), South Georgia, we measured the size of lichens ( Rhizocarpon Ram. em Th. Fr. subgenus. Rhizocarpon group) on ice-free moraine ridges around two small mountain cirques. Our aims were twofold: first, to provide age estimates for lichen colonization, and hence, deglaciation of the moraine ridges, and second, to examine the potential of applying lichenometry more widely to provide deglacial age constraints on South Georgia. In the absence of lichen age-size (dating) curves for South Georgia, we use long-term Rhizocarpon lichen growth-rates from recent studies on sub-Antarctic Islands and the western Antarctic Peninsula to calculate likely age estimates. These data suggest ice retreat from the two outermost moraines occurred between the end of the 'Little Ice Age' (post c. 1870) and the early twentieth century on South Georgia. Lichen colonization of the innermost moraines is probably related to glacier retreat during the second half of the twentieth century, which has been linked to a well-defined warming trend since c. 1950. Patterns of possible nineteenth- and twentieth-century glacial retreat identified in POH need to be tested further by establishing species- and site-specific lichen age-size (dating) curves for South Georgia, and by applying lichenometry to other mountain cirques across South Georgia.     

POST‐LITTLE ICE AGE PATTERNED GROUND DEVELOPMENT ON TWO PYRENEAN PROGLACIAL AREAS: FROM DEGLACIATION TO PERIGLACIATION

This study aims to observe post‐Little Ice Age glacier retreat and the constitutive patterned ground development at two French Pyrenean glacier forelands (Taillon Glacier and Pays Baché Glacier). Periglacial feature observations are associated with periods of deglaciation using aerial photos and archive files. Four conclusions are drawn. (1) The two glaciers have lost respectively 68% and 92% of their surface since 1850, which corroborates observations on other Pyrenean glaciers. (2) Patterned ground can develop very rapidly, sometimes only 10 years after deglaciation. (3) Patterned ground size does not systematically increase as a function of the time elapsed since deglaciation. (4) All the forms, even those developing near the Little Ice Age moraines, are active. We propose that the location, activity and size of patterned ground are more probably linked to drift characteristics and local wetness conditions than to the time elapsed since deglaciation.     

Carcass of a bowhead whale (Balaena mysticetus) found in the lateral moraine of the Jemelianovbreen glacier, eastern Svalbard

An 8 m long carcass of a bowhead whale ( Balaena mysticetus ) melted out from remnant glacier ice in the lateral moraine of the Jemelianovbreen glacier in August 1996. Folded and sheared sediment bands in the ice suggest that the whale was incorporated during an advance of the glacier. The whale's longitudinal axis was oriented parallel to the direction of the ice-flow, with the thinnest posterior part dipping upflow. The posterior section was best preserved with muscles and blubber, although the entire skin surface was strongly decomposed and only a thick fibrous surface was left of the blubber. The abdominal wall was holed, most likely by marine organisms, and partly filled with a compacted mixture of well-sorted gravelly beach sediments and fat. the whale seems to have been incorporated into the glacier together with glaciomarine sediments and carried by the flowing ice to an altitude of ca. 15 m. Jemelianovbreen is a tidewater glacier with two known surge-episodes. The first and most extensive of these occurred ca. 1900 AD and reached ca. 7 km outside the present coast-line. Radiocarbon dating of a fragment of a caudal vertebra yielded 345 ± 40 ¹⁴C years BP (1535-1660 cal. AD), suggesting that the whale lived some time during the last part of the cold period known as the Little Ice Age.     

LANDSLIDE‐GLACIER INTERACTION IN A NEOPARAGLACIAL SETTING AT TVERRBYTNEDE,JOTUNHEIMEN, SOUTHERN NORWAY

A tongue‐like, boulder‐dominated deposit in Tverrbytnede, upper Visdalen, Jotunheimen, southern Norway, is interpreted as the product of a rock avalanche (landslide) due to its angular to subangular boulders, surface morphology with longitudinal ridges, down‐feature coarsening, and cross‐cutting relationship to ‘Little Ice Age’ moraines. The rock avalanche fell onto glacier ice, probably channelled along a furrow between two glaciers, and stopped on the glacier foreland, resulting in its elongated shape and long runout distance. Its distal margin may have become remobilized as a rock glacier, but a rock glacier origin for the entire landform is discounted due to lack of source debris, presence of matrix, lack of transverse ridges, and sparcity of melt‐out collapse pits. Lichenometric dating of the deposit indicates an approximate emplacement age of ad 1900. Analysis highlights the interaction of rock‐slope failures and glaciers during deglacierization in a neoparaglacial setting, with reduced slope stability due to debuttressing and permafrost degradation, and enhanced landslide mobility due to flow over a glacier and topographic channelling. Implications for the differentiation of relict landslides, moraines and rock glaciers are discussed and interrelationships between these landforms are considered in terms of an ice‐debris process continuum.     

Recalibration of the yellow Rhizocarpon growth curve in the Cordillera Blanca (Peru) and implications for LIA chronology

A new lichen dating method and new moraine observations enabled us to improve the chronology of glacier advances in the Cordillera Blanca (Peru) during the Little Ice Age (LIA). Our results reveal that an early LIA glacial advance occurred around AD 1330 ± 29. However, a second major glacial advance at the beginning of the 17th century overlapped the earlier stage for most glaciers. Hence, this second glacial stage, dated from AD 1630 ± 27, is considered as the LIA maximum glacial advance in the Cordillera Blanca. During the 17th–18th centuries, at least three glacial advances were recorded synchronously for the different glaciers (AD 1670 ± 24, 1730 ± 21, and 1760 ± 19). The moraines corresponding to the two first stages are close to the one in 1630 suggesting a slow recession of about 18% in the total length of the glacier. From the LIA maximum extent to the beginning of the 20th century, the 24 glaciers have retreated a distance of about 1000 m, corresponding to a reduction of 30% in their length. This rate is comparable to that observed during the 20th century. Estimates of palaeo-Equilibrium Line Altitudes show an increase in altitude of about 100 m from the LIA maximum glacial extension at the beginning of the 17th century to the beginning of the 20th century. Because long time series are not available for precipitation and temperature, this glacial retreat is difficult to explain by past climate changes. However, there is a fair correspondence between changes in glacier length and the δ¹⁸O recorded in the Quelccaya ice core at a century timescale. Our current knowledge of tropical glaciers and isotope variations leads us to suggest that this common tropical signal reflects a change from a wet LIA to the drier conditions of today. Finally, a remarkable synchronicity is observed with glacial variations in Bolivia, suggesting a common regional climatic pattern during the LIA.     

TESTING LAKE SEDIMENT AND DENDROGEOMORPHIC PROXIES FOR LITTLE ICE AGE ENVIRONMENTAL CHANGE IN THE UPPER FRASER RIVER AREA,BRITISH COLUMBIA,CANADA

This study assesses Little Ice Age (LIA) lake sediment morphological and geochemical records and moraine chronologies in the upper Fraser River watershed, British Columbia, Canada, to resolve differences in paleoenvironmental interpretation and to clarify sediment production and sediment delivery processes within alpine geomorphic systems. Moose Lake (13.9 km²), situated at 1032 m a.s.l., contains a partially varved record indicating variable rates of accumulation during the last millennium that, in general, coincide with previously documented LIA glacial advances in the region and locally. Dendrochronological assessment of forefield surfaces in the headwaters of the catchment (Reef Icefield) shows that periods of moraine construction occurred just prior to ad 1770, ad 1839 and ad 1883, and some time before ad 1570. Taken collectively, increases in varve thickness within eight Moose Lake sediment cores coincide with documented glacier advances over the twelfth through fourteenth centuries, the eighteenth century, and nineteenth through twentieth centuries. Glacial activity during the sixteenth century is also indicated. While varve thickness variations in proximal and distal sediments clearly reflect glacial activity upstream of Moose Lake, the intermediate varve record is relatively insensitive to these decadal and longer‐term catchment processes. Variations in Ca and related elements derived from glaciated carbonate terrain within the Moose River sub‐catchment (including Reef Icefield) indicate gradually increasing delivery from these sources from the twelfth through twentieth centuries even where the varve thickness record is unresponsive. Elevated carbonate concentrations confirm glacial activity c. ad 1200, ad 1500, ad 1750, and ad 1900.     

Recent geomorphologic evolution of a glaciovolcanic active stratovolcano: Popocatepetl (Mexico)

The recent geomorphologic evolution of the statovolcano Popocatepetl (19°03′N, 98°35′W), including the volcanic activity and the evolution of the glacier that still exists on the north face, was assessed. Most of the data were obtained from references in historical sources and aerial photographs dating from 1945. This information was supplemented with data from fieldwork conducted between 1992 and 1995. Landform typology shows volcanic and glacial interactions. The conclusions affirm that a geomorphologic evolution of the volcano occurred since the maximum glacier advance in the Little Ice Age (LIA) and the formation of a proglacial ramp. Later, fluvioglacial gorges cut into the ramp, especially during the 1921/27 eruption. Once the glacier had shrunk to a small size and was left hanging above the steep slope, the streams disappeared, and the gorges filled with blocks that fell in snow and ice avalanches.     

新疆阿尔泰山东段冰碛物光释光测年研究

冰川是塑造地表形态最积极的外营力之一,对冰川地貌的年代学研究是重建古冰川发展史的关键,也是研究气候变化的重要途径。冰碛物是冰川作用的直接产物,代表过去发生的冰川事件,对冰碛物进行准确测年能够为重建古冰川的进退、理解区域古气候变化提供年代学支撑。本文在新疆阿尔泰山东段采集了8个冰碛物样品以进行光释光测年,利用单片再生剂量法对90~125 μm的石英颗粒进行等效剂量的测定。通过等效剂量值频率分布特征及De（t）坪区图分析得出大部分冰碛物的光释光信号晒退不彻底,所以利用一阶动力学公式对持续激发的光释光信号晒退曲线（CW-OSL）进行多组分拟合拆分,得到快速、中速、慢速3种组分,依据分离出的快速组分确定等效剂量值。研究结果显示,距今32 ka以来阿尔泰山东段区域在MIS3阶段、MIS2阶段、8.2 ka左右、全新世大暖期及新冰期等5个时段有冰川发育,冰川发育与气候变化密切相关。     

Talus Instability in a Recent Deglaciation Area and Its Relationship to Buried Ice and Snow Cover Evolution (Picacho Del Veleta, Sierra Nevada, Spain)

The southernmost glacier in Europe formed during the Little Ice Age at the foot of the north wall of Picacho del Veleta (3 398 m) in Sierra Nevada, in the southeast region of the Iberian Peninsula (lat. 37δ03‘N, long. 3δ22‘W). The glacier gradually retreated during the last century, leaving a large talus slope at the base of the wall. The unconsolidated material covering the ice masses acted as a thermal insulator. Recent bottom temperature of snow (BTS) analyses and drillings indicate that the ice still exists within the talus. Evidence from field observations made during the period 1995–2001, revealed that large mass movements occurred during the driest summers (1998 and especially, 1999 and 2000) when the talus was snow free. These conditions suggest a direct relationship between talus stability and thermal insulation from the snow cover in areas where buried ice or decaying marginal permafrost exists.     

Geological-geomorphological analysis and 14C dating of submoraine organogenic deposits within the Renardbreen outer margin, Wedel Jarlsberg Land, Spitsbergen

Amazing organogenic deposits were encountered within the terminal moraine zone of Renardbreen, north-western part of Wedel Jarlsberg Land. Pollen analyses and ^,14C dating locate the deposits at the Middle Late Subatlantic transition. The position of these deposits indicates possible glacial advances 3,500-2,000 years BP and during the Little Ice Age, respectively. Remnants of human activity at least as old as the 9th century were also found within organogenic deposits.     

Multibeam bathymetry and the depositional environments of Kongsfjorden and Krossfjorden, western Spitsbergen, Svalbard

Kongsfjorden and Krossfjorden are two ice-proximal fjords on the western coast of Spitsbergen which have been surveyed using multibeam bathymetry, sub-bottom profiling and gravity coring. Central and outer Kongsfjorden is dominated by a 30 km² outcrop of bedrock, with a thin (<10m) sediment cover. The bedrock displays a relict sub-glacial, ice-scoured topography produced during the glacial re-advances of the Weichselian (20 Ky BP) and again during the last major Holocene re-advance of the Little Ice Age (550-200 yrs BP). Drumlins and glacial flutes are common across the floor of Kongsfjorden, with lengths of 1.5-2.5 km and widths of <100 m, rising up to 10 m in water depths of <100 m. This topography is smoothed by bottom currents from the wind-driven forcing of surface waters. The flow is counter-clockwise, matching boundary layer movement under the influence of Coriolis force. Both fjords are characterized by a variable acoustic character, based on sub-bottom profile data. The deepest basins are dominated by parallel, well-laminated reflectors and an irregular-transparent acoustic character indicating the presence of Holocene-age fine-grained sediments up to 30 m thick. A parallel, irregular-transparent acoustic character with waveform morphology in inner Kongsfjorden is interpreted as moraines, originating from the 1948 and 1869 surges of Kronebreen glacier. Mass-flows are common on the flanks of topographic highs as acoustically chaotic-transparent lensoid and wedge-shaped reflectors. The sediments of outer and central Kongsfjorden are characterized by bioturbated, gas-rich homogeneous muds interpreted as being the result of the settling of fine-grained sediment and particulate suspensions.