Glacier Readvance Research Articles

The record of jökulhlaups from Summit Lake, northwestern British Columbia

Summit Lake, which is impounded by Salmon Glacier, is the largest self-draining, ice-dammed lake in Canada. Until 1961, it contained few icebergs and was stable, overflowing to the north into me Bowser River valley. The first jökulhlaup occurred in December 1961, after a lengthy period of thinning and retreat of Salmon Glacier, when a subglacial runnel developed in the weakened ice dam, allowing the lake to drain suddenly. This flood and two others in 1965 and 1967 caused major damage to the road system in the Salmon River valley south of the lake. Since 1965, with three exceptions, Summit Lake has drained annually; minor floods along Salmon River in 1966, 1969, and 1973 may record partial drainings of the lake, although other explanations are possible. Jökulhlaups in recent years have been smaller and have occurred earlier in the year than most of the early floods. Rapid water-level fluctuations associated with the annual emptying and refilling of Summit Lake have generated large numbers of icebergs, derived from the Salmon Glacier dam; these icebergs presently choke the surface of the lake. The present jökulhlaup cycle is likely to continue either until the glacier readvances or until it retreats to the point that it no longer forms an effective seal.

Glacier readvances in the Andes at 12 500–10 000 YR BP: Implications for mechanism of Late‐glacial climatic change

AbstractRadiocarbon dates from two sites in the Andes (Ecuador and Peru) confirm that glaciers culminated a readvance after 11 000 yr BP. A moraine stage, equivalent in altitude and position relative to existing glaciers, is present in most glacierized ranges, but its age is equivocal. Broadly limiting dates from Colombia and Peru suggest that the stage may be Late‐glacial, as it is younger than 12100 yr BP, but formed before the early Holocene; in southern Chile a comparable moraine stage is older than ca. 9100 yr BP. Andean glaciers appear to have advanced at least twice during the Late‐glacial interval.Glacier reconstruction from these moraine limits suggests depression of the equilibrium line altitude by at least 300–400 m in the northern and north‐central Andes, and possibly less than this farther south.Late‐glacial climatic change occurred globally and possibly reflects North Atlantic temperature and circulation changes forced by deglaciation of the northern ice sheets, migrations north and south of the Atlantic Polar Front, and the switching off and on of a ‘dust pump’ in low midlatitudes.

Evidence for Younger Dryas-age cooling on the North Pacific coast of America

A review of the palynological evidence from the Olympic Peninsula of Washington State north to the Alaska Panhandle strongly supports the existence of a climatic oscillation similar in timing and effect to the Younger Dryas cooling (11-10 ka BP) of Europe and eastern North America. The evidence includes many late-glacial pollen peaks of mountain hemlock ( Tsuga mertensiana), an indicator of cool and moist climate, reversals from forest to non-arboreal vegetation, and paleoclimate analysis using pollen-climate transfer functions on the Queen Charlotte Islands. Evidence of cooler ocean waters, based on fossil foraminifera in cores from the continental shelf, also supports an interpretation of a Younger Dryas-age climatic reversal. On the other hand, geological evidence of glacier readvances during the Younger Dryas chronozone is weak and poorly dated. Although more and better-constrained (AMS) dates are needed to confirm the timing of the Pacific Northwest cold oscillation, results so far point to maximum cooling and increased moisture between ca. 10.7-10 ka BP, followed by rapid warming in the early Holocene. Additional late-glacial sites need to be investigated in detail to confirm the geographical pattern of vegetation and climate change during this interval, which is best expressed in hypermaritime and maritime climate regions, similar to the Younger Dryas event around the North Atlantic. These results suggest that the search for causal mechanisms to drive the Younger Dryas cooling cannot be limited to events in the North Atlantic region, but should focus on possible hemispheric or global processes.

Late Weichselian glacier retreat in Kongsfjorden, west Spitsbergen, Svalbard

The chronology of Late Weichselian to Holocene deglaciation of Kongsfjorden, west Spitsbergen has been reconstructed based on the geomorphic and stratigraphic record of ice retreat, relative sea-level relationships, and 14C dating of associated marine organic materials. The seaward extent of glacial drift and fjord bathymetry constrain a secure reconstruction for the ice sheet near the mouth of the fjord at ca. 13,000 yr B.P., but do not rule out the possibility that more extensive glaciation was achieved earlier during the Late Weichselian. Regional shoreline relations, rates of emergence, and radiocarbon dating of foraminifera deposited just above till indicate that deglaciation occurred in two steps: one beginning during or just prior to the Late Weichselian Marine Limit phase at 13,000–12,000 yr B.P. and another beginning at 10,000–9500 yr B.P. The fjord was completely deglaciated by 9440 ± 130 yr B.P. A period of stable relative sea level began 10,700 yr B.P. and ended between 10,000 and 9500 yr B.P., which we take to indicate renewed glacial loading during the Younger Dryas. Glacier readvance within Kongsfjorden at this time was diminutive, suggesting that most of the Younger Dryas ice-sheet growth was confined to the eastern part of the archipelago and/or to the Barents Shelf. The two-step deglaciation of Kongsfjorden occurred during intervals of accelerated global ice-sheet melting and rapid oceanic and atmospheric warming in more temperate latitudes of the circum-Atlantic region. This coincidence most likely resulted from contemporaneous increases in the poleward transport of oceanic heat.

Paleoclimatic inferences from glacial fluctuations on Svalbard during the last 20 000 years

The climate history of western Spitsbergen, Svalbard is deduced from variations of glaciers during the last 20 000 years. A major depression of the regional equilibrium line altitude (ELA) occurred during the Late Weichselian glacial maximum (18000–13000y ago) when low summer temperatures may have caused year-round snow accumulation on the ground. This rapid expansion of the glaciers also indicates nearby moisture sources, suggesting partly open conditions in the Norwegian Sea during the summers. A rapid glacial retreat around 13 000–12 500 y BP was caused by a sudden warming. During the Younger Dryas the ELA along the extreme western coast of Spitsbergen was not significantly lower than at present. In contrast to Fennoscandia, the British Isles and the Alps, there is no evidence for readvance of local glaciers during Younger Dryas on western Spitsbergen. This difference is attributed to a much dryer climate on Spitsbergen and probably only slight changes in sea surface temperatures. In addition, summer melting in this high arctic area is more sensitive to orbitally increased insolation. Around 10 000 y BP another rapid warming occurred and during early and mid Holocene the summer temperatures were significantly higher than at present. A temperature decline during the late Holocene caused regrowth of the glaciers which reached their maximum Holocene position during the last century.

The character of deglaciation in the Berghem area, southwestern Sweden

Abstract The Berghem moraine zone has been studied within the Berghem area. Studies of stratigraphy, striae, drumlinization, till fabric, glaciotectonic deformation, morphology and till genesis show that the deglaciation was characterized by: (1) calving ice-bays in the fjord-like valleys during the initial Late Weichselian deglaciation, (2) temporary halts in glacial retreat influenced by bedrock topography and water depth, (3) a glacier readvance in the valleys while the ice front was semi-stationary on the plateaus which reached above the marine limit, and (4) a quick break-up of the valley glaciers due to the low gradient of the ice front after the readvance. The palaeogeography of the three main valleys within the investigated area differs somewhat, which is proposed to have influenced the deglaciation during the calving phase, the readvance and during the final deglaciation. It is proposed that the Berghem moraine zone should comprise deposits from both the halt in ice retreat and the readvance, and...

Holocene glacial and climate history of the Jostedalsbreen region, Western Norway; evidence from lake sediments and terrestrial deposits

The valleys surrounding the Jostedalsbreen ice cap were deglaciated during the latter half of the Preboreal Chronozone. At the end of the Preboreal Chronozone, however, a glacier readvance occurred. Terminal moraines were deposited by outlet valley glaciers from the Jostedalsbreen Plateau up to 1 km beyond Little Ice Age moraines. Inferred from the altitude of lateral moraines formed during this readvance and calculations of the equilibrium-line altitude (ELA) depression based on an accumulation area ratio (AAR) of 0.6, the average depression of the ELA was 325 + 75 −115 m below the present. By assuming a similar precipitation pattern as at present, this suggests a mean temperature decline of about 2°C. Palynological investigations from Sygneskardet, Sunndalen, indicate that climate like the present was achieved just after 9000 BP. The Holocene climatic optimum occurred during the Atlantic Chronozone, with elm ( Ulmus) stands growing at the present birch ( Betula) forest limit in Sunndalen and pine ( Pinus) growing at Styggevatnet to an altitude of at least 1160 m. During this period the mean summer temperature is estimated to have been at least 2.7 and 1.8°C warmer than at present, with and without the local climatic effect of Jostedalsbreen, respectively. An inferred rise of the ELA of about 400 m from the present altitude suggests that possibly no glaciers existed on the Jostedalsbreen Plateau during the Holocene climatic optimum. Vegetational changes as deduced from palynological studies, lowered tree limits and increased resedimentation in peat bogs indicate general climatic deterioration since the Late Atlantic Chronozone. A significant Alnus decline 6300 BP and a Betula expansion 5300 BP, as recorded from palynological studies of peat bogs in Sprongdalen, is interpreted to represent the initial Neoglaciation on the Jostedalsbreen Plateau. Lithostratigraphic evidence at a section in the upper part of Glomsdalen may indicate a minor Neoglacial phase close to 6000 BP. The first pronounced Neoglacial event in the Jostedalsbreen region, however, was bracketed between 3700 and 3100 BP. Spørteggbreen, the upper part lying ca. 30 m above the present regional glaciation threshold, was formed around 500 BP at the initiation of the Little Ice Age. Gelifluction at 1000 m altitude began after 3200-2800 BP. During the Medieval Period, glaciers were smaller than now. At the northwestern part of Jostedalsbreen an initial Little Ice Age glacier expansion is dated to have occurred after 890 ± 60 BP (A.D. 1030–1220). From the early 14th century, and especially from the mid-17th century, a severe climatic deterioration during the Little Ice Age is historically documented. Around Jostedalsbreen this advance culminated during the mid-18th century. Documents suggest that the western outlet glaciers from Jostedalsbreen reached their maximum Little Ice Age position some years before the longer eastern outlet valley glaciers. A typical depression of the ELA during the Little Ice Age of 100–150 m indicates a mean temperature decline from the present of ca. 0.5–1°C.

Paleoclimatic implications of an early Holocene glacier advance on Disko Island, West Greenland

The paper describes studies of glacial deposits and raised beaches on the island of Disko. West Greenland. Two stades in the glacial history are defined, the Godhavn stade, which represents the last major glaciation on Disko, and the Disko stade, which defines a Preboreal readvance. During the Godhavn stade, only eastern and southern Disko were affected by the extended Inland Ice, while glaciation on western and northern Disko was local in character. In connection with the deglaciation, the sea transgressed to the marine limit at c. 9,250‐9,000 BP. Immediately before, tentatively culminating around 9,300 BP, a significant readvance of glaciers on eastern Disko occurred. The marine limit rises on a transect from northwest to southeast across Disko from 60 m a.s.l. to 90 m. The paper discusses changes in equilibrium line altitude (ELA) during the deglaciation, and explains the Disko stade readvance in terms of variations in upper‐air wind conditions.

Post-glacial relative sea-level history of northwestern Spitsbergen, Svalbard

The late Weichselian and Holocene raised-beach sequences on northwestern Spitsbergen provide a detailed record of sea-level oscillations during the last deglacial hemicycle. Initial emergence commenced at ≥13 ka, coincident with local deglaciation, and until 10.5 ka was characterized by a relative slow rate of emergence (1.5 to 5 m/ka) interrupted by minor stillstands or transgressions associated with possible glacier re-advances. The orientation of paleo-spits and the paucity of whale remains at the late Weichselian marinelimit indicate that the prevailing westerly fetch was dampened by a semi-permanent sea-ice cover, allowing long shore-drift to predominate. A period of accelerated emergence (15 to 30 m/ka) between 10.5 and 9 ka is correlative with rapid deglaciation of fiords. The middle and late Holocene is characterized by two brief transgressions: one between 6.5 and 5.0 ka that did not exceed 7 m asl and a present, probable slow rise in sea level that commenced 2 to 1 ka. The strandline tilts in northwestern Spitsbergen, and the pattern and rate of emergence on Svalbard indicate that the maximum glacier loads during the late Weichselian were centered on Nordaustlandet, and on the central and eastern part of the archipelago. Northwestern and southwestern Spitsbergen were marginal to glacial loading and were deglaciated early (≥13 ka) which is presently incompatible with maximum ice sheet extent and the timing and position of deglacial margins recently reconstructed for the Barents Sea and Svalbard. Mountain ranges and large fiords probably confined major outlet glaciers to the central part of the archipelago, preventing inundation of much of western Spitsbergen by an inferred large ice sheet based in eastern Svalbard and the Barents Sea.

Late Quaternary stratigraphy and glaciology in the Thule area, Northwest Greenland: Introduction

This report contains the geological and glaciological results of the NORDQUA 86 expedition to Thule, Northwest Greenland. Coastal sections along Wolstenholme Fjord provide a detailed record of glacial and marine events during isotope stage 5 (74-134 ka), on the northern perimeter of Baffin Bay. The record has been dated by a combination of thermoluminescence and C-14 dating. Amino acid analyses of marine mollusc shells afford local and regional correlations, while periods with penetration of warm subarctic water have been identified by their foraminifer and mollusc faunas. There were two marine episodes with influx of subarctic water. Between the two marine episodes (at 114 ± 10 ka) maximum, although restricted, Weichselian ice coverage was attained. After this, and until the Late Weichselian, ice coverage was similar to or smaller than at present. In Late Weichselian times there was a readvance of glaciers, also associated with influx of subarctic water. The record provides for the first time a link between events in arctic Canada and Greenland, and shows that in the northern Baffin Bay region there is a causal relationship between hydrography and glaciation. Samples of glacier ice from two cross sections of the ice margin all show a Holocene stable isotope signal. Although there are several possible explanations for this, this finding is in agreement with the small extent of ice cover during the Weichselian. It also seems likely that the local "Tuto ice dome" did not exist during the Holocene climatic optimum.

Recent glacial history and paleoclimate of the Peruvian-Bolivian Andes

Radiocarbon dates of glacial deposits in the Peruvian-Bolivian Andes are used to place the observed phases of glaciation in a common chronological framework. The climatic conditions that may determine modern snowline are examined in order to understand the types of climatic forcing to which glaciers may have been sensitive in the past. Also considered are independent proxies of climatic change, including pollen sequences, lake-level history, and ice-core data. Late-Pleistocene glaciation in central Peru between 24 ka and 12 ka BP appears to have occurred during colder and perhaps drier conditions. In Bolivia a glacial maximum is dated to <27 ka BP and perhaps as late as ca. 16 ka BP. Because of the extreme height of snowline above the 0°C isotherm in Bolivia phases of glaciation must be correlated to not only colder conditions but also to a substantial increase in precipitation. During retreat from the last glacial maximum in Peru and Bolivia, between ca. 12 ka and 10 ka BP, there is evidence in many localities for a minor readvance of glaciers or a series of still stands. There is no evidence for early Holocene glaciation. Phases of late-Holocene glaciation in Peru that correspond in part to the Little Ice Age in the northern hemisphere appear to have been caused by a combination of colder and wetter conditions. An overall warming trend may be the cause for the retreat of many glaciers in the region since the mid-19th century.

On the origin of the drumlins of the South German Alpine Foreland

The drumlins formed during the last (Würmian) glaciation in the South German Alpine Foreland are situated in distinct topographic positions. These drumlins are found on the gently ascending Molasse socles between the glacially incised basins, and behind the terminal moraines of the (in the Rhein glacier area so-called) Inner Young Terminal Moraines. The former position has been explained as a result of differential ice thicknesses between the basins and the Molasse interfluves. The latter position remained problematical. Recent investigations in the frontal area of the past Iller glacier indicate that: (1) the formation of the drumlins date from one distinct glacier re-advance (the Luiblings Phase), and (2) the permafrost table within near-surface sediments, at the time of drumlin formation, was at a sufficient depth not to have any influence upon the formative processes at surface level. The drumlins, therefore, formed because the glacier re-advanced over decaying permafrost within non-lithified Pleistocene sediments, whereas in the past the ice had advanced over frozen ground and later over unfrozen ground. This situation, as found in front of the Iller glacier, is not an exceptional case. In comparing three other areas—the western Rhein glacier area, the Inn-Chiemsee area and the eastern flank of the Iller glacier—a general conformity of both landforms and glacial processes was found to exist. However, where slight variations do occur adequate explanations can be made.

Evidence for Wisconsinan Glaciations in the Verrill Canyon Area, Scotian Slope

AbstractA composite thickness of about 25 m of sediment has been cored from the Verrill Canyon on the Scotian Slope. It is interpreted that the majority of this sequence was deposited in a glaciomarine environment during oxygen isotopic stage 2 and the top of stage 3. These sediments, as seen in high-resolution seismic reflection profiles, are well stratified, become thicker upslope, are laterally variable in thickness, and pass upslope into possible outer shelf tills. Three wedge-shaped units of incoherent reflections interfinger with the parallel reflections and terminate in water depths greater than 700 m. These wedge-shaped units are interpreted as slumped diamict and outwash deposits. The age of the uppermost wedge-shaped unit is 26,000–21,000 yr based on extrapolation of radiocarbon dates. This unit documents a late Wisconsinan glacier readvance on the outer Scotian Shelf. The underlying wedge-shaped unit, estimated to be 70,000 yrs old, extends further west along the continental slope, and may represent a more extensive early Wisconsinan ice advance. A third wedge-shaped unit, inferred to have formed during isotopic stage 6, is possibly a remnant of the first glaciation in the study area.

Ice-sheet Moraines in southern Skye

Early research on the glacial history of Skye indicated that at the last ice sheet maximum, ice moving westwards from the Scottish mainland overran the Kyleakin Hills but was deflected around an independent ice cap centred on the Cuillins and Red Hills, and that during a subsequent readvance locally-nourished glaciers radiated outwards from these mountain areas ([Harker 1901][1]; [Clough and Harker 1904][2]; [Peach et al. 1910][3]). Recent geomorphological mapping of southern Skye has revealed abundant evidence for a single readvance of locally-nourished glaciers during the Loch Lomond Stadial of c. 11–10 ka BP ([Ballantyne 1988; Walker et al. 1988][4]; Fig. 1). During the mapping programme evidence was also found for two former ice limits that relate to the earlier encroachment of mainland ice across southern Skye. This communication describes this evidence and discusses its significance. The first former ice limit occurs c. 1 km W of Strollamus ([NG 591271]; Fig. 1), where a clear double lateral moraine up to 2 m high and composed largely of erratic granite boulders descends in a NW direction from 150 m OD to 70 m OD over a distance of 300 m. Conspicuous drift limits marking the south-westwards extent of abundant granite and gabbro erratics (derived respectively from the Eastern Red Hills Centre and the Broadford Gabbro to the SE) continue this former ice margin to both the SE and NW. The northern extent of the drift limit is truncated by a lateral moraine that marks the former margin of a glacier that . . . [1]: #ref-4 [2]: #ref-3 [3]: #ref-5 [4]: #ref-1

A reinterpretation of the Lateglacial environmental history of the Isle of Skye, Inner Hebrides, Scotland

AbstractThis paper presents a major revision of the Late Devensian Lateglacial environmental history of the Isle of Skye, Scotland, based upon a combination of geomorphological, biostratigraphical and radiocarbon evidence. The distribution of glacial and periglacial landforms, and of raised shorelines, suggests that there was only one extensive readvance of local glaciers in southern Skye following the wastage of the Late Devensian ice sheet. Pollen‐stratigraphic evidence from 10 sites inside and 4 sites outside the mapped ice limits indicates that this readvance occurred during the Loch Lomond Stadial. At that time over 180km2 of the uplands of south‐central Skye were covered by glacier ice, a much more extensive glaciation than previously envisaged. Palynological evidence from four Lateglacial profiles implies that degree of exposure to strong westerly winds was the principal factor determing vegetational contrasts on the island, and that regional differences in vegetational type were less pronounced than has hitherto been suggested. The glacial and palaeobotanical reconstructions reported here are more compatible with Lateglacial data from the Scottish mainland and Hebridean islands than were the previously‐published accounts for the Isle of Skye.

Die hochwürmzeitlichen Rückzugsphasen des Rhein-Vorlandgletschers und der erste alpine Eisrandkomplex im Spätglazial

Abstract. The Upper Pleistocene Wurm Glaciation Recessional Stades of the Alpine foreland glaciers of the Rhine area, and the first Alpine boundary complex of the Late Pleistocene. In the Rhine area of the Wurm glaciation, the recessional Stades can be morphologically subdivided by means of glacial boundary complexes. The Würm-Stem-on-the-Rhine complex is evidence for an upper Wurm readvance of the foreland glaciers after an intensive melting period (± 16 000 y BP?). The first Late Pleistocene readvance of the local northern Alpine glaciers appears as the Würm-Weissbad complex (± 14 000 y BP?), while in the main network of the glaciation no reaction is recognizable. In the Upper Pleistocene of the Wurm, the equilibrium line of the Rhine glacier was at an elevation of 1000 m. The first readvance of local glaciers in the Late Pleistocene took place at an elevation of about 1500 m.

The Late Weichselian and Holocene shoreline displacement on the west-central coast of Svalbard

Three well-developed raised marine shorelines along Nordenskioldkysten have been studied and correlated with the shoreline displacement since the last deglaciation. The marine limit of 64 m in the area is of Late Weichselian age and has been dated to 10,900- I1,OOO years B.P. An intermediate level at 50 m is estimated to be 10,600-10,000 years old and demonstrates a sea level stagnation probably caused by a glacier readvance in eastern Svalbard during the Younger Dryas. A Holocene transgression culminating shortly after 6,000 years B.P. has been stratigraphically demonstrated, and it probably correlates with the Tapes transgression of Scandinavia. No pre-Late Weichselian marine levels are found, and the large rebound can be attributed only to a Late Weichselian glaciation.

Recent glacier advances in the Premier Range, British Columbia

Aerial photography (1948–1985) and field investigations are used to reconstruct recent ice-front fluctuations for 27 glaciers (size range 0.63–17.9 km2) in the Premier Range, British Columbia. Rapid rates of frontal recession between ca. 1930 and the mid-fifties were followed by glacier readvance at many sites, culminating in the 1973–1976 period, when 90% of the monitored ice fronts were either advancing (68%) or stable. Maximum downvalley advance was about 0.5 km (median ~90 m), and 14 glaciers formed new terminal or lateral moraine ridges between 1970 and 1985. Nine of these postdate 1976; one is dated to the 1980–1981 winter using tree rings. The glacial advance is attributed to significant mass-balance changes inferred from periods of increased winter precipitation (ca. 1951–1976) and low summer temperatures (1954–1968) measured at Valemount. Warmer summers and reduced winter precipitation after 1976 account for the slight recession of ice fronts from maximum downvalley positions in the last few years.

The Late Weichselian and Holocene shoreline displacement on the west-central coast of Svalbard

Three well-developed raised marine shorelines along Nordenskioldkysten have been studied and correlated with the shoreline displacement since the last deglaciation. The marine limit of 64 m in the area is of Late Weichselian age and has been dated to 10,900- I1,OOO years B.P. An intermediate level at 50 m is estimated to be 10,600-10,000 years old and demonstrates a sea level stagnation probably caused by a glacier readvance in eastern Svalbard during the Younger Dryas. A Holocene transgression culminating shortly after 6,000 years B.P. has been stratigraphically demonstrated, and it probably correlates with the Tapes transgression of Scandinavia. No pre-Late Weichselian marine levels are found, and the large rebound can be attributed only to a Late Weichselian glaciation.

Quaternary Glaciomarine Sedimentation Interpreted from Seismic Surveys of Fiords on Baffin Island, N.W.T.

Seismic reflection surveys using a compressed air source in nine fiords on Baffin Island provide information on the amounts of sediment deposited and the relation of sedimentation to events during late Quaternary glaciation. Five sedimentary facies can be recognised in the seismic records: (A) a basal facies of ice contact glacial sediment including moraines and deformed, stratified, glaciomarine sediment, (B) a lower glaciomarine facies of well-stratified sediment deposited in an ice-proximal environment, (C) a facies of acoustically transparent sediment deposited in a lower energy environment farther from sources of glacial sediment, (D) an upper, well-stratified facies similar to facies B and also interpreted as ice-proximal, and (E) a thin facies of modern sediment on top of the other materials. These facies are tentatively correlated with glacial events on eastern Baffin Island. Facies A and B are associated with the retreat of glaciers from the outer coast and continental shelf of Baffin Island during the early Foxe Period (&gt;50,000 BP). Facies D is associated with the readvance of glaciers to form the moraines of the Baffinland drift during the Cockburn Substage of the Early Holocene. The intervening Facies C is associated with lower energy conditions and less sediment input in a long period between these events, and Facies E with the present environment in the fiords.Key words: Baffin Island, fiords, sedimentology, continuous seismic profiling, Quaternary glaciation