Marine Limit Research Articles

The relative influence of Laurentide and local ice sheets during the last glacial maximum in the eastern Chic-Chocs Range, northern Gaspé Peninsula, Quebec

Geochemical signatures, erratic dispersal, and striae indicate glacial flows in the north-central Gaspé Peninsula exclusively from Appalachian sources, except for the coastal fringe. During the last glacial maximum (LGM), ice from the Monts McGerrigle flowed northward and northwestward over the summits of the eastern Chic-Chocs Range and the coastal plateau to the Gulf of St. Lawrence. Lesser flows also occurred to the north from Mont Albert and the western Chic-Chocs Range. Where intersecting striae were noted, the older flows are associated with a locally developed ice cap. The rare occurrences of striae and erratics, and morphometric and lithological characteristics of summit diamictons, imply limited basal erosion by both local and regional ice caps. This is postulated to result from early protection of rock surfaces by the initial buildup of thin, frozen-based ice in the eastern Chic-Chocs Range. A compact till mantle in the cols and on the coastal plateau and striae parallel to col directions indicate a downslope transition to wet-based ice. Occasional gneiss boulders above the marine limit between Cap-Chat and Sainte-Anne-des-Monts indicate a slight onlap of the Laurentide Ice Sheet (LIS), but the latter was excluded from the interior of the peninsula east of Cap-Chat. Whole-rock geochemistry from three granitoid erratics on Chic-Chocs summits and one in the York River basin indicates a local Devonian rather than a Precambrian Canadian Shield source. The absence of southward downwarping of synchronous postglacial marine limits across the Gaspé Peninsula corroborates this view for the LGM.

Discussion on a revised model for the last deglaciation of eastern Scotland Journal , Vol. 164, 2007, 313–316

J. D. Peacock, M. Armstrong, M. A. E. Browne, N. R. Golledge & M. S. Stoker write: We are unable to support the view of McCabe et al . (2007) that there were significant readvances of the Scottish Ice-sheet at Lunan Bay and near Perth. The authors provide no criteria for readvances of glaciers such as terminal moraines, a second till and/or deforming bed, and rafting and overriding of marine sediments. However, we believe that the four new 14C dates in their table 1 are useful additions to knowledge. The supposed Perth Readvance in the type area . We agree that the till at the base of the Almondbank was produced by advancing ice. However, because such till is widespread in eastern Scotland, its occurrence does not of itself support the concept of a readvance, and none of the criteria noted above are satisfied. Indeed, the only indication of a possible very local readvance in the Perth area is near Moneydie, where a section formerly exposed two tills and highly deformed lacustrine silts (Paterson 1974). This we could attribute to the expected readjustment of ice-streams during retreat. Menzies & Van Der Meer (1998) concluded that the evidence here did not support a major readvance, but rather represented ‘a single winter event’. The package of sediments was described as ‘part of a tectonised, sub-glacial, deforming bed sequence’. In the upper Forth Estuary, near Grangemouth, Sissons & Smith (1965) showed that the Main Perth Shoreline is associated with the eastern limit of a stillstand or readvance of ice, which they correlated with the ‘Perth Readvance’. However, in the Tay–Earn area, the marine limit above the Main Perth Shoreline can be followed almost to Crieff, some 25 km west of Perth, where there are fluvial terraces relating to a sea level at …

Publisher's Note

Quaternary glacial stratigraphy and relative sea-level changes reveal at least four expansions of the Kara Sea ice sheet over the Severnaya Zemlya Archipelago at 79 degrees N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from raised-beach sequences that occur at altitudes up to 140 m a.s.l. Chronologic control is provided by AMS C-14, electron-spin resonance, green-stimulated luminescence, and aspartic-acid geochronology. Major glaciations followed by deglaciation and marine inundation occurred during MIS 10-9, MIS 8-7, MIS 6-5e and MIS 5d-3. The MIS 6-5e event, associated with the high marine limit, implies ice-sheet thickness of >2000m only 200km from the deep Arctic Ocean, consistent with published evidence of ice grounding at similar to 1000m water depth in the central Arctic Ocean. Till fabrics and glacial tectonics record repeated expansions of local ice caps exclusively, suggesting wet-based ice cap advance followed by cold-based regional ice-sheet expansion. Local ice caps over highland sites along the perimeter of the shallow Kara Sea, including the Byrranga Mountains, appear to have repeatedly fostered initiation of a large Kara Sea ice sheet, with exception of the Last Glacial Maximum (MIS 2), when Kara Sea ice did not impact Severnaya Zemlya and barely graced northernmost Taymyr Peninsula. (c) 2007 Elsevier Ltd. All rights reserved.

Internal Structure of Open System Pingos, Adventdalen, Svalbard: The Use of Resistivity Tomography to Assess Ground-Ice Conditions

The objectives of this project were to establish the geometry and internal structure of open system pingos in Adventdalen, Svalbard using electrical resistivity tomography. A clear distinction can be made between the electrical properties of the pingos investigated, depending upon whether they are located either above (Innerhytte pingo) or below (Hytte and Longyear pingos) the maximum Holocene marine limit. The resistivity profile at Innerhytte pingo was characterised by high values of resistivity [Formula: see text], indicating either ice-rich frozen bedrock or a lens of massive ground ice. The electrical resistivity of Hytte and Longyear pingos, both developed within fine-grained, saline marine clays, is exceptionally low (predominantly [Formula: see text]) for permanently frozen ground. This is inconsistent with the presence of a body of massive ground ice, and suggests that the internal structures of Longyear and Hytte pingos do not follow the classic model of a plano-convex pingo-core of massive injection ice. Instead, the internal structure of these landforms may be dominated by segregation ice and localised pockets of massive ice within a matrix of partially frozen, fine-grained marine muds. The high salinity of the pore waters and the fine-grained nature of the sediment cause high unfrozen pore water contents, even at temperatures well below [Formula: see text], enabling electrolytic conduction and resulting in apparently anomalously low resistivity measurements. It is therefore concluded that electrical resistivity tomography must be interpreted with care when applied to the characterisation of permafrost in areas of saline marine sediments. Future field monitoring of permafrost landforms and laboratory testing of ice-rich sediments are recommended to improve geophysical interpretation of permanently frozen materials.

Depositional origin of an adverse delta surface slope at Altermarka, northern Norway

Based on grain-size analysis of sediment samples from a delta at Altermarka, it has previously been suggested that two tills were deposited on the delta surface as a glacier planed off the delta topsets and created its adverse surface slope. In this reinvestigation of the delta, there was no evidence that a glacier overrode the surface: the topset beds remain intact and no appreciable till was found. Sediments resembling the ‘till’ samples were located, but soil processes and other sedimentary processes easily account for the wide grain-size distributions of these sediments. As a result, this study cautions against using grain-size analysis, on its own, to interpret the genesis of sediments. Other processes potentially responsible for the adverse surface slope include differential isostatic rebound, recent differential slip along ancient thrust faults, and failure of the delta surface to reach sea level. Based on the sedimentology of the topset beds and the local relative sea level history (indicating the delta (9495±70 14C yr BP) formed about the time of the local marine limit (9560–9375 14C yr BP) 17 m higher than the delta surface), the feature is determined to have built up below sea level with an adverse surface slope.

Severnaya Zemlya, Arctic Russia: a nucleation area for Kara Sea ice sheets during the Middle to Late Quaternary

Quaternary glacial stratigraphy and relative sea-level changes reveal at least four expansions of the Kara Sea ice sheet over the Severnaya Zemlya Archipelago at 79°N in the Russian Arctic, as indicated from tills interbedded with marine sediments, exposed in stratigraphic superposition, and from raised-beach sequences that occur at altitudes up to 140 m a.s.l. Chronologic control is provided by AMS 14C, electron-spin resonance, green-stimulated luminescence, and aspartic-acid geochronology. Major glaciations followed by deglaciation and marine inundation occurred during MIS 10-9, MIS 8-7, MIS 6-5e and MIS 5d-3. The MIS 6-5e event, associated with the high marine limit, implies ice-sheet thickness of >2000 m only 200 km from the deep Arctic Ocean, consistent with published evidence of ice grounding at ∼1000 m water depth in the central Arctic Ocean. Till fabrics and glacial tectonics record repeated expansions of local ice caps exclusively, suggesting wet-based ice cap advance followed by cold-based regional ice-sheet expansion. Local ice caps over highland sites along the perimeter of the shallow Kara Sea, including the Byrranga Mountains, appear to have repeatedly fostered initiation of a large Kara Sea ice sheet, with exception of the Last Glacial Maximum (MIS 2), when Kara Sea ice did not impact Severnaya Zemlya and barely graced northernmost Taymyr Peninsula.

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.

Délimitation de la limite marine tardiglaciaire dans la vallée de la rivière Saint-François, Québec méridional, Canada

À la fin de la dernière glaciation, un bras de mer appelé « Mer de Champlain » submergea la plaine du fleuve Saint-Laurent, dans la partie nord-est de l’Amérique du Nord. L’étendue maximale de cette mer postglaciaire a déjà été délimitée sur la frange des Appalaches du Québec méridional, sauf dans la vallée de la rivière Saint-François. Des travaux antérieurs ont suggéré que les eaux marines ont envahi le fond de cette vallée sur une distance d’environ 50 km au sud-est de la plaine du Saint-Laurent. Cette hypothèse est surtout fondée sur l’existence de paléoformes littorales perchées à une altitude voisine de celle de la limite marine, même si aucun fossile marin n’a été identifié jusqu’à aujourd’hui au sud-est de la ville de Richmond. Afin de délimiter l’étendue marine maximale à l’intérieur de cette vallée, la position supposée du paléorivage fut suivie, ce qui a permis de relever d’anciennes formes littorales supplémentaires. Notre reconstitution montre que, dès le début de la transgression marine, une chaîne de lacs occupa le fond de la vallée, au lieu de la Mer de Champlain. En plus des formes littorales perchées, dont l’alignement montre une discontinuité d’altitude entre les divers plans d’eau, l’existence de ces lacs est attestée par l’identification d’anciens exutoires lacustres. La reconstitution du drainage de ces paléolacs a aussi permis de localiser les différents barrages composés de dépôts glacigènes.

Deglaciation chronology and glaciomarine successions in the Malangen‐Målselv area, northern Norway

The deglaciation history of the Malangen‐Målselv fjord and valley area proximally to the Tromsø‐Lyngen (Younger Dryas) moraine at Bakkejord, Malangen, northern Norway, is reconstructed based on morphostratigraphic, lithostratigraphic and geophysical evidence, and 25 radiocarbon dates from marine shells and foraminifera. The results show that following the Skarpnes event c. 12 200 14Cyr BP, and prior to the Younger Dryas readvance, the area was deglaciated at least as far as Sandmo situated 22 km proximally to the Tromsø‐Lyngen moraine. Two moraine ridges crossing the fjord at Sandmo and buried beneath thick glaciomarine sediments are correlated with this period. The area was subsequently deglaciated between 10 300 and 9200 14Cyr BP, following the Tromsø‐Lyngen (Younger Dryas) readvance. Five ice‐front accumulations post‐dating the Tromsø‐Lyngen moraine and situated 19, 27, 42, 55 and 77 km behind it are identified and dated based on radiocarbon dates and correlation of marine limits: Målsnes (c. 10 050 14Cyr BP), Kjerresnes (c. 10 000 14Cyr BP), Solli (c. 9750 14Cyr BP), Bardufoss‐Brentmoen‐Storskogmoen (c. 9600–9700 14Cyr BP) and Alapmoen (c. 9200 Cyr BP). The largest of these, at Bardufoss‐Storskogmoen, possibly accumulated as a response to an ice advance. Fourteen dates of apparent late Allerød/Younger Dryas age (11 100–10 000 14Cyr BP), obtained from fossils in glaciomarine sediments in the Målselv valley up to 77 km proximally to the Tromsø‐Lyngen moraine, are interpreted as postdating rather than predating this moraine. Several of these are considered to be too old because of uncertain reservoir age, carbon‐dating plateaus and/or contamination. This highlights uncertainties associated with radiocarbon‐dating and the profound effect such uncertainties may have on interpreting geological events.

Relative sea level curves for the South Shetland Islands and Marguerite Bay, Antarctic Peninsula

This paper presents preliminary relative sea level curves for the Marguerite Bay region and for the South Shetland Islands. The Marguerite Bay curve is constrained by both new and previously published 14C dates on penguin remains and shells, and on two isolation basins dating back to 6500 14C yr BP. Extrapolation back to the marine limit yields a minimum deglaciation date for Marguerite Bay of ca 9000 14C yr BP. Analysis of beach clasts suggests that there was a period of increased wave activity, perhaps related to a reduction in summer sea-ice extent, between ca 3500 and ca 2400 14C yr BP. The curve for the South Shetland Islands is derived entirely from published 14C dates from isolation basins and on whalebone, penguin bone and seal bone. The curve shows an initial relative sea level fall, which was interrupted by a period in the mid-Holocene when relative sea level rose to a highstand of between 14.5 and 16 m above mean sea level (amsl), before falling again.

Late Weichselian deglaciation and sea level history of St Jonsfjorden, Spitsbergen: A contribution to ice sheet reconstruction

The elevation and age of surveyed shorelines in St Jonsfjorden, western Spitsbergen, provide a chronology for Late Weichselian deglaciation and a proxy for former ice thickness. Support is provided for previous reports of two sets of shorelines on NW Spitsbergen, the oldest (at 60 m in St Jonsfjorden) dating to a pre‐late Weichselian glaciation and the youngest documenting postglacial rebound. The remarkable survival of the older shorelines suggests that a large area of NW Spitsbergen was either covered by protective, cold‐based ice or was subject to only local glaciation during the late Weichselian even though glacier ice extended to the shelf edge in the Isfjorden Trough. A marine limit of 46 m at the mouth of St Jonsfjorden is compatible with the regional late Weichselian marine limit (LWML) dated to ∼13 ka BP. A partial relative sea level curve and equidistant shoreline diagram are produced for St Jonsfjorden and used in conjunction with relative sea level curves based on data from previous studies to produce an isobase map for 9 ka BP. The curves indicate that western sites were subject to initial slow emergence followed by rapid emergence between 10 ka and 8.2 ka BP, trends characteristic of areas affected by a full glacial sea or at least subject to early break up of a thin or discontinuous glacier ice cover. A step in the 9 ka BP shoreline long profile over the western end of the peninsula separating Isfjorden and van Mijenfjorden suggests that Holocene neotectonics may have produced anomalously high rebound rates in that area.

A 16 000-year record of near-field relative sea-level changes, northwest Scotland, United Kingdom

Isolation basins, raised tidal marshes, coastal wetlands and dune systems around Arisaig in northwest Scotland produce a ∼16 000-year record of relative sea-level (RSL) change from the time of local deglaciation following the Last Glacial Maximum (LGM) to the present. New sea-level index points from Mointeach Mhor North define the culmination of the mid-Holocene RSL highstand to ∼7600–7400 cal yr BP and 6.74±0.2 m above present. Numerous sea-level index points indicate that the RSL highstand persisted more than 1000 years before the onset of any significant RSL fall. This points to a gradual cessation of melting of the Laurentide and Antarctic ice sheets, rather than an abrupt termination. Isolation basin evidence, from a marine limit ∼34 to 38 m above present down to sites close to current sea level, constrain the acceleration of eustatic sea-level rise during meltwater pulse 1a to ∼30 mm yr −1 or ∼11 km 3 yr −1 meltwater discharge. Comparison of RSL observations with glacial isostatic adjustment (GIA) model predictions show differences in the pattern of residuals dependent upon the GIA model used. Changes to the far-field ice model components can partly explain the patterns of residuals.

Holocene and Quaternary uplift in the central part of the southern coast of the Corinth Gulf (Greece)

The southern coast of the Gulf of Corinth, Greece, has long been recognized as an area of rapid Quaternary uplift in a normal faulting environment, but the amplitude, dating and significance of this uplift remain a matter of debate, mainly due to the scarcity of reliable and detailed estimates of Holocene and longer-term uplift. Evidence of Holocene emergence is analysed for two sites in the most uplifted area of the southern coast of the Gulf of Corinth. At Mavra Litharia, the uppermost Holocene marine limit has been identified at +9.3 m and dated about 7100 14C years BP. Near Platanos, where the Holocene marine limit is above +12.5 m, in situ infralittoral boring shells at +11.5 m have been dated about 4800 14C years BP. Average uplift rates can be estimated between 2.9 and 3.5 mm/year at Mavra Litharia and possibly even greater (ca. >2.1–2.7 mm/year) near Platanos. The pattern of the variation of Holocene uplift along the coast seems to mimic the pattern of Late Quaternary terraces, well constrained in the eastern pattern of the Gulf (Corinth–Xylokastro area).

High‐arctic fan delta recording deglaciation and environment disequilibrium

AbstractStudy of a Holocene fan delta in Adventfjorden, Spitsbergen, provides new insight into the nature of high‐arctic coastal sedimentation and deglaciation dynamics. The fjord‐side, gravelly Gilbert‐type fan delta began to form at the local marine limitc. 10 ka BP, supplied seasonally with sediment by meltwater from a cirque glacier left behind by the retreating Late Weichselian ice sheet. Relative sea level had fallen by 63 m, and the fan delta reached a radius ofc. 1 km by 6 ka BP, when the relic glacier eventually melted down and fluvial activity declined. A strong influence of marine processes is recorded by the fan‐delta foreset facies, overlain by alluvium. Supplied with sediment by longshore drift, the fan‐delta front continued to advance at a lower rate, while relative sea level fell further by 5 m and ceased to fall around 5·4 ka BP. The following transgression was countered by longshore sediment supply until 4·7 ka BP, when the delta‐front beach aggraded and a spit platform began to climb onto the delta plain, recording a relative sea‐level rise of 4 m. The subsequent regression was initially non‐depositional, with the relative sea level falling by > 4 m in 200 years, outpacing fluvial supply, and the re‐emerging fan delta being swept by longshore currents. A regressive beach began to formc. 4·3 ka BP, while relative sea level gradually reached its present‐day position. The feeder braided stream was wandering across the delta plain during this time, but incised once the fan‐delta shoreline began to retreat by wave erosion and turned into a receding modern escarpment. The stream has since been adjusting its profile by gradually eroding the pre‐existing alluvium and distributing the coarse sediment supplied from catchment slopes by debrisflows and snow avalanches. Modern snowflows have also spread debris onto the abandoned fan surface. The erosional retreat of the fan delta has been accompanied by lateral shoreline accretion on both its sides. The study has important regional implications and demonstrates that Holocene fan deltas can provide a valuable record of the deglaciation history in high‐arctic terrains, where glacial deposits are scarcely preserved on land.

A review of postglacial emergence on Svalbard, Franz Josef Land and Novaya Zemlya, northern Eurasia

The pattern of postglacial emergence in the Barents Sea is pivotal to constraining the timing of deglaciation and extent and thickness of the last ice sheet in northern Eurasia. This review unites records of Holocene relative sea level from Svalbard, Franz Josef Land, and Novaya Zemlya to better understand the geometries of past ice sheet loads. Emergence data from northern Eurasia confine the maximum area of glacier loading to the northwestern Barents Sea, where >100 m of emergence is measured on Kongsøya. Deglacial unloading commenced on western and northern Spitsbergen c. 13–12 14C ka ago, and by c. 10.5 14C ka on eastern Svalbard and more distal sites on Franz Josef Land and Novaya Zemlya. The marine limit phase (c. 13–12 14C ka) on western and northern Spitsbergen is characterized by the construction of spits indicating a dominance of long-shore drift over storm-generated fetch, reflecting extensive sea-ice coverage of coastal areas. At sites in proximity to the ice sheet margin on western and northern Spitsbergen there is evidence for a transgressive–regressive cycle c. 6–4 14C ka, possibly reflecting back migration of displaced mantle material. A modern transgression is inferred from the marine erosion of 17th century cultural features and 14C ages of whalebone and terrestrial peat buried by modern storm gravels that place sea level at its present position by c. 2 to 1 ka ago. The greatest observed emergence on Franz Josef Land occurs on Bell Island, with a marine limit at 49 m aht, formed c. >10 14C ka. Available emergence data since 9 ka show rising strandlines toward the southwest at ∼0.3 m/km. The northern limit of emergence on Franz Josef Land is poorly constrained because relative sea-level data is sparse north of 80°30′N. In contrast to Svalbard and Franz Josef Land, the marine limit on northern Novaya Zemlya is only 10–15 m above high tide and formed between 6.5 and 5.0 14C ka when global sea level was stabilizing. All sites show little apparent emergence during the past 2 ka, with the youngest raised landforms at identical heights to storm beaches. This minimal glacio-isostatic signature on Novaya Zemlya and on Vaygach Island, where deglaciation commenced >10 ka ago, indicates ice sheet thicknesses of <1.5 km. The spatial variation in emergence for the Barents Sea indicates that western and northern Spitsbergen and Novaya Zemlya were near the reactive margin of the ice sheet and these areas sustained the briefest ice coverage (2–6 ka) and were probably not in isostatic equilibrium. In contrast, central and eastern Svalbard and southern Franz Josef Land were beneath a substantial ice load and probably sustained this load for c. 10 14C ka and achieved isostatic equilibrium. Isostasy residual from an ice sheet model portrays well the general pattern of uplift and load response at the centre of ice sheets, but deviates substantial at the ice sheet margin or areas covered by thin ice, like Novaya Zemlya.

Lake Terrell upland glacial resurgences and implications for late-glacial history, northwestern Washington State, U.S.A.

New geomorphic data from the Lake Terrell uplands along the western margin of the Fraser Lowland in Washington reveal moraines (and (or) a complex grounding zone) and raised marine terraces. A large ridge that almost encircles the upland is asymmetric, and its surface material consists of fine- to coarse-grained diamictons. These ridges are argued to have formed adjacent to an ice margin near the marine limit, where the depositional processes are variable (e.g., ice-rafted rainout, dumping, sediment gravity flow). Multiple crests and crosscutting relations suggest that at least two glacial resurgences occurred during deglaciation of this area. The presence of these features, and their probable extent and stratigraphic position, raise several questions about relative sea-level history and ice margin reconstructions for this area.

Topographically-controlled Deglacial History of the Humber River Basin, Western Newfoundland

The Humber River in western Newfoundland flows through a large interior basin, that influenced Late Wisconsinan ice flow from major dispersal centres to the north, in the Long Range Mountains, and to the east in The Topsails. An early southward ice flow from a source to the north covered coastal areas in the western part of the basin. Subsequent regional ice flow was southwestward to northwestward from The Topsails, while south to southwestward flowing ice from the Long Range Mountains occupied the upper Humber River valley. This flow was confluent with ice from The Topsails and moved northwestward toward Bonne Bay. Regional deglaciation began about 13 ka from the inner coast. Ice occupying the Deer Lake valley dammed glacial Lake Howley in the adjacent Grand Lake and Sandy Lake basins to an elevation up to 85 m above present lake levels, which were controlled by drainage through a western outlet feeding into St. George’s Bay. The lake was lowered by exposure of the South Brook valley outlet, and finally drained catastrophically through a spillway at Junction Brook. Marine limit at the coast was 60 m asl. Inland deltas at the head of Deer Lake and fine-grained sediment exposed in the Deer Lake valley show inundation below 45 m present elevation. This produced a narrow embayment extending at least 50 km inland from the modern coast and is named here as ‘Jukes Arm’. Dated marine macrofossils in the Humber Arm and lower Humber River valley, indicate the deltas at the head of Deer Lake formed about 12.5 ka.

New observations on the relative sea level and deglacial history of Greenland from Innaarsuit, Disko Bugt

Relative sea level (RSL) data derived from isolation basins at Innaarsuit, a site on the south shores of the large marine embayment of Disko Bugt, West Greenland, record rapid RSL fall from the marine limit (ca. 108 m) at 10,300–9900 cal yr B.P. to reach the present sea level at 3500 cal yr B.P. Since 2000 cal yr B.P., RSL rose ca. 3 m to the present. When compared with data from elsewhere in Disko Bugt, our results suggest that the embayment was deglaciated later and more quickly than previously thought, at or slightly before 10,300 cal yr B.P. The northern part of Disko Bugt experienced less rebound (ca. 10 m at 6000 cal yr B.P.) compared with areas to the south. Submergence during the late Holocene supports a model of crustal down-warping as a result of renewed ice-sheet growth during the neoglacial. There is little evidence for west to east differences in crustal rebound across the southern shores of Disko Bugt.

A new late-glacial sea-level record for St. George's Bay, Newfoundland

A new relative sea-level curve is presented for St. George's Bay, southwest Newfoundland, based on (i) a revised stratigraphic framework and depositional model for glacial and marine deposits exposed in coastal sections and (ii) 19 new radiocarbon dates on shells from emerged and submerged marine deposits, including fossiliferous diamictons. The data produce a type B sea-level curve, falling steeply from an extrapolated marine limit of 105 m above sea level at 14.0 14C ka BP, passing below modern sea level at ~10.6 14C ka BP, to a lowstand of –25 m at ~9.4 14C ka BP, and rising again close to modern sea level by 5.0 14C ka BP. Marine limits in the northern part of the bay have lower elevations (27–65 m) due to delayed ice retreat of up to 1.2 ka. Between 12.8 and at least 12.3 14C ka BP, glaciofluvial outwash graded to falling sea levels between 27 and 17 m above present throughout the bay, whereas lowstand deltas were constructed in sheltered locations at the outlets of major river systems, when sea level was 25 m below present. Establishment of the sea-level lowstand at ~9.4 14C ka BP is supported by new seismic data and radiocarbon dates from St. George's Bay and also from White Bear Bay on the south coast of Newfoundland. Short-term fluctuations in emergence rates of 1–2 m/century between 12.5 and 9.5 14C ka BP are attributed to variable eustatic sea-level rise, superimposed on a declining local glacio-isostatic adjustment.

La déglaciation de la région de Rimouski, Bas-Saint-Laurent (Québec) : indices d’une récurrence glaciaire dans la Mer de Goldthwait entre 12 400 et 12 000 BP

La distribution des dépôts de marge glaciaire de la région de Rimouski a été analysée en fonction du cadre morphostructural préglaciaire, caractérisé par un relief appalachien typique dont les barres et les sillons, orientés NE-SO, sont subparallèles à la vallée du Saint-Laurent. Cette étude met en lumière l'influence déterminante du contexte morphostructural sur le mode de déglaciation, tant à l'échelle régionale que locale. L'invasion de la Mer de Goldthwait le long du Saint-Laurent, à partir de 14 000 BP, isole progressivement une calotte glaciaire régionale dans les Appalaches. Vers 13 400 BP, la marge septentrionale de la calotte appalachienne suit le tracé de la limite marine, fixée à 140 m d'altitude entre Rimouski et Luceville. Elle s'est stabilisée le long des premières grandes barres appalachiennes qui représentaient la première ligne d'ancrage de la marge glaciaire après l'invasion marine. Durant la phase de retrait qui suit, entre 13 360 et 12 700 ans BP, des masses de glace résiduelles sont abandonnées dans la vallée de ligne de faille de la Neigette et les sillons appalachiens de Saint-Fabien qui s'encombrent de formes de décrépitude (kames et kettles). Entre 12 400 BP et environ 12 000 BP, la marge glaciaire se stabilise sur le rebord du plateau de Sainte-Blandine, à moins de 13 km du littoral actuel. Cette période se signale par une récurrence glaciaire mise en évidence dans trois sites différents. Les modalités et la chronologie de la déglaciation au-delà de la limite marine ne sont pas connues.