摘要:

A 20 m thick shallow marine sequence, capped by a Late Weichselian lodgement till, is exposed for 200111 along the river in Linnedalen on the west coast of Svalbard. Five formations are recognized: Formation A, the oldest, consists of a shallow marine, proglacial fan, of channelized sandy turbidites, possibly fed from an ice‐contact deposit. Formation B, a sequence of proglacial channels and ice‐rafted debris, was formed during a small oscillation of the glacier. Formation C, a prograding, storm‐dominated shoreline sequence, was formed during a sea level fall, assumed to be a result of glacio‐isostatic uplift.Formation D, a lodgement till formed during the last glacier advance in Linnedalen and formation E, a coarsening upwards sequence, were formed during the post‐glacial sea level fall. The subtill sequence (fm. A, B and C) is dated to between 40,000BP (radiocarbon dates) and 120,000BP (thermoluminescence and amino acid D/L ratios). The glacier front was 10 km downvalley during deposition of formations A and B, relative to the present glacier terminus, and more than 12km during the late Weichselia

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00298.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Ice‐divide migration may explain the pattern of Holocene glacier fluctuations around the Mýrdalsjökull ice cap in southern Iceland. On at least three occasions Sölheimajokull, the principal outlet glacier on the southwest flank of the ice cap, has exceeded the Little Ice Age limits of recent centuries that mark the maximum extent of neighbouring glaciers in the Holocene. Bedrock divides beneath the Mýrdalsjökull ice cap do not coincide with present ice divides. It is suggested that the ice divide migrated during the course of ice‐cap growth. At various stages during the Holocene (7000‐4500,c.3100, 1400‐1200 BP) Sólheimajokull could have drained more of the ice cap than today, so becoming more advanced than neighbouring glaciers. In the Little Ice Age (c.AD 1600–1900) the glacier could have had a smaller catchment as a result of ice‐divide migration, resulting in a more inhibited advance compared with neighbouring glaciers which reached their Holocene maximum at that time. Identification of ice‐divide migration is important for palaeoclimatic reconstructions because of the need to recognize different responses of glaciers to climate if one is to use their fluctuations as i

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00299.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00300.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Mt. Kroppefjall is situated just south of the Middle Swedish (Younger Dryas) ice‐marginal zone. Its abundance of lake basins makes it very suitable for detailed shore displacement studies close to the Younger Dryas ice margin. Altogether 12 lakes at altitudes between 157 and 78 m were studied and all but one situated above the marine limit contained marine sediments. The dating of their isolation from the sea resulted in a shore displacement curve from c. 11,200 to c. 98M)BP. The relative uplift almost ceased between 10,900 and 10,300 BP, which is mainly related to an ice readvance in the Lake Vanern basin. This period of balance between uplift and sea level rise was preceded by a relative uplift rate of 5 m/lW yr and followed by as high rates as 7–8 m/100 yr, possibly caused by a delayed uplift effect and perhaps also a local fall in sea level caused by the rapidly receding ice margin. The time difference between the formation of two delta surfaces at Odskolts Moar is estimated at 60&800 years. Shoreline diagrams along the Swedish west and east coasts, mainly based on a number of shore displacement curves, reveal large anomalies that are believed to have been caused by dammings and drainages of the Baltic basin. The southwards extrapolated shorelines indicate that the bedrock threshold in the Oresund Strait, between Denmark and Sweden, functioned as the outlet threshold for the Baltic Ice Lake during its dammed stages, while the erosion of the Store Balt and Darss Sill straits began at the culmination of the Ancylus transgression and continued during the rapid IS20 m Ancylus regress

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00301.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Unexpectedly high pollen concentrations characterize the basal, silty part of the postglacial sediments accumulated in two lakes from the Cratère du Nouveau‐Quebéc area, Ungava. These lacustrine silts and their pollen content result from early postglacial washing of a pollen bearing till. The till must therefore ahve incorporated pollen that relates to events prior to the last glacial event. The matrix of the till deposits surrounding the lakes shows outstandingly high pollen concentrations. It is hypothesized that because of the proximity of the ice divide during the last (and earlier) ice advance(s) in Ungava, the previously depoisited till and the pollen that haad accumulated in its matrix during the interglacial interval(s) were preserved in relict till plains or recycled into the till of teh last glaciation. The crater's age has been established at 1.4 Ma and holds a minimum thickness of 95 m of sediments. It is very likely filled with successive tills or related glacigenic deposits perhaps representing the whole length of time since the crater was formed. Alike the most recent till, these deposits should pollen. there is thus the prospect ofr a 1.4 Ma old pollen record for Ung

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00302.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Because many forminiferologists pay little attention to the smallest planktic foraminiferal species, the role ofGlobigerinita clarkei(Rögl&Bolli) as a fauna making species has been largely overlooked. Although it is widely distributed throughout the world, even dominating the assemblages of many areas (at least in the Quarternarty deposits), it is missing from numerous reports based on materials where it must have been present

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00303.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

A variety of glaciotectonic structueres are associated with a distinctive Middle‐ Wisconsin organic formation that is exposed at thirteen places along Michigan's Pine River. The carbonaceous material, with a14C age of about 46,000 years BP, accumulated in an extensive, weakly geogenous, oligotrophic fen that was buried by sand before being deformed. Numerous faults and folds, the latter with observed amplitudes that may exceed 5 m, have a consistent sense of easterly structural vergence indicating glacial movement from the west. Gelogic relationships here and generally accepted regional chronology indicate that deformation was produced by Late Wisconsin ice that flowed from the Lake Michigan basin. This unequivocal marker bed provides detailed information on the topography, environment, and climate associated with an ice‐free Middle‐wisconsin landscape. Equally important and unprecedented for the area, it is an especially precise measure of multiple glaciotectonic effects upon an incompetent Pleistocene organic formation of considerable e

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00304.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Lithostratigraphical and palynological investigations of a coastal cliff section at Kobbelgård, Møn (Denmark) reveal a sedimentary sequence of Weichselian age. Bedded clayey sediments are overlain by stratified silt, sand and occasional beds of clay and gravel. The clay was deposited in water, and most of the silt and sand is aeolian, forming fairly thick units of loess and sand‐loess. The lower part of the sequence forms an anticlinal structure, probably of glacio‐tectonic orìgìn. The upper part of the sequence appears to represent a depression filling. In the lower part of this, clayey layers alternating with loess deposits suggest wet conditions periodically. In the upper part, loess and fine sand were deposited, interfingering with slope sediments in a periglacial environment from around 24,000 BP almost until the Weichselian glacial maximum. Pollen investigations at the site point to three periods of vegetation. The lowest pollen sequence contains much Ericales,Empetrumand occasionally alsoPinus, and is thought to be of Early Glacial or Lower Pleniglacial age. Overlying pollen‐bearing strata with high proportions of herbs, includingArtemisia, antedate a TL dating ofc.27,000 BP. An upper pollen sequence, derived from slightly organic layers in the depression fill, points to a palaeovegetation almost exclusively of herbs, withArtemisiaas an important component. This vegetation is thought to represent a relatively moist site, and is TL dated toc

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00305.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00306.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1991.tb00307.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY