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Annmarie Robertsson - One of the best experts on this subject based on the ideXlab platform.
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early weichselian Interstadial sediments at harnosand sweden
Boreas, 2008Co-Authors: Karin Garcia Ambrosiani, Annmarie RobertssonAbstract:The till-covered organic sediments at Harnosand have been resampled and reinvestigated with respect to their micro- and macrofossil content. The sediments were deposited in a shallow freshwater basin with a sandy substratum and probably under oligotrophic conditions. The regional vegetation consisted of a shrub or herb tundra, later changing into an open Betula forest with scattered Picea and Larix. In the lake, submerged plants such as Potamogeton filiformis and Isoetes lacustris grew, together with Carex. On the shores the vegetation consisted of Betula nana, occasional Betula trees, Salix and Selaginella selaginoides. The beetle fauna suggests an average July temperature of 10–11°C. The flora indicates limited leaching and, thus, deposition during a relatively long and warm Interstadial is suggested. The Harnosand sediments are subsequently correlated with the Brorup Interstadial.
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weichselian Interstadial pollen stratigraphy from harjedalen central sweden
Grana, 1999Co-Authors: Wojciech Granoszewski, Annmarie RobertssonAbstract:Weichselian Interstadial vegetation history has been studied by means of pollen analysis of organic bearing fine-grained sediments at Dorrsvalen and Brovalltjarnen in a low mountain area in Harjedalen. The composition of the pollen flora suggests treeless vegetation consisting of shrubs and herbs. The Interstadial vegetation consisted of Betula nana, Ericaceae, Juniperus and Salix spp. mixed with herbaceous plant communities including Gramineae, Cyperaceae, Caryophyllaceae, Saxifraga, Rumex/Oxyria and Polygonum. Betula and Pinus are represented by long distance-transported pollen. During the Interstadial the climatic conditions seem to have been very harsh and continental as (cold) steppe plants reach high frequencies, e.g. Artemisia and Chenopodiaceae. The sediments are thought to have been deposited during an early Weichselian Interstadial tentatively correlated with Tarendo in Norrbotten province, northern Sweden, and Odderade in Denmark and north-western Germany. Comparisons are made with other inters...
Adrian M Hall - One of the best experts on this subject based on the ideXlab platform.
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the tolsta Interstadial scotland correlation with d o cycles gi 8 to gi 5
Quaternary Science Reviews, 2002Co-Authors: Graeme Whittington, Adrian M HallAbstract:Abstract Organic sediments, buried by till, at Tolsta Head, in north Lewis in the Scottish Outer Hebridean islands have been re-investigated. Radiocarbon dates of 32–26 kyr BP indicate correlation with the Denekamp Interstadial of The Netherlands and the Sandnes/Alesund Interstadial of Norway. The organic sediments contain an unusually detailed record of the dominantly open grassland vegetation during the Interstadial. Variations in palaeotemperature inferred from the pollen assemblages and sedimentology are provisionally matched with the δ18O record of the GISP2 ice core and correlation with the Dansgaard–Oeschger cycles GI-8–GI-5 is proposed. The Interstadial starts at 38.1k cal yr and 32.8k radiocarbon years. The termination of the Interstadial and the build-up of the Late Devensian (Weichselian) ice sheets in Scotland and North West Europe dates from 32k cal yr and 28.7k radiocarbon years. Whether the Tolsta and other contemporaneous episodes are intervals or Interstadials is also considered.
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The Tolsta Interstadial, Scotland: correlation with D–O cycles GI-8 to GI-5?
Quaternary Science Reviews, 2002Co-Authors: Graeme Whittington, Adrian M HallAbstract:Abstract Organic sediments, buried by till, at Tolsta Head, in north Lewis in the Scottish Outer Hebridean islands have been re-investigated. Radiocarbon dates of 32–26 kyr BP indicate correlation with the Denekamp Interstadial of The Netherlands and the Sandnes/Alesund Interstadial of Norway. The organic sediments contain an unusually detailed record of the dominantly open grassland vegetation during the Interstadial. Variations in palaeotemperature inferred from the pollen assemblages and sedimentology are provisionally matched with the δ18O record of the GISP2 ice core and correlation with the Dansgaard–Oeschger cycles GI-8–GI-5 is proposed. The Interstadial starts at 38.1k cal yr and 32.8k radiocarbon years. The termination of the Interstadial and the build-up of the Late Devensian (Weichselian) ice sheets in Scotland and North West Europe dates from 32k cal yr and 28.7k radiocarbon years. Whether the Tolsta and other contemporaneous episodes are intervals or Interstadials is also considered.
Christian Rolf - One of the best experts on this subject based on the ideXlab platform.
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The Toba Volcanic Event and Interstadial/Stadial Climates at the Marine Isotopic Stage 5 to 4 Transition in the Northern Indian Ocean
Quaternary Research, 2020Co-Authors: Hartmut Schulz, Kaychristian Emeis, Helmut Erlenkeuser, Christian RolfAbstract:The Toba volcanic event, one of the largest eruptions during the Quaternary, is documented in marine sediment cores from the northeastern Arabian Sea. On the crest of the Murray Ridge and along the western Indian continental margin, we detected distinct concentration spikes and ash layers of rhyolithic volcanic shards near the marine isotope stage 5–4 boundary with the chemical composition of the “Youngest Toba Tuff.” Time series of the U k′ 37 -alkenone index, planktic foraminiferal species, magnetic susceptibility, and sediment accumulation rates from this interval show that the Toba event occurred between two warm periods lasting a few millennia. Using Toba as an instantaneous stratigraphic marker for correlation between the marine- and ice-core chronostratigraphies, these two Arabian Sea climatic events correspond to Greenland Interstadials 20 and 19, respectively. Our data sets thus depict substantial Interstadial/stadial fluctuations in sea-surface temperature and surface-water productivity. We show that variable terrigenous (eolian) sediment supply played a crucial role in transferring and preserving the productivity signal in the sediment record. Within the provided stratigraphic resolution of several decades to centennials, none of these proxies shows a particular impact of the Toba eruption. However, our results are additional support that Toba, despite its exceptional magnitude, had only a minor impact on the evolution of low-latitude monsoonal climate on centennial to millennial time scales.
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the toba volcanic event and Interstadial stadial climates at the marine isotopic stage 5 to 4 transition in the northern indian ocean
Quaternary Research, 2002Co-Authors: Hartmut Schulz, Kaychristian Emeis, Helmut Erlenkeuser, Christian RolfAbstract:The Toba volcanic event, one of the largest eruptions during the Quaternary, is documented in marine sediment cores from the northeastern Arabian Sea. On the crest of the Murray Ridge and along the western Indian continental margin, we detected distinct concentration spikes and ash layers of rhyolithic volcanic shards near the marine isotope stage 5–4 boundary with the chemical composition of the “Youngest Toba Tuff.” Time series of the U k′ 37 -alkenone index, planktic foraminiferal species, magnetic susceptibility, and sediment accumulation rates from this interval show that the Toba event occurred between two warm periods lasting a few millennia. Using Toba as an instantaneous stratigraphic marker for correlation between the marine- and ice-core chronostratigraphies, these two Arabian Sea climatic events correspond to Greenland Interstadials 20 and 19, respectively. Our data sets thus depict substantial Interstadial/stadial fluctuations in sea-surface temperature and surface-water productivity. We show that variable terrigenous (eolian) sediment supply played a crucial role in transferring and preserving the productivity signal in the sediment record. Within the provided stratigraphic resolution of several decades to centennials, none of these proxies shows a particular impact of the Toba eruption. However, our results are additional support that Toba, despite its exceptional magnitude, had only a minor impact on the evolution of low-latitude monsoonal climate on centennial to millennial time scales.
J D Peacock - One of the best experts on this subject based on the ideXlab platform.
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the pre windermere Interstadial late devensian raised marine strata of eastern scotland and their macrofauna a review
Quaternary Science Reviews, 1999Co-Authors: J D PeacockAbstract:Abstract Late Devensian raised marine deposits predating the Windermere Interstadial (c. 13–11 ka BP) are found between the Moray Firth and Berwick. The widely distributed, sparsely fossiliferous Errol Clay Formation of the firths of Forth and Tay was laid down in a high-arctic environment immediately following the retreat of the Late Devensian (Dimlington Stadial) ice. In the Tay Estuary, sedimentation took place under distal glaciomarine to marine conditions at a time when there was a fully marine connection between the Scottish east coast and the then high-arctic Norwegian Sea. On the south shore of the Moray Firth, the similar, but undated Spynie Clay Formation seems to have been laid down in a wholly glaciomarine environment. Part of the macrofauna attributed to the St. Fergus Silt Formation of the NE Scottish coast may have been either misidentified, or is not in situ. The preservation of the fauna and of delicate sedimentary structures indicate that the arctic clays as a whole were laid down rapidly. It is suggested that tidal currents were minimal, and that waves were dampened by sea ice for much of the year. Bones of the ringed seal, Phoca hispida , have been recorded from 12 sites in eastern Scotland. About 40 macrofaunal taxa are present in the Errol Clay Formation, a number similar to that recorded in the Danish Younger Yoldia Clay, which is of comparable age. The faunal nomenclature is updated, and three species ( Cylichna occulta, Retusa obtusa and Lyonsia arenosa ) are added to the macrofaunal list for the Errol Clay Formation. Reports of in situ boreal molluscs and of one possibly North American species in the otherwise high-arctic assemblage are not supported by specimens in extant collections. Differential decay of the fauna below the zone of weathering in the Errol Clay Formation may have resulted from early diagenesis. Deposition of the Late Devensian, pre-Windermere Interstadial marine sediments as a whole was probably diachronous, beginning after 15–14 ka BP on the outer coast, but was confined to a short interval (c. 13.5–13 ka BP) at the type site in the Tay Estuary. In the Forth Estuary, the high-arctic marine fauna adjacent to the retreating ice-front may have survived the rapid climatic amelioration (c. 13 ka BP) at the beginning of the Windermere Interstadial (marked by the Main Perth Shoreline) for perhaps a few decades.
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late devensian and flandrian palaeoenvironmental changes on the scottish continental shelf west of the outer hebrides
Journal of Quaternary Science, 1992Co-Authors: J D Peacock, William E N Austin, I Selby, D K Graham, Rex Harland, I P WilkinsonAbstract:Examination of two radiocarbon-dated vibrocores taken from south of St Kilda at a water depth of about 155 m, a short distance within the maximum position of the Late Devensian (Dimlington Stadial) ice sheet, suggests that the St Kilda Basin became free of glacier ice after 15250 yr BP. Sedimentation in a shallow, low energy, high arctic, muddy environment continued until after 13500 yr BP. There followed a higher energy temperate episode during which water depths were roughly about 40 m: this is correlated with the latter part of the Windermere Interstadial and with the warmer interval known in shallow Scottish seas about or a little before 11 000 yr BP. The Loch Lomond (Younger Dryas) Stadial is marked in the vibrocores by the return of muddy sediments and a cold-water fauna. Relatively shallow water conditions seem to have persisted into the earliest Flandrian, when the water depth was still roughly 60 m, corresponding to a sea-level in the area 90–100 m below present. It is suggested that pack ice was widespread in the northeast Atlantic before the Windermere Interstadial and also during the Loch Lomond Stadial, when it transported shards of Icelandic volcanic ash into the St Kilda basin. Estimates of sea-surface temperature for the last part of the Windermere Interstadial are close to those derived from the deep-sea record for the same period.
Minna Valiranta - One of the best experts on this subject based on the ideXlab platform.
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early weichselian Interstadial mis 5c summer temperatures were higher than today in northern fennoscandia
Quaternary Science Reviews, 2009Co-Authors: Minna Valiranta, Hilary H Birks, Karin F Helmens, Stefan Engels, Mikko PiirainenAbstract:Abstract Only fragmentary biostratigraphical Interstadial data exist from northern European high latitudes. The palaeoenvironmental interpretations for the early part of the Last Glaciation in northern Fennoscandia are mainly based on palynological evidence that suggests open birch woodland and a sub-arctic climate. Plant macrofossils from the Sokli sediment sequence in Finnish Lapland provide different evidence of Interstadial climate conditions. The assemblage includes several species that currently have considerably more southern distribution ranges. This indicates that ca 100,000 years ago summer temperatures were warmer than today. The mean minimum July temperature may have been as high as 16 °C and the effective temperature sum may have been 1000 in day-degree units (d.d.), the modern values being 13 °C and 650 d.d., respectively. The contemporary astronomical forcing mechanisms may have resulted in a weaker north–south temperature gradient and a longer growing period, creating more favourable climate conditions compared with today.
