scholarly journals Depositional Environments and History of Late Quaternary Sediments in Hudson Strait and Ungava Bay: Further Evidence from Seismic and Biostratigraphic Data

2007 ◽  
Vol 46 (3) ◽  
pp. 311-329 ◽  
Author(s):  
Brian MacLean ◽  
Gustav Vilks ◽  
Bhan Deonarine
Keyword(s):  
Late Quaternary ◽  
Depositional Environments ◽  
Quaternary Sediments ◽  
The South ◽  
Bay Area ◽  
South Central ◽  
History Of ◽  
Ams Dating ◽  
Seafloor Sediments ◽  
Glaciomarine Sediments

ABSTRACT Regional ship-borne investigations of seafloor sediments provide further information on late Quaternary depositional environments and history in the Hudson Strait-Ungava Bay region. Greatest sediment thicknesses, up to 130 m, occur in the large basin in eastern Hudson Strait and in the western Hudson Strait basin north of Charles Island. Significant deposits are also present in basins southwest of Charles Island, along the south central part of the Strait, and in the southern part of Ungava Bay. Glacial drift deposits are widespread, but glaciomarine and postglacial sediments mainly occur in the basinal areas, with glaciomarine sediments generally predominating. Glaciomarine sediments are laterally transitional to glacial drift in the south central part of the Strait, and at many other basin margins. AMS dating of the deepest shells found within three cores from the glaciomarine sequences in the Wakeham Bay-Baie Héricart region of south central Hudson Strait yielded ages of 8390 ± 70,8420 ± 80, and 8520 ± 80 BP. Sequences underlying the dated intervals may contain time equivalents of glaciomarine sediments 1000-2000 years older found onshore in the Deception Bay area by Gray, Bruneau, and others.

A new fossil cricetid (Rodentia, Sigmodontinae) from northeastern Brazil with remarks on small mammal extinctions in the tropical Quaternary

2020 ◽  
Vol 101 (4) ◽  
pp. 1133-1147
Author(s):  
Simone B das Neves ◽  
Ulyses F J Pardiñas ◽  
Patrícia Hadler ◽  
Elver L Mayer ◽  
Ana M Ribeiro
Keyword(s):  
New Species ◽  
South America ◽  
Small Mammal ◽  
Late Quaternary ◽  
Northeastern Brazil ◽  
The South ◽  
Quaternary Deposits ◽  
Extant Species ◽  
Genetic Features ◽  
History Of

Abstract The rare cricetid rodent Bibimys Massoia, 1980 contains three extant species that are distributed in the lowlands of eastern South America between 35°S and 20°S and distinguished mostly by subtle morphological and genetic features. Several fragmented jaws belonging to this genus were recovered from Late Quaternary deposits located in northeastern Brazil, forming part of a rich archaeological and paleontological small mammal assemblage that has been recovered from caves in the Serra da Capivara, state of Piauí. This material is described herein as belonging to a new species, the most hypsodont member of the genus. The specimens also represent an extralimital occurrence of this sigmodontine, as the nearest extant population of Bibimys is ~1,200 km to the south. Because there are few reliable records of extinct small mammals from the Pleistocene–Holocene transition on the South American continent, in describing this new sigmodontine we extend the records of past biodiversity preserved in the Quaternary deposits of tropical South America. This new species likewise highlights that the Serra da Capivara deposits are promising for understanding the evolutionary history of cricetid rodents.

scholarly journals Revisiting growth and decline of late Quaternary mega-lakes across the south-central Tibetan Plateau

2020 ◽  
Vol 248 ◽  
pp. 106475
Author(s):  
Tara N. Jonell ◽  
Jonathan C. Aitchison ◽  
Guoqiang Li ◽  
James Shulmeister ◽  
Renjie Zhou ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Late Quaternary ◽  
The South ◽  
South Central ◽  
Central Tibetan Plateau

scholarly journals Constraints on the precision of SAR in equivalent dose estimations close to saturation in quartz

2011 ◽  
Vol 38 (4) ◽  
pp. 413-423 ◽  
Author(s):  
Constantin Athanassas
Keyword(s):  
Growth Curve ◽  
Late Quaternary ◽  
Equivalent Dose ◽  
Curve Shape ◽  
Large Scatter ◽  
Dose Estimation ◽  
Quaternary Sediments ◽  
The South ◽  
Of Greece

Abstract Difficulties in evaluating accurate equivalent doses for Late Quaternary sediments from the south coasts of Greece arose in the course of SAR measurements. Large scatter among apparent equivalent doses perplexed the evaluation of accurate mean estimates in circumstances where very large doses were involved. Besides, dose recovery experiments revealed that when intersection of the natural signal occurs onto the saturating segment of the growth curve, a distinct relationship between De and growth curve shape occurs. At very low slope angles, SAR tends to overestimate the recovered dose. The mechanism which controls the spread in equivalent dose estimation is investigated.

Late Quaternary Glacial History of the South Orkney Plateau, Antarctica

1990 ◽  
Vol 33 (3) ◽  
pp. 265-275 ◽  
Author(s):  
Margaret J. Herron ◽  
John B. Anderson
Keyword(s):  
Late Quaternary ◽  
The South ◽  
Ice Shelf ◽  
Radiocarbon Dates ◽  
Orkney Islands ◽  
Ice Cap ◽  
History Of ◽  
Seismic Records ◽  
Ice Conditions ◽  
History Of The South

AbstractPiston cores from the South Orkney Plateau penetrated overcompacted diamictons in water depths of up to 250 m. Detailed textural and petrological analyses of these diamictons indicate that they are basal tills. Seismic records from the plateau show a widespread surface of glacial erosion and provide additional evidence of an ice cap grounded to a depth of 250 m. Piston cores from the slope of the plateau penetrated diatomaceous muds resting directly on poorly sorted muds with very little to no biogenic material. The ice-rafted debris in these glacial-marine sediments is composed almost exclusively of material derived from the South Orkney Islands. This implies deposition beneath an ice shelf as opposed to iceberg rafting. In contrast, diatomaceous muds contain relatively abundant exotic iceberg-rafted material and reflect a glacial-maritime setting similar to that of today. The sharp contact separating diatomaceous surface sediments from basal tills and sub-ice shelf deposits indicates that the ice cap and ice shelf retreated from the plateau rapidly. Radiocarbon dates for diatomaceous muds from a glacial trough on the plateau indicate that the ice cap and ice shelf retreated from the plateau prior to 6000 to 7000 years ago. The homogeneity of surficial diatomaceous sediments suggests that sea ice conditions over the plateau have not changed radically since that time.

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