- Award ID(s):
- 1735891
- NSF-PAR ID:
- 10356422
- Date Published:
- Journal Name:
- Quaternary Research
- Volume:
- 106
- ISSN:
- 0033-5894
- Page Range / eLocation ID:
- 11 to 27
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Late Pleistocene and Early Holocene aeolian deposits in Tasmania are extensive in the present subhumid climate zone but also occur in areas receiving >1000 mm of rain annually. Thermoluminescence, optically stimulated luminescence, and radiocarbon ages indicate that most of the deposits formed during periods of cold climate. Some dunes are remnants of longitudinal desert dunes sourced from now-inundated continental shelves which were previously semi-arid. Others formed near source, often in the form of lunettes east of seasonally-dry lagoons in the previously semi-arid Midlands and southeast of Tasmania, or as accumulations close to floodplains of major rivers, or as sandsheets in exposed areas. Burning of vegetation by the Aboriginal population after 40 ka is likely to have influenced sediment supply. A key site for determining climate variability in southern Tasmania is Maynes Junction which records three periods of aeolian deposition (at ca. 90, 32 and 20 ka), interspersed with periods of hillslope instability. Whether wind speeds were higher than at present during the last glacial period is uncertain, but shells in the Mary Ann Bay sandsheet near Hobart and particle size analysis of the Ainslie dunes in northeast Tasmania suggest stronger winds during the last glacial period than at present.more » « less
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Abstract Due to difficulties in correlating aeolian deposits with coeval marine facies, sequence stratigraphic interpretations for arid coastal successions are debated and lack a unifying model. The Pennsylvanian record of northern Wyoming,
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Grain size analysis is an essential tool for classifying sedimentary environments. The main aim of the current research is to use granulometric analysis of the Bhikiysain palaeolake sequence along the Ramganga river to describe changes in the depositional environment within the lake during the late Quaternary. The granulometric analysis was conducted using a laser particle size analyser on 32 samples, collected at 10 cm intervals in a vertical palaeolake profile, at Bhikiyasain (Ramganga Basin). The results of the grain-size analysis indicate that the size distribution of the sediment is unimodal. The unimodal size distribution of the sediment suggests that the sediment was supplied via fluvial action. The Bhikiyasain Basin (29°43.106’ N; 79°15.682’ E) underwent tectonic activity around 44 ka, resulting in the ponding of the Ramganga river and the formation of palaeolake deposit. Based on grain size analysis, variation in the colour and lithofacies, the entire profile has been divided into 6 different zones (zones 1 to 6). The silt has the highest concentration in all the zones except for zones 1 and 3. Zones with high silt concentration are inferred to represent low energy depositional environments during the time of deposition. The higher amount of sand concentration in zones 1 and 3 represent higher energy depositional environment. For the whole profile, the sorting of the samples varies between 1.1 and 2.0, indicating poor sorting of the samples. The poorly sorted sediment in all six zones represents limited transportation of sediment from the catchment and also suggests that the sediment was deposited in a low energy environment. The ternary plots also signify the dominance of silt followed by sand and clay. The skewness values range from 0.1 to 0.5 which indicates that the samples are symmetrical to very finely skewed. Variability in the skewness values may be due to changes in the intensity of wind and hydrodynamic conditions of the lake. The kurtosis value ranges from 0.9-1.4, indicating the samples are platykurtic, leptokurtic and mesokurtic in nature. Variability in the kurtosis may be due to changes in the flow characteristics of the depositional medium.more » « less
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