Late Pleistocene and Early Holocene aeolian deposits of Tasmania and their climatic implications

2020 ◽  
pp. 1-24
Author(s):  
Peter D. McIntosh ◽  
Christina Neudorf ◽  
Olav B. Lian ◽  
Adrian J. Slee ◽  
Brianna Walker ◽  
...  

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.

2021 ◽  
Author(s):  
Luca Dimuccio ◽  
Thierry Aubry ◽  
Lúcio Cunha ◽  
Nelson Rodrigues

<p>In Portugal, climate fluctuations of Late Pleistocene are well-known from marine record on the western Iberian continental margin, particularly of Marine Isotope Stages 4, 3 and 2, and they include various events of secular abrupt climate changes. During cooling phases the Heinrich Events (HE) occurred, corresponding to episodes of massive ice-discharges from Northern Hemisphere ice sheets. Furthermore, several climate phases with relatively warmer conditions, known as Dansgaard-Oeschger (D-O) cycles, characterized by an abrupt warming (D-O event) followed by a more gradual cooling, took place in-between HE. This pronounced climate instability that characterizes the Last Glacial Period between ca. 80-12 ka is recorded in a variety of marine and terrestrial archives worldwide. It had a recognized impact on the bioclimatic zones and, possibly, on the Neanderthal and Anatomically Modern Human (AMH) settlements of Iberia.</p><p>Based mainly on the study of geoarchaeological records preserved in caves and rock-shelters of Iberia, a correlation framework with climate shifts has been proposed to explain the observed discontinuities between sequences containing late Middle and early Upper Palaeolithic remains. Moreover, a climate driven model has been advanced to explain the chronological differences between northern and southern Pyrenean data by a later dispersion of AMH and the persistence of last Neanderthals in Southern Iberia, which were interpreted as a direct impact of HE4 (40-38 ka) in the distribution of large ungulate populations.</p><p>Despite all these data, the exact impact of HE on terrestrial systems, the evaluation of the latitudinal differentiation of their impact and time-gap, as well as the correlation between periods of relative stabilization/soil formation and the D-O events remain to be clearly established. In addition, the whole framework relating to the Middle-to-Upper Palaeolithic transition has been excessively dependent on karst archives and it should be investigated in other geomorphological settings - among these the fluvial and Iberian plateau (“Meseta”), both present in the Côa Valley region (Douro Basin, north-east of Portugal). Alluvial and colluvial deposits preserved in the Côa Valley (e.g. at the Cardina-Salto do Boi, Quinta da Barca Sul, Penascosa, Fariseu, Olga de Ervamoira sites) have demonstrated to be a valuable record of information about Late Pleistocene sedimentary processes, depositional environments, and hunter-gatherer’s behaviour at local and regional scales.</p><p>In this context, the CLIMATE@COA project (COA/CAC/0031/2019), funded by the Fundação para a Ciência e Tecnologia (FCT), proposes an integrated multi/interdisciplinary approach based on the stratigraphical, sedimentological, geochemical, geomorphological, geoarchaeological, and geochronological analyses of terrestrial record (natural and cultural) preserved in the Côa Valley and surrounding plateau areas, with the aim to develop an evolutionary model for the region and to deduce the environmental forcing factors for such evolution - namely climate and ecosystem changes. In addition, the project’s data will allow to define better the chronology of the transition between Neanderthal and AMH and to infer on land use and social organization in its environmental context.</p>


2001 ◽  
Vol 48 ◽  
pp. 217-232
Author(s):  
Lars B. Clemmensen ◽  
Thomas Lisborg ◽  
Richard G. Bromley ◽  
Joan J. Fornós

Large, cliff-front accumulations of Late Pleistocene aeolian and colluvial deposits on southeast Mallorca provide a terrestrial record of climatic and environmental change in the Western Mediterranean during the last glacial period. The cliff-front deposits are lithified and form ramps sloping toward the southeast (i.e. seaward). Radiocarbon dating suggests that the deposits formed in Oxygen Isope Stage 3, when sea level was about 50 m lower than today, and the fossil sea-cliff situated 1.5 to 2 km from the palaeo-shore. The aeolian deposits are composed of marine carbonate sand that was transported inland episodically and accumulated in embayments along the fossil sea-cliff. The sand initially formed steadily growing and forward-moving dunes, then sloping sand ramps and finally relatively small ascending dunes. Aeolian accumulation was interrupted by erosion and colluvial ramp formation, and the cliff-front sediments can be divided into two sedimentary cycles each composed of basal colluvial deposits overlain by aeolian deposits. Colluvial deposition probably records relatively humid climatic intervals, whereas aeolian accumulation probably reflects relatively arid climatic intervals. It appears that climatic and environmental changes were rapid, and it is speculated that the dynamics of the cliff-front system on Mallorca were tied to North Atlantic millennial-scale climate oscillations.


2020 ◽  
Vol 532 ◽  
pp. 116012 ◽  
Author(s):  
Jessica B. Volz ◽  
Bo Liu ◽  
Male Köster ◽  
Susann Henkel ◽  
Andrea Koschinsky ◽  
...  

2017 ◽  
Vol 13 (4) ◽  
pp. 345-358 ◽  
Author(s):  
Marília C. Campos ◽  
Cristiano M. Chiessi ◽  
Ines Voigt ◽  
Alberto R. Piola ◽  
Henning Kuhnert ◽  
...  

Abstract. Abrupt millennial-scale climate change events of the last deglaciation (i.e. Heinrich Stadial 1 and the Younger Dryas) were accompanied by marked increases in atmospheric CO2 (CO2atm) and decreases in its stable carbon isotopic ratios (δ13C), i.e. δ13CO2atm, presumably due to outgassing from the ocean. However, information on the preceding Heinrich Stadials during the last glacial period is scarce. Here we present δ13C records from two species of planktonic foraminifera from the western South Atlantic that reveal major decreases (up to 1 ‰) during Heinrich Stadials 3 and 2. These δ13C decreases are most likely related to millennial-scale periods of weakening of the Atlantic meridional overturning circulation and the consequent increase (decrease) in CO2atm (δ13CO2atm). We hypothesise two mechanisms that could account for the decreases observed in our records, namely strengthening of Southern Ocean deep-water ventilation and weakening of the biological pump. Additionally, we suggest that air–sea gas exchange could have contributed to the observed δ13C decreases. Together with other lines of evidence, our data are consistent with the hypothesis that the CO2 added to the atmosphere during abrupt millennial-scale climate change events of the last glacial period also originated in the ocean and reached the atmosphere by outgassing. The temporal evolution of δ13C during Heinrich Stadials 3 and 2 in our records is characterized by two relative minima separated by a relative maximum. This w structure is also found in North Atlantic and South American records, further suggesting that such a structure is a pervasive feature of Heinrich Stadial 2 and, possibly, also Heinrich Stadial 3.


2013 ◽  
Vol 160 (5) ◽  
pp. 1285-1296 ◽  
Author(s):  
D. W. Foltz ◽  
S. D. Fatland ◽  
M. Eléaume ◽  
K. Markello ◽  
K. L. Howell ◽  
...  

2021 ◽  
Author(s):  
Mohamed M. Ezat ◽  
Tine L. Rasmussen ◽  
Mathis P. Hain ◽  
Mervyn Greaves ◽  
James W B Rae ◽  
...  

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