Several studies have used luminescence dating to investigate sand mobilization activity in extreme western areas and the southern margin of the Thar Desert, India. However, room exists for a chronology of sand profiles for the northern margins of the Thar Desert. The Ghaggar River flood plain at Rajasthan, northwestern India, in the northern margin of the Thar Desert, is bordered by sand dunes. Elucidation of the environmental changes of the Ghaggar Basin requires knowledge of many aspects of sand dune formation. We measured optically stimulated luminescence (OSL) using the single aliquot regenerative-dose (SAR) protocol for sand of eight palaeo-dunes and two flood silts of both sides of the present Ghaggar Basin and Chautang Basin flood plains. Their OSL ages were obtained respectively, as 15-10 ka or 5 ka, and 9-8 ka. Results of this study reinforce the hypothesis that sand dune deposition had started or had already been completed by 15-10 ka. Aeolian deposition was subdued by enhanced moisture during 9-8 ka. Our interpretation is that, at least since 5 ka, the scale of the flood plain of the Ghaggar River has remained equivalent to that of the present day.
Abstract:We determined the eruption age of basaltic rocks by application of thermoluminescence (TL) method, which is often used for TL dating, to quartz. Mafic magma only rarely includes quartz because of their mutual disequilibration. The basaltic lavas reported herein include quartz as xenocrysts, as corroborated by their rounded or anhedral shape. The basaltic lava used for this study is from the Oninomi monogenetic volcano in northern Kyushu, Japan. The volcano eruption was estimated as occurring 7.3-29 ka because the lava exists between two widespread tephras: Aira-Tanzawa ash (26-29 ka) and Kikai-Akahoya ash (7.3 ka). We succeeded in collecting ca. 200 mg of quartz by decomposition of 30 kg of the lava samples. TL measurements for the lava indicate the eruption age as 15.8 ± 2.5 ka, which is fairly consistent with the stratigraphical estimation. Although the TL method has played a considerable part in constraining the timescale of Quaternary events, its application has been limited to silicic samples. The present result demonstrates the availability of quartz for dating even of mafic rock.
Here, we assess geochronological, sedimentological, stratigraphic, and stone tool data from Shimaki, an Upper Paleolithic site in southeastern Hokkaido, Japan. Overall, we find that Shimaki's landscape context and flaked‐stone assemblage are similar to sites in Hokkaido that date to just before or at the Last Glacial Maximum (LGM). Based on several numerical ages, we suggest that the artifact‐bearing layer, including a wedge‐shaped core morphologically similar to post‐LGM specimens from Siberia, formed during the LGM, and sites like Shimaki with clear stratigraphy, relatively undisturbed cultural material, and what appear to be transitional artifact forms, may be key to answering questions about the origins of microblades, but, without human fossil remains for ancient DNA comparison, are inadequate to address the fate of Late Pleistocene Siberians.
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