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Pattern of dune accretion and its climatic implication in the southern Thar Desert margin, western India
Journal of Earth System Science ( IF 1.9 ) Pub Date : 2021-06-05 , DOI: 10.1007/s12040-021-01620-3
Shubhra Sharma , Falguni Bhattacharya , Gaurav Chauhan

The present study summarizes the existing chronometric data of fossil dunes preserved in the southern Thar Desert margin (STM). The objective is to understand the episodes of dune accretion and causes of their spatial and temporal variability along the precipitation gradient. Based on the published ages, the study identifies three major phases of dune accretion. The oldest phase-I is dated between ~25 and 17 ka (MIS-2); the second short-lived phase-II between ~15 and 12 ka, whereas the phase-III occurred between 10 and 5 ka. The second phase terminates with the deposition of fluvially reworked aeolian sand which has the presence of microlithic artifacts and corresponds to the early Holocene strengthened Indian Summer Monsoon (ISM). The study suggests that during phase-I and II, the terrain witnessed a significant reduction in the ISM for which a more southerly position of the Inter-Tropical Convergence Zone (ITCZ) is implicated. During phase-III, an oscillating ISM with overall declining trend is attributed to mid-late Holocene minor fluctuations in the ITCZ (probably proximal to modern summer position). A conspicuous absence of dune building in the northern Thar Desert during the Last Glacial Maximum (LGM) is ascribed to the prevalence of hyper-arid conditions in comparison to the relatively moist conditions in the STM due to its proximity to the Arabian Sea. After ~15 ka, both the STM and the Thar Desert show a broad synchroneity and that coincides with the gradual strengthening of the ISM.



中文翻译:

印度西部塔尔沙漠南缘沙丘堆积模式及其气候意义

本研究总结了保存在南部塔尔沙漠边缘 (STM) 的化石沙丘的现有计时数据。目的是了解沙丘堆积的事件及其沿降水梯度的空间和时间变化的原因。根据公布的年龄,该研究确定了沙丘堆积的三个主要阶段。最古老的第一阶段的日期介于 ~25 至 17 ka (MIS-2) 之间;第二个短暂的第二阶段在~15 到 12 ka 之间,而第三阶段发生在 10 到 5 ka 之间。第二阶段结束于河流改造的风积沙的沉积,其中存在微石器人工制品,对应于早期全新世加强的印度夏季风 (ISM)。研究表明,在第一阶段和第二阶段,地形见证了 ISM 的显着减少,这与热带间辐合带 (ITCZ) 的更南位置有关。在第三阶段,具有整体下降趋势的振荡 ISM 归因于 ITCZ 中晚期全新世的小幅波动(可能接近现代夏季位置)。在末次盛冰期 (LGM) 期间,塔尔沙漠北部明显没有沙丘建筑,这归因于与 STM 中由于靠近阿拉伯海而相对潮湿的条件相比,极度干旱条件的普遍存在。大约 15 ka 之后,STM 和塔尔沙漠都表现出广泛的同步性,这与 ISM 的逐渐加强相吻合。具有整体下降趋势的振荡 ISM 归因于 ITCZ 中晚期全新世的小幅波动(可能接近现代夏季位置)。在末次盛冰期 (LGM) 期间,塔尔沙漠北部明显没有沙丘建筑,这归因于与 STM 中由于靠近阿拉伯海而相对潮湿的条件相比,极度干旱条件的普遍存在。大约 15 ka 之后,STM 和塔尔沙漠都表现出广泛的同步性,这与 ISM 的逐渐加强相吻合。具有整体下降趋势的振荡 ISM 归因于 ITCZ 中晚期全新世的小幅波动(可能接近现代夏季位置)。在末次盛冰期 (LGM) 期间,塔尔沙漠北部明显没有沙丘建筑,这归因于与 STM 中由于靠近阿拉伯海而相对潮湿的条件相比,极度干旱条件的普遍存在。大约 15 ka 之后,STM 和塔尔沙漠都表现出广泛的同步性,这与 ISM 的逐渐加强相吻合。在末次盛冰期 (LGM) 期间,塔尔沙漠北部明显没有沙丘建筑,这归因于与 STM 中由于靠近阿拉伯海而相对潮湿的条件相比,极度干旱条件的普遍存在。大约 15 ka 之后,STM 和塔尔沙漠都表现出广泛的同步性,这与 ISM 的逐渐加强相吻合。在末次盛冰期 (LGM) 期间,塔尔沙漠北部明显没有沙丘建筑,这归因于与 STM 中由于靠近阿拉伯海而相对潮湿的条件相比,极度干旱条件的普遍存在。大约 15 ka 之后,STM 和塔尔沙漠都表现出广泛的同步性,这与 ISM 的逐渐加强相吻合。

更新日期:2021-06-05
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