Abstract The present study is an attempt to infer the response of the dryland fluvial sequences to paleoenvironmental change since the last glacial maximum (LGM) from the semi-arid Saurashtra region, a basaltic terrain of the Late Cretaceous age (Deccan Trap), of Western India. We employed a conventional sedimentological analysis supported by sediment geochemistry, which was constrained by optical dating. Based on detailed field investigation, we identified five terrace sequences from the valley fill deposit in the Shetrunji River basin since 18 ka (i.e. Post LGM). The sedimentary archives expose the deposition during three alternate phases of aggradation and incision, marked on the basis of morphostratigraphy and timing of landform evolution. The coastal region of western India experienced a widespread valley aggradation in response to the rising sea stand and under gradual strengthening of the monsoonal conditions around the 18–9 ka period. The Early Holocene climatic optima (9–7.5 ka) coupled with lower than present but rising sea stand, triggered the intense erosion in the valleys of Shetrunji River basin, leading to erosion/lack of sediment preservation. This was followed by the Middle Holocene period (7.5–5 ka), which experienced valley aggradation. This was ended by the incision post 5.5 ka in the lower reaches of the Shetrunji River. The sea stand was similar to present-day stand, as evidenced by the change from fluvial to the estuarine environment in the top sequence of Site-SL at 5.5 ka. The Late Holocene relative sea stand lowering ~3 ka, led to an incision in the estuarine terrace of about 2 m. The causal mechanism for triggering of this incision is most likely the relative fall in sea stand to present-day level from its Middle Holocene high stand. The Late Holocene period (3–1 ka) shows aggradation in upper reach in fluctuating hydrodynamic conditions with seasonality, followed by a relatively good monsoonal condition at

中文翻译：

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评估印度 Shetrunji 河流域（索拉什特拉）第四纪晚期旱地环境中气候触发的加积切割过程

摘要 本研究试图推断自上次冰期最大值 (LGM) 以来旱地河流序列对古环境变化的响应，来自半干旱索拉什特拉地区，这是一个晚白垩世 (Deccan Trap) 的玄武岩地形。印度。我们采用了由沉积物地球化学支持的常规沉积学分析，该分析受到光学测年的限制。根据详细的实地调查，我们从 18 ka 以来（即 LGM 后）Shetrunji 河流域的山谷填充沉积物中确定了五个阶地层序。沉积档案揭示了三个交替阶段的沉积物，以地貌地层学和地貌演化的时间为基础。印度西部沿海地区在 18-9 ka 时期由于海平面上升和季风条件逐渐加强而经历了广泛的山谷加积。早全新世气候最适（9-7.5 ka）加上低于现在但上升的海位，引发了谢特鲁尼河流域河谷的强烈侵蚀，导致侵蚀/缺乏沉积物保存。随后是全新世中期（7.5-5 ka），经历了谷地加积。这在 Shetrunji 河下游 5.5 ka 的切口后结束。5.5 ka 时，Site-SL 顶部序列中从河流环境到河口环境的变化证明了海平面与现在的海平面相似。晚全新世相对海位下降~3 ka，导致在约 2 m 的河口阶地切口。触发此切口的因果机制很可能是海位从其中全新世高位相对下降到今天的水平。全新世晚期（3-1 ka）在随季节性波动的水动力条件下显示出上游的加剧，随后是相对较好的季风条件