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The alluvial successions in the northern Gujarat alluvial plain (western India) have been investigated for reconstructing the climatic fluctuations during the last 40 ka. Alluvial architecture and geochemical proxies indicate prevalence of a strengthened Indian Summer Monsoon (ISM) with fluctuations between the late Marine Isotopic Stage 3 (MIS 3; 371 ka) to the early MIS 2 (27 ka). A gradual onset of aridity (declining ISM) after 27 ka with peak aridity at similar to 22 ka is observed. A gradual strengthening of ISM at around 18 and > 12 ka followed by a short reversal in ISM intensity between 12 and 11 ka, is attributed to the Younger-Dryas (YD) cooling event. The aeolian sand sheet dated to 6 and 3.5 ka represents the onset of regional aridity. Following this, a short-lived humid phase was observed after similar to 2 ka, which includes the Medieval Warm Period (MWP). The study suggests that the variability in the ISM to the latitudinal migration of the Inter Tropical Convergence Zone was caused by insolation-driven cooling and warming events in the North Atlantic.

The incision of the valley fill alluvium occurred in two distinct phases. The older incision phase occurred after 11 ka and before 6 ka, whereas the younger incision phase that led to the development of present day topography is bracketed between 3.5 ka and before 1 ka. The older incision phase is ascribed to the early to mid-Holocene enhanced ISM (climatically driven), whereas the younger incision seems to be modulated by the activation of basement faults (tectonically driven). (C) 2017 Elsevier B.V. All rights reserved.