Analysis of sediment provenance using geochemical and isotopic data for a post-LGM sediment core from the western Great Rann of Kachchh, India: Implications for climate control on source regions

This study addresses the nature and causes of post-Last Glacial Maxima (LGM) sedimentation in the Western Great Rann of Kachchh, Gujarat, India. Specifically, we report geochemical and isotopic data (Sr-87/Sr-86 and Nd-143/Nd-144) for a 46.5 m sediment core from the Nara River bed. These data indicate that up to the beginning of the Holocene, sedimentation mostly comprised contributions from monsoon-dominated rivers of Western Himalaya. Later in the early Holocene, a shift towards Indus-derived sediments occurred, with a minor reversal at similar to 7 ka, attributed to the rejuvenation of the Ghaggar-Hakra channel. A renewed contribution from the Indus River routed through the Nara River and through the Kori Creek (mouth of the Nara River) occurred during the mid- to late Holocene. Persistent availability of freshwater during the mid- to late Holocene helped sustain early Iron Age and medieval cultures in the region. However, significant decline in the hydrological system anchored in the shifting Indus River through the Nara channel after the medieval period, likely caused the gradual collapse of these cultures. Our study is important as it demonstrates that, if the sediment source is from regions of contrasting climatic domains (for example, monsoon-dominated western Himalaya rivers and the westerlies-dominated Indus River), temporal changes in precipitation intensities exert a first order control in modulating the sediment provenances.