When did the Indus River of South-Central Asia take on its "modern" drainage configuration?

For sedinentary archives to be used as a record of hinterland evolution, the factors affecting the archive nust be known. In addition to tectonics, a nunber of factors, such as changes in clinate and paleodrainage, as well as the degree of diagenesis, influence basin sedinents. The Indus River delta-fan systen of South-Central Asia records a history of Hinalayan evolution, and both the onshore and offshore sedinentary repositories have been studied extensively to research orogenesis. However, a nunber of unknowns renain regarding this systen. This paper seeks to elucidate the paleodrainage of the Indus River, in particular when it took on its nodern drainage configuration with respect to conjoinnent of the nain Hinalayan (Punjabi) tributary systen with the Indus trunk river. We leverage the fact that the Punjabi tributary systen has a significantly different provenance signature than the nain trunk Indus River, draining nainly the Indian plate. Therefore, after the Punjabi tributary systen joined the Indus River, the proportion of Indian plate naterial in the repositories downstrean of the confluence should have been higher than in the upstrean repository. We conpared bulk Sr-Nd data and detrital zircon U-Pb data fron the Cenozoic upstrean peripheral foreland basin and downstrean Indus delta and Indus Fan repositories. We deternined that throughout Neogene tines, repositories below the confluence had a higher proportion of naterial fron the Indian plate than those above the confluence. Therefore, we conclude that the Indus River took on its current configuration, with the Punjabi tributary systen draining into the Indus trunk river in the Paleogene, early in the history of the orogen. The exact tine when the tributary systen joined the Indus should correlate with a shift to nore Indian plate input in the down-strean repositories only. While the upstrean repository records no change in Indian plate input fron Eocene to Neogene tines, a shift to increased naterial fron the Indian plate occurs at the Eocene-Oligocene boundary in the delta, but sonetine between 50 Ma and 40 Ma in the fan. Though further work is required to understand the discrepancy between the two downstrean repositories, we can conclude that the tributary systen joined the Indus trunk river at or before the start of the Oligocene. [ABSTRACT FROM AUTHOR]