PROVENANCE OF MODERN RIVER SANDS IN THE WESTERN TARIM BASIN: IMPLICATIONS FOR THE ORIGIN OF THE TAKLIMAKAN DESERT AND UPLIFT OF THE KUNLUN

The sediments accumulating in the western Tarim Basin potentially record the evolving history of mountain uplift and erosion in the Kunlun and eastern Pamirs, as well as the development of the Taklimakan Desert. However, unraveling the paleo-history is impossible unless the tools we use are ground truthed inmodern basin. Five river sediments from the Hotian, Yarkand, and Kesile Rivers, as well as from the desert dunes are being studied to determine the primary sources of sediment. Point counting was conducted for each sample, as well bulk sediment Sr and Nd isotopes, together with U-Pb dating of detrital zircons. The sample from the Hotian River correlates best with bedrock from the Songpan Garze terrain, using Kernal Density Estimate (KDE) plots that highlight populations at 200-250 and 400-500Ma. In contrast, the neighboring Yarkand River shows a large peak around 100 Ma indicative of derivation from the Karakoram, while the Kesile shows peaks at ~300 and ~800 Ma that are unique to the Pamir sources. Desert dune sands are closest to the Kesile River and imply most of the Tarim desert is derived from the Pamirs, not the Kunlun. Comparison of old sediments and our modern rivers suggests enhanced erosion possibly linked to surface uplift of the Kunlun between 20 and 17 Ma, much earlier than previously suggested.