Detrital zircon U[sbnd]Pb geochronology of modern river sediment in the Eastern Pamir Syntaxis and its implications for the formation of the Pamir and growth of the Tibetan Plateau

Abstract

The Eastern Pamir Syntaxis links the western Tibetan Plateau with the western syntaxis of the Himalayan-Tibetan orogen. Quantifying temporal and spatial variations in uplift rates for the Eastern Pamir Syntaxis is critical for understanding the growth of the Himalayan-Tibetan orogen. To better understand these variations, we report n = 285 new detrital zircon UPb ages from sediments in modern rivers of the Eastern Pamir Syntaxis. When compared with previous work, our data, with a major age mode around ∼107 Ma, indicate that siliciclastic sediments in the Taxkorgan River were primarily derived from Cretaceous rocks. Whereas a less prominent age mode around ∼13 Ma suggests that Miocene rocks made an important sediment contribution to the Taxkorgan River. The other notable age modes are in the range of 200–300 Ma and 600–800 Ma. Our data suggest that detrital zircon UPb signatures for rivers draining the Eastern Pamir Syntaxis change significantly from south to north, and the influence of Cretaceous proto-sources gradually diminishes northward. Because Tibetan sutures are traceable into the Pamir, these data help define the distribution of late Early Cretaceous rocks associated with the closure of the Meso-Tethys within the Pamir. These data support the establishment of the modern-like river pattern in the Eastern Pamir Syntaxis contemporaneous with activity on the Kongur Extensional System in the northeast Pamir.