Cenozoic evolution of the Pamir plateau based on stratigraphy, zircon provenance, and stable isotopes of foreland basin sediments at Oytag (Wuyitake) in the Tarim Basin (west China)

Abstract

The Pamir salient is the western expression of mountain growth related to Indo-Eurasian convergence. Though a rough framework has emerged describing the tectonic evolution of the Pamir, detailed knowledge of the spatial and temporal evolution of Cenozoic deformation is necessary to determine how strain progressed through the orogenic belt. Here we present new stratigraphic, zircon provenance, and stable isotope data from Jurassic to Miocene strata along the Pamir’s northeastern margin near the town of Oytag (Wuyitake) in the Tarim Basin (west China). Prominent ∼40 Ma peaks in Oligocene to early Miocene detrital zircon grains record the erosion of an Eocene belt of shoshonitic rocks in the central to southeastern Pamir. This is roughly coincident with an ∼4‰ shift in the oxygen isotopic composition (δ 18O) of carbonates during the Eocene and/or Oligocene (from an average of −8.7‰ to −12.6‰), suggesting a reorganization of atmospheric circulation during that time. This could have been caused by uplift of Tarim Basin-bounding ranges and/or retreat of the Paratethys Sea. A subsequent change from Eocene to Jurassic aged detrital zircon grains in the early to middle Miocene indicates provenance shifted from source rocks in the central and/or SE Pamir to the hanging wall of the Main Pamir Thrust (MPT), coincident with prograding facies at that time. This suggests deformation progressed outward toward the northeast margin of the Pamir plateau in the early to middle Miocene. Our results corroborate outward advancement of Himalayan deformation, affecting all margins of the Tarim Basin by the middle Miocene.