DOI: 10.57760/sciencedb.37530
title: Cretaceous detrital zircons and related data from the Jiangcheng area in the southern Simao Basin, southeastern Tibetan Plateau
title: Cretaceous detrital zircons and related data from the Jiangcheng area in the southern Simao Basin, southeastern Tibetan Plateau

description: The Cretaceous drainage evolution of the southeastern Tibetan Plateau (SETP) remains contentious, largely due to insufficient chronological constraints. This study presents 1121 detrital zircon U-Pb ages obtained from a magnetostratigraphically dated sedimentary sequence (Jiangcheng section) in the Simao Basin, which spans from ~141.5 to 71 Ma. Our data revealed a pronounced stratigraphic variation in the detrital zircon age spectra. Samples from the upper Bazhulu, Jingxing and Mangang formations show clusters at 300-200 Ma, 490-400 Ma, 1000-750 Ma, 1950-1750 Ma and 2600-2400 Ma. A significant shift is observed within the middle-lower Mengyejing (MYJ) Formation, marked by the weakening of ancient peaks (1950-1750 Ma, 2600-2400 Ma) and the dominance of younger signatures (300-200 Ma, 490-400 Ma, 1000-750 Ma). These major peaks persisted into the upper MYJ Formation, but with a weakened 1000-750 Ma signal, a resurgence of older peaks, and a notable increase in 150-80 Ma zircon content. Based on an integrated analysis of new and published zircon provenance data, we reconstructed a three-stage Cretaceous paleo-drainage evolution history for the SETP. Stage I (~141-109 Ma): A transcontinental drainage system linked the Songpan-Ganzi, Sichuan Basin and Qiangtang to the Paleo-Pacific Ocean via the Simao and Khorat basins under a relatively humid condition; Stage II (~109-90 Ma): A saline lacustrine environment prevailed in the Simao Basin, coeval with a persistently diminished continental-scale fluvial network eastward, amidst widespread aridification; Stage III (~90-71 Ma): A Stage I-type transcontinental drainage was reestablished and moderately expanded, despite subdued fluvial activity under persistent arid climate. Overall, the Simao Basin provenance signatures reflect Cretaceous transcontinental drainage evolution from establishment, through contraction, to eventual partial recovery with modest expansion. Our results provide a refined model for Cretaceous drainage reorganization in the SETP, which was fundamentally controlled by the interplay of global/regional tectonics and paleoclimatic forcing.
description: The Cretaceous drainage evolution of the southeastern Tibetan Plateau (SETP) remains contentious, largely due to insufficient chronological constraints. This study presents 1121 detrital zircon U-Pb ages obtained from a magnetostratigraphically dated sedimentary sequence (Jiangcheng section) in the Simao Basin, which spans from ~141.5 to 71 Ma. Our data revealed a pronounced stratigraphic variation in the detrital zircon age spectra. Samples from the upper Bazhulu, Jingxing and Mangang formations show clusters at 300-200 Ma, 490-400 Ma, 1000-750 Ma, 1950-1750 Ma and 2600-2400 Ma. A significant shift is observed within the middle-lower Mengyejing (MYJ) Formation, marked by the weakening of ancient peaks (1950-1750 Ma, 2600-2400 Ma) and the dominance of younger signatures (300-200 Ma, 490-400 Ma, 1000-750 Ma). These major peaks persisted into the upper MYJ Formation, but with a weakened 1000-750 Ma signal, a resurgence of older peaks, and a notable increase in 150-80 Ma zircon content. Based on an integrated analysis of new and published zircon provenance data, we reconstructed a three-stage Cretaceous paleo-drainage evolution history for the SETP. Stage I (~141-109 Ma): A transcontinental drainage system linked the Songpan-Ganzi, Sichuan Basin and Qiangtang to the Paleo-Pacific Ocean via the Simao and Khorat basins under a relatively humid condition; Stage II (~109-90 Ma): A saline lacustrine environment prevailed in the Simao Basin, coeval with a persistently diminished continental-scale fluvial network eastward, amidst widespread aridification; Stage III (~90-71 Ma): A Stage I-type transcontinental drainage was reestablished and moderately expanded, despite subdued fluvial activity under persistent arid climate. Overall, the Simao Basin provenance signatures reflect Cretaceous transcontinental drainage evolution from establishment, through contraction, to eventual partial recovery with modest expansion. Our results provide a refined model for Cretaceous drainage reorganization in the SETP, which was fundamentally controlled by the interplay of global/regional tectonics and paleoclimatic forcing.