Detrital zircon provenance comparison between the Paleocene-Eocene Nangqian-Xialaxiu and Gongjue basins: New insights for Cenozoic paleogeographic evolution of the eastern Tibetan Plateau

Abstract

Paleogeographic reconstructions of terranes can greatly benefit from the provenance analysis of sediments. A series of Cenozoic basins provide key sedimentary archives for investigating the growth of the Tibetan Plateau, yet the provenance of the sediments in these basins has never been constrained robustly. Here we report sedimentary petrological and detrital zircon geochronological data from the Paleocene-Eocene Nangqian-Xialaxiu and Gongjue basins. Sandstone detrital modes and zircon morphology suggest that the samples collected in these two basins were sourced from recycled orogen. Detrital zircon geochronology indicates that sediments ACCEPTED MANUSCRIPTthe Nangqian-Xialaxiu Basin are characterized by two distinct age populations at 220-280 Ma and 405-445 Ma. In contrast, three predominant age populations of 207-256 Ma, 423-445 Ma, and 1851-1868 Ma, and two subordinate age populations of ~50 Ma and ~2500 Ma, are recognized in the Gongjue Basin. Comparison with detrital zircon ages from the surrounding terranes suggests that sediments in the Nangqian-Xialaxiu Basin come from the neighboring thrust belts, whereas sediments from the Gongjue Basin are predominantly derived from the distant Songpan-Ganzi Terrane with minor contribution from the surrounding areas. A three-stage Cenozoic evolution of the eastern Tibetan Plateau is proposed. During the Paleocene, the Nangqian-Xialaxiu Basin appeared as a set of small intermontane sub-basins and received plentiful sediments from the neighboring mountain belts; during the Eocene, the Gongjue Basin kept a relatively low altitude and was a depression at the edge of a proto-Plateau; since the Oligocene, the Tibetan Plateau further uplifted and the marginal Gongjue Basin was involved in the Tibetan interior orogeny, indicating the eastward propagation of the Tibetan Plateau.

Paleogene Sedimentary Records of the Paleo‐Jinshajiang (Upper Yangtze) in the Jianchuan Basin, Yunnan, SW China

“…(2017) presented a new age of 35.4 ± 0.8 Ma of the uppermost formation (Jianchuan Fm) in the Jianchuan Basin and reevaluated the same stable oxygen isotopic data to suggest a lower paleo‐elevation of ∼1.2 ± 1.2 km during the late Eocene. In comparison, the Gonjo Basin had attained a minimum average elevation of 2.1–2.5 km in the early Eocene (Tang et al., 2017; Yang et al., 2019), which implies southward flow by the paleo‐river. Thus, the sedimentary sequences deposited during the Paleocene‐early Eocene in the Gonjo Basin reflect the very early stage of the paleo‐Jinshajiang draining the Tibetan Plateau.…”

Remagnetization of Red Beds on the Tibetan Plateau: Mechanism and Diagnosis

“…The Nangqian Basin fill is dominated by reddish mudstone and siltstone, interbedded with minor limestone and gypsum (Li et al, 2018). The occurrence of Paleogene fossils and isotopic dating of the detrital zircons in red beds, intrusions, and volcanic rocks interbedded with the uppermost strata constrain the depositional age at >38 Ma (Horton et al, 2002; Spurlin et al, 2005; Zhang et al, 2019). The Shanglaxiu Basin contains thick red sandstone interbedded with muddy limestone, gypsum, and a few volcanic layers.…”

Eocene Rotation of the Northeastern Central Tibetan Plateau Indicating Stepwise Compressions and Eastward Extrusions

“…The central TP is an ideal realm for investigating the plateau deformation and uplift models. Numerous studies have supposed that the central TP had emerged tectonic uplift and crustal thickening during the Eocene inferred from dating and chemical compositions of potassic volcanic rocks, paleotopography, and crustal shortening (Chen et al, 2018; Kapp & DeCelles, 2019; L. Li, Garzione, et al, 2018; Lin et al, 2020; Miao et al, 2016; Staisch et al, 2016; Tang et al, 2017; Q. Wang, Wyman, et al, 2008; Wang et al, 2011; C. S. Wang, Dai, et al, 2014; Xu et al, 2016; Zhang et al, 2019). However, all these studies above relied on single volcanic event dating at different sites and lacked long‐term continuous dating of basin Cenozoic sediments that archive rich information on continuous shortening and uplift of the plateau and related climatic change.…”

“…Wang, Wyman, et al, 2008;Wang et al, 2011;C. S. Wang, Dai, et al, 2014;Xu et al, 2016;Zhang et al, 2019). However, all these studies above relied on single volcanic event dating at different sites and lacked long-term continuous dating of basin Cenozoic sediments that archive rich information on continuous shortening and uplift of the plateau and related climatic change.…”