Abstract
The Tethys Sea extended into the Kuqa Depression from the Paleocene to the late Eocene and provided an abundant provenance for the deposition of evaporite sequences. Until now, detailed research on the history of transgressions during the late Paleocene-early Eocene in the Kuqa Depression has been limited. Therefore, in this study, we took the upper Paleocene Talak section and the lower Eocene Xiaokuzibai section in the western part of the Depression as the research objects and analyzed the petrology, the carbon and oxygen isotopes of carbonate rocks, and the sulfur and strontium isotopes of gypsum rocks to systematically study the above issues. The δ13C, δ18O and δ34S values of the upper Paleocene evaporite sequences were determined to be between 4.2‰ and 5.7‰, between −5.2‰ and 2.4‰, and between 16.5‰ and 17.9‰, respectively. The δ13C, δ18O, δ34S, and 87Sr/86Sr values of the lower Eocene evaporite sequences were determined to be between −6.9‰ and −2.0‰, between −9.0‰ and −4.5‰, between 10.5‰ and 17.0‰, and between 0.708642 and 0.709883, respectively. The analysis results show that the evaporite sequence of the upper Paleocene was formed by transgression. The deposition of the evaporite sequence changed from continental to marine deposition, and then gradually transitioned to continental during the Early Eocene. This paper is of great significance for reconstructing the history of transgressions in the Tethys tectonic realm during this period.
Highlights
Multiple transgression-regression cycles of Tethyan seawater occurred during the Cretaceous-Paleogene, and these cycles represent major events during the geological evolution of the Tarim Basin
In the early Cretaceous, seawater invaded from west to east in the southwest of the Tarim Basin, and the transgression scope increased during the Paleocene
The δ13 C values of the upper Paleocene micritic dolomite are positive, and the variation range of the values is small, with values ranging from 4.2% to 5.7%
Summary
Multiple transgression-regression cycles of Tethyan seawater occurred during the Cretaceous-Paleogene, and these cycles represent major events during the geological evolution of the Tarim Basin. In the early Cretaceous, seawater invaded from west to east in the southwest of the Tarim Basin, and the transgression scope increased during the Paleocene. Seawater began to extend into the northern Tarim Basin (the Kuqa Depression) (Figure 1). How the transgressions of the late Paleocene-early Eocene affect the Kuqa Depression is an urgent problem that remains to be solved, with obvious significance for revealing the evolution of the Tethyan Sea. Minerals 2020, 10, 834; doi:10.3390/min10090834 www.mdpi.com/journal/minerals. Minerals 2020, 10, x FOR PEER REVIEW Figure 1. Paleogeographic sketch sketch map map of of the the Paleocene.
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