δ13Corg perturbations preserved by the interglacial Datangpo Formation in South China with implications for stratigraphic correlation and carbon cycle

Abstract

Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated “Snowball Earth ” hypothesis and the early evolution of metazoan life. The carbon cycle and redox conditions of the Sturtian-Marinoan non-glacial interval have been subjected to much controversy in the past decades because of the lack of a high-resolution stratigraphic correlation scheme. As one of the typical Sturtian-Marinoan interglacial deposits, the Datangpo Formation was widely distributed in South China with shales continuously deposited. The previous zircon dating data of the Datangpo Formation provide important ages for global constrain of the Sturtian-Marinoan non-glacial interval. Here we present a high-resolution straitigraphic study of the organic carbon isotopes of the Datangpo Formation from a drill core section in northern Guizhou Province. Based on measured episodic δ¹³C_org perturbations, three positive shifts and three negative excursions are identified. A δ¹³C_org-based chemostratigraphic correlation scheme is proposed herein that works well for the Datangpo Formation regionally. Meanwhile, the δ¹³C_org vertical gradients changed dynamically throughout the formation. This discovery implies that a significant ocean circulation overturn might have occurred in the upper Datangpo Formation, coinciding with the potential oxygenation.

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