Sedimentary environment of Ediacaran glacigenic diamictite in Guozigou of Xinjiang, China

Abstract

The Talisayi Formation found in the Guozigou region on the southern side of Sayram Lake of Xinjiang, China is a Neoproterozoic glacigenic diamictite succession that has not been adequately researched. According to its isotopic geochronology and regional stratigraphic correlation, the Talisayi Formation is equivalent to the Ediacaran glacial sediments. The present paper provides the geochemical data of the Talisayi Formation that reveals the tectonic setting and sedimentary environment in this area during the Ediacaran period. The oxides of Si, K, Na and Al and their ratios of matrix materials from glacigenic diamictites and bulk rock of siltstone and argillaceous siltstones indicate that the sedimentary environment of this formation evolved from a tectonically active region to a passive continental margin. Values of CIA (carbonate-corrected Chemical Index of Alteration) ranging from 54 to 74 show a low-middle weathering action under a glacial environment. Total organic carbon (TOC), V/Cr, Ni/Co and U/Th ratios suggest that the sediments deposited in shallow water with an oxic and weak hydrodynamic condition. There is an abrupt rise in TOC, V/Cr, Ni/Co and U/Th ratios respectively in the overlying Lower Cambrian dolomitic limestones and in the bottom of Talisayi Formation, indicating a rapidl increase in biologic productivity and a variation in redox conditions, which was probably caused by seawater mixing of deep anoxic water and surface oxic water.