A strongly positive sulphur isotopic shift in late Ediacaran-early Cambrian seawater: evidence from evaporites in the Salt Range Formation, northern Pakistan

Abstract

The Salt Range Formation in northern Pakistan is globally well-known for its extremely large evaporite deposits dated to the upper Ediacaran–lower Cambrian. This huge evaporite belt formed an area covering present-day parts of India, Pakistan, Iran, Oman, and even South China (~200,000 km2 in South China). Sulphate minerals, including anhydrite and gypsum, can continuously record seawater sulphur isotopic composition. Until now, there was only one dataset reporting the isotopic composition of evaporites in Pakistan. This study reports new data, which points to a strongly positive sulphur isotopic shift (>+30‰, VCDT values) in the Salt Range Formation in Pakistan. Based on the stratigraphic position, similarity in lithology, age, and sulphur isotope data of the evaporitic sequences, it can be inferred that the Neoproterozoic Indo-Pakistan Plate and the Yangtze Platform were closely related palaeogeographically during the terminal Neoproterozoic. This interpretation can improve understanding of the palaeogeographical evolution of the area during the Neoproterozoic, with particular reference to the origin of biogeochemical cycles and the diagenetic evolution of the evaporitic deposits