Combined paleomagnetic and isotopic data from the Doushantuo carbonates, South China: implications for the 'snowball Earth' hypothesis

摘要

We investigated the paleomagnetism and stable isotopic signatures of the Late Neoproterozoic Nantuo tillite and overlying Doushantuo carbonates (Hunan Province, South China Block). The carbon isotope profile is typical of post-glacial series commonly observed elsewhere for the upper part of the Neoproterozoic. Together with recent radiometric dates of the carbonates, a Marinoan (ca. 600 Ma) age for the Nantuo tillite, rather than a Sturtian (ca. 750 Ma) age, is preferred. The Nantuo glacial deposits and its associated cap carbonates are remagnetized. On the contrary, a positive fold test and similarities between the Australia and South China apparent polar wander paths suggest a primary remanence for the Doushantuo Formation, which yields an equatorial paleolatitude of 3±4.5°N. Four other paleomagnetic studies have found glacial sediments to be situated at low latitudes during this period. A distributed repartition of glacial deposits from low to high latitudes is shown on a new ca. 600 Ma paleogeographic reconstruction, strongly supporting the existence of a global Neoproterozoic glaciation.