Late Neoproterozoic paleomagnetic results from the Sugetbrak Formation of the Aksu area, Tarim basin (NW China) and their implications to paleogeographic reconstructions and the snowball Earth hypothesis

摘要

In order to better constrain the Neoproterozoic paleogeographic reconstruction of continents and to improve the understanding of the snowball Earth hypothesis, paleomagnetic investigations were carried out in the Aksu area of the northwestern Tarim basin. Forty-eight sites of samples were collected from the Sugetbrak and Chigebrak Formations. Twenty-four sites of sandstone and volcanic rock from the Sugetbrak Formation revealed stable characteristic remanent components (ChRm) isolated between 500 and 680 °C. The computed magnetic directions from these components are consistent and significantly distinguished from those of younger ages. Both normal and reverse polarities have been observed, and a positive fold test is revealed after bedding corrections at 95% confidence level. Anisotropy of magnetic susceptibility measurements shows primary sedimentary fabrics with weak anisotropy degrees. A paleomagnetic pole is calculated at 19.1°N, 149.7°E, k = 11.2, A95 = 9.3° with n = 24, yielding a paleolatitude of not, vert, similar27°N for the sampling area. The chemo-stratigraphic correlation of this section with reference ones reveals an average age of not, vert, similar595 Ma. A new paleogeographic reconstruction has been attempted showing general low paleolatitude positions for the Australia, South China and Tarim blocks at about 600 Ma. This observation provides new evidences for the snowball Earth hypothesis.