Paleomagnetic Study Of Neoproterozoic Leigongwu Formation In Jiangshan Of Zhejiang Province And Its Geological Implications

Paleomagnetic study of Neoproterozoic strata in South China Block is of great significance for supercontinent evolution,Snowball Earth and True Polar Wander hypothesis.One of the main Neoproterozoic scientific issues is global glaciation.In recent years,snowball Earth hypothesis was given to explain the Neoproterozoic global glaciation,however,one of the two major theoretical basis of the hypothesis,the continent was at the low latitude in the global glaciation period,only depend on a few paleomagnetic results.In addition,glacial strata division and corrections in south China are still in hot debate due to late magmatic and tectonic influence.In this study,combined with reliable,high-quality,precise aged paleomagnetic data and a review on the stratigraphy of glacial strata,to address the above issues.The top and the base of the Nanhua System and the division were highlighted.The reliable paleomagnetic results obtained from the Leigongwu Formation of the JiangShan area indicate that(1)The distribution of the glacial strata in the Yangtze Block has obvious regional characteristics.The sedimentary sequence is relatively complete in the neighboring area of Hunan-Guizhou-Guangxi and part of the area is exposed to the third-glacial stratum,such as Zhijiang and Jianhe,but the research in the neighboring area of Zhejiang-Jiangxi-Anhui is weak.The tillite of the Leigongwu Formation,which is similar to the Nantuo Formation in other areas of South China,was dominated by massive glacial till with complex gravels,such as quartzite,sandstone,limestone,gneiss and granite;The size of gravels are different,ranging from 10 ~ 30 cm in diameter.It is noteworthy that some larger gravels display scratches and etching.(2)Hytheriss loop of the Leigongwu Formation suggest the main magnetic minerals of tillite are the magnetite and hematite;(3)Thermal demagnetion results show low and high temperature components,which the later one was thought to be primary and give the paleolatitude of the South China Block about 14 degrees north latitude,consistent with the previous results that obtained from the other areas of South China,thus further supporting the snowball Earth hypothesis and its also provides a basis for the reconstruction of the Neoproterozoic paleogeography in South China.