华南早新元古代莲沱组地层磁倾角偏低研究及其古地理意义

华南莲沱组最新的年龄结果表明,其时代结束于715Ma,因此,准确确定莲沱组的古纬度对"雪球地球"的研究具有重要意义。通过对莲沱组红层进行等温剩磁各向异性研究,获得其磁倾角校正因子为0.8719,校正后的磁倾角为70.4°,对比热退磁实验测得的莲沱组磁倾角为67.8°,则其磁倾角偏低量为2.6°。通过校正前后的磁倾角分别计算古纬度,获得磁倾角偏低所引起的古纬度变化为3.9°±6°。通过对比华南与澳大利亚-东南极板块的720Ma古地理位置,发现这一时期冰碛岩从中纬度到赤道广泛分布,验证了当时的"雪球地球"环境。

Inclination shallowing study of the Early-Neoproterozoic Liantuo Formation in South China and its paleogeographic implications

New dating data indicate that the Liantuo Formation ended at 715Ma, and hence the constraint of the paleolatitude of the Liantuo Formation will shed a light on the "Snowball Earth" theory. Researchers have obtained reliable paleomagnetic results from the Liantuo Formation, but the inclination shallowing has not been considered by them. In this paper, the authors obtained a corrected parameter by conducting a remnant anisotropy research on Liantuo Formation. The inclination shallowing in Liantuo Formation is 2.6°, which results in a latitude difference of 3.9°±6°. The reconstruction of the South China and Australia block at 720Ma shows the diamictite distribution from middle latitude to tropical region, which proves the "Snowball Earth" theory.