苏北地区上前寒武系古地磁研究及我国南北方上前寒武系的对比

苏北地区上前寒武系发育一套厚约五千米以上以海相为主的未变质地层。由于其岩性和生物组合的特殊性及其所处地理和构造位置的重要性,被视为解决我国南北方上前寒武系衔接和对比的关键地区之一。近年来,本区上前寒武系在生物地层、岩石地层、同位素地质等方面已经取得了一些重要成果,但对它们在我国上前寒武系所处的位置仍持有不同意见。至今,尚未见到有关的古地磁文章发表。

STUDY ON THE PALEOMAGNETISM OF UPPER PRECAMBRIAN IN NORTHERN JIANGSU AND CORRELATION BETWEEN THE UPPER PRECAMBRIAN STRATA IN SOUTH AND NORTH CHINA

We have collected 174 oriented hand samples among them 549 specimen prepared from 46 sections of upper Precambrian in North Jiangsu, South Shandong and North Anhui Provinces. These specimens were tested in an alternating magnetic field with peak of 100-800 Oersted, and some palaeomagnetic parameters were obtained.The upper Precambrian apparent polar-wander path for North Jiangsu was set up preliminarily. It is shown that 1)the upper Precambrian apparent polar-wander path in North Jiangsu area lies in a special range near the end of the trace of upper Precambrian apparent polar-wander path of Ji County; 2)the position of virtual geomagnetic pole for Jingeryu group in Ji County is in approximate conformity with the average position of virtual geomagnetic pole for Lanlin and Xinxing groups, thus providing evidence for the stratigraphic correlation between the area and upper Precambrian beds in North China; 3)the set of upper Precambrian beds over Jushan group in North Jiangsu probably can be correlated with the Sinian beds in South China.The results of measurement showed that the beds of upper Precambrian in North Jiangsu province are mostly Normal. Most of the sedimentary beds fall between 20?-30? N latitudes. It provides palaeomagnetic evidences for the formation of purplish red sandstone, limestone, dolomite and a large amount of carbonates.