Abstract:

The latest results of high accuracy aeromagnetic survey (0.1nT) obtained in 1984 are used in this paper to divide the lower Yangtse Paraplat form into three magnetic field areas namely gentle varied positive-negative magnetic field area to the north of Tianchang-Dongtai line; the massive and streaky positive magnetic field area to the south of Anqin-north Hangzhou line; the positive anomaly zone which is between the above mentioned two and developed ongently negative background. These magnetic field zones, from north to south.are the reflection of the Haizhou Group, the Banxi Group and the Lengjiaxi Group respectively. Analyzed the magnetic fields,Tiancbang-Dongtai and Anqing-north Hangzhou rifts have been discovered by the authors. These rifts cut the Lower Yangtse Paraplat form into three blocks of different magnetic field features and controlled the development of the covery strata. The authors consider that the origin of the huge negative anomaly distributed along the Yangtse River stem from south-dipping occurrence (55?) of tbe Yangtse River rift belt. Except the basement characters and regional tectonics, the basement configuration and the development of covery strata of this region are also discussed, and the Paleozoic isopach map is work out according to the data of aeromagnetism, gravitation, seismics and logging. This map briefly shows the basic feature of Paleozoic carbonate rocks which are thicker in the north and thinner or even lacuna in the south. It is suggested that Nanjing-Nantong regionis the best of all in oil potential; northern Jiangsu the next, Jiangnan old landless favourable.