东海陆架区中北部前第三系基底综合地球物理研究

从地震、钻井资料出发，结合周边地质特征，推断东海陆架区中北部存在中生界和古生界地层。结合地震资料，正演消除了海底和新生界密度不均匀在重力场上的影响，定量反演重、磁力异常并求取了重力基底和磁性基底。重力基底的特征在东西分带的大背景下表现出“靠陆侧南北分块，靠洋侧东西分带”的特点。西湖凹陷区的磁性基底与重力基底埋深大致相同，不一致地方可能是受岩体的影响。西湖凹陷以西地区，包括海礁凸起等单元，总体出现磁性基底埋深比重力基底埋深深2km左右，初步解释为古生界地层的反映。中生界地层厚度的分布也具有东西分带和南北分块特点。西湖凹陷西缘的中生界地层厚度大，其中带中生界虽然含有一定的火山岩或火山碎屑岩，但沉积岩更多，这对下一步的油气勘探有利。

INTEGRATED GEOPHYSICS RESEARCHES ON BASEMENT STRUCTURE OF PRE-CENOZOIC SEDIMENT BASIN IN CENTRAL AND NORTHERN EAST CHINA SEA SHELF BASIN

Mesozoic and Paleozoic strata were deduced to exist in the study area on the basis of seismic and borehole data and the geological features in the adjacent areas. The gravity effects resulted from inhomogeneous densities of the sea bottom and Cenozoic strata were removed by forward modeling based on seismic data. Moreover, the gravitational and magnetic basements were obtained by quantitative inversion of gravity & magnetic anomalies. The gravity basement represented the features of block shape in south-north direction near the continent flank and stripe shape in east-west direction near the ocean flank in the overall background of stripe style in east-west direction. The magnetic basement of Xihu sag was roughly similar to the gravity basement except the effects of intrusive rocks. On the whole, the buring depth of magnetic basement to the west of Xihu sag, including the units such as Haijiao uplift, was about 2 km deeper than that of the gravity basement, which was interpreted as the effects of Paleozoic strata. The thickness distribution of Mesozoic strata also behaved itself with the features of block shape in south-north direction and stripe shape in east-west direction . The thickness of Mesozoic strata in the west area of Xihu sag was relatively large as a result of depositing certain volcanic rocks or pyroclastic rocks and large amounts of sedimentary rocks, which was beneficial to the further oil and gas exploration. Finally, the characteristics of Mesozoic thickness distribution were analyzed in the paper.