OYSTER REEFS RESPONSE TO THE REGIONAL NEOTECTONICS AND EUSTATIC SEA-LEVEL, NORTHWEST COAST OF BOHAI BAY
渤海湾西北岸牡蛎礁体对区域性构造活动与水动型海面变化的响应

The widely scattered paleo-mean sea-level indicators along the Bohai Bay supply basic foundation for reconstructing of relative sea-level change in this area. During the past 20 years, scientists had built some relative sea-level curves in this area. However, they mixed all the impacting factors to the elevation of paleo-mean sea-level indicators up when they built this curves. A spatial-temporary distribution of such seven indicators, corresponding with the regional predicted sea-level curve, is established to calculate the subsidence of each indicator. Therefore, we can distinguish the contributions of tectonics and sea-level change associated with glacio- and hydro-isostatic adjustment in the local area to the elevations of the indicators. Furthermore, with the results of stable isotopic analyses to the oyster shells in the Biaokou reef and a paleo-earthquake trace in Dawuzhuang reef, we discuss the tectonic subsidence during the buildup of the reef bodies. And we compare the result to a strong paleo-earthquake event occurred in this area with spatial distribution map and 14C dating ages. As proxies, the results of oxygen and carbon isotopic analyses to the shells, lying on different vertical positions in one section, have indicated tectonic movements and subsidence recorded in the reef body while it was building up.