Based on studies of the Holocene buried and living oyster reefi on the Oyster Reef Plain and its adjacent shallow sea area of northwest Bohai Bay, this paper has reexamined the sedimentary significance and chronology of the data related to the oyeter reefi, and further collated the formation period as well as top and bottom altitudes of each reef group. The newly discovered oldest (the late Early Holocene) reef group, I.e., Group Pre- I -1, was added to the originally determined nine reef-groups. Also, newly discovered reefi at the Binhai Lake and the airport area are tentatively assigned to the Reef V as its subgrouop V-1. Leveling for top altitude fluctuations in Dawuzhuang and other two reef sites indicates that the maximum fluctuation of the reef-top is ±0.7m, which is used as the vertical error range. The investigation of the altitude of LISL (the last irregular sandy/silty lamina) above the reef-top in five reef sites, including Beihuaidian reef, reveals that the average thickness between the reef top and the LISL is approximately 1.6m, which is the maximum vertically accreting thickness given by the local accommodation space between the MSL and MHW. It serves as evidence verifying a conclusion that the reef top corresponds to the msl. Thus, the reef top used as the sea level indicator is defined, I.e., the vertical range by adding ±0.7m to the reef top corresponds to the MSL.%以他人和本研究小组对渤海湾西北岸牡蛎礁平原、毗邻浅海区的全新世埋藏牡蛎礁和现生牡蛎礁的研究为基础,重新考订了与礁体有关的数据的沉积学意义及年龄,进一步厘定了牡蛎礁的形成时间、礁体顶板和底板的高度.在原有的9个礁群的基础上,增加了目前发现的最老的早全新世晚期礁群；在沿海低地新发现的滨海湖、空港牡蛎礁,暂作为北淮淀礁群的亚礁群.根据对大吴庄等3处礁体顶板的水准测量,发现礁顶最大起伏为±0.7m,以此作为礁顶自身的垂直误差范围.据对北淮淀等5个礁体的“最后一个砂质纹层”高度的调查,推断礁顶上覆潮间带泥层的平均厚度为1.6m.该厚度是当地海平面与平均高潮位之间的调适空间所能提供的最大堆积厚度,成为支持礁顶高度对应海平面的佐证.根据上述结果,确定了渤海湾牡蛎礁顶板作为海面变化标志点的条件.该研究是重建牡蛎礁平原全新世相对海面变化曲线和探讨其与气候变化关系的基础.
展开▼
