Konggang oyster reef in Tianjin constrained by both the Mid-Holocene environmental deteriorations and the local neotectonic faults

The buried Konggang oyster reef, located in the northwestern coast of Bohai Bay, is a newly observed reef. Systematical sampling was carried out in the reef body and the underlying and overlying muddy sediments, respectively. AMS 14C dating shows that the duration of this reef is about 2200a from 6170 to 3980cal BP. The reef, 2.3 m thick, can be divided into three parts. Its middle part, 5900-4100cal BP, is a slowly-developed stagnant period coinciding with Cold Event 4. The end of the reef development was approximately consistent with Cold event 3. According to the new AMS 14C data, the reef has been reassigned to oyster reef Group III-2. Based on scrutinizing the relationship between the oyster reef development and the neotectonic movement, the authors hold that the Holocene oyster reef plain is mainly constrained by the alignment of Haihe-Baodi-Gongbu-Jiyunhe faults. This recognition has further proved the presumption that the oyster reefs were spatially distributed mainly in the so-called "Inner Bay" of the Bohai Bay.