The Palaeoenvrioment Reconstruction Of Konggang Burried Oyster Reef And The Response To The Global Change, Northwest Coast Of Bohai Bay

In the Northwest Coast of Bohai Bay, there are lots of Oyster Reef developed in theHolocene, more than40reefs are observed by now. The reefs are all coverd by themuddy-sediments. The growth, the death and the sediments above the reef are therecord the palaeo-envrioment change.The Konggang Oyster Reef, buried in the northwest coast of Bohai Bay, is a newlyobserved reef in the recent years. systematic samples were taken from the muddy-andsandy sediments underlying the reef, inside the reef body and, finally, up to theoverlying muddy sediments. The samples were taken for the chronology，sedimentolo1g4y carbon, oxygen stable isotope and micropaleontology analyses.AMSC dating shows that the duration of this reef is about2200yrs （6170³980cal BP）. The middle part of the reef body, is the slowly developed time due to theenvironmental deterioration in the mid-Holocene. According to the new AMS¹⁴Cdating data, it belongs to the Ⅲ-2Oyster Reef Groups. Iinquirement to the relationshipbetween the oyster reef development and the neotectnic movement, it shows that theHolocene Oyster Reef Plain is formed in the area traped by theHaihe-Baodi-Gongbu-Jiyunhe faults. This recognition improved the presumption thatthe oyster reef was developed in the inner bay of the Bohai Bay.With granulometric results, sedimento-and hydraulic environment has beenreconstructed revealing the process of reef building-up from the beginning to the end.Gradually fining-up occurred from bottom to top indicating the hydrodynamicweakening upwards.The Potamocorbula laevis shells were taken from the sediment samples for thecarbon and oxygen stable isotope test, to reveal the palaeo-climate andpalaeo-envrioment records in the oyster reef, and its response to the global change. The3low δ¹⁸O values shows the cold event in the Holocene. The development of KonggangOyster Reef was limited by the climate change, the sediment hiatus in the reef bodyshows that the climate variations during about6⁴cal BP.