渤海湾西北岸滨海湖埋藏牡蛎礁古生态环境

PALAEOECOLOGICAL ENVIRONMENT REVEALED BY THE BURIED BINHAIHU OYSTER REEF ON THE NORTHWEST COAST OF BOHAI BAY

对渤海湾西北岸沿海平原滨海湖埋藏牡蛎礁的分布形态进行了综合调查,并对位于礁体中央部位的一个垂直剖面上的礁体下伏沉积物、礁体内的泥砂质充填物连续取样。综合研究表明,该埋藏礁体生长于河流入海口处,长轴方向NW—SE、沿古河床分布。礁体开始建造于2445aBP前,基底坐落于当时的潮间带下部。持续建礁约160年后,至2287aBP时,礁体建造至潮间带中部海平面位置。随着岸线的推进,河流携带的大量泥砂逐渐掩埋了平均厚度约2m的滨海湖牡蛎礁。

Holocene buried oyster reefs were widely distributed over the coastal areas in the northwest Bohai Bay. All the reefs were exclusively covered with 1 to 6 m thick muddy sediments. In the old days, it was nearly impossible to obtain the distribution of a whole individual oyster reef, and there was no proper opportunity to sample sediments throughout the whole section of a reef body, including the underlying and inside-reef-body filling muddy deposits as well. In this study, with excavator and handle driller, the distribution of the Binhaihu oyster reef is revealed and sequential sampling is also given from the underlying to the upper portion of the reef body. The results indicate that the reef, 2 m for its mean thickness and located in an estuary while it was living, extended its body along the riverbed in the direction of NW-SE. It started at 2 445 cal BP with the body-basement located on subtidal zone and at around 2 287 cal BP after nearly 160-year-buildup, the top portion of reef body reached the position of mean sea level. Then, it ceased building-up following the shoreline progradation and the reef was covered with muddy deposits.