摘要
渤海湾西岸众多的埋藏牡蛎礁体内,除正常的牡蛎壳体堆积层外,还广泛地存在一定数量的水平夹层。水平夹层的存在,可能指示了礁体的生长环境发生了变化。文章对组成礁体的正常建礁层和水平夹层中的牡蛎壳体,进行了贝壳年轮和稳定同位素分析研究,对比了水平夹层和正常建礁层中的壳体生长速率和壳体记录的稳定同位素变化范围与幅度,恢复了壳体记录的礁体生长环境,探讨了壳体同位素记录揭示的礁体水平夹层成因。结果表明,相对于相邻正常建礁层中的壳体,水平夹层中的壳体记录的季节性氧同位素变化幅度较小,这主要与壳体生长时期的季节性淡水输入变化较小或(和)年平均气温较低有关。水平夹层中的壳体记录的低温季节相对较多的淡水输入量和高温季节相对较少的淡水输入量,或(和)由于年平均气温较低而导致的壳体在一年中的生长周期缩短,是造成礁体中水平夹层形成的主要驱动因素。
Buried oyster reefs are widely distributed on the west coast of the Bohai Bay, China. Besides normally in situ build-up oyster shell layers, there are also some horizontal oyster shell interlayers in these reefs. The interlays are composed of in situ oyster shells, single valves, and change. In this paper, we selected oyster shells both from shell debris. Their existence normally build-up layers and indicated an environmental from horizontal interlayers in one section of the Dawuzhuang oyster reef body for stable isotope sclerochronological study. By counting the annual growth increments recorded in these shells, we found out that most of the shells sampled from the normally build-up layers have higher growth rates than these shells sampled from the horizontal interlayers. Results of stable isotope analysis of consecutive micro-samples obtained by drilling indicate that shells sampled from horizontal interlayers always have smaller seasonal ranges of δ^13C and δ^18O values than shells sampled from former neighboring normally build-up layers. Their small ranges of stable isotope values could mainly result from two reasons. One is that freshwater input into their living environment had smaller seasonal ranges while the horizontal interlayers formed. If more freshwater was input during cold seasons, but less freshwater was input during warm seasons, such a case could appear. The other is that the annual mean water temperature was lower while the horizontal interlayers formed. Because this temperature was lower, the growth period of oyster was shorter. It is these two factors that resulted in the formation of horizontal interlayers in the buried oyster reef in the Bohai Bay.
出处
《第四纪研究》
CAS
CSCD
北大核心
2010年第5期994-1002,共9页
Quaternary Sciences
基金
国家自然科学基金项目(批准号:40872106和40742011)
公益性科研院所基本科研业务费项目(批准号:K0919)
"中国泥质海岸带对全球变化响应的研究与趋势预测"课题(批准号:1212010911069)资助
关键词
稳定同位素
贝壳年轮
水平夹层
古环境牡蛎礁
渤海湾
the Bohai Bay stable isotope, sclerochronology, horizontal interlayer, palaeo-environment, oyster reef,the Bohai Bay
