南海北部陆架柱状沉积物记录的残留沉积
NEW EVIDENCE FOR REMNANT DEPOSITS RECORDED BY COLUMNAR SEDIMENTS IN THE SHELF OF THE NORTHERN SOUTH CHINA SEA
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摘要: 对南海北部外陆架珠江口西南的E602孔进行了粒度分析和AMS 14C年龄测定,通过沉积学分析,认为该孔沉积物形成于近滨环境,时间为全新世初期。根据岩性的变化将该孔分为上下2段,下段岩性较均匀,粒度参数变化较小,主要是风暴成因的递变悬浮沉积序列,形成于近滨上部环境;上段为均匀悬浮,为近滨下部环境。该孔下段的沉积作用主要是对晚更新世低海平面时沉积物的改造和再沉积,基本没有新的陆源物质加入,属于残留沉积或准残留沉积,只是在晚期的上段沉积中才有少量以细粒物质为主的新物源加入。Abstract: Based on AMS 14C dating and grain-size analysis for Core E602, located at the outer shelf of the northern South China Sea and southwest of the Pearl River mouth, the sedimentary environment of the core is discussed. The core was formed nearshore and deposited in early Holocene. It can be divided into two sections according to lithology. The lower section is lithologically homogeneous, and mainly composed of graded suspensions formed in storm and deposited in upper part nearshore environment, and its grain-size parameters keep relatively stable. The upper section consists of homogeneous suspension and was deposited in the lower nearshore part. Sedimentation of the lower section of Core E602 shows reworking and reconstruction of sediments deposited in late Pleistocene without new terrigenous sediment and belongs to remnant sedimentation. Only during deposition of the upper section, fine terrigenous sediments took part in the sedimentation.