东海北部外陆架MIS 6以来的沉积地层格架及古环境演化

利用最新采集的高分辨率浅地层剖面资料，结合SHD-1钻孔岩心资料，对东海北部外陆架MIS 6以来的地层结构进行了分析，建立了MIS 6以来的沉积地层格架，并对地层的地质年代进行了厘定。根据Octavian Catuneanu（2005）的层序地层学理论，研究区地层划分出海侵和高位体系域、下降期体系域、海退和低位体系域。研究表明，过孔的浅地层剖面与钻孔岩心的沉积地层有很好的对应关系。东海北部外陆架MIS 6以来可划分出7个不整合界面（D7—D1）和7个地震单元（SU7—SU1）。东海外陆架的海进层序与海退层序有规律地交替发育，它们与海平面变化曲线也有很好的对应关系。其中，地震单元SU1、SU5分别为MIS 1、MIS 5形成的海侵沉积，主要发育浅海沉积层，100 m以浅的位置发育潮流沙脊；地震单元SU2、SU4、SU6分别对应 MIS 2、MIS 4和MIS 6低海平面时期形成的河流/河口—三角洲沉积；地震单元SU3、SU4为下降期体系域，这两个亚单元分别对应MIS 3和MIS 4晚期。MIS 4—MIS 3发育厚层且分布广泛的水下三角洲，但MIS 4发育的水下三角洲的规模不及MIS 3大。总之，对MIS 6以来沉积地层格架的建立和古环境研究可为东海外陆架晚第四纪地层的海平面变化、古环境演化等相关研究提供参考。

Sedimentary stratigraphic framework and palaeoenvironmental evolution of the northern outer shelf of East China Sea since MIS 6

Based on the newly collected high-resolution shallow seismic and lithological data of the Borehole SHD-1, the stratigraphic framework of the outer shelf of the northern East China Sea since MIS 6 was established with ages. Using the method of sequence stratigraphy newly proposed by Octavian Catuneanu (2005), it is observed that the strata since MIS 6 in the study area may be subdivided into transgressive, highstand, falling, regressive and lowstand system tracts. The shallow seismic profile data fit well with the stratigraphic pattern disclosed by drilling cores, upon which 7 reflective interfaces (D7—D1) were recognized and 7 seismic units (SU7—SU1) subdivided for the strata since late Pleistocene. The transgression and regression system tracts are observed in a rather regular pattern, corresponding well to sea level fluctuation. Both the seismic units SU1 and SU5 were transgressive deposits corresponding to MIS 1, MIS5, when neritic facies prevailed, and the places less than 100 m in water depth were dominated by tidal ridge deposits. Seismic unit SU2, SU4 and SU6 correspond to MIS 2, MIS 4 and MIS 6 stage, respectively. They were deposited in regressive periods and dominated fluvial and deltaic facies sediments. The seismic unit SU3 and SU4 were the system tracts formed during the sea level falling periods, corresponding to late MIS 3 and MIS 4 respectively. MIS 4—MIS 3 are dominated by thick and widely distributed underwater deltaic deposits, but the size of the underwater deltas in MIS 4 was smaller than those in MIS 3. In conclusion, the study of sedimentary stratigraphy framework and sedimentary environment since MIS 6 may provide a good reference for sea level changes and palaeoenvironmental evolution of the East China Sea continental shelf in Late Quaternary.