황해 남부에 분포하는 언덕모양 및 단구 모양 퇴적체의 마지막 해수면 상승시기 동안 고해상 순차층서학적 발달

Abstract

A detailed analysis of high-resolution Chirp profiles, core sediments and 14C ages from the southern Yellow Sea off the Jiangsu coastal area reveals a highly complex development of transgressive and highstand deposits during the last postglacial sea-level rise. The study area is characterized by an isolated mound with adjacent terraced seafloor. In water depths of 50—60 m, the terraced seafloor consists of thin transgressive sediments directly above transgressive surface. The mound, 40.7 km long and 29.6 km wide, occurs above 40—50 m in water depth. It comprises the SSE-ward prograding sandy unit (PU) and the overlying muddy flank unit (FU) at the outer margin. The terraced seafloor with thin transgressive sediments was most likely formed when sea level rose rapidly from 58 to 45 m around about 11.6 ka. As rate of sea-level rise was attenuated from 45 to 36 m between ca. 11.6 and 9.6 ka, the nearly flat lower boundary of the PU was produced at water depths of 3742 m by ravinement process. Subsequent rapid sea-level rise from 36 to 16 m between ca. 9.6 and 9.1 ka created accommodation for the deposition of PU. Sea-level rise stagnated from 16 to 10 m between ca. 9.1 and 7.7 ka during which the Huanghe River apparently shifted south of the Shandong Peninsula and discharged directly into the western Yellow Sea. The combination of slow sea-level rise and sediment supply from the early Holocene Huanghe delta by the southward-flowing coastal currents most likely favoured the formation of the SSE-ward prograding transgressive sandy PU. The highstand muddy FU overlying the PU was accumulated after ca. 7.5—7.7 ka when sea level approached its present position and the Huanghe River shifted back to the north. Development of transgressive and highstand deposits in the study area during the last postglacial sea-level rise was highly variable in time and space in response to changes in rate of sea-level rise together with variations in sediment supply caused by