海侵驱动下的胶州湾沙脊-水道体系形成与演变

Evolution of sand ridge-channel systems of Jiaozhou Bay driven by sea transgression

胶州湾作为一个半封闭的基岩海湾,湾内、外均发育了较为完整的沙脊-水道体系。胶州湾外从崂山头到大珠山咀沿线在晚更新世低海面时(-20m)由波浪向岸输沙形成了古滨面沙坝,在随后的全新世海侵过程中,古滨面沙坝受到潮流动力的强烈改造,形成了南沙、大竹等沙脊和竹岔水道等,而赤岛沙脊、沙子口连岸沙坝等则是古滨面沙坝近岸部分的残留沙体;胶州湾内的沙脊-水道格局受到全新世海侵前原始沟谷地形的控制,海侵后沟谷被淹没成为涨、落潮通道,而沙脊则是由海侵前胶州湾入湾河流的"河口沙坝"或者"河口远端坝"等堆积而成;现代胶州湾沙脊-水道体系的演变具有明显的继承性特征。

Jiaozhou Bay is a semi-enclosed shallow coastal bay.Complete sand ridge-channel systems have evolved inside and outside the bay.A relic shoreface sand bar has been preserved at -20 m contour from the Laoshan promontory to Dazhushan head,approximately 80 km long, 10 km wide and 2.5-10 m high.It was formed in the late Pleistocene when the sea level was roughly 20 m below the present sea level.h was reformed by tidal forces during the Holocene transgression from 11 630±100 a B.P.to 5 870±170 a B.P.with several linear ridges, i.e.Nansha,Dazhu developed along the major flood/ebb channels while Chidao sand ridge and Shazikou shoreconnected sand bar are the erosion remains of the Laoshan-Dazhushan shoreface sand bar.Inside the Jiaozhou Bay, the pattern of sand ridge-channel system has been controlled by the pre-Holocene transgression topography. River valleys were drowned and turned into flood/ebb tidal channels while positive relief accumulated by river mouth bars were preserved as ridges.The evolution of contemporary sand ridge-channel systems of Jiaozhou Bay demonstrate remarkable inherited characteristics.