海南岛潮汐汊道的现代沉积特征研究*

海南岛存在着大量港湾溺谷型和砂坝泻湖型潮汐汊道。本文以两类潮汐汊道的典型──三亚砂坝泻湖型潮汐汊道和洋浦港湾溺谷型潮汐汊道为例,分析了两类潮汐汊道的成因和地貌发育体系;研究了两类潮汐汊道的现代沉积特征(粒度、重矿、地球化学、有孔虫);对比了两类潮汐汊道的发育模式和沉积模式;探讨了两类潮汐汊道的稳定性。

A STUDY ON SURFACE SEDIMENTRY CHARACTERISTIC OF TIDAL INLETS IN HAINAN AN ISLAND

There are many bay-drowned-valley tidal inlets and Sandbar-lagoon tidal inlets in Hainan island.This paper selected two tipical deputies──Yanpu Bay-drowned-valley tidal inlet and Sanya sandbar-lagoon tidal inlet, analysed and compared their geomorphological structure and surface sedimentation.and got some conclutions:(1) The difference and the similarities of developmental models about bay-drowned-valley tidal inlet and sandbar-lagoon tidal inlet:(a) The bay-drowned-valley tidal inlet system has three geomorphological units──tidal inlet and its flood tidal delta, ebb tidal delta.and so does sand bar-lagoon tidal inlet system; (b) The developmental scale of bay-drownedvalley tidal inlet is greater than that of Sanya sandbar-lagoon tidal inlet; (c) The developmental coefficients of flood tidal delta and ebb tidal delta of Yanpu tidal inlet are 0.12 and 0.44 respectively,those of Sanya tidal inlet are 1 and 2.8 respectively.(2) The difference and similarities of sedimentary models about bay-drowned-valley tidal inlet and sandbar-lagoon tidal inlet:(a) In Yanpu baydrowned-valley tidal inlet, the grain size of sediments in tidal inlet is smaller than that on ebb tidal delta and flood tidal delta.In Sanya sandbar-lagoon.the grain size of sediments is greater than that on ebb tidal delta and flood tidal delta; (b) The grain size of sediments on all geomorphological units of bay-drowned-valley tidal inlet system is smaller than that of sandbar-lagoon tidal inlet system;(c) The heavy mineral contents and ZTR of sediments in Yanpu bay-drowned-valley tidal inlet are higher than those in Sanya sand bar-lagoon tidal inlet:(d) The heavy mineral combinations of sediments on bay-drowned-valley inlet and its ebb delta and flood tidal delta are different.The heavy mineral combinations of sediments on sandbar-lagoon tidal inlet and its ebb delta and nab tidal delta are the same; (e) The foraminifer genus-Ammonia and Elphdium are common in both of the two type tidal inlets; (f) The sediments of Sanya Yuzan stream outlet have many Nummulites and Cellanthas, but that in the Yanpu area has no such materials.(3) The stability of bay-drowned-valley tidal inlet in better than that of sand-bar-lagoon tidal inlet.