杭州湾地区15000a以来层序地层学初步研究

本文从杭州湾地区末次冰期以来的地质背景入手，分析了该区晚第四纪地层层序、深切河谷形成和演化等。末次冰期低海平面时河流侵蚀切割老地层，在本区形成４０－１１０ｍ深的河谷，谷底为区域不整合面，自海向陆方向和平行海岸线方向均为一不等时面，是Ｉ类层序边界。冰后期地层为一个完整的Ｉ类层序，但存在多个小的间断面。初始海泛面也是穿时的，在深切谷地带是滞流沉积物与溯源堆积物之间的界面，在河间地则为古土壤层的顶界面；

SEQUENCE STRATIGRAPHIC STUDY ON THE HANGZHOU BAY SINCE 15000 a B. P.

This paper analyses the stratigraphic sequence of the Late Quaternary and formation and evolution of the incised valley in the Hangzhou Bay area, on the basis of the geological setting. During the last glaciation, the ancient river incised lowstand old strata, forming a large incised valley with depths of 40-110 m. At the bottom of the valley, there is an unconformity, which is non-isochronous in the landward direction and along the coastline, indicating a typical type-I sequence boundary. The postglacial sequence is a complete type-I sequence but includes many di-astems. The first flooding surface is also non-isochronous, which appears as a boundary between the lag deposits and the retrogressive aggradation in the incised valley and as the top of the pale-osol at the interfluves. The middle of the shallow marine muddy layer dated at 7000-6500 a B. P. , represents the maximum flooding surface, which is the only isochronous surface in the depo-sitional sequence. The fluvial flood-plain sediments of the transgressive system tracts is the main exploratory target of industrial biogas.