海河口地区全新世海侵层的相变与海面波动的对应关系

The Correlation Between the Marine Formation of Holocene and Sea-Level Change in the Haihe River Mouth Region

B_2孔揭示海河口地区全新世海侵层厚达19.2m,自下往上依次出现潮间滩、近岸浅海、前三角洲、三角洲湾、河口砂坝及河口边滩六个亚相,下部两个亚相呈海进层序,上部四个亚相呈海退层序。除河口边滩亚相底界外,其他所有亚相间的界面均为不连续面,显示海侵层为不连续沉积。研究表明该不连续沉积与海面波动有关.在全新世海侵高峰后,海面一直处于幅度不大(约1m 左右)的振荡运动状态,一次振荡波就在海岸线上留下一道贝壳堤,近5000余年来发生了5次振荡波,在海退平原中就有5道贝克堤与之对应。B_2孔海退层序中曲不连续面与贝壳堤基底侵蚀面相对应,也与振荡波的上升坡段相对应。海退层序所表现出来的海岸向海推进现象不是海面大幅度下降的反映,而主要是河口区沉积物迅速加积的结果。

Reserach has revealed that there exists about 19.2m marine formation of Holocene in B_2 core of the Haihe delta.Form the bottom to the surface of the formation,it can be divided into six sedimental facies:intertidal-flat deposits,shallow marine deposits, prodelta deposits,delta bay deposits,river mouth bar deposits and river mouth-side flat deposits.The two facies in the lower part,near the bottom,showed transgressive se- quence and the others regressive sequence. The boundaries of these facies are discontinuity surfaces except the base of the river mouth-side fiat deposit.This shows that the Holocene marine formation is discontinu- ous deposit.Research shows that the discontinuous deposit is referable to sea-level change. The sea-level has continuously been in the state of osillation with an amplitide of approximately lm since the highest sea-level of Holocene passed.One oscillation wave can leave a chenier on the coastline.In the last 5000 odd years oscillation wares occurred five times,which resulted in five cheniers accumulated on the regression plain of the west coast of Bohai Bay. The discontinuity surfaces in the regressive sequence of B_2 core correspond to the erosion surfaces of chenier bases and rising phase of each sea level oscillation wave. From the research we can see that the coast deposits spreading towards the sea as shown in the regressive sequence of this area does not result from a large scale sea-level falling but rapid deposition in estuary area.