渤海构造收缩与沉积充填

Tectonic Compression and Rapid Sediment Filling of Bohai Sea

通过对多年的渤海海岸线变化、水深变化、构造、卫星影像和水文等数据进行分析,讨论了渤海构造收缩和沉积充填问题。GPS观测结果清楚地显示渤海正处于构造收缩的过程中;地质记录以及长期验潮站的结果显示渤海海域的海平面正在下降;而地震剖面以及钻井数据则显示渤海盆地的基底沉降自上新世至今已大幅下降,和北黄海相比,目前已经停止沉降。渤海的构造收缩、海平面下降以及基底沉降的停止,这3个因素是决定渤海演化方向的3个关键因素,它们共同奠定了渤海正走向构造关闭的道路。渤海岸线的向海推进、渤海水深变浅作为强有力的地质证据呼应了渤海正在走向关闭的地质进程。黄河三角洲和辽河三角洲不断向渤海的淤积推进是在渤海必然走向关闭的地质构造背景下进行的,其淤积造陆效果非常明显,从而成为渤海快速关闭的主要因素。预计在400 a后黄河河口和辽河河口可能在渤海对接起来,至此渤海将不复存在;100 a后,莱州湾将被封闭。喜马拉雅山隆升的远程效应导致渤海的构造收缩和大量沉积物通过黄河进入渤海,从而从根本上导致渤海的关闭。从总体效果来说,渤海走向构造关闭的道路在短期内不会改变,同时也不会因为人为因素而产生明显变化。

Based on long-time data of base line,water depth,geological structure,satellite image and hydrology,the issue of the Bohai Sea Closing was discussed in this paper.The GPS observation results clearly show that the Bohai Sea is in the process of tectonic contraction.The geologic record and results of long-term tidal stations show that the sea level of the Bohai Sea is falling.The seismic profiles and drilling data show that the basement subsidence of the Bohai Sea basin has stopped.There are three key factors which determine the evolutionary direction of the Bohai Sea,namely the tectonic contraction,falling of sea-level and stopping of the basement subsidence of the Bohai Sea,and all these factors commonly lay the foundation for the Bohai Sea finally inevitably toward closing.The advancing of coastline of the Bohai Sea toward the sea and becoming shallow of the depth of the Bohai Sea are taken as powerful geological evidences which response geological processes of the Bohai Sea＇s closing.The deposition of the Yellow River delta and the Liaohe River delta have been constantly carrying forward the Bohai Sea under the geological background which the Bohai Sea is destined to close,and the effect of silt creating land is very apparent,thus it becomes the main factor for the Bohai Sea fast towards closing.It is expected that the Yellow River estuary and the Liaohe River estuary will combine in the Bohai Sea in 400 years later,so the Bohai Sea will disappear;and that the Laizhou bay will be closed in 100 years later.With the Bohai Sea circulation change,more substances of the Yellow River may deposit towards the Bohai Sea,as a result,the closing rate of the Bohai Sea could also be accelerated.The remote effect of the Himalayas uplift causes tectonic shrinkage of the Bohai Sea,and a large number of deposits are carried into the Bohai Sea by Yellow River,thus fundamentally causing the closing of the Bohai Sea.As a whole,these geological effects in the short term will not change,and will even not change with human being activities.