北部湾广西沿岸全新世海侵过程的区域差异

The spatial discrepancy of Holocene transgression in north Beibu Gulf of Guangxi coastline

通过分析北部湾广西沿岸3个地质钻孔的岩性、地球化学和有孔虫含量特征,确定了其沉积相序,在统一的高程坐标内,对各钻地层中沉积相的高程和年代进行了对比,分析了该区全新世以来海侵过程的区域差异;并以东亚全新世海平面波动曲线作为参照,估算了广西沿岸各主要海湾的构造沉降速度。研究表明:全新世以来,广西沿岸的海侵开始时间并不一致,这是由于各海湾构造沉降运动的区域差异造成的,东部的廉州湾构造基本稳定,而廉州湾以西则经历了较大幅度的构造沉降。构造沉降又导致了海平面波动过程的区域差异,进而影响到了地层形成,如海陆过度相沉积只发育于廉州湾以西遭受海侵时间较晚、相对海平面上升速度较低的区域。

This study analyzed the stratigraphic correlation among several cores collected from the Guangxi coastline,and discussed the spatial discrepancy of transgression since Holocene.And,using the East Asia seal level fluctuation curve as a reference,this study also estimated the rate of vertical tectonic movement in main bays offshore Guangxi Province.The results show that since Holocene the initiation time for transgression in different local regions along Guangxi coastline are different,which is due to regional differences in tectonic sinking movement among these main bays.The tectonics in the eastern part of the Lianzhou Bay is stable,and that in the western part of the bay is unstable with a sinking speed of 1to 3mm/a.The tectonic sinking process resulted in regional differences in the sea level fluctuation curves,and thereby influenced the development of stratigraphy.For example,the salt mash face can only be found in the area west to Lianzhou Bay,where experienced a relative slow local sea level rising speed.