珠江口盆地东部珠江组碳酸盐岩—碎屑岩共生区层序发育模式

Sequence stratigraphic model of carbonate—clastic rock symbiosis area of Zhujiang Formation in eastern Pearl River Mouth basin

珠江口盆地惠陆地区至东沙隆起一带珠江组时期位于陆架坡折之上,在持续海侵的背景下,发育了碎屑岩及碳酸盐岩两大岩性,为了厘清不同岩性之间的层序对应关系,利用岩性组合、生物组合、暴露标志以及地震反射特征,确定了海平面升降是控制层序样式的主要因素,识别出6个三级层序界面(SB23.03、SB21.00、SB18.00、SB17.25、SB17.10、SB15.97)及1个全区最大海泛面(MFS19.10),建立了碳酸盐岩—碎屑岩共生区的等时地层格架。在层序对比基础上建立了碳酸盐岩—碎屑岩共生区层序发育模式:海平面上升时期,主要发育退积式三角洲与向高部位退缩的碳酸盐岩地层;海平面下降时期,主要发育进积式三角洲与向侧面扩张的碳酸盐岩地层。

The Huilu area—Dongsha uplift in Pearl River Mouth basin was located on the shelf slope break zone during the Zhujiang Formation period.Under the background of continuous transgression,clastic rocks and carbonate rocks were developed.In order to clarify the sequence corresponding relationship between different lithologies,it was determined that the eustatic sea level was the main factor controlling the sequence pattern by using lithologic association,biological association,exposure marks and seismic reflection characteristics.Six third-order sequence boundaries(SB23.03,SB21.00,SB18.00,SB17.25,SB17.10,SB15.97)and a maximum flooding surface(MFS19.10)in the whole region were identified,and the isochronous stratigraphic framework of carbonate—clastic rock symbiosis area was established.On the basis of sequence correlation,a sequence stratigraphic model of carbonate—clastic rock symbiosis area is established:in the period of rising sea level,retrograded delta and carbonate strata retreating to high position are mainly developed;while in the period of falling sea level,prograded delta and laterally expanding carbonate strata are mainly developed.