珠江口盆地白云凹陷北坡上新世—第四纪陆架边缘沉积体系特征

PLIOCENE-QUATERNARY SHELF-EDGE DEPOSITIONAL SYSTEMS ON THE NORTHERN SLOPE OF BAIYUN SAG,THE PEARL RIVER MOUTH BASIN

运用珠江口盆地新采集的高分辨率多道地震资料,结合前人在本区的钻井、岩心、测井曲线及地震的综合资料,建立了白云凹陷北坡上新世—第四纪的等时地层格架,在此基础上分析了陆架边缘典型沉积体系,并初步探讨了其控制因素。研究表明,上新世—第四纪地层内识别出T0(海底)、T1(1.8Ma)和T2(5.3Ma)3个三级层序界面,划分出A、B2个三级层序。研究区地震相主要有席状平行—亚平行地震相、帚状前积地震相、透镜状前积地震相、谷状充填地震相,不同的地震相及其组合代表特定的沉积体系。地震相特征分析表明,研究区上新世—第四纪发育大规模的陆架边缘三角洲和深切水道群,深切水道是沉积物向下陆坡—深海盆输送的通道。白云凹陷北坡上新世—第四纪沉积体系的发育受陆架边缘的地形、海平面升降、沉积物供给等因素的控制。

Based on the high resolution multi-channel seismic data, drilling cores and well logs data, the Pliocene-Quaternary isochronous stratigraphic framework is established for the northern slope of the Baiyun Sag. Typical depositional systems are recognized on the northern shelf-edge and their con trolling factors are preliminarily discussed in this paper. Our study shows that there are three third- order sequence boundaries, namely, T0 （seafloor）,T1 （1.8 Ma）, T2 （5.3 Ma） and two third-order se- quences, i.e. A and B within the Pliocene- Quaternary deposits. Seismic facies, such as the sheet-like parallel-subparallel seismic facies, broom-like foreset seismic facies, lenticular foreset seismic facies, and filling seismic facies are identified. The seismic facies are products of specific types of deposition controlled by the topography of the shelf break, sea level change, sediment supply and other factors. Large-scale shelf edge deltas and extensive deep water channels have been developed in the study area since Pliocene. Channels provide conduits for transportation of terrigenous materials to the lower slope and abyssal basin.