珠江口盆地滨浅海沉积特征及主控因素

    Sedimentary characteristics and main controlling factors of coastal shallow sea in the Pearl River Mouth Basin

    • 摘要: 珠江口盆地珠三坳陷新近系珠江组是重要的含油层系,目前缺乏对琼海凸起珠江组滨浅海环境沉积特征的系统研究,制约了该地区进一步勘探。现以沉积学为指导,充分利用岩芯、钻测井及地震等分析测试资料,对珠江口盆地琼海凸起东部倾没端新近系中新统珠江组一段研究区沉积特征、沉积演化和主控因素进行了研究。结果表明:①研究区发育滨岸沉积和浅海沉积,可进一步分为临滨砂坝沉积、临滨砂坝侧缘沉积、临滨泥沉积、滨外砂坝沉积、滨外砂坝侧缘沉积和浅海泥沉积;②研究区中部发育临滨砂坝沉积、临滨砂坝侧缘沉积、滨外砂坝沉积和滨外砂坝侧缘沉积,砂坝侧缘围绕在砂坝周缘沉积,整体呈NE—SW向展布,平行岸线分布;③自下而上,依次由滨岸沉积向浅海沉积过渡,西南部和东北部砂体连续叠置,规模先减小再增大,泥岩厚度增大,中间砂体薄,边缘厚;④主控因素包括古地貌、海平面升降、物源、波浪及海流作用等。古地貌影响着沉积环境,相对海平面控制着相带的类型,物源的供给决定砂坝规模的大小,波浪和海流控制着砂体的形态。

       

      Abstract: Neogene Zhujiang Formation in Zhusan Depression of Pearl River Estuary Basin is an important oil-bearing series, but it lacks the coastal shallow sea environment of Zhujiang Formation in Qionghai Bulge The systematic study of sedimentary characteristics restricts the further exploration in this area. With the guidance of sedimentology and the full use of core, drilling, logging and seismic data, the sedimentary characteristics, sedimentary evolution and controlling factors of the first member of the Miocene Zhujiang Formation in the study area of the eastern dip end of the Qionghai Bulge in the Pearl River Estuary Basin are studied. The results show that: ① The research area develops coastal and shallow sea sediments, which can be further divided into nearshore sandbar sediments, nearshore sandbar lateral margin sediments, nearshore mud sediments, offshore sandbar sediments, offshore sandbar lateral margin sediments, and shallow sea mud sediments. ② The central part of the research area is characterized by the development of nearshore sandbar deposits, nearshore sandbar lateral margin deposits, nearshore sandbar deposits, and nearshore sandbar lateral margin deposits. The sandbar lateral margin is surrounded by sediment around the sandbar periphery and is distributed in an NE-SW direction, parallel to the coastline. ③ From bottom to top, there is a transition from coastal sedimentation to shallow sea sedimentation, with continuous stacking of sand bodies in the southwest and northeast. The scale first decreases and then increases, and the thickness of mudstone increases. The middle sand body is thin, and the edges are thick. ④ The main controlling factors include paleogeomorphology, sea level rise and fall, provenance, wave and current action, etc.The paleogeomorphology controls the sedimentary environment, the relative sea level controls the type of facies belt, the provenance supply controls the size of the sand bar, and the wave and current control the shape of the sand body.

       

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