The Study On Carbonate And Reefs Distribution Of Baiyun Deep-water Area In Pearl River Mouth Basin

The research area of this thesis is the Baiyun Deep-water Zone of the Pearl River Mouth Basin,which is located in the deep water area with a depth of over 300 m around the Baiyun sag and its peripheries,and the main study is about the Oligocene Zhuhai Formation and the Miocene Zhujiang Formation.Based on sufficient researching of study methods and achievements of deep water carbonate rocks over the world,the tectonic history of the South China Sea and Cenozoic carbonate researches of sedimentary basins in the South China Sea,the tectonic and sedimentary history of the Pearl River Mouth Basin,and combined with well data,wireline logs,thin sections and seismic data,the sedimentary history and the development of carbonate rocks of the Baiyun Deep-water Zone would be studied.With the studying of previous studies and combination with seismic well tie,identification marks of carbonate rocks and reef in deep water is set,recognized suspected reefs are recognized,the distribution regularity,the development model and controlling factors of carbonate rocks and reefs are analyzed.The Pearl River Mouth Basin experienced six main tectonic events in Cenozoic.The Nanhai event is also called ?thalassogenic?,related to the first extension of the New South China Sea,which transformed the continental facies into marine facies in study area.The Baiyun event,related to the second extension of the New South China Sea,caused a large scale transgression which shifted slope break from the southern boundary of the Baiyun sag to the northern part of the Baiyun sag.The study area was transformed the shallow marine shelf facies into deep marine slope facies.By comparison between other basins within the South China Sea,the study area has the tectonic background to develop carbonate rocks and reefs.Based on researches of well lithology,wireline logs,thin sections,geochemical detections and the scanning electron microscope data within the study area,it has confirmed that the study area has the sedimentary background to develop carbonate rocks and reefs.By using seismic well tie and seismic interpretation,the seismic appearances of carbonate rocks can be established.Due to interpretation of 2D and 3D seismic data,few expansive carbonate platforms and 58 carbonate reefs are detected within the study area.Based on the interpretation of seismic data and combination with all available data,the distribution of carbonate rocks and reefs is summarized.Cenozoic carbonate rocks and reefs in the Baiyun Deep-water Zone mainly developed in SQ26.0 and SQ24.8 of the Zhuhai Formation and SQ23.03,SQ21.0 and SQ17.25 of the Zhujiang Formation,and distributed at the Dongsha uplift,the Shunhe uplift and the Yunli low-uplift.There are two types of carbonate platforms in the study area,which are ancient uplift rimmed carbonate platform and volcanic reef of carbonate platform.The Nanhai event,the Baiyun event and the 19.1Ma transgression have significant influence on distribution and development of carbonate rocks and reefs in study area.The extension of the New South China Sea caused a tectonic subsidence of the Baiyun Sag,which caused a large scale transgression therefore caused the transformation of sedimentary facies(from continental facies to marine facies)in study area.After the Nanhai event,carbonate rocks and reefs developed at the Shunhe uplift,middle part of the Baiyun sag.After the Baiyun event,carbonate rocks and reefs developed at the Dongsha uplift and the Yunli low-uplift where were away from clastic sources.Because of the 19.1Ma transgression,most of the platform were submerged(dissapeared),only locally high points(the Dongsha uplift)on the platform developed limestone.Controlling factors of development and distribution of carbonate rocks and reefs are tectonic effects,and global sea-level changing.