论文部分内容阅读
以最新钻取的SE2孔沉积物为重点研究对象,对晚第四纪以来钱塘江下切河谷充填物的沉积特征和沉积相进行了精细研究,重建了研究区地层结构和层序地层格架,总结了强潮型钱塘江河口湾和下切河谷的沉积模式。钱塘江下切河谷充填物自下而上依次发育河床、河漫滩、古河口湾、近岸浅海和现代河口湾5种沉积相类型,表现为一个较完整的Ⅰ型层序,其内部层序界面、初始海泛面、最大海泛面、海侵和海退潮流侵蚀面、体系域内海侵面发育。钱塘江下切河谷充填物自海向陆可划分为海向段、近海段、近陆段和陆向段4段,各段沉积序列和海陆相互作用程度不同。在钱塘江下切河谷充填物中海陆过渡部位首次明确划分出了古河口湾相,并对其沉积特征和分布模式进行了初步探讨;其形成时间在9000 a BP左右,具有与现代河口湾不同的沉积特征,表现为中部为潮道砂体沉积,向陆渐变为受潮流影响的河流沉积,两侧被潮坪或盐沼沉积包围,沉积物在平面上自陆向海呈现粗—细—粗的分布模式。现代河口湾平面上自陆向海依次发育受潮流影响的河流沉积、粉砂质砂坎、潮道—潮流砂脊复合体和湾口泥质沉积区,沉积物呈现粗—细—粗—细的分布模式,与大多数河口湾常见的粗—细—粗的分布格局明显不同。
Based on the newly drilled SE2 pore sediments, the sedimentary facies and sedimentary facies of the undercut Qiangtang River valley deposits since the late Quaternary have been studied. The stratigraphic structure and sequence stratigraphy framework of the study area have been reconstructed. This paper summarizes the depositional patterns of the Qiangtang-Qiantang River estuary and the undercut valley. There are five types of sedimentary facies in the riverbed, river floodplain, Furukawa Bay, coastal shallow sea and modern estuary from bottom to top in the Qiantang River undercut valleys. They are characterized by a relatively complete type I sequence, The initial sea surface, the maximum sea surface, the transgression and the receding tidal current erosion surface, and the systemic inland sea surface development. The fillings of the Qiantang River undercut valleys can be divided into four sections from seaward to offshore, to the offshore section, near-shore section and the continental section. The sedimentary sequence of each section is different from that of sea-land interaction. For the first time, the Guhekou Bay facies was clearly divided for the first time in the sea-land transitional part of the filling river valley under the Qiantang River and its sedimentary characteristics and distribution patterns were discussed. The formation time was about 9000 a BP, which was different from that of the modern estuary Sedimentary characteristics are as follows: sediment of tidal channel sand body in the middle part, gradual change of tidal current into fluvial sediment influenced by tidal current, surrounded by tidal flat or salt marsh sediment on both sides, and the sediment has coarse-thin-coarse distribution mode. In modern estuarine plain, river sediments, silty sand ridge, tidal channel-tidal current sand ridge complex and mudflat depositional area in the bayou are developed in turn from the coast to the sea, and the sediments show a coarse-thin-coarse-thin distribution pattern , Which is obviously different from the common coarse-thin-coarse distribution pattern in most estuaries.