Interactive Land And Sea Sediment Since The Late Pleistocene In Tianjin Urban Area

This paper in the system summarizes in the domestic and foreign Quaternary Period environmental research present situation foundation, on the basis of previous research results have been relying on the project closely and, began from the bores study, through the lothological description, the depositional cycle and massive effective measurement data, pollen, microfossils, use synthesis-multiple stratum division methods to divided rock Quaternary stratum in Tianjin urban area, calibrated and determined the program of Quaternary stratigraphic division in the study area systematically, and determined the program of stratigraphic correlation in Tianjin urban area. According the lithological characteristics of the sediments in this study area to identify the type of sedimentary facies, through combination of pollen analysis and geochemical characteristics, analyzed the climate change in this study area, and then analyzed the evolution characteristics of depositional environment since the late Pleistocene. Such main conclusions can be drawn from the study:1. Determined the program of Quaternary stratigraphic division and Stratigraphic correlation in Tianjin urban area, and divided stratum into Yangliuqing formation(Qp1y)of the lower Pleistocene Series,Tonglou formation(Qp2to)of the middle Pleistocene Series, Tanggu formation(Qp3ta)of the upper Pleistocene Series, and Tianjin formation(Qht) of Holocene Series,according to three skeleton bore of project research and a lot of previous research results, especially 14C、OSL measurement data、pollen and so on..2. Base upon data on lithology , detailly analyzed pollen for CQJ3 bore, and divided four spore-pollen zones combination since late Pleistocene.Combined with the analysis data on geochemistry,this paper discussed climatic characteristics since late Pleistocene,and put forward that paleoclimatic environment evolution has experienced four climatic periods generally: IV2、(14.8-5.6m)Sparse forest grassland, mild and more met climate IV1、(22.1-14.8m)Broad-leaved forests grassland,warm climatet III、(23.75-22.1m)Sparse forest swamp grassland,climate and humid climatet II、(30.7-23.75m)Sparse forest grassland, cold-dry climate I、(77.1-60.4m)Broad-leaved forest grassland, warm climatet3. According to epideictic different features of Quaternary sediments in different periods, for example, color, structure, lithology, sedimentary rhythm and microfossils, divided lithofacies, identify types of sedimentary facies since late Pleistocene, including alluvial facies, marine facies, swamp facies and lacustrine facies.4. Discussed evolution characteristics of Quaternary depositional environment in the study area detailedly, base on stratum and sedimentary analysis.On late Pleistocene, terrain is higher in north than in south, and higher in west lower in east, and sediment based mainly on channel deposit,occurred twice long time marine transgression diachronically, which showed significantly in the southeast and loss the second marine layer in the northwest. In Holocene, sedimentary thickness is thin because of the shorter time. The sedimentary include one marine layer that distributed by all study area.