Establishment Of Diatom-salinity Transfer Function And Reconstruction Of Paleo-salinity In The Minjiang Estuary And Its Adjacent Sea Area

In this paper,diatoms are analyzed where are in surface sediment samples in Minjiang Estuary.The data of surface diatom and environmental data are sorted reasonably.The distribution characteristics of diatoms in the surface layer of Minjiang Estuary and their relationship with environmental factors were analyzed.The transfer function between diatom-salinity was established by using the surface diatom data in the study area,and the paleosalinity of sediment samples from boreholes in the study area was restored by the transfer function.At the same time,combined with stratigraphic division and diatom assemblage in the study area,the sea level change and transgression history of Minjiang Estuary since late Pleistocene were analyzed.The principal results are as follows:1.The surface diatom is divided into 4 diatom assemblages through sequencing,including 2 subbands.? band was significantly affected by inshore seawater;The ?band is controlled by water depth and influenced by tidal action.?1 band affected by tide and Minjiang river runoff;?2 band is also subject to the interaction of tide and Minjiang river runoff,but the hydrodynamic action is stronger.2.By deleting the MJ1 station and fresh water species in the MJ3 station,and establishing the function under the WA-PLS model,it is concluded that the Component 5 model in the WA-PLS model has the largest correlation coefficient(R2=0.98851) and the minimum root mean square error(RMSE=0.63794),the maximum deviation is only 2.0631,and the Component 5 model is determined as the optimal conversion function.3.According to the diatom-salinity transfer function,the salinity values of three boreholes in Minjiang Estuary have been reconstructed.The results show that the salinity value of reconstructing drilled hole of 1%DZK001 is 2.80?8.39,that of DZK003 is 0?9.65 between brackish water and brackish water,and that of fresh water to light brackish water is 0?9.65.The salinity value of DZK014 borehole reconstruction between brackish water and brackish water is 0?6.55,which is between fresh water and brackish water.4.Minjiang Estuary reveals that the strata are Upper Pleistocene and Holocene Series.The upper Pleistocene sediments are composed of gray pebble layer,silt and silt soil,and the thickness of the sediments varies greatly,with a range of 20m-30m.The sediment thickness of the layer is mainly marine sedimentary,and the thickness of the silt increases gradually along the estuary;The lower Holocene sediments are composed of dark gray silt and silt soil.The thickness of this layer varies from 5m?20m The upper reaches of the estuary gradually change from marine to continental,and the estuary is mainly composed of marine facies or sea and land intersections;In the Middle Holocene,the main silt and sand were mainly silt and sand.The thickness of the whole sediment changed slightly,and the variation range was about 3m?7m.The upper reaches of the estuary were continental deposits,and the estuary area was marine sediments;During the late Holocene,the sediment thickness of gray silt,gray-yellow fine sand and mixed fill changed unevenly,which was mainly caused by human engineering activities.5.Since the late Pleistocene,three transgressions occurred in the study area:The first transgression occurred in the late Pleistocene Yumu subglacial period,and the transgression was "Fuzhou transgression";The second transgression occurred in the early Holocene;The third transgression occurred during the middle Holocene,and the transgression was "Changle transgression".