The Characteristics Of Topography And Sediment On The Southwest Indian Ridge

The seafloor is an important geological interface of the hydrosphere,biosphere and lithosphere.The seafloor topography is an important symbol of tectonic movement and magmatic activity.It is of great significance for studying the evolution of climate,sedimentary processes and exploration of seabed resources.In this paper,based on the shipborne multi-beam data of the Southwest Indian Ocean mid-ridge(46°~47°E)obtained from the 39 IV segment of the Chinese Ocean,the water depth and backscattering intensity data were extracted separately to carry out quantitative research on the seabed topography and bottom features,It is helpful for scientific research and resource exploration of the seabed.In this study,the depth data with a resolution of 50 m was used to extract terrain feature factors,and GIS and remote sensing technology were used to complete the quantitative classification of topography in the study area,which was divided into five categories: depression,high mountain,slope,flat land and low uplift.Therefore,based on the existing geological background,geomorphic genesis and other data,2 linear feature classes,10 surface units and 4 inferred unit landform types are divided,and the regional seabed landform map is drawn.The topography and geomorphic characteristics of the study area were analyzed from three aspects: tectonic characteristics,magmatic activity,and erosion and sedimentation.It was found that the axis of the oceanic ridge segment was dominated by rifts,and axial volcanic ridges(AVR)were developed in the valley and were expanding.The landforms of the valley walls on both sides are different,and the faults in the south wing are obviously developed.It is speculated that the supply of magma in this ocean ridge segment is weakening and the tectonic activity is increasing;and there is an asymmetric expansion in the axis,and its evolutionary process alternates between the magmatic active period and the tectonic active period.Using sonar images and camera line data for bottom analysis,it was found that sediments,rock breccias(basalt breccia is predominant),pillow-shaped basalt and debris are mainly distributed in the study area;rock mats or lava flows can be seen at the faults;At the same time,there are a small number of biological enrichment areas and alteration areas.Through statistical analysis,it is found that there is a good correspondence between the backscattering intensity and each sediment,which can effectively express the three kinds of sediments of bedrock,breccia and sediment.The corresponding trend of the backscattering intensity is: sediment <rock Breccia <bedrock.It reveals that in deep water,the backscattering intensity of multi-beam sonar can reflect the change of the bottom quality of the seabed.In this paper,the unsupervised classification of sonar images based on texture features can quickly and widely obtain different bottom sediment distribution ranges.Compared with simple statistical classification,it does not require a large amount of sample data to obtain a schematic map of bottom sediment distribution in the study area.Provide reference for mapping work.By analyzing the topography in the typical geomorphic unit in the region-the spatial characteristic distribution of the backscattering intensity,it is found that there are differences in the backscattering intensity distribution corresponding to different geomorphic units,and the distribution characteristics of sediments in the geomorphic units are summarized: sediment Widely distributed on the ocean floor,mostly concentrated in sedimentary depressions and sedimentary plains;rock breccias are mostly distributed in off-axis highlands and axial volcanic ridges and other structurally active areas;bedrock is mainly distributed in fault cliffs and axial volcanic ridges are newly exposed Of the earth's crust and other lava flows.The comprehensive analysis of the topography and bottom features helps to further reveal the magma and tectonic activities of the ocean floor,and is of great significance to the exploration of marine resources.