| The Yap Trench is located on the east side of the Yap Island Arc and the Yap Islands in the western Pacific Ocean and connected to the north by the Mariana Trench,the world's deepest trench.It is the subduction convergence zone of the Pacific plate and Caroline plate to the Philippine plate,an important component of the typical "trench-arc-basin" system,and an important area for ultra-deep marine scientific research.Therefore,this paper analyzes the high-resolution water depth data and surface sediment data in the northern Yap Trench and its adjacent waters(9°48'?3°11 'N,132°?143°36'),focuses on the geomorphological features and controlling factors in the northern Yap Trench(10°14'?12°07'N,138°07'?139°50'E),and discusses the influence of topography on surface sediment,and obtains the following results:There are large-scale ridge-trough landforms with different distribution directions in the West Philippine Basin and Parece Vela Basin.This landform was formed when the sea floor of the basin expanded,and the distribution direction of the ridge-trough landform corresponds to the expansion direction of the sea basin.The subduction plate at the "Challenger Deep" in the southern part of the Mariana Trench has its particularity,with horst,graben,terrace and other landforms developed on it,which is quite different from other areas in the Mariana Trench.The topography and geomorphology in the northern Yap Trench are very complex and mainly controlled by tectonic movement(10°14'-12°07'N,138°07'?139°50'E).The geomorphology in this area is classified into four levels of geomorphic units,and Yap Trench belongs to two levels of geomorphic units.The northern segment of Yap Trench and the southwest segment of Mariana Trench are typically vertically intersected in this area.This special subduction form makes the two trenches at the intersection have segmented characteristics and develop landforms such as uplift,depression and faults.Judging from the geomorphological features,the spreading center of the Parece Vela Basin was located near 137°35'34"E about 20Ma ago,and the ancient subduction zone in the eastern part of the West Vera basin was located about the eastern part of the present Yap Trench.The Yap Trench was not formed by the evolution of the southern tip of the ancient Izu-Bonin-Mariana Trench,but probably by the transformation of the spreading center exposed by the Parece Vela Basin.The North Yap Cliff at the northernmost end of the Yap Trench evolved from the spreading center of the Parece Vela Basin and is now a residual structure,mainly affected by the Yap subduction zone.The geomorphology of the study area is complex and has a strong influence on surface sediments.The results of particle size characteristics of surface sediments in the study area show that the average particle size of surface sediments is different and the sorting degree is very poor.The proportion of sand content in sediments in Kyushu-Palau Ridge region and Parece Vela Basin region is very high.The areas with high silt content are mainly concentrated at the junction of Parece Vela Basin,Kyushu-Palau Ridge and Yap Island Arc.The clay content of sediments in the whole study area is relatively low.The distribution results of chemical composition in the surface sediments show that in highland or positive topographic areas,such as raised topography such as seamounts and hills,the content of silicon in the surface sediments is relatively small.However,in depressions or negative terrain areas,such as depressions,troughs and other depressions,the surface sediments have a large content of silicon,so it is more conducive to the enrichment of siliceous bioclasts in this negative terrain. |
PDF Full Text Request