| The Arctic is a key region in the Earth's climate system,both a sensitive responder and an active participant in global climate change.In order to figure out the grain size and mineralogical characteristics,distribution,provenance and transportation route of sediments in Arctic Ocean,grain size,XRD analysis of bulk minerals and clay minerals of 84 surface sediment samples in the Western Arctic Ocean and Bering Sea were analyzed,the following points are obtained:Grain size distribution characteristics and analysis:(1)On the side of Russia,except for the sediments on the shelf of the Kara Sea,the other sea areas have similar grain size characteristics,that is,the sediments are mainly silt and clay with fine grain size,which is related to the sub-glacial sedimentary environment in the region.(2)On the side of Alaska,due to the higher hydrodynamic conditions in the Bering Strait,the sediments near St.Lawrence Island have larger grain size and are dominated by sand components.Further north,the hydrodynamic conditions decrease and salinity increases which lead to the gradual decrease of coarse components and the gradual increase of fine components.Bulk minerals distribution characteristics and analysis:(1)On the side of Russia,the sediments contain high amounts of mica and chlorite,which are from the clastic rocks of the Siberian continent and transported to the sea by rivers and coastal currents.The sediments in the eastern Laptev Sea are rich in potassium feldspar and plagioclase,which are detrital materials from the New Siberian Islands,several of which are transported to the Canadian basin by sea ice under the Transpolar Drift and Beaufort Gyre.(2)On the side of Alaska,the contents of feldspar minerals and chlorite in the sediments of the Aleutian Basin are high,but the content of quartz is very low.The sediments of the Yukon River contain high levels of plagioclase and hornblende,and the river sediments entering the Bering Sea are transported to the Arctic Ocean by currents,so that the mineral characteristics of the bottom of the Chukchi Sea and bering Sea shelf are similar.The sediments in the Amerasian basin are rich in chlorite,mica,pyroxene and dolomite.Chlorite and mica are multiple inputs,pyroxene is associated with anchor ice on the Laptev sea shelf,and dolomite comes from the Canadian Arctic Islands and Mackenzie River.(3)The Alaskan continent has experienced strong weathering,which contribute more to arctic ocean sediments than the Siberian continent.Clay minerals distribution characteristics and analysis:(1)A large number of montmorillonite clasts were found in the surface sediments of the Eastern Kara Sea shelf and the western Laptev Sea shelf,which are related to Siberian basalt,the clasts were transported to the sea by rivers and migrated eastward by Siberian coastal current and sea ice.The high value of montmorillonite in the Aleutian arc is related to the igneous composite.(2)The illite high values are mainly concentrated in the shelf sediments near Aion Island and the adjacent Chukchi Mountains,and the illite-rich sediments migrate eastward to the Chukchi Sea shelf by the Siberian coastal current.(3)The high chlorite content is mainly in the Aleutian Basin,which is the chlorite-rich sediment brought by Pacific water.(4)Kaolinite in Arctic sediments is associated with kaolinite-rich paleosoils and shales in Alaska,and the strata with kaolinite in the eastern Siberian Craton.According to the grain size components of surface sediments and the assemblages of bulk mineral,five regions with distinct sedimentary compositions and different sources of sediment can be distinguished:(1)The Siberian Continental shelf,the western and northern parts of the Chukchi Sea shelf and the Aleutian Basin,which are characterized by high mica,chlorite and silt,the sediments there mainly came from the of the Siberian Continent coastal erosion.(2)The eastern Chukchi Sea shelf and western Bering Sea shelf,which is a transition zone,and characterized by quartz and plagioclase and rich in silt,the sediments there is a mixture of coastal erosion of Siberia and Alaska Continent and river erosion of Yukon River.(3)The high Arctic Ocean,is characterized by extremely high content of mica and dolomite in sediments,combined with little chlorite and pyroxene,which is the sunk of sediments from the surrounding continental and Marine shelf sediments.(4)The edge of Lay Point and the western Alaska,the content of sand and quartz is extremely high in sediments,which is the result of coastal eroding by the Alaskan coastal current.(5)Yukon Mouth and southern of Chukchi Sea shelf,the sediments are characterized by coarse-grains containing quartz and plagioclase,with a small amount of amphibole,which is mainly from the eroding of andesite rock in the Yukon Basin.Based on the bulk minerals,clay minerals and end member analysis,three sedimentary end members are deciphered:(1)Sediments from the coast of Kara-Laptev-East Siberian Sea and semi-consolidated surface sediments from the Koyukuk-Kuskokwim Basin.(2)Cenozoic-Mesozoic andesites and basalts in the Yukon River Basin and the southern Alaska Peninsula.(3)Quaternary unconsolidated and semi-consolidated sediments,Cretaceous sandstones,Silurian-Ordovician shales along the western coast of Alaska,and Devonian quartz sandstone from Brooks Ridge. |
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