Rock Magnetism And Sediment Dynamics Of Paleogene At Western Shara Murun River In Erlian Basin

Depositional environment is an important part of researching the past global change.Judge sedimentary dynamics of sediment type and direction are reliable ways to determine depositional environments.Magnetic minerals in the rock to be sensitive to the record type and direction of sediment dynamic,so the anisotropy of magnetic susceptibility(AMS)is an effective method to solve this problem.The AMS result in Ula Usu,the orientations of Kmax are clustered most at NE and SW from all data with layers including Tukhum Formation(late Paleocene)and Shara Murum Formation(early to mid-Eocene).Major Kmax of the Tukhum Formation(lower part of the section)with the age of late Paleocene are mainly in the bi-modal at NE and SW.The linear tendency of tilted Kmin directions(tensor mean or vector mean)could only be effectively identified the dynamic direction and the real current through Bingham axial distribution.Kmax bared more than one paleocurrent model which give rise to the difficult of speculating their rigorous tendency.Kmax is generally perpendicular to the flow direction with increased strong current,with best fits plane sloped to the upstream direction in the lower part.In our depiction,hydraulics increased from moderate to strong current through Paleocene to Eocene at Ula Usu section when the paleocurrent route kept the same.The AMS result in Ulan Gochu also exhibits that the major orientations of Kmax are located around the NE and SW quadrant from all data with layers including Shara Murum Formation(mid-Eocene),Ulan Gochu Formation(late Eocene)and Baron Sog Formation(early Oligocene).For Shara Murum Formation,it could be equivalent to the overlapping part in the Ula Usu section by a similar implication for paleocurrent in NWW which showed AMS a repeatable result in the southern Erlian basin.In the Ulan Gochu and Baron Sog Formations(the middle and upper part of the section),Major Kmin showed a clockwise rotation developed from the lower hemisphere and the great circle inferred through the V1 and V2 in Bingham distribution implied the paleocurrent toward the NW and NNW(327° and 339°,respectively).Kmax lied near perpendicular to the flow route with best plane tilted to the upstream direction through all the section.At Wulanhuxiu site sandstone,The distribution of major AMS ellipsoid axis magnetic declination is N-S.Due to the sandstone show the strong water power,the sedimentary dynamic direction is E-W,Which is consistent with the distribution of the magnetic declination of the minor AMS ellipsoid axis(NWW).At Wulanhuxiu mudstone,Due to the weak water power,the distribution of the minor AMS ellipsoid axis is central of the polar stereographic projection.The distribution of major AMS ellipsoid axis is near of four main directions.Choosing four respective samples at Baron Sog Formation,Ulan Gochu Formation,Shara Murun Formation and Tukhum Formation,to measure the magnetic susceptibility change with temperature.By the way,all of sections magnetic minerals are magnetite and hematite.Through the investigation of AMS and the result of statistical analysis to calculate the sedimentary dynamic direction is correlation with three sections,which indicates the AMS has high quality identification of sedimentary dynamic direction when macroeconomic conditions are invisible.