Rock magnetic characteristics of sediments in the Nihewan Basin and its relationship with Datong volcanic activity
The Nihewan layer is a huge,non-dated Quaternary lacustrine sedimentary layer deposited in the Nihewan Basin of China,and is also an internationally recognized Quaternary standard strata.In recent years,a large number of paleoanthropological sites and mammal fauna have been found in the Nihe Bay layer;At the same time,frequent volcanic activity in the late Pliocene and late Pleistocene in the basin formed the famous Datong Quaternary volcanic group,leaving rich traces in the lacustrine sedimentary layer and loess sedimentary layer.Therefore,stratigraphic chronology and paleoclimatology research in the Nihewan Basin are of great significance for the study of human evolution,mammalian community evolution,regional geological evolution and environmental change.Petromagnetism can identify the type,content and particle size of magnetic minerals in sediments,which is the basis for magnetic stratigraphy dating and environmental evolution research using environmental magnetism.Therefore,relying on the CZ01 scientific research hole of the Institute of Earth Environment,Chinese Academy of Sciences(hole depth 305.83 m),this paper carried out detailed laboratory tests and systematic rock magnetism research,and analyzed the rock magnetism experiments such as isothermal residual magnetism acquisition curve,magnetic susceptibility change curve with temperature,hysteresis loop,FORC diagram,low temperature residual magnetism and magnetic susceptibility,aiming to explore the history of volcanic activity and the source of sediment magnetic material in Datong Basin.The specific research content and research results are as follows:(1)Detailed analysis of the composition and characteristics of magnetic minerals in the sediment of Nihewan showed that magnetite with low coercivity was the mainstay,and some layers contained high coercivity hematite,which was less affected by late diagenesis after formation deposition.(2)The analysis and study of the source of magnetic minerals was carried out,and the results showed that the magnetic minerals in the basin mainly came from exogenous detrital input,and autogenic magnetite was only generated in a few locations,and the proportion was very low.(3)According to the high level of magnetic susceptibility anomalies and the high susceptibility-low Rb/Sr ratio layer in the loess sedimentary profile,it is inferred that the Nihewan Basin has experienced at least a dozen volcanic active periods since the Quaternary,and each active period has had multiple intensive volcanic eruptions,which provides valuable information for the history of regional volcanic activity and confirms that the Datong volcanic activity is much more than the four volcanic active periods studied by previous studies.
NETL
NSTL
万方数据
维普
