The Study Of The Datong Volcanic Activity Records In Lacustrine Deposit And Loess Deposit

Datong Basin is located in the north of Shanxi and Shaanxi graben which lies inNNE shear extensional rift basin tectonic geomorphology pattern in China. In theQuaternary period, tectonic activity occurred along with large-scale volcanic activity,Datong Basin is the new generation of rift basin,the formation and evolution of thebasin is completely controlled by the new tectonic movement, the developmentprocess of the basin controlled by tectonic movement has a causal relationship withouter mantle activities.Volcanic activity should be phased in time, that is active and quiet period. In avolcanically active period, in addition to produce the volcanic eruption itself, volcanicactivity also in the general area, in many geological record left traces of its influence.During the Quaternary the Datong volcanic activity, volcanic eruptions interspersedamong the fluvial-lacustrine strata, loess-paleosol.Collecting samples at the Chen Zhuang lake sedimentary profile and Jin Shanloess deposition profile which are far away from volcanic cone, we described thesedimentary characteristics, and the samples were the physical and chemicalcharacteristics of magnetic susceptibility, chemical element content and particle sizemeasurement and analysis.1）When volcanic activity occurs, the physical and chemical characteristics ofsediments will change significantly. Containing pozzolanic material lacustrinedeposition profile and the deposition layer of loess deposition profile susceptibilityabnormally elevated significantly higher content of Fe and other metal elements, andsediment coarsening.2）Sedimentary section in this article the sampling chenzhuang Lake phase sediment characteristics reflect the area took place over three volcanic activity, eachvolcano during the period, several eruptions, the Jinshan loess deposition profilescorresponding to the two volcanic activity, and profiles chenzhuangrendered aftertwo volcanic activity there is a good correlation.3）Further demonstrated volcanically active and quiet period Datong ancientlake lake retreat-slow transgressive corresponding.Predecessors the Datong volcanic area multi for the study period of volcanicactivity, lack of study the evolution of the volcanic activity and regional lakeenvironment, the study by the the Datong volcanic eruption stage Datong Basinevolution and tectonic movement of the Datong Basin area specificcorrelation study.When a strong upper mantle activity occurs, the basin crustal uplift relative to thesurrounding mountain areas and basin uplift the crust, so that the basin will generatea substantial Quick Lake regressive events, the lake water storage space smaller,lacustrine sediment grain coarsening. According to this paper, experimental,lacustrine deposition profile (profiles chenzhuang) of volcanic ash-rich layer that iscorresponding to abnormal high values of the magnetic susceptibility and Fe contentappears in the coarse particles Lake retreat sedimentary sequence, and>63μm thegrit content has a good consistency. It provides evidence to prove that volcanicactivity was associated with the large and rapid regression of ancient lake andvolcano quiet period was associated slightly slow transgressive of ancient lake.