Study On The Sedimentary Characteristics Of Quaternary Shallow Layer And Geological Model Building Of Shanghearea

The results of Shallow seismic exploration indicate that the characteristics of surfacesediment are directly related to the seismic data acquisition and processing, and are theimportant factors of high-resolution exploration. In recent years, seismic response variedwidely in Shanghe area, between the Tuhai River and Tuma River it was extremelyunintelligiable. As a direction of sedimentolology theory, combined with geophysics andgeotechnical to research the Quaternary shallow layer of the study area and create geologicalmodel of the shallow layer，and find the optimum excitation layer. It can help to determine thedeployment the location and the depth of drilling well, which can make better effect.Since the late Pleistocene, the Shanghe area in Shandong province which is located inthe Yellow River drainage was influenced by the frequent migration, swings and floods of theYellow River. As a result, the Quaternary surface deposited Yellow River ancient channel.The research has studied the Yellow River paleochannels in Shanghe area, Shandongprovince, using shallow coring data, grain size characteristics, static sounding data and thefossil records. The results indicate that：The lithology is mainly silt, shale layer and theiralternations. There are abundant yellow-brown argillaceous silt and silty clay in the study area,when yellow-brown silts appear as thick layers. In silt layers the beddings develops well,typical of the trough cross-bedding. It’s a typical kind of channel deposit.On the whole, shalelayer develops less, thinner, and it is mainly dark and tan, partially red. Rich snail fossils inthe dark argillaceous layers represent the river flood plain sedimentary environment underhumid climate conditions, while mud crack in the red mud is on behalf of the floodplaindeposit. The interactions of the silt and clay shown in field sections represent the developmentand evolution of the different river phases and the frequent alternating layers of silt and clayin the profile are the result of river migration and proliferation.The paleochannel deposition has obvious phases, and the sediments which are shallower than30meters develop three phases of tapering bottom-up depositional cycles, and all thesecycles have typical dual structure of rivers, corresponding to the three different periods of theYellow River ancient channel deposits. It can be also concluded that the paleochannel extendfrom the southwest to the northeast. Affected by terrain, climate, hydrodynamic conditionsand other factors, the development and distribution of paleochannels of the three phasesshows properties of inheritance and difference. They mainly distribute between the TuhaiRiver and the Tuma River in the study area, with a width of about4.0kilometers.Paleochannels of the third phase formed from late period of the Late Pleistocene to Early Holocene. Atthat time, the climate transformed from Last Glaciation to post glacial period, which was coldand dry， therefore the paleochannels widely distributed, and of which the sediments werecomparatively coarse；Paleochannels of the second phase developed in early to middleHolocene, during the post glacial period, when the climate was warm, humid andpaludification was common and flood fans developed; Paleochannels of the first phase formedin middle Holocene, the characteristics of the channels in the first stage are similar to modernYellow River, whose sediments’ grain sizes are fine.