Contrast Of Stratum Division And Constructive Analysis Of Fault Activities About Quaternary Layers In Suzhou City Area

The research area is located at north margin of the Yangtze paraplatform-lowerYangtze syneclise-Dean and Suzhou fold belt. Among the research of active fault,research on framework of Quaternary layers and basin evolution has become oneimportant subject in stratigraphic research. The Quaternary layers in this regionbelong to transitional environment and fluviolacustrine environment, and the layershere are completely developed and its sequence is clear. This dissertation is going toresearch the contrast of stratum division and framework of Quaternary layers inSuzhou City area, and discuss the specific location and constructive characteristics ofHusu Fault (F2).By analyzing rock property, color feature, sedimentary cycle, sedimentaryenvironment, the lower and upper formations and contact relation of drillingsediments, and its comparison with standard drill (BK1, BK2) and neighboring area,and by synthesizing previous research, this dissertation ascertains the method fordivision and comparison of rock strata. The dividing method of rock strata andchronostratigraphy in Quaternary are basically similar. The Quaternary layers areclassified as Haimen Formation in lower Pleistocene (Qp~1H), Qidog Formation inmiddle Pleistocene (Qp~2Q), Gehu Formation (Qp~3G) and Kunshan Formation (Qp~3K)in upper Pleistocene and Rudong Formation in Holocene (QhR). Besides, there stilldevelop Yancheng Formation in Neogene (N2Y), Pukou Formation in upperCretaceous (K2P) and Qixia Formation in Permian under the Quaternary layers.By analyzing drill across the fault in Quaternary at Jingnanlu site, Suzhou (HusuFault F2), synthesizing artificial seismic exploration results and combining materialsof seismogeology and tectonic geology, this dissertation discusses the location ofupper faulted point of F2and its characteristics of tectonic activities since theQuaternary. The depth of upper faulted point at Husu Fault F2is130m, the strike ofF2is NE, and the dip is SE. The F2is a normal fault with the bottom boundary of Qp~2as its upper fault plane, which is the top boundary of Pliocene. There are6fracture planes can be identified in strata under the Quaternary, they have a increasing trendfrom top to bottom and the offset of basement plane is of11.5m. Comprehensiveanalyses told that the latest active time of F2is early Pleistocene. Besides, accordingto the comparison between artificial seismic exploration results, practical drillingexploration results across the fault and previous research, it’s not hard to find out thatthe practical location of F2is a little inclining to the west of location measured before.The above conclusions provide important materials for comprehensive identificationof fault activity and evaluation of its seismic hazard.