Lithology of Lower Jurassic deposits in the southeast of West Siberia

The petrographic composition of a wide spectrum of granulometric varieties of Lower Jurassic deposits exposed by boreholes in the southeast of the Wes t-Siberian Plate is considered. It has been established that the elastic pa rt of these deposits consists mainly of quartz and graywacke. The compositi on of clay matter or mudstones as well as cement of gravelstones, sandstone s, and siltstones was studied in detail; its dependence on rock grain sizes is shown. Lower Jurassic deposits in studied sections are mainly of contin ental genesis.