Abstract: Lacustrine oil shales can be divided into shallow lake and deep lake deposits in termsof their sedimentary environments. The former can be playa, ectogenic meromictic andshallow saline lakes; and the later is related to stratified lake. The oil shales are located inthe middle part of a transgressive-regressive cycle (whose scale is variable), whether theyare shallow or deep lake oil shales in origin. As one of condensated sections of continentalstrata, if oil shales can be marks between transgressive system tract and highstand systemtracts (the maximum flooding surface or the maximum flooding zone) depends on their position in the sequence and on if there is other condensated section above the shales.