lower and middle jurassic

The early Middle Jurassic was an major coal-forming period in the region, when the Lower Yaopo Formation of lacustrine-deltaic and swamp facies was deposited.

中侏罗世早期是全区重要的成煤期，下窑坡组为湖泊—三角洲及沼泽相。

In terms of molecular geochemistry indexes, the hydrocarbon source rocks both in lower Jurassic and middle Jurassic can be classified as lake facies and swamp facies.

根据分子地球化学指标，下侏罗统和中侏罗统烃源岩都可划分为湖相和沼泽相两类。

The strata of Mesozoic and Cenozoic in the basin can be divided into three parts, Middle Jurassic (Longjiagou Formation ), Lower Cretaceous and Upper Miocene (Baode Formation ).

根据化石组合，龙家沟盆地的地层可划分为中侏罗统龙家沟组，上白垩统及上中新统保德组。