the 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。

Permo Carboniferous coal series have relative good coal gas potential, dark mudstones in lower Jurassic, lower part of Middle Jurassic and lower Cretaceous are the best source rocks.

区内石炭—二叠纪煤系具有良好的煤型气及一定的煤层气潜力，中、下侏罗统和下白垩统暗色泥岩类是最具生油潜力的烃源岩系。

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。