Lower Middle Jurassic的意思|示意

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。

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。

According to geological age, it may be divided into Upper Triassic coal-bearing formation and Lower-Middle Jurassic clastic rock formation.

根据它的地质时代，划分为上三叠统含煤建造和中下侏罗统碎屑岩建造。

Its wall rocks consist of the regional metamorphic rock, series of Mayuan formation and middle-lower Carboniferous series as well as lower Jurassic Lishan formation.

其围岩有麻源组和中下石炭统的区域变质岩系及下侏罗统梨山组地层等。

Therefore, the Lower-Middle Jurassic is selected as the main target horizon for sandstone-hosted uranium deposit, and the Lower Cretaceous as the minor one.

因此，将中下侏罗统确定为本区的主要找矿目标层，下白垩统为次要找矿目标层。

The Middle and Lower Jurassic with thick coal seam is widely distributed in Northwest China.

西北地区中、下侏罗统煤层广布，厚度较大；