The middleJurassicseries Yanan Formation of in Lingwu coalfield is a lacustrine deltaic deposit.
灵武煤田的中侏罗统延安组含煤岩系为一湖泊三角洲沉积。
2
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.