This is a black shale that is an important source of local fossils.

The black shale was formed in the deep ocean when the water had no oxygen.

The south peak is a sharp pinnacle of black shale.

Above this is black shale containing the Lantian biota fossils.

The highest part of the formation is black shale again.

All three seemed weary and no one spoke until the cliffs changed and they passed under the shadow of the black shale.

Mudrocks, especially black shale, are the source and containers of precious petroleum sources throughout the world.

Its sides were neither high nor sheer, just slopes of black shale rising no more than fifty feet.

The cuesta region contains coal, black shale and some oil shales.

They were in a Precambrian outcrop of black shale.