For once I wish I took a camera with me on a ride.
On a ride yesterday around Win Hill in the Peaks the Foresters were logging and had cleared a circa 10metre high cut onto the land. This showed a slice of land down (like a piece of cake), the grass, then loose earth, hardening slate (brittle still) then a layer of sold gritstone (probably 1/2meter horizontally), then...... the blackest solid bedrock that I've ever seen- circa 5metres high This only went on for circa 10meters along the cleared trail. Then it shifted to layered gritstone again?
Oily looking stuff- could it be oil!?!!