Thornton Force - Geology
The water pours out of the limestone onto rocks belonging to the Lower Ordovician (Arenig) Ingleton Group laid down 500 million years ago. The time gap between the horizontally bedded limestone and the steeply dipping turbidite sandstones is about 170 million years. This is known as an unconformity. . An uncomformity occurs when something happens to disrupt the steady rain of sediment onto a sea floor, or prevents the fine dust being blown onto a plain that would normally turn into rock over millions of years.
Close by in this area are geological features known as "dykes". A term I had never heard of, other than the word we use for a stone wall.