These quarry pits are quite mysterious and had a field officer from the British Geological Survey puzzled.
Why dig so many small pits? They are too close together for trial pits and not an efficient way to quarry stone. They may have been dug by individuals, so far I have found no records of them. They are not even shown on any Ordnance Survey Maps, even though you can fall in to some of them.
These pits were missed by an archaeological survey that claimed to have surveyed the area.
Here is a detail of “spoil” from a quarry pit, the stone is known as “Haslingden Flags”.
See them from aerial photographs
They can even be seen from satellite pictures and cover a few acres, see the aerial view here.