These dimples in the surface of a stone in the wall at Blacker Hall Farmshop Cafe look to me like fossil raindrops. Rain fell onto soft wet sand causing those little craters then another pulse of sediment covered them and the process of lithification started, turning the beds of sand into sandstone.
This is coal measures sandstone so this happened about 300 million years ago. At that time large river deltas extended across this part of Yorkshire.
The bed of sand must have been temporarily above water level for the raindrops to make their mark, so this would have been on the exposed upper surface of the sand. What appear to traces of bedding run across this block of sandstone, suggesting we’re actually looking at a side view of the bed of sand but I think the explanation for this might be that parallel bands of minerals have settled out as the sand gradually became dewatered and iron rich minerals were deposited.
Perhaps I need to take my pocket microscope next time we call at the cafe. The buckwheat pancake with strawberries, blueberries and Nutella makes that an attractive proposition for a geology field trip.
