Geograph - photograph every grid square

This is a close look at part of the Permo-Triassic NJ1069 : Rotten Rock. Near the foot, and just above the centre, are cross-bedding made by sand cascading down the downstream faces of ripples in the bed of a watercourse, which only had the power to move small grains of sand, flowing from left to right. The bottom one is in fact two separate series of such cross-bedding, one on top of the other. The coarser beds with were laid down when there was a spate flowing fast enough to move much larger pebbles, for example after a sudden cloudburst. These beds are deposited quite quickly, and tend not to contain the cross-bedding characteristic of gentler streams.