Fractured rock at Lacy's Caves

Lacy's Caves are by the River Eden at Little Salkeld. They are carved into soft desert sandstone laid down when Britain was at the same latitude as the Sahara Desert. The sandstone is so soft that you can rub grains off with your hand. At first I thought that the harder layers may just have been laid down at different times but then I noticed that they weren't layers at all and in fact intersected each other in a check pattern. They must be fractures caused by some sort of shearing earth movement. The fractures would then fill with some sort of hot mineral salt solution. The water evaporated leaving the harder mineral layers to resist erosion better than the surrounding sandstone.