Sedimentary structures - mud cracks and rain droplets

Very occasionally, it's possible to find ancient raindrops preserved in sedimentary rocks. These imprints tell us a couple of things, a) the host sediment was either under very shallow water or at the Earths surface so it's highly likely to be of terrestrial (as opposed to marine) origin and b) the overlying sediment was deposited in a very low energy environment so as not to disturb the imprints.

 

The image above displays two lovely modern sedimentary features, mudcracks and rain drop craters. Interestingly, we can see that in the middle of the images the raindrops imprints get fuzzy before stopping. We can therefore assume this is the border of a puddle that existed either before the rainfall or soon after as either the water absorbed the impact of the raindrop creating no mini-crater or the water encroached and wore the imprint away.

Think about how fragile these mudcracks and raindrop craters are, they'd be erased by the next large rainfall if not covered over and protected. The likelyhood of raindrop preservation is very low, so if you do happen to find some take a moment to marvel at the numerous process that had to occur to create that rock!