File:Curled mudcracks with raindrop imprints (modern; Kodachrome Basin, Utah, USA) 1.jpg

English: Mudcracks are diagnostic sedimentary structures indicating subaerial exposure of sediment surfaces, with alternating wet & dry conditions. They are much more common that raindrop imprints, which indicate the same environmental setting. Mudcracks are most likely to occur in fine-grained siliciclastic sediments, fine-grained carbonate sediments, and in some evaporitic settings.

Mudcracks are distinctive and easy to identify, but they do vary in appearance. The cracks themselves vary in width, depth, and areal density. Mudcrack polygons also vary in size & shape. Mudcracks sometimes have curled-upward edges. The examples shown above are developed in a thin, dark reddish-brown mud layer atop unlithified sand.

The curled mudcracks shown above have small, circular pits - these are raindrop imprints, which are scarce, but highly diagnostic sedimentary structures. They absolutely demonstrate that a particular bedding plane was subaerially exposed - it had to be land. Raindrop imprints are expected to be small circular to subcircular pits or craters on fine-grained siliciclastic sediment surfaces. They may be associated with mudcracks and terrestrial fossils (such as fossil ferns).

Locality: small wash in northern Kodachrome Basin, northern Kane County, southern Utah, USA