Reference work entry
A mud crack is also known as a drying crack or turtle shell crack. It is a layer structure in sedimentary rocks. Mud cracks are formed by the drying and dehydration of unconsolidated muddy sediments under the sun. The fissures are filled with sand and silty sand from the overlying layer. Mud cracks appear in plan view as irregular polygons, and they are V-shaped or U-shaped in cross-section. They are common on the top surface of clay rock and limestone, but imprints are often left on the bottom of the overlying strata. Mud cracks usually occur in coastal zones, tidal belts, and natural river embankments with intermittent exposure to sunlight. Hence, they can be used as markers for the identification of the depositional environment. V-shaped cracks are also an effective indicator of the top and bottom of rock strata (Fig. 30).
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