Mud Cracks : Desiccation and Syneresis Cracks

Mud cracks are the fracture patterns that formed in the muddy sediments, in sub-aerial environment. They are of two types :-

1. Desiccation Cracks
2. Syneresis Cracks

Desiccation Cracks

• Caused by evaporation of water from wet sediments
• Polygonal and well-defined in shape
• Often deep and V-shaped, wider at the top and tapering downward
• Common in sub-aerial exposures (dried up lakes, floodpalins)
• Indicates alternating wet-dry cycles in the past

Syneresis Cracks

• Form sub-aqueously (underwater), not from drying, but due to chemical changes in pore water.
• Often caused by salinity changes, especially in clay-rich sediments
• Usually irregular, discontinuous, and more angular than desiccaiton cracks
• Occurs in marine or brackish water environments, such as lagoons or estuaries
• May be associated with flocculation or shrinkage from ionic reactions

Why are mud cracks important ?

1. Indicate past climate and environmental conditions.
2. Used to interpret paleoenvironmens in sedimentary rocks.
3. Can help identify ancient floodplains, playas and tidal flats.