Most trace fossils are difficult if not impossible to assign to a particular organism, but paleontologists think that these burrows common in Coastal Plain sediments were made by callianasid shrimp due to their knobby exterior. These burrows can extend for meters and sometimes twist and turn forming a three dimensional framework. The burrows are often stained and cemented by iron oxide since they are usually groundwater conduits through sediment. Shrimp and other burrowing animals churn up the material on the sea floor, distorting or obliterating bedding and layering of sediment. This burrowing action commonly mixes geologic formations at their boundaries.
M. J. O'Donnell