Burrows are common to abundant in much of the Permian Phosphoria Formation and correlative units in western Wyoming and adjacent states. Surface traces are rare. Coarse phosphorite units are characterized by straight, full-relief traces with fine-grained fillings. They are commonly horizontal but some are vertical. Sandstones contain burrows varying greatly in orientation and regularity. Carbonate rocks and certain cherty units typically contain burrows similar to those of modern crustaceans; the burrows are filled with skeletal material, fine-grained carbonate rock, phosphorite, or chert.

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Absence of primary sedimentary structures in certain units is probably due to bioturbation. Units with high concentrations of burrows near the top suggest rapid deposition. Straight vertical burrows in certain marine sandstones may be insect burrows in barrier-island environments.

Cylindrical, irregular chert nodules are characteristic of most carbonate units. Some nodules are isolated but others coalesce into beds. The carbonate matrix in many places has flow structures around the chert nodules suggesting relatively early lithification of the chert. Some cherty beds contain irregularly cylindrical carbonate bodies. The cylindrical bodies, both chert and carbonate rock, are interpreted as burrow fillings. Burrows filled with material coarser and more permeable than the host sediments were sites of chertification. In beds in which the opposite conditions prevailed, the interburrow material was silicified. Because large burrows with coarse-grained fillings are abundant and in many places penetrate less permeable sediments, they may have functioned as important fl id conduits during early diagenesis.

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