TRACE FOSSILS IN THE TYPE AREA OF THE VIRGIN MEMBER OF THE MOENKOPI FORMATION (LOWER TRIASSIC), WASHINGTON COUNTY, UTAH

In its type area in southwestern Utah the Virgin Member of the lower Triassic Moenkopi Formation is a shelf deposit. It is a shale-siltstone/mudstone-limestone sequence deposited as a result of transgressive-regressive events.

The metazoans were still recovering from the great Permian extinction, but the presence of Thalassinoides, Rossellia, and unnamed escape burrows suggests metazoan life forms were making a come back. Most of the organisms are small, but a few larger trails, up to two centimeters wide, show a general size increase. Normal marine water conditions are indicated by the presence of crinoid parts. Because of the broad aerial extent of the Virgin Member multiple facies with related faunal elements are present.