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The AAPG/Datapages Combined Publications Database

Utah Geological Association


Geology of Northern Utah and Vicinity, 1999
Pages 123-140

Sedimentology and Ichnology of a Bioturbated Interval in the Nugget Sandstone, a Jurassic Eolianite, Near Peoa, Northeast Utah

R. Craig Sanders, M. Dane Picard


The Nugget Sandstone, a Jurassic eolianite, has yielded few fossils. In addition, there are few studies of trace fossils in eolianites anywhere. The trace fossils discussed here, which are found immediately north of Peoa, Utah, are therefore significant as a reflection of life in the Early Jurassic Nugget sand sea.

The trace fossils in the Nugget Sandstone are mostly meniscate burrows similar to those of other eolianites, including some that are roughly parallel with bedding and others that lack a preferred orientation. Most are assignable to the ichnogenera Taenidium and Entradichnus, and some may belong in the ichnogenus Beaconites. Tracks of a small vertebrate are exposed in one outcrop, and are predominantly directed upslope. These are assigned to the ichnogenus Brasilichnium. A few invertebrate (scorpionid?) tracks were found in float.

The positions of the trace fossils indicate that the burrowed intervals formed on the middle or upper lee slopes of sand dunes. The depositional history of the thicker burrowed interval is reconstructed from an analysis of the bedding types, granulometry, and depositional slopes within that interval.

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