Remnants of Cruising Trilobites: The Application of Cruziana in North American Stratigraphy

The occurrence of Cruziana, a common trilobite trace fossil, has been established as an effective stratigraphic marker within otherwise nonfossiliferous, siliciclastic rocks from the paleocontinent Gondwana¹. The Gondwanan Cruziana stratigraphy provides an ichnostratigraphic paradigm that can be tested on the Laurentian paleocontinent. The goals of this project are: 1) to determine if the ichnostratigraphic scheme that has proven extremely valuable in Gondwanan and peri-Gondwanan sequences can be utilized in Laurentian sequences, and 2) to verify or negate the use of particular Cruziana species as global index fossils, thereby determining their relevance for large-scale stratigraphic correlations.

We examined Cruziana specimens from across the United States, ranging from the lower Cambrian to the lower Pennsylvanian. Distinctions between different species of Cruziana are based on appendage impressions and scratch patterns. Comparative analysis of North American Cruziana using morphological variation, specifically limb differentiation and overall size and shape of both the trace and its internal markings, indicates that stratigraphic correlation is possible on the Laurentian paleocontinent. However, fundamental differences between peri-Gondwanan/Gondwanan and Laurentian forms of Cruziana suggest that global correlation may not be possible.

¹ Seilacher, A., 2007, Trace Fossil Analysis: Berlin Heidelberg, Springer-Verlag, 191 p., 66 pl.