Trace Fossils in Eolian Facies of the Upper Triassic-Lower Jurassic Dinosaur Canyon Member, Moenave Formation, Northern Arizona

The Dinosaur Canyon Member of the Moenave Formation, of Late Triassic to Early Jurassic (Rhaetian-Hettangian) age, consists predominantly of sandstones and mudstones deposited by sheet and channelized flow and by eolian processes. We document several previously undescribed biogenic structures in these strata. At one location, eolian dune sandstone hosts the lined, smooth-walled burrow Palaeophycus heberti (Saporta); these may be the nesting burrows of small sand wasps, or alternatively, the burrows of sand-treader camel crickets. Eolian dune facies that host abundant rhizoliths also are typically bioturbated. Circular markings that are convex in epirelief are assigned to Pustulichnus gregarious Ekdale and Picard. Unlined, non-ornamented burrows are unassigned. We speculate that both of these also were formed by the burrowing activity of one of the many species of sand wasp. Rhizoliths are particularly prominent at the tops of eolian dune sandstone beds and locally may host termite nests. Stabilization of the landscape by plants permitted pedogenic alteration of the sediments.

Keywords:

• Moenave Formation
• Palaeophycus heberti
• Pustulichnus gregarious
• rhizoliths
• eolian

ACKNOWLEDGEMENTS

We wish to thank Luis Buatois for sharing his expertise in trace fossil identification. We also extend thanks to John Pollard and Roland Goldring for constructive reviews that improved this manuscript substantially. The Navajo Nation, through its Mineral Department, generously granted permission to undertake field work. Pete Reser assisted in the field.