New Mexico Geological Society Annual Spring Meeting — Abstracts

Zoophycos comprises a diverse group of spreite burrows that range in age from Ordovician to Recent. It is generally thought to be the feeding trace of various worm-like animals and to indicate poorly oxygenated paleoenvironments with low sedimentation rates. There are only a few published reports of Zoophycos from New Mexico, and these are primarily from Carboniferous strata. We add to this sparse record an occurrence of Zoophycos at Whiskey Canyon in the Mud Springs Mountains. Here, the Zoophycos fossils occur in a 0.6-m-thick bed of coarse crinoidal limestone (crinoidal wackestone) near the top of the Elephant Butte Formation of Thompson, which is near the top of the Red House Formation of Kelly and Silver.

We collected a representative specimen preserved in convex hyporelief. It shows clockwise, alectorurid (“cock’s tail”) spreite on the bedding surface. Because neither a marginal tube, nor a vertical generating tunnel is preserved, the specimen can only be assigned to cf. Zoophycos ichnosp. The overall width is about 27 cm, which is average size for Paleozoic forms. Zoophycos is a classic trace fossil long interpreted as characteristic of relatively deep, poorly oxygenated sea bottoms. However, protected lagoonal settings of moderate depth are also known to produce Zoophycos, and we interpret the Mud Springs record as a shallow marine setting with restricted circulation. The Zoophycos bed is in the middle of a 20-m-thick succession of wavy to even bedded limestone units (0.6-2.8 m thick) and covered intervals (0.6-2.9 m thick) that probably represent shale intervals. These limestone units are all dark gray, micritic and contain some chert in the lower and upper part. The lime mudstone in the upper part of the section, above the Zoophycos bed, is bioturbated. Common fossils are brachiopods and crinoid fragments. The muddy texture of the limestone units indicates deposition in a low-energy shelf environment below the storm wave base.