New Mexico Geological Society Annual Spring Meeting — Abstracts

Recent screenwashing of material from the Tecovas Formation (Triassic, Carnian) near Kalgary, Texas by the New Mexico Museum of Natural History has produced a small but stratigraphically important calcareous microfauna in addition to many vertebrates. The most common microfossil found is a new punctate species of Spirorbis. Also present are a single species of Darwinula and another of Gerdalia, darwinulid ostracods found in many other Triassic nonmarine microfaunas. The Carnian age of this fauna puts it at an age intermediate to other calcareous microfaunas reported from the southwestern united States, and it is the first reported fauna from the Dockum Group. The microfauna differs from other described faunas in lacking a charophyte microfloral element. In this it resembles undescribed calcareous microfossil assemblages from the lower Chinle Formation at Ojo Huelos, New Mexico and from the Monitor Butte Member of the Chinle Formation in Utah. The low diversity darwinulid ostracode element is also shared by these assemblages. The fauna suggests a fluvial/ lacustrine environment. The Spirorbis has impressions of plants on some specimens, suggesting attachment to either aquatic plants washed into the aquatic environment. The punctae in the tube walls of the Spirorbis might have served a respiratory or excretory function.