New Mexico Geological Society Annual Spring Meeting — Abstracts

The Triassic section exposed near Lamy is approximately 410 m thick and can be divided into three distinct units that correspond to the Middle Triassic Anton Chico Formation and the Upper Triassic Santa Rosa and Chinle Formation. The Anton Chico Formation is up to 37 m thick and composed of reddish gray, trough-crossbedded litharenite and conglomerate. It lies unconformably on the Permian Bernal Formation and is unconformably overlain by the Santa Rosa Formation in sec. 7, T12N, R11E, and has yielded fragments of capitosauroid labyrinthodont dermal armor indicative of an Early-Middle Triassic age. The Santa Rosa Formation is about 140 m thick and dominated by yellowish brown, trough-crossbedded quartz-arenite. It is overlain by the Chinle Formation in sec. 28 T15N, R11E. Outcrops in secs. 9 and 11, T12N, R10E and in Sec. 29, T12N, R11E expose about 230 m of redbeds of the Chinle Formation, which consists of mudstone-dominated and sand-stone dominated intervals. It in unconformably overlain by the Entrada Sandstone in sec. 9 T12N, R10E. Fossil-bone fragments from the Chinle Formation include phytosaur and metoposaurid labyrinthodont remains and are of Late Triassic age. The vertical succession of Triassic strata near Lamy is similar to the stratigraphic succession in east-central New Mexico, suggesting that the two areas existed within the same Triassic depositional basin and experienced similar depositional cycles or events.