MAGNETOSTRATIGRAPHY AND FACIES VARIATION IN THE UPPER TRIASSIC SALITRAL FORMATION (CHINLE GROUP) IN THE CHAMA BASIN, NORTH-CENTRAL NEW MEXICO

The Upper Triassic Chinle Group was deposited by a vast fluvial system that extended from Texas to Idaho and Utah to Nebraska. Chinle strata consists predominantly of red to purple mudstone with some red to orange siltstone and red to buff sandstone. In the Chama Basin of north-central New Mexico, the Salitral Formation, together with the Shinarump Formation, comprise the lower third of the Chinle Group. Vertebrate biostratigraphy indicates the Salitral Formation is Adamanian (Carnian) in age. A preliminary magnetostratigraphic compilation of red mudstones and buff sandstones of the Salitral Formation can be tentatively compared with similar age sections in the Newark Supergroup of eastern North America and the Tethyan region of Europe. Based on biostratigraphic correlations, the Salitral Formation should be equivalent to some portion of the Newark Supergroup's magnetozones E1-E13.

Salitral Formation lithology varies considerably laterally where exposed across its outcrop belt in the Chama Basin. The most noticeable lithologic change is within the lower half of the Salitral Formation in the Youngsville Member. In the southern Chama Basin, this unit is a green mudstone lying directly on sandstones of the Shinarump Formation. However, the Youngsville Member is interbedded with discontinuous sandstone channels that are identical in composition to the Shinarump Formation to the north and west, such that the contact between the Shinarump and Salitral formations becomes much less distinct and more gradational. These lateral facies variations suggest that the early Chinle depositional system was more complex than has previously been described.