Triassic Stratigraphy, Biostratigraphy and Correlation in East-Central New Mexico

Triassic strata in east-central New Mexico are siliciclastic red beds of Middle and Late Triassic age. As much as –500 m thick, the Triassic section is assigned to the Middle Triassic Moenkopi Formation (Anton Chico Member) and overlying Upper Triassic Chinle Group (Santa Rosa, Garita Creek, Trujillo, Bull Canyon and Redonda Formations). The Anton Chico Member of the Moenkopi Formation is as much as 46 m thick and is mostly trough crossbedded micaceous litharenite. It disconformably overlies Middle Permian red beds of the Artesia Group, and is disconformably overlain by the Upper Triassic Santa Rosa Formation. The Santa Rosa Formation consists of three members: (1) basal, Tecolotito Member, as much as 34 m thick and mostly grayish-orange, trough crossbedded and ripple laminated quartzarenite; (2) medial, Los Esteros Member, as much as 44 m thick and mostly red-bed mudstone; and (3) upper, Tres Lagunas Member, as much as 46 m thick and mostly orange and yellowish brown, crossbedded quartzarenite. The Garita Creek Formation conformably overlies the Tres Lagunas Member and is as much as 76 ID thick and mostly red-bed mudstone. It is disconformably overlain by the Trujillo Formation, a medial sandstone complex of the Chinle Group as much as 68 m thick. The Bull Canyon Formation conformably overlies the Trujillo and is as much as 110 in thick and mostly red-bed mudstone. We name a new unit in the Bull Canyon Formation, the Saladito Point Bed, for a discrete, laterally persistent sandstone 12.2 m thick and approximately 30 m above the base of the formation. The Bull Canyon Formation is disconformably overlain by the Redonda Formation, which is up to 92 m thick and mostly laterally continuous, repetitive beds of red-bed sandstone and siltatone. The Middle Jurassic Entrada Sandstone disconformably overlies the Redonda Formation, although the Triassic section is also erosionally truncated locally by younger units throughout east-central New Mexico