The Santa Rosa Sandstone (Triassic) occurs at depths of less than 2,000 ft (610 km) over most of northeastern New Mexico. Two major, presently unproductive heavy oil accumulations are known to exist in the Santa Rosa Sandstone in New Mexico: the Santa Rosa tar sands near the town of Santa Rosa in central Guadalupe County and a subsurface accumulation near the town of Newkirk in northeast Guadalupe County.

The Santa Rosa Sandstone is 67–350 ft (20–107 m) thick in northeastern New Mexico. It overlies the Artesia Group (Permian) with regional angular unconformity and is subdivided into three regionally recognizable units: a lower sandstone unit 18–140 ft (5–43 m) thick, a middle mudstone unit 0–144 ft (0–44 m) thick, and an upper sandstone unit 7–150 ft (2–46 m) thick. The lower and upper units are blanket deposits of braided streams and consist mostly of fine to medium-grained porous sandstones and minor red mudstones. The middle unit is lacustrine, consisting chiefly of red mudstones and minor sandstones.

Structures on the Santa Rosa Sandstone are mostly northwest to northeast-trending gentle folds superimposed on a southeast regional dip of 0.4°.

The two heavy oil accumulations occur in the upper sandstone unit. Shows of asphaltic hydrocarbons occur in the lower unit. Stratigraphic and petrographic studies indicate that good reservoirs are widespread in the lower and upper sandstone units in northeastern New Mexico. The blanket geometry of the lower and upper sandstone units indicates that structure should play an important or even dominant role in the trapping of undiscovered hydrocarbons in the Santa Rosa Sandstone.

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