Pennsylvanian oil possibilities of San Juan Basin, Four Corners region; Colorado-New Mexico

The San Juan basin is a post-Pennsylvanian tectonic subsidence area closely related in its early sedimentational history to the Paradox geosyncline. During early Pennsylvanian time, this region was subjected to widespread erosion, but received high-shelf Pinkerton Trail carbonates and fine gray clastics related to the Cordilleran geosyncline, followed by Cherokee subsidence to form a through-going seaway in whose deeper parts evaporites of the Paradox formation were deposited, succeeded by coarse arkosic clastic invasion from the strongly activated San Luis and Penasco positives on the E and fine-grained red clastics from the Zuni-Defiance positives on the W and SW. Normal marine waters persisted during the deposition of the Honaker Trail-late Madera sediments, succeeded by filling of the seaway with red continental clastics across the Pennsylvanian-Permian temporal boundary everywhere except in the medial parts of the seaway where marine Wolfcamp carbonates were deposited. The SW and W shelf of this seaway, with its sediment-controlling "spurs" and "sags," appears to be a locale where commercial oil should be present in Pennsylvanian strata.