Major tectonic boundaries along the Rio Grande rift are mostly listric normal faults that controlled late Cenozoic sedimentation in the rift. Potential hydrocarbon source and reservoir rocks occur in Cretaceous, Jurassic, and Pennsylvanian units beneath presumably barren upper Cenozoic continental sediments. Largest of the grabens and half-grabens comprising the rift is the Albuquerque basin, which was explored during the last decade with several deep tests. Upper Cenozoic strata generally dip gently toward the basin center except near bounding faults where "reverse drag" has beds on the downthrown block dipping toward the growth faults marking the basin margins. Most bounding faults are covered with surficial sediments, but at a few localities with good, deep exposures,

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stratigraphically deeper beds have undergone more "reverse drag" than higher strata. Thus, these reversals of dip adjacent to bounding faults may provide structural traps along the margins of the Albuquerque basin.

Recent deep wells were drilled in the central part of the Albuquerque basin on structural highs, probably intragraben horsts. Most of these recent tests were tight holes, but encouraging hydrocarbon shows were encountered. The margins of the Albuquerque basin have not been tested yet, but there may be numerous traps where "reverse drag" is present. These structures could have trapped hydrocarbons where potential reservoir rocks (mainly sandstones) and source beds (mainly organic-rich marine shales of the Cretaceous and Pennsylvanian, and organic-rich laminated limestone of the Jurassic Todilto Formation) occur.

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