The integration of regional Cretaceous stratigraphy, surface mapping of different structural styles, seismic data, and accumulating subsurface well control has blended over the past 16 years into a regional Cretaceous play encompassing many of the subbasins of the Rio Grande rift from Texas, north through New Mexico, and into the San Luis basin of southern Colorado.

Different structural styles, as well as changing stratigraphy, can make exploration in one of the subbasins a very different problem from exploration in another. Remnant structures of pre-rifting tectonics vary radically along the course of the rift from north to south, and are present and preserved beneath the subsequent rift-valley fill. Although the same basic tectonic causes for the rift are common throughout its length, this later Tertiary tensional event was imposed across all previous structural grains from Precambrian to Laramide.

In areas such as the northern Albuquerque basin, which was relatively undisturbed by Laramide thrusts, the predominant structural style is listric faulting caused by the rift. However, areas such as the Espanola basin show strong evidence of pre-rift thrusting during the Laramide orogeny. This structural style is still quite evident, and in places is the predominant style preserved beneath Tertiary valley fill.

In other areas, such as the San Luis basin, the rift has superimposed itself across earlier block faulting that occurred during the Precambrian and late Paleozoic and was modified by Laramide thrusts. The area was then covered by Oligocene-Miocene volcanics and rift-valley fill.

Such complex tectonic history makes exploration in the various subbasins of the rift extremely difficult. It also presents rare opportunities for hydrocarbon exploration in potential new provinces where abundant stratigraphic and structural trap potential is combined with adequate source rocks and a favorable maturation history.

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