BROADHEAD, RONALD F.
New Mexico Bureau of Mines and Mineral Resources, a Division of New Mexico Tech, Socorro, New Mexico

Abstract: Petroleum Source Rocks in Pennsylvanian Elevator Basins of New Mexico

The Tucumcari, Estancia, Vaughn, and Carrizozo Basins are located in northeast and central New Mexico. These basins began to form during the Early to Middle Pennsylvanian. Tectonic development continued through the Early Permian. They were formed along the flanks of the late Paleozoic Sierra Grande and Pedernal uplifts in a strike-slip setting.

These basins were dominated by shallow-shelf deposition. Along the boundaries with adjoining uplifts, these basins have component elevator basins: long, narrow, and structurally deep troughs bounded by high-angle faults. Most are elongate parallel to the axes of the adjoining uplifts. Bounding faults have vertical offsets that can exceed 5,000 feet. Basin width ranges from two to ten miles.

Early to Middle Pennsylvania strata in the elevator basins are gray to black shales and sandstones. The shales are mature petroleum source rocks. Total organic carbon (TOC) can exceed 9% in black shales. Kerogens range from gas-prone woody types to oil-prone amorphous types. Greater depth of burial in the elevator basins as compared to the adjoining uplifts and shelf areas has resulted in increased levels of thermal maturation within the basins. Hydrocarbons generated within the basins have migrated upward along the bounding faults and into reservoirs on adjacent shelves as well as also being trapped in sandstones within the elevator basins.

AAPG Search and Discovery Article #90918©1999 AAPG Southwest Section Meeting, Abilene, Texas