Late paleozoic tectonic and sedimentologic history of the Penasco uplift, north-central New Mexico
Adams, Roy Donald
Anderson, John B.
Master of Arts
The Paleozoic Peiiasco Uplift, located on the site of the present Nacimiento Mountains of north-central New Mexico, acted as a sediment source and modifier of regional sedimentation patterns from Middle Pennsylvanian to Early Permian time. The earliest history of the uplift is still poorly defined. Orogenic activity may have started as early as the Late Mississippian, or there may have been quiescence until after deposition of the Morrow-age Osha Canyon Formation and prior to deposition of the Atoka-age Sandia Formation. Coarse, arkosic siliciclastic sediments interbedded with fossilferious carbonates in the Madera Formation indicate that by early Desmoinesian time the Peiiasco Uplift had risen sufficiently to expose and erode Precambrian rocks. Paleotransport indicators in the arkosic sediments show transport away from the uplift. Throughout the remainder of the Pennsylvanian, the Peiiasco Uplift was a sediment source. The siliciclastic sediments derived from the Peiiasco Uplift formed a wedge that prograded out onto and interfingered with carbonate sediments of a shallow normal marine shelf. A change in paleotransport directions from northeasterly to southwesterly occurs on the east side of the Peiiasco Uplift and is due to the arrival of a flood of siliciclastic sediments derived from the Uncompahgre-San Luis Uplift to the northeast. This flood of sediments at or near the Permo-Pennsylvanian boundary, as dated by fauna in the uppermost Madera Formation, quickly breached the waning Penasco Uplift. Polycrystalline/total quartz ratios show that though breached, the Penasco Uplift continued as a sediment source during most, if not all, of Abo time. By the end of the Wolfcampian when Abo deposition ceased, the Penasco Uplift was no longer a sediment source and did not modify regional sedimentation patterns. Field relationships show that the two members of the Madera Formation, the lower gray limestone member of Atokan to Virgilian age, and the upper arkosic member of Desmoinesian to Virgilian age, are laterally equivalent and interfingering facies. The Abo to Madera formations are also, in part, laterally equivalent and interfingering. The Abo Formation ranges in age from Late Pennsylvanian to the end of the Wolfcampian in the Permian. The base of the Leonardian age Yeso Formation is gradational with the top of the Abo Formation.