Origins of the Salado, Seven Rivers, and San Andres salt margins in Texas and New Mexico: Revision 1: Topical report

The present boundaries of the San Andres, Seven Rivers, and Salado salts generally lie along the periphery of the Palo Duro and Tucumcari Basins. Various geologic mechanisms occurring singularly or in combination determined the positions of the salt margins. These mechanisms include nondeposition of salt and syndepositional and postdepositional dissolution. In New Mexico, San Andres units pinch out against the Pedernal and Sierra Grande Uplifts, indicating that nondeposition established the original salt margins there. Syndepositional dissolution of exposed Upper San Andres salts occurred in response to Guadalupian upwarp of the basin margins. Triassic erosion differentially removed Permian salt-bearing formations along the uplifts. Late Tertiary dissolution is indicated by fill of north-south trending collapse valleys. In Texas, Guadalupian upwarp along the Amarillo Uplift caused pinchout of Units 2 and 3 in the Lower San Andres and influenced the deposition of subsequent salt-bearing strata. The discontinuity of Upper San Andres evaporites across the Amarillo Uplift suggests syndepositional dissolution. Along the eastern and northeastern basin margin, dissolution may have accompanied Triassic erosion of locally uplifted Upper Permian strata. Tertiary dissolution is recognized beneath anomalously thick Ogallala Formation sections that overlie collasped Permian strata. 49 refs., 31 figs., 2 tabs.