Tectonic implications of mid-Tertiary dikes in west-central New Mexico

The N30° 35°W trend of three long basaltic andesite dikes in west-central New Mexico indicates a least principal horizontal stress direction of N55° 60°E at the time the dikes were emplaced 28 m.y. ago. This stress direction agrees with recently proposed tectonic models for the region, suggesting that northeast-southwest extension was pervasive over both the early Basin and Range and Colorado Plateau provinces and the southern Rocky Mountains at this time.