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AAPG Rocky Mountain Section Meeting

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Stress Provinces of the Rocky Mountains; How the Rockies were Constructed

Abstract

Approximately 600 stress indicators have been utilized to compartmentalize the Central Rocky Mountains into 14 ‘stress provinces’ that owe their derivation to Laramide compression or Cenozoic extension. Laramide-age stress provinces dominate eastern Utah, and most of Colorado and Wyoming. Within these states, six distinct principal stress (S_Hmax) provinces are recognized; Colorado Plateau (CP), Piceance Basin (PB), Rawlins Uplift (RU), Wind River Basin (WRB), Greater Green River Basin (GGRB), and the Bighorn Basin (BHB). These provinces are mostly bounded by tectonic elements that exploited boundaries and/or weaknesses in Precambrian terrane. S_Hmax is predominantly WNW-ESE to NW-SE in the west and NE-SW in eastern Wyoming and Colorado. However, complexity and rotation of stress is present and appears to be dependent on Precambrian boundary conditions. East of the Front Range, five stress provinces are recognized. The Powder River Basin (PRB) is part of the Wyoming Craton, but the NE-SW stress domain extends uninterrupted into the northern Great Plains Province. Three provinces are recognized in eastern Colorado; the Denver Basin (DB), Central Plains (CP) and the Las Animas Basin (LAB), coincident with the Proterozoic Yavapai-Mazatzal suture zone. The Denver Basin extends northward into southeast Wyoming. Stress is associated with a series of NEtrending wrench fault zones compartmentalize the basin, with intervening NWtrending antithetic stress indicators. In northeast New Mexico, a domain of S_Hmax with an orientation of WNW-ESE is loosely defined as the Ouachita Extension (OE). Cenozoic extension created three stress provinces; the Raton Basin (RB) and San Juan Basin (SJB) are the dominate provinces in New Mexico, and the Basin and Range Province in western Utah that extends northwards into Wyoming. Principal stress orientation (S_Hmax) is predominantly North-South. In Utah, the seismically active Wasatch Hingeline defines the boundary between the Colorado Plateau and Basin and Range. Seismicity is also present in the Raton Basin along the Vermejo Park fault and north-trending structural features extending into Colorado. Recognition of these provinces provides a better understanding of how the Rocky Mountains were constructed and managing exploitation of resources.