Luncheon – October 21, 2005

Title: Gravity and Magnetic Studies of the Southern Rocky Mountain Crust: Basins to Basement
Speaker: G. Randy Keller, Department of Geological Sciences University of Texas at El Paso
Luncheon Date: October 21, 2005
Publication: The Outcrop, October 2005, p. 5

The Rocky Mountains have intrigued researchers and explorationists ever since the gold rush days. These mountains are a tectonic puzzle because of their complex history and their distance from plate margins that usually make driving mechanisms evident. From a petroleum exploration point of view, the formation of the Ancestral Rocky Mountains, the Laramide orogeny, and late Cenozoic extension and uplift are of primary interest. There has been an increasing emphasis on gravity and magnetic data in studies of this region, and these data have been particularly effective when used in an integrated fashion with seismic and drilling data. Rifting during the late Precambrian and Cambrian effected large areas of the southwest and created sedimentary basins that have in many cases survived to the present. In at least some cases, these strata contain both source and reservoir rocks. Thus, there is a frontier defined by stratigraphic depth. In addition, younger structures such as those associated with the Ancestral Rocky Mountains have often been affected by older rift structures preserving Cambrian and older strata. Gravity and magnetic data have played a major role in studies that reveal the deep manifestation of Ancestral Rocky Mountain structures including the deep basin structure and structure of the uplifts, and these data show that the scale of these structures is impressive in a global context. The structures extending across Oklahoma and the Texas panhandle into New Mexico have been referred to as the Southern Oklahoma or Wichita aulacogen, which can be interpreted to extend along this trend as far northwest as the Uncomphagre uplift in Utah. The deformation that formed the Ancestral Rocky Mountains is a massive inversion of these rift structures and is due to a plate collision in the late Paleozoic. These structures form one of North America’s major petroleum provinces. The Laramide orogeny also produced considerable crustal scale deformation in the form of large basement uplifts and deep productive basins. Finally, late Cenozoic uplift and extension formed a series of basins that gravity and magnetic data show are deep and complex.