New Observations on the Extent of Cambrian Rifting In Colorado: An Update

The Ancestral Rocky Mountains are an enigmatic set of major Late Paleozoic structures that extend across much of the central third of the U.S. The largest of these structures is the Southern Oklahoma aulacogen (SOA) that was initially a failed Cambrian-aged rift and was inverted from a to form a series of large uplifts and flanking basins during the Ancestral Rocky Mountain orogeny. Considerable geophysical data that reveal the deep manifestation of Ancestral Rocky Mountain structures in Oklahoma and Texas are available, and these data show that the scale and complexity of these structures is impressive and that they may extend into Colorado. The Wet Mountains of southern Colorado contain little known outcrops of Cambrian aged mafic and ultramafic intrusions. These mountains lie in a position that could be considered a NW splay of the SOA rifting. In addition to a new regional survey, the joint Oklahoma State University and University of Oklahoma field camp group conducted a gravity and magnetic survey of the region of the Gem Park and McClure Mountain mafic and ultramafic complexes in the Wet Mountains for the second consecutive year. As would be expected, these Cambrian-aged intrusives produced strong gravity and magnetic signatures. The results, when merged with regional gravity and magnetic data, indicate that a large (>1000 km2) portion of the Wet Mountains is underlain by Cambrian mafic igneous rocks. In addition, regional seismic refraction/wide angle reflection data from the Continental Dynamics of the Rocky Mountains Project (CDROM) support the above interpretation by correlating the northern Wet Mountains with high velocity (~6.20 km/s) material that extends from near the surface to a depth of about 10 km.