Structures in the Rio Grande and Kenyan Rift: A comparison

Abstract

The Rio Grande rift gradually widens from its northern terminus in Colorado to southern New Mexico, Texas, and the northern portion of the state of Chihuahua, Mexico, where it appears to merge with the Basin and Range province. In a similar fashion, the Kenya rift widens from the apex of the Kenya topographic dome near Nairobi northward toward the Lake Turkana region, where the rift becomes diffuse as it enters Ethiopia. Recent studies in Kenya conducted by the Kenya Rift International Seismic Project (KRISP), project PROBE, and Amoco have provided a much improved picture of structural relationships in this rift zone. In the Rio Grande rift, efforts by many workers continue to reveal an ever clearer picture of structural relations. These two rift zones appear to possess some common characteristics which may be useful in studies of other rift zones. A combination of data indicate that the wider portions of both rifts are also the most extended. This observation is in agreement with the decrease in elevation and crustal thickness as the rifts widen. In both rifts, the subsurface structure of the basins is much more complex than the surface expressions would indicate. Half-graben geometrics predominate, but the relations between major faults and rift flank topography is not always that which would be expected. The most extended regions of these rifts seem to have preserved the thickest pre-rift sedimentary sections. This relationship is effected by pre-rift geologic history, but does suggest these regions would be the best exploration targets.