Load-induced subsidence of the Ancestral Rocky Mountains recorded by preservation of Permian landscapes

The Rocky Mountains dominate the landscape of the western United States, but an older system of mountains occupied much the same space roughly 300 million years ago.

These "Ancestral Rocky Mountains" have long puzzled geoscientists because they formed far from a plate boundary and have thus eluded simple explanations. Gerilyn S. Soreghan and colleagues present an analysis of both new and old data from this system, which indicates that the mountain evolution was linked to an ancient, dense crustal root that influenced the trend of the old mountains and that ultimately hastened their demise.

This root formed during rifting of the North American continent more than half a billion years ago and underlies a region extending from southern Oklahoma to western Colorado.

Remarkably, remnants of the approx. 300 million-year-old landscapes formed by these mountains remain relatively intact in parts of Oklahoma and Colorado, forming the most ancient landscapes ever documented in North America -- among the most ancient in the world.

More information:
Gerilyn S. Soreghan et al., Conoco-Phillips School of Geology & Geophysics, University of Oklahoma, Norman, Oklahoma 73019, USA. Posted online 11 April; doi: 10.1130/GS681.1

Provided by Geological Society of America