The central Rocky Mountains and adjacent Great Plains of western North America is a region of high topography that runs along the backbone of the continent.
When and how the region reached its current elevation is the subject of debate. To date, most studies have focused on the last major mountain building event that occurred between approx. 45 and 75 million years ago. More recent constraints on uplift history are sparse.
In this paper, Majie Fan and colleagues present results from volcanic glass hydrogen isotope ratios deposited over the last 35 million years that constrain the timing of uplift.
Their samples were collected along a transect following the gradual eastward decrease of elevation and increase of surface water hydrogen isotope ratios. They show that the present gradient of surface-water hydrogen isotope ratios was established before 35 million years ago.
These results, when considered with other published paleoelevation studies, suggest that the central Rocky Mountains and adjacent Great Plains underwent uplift during the late Eocene, and have not undergone any large-magnitude (i.e., greater than about 500 m) surface uplift since that time.
They show that this differential uplift caused regional drying in the region over the past 35 million years.
Article: Middle Cenozoic uplift and concomitant drying in the central Rocky Mountains and adjacent Great Plains, Majie Fan et al., 24 April 2014, http://dx.doi.org/10.1130/G35444.1