Shell Colloquium Series Fall 2011

November 10th, 3:30 pm, Room A235, Sarkeys Energy Center

The acquisition of Global Positioning System (GPS) geodetic data for well

over a decade has allowed estimates of contemporary, instantaneous vertical-axis ro-

tation rates of continental lithosphere in deforming zones. How these estimates com-

pare with those provided by paleomagnetic data, which integrate rotation over some

interval of geologic time, is of considerable interest because of the ultimate ability to

better understand processes responsible for crustal rotations. We compile most paleo-

magnetic data from the western US that provide quantitative information on the mag-

nitude and sense of vertical axis rotation of crustal elements, approximately since the

cessation of crustal shortening related to Sevier-style fold/thrust belt and/or Laramide

-style basement-involved deformation. Although the existing paleomagnetic data

bearing on vertical-axis rotations in the western US is impressive in scope, estimating

an accurate rotation rate from individual studies is not simple. Many studies are

flawed by lack of quality paleomagnetic information. In some cases, however, the

paleomagnetic and geodetic observations are quite comparable (e.g., mid-Miocene

Columbia River basalts).

ConocoPhillips School of Geology & Geophysics The University of Oklahoma

100 East Boyd St., Ste 710, Norman, Oklahoma 73019

Phone: (405) 325-3253; Fax: (405) 325-3140

www.geology.ou.edu

Dr. John Geissman University of Texas, Dallas

"How does the permanent record (paleomagnetic

data) of crustal vertical axis rotations in the west-

ern US Cordillera compare with the growing (but

short) geodetic record?"