I THOUGHT THAT WAS THE LARAMIDE OROGENY!

Map
Sevier Thrust System
Middle Jurassic Back-bulge Basin
Late Jurassic to Early Cretaceous Forebulge High
Early Cretaceous Thrust Faulting
Late Cretaceous Thrust Faulting
Late-Phase Thrusting
The End of Thrusting
I Thought that was the Laramide Orogeny!
Advances

The Sevier orogeny is often confused with the Laramide orogeny, even by geologists, because they overlap in time and location.

The Laramide orogeny developed in the Late Cretaceous and continued into the Oligocene epoch, mostly synchronous with late stages of the Sevier orogeny. Laramide structures were produced in central and eastern Utah, western Colorado, and most of Wyoming -- thus, some overlap eastern Sevier thrust belt structures.

Classic Laramide structures in Utah include the Uinta Mountains uplift, the San Rafael Swell, and the Circle Cliffs (Waterpocket Fold). Some structures, such as the Uinta Mountains, were affected by both events. The two orogenies were produced by the same crustal shortening event, collision of the Farallon and North American plates, but they are distinguished by style of deformation.

The Sevier orogeny defines a more western event that took advantage of weak bedding planes in thick Paleozoic and Mesozoic sedimentary rock. Shortening in basement metamorphic and igneous rocks was transferred tens of miles eastward along the weak shale and evaporite layers, producing “thin-skinned” thrust faulting that, in its eastern part, only involved sedimentary strata.

In contrast, the Laramide orogeny produced “basement- cored” uplifts because thin sedimentary rock in those areas did not easily “decouple” from the basement rock.

Over the past few decades, study of the geometry, tectonic forces, and dating of thrust systems produced some of the most exciting advances in geology. Utah has been at the center of some of this work. This is a brief overview of the development and evolution of the Utah thrust system, synthesizing the work of many geologists.