Department of Geology and Geological Engineering
Van Tuyl Lecture Series- Fall 2014
4:00-5:00 p.m. in Berthoud Hall Room 241
Thursday, October 23, 2014
Dr. Stephen Marshak
Department of Geology
School of Earth, Society, & Environment
University of Illinois at Urbana-Champaign
“Tectonics of the United States Midcontinent: Emerging Insight from the
Earthscope "OIINK" Project”
Abstract: The present-day topographic character of the Rocky Mountains and
Colorado Plateau provinces contrasts markedly with that of the Midcontinent
province (Interior Plains and plateaus), even though all these areas are underlain
by similar cratonic-platform crust. Lack of dramatic topography leads to the
impression that the Midcontinent has been tectonically stable through the
Phanerozoic. In fact, the region hosts a half-billion year record of tectonic
activity, recorded by broad epeirogenic movements of basins, arches, and domes,
and by localized development of fault-and-fold zones. Notably, structural relief
of the Great Unconformity (the boundary between Precambrian basement and
Phanerozoic cover) in parts of the Midcontinent is comparable to that found in
the Rocky Mountains province. Recent results from the OIINK (Ozark-IllinoisINdiana-Kentucky) project, a part of EarthScope, yield a clearer image of the
Midcontinent's structural architecture, and of contrasts between it and the Rocky
Mountain Province. This image provides a foundation for relating shallow
Midcontinent structures to deeper crustal features, for understanding the
distribution of contemporary seismicity, and perhaps for explaining why the
Midcontinent and the Rockies behaved differently in response to orogenic stress
during the Phanerozoic.