Geological Society of America

T316 Earth History in the Broadest Context—Ophiolites, Global Tectonics, and Public Awareness of Earth Science II: Celebrating the Contributions of Eldridge Moores

Wednesday, 28 September 2016
1:30 PM - 5:30 PM
Room 203

STRUCTURAL AND GEOMORPHOLOGICAL MANIFESTATIONS OF THE CRUSTAL BOUNDARY BETWEEN THE ILLINOIS BASIN AND OZARK DOME: IMPLICATIONS FOR MIDCONTINENT TECTONICS

Paper number: T316-9
Program: Technical Sessions
Time: 3:40 PM – 3:55 PM

Authors

Michael S. DeLucia Presenting Author
University of Illinois, Champaign, IL
Timothy Larson
University of Illinois at Urbana-Champaign, Champaign, IL
Mary Seid
Illinois State Geological Survey, Champaign, IL
Stephen Marshak
University of Illinois, Urbana, IL
Alison Anders
University of Illinois at Urbana-Champaign, Urbana, IL
Gary Pavlis
Indiana University, Bloomington, IN
Xiaotao Yang
Indiana University, Bloomington, IN
Hersh Gilbert
Purdue University, West Lafayette, IN
Chen Chen
Purdue University, West Lafayette, IN
Michael W. Hamburger
Indiana University, Bloomington, IN

Abstract

The tectonic relationship between epeirogenic features, fault-and-fold zones, and topography in the cratonic platform of the United States remains an open question. To address this question, we have plotted a compilation of structural traces (the intersection of Midcontinent fault-and-fold zones with the ground surface) on a DEM of the region. This plot reveals a correlation between these traces and both local-scale and regional-scale topographic features. Specifically, individual traces control stream orientation and align with boundaries of local escarpments. They also underlie a set of subtle, NW-trending ridges, whose shapes represent the surface manifestation of positive flower structures indicative of transpressional deformation. Local pull-apart basins, similarly, are indicative of transtensional deformation. At a regional scale, fault-and-fold zones align with both the NE and SE boundaries of the Ozark Plateau, suggesting that the St. Francois Mountains represent the exhumed corner of a tilted crustal block. Results from the EarthScope OIINK array emphasize that the edge of this crustal block correlates with an up to 7.5 km-high step in the subsurface elevation of the Great Unconformity. It also coincides with a belt of seismicity, a region of low-velocity seismic waves, and a significant drop in Moho depth. The persistence of topography in the Ozark Plateau and of bordering ridges hints that displacements along the boundary between the Illinois Basin and the Ozark Dome, known to be significant during the Paleozoic, are still sufficient to maintain uplift through post-Paleozoic time. Examination of drainages in the plateau indicate that streams display typical graded profiles, but do not have obvious knick points, implying uplift is not rapid or localized enough to generate knick points. Overall, the spatial association of upper-crustal faults, deep-crustal steps, topography, and seismicity, along the boundary of between the Ozark Dome and the Illinois Basin, emphasizes that faulting serves a significant role in the evolution of regional, long-lived epeirogenic features, and that these structures continue to exert a subtle control on topography in post-Paleozoic time.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-286885

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.