T170 Folds and Folding: Form, Process, and Consequences (Posters)

Monday, 26 September 2016
9:00 AM - 6:30 PM
Exhibit Hall E/F

PERICLINAL FOLDING IN THE OZARK PLATEAU: A RECORD OF LOCAL KARST COLLAPSE OR REGIONAL TECTONIC FORCES?

Paper number: T170-12
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

  • Chao Liu Presenting Author
    Missouri University of Science and Technology, Rolla, MO
  • John Hogan
    Missouri University of Science and Technology, Rolla, MO
  • Andreas Eckert
    Missouri S&T, Rolla, MO

Abstract

The Ordovician Rubidoux Formation of the Ozark Plateau, Missouri is typically identified as mechanically competent sub-horizontal beds of medium grained sandstone. North of Licking, MO, the Rubidoux Formation was deformed into a series of dome-and-basin shaped buckle folds, exposed in road cuts over a distance of ~10 km. Such folds are highly unusual within the Ozark Plateau and their origin remains controversial.

Three major hypotheses have been proposed based on field observations and stereographic analysis. Given the pervasive distribution of karst collapse throughout Missouri, one hypothesis to explain these folds is that the Roubidoux Formation sagged into collapsed caverns. A second hypothesis is that these folds are the result of compression induced in a possible transpressive zone between two left-lateral strike-slip faults. A combination of the two processes is also possible.

Field measurements of 37 fold structures including more than 300 recordings of bedding attitudes and stereographic projections confirm that the Roubidoux folds are periclinal folds. They elongate along N59E to S59W, with the maximum shortening occurring along N60W to S60E. The uniformity of the fold orientations over this large distance is inconsistent with an origin by sag folding related to karst collapse. While the orientation of the shortening direction is inconsistent with the general trend of midcontinent deformation structures (i.e. Cox, 2009 reports a NE-SW shortening direction), two possible left-lateral strike-slip faults mapped to the north and south of the folding zone may have locally reoriented the stress field. This is supported by a simple 2D finite element model indicating that transpressional deformation in a restraining jog results in localized shortening direction consistent with the distribution of the observed periclines.

It is concluded that a regional tectonic event induced localized buckle folding whereby local karst effects may have contributed in forming the initial perturbation.

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

doi: 10.1130/abs/2016AM-286300

© 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.