Paper No. 30-8
Presentation Time: 10:30 AM-10:45 AM
THREE-PHASE LATE PALEOZOIC DEFORMATION OF THE SOUTHERN OZARK DOME, WESTERN BUFFALO RIVER REGION, NORTHERN ARKANSAS
HUDSON, Mark R., U.S. Geol Survey, Box 25046, MS 980, Denver, CO 80225-0046, mhudson@usgs.gov.

Recent geologic mapping and kinematic studies within Ordovician-Pennsylvanian sedimentary rocks in the western Buffalo River region reveal three phases of late Paleozoic deformation in the southern Ozark dome. Early ENE-directed shortening, D1, was followed by N- to NNE-directed extension, D2, and then by N- to NNW-directed shortening, D3. D1 accommodated localized ENE shortening in the >4-km-long Kyles Landing reverse fault and associated fold. This structure deforms upper Mississippian strata but is unconformably overlain by lower Pennsylvanian strata. D2, N- to NNE-extension, was widespread in the area and recorded by WSW- to WNW-striking normal faults, NE-striking dextral strike-slip faults, and variably oriented monoclinal folds. D2 deformation affects lower Pennsylvanian strata but is older than probable Early Permian lead-zinc mineralization that was localized along D2 faults. Finally, during D3 deformation, selected D2 structures were reactivated to accommodate N- to NNW-directed shortening. D3 reactivation of the SSE-dipping Compton normal fault is indicated, in its hanging wall, by the presence of small strike-slip faults that cross cut D2 extensional deformation bands and, in its footwall, by the presence of an ENE-elongate anticline cored by a small thrust fault having a 170° slip azimuth. Regionally in northern Arkansas, D3 is recorded by N- to NNW-directed compression axes in published calcite-twin studies and by a prominent joint set.

Multiphase deformation of the western Buffalo River region is interpreted as a midcontinent response to evolving Late Paleozoic continent-margin orogenic belts. Speculatively, D1 reflects late Mississippian-early Pennsylvanian shortening due to far-field stresses radiating from an initial Alleghanian-Ouachita indentation of the southeast continent margin. D2 extension reflects Pennsylvanian down-flexure of the southern continent margin adjacent to the growing Ouachita thrust load, and D3 reflects shortening during final Permian closure of the Ouachita orogenic belt.

2002 Denver Annual Meeting (October 27-30, 2002)
Session No. 30
Structure and Tectonics of the Midcontinent, North America
Colorado Convention Center: C207
8:00 AM-12:00 PM, Sunday, October 27, 2002
 

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