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3D Structural Analysis of the Benton Uplift, Ouachita Orogen, Arkansas

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Title: 3D Structural Analysis of the Benton Uplift, Ouachita Orogen, Arkansas
Author: Johnson, Harold Everett
Abstract: The date for the formation of the Benton Uplift, Ouachita orogeny, is bracketed by Carboniferous synorogenic sediments deposited to the north and Late Pennsylvanian to Early Permian isotopic dates from the weakly metamorphosed rocks within the uplift. We address the largely unknown structural history between these two constraints by presenting an improved 3-dimensional kinematic model using better constrained retrodeformable sections. These new sections are based on all surface and subsurface data, new zircon fission track dates and thermal maturation data including new ‘crystallinity’ data to constrain the maximum burial depth. Concordant zircon fission track ages range from 307 ± 18.8 Ma to 333.4 ± 38.9 Ma or from the Late Devonian to Early Permian. Maximum ‘crystallinity’ of both illite and chlorite indicate these exposed rocks experienced a temperature of ~300°C across the eastern Benton Uplift. This temperature is consistent with reconstructed burial depths using cumulative stratigraphic thickness without having to call on structural thickening. Comparing coarse and fine clay fractions, computed temperature for the fine clay fraction is less by ~100°C than that of the coarse clay fraction. This difference is the same for all formations studied. This uniform difference in temperature may indicate cooling of the orogen as it deformed or more than one thermal event.
Subject: Ouachita orogen
Benton Uplift
Ouachita Mountains
Retrodeformable cross sections
Illite crystallinity
Chlorite crystallinity
Thermal maturation
Zircon fission track dating
Compressional tectonics
Arkansas geology
URI: http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10640
Date: 2011-12


Johnson, Harold Everett (2011). 3D Structural Analysis of the Benton Uplift, Ouachita Orogen, Arkansas. Master's thesis, Texas A&M University. Available electronically from http : / /hdl .handle .net /1969 .1 /ETD -TAMU -2011 -12 -10640.

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