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

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

USING THE SPATIAL ANALYSIS OF A STRUCTURE CONTOUR MAP TO COMPARE FOLD HINGE AND FAULT ORIENTATIONS WITHIN THE HARPETH RIVER FAULT ZONE, A CRATONIC FAULT AND FOLD ZONE IN CENTRAL TENNESSEE

Paper number: T170-13
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

  • Mark Abolins Presenting Author
    Middle Tennessee State University, Murfreesboro, TN

Abstract

The investigator used a digital structure contour map to estimate the orientation of macroscale fold hinges within the Harpeth River fault zone (HRFZ), a largely aseismic cratonic fault and fold zone on the northwest flank of the Nashville dome, central Tennessee. The structure contour map depicts the elevation of the top of the Ordovician Carters formation. Most strata on the northwest flank of the dome dip northwest, but HRFZ strata have dip azimuths of 22.5o-157.5o within four domains having areas of 3.7-34.4 km2 and totaling 49.7 km2. The investigator manually segmented the edges of the domains into 26 relatively linear curves, interpreted as fold hinges. Then he used the ArcGIS Spatial Statistics Directional Distribution Tool to fit standard deviational ellipses to each of these curves. The orientation of the long-axis of each ellipse provided an estimate of the orientation of the fold hinge, and the eccentricity of each ellipse provided a measure of the linearity of the hinge. Finally, he compared the orientation of the hinges with the published orientation of HRFZ faults. For the published study, the investigator had manually mapped four HRFZ normal fault zones on the basis of mesoscale structures and visual interpretation of the structure contour map.

Application of the Directional Distribution Tool showed that 8 of 26 hinges (31%) trend 335o-350o, closely approximating the published 331o-358o strike of macroscale HRFZ faults. Also, the 1st and 4th most linear hinges coincide with segments of the Arno fault zone, the zone associated with the greatest structural relief within the HRFZ. Two hinges (ranking 21st and 22nd in linearity) coincide with two of the five segments of the McDaniel fault zone, the zone associated with the 2nd greatest structural relief. However, 11 of 26 hinges (42%) trend 000o-030o, including the 3rd most linear hinge. Although these hinges do not parallel macroscale HRFZ faults, they share the published trend of many Midcontinent faults and folds, indicating that the folds may have formed through the reactivation of cratonic basement structures. Most of the rest of the hinges (23%) trend 055o-085o, and this group includes the 2nd most linear hinge. These hinges are approx. orthogonal to the HRFZ faults and, therefore, folding may have accommodated along-strike variations in extension.

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

doi: 10.1130/abs/2016AM-287942

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