Fabrics in the mid-crustal Bronson Hill zone of the southern New England Appalachian orogen record a range of apparent finite strains and conflicting kinematics, but structural relationships indicate coeval development. At the smallest scale of this study, shortening was accommodated in granitic orthogneiss, while transcurrent deformation was partitioned into relatively thin zones of metastratified rocks along the margins. The Monson orthogneiss can be broadly characterized by subvertical to steeply dipping S>L tectonites, subvertical to subhorizontal stretching lineations, closed to isoclinal folds, and dextral/reverse kinematics. The east-bounding Conant Brook shear zone and Greenwich syncline are characterized by steeply dipping mylonitic foliations, a range of lineations, and dextral/reverse kinematic indicators. The west-bounding Mt. Dumplin high strain zone is comprised of steeply dipping mylonites, subhorizontal lineations, and sinistral/normal kinematics. These structures reflect coeval partitioned dextral transpression, vertical extrusion, and north-directed lateral escape of the orthogneiss that was facilitated by bounding conjugate shear zones. Comparison of structural subdomains with transpressional modeling indicates vertical pseudo-monoclinic to inclined triclinic coaxial to simple shear influenced transpression. Compatibility between laterally adjacent subdomains was maintained by meso-/microscale partitioning. Absolute and relative timing constraints show that transpression was sustained from 330 Ma to 300Ma.
|Number of pages||17|
|Journal||Journal of Structural Geology|
|State||Published - Oct 2013|
Bibliographical noteFunding Information:
This work was funded by EDMAP grant 06HQAG0066 and the University of Kentucky Department of Earth and Environmental Sciences . We appreciate the use of facilities at the University of Massachusetts (EPMA Ultrachron Laboratory), University of California at Los Angeles (Keck SIMS Laboratory), the University of Michigan, and the University of Kentucky. We would also like to thank Scott Giorgis, Joe Kopera, Mike Williams, and Bob Wintsch for insightful discussions. Reviews by Scott Giorgis greatly enhanced the quality of the final manuscript, and the editorial handling of Cees Passchier is appreciated.
- New England Appalachians
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