Abstract

The Honey Hill fault is a thick slab of highly strained (cataclastic) rock formed from units lying within 1 km of the contact between quartz-feldspar rocks (basement) and the varied, but generally more micaceous, rocks (mantle) overlying them. The cataclastic rocks evolved from sillimanite-zone units through progressive reduction in grain size without retrogression, a reduction effected by a variety of mechanisms acting primarily on quartz and biotite. This evolution is presented schematically as the cumulative result of cataclastic deformations near the basement-mantle boundary during F1 (disharmonic folding of the mantle related to the formation of an anticlinorium having a north-south axial surface located at the present Rhode Island-Connecticut boundary), F2 (development of an anticline having an east-west axial surface parallel with and just north of the present coastline), and post-F2 (development of more localized domes and anticlines warping the Honey Hill fault and earlier folds).

The intensity of cataclastic deformation depends not on the “displacement,” but on the location and amplitude of successive anticlines and domes and on ductility contrasts between contiguous rock masses. The model (hypothesis) is based on a comparison of three areas located along the 40-mi trace of the fault. Differences between any two areas are related to differences in their positions relative to the crest of each of the successive domes or anticlines.

The Honey Hill fault is neither a simple thrust fault nor a fundamental fault; the cataclastic rocks seem to result from displacements parallel to the zone and flattening normal to it, both related in large part to relative upward movement of basement at different places at different times from Late Devonian to Permian(?).

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