Regional implications of contrasting structural and metamorphic intensity across a mylonite zone in central Vermont
- Univ. of Vermont, Burlington, VT (United States). Dept. of Geology
The Stowe Formation (west) and the Missisquoi Group (east) in central Vermont are separated by the 150 meter wide Roxbury mylonite zone. This zone marks an inversion in metamorphic grade and an abrupt change in the amount of separable superposed structures and structural style across strike. The Stowe Formation consists of polydeformed garnet grade schists, greenstones and serpentinites. The dominant fabric is axial planar to isoclinal reclined folds (N 5 E, 89 E) and is often decorated with mineral stretching lineations and quartz rods (S 49 E, 85). An older pervasive foliation is recognized by interfolial isoclinal fold hinges. The Missisquoi Group consists of bedded, chlorite grade quartz-feldspar meta-sandstone, meta-siltstones, grey bedded phyllite, and black slate and phyllite that record only a single pervasive phase of deformation. The fabric is a spaced to closely-spaced cleavage (N 14 E, 86 W), decorated with mineral stretching lineations (N 4 E, 83) in fault zones and is axial planar to mesoscopic and megascopic isoclinal reclined folds. The West Brookfield syncline is cored by black slate of the Lower Devonian Northfield Formation and rimmed by the Upper Silurian Shaw Mountain Formation and the older, Ordovician Cram Hill Formation. The contact between the Shaw Mountain Formation and the Cram Hill Formation is an angular unconformity, the Silurian-Devonian unconformity, and is folded by the West Brookfield syncline. Large-scale folds are cored by Silurian and Devonian rocks, and faults cut the unconformity. Thus the fabric of the Missisquoi Group is considered to be Acadian. West of the Roxbury mylonite zone however, megascopic isoclinal synclines cored with Missisquoi Group rocks have not been recognized and northeast-trending lineations are mixed with numerous southeast-trending lineations which decrease to the west.
- OSTI ID:
- 5579554
- Report Number(s):
- CONF-9303211-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:2; Conference: 28. annual Geological Society of America (GSA) Northeastern Section meeting, Burlington, VT (United States), 22-24 Mar 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
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