Forbes Hill conglomerate and breccia in the Ira and Hortonville Formations

Black slate containing angular to irregular chips of greenish-gray to yellowish-gray slate, quartz wacke, and limestone; interpreted by Zen (1961) as sedimentary wildflysch. Part of the Taconic Allochthon. Wildflysch-like conglomerates within the Hortonville, Ira, and Walloomsac Formations occur as local areas of black slate rich in inclusions of quartzite, greenish-gray slate, wacke, and punky-weathering bluish-gray limestone, interpreted as sedimentary breccias, deposited in front of the advancing Taconic allochthon (Upper Ordovician) (Zen, 1961; Potter, 1972; Fisher, 1985). Exposed near the western and northern margin of the allochthon and in the Bennington area at the type Whipstock. Here and at many localities the Forbes Hill and Whipstock breccias are tectonic breccias formed in situ by disruption of thin to thick beds, laminae, and carbonate-quartz-sulfide veins rather than clastic sedimentary rocks. The cleavage and related folding commonly is a late strain-slip cleavage characterized by a strong down-plunge lineation parallel to reclined hingelines of minor folds of foliation and compositional layering. Units are retained although interpretation as sedimentary wildflysch deposits is in part questionable.
State Vermont
Name Forbes Hill conglomerate and breccia in the Ira and Hortonville Formations
Geologic age Upper Ordovician
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metaclastic > SlateBlack slate containing angular to irregular chips of greenish-gray to yellowish-gray slate, quartz wacke, and limestone; interpreted by Zen (1961) as sedimentary wildflysch.
Minor
Sedimentary > Carbonate > LimestoneBlack slate containing angular to irregular chips of greenish-gray to yellowish-gray slate, quartz wacke, and limestone; interpreted by Zen (1961) as sedimentary wildflysch.
Sedimentary > Clastic > Sandstone > GraywackeBlack slate containing angular to irregular chips of greenish-gray to yellowish-gray slate, quartz wacke, and limestone; interpreted by Zen (1961) as sedimentary wildflysch.
References
NGMDB product
Counties Rutland