Abstract
This progress report describes major geological features of three segments of a profile across southern New England: (1) the Clinton—Boston, (2) the Boston—Narragansett Basins, and (3) the Narragansett Bay cross sections. Segment (1) is a traverse across four tectonic blocks from the Merrimack synclinorium across the Clinton—Newbury and Bloody Bluff fault zones and across the southwestern tip of the Boston Basin. The Clinton—Newbury and Bloody Bluff fault zones together may define the suture between the North American plate and the Avalonian terrain of the Eur-African plate. The Avalonian plate may have been overridden by the North American or vice versa, these two faults in any case mark the northwestern and southeastern boundaries of crustal underplating. These tectonic features probably formed during the Acadian, although their present geometry was defined during the Alleghanian orogeny. The Boston and Narragansett basins, segments 2 and 3 are within the Avalonian platform. The age of the cover rocks of the former is uncertain but arguments for a Late Precambrian—Cambrian age are presented; those of the Narragansett Basin are fossiliferous Pennsylvanian. The northwestern part of the Avalonian platform is characterized by SE-directed, NW-dipping, thrusts and highangle reverse faults; the southeastern part of the platform, on the other hand, is characterized by NW-directed, SE-dipping faults. In the Narragansett Basin the Alleghanian (Variscan) orogeny is a major orogenic event consisting of the following elements: (1) isoclinal folding and refolding associated with thrusting; (2) upper amphibolite facies Barrovian regional metamorphism; and (3) intrusion of probably anatectic granites.
Published Version
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