Stratigraphic- tectonic subdivisions of southern New England

Pre-Carboniferous rocks of S New England and SE New York divide into five stratigraphic-tectonic zones based mainly on the ages and types of Precambrian, Cambrian, and Ordovician rocks. From W to E they are: I) Manhattan-Williamstown Zone with Grenvillian and some Late Precambrian basement and unconformable cover of Cambrian-Ordovician clastics and carbonates; II) Greenwich-Rowe Zone and Precambrian and Late Precambrian(?) continental basement (IIA) or Late Precambrian-Early Paleozoic oceanic crust (IIB) overlain by Cambrian-Ordovician clastic and volcanic cover; III) Haddam- Warwick Zone of Late Precambrian gneisses and quartzose sedimentary rocks along with other gneisses of uncertain age, possibly Ordovician, overlain with apparent unconformity by Middle Ordovician volcanics and the black shales: IV) Milford-Nashoba Zone with basement rocks of Late Precambrian and uncertain age as in Zone III, but overlain by a probable Middle Ordovician section dominated by oxidized shales with lesser black shales and volcanics: and V) Dedham Zone with unmetamorphosed to weakly metamorphosed Late Precambrian volcanic, clastic, and plutonic rocks overlain unconformably by Cambrian clastic strata of the Baltic faunal realm.-from Authors Dept of Geol & Geog, Univ of Massachusetts, Amherst, Mass 01003, USA.English