Open-File Report 03-225:
Figure 1. Geologic Province
The bedrock geology of the New England region has been divided into 11 geologic provinces. Each province group shares common features of (1) lithology, (2) age of formation, (3) geologic setting, and (4) tectonic history. The province groups generally occur as northeast trending belts that follow the structural fabric of the Appalachian foldbelt and faults in New England. The geologic province groups, listed in general order from west to east, are:
- Grenville Belt: Includes areas of Grenville Basement (PreCambrian Y metamorphic rocks) in western Connecticut, Massachusetts, and Vermont. Principally granitic gneiss and metasedimentary rocks. Includes some Cambrian metasedimentary rocks deposited on Precambrian basement.
- Grenville Shelf Sequence: Principally carbonate rocks and other metasedimentary rocks deposited in a carbonate shelf sequence overlying Grenville basement in western Connecticut, Massachusetts, and Vermont.
- Eugeosynclinal Sequence: Includes slates and pelitic metamorphic rocks in the Taconic Range and schists east of the Grenville Belt. Principally Cambrian to Ordovician pelitic metasedimentary rocks, including metavolcanic layers and lenses of ultramafic rocks.
- Waits River-Gile Mountain Belt: Principally Devonian variably-
calcareous metasedimentary rocks in eastern Vermont and the northern Connecticut valley in Massachusetts, intruded by Devonian granite.
- Mesozoic Basin: Triassic to Jurassic age sediments and basalt flows deposited in localized rift basins in central Connecticut and Massachusetts. Intruded by Jurassic diabase and basalt dikes.
- Bronson Hill Belt: Localized along the eastern Connecticut valley from Connecticut to western New Hampshire and northern Maine. Principally Ordovician igneous and metavolcanic rocks overlain by Ordovician to Devonian metasedimentary rocks. Sulfidic schists and mafic rocks are common. Intruded by Devonian granites.
- New Hampshire - Maine Sequence: Covers eastern Connecticut, central Massachusetts, eastern New Hampshire, and central Maine. Principally Silurodevonian metasedimentary rocks and Silurodevonian and younger igneous rocks, principally granite.
- Coastal Maine: Localized along northeastern coastal Maine. Principally PreCambrian Z to Silurian metasedimentary and metavolcanic rocks intruded by Devonian granites. Large granite bodies in the Coastal Maine Province are shown separately.
- Avalon Province: Localized in eastern Massachusetts, Rhode Island, and coastal Connecticut. Principally Precambrian Z granite and granitic gneiss and metasedimentary rocks of Precambrian Z to Ordovician age. Intruded by Ordovician to Devonian granites. Cretaceous sediments and thick areas of Quaternary glacial sediments occur in southern coastal areas.
- Narragansett Basin: Permian conglomerates and other sediments deposited in fault-bounded basins in Avalon province rocks in southeastern Massachusetts and Rhode Island.
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