Five belts of metamorphosed sedimentary and volcanic rocks underlie southwestern Maine and southeastern New Hampshire: Middle Ordovician Falmouth-Brunswick sequence; Middle and Late Ordovician Casco Bay Group, and Late Ordovician to Early Silurian rocks of the Merribuckfred Basin; Late Ordovician to Early Silurian rocks of the East Harpswell Group; Silurian to Early Devonian rocks of the Central Maine Basin; and highly tectonized enigmatic rocks of the Rye complex of uncertain age. Stratigraphic reassessment and new U/Pb zircon ages support a model of east-directed Middle Ordovician subduction beneath Miramichi, a peri-Gondwanan block, and formation of the Falmouth-Brunswick–Casco Bay volcanic arc complex that is roughly correlative with arc activity on strike in New Brunswick. Passive Late Ordovician sedimentation in a reducing restricted backarc basin followed. Late Ordovician to Early Silurian volcanic rocks and volcanogenic sediments (East Harpswell Group) support west-directed subduction under the Miramichi block. Late Ordovician to Early Silurian turbidites accumulated in the Merribuckfred Basin between the Falmouth-Brunswick–Casco Bay arc and Ganderia to the east. The collision of Ganderia with the Falmouth Brunswick arc in Late Silurian time represents an early phase of the Acadian orogeny, during which the Merribuckfred rocks were deformed, metamorphosed, intruded, and uplifted. Simultaneously and inboard, the Central Maine Basin received sediment eroded mostly from Laurentia. Later, during the Late Silurian and Early Devonian, uplifted Merribuckfred basin rocks became the major source of sediments for the Central Maine Basin. A later phase of the Acadian orogeny resulted in Middle Devonian deformation, metamorphism, and intrusion of rocks of all six belts.

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Abstract The geologic strip-map for Transect E-l cuts a swath from the Thousand Islands region on the New York-Ontario border to the Atlantic Ocean floor off Georges Bank (see Fig. 1). It includes portions of New York, Ontario and of all of the New England states. The western part, mainly in New York, belongs to the North American craton. The remainder of the onland portion, east of Logan's Line, belongs to the Appalachian Orogen. Southeastward from Logan's Line the transect crosses a series of distinctive terranes. Several of these terranes are believed to be exotic, and to have been accreted to the North American craton during the Paleozoic. Superposed on these are several grabens and half-grabens containing early Mesozoic sediments and mafic volcanics. There are also Mesozoic eruptive complexes of an alkalic nature cutting across the Appalachian Orogen from southern Quebec, across New England, and continuing as a chain of seamounts offshore. Cenozoic rocks are limited to a small, but significant occurrence near Brandon, Vermont (BL on Fig. 2) and a few occurrences in the Cape Cod region and on the adjacent islands in southeastern Massachusetts. Offshore the corridor passes over the Gulf of Maine and Long Island Platforms, thence across Georges Bank and into the North Atlantic Basin. The Gulf of Maine and Long Island Platforms (Fig. 2) are underlain by Paleozoic metamorphic and plutonic rocks and early Mesozoic grabens, as in the adjacent onland regions, but are partially covered offshore by a 1-3 km section of late Mesozoic and

Location The Belknap Mountains Complex is located in the Lakes Region of central New Hampshire. It is an easy two-hour drivefrom the Boston area via I-95 to Portsmouth, New Hampshire, and north on New Hampshire 16 and 11 (Fig. 1). Thegeologic map of the area, modified from Modell (1936) by Bothner and Gaudette ( 1971 ), occupies parts of the Winnipesaukee (Quinn, 1941), Gilmanton (Heald, 1955), Wolfeboro (Quinn, 1953), and Alton (Stewart, 1961) 15-minute Quadrangles. Most field localities are along main highways and secondaryroads, foot trails, and ski slopes, as indicated on the topographicbase. Permission should be requested from local landowners forexamination of exposures away from main roads and on theshore and islands of Lake Winnipesaukee (e.g., Rattlesnake and Diamond islands, and the old Conway Granite Quarry).