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A section comparable in general aspect to that presented by Bell (1971) for northeastern Massachusetts is present in the New London area, southeastern Connecticut (Fig. 1). Disregarding a fossiliferous sequence, which is possibly in a different structural block, Bell described a 12,800-m-thick metamorphosed sequence of interbedded volcanic, volcaniclastic, and sedimentary rocks overlying a 1,520-mthick sequence of metamorphosed quartzose and calcareous sedimentary rocks containing some volcaniclastic material. In the New London area, an upper, primarily volcanic sequence as much as 3,100 m thick (composed of amphibolite, hornblende and biotite gneisses, and some schist) overlies a primarily sedimentary section at least 1,860 m thick (consisting of quartzite, quartz-rich schist, pelitic and feldspathic schists, and some calc-silicate rocks, gray biotite gneiss, and amphibolite). The upper sequence in the New London area consists largely of metamorphosed volcanic and volcaniclastic rocks and related meta-intrusive rocks as well as small amounts of sedimentary rocks; the lower sequence primarily consists of metamorphosed quartzose and calcareous sedimentary rocks with lesser amounts of intercalated volcanic and volcaniclastic material. The two sequences have been complexly folded and are intercalated with granitic gneiss. Primary sedimentary features useful in determining tops of beds are rarely seen. Individual units show appreciable differences in thickness in different areas. Both sequences are pre-Silurian in age, and most probably the rocks range in age from late Precambrian or Cambrian to Ordovician.

Accurate estimates of thicknesses in the New London area are difficult to achieve because of the complex structure and numerous granitic intrusions. Sections have been measured...

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