Bedrock Geology of the Bath 1:100,000 Map Sheet, Coastal Maine

Fredericton Sequence

The Fredericton sequence, exposed in a belt extending from the Bath map sheet (Figure 3) through eastern Maine (Figure 1) to Fredericton, New Brunswick, typically consists of metamorphosed calcareous turbidites and pelites. It is represented by the Flume Ridge and Digdeguash Formations in eastern Maine (Ludman, 1987) and by the Bucksport and Appleton Ridge Formations in mid-coast Maine (Bickel, 1976; Berry and Osberg, 1989). Of these, only the Bucksport is exposed in the Bath map sheet (Figure 2).

Bucksport Formation (SOb)

The Bucksport Formation consists dominantly of fine-grained 5-cm-bedded to massive, medium brownish gray quartz-plagioclase-biotite-hornblende granofels, with 2 to 10 cm beds of medium greenish gray calc-silicate granofels. Some exposures lack calc-silicate rock but these intervals, with the available outcrop, cannot be resolved into distinct mappable subunits. Rusty weathering biotite-muscovite-quartz schist in intervals 1 to 3 meters thick occurs sporadically throughout the formation. Aluminous pelitic interbeds are virtually lacking. Coarse grained irregularly-textured (1 to 4 cm) motley green and orangish skarn-like calc-silicate rock with grossularite, diopside, and hornblende occurs at scattered locations in the formation, close to the thrust contact with the Cape Elizabeth Formation in the East Boothbay-Boothbay Harbor area.

All exposures of the Bucksport Formation in the Boothbay Harbor-Pemaquid area are very extensively injected by pegmatite ranging from thin lit-par-lit stringers a few centimeters thick to sills, dikes, or irregular masses up to 20 meters wide (Figure 21). Between these, the granofelsic texture and bedding are usually well preserved. Some exposures that appear to be more feldspathic are migmatized and gneissic. In the contact zone with the Cross River Formation in the Johns River-Bristol area (Figure 5), the rocks of the Bucksport Formation are strongly gneissic.



Introduction   Central Maine sequence   Falmouth-Brunswick sequence   Casco Bay Group   East Harpswell Group   Fredericton sequence   Megunticook sequence   Benner Hill sequence   Sequence uncertain   Correlations   Intrusives   Structure   Metamorphism   Timing   Minerals   Acknowledgements   References  


Last updated on February 1, 2008