Fitch Formation

Sulfidic calc-silicate and minor sulfidic schist. Although the text and figures of this report show the Fitch as Silurian, a footnote [added just before this report went to press] cites a change in age from Silurian to Early Devonian based on conodonts found at the Bernardston, MA, locality, as reported in Elbert and others (1988). In Bronson Hill anticlinorium in MA, Fitch occurs as lenses between Clough Quartzite and Littleton Formation. Most common rock types in MA are gray, massive to weakly bedded, quartz-labradorite-biotite granulite containing a moderate amount of some combination of calc-silicate minerals (calcic amphibole, zoisite or clinozoisite, diopside, sphene, and microcline); commonly interbedded with biotite-free granulite that contains same calc-silicate minerals. One small exposure consists of nearly pure calcite marble. Larger lenses of Fitch consist of varieties of schist, similar to Partridge Formation. Best exposures are in low hills west of village of Orange, northeast of junction of MA Hwys 2A and 78. As shown on MA State bedrock geologic map, Fitch everywhere overlies Clough Quartzite and is never in contact with Partridge. Fossils dating the Fitch as Pridolian (Harris and others, 1983) are all from Littleton, NH, area [however, see mention of footnote, above]. [Papers presented as chapters in U.S. Geological Survey Professional Paper 1366 are intended as explanations and (or) revisions to MA State bedrock geologic map of Zen and others (1983) at scale of 1:250,000.] (Hatch and others, 1988).
State Massachusetts
Name Fitch Formation
Geologic age Upper Silurian
Lithologic constituents
Metamorphic > Metasedimentary > Calc-silicate-rocksulfidic calc-silicate
Metamorphic > Schistminor sulfidic schist
Comments Part of Merrimack Belt (Silurian, Devonian and Pennsylvanian Rocks). Secondary unit description per MA006. Conodonts indicative of earliest Devonian 'woschmidti' to 'eurekaensis' Zones recovered from regionally metamorphosed marbles of the lower amphibolite facies of the Fitch Formation at the fossil locality near Bernardston, MA, refine the age of the Fitch in this area and extend the regional upper age limit of the Fitch, and confirm the existence of the inverted limb of the Bernardston nappe per MA008.
NGMDB product
Counties Hampshire - Worcester