Hence the Litchfield pluton is interpreted to intrude Late Ordovician (?) to Silurian metamorphosed turbidites (mostly thin-bedded schist, granofels
, quartzite, and more rarely impure carbonate rocks) of the Central Maine Sequence (Osberg 1988; Marvinney et al.
At higher regional metamorphic grade and around the margins of plutons, the more pelitic beds are composed of andalusite-garnet-sillimanite schist, granofels
, and migmatite.
As metamorphic grade increases, the Halifax Formation is characterized by the development of porphyroblastic staurolite and andalusite granofels and schist.
The northern margin of the pluton has an irregular outline due to the abundance of garnet-sillimanite granofels and schist xenoliths.
Overlying the basal quartzite and conglomerate, the Megunticook Formation is mainly comprised of quartz-mica schist, typically containing small garnet, calc-silicate rocks, chiastolitic quartz-biotite schist, and thin bedded quartzite and schistose quartz-plagioclase-mica granofels
(Berry and Osberg 1989; Tucker et at.