Ages from 17 new graptolite localities have made possible refinements in Silurian and Silurian-Devonian stratigraphy in the Kingsbury and Skowhegan quadrangles and indicate major facies changes in the Silurian metasedimentary rocks of central Maine. Northwest of the Currier Hill syncline, the observed sequence is: Sangerville Formation (upper Llandovery through lower Wenlock)—variably bedded meta-graywacke and pelite with minor polymict granule conglomerate, ribbon limestone, and carbonaceous pelite; Eddy Formation (lower Ludlow)—rusty weathering sulfidic carbonaceous pelite and non-carbonaceous quartzose sandstone and granule conglomerate; Brighton Formation [Silurian-Devonian(?)]—massive biotite-quartz granulite with minor calc-silicate granulite beds and pods (lower member) and thinly interbedded biotite-quartz granulite and biotite-muscovite phyllite (upper member); Solon Formation [Lower Devonian(?)]—nearly homogeneous slate with occasional rhythmically interbedded quartzose sandstone and slate.
Southeast of the Currier Hill syncline, the sequence is similar but there is a decrease in grain size in most units accompanied by an increased amount of pelite and a drastic thinning of Sangerville bedding to produce a pinstriped unit (transitional Sangerville). My interpretation of the facies relationships suggests a sequence that becomes finer to the east with a source of sediments to the northwest. Correlations based on projection of these facies changes and on fossil ages wherever possible yield the following:
Seboomook Formation Madrid Formation Smalls Falls Formation Perry Mountain Formation Rangeley Formation
Solon Formation Brighton Formation Eddy Formation Sangerville Formation
Vassalboro Formation Waterville Formation Mayflower Hill Formation