Figure 3. A portion of the geologic map Reconnaissance Bedrock Geology of the Presque Isle Quadrangle, Maine (Plate 1 of Boucot and others, 1964). Haystack Mountain is underlain by Ordovician rocks (Ovs) in the core of the Castle Hill anticline. Successively younger rocks of the Pyle Mountain Formation (Opm) and Silurian units (Sf, Sp, Spl) are exposed on the east and west flanks of the fold. The Ordovician rocks are now assigned to the Winterville Formation (Roy and Mencher, 1976).
Last updated on November 7, 2008