Geology at Mt. Pisgah, Winthrop and Wayne, Maine

The Mt. Pisgah Conservation Area includes 730 acres of forested hills in the towns of Winthrop and Wayne that are either owned by or under conservation easements with the Kennebec Land Trust. This includes an easement on property that includes the historic fire tower, now owned by the Town of Winthrop. On a clear day the views from the tower (open to the public) are outstanding. An excellent trail leads from a small parking area on Mt. Pisgah Road to the summit.

The area around Mt. Pisgah is underlain with a number of igneous and metamorphic rock units as illustrated in Figure 1. The metamorphic rocks are all Silurian in age (443-417 Ma) and the igneous rocks that intrude them, primarily the Androscoggin Lake igneous complex underlying Androscoggin Lake, are Carboniferous (~330 Ma). Following the mountain building episode that folded and metamorphosed the rocks, the landscape experienced hundreds of millions of years of erosion, culminating with the last glacial episode.

The best place to view the rocks at Mt. Pisgah is at the base of the fire tower, about a mile up the trail. The following are examples of features in the rocks.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Further reading

Creasy, John W., 1983, Field trip 11; Bedrock geology of the Androscoggin Lake igneous complex, Wayne and Leeds, Maine, in Hussey, A. M., II, and Westerman, D. S. (editors), Field trips of the Geological Society of Maine, 1978-1983: Geological Society of Maine, Maine Geology, Bulletin no. 3, p. 99-106.

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Text and photos by Robert G. Marvinney

Originally published on the web as the April 2009 Site of the Month.

Last updated on November 12, 2009

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