Geologic and Other Anomalies in Crawford Lake, Maine

Evelyn S. Sawyer^1,*, Brian P. Tarbox², Marjorie B. Eno¹, and Alexander U. Falster³

¹Rangeley Research, LLC, 76 Pine Street, Freeport, ME 04032. ²Southern Maine Community College, South Portland, ME 04106. ³Maine Mineral and Gem Museum, Bethel, ME 04217. *Corresponding author.

Northeastern Naturalist, Volume 33, Issue 2 (2026): 187–196

First published early online: 4 May 2026

Abstract
On SCUBA dives in Crawford Lake, ME, we found an unusual rock outcrop with large cavities (>1 m) and thin (<1 cm) vertical plates characteristic of a tafone. On the upper surface of the outcrop were numerous ferromanganese concretions scattered among objects that appeared to be artifacts (“apparent artifacts”). Since concretions or tafoni have not been reported in Maine, our objective was to investigate their origin, and their possible relation to human activity and to lake organisms. Concretions were iron-dominant, size limited, and habitat for Fe and Mn bacteria that power a redox cycle. The Mn redox cycle has current and potential benefits to lake water and organisms. Mineral analysis of the tafone and most apparent artifacts showed that they likely result from natural processes.

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