TWO DECADES OF OVERLAP BETWEEN PROFESSORS MARLAND P. BILLINGS AND JAMES B. THOMPSON, JR. IN THE DEPARTMENT OF GEOLOGICAL SCIENCES, HARVARD UNIVERSITY, AND THE IMPACT ON THE UNDERSTANDING OF NEW ENGLAND BEDROCK GEOLOGY

Celebration of James B. Thompson, Jr.’s 90^th birthday, followed shortly by his death in November, 2011, provides opportunity to reflect on the impact of two remarkable decades of overlap (1949-1972) of Thompson (petrology) and Marland P. Billings (structure) at Harvard University, on the knowledge of bedrock geology of New England. Together they supervised about 25 Ph.D. students, a major part of whose theses was the making of a geologic map of a New England area commonly the size of a 15’ quadrangle. Representative thesis areas are in Connecticut (R. Dixon), Massachusetts (E. Grew, S. Norton, P. Robinson, P. Toulmin), the Taconics (E. Zen), northern Vermont (A. Albee), the Connecticut Valley (L. Hall, D. Rumble, C. Hepburn, N. Trask), northern New Hampshire (J. Green, N. Hatch,), and Maine (A. Boucot, A. Griscom, C. Guidotti, D. Harwood, D. Milton, K. Pankiwski, D. Rankin, D. Stewart, J. Warner). Collectively the thesis mapping of this group provided a framework for much of the understanding of New England geology today, albeit largely in pre-plate tectonic days.

Crucial to this effort was the melding of stratigraphy, structure, and metamorphism in the Littleton-Moosilauke area, NH in the classic 1937 paper by Billings, and the beginning of the extrapolation of that work by Billings and earlier students such as J. Hadley, F. Kruger, G. Moore, and W. White. Thompson’s imaginative and creative application of Billing’s stratigraphy combined with mapping and structural analysis led to the hypothesis of a large fold nappe (Skitchewaug) with at least 10 miles of west-directed overfolding that preceded doming in the Bronson Hill anticlinorium. Work with T. Clifford, Robinson, and Trask delineated in 1968 three giant fold nappes similar to those of the Pennine zone of the Alps. Controversy continues over several aspects of this story, but the 1968 paper in the Billings Volume remains a classic and has stimulated many other studies.

Gravity studies by Francis Birch and students R. Bean, W. Joyner, and W. Diment added a third dimension to the understanding of New England. The Mt. Cube area, NH, subject of at least 4 Ph.D. theses (2 at Harvard: Hadley and Rumble) plus mapping by others (R. Moench and D. Rankin) offers an example of the still evolving understanding of New England. ‘And lo! stratigraphy led all the rest’ (Billings, GSA Bull., 1950).