IN REMEMBRANCE OF WILLIAM A. (BILL OR TOM) THOMAS

William A. (Bill) Thomas grew up in southeastern KY Appalachia. He was an exceptional scientist, leader of scientists, mentor of students, and an outstanding person and family man. Bill served on the faculties of five universities and retired as a visiting scientist with the Alabama Geological Survey. Bill’s many scientific contributions range from sedimentary and structural geology to tectonics. He also spent many years in GSA service on committees, GSA Council, and as President (2005). He helped save the GSA Bulletin from extinction (1979-1988) and contributed to the GSA DNAG Project.

Bill Thomas is remembered for his scientific contributions: confirming the source in Laurentia of the Argentine Precordillera; tectonic inheritance at transform faults perpendicular to the Iapetan Laurentian margin, how they controlled the eventual shape of the Appalachian externides; solved the problem of Appalachian-Ouachita connections; recognized and named a new structure—mushwads; and made many contributions to Appalachian geology. He recognized that detrital zircons in Appalachian clastic wedges from one orogeny appear in wedges from the next—Thomas’ Law.

A recent contribution was a tectonic synthesis of the southern-central Appalachians and Ouachitas (Encyclopedia of Geology, 2021). It depicts their tectonic history from New York to western Texas and northern Mexico, from Neoproterozoic breakup of Rodinia to amalgamation of Pangea through the Early to mid-Mesozoic and middle Cenozoic degradation of the chain. This history was marked by times of uplift and leveling with continental margin clastic separating carbonate deposition. Modern Appalachian topography formed during the late Miocene-Pliocene.

I am honored to have worked with Bill and to be considered a friend of he and his family.