Discovery of Mount Mazama cryptotephra in Lake Superior (North America): Implications and potential applications

• Main Authors: Spano, NG, Lane, CS, Francis, SW, Johnson, TC
• Format: Article in Journal/Newspaper
• Language: English
• Published: Geological Society of America 2017
• Subjects: 37 Earth Sciences; 3709 Physical Geography and Environmental Geoscience; 3705 Geology; Greenland; Greenland ice core; ice core; Newfoundland
• Online Access: https://www.repository.cam.ac.uk/handle/1810/270162; https://doi.org/10.17863/CAM.16996

Tephrochronology is a widely applied method recognized for its exceptional precision in geologic dating and stratigraphic correlation. Tephra from the ~7.6 kyr B.P. Mount Mazama caldera-forming (”climactic”) eruption have been widely identified and applied as stratigraphic isochrons sediments of northwestern North America, as well as in the Greenland ice core records. Recent findings of a microscopic tephra accumulation, or cryptotephra, from Mazama in Newfoundland indicated that this horizon should also be found in Lake Superior sediments. We present findings that confirm the presence of Mazama ash in two sediment cores from the Lake Superior basin, which indicates its likely presence in the rest of the Laurentian Great Lakes and in deposits throughout much of eastern North America and beyond. The ubiquity of this stratigraphic horizon should be applicable to a higher resolution evaluation of climatological, ecological, and archaeological events during the early- to mid-Holocene thermal maximum throughout much of North America. This research was supported by a Regents Professor grant by the University of Minnesota to Johnson