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Brad Johnson, Ph.D.
Research Scientist
Bedrock mapping, structural geology, mineral deposits
1955 East Sixth Street
PO Box 210184
Tucson, AZ 85721
Education
- Geology 2-year program, Santa Barbara City College, California
- B.S. 1982 (Geology), Northern Arizona University, Flagstaff, Arizona
- M.Sc. 1987 (Earth Sciences), Carleton University, Ottawa, Ontario, Canada
- Ph.D. 1994 (Earth Sciences), Carleton University, Ottawa, Ontario, Canada
Current & Recent Projects
- Bedrock mapping of 1:24,000-scale quadrangles in collaboration with other AZGS geologists as part of the STATEMAP program. Recent projects have featured:
- Deformed, contact-metamorphosed, Cu-mineralized Paleozoic and Mesozoic sedimentary rocks intruded by Late Cretaceous and Paleogene granites in the Santa Rita Mountains of southeastern Arizona.
- Jurassic granitic to dioritic plutons and Proterozoic to Jurassic metamorphic rocks in the Dome Rock Mountains, western Arizona.
- Polydeformed Paleoproterozoic schist overlain by Mesoproterozoic and Paleozoic sedimentary rocks, all intruded and locally mineralized (Cu-Zn) by Paleogene granite in the Little Dragoon Mountains, SE Arizona.
Research Interests
- Cordilleran tectonics
- Magmatic and hydrothermal systems, their relationships to tectonic processes and mineral deposits, and emplacement of plutons
- Laramide and post-Laramide structural geology, especially of southern Arizona and adjacent areas
- Proterozoic geology
- Paleozoic stratigraphy of southern Arizona (e.g., which carbonate units are these little fault slices made of, and why does the Earp Formation look so different here than in the last fault block?!)
- Metamorphic core complexes and extensional detachment systems
Bio
Johnson has been doing regional and detailed bedrock mapping since 1979 and has worked in Canada, the United States, and México. He is experienced with a wide range of rock types and geological settings and specializes in plutonic rocks, deformed crystalline rocks, mineralized and altered rocks, and structural geology. Past projects outside of Arizona have included mapping and interpretation of a Paleoproterozoic strike-slip sedimentary basin in the Northwest Territories of Canada, structure and tectonic evolution of polydeformed metamorphic rocks and Paleogene low-angle extensional shear zones in the Shuswap metamorphic complex of British Columbia, the geological setting of an Upper Jurassic volcanogenic massive sulfide deposit in central México, and detailed mapping of Archean layered ultramafic rocks in the Stillwater Complex of Montana. Projects in Arizona have mostly been in the context of the STATEMAP program, in collaboration with other AZGS geologists.