precambrian

Arizona’s Proterozoic Geology Revealed: Geologic maps of Phillip Anderson

From the Arizona Geological Survey:

Phil Anderson (Ph.D., University of Arizona) had a genius for mapping and interpreting the Proterozoic geology, tectonics, and mineral deposits of the Southwest. Unfortunately, his mapping was never made public, until now.

From the mid-1970s to the early 1990s, Phil traversed Arizona’s Transition Zone visiting and studying nearly every exposure of Proterozoic rocks. He described this work in his 1986 dissertation, ‘The Proterozoic tectonic evolution of Arizona’, and two subsequent papers from the Arizona Geological Society’s Digest 17, but he did not disclose his geologic maps. He issued, instead, small-scale, state-wide overviews of the distribution of Proterozoic rocks.

Phil passed away in Payson, Arizona, in Feb. 2012. In Sept. 2017, Donna Smart, Phil’s widow, donated Phil’s geologic map products and files – his life’s work – to the Arizona Geological Survey. Steve Reynolds (ASU Earth and Space Science Exploration) then organized and led a team of geoscientists in salvaging, reviewing, and selecting Anderson’s geologic maps to release as ‘The Philip Anderson Arizona Proterozoic Archive.

According to Reynolds and others (2017), the “Precambrian geologic maps of the Bradshaw Mountains, Central Arizona” represents the most significant collection of geologic maps ever released for the Proterozoic of Arizona. The Bradshow Mountains contributed map includes the following elements.

  • Reynolds & others (2017) contextualizing Anderson’s contribution to the Proterozoic of Arizona;
  • 11 geologic topographic quadrangles (1:24,000) from central Arizona’s Bradshaw Mountains, with key and legend;
  • A suite of geologic, structural, and tectonic illustrations;
  • 9 sub-regional geochemical plots;
  • 2 papers (totaling 150 p.) authored by Phil Anderson and published in the Arizona Geological Society’s Digest 17.
  • This is the first of a suite of Anderson geologic map products that we plan to release. The remaining Anderson collection comprises dozens of other topographic maps with original geologic observations and notes regarding structures and mineralogy. It will take several hundred hours to review, process, and prepare these materials for release.

    In the meantime, researchers working in the Proterozoic of Arizona’s Transition Zone are advised to reach out to the AZGS with specific requests for information.

    Acknowledgments. We thank Donna Smart for preserving and donating Phil Anderson’s geologic research. We thank, too, David Briggs (President) and the Arizona Geological Society Executive Committee for their generous permission to include Phil’s two papers from AGS Digest 17.

    References

    Anderson, Phillip, 1986, The Proterozoic tectonic evolution of Arizona; Tucson, University of Arizona, unpublished PhD dissertation, 416 pages.

    Anderson, Phillip, 1989a, Proterozoic plate tectonic evolution of Arizona, in Jenney, J.P., and Reynolds, S.J., 1989, Geologic evolution of Arizona: Tucson, Arizona Geological Society Digest 17, p. 17 – 55.

    Anderson, Phillip, 1989b, Stratigraphic framework, volcanic plutonic evolution, and vertical deformation of the Proterozoic volcanic belts of central Arizona, in Jenney, J.P., and Reynolds, S.J., 1989, Geologic evolution of Arizona: Tucson, Arizona Geological Society Digest 17, p. 57 -147.

    Reynolds, S.J, Conway, F.M., Johnson, J.K., Doe, M.F., Niemuth, N.J., 2017, The Phillip Anderson Arizona Proterozoic Archive. Arizona Geological Survey Contributed Report CR-17-D, 2 p.

    On a personal note: I had the opportunity of working with Phil on a project of evaluating the United Verde mine, at Jerome. Arizona. The ore is hosted by Precambrian volcanic rocks. For a description of that deposit type, see my post  https://wryheat.wordpress.com/2010/01/11/ancient-undersea-volcano-in-arizona/

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