Education

• B.S., University of Kansas
• M.S., New Mexico Tech
• Ph.D., University of Calgary

Bio

Having devoted an inordinately large part of my life to geologic mapping, I have authored over 100 original maps.  After a career delineating, defining, and understanding 1:24,000 scale geologic contacts, I look forward to a future of studying and writing about the somewhat bigger picture of how plate tectonics really works.  My thinking is based on field expertise in dozens of orogenic belts, mostly in western North America.  Others include the Wopmay (Canadian shield), Appalachian (Ouachita), and the Alpide (Turkey) orogenic belts. 

For my PhD in British Columbia [1], I noted evidence that favored an Alpide-style (foreland, not retro- or back-arc) fold-thrust belt origin for the Canadian Cordillera.  In an attempt to reconcile my observations with the seemingly contradictory, and widely accepted evidences for retro-arc thrusting associated with magmatism at nearly the same time, I invoke a poorly understood, and apparently sparsely represented style of subduction that involves overturning the subducted plate so that it winds up under itself – hence the term auto-subduction [2].  The theory is based on two key field observations in southern Arizona: 1) an ~75 Ma angular unconformity, deemed insignificant, or nonexistent by others, separates a thin-skinned style “Sevier-like” low-metamorphic grade fold-thrust belt from thick-skinned style “Laramide” volcanic and sedimentary rocks throughout southern Arizona, 2) the combined great abundance of oceanic mantle lithosphere, and paucity of oceanic crustal “clasts” within the Orocopian schists, suggests structurally, that the subducted plate from which they were scrapped was steeply inverted and west-facing, not gently east-dipping.  Arizona’s greatest mineral wealth, its porphyry copper deposits, are in my mind the result of North America overriding, or auto-subducting the oceanic “leader” of its own tectonic plate.

Despite my interest in fold-thrust belts, most of my field experience has been in volcanic rocks, and after nearly four decades with principal field colleagues Bob Osburn, Brad Johnson, Sam Bowring, Steve Skotnicki, Wyatt Gilbert, Shari Kelly, Robert Hildebrand, and Stephen Enders, have helped discover or refine over a dozen calderas, and unraveled the structural and eruptive histories of dozens of volcanic fields throughout the southwestern United States.  Principal examples include the mid-Tertiary Superstition, Kofa, Morenci, Black Mountains (Peach Spring Tuff), Mogollon-Datil (NM), and Laramide volcanic fields of southeastern Arizona.

For nearly two decades, I have taught a field short course, Whole Lava Love, that has been recognized for credit at over two dozen American Universities, and been taken by hundreds of students, professionals, and enthusiasts.  The course’s shows students how to identify time-lines in volcanic sequences by seeing through the mesmerizing effects of volcanic texture.

I entered the fray firmly on the side of Survey colleagues Kyle House, Phil Pearthree, and Jon Spencer’s spill-over theory for the origin of the Grand Canyon after a field research trip to the Powder Rim of southern Wyoming [3].  There I re-discovered field evidence in a remote area that had been neglected for over 100 years that put an important formation, the Bishop Conglomerate, back where both Samuel Emmons and John Wesley Powell [4] had originally placed it, in the upper Neogene.  In its proper stratigraphic position, the Bishop Conglomerate fulfilled a key, and up to the then missing, role in the spill-over theory story for the origin of the Grand Canyon; the north-flowing river gravel facies of the Bishop at Powder Rim was evidence of the hypothetical “other river” that drained the Colorado Plateau up until the spill-over occurred.