The Mojave-Sonora megashear model was challenged at the monthly dinner meeting of the Arizona Geological Society, by Alex Iriondo, from the Universidad Nacional Autonoma de México.
Alex laid out the basis for the Caborca oroclinal bend in southwest Laurentia to replace the model of hundreds of kilometers of left-lateral strike-slip motion of northern México in Jurassic time. Alex argued the megashear model is too simplistic to explain the paleoprotozoic provinces in northwestern Mexico.
His talk generated some of the most intense discussions I've seen at one of these meetings. Responding to a question about the role of personalities in the prevailing view of the region, Alex explained that he felt the megashear model has held back alternative ideas for two decades because of the professional reputations and force of personalities of the megashear model proponents. [right, Alex answers a question from Don Hammer following the talk]
I have not followed the debate over the megashear in recent years but last night I definitely felt the intensity of being in the midst of a classic geologic debate. Is this an outrageous hypothesis that is not supported by the data or a paradigm shift that is tossing out the old guard?
This is one of the things that makes science so exciting.