Dr. Paul Heller, Chair of the University of Wyoming’s Geology and Geophysics Department (and an awesome teacher), will talk to members about the “Timing and Magnitude of Mountain and Mantle Uplift During the Laramide Orogeny.
Thank you Dr. Teller, that was awesome. So clear even a simian mind like mine can understand. (Conjugate Shatsky Rise) is now permanently in my vocabulary. Few things interest me as much as orogeny discussions. It even sounds kinky : ) Geology is tough but it sure can be fun. Thanks to brilliant people like you, we have the models that fulfill our imagination's painting of mantle / crustal dynamics. Since working for a civil engineering lab in the 70s, it's been a passionate part time pursuit. It has made my life exciting in a thousand ways. Thanks for sharing it with us. Geology is not for "wimps". Only the strong, the disciplined, and the brave need apply.
I note in the comments that the presenter has passed away. Too bad. Since this presentation and 2008 with the earliest seismic tomography, that science has come a long, long way. Much of what is presented here seems very dated, but ironically in geology, seven years is a long, long time. Today (2023) Karin Sigloch and Basil Tikoff's work with seismic tomography and tectonic interpretation, provide interesting detail not available in 2016. The questions at 53:00 about the "mineral belt" is particularly relevant today with the current studies, IMHO.
The current thinking is that flat slabs peeling away leaving a single stretched thin upper crust is why most the Carlin and epithermal deposits exist in Nevada right? California seemed to follow the same pattern when the bottom plate fell away then the minerals were deposited. I read that paper you referred to a while back and it’s really interesting at least the parts I understood:) The major difference that stood out to me is the way North American accreted the land was different than previously thought, it didn’t get scraped off the farralon or JDF plate as it was subducted under NA, and it was more that North America swallowed several spreading ridges and their associated seamount and arcs. That actually makes more sense because you’d have to accrete endless Hawaii size or Shatsky island chains to build all the western states.
The conjugate Shatsky oceanic plateau idea doesn’t hold water, IMO. Every oceanic plateau collision we know about from the geological record is the site of major accretion of oceanic crust, for example, the Siletzia oceanic plateau terrane in coastal Oregon. The reason being, Oceanic Plateaus are much too buoyant too subduct. As the late Dr. Heller points out early in this video, there is simply no record of accretion of an oceanic plateau. However, what does seem to fit the bill is an aseismic ridge subducting, exactly what is causing flat slab subduction and foreland basement involved thrusts in South America today. So though I have that nit to pick about this talk, I think everything Dr. Heller says can easily be applied to the more likely cause of subduction of an aseismic ridge, rather than a conjugate of the Shatsky rise. The same goes for the proposed conjugate Hess Rise, which is shown by the letter “H” in one of his diagrams, but not discussed, and has been invoked to explain deep inland basement involved thrusting in the laramide of Mexico and Texas. Aseismic ridges, as we see offshore of South America today, on the subducting Nazca plate can occur in related groups, and cause multiple segments of flat slab subduction along a single active margin. I really enjoy this lecture, though, and the flexural and dynamic topography modeling that Dr. Heller presents here as explaining the Western Interior Seaway. Only issue I have is that Sevier deformation began as much as 40-50 million years before the main phase of Laramide deformation, and the WIS penetrated the interior of the content from both north and south, but mainly from the north, by 120 Ma. By the beginning of the Laramide it was well-developed with deep water facies (Mowry Shale) already. So it seems unlikely that the kind of “suction” force between the slab and the upper plate that Dr. Heller describes is responsible for the formation of the WIS. In fact, in most models of the flat slab, there is coupling of the slab to the upper plate-no room for a narrow mantle wedge under the upper plate. But I like to rewatch this lecture from time to time-thanks for making it available.
Worst idea ever; let's put a camera next to an old man that happens to be cutting steak and potatoes on a dinner plate. Has to cut EVERY thing up into little pieces and chew up tiny pieces of steak then almost chok and REPEAT all over again!!!!!!! God this is so unbelievably terrible to listen to. Why people give lectures as people eat dinner is something that will never make any sense.
