So great. My sons didn’t want to watch but gradually started paying attention and are now waiting for the next one. There is no boring terrain in geology.
@@Sciencein10 Heh. I'm sure generations of American geologists have pronounced Quebec like Kwuh-bec, too. Canadians, not so much. Canadians pronounce the Qu in Quesnell BC (the locale for which the terrane ia named) more variably, depending on linguistic background), but none of them sound the 's'. Many Cordilleran formations are named after native terms. It's always worth learning these terms with the community of speakers who gave birth to the term in mind.
First off I want to say that the star real helps. But I have some questions about the passive margin that is created with the initial breakup of Rodinia. The map style changes after that and a bunch of time is skipped so I am just trying to make sense of what is taught about happens to that ocean crust that is being created between Laurentia (where the star is) the Australian and East Antarctica plates. It seems like it is very similar to the mid Atlantic riff. So if that’s the case than a passive margin, transitioning from the continental crust of Laurentia to the oceanic crust to its west should still be there. And a fairly significant chunk of oceanic plate at that. Here’s my issue, I’ve always had an issue with the breakup of Pangea, especially on the west coast, having to deal with the Faralon plate subducting right away. It just seems like it’s an additional variable that would keep Pangea together. Having a passive margin off the west coast of Pangea, with westward subduction, would add slab pull as a variable to help tear Pangea apart. There is a bunch of tomography research to support this idea too. Looking under the west coast the Faralon plate is just not there in its current place. The work of Karin Sigloch actually seems to show that the Faralon, which in her work is actually the extended oceanic crust from the passive margin of west coast Pangea. I know the traditional model teaches that Pangea separated and subduction of an oceanic crust began right away, but like I said the Tomograpghy of subducted plates seems to suggest the old model doesn’t really work anymore. I guess I’m just wondering your thoughts. I love detail you go into in this series. Actually showing locations that highlight the different processes over the millions of years of tectonic activity. Sorry if this was long.
What is the blank terrain between the "accreted" Siletz Terrane and the Terranes to the East? Why does the Siletz Terrane even have an "identified" Eastern margin if the quaternary deposits and sills hide what could extend underneath? Could the Cretaceous Columbia Embayment floor (that the Cascade Range and Columbia Basalt Group hide spectacularly well) be obducted oceanic terrain that the Siletz Terrane accreted to?
The Columbia Embayment was filled in part by Siletzia, and otherwise by later volcanics and extension-related sediments. The main reason it’s blank on that map is that it’s inaccessible to geologists because no exotic terranes outcrop in that area. This blank area is covered by Tertiary volcanics, Cascade volcanics, Columbia River Flood Basalts, and volcanics associated with the passing of the Yellowstone Hotspot, Tertiary trench rollback and extension/clockwise rotation of Oregon, and farthest northwest reaches of Basin and Range extension. Additionally, there are some Paleogene extensional basin sediments. It’s highly likely that accreted Mesozoic terranes form the basement under this thick layer of mostly young volcanics and volcanicclastics, but unfortunately there are very few boreholes and most of what people can deduce comes from geophysical data.
There's certainly more terrane rocks there- but it's all been covered up by younger volcanics and volcaniclastic rocks (along with a huge range of sediments that were deposited in basins that were present where the modern west cascade foothills and Puget Sound/ Salish sea area are)
