[WIP] World of Aduhr

[Charerg]

So, I mentioned I would post something about the geologic history of C. Eocidar's western mountain belts (dubbed the "Eocidarian Cordillera" since they're mostly inspired by the real-world mountains of that name). I actually have a fair bit worked out for how various parts of the mountain range formed, ranging from different terranes docking with Eocidar to subduction of submarine plateaus. But since I keep most notes in my head it's all a bit disorganized, and this post ended up being mostly about the history of the C'thuana terrane, so I guess I'll call this post "part one" on this topic.

With the intro out of the way, let's dive in and take a look at Aduhr 200 Mya:
200 Mya.PNG
Needless to say, this is all very WIP still and the further back in time we go, the less detailed things become. But at present the C'thuana terrane is envisioned as originating from the southern margins of Panwara, diverging at about 250 Mya. The main reason for the divergence is the NW movement of Panwara: there is a retreating subduction zone on the southward margin of the continent, and this causes the C'thuana block to break off. Overall, a similar process to what went on with Japan diverging from mainland Asia, or Stikinia from Laurentia for an even better example.

Next up, a few screenshots from the ages 150 and 100 Mya:
150 Mya.PNG100 Mya.PNG

At 150 Mya, it can be seen how Panwara begins to break up, and the subduction zone south of the supercontinent has shifted into rapid advance from its former state. This cause a new subduction zone to form at the southern margins of Nomune (the southernmost piece), subducting the now-quite-aged crust of the "C'thuana Sea". At 100 Mya, the mid-oceanic ridge is subducted and the C'thuana Plate itself falls under slab pull, beginning to once again converge with Eocidar.

Finally, here's a look at Eocidar 50 Mya:
50 Mya.PNG
Here, the C'thuana terrane is on the verge of colliding with Eocidar, a process that will eventually close off the western interior sea. To the north of the continent, the collision between Urgaleon and Eocidar is proceeding, which will result in the opening of the Trans-Eocidarian Rift, breaking the continent in two (the epeirogenic uplift, normal faulting and flood basalts released as part of this process will close off the eastern interior sea). Besides the C'thuana terrane, there are also two smaller terranes (K'wira and T'kalo) that have been accredited to Eocidar at a later date than C'thuana. As their exact movements remain a bit in flux, I decided not to go in too deep about those just yet (maybe in future if I ever complete the tectonic model for that Indonesia-like region SW of Eocidar).

And with that, I think we can close off "part one". The next part will discuss the northern portions of the cordillera and how they acquired their present-day structure.

[HandwaviumAdAbsurdum]

I came across this project a few days back and I was taken aback. I have never before come across a worldbuilding project which has put this much emphasis on geological plausibility. All the time you've spent refining your plate motion model in gplates has really paid off. Much of your topology looks very convincing, and is testament to the astounding level of research and study you've put into this project. For example, the concave shape of the Eocidarian Cordillera is very reminiscent of the Bolivian Orocline, both in terms of its curvature and its elevation, and I can see how they very well might have shared a similar tectonic evolution. I also have to say that the basin and range topography at the northeastern end of the Great Akanrian Trough is absolutely inspired.

If I have one criticism, however, it would be that your rift systems are maybe a bit too linear. You have these unbroken, gently curving lines, when what one would expect lots of smaller unconnected rift basins following a general axis of extension. In some areas you might even have multiple rift basins running parellel to each other.

This criticism does not apply to the Great Akanrian Trough which has clearly reached a far more advanced stage of extension. The width of the trough suggests to me that it should be mostly submerged, and may have begun seafloor spreading at its widest portions before becoming inactive. The remainder would have reached a transitional stage with a thin veneer of continental lithosphere. After this one would expect a degree of postrift subsidence of not just the trough itself, but also the flanking horsts. Then we need to take into account 140 million years of sediment being deposited, but even then I still think it would be more reasonable for more of the trough to be submerged. What I have in mind is something along the lines of the Bay of Fundy, at least for the southwestern part of the trough, getting progressively deeper as the trough widens. At northeasterns portion, I'm thinking something more along the lines of the Mozambique Channel or Davis Strait, with oceanic lithosphere overlain by thick sediment.

Speaking now from more of a geopolitical point of view, this alternative setup would have some interesting implications. Two strategically important locations would emerge: one south of the Ilanga fault blocks where we already see something very reminscent of the Strait of Hormuz. This narrowing of the gulf serves as not only a viable crossing point but also a vital choke point, where shipping going in and out of the gulf can be controlled. A longer gulf would only increase the strategic importance of this choke point. There would also now be a narrow land route between the southwestern end of the gulf and the ocean which would serve as a narrow isthmus connecting Akanrias with the rest of the continent, very much akin to the Isthmus of Suez connecting Africa and Eurasia. To me, at least, this would be a desirable consequence, but if it isn't to you then you could explain the current topography of the region by having this area move over a hotspot and causing uplift that way.

Keep up the good work. I'll be following this project eagerly!