Are scattered thrust uplifts possible?

[jennawest]

I am working on modeling the landscape of Wyoming during the Laramide orogeny which was a period where scattered basement-cored thrust uplifts occurred. I am looking for a way to make each block uplift by thrusting so a foreland basin is formed on the thrust side of each unit. A map of what my uplifts need to look like is in the attached folder, the file is called "Dickinson et al, 1988 map"

If I use *.UNIT files with no faults, just blocks set to a certain elevation, I do not get the foreland basins on a particular side of the unit (nofault.ps). But when I add thrust faults on one side of each unit I get a "hole" on the back of the unit where the unit started and has moved away from. I know TISC uses a mass balance approach so if you want to add a thrust block to the model, the back of the thrust has a hole where the sediments have moved out of to create uplift on the front of the thrust. To get around this you extend the block outside of the model domain so the hole is not visible (like in your demo 6_deformation). I was wondering if it is possible to get around this because the distribution of my uplifts means that the backs of the thrusts cannot be outside of the model domain. I have been working with the idea that maybe I can have each of the units move at different time periods so I can extend them outside of the model domain without interfering with each other but I have yet to be successful with this approach. I apologize that what I'm sending you is such a mess. I know that a way to get around this is to split the study area into smaller sections but I am trying to avoid that because it doesn't match the original project goals. Also, do you know why there are foreland basins on either side of the thrust belt even though it's moving in one preferential direction? It would seem it goes against the classic foreland basin model that has a foredeep on one side of the thrust.
60ma_thrust.zip

[danigeos]

Jenna, thanks you for the relatively clear question. There are some wording issues and i am not 100% i follow everything, but here is my interpretation:

Your tectonic map is very complex but at the same time very sketchy, as usual with tectonic maps. You need a structural geologist (assuming you are not) to help you interpret how those faults may 1) connect with each other in the map; and 2) more important: how do they connect in depth to some sort of detachment level. Besides, you need to know the amount of shortening and the direction of motion of each block. In the end, you need to tell TISC or any other tectonic software what is the geometry of the rigid blocks, how they connect to a plate boundary, and how much do they move.
That's why all models with faults in the demos have their faults connected to the boundary. In the real world, each block must be pushed by some external force, ultimately linked to a plate boundary, so to speak.

When you have a thrust ramp, its load generates isostatic subsidence both in front and behind that thrust. If the fault roots at a horizontal flat detachment level, you will get a frontal and a back depression/basin. Maybe you can understand this better in demo/Example_D of the sister code tAo?
https://github.com/danigeos/tao-geo

As you see in that example, if you don't have subsidence behind in the real world, it maybe because your real fault is 'listric'. And TISC can reproduce that too.

So the answer is: YES.
But first you need to understand the 3D kinematics of the tectonic blocks of your region.

An alternative for you could be using static (fault 0, vel_x=vel_y=0) loads that simply modify topography at your will, and then you separately justify the amount of topography you generate while focusing on drainage changes... Do you have indications that isostasy is relevant in those basins? Do you have a cross section where i can see the sedimentary structure? We can continue this discussion via email if you prefer.