Assuming I have managed to attach the drawing, which took a lot of finding as TC seems to hide them very well.....
For the non-geologists, this odd-looking effort is a diagram of an anticline (an upwards fold in the rocks) with the nearer "limb" fractured and displaced by a fault , then the whole structure partially lowered by erosion. The fault-plane is the ski-jump-like surface across the sectioned part.
These structures arise from tectonic forces compressing the continent laterally, crumpling the originally-flat rocks rather like pushing a rug against a wall. As the force continues against increasing resistance the fold's trailing limb breaks into fault-blocks that become pushed up their fault-planes.
It is in grey scales because I intend it to illustrate an article I am preparing for a caving-club magazine, explaining these geological features. (Some cave passages are developed along fault-planes.) The magazine has full-colour covers but grey-scale photographs inside.
As a TurboCAD exercise, I experimented with assorted methods for free-hand drawing the shapes flat then extruding them to form the strata. I had also to work out how to make them look solid: one refused to extrude as a solid and I had to start again from the original 2D drawing.
Originally I had used hatchures as these give better contrasts, but they don't seem to like being extruded. Or if they do, I couldn't see how to make them. The diagram doesn't stand too much enlarging due to accumulated errors in a lot of copying and re-drawing, but these won't be noticeable in magazine-page size. I had hoped to copy each spline once so it would form the next stratum's border but couldn't quite make it work.
In order to process each piece of stratum I drew the outline in place but then moved its entities down from the main drawing, into clear space where I could chivvy everything into Joining where I'd not succeeded in using the Vertex snap; then fill the shape. My main method with such a problem is to extend the lines to cross then trim them back. I've not worked out what limits the Meet 2 Lines tool has, but I've never had much luck with it.
The fault-plane is just an extruded, thick spline line.
To break each stratum which originally draped across the whole anticline, I made a copy used the fault spline as the trim line relevant to each part, then linked the stratum borders (the "bedding-planes" in geology terms) with a simple, straight line.
I was also plagued with "orphan" scraps of lines, all having to be rooted out; from the many attempts to make it all work. Sometimes the splines wanted to break up into dozens of individual lines until I had a vague idea where I might have been going wrong. Also, TC appeared to want to keep putting everything on individual work-planes.
I've probably gone as far as I need and indeed can with the artwork, except for one thing, and would be very grateful if someone could tell me the secret. I would like to annotate it but can't see how to make the text-boxes appear on the rendering. They show in wire-frame, but that's not much use!
There is a second type of geological fault relevant to the article, but if anything it may be harder to draw reasonably realistically.