The "rock types" go, from bottom to top, granitic basement (dark red), immature sandstone (speckled pink), gradational shale (black to brown), limestone (tan), mature sandstone (speckled white), then either vegetation (green) or basalt and magma (speckled black or red). I also threw in some structure, including two normal faults making a horst and an unconformity between the limestone and mature sandstone. The handle is a basalt porphyry mafic dike (one of the more creative ideas I had during the whole process) connecting to the erupting volcano.
Although I had no specific locale in mind, I would say the base is mostly based off of Missouri geology. The granite is the "Missouri Red" granite that I've seen near the St. Francois Mountains that I've discussed before. The knob is some of the Precambrian topography associated with these granites, as they are older than the sedimentary rocks above them. The immature sandstone above the granite is the Lamotte Sandstone which tends to be immature and conglomeritic at the base (and is therefore full of feldspar and rather pinkish: more of an arkose than a sandstone). Above that I just wanted to transition through the typical transgressional sequence of rocks that every geology student learns about. And, of course, the classic "warning" of seeing a limestone (no specific one in mind here: would probably be a dolomite in this sequence if I was trying to stay true to the deeper Missouri geology) next to a sandstone (indicating a regression, erosional surface, and deposition of a sandstone, forming an unconformity). I'm going to go ahead and call the mature sandstone the St. Peter Sandstone, which I always enjoy looking at (since it exists both up in Minnesota, the land of my undergraduate studies, and in Missouri, the land of my graduate studies). And of course the horst. I just really like drawing horsts and grabens.
|A good view of the rock layers. I inentionally added a little granitic "knob" without faults, as a sort of Precambrian topography.|
|Mafic dike handle connecting to the volcano (which is erupting, of course). The speckled black paint made for a good basalt porphyry.|
I mostly drew this as I went, so there are some things which are not "accurate". I could always show it to someone as a sort of "spot the geologic inaccuracies" game.