Very interesting! I'm trying to find what you're referring to. What series (or complex/association) are you talking about, the Peoga? Forgive me, but I'm not at all familiar with that area.
The down wind area in Jennings County Indiana has a feldspar based soil ~ fairly typical of a sort of ancient volcano.
Typical for plutonic source, too. Is there other evidence of this being volcanic along with the plutonic?
So this sucker has been toking off and on for probably a couple of hundred million years spewing stuff on Jennings County. That suggests there's an even deeper heat source closer to the mantle ~ maybe a plume like the one under under Oregon, Idaho and Wyoming (Yellowstone).
Suggests to me that someone's timeline is off. Gondwanaland was still together back then, and Jennings County was on Laurasia. I doubt a plume was following Jennings County around the globe. :-)
Are these hypotheses of yours or are they someone else's work? This whole topic will have absolutely no useful or positive impact on my life, so it's just the type of thing that catches my attention!
We have an ancient volcanic vent in Fairfax county just like the one at Crothersville. It's been covered over for tens of millions of years, but it is detectable at the surface. The headquarters for the Coast and Geodetic Survey is there ~ and the main driveway out front CIRCLES THE TOP! Very cute way to tell us about it.
I'm confused by your description. I'm guessing you're referring to the USGS in Fairfax County, Virginia, not Indiana or the NGS...? If so, I think it's near some diabase with surrounding hornfels, but I don't think it's on any sort of volcanic vent, per se. It's just the typical Triassic rifting, and the USGS driveway doesn't circle any of the ones nearby. Or are you referring to a historical location (Coast and Geodetic Survey was absorbed by NOAA decades ago)?
I came across this, which describes Indiana tectonic features.
We call the area "the ten acres" because my Great Grandfather, and on back, owned it. If you get ahold of satellite pictures of the area you can see the circular formation from space ~ it's a soil difference. It affects the plant growth, and you can detect it on the ground as well ~ PLUS, the site has both a cold spring and a hot spring! Paleo-Indians lived there for thousands of years making use of the hot spring.
Part of the site has some glacial till on it ~ called locally "The Knobs". There's a town called Dudleytown at the top of one of the hills.
This site is also the only site in Indiana where you can find native mica as well as copper.
That pretty well covers how ancient the site is ~ but no gold. You have to go about 45 miles NW of there to find gold ~ it's all on hilltops ~ part of the evidence for that comet that may have hit the residual ice sheet in Canada about 11,000 years back (creating the younger Dryas). It hit right on a major gold bearing region in Canada and splashed that stuff all over the lower Midwest.
Getting back to the pluton ~ the surveys into the Cincinatti Arch began revealing some of the structures but I think it's a bit deeper than current info can show. The more recent techniques ~ like the ones used to reveal the plume cutting the Juan de Fuca plate in two under Oregon ~ haven't been used there, but I'd imagine there are plenty of folks who would like to do that pretty soon!
Way back when they had that big quake in Alaska that wiped out downtown Anchorage I just happened to be inside the Geology building at Indiana University ~ on the ground floor. The seizmograph was set up to print out right there in the lobby ~ big open room, hooked up to the machinery, and the arm would swing an inch here, and an inch there, and everything was good.
I thought I'd just watch it a while and the doggone arm went darned near off the graph ~ and came back ~ and went back and so on for HOURS. None of us watching that graph knew what it was about until the next day but we knew a continent had moved. That particular location went straight up about 10 inches over a couple of weeks.
Two things happened as a consequence of that event ~ (1) I decided to never relocate to Anchorage, and (2) I spent a lot of time reading geology texts and reports for therest of my life.
You know the Appalachians have no active volcanic activity. At the same time you get down near the Southern end in Alabama you can find volcanic cones all over the place, particular inand around Anniston and the Talladega National Forest. Had AIT in and amongst some of them so I got to know them well. They appear to have been mid-ocean volcanos that got swept up when the continents smacked together ~ I would imagine some of the hot spots did too.