An Ohio Geomystery

Cross-posted at Highly Allochthonous. There are some good comments there.

I had the good fortune of going out in the woods a few days ago with colleagues here at Kent State University. We were in a second growth forest, probably fairly typical for this part of northeastern Ohio. The upland forest had lots of maple trees, and the bottomland forests had cottonwood and sycamore. The forest is underlain by many meters of till (with silicic clasts) and below that are various sedimentary rocks. I was there to take a look at some small streams and wetlands as potential field and teaching sites. Towards the end of our tour, my colleague brought us past this site:

My first view of the geo-mystery

My second view of the geo-mystery

My colleague described the site as the ruins of a “sugar shack”, which I connected with the maple trees to mean that this was the foundation of a small-scale maple syrup or sugar production facility.

But what really caught my eye were the tabular black rocks, which seemed completely out of character for the region.

Close-up of the black rocks. Wading boot for scale.

So, I know what the black rocks are and I have a pretty good idea of why they are there, but I don’t know where they originated. I’d like to hear from our readers what they know or can deduce about these mysterious black rocks of northeastern Ohio, so share your thinking in the comments. I bet together we can get to pretty good story of the human history of these geopuzzling erratics.