Susan Haddon

Thanks for all of your input. Michael, that sounds plausible. If I see anything else suspect, I’ll post again.

Michael Cox wrote:I suspect that you are seeing the remains of a natural biological process.

http://askanaturalist.com/what-is-this-oily-sheen-on-the-marsh/

The manure and bedding decomposing can produce oil like substances, which can be trapped in areas of high concentration. I suspect that the clay layer acts like a barrier.

Hard to say for certain without better photos and a more in depth exploration of the site, but I wouldn't be too concerned.

Here are some pics of the site. I added water to the clay and of course it just sits there. I need better drainage here.
I don’t know about fracking in my area. It’s probably like someone mentioned where a previous owner drained their oil there.

Cleaning up under my barn where my horses hang out, I dug about 10” down and found clay with what appears to be a layer of oil. It’s black and just at the surface of the red clay soil. I’ve been using the manure I collect here for my compost so I’m disappointed to find this underneath it all. What do you guys recommend I do?
My thoughts are to shovel that layer away and toss it. Then what? What should I begin to replace it with? My horses and chickens spend a lot of time in this area. It’s about 30’ x 40’. Thanks for your help!