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A few weeks ago I had the opportunity to look for fossils among additional Pierre Shale outcrops in the Sheyenne River Valley. I didn't post anything about that trip as it came up a bit short and read like my last Pierre Shale trip with more partial specimens. Today I went back to the area to look again, and also made it to an outcrop of the Gregory Member. Low water levels made for a great collection from the Gregory. The DeGrey was rather typical. The side of one of the so-called "Indian Mounds" of the DeGrey member and a frog which was hanging out on the mound. This portion of the river is also the DeGrey. The DeGrey is well exposed in many parts of the state but is often poor in fossils. That fantastic looking ravine produced nothing, not even fragments. Glacial till and boulders are often mixed into the worn outcrops. Some things still grow in the worn shale. Prairie Crocus (Anemone patens) coming up from a few weeks ago. Exposures of the Gregory. The mark of the Gregory, tan claystones compared to the mark of the typical DeGrey, iron manganese carbonate concretions. Frogs were everywhere. I counted 19 frogs in a 7 foot line along the bank here. Freshwater mussels are abundant in the Sheyenne and the low water beached several. Many became muskrat and raccoon snacks. This male Fatmucket (Lampsilis siliquoidea) was one that survived the feast. The first fossil from the Gregory, a nice Baculites.
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I have an ambivalent relationship with the Pierre Shale. I try and try to find good sites that produce fossils but the end result is usually a fossil-less site. For a long time I quit trying exposures of Pierre Shale even though it's the closest fossil bearing exposure to where I live. About a year ago I decided to try the Pierre Shale again because it was close and I was too tired to go elsewhere, like the Fox Hills Formation in Central ND. Mostly I found worn Inoceramus fragments but to my surprise I found a nicely preserved caudal vertebrae from a mosasaur among float material. Following that I began to try the Pierre a little more and today, after finally getting landowner permission, I spent the day at a site with extensive exposures. Most of the Pierre Shale exposures in East-central North Dakota are of the DeGrey Member. The most obvious feature of this member is a large amount of iron manganese carbonate concretions. The few fossils I find in the Pierre here are usually in these worn concretions. The first fossils I found didn't come from the Pierre at all but came from glacial erratic limestone. I occasionally find older material like this among the tons of glacial material that blankets most of this part of the state but rarely do I find such well preserved/unworn specimens. Some nice brachiopods to start. I was happy to collect some of these among a split limestone boulder despite the lack of specific age/locality data. Moving towards the actual Pierre Shale deposits there is distinct worn shale with bands of worn concretions. The large tract of land I had permission to collect on was covered in these exposures.
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