A steady six-hour stint at the Hungry Hollow site in Arkona was a productive outing. I began in the north pit and found an Eldredgeops Rana roller in under ten minutes, but the fossil gods only pay out at the beginning or end of a trip, or not at all, so the rest of the trip was dry when it came to any other rollers. I plucked it from the ground near the big mound of piled up Arkona "shale."
Here, your intrepid fossil adventurer is poised to begin the day with his new Estwing rock hammer and assorted gear.
It wasn't too hot, but it could get buggy in some places. After I ventured through the woods to get to the two main river exposures, that was when the biting deer flies found their new meal. I could only work the exposures of the Widder formation for about an hour before it became intolerable. I hauled out some modest chunks of Widder shale from the wall, but it was awkwardly placed a little too high from the scree, and pretty much vertical with no convenient handholds. So it was back to the south pit for me.
Here's a fairly representative assortment of some of the small pieces I pulled from the Arkona layer. The first two in the first row are very likely fish armour plates. Second row: crinoid sections/columns of varying types. Third row: two goniatites followed by a bactrites. Fourth row include three trilobite roller fragments, three platyceras in ascending size, a brachiopod, and a brassy-coloured mussel. Fourth row: two button corals, my lovely roller (pictured alone below), and just some odds and sods including a British 5p piece found in the mud.
Working the south pit floor is where you're most likely to encounter scattered, weathered out bits from the Arkona layers. There are plenty of brachiopod shells, mostly poorly preserved, cephalopods, and crinoid stalks like the one pictured above. The lustre of this particular one shows a heavy degree of pyritization, which is the first stage to its rusting to nothingness if left out to weather any further.
And here is my fully intact roller from the side view. Not terribly large (a little over a centimetre wide), but with no flaws.
A closeup of the Arkona sectioned off with a crinoid stem (indicated by the head of the rock pick). I got talking to Rick who comes often to dig through these layers in search of intact crinoid crowns. The trick is to dig past the "blooms" that form when the exposed mudstone/clay goes through the wet/dry cycle and bakes (this stuff was actually extracted to make drainage tiles). It can be tricky to work with given its clay-like softness and no bedding planes, and the state of preservation is quite fragile. Much of the Arkona layers are sparsely or non-fossiliferous, as they are basically composed of mud deposits with very thin fossil layers and shelly limestone pavement. A very interesting explanation of how stormy these seas were in reworking the sea bottom environments (and the short growth windows due to poor oxygenation), and how it impacted growth among the benthic creatures can be found here. My thanks to TFF member doushanto for the reference.
Speaking of references, this is a generalized stratigraphy of the Hamilton Group, which includes the "big three" in this area. In ascending order they are the Arkona (more mudstone than shale), Hungry Hollow formation, and the Widder formation which, in some points, does not reach its top end due to weathering. This image is from Wright and Wright (1961) "A Study of the Middle Devonian Widder Formation in Southwestern Ontario" available via the University of Michigan. Read it here. Just a few remarks: the units listed here that seem to form ledges are generally sparse or non-fossiliferous and are largely erosion resistant. Some of the best places to hunt for Greenops trilobites would be either in the units under those ledges, or occasionally above them. They may appear in other units as well, but you'll be more likely to find them in death assemblages (thanatocoenosis) or by other forms of deposition. A good resource if you're looking to have a checklist of the biota in each of these formations in the Hamilton Group would be Stumm and Wright (1958) "Check List of Fossil Invertebrates Described From the Middle Devonian Rocks of the Thedford-Arkona Region of Southwestern Ontario" - although this is a foundational resource, it could use a serious update to reflect some of the newly discovered species since then.
Deb joins me after a day at the cottage, going through a pile of recently carved out Arkona mudstone. It just comes apart in your hands.
And some other odds and ends of the day. Top right is a busy vermiculated bunch of crinoid stems from the Arkona, while the large piece on the right is a bit more firmer substrate of the same. Bottom left is a larger shell, and to its immediate right are two Greenops trilobite tails from the Widder. I didn't spend as much time in the Widder due to the biting flies, so no full specimens were found.