Keeping closer to home, I've managed to pull some interesting if not typical specimens from the Dundee Formation along the Thames River. I even found a pitifully small trilobite pygidium (really not worth showing). The more visually interesting specimens happen to be coral, a few brachiopods, and bivalves. Unless otherwise indicated, these are all from the Dundee Formation, of the Devonian age, Eifelian stage. Not shown in these images were the plentiful and more robustly ribbed Brevispirifer lucasensis. So, let's show rather than tell:
A fairly well-preserved chunk of colonial coral (?Favosites sp.). I don't usually go in for coral, but this one was a must-have.
Another busy hash-plate containing some rugose corals (?Zaphrentis sp.), a brachiopod (Rhipodomella sp.) and a bryozoan (Fenestella sp.).
Now that I'm back on campus teaching again, I took a few more pictures of the fossils in the wall of the Visual Arts Centre. The picture above already appears in my pre-blog entry, and I had misidentified it as a coral rather than a sponge (although it is nicknamed a "sunflower coral" due to its resemblance to a sunflower). It is a Fisherites ?occidentalis (formerly Receptaculites occidentalis, Blainville 1830, genus changed in 1979, Finney & Nitecki). The building's composition is Tyndall Stone (trademark of Gillis Quarries), Ordovician in age (Maysvillian stage), in the Selkirk Member of the Red River Formation quarried in Manitoba - incidentally the same material used in the Parliament Building. It is a dolomitic limestone mottled by many corals and thalassinoides.
Another image of the same limestone sporting two fairly large nautiloids side by side, siphuncle showing in the specimen on the right. There are also several large gastropods if you take the time to scan the exterior of the building.
And here is one such gastropod, Hormotoma sp.
The mottling of this limestone was a bit of a puzzle for some while. The mottling is something of enormous interest for the ichnologist (study of fossil burrows and traces). Here are some helpful papers on the subject:
Kendall, A.C., 1977. Origin of dolomite mottling in Ordovician limestones from Saskatchewan and Manitoba. Bulletin of Canadian Petroleum Geology, v. 25, p. 480-504.
Myrow, P.M., 1995. Thalassinoides and the enigma of early Paleozoic open-framework burrow systems. Palaios, v. 10, p. 58-74. (PDF)
Sheehan, P.M. and Schiefelbein, D.R.J., 1984. The trace fossil Thalassinoides from the Upper Ordovician of the eastern Great Basin: deep burrowing in the early Paleozoic. Journal of Paleontology, v. 58, p. 440-447.
And that is all from me for now. I'll be heading back to the Penn Dixie site in early October, now as a new and proud member of the Hamburg Natural History Society, for a two day dig.
The first step is admitting one has a problem!
When Deb and I went to the Home Depot to pick up some foam to seal an area around the pipe, I found myself "wandering" over to the hammer section where I pondered whether to buy a 3' wrecking bar to supplement my smaller pry bar, a new cold chisel with a longer head, and a 4lb blacksmith sledge to go with my regular 4lb sledge. Deb played enabler by telling me I should get them. So I did. But that obliged me to try them out since we are planning to return to Penn Dixie in early October.
So we went to Arkona's Hungry Hollow. And let me tell you that lugging that many pounds of tools and supplies around through a lot of brush and tough terrain ain't always easy!
Unless one wants to be contented with surface collecting of whatever stuff may weather out of the cliff through the process of erosion, the only real and serious way to get at some very nice specimens is to carve slabs out of the wall for splitting. To do that, one has to create a "bench," which is like a long notch in the wall where one can sit and lever out slabs to the left, right, and down.
So we were ready to get started on continuing a bench in the cliff face we found some months back, that we've been steadily extending. I worked a bit on an upper bench that I eventually connected to the lower bench, and created another even lower bench than the one Deb was working on. Having the 3' wrecking bar was making this a lot more efficient (but still back breaking work!). It isn't easy making benches, or even sometimes extending them - there can be a crazy amount of overburden clumped together and slumped over. I've had to go through several feet of the stuff in depth before hitting the actual wall. The other problem can be natural underground springs that leak through the shale, making it wet, muddy, and crumbly. There are plenty of fossils in those, but they just crumble or turn to mud. One has to go deeper into the wall to find dry shale.
Once we were able to cut deep into the cliff face, we found that some of the more trilobite-filled layers were within about a 4 inch area. This picture hardly does any justice to how much rock and overburden was removed. This multi-level bench is aboout 3-4' deep, 7-8' high, and about 15' wide. At a few points I was able to exploit a major crack or fissure to send a few hundred pounds of debris and shale chips tumbling down. There are layers that are just choked with large spirifers. I found a few that had some nautiloids more commonly spread throughout.
Here you can see the bench-build from two different angles. Again, it's difficult to really convey the amount of work we did.
What does five hours of breaking rock get you? Well, for Deb, a full Greenops widderensis. Given the gazillions of moult pieces we keep finding in the Widder Formation, a full specimen is not common. And they are very delicate, so we took several precautions in transport back to the car. But, just to put the spotlight on Deb - this was her fantastic fossil find.
And I'll end his post with just some recent pics as I try to organize some of the recent and past finds. The first is a tray with bays - on the left mostly complete prone and semi-prone Eldredgeops rana; in the centre my accumulation of crinoid stems and sections; on the right a hodge-podge of mostly complete rollers with one Crassiproetus marginatus(?) pygidium since I haven't found a home for it. The final image below is my fully prepped out double roller from Penn Dixie.
Now with a whole new batch of trilobites from Penn Dixie (see my blog post on that experience here), it is time to learn how to prep. This will be my first time attempting this. Practicing on less valuable finds is a must at first. I don't have the space to go the full air compressor / vacuum system, so it will just have to be dental picks and a Dremel engraver with a lot of attachments. But here is the work so far.
Here's part of the workspace, nice and outdoors - but it is still important to observer safety (so a dust mask to block out all that very fine rock dust, and eye protection is a must).
Some of the steps in the prep: from initial state, matrix removal, more matrix removal and oil application for testing. There is more to be done to buff out the scratch lines and uncover a bit more of the specimen on the left.
This one below began with a lot of matrix, which I kept removing, leaving this one thumb-holder tag. On the right-hand side, the almost complete roller - just need to get the dental picks into the pleura to scratch off some tenacious matrix bits.
While removing matrix with a hammer and pin, you'll sometimes discover some surprises...
This is just interesting, although specimens are incomplete, yet we have two cephalon moults, in a kind of mirror positioning. Note the detail on the lenses of the schizochroal eye in the bottom one. It is said that such advanced eyes are possibly evidence that these benthic creatures were not scavengers, but active predators. As trilobites continued to develop in an environment with increasing numbers of predators (and the size thereof), they lost such advanced ocular features and most likely became scavengers again. As another possible proof of a predatory lifestyle, the hypostome (conterminant as opposed to natant) on this species (Eldredgeops rana) was far more developed and anchored to the anterior cephalon - a feature most commonly found in such animals as ticks - and their large "noses" (glabella) were like "gastric mills" for digestion more suggestive of predatory lifestyle (see Fortey and Owens, 1999). Some were still particle feeders, but those would be the smaller ones; otherwise, they were equipped with the front-loaded gastric apparatus to consume and digest larger bits of prey.
This dirty little roller is going to need to be freed up a bit more before getting a cleaning. Their ability to enrol was a defensive feature not unique to this species, and can be seen in modern day examples such as sow/pill bugs. The cephalon would form a tight seal with the underside of the pygidium, allowing their tough carapaces to shield their soft underparts.
A complete surprise - a chunk I decided to split revealed a nice little assemblage
We're back from two fantastic and productive days at the Penn Dixie site near Buffalo, NY. We packed all the necessary items to make sure we had all we needed:
This gives a fairly good idea of the kinds of fossils one is likely to encounter at Penn Dixie. Penn Dixie was once a quarry that is now owned and operated by the Hamburg Natural History Society. It boasts a lot more than just fossils, including ornithology, astronomy, and plenty of nature paths - but by far one of the biggest draws is the massively exposed 380 million year old shallow marine environment just teeming with fossils that visitors are allowed to extract and keep with the only limit being how much one can carry or fit in the car.
The volunteer staff are second to none. They are dedicated, immensely helpful, friendly, engaging, and passionate about fossils. For a nominal entry fee (adults $9, children under 12 $7, children under 2 free), you get full access for the day. I would advise trying it out for a day, and if you could see yourself coming back again (and again), consider the more cost-affordable option of buying an annual membership, which also has the benefit of supporting the incredible array of programs they offer, such as Digging with the Experts.
So here I am with PD volunteers Jay and "Dr Phil." Jay and I know each other from The Fossil Forum and we arranged that he'd show me around. We spent the whole day doing what any fossil collector would do: seek and collect fossils.
Here's a view of the site itself. You can easily pick up some of the fragments and likely come across trilobite fragments, horn corals, or brachiopods. For more hardcore fossil nuts like myself, bring some tools and have at the layers: dig about a foot or two of overburden and start making a bench. from which to haul out large shale slabs from the Windom Member of the Moscow Formation.
Here's a fairly representative and typical assemblage of trilobite moults, a few horn coral, and some worm burrows. I spent a lot of the day continuing on the bench started by my compatriot Canadians the week before. They had a rock saw, but in all fairness, I was the rock saw this time using a lot of sledge-hammer/chisel and pry bar action.
Talk about beginner's luck. I wasn't even looking for nautiloids, but I managed to split open a slab and find this fragment of a fairly large predator, Spyroceras. It may be one of the biggest ones ever found at the site.
More beginner's luck: full specimens of Greenops boothi are not easy to find compared to the large number of Eldredgeops rana. I am fairly positive that this one will be full once I prep it by removing the matrix obscuring its head. This is a bit of a contrast from where I usually hunt at Hungry Hollow since Greenops is generally the dominant trilobite in the Widder Formation.
On the first day Deb and I came away with so many trilobites that they wouldn't all fit in a single photo. This four-panel spread shows some of our best. If you look carefully, you can see some full prone Eldredgeops, plenty of rollers that need to be prepped out (and some prone ones I think may be full - but only my prep skills will determine if this is true). We also have a bucket of material encrusted with rollers that we still need to split and practice prepping on. I'll show some closeups of some of the trilobites below:
There are a lot more pics, of course, but this is a good sample. Upper left is a small cluster of popped out rollers; upper right an assemblage that might prep out nicely; bottom left a prone missing its pygidium; and bottom right a buried roller beside an impression of another roller. Not bad for the first day! We got there at about 11 am and went right until almost 5 pm. We were pretty whipped after breaking rocks... in the hot sun, I fought the law and... ok, no, but it was pretty physically demanding work for an awesome reward!
Mass extraction exercise. On the left is just getting started on day one, and on the right, I've already taken out a smaller slab from a bench I was continuing in a productive layer to get the morning started. You can see the bench behind my left boot. By the end of the day, I managed to remove about 15 or more 2'x3'x1' slabs just using chisel, pry-bar, sledge-hammer, and sheer force. I was looking for an assemblage today, so wasn't going to fool around with smaller chunks; instead, I threw them in a growing pile of discards, encouraging others to sift through them while I drove, wiggled, tanked, hauled, smashed, and split. At one point I managed to lift a slab of well over 200lbs, walk it away from my bench, place it with the bedding plane up, and start the process of splitting. Yes, I was the hulk - but, boy, did I pay for it after!
This is a view from the pit on the northwest side. This trench had been dug out almost to the water table level for the Dig with the Experts event back in May, perhaps the biggest one ever with the most ambitious excavation.
There are so many more pictures. We did find a lot more trilobites on the second day, but I want to begin prepping them before posting more pics (for the next blog entry). Here is just a mini slideshow of various scenes at Penn Dixie: