Over the span of about ten days, I've been able to squeak out some very local prospects, rummaging through river worn glacial erratics at various spots. These are always the source ingredients of mixed Devonian salad, but after a time it is much easier to pick out the formations on the basis of recognizable matrix types. For instance, it is fairly easy to pick out Bois Blanc Fm material since it is, by volume, a whole lot of chert with the appearance of sometimes giant coral that are blue in colour. Whenever I encounter that lithologic type, I get excited as it provides a reprieve from the usual crappier layers of the Dundee Fm with its litany of burrows or brachs. That excitement can easily turn into frustration when one sits down to split, as we are talking about sometimes dense balls of hard chert, the striking of which sends up little flinty missiles that can slash exposed skin. There is a good reason why First Nations made their tools from this kind of stuff! Locked in the chert are fossils, sometimes incredibly diverse and numerous ones, amidst all the horn and tabulate coral. Brachs, gastropods, occasional bryozoans, and of course trilo-parts appear. The one challenge is that, apart from the occasional sandier parts, there are no bedding planes and so this rock fractures where it wants to fracture, generally right through fossils. This means collecting all the pieces, and potentially gluing them back together to be prepared at home... ...And there is no fresher hell than working with solid chert. At times it is like trying to scratch a block of iron with a butter knife. And extra special care is required to move slowly as chert likes to shatter and chip along its own crystal form, at times conchoidally (in mass clumps) or just as partial crystals, and it can take fossil shell with it. With that long preamble out of the way,. 2021 was not so much the year of the Terataspis as it was in 2020 with that one bountiful (now vanished) site. Not even a trace had been found in any of the local erratics across many locations. But, I decided to take a look at some other spots I had either only skirmished or turned my nose up at in the past. Time to perform due diligence in the Devonian, as I may be the only person who spends this much time in it around here! The first stop was about 20 minutes from my home. Finding the right matrix, the trilo-fauna began appearing in fragmentary form (as usual): Pseudodechenella, Crassiproetus, Calymene platys, and the phacopidae (either Burtonops or Viaphacops -- never enough of the specimen left to make that diagnostic distinction). And then appeared the distinct tuberculate and large fragments of Terataspis. Where is it, you might be asking. It's there, and it's buried. Some closeups: Some of the images make it a challenge to see, but this is a pygidium part that continues into the (miserable) rock. At a second spot (also a 20 minute walk from my house), more to be had: Again, issues showing depth and so forth creates a challenge in showing what is here, but this is a pygidial spine with its characteristic branching. I prepared the one piece and eventually glued on the other after reducing the matrix size... None too easy as the Dremel diamond wheel struggled while throwing showers of sparks, so it meant careful work with the angle grinder, and then back in the box for the tedious grind with the ME-9100. I neglected to snap a photo of the single piece that had been worked fairly significantly prior to gluing the top part back on, which has obscured a lot of the work I've done. Without the piece in hand, depth perception issues, lighting, and the usual impediments of photography make this specimen look... hopelessly unclear! In hand, however, it is fairly identifiable. It is simply in that in-between crappy state that occurs to so many prep projects that require glue-downs. The fragment is fairly 3D with branches extending upward at an angle, so a lot of care is needed (and a lot of patience to get through this hard chert!). And then it was back to site #2 for more. This is the ventral shell of the glabella and glabellar furrow. I had to glue it all back together on account of the way these rocks shatter, but it is a substantially sized piece measuring at least 5+ cm wide. Upon zooming in on the furrow, one can see beekite rings. And here be the steinkern. That is one big glabella, and there is more of the fragment in the rock. The question turns on whether or not to glue the ventral shell to the steinkern and prep down. I am thinking it should have at least one or maybe both lobes, but obviously no cheeks.
I did find one other fragment of lesser interest, and even a few very tiny bits I left in the field. I wouldn't say this makes for a photo finish for the season, but as the clock runs out and the temps drop further with snows coming, I can't say this is the worst way to end an otherwise pretty good season with a lot of interesting trilo-surprises. Next post may either be the results of some prep or purchase, or possibly the end of season wrap-up. Comments are closed.
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Kane Faucher
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February 2024
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