With the warmer weather, I've managed to get out four days over a number of spots, mostly in the Dundee Formation. Most of these trips were checking in on mostly tapped out locations near me, but a few new prospects were thrown in. With the exception of the last site in sequence, I didn't take home much. What I did take home was fairly paltry and fragmentary. The Dundee Formation is highly variable. An enormous formation, it may have six main lithofacies listed, but this does not account for lateral variation where some spots may be more chert-dominant or sandier pulses intermixed. It would actually make some sense to split the formation up into distinct members. Much of the work in the Dundee (Uyeno et al., Birchard) focuses on conodont zones, which can be particularly useful when it comes to gradational facies, but not enough is said about the macrofauna. There is very good reason why fossil collectors do not flock to Devonian rocks earlier than Arkona: they are miserably hard, sometimes erosion-resistant, other times crumbly, or have very poor preservation. At other times, it is nothing but coral and fragments. The only tool I ended up using in the field was my hand sledge. All that being said, there is a need to explore the formation in much more detail and to persist (in my case) in creating a reliable trilobite faunal list of these units. Some of these units are more cooperative and trilobite-dense than others. SITE 1 The material is very ugly. Pitted, occasionally dominated by a vermiculating chalky chert, or even crystalline chert that breaks conchoidally in blocs. There can be fossils (and even trilobites) in this material, but it takes patience and a keen eye. Any trilobites tend to blend with the pattern and colouring of the matrix if it is this mottled, making them much harder to see. Occasionally, substantially large coral colonies can be found as in the photo on the left. On the right, an infrequent sandy pulse containing some small rostroconch and ramose bryozoan fragments. The chances of finding more fossils occurs in this lithology, and generally the presence of bryozoans increases the odds of finding trilobites as they seemed to like to party together. The biggest rostroconchs at this location. They were not rare, but hardly common -- again, appearing mostly in the sandier pulses. Other notable bedding varieties included similar material to that of Amherstburg with the dark brown on brown tangles of horizontal burrow traces appearing as stains. The only evidence of trilobite after a few hours of busting this material. I reason this is an Odontocephalus on account of the pygidial ribbing, size, and morphology of the pygidial axis. A quick exploratory prep to reveal more of the features was a bit problematic due to the crystalline nature of the matrix and its relationship with the shell. I would return to this site a few days later for a more proper examination. Site 2/3 A small one-day break from the Dundee saw me out exploring the early Devonian. The focus here would be the Bois Blanc Formation -- itself another immense geologic unit with a lot of variation both vertically and laterally. Unfortunately for me, I was in the wrong spot. A visit to the Silurian-Devonian contact was absolutely devoid of fossils save for one very abraded coral, all of it set in finely bedded, large-bloc sandstone possibly indicative of shoreline or even sabkha. The Bois Blanc Formation finds were fairly underwhelming. In terms of trilobite genera, a few Anchiopsis pygidia, a Crassiproetus pygidium, and on the reverse side of this rock a fairly disarticulated Burtonops. Judging by the grainy matrix, it just isn't a suitable facies for finding well preserved trilobites. Site 1 Again Returning to the first site for a more systematic analysis, a few more trilobite genera were found. On the left is Mystrocephala, and on the right a plump Crassiproetus. Pseudodechenella are generally like cockroaches in this formation, but only a few fragments of them were found at this location. On the right, another plump but crushed Crassiproetus. Calcite crystal clusters occasionally appeared, either in the rhombohedral form as seen in this photo, or as pyramidal points as vugs in the rock. On the right is perhaps what we can call my "prize" find of the day: an Odontocephalus entirely composed of chert. Sadly, the posterior pygidial process is gone, but this differs from the same genus at another location on account of its width. Site 4 This site is by far the most productive, and a known one to me as I had collected there numerous times last year. It is composed of a sandier facies with beds supported by giant brachiopods to the extent that it seems more brach than matrix. This material also boasts an impressive abundance of rostroconchs, as well as a virtual buffet of Devonian fossils: bryozoans, gastropod steinkerns (high and low spired), occasional coral, rare stromatoporoids, and of course trilobites -- always fragmentary. The paucity of coral and absence of crinoidal debris is suggestive of possibly an upper shelf and near-shore tidal environment. The material is well sorted and certainly not in life position. Many of the fossils are silicified, apparent by the white chalky film on the trilobites and rostroconchs, but the brachiopods seem to maintain their natural shiny nacre. Splits along what amounts to busy bedding planes will commonly separate between the trilobite's delicate chalky shell and the steinkern. Only about 10% at most of these rocks are viable for splitting if they have developed cracks due to water-erosive forces and the presence of profuse brachiopods that make for a natural weakness in the rock. Still, the only tool required again is a hand sledge. The rest of the rocks are poorly fossiliferous crystalline chert horizons or a poorly fossiliferous orange sandy facies where a few broken fossils appear sporadically. By volume, Pseudodechenella are the most conspicuously present in this material, sometimes appearing between 3-12 times on a single plane as pygidia and free cheeks. On the right is a partially covered and small Coronura that I will be doing some light prep to reveal more of to determine if the pygidium is complete. And, by volume, Coronura takes second prize, albeit usually as fragments -- usually just a fragment of a single pleura! This should not be surprising given their customary large size (up to 50 cm) and the tidal churn that has a higher probability of disarticulating larger examples. They simply cannot survive the tides. On the left was my first of the day's encounters with the Odontocephalus n. sp., in this case just a tiny fragment of the anterior cephalic denticles. On the right, a rare sight: a solitary brachiopod. The size and wings are not what make it rare, but that it appears largely alone in these profuse layers. My first encounter of the day with the pygidium of Odontocephalus. This one is in rough shape and not diagnostic enough for me to keep. The rest of the day would not yield the greatest pygidia of this undescribed species. On the right is how the Coronura usually appear: fragment of a pleura. Another Odontocephalus with skin on one side and steinkern on the other. This was by far the best preserved example of this species for the day. An oddball, and possibly plant material as opposed to an in-filled burrow. On the right, positive and negative of a smaller Coronura. Almost! One of the important diagnostic features to describe this species is to have a very crisp and complete pygidial posterior process. This one is achingly close. On the right is another oddball that looks like an almost complete trilobite. I will be putting this under the scope and scribe soon. I brought this home for archiving purposes to show the general fauna in this facies. The red numbers indicate a convenient index of the most common trilobites in this material, neatly lined up: 1. Odontocephalus 2. Pseudodechenella. 3. Coronura. The bottom line? I'm doing my due diligence in frustrating, commonly parsimonious, brutally hard, and unforgiving formations to complete the trilobite faunal list, but also to secure scientifically significant specimens. This year so far has been a bit of a disappointment, so I'm hoping my fortunes change soon as the season progresses. I may need a break from the local haunts to collect outside of southwestern Ontario if I hope to find complete trilobites. UPDATE: I performed some preliminary scribing on the oddball piece and confirmed that it is indeed a trilobite, albeit broken and missing some parts from what nature took away from it. Still a lot more to uncover on its left side, this is indisputably a Pseudodechenella sp. Although ridiculously common in the Dundee from cheeks, pygidia, and isolated pleural bits, it is a rare treat when they come out nearly complete like this. One of the tell-tale signs apart from the morphology of the pygidium is the pair of nodes positioned at the posterior lateral sides of the glabella. It will take some care and time to make this one more presentable, but I'll go ahead and declare this first blood on a (near) complete trilobite for 2021.
It's truly spring. The snow is virtually gone down here in SW Ontario. We even recorded a high of 20 C this week (although the temps look to dip toward more seasonal norms for the following week). I have been out in the field, checking on my crops, and prospecting a relatively untouched one. I can tell you I whiffed three times, and ate more than my share of Devonian trash salad. But on the upside I can say I bumped into 7 trilobite species this week, even if all of them were fragmentary. Most of my time was spent in the Dundee Fm, with some little bolts of Bois Blanc Fm as the vicissitudes of glacial errata doth provide on its own whims and mercies. All three spots were local, so my expectations were already fairly low; and I have a few other local spots to check in on or prospect. I am doubtful of any game-changers until I am on the road again by the end of this semester. I hardly took photos. I barely took anything home, and of that fairly underwhelming. But here is a photo roll of some work in the Dundee today: So in the mix of mixed up stuff would be a lot of packstone filled with crinoidal debris, but also the larger brachs and rostroconchs I would find at a place outside of town. In fact, the lithology is identical. Unfortunately, that particular facies is in a distinct minority (about 1% of the material, clustered in one area). Definitely Pseudodechenella sp. pyigidia (there were much more than pictured), an Odontocephalus n. sp. pygidium (that was the only piece I took home on account of collecting all examples in the hopes of a formal description one day), and some heartbreaking Coronura aspectans fragments. I can safely cross this spot off my list of "return visits." But this week wasn't all bad. I got a prep job done and some great stuff from the Postal Formation. First up, loose-end prep. Since my Pferd stylus shattered, and it will be six weeks to get a replacement, any prep will have to mostly rely on abrasion. I was looking in my display cabinet and noticed some trilobites that I had parked in there that I didn't really spruce up. Back when I found this one several years back (a Flexicalymene senaria roller), I didn't have the tools or techniques to do more than stick it in a membrane holder with its other cousins. The site where this was found has been closed to collectors now for several years, and it is a tragedy -- we are talking full exposures of the Bobcaygeon and Verulam Fms in Simcoe County. When it came to trilobites or cystoids, pure gold flowed out of this quarry. I was too recently back into collecting to appreciate that, nor was I skilled enough to read the rocks far better. So this was the dirty bugger: It's just a Flexi roller, right? These things roll on out of the walls and into talus. They are common to the point of nuisance. Well, maybe not so much in Ontario as opposed to Indiana roadcuts, but they rarely get much love. People prefer prones. Many of these rollers I see on the market are just brutal blasts that fur over the finer microsculpture. I decided to take my time with this one under lower pressures. Result. I could do just one more minor pass and blow out the dolomite, but all the tiny granulations are intact. Sadly, it is missing the tips of the cheeks, but this is still a job done with care. For me, it was a loose end that needed tying up. As temps dip again, I may dig around for similar adventures. Ironically, I've prepped tons of F. senaria prone, but not rollers. I mentioned the Postal Formation, most often so kind. First up is a prep job for me, but I have to wait until my Pferd stylus arrives. This represents winter prep project 4 of 4, Dysplanus acutigenia. It is fully enrolled. I might decide to free it of its matrix entirely, but that is a decision I can make once I get into it. Here's a real gem. The photos hardly do it justice. This is a semi-prone Calymene clavicula of the Silurian Henryhouse Formation, Arbuckle Mountains, Oklahoma. Most of the ones I've seen are just disarticulated messes. This one my good friend sent my way. And this other acquisition was a surprise. When one hears of the McKay Group, one expects the usual Cambrian suspects, but this is a more obscure taxon. Kendalina greenensis from Bull River Valley, BC. So, the season is too early for me to expect my "Terataspis moment" like I had back in May 2020, or the species list busting trips to Manitoulin and Quebec, but rest assured those very productive trips are in the finalization stage. I'm not sure I can top 2020, but I sure can try -- time, opportunity, and my tools willing!
As the fourth of the bugs is set to arrive over a month from now, this will have been my final prep of the winter season as I transition to the collecting phase this coming week. This still needs a lot of love, but my Pferd scribe stylus shattered. With a shipping date of six weeks for a replacement, I'll put this aside for now. It was initially sold as a Hollardops, but I could tell it wasn't on account of the long, pointy pygidial lappets. I reasoned it might be a Metacanthina initially. Like I said, still needs a bit more love, but I'll put it aside for now as a work in progress because I freely admit that it looks like trash in its current state. I've already done some very light resto in the cracks that were missing pieces of shell. As my friend SM pointed out, it is not a Metacanthina. I could tell that the genal spines were too big and broad relative to the rest of the body, and the pygidial lappets in their more splayed attitude strongly suggest this is a better fit with Mrakibina cattoi. At 5 cm on the nose (2") it is a pretty good size for the species. It is actually a bit more relieving that it turned out to be this taxon rather than Metacanthina, as that genus among the Moroccan asteropygids is a hot mess with way too many undescribed species.
Likely starting Tuesday, I'll be out in the field. My early season focus will be on Devonian deposits at a number of undisclosed locations, including a prospect here and there. It is time to put down the prep tools and replenish my stock while doing my usual chasing after trilobite taxa that have been underreported, or not reported at all. I continue to do my scientific duty by collecting all examples, which sit in numerous flats, in the off-chance that someone may decide to work on revising some of our Devonian bugs. If any formal descriptions are in the offing, no one will bother erecting a new taxon without having numerous examples to draw on, so it behooves me to do my part -- not that anyone is working on Ontario's Devonian trilobites at the moment since it isn't quite sexy enough to secure research funding. So goes the vicissitudes of research! My next update may show a few finds, but obviously location information will be withheld. Some of the finds may have to wait until the end of the season. |
Kane Faucher
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February 2024
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