Yesterday was a good day to get out and prospect, what with the nice weather and the fact that the flora hasn't grown in yet (just some budding on the underbrush). So off we went to check on a lead I got back in November, to a spot atop the Niagara escarpment. My maps indicated that the material would be Silurian in age. To my great and utter shame (or from lack of opportunity), I have yet to find any Silurian trilobites in Ontario. That being said, Silurian outcrops represent a narrow band in southwestern Ontario, with much of it being blank evaporites, anhydrites indicative of salt which is mined (yes, we have salt mines -- a perfect place to send one's children!).
The site was an abandoned quarry where the main pit was flooded some many decades ago. The exposures were apparent, and mostly around the fake lake, running the circumference (probably a good 500-750 metres) and a depth from top to waterline of about 3-5 metres. The first thing was to check each interval along the strata. Here is just a small section of the exposed stepped wall:
A lot going on. Some layers were more blocky and massive, others were thin and seemingly calcareous. But whether they were thick or thin, they were almost entirely blank with some tough, dense tiny mineralization when split. It looks a lot more promising than it actually is. Lumpy, muddy, and blank with only a few tiny brachiopods on very rare occasion, and some burrows, and pretty tough to break cleanly. But that is the Silurian for you: plenty of largely blank layers from less than ideal deposition and preservation. There are some layers in the Silurian here that are exceptional; this was not one of them!
From the sensational Silurian! This was my major haul from probing those layers. Muddy little brachs. Well, live and learn! So off we went to do a site-seeing stop.
The Devil's Punchbowl's stratigraphic range, oldest to youngest, would be Queenston Fm (upper Ordovician) to the Lockport Fm (middle Silurian). It's a conservation area, so any excavation would be quite illegal. So, it's a take photos, leave footprints visit.
Here's a nice view of the Lockport Fm that caps much of the escarpment. Both the Ancaster and Gasport Members are shown here. Buried beneath my feet would be the coveted Rochester Fm shale, home of the great Silurian trilobites. Sigh.
There are fossils in it, of course. In the ceiling of a small cavern, a nautiloid impression. Lots of nature to see, and likely a place we'll visit later in the year by hitting the paths. So off we went to hit up one more location before heading home. This time, it was an engagement in younger rocks: the lower Devonian, Bois Blanc Fm.
The photograph washes the colour out a bit, but there is the tell-tale blue chert of the Bois Blanc Fm. We arrived at the area, at which point I got out of the car and did a very quick field scan. It was not the ideal spot to start digging, so we opted to go on a bit farther to find a better outcrop with a different faunal constituency and composition ratio. Prospecting is serious work, well beyond the weekend warrior's penchant for, say, just going to fossil parks and breaking a few small rocks with a mallet!
There are layers in the Bois Blanc that are just choked with corals, forming considerable reef systems and bioherms. The rocks here are not terribly ideal for faunal diversity, and so I'm moving on...
Now here we go. Yes, there will still be corals blocking the view, but these layers are a thinner, blue-grey, highly calcareous shale that splits nice and easy. It has the same colour and consistency as the Verulam Formation, and the similar issue of not always being able to make out the fossils from the matrix when freshly split as opposed to weathered. In the shot above, what appears to be a crinoid head is rolling along with a toppled rugose coral.
Aha! Bingo. There's not much left to the trilobite pygidium here, but I have an eye for trilobitic shell material. Only the margin is preserved here with the underlying coral poking through. This was all the evidence I needed to get cracking into this layer. I knew there would be bugs, but the question remains as to what will result in the best return on investment in each layer?
A much more definitively diagnostic trilobite tail. Just as a refresher, the (work in progress) list of trilobites in the Bois Blanc include the following:
?Dalmanites comis (Hall & Clarke)
? Dalmanites phacoptyx
?[Kettneraspis] callicera [The Acidaspis of Hall & Clarke]
Pseudodechenella sp. aff. clara
Pseudodechenella sp. aff. nodosa
Note that the only phacopidae in the group is Burtonops cristata. There is a species with less microsculpture (Viaphacops pipa) that I need to add to the list here. So, let's settle the difference and call it Burtonops sp. -- At least for now. As a small sidenote, these two species were once Phacops cristata and Phacops pipa (and before that, Phacops cristatus var. pipa). Well, once all the Phacops of eastern North America were taonomically reclassified so that Phacops does not apply here as they do in Morocco, names were changed (for example, Phacops rana = Eldredgeops rana). And so these very, very similar species got split into two genera: Burtonops and Viaphacops. Confused yet?
Another Burt the Bug, this one enrolled and crushed to show the anterior/ventral side. This shale is fragile in spots, which is good to know when it comes to likely preservation (and the need to keep the field kit well-stocked in super glue). That horn-like feature to the left? Not quite sure what it is. I have some ideas that range from the banal to the wishful.
So not a bad outing at all. It began as a failed prospect and turned into something very promising. I only spent 45 minutes at this new spot, and there is a good amount of material to get through. There is some urgency, though: the spot is slated for development and will be buried under houses as soon as construction projects are given the green light to resume. It means I need to hope for the grand trifecta of time, weather, and opportunity to make the most of the spot before it is gone forever.
And this also makes the 40th day of the 2020 season. Out of three slated prospect areas, only one was viable, but batting .333 is not bad at all given that prospecting new sites usually has a success rate of about 1 out of 10. I've also encountered one other site by accident (the Onondaga stuff). So far, I've visited 6 spots total, 4 of which are viable. I haven't even been to Arkona yet this year! This is pretty good given that the borders are shut tight, and it is doubtful that our one last quarry in the Ordovician will be letting us in this spring.
Of course, this is just the first few steps into an adventure that may see me in much longer, sustained periods of prospecting, farther from home. As always, I'll keep this place updated when I can.