It is still rather remarkable that I'm able to get out for fossil adventures this late in the year, although there is no doubt that winter will have its final say in the days to come, possibly as soon as New Year's Eve.
On December 27, myself and two other collecting comrades made our way to another part of the Devonian of Ontario for an all-day dig event at an undisclosed location. The focus may have been on crinoids, but other stuff came out, too.
Preservation can be a bit iffy on this material, but here is a crinoid terminating at the top with a calyx and its attendant spinplatycerid. It will look a lot nicer once I get it in the prep lab.
A collection of calyxes, still dusty from the field. The one near the bottom still has some of its arms showing. These should all prep out nicely.
A calyx parked between an interesting plant fragment above, and crinoid arms below.
Closeup of the underside of a calyx showing the stem/cup attachment.
A real oddball we found. This is plant material, but note the fascinating barbs.
Trilobites, too, although they tend to show up rather small in this layer (larger ones are quite flaky and do not preserve well). A trio of Eldredgeops rana rollers on the left, and a mini roller on the right (a few millimetres wide!).
In all, a good outing and everyone came away with something. But today (December 28), it is back to my spot for another go at the Amherstburg material in search of more lichids and the dim hope of a complete proetid before the snows be a-blowin'. I'll update this post later with whatever I may find if I don't strike out.
Managed to spend two more days at my site. No major fireworks to close out the collecting season, which I officially put to bed on December 30th, 2019. I'm mostly left with second- and third-best rocks at this point that tend to be harder and more often blank or small bits. Still somewhat productive, though.
An Echinolichas in pretty poor shape. I found another similar one the day before that was in even worse condition. That being said, it pays to split the harder/blanker intervals as this lichid likes to appear alone.
Bit of a blurry shot since I was too lazy to bring out the Olympus, but it is likely another tiny Mystrocephala stummi.
I picked these up because they were interesting. The first is a completely chert-ified rugose coral slice, and the second is a monster Strophodonta brachiopod.
It is always sad to bid farewell to a collecting season, but there are a few things I won't miss... The brutally tough stone, the bullet-like shards that strike my shins and face, the tedious process of having to unlock rock that stubbornly holds on even if it wiggles, the endless parade of corals and rostroconchs.
And I've already dipped into post-season activities in spending a few hours in the prep lab and getting back to drawing and research. This blog will not be left in winter silence!
"Yes, this was the last day... I mean it this time!" -- Given the number of times I called an end to the 2019 fossil season (November 1st, 20th, and 26th), I seem to have embodied the postmodernist novel's unreliable narrator.
But when the temperatures are going above freezing, and there is little to no snow on the ground, why would I wait until spring? As the winter forecast is calling for brutal snowstorms, the polar vortex, and likely a long delay for spring, getting out there whenever the conditions are lined up makes complete sense. This is the unexpected surprise opportunity after returning from Jamaica.
These are the shortest days of the year, so I had to wait until about 8 am for the sun to rise, and then another hour for it to warm things up a bit. When I reached my Amherstburg Fm site, the ground was still frozen (including some of the rocks), with some snow and ice. But after a few hours the temperature soared to about 6 Celsius(!), but not warm enough to melt the snow in the rocks' shadows.
It was not the trip of all trips, but I did okay for this being late December.
This was first blood: a Crassiproetus crassimarginatus pygidium. This, and several other proetid pygidia, I left in the field since it would have taken too much effort to reduce the matrix just for these. And, like most trips, this was the rock that would pay out while subsequent rocks would be largely duds.
More "leave 'em in the field" specimens, mostly of the large brachiopod, Strophodonta. How big? The largest of the bunch has a width of about 3+ inches (~7.5 cm).
The nice articulation of this rostroconch (Conocardium cuneus) persuaded me to bring it home.
The tripmaker was also a heartbreaker. Pictured here is an Acanthopyge contusa pygidium, but with very nicely defined pygidial spines. Sadly, it's an impression that I noticed some time after I had been steadily reducing the bloc, and my search for the positive was to no avail -- likely lost to flying hammer blows or as a chip fallen through the cracks. I also found an actual positive of another example, but the preservation is so poor that I can't bring myself to post it here.
But it isn't over yet. Today promises to reach 8 degrees celsius, full sun, so I'll be returning. This post will be updated later.
Another not so productive day; plenty of rock split, but nothing much to show for it. A good chunk of time is spent searching for the right rocks. The fossiliferous ones with trilobites are very hard to find amid the usual blank, sparse, or complete blanks. I thought I would dedicate this portion to the process.
Scouting the right rock requires a bit of eyeballing of the outside to determine what sort of fauna (if any) would be on the inside. I also go by colour and texture, so if it is grey-white, tan, or brown, then I might go to town. Those rocks that have these features but appear blank on the outside or with too many tightly packed black wispy mineralization lines are generally either blank, filled with mineralization trails with the occasional small rostroconch or coral, or just sandy matrix supported colonial coral tubes with nothing else. If the matrix grain is too large (like sand), it is unlikely to support much else but coral and small brachs. If the rock is too fissile, it is usually also too bituminous and contains a few toppled corals and mostly dimpled stromatoporoids -- which is an indication that I'm too high up at the cap of the reef, which may have been subaerial or at least far too high energy for anything but the sturdiest to settle.
Finding a rock that meets the criteria of colour, texture, and promising vertical appearance does not guarantee that the interior will be a "trilobonanza" either. Some of these may contain just shredded bryozoans and a few small brachs, amid some toppled and broken rugose corals. When seeing that, I know the deposition conditions were far too sediment-worked and high energy to support trilobites. They may also be incredibly dense so that there is no chance of hitting a bedding plane. And by dense, I mean even harder to split than they already are. That stuff breaks in fractured, conchoidal chunks wherever the rock is weakest. Not good.
Once I come upon one of those rare rocks that seem to meet my criteria from experience with this material, I spot check the top and bottom where possible to get a sense of what "chapter" I am in the story. I know, for instance, that a top portion containing large horn coral means I have to split down a few inches below it. After that, I may also see if I can cleave a piece vertically or work my way down that way to pinpoint the busy bedding planes.
One indication that shows promise is in finding larger fauna, such as big brachiopods and intact fenestellate bryozoans. Of course, if the plane is busy in general, that can be an indication, but again not always: at times it is busy with just tiny fragments. Or filled with vermiculating tube coral. Or just branching bryozoans.
If the rock has even a single trilobite fragment showing, such as a free cheek, a genal spine, or a pygidium, it is marked for excavation and splitting. Again, there are no guarantees that the rest of the rock will be as generous.
This is an example of the process. I've wrestled even larger, armour stones, from these piles, so this is not the most challenging example:
As this rock showed some promise, I cleared away some of the overlying rock to the upper left so as to have a closer look at its layers. Compounding the difficulty was that this was early morning, and the mud is frozen, as are some of even the smaller rocks that need to be tapped with the hammer before removing. In this image, I've already done some exploratory slicing of the top and was intrigued with what I was seeing enough to continue.
Clearing away more debris around the rock. At this point, I'm unsure just how deep this runs. The small pry bar is not budging this, and I usually stop trying when the bar starts bending. What I would learn later is that this rock was running under the even larger rock to the upper right. Sometimes it is a game of unlocking rocks whereby you need to unlock the rock by removing those around it, but then you find those other rocks are also locked in by other rocks, and so on. I try to limit those instances as sometimes it seems never-ending, and I will encounter a rock that weighs over 600 pounds that I just can't budge.
By this point, it has been nearly an hour. I've done some exploratory chiseling, but the rock is too thick and dense to get clean slices. Instead, it tends to fracture upwards, which is useless as it creates rounded concavities that make splitting impossible. So why not use the sledge and swing it against the exposed upper left? No dice. All that smashing achieves is a mashing and denting. How about a chisel? Can't go too deep down on this as I'll just end up driving the chisel in about an inch and creating tons of powder and no break. What about coming from the lower right? A sensible approach...but this is a game of angles at times and what this picture does not show well is that the rocks on the lower right are on an incline while the main rock is on a slight inverted incline, which means the chisel won't go in straight.
When all else fails, and no measure of even the most awkward angles of hammer and chisel will work, or pry bar will budge for clean extraction, it is time for brute force. In this case, I exploit any visible weakness in the rock and go for a vertical split. It's not ideal as it might cleave through fossils, but sometimes you need to break eggs to make an omelette. Having exposed a chert area with a hairline fracture, in goes the chisel and down comes the sledge hammer. It isn't a big chunk, but it may help going forward. This is the beginning of the momentum in removing this one. Sometimes those cracks are superficial, and sometimes I have to repeat this chunk-split approach a few times if the rock is even larger than this one.
Hundreds of hammer blows later and some artful chisel-action, I'm able to split the top off this one. The pry bar was needed to remove it as it was partially stuck under the bigger rock, and that meant gradual push/pull in a game of inches to slide and wrestle it off. That leaves just the lower half, which is still deeply lodged in the dirt and debris.
Inspection time. Let's have a look at the upper portion. Apart from a big brach and a few big bryozoan pieces from about an hour earlier when slicing the uppermost part, this seems to have a bit of promise. I set it aside for splitting later.
Both pieces are out! The one on the left is actually quite thick (about a foot on its widest edge). A Crassiproetus pygidium is showing at the top of this one, and you can make out its impression on the rock right next to it. I'll still need the sledge to split these into more manageable pieces for the rock hammer. From observation, I note that this entire rock has just two active bedding planes. Sometimes even the bigger rocks may only have one thin plane, and these are very tightly packed. The rest of the layers tend to be sparse, broken bits or entirely blank.
So, the result of about 90 minutes of hard work and frustration? A 3 mm wide pygidium of what I suspect to be Mystrocephala. Yes, all that work and splitting for a 3 mm fragment. If I specialized in collecting non-trilobite fossils, this rock would have been more gainful. As disappointing as the ROI is on this bloc, at least it was something! Other instances have led to zip, or sometimes the rock that just keeps on giving. There's never really much certainty until you excavate and split them.
Six hours of scouting and pounding through mostly blanks and bits didn't net me much more today other than this fragment of an Acanthopyge pygidium, with some kind bryozoanal growth on its left side. I've had better days! But, the viable rocks are getting much harder to come by, and I'm having to default to the B- and C-piles.
I'm not going to say the season is done yet. There looks to be a few more good days in the forecast for one more go. I've marked two so-so potential blocs for splitting that I'll get to first so as to save time on scouting.
Xmas Eve: Totally skunked. It seemed what few potentially viable rocks I could find were just loaded with corals and uninteresting fragments, so I came home with nothing despite putting in a good six hours. I had queued up a few larger rocks two days earlier for splitting, but those were a bust. However, no sense in complaining, and this might have been only the second or third time I've ever come back with absolutely nothing to show for the effort.
Boxing Day: A much better outing than the last one. Although I can't say I came back swimming in riches, I did have much more luck.
On the left is the impression of another Echinolichas eriopis. The positive side is only one half of the pygidium, and seems resistant to good photography which would otherwise show its nice pygidial rib annulations. On the right is a lichid genal spine / free cheek that is still attached to the glabella (which itself is under a bit of matrix for me to remove). This would be a first in finding an attached cheek to this lichid (possibly Acanthopyge, but I'll have to uncover the glabella to be certain).
The new trick is not to turn my nose up at a certain B-pile type of rock that is largely blank, but of the right strata (not grey, but the light tan colour). What is blank can quite surprisingly display a sudden busy layer, but it is not obvious when reading the rock's vertical record. It means persistent trial and error splitting. I've now queued up over ten metric tons of this type material for my next return, which likely won't be until tomorrow (Saturday, December 28) as I'm due to hang out with some of my fossil buddies on a trip to Arkona today.
So just when I come to desperation (yet again) that I've exhausted my site's possibilities, a bit of itinerant, exploratory splitting has opened up new possibilities. Granted, the rock is perversely dense, frustrating in many places, and some of the rocks marked for breaking down are the size of a trunk, but I'm nothing if not determined.
I'll likely have tomorrow and Monday to get at them in search of more lichids. After that, it is likely that winter will bury and freeze all hunting trips until spring. Still, this welcome and unexpected extension of the season means I have to make the most of it!