Spring roundup

Field time has fallen into its usual summer doldrums, but I did manage to get out in the springtime to a number of places. This post will give a few highlights. 

Apart from some more or less local Devonian dabbling in the early part of the spring, there was not much from those prospects worth reporting beyond filling in some interesting geological gaps with respect to lateral facies changes in southwestern Ontario. It would not be until mid-May when I would find myself in Quebec City area, and even up north in Lac St Jean. 

Quebec City Area

The Neuville Fm (somewhat equivalent to Ontario's Cobourg Fm) is no mystery to those who live or visit the Quebec City area for fossils as it is one of the most wide-ranging of the Ordovician formations to be encountered. I can post a few finds made with a couple of good fossil comrades across several already known locations just to give others a taste of what is typical. What is more interesting is the taphonomic differences as we proceed laterally across the sequence. For those who are keen on such details, I would recommend some of the classic works of Foerste. 

Some crinoids. By far, the most common crinoid would be Ectenocrinus, followed in lesser abundance by Dendrocrinus, and the diminutive Cincinnaticrinus. There is currently a fulsome revision being done on the crinoids of the Neuville Fm that may include some variants of the already known genera, if not add some that have yet to be known in the literature. At times, one can be fortunate to find pieces -- or complete articulated examples -- of trilobites. Possible, but certainly far from common. 

The most abundant trilobites in the Neuville are Ceraurus pleurexanthemus and Flexicalymene senaria. A half dozen examples pictured above are in various states of preservation and orientation (one location commonly had them flipped in the ventral aspect). Typically speaking, the more buried the bug (as in the third image in this cluster), the better the chance it will be complete without any missing eyes, genal or pygidial spines. 

The other common trilobite is Flexicalymene senaria. In some locations, they could come out quite large. In fact, of the three of us collecting one site, we each came away with an example of about 5cm (2"). Pictured above are a few I brought home, including a roller, a contraflexed one somewhat on its side, a plate of three (dorsal, vental, and roller), and two others where the one on the left is complete, but I suspect the larger one on the right will be incomplete (or have its cephalon tucked underneath). 

Inasmuch as this taxon is considered common to the point of being essentially the cockroaches of the Neuville, there are some facies where they are entirely absent, whether that be vertically down the stratigraphic column, or laterally pending the depositional environment (nearshore, below or above tidal wave base, etc.). In fact, in one location they are replaced entirely by a different calymenid, Gravicalymene cf. magnotuberculata, in a zone where even Ceraurus are scarce to absent. 

That said, there is one uncommon to rare trilobite one might encounter in the material, and it also represents my trip maker: this large Meadowtownella​ n.sp. Just a surface find, and although that edge is cruel, it still has one intact cheek, which is far from typical for this trilobite.

Lac St Jean

3-4 hours north, via a picturesque winding highway through the mountainous Canadian shield with its sprawling pines, we arrive at Lac St Jean. Very much akin to Timiskaming in northern Ontario, Lac St Jean is also an outlier, set in a valley surrounded by shield rock. Both areas boast paleozoic onlap deposition. Mountains give way to flat farmland. 

The major researchers of this area would include those such as Desbiens and Lésperance. It was, in fact, Desbiens' thesis that provides a great deal of geologic context (including a tantalizing list of potential trilobites!). All that said, the main limestone formations (by order of oldest to newest) Simard, Shipshaw, Galets, and the shale formation of Pointe Bleue, all tend to be fairly high energy environments, so that mostly only the hardiest organisms not prone to a lot of disarticulation such as brachiopods, gastropods, and the occasional Fisherites tend to appear complete. Trilobites are a very distinct minority, usually only showing as parts. Some of the formations are massively dense blocs, or very hummocky. The number of complete trilobites found in the area in the last 40 or so years could likely be counted on two hands (considering just the limestone formations, not the uppermost shale where the olenids reside). 

Just as a souvenir, I picked up a small Fisherites, a pair of gastropods (high spired and plani-spiralled). To the right is a rather sad Triarthrus eatoni. There was once a location to find a lot more of these, but sadly the area is off limits. The lakeshore has also been rehabilitated with riprap, so all that may be left are gravel quarries and construction sites. 

Scanning the limestone is a slow and steady process of looking closely, flipping rocks, and taking your time. Many of these locations have not been worked in decades, and have seen many other collectors over the years. That said, there is always the potential for surprises. Finding fragments of trilobites in this material is not a form of failure here, especially if they are rare. In the literature, there is some controversy over taxonomic assignment and even age correlation to Ludvigsen's 7 Ontario zones, so there is a chance that this "arctic fauna" might represent new species. To the left is the cephalon of the diminutive lichid, Hemiarges paulianus​, and on the right the thoracic segments of a cheirurid. 

A typical hash plate from the busier intervals of the Shipshaw Fm. If one looks closely, there are some cheirurid parts. On the right side are two Calyptaulax ​heads. 

Even Flexicalymene fail to be as common as they are in equivalent aged strata. On the right is another cheirurid fragment, but the ornamentation suggests a species that is more exotic than the more common variety. 

Thaleops parts were relatively the most numerous, alongside Isotelus pieces, so I plucked only the best examples. On the right is the nice prize of a hypostome belonging to Hypodicranotus. So although no great shakes in the finding department, it was a lovely experience and a geologically fascinating area. In some locations, one could see the abrupt disconformity between the Precambrian anorthosite and the overlying Ordovician strata. 

miscellanea

I had entrusted a friend of mine to perform some prep on my behalf, as my equipment has been very capricious as of late. I had found this asaphid back in November under nail-biting circumstances in having to extract it from a giant bloc without a saw. I had my suspicions it was the rarer Ectenaspis as opposed to the more common Isotelus (complete examples of either are worth keeping, but the former is a rare delight). After extraction in its ventral state and safe transport home, I slathered the exposed ventral side with tons of Paraloid to stabilize it. My prep buddy said it was likely an Isotelus, but after some time with it he gave me the good news that it was indeed an Ectenaspis.​

Highest kudos to my friend's prep expertise here. This one is almost paper thin! In fact, if I hold it up, I can see light through the anterior cephalic projection. Adding to the agony of this prep were some stubborn, caked on bryozoans that decided to make a home on this one's carcass. Although some of the pleural tips are missing (I did find it ventrally in a bloc that had weathered a bit), it's still a cabinet sitter.

Upon my return home, there was a package waiting for me from an auction I had won. 

L: petrified wood from Blue Forest in Wyoming, with chalcedony. 
R: St Clair fern and leaf from the Florissant in Colorado.

L: A lovely collection of shells from the Tamiami Fm of Venice, Florida
R: A good assortment of shark teeth from the Peace River in Florida, with a gator tooth at the bottom. 

L: A few crinoid parts from the Mississippian Burlington limestone of Iowa
R: A rare cookie cutter shark tooth (Isistius triangulus​) from North Port, Florida

L: Devonian brachiopods from the CerroGordo Fm of Iowa + a Prasopora from the Ordovician Decorah shale (also from Iowa)
R: Hormotoma major, Hormotoma trentonensis, Lophospira fillmorensis (Ordovician, Galena Fm, Fillmore Cty, Minnesota); Liospira obtusa (Ordovician, Decorah shale, Iowa); Clathrospira subconcinna (also from the Galena Fm of Minnesota).

L: My real auction target was this complete enrolled Anataphrus vigilans from the Maquoketa Fm (Elgin Mbr), Clermont, Iowa in the Cooper Quarry.
R: A surprise gift in the auction package was this Menomonia calymenoides from the Cambrian Eau Claire Fm of Strum, Wisconsin -- a rarity in finding this one complete.

​I think the blog is pretty much caught up now!