New Backyard Site

[Ludwigia]

It is fascinating though, isn't it, having your own personal field (or scree pile in this case) of research, so to speak?

[Kane]

3 minutes ago, Ludwigia said:

It is fascinating though, isn't it, having your own personal field (or scree pile in this case) of research, so to speak?

It is... and frustrating, too.  I've located a recent (2018) PhD dissertation on Ontario stratigraphy from the upper Silurian to Mid-Devonian where I can read up on the drill core samples. The biostratigraphy sections are a bit thin and dated, though (I already have much of the material the author cites, and a lot of it is pretty old!). 

[ynot]

Those are some amazing finds Kane.

Be careful You don't get spoiled with all that bounty!!!

[Jeffrey P]

Congratulations Kane. Those two trilobite specimens are fantastic finds. Very enterprising of you to exploit your local stones in such a productive manner. 

[Kane]

15 minutes ago, Jeffrey P said:

Congratulations Kane. Those two trilobite specimens are fantastic finds. Very enterprising of you to exploit your local stones in such a productive manner. 

If there are aome early Devonian specimens you desire, I’ll take you here, in addition to middle Devonian deposits st Hungry Hollow.

[MeargleSchmeargl]

Man, if only stuff this good was a short walk away! 

 

As much as I love Conasauga bugs, it wouldn't beat a backyard site, especially one pumping out goodies like these.

 

So I know Terataspis grandis is rare, seeing the absurd hype surrounding it (and malcom stating there's only ever been 2 whole ones found), but what are the number stats for finding any evidence of these guys, just to have a ballpark figure?

[Kane]

I really have no stats on that.  The matrix in which they appear is brutally hard and tends to shatter. Hunting bugs in the Devonian is not always easy. I would also think that their numbers were not that high given their status as apex predators (perhaps an inference due to their size and appearance!). I wouldn't say the hype is absurd, though! They are definitely bucket list items for serious trilobite collectors. I've never even seen a fragment for sale online. 

[markjw]

These are just phenomenal. I've been perusing the pictures like a new textbook.

[Kane]

Continuing with this thread to post a bit of a loosely collated field report after numerous visits to the site over the last two weeks. Kicking this off will be a few images of the rocks themselves. The purpose is to be able to read this exploded jigsaw puzzle a bit better. These are not rocks I took home!

 

Chalky nodules of varying sizes, devoid of fossils:

 

Rock showing layering. A very active coral layer at the top grading into wispy bituminous layers, and eventually to largely blank deposition.

[Kane]

Large colonies such as these are relatively common. Any associated layers are either blank or contain infrequent small brachiopods.

Some of the chalky nodular layers are highly fossiliferous; other times simply blank sandstone. To the lower left is a common vermicular coral hash containing nothing but more of the same inside.

[Kane]

Most times, rock showing these speckled corals are devoid of any other fauna, but not always. 

Another one of the impressive reef-builder domes; in this case, it extends almost the entirety of this rock. 

[Kane]

The more promising rocks will contain larger bryozoan colonies such as this one.

Not entirely representative, but there are some layers that are entirely riddled with these dark mineralization tracks with no other traces of fauna.

[Kane]

In the sandier/muddier rocks, gastropods and cephalopods are more common, but at the exclusion of any other fauna with the exception of the occasional small rostroconch or brachiopod. 

Another typical hash containing both rugose and tabulate coral (in cross section lower left), branching bryozoans and disarticulated white skeletal material.

Cooperative bedding planes are a luxury. In this case, lenticular coral can be seen, but many of these rocks tend to shatter rather than split.

[Kane]

Coral examples abound in this reef environment. A dirty dome:

 

Another substantial colony:

This is a single chunk of tabulate coral:

[Kane]

A typical brachiopod from the sandier layers. These can occur in abundance, and occasionally in more laminated material will easily pop out of the matrix.

Coral cross-section and a small Rhipodomella-type brachiopod.

Example of the very dark bituminous layers, which split easily but are mostly a mush of coral and a few branching bryozoans. To the right is a cross section of coral seemingly replaced by the chalky nodules.

[Kane]

Notes:

 

Consistency of rock types across the entire site suggests a single source quarry. The material would have been considered unsuitable for cement or other industrial purposes.

 

Limitations include the plain fact of these rocks being displaced from their stratigraphic context, and the perversely tough matrix in many cases that resists fracture and/or absence of clear bedding planes. The vast majority of the rocks are the light-grey limestone type that is poorly fossiliferous (consisting of a very limited and monotonous faunal presentation), making up at least 80% of the site material.

 

Several hundred rocks have been inspected and split over a period of two weeks. 

 

Unlike the Bois Blanc (hereafter the BB) Fm, there is no evidence of Paraspirifer acuminatus, and just a single instance of crinoid (not even bits are present in all but one or two cases across hundreds of rocks). The faunal assemblage seems more similar in description to Amherstburg / Formosa Reef, but entirely lacking in all of its trilobite genera save for Crassiproetus. Unlike BB Fm, there has thus far been no evidence of Anchiopsis. The isolated fragment of Terataspis grandis can be treated like an index fossil for the BB, but the absence of other typical BB fauna is perplexing — unless this can be explained by the specific endemic qualities of this niche community and its depositional conditions. It should be noted that Crassiproetus crassimarginatus is unsuitable for determining a specific formation given its range from the BB to the Dundee.

 

What is known is that there are a large number of reef-builders. Also, there is a broad range for most of the fauna that can appear in adjacent formations, frustrating my ability to identify index fossils endemic to any specific formation with any strong degree of confidence. Moreover, the abundance of Crassiproetus suggests a shallow marine reef environment given that they behaved in a way that is similar to illaenimorphs (although not as effaced as Ordovician illaenids).

 

Volumetrically in terms of trilobite specimens, Crassiproetus dominates, with Pseudodechenella being a distant second on account of less numerous examples, exclusively disarticulated genal spines, librigena, and pygidia. Trilobites almost without exception appear associated with the presence of fenestellate bryozoans, suggesting a preferred environment. No trilobites have been found in the muddy gastropod /cephalopod layers, nor the largely barren small brachiopod layers with occasional rugose coral. The beds with less numerous, fragmented bryozoans correspond with an equivalent reduction of trilobite appearances and size, favouring more Pseudodechenella fragments. This might suggest an environment where material was swept in and disarticulated en route, or the nature of tides sifting and sorting by size.

 

Rock grades from hard, thinly bedded light grey limestone containing some small coral colonies (or massively bedded containing large domal colonies) to a mostly blank interval containing small brachiopods and the occasional rugose coral; alternatively, it can also grade into a large grained sandy matrix containing almost exclusively abundant rostroconchs (mostly small) with occasional small brachiopods. This then grades into a very thinly bedded interval of almost vermicular rugosan colonies, with some lenticular examples. At some points in this arrangement, it will split into very bituminous layers that may contain some branching bryozoans. Below this may be an interval of highly fossiliferous layers containing larger fauna in a more settled environment containing large Strophodonta-like brachiopods, thickets of different species of fenestellate bryozoans, large rostronchs (with differing levels of preservation), trilobites, and assorted smaller finely ribbed brachiopods. All the material is a very distinct white skeletal material that stands out on a brown matrix that weathers from dark brown to a very light beige. Some of these rocks may be topped by the presence of very light grey chalky nodules of different sizes, almost all of which are devoid of fossils. The presence of these nodules may speak to nutrient availability in the paleoenvironment.

[Kane]

Does lightning strike twice? Spent two hours out back today and found another fragment of Terataspis. I also managed to retrieve the impression.

 

There's still more of the rock to go through, but it is buried deep, weighs over a ton, and the chisel is just not gaining purchase. I'll go back another day when I'm refreshed. Finding this made me feel pretty satisfied for the day.  

[Malcolmt]

Next thing you know you will be pulling up a complete one from that pile.

 

[digit]

24 minutes ago, Malcolmt said:

Next thing you know you will be pulling up a complete one from that pile.

We'll keep the Golden Drool Bucket on hand just in case.

 

 

Cheers.

 

-Ken

[Kane]

While putting some of my uncertain rocks under the microscope, I came upon this. Could this be fragment number three, or am I being too hopeful and microscope bleary-eyed? 

[Kane]

40 minutes ago, Kane said:

While putting some of my uncertain rocks under the microscope, I came upon this. Could this be fragment number three, or am I being too hopeful and microscope bleary-eyed? 

 

 

Whoops! False alarm. I'm a silly goose. 

 

The orientation is upside down. This is more a match for Acanthopyge contusa. Image from Ludvigsen, R. (1979) Fossils of Ontario Part 1: The Trilobites. 

 

It looks like I can remove a bit more matrix to reveal the rest of the cephalon. But, hey, it's another lichid! 

[ynot]

Way cool finds Kane!

[Kane]

Thanks! Two lichids in a day definitely makes me happy. 

[Kane]

7 hours of wrestling 300+lb rocks locked into one another, and then trying to split them (they make granite seem like butter). The usual finds, but the trip-maker would be my second cephalon example of the rare lichid Acanthopyge contusa.

[ynot]

6 hours ago, Kane said:

the trip-maker would be my second cephalon example of the rare lichid Acanthopyge contusa.