Season 2, Episode 1: SUmmer Solstice
It's summer!
Welcome back! Last season started in the autumn, so it has not been that long since last we went on our small fossil expeditions around London, Ontario. I am getting started a bit earlier this year with what I hope to be some slightly more exciting locations (but nothing outside of Ontario).
In my ongoing struggles against that most recalcitrant substance “frenemy,” tobacco, I try to stay cigarette-free by going on very long walks where, in a week, I might cover over 100 km as I wend my way through some rugged trails in provincial parks or what are called “areas of environmental significance” (the areas formerly known as “conservation areas”).
Viewers of last season may recall my finding a mucrospirifer behind the Boler Ski complex, near a dug out artificial “lake” of sorts. I reasoned that it must have been a castaway from the Arkona Formation or thereabouts (I doubt it was Widder Fm, or Hungry Hollow Fm). But where there is one, there is bound to be more. Unfortunately, the season was cut short by that most rude and intrusive of guests, winter.
And it was a very, very long winter that gave us in the neighbourhood of eight feet of total snow accumulation. And it was in no hurry to leave us, either.
So a return to that dug out, watery pit did indeed reveal that there would be more spirifers. So many, in fact, that in two short 1-2 hour visits - and with a bit of patience scanning the surface of the dried clay and scrabble - I acquired quite a number of them as they sit right on the surface (erosion does a lot of the dirty work clearing away unwanted clay and dirt).
This episode is just a season opener, so let's just throw some pictures on here for now.
Welcome back! Last season started in the autumn, so it has not been that long since last we went on our small fossil expeditions around London, Ontario. I am getting started a bit earlier this year with what I hope to be some slightly more exciting locations (but nothing outside of Ontario).
In my ongoing struggles against that most recalcitrant substance “frenemy,” tobacco, I try to stay cigarette-free by going on very long walks where, in a week, I might cover over 100 km as I wend my way through some rugged trails in provincial parks or what are called “areas of environmental significance” (the areas formerly known as “conservation areas”).
Viewers of last season may recall my finding a mucrospirifer behind the Boler Ski complex, near a dug out artificial “lake” of sorts. I reasoned that it must have been a castaway from the Arkona Formation or thereabouts (I doubt it was Widder Fm, or Hungry Hollow Fm). But where there is one, there is bound to be more. Unfortunately, the season was cut short by that most rude and intrusive of guests, winter.
And it was a very, very long winter that gave us in the neighbourhood of eight feet of total snow accumulation. And it was in no hurry to leave us, either.
So a return to that dug out, watery pit did indeed reveal that there would be more spirifers. So many, in fact, that in two short 1-2 hour visits - and with a bit of patience scanning the surface of the dried clay and scrabble - I acquired quite a number of them as they sit right on the surface (erosion does a lot of the dirty work clearing away unwanted clay and dirt).
This episode is just a season opener, so let's just throw some pictures on here for now.
I very much encourage you to visit Komoka Provincial Park with its lush and interesting trails along the Thames River, and for sometimes drastic changes in biomes from typical (but beautiful) Carolinian forest to beds of ferns, to open grass fields, to pine areas where the ground is choked in needles.
Because I know viewers of last season were so worried that I wouldn't post a picture of yet another coral. This was along a limestone wall at the end of Warbler Woods, north end.
Ok, so we're back behind the biggest "mountain" at the Boler ski complex. At this time of year, our amphibious friends have graduated from tadpoles to frogs. This spotty and spiffy fellow is no larger than your pinkie fingernail.
Now there's a spirifer haul! 32 new specimens acquired from the Boler "lake" in about 3 hours.
This spirifer is ready for its (blurry) closeup. Are you as thrilled as I am with these nicely articulated specimen? Somewhat resembles a pirogi.
Vuggy cross-section of rugose coral showing some banding, slightly encrusted with calcite. Location: manmade lake near Optimist Park / Boler Mountain.
A hash of brachiopods and solitary rugose corals. Location: landscape slab at Springbank Park
Site shot of pit behind Boler Ski hill where a majority of my spirifer finds have come from. What makes this site a bit odd would be that it does not seem conformable to the lithofacies generally present in this area of the Dundee Fm. There also seems to be no other fauna present, but explainable on account that there are no large stones here.
MORE ABOUT THE DUNDEE FM
(I will be abstracting from "Stratigraphy and Facies of the Middle Devonian Dundee Formation," Ontario Geological Survey Open File Report 5848, 1993)
MORE ABOUT THE DUNDEE FM
(I will be abstracting from "Stratigraphy and Facies of the Middle Devonian Dundee Formation," Ontario Geological Survey Open File Report 5848, 1993)
The broad extent of the Dundee Fm is evident in the map above, and a simplified stratigraphy appears to the left to give some context. The dominant lithology includes, according to the Dunham scale, mudstone and wackestones, with most of them fossiliferous. Overlying the Dundee Fm is a heck of a lot of overburden and glacial till (deposits left over from the retreat of the Wisconian Glacier some 14,000 years ago), and floatstones. The Dundee Fm touches to the west on the Hamilton Group, and toward the northwest the Arkona, Widder, Ipperwash, and Kettle Point Formations.
In Descending order of age, the Dundee Fm can be broken down into 6 predominant lithofacies:
1. Bioturbated, dolomitic / sandy wackestones. Fauna include crinoidal pieces, brachiopods, and solitary rugose corals. The maritime conditions of the Dundee time were regular.
2. Thin bioclastic pulses in a cherty wackestone matrix. Fauna are dominantly crinoidal, with trilobites, grastropods, tentaculites, solitary rugose corals, tabulate corals, some bryozoa and colonial rugose corals. The maritime conditions of the Dundee time were stormy.
3. Dark brown, thin-bedded mudstone. Although less fossiliferous, there is evidence of brachiopods, solitary rugose corals, crinoid fragments, and tentaculites. The maritime conditions of the Dundee time were akin to a lagoon and dysaerobic.
4. Course grainstones and rudstones in this facies. Fauna include crinoids, brachiopods, trilobites and solitary rugose corals. The maritime conditions of the Dundee time were fairly deep waters.
5. Massive, bedded, bioturbated, argillaceous mudstones and wackestones. Dark brown to purplish and mottled (mottles are dark grey to blue and about 1 cm in diameter). The fauna includes both articulated and disarticulated brachiopods, crinoidal fragments of up to 2-3 cm in diameter, thin-valved ostracods, rugose corals of the Cystiphillum species. The maritime conditions of the Dundee time were deep waters with occasional non-deposition.
6. Light brown, dominantly crinoidal wackestones with thick packstone pulses. The fauna is similar to (5) above, and the maritime conditions were shallow and intertidal.
Most of the Dundee Fm limestone I find in London either include the lithofacies (1) and (3), with occasional bouts of (6). Along the Thames River, one may find a slight variety of the above, but much of that is floatstone. Otherwise, the Thames River is dominated by a variety of igneous float and Quaternary deposits that are all mixed in with the Devonian stones.
So, enough about the Dundee Fm. It's time to move up in the geochronology. Stay tuned in the coming weeks as I visit the much picked-over Hungry Hollow Fm near Arkona, Ontario.
In Descending order of age, the Dundee Fm can be broken down into 6 predominant lithofacies:
1. Bioturbated, dolomitic / sandy wackestones. Fauna include crinoidal pieces, brachiopods, and solitary rugose corals. The maritime conditions of the Dundee time were regular.
2. Thin bioclastic pulses in a cherty wackestone matrix. Fauna are dominantly crinoidal, with trilobites, grastropods, tentaculites, solitary rugose corals, tabulate corals, some bryozoa and colonial rugose corals. The maritime conditions of the Dundee time were stormy.
3. Dark brown, thin-bedded mudstone. Although less fossiliferous, there is evidence of brachiopods, solitary rugose corals, crinoid fragments, and tentaculites. The maritime conditions of the Dundee time were akin to a lagoon and dysaerobic.
4. Course grainstones and rudstones in this facies. Fauna include crinoids, brachiopods, trilobites and solitary rugose corals. The maritime conditions of the Dundee time were fairly deep waters.
5. Massive, bedded, bioturbated, argillaceous mudstones and wackestones. Dark brown to purplish and mottled (mottles are dark grey to blue and about 1 cm in diameter). The fauna includes both articulated and disarticulated brachiopods, crinoidal fragments of up to 2-3 cm in diameter, thin-valved ostracods, rugose corals of the Cystiphillum species. The maritime conditions of the Dundee time were deep waters with occasional non-deposition.
6. Light brown, dominantly crinoidal wackestones with thick packstone pulses. The fauna is similar to (5) above, and the maritime conditions were shallow and intertidal.
Most of the Dundee Fm limestone I find in London either include the lithofacies (1) and (3), with occasional bouts of (6). Along the Thames River, one may find a slight variety of the above, but much of that is floatstone. Otherwise, the Thames River is dominated by a variety of igneous float and Quaternary deposits that are all mixed in with the Devonian stones.
So, enough about the Dundee Fm. It's time to move up in the geochronology. Stay tuned in the coming weeks as I visit the much picked-over Hungry Hollow Fm near Arkona, Ontario.