It has to be over ten years since I signed up to receive The Alchemist Newsletter from ChemWeb.com. Over that period the newsletter has notified me of many interesting developments in many different fields. Each issue of the newsletter provides a series of well written, short summaries of recent developments with links to the articles or press releases. I’d encourage anyone with an interest in chemistry to sign up. Not only is it interesting, but it’s free.
An issue of The Alchemist Newsletter from December was particularly enlightening as a summary with the deceptive title “Rust never sleeps” details developments in determining the atomic structure of the surface of magnetite . Interestingly Magnetite, which I think of solely as the magnetic iron ore, has an increasingly prominent role in catalysis, hydrogen production, spintronics, and drug delivery systems. Further, the properties of magnetite are governed by missing iron atoms in the sub-surface layer. The surface of magnetite is not Fe3O4 but instead is Fe11O16.
The Alchemist Newsletter links to the following press release:
http://www.eurekalert.org/pub_releases/2014-12/vuot-tfd120314.php
That press release mentions:
“Perhaps the most surprising property of the magnetite surface is that single atoms placed on the surface, for instance gold or palladium, stay perfectly in place instead of balling up and forming a nanoparticle. This effect makes the surface an extremely efficient catalyst for chemical reactions...
Instead of a fixed structure of metal atoms with built-in oxygen atoms, one rather has to think of iron-oxides as a well-defined oxygen structure with little metal atoms hiding inside. Directly below the outermost atomic layer, the crystal structure is rearranged and some iron atoms are absent.
It is precisely above such places of missing iron atoms that other metal atoms attach. These iron-vacancy-sites are regularly spaced, and so there is always some well-defined distance between gold or palladium atoms attaching to the surface. This explains why magnetite surfaces prevent these atoms from forming clusters.”
If you are like me one of the things that you remember from your first geology course is that Magnetite has the formula Fe3O4 and that Hematite has the formula Fe2O3. It’s a bit of a shock to think that the formulas change at the surface.
That article made me ask myself which mineral formulas I could still remember. There were thirty-one in total (and only five were native elements).
Christopher Brett
Perth, Ontario
Journal Reference:
R. Bliem, E. McDermott, P. Ferstl, M. Setvin, O. Gamba, J. Pavelec, M. A. Schneider, M. Schmid, U. Diebold, P. Blaha, L. Hammer, G. S. Parkinson. Subsurface cation vacancy stabilization of the magnetite (001) surface. Science, 2014; 346 (6214): 1215 DOI: 10.1126/science.1260556
Friday 30 January 2015
Friday 7 November 2014
A Contest to Find the Largest Glacial Erratic in Lanark County
In 2016 the Town of Perth, Tay Valley Township, Drummond North Elmsley Township and Beckwith Township will celebrate the 200th Anniversary of the founding of the Perth Military Settlement and the arrival of the first settlers and War of 1812 veterans to our area.
I’ve been wondering for some time now how to tie this in with Ontario Highland Tourism’s promotion of Lanark County as a geotourist destination. After months of thought, and a few bottles of red wine, I’ve decided that what Lanark needs is an annual contest to find the largest glacial erratic in Lanark County that has not previously been mentioned on this web site or in a scientific report or that has not previously won a prize in a similar contest. The first contest would start in November, 2015 and will end in November 2016, with the winner and the erratic announced in December, 2016.
The beauty of this contest is that almost everyone in Lanark is blessed with glacial erratics left by the retreating glaciers. Some farmers may use a different word than “blessed” to describe the boulders in their topsoil, but those would be the ones without an understanding and appreciation of Lanark’s glacial history. As mentioned in previous postings, about 79 thousand years ago the Wisconsin glacial period started, glaciers formed, advanced and retreated, and at their maximum extent covered most of Canada and extended down into the United States. Lanark County was covered by a glacier two kilometers in thickness. When the glaciers finally retreated from Eastern Ontario about 11,000 years ago they left behind ample evidence of their former presence in Lanark County including eskers, glacial till, glacial striae and glacial erratics – all to be admired and appreciated.
I have not yet finalized the rules, categories, number of judges, entrance form and waiver, but expect that to get the contest up and running over next summer. The reason that I publicize it at this point is that I’m open to suggestions and welcome the help of everyone that wants to get involved. (It is not that I’m desperate for an article for a blog posting.)
In addition to the prize for the largest erratic, I propose prizes for the winners of a number of categories:
- largest erratic on an operating farm or maple sugar bush
- largest erratic at a sand or gravel quarry
- largest erratic within a town’s boundaries
- largest erratic other than on an operating farm or maple sugar bush, at a quarry or within a town’s boundaries
- best use of an erratic in garden landscaping
There will necessarily have to be some exclusions, including.
- not underwater
- verifiable
- not previously moved.
For the benefit of those that have recently moved to Lanark County from the city, I note that
where the glacial erratic occurs with other boulders in row along a fence line, this is an obvious exclusion as the erratic has been previously moved. I expect that some whiners are going to say that many large erratics along fence lines are too heavy to have been moved. However, men were men and oxen were oxen when Lanark was first settled. No stone that I have seen is too large not to have been moved by the first settlers. (I have to admit that I had considered adding a category ‘largest erratic along a fence line’ in order to be as inclusive as possible, but decided against this as it rewards those that have destroyed their geologic heritage.)
In addition, no one can enter that is related to one of the persons running the contest. This is an obvious exclusion as I have some large glacial erratics on my property, and I would not want to be accused of running a contest, or finagling the categories, merely so that one of my erratics could win.
I had considered running this contest in conjunction with the Annual Perth Fair that is held the first weekend in September, requiring that all entrants bring their erratics in for judging, much the same as people weigh in their pumpkin and gourds for largest pumpkin contests. However, most erratics should not be moved, as this affects their scientific value. While you would like to think that people would replace their erratics exactly where they take them from, this is unlikely to be the case. Also, I’ve talked with some of the people that run the fair, and there is a fear that people that loose would just leave their erratics for the operators of the fair to dispose of. I see that as a real concern, and not raised merely to disassociate themselves as far as possible from the contest. Who wants to be left with five ton boulders lying all around the place?
I suspect that some will argue that this contest unfairly gives those of Irish descent an unfair advantage. I make that statement because eight years ago when I mentioned to my dentist in Ottawa that I had moved to Tay Valley Township in Lanark County he told me that he had been born and raised in Lanark County, that the English had received the good land and the Irish the rocky land. Memories run deep in Lanark County. His family was Irish . I can only say ‘play the hand that you are dealt.’ If this contest does give those of Irish descent an unfair advantage, then it is poor compensation for having farmed rocky land for 200 years.
Some will suggest that I’m just too lazy to get out there to find the erratics myself, or that I’m just trying to drum up readers for my blog. I have no answer for that other than to say that I have lots of glacial erratics on my own property, and I’m not interested in a reader that reads my blog only because he or she wants to win the contest.
I should mention that not all boulders are glacial erratics. Long time residents of Perth will recall the large black boulder that for many years was a fixture on Wilson Street in front of the Perkins GM building. That was not an erratic. It was a gabbroic boulder with too many fresh surfaces to have been polished and transported by a glacier. Another clue is that it was resting first on asphalt and later on paving stones. The glaciers retreated from Perth thousands of years before that asphalt was laid down or the paving stones put in place.
A further exclusion is that the rock must not be the same as and in contact with the underlying rock. In addition, the contest organizers will exclude all rocks that have just broken off an outcrop and rolled down the hill. I also fear that if the contest takes off, some will be sandblasting rocks to make them look like rounded and polished glacial erratics. Accordingly, three geologists will be needed as scrutineers and judges to determine the winner, plus one lay person in the event of a tie. Some will ask how you can possibly have a tie with three people as the judges. The answer is that some geologist have more than one opinion on a subject, and some hedge their bet. For example, Who hasn’t looked at a granitic boulder and wondered if it was granite or merely granitic gneiss? Who hasn’t looked at an outcrop of sandstone and wondered whether it is Potsdam sandstone or March sandstone, and does anyone really care which it is?
Above I mentioned that excluded from the contest will be glacial erratics that were previously mentioned on this web site, in a scientific report or that have previously won a prize in a similar contest. Those exclusions are necessary to prevent numerous people from entering the same erratics. For those that have not read each of my blog postings, this excludes both (a) the glacial erratic, then known locally as Samson’s Shoulder Stone (and now sadly forgotten), that can be found about 11.26 kilometers east of Perth along County Road 10 (the Franktown Road if you are heading to Ottawa, and the Perth Road if you are headed to Perth) reported on in 1932 by Dr. Morley Wilson of the Geological Survey of Canada that was featured in Volume 46 of the Canadian Field-Naturalist and (b) the glacial erratics at Wheeler’s Pancake House and Sugarbush.
I’ve decided against offering a monetary prize, which would only pit neighbour against neighbour, husband against wife, and fathers and mothers against their children. Instead, the prize will be a certificate, a photograph of the winner and his/her erratic published in the Perth Courier, and the photograph of the annual winner on a plaque kept at the Perth Museum. I can see the plaque now: 2016 - a photograph of a granitic or gabbroic boulder from Lanark Highlands.
I realize that there could be a problem with the contest ending during deer hunting season. My wife has pointed out that this automatically disqualifies half of the male population of Lanark County, as men put things off to the last minute and will be too busy during deer hunting season to enter. My answer to that is that women hunt. Some hunt deer, some hunt for men and some are always on the hunt for new pair of shoes. Women hunt. I should note in passing that while I would normally assume that one of my wife’s comments directed at all men is somehow directed at me, I don’t hunt.
Every contest requires a mathematical, time limited, question in order to take it out of the anti-gambling provisions of the Criminal Code. I propose: What is the weight of your glacial erratic, to the nearest ten kilograms, assuming that most common rocks composed mainly of silicates weigh about 160 pounds per cubic foot? Some people will complain that this is a trick question designed to catch those that don’t realize that both pounds and kilograms are mentioned. Others will complain that it is a trick question designed to catch those whose erratics are comprised of marble or limestone (both carbonates, not silicates). Some will complain that we should never have adopted the metric system. Others will just complain. However, no one said that it had to be an easy question. To overcome any concerns I propose giving each entrant two tries over two days.
Of course, that mathematical question will require that all entrants sign a Waiver acknowledging that the contest organizers (a) do not encourage, condone or recommend the lifting of bounders to determine their weight and (b) are not responsible for medical or other expenses where the entrant tries to weigh the erratic. Other parts of the waiver still have to be drafted.
When to hold the awards ceremony? The obvious date is December 24 to commemorate the signing of the peace treaty that ended the war of 1812 (the Treaty of Ghent was signed on December 24, 1814) as this led to the founding of the Perth Military Settlement. However, my wife has reminded me that I am usually busy on that day finishing my Christmas shopping. I’m open to suggestions.
There is another obvious issue: When in November to close the contest? For the first year I have arbitrarily chosen November 11th, because it is a day that is easy to remember and because it commemorates the Battle of Crysler's Farm in Lower Canada. What better day then to commemorate the decisive British and Canadian victory on November 11, 1813 which convinced the Americans to abandon their campaign down the St. Lawrence River! However, many Lanark County residents have 11th of November booked each year, and that ceremony is the more important one. For subsequent years I propose that 31 sequentially numbered counters be placed in a bag and that each year’s winner draw the date for the next year, with the contest to close on the day drawn. I do realize that there are 30 days in November. Where number 31 is drawn the contest will not be held the following year. Some will complain that it should end on the same day each year so people can plan. Some will complain that if it is not held one year, then it is not an annual contest. However, it is, after all, an erratic contest.
Christopher Brett
Perth, Ontario
Addendum (November 11th):
The Town of Perth may have a connection to the Battle of Crysler’s Farm. In front of the Court House in Perth can usually be found two brass three-pounder light infantry cannons. (One is currently missing, and is hopefully just out for repair.) The cannon on the left (as you are looking at the Court House, and the one that remains) bears the inscription ‘J. & P. VERBRUGGEN, FECERUNT A 1775.’ The other cannon is reported to bear a nearly identical inscription. The word 'fecerunt' is a Latin word that translates into English as 'made, constructed, cast.' The cannons were undoubtedly cast at the Royal Brass Foundry at Woolwich, England where Jan Verbruggen and his son Pieter were the master founders from 1770-86. The cannons are said to have an interesting history: they were captured by the Americans from the British at the Battle of Saratoga, and were recaptured by the British regulars and Canadian militia at the Battle of Crysler’s Farm. Later they were presented to the Perth Military Settlement.
I’ve been wondering for some time now how to tie this in with Ontario Highland Tourism’s promotion of Lanark County as a geotourist destination. After months of thought, and a few bottles of red wine, I’ve decided that what Lanark needs is an annual contest to find the largest glacial erratic in Lanark County that has not previously been mentioned on this web site or in a scientific report or that has not previously won a prize in a similar contest. The first contest would start in November, 2015 and will end in November 2016, with the winner and the erratic announced in December, 2016.
The beauty of this contest is that almost everyone in Lanark is blessed with glacial erratics left by the retreating glaciers. Some farmers may use a different word than “blessed” to describe the boulders in their topsoil, but those would be the ones without an understanding and appreciation of Lanark’s glacial history. As mentioned in previous postings, about 79 thousand years ago the Wisconsin glacial period started, glaciers formed, advanced and retreated, and at their maximum extent covered most of Canada and extended down into the United States. Lanark County was covered by a glacier two kilometers in thickness. When the glaciers finally retreated from Eastern Ontario about 11,000 years ago they left behind ample evidence of their former presence in Lanark County including eskers, glacial till, glacial striae and glacial erratics – all to be admired and appreciated.
I have not yet finalized the rules, categories, number of judges, entrance form and waiver, but expect that to get the contest up and running over next summer. The reason that I publicize it at this point is that I’m open to suggestions and welcome the help of everyone that wants to get involved. (It is not that I’m desperate for an article for a blog posting.)
In addition to the prize for the largest erratic, I propose prizes for the winners of a number of categories:
- largest erratic on an operating farm or maple sugar bush
- largest erratic at a sand or gravel quarry
- largest erratic within a town’s boundaries
- largest erratic other than on an operating farm or maple sugar bush, at a quarry or within a town’s boundaries
- best use of an erratic in garden landscaping
There will necessarily have to be some exclusions, including.
- not underwater
- verifiable
- not previously moved.
For the benefit of those that have recently moved to Lanark County from the city, I note that
where the glacial erratic occurs with other boulders in row along a fence line, this is an obvious exclusion as the erratic has been previously moved. I expect that some whiners are going to say that many large erratics along fence lines are too heavy to have been moved. However, men were men and oxen were oxen when Lanark was first settled. No stone that I have seen is too large not to have been moved by the first settlers. (I have to admit that I had considered adding a category ‘largest erratic along a fence line’ in order to be as inclusive as possible, but decided against this as it rewards those that have destroyed their geologic heritage.)
In addition, no one can enter that is related to one of the persons running the contest. This is an obvious exclusion as I have some large glacial erratics on my property, and I would not want to be accused of running a contest, or finagling the categories, merely so that one of my erratics could win.
I had considered running this contest in conjunction with the Annual Perth Fair that is held the first weekend in September, requiring that all entrants bring their erratics in for judging, much the same as people weigh in their pumpkin and gourds for largest pumpkin contests. However, most erratics should not be moved, as this affects their scientific value. While you would like to think that people would replace their erratics exactly where they take them from, this is unlikely to be the case. Also, I’ve talked with some of the people that run the fair, and there is a fear that people that loose would just leave their erratics for the operators of the fair to dispose of. I see that as a real concern, and not raised merely to disassociate themselves as far as possible from the contest. Who wants to be left with five ton boulders lying all around the place?
I suspect that some will argue that this contest unfairly gives those of Irish descent an unfair advantage. I make that statement because eight years ago when I mentioned to my dentist in Ottawa that I had moved to Tay Valley Township in Lanark County he told me that he had been born and raised in Lanark County, that the English had received the good land and the Irish the rocky land. Memories run deep in Lanark County. His family was Irish . I can only say ‘play the hand that you are dealt.’ If this contest does give those of Irish descent an unfair advantage, then it is poor compensation for having farmed rocky land for 200 years.
Some will suggest that I’m just too lazy to get out there to find the erratics myself, or that I’m just trying to drum up readers for my blog. I have no answer for that other than to say that I have lots of glacial erratics on my own property, and I’m not interested in a reader that reads my blog only because he or she wants to win the contest.
I should mention that not all boulders are glacial erratics. Long time residents of Perth will recall the large black boulder that for many years was a fixture on Wilson Street in front of the Perkins GM building. That was not an erratic. It was a gabbroic boulder with too many fresh surfaces to have been polished and transported by a glacier. Another clue is that it was resting first on asphalt and later on paving stones. The glaciers retreated from Perth thousands of years before that asphalt was laid down or the paving stones put in place.
A further exclusion is that the rock must not be the same as and in contact with the underlying rock. In addition, the contest organizers will exclude all rocks that have just broken off an outcrop and rolled down the hill. I also fear that if the contest takes off, some will be sandblasting rocks to make them look like rounded and polished glacial erratics. Accordingly, three geologists will be needed as scrutineers and judges to determine the winner, plus one lay person in the event of a tie. Some will ask how you can possibly have a tie with three people as the judges. The answer is that some geologist have more than one opinion on a subject, and some hedge their bet. For example, Who hasn’t looked at a granitic boulder and wondered if it was granite or merely granitic gneiss? Who hasn’t looked at an outcrop of sandstone and wondered whether it is Potsdam sandstone or March sandstone, and does anyone really care which it is?
Above I mentioned that excluded from the contest will be glacial erratics that were previously mentioned on this web site, in a scientific report or that have previously won a prize in a similar contest. Those exclusions are necessary to prevent numerous people from entering the same erratics. For those that have not read each of my blog postings, this excludes both (a) the glacial erratic, then known locally as Samson’s Shoulder Stone (and now sadly forgotten), that can be found about 11.26 kilometers east of Perth along County Road 10 (the Franktown Road if you are heading to Ottawa, and the Perth Road if you are headed to Perth) reported on in 1932 by Dr. Morley Wilson of the Geological Survey of Canada that was featured in Volume 46 of the Canadian Field-Naturalist and (b) the glacial erratics at Wheeler’s Pancake House and Sugarbush.
I’ve decided against offering a monetary prize, which would only pit neighbour against neighbour, husband against wife, and fathers and mothers against their children. Instead, the prize will be a certificate, a photograph of the winner and his/her erratic published in the Perth Courier, and the photograph of the annual winner on a plaque kept at the Perth Museum. I can see the plaque now: 2016 - a photograph of a granitic or gabbroic boulder from Lanark Highlands.
I realize that there could be a problem with the contest ending during deer hunting season. My wife has pointed out that this automatically disqualifies half of the male population of Lanark County, as men put things off to the last minute and will be too busy during deer hunting season to enter. My answer to that is that women hunt. Some hunt deer, some hunt for men and some are always on the hunt for new pair of shoes. Women hunt. I should note in passing that while I would normally assume that one of my wife’s comments directed at all men is somehow directed at me, I don’t hunt.
Every contest requires a mathematical, time limited, question in order to take it out of the anti-gambling provisions of the Criminal Code. I propose: What is the weight of your glacial erratic, to the nearest ten kilograms, assuming that most common rocks composed mainly of silicates weigh about 160 pounds per cubic foot? Some people will complain that this is a trick question designed to catch those that don’t realize that both pounds and kilograms are mentioned. Others will complain that it is a trick question designed to catch those whose erratics are comprised of marble or limestone (both carbonates, not silicates). Some will complain that we should never have adopted the metric system. Others will just complain. However, no one said that it had to be an easy question. To overcome any concerns I propose giving each entrant two tries over two days.
Of course, that mathematical question will require that all entrants sign a Waiver acknowledging that the contest organizers (a) do not encourage, condone or recommend the lifting of bounders to determine their weight and (b) are not responsible for medical or other expenses where the entrant tries to weigh the erratic. Other parts of the waiver still have to be drafted.
When to hold the awards ceremony? The obvious date is December 24 to commemorate the signing of the peace treaty that ended the war of 1812 (the Treaty of Ghent was signed on December 24, 1814) as this led to the founding of the Perth Military Settlement. However, my wife has reminded me that I am usually busy on that day finishing my Christmas shopping. I’m open to suggestions.
There is another obvious issue: When in November to close the contest? For the first year I have arbitrarily chosen November 11th, because it is a day that is easy to remember and because it commemorates the Battle of Crysler's Farm in Lower Canada. What better day then to commemorate the decisive British and Canadian victory on November 11, 1813 which convinced the Americans to abandon their campaign down the St. Lawrence River! However, many Lanark County residents have 11th of November booked each year, and that ceremony is the more important one. For subsequent years I propose that 31 sequentially numbered counters be placed in a bag and that each year’s winner draw the date for the next year, with the contest to close on the day drawn. I do realize that there are 30 days in November. Where number 31 is drawn the contest will not be held the following year. Some will complain that it should end on the same day each year so people can plan. Some will complain that if it is not held one year, then it is not an annual contest. However, it is, after all, an erratic contest.
Christopher Brett
Perth, Ontario
Addendum (November 11th):
The Town of Perth may have a connection to the Battle of Crysler’s Farm. In front of the Court House in Perth can usually be found two brass three-pounder light infantry cannons. (One is currently missing, and is hopefully just out for repair.) The cannon on the left (as you are looking at the Court House, and the one that remains) bears the inscription ‘J. & P. VERBRUGGEN, FECERUNT A 1775.’ The other cannon is reported to bear a nearly identical inscription. The word 'fecerunt' is a Latin word that translates into English as 'made, constructed, cast.' The cannons were undoubtedly cast at the Royal Brass Foundry at Woolwich, England where Jan Verbruggen and his son Pieter were the master founders from 1770-86. The cannons are said to have an interesting history: they were captured by the Americans from the British at the Battle of Saratoga, and were recaptured by the British regulars and Canadian militia at the Battle of Crysler’s Farm. Later they were presented to the Perth Military Settlement.
Tuesday 4 November 2014
Layering in the Mealy Mountains Anorthosite Complex, Labrador
In my last posting I mentioned that I had seen spectacular layering in anorthosite intrusions in Labrador. Below are photographs that I took of layering in the anorthosite plutons that form the Mealy Mountains in Labrador. The person that is the scale in the photographs is Dr. Ron Emslie of the Geological Survey of Canada, who was about average height for a world renowned expert on anorthosites.
Ron described the layering as follows:
“Within leucotroctolite, leucogabbro and anorthosite, igneous mineral layering on a scale of 1 cm to 10 m, or more, is common (Fig. 33. 2). Where rock exposure is good, layers or layer contacts can be found on most clean subvertical rock surfaces more than a few metres high. In leucotroctolite the mineral layering involves differences in proportions of olivine and plagioclase,
whereas in leucogabbro and anorthosite, variations in pyroxene and plagioclase proportions are the chief cause. In addition to mineral layering, manifestation of layers is due to differing plagioclase grain sizes and shapes and in some cases, plagioclase colour particularly in leucogabbro and anorthosite. Dark layers in some anorthositic rocks were found to consist of darker coloured plagioclase than that in the enclosing host rock. Such "dark plagioclase" layers were evident in some places even where the enclosing rock contained a noticeably higher proportion of ferromagnesian minerals. Large areas of the complex have relatively consistent layering attitudes. For example, the northwestern part of the complex has dips to the northwest
and west at angles less than 30 degrees. Other areas have remarkably discordant layer attitudes over short distances and sometimes even within the same outcrop. Such discordance seems to be a primary igneous feature of the crystal accumulation process and is not due to superimposed deformation.”
(Emslie, R. .F (1976), Mealy Mountains Complex, Grenville Province, Southern Labrador,
Report of Activities Part A; Geological Survey of Canada, Paper no. 76-1A; p. 165-170
http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=123988
http://ftp2.cits.rncan.gc.ca/pub/geott/ess_pubs/119/119844/pa_76_1a.pdf )
Christopher Brett
Perth, Ontario
Suggested Readings
Emslie, Ronald F. (1975), Nature and Origin of Anorthosite Suites, Geoscience Canada, Volume 2, Number 2, pages 99-104
http://journals.hil.unb.ca/index.php/GC/article/view/2912
Emslie, Ronald F. (1980) , Geology and Petrology of the Harp Lake Complex, Central Labrador- an example of Elsonian Magmatism. Geological Survey of Canada, Bulletin 293, 136 pages
http://data.gc.ca/data/en/dataset/96d2a3bc-c79d-57f1-8169-24e01d431893
Hamilton, Michael A. , Scoates, James S. and Rämö, O. Tapani (2010)
The Petrology of Anorthosites, Related Granitic Rocks, and UHT Assemblages: a Tribute to Ronald F. Emslie, Can Mineralogist, volume 48, pages 705-710
http://canmin.geoscienceworld.org/content/48/4/705.full
Ron described the layering as follows:
“Within leucotroctolite, leucogabbro and anorthosite, igneous mineral layering on a scale of 1 cm to 10 m, or more, is common (Fig. 33. 2). Where rock exposure is good, layers or layer contacts can be found on most clean subvertical rock surfaces more than a few metres high. In leucotroctolite the mineral layering involves differences in proportions of olivine and plagioclase,
whereas in leucogabbro and anorthosite, variations in pyroxene and plagioclase proportions are the chief cause. In addition to mineral layering, manifestation of layers is due to differing plagioclase grain sizes and shapes and in some cases, plagioclase colour particularly in leucogabbro and anorthosite. Dark layers in some anorthositic rocks were found to consist of darker coloured plagioclase than that in the enclosing host rock. Such "dark plagioclase" layers were evident in some places even where the enclosing rock contained a noticeably higher proportion of ferromagnesian minerals. Large areas of the complex have relatively consistent layering attitudes. For example, the northwestern part of the complex has dips to the northwest
and west at angles less than 30 degrees. Other areas have remarkably discordant layer attitudes over short distances and sometimes even within the same outcrop. Such discordance seems to be a primary igneous feature of the crystal accumulation process and is not due to superimposed deformation.”
(Emslie, R. .F (1976), Mealy Mountains Complex, Grenville Province, Southern Labrador,
Report of Activities Part A; Geological Survey of Canada, Paper no. 76-1A; p. 165-170
http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=123988
http://ftp2.cits.rncan.gc.ca/pub/geott/ess_pubs/119/119844/pa_76_1a.pdf )
Christopher Brett
Perth, Ontario
Suggested Readings
Emslie, Ronald F. (1975), Nature and Origin of Anorthosite Suites, Geoscience Canada, Volume 2, Number 2, pages 99-104
http://journals.hil.unb.ca/index.php/GC/article/view/2912
Emslie, Ronald F. (1980) , Geology and Petrology of the Harp Lake Complex, Central Labrador- an example of Elsonian Magmatism. Geological Survey of Canada, Bulletin 293, 136 pages
http://data.gc.ca/data/en/dataset/96d2a3bc-c79d-57f1-8169-24e01d431893
Hamilton, Michael A. , Scoates, James S. and Rämö, O. Tapani (2010)
The Petrology of Anorthosites, Related Granitic Rocks, and UHT Assemblages: a Tribute to Ronald F. Emslie, Can Mineralogist, volume 48, pages 705-710
http://canmin.geoscienceworld.org/content/48/4/705.full
Monday 27 October 2014
Layering in the Lavant Gabbro Complex, Lanark County, Ontario
The Lavant Gabbro Complex, which lies northwest of Perth, is purported to be the largest mafic body in the Grenville Province of Ontario. It covers approximately 250 square kilometers.
The following simplified geologic map shows the extent of the Lavant Gabbro Complex.
The towns of Lanark, Almonte, Carleton Place and Clyde Forks are shown on the map. The town of Perth is under the Legend.
The Lavant Gabbro Complex falls within the Sharbot Lake Terrane (sometimes called the Sharbot Lake domain) of the Central Metasedimentary Belt of the Grenville Province, Canadian Shield. The Sharbot Lake Terrane is comprised of marbles and metavolcanic rocks that have been intruded by gabbroic and granitic plutons. It is bounded on the east by the Maberly shear zone and on the west by the Robertson Lake shear zone (sometimes called the Roberton Lake mylonite zone). The metavolcanic rocks falling within the Sharbot Lake Terrane are not shown on the above map.
Much of the Lavant Gabbro Complex was mapped in detail in the 1980's by Liba Pauk, J. M. Wolff and Michael Easton of the Ontario Geological Survey, and outcrops of the complex can be easily found along a number of roads that cross the complex.
Fernando Carfu and Michael Easton in a paper published in 1989 described the complex as follows:
“The Lavant gabbroic complex is a composite intrusion, roughly 50 km long and up to 15 km wide. It consists of (i) a voluminous mafic suite, dominated by medium-grained gabbro to diorite, locally showing igneous layering and crosscutting relationships between several compositionally distinct phases; and (ii) a slightly younger granodiorite–monzogranite suite, which forms several small intrusive bodies and dikes cutting the gabbro. The intermediate to felsic phases occur mainly in the structurally higher part of the complex, and also intrude adjacent supracrustal rocks, including the marbles. Metamorphic grade of the complex varies from upper greenschist facies in the north to lower amphibolite facies in the south. Contact relationships are complex, and inclusions, roof pendants and slivers of all the country rocks are present. The gabbro body does not have an extensive contact aureole...”
They determined an age of 1224 ± 2 Ma for the gabbroic and associated monzogranitic rocks of the Lavant complex.
I’ve always been interested in layering in igneous rocks, and saw numerous examples of layering in anorthosite bodies in Labrador when I was employed as a summer student by the Geological Survey of Canada. I wondered whether any examples of layering in the Lavant Gabbro complex could be easily found.
In her Report 253 published in 1989 Liba Pauk of the Ontario Geological Survey mentioned:
“Primary rhythmic and graded layering of pyroxene cumulus occurs in a roadcut 1.2 km northwest of Black Creek Meadow (Photo 5). The layers strike 90 degrees and dip 30 degrees to the south. The primary rhythmic layering was also recorded ... some 1.5 km east of the map area at roadcuts of Lavant County Road 16.”
Her Photo 5 shows spectacular layering. The caption to her photo reads: Primary graded rhythmic layering in the Lavant Gabbro Complex. The only exposure found in the map area is located along Joes Lake Road, 1.2 km northwest of Black Creek Meadow.”
I did find her outcrop, but as it is now overgrown and covered with moss or lichen, the layering is no longer visible. For those looking for the outcrop, please note that the “Joes Lake Road” mentioned by Liba Pauk has been renamed Black Creek Road, and that the outcrop is on the east side of the road 1.3 km north of where Black Creek crosses the road. (More importantly, the current Joes Lake Road that is just south of Joes Lake is not the Joes Lake Road mentioned by Liba Pauk.)
In a paper published in 1994 Graham C. Wilson of the Ontario Geological Survey mentioned:
“The best layering observed in this area, and indeed in the course of the whole project, was observed in a satellite body on the east side of the main intrusive mass, west of Hopetown. The layers (Fig. 5c) are graded, and reflect modal variation between light feldspar and dark minerals (pyroxene or secondary amphiboles).”
Figure 5c appears at page 147 of Wilson’s report 5580. It shows spectacular layering. I did not find that outcrop, but did find two outcrops west of Hopetown on the north side of County Road 16 (a kilometer or so west of Highway 511) that show layering in the gabbroic rocks. Below are photographs of the two outcrops:
While the layering in the second outcrop is much better than the photograph shows, neither outcrop compares with the spectacular layering that I saw in Labrador.
In his Report 5693 published in 1988 Michael Easton of the Ontario Geological Survey also reported on primary igneous layering within the Lavant Gabbro Complex, which he mentioned consisted “of a variety of gabbro phases, ranging from gabbro to diorite to pyroxene gabbro to gabbroic anorthosite.” I have not yet found the time to look for his occurrences.
Christopher Brett
Perth, Ontario
References and Suggestions for Further Reading
Carfu, Fernando and Easton, R. Michael (1989), Sharbot Lake terrane and its relationship to Frontenac terrane, Central Metasedimentary Belt, Grenville Province: new insights from U-Pb geochronology, Can. J. Earth Sci. 34: 1239-1257
http://www.nrcresearchpress.com/doi/pdf/10.1139/e17-099
Easton, R. Michael (1988), Geology of the Darling Area Lanark and Renfrew Counties; Ontario Geological Survey, Open File Report 5693, 206 pages, at pages 60-66, Accompanied by Map 3113
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/OFR5693/OFR5693.pdf
Easton, R. Michael and DeKamp, E.A. (1987), Darling Area, Lanark and Renfrew Counties; Report 34 at pages 220-228, in Ontario Geological Survey Miscellaneous Paper 137, Summary of Field Work and Other Activities 1987
Pauk, Liba (1989a), Geology of the Dalhousie Lake Area, Frontenac and Lanark Counties; Ontario Geological Survey Report 245, 57 pages, at pages 17-23, Accompanied by Map 2512
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/R245/r245.pdf
Pauk, Liba (1989b), Geology of the Lavant Area, Lanark and Frontenac Counties; Ontario Geological Survey Report 253, 61 pages, at pages 26-29, Accompanied by Map 2515
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/R253/R253.pdf
Wilson, G.C. (1994), Mafic-ultramafic intrusions, base-metal sulphides, and platinum group element potential of the Grenville province of southeastern Ontario: Ontario Geological Survey, Open File Report 5880, 196 pages at pages 125-128
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/OFR5880/OFR5880.pdf
Wolff, J. M., 1985, Geology of the Sharbot Lake Area, Frontenac and Lanark Counties, Southeastern Ontario; Ontario Geological Survey Report 228, 70 pages at pages 29-37, accompanied by Map 2471
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/R228/R228.pdf
The following simplified geologic map shows the extent of the Lavant Gabbro Complex.
The towns of Lanark, Almonte, Carleton Place and Clyde Forks are shown on the map. The town of Perth is under the Legend.
The Lavant Gabbro Complex falls within the Sharbot Lake Terrane (sometimes called the Sharbot Lake domain) of the Central Metasedimentary Belt of the Grenville Province, Canadian Shield. The Sharbot Lake Terrane is comprised of marbles and metavolcanic rocks that have been intruded by gabbroic and granitic plutons. It is bounded on the east by the Maberly shear zone and on the west by the Robertson Lake shear zone (sometimes called the Roberton Lake mylonite zone). The metavolcanic rocks falling within the Sharbot Lake Terrane are not shown on the above map.
Much of the Lavant Gabbro Complex was mapped in detail in the 1980's by Liba Pauk, J. M. Wolff and Michael Easton of the Ontario Geological Survey, and outcrops of the complex can be easily found along a number of roads that cross the complex.
Fernando Carfu and Michael Easton in a paper published in 1989 described the complex as follows:
“The Lavant gabbroic complex is a composite intrusion, roughly 50 km long and up to 15 km wide. It consists of (i) a voluminous mafic suite, dominated by medium-grained gabbro to diorite, locally showing igneous layering and crosscutting relationships between several compositionally distinct phases; and (ii) a slightly younger granodiorite–monzogranite suite, which forms several small intrusive bodies and dikes cutting the gabbro. The intermediate to felsic phases occur mainly in the structurally higher part of the complex, and also intrude adjacent supracrustal rocks, including the marbles. Metamorphic grade of the complex varies from upper greenschist facies in the north to lower amphibolite facies in the south. Contact relationships are complex, and inclusions, roof pendants and slivers of all the country rocks are present. The gabbro body does not have an extensive contact aureole...”
They determined an age of 1224 ± 2 Ma for the gabbroic and associated monzogranitic rocks of the Lavant complex.
I’ve always been interested in layering in igneous rocks, and saw numerous examples of layering in anorthosite bodies in Labrador when I was employed as a summer student by the Geological Survey of Canada. I wondered whether any examples of layering in the Lavant Gabbro complex could be easily found.
In her Report 253 published in 1989 Liba Pauk of the Ontario Geological Survey mentioned:
“Primary rhythmic and graded layering of pyroxene cumulus occurs in a roadcut 1.2 km northwest of Black Creek Meadow (Photo 5). The layers strike 90 degrees and dip 30 degrees to the south. The primary rhythmic layering was also recorded ... some 1.5 km east of the map area at roadcuts of Lavant County Road 16.”
Her Photo 5 shows spectacular layering. The caption to her photo reads: Primary graded rhythmic layering in the Lavant Gabbro Complex. The only exposure found in the map area is located along Joes Lake Road, 1.2 km northwest of Black Creek Meadow.”
I did find her outcrop, but as it is now overgrown and covered with moss or lichen, the layering is no longer visible. For those looking for the outcrop, please note that the “Joes Lake Road” mentioned by Liba Pauk has been renamed Black Creek Road, and that the outcrop is on the east side of the road 1.3 km north of where Black Creek crosses the road. (More importantly, the current Joes Lake Road that is just south of Joes Lake is not the Joes Lake Road mentioned by Liba Pauk.)
In a paper published in 1994 Graham C. Wilson of the Ontario Geological Survey mentioned:
“The best layering observed in this area, and indeed in the course of the whole project, was observed in a satellite body on the east side of the main intrusive mass, west of Hopetown. The layers (Fig. 5c) are graded, and reflect modal variation between light feldspar and dark minerals (pyroxene or secondary amphiboles).”
Figure 5c appears at page 147 of Wilson’s report 5580. It shows spectacular layering. I did not find that outcrop, but did find two outcrops west of Hopetown on the north side of County Road 16 (a kilometer or so west of Highway 511) that show layering in the gabbroic rocks. Below are photographs of the two outcrops:
While the layering in the second outcrop is much better than the photograph shows, neither outcrop compares with the spectacular layering that I saw in Labrador.
In his Report 5693 published in 1988 Michael Easton of the Ontario Geological Survey also reported on primary igneous layering within the Lavant Gabbro Complex, which he mentioned consisted “of a variety of gabbro phases, ranging from gabbro to diorite to pyroxene gabbro to gabbroic anorthosite.” I have not yet found the time to look for his occurrences.
Christopher Brett
Perth, Ontario
References and Suggestions for Further Reading
Carfu, Fernando and Easton, R. Michael (1989), Sharbot Lake terrane and its relationship to Frontenac terrane, Central Metasedimentary Belt, Grenville Province: new insights from U-Pb geochronology, Can. J. Earth Sci. 34: 1239-1257
http://www.nrcresearchpress.com/doi/pdf/10.1139/e17-099
Easton, R. Michael (1988), Geology of the Darling Area Lanark and Renfrew Counties; Ontario Geological Survey, Open File Report 5693, 206 pages, at pages 60-66, Accompanied by Map 3113
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/OFR5693/OFR5693.pdf
Easton, R. Michael and DeKamp, E.A. (1987), Darling Area, Lanark and Renfrew Counties; Report 34 at pages 220-228, in Ontario Geological Survey Miscellaneous Paper 137, Summary of Field Work and Other Activities 1987
Pauk, Liba (1989a), Geology of the Dalhousie Lake Area, Frontenac and Lanark Counties; Ontario Geological Survey Report 245, 57 pages, at pages 17-23, Accompanied by Map 2512
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/R245/r245.pdf
Pauk, Liba (1989b), Geology of the Lavant Area, Lanark and Frontenac Counties; Ontario Geological Survey Report 253, 61 pages, at pages 26-29, Accompanied by Map 2515
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/R253/R253.pdf
Wilson, G.C. (1994), Mafic-ultramafic intrusions, base-metal sulphides, and platinum group element potential of the Grenville province of southeastern Ontario: Ontario Geological Survey, Open File Report 5880, 196 pages at pages 125-128
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/OFR5880/OFR5880.pdf
Wolff, J. M., 1985, Geology of the Sharbot Lake Area, Frontenac and Lanark Counties, Southeastern Ontario; Ontario Geological Survey Report 228, 70 pages at pages 29-37, accompanied by Map 2471
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/R228/R228.pdf
Wednesday 17 September 2014
Lake Iroquois and the Glaciofluvial Deltaic Deposit at Joes Lake, Lanark Highlands, Ontario
About 18,000 years ago the Laurentide Ice Sheet reached its maximum thickness and southward extent, covering Eastern Ontario with a thickness of over two kilometers of ice, and extending southward to New York City. The southern edge of the glacier then started to retreat northward. In the 1,500 year period starting about 12,500 years ago eastern Ontario changed from ice covered to ice free. As the edge of the glacier retreated northward melt water from the retreating glacier formed a proglacial lake, Lake Iroquois, a precursor of Lake Ontario. Lake Iroquois covered all of present day Lake Ontario and extended northward abutting on the retreating glacier. In its early stages Lake Iroquois covered Kingston and all of Prince Edward County, and then grew larger and extended northward as the glacier retreated. There were two factors that allowed Lake Iroquois to extend northward and cover what is now dry land. First, the weight of the Laurentide Ice Sheet had depressed much of Eastern Ontario from 175 to 230 meters. Second, the retreating glacier formed an ice dam that prevented Lake Iroquois from draining down what is now the St. Lawrence River. (The lake drained from an outlet at Rome, New York and then to the Hudson River.)
Twenty-two years ago Inez M. Kettles of the Geological Survey of Canada issued a report on the glacial deposits in Lanark, Frontenac and Leeds Counties. (See: Kettles, I.M., 1992, Glacial Geology and glacial sediment geochemistry of the Clyde Forks - Westport area of Ontario, Geological Survey of Canada, Paper 91-17. The report can be downloaded from:
http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=133492).
Inez Kettles reports that glacial Lake Iroquois covered much of Lanark County, extending at least as far northward as Joes Lake in the Township of Lanark Highlands. (Joes Lake is the name of both a lake and small village. It is about 45 kilometers north west of Perth and is known for its fishing and magnificent views. It is named for an Algonquin who had a camping spot over the lake and was known to walk to and from Perth. I drove.)
Inez Kettles reported a large delta at Joes Lake that she identified as a proglacial subaerial outwash that she believes was built within 3 km of the retreating ice margin. She mentions that “The exact position of the ice margin as the delta was forming, is however, uncertain and it is possible that the delta is an ice contact deposit. The cobbly, bouldery texture of some foreset beds exposed at Joes Lake and the presence of a well developed kettle hole on the delta surface indicate that these sediments were deposited close to the ice. It is also possible that some sediments mapped as ice contact glacial deposits in the channel north of and leading to the delta, were deposited as proglacial outwash.”
Last year Victoria Lee of the Ontario Geological Survey issued a report on the aggregate resources of Lanark County that covered the glacialfluvial deposits, including the gravel pit at Joes Lake. (See, Lee, V.L. 2013, Aggregate resources inventory of the County of Lanark, southern Ontario: Ontario Geological Survey, Aggregate Resources Inventory Paper 189, 85 p. Her report can be downloaded from:
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/ARIP189/ARIP189.pdf )
When discussing the deposit at Joes Lake Victoria Lee mentions: “The deposit is a large glaciolacustrine deltaic deposit. The delta is inferred to have been deposited close to the ice margin ... The deposit material, ranging from cobble-sized to silt, is well sorted with distinct layers of cobbles, gravel, sand and silt-rich layers. ... Well-defined terraces mark the boundaries of the deposit. One licensed pit (Pit No. 3) and one unlicensed pit (Pit No. 55) have been developed in the resource area. Face heights in the pits range from 4 to 10 m; however, available borehole records indicate the potential for more than 15 m of sand and gravel locally. Calcite cementation within the deposit holds material 30 degrees off the vertical and cause potential problems during extraction...”
Below are photographs taken at the sand and gravel pit in the proglacial subaerial outwash deposit just to the north of Joes Lake along the Lavant Darling Road.
The last two photos show underlying beds of cobbles and sand that are truncated by later deposited layered beds of cobbles and sand.
Inez Kettles’ report covers large parts of Lanark, Frontenac and Leeds counties. Figure 10 to the report is a map that covers Clyde Forks, Sharbot Lake, Tichborne, Westport, Morton, Smiths Falls and Carleton Place. It shows selected glaciofluvial deposits and glacial striae, and gives a good indication of the direction the glacier was moving. Figure 11 shows the distribution of drumlins in the Clyde Forks, Westport, Smiths Falls and Ottawa area. Both figures are worth a look.
In 1936 A.P. Coleman of the Ontario Department of Mines published a report on Lake Iroquois with an accompanying Map No. 45f entitled Lake Iroquois and Related Ice Front at the Time of the Rome Outlet (Scale, 5 miles to the inch). It is worth a look. Below I’ve provided a copy of the map. The part shaded green is the retreating glacier. The part in blue, which covers Prince Edward County and Kingston, is Lake Iroquois.
The copy doesn’t do justice to the map, which can be downloaded from http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/ARM45F/ARM45F.pdf
Christopher Brett
Perth, Ontario
Twenty-two years ago Inez M. Kettles of the Geological Survey of Canada issued a report on the glacial deposits in Lanark, Frontenac and Leeds Counties. (See: Kettles, I.M., 1992, Glacial Geology and glacial sediment geochemistry of the Clyde Forks - Westport area of Ontario, Geological Survey of Canada, Paper 91-17. The report can be downloaded from:
http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=133492).
Inez Kettles reports that glacial Lake Iroquois covered much of Lanark County, extending at least as far northward as Joes Lake in the Township of Lanark Highlands. (Joes Lake is the name of both a lake and small village. It is about 45 kilometers north west of Perth and is known for its fishing and magnificent views. It is named for an Algonquin who had a camping spot over the lake and was known to walk to and from Perth. I drove.)
Inez Kettles reported a large delta at Joes Lake that she identified as a proglacial subaerial outwash that she believes was built within 3 km of the retreating ice margin. She mentions that “The exact position of the ice margin as the delta was forming, is however, uncertain and it is possible that the delta is an ice contact deposit. The cobbly, bouldery texture of some foreset beds exposed at Joes Lake and the presence of a well developed kettle hole on the delta surface indicate that these sediments were deposited close to the ice. It is also possible that some sediments mapped as ice contact glacial deposits in the channel north of and leading to the delta, were deposited as proglacial outwash.”
Last year Victoria Lee of the Ontario Geological Survey issued a report on the aggregate resources of Lanark County that covered the glacialfluvial deposits, including the gravel pit at Joes Lake. (See, Lee, V.L. 2013, Aggregate resources inventory of the County of Lanark, southern Ontario: Ontario Geological Survey, Aggregate Resources Inventory Paper 189, 85 p. Her report can be downloaded from:
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/ARIP189/ARIP189.pdf )
When discussing the deposit at Joes Lake Victoria Lee mentions: “The deposit is a large glaciolacustrine deltaic deposit. The delta is inferred to have been deposited close to the ice margin ... The deposit material, ranging from cobble-sized to silt, is well sorted with distinct layers of cobbles, gravel, sand and silt-rich layers. ... Well-defined terraces mark the boundaries of the deposit. One licensed pit (Pit No. 3) and one unlicensed pit (Pit No. 55) have been developed in the resource area. Face heights in the pits range from 4 to 10 m; however, available borehole records indicate the potential for more than 15 m of sand and gravel locally. Calcite cementation within the deposit holds material 30 degrees off the vertical and cause potential problems during extraction...”
Below are photographs taken at the sand and gravel pit in the proglacial subaerial outwash deposit just to the north of Joes Lake along the Lavant Darling Road.
The last two photos show underlying beds of cobbles and sand that are truncated by later deposited layered beds of cobbles and sand.
Inez Kettles’ report covers large parts of Lanark, Frontenac and Leeds counties. Figure 10 to the report is a map that covers Clyde Forks, Sharbot Lake, Tichborne, Westport, Morton, Smiths Falls and Carleton Place. It shows selected glaciofluvial deposits and glacial striae, and gives a good indication of the direction the glacier was moving. Figure 11 shows the distribution of drumlins in the Clyde Forks, Westport, Smiths Falls and Ottawa area. Both figures are worth a look.
In 1936 A.P. Coleman of the Ontario Department of Mines published a report on Lake Iroquois with an accompanying Map No. 45f entitled Lake Iroquois and Related Ice Front at the Time of the Rome Outlet (Scale, 5 miles to the inch). It is worth a look. Below I’ve provided a copy of the map. The part shaded green is the retreating glacier. The part in blue, which covers Prince Edward County and Kingston, is Lake Iroquois.
The copy doesn’t do justice to the map, which can be downloaded from http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/ARM45F/ARM45F.pdf
Christopher Brett
Perth, Ontario
Wednesday 20 August 2014
A Selection of Fossils from the March Formation in Lanark County, Ontario - Part 2
My posting entitled A Selection of Fossils from the March Formation in Lanark County, Ontario from September 13, 2013 contained photographs of fossils from a quarry in Lanark County about a five minute drive north of Perth. On Tuesday I was at the quarry to order a load of gravel for my driveway, and took the opportunity to look for fossils. Below are photographs of three surfaces that show burrowing parallel to the bedding plane. Two photographs are provided for each surface.
Interestingly, the quarry manager told me that they have crushed 65,000 tons of rock since I was there last.
Christopher Brett
Perth, Ontario
Interestingly, the quarry manager told me that they have crushed 65,000 tons of rock since I was there last.
Christopher Brett
Perth, Ontario
Thursday 14 August 2014
Blasting of Outcrops Along Highway 15, including at Elgin
Since the spring the Province of Ontario has been widening Highway 15 between Crosby and the turn off at Hwy 32 to Gananoque, and has been blasting most of the outcrops along Highway 15. A lot of fresh rock has been exposed. Unfortunately, most of the blasted rock has been used to construct the roadbed for the new highway (rather than being saved for geologists and rock hounds).
The geology is complicated. There are good outcrops of Potsdam Group sandstone of late Cambrian age, and outcrops of Precambrian plutonic igneous rock and Precambrian high grade metamorphic rock. The Precambrian basement rocks are part of the Central Metasedimentary Belt of the Grenville Province. I mentioned in my last posting that the Central Metasedimentary Belt is subdivided into a number of terranes. Each of these terranes is characterized by distinct rock assemblages and mineral deposits. This stretch along Highway 15 falls within the Frontenac terrane of the Central Metasedimentary Belt. The Frontenac terrane comprises metamorphosed sedimentary rocks (metaquartzite, quartzofeldspathic gniesses, marble), lacks volcanic rocks, and was affected by the intrusion of plutonic rocks and intense metamorphism in the period of about 1190-1160 Ma. The Frontenac Terrane is preserved at upper amphibolite to granulite facies.
Wynne-Edwards (1967), who conducted the most comprehensive study of these rocks, concluded that the “metamorphic rocks most reasonably represent a sequence of marine sediments deposited in a stable area of relatively shallow water, and brought by deep burial into a metamorphic environment with high temperature and confining pressure [where they were intensely deformed, folded and refolded.] ...The metasedimentary rocks of the Westport map-area are dominantly stratiform quartz-biotite-feldspar gneisses, coarsely crystalline calcite marble ... and smaller amounts of quartzite... Granitic material in the form of pods, layers or lenses is present in all these rocks. ... In addition to this granitic material, large concordant plutons of quartz monzonite and monzonite occur at certain places, particularly in belts of crystalline limestone. These monzonites post-date the main period of metamorphism and have altered gabbroic rocks previously emplaced at the same sites. Diabase dykes and younger porphyritic andesite dykes cut all these rocks. ...
An extended period of erosion before the deposition of the Paleozoic rocks exposed the highly metamorphic rocks at the surface and established much of the existing topography. In some places the ancient land surface is preserved as a deep zone of oxidation and weathering below the Nepean sandstone.”
(Wynne-Edwards, H. R., 1967, Westport map Area, Ontario, With Special Emphasis On the Precambrian Rocks, Geological Survey of Canada, Memoir 346, 142 pages at pages 108, 4 and 5
http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=100533 )
Below I’ve provided an extract from the Geological Survey of Canada’s Map 1182A, Westport, Ontario, compiled by H.R. Wynne-Edwards. This shows the geology along Highway 15 from Crosby (at the top left corner of the map) to south of Morton. The large pink oval shape at the bottom right corner of this map extract is the Lydnhurst quartz monzonite pluton.
Below is part of the legend for Wynne-Edwards’ geologic map.
The complete map can be downloaded from http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=108032
Those that have driven along Highway 15 this past summer will have noted that the outcrops of Potsdam Group sandstone at Elgin have changed. In some ways you can see more as the rock is fresh, but some of the weathered surfaces are gone. Below are photographs of three sandstone outcrops near Elgin (the first two showing the unconformity) .
Sam_0544 - Northeast corner of Hwy15 and the main road into Elgin
Sam_0547 - other side of Hwy 15
Sam_0552 - just south of Elgin, west side of road
(If you visit, you might consider taking a stiff broom to clear off the outcrops..)
Below is a photograph of an outcrop of Nepean Formation, Potsdam Group, sandstone. This outcrop is north of Morton on the east side of Highway 15. The ruler is along an inch thick bed of rounded quartz pebble conglomerate that extends the length of the outcrop.
Below I’ve provided photographs of outcrops of gneiss at and just south of Morton, together with close up photographs of pods of granitic material in the gneiss.
South of Morton there are also fresh outcrops of Wynne-Edwards’ Lydnhurst quartz monzonite pluton
I’ve found that looking at the outcrops on the weekends works best, as you do not have to dodge the construction vehicles.
Christopher Brett
Perth, Ontario
+++++++++++++++++++++
Addendum:
Wynne-Edwards (1967) did not place the Precambrian rocks that he mapped within a plate tectonics setting, as the theory had not been extended to the Precambrian at the time he conducted his field work and published his memoir. Since that time the general adoption of the theory has led to these rocks being placed in a plate tectonics setting. See, for example:
Davidson, A., and van Breemen, O. (2000), Age and extent of the Frontenac plutonic suite in the Central metasedimentary belt, Grenville Province, southeastern Ontario; Geological Survey of Canada, Current Research 2000-F4,
James M. McLelland, Bruce W. Selleck and M.E. Bickford (2010), Review of the Proterozoic evolution of the Grenville Province, its Adirondack outlier, and the Mesoproterozoic inliers of the Appalachians, The Geological Society of America, Memoir 206, p. 1-29.
Jeff Chiarenzelli, Sean Regan, William H. Peck, Bruce W. Selleck, Brian Cousens, Graham B. Baird and Catherine H. Shrady (2010), Shawinigan arc magmatism in the Adirondack Lowlands as a consequence of closure of the Trans-Adirondack backarc basin, Geosphere 2010;6;900-916
All are available online.
The geology is complicated. There are good outcrops of Potsdam Group sandstone of late Cambrian age, and outcrops of Precambrian plutonic igneous rock and Precambrian high grade metamorphic rock. The Precambrian basement rocks are part of the Central Metasedimentary Belt of the Grenville Province. I mentioned in my last posting that the Central Metasedimentary Belt is subdivided into a number of terranes. Each of these terranes is characterized by distinct rock assemblages and mineral deposits. This stretch along Highway 15 falls within the Frontenac terrane of the Central Metasedimentary Belt. The Frontenac terrane comprises metamorphosed sedimentary rocks (metaquartzite, quartzofeldspathic gniesses, marble), lacks volcanic rocks, and was affected by the intrusion of plutonic rocks and intense metamorphism in the period of about 1190-1160 Ma. The Frontenac Terrane is preserved at upper amphibolite to granulite facies.
Wynne-Edwards (1967), who conducted the most comprehensive study of these rocks, concluded that the “metamorphic rocks most reasonably represent a sequence of marine sediments deposited in a stable area of relatively shallow water, and brought by deep burial into a metamorphic environment with high temperature and confining pressure [where they were intensely deformed, folded and refolded.] ...The metasedimentary rocks of the Westport map-area are dominantly stratiform quartz-biotite-feldspar gneisses, coarsely crystalline calcite marble ... and smaller amounts of quartzite... Granitic material in the form of pods, layers or lenses is present in all these rocks. ... In addition to this granitic material, large concordant plutons of quartz monzonite and monzonite occur at certain places, particularly in belts of crystalline limestone. These monzonites post-date the main period of metamorphism and have altered gabbroic rocks previously emplaced at the same sites. Diabase dykes and younger porphyritic andesite dykes cut all these rocks. ...
An extended period of erosion before the deposition of the Paleozoic rocks exposed the highly metamorphic rocks at the surface and established much of the existing topography. In some places the ancient land surface is preserved as a deep zone of oxidation and weathering below the Nepean sandstone.”
(Wynne-Edwards, H. R., 1967, Westport map Area, Ontario, With Special Emphasis On the Precambrian Rocks, Geological Survey of Canada, Memoir 346, 142 pages at pages 108, 4 and 5
http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=100533 )
Below I’ve provided an extract from the Geological Survey of Canada’s Map 1182A, Westport, Ontario, compiled by H.R. Wynne-Edwards. This shows the geology along Highway 15 from Crosby (at the top left corner of the map) to south of Morton. The large pink oval shape at the bottom right corner of this map extract is the Lydnhurst quartz monzonite pluton.
Below is part of the legend for Wynne-Edwards’ geologic map.
The complete map can be downloaded from http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=108032
Those that have driven along Highway 15 this past summer will have noted that the outcrops of Potsdam Group sandstone at Elgin have changed. In some ways you can see more as the rock is fresh, but some of the weathered surfaces are gone. Below are photographs of three sandstone outcrops near Elgin (the first two showing the unconformity) .
Sam_0544 - Northeast corner of Hwy15 and the main road into Elgin
Sam_0547 - other side of Hwy 15
Sam_0552 - just south of Elgin, west side of road
(If you visit, you might consider taking a stiff broom to clear off the outcrops..)
Below is a photograph of an outcrop of Nepean Formation, Potsdam Group, sandstone. This outcrop is north of Morton on the east side of Highway 15. The ruler is along an inch thick bed of rounded quartz pebble conglomerate that extends the length of the outcrop.
Below I’ve provided photographs of outcrops of gneiss at and just south of Morton, together with close up photographs of pods of granitic material in the gneiss.
South of Morton there are also fresh outcrops of Wynne-Edwards’ Lydnhurst quartz monzonite pluton
I’ve found that looking at the outcrops on the weekends works best, as you do not have to dodge the construction vehicles.
Christopher Brett
Perth, Ontario
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Addendum:
Wynne-Edwards (1967) did not place the Precambrian rocks that he mapped within a plate tectonics setting, as the theory had not been extended to the Precambrian at the time he conducted his field work and published his memoir. Since that time the general adoption of the theory has led to these rocks being placed in a plate tectonics setting. See, for example:
Davidson, A., and van Breemen, O. (2000), Age and extent of the Frontenac plutonic suite in the Central metasedimentary belt, Grenville Province, southeastern Ontario; Geological Survey of Canada, Current Research 2000-F4,
James M. McLelland, Bruce W. Selleck and M.E. Bickford (2010), Review of the Proterozoic evolution of the Grenville Province, its Adirondack outlier, and the Mesoproterozoic inliers of the Appalachians, The Geological Society of America, Memoir 206, p. 1-29.
Jeff Chiarenzelli, Sean Regan, William H. Peck, Bruce W. Selleck, Brian Cousens, Graham B. Baird and Catherine H. Shrady (2010), Shawinigan arc magmatism in the Adirondack Lowlands as a consequence of closure of the Trans-Adirondack backarc basin, Geosphere 2010;6;900-916
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