I find it interesting, when considering how the theory of the origin of the Potsdam Group sandstones (of Ontario, Quebec and New York State) has evolved over time, to note that numerous early writers made insightful comments, but were ignored or had their contributions overlooked. In this posting I will mention a few of the geologists who deserve more credit. While the title to this posting singles out Emmons, Logan, Grabau and Greggs, numerous others made insightful comments.
Ebenezer Emmons named the Potsdam sandstone. His earliest downloadable report dates from 1842. In this report he mentions that the Potsdam sandstone is found with conglomerate and that there a number of varieties of sandstone. He identifies two principal varieties: 1st a sandstone variety that he subdivides into two further varieties found at quarries (a) at Potsdam (St. Lawrence County), and (b) at Bangor (Franklin County) and “Moore” (later spelt Mooers) ; 2nd a sandstone found at Keeseville, Whitehall and Kent, which he later says he has sometimes given “a compound name– the Potsdam and Keeseville sandstone”. He also mentions other varieties of sandstone. Interestingly, his sandstone from the Potsdam quarry we would now call the Hannawa Falls Formation; his sandstone from Mooers area is likely the one we would call the Ausable Formation sandstone (for rocks in New York State; or the Covey Hill Formation, for rocks in Ontario and Quebec), and his sandstone from Keeseville we could call the Keeseville Formation (or Nepean formation, for rocks in Ontario; Cairnside Formation, in Quebec).
In addition, Emmons comments that “Though the rock is generally even-bedded, I have noticed several places where it has been subject to violent forces, so as to greatly derange the strata”, and included drawings of folded and faulted outcrops. He also comments on the differences in beds, singling out materials “that appear to have been borne along by a moderate current, which has been given a diversity of stratification resembling inclined beds”, and includes a drawing of such strata, a drawing that looks like fluvial facies.
Emmons (1846) summarizes the Potsdam sandstone, summarizes the varieties of sandstone, and notes that “In many places it is a coarse conglomerate”.
Logan makes at least the following important points:
- the Potsdam sandstone that is found in New York state extends into the Provinces of Ontario and Quebec (Logan 1844; Logan 1863)
- the Potsdam sandstones at Beauharnois which produced Protichnites trackways contain both wave ripple marks and wind ripples– they are littoral sandstones (Logan, 1860; Logan, 1861, Logan, 1863 )
- The Potsdam sandstone is better referred to as part of the Potsdam Group as the “sandstone is a member of a series of strata” and includes conglomerate (Logan 1863)
Intriguingly, both Logan’s identification of wind ripples and his comment that the Potsdam sandstones at Beauharnois are littoral sandstones were referred to in papers published for over forty years, but then disappeared from the literature.
Professor Amadeus W. Grabau makes the following points:
- where the Potsdam is “a transgressive overlapping series of strata deposited by a transgressing sea, the basal sand member would naturally rise in the series in the direction of transgression and overlap, and that hence a basal sand is not everywhere of the same age” (Grabau, 1909; also Grabau, 1913)
- the earlier parts of the Potsdam are of continental origin, commenting: “in many, if not in most, regions the Paleozoic series begins with a formation of continental origin, the upper portion of which was reworked by the transgressing sea”; “the Potsdam sandstone, ... in many sections, still shows characters pointing to torrential or eolian origin of a considerable portion of the rock”; and “In many cases this northern “Potsdam” sandstone shows evidence of continental origin in pre-marine time by the occurrence of well-marked torrential cross-bedding in parts which apparently have not been reworked.”
- the Potsdam sandstone includes both quartz sandstone and arkosic sandstone (Grabau, 1920).
Professor Greggs, in combination with co-authors from the Geology Department at Queen’s University at Kingston, differentiated between typical Nepean and typical Potsdam (Hannawa Falls) sandstones, finding that both occurred in Ontario and both occurred in New York State, noting that “These sandstone units appear to bear consistent stratigraphic relationships to one another” [Greggs and Bond, 1972]. Further, “Periods of erosion punctuated the development of the Potsdam sandstones (Cushing, 1910; Chadwick, 1919; Clarke, 1966), and at some stratigraphic horizon not yet determined by detailed field studies, the environment of deposition of the Potsdam appears to have changed from continental, wind-blown sandstones, possibly reworked by coastal waters, to a shallow marine depositional environment.” [Greggs and Gorman, 1976]
Interestingly, Professor Greggs’ distinction between the shallow marine Nepean sandstone and typical continental, wind- blown Potsdam (Hannawa Falls) sandstone in part reflects the distinction drawn by Ebenezer Emmons (1842) who distinguished between the variety at Keeseville and the other at Potsdam, St. Lawrence County.
(Numerous others who studied and reported on the rocks of New York State, including Professor Cushing, distinguished between the varieties of Potsdam sandstone. There are just too many to summarize.)
Christopher Brett
Perth, Ontario
References
Emmons, Ebenezer, 1842
Survey of the Second Geological District, In Geology of New York, Part II; W. & A. White & J. Visscher, Albany, New York
Emmons, Ebenezer, 1846
Agriculture of New York; C. Van Benthuysen & Co., Albany, New York
Grabau, Amadeus W., 1909
Physical and Faunal Evolution of North America during Ordovicic, Siluric, and Early Devonic Time, The Journal of Geology, Volume 17, 209-252
Grabau, Amadeus W., 1913
Principles of Stratigraphy; A.G. Seiler and Company, New York
Grabau, Amadeus W., 1920
A Comprehensive Geology; Part 1, D. C. Heath & Co., New York
Greggs, R. G. and Bond, 1972
A principal reference section proposed for the Nepean Formation of probable Tremadocian age near Ottawa, Ontario. Canadian Journal of Earth Sciences, 9, pp. 933-941.
Greggs, R.G. and Gorman, W.A. 1976
Geology of the Thousand Islands, by Parks Canada
http://www.oliverkilian.com/ecology/thousand-islands/island-insights/geology/rocks.html
Logan, W. E., 1844
Geological Survey of Canada, Report of Progress For the Year 1843
Logan, W. E., 1860
On the Tracks of an Animal lately found in the Potsdam Formation , read before the Natural History Society of Montreal in June, 1860, volume V of The Canadian Naturalist and Geologist, article XXXIX, pages 279-285
Logan, W. E., 1861
Considerations relating to the Quebec Group, and the Upper Copper-bearing Rocks of Lake Superior; read before the Natural History Society of Montreal in May, 1861, volume VI of The Canadian Naturalist and Geologist, page 199-207
Logan, W. E., 1863
Geology of Canada, Geological Survey of Canada, Report of Progress from its commencement to 1863,
Saturday 4 March 2017
Thursday 2 March 2017
Sandstone Filled Cracks Extending into Marble at an Outcrop Near The Cat’s Meow
In my last blog posting I mentioned that Dr. Easton (2015) had reported “A previously unknown exposure of Potsdam group sandstone and conglomerate that he “identified on the north side of Highway 7 approximately 5 km west of Wemyss (385510E 4967646N)” and that the outcrop is worth a visit. The outcrop is just east of signs on Highway 7 for The Cat's Meow, an upscale inn for cats, at 20619 Highway 7.
Dr. Easton describes the outcrop as follows:
“A previously unknown exposure of Covey Hill Formation strata, or possibly the Abbey Dawn Formation of Sanford and Arnott (2010), was identified on the north side of Highway 7 approximately 5 km west of Wemyss (385510E 4967646N). Here, a channel, at least 3 m deep and up to 20 m wide, was cut down into weathered calcite marble. The deeper (>3 m) west side of the channel is filled with red-weathering pebbly conglomerate containing subangular to subrounded rock fragments and quartz pebbles, which grade upward into thin-bedded reddish coarse sandstone. The shallower (~2 m) east side of the channel consists of red mudstone and siltstone beds (up to 1 cm thick) that immediately overlie the marble basement, and which are overlain, in turn, by thin-bedded reddish coarse sandstone.”
I visited the outcrop last year. Fifty percent of the outcrop is marble. I noted that Dr. Easton had described the sandstone and conglomerate at the center and east end of the outcrop. A small amount of sandstone/mudstone also occurs at the west end of the outcrop in cracks in the marble. There are vugs in the marble filled with calcite crystals. There is a small hematite gossan at the west end of the outcrop and a larger example in the center of the outcrop. At least two faults cut the outcrop. I would not have identified the sandstone/conglomerate as the Covey Hill Formation strata or the Abbey Dawn Formation. The sandstone is more likely the Hannawa Falls Member of Sanford and Arnott (2010) /the Hannawa Falls Formation of Lowe (2016).
The most interesting feature of the outcrop is the beds of siltstone/mudstone at the base of the sandstone, which drape over the marble and underlie a thin friable layer comprised of pea sized pebbles of marble.
Attached are three of the photos that I took. The first shows sandstone fissures in the marble at the west end of the outcrop. The second photo shows siltstone/mudstone layers draped over the marble and underlying a friable layer; overlain by massive sandstone beds. The base of blue ruler is along the contact with the Grenville marble. The third photo shows the hematite gossan and possibly a fault.
There have been numerous reports in the literature of tongues of sandstone extending into the underlying marble. Where the sandstone is described it is invariably a dark red sandstone, possibly what we would now identify as the eolian Hannawa Falls Formation of the Potsdam Group. Below are a few of the less often cited reports:
Helmstaedt, Gorman & McBride (1987) in a field trip guide for the Kingston, Ontario area mention a “paleokarst cave” near the entrance to the Portland Conservation Area, on the east side of Highway 38, about 2 km south of Verona, noting that a “Cut on east side of road shows a paleokarst cave in Precambrian marble filled with sandstone breccia of Nepean Formation (Fig. 11). Sandstones with local cross-bedding extend as horizontal ‘tongues' into the marble.” [Note: this guide appears to have been written when all of the sandstones of the Potsdam Group were referred to in Ontario as Nepean Formation.]
Smyth (1893, at page 104) reports that “North of Gouverneur [New York] the [crystalline] limestone and sandstone are in direct contact... From the irregular line of contact it is clear that the material of the sandstone was deposited upon a [crystalline] limestone surface that had been subject to erosion. An interesting confirmation of this conclusion is seen in the presence of narrow, irregular cracks extending several feet into the [crystalline] limestone and filled with sandstone.”
Winchell (1893, pages 107-108) reports on a trip to look at the Potsdam sandstone in Upper New York State. He also reports on hematite ore bodies in marble noting that for many occurrences the ore lies “at the base of the Potsdam.” For outcrops near Richland, New York, he noted that “The sandstone grades into soft hematite, which appears like a good ore. The upper surface of the marble is fissured in places, and the hematitic material of the sandstone extends down into these fissures (fig. 7).”
Cushing et al (1910) reported on the Geology of the Thousand Islands Region, New York State. They reported a “dark red, very thoroughly indurated and vitreous sandstone that differs from the general run of sandstone in the district” and that “all the sand-filled cracks seen in the Grenville [crystalline] limestone were filled with this type of sandstone...”.
Cushing and Newland (1923) report on sand filled cracks in marble mentioning that outcrops “may be seen in several places in the Gouverneur quadrangle” and that “on the bared [crystalline] limestone surfaces the red sandstone stands out in relief”.
Professor Bruce Selleck (2005) of Colgate University in a field trip guide mentions “Sand from the Potsdam is also found within open fractures and filling hydrothermal karst tunnels and pipes [in marble]. These fillings are often deeply colored red or maroon by abundant hematite cement, and the sand is usually tightly cemented by quartz and carbonate minerals, but rounded sand grains can usually be seen with a hand lens. Some of the conglomerates within the Potsdam contain chert clasts that are the result of silicification of marble clasts. Pebbles of jasper and clasts of laminated sandstone that had been silica-cemented, reworked and re-deposited are also present in the conglomerate and pebbly sandstone beds.
Professor Selleck commented on the association of hematite and the Potsdam as follows:“The hematite deposits also share the common presence of nearby or directly overlying inliers of Potsdam Sandstone (Chamberlain 1984). The paragenesis of the hematite deposits is generally interpreted as multi-stage with pre-Potsdam surface weathering of Proterozoic iron sulfide leading to accumulation of locally thick gossans of limonite/hematite prior to Potsdam Sandstone deposition (Chamberlain 1984). Post-Potsdam reconstitution of the iron oxides involved hydrothermal fluids that dissolved and re-deposited hematite within Potsdam Sandstone as thick botryoidal masses, specular crystalline aggregates, veins and disseminated cements in sandstone and highly altered Proterozoic basement gneiss.” There are too many other reports of hematite at the Potsdam/Grenville marble interface to mention.
Christopher Brett
Perth, Ontario
---------------------------------------------------------------
References
Cushing, H.P., Fairchild, H.L., Ruedemann, R. And Smyth, C.H. Jr., 1910
Geology of the Thousand Islands Region, New York State Museum Bulletin No. 485 at pages 62-63
Cushing, H.P., and Newland, D. H., 1925
Geology of the Gouverneur Quadrangle, New York State Museum Bulletin No. 259 at page 49 and Plate 11
R. M. Easton, 2015
Project Unit 15-014. Precambrian and Paleozoic Geology of the Perth Area, Grenville Province, in Summary of Field Work and Other Activities, 2015. Ontario Geological Survey, OFR 6313
at pages 18-1 to 18- 13
http://www.mndm.gov.on.ca/en/news/mines-and-minerals/summary-field-work-and-other-activities-2015
Helmstaedt, H.H., Gorman W.A. & McBride, S.L. 1987
Field Tripping: Geology of the Kingston Area,
By the Department of Geological Sciences, Queen's University, Kingston,
www.whaton.uwaterloo.ca/waton/s906.html
Lowe, D.G., 2016
Sedimentology, Stratigraphic Evolution and Provenance of the Cambrian – Lower Ordovician Potsdam Group in the Ottawa Embayment and Quebec Basin;
Doctoral Thesis, University of Ottawa,
http://www.ruor.uottawa.ca/handle/10393/35303
Sanford, B.V. and Arnott, R.W.C., 2010
Stratigraphic and structural framework of the Potsdam Group in eastern Ontario, western Quebec, and northern New York State. Geological Survey of Canada, Bulletin 597, 85 pages
publications.gc.ca/collections/collection_2010 /nrcan/M42-597
Selleck, B., 2005
Exploring the root zone of an ancient fault-driven hydrothermal system in the Adirondack Lowlands, New York; NYSGA Field Trip Guidebook, 77th Annual Meeting, 12-31
Smyth, C. H., Jr., 1893
Geological Reconnoissance in the Vicinity of Gouverneur, N. Y.; Transactions of the New York Academy of Sciences, Vol. XII, pages 97-108 at 104
Winchell, N. H., 1893
The Potsdam sandstone at Potsdam, New York; in Field Observations of N. H. Winchell in 1892;
The Geological and Natural History Survey of Minnesota, Twenty-first Annual Report for the year 1892, pages 99- 111
Dr. Easton describes the outcrop as follows:
“A previously unknown exposure of Covey Hill Formation strata, or possibly the Abbey Dawn Formation of Sanford and Arnott (2010), was identified on the north side of Highway 7 approximately 5 km west of Wemyss (385510E 4967646N). Here, a channel, at least 3 m deep and up to 20 m wide, was cut down into weathered calcite marble. The deeper (>3 m) west side of the channel is filled with red-weathering pebbly conglomerate containing subangular to subrounded rock fragments and quartz pebbles, which grade upward into thin-bedded reddish coarse sandstone. The shallower (~2 m) east side of the channel consists of red mudstone and siltstone beds (up to 1 cm thick) that immediately overlie the marble basement, and which are overlain, in turn, by thin-bedded reddish coarse sandstone.”
I visited the outcrop last year. Fifty percent of the outcrop is marble. I noted that Dr. Easton had described the sandstone and conglomerate at the center and east end of the outcrop. A small amount of sandstone/mudstone also occurs at the west end of the outcrop in cracks in the marble. There are vugs in the marble filled with calcite crystals. There is a small hematite gossan at the west end of the outcrop and a larger example in the center of the outcrop. At least two faults cut the outcrop. I would not have identified the sandstone/conglomerate as the Covey Hill Formation strata or the Abbey Dawn Formation. The sandstone is more likely the Hannawa Falls Member of Sanford and Arnott (2010) /the Hannawa Falls Formation of Lowe (2016).
The most interesting feature of the outcrop is the beds of siltstone/mudstone at the base of the sandstone, which drape over the marble and underlie a thin friable layer comprised of pea sized pebbles of marble.
Attached are three of the photos that I took. The first shows sandstone fissures in the marble at the west end of the outcrop. The second photo shows siltstone/mudstone layers draped over the marble and underlying a friable layer; overlain by massive sandstone beds. The base of blue ruler is along the contact with the Grenville marble. The third photo shows the hematite gossan and possibly a fault.
There have been numerous reports in the literature of tongues of sandstone extending into the underlying marble. Where the sandstone is described it is invariably a dark red sandstone, possibly what we would now identify as the eolian Hannawa Falls Formation of the Potsdam Group. Below are a few of the less often cited reports:
Helmstaedt, Gorman & McBride (1987) in a field trip guide for the Kingston, Ontario area mention a “paleokarst cave” near the entrance to the Portland Conservation Area, on the east side of Highway 38, about 2 km south of Verona, noting that a “Cut on east side of road shows a paleokarst cave in Precambrian marble filled with sandstone breccia of Nepean Formation (Fig. 11). Sandstones with local cross-bedding extend as horizontal ‘tongues' into the marble.” [Note: this guide appears to have been written when all of the sandstones of the Potsdam Group were referred to in Ontario as Nepean Formation.]
Smyth (1893, at page 104) reports that “North of Gouverneur [New York] the [crystalline] limestone and sandstone are in direct contact... From the irregular line of contact it is clear that the material of the sandstone was deposited upon a [crystalline] limestone surface that had been subject to erosion. An interesting confirmation of this conclusion is seen in the presence of narrow, irregular cracks extending several feet into the [crystalline] limestone and filled with sandstone.”
Winchell (1893, pages 107-108) reports on a trip to look at the Potsdam sandstone in Upper New York State. He also reports on hematite ore bodies in marble noting that for many occurrences the ore lies “at the base of the Potsdam.” For outcrops near Richland, New York, he noted that “The sandstone grades into soft hematite, which appears like a good ore. The upper surface of the marble is fissured in places, and the hematitic material of the sandstone extends down into these fissures (fig. 7).”
Cushing et al (1910) reported on the Geology of the Thousand Islands Region, New York State. They reported a “dark red, very thoroughly indurated and vitreous sandstone that differs from the general run of sandstone in the district” and that “all the sand-filled cracks seen in the Grenville [crystalline] limestone were filled with this type of sandstone...”.
Cushing and Newland (1923) report on sand filled cracks in marble mentioning that outcrops “may be seen in several places in the Gouverneur quadrangle” and that “on the bared [crystalline] limestone surfaces the red sandstone stands out in relief”.
Professor Bruce Selleck (2005) of Colgate University in a field trip guide mentions “Sand from the Potsdam is also found within open fractures and filling hydrothermal karst tunnels and pipes [in marble]. These fillings are often deeply colored red or maroon by abundant hematite cement, and the sand is usually tightly cemented by quartz and carbonate minerals, but rounded sand grains can usually be seen with a hand lens. Some of the conglomerates within the Potsdam contain chert clasts that are the result of silicification of marble clasts. Pebbles of jasper and clasts of laminated sandstone that had been silica-cemented, reworked and re-deposited are also present in the conglomerate and pebbly sandstone beds.
Professor Selleck commented on the association of hematite and the Potsdam as follows:“The hematite deposits also share the common presence of nearby or directly overlying inliers of Potsdam Sandstone (Chamberlain 1984). The paragenesis of the hematite deposits is generally interpreted as multi-stage with pre-Potsdam surface weathering of Proterozoic iron sulfide leading to accumulation of locally thick gossans of limonite/hematite prior to Potsdam Sandstone deposition (Chamberlain 1984). Post-Potsdam reconstitution of the iron oxides involved hydrothermal fluids that dissolved and re-deposited hematite within Potsdam Sandstone as thick botryoidal masses, specular crystalline aggregates, veins and disseminated cements in sandstone and highly altered Proterozoic basement gneiss.” There are too many other reports of hematite at the Potsdam/Grenville marble interface to mention.
Christopher Brett
Perth, Ontario
---------------------------------------------------------------
References
Cushing, H.P., Fairchild, H.L., Ruedemann, R. And Smyth, C.H. Jr., 1910
Geology of the Thousand Islands Region, New York State Museum Bulletin No. 485 at pages 62-63
Cushing, H.P., and Newland, D. H., 1925
Geology of the Gouverneur Quadrangle, New York State Museum Bulletin No. 259 at page 49 and Plate 11
R. M. Easton, 2015
Project Unit 15-014. Precambrian and Paleozoic Geology of the Perth Area, Grenville Province, in Summary of Field Work and Other Activities, 2015. Ontario Geological Survey, OFR 6313
at pages 18-1 to 18- 13
http://www.mndm.gov.on.ca/en/news/mines-and-minerals/summary-field-work-and-other-activities-2015
Helmstaedt, H.H., Gorman W.A. & McBride, S.L. 1987
Field Tripping: Geology of the Kingston Area,
By the Department of Geological Sciences, Queen's University, Kingston,
www.whaton.uwaterloo.ca/waton/s906.html
Lowe, D.G., 2016
Sedimentology, Stratigraphic Evolution and Provenance of the Cambrian – Lower Ordovician Potsdam Group in the Ottawa Embayment and Quebec Basin;
Doctoral Thesis, University of Ottawa,
http://www.ruor.uottawa.ca/handle/10393/35303
Sanford, B.V. and Arnott, R.W.C., 2010
Stratigraphic and structural framework of the Potsdam Group in eastern Ontario, western Quebec, and northern New York State. Geological Survey of Canada, Bulletin 597, 85 pages
publications.gc.ca/collections/collection_2010 /nrcan/M42-597
Selleck, B., 2005
Exploring the root zone of an ancient fault-driven hydrothermal system in the Adirondack Lowlands, New York; NYSGA Field Trip Guidebook, 77th Annual Meeting, 12-31
Smyth, C. H., Jr., 1893
Geological Reconnoissance in the Vicinity of Gouverneur, N. Y.; Transactions of the New York Academy of Sciences, Vol. XII, pages 97-108 at 104
Winchell, N. H., 1893
The Potsdam sandstone at Potsdam, New York; in Field Observations of N. H. Winchell in 1892;
The Geological and Natural History Survey of Minnesota, Twenty-first Annual Report for the year 1892, pages 99- 111
Saturday 31 December 2016
Ontario Geological Survey Remapping the Perth Map Sheet
I was driving into Perth in August when I noticed an individual taking a sledge hammer to an outcrop of granite along Scotch Line (County Road 10) within the town limits of Perth. My initial thought was that it must be a geologist taking a sample to age date the granite, so I stopped, introduced myself, and asked the individual if that was what he was doing. I was glad that I’d stopped. It was Dr. Michael Easton of the Ontario Geological Survey and he was collecting a sample in order to later determine its age. I suspect that this was the first time he has been asked the question of whether he was collecting a sample in order to age date the rock. (I often get asked in an accusing tone to explain what I’m doing when I just stop to look at an outcrop.)
Dr. Easton was good enough to tell me that he was working on the Perth map sheet and that his initial report had been published in the Summary of Field Work and Other Activities, 2015. The following is a link to that report.
Easton, R. M., 2015
Project Unit 15-014. Precambrian and Paleozoic Geology of the Perth Area, Grenville Province; in Summary of Field Work and Other Activities, 2015. Ontario Geological Survey, OFR 6313
at pages 18-1 to 18- 13
http://www.mndm.gov.on.ca/en/news/mines-and-minerals/summary-field-work-and-other-activities-2015
Dr. Easton has recently sent to me electronic copies of two recently published reports from this year’s field season that deal with rocks in the Perth area:
Easton, R.M., 2016a.
Precambrian and Paleozoic geology of the Perth area, Grenville Province; in Summary of Field Work and Other Activities, 2016, Ontario Geological Survey, Open File Report 6323, p.17-1 to 17-13.
Easton, R.M., 2016b.
Metasomatism, syenite magmatism and rare earth element and related metallic mineralization in Bancroft and Frontenac terranes: A preliminary deposit model; in Summary of Field Work and Other Activities, 2016, Ontario Geological Survey, Open File Report 6323, p.18-1 to 18-9.
Both reports can be downloaded from:
http://www.mndm.gov.on.ca/en/news/mines-and-minerals/summary-field-work-and-other-activities-2016
In his reports from 2015 and 2016a, Dr. Easton discusses A) the medium-pressure granulite- and upper amphibolite-facies rocks of the Frontenac terrane, B) the upper greenschist- to lower amphibolite-facies rocks of the Sharbot Lake domain, C) separated by the Maberly shear zone, and includes maps showing the locations of the terranes and shear zone. Easton 2015 discusses the Maberly Shear Zone and directs one to a “spectacular, 150 m long roadcut on the south side of Highway 7 (385925E, 4967751N) [which is] a microcosm of the Maberly shear zone, and consists of alternating panels, 10 to 15 m wide, of marble breccia interlayered with thin-layered, highly flattened, compositional silicate tectonites.” For anyone that has not previously driven out to look at the shear zone, the outcrop is worth a look. Below is a photograph of the outcrop.
The ruler in the photo is one meter long.
Easton (2015 and 2016a) divided the Frontenac terrane in the Perth map area into 3 subdomains, and reports on differences in the marbles present in the 3 subdomains of the Frontenac terrane. His petrographic study of rocks in the Frontenac terrane suggests metamorphic pressures and temperatures higher than previously reported for the Perth Map sheet. He found assemblages suggesting “pressures and temperatures greater than 8 kilobars and higher than 670◦C” and other assemblages “indicating metamorphic pressures as high as 11 to 14 kilobars and temperatures approaching 1000◦C.” He notes that “a significant metamorphic pressure change occurs along a north-northeast-trending fault located southeast of Smiths Falls”, a “fault that trends north-northeast from Chaffey’s Lock to Portland to Glen Elm just south-southeast of Smiths Falls”, which he names the Chaffey’s Lock fault. He puts the Perth map area in bathozone 6 of Carmichael, noting that bathozone 4 conditions exist 20 km south of the Perth map area near Lyndhurst, adding that a "difference of 2 kilobars between the Perth and Lyndhurst areas would involve at least a vertical displacement of 7 km” across the fault but because the fault “places rocks of the Nepean Formation against rocks of the upper March and Oxford formations” there was “no more than 100 m of post-Ordovician displacement across the fault.”
In his reports from 2015 and 2016, Dr. Easton also discusses the metallic mineral potential of the Perth map sheet, principally the potential for Kiruna-Type magnetite-apatite mineralization and the rare earth potential of numerous mica-apatite deposits. Dr. Easton mentions finding “a strontium equivalent of the mineral haunghoite (BaCe(CO3)2F). A strontium equivalent of haunghoite has not been previously identified, and this may represent a new mineral species.”
He also discusses the industrial mineral potential (sandstone as potential source for silica; marble as a carbonate source; vermiculite), and includes analyses of sandstones and marbles.
While Dr. Easton’s reports concentrate on Precambrian rocks, he also mapped the Paleozoic rocks (the Cambrian to Lower Ordovician Covey Hill and Nepean formations, the Lower Ordovician March and Oxford formations, and the Middle Ordovician Rockcliffe Formation). In his reports Dr. Easton mentions that he has found a number of previously unknown exposures of Potsdam Group sandstone and conglomerate (both Covey Hill and Nepean formations). A previously unknown exposure of Potsdam group sandstone and conglomerate that he “identified on the north side of Highway 7 approximately 5 km west of Wemyss (385510E 4967646N)” is worth looking at.
The 2017 Annual meeting of the Geological Association of Canada/Mineralogical Association of Canada will be held in Kingston, Ontario from May 14-18, 2017 and will coincide with the 175th anniversary of the founding of the Geological Survey of Canada by the legislature of the Province of Canada in 1842, in Kingston, Canada West. As part of the conference Dr. Michael Easton of the Ontario Geological survey will be leading a one day field trip on May 14th entitled New Insights into the Tectonic and Metamorphic Architecture of the Composite Arc Belt and the Frontenac-Adirondack Belt near Perth, Ontario, Grenville Orogen which highlights the results of his recent mapping, geochemistry, petrology and new geophysical data collected in the Perth area. See: http://www.kingstongacmac.ca/en/field-trips/
Christopher Brett
Perth, Ontario
Dr. Easton was good enough to tell me that he was working on the Perth map sheet and that his initial report had been published in the Summary of Field Work and Other Activities, 2015. The following is a link to that report.
Easton, R. M., 2015
Project Unit 15-014. Precambrian and Paleozoic Geology of the Perth Area, Grenville Province; in Summary of Field Work and Other Activities, 2015. Ontario Geological Survey, OFR 6313
at pages 18-1 to 18- 13
http://www.mndm.gov.on.ca/en/news/mines-and-minerals/summary-field-work-and-other-activities-2015
Dr. Easton has recently sent to me electronic copies of two recently published reports from this year’s field season that deal with rocks in the Perth area:
Easton, R.M., 2016a.
Precambrian and Paleozoic geology of the Perth area, Grenville Province; in Summary of Field Work and Other Activities, 2016, Ontario Geological Survey, Open File Report 6323, p.17-1 to 17-13.
Easton, R.M., 2016b.
Metasomatism, syenite magmatism and rare earth element and related metallic mineralization in Bancroft and Frontenac terranes: A preliminary deposit model; in Summary of Field Work and Other Activities, 2016, Ontario Geological Survey, Open File Report 6323, p.18-1 to 18-9.
Both reports can be downloaded from:
http://www.mndm.gov.on.ca/en/news/mines-and-minerals/summary-field-work-and-other-activities-2016
In his reports from 2015 and 2016a, Dr. Easton discusses A) the medium-pressure granulite- and upper amphibolite-facies rocks of the Frontenac terrane, B) the upper greenschist- to lower amphibolite-facies rocks of the Sharbot Lake domain, C) separated by the Maberly shear zone, and includes maps showing the locations of the terranes and shear zone. Easton 2015 discusses the Maberly Shear Zone and directs one to a “spectacular, 150 m long roadcut on the south side of Highway 7 (385925E, 4967751N) [which is] a microcosm of the Maberly shear zone, and consists of alternating panels, 10 to 15 m wide, of marble breccia interlayered with thin-layered, highly flattened, compositional silicate tectonites.” For anyone that has not previously driven out to look at the shear zone, the outcrop is worth a look. Below is a photograph of the outcrop.
The ruler in the photo is one meter long.
Easton (2015 and 2016a) divided the Frontenac terrane in the Perth map area into 3 subdomains, and reports on differences in the marbles present in the 3 subdomains of the Frontenac terrane. His petrographic study of rocks in the Frontenac terrane suggests metamorphic pressures and temperatures higher than previously reported for the Perth Map sheet. He found assemblages suggesting “pressures and temperatures greater than 8 kilobars and higher than 670◦C” and other assemblages “indicating metamorphic pressures as high as 11 to 14 kilobars and temperatures approaching 1000◦C.” He notes that “a significant metamorphic pressure change occurs along a north-northeast-trending fault located southeast of Smiths Falls”, a “fault that trends north-northeast from Chaffey’s Lock to Portland to Glen Elm just south-southeast of Smiths Falls”, which he names the Chaffey’s Lock fault. He puts the Perth map area in bathozone 6 of Carmichael, noting that bathozone 4 conditions exist 20 km south of the Perth map area near Lyndhurst, adding that a "difference of 2 kilobars between the Perth and Lyndhurst areas would involve at least a vertical displacement of 7 km” across the fault but because the fault “places rocks of the Nepean Formation against rocks of the upper March and Oxford formations” there was “no more than 100 m of post-Ordovician displacement across the fault.”
In his reports from 2015 and 2016, Dr. Easton also discusses the metallic mineral potential of the Perth map sheet, principally the potential for Kiruna-Type magnetite-apatite mineralization and the rare earth potential of numerous mica-apatite deposits. Dr. Easton mentions finding “a strontium equivalent of the mineral haunghoite (BaCe(CO3)2F). A strontium equivalent of haunghoite has not been previously identified, and this may represent a new mineral species.”
He also discusses the industrial mineral potential (sandstone as potential source for silica; marble as a carbonate source; vermiculite), and includes analyses of sandstones and marbles.
While Dr. Easton’s reports concentrate on Precambrian rocks, he also mapped the Paleozoic rocks (the Cambrian to Lower Ordovician Covey Hill and Nepean formations, the Lower Ordovician March and Oxford formations, and the Middle Ordovician Rockcliffe Formation). In his reports Dr. Easton mentions that he has found a number of previously unknown exposures of Potsdam Group sandstone and conglomerate (both Covey Hill and Nepean formations). A previously unknown exposure of Potsdam group sandstone and conglomerate that he “identified on the north side of Highway 7 approximately 5 km west of Wemyss (385510E 4967646N)” is worth looking at.
The 2017 Annual meeting of the Geological Association of Canada/Mineralogical Association of Canada will be held in Kingston, Ontario from May 14-18, 2017 and will coincide with the 175th anniversary of the founding of the Geological Survey of Canada by the legislature of the Province of Canada in 1842, in Kingston, Canada West. As part of the conference Dr. Michael Easton of the Ontario Geological survey will be leading a one day field trip on May 14th entitled New Insights into the Tectonic and Metamorphic Architecture of the Composite Arc Belt and the Frontenac-Adirondack Belt near Perth, Ontario, Grenville Orogen which highlights the results of his recent mapping, geochemistry, petrology and new geophysical data collected in the Perth area. See: http://www.kingstongacmac.ca/en/field-trips/
Christopher Brett
Perth, Ontario
Thursday 1 December 2016
Gypsum Pseudomorphs that formed in the Sabkha Environment of the Potsdam Group
“Sabkhas are supratidal, forming along arid coastlines and are characterized by evaporite-carbonate deposits with some siliciclastics” Wikipedia .
In my October 7, 2016 blog posting I mentioned that I had attended the official re-opening and rededication of the Metcalfe Geoheritage Park in Almonte, Lanark County. While I was there and admiring structures preserved in Potsdam sandstone slabs that had been rescued during the enlargement of Highway 417 in Kanata, Dr. Donaldson suggested that I should look at other rescued slabs of sandstone that had been placed in the Last Duel Park in Perth, Ontario. Below are three photographs of slabs that now reside in the Last Duel Park.
I believe the structures shown in the first two photographs to be relic pseudomorphs of gypsum rosettes. The third photo shows convolute, tightly folded sandstone beds, that were held together likely as the result of microbial binding.
My October 31st blog posting mentioned that I had attended the second day of the Niagara Peninsula Geological Society Field Trip to Eastern Ontario and visited the Potsdam sandstone quarry at Ellisville. While there Paul Musiol of Kingston pointed out an interesting structure that he had found in the sandstone. Below is a photograph of Paul’s find.
I told Paul that my best guess is that his structure is a pseudomorph of gypsum or another evaporite mineral (barite).
The addendum to my blog posting from December 29, 2015 summarizes various reports on
on evaporites in Potsdam sandstone. Recently, in his doctoral thesis, Dave Lowe described gypsum and evaporite pseudomorphs found in Potsdam sandstone:
David G. Lowe, 2016
Sedimentology, Stratigraphic Evolution and Provenance of the Cambrian – Lower Ordovician Potsdam Group in the Ottawa Embayment and Quebec Basin;
Doctoral Thesis, University of Ottawa,
http://www.ruor.uottawa.ca/handle/10393/35303
Dave has recognized six siliciclastic paleoenvironments in the Potsdam: a) braided fluvial, b) ephemeral fluvial, c) aeolian erg, d) coastal sabkha, e) tide-dominated marine and f) open-coast tidal flat. He discusses the coastal sabkha environment and the formation of gypsum pseudomorphs at pages 87-92 of his thesis. His figure 3.8 at page 90 is worth a look, as it provides photographs of evaporite minerals, pseudomorphs and textures in coastal sabkha strata. Figure 3.8A shows impressions of sparry, nodular radiating mineral aggregates in sandstone from Kanata, which Dave compared to evaporitic desert rose nodules. He recognized possible swallowtail twin textures suggesting that the nodules were originally formed as gypsum. His Figure 3.8B shows cubic impressions possibly of halite in sandstone. His Figure 3.9 shows kinked and tightly-folded sandstone intraclasts in coastal sabkha strata.
Those with an interest in microbial binding in the sabkha environment might also want to read pages 201-203 of Dave’s thesis.
Christopher Brett
Perth
In my October 7, 2016 blog posting I mentioned that I had attended the official re-opening and rededication of the Metcalfe Geoheritage Park in Almonte, Lanark County. While I was there and admiring structures preserved in Potsdam sandstone slabs that had been rescued during the enlargement of Highway 417 in Kanata, Dr. Donaldson suggested that I should look at other rescued slabs of sandstone that had been placed in the Last Duel Park in Perth, Ontario. Below are three photographs of slabs that now reside in the Last Duel Park.
I believe the structures shown in the first two photographs to be relic pseudomorphs of gypsum rosettes. The third photo shows convolute, tightly folded sandstone beds, that were held together likely as the result of microbial binding.
My October 31st blog posting mentioned that I had attended the second day of the Niagara Peninsula Geological Society Field Trip to Eastern Ontario and visited the Potsdam sandstone quarry at Ellisville. While there Paul Musiol of Kingston pointed out an interesting structure that he had found in the sandstone. Below is a photograph of Paul’s find.
I told Paul that my best guess is that his structure is a pseudomorph of gypsum or another evaporite mineral (barite).
The addendum to my blog posting from December 29, 2015 summarizes various reports on
on evaporites in Potsdam sandstone. Recently, in his doctoral thesis, Dave Lowe described gypsum and evaporite pseudomorphs found in Potsdam sandstone:
David G. Lowe, 2016
Sedimentology, Stratigraphic Evolution and Provenance of the Cambrian – Lower Ordovician Potsdam Group in the Ottawa Embayment and Quebec Basin;
Doctoral Thesis, University of Ottawa,
http://www.ruor.uottawa.ca/handle/10393/35303
Dave has recognized six siliciclastic paleoenvironments in the Potsdam: a) braided fluvial, b) ephemeral fluvial, c) aeolian erg, d) coastal sabkha, e) tide-dominated marine and f) open-coast tidal flat. He discusses the coastal sabkha environment and the formation of gypsum pseudomorphs at pages 87-92 of his thesis. His figure 3.8 at page 90 is worth a look, as it provides photographs of evaporite minerals, pseudomorphs and textures in coastal sabkha strata. Figure 3.8A shows impressions of sparry, nodular radiating mineral aggregates in sandstone from Kanata, which Dave compared to evaporitic desert rose nodules. He recognized possible swallowtail twin textures suggesting that the nodules were originally formed as gypsum. His Figure 3.8B shows cubic impressions possibly of halite in sandstone. His Figure 3.9 shows kinked and tightly-folded sandstone intraclasts in coastal sabkha strata.
Those with an interest in microbial binding in the sabkha environment might also want to read pages 201-203 of Dave’s thesis.
Christopher Brett
Perth
Monday 31 October 2016
The Ellisville Potsdam Sandstone Quarry Revisited
A week ago Sunday I had the pleasure of attending the second day of the Niagara Peninsula Geological Society Field Trip to Eastern Ontario and revisiting the Potsdam sandstone quarry at Ellisville.
On Saturday they had visited the Frontenac Lead Mine and the Canadian Wollastonite Quarry, and as I understand it had an enjoyable time, despite the rain.
On Sunday we had great weather and I believe that everyone found something of interest.
Below are two specimens that were discovered when I was with the person who found the specimen.
Peter Lee found and collected the cylindrical structure shown in the following two photographs .
The first photo shows a top view while the second shows the top and a cross-section. While the cylindrical structure was found in a loose slab, I believe that the top of the slab represents the true top as the slab was quite large. The concentration of hematite at the edge of the cylindrical structure and the fact that the hematite staining shows that banding in the surrounding rock goes only so far into the structure, are both interesting features.
Below is a photograph of a Climactichnites wilsoni trail that was collected by Paul Musiol of Kingston.
Paul spotted the specimen when I was standing next to him (and we were discussing whether a large slab displayed a Protichnites trackway). I told Paul that it was Climactichnites and that finding a Climactichnites specimen in Eastern Ontario is important because it rarely occurs. In Eastern Ontario only the Glen Quarry near Perth and a small quarry near Battersea have yielded specimens of Climactichnites.
The type locality for Climactichnites wilsoni is the Glen quarry, which is located a mile north of Perth, Ontario. However, the only specimens collected from that (now abandoned and flooded) quarry were collected from 1859 to 1882 by Dr. James Wilson of Perth and by Mr. Richardson of the Geological Survey of Canada. Those specimens can be found in the collections of the Matheson House Museum in Perth, the Royal Ontario Museum in Toronto, the Redpath Museum in Montreal, the Geological Survey of Canada and the National Museum of Scotland. Other specimens of Climactichnites have been collected well over two decades ago from a small (now abandoned and flooded) quarry near Battersea, Ontario and can be seen on display at the Miller Museum at Queen’s University, Kingston, Ontario.
The Climactichnites wilsoni trackway that Paul found is also important because most specimens of this trace fossil are quite a bit larger. Getty and Hagadorn (2005) wrote a paper on Small Climactichnites Trackways and reported on small trackways 2 to 3 cm wide. In a later paper Getty and Hagadorn (2009) reported on 304 Climactichnites wilsoni trackways, noting most trails are 2 to 18 cm wide with the smallest trail being 0.8 cm wide. Paul’s specimen is among the smallest reported.
The Ellisville quarry displays at least three facies of the Potsdam Group. The cylindrical structure was found in the Hannawa Falls Formation. The specimen of Climactichnites wilsoni was found in the Nepean Member of the Keeseville Formation.
While I was on the field trip Ashley Pollock of the Niagara Peninsula Geological Society (“NPGS”) mentioned that they will likely repeat the field trip next year, but earlier than October. Those wanting to attend should check the NPGS web site at www.ccfms.ca/clubs/NPGS/ And should consider joining the NPGS: Family Membership is $20 while Individual Membership is $15. The NPGS is an affiliated member of the Central Canadian Federation of Mineralogical Societies (“CCFMS”). In the past NPGS field trips have been open to other clubs that are members of the CCFMS.
Christopher Brett
Perth, Ontario
Paleobiology of Climactichnites, an Enigmatic Late Cambrian Fossil. Smithsonian Contributions to Paleobiology, number 74, 74 pages, frontispiece, 58 figures.
Patrick Ryan Getty and James W. Hagadorn, 2005
Small Climactichnites Trackways: Their Abundance and Implications for Trackmaker Physiology, 2005 Salt Lake City Annual Meeting (October 16-19, 2005), Paper No. 219-16
Patrick Ryan Getty, James Whitey Hagadorn, 2008
Reinterpretation of Climactichnites Logan 1860 to Include Subsurface Burrows, and Erection of Musculopodus for Resting Traces of the Trailmaker, Journal of Paleontology, November 2008
82 (6), 1161-1172 ; DOI: 10.1666/08-004.1
Patrick R. Getty and James W. Hagadorn, 2009
Palaeobiology of the Climactichnites Tracemaker, Palaeontology, Vol. 52, Part 4, 2009, pp. 753–778
My Blog Postings from:
Thursday, 31 January 2013
On the trail of Climactichnites wilsoni - Part 1: Specimens Collected from a Quarry near Perth, Ontario
Monday, 11 February 2013
On the trail of Climactichnites wilsoni - Part 2: References to the Quarry Near Perth in the Scientific Literature, and the Geologic Mapping of Lot 6
Monday, 6 May 2013
On the trail of Climactichnites wilsoni - Part 3: A quarry about a mile from Perth as the town existed in 1859
Tuesday, 21 July 2015
Reports of the Trace Fossil Climactichnites found in Central Texas
Thursday, 16 July 2015
Burrows or Not Burrows - Part 2
On Saturday they had visited the Frontenac Lead Mine and the Canadian Wollastonite Quarry, and as I understand it had an enjoyable time, despite the rain.
On Sunday we had great weather and I believe that everyone found something of interest.
Below are two specimens that were discovered when I was with the person who found the specimen.
Peter Lee found and collected the cylindrical structure shown in the following two photographs .
The first photo shows a top view while the second shows the top and a cross-section. While the cylindrical structure was found in a loose slab, I believe that the top of the slab represents the true top as the slab was quite large. The concentration of hematite at the edge of the cylindrical structure and the fact that the hematite staining shows that banding in the surrounding rock goes only so far into the structure, are both interesting features.
Below is a photograph of a Climactichnites wilsoni trail that was collected by Paul Musiol of Kingston.
The type locality for Climactichnites wilsoni is the Glen quarry, which is located a mile north of Perth, Ontario. However, the only specimens collected from that (now abandoned and flooded) quarry were collected from 1859 to 1882 by Dr. James Wilson of Perth and by Mr. Richardson of the Geological Survey of Canada. Those specimens can be found in the collections of the Matheson House Museum in Perth, the Royal Ontario Museum in Toronto, the Redpath Museum in Montreal, the Geological Survey of Canada and the National Museum of Scotland. Other specimens of Climactichnites have been collected well over two decades ago from a small (now abandoned and flooded) quarry near Battersea, Ontario and can be seen on display at the Miller Museum at Queen’s University, Kingston, Ontario.
The Climactichnites wilsoni trackway that Paul found is also important because most specimens of this trace fossil are quite a bit larger. Getty and Hagadorn (2005) wrote a paper on Small Climactichnites Trackways and reported on small trackways 2 to 3 cm wide. In a later paper Getty and Hagadorn (2009) reported on 304 Climactichnites wilsoni trackways, noting most trails are 2 to 18 cm wide with the smallest trail being 0.8 cm wide. Paul’s specimen is among the smallest reported.
The Ellisville quarry displays at least three facies of the Potsdam Group. The cylindrical structure was found in the Hannawa Falls Formation. The specimen of Climactichnites wilsoni was found in the Nepean Member of the Keeseville Formation.
While I was on the field trip Ashley Pollock of the Niagara Peninsula Geological Society (“NPGS”) mentioned that they will likely repeat the field trip next year, but earlier than October. Those wanting to attend should check the NPGS web site at www.ccfms.ca/clubs/NPGS/ And should consider joining the NPGS: Family Membership is $20 while Individual Membership is $15. The NPGS is an affiliated member of the Central Canadian Federation of Mineralogical Societies (“CCFMS”). In the past NPGS field trips have been open to other clubs that are members of the CCFMS.
Christopher Brett
Perth, Ontario
References and Suggestions For Further Reading on Climactichnites
Yochelson, Ellis L., and Mikhail A. Fedonkin, 1993Paleobiology of Climactichnites, an Enigmatic Late Cambrian Fossil. Smithsonian Contributions to Paleobiology, number 74, 74 pages, frontispiece, 58 figures.
Patrick Ryan Getty and James W. Hagadorn, 2005
Small Climactichnites Trackways: Their Abundance and Implications for Trackmaker Physiology, 2005 Salt Lake City Annual Meeting (October 16-19, 2005), Paper No. 219-16
Patrick Ryan Getty, James Whitey Hagadorn, 2008
Reinterpretation of Climactichnites Logan 1860 to Include Subsurface Burrows, and Erection of Musculopodus for Resting Traces of the Trailmaker, Journal of Paleontology, November 2008
82 (6), 1161-1172 ; DOI: 10.1666/08-004.1
Patrick R. Getty and James W. Hagadorn, 2009
Palaeobiology of the Climactichnites Tracemaker, Palaeontology, Vol. 52, Part 4, 2009, pp. 753–778
My Blog Postings from:
Thursday, 31 January 2013
On the trail of Climactichnites wilsoni - Part 1: Specimens Collected from a Quarry near Perth, Ontario
Monday, 11 February 2013
On the trail of Climactichnites wilsoni - Part 2: References to the Quarry Near Perth in the Scientific Literature, and the Geologic Mapping of Lot 6
Monday, 6 May 2013
On the trail of Climactichnites wilsoni - Part 3: A quarry about a mile from Perth as the town existed in 1859
Tuesday, 21 July 2015
Reports of the Trace Fossil Climactichnites found in Central Texas
Thursday, 16 July 2015
Burrows or Not Burrows - Part 2
Friday 7 October 2016
The Metcalfe Geoheritage Park in Almonte, Lanark County; and Geoheritage Day 2016
This posting covers a few of the ways that our Geoheritage is promoted in Eastern Ontario.
The park displays over twenty large specimens of local rocks: sedimentary rocks of Ordovician age, as well as local igneous and metamorphic rocks of Precambrian age. The following are photographs my two favourite specimens that are on display:
The first photograph shows desiccation cracks in sandstone, and provides evidence of microbial mats (otherwise such large shrinkage cracks would not be preserved in sandstone). This specimen was discovered during the construction of the Almonte hydro electric generating station that is within a hundred meters of the park. The second shows stromatolites in local limestone.
In addition to the rocks on permanent display, the park incorporates space for two guest rocks. Presently the two guest rocks on display are a specimen of Gowganada Conglomerate from the Elliot Lake Area and a specimen of Mica Schist.
Two brochures are available at the site: first, a coloured brochure with photographs and descriptions of all of the specimens; second, a black and white brochure with descriptions of the two guest rocks. In the near future visitors will be able to use their mobile phones to digitally link each specimen with a website that will provide information on the specimen, as the Association of Professional Geologists Education Foundation is funding a project for a QR code system to link QR code signage for each specimen to web pages with content on each specimen.
The park is located in a beautiful setting beside the Mississippi River in Almonte within easy walking distance of a number of restaurants, and is worth a visit. Ample parking and benches are provided.
Each year volunteers from the Department of Earth Sciences at Carleton University and the Ottawa-Gatineau Geoheritage Committee act as hosts at a number of sites throughout the National Capital Region (both in Ottawa, Ontario and in Quebec) where people can go to admire outcrops and learn about the geology of the site. This year’s Geoheritage Day takes place on Sunday, October 16th. These are the sites they are hosting this year:
Champlain Bridge Stromatolites, Gatineau
Champlain Lookout, Gatineau Park
Hogs Back Park, Ottawa
South March Highlands Hike, Kanata (Starts at 10 a.m.)
Cardinal Creek Karst, Orleans
Mer Bleue Bog, Orleans
Pinhey Sand Dunes, Nepean
The Haycock Iron Mine, Cantley, Quebec
Carleton University Earth Sciences Sample Preparation Laboratory
Details and a map can be obtained at the following web page.
http://www.earthsci.carleton.ca/outreach/explore-geoheritage-day
My November 6, 2013 blog posting reviewed this brochure. A pdf copy of the brochure can be downloaded from:
http://sgraycomm.files.wordpress.com/2013/08/murphys-point-bike-loop-aug5-13-final-download-small.pdf
This brochure can be downloaded in pdf format from the Stephanie Gray’s web site at:
https://sgraycomm.files.wordpress.com/2013/08/perth-geohistory-booklet-sept20-small.pdf
Christopher Brett
Perth, Ontario
Suggested Readings
Anonymous
Ottawa Gatineau Geoheritage
www.ottawagatineaugeoheritage.ca/
Anonymous
The Almonte Geoheritage Project
https://luc-lafreniere-kec0.squarespace.com/s/Almonte-geoheritage-project.pdf
J. Allan Donaldson, 2009
Geoheritage 2. Examples of Geoeducation, Geoconservation and Geo-rescue Projects in Ontario
Geoscience Canada - Journal of The Geological Association of Canada, Volume 36, Number 3
https://journals.lib.unb.ca/index.php/gc/article/view/12590/13466
J. Allan Donaldson, 2012
The Ottawa-Gatineau Geoheritage Committee Enters its Second Decade. GAC-MAC Joint Annual Meeting, St. John’s 2012, Abstracts Volume 35, pages 35-36
www.mineralogicalassociation.ca/doc/StJohns2012_GAC-MAC_Abstracts.pdf
The Metcalfe Geoheritage Park in Almonte, Lanark County
The Metcalfe Geoheritage Park in Almonte is Canada’s first municipal geoheritage park. On September 24th I attended the official re-opening and rededication of the park, which in the past year has undergone a transformation, including the movement of the specimens, the construction of a short walking trail, the building of concrete slabs on which to display the specimens, and the addition of signage.
The park displays over twenty large specimens of local rocks: sedimentary rocks of Ordovician age, as well as local igneous and metamorphic rocks of Precambrian age. The following are photographs my two favourite specimens that are on display:
The first photograph shows desiccation cracks in sandstone, and provides evidence of microbial mats (otherwise such large shrinkage cracks would not be preserved in sandstone). This specimen was discovered during the construction of the Almonte hydro electric generating station that is within a hundred meters of the park. The second shows stromatolites in local limestone.
In addition to the rocks on permanent display, the park incorporates space for two guest rocks. Presently the two guest rocks on display are a specimen of Gowganada Conglomerate from the Elliot Lake Area and a specimen of Mica Schist.
Two brochures are available at the site: first, a coloured brochure with photographs and descriptions of all of the specimens; second, a black and white brochure with descriptions of the two guest rocks. In the near future visitors will be able to use their mobile phones to digitally link each specimen with a website that will provide information on the specimen, as the Association of Professional Geologists Education Foundation is funding a project for a QR code system to link QR code signage for each specimen to web pages with content on each specimen.
The park is located in a beautiful setting beside the Mississippi River in Almonte within easy walking distance of a number of restaurants, and is worth a visit. Ample parking and benches are provided.
Geoheritage Day - Sunday, October 16, 2016 - 10 am to 3 pm
Each year volunteers from the Department of Earth Sciences at Carleton University and the Ottawa-Gatineau Geoheritage Committee act as hosts at a number of sites throughout the National Capital Region (both in Ottawa, Ontario and in Quebec) where people can go to admire outcrops and learn about the geology of the site. This year’s Geoheritage Day takes place on Sunday, October 16th. These are the sites they are hosting this year:
Champlain Bridge Stromatolites, Gatineau
Champlain Lookout, Gatineau Park
Hogs Back Park, Ottawa
South March Highlands Hike, Kanata (Starts at 10 a.m.)
Cardinal Creek Karst, Orleans
Mer Bleue Bog, Orleans
Pinhey Sand Dunes, Nepean
The Haycock Iron Mine, Cantley, Quebec
Carleton University Earth Sciences Sample Preparation Laboratory
Details and a map can be obtained at the following web page.
http://www.earthsci.carleton.ca/outreach/explore-geoheritage-day
Murphys Point Bike Loop: A Geological Interpretation, by Bradley S. Wilson
My November 6, 2013 blog posting reviewed this brochure. A pdf copy of the brochure can be downloaded from:
http://sgraycomm.files.wordpress.com/2013/08/murphys-point-bike-loop-aug5-13-final-download-small.pdf
Introduction to the Geodiversity of Perth: A Self-Guided Tour of Rocks on Display at the Crystal Palace, Tay Basin, Perth, Ontario, by Dr. J Allan Donaldson
This brochure can be downloaded in pdf format from the Stephanie Gray’s web site at:
https://sgraycomm.files.wordpress.com/2013/08/perth-geohistory-booklet-sept20-small.pdf
Christopher Brett
Perth, Ontario
Suggested Readings
Anonymous
Ottawa Gatineau Geoheritage
www.ottawagatineaugeoheritage.ca/
Anonymous
The Almonte Geoheritage Project
https://luc-lafreniere-kec0.squarespace.com/s/Almonte-geoheritage-project.pdf
J. Allan Donaldson, 2009
Geoheritage 2. Examples of Geoeducation, Geoconservation and Geo-rescue Projects in Ontario
Geoscience Canada - Journal of The Geological Association of Canada, Volume 36, Number 3
https://journals.lib.unb.ca/index.php/gc/article/view/12590/13466
J. Allan Donaldson, 2012
The Ottawa-Gatineau Geoheritage Committee Enters its Second Decade. GAC-MAC Joint Annual Meeting, St. John’s 2012, Abstracts Volume 35, pages 35-36
www.mineralogicalassociation.ca/doc/StJohns2012_GAC-MAC_Abstracts.pdf
Thursday 29 September 2016
Eighty-one feet of Dark Grey Paleozoic Shale was Logged under the Potsdam by Bruce A. Liberty in Core from a Hole Drilled at Knowlton Lake, Ontario and reported in a Geological Survey of Canada Paper published in 1971
I expect that many people reading the title of this posting, if they have a working knowledge of the sedimentary rocks of Eastern Ontario, will read the title at least twice, and will ask themselves the following three questions:
- How can there be Paleozoic shale under the Potsdam given that the Potsdam Group is considered to be the oldest sedimentary series in Eastern Ontario?
- If Liberty reported shale under the Potsdam, why hasn’t anyone followed up on it?
- How does this shale formation tie in with Dalrymple, Narbonne and Smith’s 1985 paper “Eolian action and the distribution of Cambrian shales in North America” (Geology, 13, 607–610)?
I have to admit that I can’t presently answer those questions and may not have an answer until 2018. Below I’ve provided the source for the title, a summary of my investigations, what I hope to find, and why it will take to 2018.
The title to this posting is derived from statements in the following paper and in the legend to the following map.
Liberty, B. A, 1971. Paleozoic geology of Wolfe Island, Bath, Sydenham and Gananoque map areas, Ontario. Geological Survey of Canada Paper 70-35, 1971, ; 12 pages (4 sheets), doi:10.4095/102360
Liberty, B. A, 1970 , Geology Sydenham Ontario, Map 17-1970, Geological Survey of Canada , Preliminary Series, to accompany Paper 70-35. Geology by B. A. Liberty, 1961, 1964, 1966
Liberty devotes the first paragraph at page 2 of his paper to the Potsdam Formation, and concludes with the following three sentences:
“At least 70 feet of the formation occur in outcrop in the area and a boring at Knowlton Lake indicates a total thickness there of 149 feet. An additional 81 feet of dark grey Paleozoic shale was logged, by the writer, at the base of the formation in the first Dominion Observatory boring
at Knowlton Lake. This unit is separated as a lower member at this one location only.”
I thought at first that Liberty’s reference to “81 feet of dark grey Paleozoic shale” at the base of the Potsdam must have been a mistake, but on his accompanying Map 17-1970 Liberty has the legend:
“2 POTSDAM SANDSTONE: red, white, grey and yellow, evenly textured, fine-grained sandstone, and siltstone: in Knowlton Lake area this formation includes 81 feet of underlying dark grey shale as lower member (not included above).” [my emphasis]
One of my initial thoughts was that someone else must have noted Liberty’s statements and commented on the underlying shale. While I found that a number of authors reference Liberty’s paper, I’ve been unable to find a reference to the shale. For example, when Carson (1981a, 1981b) re-mapped this area for the Ontario Geological Survey he referenced Liberty’s earlier work, but doesn’t mention the shale. Carson (1981a) mentions that “Geological mapping of the Kingston area involved the reexamination of three map-areas previously mapped by B.A. Liberty for the Geological Survey of Canada (Liberty1971)” and that “Although no fossils have been recovered from the Potsdam formation, it is considered to be of Cambrian age (Liberty 1971)” , but doesn’t mention the shale. Carson (1981b) mentions that “Liberty (1971) estimated a total thickness in excess of 21 m” for the Potsdam Formation, but doesn’t mention the shale.
Carson, D.M., 1981a: No. S13 Paleozoic Geology of the Kingston Area, Southern Ontario; in Ontario Geological Survey Miscellaneous Paper 100, Summary of Field Work, 1981, pages 134-136
Carson, D.M., 1981b: Paleozoic Geology of the Tichborne-Sydenham Area, Southern Ontario; Ontario Geological Survey Preliminary Map P. 2413, Geological Series. Scale 1:50000. Geology 1980.
Sanford and Arnott (2010, GSC Bulletin 597, page 14) mention that Liberty (1971) “established the presence of a large number of sandstone outliers, which were identified as a single unit, the Potsdam Formation” but again fail to mention Liberty’s description of the shale.
I knew from prior research that Liberty had been an authority on the Paleozoic rocks of Ontario. (Liberty authored or co-authored over fifty papers and maps for the Geological Survey of Canada on the Paleozoic sedimentary rocks of Ontario that were published over a period from about 1950 to 1973.) As he had a wealth of knowledge on the Paleozoic rocks of Ontario, I thought it unlikely that he could have mistaken, for example, Precambrian shale for Paleozoic shale. I could have looked briefly at the core and assumed black shale to be Paleozoic, but Liberty logged the core and made that decision. Accordingly, why did he think the shale was Paleozoic in age? The answer to that question has to be found in the core and in his notes from when he logged the core.
I expect everyone reading this posting is asking themselves the question “Where would one look for the core from the Dominion Observatory boring at Knowlton Lake and for Liberty’s notes when he logged the core?” I expect that there are many others like me who grew up in Ottawa knowing that the Dominion Observatory was on Carling Avenue in Ottawa, that geophysicists had been associated with the observatory, and that those geophyicists later worked for various sections of Energy Mines and Resources, now Natural Resources Canada, and worked with the geologists at the Geological Survey of Canada, also now Natural Resources Canada, and would check first with the Natural Resources Canada.
As a first stab at finding the core I looked on GEOSCAN, Natural Resources Canada’s online database of Geological Survey of Canada publications. I did locate "A user's guide to core-storage facilities in Canada ', Geological Survey of Canada Paper 84-23, 1985 doi:10.4095/120217 " but it wasn't much help, other than for telling me that the Ontario Geological Survey had core from Eastern Ontario stored at Tweed.
I then sent an email to a contact at the Geological Survey of Canada/Natural Resources Canada and was told that they didn’t have the core or Liberty’s notes.
Next I sent an email to the District Geologist at the Ontario Geological Survey in Tweed and was told they didn’t have the core.
Partly in desperation, I sent emails to two geologists (both retired, but still active) that I knew had worked for Energy Mines and Resources or the Geological Survey of Canada at the same time as Liberty. The first, a geophysicist, replied that he had no idea where the core would be, that after the GSC, Bruce Liberty was at Brock University and Guelph, that I might look there for his records, but that many records had been tossed out on various reorganizations. The second, a geologist, also had no knowledge of the core, but noted “Instead of older Paleozoic, perhaps it is an unrecognized unit of post-Grenville Proterozoic strata, or maybe a thick patch of regolith developed on Grenville? I've seen shale-like regolith of unknown thickness below Potsdam SS elsewhere.”
I also sent an email to Mark Badham, the curator of the Miller Museum at Queen's, asking if he had any knowledge of the core. He assumed that I was talking about three drill holes drilled by the Dominion Observatory at the Holleford Crater and sent me the following paper by Brian St. John.
Brian E. St. John, 1968
Paleolacustrine arenites in the Holleford meteorite Crater, Ontario. Canadian Journal of Earth Sciences, 5, 935-943 www.nrcresearchpress.com/doi/pdf/10.1139/e68-090
Mark also told me that Queen’s has select pieces of the core from the three drill holes, mostly from the sediment layers in the crater.
I'd forgotten how close the Holleford crater was to Knowlton Lake, but suspect that Brian St. John's work does not explain Liberty finding shale below the Potsdam. Brian St. John comments on three holes drilled within the boundary of the crater. None of these intersected Potsdam sandstone. The drill hole I'm looking for would be outside the crater, but only a half mile due south of Diamond Drill Hole 3 on Brian St. John's Figure 1, and on the southwest shore of Knowlton Lake.
Brian St. John reported that the Holleford Crater is filled by sedimentary rocks which he divided into seven lithic units. The top two units, his Units 6 and 7, he correlated with the Rideau formation and the Pamela formation that outcrop in Eastern Ontario. He included a basal “explosion breccia” which he designated unit 1, overlain by unit 2, a thin breccia layer, both related to the meteor impact. His units 3, 4 and 5 are:
Unit 3: calcareous shales and argillaceous limestones and sandstones, which contain a small quantity of carbonaceous matter, “which imparts a black colour to most of the unit”,
Unit 4: gray calcareous quartz arenite, and
Unit 5: white calcareous quartz arenite.
It is only St. John’s unit 3 that sounds remotely like Liberty’s “ 81 feet of dark grey Paleozoic shale.” While I suspect that St. John’s unit 3 is not Liberty’s shale, if Liberty’s shale is the same shale that St. John reported then it answers a question St. John posed in his paper as to whether the crater is pre-Potsdam or post-Potsdam.
I was subsequently contacted by my source at the GSC/NRC. She had done some more sleuthing and told me that “The core might be stored at our Tunney’s Pasture collections facility but I’m afraid that the collections are closed for the next many months as we are moving out of the building. If [another person at the GSC/NRC] is not able to help out with information, I’m afraid you will have to wait until the collection is reopened in 2018. There is no one from collections who can look this up at this time.” Accordingly, it appears that my search will be placed on hold until 2018.
In 2018 it will be interesting to see if the core stored at Tunney’s Pasture is the core from the three holes drilled within the Holleford Crater, or from the hole I’m looking for that was drilled at the edge of Knowlton Lake. If the core can be located, is Liberty’s “dark grey Paleozoic shale” actually Paleozoic shale, or is it Precambrian shale or Precambrian regolith? If it is shale, does it correlate with the shale within the Holleford Crater? If it is a new formation that is older than the Potsdam what secrets will it yield?
What is interesting about Liberty’s report from 1971 is how much has changed. In 1971 when Liberty logged 81 feet of dark grey Paleozoic shale he did so before geologists recognized the Ediacaran/Vendian period, before geologists were interested in Ediacaran/Vendian fossils, and before geologists were interested in small shelly fossils. What prompted Liberty to identify the core as being Paleozoic shale? Did he see find small shelled fossils?
The core in the possession of Queen’s, particularly the carbonaceous material, might also be worth a fresh look with modern techniques. In 1968 when Brian St. John looked at the sedimentary rocks in the Holleford crater he did so before the Queen’s Geology Department had a scanning electron microscope. I can remember using the electron microscope in the Geology Department at Queen’s. I had to modify the software every time I went on the machine, and then had to take my results over to campus mainframe computer to get the results of my analysis. Today when results are available instantaneously, it would be a shame not to re-analyze St. John’s core.
Christopher Brett
Perth, Ontario
Below is an extract from Liberty's map 17-1970. On the map I’ve used red squares to show the locations of the three Dominion Observatory drill holes within the Holleford meteorite crater that were described by Brian St. John. I’ve shown in acquamarine where Potsdam sandstone outcrops at the southwest corner of Knowlton Lake, and where I believe Dr. Bruce A. Liberty reported the Dominion Observatory drill hole where he logged “ 81 feet of dark grey Paleozoic shale” at the base of the Potsdam. Liberty's Unit 1 is Precambrian; Unit 2, Potsdam Formation; Unit 3, Shadow Lake Formation; Unit 4, Gull River Formation, Member A; Unit 5, Gull River Formation, Member B.
- How can there be Paleozoic shale under the Potsdam given that the Potsdam Group is considered to be the oldest sedimentary series in Eastern Ontario?
- If Liberty reported shale under the Potsdam, why hasn’t anyone followed up on it?
- How does this shale formation tie in with Dalrymple, Narbonne and Smith’s 1985 paper “Eolian action and the distribution of Cambrian shales in North America” (Geology, 13, 607–610)?
I have to admit that I can’t presently answer those questions and may not have an answer until 2018. Below I’ve provided the source for the title, a summary of my investigations, what I hope to find, and why it will take to 2018.
The title to this posting is derived from statements in the following paper and in the legend to the following map.
Liberty, B. A, 1971. Paleozoic geology of Wolfe Island, Bath, Sydenham and Gananoque map areas, Ontario. Geological Survey of Canada Paper 70-35, 1971, ; 12 pages (4 sheets), doi:10.4095/102360
Liberty, B. A, 1970 , Geology Sydenham Ontario, Map 17-1970, Geological Survey of Canada , Preliminary Series, to accompany Paper 70-35. Geology by B. A. Liberty, 1961, 1964, 1966
Liberty devotes the first paragraph at page 2 of his paper to the Potsdam Formation, and concludes with the following three sentences:
“At least 70 feet of the formation occur in outcrop in the area and a boring at Knowlton Lake indicates a total thickness there of 149 feet. An additional 81 feet of dark grey Paleozoic shale was logged, by the writer, at the base of the formation in the first Dominion Observatory boring
at Knowlton Lake. This unit is separated as a lower member at this one location only.”
I thought at first that Liberty’s reference to “81 feet of dark grey Paleozoic shale” at the base of the Potsdam must have been a mistake, but on his accompanying Map 17-1970 Liberty has the legend:
“2 POTSDAM SANDSTONE: red, white, grey and yellow, evenly textured, fine-grained sandstone, and siltstone: in Knowlton Lake area this formation includes 81 feet of underlying dark grey shale as lower member (not included above).” [my emphasis]
One of my initial thoughts was that someone else must have noted Liberty’s statements and commented on the underlying shale. While I found that a number of authors reference Liberty’s paper, I’ve been unable to find a reference to the shale. For example, when Carson (1981a, 1981b) re-mapped this area for the Ontario Geological Survey he referenced Liberty’s earlier work, but doesn’t mention the shale. Carson (1981a) mentions that “Geological mapping of the Kingston area involved the reexamination of three map-areas previously mapped by B.A. Liberty for the Geological Survey of Canada (Liberty1971)” and that “Although no fossils have been recovered from the Potsdam formation, it is considered to be of Cambrian age (Liberty 1971)” , but doesn’t mention the shale. Carson (1981b) mentions that “Liberty (1971) estimated a total thickness in excess of 21 m” for the Potsdam Formation, but doesn’t mention the shale.
Carson, D.M., 1981a: No. S13 Paleozoic Geology of the Kingston Area, Southern Ontario; in Ontario Geological Survey Miscellaneous Paper 100, Summary of Field Work, 1981, pages 134-136
Carson, D.M., 1981b: Paleozoic Geology of the Tichborne-Sydenham Area, Southern Ontario; Ontario Geological Survey Preliminary Map P. 2413, Geological Series. Scale 1:50000. Geology 1980.
Sanford and Arnott (2010, GSC Bulletin 597, page 14) mention that Liberty (1971) “established the presence of a large number of sandstone outliers, which were identified as a single unit, the Potsdam Formation” but again fail to mention Liberty’s description of the shale.
I knew from prior research that Liberty had been an authority on the Paleozoic rocks of Ontario. (Liberty authored or co-authored over fifty papers and maps for the Geological Survey of Canada on the Paleozoic sedimentary rocks of Ontario that were published over a period from about 1950 to 1973.) As he had a wealth of knowledge on the Paleozoic rocks of Ontario, I thought it unlikely that he could have mistaken, for example, Precambrian shale for Paleozoic shale. I could have looked briefly at the core and assumed black shale to be Paleozoic, but Liberty logged the core and made that decision. Accordingly, why did he think the shale was Paleozoic in age? The answer to that question has to be found in the core and in his notes from when he logged the core.
I expect everyone reading this posting is asking themselves the question “Where would one look for the core from the Dominion Observatory boring at Knowlton Lake and for Liberty’s notes when he logged the core?” I expect that there are many others like me who grew up in Ottawa knowing that the Dominion Observatory was on Carling Avenue in Ottawa, that geophysicists had been associated with the observatory, and that those geophyicists later worked for various sections of Energy Mines and Resources, now Natural Resources Canada, and worked with the geologists at the Geological Survey of Canada, also now Natural Resources Canada, and would check first with the Natural Resources Canada.
As a first stab at finding the core I looked on GEOSCAN, Natural Resources Canada’s online database of Geological Survey of Canada publications. I did locate "A user's guide to core-storage facilities in Canada ', Geological Survey of Canada Paper 84-23, 1985 doi:10.4095/120217 " but it wasn't much help, other than for telling me that the Ontario Geological Survey had core from Eastern Ontario stored at Tweed.
I then sent an email to a contact at the Geological Survey of Canada/Natural Resources Canada and was told that they didn’t have the core or Liberty’s notes.
Next I sent an email to the District Geologist at the Ontario Geological Survey in Tweed and was told they didn’t have the core.
Partly in desperation, I sent emails to two geologists (both retired, but still active) that I knew had worked for Energy Mines and Resources or the Geological Survey of Canada at the same time as Liberty. The first, a geophysicist, replied that he had no idea where the core would be, that after the GSC, Bruce Liberty was at Brock University and Guelph, that I might look there for his records, but that many records had been tossed out on various reorganizations. The second, a geologist, also had no knowledge of the core, but noted “Instead of older Paleozoic, perhaps it is an unrecognized unit of post-Grenville Proterozoic strata, or maybe a thick patch of regolith developed on Grenville? I've seen shale-like regolith of unknown thickness below Potsdam SS elsewhere.”
I also sent an email to Mark Badham, the curator of the Miller Museum at Queen's, asking if he had any knowledge of the core. He assumed that I was talking about three drill holes drilled by the Dominion Observatory at the Holleford Crater and sent me the following paper by Brian St. John.
Brian E. St. John, 1968
Paleolacustrine arenites in the Holleford meteorite Crater, Ontario. Canadian Journal of Earth Sciences, 5, 935-943 www.nrcresearchpress.com/doi/pdf/10.1139/e68-090
Mark also told me that Queen’s has select pieces of the core from the three drill holes, mostly from the sediment layers in the crater.
I'd forgotten how close the Holleford crater was to Knowlton Lake, but suspect that Brian St. John's work does not explain Liberty finding shale below the Potsdam. Brian St. John comments on three holes drilled within the boundary of the crater. None of these intersected Potsdam sandstone. The drill hole I'm looking for would be outside the crater, but only a half mile due south of Diamond Drill Hole 3 on Brian St. John's Figure 1, and on the southwest shore of Knowlton Lake.
Brian St. John reported that the Holleford Crater is filled by sedimentary rocks which he divided into seven lithic units. The top two units, his Units 6 and 7, he correlated with the Rideau formation and the Pamela formation that outcrop in Eastern Ontario. He included a basal “explosion breccia” which he designated unit 1, overlain by unit 2, a thin breccia layer, both related to the meteor impact. His units 3, 4 and 5 are:
Unit 3: calcareous shales and argillaceous limestones and sandstones, which contain a small quantity of carbonaceous matter, “which imparts a black colour to most of the unit”,
Unit 4: gray calcareous quartz arenite, and
Unit 5: white calcareous quartz arenite.
It is only St. John’s unit 3 that sounds remotely like Liberty’s “ 81 feet of dark grey Paleozoic shale.” While I suspect that St. John’s unit 3 is not Liberty’s shale, if Liberty’s shale is the same shale that St. John reported then it answers a question St. John posed in his paper as to whether the crater is pre-Potsdam or post-Potsdam.
I was subsequently contacted by my source at the GSC/NRC. She had done some more sleuthing and told me that “The core might be stored at our Tunney’s Pasture collections facility but I’m afraid that the collections are closed for the next many months as we are moving out of the building. If [another person at the GSC/NRC] is not able to help out with information, I’m afraid you will have to wait until the collection is reopened in 2018. There is no one from collections who can look this up at this time.” Accordingly, it appears that my search will be placed on hold until 2018.
In 2018 it will be interesting to see if the core stored at Tunney’s Pasture is the core from the three holes drilled within the Holleford Crater, or from the hole I’m looking for that was drilled at the edge of Knowlton Lake. If the core can be located, is Liberty’s “dark grey Paleozoic shale” actually Paleozoic shale, or is it Precambrian shale or Precambrian regolith? If it is shale, does it correlate with the shale within the Holleford Crater? If it is a new formation that is older than the Potsdam what secrets will it yield?
What is interesting about Liberty’s report from 1971 is how much has changed. In 1971 when Liberty logged 81 feet of dark grey Paleozoic shale he did so before geologists recognized the Ediacaran/Vendian period, before geologists were interested in Ediacaran/Vendian fossils, and before geologists were interested in small shelly fossils. What prompted Liberty to identify the core as being Paleozoic shale? Did he see find small shelled fossils?
The core in the possession of Queen’s, particularly the carbonaceous material, might also be worth a fresh look with modern techniques. In 1968 when Brian St. John looked at the sedimentary rocks in the Holleford crater he did so before the Queen’s Geology Department had a scanning electron microscope. I can remember using the electron microscope in the Geology Department at Queen’s. I had to modify the software every time I went on the machine, and then had to take my results over to campus mainframe computer to get the results of my analysis. Today when results are available instantaneously, it would be a shame not to re-analyze St. John’s core.
Christopher Brett
Perth, Ontario
Below is an extract from Liberty's map 17-1970. On the map I’ve used red squares to show the locations of the three Dominion Observatory drill holes within the Holleford meteorite crater that were described by Brian St. John. I’ve shown in acquamarine where Potsdam sandstone outcrops at the southwest corner of Knowlton Lake, and where I believe Dr. Bruce A. Liberty reported the Dominion Observatory drill hole where he logged “ 81 feet of dark grey Paleozoic shale” at the base of the Potsdam. Liberty's Unit 1 is Precambrian; Unit 2, Potsdam Formation; Unit 3, Shadow Lake Formation; Unit 4, Gull River Formation, Member A; Unit 5, Gull River Formation, Member B.
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