Dave Forsyth’s Photographs of Aspidella from the Richmond Quarry, Lanark County

 I have previously mentioned Dave Forsyth in four of my earlier postings (November 29, 2013; January 29, 2014; August 27, 2015; September 22, 2016).  Dave is a retired geophysicist who has been interested in the rocks of eastern Ontario at least since 1968 when he authored a Bachelor’s thesis with the title “Studies in the Potsdam”.   Dave spent his career with the Earth Physics Branch and the Geological Survey of Canada, Department of Energy, Mines and Resources, Ottawa .   Since his retirement Dave has co-authored at least three geological field trip guides on the rocks of eastern Ontario, and has been active leading geological field trips for the Macnamara Field Naturalists’ Club, Arnprior, the Niagara Peninsula Geological Society and The Grenville Land Stewardship Council.  

Last year I mentioned in numerous blog postings (Brett, 2019a-f) that I had found the Ediacaran fossil Aspidella and Ediacaran rocks at Tackaberry’s active quarry on Highway 7 about five kilometers (three miles)  north of Perth, Lanark County, Ontario.   Last year I sent the information to Dave and he replied that a number of years ago he had seen similar structures at an abandoned quarry close to Tackaberry’s active quarry, had photographed them, and would look through his collection of photographs for photos that he had taken at that time.   This year Dave sent to me photographs from his 2008 visit to the Richmond quarry, which is located about one and a half kilometers to the west of Tackaberry’s active quarry.  Below are three of the photos that Dave sent to me.

Dave Forsyth retains ownership of the copyright in the photos.  They cannot be reproduced without his consent and credit being given to him as the photographer and owner of copyright in the photos.

I believe that the concentric features that Dave photographed are the Ediacaran fossil Aspidella.    The third photo also shows many obscure markings, a few of  which I have marked with  neon pink boxes around the features.   Some appear to be stalks, fronds, and the trace fossil Helminthopsis.  Other obscure forms might be algae or an Ediacaran fossil such as Kimberella.

Below is a map showing the location of Tackaberry’s active quarry (red square) and the abandoned Richmond quarry (blue square).    The map is based primarily on extracts from Ontario Geological Survey’s Maps P. 2724 and P. 2725 by Williams and Wolf (1984a, b).  It also contains changes based on Wilson, Liberty  and Reinhardt’s (1972) map.

 The two quarries are located about six kilometers directly north of Perth in Drummond North Elmsley Township.  The quarries are  located in an irregular shaped area of flat lying sedimentary rocks covering approximately 140 square kilometers that I have previously designated the “Drummond Sequence”  that has  been mapped by the Ontario Geological Survey (Williams and Wolf, 1984a, b): and by the Geological Survey of Canada (Wilson and Dugas, 1961; Wilson, Liberty,  and Reinhardt, 1972) as  Ordovician March Formation rocks (interbedded quartz sandstone, dolostone and sandy dolostone).  Finding the Ediacaran fossil Aspidella at the two quarries strongly suggests that the underlying rocks are of Ediacaran age.

The Drummond Sequence falls within the old Drummond Township (now Drummond North Elmsley Township).    On Map P2725 Williams and Wolf (1984a) have mapped the March formation (and hence, the Drummond Sequence) as extending northwest into the old Lanark Township (now the Township of Lanark Highlands).  Their mapping contradicts earlier mapping by Wilson, Liberty  and Reinhardt (1972) who mapped Nepean sandstone, and Precambrian marble, amphibolite and gneiss in that part of  old Lanark Township where Williams and Wolf (1984a) have mapped the March formation.  I have preferred Wilson, Liberty  and Reinhardt’s (1972) map and have shown their rock units in the northwest corner of the attached map.  Interestingly, Wilson and Dugas (1961) mapped a small area of Nepean sandstone ( 2 miles by 1/4 mile) not shown by Williams and Wolf (1984a, b) that falls  within the Drummond Sequence.

Williams and Wolf (1984a, b) show  the block that is the Drummond Sequence as bounded by faults that separate it on the west from Cambrian Nepean Formation Sandstone, on the southeast from March Formation,  on the Northeast from Cambrian Nepean Formation Sandstone, on the north and northwest from plutonic and metamorphic rocks of the Grenville Province of the Precambrian Shield.   As I have preferred Wilson, Liberty  and Reinhardt’s (1972) map, the Drummond Sequence is not bounded in the northwest by faults mapped by  Williams and Wolf (1984a) .  Intriguingly, Easton (2017) shows an additional  geophysically defined fault trending southwest- northeast that falls just north of the two quarries.   See Easton’s  (2017)  Figures 18.3. A) and B).

The rocks at the top of the Drummond Sequence have been mapped as the Ordovician March Formation by both the Ontario Geological Survey and the Geological Survey of Canada.  I found no body fossils in these rocks, but found trace fossils suggesting that the rocks are Ordovician (or Cambrian) in age (see photos Sam_0180,  Sam_182 and Sam_0525 shown on my September 13, 2013  blog posting).   The trace fossils are similar to ones found by others in March (Theresa) Formation rocks in New York State.   At Tackaberry’s active quarry the March Formation beds are at most a few meters thick..   

At Tackaberry's active quarry, in the  rocks that are mapped as the March Formation, is a meter thick  layer of rock coloured pink and buff and showing Liesegang banding and rings (Brett, 2012a, first five photographs) likely caused by diagenetic processes involving the circulation of subsurface waters.    The altered rock can be found in outcrops along Highway 7 just north of Perth where the rocks weather grey but the pink colour and the chemical banding in the rocks can still be seen.  Below that layer are tens of meters of flat lying, thin siltstone and sandstone beds bearing Ediacaran fossils (mainly Aspidella) and showing ripple marks (Brett 2019b) and microbial mat textures (Brett2012b, Brett2019c).  Minor carbonate beds are present.   At the base of the quarry are thick sandstone beds that exhibit polygonal cracking (Brett2019c, ninth photo), and which have not yielded any fossils.

For ease of future reference I will define the ‘Drummond Formation’ as that part of the Drummond Sequence that consists of interbedded Ediacaran quartz sandstone, siltstone and minor carbonate rock.   The quartz sandstones and siltstones are thinly to thickly bedded, fine grained, and well sorted. The sandstones and siltstones are coloured light grey, dark grey, brown, buff and reddish brown.   Ripple marks and microbial mat textures are common. Liesegang banding is present in a layer close to the top of the sequence.  Aspidella and other Ediacaran fossils are present.

 Dr. Easton of the Ontario Geological Survey mapped the Precambrian geology of the Perth and Carleton Place areas over the last five years.   He has a map in preparation -- Precambrian geology of the Perth area; Ontario Geological Survey, Preliminary Map P.3818 -- that will hopefully shed some light on the faults and rocks of the Drummond Sequence.     Dr. Easton (2018) noted that  “Most of the major faults shown on the Paleozoic geology map of Williams and Wolf (1984[b]) located solely in Precambrian rocks present in the western half of the Carleton Place map area could not be validated by geology or geophysics.”  The Carleton Place map area covers the northern half of the Drummond Sequence.

Christopher Brett
Ottawa, Ontario


REFERENCES and SUGGESTED READING

Brett, C.P., 2012a
Mud cracks, Liesegang bands and Liesegang rings, and possible Soft-Sediment Deformation Structures in Sedimentary Rocks of Lanark County, Ontario in an Area Mapped as March Formation. Blog posting, 19 October 2012
http://fossilslanark.blogspot.com/2012/10/

Brett, C.P., 2012b
From Trails, to Mud Cracks to Evidence of Microbial Mats: Different Theories For Curved Lines in the troughs of ripple marks in Sandstone.  Blog Posting 5 November 2012
http://fossilslanark.blogspot.com/2012/11/from-trails-to-mud-cracks-to-evidence.html

Brett, C. P., 2019a
Concentric Structures in the Sedimentary Rocks of Lanark County, Ontario that are identical to the Ediacaran Holdfast Aspidella.  Blog posting dated  8 March 2019 -
http://fossilslanark.blogspot.com/2019/03/holdfasts-in-lower-ordovician-march.html

Brett, C. P., 2019b
 Fossil Ripple Marks in Rocks Near Perth Ontario. Blog posting dated 17 March 2019,

Brett, C. P., 2019c
Possible Fossil Microbial Mat Structures in Rocks Near Perth, Ontario.  Blog posting dated 28 March 2019.

Brett, C. P., 2019d
A Selection of Fossils from the ‘March Formation’ in Lanark County, Ontario - A Correction.  Blog posting dated  24 March 2019
http://fossilslanark.blogspot.com/2019/03/a-selection-of-fossils-from-march.html

Brett, C. P., 2019e
If the Ediacaran discoid holdfast Aspidella, why not Ediacaran Stalks, Spindles and Fronds in Lanark County?   Blog posting dated   29 March 2019
http://fossilslanark.blogspot.com/2019/03/if-ediacaran-discoid-holdfast-aspidella.html

Brett, C. P., 2019f - Tubular Structures in the Ediacaran Drummond Sequence in Lanark County, Ontario.  Blog posting dated  22 October 2019   http://fossilslanark.blogspot.com/2019/

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   

Easton, R.M. 2016. 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., 2017
Precambrian and Paleozoic Geology of the Carleton Place Area, Grenville Province.  Project SO-17-001, Chapter 18 in Ontario Geological Survey 2017. Summary of Field Work and Other Activities, 2017; Ontario Geological Survey, Open File Report 6333, 408p.

Easton, R. M. 2018
Precambrian Geology and Mineral Potential of the Carleton Place Area, Grenville Province . Chapter 14. Project SO-17-001. In Ontario Geological Survey 2018. Summary of Field Work and Other Activities, 2018; Ontario Geological Survey, Open File Report 6350, 426p.

Easton, R.M., 2020 [in press].
 Precambrian geology of the Perth area; Ontario Geological Survey, Preliminary Map P.3818, scale 1:50 000.

Williams, D.A., and Wolf, R.R., 1984a
Paleozoic Geology of the Perth Area, Southern Ontario; Ontario; Geological Survey, Map P. 2724, Geological Series-Preliminary Map, scale 1:50 000. Geology 1982.
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/P2724/P2724.pdf

Williams, D.A., and Wolf, R.R.,  1984b
Paleozoic Geology of the Carleton Place Area, Southern Ontario; Ontario Geological Survey, Map P. 2725, Geological Series-Preliminary Map, scale 1:50 000. Geology 1982.

Wilson, A. E., Liberty, B. A., and Reinhardt, 1972,
Geology Carleton Place, Ontario.  Map 1362, Geological Survey of Canada. Scale 1:50,000
Paleozoic geology by A. E. Wilson, 1946.  Paleozoic compilation by B. A. Liberty, 1963, with changes and additions by E. W. Reinhardt, 1972.  Precambrian geology and compilation by E. W. Reinhardt, 1963, 1969, 1972

Wilson, M E; Dugas, J., 1961
Geological Survey of Canada, "A" Series Map 1089A, 1961, 1 sheet; https://doi.org/10.4095/107951 

 FIELD TRIP GUIDES, ETC., CO-AUTHORED BY DAVE FORSYTH

Donaldson,  Al, Forsyth, Dave,  Findlay, Chris  and Bud Andress, 2010
Fall geology/ecology boat tour - St Lawrence River  1000 Islands.  October 17, 2010.
http://www.frontenacarchbiosphere.ca/explore/fab-education/geology/st-lawrence-river-thousand-islands-geology-boat-tour

Forsyth, D.A. and Forsyth, M.E. 2013a
Madawaska to Macnamara Trail and Macnamara Trail Geotours. Macnamara Field Naturalists Club.    www.mfnc.ca
https://mfnc.ca/wp-content/uploads/2013/02/arnpriorgeotour.pdf

Forsyth, D.A. and Forsyth, M.E.,  2013b
A  geology primer for the Morris Island Conservation Area..  Macnamara Field Naturalists Club.
https://mfnc.ca/wp-content/uploads/2013/02/morrisislandconversationarea_geology.pdf

Forsyth, D.A. and Forsyth, M.E., 2011,
Pillars in the Park, GAC/AGC - MAC/AMC - SEG - SGA  Joint Annual Meeting, Ottawa 2011, Abstracts Volume 34, at page 66
https://gac.ca/wp-content/uploads/2018/11/2011_Ottawa2011AbstractsVolume.pdf

Forsyth, D.A., 2011
Evidence and Hypothesis – How the Sandstone Cylinders Formed
GAC/AGC - MAC/AMC - SEG - SGA  Joint Annual Meeting, Ottawa 2011, Abstracts Volume 34, at pages 66-67
https://gac.ca/wp-content/uploads/2018/11/2011_Ottawa2011AbstractsVolume.pdf

Dr. Easton’s Sandstone Outcrop at Gillies Corners, Lanark County - Part 2

 I dropped over to look at Dr. Easton’s outcrop this week.  Below are two photographs (347 and 351) of the rounded, nodular pseudomorphs of evaporite minerals.  The nodules originally could have been any of gypsum, anhydrite, halite, barite, phosphate.

Below is a better photograph of Dr. Easton’s outcrop (356) showing the March formation at the top and the underlying Nepean formation.    

In addition below is a photograph (366) of a piece of the fine grained  buff sandstone that is arguably wind blown (aeolian erg) sandstone.  I wetted the sample so that the layering is visible.  The numbers on the blue ruler record centimeters.  

 

Another Outcrop on Malcolms Way

I also looked at an outcrop that is about 150 meters to the east along Malcolms Way.  Below are two photographs (359 and 362) showing the darker March formation on top and the underlying Nepean formation.  The  silver ruler is a meter stick with inches and centimeters numbered.

Christopher Brett
Ottawa

Addendum (September 15, 2020):  Another interpretation of the outcrops is that all of the rock is March (Theresa) formation.  This is because interbedded with typical March sandy dolomites and dolomites one finds beds of  siliceous sandstone identical to Nepean sandstone.   This can be seen in outcrops of the March (Theresa) formation at the outskirts of Smith Falls heading north on Highway 15. 

Interestingly, Keith’s map 1946-9 of the distribution of Potsdam sandstone in Eastern Ontario (which was in part based on mapping by Morley E. Wilson and by Alice E. Wilson)  shows an area of Potsdam sandstone where “Calcareous and argillaceous sandstone predominate”extending to Gilles Corners.  Some areas on Keith’s map where “Calcareous and argillaceous sandstone predominate” are now mapped as Potsdam Group sandstone and some as the March formation. 

SUGGESTED READING -  SABKHA NODULES

Bréhéret, Jean-Gabriel and Brumsack, Hans-J., 2000
Barite concretions as evidence of pauses in sedimentation in the Marnes Bleues Formation of the Vocontian Basin (SE France).  Sedimentary Geology 130(3):205-228  February 2000  
https://doi.org/10.1016/S0037-0738(99)00112-8
 
Butrenchuk, S., 1996
Phosphate Deposits  in British Columbia.  British Columbia  Geological Survey Branch., Bulletin 98, 136 pages
http://cmscontent.nrs.gov.bc.ca/geoscience/PublicationCatalogue/Bulletin/BCGS_B098.pdf
 
Fryberger, Steven G.; Abdulkader M. Al-Sari; Thomas J. Clisham, 1983 

Eolian Dune, Interdune, Sand Sheet, and Siliciclastic Sabkha Sediments of an Offshore Prograding Sand Sea, Dhahran Area, Saudi Arabia
AAPG Bulletin (1983) 67 (2): 280–312.
https://doi.org/10.1306/03B5ACFF-16D1-11D7-8645000102C1865D
 
Garden,U.R.; S.C.Guscott, S.D.Burley , K.A. Foxford, J. J. Walsh and J. Marshall, 2001
An exhumed palaeo-hydrocarbon migration fairway in a faulted carrier system, Entrada Sandstone of SE Utah.  Geofluids (2001)1, 195 -213
https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1468-8123.2001.00018.x

Ge, Y.,  C. L. Pederson, S. W. Lokier, J. P. Traas, G. Nehrke, R. D. Neuser, K. E. Goetschl,
A, Immenhauser,  2020
Late Holocene to Recent aragonite-cemented transgressive lag deposits in the Abu Dhabi lagoon and intertidal sabkha.  Sedimentalogy, Volume67, Issue 5, Pages 2426-2454
https://doi.org/10.1111/sed.12707

Keith, M. L.,1946
Sandstone as a  source of silica sands in southeastern Ontario; Ontario Dept. Mines, Vol.55, pt.5, 36p. (published 1949). Accompanied by Map 1946-9, scale l inch to 2  miles

McMackin, Matthew and William Godwin, 2016
Sabkha, in Encyclopedia of Engineering Geology (pp.1-2),Editors: P.  T. Bobrowsky, B. Marker
DOI: https://doi.org/10.1007/978-3-319-73568-9_26
DOI: 10.1007/978-3-319-12127-7_248-1

West, Ian M., Y. A. Ali; M. E. Hilmy, 1979
Primary gypsum nodules in a modern sabkha on the Mediterranean coast of Egypt.
Geology (1979) 7 (7): 354–358.
https://doi.org/10.1130/0091-7613(1979)7<354:PGNIAM>2.0.CO;2

Zhou, X.,  D. Chen, S. Dong, Y. Zhang,  Z. Guo, H.Wei, H.Yue, 2015
Diagenetic barite deposits in the Yurtus Formation in Tarim Basin, NW China: Implications for barium and sulfur cycling in the earliest Cambrian. Precambrian Research  Volume 263, July 2015, Pages 79-87 https://doi.org/10.1016/j.precamres.2015.03.006 See Figure 3.

 

Dr. Easton’s Sandstone Outcrop at Gillies Corners, Lanark County

Over the past five years Dr. Michael Easton of the Ontario Geological Survey has been mapping the Precambrian rocks of Eastern Ontario.  This is Dr. Easton's 2017 report of a previously unreported outcrop of Nepean Formation sandstone in Lanark County:    
 
“The northeastern boundary of the geophysical anomaly may also be fault bounded because a  previously undocumented inlier of Nepean Formation rocks occurs at Gillies Corners (UTM 413795E 4984105N), 4.3 km southwest of Frankto[w]n, immediately south of the northwestern boundary of the geophysical anomaly (see Figure 18.3A).   This sudden appearance of a stratigraphically lower unit in an area underlain by rocks of the stratigraphically higher March Formation, suggests that if a fault is present, it is down-dropped to the north.”

Dr. Easton’s location UTM 413795E 4984105N  converts to Latitude : 45.005155 deg, or 45 deg 0 min 18.558 sec.  Longitude: -76.093858 deg, or -76 deg 5 min 37.889 sec.   Plugging 45.005155, -76.093858 into Google will show the location of the outcrop.

In June I took County Road 10 when I was driving back to Ottawa from Perth, and stopped at Gillies Corners to look at Dr. Easton's outcrop of Nepean Formation sandstone.    [While the road is mapped as Perth Road, as Drummond Concession 2 and as County Road 10, most in Perth call it the Franktown Road.   Those living in Franktown call it the Perth Road.  I have yet to meet anyone in Perth who calls it County Road 10, but it is identified as such by those from Ottawa and on Google Maps.]

The sandstone outcrops on both sides of Malcolms Way,  with the best outcrops about 100 meters east of Gillies Corners Side Road.   The better outcrop, on the north side of Malcolms Way,  is about  30 yards long and 5 feet high and is flat lying, fresh sandstone.   Most of the outcrop is Nepean formation white to buff sandstone.   There are additional smaller, badly weathered,  outcrops to the east along Malcolms Way.

Four photographs of the best outcrop are provided below [331, 339, 340, 341] :

The ruler in the photographs is a meter stick, with inches and centimeters marked.

The second photograph shows a layer of dark rock at the top, which is likely March formation (or younger Oxford formation), with an uncomformity between the underlying Nepean Formation sandstone and the overlying March Formation.   (The weathered dark rock also outcrops further east along Malcolms Way.)

 In earlier blog postings I mentioned that Dave Lowe (2016 )  has recognized six siliciclastic paleoenvironments in the Potsdam Group sandstones:  a) braided fluvial,  b) ephemeral fluvial, c) aeolian erg, d) coastal sabkha, e) tide-dominated marine and  f) open-coast tidal flat.   Interestingly, the Nepean formation sandstone at this location displays at least two and possibly three different facies.

A layer that extends over much of the length of the outcrop that is full of rounded, nodular pseudomorphs of evaporite minerals,  is Dave Lowe’s coastal sabkha facies.  See the second and third photos.  My third photo compares well with Dave Lowe’s (2016) photo 3.8A which he describes as “Impressions of sparry, nodular radiating mineral aggregates from Kanata, ON (locality 14),” which is behind Kanata’s Walmart.

At the top of the Nepean formation sandstone at this outcrop is a layer with vertical burrowing (second and fourth photo’s).  I had originally thought this to be Dave Lowe’s marine facies, but it is more likely burrowing in the sabkha facies sediments.

Most of the lower two thirds of the outcrop is a fine grained, white to buff sandstone that is arguably wind blown (aeolian erg) sandstone.

 Williams and Wolf’s (1984) Map P.2725 puts Gillies Corners in the March Formation,  and placed the fault bounded boundary between the Nepean and March at about four kilometers west of Gillies Corners.  Below is a map compiled from   Williams and Wolf’s (1984) Maps P.2725 and P.2724 upon which I have plotted the location of Dr. Easton’s outcrop with a red square.

Wilson, Liberty, and Reinhardt’s (1972) geologic map covers the  area north of where I have written ‘GILLIES CORNERS’ on my map.  They also mapped Gillies Corners as falling within the March Formation and show the boundary between the Nepean and March at about four kilometers west of Gillies Corners.  Interestingly, they also plot a small area of Nepean Sandstone (about a kilometer long and 200 meters wide)  about five kilometers north of Dr. Easton’s outcrop, along Line Road 6 where it  intersects  Gillies Corners Side Road.  I’ve marked this small area on the map with a blue oval shape.

 Curiously, an additional outcrop of Nepean sandstone appeared on Wilson,, Liberty and Reinhard’s (1964) preliminary  Map 7-1964, that did not appear on the finished map.  This was a small area along Gillies Corners Side Road about three kilometers north-northwest of Dr. Easton’s outcrop.  Intriguingly, Reinhardt, who was the last to edit the Paleozoic compilation, was an expert on Precambrian rocks rather than Paleozoic rocks.

Jean Dugas, for his 1952 doctoral thesis, mapped the geology of the Perth map area, which included the area south of Gillies Corners.  GSC Map 1089A by Wilson and Dugas (1961) replicates a map that is part of his thesis.  Dr. Morley Wilson is credited as the first author as part of the map-area had been surveyed in 1930 by Dr. Morley  Wilson, who mapped most of Palaeozoic area on the eastern part of the sheet.  Wilson and Dugas’ map shows a number of areas of Nepean sandstone that do not appear on Williams and Wolf’s (1984) Maps P.2725 and P2724.  For example, their map 1089A shows small occurrences of Nepean sandstone 4 km southwest of Gillies Corners, 4 km south of Gillies Corners, and 3 km east-southeast of Gillies Corners.  The largest of these is 1.5 miles long and 1/4 mile wide and cuts across County Road 10 just west of Cockburn Creek.

It has been over seventy years since Dr. Alice E. Wilson mapped the Paleozoic geology north of Gillies Corners and ninety years since Dr. Morley E. Wilson  mapped the Paleozoic geology south of Gillies Corners, and some outcrops that they found are now difficult to find.  What would have been farmland when they mapped the area is now overgrown with brush and trees.   Other outcrops are obscured by housing developments.

I brought Dr. Easton’s outcrop to the attention of  two geologists who have worked on the Nepean Formation and March Formation and sent them the photos.   One commented “The disconformable contact with the March/Theresa  is very interesting — we generally only see that kind of a relationship in association with a fault.”   The other noted that “A disconformable contact at the “Nepean-March” ... formation boundary has been a contentious issue over the years.”

The outcrop is worth a visit if you are interested in the Nepean Formation of the Potsdam Group.

Recent Comments on Potsdam sandstone

Below I’ve provided a few of the more recent commentaries on Potsdam sandstone.  Landing et al. (2019), Lowe et al. (2019) and Brink et al. (2019) have contradictory views.   

I’ve also included two papers by Bernius who reported on core from the GSC’s Borehole Geophysics Test Area at Bell’s Corners, Ottawa. His papers have been overlooked   What is particularly interesting is that the core contains a 50 cm thick shale layer in the Nepean Formation.   Bernius also found that the upper contact of the Nepean formation with the March Formation is a disconformity. 

Christopher Brett
Ottawa

Addendum (September 15, 2020): Another interpretation of the outcrop is that all of the rock is March (Theresa) formation.  This is because interbedded with typical March sandy dolomites and dolomites one finds beds of  siliceous sandstone identical to Nepean sandstone.   This can be seen in outcrops of the March (Theresa) formation at the outskirts of Smith Falls heading north on Highway 15. 

Interestingly, Keith’s map 1946-9 of the distribution of Potsdam sandstone in Eastern Ontario (which was in part based on mapping by Morley E. Wilson and by Alice E. Wilson)  shows an area of Potsdam sandstone where “Calcareous and argillaceous sandstone predominate”extending to Gilles Corners.  Some areas on Keith’s map where “Calcareous and argillaceous sandstone predominate” are now mapped as Potsdam Group sandstone and some as the March formation. 

Keith, M. L.,1946
Sandstone as a  source of silica sands in southeastern Ontario; Ontario Dept. Mines, Vol.55, pt.5, 36p. (published 1949). Accompanied by Map 1946-9, scale l inch to 2  miles


++++++++++++
REFERENCES AND SUGGESTED READING

Bernius, G. R., 1981,
Boreholes Near Ottawa for the Development and Testing of Borehole Logging Equipment - A preliminary Report GSC Paper 81-1C, p. 51-53
 
Bernius, G. R., 1996,
Borehole Geophysical Logs from the GSC Borehole Geophysics test site at Bell’s Corners, Nepean, Ontario, GSC Open File 3157, 38 pages, doi:10.4095/207617 (pdf  6427 KB)

Brett, C. P.,  2016
Gypsum Pseudomorphs that formed in the Sabkha Environment of the Potsdam Group.   Blog posting December 1, 2016
http://fossilslanark.blogspot.com/2016/12/gypsum-pseudomorphs-that-formed-in.html

Brett, C. P., 2017
Why has hardly anyone referred to core from the GSC’s Borehole Geophysics Test Area at Bell’s Corners, Ottawa, when the core contains a 50 cm thick shale layer in the Nepean Formation and the core straddles the boundary between the Nepean Formation and the overlying March Formation?”      Blog posting dated May 22, 2017
http://fossilslanark.blogspot.com/2017/05/

Brink R, Mehrtens C, Maguire H, 2019
Sedimentology and petrography of a lower Cambrian transgressive sequence: Altona Formation (Potsdam Group) in northeastern New York.  Bulletin of Geosciences, 94, 369-388
http://www.geology.cz/bulletin/contents/art1728

Dix, G.R., Salad Hersi, O., and Nowlan, G.S., 2004,
The Potsdam–Beekmantown Group unconformity, Nepean Formation type section (Ottawa, Ontario): a cryptic sequence boundary, not a conformable transition: Canadian Journal of Earth Sciences, v. 41, no. 8, p. 897–902,  https:// doi .org /10 .1139 /e04 -040 .

Dugas, Jean, 1952,
 Geology of the Perth map area, Lanark and Leeds Counties, Ontario; Ph. D., McGill, 189 pages, four  maps.  
http://www.collectionscanada.gc.ca/obj/thesescanada/vol2/QMM/TC-QMM-124004.pdf
https://escholarship.mcgill.ca/concern/theses/t435gh12d

Easton, Michael, 2017
Precambrian and Paleozoic Geology of the Carleton Place Area, Grenville Province,  pages 18-1 to 18-18 In Summary of Field Work and Other Activities 2017, Ontario Geological Survey, Open File Report 6333,
http://www.geologyontario.mndm.gov.on.ca/mndmaccess/mndm_dir.asp?type=pub&id=ofr6333

Landing, E., Salad Hersi, O.,  Amati, L., Westrop, S.R., Franzi, D.A., 2019
Early Paleozoic rifting and reactivation of a passive-margin rift: Insights from detrital zircon provenance signatures of the Potsdam Group, Ottawa graben: Comment. GSA Bulletin; March/April 2019; v. 131; no. 3/4; p. 695–698; https://doi.org/10.1130/B35104.1; published online 25 January 2019.

Lowe, David G., 2016
Lower Ordovician Potsdam Group in the Ottawa Embayment and Provenance of the Cambrian – Lower. Ordovician Potsdam Group in the Ottawa. Embayment and Quebec Basin. David G. Lowe. Doctoral Thesis submitted to the University of Ottawa
https://ruor.uottawa.ca/
http://hdl.handle.net/10393/35303
http://dx.doi.org/10.20381/ruor-261

Lowe, David G, and R.W.C. Arnott, 2016
 Composition and Architecture of Braided and Sheetflood-Dominated Ephemeral Fluvial Strata In the Cambrian–Ordovician Potsdam Group: A Case Example of the Morphodynamics of Early Phanerozoic Fluvial Systems and Climate Change
Journal of Sedimentary Research, v. 86, i. 6, p. 587-612, Published in June 2016, doi:10.2110/jsr.2016.39  

Lowe, D.G., Arnott, R.W.C., Chiarenzelli, J.R., and Rainbird, R.H., 2018,
Early Paleozoic rifting and reactivation of a passive-margin rift: Insights from detrital zircon provenance signatures of the Potsdam Group, Ottawa graben: Geological Society of America Bulletin, v. 130, no. 7/8, p. 1377–1396, https:// doi .org /10.1130 /B31749 .1 .

Lowe, D.G., Arnott, R.W.C., Chiarenzelli, J.R., and Rainbird, R.H., 2019,
Early Paleozoic rifting and reactivation of a passive-margin rift: Insights from detrital zircon provenance signatures of the Potsdam Group, Ottawa graben: Reply. Geological Society of America Bulletin, March/April 2019, v. 131, no. 3/4, pages 699-703; published online January 25, 2019.  https://pubs.geoscienceworld.org/gsa/gsabulletin/article/131/3-4/699/568492/Early-Paleozoic-rifting-and-reactivation-of-a

Lowe, David G.;  Arnott, R.W.C.; Nowlan, G.; McCracken, A.D., 2017
Lithostratigraphic and allostratigraphic framework  of the  Cambrian-Ordovician Potsdam Group and correlations  across Early Paleozoic southern Laurentia.  Canadian Journal of Earth Sciences  2017, 54(5): 550-585, https://doi.org/10.1139/cjes-2016-0151

Williams, D.A., and Wolf, R.R.,  1984a
Paleozoic Geology of the Carleton Place Area, Southern Ontario; Ontario Geological Survey, Map P. 2725, Geological Series-Preliminary Map, scale 1:50 000. Geology 1982.

Williams, D.A., and Wolf, R.R., 1984b
Paleozoic Geology of the Perth Area, Southern Ontario; Ontario; Geological Survey, Map P. 2724, Geological Series-Preliminary Map, scale 1:50 000. Geology 1982.

Wilson, Alice E., Liberty, B. A., and Reinhardt, E.W., 1964,
Geology Carleton Place, Ontario.  Map 7-1964, Preliminary Series, Geological Survey of Canada. Scale 1:50,000 Paleozoic geology by A. E. Wilson, 1946.  Paleozoic compilation by B. A. Liberty, 1963. Precambrian geology and compilation by E. W. Reinhardt, 1963.

Wilson, Alice E., Liberty, B. A., and Reinhardt, E.W.,  1972,
Geology Carleton Place, Ontario.  Map 1362, Geological Survey of Canada. Scale 1:50,000
Paleozoic geology by A. E. Wilson, 1946.  Paleozoic compilation by B. A. Liberty, 1963, with changes and additions by E. W. Reinhardt, 1972.  Precambrian geology and compilation by E. W. Reinhardt, 1963, 1969, 1972

Wilson, Morley E. and  Dugas, Jean,  1961,
Map 1089A, Geology, Perth, Lanark and Leeds Counties, Ontario, Geological Survey of Canada; Geology by Morley E. Wilson, 1930 and Jean Dugas, 1949; Descriptive notes by Jean Dugas.
https://doi.org/10.4095/107951