I have to admit that I cannot answer that question and that I’m writing a blog posting on the topic in the hopes that someone will be able to provide an answer.
Below I’ll set out what was reported in the literature and will discuss why the core should be looked at with fresh eyes.
In 1981 and 1984 the Geological Survey of Canada drilled six vertical 75 mm (2.95 inch) holes at the Borehole Geophysics Test Area on the grounds of Natural Resources Canada’s CANMET Research Complex located at Bell’s Corners, Ottawa (Bernius, 1981; Killean, 1986; Bernius, 1996; Mwenifumbo et al., 2005). Four of the holes are spaced along a 100 m line (at intervals of 10m, 20m and 70 m), while the other two were positioned to form two equilateral triangles with sides of 30 m and 100 m. The three deepest holes were drilled to 300 m. The boreholes are used to calibrate instruments for borehole geophysical measurements such as porosity, resistivity, etc.
Bernius (1981, 1996) reported on the core. The drill holes intersected about 65 m of Paleozoic rocks that dip at a low angle and thicken slightly to the north-northwest, underlain by Precambrian igneous and metamorphic rocks. The core revealed (progressing down the holes):
Paleozoic
- 11 to 16 metres of Oxford Formation grey to reddish brown, sandy domomite;
- 4 metres of March Formation comprised of a massive quartz arenite on the top and a light-grey coloured dolomitic sandstone at the bottom
- Nepean Formation comprised of (still progressing down the holes):
- 16 metres of pure, well sorted, massive, white sandstone
- a 50 cm layer of reddish-brown shale
- 27 metres comprised of a sequence of cross-bedded sandstones with fifteen bioturbate layers that range in thickness from 2 cm to 10 cm and alternate with the cross-bedding, with zones of vertical worms holes of the species skolithos, Diplocraterion and Arenicolites
- a thin 5 cm layer of quartz-feldspar orthoconglomerate
Precambrian
- a 15 - 17 metre highly altered/weathered zone, a saprolite layer, in the Precambrian rocks
- syenites, granites and gneisses
Bernius (1996) mentions that the upper contact of the Nepean formation with the March Formation is a disconformity and that there is a sharp unconformity between the Paleozoic sequence and the Precambrian rocks.
The Borehole Geophysics Test Area is about a kilometer south of what is (or was) arguably a reference section for the Nepean Formation sandstone of the Potsdam Group that is found along highway 417 in Kanata (Greggs and Bond, 1972). Further, that section has been used by a number of authors (Greggs and Bond, 1972, 1977; Bond and Greggs, 1973; Brand and Rust, 1977a, b; Dix et al., 2004; Sanford and Arnott, 2010; Lowe et al., 2017 ) to try to settle the boundary between the Nepean formation and the overlying March formation. An interesting question is “Why has no one looked at the core from the Borehole Geophysics Test Area to help resolve where to place the boundary between the Nepean Formation and the March Formation?” (Other than perhaps the obvious answer that it was overlooked.)
A second issue is what to make of the 50 cm thick shale layer that Bernius (1996) reports in the Nepean Formation. The shale layer is interesting because I can find no reference to anyone else reporting a shale layer in the Nepean Formation of Ontario. (Dolostone, mudstone and siltstone are reported in the Nepean Formation, but no shale.) I had initially wondered if perhaps the reference to 50 cm should be perhaps 5cm, but note that later in the report, when discussing the geophysical logs for the Nepean Formation, Bernius (1996) mentions that “From 36.8 m to 37.4 m there is a distinctive impure shaley layer. The increase in the potassium log in this layer is due to the clay minerals, while the electrical log responses... also indicate the presence of more conductive materials....”
It is possible that the shale layer marks the boundary of the Nepean with the March (Theresa). I make that suggestion because Bernius (1996) states that the 50 cm layer of reddish-brown shale separates two units of the Nepean Formation, a lower bioturbated and cross-bedded unit, and an upper, very pure , well sorted, white sandstone; and Bernius correlated his lower bioturbated layer with Greggs and Bonds’ upper bioturbated section which they placed just below the boundary the Nepean and the March (Theresa). Bernius noted that the boreholes are a kilometer south of the road cut on Highway 417 that Greggs and Bond suggested for the principal reference section for the Nepean; but failed to consider that the shale could be the boundary between the Nepean (Keeseville) and the March (Theresa), and that his sorted, white sandstone could be part of the March. It is also possible that all of Bernius’ sandstone is March formation sandstone.
Bernius (1981) and Bernius (1996) have barely been mentioned. Williams (1991) cites Bernius (1981) in three locations to refer to the 17 m alteration zone at the top of the Precambrian, for Bernius’ measured thickness for the Nepean at the CANMET complex, and for the thickness of the March Formation. Mwenifumbo et al. (2005) direct one to Bernius (1996) for a discussion of the geology of the area and core. Pilkington and Todoeschuck (1990) cite Bernius (1981) as the source for their cryptic summary of the geology.
Christopher Brett
Perth, Ontario
Addendum, November 14, 2021:
In a recent paper released on September 13, 2021 Crow et al. (2021) provided new geophysical data from the drill holes at the GSC’s Borehole Geophysics Test Site. They also re-logged the drill core. Their description of the rocks differs slightly from Benius’ description. For example, they have adopted more current names for the formations, don’t mention the layer of reddish brown shale, and assign more rock to the Theresa (formerly the March) Formation, and less rock to the Beauharnois (formerly lower Oxford) Formation. This is their description of the Paleozoic rocks:
“Keeseville (Nepean) Formation (core depths 20.45 – 64.30m)
The contact with the basement occurs at a 20cm thick quartz conglomerate with some brownish limonitic layers (Bernius, 1996). A 5.2m-long interval of white quartz sandstone overlies the conglomerate. Overlying this is a sandstone sequence characterized by alternating bioturbated and cross-bedded sandstone, both with variable amounts of hematite (visible iron staining), glauconite and limonite. There are 23 bioturbated layers identified, ranging in thickness from 5 to 83cm. Burrows are frequently seen in this interval. The upper 16m of the Keeseville Formation is characterized by massive, white quartz arenite with some dark laminae and irregular layers.
Theresa and Beauharnois Formations (core depths 5.30 (top of core) – 20.45m)
The Theresa Formation is composed of interbedded sandy calcareous dolostone and calcareous
sandstone. The base of the formation contains a distinct dark grey layer of uranium-bearing and
chalcopyrite-rich pyrobitumen (Charbonneau et al., 1975; Bernius, 1996) also known as thucolite (see Hoekstra and Fuchs, 1960). The core transitions upward into a grey, fine to medium crystalline dolostone, containing a few very thin interbeds of fine grained quartz sandstone. Calcite-filled cavities are observed in core. The upper several metres of core are broken and fractured, with visible weathering along vertical fracture surfaces. The transitional nature of the Theresa Formation upward into the Beauharnois Formation leaves assigning the contact between the two open for re-examination. The local thickness of the Theresa Formation has been interpreted to be about 10m, suggesting that the upper few metres of core could be Beauharnois Fm.”
Crow, H L; Brewer, K D; Cartwright, T J; Gaines, S; Heagle, D; Pugin, A J -M; Russell, H A J
2021 New core and downhole geophysical data sets from the Bells Corners Borehole Calibration Facility Ottawa, Ontario. Geological Survey of Canada, Open File 8811, 2021, 36 pages, https://doi.org/10.4095/328837 Released: 2021 09 14
See also my two blog postings from October, 2021 entitled Abandoned Nepean Sandstone Quarries and Outcrops in the Greenspace West of Bells Corners -
References
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)
Bond, I.J., and Greggs, R.G. 1973.
Revision of the March Formation (Tremadocian) in southeastern Ontario. Canadian Journal of Earth Sciences, 10 : 1140–1155. 10.1139/e73-098
Brand, U., and Rust, B.R., 1977a
The age and upper boundary of the Nepean formation in its type section area near Ottawa, Ontario. Canadian Journal of Earth Sciences, 14: 2002–2006.
www.nrcresearchpress.com/doi/abs/10.1139/e77-171 #.WR-TQbiN0r0
Brand, U., and Rust, B.R., 1977b
The age and upper boundary of the Nepean formation in its type section area near Ottawa, Ontario: Reply. Canadian Journal of Earth Sciences, 14: 2671–2673. 10.1139/e77-233
Dix, George R., Salad Hersi, Osman, and Nowlan, Godfrey S., 2004
The Potsdam-Beekmantown Group boundary, Nepean Formation type section (Ottawa, Ontario): a cryptic sequence boundary, not a conformable transition, Canadian Journal of Earth Sciences, 2004, 41(8): 897-902, http://www.nrcresearchpress.com/doi/pdf/10.1139/e04-040
Greggs, R. G. and Bond, I. J., 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. www.nrcresearchpress.com/doi/abs/10.1139/e72-078
Greggs, R. G. and Bond, I. J., 1977
The age and upper boundary of the Nepean formation in its type section area near Ottawa, Ontario: Discussion. Canadian Journal of Earth Sciences, 14: 2669–2671. 10.1139/e77-232
Killean, P.G., 1986,
A System of Deep Test Holes and Calibration Facilities for Developing and Testing New Borehole Geophysical Techniques, GSC Paper 85-27, p. 29-46; (pdf 54803 KB); doi:10.4095/123600; in, Borehole geophysics for mining and geotechnical applications; Killeen, P G (ed.); Geological Survey of Canada, Paper 85-27, 1986;
Lowe, David G.,, Arnott,R.W.C., Nowlan, Godfrey S., 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, Published on the web 6 February 2017, doi: 10.1139/cjes-2016-0151
Mwenifumbo, C.J., Elliott, B.E., Hyatt, W.G., Bernius, G.R., 2005
Bells Corners calibration facilities for downhole and surface geophysical equipment. Geological Survey of Canada, Open File 4838, 18 p. http://geochem.nrcan.gc.ca/cdogs/content/pub/pub10463_e.htm
Pilkington, M. And Todoeschuck, J.P., 1990
Stochastic inversion and scaling geology; Geophys. J. Int. 102, 205-217
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
Williams, D.A., 1991
Paleozoic Geology of the Ottawa-St. Lawrence Lowland, Southern Ontario; Ontario Geological Survey, Open File Report 5770, 292p, at 29,46 and 56
