Residents of Eastern Ontario will be familiar with the outcrops of stromatolites along the Ottawa River. The most well known outcrop is in the bed of the Ottawa River on the Quebec side, just over the Champlain Bridge. Other well known outcrops are at Kitchissippi Lookout near Westboro Beach, at an outcrop just east of Port O’Call Marina near Dunrobbin, and at Fitzroy Provincial Park. Stromatolites are also visible in the walls of the transitway from the pedestrian bridge at the end of Roosevelt Avenue in Westboro, Ottawa.
What is less well known is that fossil thrombolites are also visible along the Ottawa River. While thrombolites and stromatolites are both microbial structures, stromatolites have a layered structure while thrombolites lack the layers and have a clotted structure. Most who write on stromatolites and thrombolites assign the presence of
the structures to different facies, where the growth of the two
structures was regulated by different microbial assemblages in response
to changes in environmental factors including sea levels.
In 2015 I noted that Donaldson and Chiarenzelli’s (2004a) field trip guide mentioned that stromatolites were visible in limestone at Kitchissippi Lookout, along the Ottawa River. When I visited the outcrop in 2015 I found both stromatolites and thrombolites. The outcrops with stromatolites can be found in with the shrubs and trees, while the thrombolites are down at the edge of the river. More specifically, the thrombolites are about two meters lower in the stratigraphic column.
Eight days ago I again visited Kitchissippi Lookout to take photographs of the stromatolites and thrombolites. The passage of time has not been kind to the outcrops of stromatolites. Below are photographs of the most photogenic of the stromatolites.
Other examples are present. The stromatolites are not as impressive as they once were (for example, see Quentin Gall’s photograph on Ottawa-Gatineau Geoheritage Project’s web site, mentioned below ).
What I really visited Kitchissippi Lookout for was to make sure that fossil thrombolites and trace fossils could still be found. Below are photographs that I took in 2015 and 2021 of loose slabs that show thrombolites.
The thrombolites are up to 9 cm in diameter. Similar slabs are present close to the water’s edge. Additional thrombolites can be seen in the bedrock. Below is a photograph, taken in 2015, showing the internal structure of broken thrombolites in the outcrop.
In 2015 well developed fossil trace fossils were also visible in bedrock at the water’s edge. The below photograph shows burrowing.
I could not find the outcrop with trace fossils when I recently visited. However, sand and gravel has been washed in by the river and the trace fossils might still be found with a bit of effort.
Thrombolites Beside Champlain Bridge and at Brebeuf Park
What prompted my re-attendance at Kitchissippi Lookout was that on September 16th I (and numerous others) had received an email from Dr. Al Donaldson telling me (and the others) that the Ottawa River had dropped to a level that Dr. Donaldson had “never before seen, allowing direct access to strata directly below the unit of stromatolites beside Champlain Bridge ... [The river] is more than half a metre lower than I’ve seen it since I first moved to Ottawa in 1959, allowing the source bedrock of the fossil-rich slabs to be seen in direct contact with the overlying layer of stromatolites. Remarkably, the lowermost well-layered stromatolites appear to be widely cored by silicified thrombolites (laminae-free domal structures) that contain abundant fossils resembling shells of modern clams and snails that make up the cores of thromboliitic stromatolites still actively growing in Shark Bay, Australia.”
Dr. Donaldson has taken a number of photographs of the thrombolites including photographs of [a] unlinked non-laminated thrombolites up to 15 cm in diameter, and [b] an oblique view of closely packed thrombolites, showing characteristic internal clotting. The thrombolites are in the bed of the Ottawa River at the Champlain Bridge occurrence and in the bed of the Ottawa River at Brebeuf Park, Gatineau, Quebec. Brebeuf Park is about two kilometers east of the Champlain Bridge.
Unfortunately, I failed to go over in time to look at the outcrops. I received an email from Dr. Donaldson telling me that he had gone over “to Brebeuf Park soon after sunrise on Saturday [September 25], only to find the water had risen almost 1 m overnight.” The thrombolites are back underwater.
I will have to hope that next summer is as dry as the summer of 2021, so that the thrombolites are again visible at the Champlain Bridge and at Brebeuf Park. However, as the last time the river was that low was sixty-two years ago, I’m not that hopeful.
Links to Online Photographs of Stromatolites Along the Ottawa River
While there are lots of web sites with photographs of the stromatolites in the bed of the Ottawa River just over the Champlain Bridge in Quebec, the best photographs can be found on the Géo-Outaouais web site: Colonie de stromatolites à Gatineau
http://geo-outaouais.blogspot.com/search?q=stromatolite
Some of the best photographs of the stromatolites at Westboro Beach/ Kitchissippi Lookout are Quentin Gall’s photographs on the web site of the Ottawa-Gatineau Geoheritage Project, Stop 5, Westboro Beach [Kitchissippi Lookout] Stromatolites, ... and trace fossils fossils
https://www.ottawagatineaugeoheritage.ca/subsites/5
The best photographs of the stromatolites along the transitway can be found on the Géo-Outaouais web site: Stromatolites du Transitway, à Ottawa : suite
http://geo-outaouais.blogspot.com/2011/11/stromatolites-du-transitway-ottawa.html
Some of the better photographs of the stromatolites just east of Port O’Call Marina near Dunrobbin can be found on my October 26, 2015 blog posting entitled “A Good Year to Look at the Stromatolites along the Ottawa River - Part 2, near Dunrobin .
http://fossilslanark.blogspot.com/2015/10/a-good-year-to-look-at-stromatolites_26.html
Donaldson , and Chiarenzelli ( 2004b) include a photograph of the laterally linked stromatolites of the Oxford Formation in the bed of the Ottawa River at Fitzroy Provincial Park.
I believe that the paper by Nehza and Dix (2012) is the only one to mention both the stromatolites and the thrombolites in Eastern Ontario. Bernstein and Hofmann (1989) gave a talk at a GAC/MAC annual meeting on stromatolites, oncolites and thrombolites of the Beekmantown Group, and an abstract of the talk is cited in a few papers, but I have not yet been able to track it down.
Christopher Brett
Ottawa
References and Suggested Reading
Bernstein, L. and Hofmann, H.J. 1989
Lower Ordovician stromatolites, oncolites and thrombolites, Beekmantown Group, Ottawa - St. Lawrence Lowland, Quebec and Ontario. Geological Association of Canada, Abstracts with Programs, v.14, p. A86.
Brett, Christopher, 2015a
A Good Year to Look at the Stromatolites along the Ottawa River. [In Quebec just across the Champlain Bridge from Ottawa.] Blog posting dated Thursday, October 1, 2015
http://fossilslanark.blogspot.com/2015/10/a-good-year-to-look-at-stromatolites.html
Brett, Christopher, 2015b
A Good Year to Look at the Stromatolites along the Ottawa River - Part 2, near Dunrobin . Blog posting dated Monday, 26 October 2015
http://fossilslanark.blogspot.com/2015/10/a-good-year-to-look-at-stromatolites_26.html
Brett, Christopher, 2020a
Stromatolites in the Ordovician Oxford Formation, Eastern Ontario . Blog posting dated Friday, September 4, 2020
http://fossilslanark.blogspot.com/2020/09/stromatolites-in-ordovician-oxford.html
Donaldson, J.A., 1963
Stromatolites in the Denault Formation, Marion Lake, Coast of Labrador, Newfoundland; Geological Survey of Canada, Bulletin 102, 1963, 33 pages, https://doi.org/10.4095/123903
Donaldson, J. Allan and Jeffrey R. Chiarenzelli, 2004a,
Stromatolites and Associated Biogenic Structures in Cambrian and Ordovician Strata in and Near Ottawa, Ontario; 76th Annual Meeting, Field Trip Guidebook, New York State Geological Association, 283 pages, Trip F-1, at pages 1-20. [Stop 1. Limestone, Ottawa Group (Ordovician) at Kitchissippi Lookout. ... a 20 cm bed of limestone containing laterally linked domal stromatolites with a synoptic relief of 10 cm. Stop 4. Stromatolites in Pamella formation (Ordovician), Fablewood. Figure 4. Plan-view photograph of stromatolite exposures in Gatineau, Quebec (STOP 4).
Donaldson, J. Allan, and Chiarenzelli, J. R., 2004b,
Precambrian Basement and Cambrian-Ordovician Strata , as Displayed in Three Provincial Parks of Canada, 76th Annual Meeting, Field Trip Guidebook, New York State Geological Association, 283 pages, Trip A-I, at pages 63-78. [Figure 4: Laterally linked stromatolites of the Oxford Formation, Fitzroy Harbour Provincial Park.]
Eljalafi, Abdulah, 2017
Lithofacies, diagenesis, and chemostratigraphy of the micobialite and marginal lacustrine carbonate units within the Green River Formation, Eastern Uinta Basin , Colorado and Utah. Master of Science Thesis , Colorado School of Mines, 137 pages
https://mountainscholar.org/bitstream/handle/11124/171849/Eljalafi_mines_0052N_11381.pdf
Eljalafi, Abdulah and J Frederick Sarg, 2018
Lacustrine Microbialite Architectural and Chemostratigraphic Trends: Green River Formation, Eastern Uinta Basin, Colorado and Utah* Search and Discovery Article #51522 (2018)**
https://www.researchgate.net/publication/347901627_Lacustrine_Microbialite_Architectural_and_Chemostratigraphic_Trends_Green_River_Formation_Eastern_Uinta_Basin_Colorado_and_Utah
Greggs R.G. and Sargent M.W., 1971
Algal bioherms of the Upper Gull River Formation (Middle Ordovician) near Kingston, Ontario. Canadian Journal of Earth Sciences, 8(11): 1373–1381. https://cdnsciencepub.com/doi/pdf/10.1139/e71-126
Palmer, James R., 1991
Distribution of Lithofacies and Inferred Depositional Environments in the Cambrian System, pages 9-38, in Geology and Mineral Resource Assessment of the Springfield 1 x 2 Quadrangle, Missourri, as Appraised in September, 1985; edited by James A. Martin and Walden P. Pratt
U.S. Geological Survey Bulletin 1942
Käsbohrer, Fabian and Jochen Kuss, 2021
Lower Triassic (Induan) stromatolites and oolites of the Bernburg Formation revisited – microfacies and palaeoenvironment of lacustrine carbonates in Central Germany. Facies (2021) 67:11 https://doi.org/10.1007/s10347-020-00611-y
Mayr, U. And de Freitas, T, 1998
Cambrian to Upper Ordovician carbonate platform, p. 21-56 in Mayr, U (ed.); de Freitas, T (ed.); Beauchamp, B (ed.); Eisbacher, G (ed.); The geology of Devon Island north of 76̊, Canadian Arctic Archipelago. Geological Survey of Canada, Bulletin 526, 1998, 500 pages (1 sheet), https://doi.org/10.4095/209767
Nehza, Odette and George R. Dix, 2012
Stratigraphic restriction of stromatolites in a Middle and Upper Ordovician foreland-platform succession (Ottawa Embayment, eastern Ontario). Canadian Journal of Earth Sciences, 2012, 49(10): 1177-1199, https://doi.org/10.1139/e2012-048
