A Plucked, Glacially Polished, Flat Outcrop of March (Theresa) Formation Rock East of Perth

 [Rewritten and Corrected  October 19, 2021.  I originally visited this outcrop in September, 2020.  I visited the outcrop again on October 18, 2021.   A more thorough examination of the outcrop has convinced me that the plucked texture records deformed stromatolites and biofilms.]

Below are photographs of a flat, glacially polished, flat outcrop exhibiting a plucked, curved texture.  The outcrop is about four kilometers due east of Perth, Ontario.  The rock has been mapped by Wilson and  Dugas (1961) of the Geological Survey of Canada (Map 1089A) and by Williams and Wolf (1984) of the Ontario Geological Survey (Map P2724) as the March Formation interbedded quartz sandstone, sandy dolostone and dolomite.   The March Formation of Ontario is equivalent to the Theresa Formation of Quebec and New York.   

The top surface of the outcrop is badly weathered sandstone.  The plucked texture is about a half inch (1 1/2 centimeters)  deep.  The ruler in the photographs is a meter stick (recording cm and inches).  The underlying beds, which can be observed about 50 meters to the north of the flat outcrop, are comprised of at least ten meters of sandstone and sandy dolostone–undoubtedly the March (Theresa) formation.

 

 

In my September, 2020 posting I suggested three possible origins for the plucked texture:

- trace fossils formed by deposit feeders;

-the trace fossil  Furchenstein, which Othenio Abel (1935) had figured in his text ‘Vorzeitliche Lebensspuren’

- deformed stromatolites or biofilms much like outcrops in Nepean sandstone in Kanata.

My recent (October, 2021) examination of the outcrop has convinced me that the plucked texture records deformed stromatolites and biofilms.  I will include further photographs of the outcrop in a posting in October, 2021.

 The closest looking named trace fossils I could find were Ophiomorpha irregulaire,  Megagrapton submontanum, and Megagrapton submontanum (See López Cabrer  &  Oliver, 2015, figures 3b, 4a, 5, 6 and 2c;  Mourad et al., 2020, figures 4E, 4F; and  Uchman , 1998, figures 104, 105), but none were bang on. 9.

Here is Othenio Abel’s drawing of Furchenstein.

‘Furchenstein’ translates into English as ‘grooved stone’ or ‘furrowed stone.’  Abel noted that his drawing was about 1/8 natural size. When enlarged eight times the grooves  would be about the same size as I observed.   Abel’s  specimen was collected from the alpine lake near Mondsee in the Austrian Alps.   In the text of ‘Vorzeitliche Lebensspuren’ Othenio Abel comments (p. 371-372)  that the ‘Furchenstein’ shown in Figure 309 is typical of flysch sandstones of the Austrian Alpine lake district.    He explains the texture by strong algae growth which decomposes the surface of the sandstone and by insects and other animals eating feeding channels in the sandstone. The current view of Furchenstein  is that the furrows result from Cyanobacteria eating into the rock, which may be assisted by some species of boring mushrooms, and that grazing animals such as snails or some larvae may further hollow out the furrows (see Müller-Stoll, 1986, Whitton  and Mateo, 2012, and German Wikipedia under ‘Furchenstein’).  
        

Trace Fossils Observed in Loose Slabs to the North of the Plucked Outcrop

Below of two photographs of a loose slab of underlying March Formation rock (a sandstone to sandy dolomite) exhibiting a more convincing trace fossil (simple, mostly straight or almost straight, some slightly curved, flattened cylindrical, subhorizontal, about 2 to 5 mm in width, 2 to 3 cm in length, unbranched, some overlapping, in places a chaotic mess; likely made by a deposit feeder; somewhat like Planolites beverlyensis [see figure 14 G in Erickson and Bjerstedt, 1993]   or the burrowing pattern of the trace fossils Arthrophycus linearis or minimus but lacking features of those traces). 

The numbers on the rulers in the above two photographs record inches on top and centimeters below.

Below is a photograph of another loose slab from the same location, exhibiting circular structures, that is perhaps a bed sole exhibiting the trace fossil Bergaueria,  or perhaps a bed top exhibiting the trace fossil Monocraterion. 

 

Christopher Brett
Ottawa

References and Suggested Reading

Abel, Othenio, 1935,
Vorzeitliche Lebensspuren.  Jena: Gustav Fischer, 644 pages

Anonymous, 2020 

Furchenstein, German Wikipedia  https://de.wikipedia.org/wiki/Furchenstein

Bjerstedt, T. W., and J. M. Erickson, 1989
Trace fossils and bioturbation in peritidal facies of the Potsdam-Theresa Formations (Cambrian–Ordovician, northwest Adirondacks): Palaios, v. 4, p. 203–224, doi:10.2307/3514770.     https://www.jstor.org/stable/3514770

Brett, Christopher, 2015
In 1924 a report of Stromatolites in Nepean Sandstone by Dr. Morley E. Wilson of the Geological Survey of Canada, and Other Reports of Stromatolites and Biofilms in the Potsdam,
Blog posting dated November 4, 2015
http://fossilslanark.blogspot.com/2015/11/in-1924-report-of-stromatolites-in.html

Erickson,  J.  Mark, 1993 
 Cambro-ordovician stratigraphy, sedimentation, and ichnobiology of the St. Lawrence  lowlands  - frontenac arch to the Champlain Valley  of New York, Field trip A3 
https://ottohmuller.com/nysga2ge/Files/1993/NYSGA 1993 A3 (1) - CAMBRO-ORDOVICIAN STRATIGRAPHY, SEDIMENTATION, AND ICHNOBIOLOGY OF THE ST. LAWRENCE LOWLANDS - FRONTENAC ARCH TO THE CHAMPLAIN VALLEY OF NEW YORK.pdf

Erickson,  J. M. and Bjerstedt, T. W.,   1993
Trace Fossils and Stratigraphy in the Potsdam and Theresa Formations of the St. Lawrence Lowland, New York.     In  Field Trip Guidebook (pp.A3 1-21)Edition: 65th Annual Meeting Chapter: A3Publisher: New York State Geological Association 
https://www.researchgate.net/publication/306145931_Trace_Fossils_and_Stratigraphy_in_the_Potsdam_and_Theresa_Formations_of_the_St_Lawrence_Lowland_New_York

López Cabrer, María I. & Eduardo B. Oliver, 2015
Ophiomorpha irregulaire and associated trace fossils from the Upper Cretaceous of Patagonia, Argentina: Palaeogeographical and ethological signifi cance. Spanish Journal of Palaeontology
29 (1), 33-44.

Mourad, Belaid ; Cherif Amine , Olev Vinn, Mohammed Nadir Naimi, 2020
First record of trace fossils from the Oxfordian Argiles rouges de Kheneg Formation (Tiaret, northwestern Algeria).   Geologia Croatica 73(2):85-94

Müller-Stoll,  Wolfgang R. , 1986
Der Cyanophyceen-Bewuchs der Furchenoder Hirnsteine des Bodensees. [The cyanophycean growth on the furrows or brain stones of Lake Constance]  Carolinea  44:51–60
https://www.zobodat.at/pdf/Carolinea_44_0051-0060.pdf

Selleck, Bruce Warren, 1985
Paleoenvironments and Petrography of the Potsdam Sandstone, Theresa Formation and Ogdensburg Dolomite (u. Camb.-l. Ord.) of the Southwestern St. Lawrence Valley, New York
https://www.nysga-online.net/wp-content/uploads/2019/06/NYSGA-1978-A6-Paleoenvironments-of-the-Potsdam-Sandstone-and-Theresa-Formation-of-the-Southwestern-St.-Lawrence-Lowlands.pdf

Stigall, Alycia L., 2020
Chondrites, in  Atlas of Ordovician Life - Exploring the fauna of the Cincinnati region,
http://www.ordovicianatlas.org/atlas/ichnofossils/chondrites/

Uchman, A. (1998): Taxonomy and ethology of flysch trace fossils: revision of the
Marian Ksi.zkiewicz collection and studies of complementary material.. Ann Soc
Geol Polon, 68,105.218.

Whitton, Brian A. and Pilar Mateo, 2012
Rivulariaceae .  Chapter 22 (pp.561-591 ) in book: B.A. Whitton (ed.), Ecology of Cyanobacteria II: Their Diversity in Space and Time.   Springer Science+Business Media B.V. , 760 pages   DOI: 10.13140/2.1.2976.3361

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

Williams, D.A., 1991
Paleozoic Geology of the Ottawa-St. Lawrence Lowland, Southern Ontario; Ontario Geological Survey, Open File Report 5770, 292 pages; March Formation at 48-57.
http://www.geologyontario.mndmf.gov.on.ca/mndmaccess/mndm_dir.asp?type=pub&id=OFR5770

Williams, D. A. And Wolf, R.R., 1984
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