A Field Trip to the Ellisville Potsdam Sandstone Quarry

Last Sunday I visited the sandstone quarry at Ellisville, Ontario as part of an annual field trip organized by the Niagara Peninsula Geological Society.  It was sunny with a cool breeze – a perfect day to visit a quarry.

While only a few attended, something of interest was found by everyone.

Miniature Chevron Shaped Sand Dunes

Below is a photograph  of a texture in the sandstone that I’d never seen before, namely miniature chevron shaped sand dunes.

The simplest explanation is that the dunes are wind-generated dunes, with the arms pointing downwind, similar to Barchan dunes that one would see (on a much larger scale) in a desert.  However, I’ve noted references to the formation of chevron shaped dunes in experiments conducted in a water tank, so the chevron shaped dunes in the photograph could be water generated.

The Climactichnites burrowing trace: Climactichnites youngi.

Below are photographs of burrowing in sandstone. At least fifteen separated burrows are visible on the surface of the specimen.   I noted the specimen while walking with Peter Lee of Gananoque and Paul Musiol of Kingston.  I believe that the specimen shows the Climactichnites burrowing trace: Climactichnites youngi.   While not that obvious from the photographs, the burrows appear at a number of different levels in the specimen.

Subsequently Peter Lee found another specimen showing similar burrowing.

The Niagara Peninsula Geological Society may be scheduling another field trip to the quarry this October in conjunction with a trip to the Wollastonite mine along Highway 15 and the Frontenac Lead Mine.   Check their web site  http://www.ccfms.ca/clubs/NPGS/    and Facebook page
https://www.facebook.com/groups/1392693367698780/   for updates.

At the end of this email I’ve provided the dates and titles of my earlier blog postings where I  provided photographs of trace fossils and textures in the sandstone that were found at the Ellisville Quarry.
   
Christopher Brett
Ottawa, Ontario


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Monday, 31 October 2016
The Ellisville Potsdam Sandstone Quarry Revisited

Thursday, 16 July 2015
Burrows or Not Burrows - Part 2

Tuesday, 18 August 2015
If there's something strange in your neighborhood, who you gonna call?

Monday, 12 August 2013
The Trace Fossil Diplichnites – A New Occurrence in Eastern Ontario

Tuesday, 9 July 2013
A New Occurrence of Protichnites in Potsdam Group Sandstone near Kingston, Ontario

Thursday, 20 June 2013
A Few Trace Fossils in Potsdam Group Sandstones of Eastern Ontario

Abraham, Logan and Owen: The Discovery of the First Protichnites trackways – Part 2

[Part 1 of this article was posted August 29, 2013.]

In 1851 Logan took to London a small slab of sandstone and a plaster cast of a 12 ½ foot slab from a quarry on the left bank of the river St. Louis, at the village of Beauharnois and on April 30, 1851 both he and Professor Owen  read papers before the Geological Society of London.

In 1852 Logan took to London three slabs and 100 casts (in total, about 350 feet of track). One of the slabs, 12 ½ feet in length, was the original of the cast he had taken in 1851.  

In a paper read March 24, 1852 before the Geological Society of London, Logan described the geology of the area and the finding of five new localities of foot-prints.   Two localities were in the vicinity of Beauharnois: the first, in the field of Mr. Henault, a half mile west of the quarry in which the first impressions were discovered; the second, two and a half miles further west at the mouth of the Beauharnois Canal.   The other three new locations were in the vicinity of Point Cavagnol (about 15 miles west of the first locality – the quarry in the village of Beauharnois); on the  Island of St. Généviève in the St. Lawrence River, south of Montreal Island (about 7 miles north of the village of Beauharnois); and on the Riviere du Nord, at Lachute,  in the Seignory of Argenteuil (about 35 miles north east of the first locality).
               
In a paper also read March 24, 1852 before the Geological Society of London, Professor Owen (1852) described and named six tracks, stating that he had selected from the casts and slabs that Logan had brought to London “the best marked and most intelligible portions for [his] descriptions.”    Logan (1863) noted that in view of the “various differences in the tracks, Professor Owen has given separate specific provisional names to several of them, not for the purpose of indicating a positive specific difference in the animals which have impressed them, but for the convenience of reference.”  Professor Owen distinguished between two different genera and four different species.

The six tracks that were named by Professor Owen and which in his paper were accompanied by plates showing the tracks, follow:

1.  Protichnites septem-notatus    Plate IX
2.  Protichnites  octo-notatus      Plate X
3.  Protichnites  latus      Plate XI
4.  Protichnites  multinotatus   Plate XII
5.  Protichnites  lineatus     Plate XIII                   
6.  Protichnites  alternans     Plate XIV

Copies of those six plates form part of my March 7, 2014 blog posting.  They are shown together below.

Five of those named tracks came from Mr. Henault’s field.  The sixth,  Protichnites  multinotatus, came from near the first one discovered, namely the track at the quarry on the St. Louis River at the village of Beauharnois.

Professor Owen included a seventh plate, Plate XIV.A, remarking that it is for a slab  “the casts of which were first brought over by Mr. Logan during the preceding year.”   Plate XIV.A therefore shows part of the original 12 ½ foot specimen described by Logan (1851) and Owen (1851) and taken to London in 1852.  It is shown below.

To understand why Professor Owen named six tracks it helps to translate the Latin names (provided in Billings, 1857) and to consider part of his Owen’s description:

1.  Protichnites septem-notatus   -   seven marked  - a repeating pattern of fourteen impressions of footprints, seven on the left of the medial line and seven on the right
2.  Protichnites  octo-notatus - eight marked  - a repeating pattern of sixteen impressions of footprints, eight on the left of the medial line and eight on the right
3.  Protichnites  latus    - broad  - “the impressions of the feet are deeper and larger”, the track would seem to have been made “by a different species having a body broader in proportion to its length
4.  Protichnites  multinotatus  - many marked  - “ a strong deviation of the intermediate groove from the mid-line between the two lateral series of impressions”
5.  Protichnites  lineatus - linear - the median “impression preserves in some parts... a considerable and equal depth; ... the lateral impressions... are represented by continuous grooves rather than by a succession of pits.”                
6.  Protichites  alternans  - alternate - “the opposite impressions of the series are not symmetrical; for where the impressions are widest apart on the left, those on the right...are nearest together... These impressions indicate a waddling gait, or an alternate oblique movement side to side...”.

It is also helpful to consider the following drawing of Protichnites septem-notatus  from Owen (1860) where he has circled the repeating sets of seven footprints.

While Owen (1852) described the tracks in detail, I find his descriptions hard to follow.  The best description is by Logan (1852b at pages 10 - 12):

“The track and footsteps, when the specimens are most perfect, in general present a median groove  more or less flat, and of different proportionate widths in different specimens, with a number of footprints on each side in answering pairs; certain sets or numbers of these answering pairs have homologous repetitions throughout the whole length of the track, as if they were the result of successive applications of the same impressing instruments, and the numbers of answering pairs in the homologues of different tracks are sometimes different, constituting something which may be considered analogous to difference of species. The homologues  in different tracks appear to have sometimes seven and sometimes eight answering pairs of pits, and it is difficult to say whether the pits are to be taken as  impressed by the extremities of so many legs, thus giving the animal fourteen legs in the one case, and sixteen in the other, or whether some of the impressing points are to be grouped in twos or threes, .... The median groove in most of the tracks is so uniformly in the middle between the footprints, as to favor the supposition that it may be occasioned by the effect of an immoveable breastplate or plastron, but in one remarkable instance, at a bend in the track, the groove gradually leaves the middle, and while it seems impressed with more than usual force, approaches and partially obliterates the footprints on the convex side, as if the impressing part had been the extremity of a tail, which, when the body turned to one side, interfered with the footprints in the rear, on the other. A feature common to all the grooves is, that each repetition or homologue of the footprints is accompanied with a deepening and shallowing of the groove, giving it the appearance of a chain of shallow troughs, which, when the impression is light, are separated from one another by intervals of the ungrooved surface. The groove is often but faintly indicated, and occasionally it is not perceptible; and frequently it happens when this occurs, that the footprints are stronger and deeper than when the groove is more conspicuously impressed. In some of the tracks, while the groove is straight, the exterior limits of the footprints offer a congeries of segments of a circle, convex on the outside, but those on opposite sides of the groove alternate, the segment on the one side, starting from the middle of the segment on the other, and giving to the whole series of footprints in the track a serpentining course, as if the animal had waddled in its gait. In one of the tracks there are three narrow grooves instead of footprints on each side, of the main one, for a certain distance, as if the limbs of the animal had been dragged along the bottom, while the body was afloat. ...  The generic term for the whole is Protichnites, and the specific names are, P. septemnotus., P. octonotatus, P. multinotatus,  P. alterans,  P. lineatus.”

A Plan of Mr. Henault’s Field at Beauharnois

   
Logan (1852) included a plan of Mr. Henault’s field at Beauharnois, the source for five of the six Protichnites specimens figured by Owen (1852).   Below is an edited version of Logan’s plan of the field.

Note that the scale is in chains (1 chain = 22 yards = 66 feet = 20.1 Meters); that the plan shows the direction of ripple marks on the bedding;  that I’ve shown the tracks in magenta; and that the tracks are on a number of different bedding planes.

Logan (1852) reported  ten tracks in area A, seventeen tracks in area B, six tracks in area C,  and ten tracks in an area that is a few yard to the east of area C.   Within a length of four chains (about 90 yards or 80 meters) Logan found 43 tracks.

All of the 43 tracks were between 4 inches and 6 1/2 inches wide, except for one that was 3/4 of an inch wide.   The longest track is 28 feet six inches long while the shortest was one foot long.  Twenty-six of the tracks from areas A, B and C were on smooth surfaces while seven of the tracks from areas A, B and C were on ripple marked surfaces.  (For the fourth area Logan did not identify the surface.)

Logan (1852) included additional plates showing closeup views of areas A, B and C.  Amended versions showing parts A and B are provided below.  Logan numbered each track on Part A and Part B and in his paper provided the length and width of the tracks.  Logan's plates also included numbers (that I've shown in blue with a blue square) corresponding to Owen's names for the tracks.

The plan of  part A shows the tracks that are  numbers 1, 5 and 6  of Professor Owen’s descriptions, namely:
1.  Protichnites septem-notatus (seven marked)
5.  Protichnites  lineatus (linear) 
6.  Protichnites  alternans (alternate)
For part A, seven of the tracks were on a smooth-surfaced bed, while two of the tracks (Logan's 9 & 10) were on a surface 2 inches lower showing ripple-marks, while the tenth track (Logan's 8) was "on a surface still lower by about 1 inch, but showing no ripple-mark."

The plan of  part B shows the tracks that are  numbers 2  and 3 of Professor Owen’s descriptions, namely:
2.  Protichnites  octo-notatus    (eight marked)
3.  Protichnites  latus    (broad)  
Of the seventeen tracks on part B, twelve tracks are on a smooth surface and five tracks (Logan's 13, 14, 15, 16, 17) are on a ripple marked surface 2 inches below the smooth one.

Logan (1863) provides various measured sections of Potsdam sandstone, including a section from Beauharnois in the vicinity of Henault’s field (1863, pages 105-106), where he describes the beds and indicates where ripple marks, wind marks, Protichnites tracks and Scolithus occur.   Based on his observations,  Logan (1860) suggested that “The crustacean which impressed the tracks at Beauharnois must have been a littoral animal..."   

Additional Locations for Protichnites Trackways Provided by Logan

Subsequent to giving his talks in London, Logan provided other localities where Protichnites tracks were found:

 - Protichnites, at Perth, Ontario in association with Climactichites (Logan, 1863, pages 93 and 107);
- in Lansdowne and Bastard township, Ontario (Logan, 1852b, page 10)
- “about a mile N. W. of Cuthbert's mills on the Chicot there is an exposure of fine grained white sandstone, characterized by Protichnites” (Logan, 1863, page 93);
 - Protichnites, on a peninsula on the north side of the Ottawa River, about seven miles below the mouth of the Petite Nation, (Logan, 1863, page 94);
- in the vicinity of Pointe du Grand Detroit in Vaudreuil, twelve miles west of the locality at the Beauharnois canal (Logan, 1863, page 90);.

Murray (1852, page 67) provides the best description of the tracks from near Pointe du Grand Detroit:

“[A]bout twenty-five acres above the Pointe du Grand Detroit, fine grained white quartzose sandstones were met with in beds of from six inches to two feet thick. Some surfaces displayed ripple-mark, and on one, trails and footprints of a species of animal exist, similar to the tracks occurring at Beauharnois, in the same description of beds. The largest of the tracks measures eight and a-half inches across, and the trail is visible for four feet, and gradually becomes obliterated at end. On the same surface, twenty yards farther up the stream, three additional tracks of the same sort were observed, each-one traversing the other two; two of these measured four inches across, and the third four and a-half inches; the last is distinct for three feet in length, and the other two, one foot eight inches, and one foot three inches respectively. The groove in the middle between the footprints on each side, so frequently seen at Beauharnois, occurs only in one of the smaller trails.”

I have provided  his full description, because most of the tracks were missing the groove in the middle and now would be identified as Diplichnites.

Pointe du Grand Detroit is now better known as Quarry Point and falls in Hudson, Quebec.  The stream that Murray referred to is likely the Vivery River/Vivery Creek.

Additional  reports of Climactichnites and Protichnites Trackways from Beauharnois

Others have reported on Climactichnites and Protichnites trackways from Beauharnois, including
Walcott (1914 at pages 261 and 277 ), who collected specimens from “Rogier’s farm just west of the town of Beauharnois”.    Yochelson and  Fedonkin (1993) mention that  “an exceptionally large slab containing numerous examples of both Climactichnites and Protichnites were collected from ‘a mile west of Beauharnois, Quebec’” by Walcott.   This is the large slab that is the frontispiece to their article and was at the date of their article “on public display off the east side of the Rotunda on the first floor of the National Museum of Natural History, Smithsonian Institution, Washington, DC.”

Clark and Usher (1948) reported that a quarry in Potsdam sandstone at Melocheville, which is about 3 km to the west of the original quarry at Bearharnois, had specimens of Climactichnites exposed on the quarry floor.  

 More recently, Lacelle, Hagadorn and Groulx (2012) reported on Climactichnites and Protichnites  trackways in the Keeseville Formation of the Potsdam sandstone at Beauharnois, together with other trace fossils, from which they concluded that “these fossils were produced in shallow marine to intermittently emergent sand-dominated coastal environments, with tracemakers occupying pools, channels, levees, floodplains, and on windy sand flats.”

Even more recently Splawinski,  Patterson and  Kwiatkowski (2016) reported Diplichnites trackways in the Cairnside formation of the Potsdam sandstone at Beauharnois,  Québec, noting that they found  “sedimentary structures and trace fossils indicative of supratidal, intertidal, and shallow-marine lithofacies.” 

Christopher Brett

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Addendum

Briefly Consider the following.

Two Protichnites tracemakers walk into a bar.  One says to the other “I’d lost track of you.”
   
Two Protichnites tracemakers walk into a bar.  One comments on his friends disheveled appearance, and is chastised “What do you expect, I was caught in the Cambrian Explosion!”

Three Protichnites tracemakers walk into a bar.  Two of them should have ducked.

A Protichnites tracemaker walks into a bar, orders a scotch on the rocks, and  the bartender asks  “Any particular kind?”   The tracemaker replies    “Any single malt whisky on quartz arenite– littoral or eolian is fine.   I’m not particular. ” (Is that just being siliclastic?)

What did the Protichnites tracemaker say when it ran into a long lost friend while exploring the eolian sand dunes?  “Long time no sea.”

If a paleontologist gives a talk commenting on Logan’s Holmesian reasoning in deducing that Protichnites tracemakers inhabited tidal flats, should the paleontologist conclude with the statement  “Sedimentary my dear Watson”?

Why is it hard to interview a Protichnites tracemaker?  All they want to do is make tracks.

Ichnologists are dogmatic.  It’s as if everything is written in stone.

Did you hear about the absent minded Ichnologist that was studying Protichnites?  He  kept getting off track.
       
Sir William E. Logan was a great fiction writer.   The problem is that everyone takes him littorally.

The theory that the Protichnites tracemaker was a trilobite is not that far fetched.  It should get equal Billings.

Did you hear about the  Protichnites tracemaker that was tired of sleeping on sand?  He bought a Walcott?

 Do Protichnites tracemakers  travel light because they don't Owen anything?

Did you hear that Protichnites tracemakers went on strike for equal treatment with Climactichnites tracemakers?   They wanted a resting trace.

When the Protichnites tracemaker asked the Climactichnites tracemaker why it didn’t venture inland, the Climactichnites tracemaker responded  “Tidal flat.  Sand dune hilly.”

Did you hear about the Euthycarcinoid that disappeared without a trace?  Probably not.
   
Did you hear about the  Protichnites tracemaker that was always contradicting itself?  Kept saying “That’s not what I sediment.”

Why don’t Protichnites tracemakers commit crimes?  They’re easy to track down.   

Did you hear about the foolish Euthycarcinoid that robbed a bank?   The police were able to trace the funds.

Did you hear about the Euthycarcinoid that was born on the wrong side of the tracks? He made good.

Protichnites tracemakers were too vain to hang out with Trilobites.  They didn’t want to become dated.       

If a fossil is defined as a markedly outdated or old-fashioned person or thing, why does the study of Ichnology never get old?

The Pike Lake Pluton - A Layered Syenite Intrusion in Lanark County

The Pike Lake Pluton lies about 12 kilometres (8 miles) south of Perth between Pike Lake and Black Lake.  It falls mainly within North Burgess Township of Lanark County (now Burgess Ward of Tay Valley Township), and extends westward into North Crosby Township of Leeds County.

The Pike Lake Pluton is comprised of syenite and  has been dated at 1178 ±  3 Ma by Davidson and van Breemen  (2000), who placed it in the Frontenac terrane of the Central Metasedimentary belt of the Grenville Province.  

The pluton is shown on  the following geological map and described in   Jean Dugas' doctoral thesis, where it is identified as the Black Lake body.

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

Dugas, Jean, 1952,
 Geology of the Perth map area, Lanark and Leeds Counties, Ontario; Ph. D., McGill, 189 pages, four  maps.     Map 1089A replicates a map that is part of the  thesis.
http://www.collectionscanada.gc.ca/obj/thesescanada/vol2/QMM/TC-QMM-124004.pdf
http://digitool.library.mcgill.ca/thesisfile124004.pdf
  
Below is an extract from Map 1089A  showing the Pike Lake  pluton.

The Bedding (Igneous Layering)

Worth noting on Map 1089A is that bedding (igneous layering)  is shown for at least 22 locations within the boundaries of the pluton, and that at 14 locations the map shows foliation.   Further, in the text of his thesis Dugas (1952) remarked on the good bedding within the syenite body and included a spectacular photo of bedding in the syenite body (his photo number  54 at page 159 of his thesis).   Dugas places the outcrop shown in  photo  number  54 in Lot 24, Concession VI of North Burgess township.   (Locating that outcrop is problematic as his Black Lake syenite body (the Pike Lake pluton) does not appear to outcrop in Lot 24 of Concession VI.)

One interesting feature within the Pike Lake Pluton, that is shown on the above extract from Map 1089A, is a thin lens of pyroxenite syenite along the Eastern margin (close to Black Lake)  that is parallel to the bedding and extends over a length of at least one and a half miles (2.4 kilometers).  The lens appears to be about 1/16 of a mile (100 meters) thick.  It would be interesting to determine whether this is layering within the syenite body, or a separate intrusion.

The Syenite

Jean Dugas (1952) identified four main syenite bodies within his map area: the McGowan-Lanark body, the Bathurst body, the Crosby body and the Black Lake body.   What recent authors call the Pike Lake pluton, Jean Dugas called the Black Lake body. 

Jean Dugas summarized the common characteristics of the four main syenite bodies as follows (pages 52-53):

“1. The rock is commonly pink though it may grade to grey or brown where magnetite is most abundant. The brown coloring is probably caused by staining of the feldspars by iron hydroxide.
2. The rock varies in grain size from 1 mm. to 5 mm. and may be porphyritic.
3. The predominant mafic minerals are biotite and hornblende (near hastingsite in composition), pyroxene being only minor in amount.
4. The magnetite-ilmenite content is high, though not uniformly distributed. All syenite bodies give strong magnetic anomalies, though sections are poorly magnetic.
5. Accessory minerals are mainly apatite and sphene, the latter commonly forming a rim around magnetite crystals.  Sphene is probably secondary after ilmenite (cf'. photo no. 71 p. 54).
6. The feldspars are microcline and oligoclase (Ab. 85).
7. The foliation is prominent near the margins of the body.
8.  Migmatitic complex of' granite and syenite is common along the margins of these larger syenite masses. “

He also comments specifically on the Black Lake Body:

At pages 51-52,
"Another lens-shaped body (Black Lake body) lies between Pike Lake and Black Lake. This body has a maximum width of slightly more than a mile and extends for more than four miles."

At pages 59 - 60
“Black Lake body
This is one of the most interesting of the syenite bodies. The rock at the center of the body, though variable in grain size and color, is typically brownish, medium grained and massive. Away from the center of the body, the syenite has similar composition but is very well banded   (ct. photo no. 54 p. 159).  Further from the center the rocks are syenite-granite migmatite and on the outer edges are garnet gneiss. Good exposures of the latter occur on the shore of Pike Lake. Reference to this body is made in subsequent chapters."
           
At pages 152, 153
“Magnetic Data
Glancing at the geological map and the air survey magnetic contour intervals, there can be no doubt that all major magnetic anomalies are caused by syenite or quartz syenite bodies. ... [T]he Black Lake body is probably the best example of a sharp magnetic anomaly, though readings do not exceed 1,700 gammas. Contacts could have been traced fairly accurately from the magnetic contours alone.”

At pages 158, 161
“No absolute evidence of the magmatic origin of the syenites, granites and diorites can be given. The beat example of these features is within the Black Lake syenite body ( cf. figure p. 160). The center of this body is massive and around the massive rocks, without sharp contact, very well bedded  rocks (cf. photo no. 54, p. 159) have obviously an igneous syenite composition. The rock then grades to a migmatitic complex of syenite-granite and, on the shore of Pike Lake, to a typical biotite-garnet gneiss.”
   

OGS Re-mapping the Perth Sheet

In my blog posting from last December I mentioned that Dr. Easton of the Ontario Geological Survey is currently remapping the Perth Sheet.  Within the Perth map area Dr. Easton (2015, 2016a) has divided the Frontenac terrane  into 3 subdomains:  the western, central and eastern subdomains.   From the text of his reports it appears that he places the Pike Lake Pluton within his western subdomain, commenting (2015, at page 18-6): “Frontenac suite intrusions in the western subdomain consist of pre- to syntectonic (e.g., Pike Lake pluton, 1178±4 Ma), syntectonic (e.g., Bennett Bay pluton, 1164±2 Ma) and posttectonic (e.g., North Cosby pluton, 1157±3 Ma) intrusions (all ages from Davidson and van Breemen 2000). This relative age range is also observed in the smaller Frontenac suite intrusions. Older intrusions, especially the smaller bodies, appear to be more quartz rich (quartz syenite, quartz syenite) than the younger intrusions (syenite, monzonite).”    He also notes that “The western subdomain consists of both felsic and mafic Frontenac suite intrusions that are rimmed by migmatitic, compositionally varied, quartzofeldspathic gneisses that are commonly cut by smaller irregular bodies and sills of Frontenac suite intrusive rocks. It is not clear if these smaller intrusive bodies are simply sheet-like injections of magma emplaced during deformation, or if they represent cupolas or roof-pendants of a larger intrusive body at depth.”    His final report should be worth reading.

Christopher Brett
Perth

References and Suggested Reading

Davidson, A. and van Breemen, O., 2000
Age and extent of the Frontenac plutonic suite in the Central metasedimentary belt, Grenville Province, southeastern Ontario; Geological Survey of Canada, Current Research 2000-F4; Radiogenic Age and Isotopic Studies: Report 13; 15 pages;
https://books.google.ca/books?isbn=0660182300
publications.gc.ca/collections/Collection-R/GSC-CGC/M44-2000/M44-2000-F4E.pdf

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  
              
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 of Dr. Easton's 2016  reports can be downloaded from:
http://www.mndm.gov.on.ca/en/news/mines-and-minerals/summary-field-work-and-other-activities-2016

Outcrops of Orbicular Granite in Lanark County, Ontario

“Orbicular granite (also known as orbicular rock or orbiculite) is an uncommon plutonic rock type which is usually granitic in composition. These rocks have a unique appearance due to orbicules - concentrically layered, spheroidal structures, probably formed through nucleation around a grain in a cooling magma chamber. Almost one third of known orbicular rock occurrences are from Finland. The occurrences are usually very small.”
https://en.wikipedia.org/wiki/Orbicular_granite

There is a tremendous amount written on orbicular rocks.  Kennan and  Lorenc (2008) provide a discussion of the early discoveries of orbicular rocks.  They mention that “In 1802, Leopold von Buch described some outcrops of orbicular granite in the Karkonosze granite, Lower Silesia, Poland. ...  The Silesian discovery predates that of the well-known orbicular diorite (Napoleonite) in outcrop on Corsica and, thus, may be the first ever record of this distinctive rock type in its geological context.”

David Levenson (1989) provides the following summary: “Orbicular rocks are nonsedimentary rocks that contain concentric shells of different texture and/or mineralogy about a central core. Occurrences have been described from every continent, and orbicules have been found in ultramafic to felsic, igneous, and metamorphic rocks. Host rocks are fine- to coarse-grained, and include dykes, sills, stocks, batholiths, lavas, gneisses, schists, and migmatites. Orbicular facies are generally local, less than several hundred meters in greatest dimension. ... Orbicules range from <3 cm to >30 cm in diameter. Shells number from one to more than twenty, and may be spaced irregularly or in geometrical progression.”

Numerous theories have been advanced to explain the formation of orbicular rocks.  Sage (1987), who noted that they occur in magmatic, metamorphic and migmatic terrains and have various compositions, provides a list of eight proposals from Levenson (1966) and mentions a ninth advanced by Elliston (1984).  The nine theories are: liquid immiscibility; fluctuations of a melt about a eutectic or eutectoid due to variations in pressure and temperature; reactions between magmas and xenoliths; xenoliths moving through parts of magma of different compositions; crystallization of concentric envelopes of contrasting composition in a highly viscous magma that retards viscous diffusion; excessive crystallization of one component around a nucleus, followed by excessive crystallization of a second component, as a result of  alternating supersaturation;  rhythmic supersaturation and crystallization about centres in a magma in a manner analogous to Leisegang ring formation;  layers built up on a previously formed nucleus in a silicate melt, with diffusion of material, and crystallization later than the formation of the orbicular structure.   More recent theories involve nucleation in small pockets of H2O-rich superheated silicate melt, with the orbicule shell structures crystallizing and growing from supercooled boundary layers within the  magma  (Owen, 1991; Ort, 1992; Grosse et al, 2010; Smillie and Turnbull,  2014).

Lanark's Outcrops

What is not widely known is that Lanark County is home to at least three occurrences of orbicular granite, which are mentioned in the notes to the following map and described in the following doctoral thesis.

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

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
http://digitool.library.mcgill.ca/thesisfile124004.pdf

Surprisingly, the outcrops of orbicular granite are not mentioned in the following paper:

Dugas, Jean, 1950,
Perth map-area Lanark and Leeds Counties Ontario; Geological Survey of Canada, Paper no. 50-29, 1950; 22 pages (1 sheet), https://doi.org/10.4095/101399

In the descriptive notes to Map 1089A,  Jean Dugas mentions:

“Small bodies of granite are exposed in various parts of the map-area.  Among these, and too small to be mapped separately, are exposures of an ‘orbicular’ granite, composed of granite ovoids and basic rims.  These can be best observed on lot 20, con. 1, North Crosby township.”

I have to admit I’ve known about that reference for over five years and have not yet made the time to visit the occurrence, largely because the two options are (a) to ford a stream and walk across a swamp, or (b) launch my canoe at the far end of Pike Lake and paddle to the outcrop.

Jean Dugas (1952) discusses the occurrences of orbicular granite at pages 67-73 of his doctoral thesis. He mentions three occurrences:
- on lot 20, concession I of North Crosby township, on the southwest end of Pike Lake;
- on lot 16, concession VIII of North Burgess township (to the northeast of Pike Lake);
- on lot 18, concession III of South Sherbrooke township, north of Christie Lake.   
Outcrops of granite on those lots and concessions in North Crosby township and North Burgess township are shown on Map 1089A.   On the following extract from Map 1089A I've shown the three locations by florescent pink boxes.

At page 68 of his thesis Jean Dugas includes four photographs of the outcrops: three photographs of the outcrop  on lot 20, concession I of North Crosby township; one of the outcrop on lot 16, concession VIII of North Burgess township; but none of the outcrop on lot 18, concession III of South Sherbrooke township.  At page 70 he includes photographs of thin sections from the outcrop in North Crosby township.
   
Jean Dugas (1952)  mentions (at pages 67, 69; 72-73) that the outcrop near the southwest end of Pike Lake “can be observed very plainly. A scarp on the east side shows a good exposure of rock. The band may reach 20 feet in width. It seems to be in the form of a lens: at a distance of 1000 feet from the best exposure, it is only about two feet wide. It is composed of rounded pieces of granite, in places longitudinally arranged along the strike and dip and surrounded by a thin, very basic rim of amphibolite composition. The size of the granite pieces ranges from one inch to more than one foot and the rim is one half to one inch wide. The shape of the granite and the interstitial material approaches that of pillow structure (cf. photo no. 13, p. 68). The granite is composed of pink microcline and quartz with a few pyroxene crystals penetrating from the basic rim (cf. photo no. 17, p. 70). The rim itself is composed of augite and oligoclase for the most part.
...
The study of the Perth orbicular granite is particularly difficult as there is no recognizable matrix and no non-orbicular granite in adjacent areas from which the rock may have derived. However, it is remarkable that the center of orbicules is free from ferric minerals and there is sharp increase of these towards the rim. No microcline is observed in the rim and the composition is esboitic (oligoclasic). There is also evidence of replacement between sodic feldspar and microcline (cf. photo no. 18, p. 70).”

In his thesis Jean Dugas also describes a leopard pegmatite from Lot 12, concession V of North Burgess township and includes a photograph of the outcrop at page 79.   He mentions “At the Silver Queen mine, a pegmatite shows locally a faint sinuous system of black stringers composed of ferromagnesian minerals.  This type of pegmatite has been called ‘leopard pegmatite’ (c.f'. photo no. 2l, p. 79), and is probably of orbicular nature.”

The best references to orbicular rocks that I have been able to find are the following French language GEOWIKI articles: 

Les roches orbiculaires
http://www.geowiki.fr/index.php?title=Les_roches_orbiculaires

Les types de roches orbiculaires
http://www.geowiki.fr/index.php?title=Les_types_de_roches_orbiculaires

Liste des occurrences dans le monde
http://www.geowiki.fr/index.php?title=Liste_des_occurrences_dans_le_monde    

Interestingly that list of worldwide occurrences of orbicular rocks does not include the outcrops in Lanark County.

Also worth a look are the following videos on the Granito Orbicular of Chile: 
https://www.youtube.com/watch?v=j_yx3sTz3co    5:08
https://www.youtube.com/watch?v=HkfIiGNl41A    1:33
https://www.youtube.com/watch?v=yaMEfVZMvPc      1:02

Christopher Brett
Perth, Ontario


References and A Reading List on Orbicular Rocks:

Adams, Frank. D., 1897
 Nodular granite from Pine Lake, Ontario;  Geological  Society  of  America
Bulletin,  vol. ix, pp. 163-172; reprinted as McGill University, Papers from the Department of Geology, No. 8. ,  https://archive.org/details/cihm_02281       

Affholter, Kathleen A. and Lambert,  E. E., 1982
Newly described occurrences of orbicular rock in Precambrian granite, Sandia and Zuni Mountains, New Mexico; in  Wells, S. G.; Grambling, J. A.; Callender, J. F.; [eds.] New Mexico Geological Society Guidebook, 33rd Field Conference, Albuquerque Country II, 1982, pages 225-232
https://nmgs.nmt.edu/publications/guidebooks/downloads/33/33_p0225_p0232.pdf

Blake, William P., 1904
Origin of Orbicular and Concretionary Structures, Transactions of the American Institute of Mining Engineers, vol. XXXVI,  677- 682
library.aimehq.org ...bulletin of the AIME 1905 1-6-047.pdf

Bräunlich, Matthias
Orbiculite - eine Auswahl:
http://www.kristallin.de/orbiculite/kugelgesteine2.htm#Anker1
Orbicular Rocks
http://www.kristallin.de/orbiculite/orbicular_rocks1.htm

Elliston, John N. 1984,
Orbicules: An indication of the crystallisation of hydrosilicates, I;  Earth-Science Reviews, Volume 20, Issue 4, August 1984, Pages 265-344
https://doi.org/10.1016/0012-8252(84)90021-7
   
Enz, Robert D., Albert M. Kudo, and Douglas G. Brookins; 1979
Igneous origin of the orbicular rocks of the Sandia Mountains, New Mexico, Geological Society of America Bulletin, February, 1979, v. 90, p. 138-140
https://doi.org/10.1130/GSAB-P2-90-349

Grosse, Pablo; Toselli, Alejandro J.; and  Rossi, Juana N., 2010
Petrology and geochemistry of the orbicular granitoid of Sierra de Velasco (NW Argentina) and implications for the origin of orbicular rocks; Geological Magazine, vol. 147,  no. 3, 451-468
DOI: 10.1017/S0016756809990707
   
Hitchcock, Edward; Edward Hitchcock, jr., Albert D. Hager, Charles H. Hitchcock. 1861
Report on the Geology of Vermont: descriptive, theoretical, economical, and scenographical.  Vol. 2, pp. 563, 564, 721, (the nodular granite of Craftsbury; the Craftsbury pudding granite)
https://babel.hathitrust.org/cgi/pt?id=mdp.39015086763169;view=1up;seq=20

Hudec, P. P.,  1964
Geology of the Big Trout Lake Area District of Kenora (Patricia Portion); Ontario Department of Mines, Geological Report No. 23 “A rather peculiar orbicular volcanic rock has been observed ... [which] consists of very fine-grained siliceous and chloritic concentric features, with fine quartz  in the centre, a ring of fine chlorite around it, surrounded by a ring of chlorite of different composition.   The large rings  (1/2  to l  inch   in   diam.) have small orbicular features within them.   The rock is dark, hard, and brittle.”

Kemp, J. F., 1894
An orbicular Granite from Quonochontogue, Beach, Rhode Island, Transactions of the New York Academy of Sciences, Volumes 13-14, pages 140 - 144
https://books.google.ca/books?id=AcoAAAAAYAAJ

Kennan, Pádhraig S. And Lorenc, Marek W.,  2008
Orbicular granite near Jelenia Góra in southwestern Poland: the first outcrops; 
Mineralogia, Volume 39, Issue 3-4, pp. 79-85
Open Access: DOI: https://doi.org/10.2478/v10002-008-0006-4

Kessler, H.S. and Hamilton, W.E., 1904      
The Orbicular Gabbro of Dehesa, California; American Geologist, Vol. Xxxiv, No. 3, 123-140 with five plates 
https://archive.org/stream/panamericangeolo341904desm#page/n165/mode/2up   

Lahti, S. (Editor), 2006
Orbicular Rocks in Finland 2005, with contributions by P. Raivio and I. Laitakari.
Espoo (Geological Survey of Finland) ISBN: 951-690-911-6. , 177 pages

Lawson, Andrew C., 1904
The Orbicular Gabbro of Dehesa, San Diego County, California;   Volume 3, Issue 17 of University of California publications: Bulletin of the Department of Geology; pp 383-396
https://archive.org/stream/bulletinofde319021904univ#page/n549/mode/2up

Levenson,  David  J., 1966,
Orbicular  rocks:  A  review:  Geological  Society  of  America Bulletin, v. 77, p. 409- 426
http://dx.doi.org/10.1130/0016-7606(1966)77[409:ORAR]2.0.CO;2
   
Levenson,  David J. (1989)
Orbicular Rocks; in Petrology, Encyclopedia of Earth Science, pp 415-416, Springer
link.springer.com/10.1007/0-387-30845-8_168
DOI   10.1007/0-387-30845-8_168

Ort, Michael H., 1992
Orbicular volcanic rocks of Cerro Panizos: Their origin and implications for orb formation;
Geological Society of America Bulletin, August 1992, vol. 104 no. 8 1048-1058
DOI: 10.1130/0016-7606(1992)104<1048:OVROCP>2.3.CO;2

Owen,  J. Victor, 1991
Significance of epidote in orbicular diorite from the Grenville Front zone, eastern Labrador; Mineralogical Magazine, June 1991, Vol. 55, pp. 173-18I
http://www.minersoc.org/pages/Archive-MM/Volume_55/55-379-173.pdf

Sage, R. P., 1987
Geology of Carbonatite-Alkalic Rock Complexes in Ontario: the Prairie Lake Carbonatite Complex, District of Thunder Bay; Ontario Geological Survey Study 46, 91 pages at 20-22
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/S046/S046.pdf

Smillie, Robert W. and Turnbull, Rose E,  2014
Field and petrographical insight into the formation of orbicular granitoids from the Bonney Pluton, southern Victoria Land, Antarctica; Geological Magazine,   Volume 151, Issue 3,  May 2014, pp. 534-549           DOI: https://doi.org/10.1017/S0016756813000484

Watson, Thomas Leonard, 1904
Orbicular Gabbro-Diorite from Davie County, North Carolina; The Journal of Geology, Volume 12, pp 294 - 303    https://archive.org/details/jstor-30055824

Zihkel, Ferdinand, 1894
Lehrbuch der Petrographie, 2d ed., vol. 2, pages 50, 51-
https://archive.org/stream/lehrbuchderpetr01zirkgoog#page/n59/mode/2up

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?

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

Andrew’s Outcrops

Andrew is one of the many polite teenagers that Lanark County produces by the bushel load.   He also has a keen interest in geology.  This past weekend I took the opportunity to visit outcrops that Andrew had been telling me about.  

Most of the outcrops that Andrew showed me consist of flat lying sandstone exhibiting paired vertical burrows on the top surface.   I expect that everyone would identify this sandstone as a shallow marine facies of the Nepean (upper Keeseville) Formation of the Potsdam Group.   Below are photographs of the top surfaces of  two such sandstone outcrops, each showing paired vertical burrowing.

One outcrop stood out as being particularly impressive and is likely worth a second visit.  Below are photographs of this outcrop.This outcrop can be divided into three parts, with at least two visible unconformities (separating layers 1 and 2; and separating layers 2 from 3).  Starting from the base you notice:
1.)  at least 30 vertical feet of a silicious quartz cobble conglomerate; 
2.)  followed by a foot of sandstone with layers of quartz pebbles and a pitted layer (that may represent eroded evaporite minerals?);
3.)  with a top layer showing bedded  sandstone cut by vertical burrows, some of which extend down into the middle layer (perhaps evidencing the transgression of Cambrian/Ordovician seas and the reworking of fluvial sandstone?).

The two lower layers are of continental/fluvial origin, while the upper layer is of shallow marine origin.  

The first three photographs show the basal quartz cobble conglomerate.   The fourth photograph shows two unconformities, with the basal quartz cobble conglomerate at the bottom of the photo.   The fifth photo shows vertical burrowing and an uncomformity.  The sixth photo shows vertical burrowing in the top layer (shallow marine sandstone), overlying what appears to be two fluvial events: a pebble layer, over  sandstone, over a pebble layer, over sandstone (with the pebble layers possibly being lag deposits formed by aeolian deflation?).

           
I expect that everyone would assign the top burrowed bed to a shallow marine facies of  the Nepean (upper Keeseville) Formation.    Most people would likely  assign the quartz cobble conglomerate bed  to the Covey Hill (Ausable) Formation of the Cambrian/Ordovician Potsdam Group, with some assigning it a Precambrian age.   The middle bed is likely a fluvial facies of the Nepean (lower Keeseville) formation.

Andrew also showed me a mica mine in the Precambrian rocks and a lichen covered, deeply fractured, sandstone ridge that lies on an adjoining property

The photographed outcrops fall within Lot 7 of Concession VIII in North Burgess Township (now Burgess Ward of Tay Valley Township), about four miles (6.5 kilometers) south of Perth, and west of the intersection of Stanley Road with the road to McLaren Lake.   The lichen covered sandstone ridge can be found east of the road to McLaren Lake, on Lot 8 of Concession VIII.

If you were one of the original settlers who had been granted the land upon which Andrew’s parents have their house, or granted one of the adjoining lots, I suspect you’d have complained about the lack of soil.  If you have an interest in geology, which Andrew has, you’d be pleased to be living there.

Christopher Brett
Perth, Ontario   

Suggested Reading:
David G. Lowe, R.W.C. Arnott, Godfrey S. Nowlan, A.D. McCracken, 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

The Cylindrical Structures in Lanark County reported in Jean Dugas’ 1952 Doctoral Thesis

In my  August 27, 2015 blog posting I mentioned that Jean Dugas,in the notes to geological  Map 1089A, reported that cylindrical or conical structures in sandstone can be found in North Elmsley Township,  Lanark County.   He commented:

“Peculiar bands showing cylindrical or conical structures noted in the Nepean formation, and best observed on lot 24, Con. VI, North Elmsley tp., are the same composition as the surrounding sandstone , but cut sharply across the beds and are themselves bedded parallel with the walls of the structures.  They are probably formed by slumping of the sand due to water action.”

Morley E. Wilson and Jean Dugas, 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.
                 
In my August 27, 2015 blog posting I also mentioned that I had not been able to find  Dugas’ occurrence on Lot 24 or his thesis.

I  recently located and read Jean Dugas’ doctoral thesis:

Dugas, Jean, 1952,
 Geology of the Perth map area, Lanark and Leeds Counties, Ontario; Ph. D., McGill, 189 pages, four  maps.          

In his thesis he includes five clear  photographs of the conical and cylindrical structures, and good written descriptions of the structures, together with a review of the leading papers discussing theories for their origin.  He concludes that his structures, because of their conical shape, were formed by slumping, and suggests that “as most of the structures are underlain by [crystalline] limestone and it is common to find solution cavities in the [crystalline] limestone” the slumping was likely into cavities in the limestone.

Interestingly, while the the captions to his photographs place the structures on lot 24, the  text of Jean Dugas’ thesis mentions that the structures are found on lot 23.   Both the text and the captions place the structures in concession VI.  In the text of his thesis he comments (at page 99):
      
"Good exposures of an unusual structure in the Nepean sandstone can be seen on lot 23, concession VI of North Elmsley township. A section of the sandstone shows a decisive break in bedding. Across the stratification, two conical structures occur with the apex down, about six feet high and five feet at the base of the cone (cf. photos nos. 29,  30,  31, p. 100). There is a distinct irregular banding, the bands being slightly twisted (cf. photos nos. 31, p. 100, and 32, p. 101). In horizontal section the structure is obviously concentric, forming a circle or a spiral (cf. photo. no. 33 , p. 101).  Though no other exposures of vertical sections have been found, concentric layers were observed at other places in the sandstone.”

Lots 23 and 24 of Concession VI in North Elmsley Township are a few kilometers west of Rideau Ferry and lie south of County Road 1.   Perhaps armed with the photographs I will have better luck locating the outcrops, particularly if I look in both lots.

Christopher Brett
Lanark County