On the trail of Climactichnites wilsoni - Part 1: Specimens Collected from a Quarry near Perth, Ontario

Over one hundred and fifty years ago Sir William E. Logan of the Geological Survey of Canada announced to the world the finding of a "new and remarkable" fossil track in sandstone from a locality "in the neighbourhood of Perth" ... "for the discovery of which we are indebted to my friend Dr. James Wilson of Perth, who sent me specimens of it in the month of November last." Logan considered the tracks to be "those of some species of gigantic mollusc". He concluded his article with the sentence "From the resemblance of the track to a ladder, the name proposed is Climactichnites Wilsoni, the specific designation being given in compliment to its discoverer, Dr. Wilson." Sir William Logan announced the finding of the fossil in a paper entitled On the Tracks of an Animal lately found in the Potsdam Formation that he read before the Natural History Society of Montreal in June, 1860, and that was published later that year in volume V of The Canadian Naturalist and Geologist.

Dr. James Wilson (1798-1881), who discovered the first fossils of Climactichnites, was a medical graduate of Edinburgh University who emigrated to Canada and practiced as a physician in Perth, Ontario from 1821 to 1869, and then retired to Scotland. Dr. Wilson was an amateur mineralogist and geologist who is credited with being the first to find the trace fossil Climactichnites Wilsoni, Perthite and Peristerite. In addition, he found outcrops that later became apatite (phosphate) and mica mines, and numerous mineral occurrences. In October, 2012 the Perth Museum at Matheson House in Perth, Ontario opened to the public its new Geology Exhibition, which features a display of part of the mineral and fossil collection of Dr. James Wilson, including the two specimens of Climactichnites wilsoni that are shown below.

The specimen on the left is the overlying impression or natural cast in the sediment laid down on top of the original trail. The specimen on the right records the original trail. The lateral ridges that are shown in the specimen on the right were formed by creature that made the original trail and are recorded as indentations in the overlying bed. The tracks are about six inches (15 cm) in width. The two specimens are not mirror images of one another, and while they may be parts of the same track, are not two parts split from the same rock. While Logan suggested that the track looked like a ladder, I expect that most people would be more likely to describe it as looking like a motorcycle track in sand.

It should be kept in mind that Climactichnites Wilsoni is a trace fossil (not a body fossil). It is the track, or surface trail, of a soft bodied creature –an unknown and unnamed tracemaker (probably a giant slug or another mollusc)– that was among the first to exit the oceans and ‘walk’ on land. The presence of lateral ridges in the specimens found at Perth confirms that they are surface trails.

In addition to the specimens in the Perth Museum, other specimens of the trace fossil Climactichnites wilsoni that were collected from the quarry near Perth can be found in the collections of the Royal Ontario Museum in Toronto, the Redpath Museum at McGill University in Montreal, the Geological Survey of Canada and the National Museum of Scotland. All of the specimens were collected in the period from about 1859 to 1882.

A specimen in the collection of the Geological Survey of Canada is particularly impressive. Not only is it a very large specimen, it displays a number of crossing trails of Climactichnites and clearly shows the trail of the trace fossil Protichnites. Measuring seventy-six square feet (and being about ten feet high by seven feet wide), it hung on the wall in Sir William Logan’s office in Montreal until he retired, and when the GSC was moved to Ottawa was on display at the Geological Survey of Canada’s museum in Ottawa until at least 1901. It is not currently on display.

It is interesting to consider the effort that went into collecting the specimen that hung on the wall in Sir William Logan’s office in Montreal. Sir William Logan (1860) in his article On the Track of an Animal lately found in the Potsdam Formation mentions " in the beginning of December, I sent Mr. Richardson to Perth, where he was guided to the quarry by Dr. Wilson, and shewn the bed in which the tracks occur. The quarry, of which the strata are nearly horizontal, is about a mile from the town, and with the aid of Mr. Glyn, the proprietor, Mr. Richardson obtained in fragments, a surface which measures about seventy-six square feet. To obtain this required a good deal of patience, for there was half a foot of snow on the ground, and from under this it was necessary to remove between two and three feet of rock in order to reach the bed. The rock is a fine grained white sandstone ... and of that pure silicious character which is so well known to belong to the Potsdam formation wherever it is met with. The tracks are impressed on a bed which varies in thickness in different parts from an inch to three inches. When the upper bed was removed large portions of the track-bearing bed came away with it, and it was necessary to separate the layers. This was done by heating the surface with burning wood placed upon it, and then suddenly cooling it with the application of snow. " (Canadian Naturalist and Geologist, 5, 279-285, at page 282).

One of the specimens in the possession of the Redpath Museum is prominently on display in the main stairway at that museum, and also features both the trace fossil Climactichnites and the trace fossil Protichnites.  That specimen is the larger of the two specimens shown the photograph to the left, which appeared in a paper by Sir J. William Dawson, read May 14, 1890, entitled On Burrows and Tracks of Invertebrate Animals in Palaeozoic Rocks , and Other Markings; (1890) London Quart. Journal Geol. Soc. 46, pp. 595-617. This is again a large specimen, being over six feet in height, with the trails being about six inches (15 cm) wide.

While Dawson gives no indication of source other than that they are from the Potsdam Sandstone of Ontario, the specimens were collected by Mr. Richardson in about 1882, and are likely the last reported specimens of Climactichnites collected from the quarry near Perth. The story behind their collection is interesting.  The Geological Survey of Canada had been headquartered in Montreal before Confederation. In 1881 the Geological Survey of Canada, the Geological Survey of Canada Museum, and its rock, mineral and fossil collections were moved to Ottawa. Sir William Logan, in his will, left funds to collect replacement specimens for a museum in Montreal. Replacement specimens of Climactichnites, Protichnites and other fossils were collected by Mr. Richardson, and other fossils were purchased, for display in Montreal. The Report on the Peter Redpath Museum of McGill University, No. 11, January, 1883, mentions at page 16 under the heading Part V. - Notice of Collections, Logan Memorial Collection that specimens added to the collection included a "Series of large slabs of Protichnites and Climactichnites, collected by Mr. Richardson, at Perth, Ontario."

The specimen at the Royal Ontario Museum is not currently on display but could be included along with other Potsdam trace fossils in the ROM’s new Gallery of Early Life which is scheduled to open to the public in 2014. A curator at the ROM sent me an email stating that the specimen was collected by "J. Wilson", which I assume identifies Dr. James Wilson.

The specimens in the collection of the National Museum of Scotland (formerly the Edinburgh Museum of Science and Art) are not currently on display, and have been overlooked by those that have published articles on Climactichnites. The Report of the Keeper of the Natural History Collections for the year 1875, that is in the Report of the Director of the Edinburgh Museum of Science and Art for 1875, appears to provide the only published description of these specimens. It mentions that "Dr. James Wilson has presented three valuable slabs from the Potsdam sandstone of Canada, one of which displays the supposed Crustacean track Protichnites, while on the other two are seen splendid examples of the still more remarkable and problematical Climactichnites Wilsoni." The current Principal Curator, Paleobiology, National Museum of Scotland, in answer to an email that I sent to him, has confirmed the specimens are in the museum’s specimen register: Climactichnites wilsoni under number 1875.24.1 and Protichnites under 1875.24.2.

Twenty years ago the Smithsonian Institute in Washington, D.C., published an extensive review of Climactichnites that summarized the geologic distribution of this fossil. See: "Paleobiology of Climactichnites, an Enigmatic Late Cambrian Fossil by Ellis L. Yochelson and Mikhail A. Fedonkin, 1993, Number 74, Smithsonian Contributions to Paleobiology. The publication is available free over the internet and I would encourage anyone interested in this fossil to download the publication. Googling the title and the names of the authors should provide the paper.

In their publication Yochelson and Fedonkin (1993) published photographs of Climactichnites specimens collected from the quarry near Perth. Figure 18 shows the specimen owned by Geological Survey of Canada that hung on the wall in Sir William Logan’s office, Figure 55 shows the specimen on display at the Redpath Museum in Montreal, and Figure 42 shows the specimen at the Royal Ontario Museum in Toronto. Portions of those specimens are shown in other figures in their article.

More recently Patrick R. Getty and James W. ("Whitey") Hagadorn have published a series of papers dealing with Climactichnites, including Getty, P.R. and Hagadorn, J. W. (2008) Reinterpretation of Climactichnites Logan 1860 to Include Subsurface Burrows, and Erection of Muscoulopodus for resting traces of the Trailmaker, Journal of Palaeontology, V. 82, pp. 1161-1172, and Getty, P.R. and Hagadorn, J. W. (2009) Paleobiology of the Climactichnites Tracemaker, Palaeontology, Vol. 52, pp. 753-778. Both papers can be downloaded over the internet. These papers should be read by anyone with a serious interest in the fossil.

I’d like to conclude this posting by looking at the ages of the three major players. James Richardson was born in March, 1810 and died in November, 1883. He was three months shy of fifty when he first visited the quarry in 1859 (dug through half a foot of snow, dug through two to three feet of rock, and separated rock layers by heating the surfaces with burning wood and quenching with snow) and was in his early seventies when he collected the specimens for the Peter Redpath Museum. Dr. James Wilson (1798-1881) was 61 when he sent the first specimens to Sir William Logan (1798–1875), who was 62 when he delivered the paper announcing the finding of a "new and remarkable" fossil track in sandstone about a mile from Perth. Makes one feel young.

Christopher P. Brett
Perth, Ontario

I believe that I located the quarry where James Richardson collected the first specimens of Climactichnites that were described by W. E. Logan.   See my following blog postings.

Monday, 11 February 2013

On the trail of Climactichnites wilsoni - Part 2: References to the Quarry Near Perth in the Scientific Literature, and the Geologic Mapping of Lot 6 

https://fossilslanark.blogspot.com/2013/02/

Monday, 6 May 2013

On the trail of Climactichnites wilsoni - Part 3: A quarry about a mile from Perth as the town existed in 1859   https://fossilslanark.blogspot.com/2013/05/

Perthite from Burgess Ward, Tay Valley Township, Lanark County, Ontario

In an earlier posting I described two outcrops of pegmatite containing perthite, an exsolution texture in feldspar, that are found approximately 8.5 kilometers (five miles) south of the Town of Perth in North Burgess Township, Lanark County. The outcrops are on the west side of Elm Grove Road and on the northeast side of Glenn Drive. The legal description for the land for the purposes of the Land Titles Office is still North Burgess Township, but the municipality is now called Tay Valley Township (which formed through the amalgamation of the three former townships of North Burgess, Bathurst and South Sherbrooke). In Tay Valley Township the names of the three former townships are maintained in the names of Burgess Ward, Bathurst Ward and South Sherbrooke Ward. Both outcrops are in Concession VI of North Burgess township. The outcrop on the west side of Elm Grove Road falls in the third lot of Concession VI, as does  the outcrop on the northeast side of Glenn Drive. 

The original specimens of perthite were collected by Dr. James Wilson in about 1841 from what is now Lot 3, Concession VI of North Burgess Township. Unfortunately the exact locality is not known. However, as the pegmatite outcrops containing Perthite on Elm Grove Road and on Glenn Drive fall in the third lot of Concession VI, it is possible that one of these  was the original location where perthite was found.  Regrettably, the outcrop on Glenn Drive is the front yard of a home and is out of bounds for collecting. However, the outcrop on the west side of Elm Grove Road can be easily accessed and sampled. It can be easily found as it is about 50 meters south of the second (and southerly) intersection of Glenn Drive with Elm Grove Road, and is the only pink outcrop on the west side of Elm Grove Road north of where Long Lake Road intersects Elm Grove Road. I recommend against parking on the west side of Elm Grove Road close to the outcrop as the shoulder of the road is quite narrow (and the ditch is quite deep). The safest parking is on Glenn Drive.

Below are photographs of the outcrop on Elm Grove Road.

It is interesting to trace the development of the term perthite, from its origin to how it is used today, and to look at some of the early mineralogists who studied Perthite. It is also interesting to trace the development of Burgess Township and to look at when North Burgess became part of Lanark County.

Dr. James Wilson (1798-1881), a physician and surgeon in the Town of Perth who had emigrated to Canada from Scotland, found the first occurrence of perthite approximately 8.5 kilometers south of the Town of Perth, on property between Adam Lake and Otty Lake, in what was then Burgess Township, in Upper Canada (now Ontario). Dr. Wilson collected the specimens from an outcrop on property farmed by Thomas Dobbie (also spelt Dobie on some deeds, and later mispelt as Dobey by various members of the Geological Survey of Canada) who acquired the whole of Lot 3 in 1838 and sold the property in deeds dated 1863 and 1872. Dr. Wilson sent the specimens to Dr. Thomas Thomson, Regius Professor of Chemistry at the University of Glasgow in Scotland, who in 1842 named the ‘mineral’ Perthite, after the Town of Perth.

Perthite was found by Dr. Wilson on property that was then in Burgess Township, Leeds County, Johnstown District, Upper Canada. In 1842 Upper and Lower Canada were united to form the Province of Canada, with Upper Canada being renamed Canada West while Lower Canada became Canada East. Upon Confederation in 1867 Canada West was renamed Ontario and Canada East was renamed Quebec. In 1842 Burgess Township was split into North Burgess Township and South Burgess Township. North Burgess Township was attached to the jurisdiction that became the present Lanark County while South Burgess Township remained in what became the United Counties of Leeds and Grenville. The lot and concession numbers of the old Burgess Township were not changed. For example, Lot 3, Concession VI of Burgess Township is now Lot 3, Concession VI of North Burgess Township.

Today perthite is recognized as an exsolution texture in alkali feldspars consisting of two feldspar minerals: a potassium rich alkali feldspar (orthoclase or microcline) and a sodium rich alkali feldspar (albite). The original feldspar crystallized deep within the crust at high temperatures and pressures as homogeneous crystals. On decreasing temperature (and possibly pressure as the rock rose in the earth’s crust) the original homogeneous crystals unmixed (recrystallized) into two feldspar minerals. In perthite orthoclase or microcline makes up a greater proportion of the specimen than albite, and albite is considered to have exsolved from the original homogeneous crystal. (Where albite makes up the greater proportion of the specimen, it is called antiperthite.)

In perthite from Burgess Township the potassium rich alkali feldspar is a brownish red, while the albite is off white (arguably, Caucasian flesh pink). The albite makes up about 30% to 50% of the perthite. As the potassium rich alkali feldspar is the predominant mineral and dominant colour, the specimens as a whole appear to be a dull, pinkish to brownish red on fresh surfaces and a much darker brownish red on weathered surfaces. In perthite from Burgess Township the potassium rich alkali feldspar and albite occur as parallel interlaminated lamellae generally 1 to 2 mm thick that pinch and swell. Some of the lamellae are up to at least 80 mm long. In four specimens that I collected the lamellae are at about a 70 degree angle to the best cleavage plane. In two specimens additional fine lamellae can be seen (with the aid of a 10x hand lens) within the lamellae of potassium rich alkali feldspar. A number of specimens that I collected show one perfect cleavage plane, while others show two cleavage planes. One specimen shows two cleavage planes and two parting planes. Tilting a cleavage plane in light gives a silvery to golden glow (from both feldspars), much the same as the reflection of light off mica. If cut properly, cabochons made from perthite from this locality should show the silvery to golden glow.

In perthite from Burgess Township the potassium rich alkali feldspar is likely microcline. In the early papers it is called orthoclase. However, microcline was only identified as a separate mineral three and a half decades after perthite was found. Appendix III, 1875 - 1882, by Edward S. Dana (1882), to the Fifth edition of Dana’s Mineralogy, credits Breithaupt (1876) with using Microcline "to designate a new feldspar mineral established by him: a triclinic potash feldspar" that is "near orthoclase in form and in habit" with a composition the same as orthoclase. Dana (1882) also mentions that "A large part of the potash feldspar, previously called orthoclase, is in fact microcline. .... The perthite of Canada is in part microcline (J. Min., 1879, 389)."

August Breithaupt (1791-1873) was a professor of mineralogy at the Freiburg Mining Academy and is credited with the discovery of 47 valid mineral species. He was one of the leading mineralogists of his time and perhaps of all time. He named both orthoclase and microcline, and studied perthite. He developed the concept of mineral paragenesis, made numerous contributions to crystallography and wrote a number of German language text books on mineralogy.

Dr. Thomas Thomson (1773 - 1852), M.D., who named Perthite, was a leading chemist of his day. In 1831 he gave Silicon its current name and in 1820 he identified a new zeolite, named Thomsonite in his honour. However, he botched the analysis of Perthite. Dr. Thomson announced Perthite to the world in a paper read before the Glasgow Philosophical Society on November 2, 1842, and published in 1843 in Volume XXII of the Philosophical Magazine. Here is the first part of his report: 



"2. Perthite. – The next mineral I have to notice I distinguish by the name Perthite. It was sent to me by Mr. Wilson, a surgeon in Perth, a township of Upper Canada; hence the name by which I distinguish it. It is very much connected with feldspar in appearance, and was sent as a variety of that mineral.
The colour of the specimen sent to me is white: it consists of a mass of crystals so united together as to form a kind of tesselated pavement. The crystals are obviously four sided prisms, apparently rectangular, but not susceptible of measurement, because they cannot be isolated.
The lustre is vitreous; the hardness is rather less than that of feldspar; but the specific gravity, which is 2.586, is identical with that of some of the varieties of that mineral. It’s constituent elements were found to be
Silica        76
Alumina    11.75
Magnesia    11.00
Protoxide of iron 0.225
Moisture         0.65
                 99.625"See: Thomson, T. (1843), Notice of Some New Minerals, Philosophical Magazine, New Series, Volume XXII, page 188 at page 189.

Today, 170 years later, it would be obvious to anyone that has a taken a mineralogy course, and can remember the formulas for feldspars, that finding that much magnesium in feldspar and finding that little aluminum in feldspar, were errors. Dr. Thomson’s description of the specimen as "a kind of tesselated pavement" confirms that he was looking at Perthite, however his description of the colour as "white" is at odds with specimens from this location unless he was describing only the albite portion.

Interestingly, The Hunterian Museum and Art Gallery, University of Glasgow, has a photograph on its web site of what may be the original specimen of Perthite sent by Dr. Wilson to Dr. Thomson.   See:

http://www.huntsearch.gla.ac.uk/cgi-bin/foxweb/huntsearch/LargeImage.fwx?collection=all&catno=M2361&mdaCode=GLAHM&filename=M2361a.jpg#caption


Within a decade after Dr. Thomson’s paper was published, T. Sterry Hunt, Chemist and Mineralogist to Canada’s Geological Survey, in three papers (two of which were almost identical), had provided a more accurate analysis and description of perthite, from specimens provided by Dr. Wilson, of Perth, in part to correct Dr. Thomson’s "unfortunate want of precision in his mineralogical description" and that Dr. Thomson’s chemical composition "seemed but little accordant" with perthite’s physical properties.

Thomas Sterry Hunt (1826 - 1892) was the Canadian Geological Survey’s Chemist and Mineralogist from 1847 to 1872, when he resigned to become Professor of Geology at the Massachusetts Institute of Technology. During his career he authored numerous papers on chemistry, mineralogy and geology. Wikipedia also reports that he was the first to link climate change to concentrations of carbon dioxide in the atmosphere.

The following is from T. Sterry Hunt’s report from1847.

"In company with Dr. Wilson I then proceeded to examine the locality from which he had obtained the specimens described by Dr. Thompson of Glasgow as perthite. It is nothing more than a reddish feldspar which makes up a large portion of an intrusive mass of granite in the limestone. The perthite occurs in large individuals of three to four inches in diameter. It is of different shades of reddish-brown, the colours being arranged in bands, and the surfaces of cleavage parallel to P. Present golden reflections like the sunstone. From the analysis of Dr. Thompson it would appear that the mineral, unlike other feldspars, contains no potassium, which is according to him replaced by calcium, and it was upon this chemical difference principally, that he predicated its distinctiveness as a species. It has however been analysed by my pupil Mr. Hartley, in the Laboratory of the Survey, and the results show that it contains both potassium and sodium, and is indeed quite similar in composition to other feldspars. This locality is in the third lot of the sixth concession of Bathurst."  [Comment: Bathurst should be Burgess, and Dr. Thompson’s name should have been spelt as Dr. Thomson.][As quoted in Smith, W. H. (1851), Canada: Past, Present and Future, Volume II, at pages 327-328.]

The following is part of T. Sterry Hunt’s report on perthite from the Report of Progress for 1850 - 1851 (at pages 36 -37):

"Perthite. It is found in the township of Burgess, and, mixed with quartz, forms a pegmatite rock, in which large cleavable masses of the feldspar are occasionally met with. Its cleavage form is apparently monoclinic, and its hardness is 6. upon the scale of Mohs; – specific gravity from 2.576 to 2.579, of a darker fragment 2.583; lustre vitreous inclining to pearly; colour light flesh-red alternating with reddish to pinchbeck-brown, the two colours forming bands from half a line to a line in width, coincident with one of the planes T, often however, interrupted and mingling with one another. The darker bands exhibit on the cleavage surface T, when viewed perpendicularly, a golden reflexion like the variety known as aventurine feldspar, and polished specimens of the mineral in the possession of Dr. Wilson show that it is available for ornamental purposes. The colours of this feldspar become darker on exposure to the action of the weather. The analytical results [follow] ...

                         I                        II
Silica................   66.44............. 66.50
Alumina............... 18.35.........   19.2
Peroxyd of iron..... 1.0
Lime..................... .67 ............. .56
Magnesia.........      .24............... .24
Potash................ 6.37............. 6.18
Soda.................. 5.56.............  5.56
Water, (loss on ignition). .40 ...... .44
                               99.03         98.73

It is evident from these analyses, that the composition of this feldspar is precisely that of orthoclase, to which species it had already been previously referred by Shepard, Dana and myself, (see my Report for 1847-48, p. 135). The proportion of soda is larger than is generally met with in this species, but there are instances of orthoclase in which the greater portion of alkali is soda."

Hunt, T.S. (1852), Report of T.S. Hunt, Esq., Chemist and Mineralogist to the Provincial Geological Survey, in Geological Survey of Canada, Report of Progress, 1850-51, at pages 36 -37. He published an almost identical paper in the Philosophical Magazine. See: T. S. Hunt (1851) Examination of some Canadian Minerals, Philosophical Magazine, Volume 1, Fourth Series, Pages 322 -328

T. Sterry Hunt’s 1847 report and his 1851 paper in the Philosophical Magazine unfortunately introduced an error that the specimens were from Bathurst Township, which has been repeated in later papers and texts, including some published within the last twenty years. The type location was in Burgess Township (later North Burgess Township, and now Tay Valley Township).

Sir William E. Logan (1863) describes perthite in his book Geology of Canada, Geological Survey of Canada - Report of Progress from its commencement to 1863, at pages 474 and 833, confirming that the specimens were obtained from "the third lot of the sixth range of Burgess."

It took another ten years for mineralogists to accept that perthite was an inter growth of albite and orthoclase. T. Sterry Hunt (1871) in a paper entitled On the Laurentian Limestones of North America, in a footnote to the perthite of Burgess, mentions "It has since been shown by Gerhard to be made up of thin layers of reddish orthoclase and whitish albite. See Dana’s Mineralogy, fifth edition, page 356." The thesis by Gerhard (1861), entitled Lamellari Orthoclasi et Albitae in Perthite Alisque Feldspathis Observata, is available on the internet from a number of sites. (While it is in Latin, some parts are understandable.) Mineralogy texts and papers published towards the end of the 1800's generally credit Gerhard and/or Breithaupt with determining that Perthite is interlaminated orthoclase and albite. (See, for example: Hoffman, G.C. (1889), Annotated List of the Minerals occurring in Canada, Proceedings and Transactions of the Royal Society of Canada of Canada, Volume VII, page 65 at page 94, where Hoffman
commented "The Perthite of Dr. Thompson (a flesh-red aventurine feldspar, which as shown by Breithaupt, consists of interlaminated albite and orthoclase) occurs in large cleavable masses, in pegmatite veins, cutting Laurentian strata, in the township of North Burgess, Lanark county, province of Ontario." And see: Jukes, J. B. (1872) The Student’s Manual of Geology, Third Edition, at page 76, which contains the comment "But it was Breithaupt’s and Gerhard’s investigation on perthite that clearly showed that many potash feldspars consisted of alternate lamellae of orthoclase and albite.")


In 1888 Eugene Coste introduced some confusion into the source for perthite from Burgess Township when he commented:

"PERTHITE.– Perthite occurs in large cleavable masses in thick pegmatite veins, cutting the Laurentian strata, and is often made up of flesh-red and reddish-brown bands of orthoclase and albite, interlaminated. When cut in certain directions it shows beautiful golden reflections like aventurine, and being susceptible of a high polish, is adapted for an ornamental stone for use in jewellery. It is also found in considerable quantity in Burgess, Ont., about seven miles southwest of the town of Perth, and near Little Adams Lake on what was formerly called Dobey Farm."See: Coste, E. (1888) Report on the Mining & Mineral Statistics of Canada for the year 1887, in Geological and Natural History Survey of Canada, Annual Report, 1887, part S, at page 75S.

Coste (1888) introduced the following errors: "Burgess, Ontario" should be the "Township of North Burgess", "southwest of the town of Perth" should be "south of the town of Perth" or "south, south east of the town of Perth", "Dobey" should be "Dobbie", and "Little Adams Lake" should be "Adam Lake".  (While Adams Lake appears on some maps, Adam Lake is the correct name.  There is no Little Adams Lake.)

The whole of Coste’s description was quoted at page 341 of William A. Parks’ 1912 publication, Report on the Building and Ornamental Stones of Canada, Volume 1, Mines Branch, Report 100. Parks (1912) is the source most often relied upon for perthite being found on the ‘Dobey’ farm.

In the latter half of the 20^th century Ann P. Sabina of the Geological Survey of Canada authored a number of informative books on rock and mineral collecting that contained directions to many of the classic collecting sites in Canada. I have six of her publications. She describes the perthite locations in North Burgess Township in both:

Sabina, Ann P. (1965), Rock and Mineral Collecting in Canada, Volume II, Ontario and Quebec, G.S.C. Miscellaneous Report 8, at page 118 (map at page 116); and

Sabina, Ann P. (1968), Rocks and Minerals for the Collector, Kingston, Ontario to Lac St-Jean, Quebec, G.S.C. Miscellaneous Paper 67-51, at pages 36-38 (map at page 28).

The two perthite locations on Elm Grove Road and on Glenn Drive are likely the two perthite locations mentioned in her publications. However, since she wrote her publications roads have been rerouted, widened, paved and renamed, and what was the Dobbie farm has converted in part to a small subdivision. Glenn Drive did not exist when she wrote her publications and the outcrop presently on Glenn Drive is likely the one that Sabina (1968) describes as "Clearing on farm on left. The dyke containing perthite is exposed in the farm about 100 yards north of this point." The outcrop presently on Elm Grove Road is likely the one that Sabina (1968) describes as "Perthite exposure in woods on right side of road. The dyke has been dynamited and specimens can be obtained from broken blocks near it."

In her description of perthite Sabina (1965) mentions that "One of the first occurrences from which the mineral was obtained is the Dobey farm near the west side of Adam Lake, about 8 miles southeast of Perth. The exact location is not known." referencing Parks (1912).

Sabina (1965) also stated:
"A pegmatite dyke of perthite and quartz outcrops in two places in lot 4, concession 6, North Burgess township, between Otty and Adam lakes. Dugas (1952) mentions that the name "perthite" was first applied to the feldspars from this dyke. The dyke strikes north. It is exposed adjacent to the road and at another place about 1200 feet to the north. ... Reference: Dugas, J.: Dept. Geol. Sci., McGill Univ., Ph.D. Thesis, 1952, p. 78."

Sabina mistakenly placed both occurrences in lot 4.    This was likely a typographical error, as both fall on lot 3.  
It was also an unfortunate turn of phrase for Sabina (1965) to suggest that the perthite "was obtained on the Dobey farm near the west side of Adam Lake." This has been taken by some to mean that perthite was found by Dr. Wilson "on the Dobey farm near the west shore of Adam Lake." The Dobbie farm consisted of 200 acres that abutted on and is west of Adam Lake. The two perthite locations on Elm Grove Road and on Glenn Drive are west of Adam Lake, but the outcrop on Elm Grove Road is at least 600 metres west of Adam Lake while the outcrop on Glenn Drive is at least 700 metres west of Adam Lake.

An Ontario Department of Mines paper on the web entitled Bibliography of Theses On The Precambrian Geology of Ontario, compiled by R. M. Ginn in 1961, provides the following information on the thesis by Dugas that was referred to by Sabina :

Dugas, Jean, 1952, Geology of the Perth map area, Lanark and Leeds Counties, Ontario; Ph. D., McGill Jean Dugas is one of the geologists responsible for the Geological Survey of Canada’s Map 1089A - Geology of Perth, Lanark and Leeds Counties, Ontario, published in 1961 (Geology by M. E. Wilson, 1930 and Jean Dugas, 1949. Descriptive Notes by Jean Dugas). The map can be downloaded free of charge from the GSC’s web site. This map shows the location of the pegmatite outcrop that is now on Elm Grove Road, and shows a pegmatite dyke that may be the one that outcrops on Glenn Drive. Interestingly this map also shows a third outcrop of pegmatite on lot 3, approximately a quarter mile north west of the outcrop on Elm Grove, and shows additional pegmatite outcrops further to the west of Lot 3. I have not yet made time to check those outcrops for perthite.

That pegmatite dykes bearing perthite may be found to the west of lot 3 is confirmed in notes to a mineral exhibit prepared for the Pan-American Exposition, at Buffalo, New York held in 1901, where a number of specimens of perthite from North Burgess township, Lanark County were exhibited by Ontario’s Bureau of Mines. Most were simply said to be from North Burgess township, but others were from Lots 5 and 8, Concession VI, N. Burgess township. (See: Gibson, T. W. (1901), Mineral Exhibit of the Province of Ontario, Collected and Prepared by the Bureau of Mines, Descriptive Catalogue.)


Christopher P. Brett
Perth, Ontario

“Perth stone” Purple-banded Sandstone From the Hughes Quarry, Lanark County, Ontario

A distinctive purple-banded sandstone is featured in many residences and public buildings in Perth and in Lanark County that were constructed in the 1800's and in a few buildings constructed up until the mid-1900's. This sandstone is often referred to as the "Perth stone". The characteristic feature of this stone is broad bands of purplish hue which vary from narrow lines to 25 cm (10 inches) in thickness. In some cases the entire dressed stone shows the purplish hue, while in other cases the stone has a purple banded part and a white top. In some cases the entire walls of a building have been constructed of Perth stone. In other cases the Perth stone has been used as accents or trimmings surrounding windows and doors, or as the base of a wall, while a white sandstone has been used for the remainder of the wall. The Perth stone was used because of its distinctive purple-banding, but also because it was readily cut and could be quarried in large blocks. Walking around Perth one can see some very large blocks of the Perth stone that have been used as lintels above windows and doors, as door sills, as foundation stones, topping stone fences, and as stairs.

Good examples of the Perth stone can be seen in Perth in the walls of the Methodist church on Gore Street, the Royal Bank Building on Gore Street, Mr. Code’s residence on Herriott Street (opposite Code’s Mill), a house at the corner of Drummond Street and North Street, a house at the end of Inverness Avenue (likely constructed only about 50 years ago), and The House of Industry for Lanark County erected in 1902 (now the Perth Community Care Centre) at 101 Christie Lake Road.  Perth stone was also used as the foundation of the Perth Carnegie Library (now the McMillan Building, 77 Gore Street East, Perth).   In Lanark County the Perth stone can be found as the outer walls of stone farmhouses on Elm Grove Road and Scotch Line and as the outer walls of the century old post offices in Smiths Falls (corner of Russell St. East and Market Street), Almonte (73 Mill Street) and Arnprior (35 Madawaska Street, now the Arnprior and District Museum).   The three Post Offices were designed by Thomas Fuller, Canada's Chief Dominion Architect from 1881 to 1896 and earlier a member of the firm of architects that had designed the Centre Block and Parliamentary Library of Canada's Parliament Buildings.  The former Almonte Post Office is a National Historic Site of Canada.

Below are three photographs of the house on Inverness Avenue.

Below is a photograph showing Perth stone used as trimmings for Mr. Code's residence on Herriott Street.

Below are photographs of the house at the corner of Drummond Street and North Street.

The Perth Stone sandstone is part of the Potsdam Group sandstones, and has been mapped most recently as Nepean Sandstone. The colour purple is likely due to the iron staining in the cement binding the quartz grains in the sandstone, and reveals burrowing in sediment that became the sandstone.

The Perth Stone was quarried from the Hughes quarry in Lot 26, Concession VII, North Elmsley Township (now Drummond/North Elmsley Township), Lanark County.  The inside of the Lanark County administration building (99 Christie Lake Road) features three walls constructed of rock found in Lanark County.  One of the inside walls is constructed of Perth stone from the Hughes quarry.

The Hughes quarry is described in two publications:

(A) Building Stones of Ontario, Part 1V, Sandstone, by D.F. Hewitt, Industrial Mineral Report No. 17, 1964, Ontario Department of Mines, and
(B) Report on the Building and Ornamental Stones of Canada , Vol. I, by William A. Parks, Mines Branch Report No. 100, 1912

Both are available for download as pdf documents free of charge on the web.


D.F. Hewitt (1964) described the Hughes Quarry as follows:

"There are two quarries operated intermittently on the Hughes property in lot 26, concession VII, North Elmsley township, Lanark County. In one opening there is 2 to 4 feet of thin bedded, medium-grained grey and purple mottled Potsdam sandstone. Random flagstone 2 to 3 inches thick is the principal production. A second quarry 1/4 mile south of the road exposes 3 to 4 feet of medium bedded, even bedded, grey and purple mottled Potsdam sandstone in 8 to 10 inch beds. These beds are used for ashlar building stone. There is some rusty mottling in the sandstone. Describing the stone from this quarry Parks (1912, p.129) says that "the characteristic feature of the colour of this stone is the broad bands of purplish hue which vary from narrow lines to 8 or 10 inches in thickness. Much of the intermediate material is of a yellow colour fading to white. The physical properties of the stone are as follows:
Specific gravity 2.65
Weight per cubic foot, Ibs. 150.38
Pore space, percent 8.97
Crushing strength, Ibs. per square inch 15459.
Transverse strength, Ibs. per square inch 417."

William A. Parks (1912) described the Hughes Quarry as follows:

"On this property the valuable stone occurs on a knoll overlooking a small lake and is exposed over an area of about 50 acres. In descending order the sequence of beds is as follows: —
12 to 18 inches — Purple-banded stone with three inch white top — 229.
10 inches — Purple-banded stone — 228.
4 inches — Soft, white stone with brown spots — 230.
Beneath is a hard, flinty type of white sandstone with brown spots and checks and with a tendency to break in a direction inclined to the bedding. All the beds dip westward at a low angle and pass under a heavy overburden, beneath which it is possible that more of the good stone may be obtained. This purple stone is unique, and is described in detail below.
The stone: No. 228. — The characteristic feature of the colour of this stone is the broad bands of purplish hue which vary from narrow lines to 8 or 10 inches in thickness. ... Much of the intermediate material is of a yellow colour fading to white. A general idea of the stone may be obtained by imagining bands of a darker purple ... alternating with bands [of a yellow colour fading to white], and fading into a yellowish white. Under the microscope the stone presents a mosaic of small quartz grains, seldom more than 1/4 mm. in diameter, closely apposed, and with a minimum of ferruginous and argillaceous cement. It is entirely to this cement that the rock owes its characteristic colour.
... From this quarry some very large blocks of stone have been obtained — one 30 feet long, 2 feet wide and 18 inches thick is said to have been quarried. Unfortunately most of the good stone has been removed, and, unless prospecting down the hill reveals a further supply, the purple stone is practically exhausted. The practice in quarrying was to break the stone with wedges,  very little powder having been employed. With the bedding, the stone breaks freely, and across the beds a good uniform break is obtained by lining and striking with a hammer. Much valuable stone was destroyed and the regular development of a quarry hindered by allowing contractors to quarry their own stone; in consequence of this, the exposure was picked over and no proper quarry ever opened. Contractors paid the owners $2 per cord for the privilege of operating. The following list indicates the prices obtained for the stone at the quarry: —
Sills, 40 cents per running foot.
Lintels, 40 to 50 cents per running foot.
Door sills, 60 cents per running foot."

The Hughes quarry is on land still owned by the Hughes family. I was lucky to be given a tour of the property in late November by Alan Hughes, and was shown both the former flagstone quarry, and the quarry that was most recently the source for the Perth Stone. While there is no output at present there is abundant Perth stone that could be quarried. Below are photographs of the quarry.

The "Perth stone" purple-banded sandstone outcrops in a drainage ditch on Hughes Road approximately 200 meters east of the quarry and opposite 348 Elm Grove Road, approximately 1.1 km northwest of the Hughes Quarry.   This outcrop on Elm Grove Road displays paired vertical worm holes (probably the trace fossil Diplocraterion) on the glacially polished top surface of the outcrop, as does an outcrop on the other side of Elm Grove Road.   Below is a photograph of the outcrop on Elm Grove road.

The outcrop is up to two feet high and extends about 20 meters along Elm Grove Road. One thin band in the outcrop could have a high calcareous content, as it is dissolving.




Christopher P. Brett
Perth, Lanark County, Ontario

An Iron Ore Deposit in the Potsdam Sandstone of Eastern Ontario: The Hematite Deposit Between Delta and Furnace Falls

An early report that describes the rocks of Lanark County is the Report on the Geology of a Portion of Eastern Ontario by R.W. Ells that was published in 1904 by the Geological Survey of Canada. The report covers the northern three quarters of Lanark County and covers adjacent parts of Renfrew, Addington, Frontenac and Carleton counties. In his report Ells traces the Potsdam sandstones from Renfrew down to south of Perth. One part in the report that caught my eye included comments on iron ore deposits in the Potsdam sandstones. Ells commented:
"While the sandstones as a rule are grayish or sometimes yellowish; in places they are often coloured red through the presence of hematite. This sometimes assumes the form of ore deposits of this mineral, capable of being mined. These deposits are usually in the form of irregular pockets and vary in quality from the impregnated sandstones, in which the siliceous matter predominates to an iron ore of considerable purity."I found that intriguing because, while I am aware of numerous former iron ore mines in the Precambrian Shield of Eastern Ontario, I could not recall anyone mining iron ore in Potsdam sandstone. Unfortunately, the map that accompanied Ells’ report does not show the location of the hematite deposits.

I decided to do further research on the matter and started by trying to determine the source for the iron ore that had been smelted at Furnace Falls, Ontario. I chose this location because Furnace Falls, which is now known as Lyndhurst, is the location for Ontario’s first iron ore smelter and because directly to the north of Lyndhurst (and south of Delta, Ontario) are many dark red beds of Potsdam sandstone (and it is known that the red colouring of the sandstone is due to iron oxide). Lyndhurst is located about 25 kilometers south of Lanark County in the United Counties of Leeds and Grenville. I struck gold (or, more accurately, iron), as the hematite that was smelted at Furnace Falls was mined from Potsdam sandstone beds approximately five kilometers (three miles) north of Lyndhurst (and one kilometer south of Delta, Ontario).

An historical plaque on a rock cairn in Lyndhurst provides a brief history of the smelter.

The plaque states:
"Lansdowne Iron Works
Forges Lansdowne
While the existence of local ore was well known and various petitions had been made to erect a foundry, it was not until 1801 that Wallis Sunderlin, a Vermont founderer, established the first iron works in Upper Canada at Furnace Falls. The works, which included both a furnace for the production of cast iron and a forge for the manufacture of wrought iron, were operated with limited success by Sunderlin and his associates until destroyed by fire in 1811. Attempts in 1815-16 to re-establish the works to supply the Kingston dockyard were ended with the agreement to limit armaments on the Great Lakes."

A newsletter published in 2004 by the Leeds and Thousand Islands Historical Society provides additional information on the iron smelter: "By 1795, it was known that the big falls on the Gananoque river had all the resources needed to develop an iron smelter. Wallis Sunderlin, an ironmaster from Tinmouth, Vermont, received assent from the Executive Council in 1800. The Lansdowne Iron Works was completed in 1802 being the first in Upper Canada. Sunderlin was granted 1200 acres to supply fuel for the blast furnace. The Furnace produced domestic cast iron items, pig iron, and wrought iron. ... In 1811 the smelter and mill complex was destroyed by fire. Sunderlin died that year and his family moved back to the United States... With the outbreak of war in 1812 no effort was made to rebuild the furnace."

A number of publications of the Geological Survey of Canada and the Ontario Department of Mines confirm that the iron ore that was smelted at Furnace Falls came from hematite deposits in Potsdam sandstone mined from Lot 25 (and possibly Lot 24) in the tenth concession of Bastard Township (near the township line with Lansdowne township), between Delta and Furnace Falls.  Murray (1852) of the Geological Survey of Canada provides an early description of the ore deposit:

"The cliff of ferruginous sandstone, which occurs on the twenty-fifth lot of the tenth concession of Bastard, displaying a vertical height of about thirty feet, brown in the lower and deep red in the upper part, owes its color to the presence of peroxide of iron, which is mingled with the siliceous grains, apparently cementing them together, and sometimes being pulverent, staining the fingers with a red shining powder. In a three feet bed, which occurs within about three feet of the top, the oxide passes into the form of strongly coherent scaly red iron ore, in which thin seams and spangles of crystalline specular iron ore occur. The parts so marked run in layers in the bed, and alternate with layers of the sandstone of a yellow and less ferruginous character. The concentration of the ore is greatest towards the middle of the bed, where nodules and patches of pure red hematite, running with the stratification, occur at intervals of a few inches, the thickness they display not exceeding a couple of inches. About forty years since an attempt was made to mine the ore for the supply of a furnace erected at Furnace Falls, but the quantity in the locality worked was not sufficient to give a profitable result."

From Murray’s description it would appear that there is a well defined stratigraphic control for the ore body and, accordingly, that the iron deposit is the same age as the host sandstone.

The deposit appears to have been fairly extensive. Murray mentions that the cliff in Lot 25 extends into Lot 24, that similar rocks that contain small seams, patches and streaks of specular iron can be found in Lot 23 of Concession X of Bastard Township, in the adjacent ninth lot of the twelfth concession of Lansdowne Township and in the 9^th Concession of Lansdowne Township.

A little over a century after the smelter at Furnace Falls was destroyed the hematite deposit was tested for ore. The Ontario Department of Mines, and J.F. Wright of the Geological Survey of Canada, provide details of the testing of the property. Wright (1921) comments:
"From October 1918 Drainey Brothers of Toronto worked these deposits, except in winter, until November 1919. In August 1919 the Consolidated Iron and Steel Corporation took over the property. Three small shafts and some prospect pits were sunk and four carloads of ore were shipped, which according to the smelter records, averaged 68 per cent iron. About one carload of ore was left on the dump." The Ontario Department of Mines’ Twenty-ninth Annual Report (1920) mentions that The Consolidated Iron and Steel Corporation, Limited "had an option on some 600 acres in Leeds County about half way between Delta and Lyndhurst Stations on the Brockville and Westport railway in concession X of the township of Bastard and the adjoining portions of the township of Lansdowne." However, nothing appears to have come of Consolidated Iron’s testing of the deposit in 1919 and the shipment of four railroad cars of hematite. Four years later when M. B. Baker (1923) reported on the geology of Leeds County for the Ontario Department of Mines he commented that "a number of pits were opened up, but shipping ore was not found in any appreciable tonnage."

Wright (1921) provided a map of the deposit (see below) and additional details on the deposit, which he placed in Lot 23, Concession X, Bastard Township.


Shaft No. 1 (16 feet). The ore occurred in irregular shaped pockets. The ore is either massive hematite mixed with specular hematite, siderite and calcite or sandstone impregnated with hematite.

Shaft No. 2 (20 feet). The ore occurs along a fracture zone along which the sandstone is impregnated with hematite, and as veins of hematite, from 1 to 2 inches wide.

Shaft No. 3 (15 feet) . The ore body consists of two irregularly shaped veins of massive hematite from 3 to 6 inches wide.

Wright proposed the following origin for the ore: "The iron minerals appear to be due to solutions circulating along joint planes or fracture zones in the sandstone. The most likely source for the ore minerals is the weathering of overlying sedimentary formations containing iron, probably in the form of carbonate. ... The iron was probably carried down as ferrous carbonate and after or during precipitation was oxidized to the ferric oxide hematite. The solutions filled all the open spaces, spread into the sandstone, and replaced the calcareous cement but only slightly the quartz."

I mentioned above that Murray (1852) described a well defined stratigraphic control for the ore body–an ore zone that is a three foot bed three feet from the top of a 30 foot cliff of sandstone– and stated that the hematite runs with the stratification, alternating with layers of the sandstone. Wright’s (1921) description of the deposit (namely that the ore occurs in veins, fracture zones and pockets), and his suggestion for its origin, are at odds with Murray’s (1852) description. It is hard to reconcile Murray’s stratabound description for the ore zone with Wright’s description. It possible that Murray was describing different aspects of the deposit than Wright . Murray’s description was for Lot 25 while Wright described a deposit in Lot 23. It is also possible that the good stratabound ore that was present when Murray looked at the deposit had been mined out by the time that Wright looked at the deposit.

Those interested in locating the original ore deposit should consult the Geological Survey of Canada’s Map 1182A, Geology Westport Ontario, which can be downloaded free of charge over the internet from the GSC. An extract from the map is provided below.  Hematite occurrences in sandstone in Lot 25, Concession IX of Bastard Township are shown on the extract by "x hem".

I drove down to Delta and briefly looked for the deposit, but as it was deer hunting season did not venture into the woods. I did find an outcrop of massive hematite and  rock impregnated with hematite southeast of Delta (and within a kilometer of the original deposit)  in an area that is mapped as Potsdam Group sandstone by both the Geological Survey of Canada and the Ontario Geological Survey. However, the outcrop is too badly altered to hematite to positively identify it as sandstone. A photograph of the outcrop and a photograph of three specimens of hematite from the outcrop are shown below.   The outcrop consists of both (1) massive hematite mixed with specular hematite and (2) host rock impregnated with hematite.

The outcrop is on both sides of County Road 42 a kilometer southeast of Delta, about 50 meters before the Hicock Road turn off to Lyndhurst. It is possibly altered Covey Hill sandstone and conglomerate (the lower part of the Potsdam Group). Twenty meters closer to Hicock Road , and at a higher elevation, is an outcrop of that is obviously sandstone (possibly Nepean Sandstone - the upper part of the Potsdam Group). The outcrops can be seen in Google Street View. I assumed there was an unconformity between the hematite bearing beds and the beds that are possibly Nepean sandstone, but didn't look for it.

Addendum (January 25, 2022): Ken Watson and Art Shaw have researched the sources for iron ore smelted at Furnace Falls. It appears the Murray (1852) was wrong and that I was wrong, as the deposit just south of Delta, and east of Lower Beverley Lake, was discovered after the smelter at Furnace Falls ceased operations.  This is set out in detail in my January 25, 2022 blog posting.  Worth reading are the recent articles by Art Shaw and Ken Watson that are posted on  the web site for the Old Stone Mill at Delta, Ontario, and Lieutenant  Baddeley's (1831) report on the Lower Beverley Lake Deposit found in ‘An Essay on the localities of Metallic Minerals in the Canadas, with some  notices of their Geological associations and situations etc.’ published in the  Transactions of the Literary & Historical Society of Quebec, volume 2, 332- 426  at pages  336-7, 347, 383- 386  https://archive.org/details/transactionsofli02lite/page/332/mode/2up

Christopher P. Brett
Perth, Ontario

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From Trails, to Mud Cracks to Evidence of Microbial Mats: Different Theories For Curved Lines in the troughs of ripple marks in Sandstone

The above photographs shows curved lines in the troughs of ripple marks in sandstone. The ripple marks are evidence of wave action in an aquatic environment, but it is the curved lines that are the most important feature of each photo. These sinuous, circular, branching lines that are confined to the troughs between wave ripples are a special kind of microbial mat shrinkage structure. They are fairly common in the fossil record, in the past were given the unpronounceable names Manchuriophycus (for sinuous curved lines) and Rhysonetron (for corrugated circular and sinuous lines), and have now been reinterpreted as resulting from the shrinkage of a microbial mat.

The photographs show two specimens that were found about a five minute drive directly north of Perth in Drummond Township, Lanark County in an area that is mapped as March Formation, which is generally thought to be Early Ordovician in age. The March Formation (the Theresa Formation in New York State and in the Province of Quebec) is younger than the underlying Nepean Formation sandstones. The Nepean Formation (Keeseville Formation in New York State; Cairnside Formation in Quebec) sandstones form the upper part of the Potsdam Group in Eastern Ontario.

Others have reported microbial mat structures in the underlying Potsdam Group sandstones of the Ottawa Embayment. A specimen showing circular and sinuous cracks confined to troughs in wave ripples was reported in Potsdam Sandstone from Canada in a paper read before the Geological Society of London in 1890 by Sir J. William Dawson, one of Canada’s famous geologists. Below is a photograph of the drawing from his paper.

Dawson described the figure as follows:

"Fig. 14 shows a rippled surface in Potsdam Sandstone with marks of worms or molluscs, arranged in the hollows of ripples. The marks are simple trails, of that curious circular or chain-like form sometimes observed, and seem to have been made by animals creeping in the furrows between the ridges of the ripples in the ripple-marks."

[Dawson (1890), On Burrows and Tracks of Invertebrate Animals in Palaeozoic Rocks, and other Markings, Vol. 46, The Quarterly Journal of the Geological Society of London, 595 at 610-611.]




While almost everyone would now agree that Dawson was wrong, he made the above observation approximately 100 years before the feature was commonly accepted as resulting from the shrinkage of a microbial mat. Today I can easily identify the structure as a mat shrinkage structure because I spent part of this past winter reading a number of papers on microbial mat features preserved in sandstones and this is one of the most common textures pictured in the articles. I would not have made that identification without the benefit of those papers.

It is interesting to look at the literature to see how others interpreted these structures. Similar structures were found in the middle of the last century in sedimentary rocks of the Precambrian Shield and attracted varied interpretations. The following is a sampling of these interpretations.

Wheeler and Quinlan (1951) reported on sinuous traces lying in the troughs on the bedding surfaces of ripple marked quartzites in Precambrian rocks in Idaho and Montana, and identified the sinuous traces as mud cracks. They rejected an earlier identification of similar structures in Huronian quartzites from Montana as "trails" or "burrows".

A slab with vermiform markings was found near Sault St. Marie in Precambrian (Upper Huronian) arkosic sandstone. These were interpreted by Frarey, Ginsburg and McLaren (1963) as bodies analogous to the tubes of modern annelids (i.e., worms). They considered and ruled out an origin by desiccation crack filling.

In 1965 similar corrugated specimens were found in Precambrian (Upper Huronian) arkosic rocks east of Flack Lake near Elliot Lake, Ontario. Hofmann (1967) described them as questionably organic, but did not rule out an inorganic origin (the possibility that they were mudcrack fillings, injection or crystal growth was considered). He assigned them the names Rhysonetron lahtii and Rhysonetron byei.

Grant M. Young in articles published in 1967 and 1969 in the Canadian Journal of Earth Sciences reported on similar structures in Huronian Rocks near Elliot Lake, Ontario. He described the beds as cherty quartzites and described the structures as crescent ridges and sinuous ridges in ripple troughs. In his 1967 article he found the origin difficult to explain in terms of inorganic processes, and favoured an organic origin, with some of the structures being probably the casts of vermiform organisms. In his 1969 article he reported that new evidence indicated that the corrugated vermiform structures were formed by the infilling of shrinkage cracks in fine grained sediments, that the cracks were not dessication cracks caused by subaerial exposure, and that the structures were probably formed in sediments containing water.

J. Allan Donaldson (1967) observed modern structures along the margins of ponds. He found "tunnel-like ridges in relatively flat algal mats... [where] the ‘tunnels’ appear as distinct linear, curved, and sinuous ridges that commonly branch and typically taper and disappear over short distances..." He proposed that "at least some of the Huronian vermiform structures may be related to algae rather than to metazoans" and noted that "a muddy environment is not essential for algal growth" and that "algal mats may completely decay subsequent to burial, leaving only the structures they served to create as a record of their former presence."

Hofmann (1971) in his publication Precambrian Fossils, Pseudofossils and Problematica in Canada, Geological Survey of Canada Bulletin 189, reported on a new specimen from the Precambrian rocks near Flack Lake which showed "that the corrugated spindles (Rhysonetron lahtii ) are arranged in a distinct shrinkage crack pattern, and that a biogenic origin can no longer be considered." However, he rejected a mud crack hypothesis (in part because of the paucity of mud), concluding that the specimens "make it evident that the rhysonetron stucture is a Manchuriophycus-type pattern that has undergone unusual diagenetic modification... that involve[d] the reduction, if not elimination, of the pelitic layer, possibly by solution under considerable pressure." He concluded that "Rhysonetron is a sedimentary-diagenetic structure, resulting from shrinkage crack filling, modified by compaction and injection processes, and ... accompanied by almost total removal of the pelitic layer."

Fast forward to the present. Bosch and Eriksson (2008) report on vermiform structures in ripple troughs in 2.1 billion year old sandstones near Pretoria, South Africa. They describe them as "connected or disconnected, curved spindles or rods along the troughs of the ripple marks, resembling worm burrows. These casts form very shallow moulds, up to 2mm deep, on the bedding surfaces and protrude up to 3mm above the bedding surfaces. In plan they curve, branch, taper and may also be longitudinal, and sometimes they overlap." In their analysis of these vermiform curved markings they follow Donaldson (1967), concluding that the sinuous forms found in the South African specimens equate to "a special form of microbial shrinkage crack, normally developed within the thicker mats that occur within the troughs between ripples...".

It is interesting that there have been many theories for these sinusoidal and curved lines in sandstone. As they resemble burrows, it is not surprising that they have been mistaken for burrows. As they resemble mud cracks, it is not surprising that they have been mistaken for mud cracks. However, the curved lines in sandstone resemble curved and sinuous ridges formed on modern microbial mats, and are best explained as a microbial mat shrinkage feature. The solution to their origin is an example of a basic concept of geology that the natural laws and process that operate now have operated in the past. The present is the key to the past.

Added November 12^th:   Below I’ve provided two photographs of specimen that shows a similar texture on a bed surface that does not show ripple marks. Here the spindles or rods curve and taper, and sometimes overlap.

Chris Brett
Perth

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Mud cracks, Liesegang bands and Liesegang rings, and possible Soft-Sediment Deformation Structures in Sedimentary Rocks of Lanark County, Ontario in an Area Mapped as March Formation

Added: November 30, 2012:

Above I’ve provided photographs of brightly coloured and patterned beds of rock together with photographs of specimens from those beds and underlying beds. These pink banded beds can be found in outcrops along Highway 7 just north of Perth where the rocks weather grey but the pink colour and the banding in the rocks can still be seen. Fresh outcrops are found in the Tackaberry aggregate quarry on Highway 7 about a five minute drive north of Perth. The most brightly coloured of the beds lie close to the top of the sequence of rocks in the quarry, and are at the north end of the quarry. This outcrop near the top of the quarry changes with every visit, as the area appears to be being cleared for blasting. The best specimens were obtained from this location in the quarry, but samples can also be found in the blast piles throughout the quarry.

The photos show a number different features:   polygonal cracks (likely mud/desiccation cracks) on the surface of beds;   clearly visible coloured chemical banding that cuts across the bedding planes, that was likely caused by diagenetic processes involving the circulation of subsurface waters, and is probably Liesegang banding and Liesegang rings; and possible soft-sediment deformation. The most striking colour variation in the rocks is due to the polygonal cracks and the chemical banding. However, there are patterns in the rocks that to me suggest soft sediment deformation. It has been suggested to me by a geologist with more knowledge of sedimentary rocks than I have that I should "examine the outcrop very carefully in cross-section, looking for convincing examples where grain-size changes ... outline the ‘deformation’ features" before I can reach the conclusion that there is soft sediment deformation. I would be interested in any reader’s comments on whether the photos show this feature.

Liesegang banding is an interesting term. To geologists it means irregular concentric yellow to orange to red to brown banding and rings in rocks where the banding and rings represent the precipitation lines of iron rich and manganese minerals following the infiltration of ground waters, with the families of bands or rings separated in the direction perpendicular to the diffusion of the ground water. There are frequently different sets of precipitation bands oriented in different directions, often cross-cutting the bedding planes, often cross-cutting older dissolution patterns, and sometimes obscuring the sedimentary structures. In some rocks the banding represents numerous precipitation events over long periods of time.

The rocks along this stretch of Highway 7 are mapped by the Ontario Geological Survey as March Formation (in Quebec and New York State, Theresa Formation) and the sequence of rocks in the quarry truly represents the transition or passage beds of Sir William Logan. (Anything goes.) It would be great if the there is soft sediment deformation in the rocks. Some of my favorite papers on the geology of Eastern Ontario deal with the faulting along the St. Lawrence River and along the Ottawa River, and the theories of the St. Lawrence Rift Valley and the Ottawa-Bonnechere Graben that are evidenced by the faults along the two rivers. Soft sediment deformation, particularly seismites (sedimentary beds disturbed by siesmic waves from earthquakes) would support movement along those faults during the late Cambrian and early Ordovician and would be worth documenting. Hopefully, someone with access to thin sections and a scanning electron microscope will look at the beds before they are quarried out.

Anyone wishing to study the pink banded beds and wanting access to the best specimens would be wise to collect them early next summer, as the overburden is being cleared off, which is the step before blasting.  I made the comment to an employee at Tackaberry that "rocks don’t move" and was corrected that "they do at this quarry". Here today, crushed tomorrow.

Christopher Brett
Perth, Ontario