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

GSC Memoir 241 - Alice E. Wilson’s Reading List

Growing up in Ottawa one of my earliest sources on the geology of the Ottawa area was an article by Alice E. Wilson entitled A Guide to the Geology of the Ottawa District that had been originally published in Volume 70 of The Canadian Field-Naturalist in 1956. The article had been reprinted and was sold as a bound issue through the Victoria Memorial Museum in Ottawa (often referred to as the ‘Dinosaur Museum’, but now properly called the Museum of Nature). It was a great publication. The article summarized the geology, had plates showing the common fossils, provided field trips, contained cross-sections across Ottawa, and contained maps showing faults and field trips. That article in combination with David M. Baird’s book a Guide to the Geology and Scenery of the National Capital Region, Donald Hogarth’s reprinted article from The Canadian Field-Naturalist entitled A Guide to the Geology of the Gatineau-Lievre District, and Ann P. Sabina’s various guidebooks on mineral collecting sites, provided a very good introduction to the geology and collecting sites of the Ottawa area.

Six years ago my wife and I moved to Tay Valley Township, which is south of Perth, and in the southern part of Lanark County. One of the first things I did was to order the geological maps of this area that had been published by the Ontario Geological Survey and the Geological Survey of Canada, and to re-read the chapters covering Eastern Ontario that were in the Ontario Geological Survey’s 1992 publication entitled Geology of Ontario. Over the past few years I’ve been reading the more recent articles that are available online on the sedimentary rocks of Eastern Ontario, Northern New York and Quebec south of Montreal. I was thrilled when in 2010 the Survey published Sanford and Arnott’s Bulletin 597 entitled Stratigraphic and structural framework of the Potsdam Group in eastern Ontario, western Quebec and Northern New York State. Not only is it a good read, but many of the important outcrops noted on the maps are an easy driving distance from where I live.

Towards the end of this summer I decided that I should acquire a copy of the Geological Survey of Canada’s Memoir 241 by Alice E. Wilson that is entitled Geology of the Ottawa-St. Lawrence Lowland, Ontario and Quebec, that had been published in 1946 and covers the Paleozoic rocks of what is now commonly referred to as the Ottawa Embayment. I made that decision because every article and publication that deals with the sedimentary rocks found in Lanark County refers to that memoir. I was fortunate to be able to acquire it online. Having read the book, I wish I’d bought it sooner. This is because Nepean Sandstone, March Formation interbedded dolostones and sandstone, and Oxford Formation dolostones make up the bulk of the sedimentary rocks of Lanark county, and this is the publication that defines those formations. GSC Memoir 241 is also worth buying for the maps, even if they fail to cover much of Lanark county.

However, it is the Bibliography at the end of the book that is the real reason why, sixty-six years after it was published, that everyone reading this blog posting should try to acquire the publication. Alice E. Wilson devotes six and a half pages to a list of articles on the geology of the Ottawa Embayment, and seven and a half pages to an additional listing of articles on palaeontology that cover fossils found in the Ottawa Embayment. There are many of the expected references. These include the papers by Sir William Logan, Owen, Billings and Ami on Climatichnites and Protichnites, Sir William Dawson’s paper on burrows and tracks in Palaeozoic rocks, papers by Logan, Ells, Vennor on geology, and W.A. Parks’ classic on building and ornamental stones found in quarries in Ontario, that I’m sure everyone that has seriously looked at the Ottawa Embayment has read. In addition there are some real gems listed in the bibliography that would be almost impossible to find without these lists, and to my knowledge are not summarized elsewhere.

Some papers listed  in the bibliography are  of interest for the collector and the amateur interested in Lanark County’s geoheritage. These include, for example, a reference to Samson’s Shoulder Stone, a large glacial erratic found near Perth, and a reference to an abandoned quarry east of Perth that was not mapped by the Ontario Geological Survey when they re-mapped the Paleozoic rocks of Eastern Ontario in the early 1980's .

Other papers listed in the bibliography are potentially of interest to academics, including over thirty by Elkanah Billings, one of Canada’s most famous paleontologists. The most intriguing that I have found so far is one cited by Alice E. Wilson as Billings, E. (1860) Additional Note on the Potsdam Fossils: Amer. Jour Sci. (2) 30, pp 242-243, 337-338. This is a reference to a trilobite found in the Potsdam sandstones of New York which is not referred to in the recent literature. There are actually two articles:

Article XXIV - Description of a new Trilobite from the Potsdam Sandstone; by Frank H. Bradley, with a note by E. Billings (1860), American Journal of Science and Arts, Volume 30, Second Series, pages 241-243

Article XXX - Additional Note on the Potsdam Fossils; By E. Billings (1860), American Journal of Science and Arts, Volume 30, Second Series, pages 337-338.

Here Bradley and Billings report on finding a number of specimens of the trilobite Conocephalites Minutae in Potsdam sandstone at High Bridge, near Keeseville, New York. This may be important because trilobites can sometimes be used to date rocks and trilobites have rarely been found in the Potsdam sandstones.

The above photo shows the drawing of the trilobite from the article. I took the photo of my computer screen when I was looking at the full article on Google Books. Anyone wanting to read the full article should be able to find it by searching with Google.

For those not familiar with Alice E. Wilson (1881 - 1964), the following points are worth noting:

- she was the first female geologist in Canada and the first woman to hold a professional position with the Geological Survey of Canada ("GSC")
- the GSC granted her a leave of absence and she obtained her doctorate in geology from the University of Chicago in 1929 at age 48
- she carried out extensive research on the sediments and fossils of the Ottawa-St. Lawrence lowlands, mapping over 16,000 square kilometers, and was a highly respected expert in the field of paleontology
- when she officially retired from the GSC in 1946, at age 65, five people were hired to replace her
- Dr. Wilson kept her office at the GSC after retirement, continuing to visit and carry out field work, and gave up her office in 1963 at age 82.

My source for the above is an undated National Research Canada fact sheet entitled: Trailblazer – Alice Evelyn Wilson, 1881-1964, First Woman Geologist Left Her Mark in Stone. What this fact sheet fails to mention is that for over thirty years she was the authority on the Paleozoic in Eastern Ontario, and published many papers on the Ordovician fossils and geology of Eastern Ontario.

Happy reading,

Chris Brett
Perth, Ontario

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New Display of Dr. James Wilson’s Mineral And Fossil Collection at the Perth Museum

On October 14, 2012 the Perth Museum at Matheson House on Gore Street in Perth, Ontario will be opening to the public its new Geology Exhibition, which will feature a display of part of the mineral and fossil collection of Dr. James Wilson, one of Canada’s most important amateur geologists. The Perth Museum began in 1925 with the donation of the mineral and fossil collection of Dr. James Wilson and it is fitting that this display features his collection.

Dr. James Wilson (1798-1881) was a medical graduate of Edinburgh University in Scotland who emigrated to Canada and practiced as a physician in Perth, Ontario from 1821 to 1869. Dr. Wilson had no formal training in geology, but was an amateur mineralogist and geologist. Today Dr. Wilson is remembered for being the person who first found four things:
 - first, Perthite, an exsolution texture in feldspar;
 - second, the trace fossil Climactichnites Wilsoni, the track of a giant slug from the Cambrian that was one of the first creatures to exit the oceans and ‘walk’ on land;

 - third, the semi-precious mineral Wilsonite; and

 - fourth, Peristerite, a variety of Albite with bluish opalescence.

Perthite was found by Dr. Wilson in pegmatite approximately 10 kilometers south of Perth in North Burgess Township. Climactichnites was found by Dr. Wilson in a quarry in Drummond Township about a mile north of the town of Perth. Wilsonite  and Peristerite were found in Bathurst Township, which is west of Perth.  Both Climactichnites Wilsoni and Wilsonite were named after Dr. Wilson by members of the Geological Survey of Canada.

The display in the Perth Museum’s new Geology Exhibition will include samples of Wilsonite and Perthite. Also on display are a silver brooch featuring Wilsonite and a silver necklace featuring Perthite, both made for the exhibit by Stephen Clark of Lanark County. In addition the exhibit will include two specimens of Climactichnites Wilsoni from Dr. Wilson’s collection. Photos of the two specimens of Climactichnites are provided below.  The tracks are about 15 cm (6 inches) wide.

The astute reader of this blog will note that one is an original trail on a bed top while the other is the natural cast from an overlying bed sole, that they are not mirror images of one another, and that while they may be parts of the same track, are not two parts split from the same rock.

To the left I’ve provided a photograph of a specimen of gastropods collected from North Burgess Township in Lanark County that will be part of the display.

Other fossils that will be included in the display are fossil fish from the Leda Clay in Green’s Creek (then in Gloucester Township and now part of the City of Ottawa) and stromatoporoids.

Michael Bainbridge has provided the following photographs of Wilsonite, Perthite and the jewellery made by Stephen Clark for the new Geology Exhibition.

While Dr. Wilson is remembered today for Perthite, Climactichnites Wilsoni and Wilsonite, Dr. Wilson should be remembered for much more than this. He was instrumental in bringing many mineral, fossil and rock occurrences to the attention of the Geological Survey of Canada, he accompanied members of the survey to the rock, mineral and fossil locations, and he was instrumental in the development of the apatite mines (for use as a fertilizer) and mica mines in North Burgess Township. He was also an avid collector of minerals and fossils, and the Town of Perth is fortunate to have his collection form part of the collection of the Perth Museum.

Sir William Logan, the first head of the Geological Survey of Canada, acknowledged Dr. Wilson’s contribution to the study of geology in the Preface to his book the Geology of Canada with the following words:

"Although Dr. James Wilson, who practised during many years as a physician at Perth, in the county of Lanark, has personally communicated little to the public, he has devoted considerable attention to the natural history of the district in which he resided, and has enriched the mineralogy of the province by the discovery of several very interesting species. To him  we are indebted for pointing out the sandstone bed near Perth, from which were obtained the specimens of Climactichnites Wilsoni; and we have on several occasions, received from him information regarding the occurrence in his own neighborhood of minerals capable of economic application." [Logan (1863), Geology of Canada, Geological Survey of Canada, Report of Progress from Its Commencement to 1863; Page xi]

The text of the Geology of Canada hints at the extent of Dr. Wilson’s contributions. Dr. Wilson is mentioned in the text of the Geology of Canada as providing specimens resembling  Stromatopora rugosa [that were later named Eozoon canadense]  (at page 48, 49); as the person who discovered Climactichnites in a quarry in Drummond Township (pages 107, 108); as the person who discovered the mineral Wilsonite in Bathurst Township (at page 467 and 483); as providing information on the location and thickness of a bed of iron ore in South Sherbrooke Township (page 674); as discovering plumbago (graphite) of a good quality in the township of Burgess (page 795); as providing specimens of a "fine red granite" for possible use as a building stone (page 812); as finding a "pale green serpentine, marked with red" in Burgess Township for use as an ornamental stone (page 824); and as bringing to public notice the locations of the minerals Peristerite in Bathurst Township and Perthite in Burgess Township (page 833).

In the first line of the preceding paragraph I deliberately used the word "hints" in "hints at the extent of Dr. Wilson’s contributions" because his name is often mentioned in earlier reports by the Geological Survey of Canada, and in other literature from the mid 1800's. For example, in Volume II of Canada: Past, Present and Future, Being a Historical, Geographical, Geological and Statistical Account of Canada West, by W. H. Smith that was published in 1851, the author describes (at pages 325 - 330) a visit to Perth by Mr. Sterry Hunt of the Geological Survey of Canada, and provides an account of the mineral localities visited by Mr. Hunt in company with Dr. Wilson and mineral specimens in Dr. Wilson’s collection. Mr. Hunt starts off his report on the geology of the Perth area by noting "This has already been explored to a considerable extent by Dr. Wilson, of Perth, a gentleman who, notwithstanding the duties of an extensive practice, has been able to devote considerable attention to the natural history of his district, and to enrich the mineralogy of the Province by the discovery of many very interesting minerals." Mr. Hunt then describes visiting various outcrops in the company of Dr. Wilson to look at the minerals apatite, copper pyrites, silvery mica, corundum, perthite, and sphene. He also provides a description of a "vein of heavy spar or sulphate of barytes in gneiss," noting that "I was not able to examine the vein in person, but, am indebted for the above account of it, to the accurate observations of Dr. Wilson, and the specimens kindly furnished to me by him. The book also quotes Mr. Hunt as saying "There were many other interesting minerals which had been observed by Dr. Wilson, and which I should have visited but that the localities were often such as could not be found without a guide, but with great difficulty, and the professional duties of Dr. Wilson prevented him from accompanying me." The minerals that he was able to describe based on Dr. Wilson’s specimens included peristerite from Bathurst Township, labradorite from Drummond Township, black tourmaline and bytownite from Bathurst Township, manganesian hornblende and asbestos from Lanark Township, anthophyllite, and spodumene from Bathurst Township.


The preparation of the display for the new Geology Exhibition at the Perth Museum has been co-ordinated by Michael Bainbridge, Recreational Geology Project Co-ordinator for the Ontario Highlands Tourism Organization. Dr. Al Donaldson (formerly a professor of Geology at Carleton University), Beth Halfkenny, Curator, Department of Earth Sciences, Carleton University, and others have helped prepare the display. The Museum is fortunate to have Dr. Donaldson working on the display. Not only is he a tireless promoter of Geoheritage in the Ottawa valley, he is an expert on stromatolites and stromatoporoids, and was able to identify one of the samples as stromatoporoids.


See you at the Perth Museum.

Regards,
Chris Brett

Perth, Ontario

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Addendum:
Additional samples of Stephen Clark’s custom jewellery can be seen at
http://artisanontario.ca/stephen-clark/
http://twohorsegallery.com/?page_id=52
and on his web site at http://www.smallwonderjewellery.com/

Field Trip to Outcrops Near Perth, Ontario

This posting is a field trip guide to outcrops in Potsdam Group sandstone near Perth that contain trace fossils. All of the outcrops can be visited in less than four hours.

Outcrop 1: Dodds & Erwin parking lot, 2870 Rideau Ferry Road, County Road 1, Perth. (Within Town of Perth) -  Photo 1 -  Paired U-burrows
This outcrop is a glacially polished, flat outcrop of Nepean sandstone that falls within the town of Perth’s boundaries and functions as the parking lot for Dodds & Erwin and adjacent businesses. The irregular shaped flat outcrop/parking lot is about the size of four football fields. It is approximately 300 meters south of Scotch Line (County Road 10), on the Northeast side of Rideau Ferry Road (County Road 1). The outcrop is full of abundant vertical worm holes, including paired u-burrows (probable Diplocraterion, but possibly Arenicolites) . The glacially polished surface shows two directions of glacial striae.

Outcrop 2: Waste Management Site, 666 Wild Life Road - at Southern boundary of Perth - Photo 2.
A similar outcrop to the one at the Dodds & Erwin parking lot can be found just inside the entrance to the Town of Perth’s dump, on the north side of Wild Life Road, West of Rideau Ferry Road, approximately one kilometer southwest of the Dodds & Erwin parking lot. The glacially polished, flat outcrop is about 30 meters by 20 meters. It displays abundant vertical worm holes, including paired u-burrows (Diplocraterion?) and, in one location, ripple marks. The dump is open Tuesday, Wednesday, Friday 8 am to 4:30 pm, and Saturday from 8 am to noon.

Outcrop 3: Quarry on Wild Life Road - Photo 3
On the opposite side of Wild Life Road from the town dump is a large (60 meter by 30 meter), water filled, Nepean sandstone quarry. The rock around the top of the quarry (close to the road) is a flat surface showing abundant vertical worm holes (Skolithos?) and bioturbation. Because of the water in the quarry it is almost impossible to access the walls of the quarry (while an extension ladder might work at the shallow end, this is not recommended).
The dump and the quarry can be easily seen on Google Maps and Google satellite view. In the satellite view you can identify the shallow and deep ends of the quarry.

Outcrop 4: 348 Elm Grove Road - Photo 4 - Perth stone
Many buildings in Perth are made with Perth stone, or accented with Perth stone, a purplish and white Potsdam Sandstone that shows incredible bioturbation. It was mined in the late 1800's from the Hughes Quarry, off Hughes Road, about 8 kilometers southeast of Perth. The Hughes Quarry is overgrown. However, the Perth stone outcrops approximately one kilometer to the west of the Hughes Quarry, opposite 348 Elm Grove Road. This outcrop, up to two feet high and 20 meters long, displays vertical worm holes on a glacially polished surface, as does an outcrop on the other side of Elm Grove Road.

Outcrop 5: West side of Elm Grove Road, just south of the second intersection with Glen Drive, and north of Long Lake Road
This location, one of three outcrops on a pegmatite dyke (not Potsdam Group sandstone), is likely the type locality for Perthite, an exsolution texture in feldspar.  (See Ann P. Sabina (1965), Rock and Mineral Collecting in Canada, Vol. II, Ontario and Quebec, GSC Miscellaneous Report 8, Page 118.)Specimens can be easily found. The second outcrop lies about 300 meters to the north, but is the front lawn for a house in a subdivision, and is out of bounds for collecting.   The third outcrop is likely another 500 meters to the north.   Photo 5 - specimen of Perthite collected this year

Outcrop 6: South West Corner of Narrows Lock Road and Powers Road - 18 minutes Southwest of Perth - Photo 6
This is a good exposure of vertical worm holes (Arenicolites??) on a flat outcrop about 10 meters by 10 meters. I suspect that the sandstone is Covey Hill rather than Nepean sandstone, as the same worm holes and rock can be found 30 meters to the north along Powers Road in a barely visible outcrop where the rock under the worm hole bed is a red bed sandstone.

Outcrop 7: Stanley Road, East of Narrows Lock Road - 15 minutes Southwest of Perth - Photo 7 - Diplocraterion cross-section
This past summer a drainage ditch has been dug on the north side of Stanley Road. For about 150 meters the trench cuts through flat lying sandstone, and provides an outcrop from a few inches up to 4 feet high. The rock taken from the ditch has been dumped in five locations along Stanley Road: three areas where it has been used to cover culverts and to make laneways, and two large piles (15 feet long by five feet high by five feet wide) where I expect it will be used to cover culverts and make laneways.   The sandstone is mostly speckled with rust, with some solid grey sandstone and one 6 cm thick siliceous bed that is a dusty rose colour. Quinoa sized (2-4 mm) rounded quartz, very coarse sand/very fine gravel, occurs in a few beds. I found a few samples of ripple marks with varying wavelengths, a few samples of worm tunnels parallel to the bedding surface, two samples with worm tunnels between the ripple marks, a sample with Diplocraterion and two specimens (which, sadly, are no longer with us) that were a chalk like substance showing well defined worm burrows parallel to the bedding that when rubbed disappeared.
　
Outcrop 8: Bowes Side Road just south of Tay River
This is another outcrop of Nepean Sandstone that displays abundant vertical worm holes including paired U-shaped worm holes (probable Diplocraterion), and shows ripple marks. The sandstone outcrops on both sides of the road (close to a private museum) just south of where the road crosses the Tay River. This outcrop is 10 minutes west of Perth.  Photo 8 - note that centres of tubes are preserved in the Diplocraterion.

Let me know if you enjoy the tour.
Regards,

Chris Brett

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Fossils and Trace Fossils in Lanark County - an Overview

This past summer I’ve been collecting and photographing trace fossils in the sedimentary rocks of Lanark County, and the adjacent counties, in Eastern Ontario. The sedimentary rocks in Lanark County are generally considered to be of Upper Cambrian to Lower Ordovician in age. The fossils that I found fall within three main groups of rocks:
1) Fossils from the Potsdam Group/ Nepean Sandstones
2) Fossils from the March Formation (Mostly Sandstone and Dolostone, but also some shale)
3) Fossils found in rocks in Drummond Township that are mapped as the March Formation, but appear to be much older (herein, the Drummond Sequence) - Mostly Sandstone and Carbonate, but also shale and mudstone.

Group 1 - Fossils of the Potsdam Group/ Nepean Sandstones  (First Two Photos)
There are numerous examples of vertical worm burrowing in sandstone outcrops within a fifteen minutes drive of Perth, Ontario, including paired burrows (Diplocraterion, Arenicolites) and single burrows (Skolithos). In addition I found a few example of horizontal burrowing.
Good examples of vertical worm burrows can be seen at outcrops at
1.1 Dodds & Erwin parking lot, 2870 Rideau Ferry Road, County Road 1, in Perth.
1.2 Waste Management Site, 666 Wild Life Road - Southern boundary of Perth
1.3 Bowes Side Road, just south of where it crosses the Tay River - 10 minutes west of Perth
1.4 South West Corner of Narrows Lock Road (County Road 14) and Powers Road - 15 minutes Southwest of Perth

Group 2 - March Formation (third photo)
My best specimens from the March Formation have been sampled from the Phillipsville bluff, which is just south of the Town of Phillipsville, in the Township of Rideau Lakes, United Counties of Leeds and Grenville, about an hour southwest of Perth. The bluff has been mapped both as Nepean Formation and as March Formation, but most often as March Formation.

The bluff is about 20 meters high at its maximum height and runs for a few hundred meters along Hughes Road. It is mainly composed of horizontal beds of sandstone which display vertical worm holes and bioturbation. There are a few easily accessed one cm to five cm thick beds of shale and dolostone where I found a few fossils of the brachiopod Lingula and abundant fossil shards (that I assume to be of same brachiopod). Trace fossils found in the shale beds are of three main shapes: pyramids (photo 3) , bottle caps and egg shapes.  The pyramid shapes are possibly tracks, while the egg shapes might be resting traces.

Group 3 - Drummond Sequence (last four photos)
Directly north of Perth (in Concessions III, IV, V, etc. in Drummond Township) is an area that has most recently been mapped as March Formation, but the rocks differ from other areas that have been mapped as March Formation. The block is bounded by faults that separate it on the west from Nepean Sandstone, on the southeast from March Formation, and on the Northeast from Nepean Sandstone. It is, admittedly, inter-bedded carbonate and sandstone, the key characteristics of March Formation. However, I have not yet found any shelled fossils in the Drummond Sequence, the trace fossils I have found differ from those that I have found in the Nepean Formation and in beds that I accept as March Formation, and the Drummond Sequence does not look like typical March Formation.
Factors that separate the Drummond Sequence from March Formation include:
1. Absence of shelled fossils.
2. Abundant, multicoloured, desiccation cracks in sandstone, carbonate and shale.
3. The carbonate layers are more brightly coloured, especially on fresh surfaces where the rocks appear as rose & white, and brown & white. While the carbonates weather grey, the rose streaks can be seen on the weathered surfaces, and the rock can be mapped on this basis.
4. Abundant horizontal burrowing.
5. The more abundant range and selection of trace fossils that I have found (including, many of which I cannot identify).
In addition, Sir William Logan found Climactichnites and Protichnites at a quarry in Lot 6, Concession 3, Drummond Township that falls within the Drummond Sequence. Both Climactichnites and Protichnites are thought to be Late Cambrian, Potsdam Group fossils that have not been found in the March Formation.
It is possible that Drummond Sequence is a thin veneer of March Formation carbonates overlaying Nepean Sandstone. However, the trace fossils I’ve been finding suggest that it might be older than Upper Cambrian, the age of the  Nepean Formation of the Potsdam Group.
Regards,

Chris Brett

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