Frothed Sandstone and Cylindrical Structures Found in Potsdam Sandstone

If you  love coffee and in the past decade have visited Perth, Ontario you have undoubtedly stopped at Coutts Coffee at Code’s Mill (corner of Herriott and Wilson Streets).  Coutts Coffee roasts their own coffee beans and consistently provides an excellent cup of coffee.   I’ve particularly liked going for coffee because two types of Potsdam sandstone were used in the construction of Code’s Mill, and in the construction of  Mr. Code’s house which is to be found directly across Herriott Street from Code’s Mill, and on my walk over I pass the Royal Bank building which is also made of Potsdam sandstone.   “Perth stone”, a distinctive purple-banded sandstone from the Hughes Quarry in Lanark County, was used as an accent stone in the construction of all three buildings.   (See my blog posting from Monday, December 17, 2012 for a description of the Hughes Quarry.)   There are also interesting structures in the March/Theresa flagstones used as the floor of the atrium at Code’s Mill.  It is worth the price of a cup of coffee just to admire the various stones.

This summer Coutts Coffee opened a new location on Gore Street East in Perth beside the Tay River.  It will be closing the outlet in Code’s Mill in December.   Code’s Mill incorporates five buildings built from 1842 and 1932, with the three-storey building facing onto Herriott Street having been built in 1903.   Interestingly, the new location is also in an historic building made of Potsdam sandstone.  It was constructed about 1845 for the then Sheriff of Bathurst District (the predecessor of Lanark County).

At the new location it is a stone that was used in the construction of an original fireplace that will be of most interest to geologists.  Below are two photos of that stone.

The photos show what I believe to be cross-sections of cylindrical structures and frothed sandstone (under the ruler).   I believe that the frothed sandstone was injected/frothed by water flowing through the sandstone.   The stone is clearer than the photos and is worth a look, as you sip your coffee.

An Occurrence 4.5 kilometers south of Elgin (2 miles north of Brier Hill)

In my blog posting from  August 27, 2015 I mentioned an occurrence 4.5 kilometers south of Elgin that shows numerous cylindrical structures and provided photographs of a number of small structures from that location.   Subsequently I determined that this location was first mentioned by Dr. Wynne-Edwards (1967, GSC Memoir 346, at page 120):

“Vertical cylindrical concretions resembling tree trunks, the best examples of which are exposed in a 30-foot cliff beside the road west of Lower Beverley Lake 2 miles north of Brier Hill, occur in the lower parts of the formation and cut across the bedding. Most of the concretions there taper out downward and are about a foot in diameter, but the mould of a much larger one was left in the cliff face as a cylindrical indentation more than 6 feet wide. Hawley and Hart (1934) attributed these concretions to the upward flow of water and the consequent development of tubular bodies of quicksand that disrupted the bedding in the as yet unconsolidated sand.”

This is the same occurrence that  I described, because 4.5 kilometers south of Elgin is  2 miles north of Brier Hill.

I revisited the occurrence last August with Dr. Donaldson and took the following pictures:

In the first photograph the angular holes that have weathered out of the sandstone could represent casts of gypsum.  The photo could also show multiple stages of dewatering, as the smaller cylinder cuts into the larger cylinder.  The last two photos are interesting because they show frothed sandstone and conglomerate around the edges of the cylinder.   The conglomerate is not present in the rock surrounding the cylinders and  must have been pushed up from below or pulled down from above  (there is a conglomerate a little higher in the stratigraphic column).

The Elgin/Brier Hill occurrence is worth a visit as there are over 200 small structures with a diameter 2 to 6 inches, a number a foot in diameter, plus a number as big or bigger than those at the Hughes quarry in Pittsburgh Township near Kingston Mills.   I have to admit that I have not yet seen the largest ones: Dr. Dave Forsyth was good enough to send me a photo of them. 

The number of cylindrical structures at the Elgin/Brier Hill occurrence rivals the number of cylindrical structures found at Victoria Island and described in the following paper: 
Mathieu, J., Turner, E.C., and Rainbird, R. H., 2013
Sedimentary architecture of a deeply karsted Precambrian-Cambrian unconformity, Victoria Island, Northwest Territories; Geological Survey of Canada, Current Research 2013-1, 15 p.
  

Cylindrical Structures and Sand Injectites

      
I’ve noted that cylindrical structures in Potsdam sandstone have features in common with sandstone injectites that  form by the flow of a mobilized sand slurry through fractures in
overlying rock.   Interestingly, most sedimentary injectite systems are explained by elevated pore fluid pressure combined with a catastrophic triggering mechanism, likely seismic shaking.  An article that I found helpful is:

Sherry, T. J., C. D. Rowe, J. D. Kirkpatrick, and E. E. Brodsky (2012), Emplacement and dewatering of the world’s largest exposed sand injectite complex, Geochemistry Geophysics  Geosystems, Volume 13, No. 1, 17 pages,  Q08008, doi:10.1029/2012GC004157.  

The article is worth reading because their figured laminae look like the bands that we in Eastern Ontario see in our cylindrical structures, and the authors provide a compelling explanation for the formation of the laminae.

Sherry, Rowe, Kirkpatrick, and  Brodsky  report that the injectite complex in California contains granular textures that record processes of sand slurry flow, multiple pore fluids, and dewatering after emplacement.    They suggest that compaction of the injectite deposit and pore fluid escape caused spaced compaction bands and dewatering pipes which created  laminae.   They describe alternating 6 mm thick laminae of iron oxide-cemented and uncemented sand and mention that the laminae are always locally parallel and consistent in thickness.    They suggest that during sand emplacement, the system must have transitioned from a flowing to geometrically locked grain geometry.  They suggest that iron oxide, precipitated from fresh pore water at a later stage, is preferentially concentrated in alternating laminae, that iron oxide cement occurs in the laminae with slightly higher apparent aspect ratio (consistent with stronger shape lineation). They suggest this reflects a difference in the permeability of the laminae, caused by and preserved from the initial orientation of the sand grains, that affected late stage groundwater flow.   

It would be an interesting exercise to look as closely at the orientation of the sand grains, and cement in Eastern Ontario’s cylindrical sandstone structures, as Sherry, Rowe, Kirkpatrick, and  Brodsky looked at the orientation of grains and cement in the sand injectite complex that they studied.


I’ve previously written about cylindrical structures and below  provide the dates and titles of my blog posts.

Christopher Brett
Perth, Ontario


January 29, 2014  - Cylindrical Structures in Potsdam Group Sandstone in Eastern Ontario
August 27, 2015 - Cylindrical Structures in Potsdam Group Sandstone in Eastern Ontario - Part 2
September 28,  2015 - A Map Showing the Location of Cylindrical and Conical Structures in Potsdam (Group) Sandstone of Ontario and New York
October 22, 2015  - Soft-Sediment Deformation (Seismites) in Nepean Sandstone Close to the Rideau Lake Fault - Cylindrical structures in Sandstone: A Type of Soft-Sediment Deformation Sometimes Linked to Seismic Activity
December 23,  2015 Dewatering Structures, Biofilm Structures, Glacial Striae and Chatter Marks in Potsdam Sandstone near Newboro, Eastern Ontario