Soft-Sediment Deformation (Seismites) in Nepean Sandstone Close to the Rideau Lake Fault

Soft-sediment deformation structures are deformations that occur in sediments that have not undergone lithification before the deformation structures form.  They are the result of liquefaction or fluidization in water-saturated unconsolidated sediments.  Liquefaction or fluidization may be caused by various  processes.  Soft-sediment deformation structures related to seismically induced liquefaction or fluidization are named seismites.

Below are photographs that I took over two years ago of an outcrop of Nepean sandstone that I found in June, 2013  that is less than a kilometer southwest of the lock at The Narrows on the Rideau Canal.

The pen in the first photo is about 15 cm long.

The photographs show deformed beds of Nepean Sandstone that occur above flat lying beds of sandstone and below flat lying beds of sandstone.   These deformed beds are also less than a kilometer south of the Rideau Lakes Fault that was identified by Wynne-Edwards (1967).  I believe the deformed beds in the Nepean sandstone to be seismites that could have resulted from movement along the Rideau Lakes Fault, which suggests that the fault was active in the Cambrian.    Below is an extract from Wynne-Edwards’ map of the Westport area showing the location of the outcrop that I photographed in relation to the Rideau Lakes Fault.

Wynne-Edwards (1967) identified the Rideau Lakes Fault as a major structural feature at least 100 miles (160 kilometers) long.  He mentions that “there is abundant evidence that the shear zone represents a Precambrian wrench fault of major proportions. ... Although post-Ordovician movement can be demonstrated in several places, evidence that the Rideau Lakes fault originated before the deposition of these sediments in abundant.”   As evidence of Precambrian movement he mentions that “On Turnip Island in Rideau Lake, a shear zone 10 feet wide is in the Precambrian rocks beneath the basal Cambro-Ordovician conglomerate, and consists of a soft mass of serpentine and talc separating a sheared quartzo-feldspathic rock from shattered crystalline limestone.”  As evidence of post-Ordovician movement he mentions that “At Narrows Lock, the fault separates Ordovician limestone from Precambrian monzonite, and is marked by a linear gully containing boulders of brecciated limestone.”  As noted above, I believe that the deformed beds that I photographed provide evidence that the fault was also active in the Cambrian (the accepted age of the Nepean formation sandstones) .

A recent paper by Hilbert-Wolf,  Simpson, Simpson, Tindall and Wizevichz (2009) summarized
criteria that permit the interpretation of soft-sediment deformation initiated by seismic activity.  They mention that:

“Generally accepted seismite criteria include: (1) a clear association with potential originating faults, (2) observed deformation that is consistent with seismic origin, (3) a widespread occurrence that is temporally constrained, (4) systematic change in intensity or increase in frequency towards possible epicentre, (5) exclusion of other causal mechanisms, (6) recurrence of deformed horizons over time, (7) underlain and overlain by undisturbed horizons, and (8) faults associated with wedges of interclastic breccias, conglomerates, or massive sandstones. The more criteria that are satisfied the greater the likelihood features are of seismic origin.  In addition, soft-sediment deformation should cross-cut regional and local facies boundaries.”
[Citations Omitted]   

The outcrop that I’ve found meets their first, second, and seventh criteria.

Disruption of Stromatolite Zones in Nepean Sandstone By Seismic Activity

Others have proposed that seismic activity has caused soft-sediment deformation in the Nepean formation sandstone.  In my last posting, on Stromatolites, I mentioned a field trip guide by Donaldson and Chiarenzelli (2004).    For two of their stops they proposed that seismic activity had caused deformation in a stromatolite unit in Nepean sandstone.  Their Stop 7 was at an outcrop of Nepean Formation quartz arenite that displayed cross-sections of random tilted,  laminated, domal stromatolites.  They suggest that “to account for the random tilted arrangement of stromatolites” their model “requires early cementation of the stromatolite unit above a still-unlithified substrate of water charged sand.  As a result of a seismic disturbance, the rigid unit of laterally linked silica-cemented stromatolites snapped apart along the thin inter-stromatolite links, allowing the now-separated heads to rotate and founder in random directions into the overpressurized sand.”
 

Cylindrical structures in Sandstone: A Type of Soft-Sediment Deformation Sometimes Linked to Seismic Activity

A number of my recent postings have been on cylindrical structures in Potsdam Group sandstones.   These cylindrical structures are a type of soft-sediment deformation.    The generally accepted view is that these are dewatering structures resulting from springs.  The leading paper is by Hawley and Hart (1934), who proposed that the cylindrical structures were formed “by circulating waters at some time following the deposition of the sandstone. .. [T]hat following, or throughout, the period of deposition of the sandstone, possibly while it was still submerged, there appeared on top of the sands a series of springs, fed by columns of water rising from an unexposed horizon, such as the basal conglomerate or the underlying pre-Cambrian rocks.   The nature of the adjacent landmass and the structure of the basement rocks... must have controlled the locus of the springs, their rate of flow, and the hydrostatic head.”

Recently Dave Forsyth (2011), when discussing the Cambrian cylindrical structures found in Potsdam (Group) sandstones of southeastern Ontario and northern New York wrote that “The structures are considered to represent the result of vertically upward water flow originating near or at the Grenville basement to produce spring-like conduits of fluidized sand. ... [T]he combination of fluctuating water table, basement relief on the order of 100 meters and well sorted mainly medium to coarse grained quartz grains, enabled the formation of conduit structures of fluidized sand.  The apparent lack of an aquifer cap suggests conduit formation resulted from an unconfined, water table aquifer as opposed to being artesian. ... Changing water table conditions produced a variable internal conduit structure featuring truncated earlier structures and internal concentric annular rings. ”

Intriguingly, many recent papers on cylindrical and conical structures found in sandstone (that is not Potsdam Group sandstone) debate whether the cylindrical and conical structures formed as a result of seismic shock.   For example, see Mathieu, Turner, and Rainbird (2013), who provide a recent review of the issue,  note that the “means by which these cylinders developed is controversial, particularly with respect to the mechanism of fluidization.” and mention that in some studies sediment liquification “was attributed to a seismic event.”   They also note that “It could be argued that multiple seismic events could account for the pulsing flow or the cross-cutting relationships between cylinders.”   However, for their cylinders in Cambrian sandstones on Victoria Island in the Northwest Territories, they reject a seismic trigger and conclude that “the pillar-like structures are attributed to water escape through submarine springs, where groundwater flowing through the karst network emerged onto the Cambrian seafloor.” 

The only publication that I’ve found that suggests that the cylindrical and conical structures in the Potsdam Group sandstones of the Ottawa Embayment may have resulted from seismic activity was by Shrock (1948), who raised the possibility that the cylindrical structures from the Cambrian sandstones found near Kingston may have been formed as a result of seismic shock, but acknowledged that “in reply to a query from the author, Dr. Hawley wrote that he had found no evidence to support” this theory.   Would the answer be different today when geologists are aware that the faults along the St. Lawrence River and along the Ottawa River have been active since the Pre-Cambrian, when seismites have been found in the Nepean Formation close to the Rideau Fault that has been active since the Pre-Cambrian, and when soft-sediment deformation of a stromatolite bed in the Nepean Formation resulted from seismic disturbance?

One feature that may (or may not) lend support to the suggestion that seismic activity initiated  the fluidization that led to the formation of the cylindrical structures is the presence of large numbers of spheroidal concretions in association with a number of the cylindrical columns.  For example,

(A)  Anglin, Boyle and James (1888), which was the first published  report on Canadian cylindrical columns in Potsdam sandstone, mention specimens from the Gildersleeve’s Cataraqui Stone Quarries ten miles from Kingston, and report that Dr. A. R. C. Selwyn, Director of the Geological Survey of Canada “is of opinion that in all probability the columns have been formed by the filling up of what were geyser tubes, or passages for the emission of hot water from some ancient gushing wells like those of Iceland. In association with the columns are found large numbers of roughly spheroidal nodules, or concretionary bodies, also of sandstone, measuring from one to five or six inches in diameter, which to the unscientific mind suggest an idea of fossilized fruit.  It is noticeable that in every case these are marked by an encircling groove.” 

(B)  Franklin Hough (1853), mentions the cylindrical structures in the sandstones at Rossie, New York  and comments “In some places the rock is made up of balls, having a concentric structure like the coats of an onion ... In the vicinity of the iron mines at Rossie, this spheroidal structure is very common and makes up the whole of the rock.  They are of all sizes, from a pen to an orange”

I make the suggestion that the presence of spheroidal concretions might lend support to seismic activity being related to the formation of the cylindrical structures, as there are reports where seismic activity has resulted in soft-sediment deformation structures in the form of balls and pseudo-nodules (for example, Bowman,  Korjenkov, and Porat,  2004).  While I concede that concretions are associated with hot springs and with mineral springs, there is at least one report of “ball-and-pillow” structures in Potsdam sandstones: Salad Hersi and Lavoie (2000) on a stratigraphic section of the Cairnside Formation sandstone (the Quebec equivalent of Ontario’s Nepean Formation sandstone, and New York State’s Keeseville sandstone), show ball-and-pillow structures at three horizons and mention in their report that ball-and-pillow structures “are locally well developed” in the Upper Unit of the Cairnside.  

Christopher Brett
Perth, Ontario

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References:

Anglin, T. W., Boyle, D., and James, C.C., 1888
Mineral Exhibit of the Province of Ontario, Descriptive Catalogue, Centennial Exposition of the Ohio and Central States; Cincinnati, July 4 to October 27, 1888, 64 pages  at page 34
https://books.google.ca/books?id=_MdCAQAAMAAJ

Bowman, D.,  Korjenkov, A. and Porat, N., 2004
Late-Pleistocene seismites from Lake Issyk-Kul, the Tien Shan range, Kyrghyzstan;
 Sedimentary Geology 163 (2004) 211–228
 http://activetectonics.la.asu.edu/N_tien_shan/Seismite.pdf

Donaldson, J. Allan  and Chiarenzelli, Jeffrey R., 2004
Stromatolites and Associated Biogenic Structures in Cambrian and Ordovician Strata in and Near Ottawa, Ontario; 76th Annual Meeting, Field Trip Guidebook, New York State Geological Association, 283 pages, at pages 1-20. 

Forsyth, D.A.,  2011,
Evidence and Hypothesis– How the Sandstone Cylinders Formed;
GAC/AGC - MAC/AMC - SEG - SGA  Joint Annual Meeting, Ottawa 2011, Abstracts Volume 34, at page 66    www.mineralogicalassociation.ca/doc/Ottawa2011AbstractsVolume.pdf

Hawley, J. E. and Hart, R. C.,  1934
Cylindrical Structures in Sandstone;
 Bulletin of the Geological Society of America, Volume 45, pages 1017-1034

Hough, Franklin B., 1853
A History of St. Lawrence and Franklin Counties, New York, from the earliest period to the present time; Albany, Little & Co., 708 pages, at page 678.

Hilbert-Wolf, Hannah L.,  Simpson,  Edward L., Simpson, Wendy S., Tindall, Sarah E. and
Wizevichz, Michael C.,  2009,
Insights into syndepositional fault movement in a  foreland basin; trends in seismites of the Upper Cretaceous, Wahweap  Formation, Kaiparowits  Basin, Utah, USA;
Basin Research (2009)   doi: 10.1111/j.1365-2117.2009.00398.x
   
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.

Salad Hersi, O. and Lavoie, D., 2000
Lithostratigraphic revision of the Upper Cambrian Cairnside Formation, upper Potsdam Group, southwestern Quebec; Geological Survey of Canada, Current Research 2000-D4, 8 pages

Shrock, R.R., 1948
Sequence in Layered Rocks: A Study of Features and Structures Useful for Determining Top and Bottom Order of Succession in Bedded and Tabular Rock Bodies;
McGraw Hill, New York, 507 pages, at pages 136, 220 and 221

Wynne-Edwards, H.R.,  1967,
Map 1182A, Geology, Westport, Ontario; to accompany Memoir 346, Westport Map-Area, Ontario, With Special Emphasis on the Precambrian Rocks, Geological Survey of Canada.

Wynne-Edwards, H.R., 1967,
Westport Map-Area, Ontario, With Special Emphasis on the Precambrian Rocks;
Geological Survey of Canada,  Memoir 346, 146 pages
http://geoscan.nrcan.gc.ca/starweb/geoscan/servlet.starweb?path=geoscan/fulle.web&search1=R=100533