The Novel Coronavirus (COVID-19) and Problems with Statistics

That there have been over forty-three  thousand confirmed cases of  novel Coronavirus (COVID-19) and over 1,000 deaths is both tragic and troubling. 
   
A number of people have questioned the statistics surrounding the outbreak.  My main concern with the statistics being provided is the estimate that the mortality rate is 2% of confirmed cases.   I am not suggesting that when reported deaths are compared with confirmed cases the death rate does not appear  to be 2 percent.   However, that calculation never took into account  the confirmed cases where the person had neither died nor recovered, and that many of those patients will die.    The simplest way of explaining this is that on February 11th there were  43,103 total cases worldwide, 1,116 deaths and 5,127 recoveries. This leaves 36868 confirmed cases being treated.  It is reasonable to expect that many of those will die, particularly as WHO reports 7333 severe cases in China.  If one applies WHO’s estimate of two percent, then we can expect about 700 of those additional confirmed cases to die, which paradoxically results in a mortality rate of about four percent.

The Mortality Rate has Increased

A second problem with fixating on 2 percent when comparing deaths with confirmed cases is that the death rate is increasing.   This can be seen from the following:
-  As of February 5  there were 24363  confirmed cases in China and 491  deaths in China, which is a death rate of  2.01 % .     
- As of February 7 there were 31 211  confirmed cases in China and 637 deaths in China, which is a death rate of 2.04 %
- As of February 8 there were  34 598 confirmed cases in China and 723 deaths in China, which is a death rate of 2.09 %
 - As of February 9  there were  37 251  confirmed cases in China and  812  deaths in China, which is a death rate of 2.18%.  
 - As of February 10  there were  40 235  confirmed cases in China and  909 deaths in China, which is a death rate of 2.25 %.     
-  As of February 11 there were 42 708  confirmed cases in China and 1017 deaths in China, which is a death rate of 2.38 % .
       
The mortality rate is going up because deaths continue to increase while the increase in the number of confirmed cases has slowed down.   It is reasonable to assume that the mortality rate will keep increasing for at least the next two weeks.  This is because  China’s efforts to quarantine the disease will become even more successful and the number of additional confirmed cases will drop off.   As additional cases drop off, deaths will start to catch up with cases, and the mortality rate will increase.

Severe Cases

An additional  reason to question that the mortality rate will be close to two percent is that China and the World Health Organization are  releasing figures for  severe cases and  recoveries 

WHO’s Novel Coronavirus (2019nCoV) Situation Report –21 which provides  data reported as of February 10th lists 6484 severe cases in China.  WHO’s Situation Report -22 which provides  data reported as of February 11th lists 7333 severe cases in China   If one assumes that all of the Severe cases result in death, then the mortality rate for Coronavirus for February 10th is 18 percent [= 100 (909  + 6484)/ 40 235] and for  February 11th is 19.5 percent [= 100 (1017  + 7333)/ 42708].   However, as WHO defines a Severe illness according to any of the following criteria: (1)  shortness of breath ; (2) respiratory rate more than 30 bpm; (3) hypoxemia; (4) chest X-ray with multilobar infiltrates or pulmonary infiltration progressed more than 50% within 24 - 48 hours,  not all with severe coronavirus will die.   Conversely, not all confirmed cases have yet had time to develop into severe cases, and one would expect many recent cases to become severe.

A recent study of 138 patients with confirmed coronavirus  admitted to Zhongnan Hospital of Wuhan University from January 1 to January 28, 2020 provides some guidance on the mortality rate for severe cases.   As of February 3 (the closing date for the study), Dr. Dawei Wang and the additional  authors found that 36  of the patients (26%) required admission to the intensive care unit, 6 had died (4.3%), 85 patients (61.6%) were still hospitalized, and 47 patients (34.1%) had been discharged.  Of the 36 patients admitted to the ICU, 11 were still in the ICU, 9 had been discharged to home, 10 had been transferred to the general wards, and 6 had died. Of the 11 patients who remained in the ICU, 6 received invasive ventilation and 5 noninvasive. 

If one splits the 36 ICU patients into two groups [Dead plus invasive ventilation ] and [ discharged, plus transferred to general ward, plus noninvasive] this suggests a mortality rate of 33%  [= 12/36 x 100] for severe cases.   If one compares only those who died with the total of those who had been discharged from ICU and those transferred to general ward, this suggests a mortality rate of 24  % [= 100x 6/(6+9+10)]

If one then recalculates the death rate for Situation report 21 (February 10th) assuming 33% of severe cases are considered likely to die, then the mortality rate is 7.6%   [= 100 (909 + .33 x 6484) / 40235] resulting from 3048 actual and estimated deaths.  If one recalculates the death rate for Situation report 21 assuming 24% of severe cases are considered likely to die, then the mortality rate is 6%   [= 100 (909 + .24 x 6484) / 40235] resulting from 2465 actual and estimated deaths.

Recoveries

As of February 11th  there were 1018 deaths worldwide and 5,127  recoveries worldwide.   Assuming that  those still undergoing treatment will show the same ratio between deaths and recovery, those numbers  equate to a mortality rate of 16.5%.

On a positive note, the mortality rate based on that calculation appears to be dropping. 
                                   

Deaths Trail New Cases

Another reason to question that the death rate is two percent is that deaths always trail new cases. By this I mean that it takes weeks for a person infected with the disease to either recover or die.    A tragic example of this is the recent death of doctor Li Wenliang, the person who first raised the alarm.  It is reasonable to assume that he was infected in December or the first two weeks of January.   He died on February 7th.   He may not have shown symptoms until about ten to fourteen days after infection.   If so then his treatment lasted about two to  three weeks.

At this point in time there is no way of calculating the  average length of time that it takes for those who are confirmed with Coronavirus to die (or recover).  In their paper Dr. Dawei Wang and the other medical doctors report the time from onset to dyspnea was 5 days and 8 days to ARDS (acute respiratory distress syndrome ).    For the purpose of an example, I will assume that on average it takes on average ten days for those who are confirmed with Coronavirus to die (or recover).  On February 1st there were 11821 confirmed  cases in China.  If one assumes that the total deaths in China as of February 11  mainly result from those that were reported cases on February 1st, then the mortality rate is 5.9%.   [= 100 x 1017/ 11831].
   

Comparison with SARS and MERS

   
Severe acute respiratory syndrome (SARS) is a viral  disease caused by the SARS coronavirus (SARS-CoV).    Middle East respiratory syndrome (MERS) ] is a viral infection caused by the MERS coronavirus (MERS-CoV).   For SARS there were 774 deaths out of 8,096 reported cases for a mortality rate of 9.6 percent.  Over 2,000 cases of MERS were  reported with about 600 deaths, with a mortality rate of about 30%.    A mortality rate of from 6% to 16.5% for the current coronavirus outbreak  accords with the mortality rates for SARS and MERS.

Perplexingly, my calculations are only applicable to confirmed coronavirus cases in China.  The mortality rate outside China appears to be less than one percent.

Sincerely,
Christopher Brett
Ottawa
   

References

Dawei Wang, MD ; Bo Hu, MD ; Chang Hu, MD ;   Fangfang Zhu, MD ; Xing Liu, MD; Jing Zhang, MD ; Binbin Wang, MD; Hui Xiang, MD; Zhenshun Cheng, MD; Yong Xiong, MD; Yan Zhao, MD; Yirong Li, MD; Xinghuan Wang, MD; Zhiyong Peng, MD, 2020
Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus–Infected Pneumonia in Wuhan, China | Critical Care Medicine | JAMA | 
JAMA. Published online February 7, 2020. doi:10.1001/jama.2020.1585
https://jamanetwork.com/journals/jama/fullarticle/2761044

World Health Organization
SITUATION REPORT  - 5 ;  25  JANUARY 2020
Severe illness: According to any of the following criteria:  (1)  shortness of breath ; (2) respiratory rate more than 30 bpm; (3) hypoxemia; (4) chest X-ray with multilobar infiltrates or pulmonary infiltration progressed more than 50% within 24 - 48 hours.

Tubular Structures in the Ediacaran Drummond Sequence in Lanark County, Ontario

In my March blog postings I reported finding the Ediacaran fossil Aspidella together with  Ediacaran fronds and various microbial mat structures, in sedimentary rocks northeast of Perth, Ontario that I designated  the Drummond Sequence.   Below  are two of the more convincing photographs.

As noted in earlier posts, I believe that there is at most a thin veneer of lower Ordovician March Formation at the top of the Drummond Sequence and that most of the rocks in the sequence are Ediacaran in age. 

I looked through my collection of photographs from the Drummond Sequence for slabs with a similar style of preservation to that shown in the first of the above two photographs.   Below is  one such photograph showing tubular structures together with an enlarged extract from the photo.

I believe that the photographs shows an Ediacaran tubular fossil rather than stalks, but this is not clear.

Below are two photos of another slab displaying the same style of preservation.

Again it is not clear whether the tubular structures represent tubular fossils or stalks.

Similar tubes are shown below in a different mode of preservation:

Christopher Brett
Perth, Ontario

A Concentric Circular Structure in Rocks of the Ottawa Embayment that are Mapped as the Ordovician Gull River Formation

In my March, 2019 blog postings I reported finding the concentric, circular, Ediacaran fossil Aspidella together with  Ediacaran fronds and various microbial mat structures, in sedimentary rocks northeast of Perth, Ontario that I designated as the Drummond Sequence.   The Drummond Sequence is found in Drummond/North Elmsley Township in  Lanark County.  The rocks at the top of the Drummond Sequence have been mapped as the Ordovician March Formation by the Ontario Geological Survey, but it is not clear that they belong to the March Formation. 

In various blog postings dated from 2014 to 2016 I mentioned and included photographs of cylindrical dewatering structures in the Cambrian Potsdam sandstone of Eastern Ontario.

Below are photographs of a circular structure observed in a slab of rock at a quarry  in the United County of Leeds and Grenville, Ontario that has been mapped as the Ordovician Gull River Formation by the Ontario Geological Survey.

The outermost of the light coloured inner concentric rings is about five inches in diameter.  The darker  spiral ring is about a foot in diameter.

 My initial guess for this structure was that it is more likely to be a cross-section of a dewatering structure or  a cross-section of a concretion, than an Ordovician  fossil.  However, the specimen bears more that a passing similarity to some photographs of Eldonids including Eldonia ludwigi from the Cambrian Burgess Shale (Walcott, 1914, Figure 5 at  page 47, and Plates  9-12;  Caron et al., 2010, Figure 1; MacGabhann, 2012, volume 2, Figure 4.02 - 4.18),   Eldonia berbera (Alessandrello and Bracchi, 2003) and Eldonia eumorpha (Chen et al., 1995; Anonymous, 20??), all Cambrian or Ordovician in age .  If it is a fossil Eldonid then the dark gray spiral structure is probably a digestive organ, while the light  patches and light grey ribbons outside of the dark spiral are part of the outer ring.

 An alternate interpretation is that this represents a concentric microbial discoid structure similar to microbial-related biogenic structures from the Middle Ordovician slates of northern Portugal reported by Neto de Carvalho, Couto, Figueiredo and Baucon (2016)

The part and counterpart of the slab were available for collecting, but both were too heavy for me to lift.  The slabs are at the edge of a blast pile at the quarry.  I did not ask when the pile is slated to be crushed, but it will likely be before next spring.

Despite an hour searching, no other fossils were found in these beds.

These rocks have been mapped as the Gull River Formation by the Ontario Geological Survey.  Williams (1991)  notes that “Brachiopods, bryozoa, corals, crinoids, ostracods, gastropods, pelecypods, cephalopods, trilobites, and stromatolites are abundant” in the Gull River formation. I
found no indication of any of those fossils at this location.  An individual who has looked at these beds told me prior to my search that there are no fossils at this location.  However, the OGS reports an ostracod in shale from this location that had earlier been reported from this formation in Aylmer, Quebec (just across the river from Ottawa) by Raymond (1911,  p.190) and described and figured by Jones (1891, page 65, plate 11, figures 7 and 8).  One figured specimen from Aylmer is 4.1 mm in length with a  height of 2.5 mm.  It  could easily have been overlooked by me.  

I did find a small trace fossil in an outcrop of an overlying chalky bed that may or may not to be part of the sequence mapped by the Ontario Geological Survey as the Gull River Formation.  Below is a photograph of this trace fossil.  The numbers on the ruler record centimeters.

This specimen was found in a bed on an upper bench at the quarry that is scheduled for blasting next spring.

Christopher Brett
Ottawa

Addendum, July 14, 2022:  My interpretation of the photographs of this circular structure has been bothering me since my initial posting.  Accordingly,  I've changed the emphasis of the paragraph under the first three photographs.  I have not been back to the quarry to look for the specimens.

Referenced, And Suggested Reading

Alessandrello, Anna and Bracchi, Giacomo , 2003

Eldonia berbera n. sp., a new species of the enigmatic genus Eldonia Walcott, 1911 from the Rawtheyan (Upper Ordovician) of Anti-Atlas (Erfoud, Tafilalt, Morocco).  Atti della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale in Milano, Vol. 144, pages 337-358

https://www.biodiversitylibrary.org/part/324891

 https://www.biodiversitylibrary.org/page/58420660#page/341/mode/1up

Anonymous, 20??

Eldonia eumorpha Enigmatic Taxon from Chengjiang. 

http://www.fossilmuseum.net/Fossil_Sites/Chengjiang/Eldonia-eumorpha/Eldonia.htm

Brett, Christopher, 2014-2016
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  -  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
September 22,  2016 - Frothed Sandstone and Cylindrical Structures Found in Potsdam Sandstone
Fossilslanark.blogspot.ca

Brett, Christopher, 2019a
Concentric Structures in the Sedimentary Rocks of Lanark County, Ontario that are identical to the Ediacaran Holdfast Aspidella.  http://fossilslanark.blogspot.com/2019/03/holdfasts-in-lower-ordovician-march.html

Brett, Christopher, 2019b
If the Ediacaran discoid holdfast Aspidella, why not Ediacaran Stalks, Spindles and Fronds in Lanark County?
http://fossilslanark.blogspot.com/2019/03/if-ediacaran-discoid-holdfast-aspidella.html

Chen Jun-yuan, Zhu Mao-yan, & Zhou Gui-qing. 1995. 

The Early Cambrian medusiform metazoan Eldonia from the Chengjiang Lagerstatte. Acta Paleontologica Polonica 40, 3, 213-244. 

  https://www.app.pan.pl/archive/published/app40/app40-213.pdf

Caron, J.; Conway Morris, S.; Shu, D.; Soares, D., 2010. 

In Soares, Daphne (ed.). "Tentaculate fossils from the Cambrian of Canada (British Columbia) and China (Yunnan) interpreted as primitive deuterostomes". PLOS ONE. 5 (3): e9586. Bibcode:2010PLoSO...5.9586C. doi:10.1371/journal.pone.0009586. PMC 2833208. PMID 20221405.

Jones, T. Rupert, 1891
6. BEYRICHIA CLAVIGERA (sp. nov.), 7. BEYRICHIA CLAVIGERA (sp. nov.) Var. CLAVIFRACTA (nov.)., in Contributions to Canadian Micro-Palaeontology. Part III. Geological Survey of Canada, (pages numbered 59-99 ; plus plates), at page 65, and plate 11, figures 7 and 8
https://doi.org/10.4095/106564

MacGabhann, Breandán Anraoi, 2012

A Solution to Darwin's Dilemma: Differential Taphonomy of Ediacaran and Palaeozoic Non-Mineralised Discoidal Fossils.  Ph.D. Thesis.  National University of Ireland, Galway .  Volume 1 - Text and References (1.104Mb)  Volume 2 - Figures and Tables (27.43Mb).   http://hdl.handle.net/10379/3406  Collections:  NUI Galway Theses (PhD Theses)

Neto de Carvalho, C. , Couto, H., Figueiredo, M. V., and A. Baucon, 2016
Microbial-related biogenic structures from the Middle Ordovician slates of Canelas (northern Portugal).  Comunicações Geológicas (2016) 103, Especial I, 23-38
https://www.academia.edu/30274936/Microbial-related_biogenic_structures_from_the_Middle_Ordovician_slates_of_Canelas_northern_Portugal_?auto=download

Raymond, P. E, 1911
Preliminary Notes on the "Chazy" Formation in the Vicinity of Ottawa. The Ottawa Naturalist, Volume 24, Number 11, p.189-197,
https://www.biodiversitylibrary.org/item/94742#page/201/mode/1up

Williams, D.A., 1991.
Paleozoic Geology of the Ottawa-St. Lawrence Lowland, Southern  Ontario; Ontario Geological Survey, Open File Report 5770, 292p.

Walcott, Charles D., 1914.

No. 3  Middle Cambrian Holothurians and Medusae, pp. 41 -68,  pls  8-13, in Cambrian geology and paleontology, II. Smithsonian Miscellaneous Collections, Volume 57

https://archive.org/details/smithsonianmisce571914smit/page/n166/mode/1up?view=theater

The K-Bentonite Occurrence at Tenth Line Rd. and St. Joseph Blvd, Ottawa and Historical References to Bentonite Clay

Since my July 28, 2019 and August 7, 2019 blog postings I’ve continued to find articles referring to K-Bentonite (altered volcanic ash) in Eastern Ontario.   For example:
-   Kolata, Huff and Bergström (1996) briefly described an Ordovician K-bentonite bed at a quarry near Aylmer, Quebec (just across the river from Ottawa) noting that this bed is as much as 17 cm thick.  
- Salad Hersi (1998) reported on a Bentonite layer in a roadcut at the intersection of Tenth Line Rd. and St. Joseph Blvd. in Orleans, Ontario (now part of Ottawa),  within the Hull Formation about 1 meter below the base of the Verulam Formation.  
- Kierman (1999) analyzed those two K-Bentonites from the Ottawa Embayment: one at the Klock Quarry in Aylmer, Quebec, and the second near the intersection of St. Joseph Blvd. and Tenth Line Rd. in Orleans, Ontario about 1 m below the base of the Verulam Formation.
- Dix and Jolicoeur ( 2011) discuss bentonite layers in the Ordovician Billings Formation and Carlsbad Formation, Eastern Ontario. 
-  Oruche, Dix and Kamob (2018) report on the Millbrig K-bentonite volcanic ash bed and the bentonite bed in the Hull Formation in the Ottawa embayment, tracing both across Eastern Ontario.   
- Carrier (2018) reports on two bentonite layers in the Ordovician limestone at the Clark Quarry in Stittsville in the west end of Ottawa.

On August 16, 2019 I visited the outcrop at the southeast corner of the intersection of Tenth Line Road  and St. Joseph Boulevard in Orleans.  The K-bentonite bed is about two centimeters thick,  is concordant with the underlying and overlying strata,  is a chalky white colour, is recessive, has both a gritty and soapy feel, and extends over the length of the outcrop (at least 30 meters).  No visible crystals are present.  Many articles report that often a K-bentonite bed can be found because plants preferentially grow in the K-bentonite, and this feature was observed at this outcrop.  I took the following photographs of the K-bentonite bed at that location.

Historical References to Bentonite Clay

Many early references to what we now call bentonite clay refer to it as soap clay,  mineral soap, edible clay or edible earth.   Selwyn (1874), for an occurrence near Edmonton mentions “Immediately above the coal seam is a layer of a brown greasy clay six or eight inches thick. This clay works into a lather like soap, and Dr. Hector says it was used by the women at the fort for washing blankets. A sample of it, analysed by Mr. Hoffmann in the Survey laboratory, shews it to be a hydrous silicate of alumina*...    * For analysis of this soap-clay see Appendix.”.   McConnell (1889) in a report on the Yukon and MacKenzie Basins mentions “The most interesting part of this section was under water at the time of my visit, and can only be examined in the autumn. ... The edible clay bed ... was just visible below the surface of the water, and a specimen was dug up with the paddle. This clay is of a light yellowish color, and is highly plastic. It is used for whitewashing purposes, and in former times served the Indians as a substitute for soap.”  Allan and Sanderson (1945) identify Selwyn’s and McConnell’s reports as the earliest references to bentonite in Western Canada.

Condra (1908) was the first to link bentonite with volcanic ash commenting “ Professor Todd has noted the existence of a thin but very persistent layer of clay closely resembling bentonite near the middle of the Carlile formation. It varies from 1 1/2  to 3 inches thick. .. . It is suggested that it may originally have been a thin stratum of volcanic ash.”   Others to make the connection were Hewitt (1917) and Wherry (1917).  Keele (1920) might have been the first in Canada to write that bentonite formed from weathered volcanic rocks commenting "The clay is deposited in a flat at the base of outcrops of volcanic rocks and is evidently composed of the weathered products of these rocks" and "volcanic rocks are the source for that gelatinous clay known as bentonite."

Over the course of three papers, Professor W. C. Knight of the University of Wyoming identified novel clay deposits in Wyoming and named the clay Bentonite.  In the first paper, Knight (1893) reported on large beds of ‘fire clay’ in Wyoming, specifically mentioning localities at Rock Creek station on the railroad line (from which several carloads of clay had been shipped to New York) and at Crook County where “a bank of clay has been discovered in Cretaceous rocks which has been called mineral soap or Saponite. The clay when moistened has an  unctuous feeling resembling soap; but in chemical constituents it could not be classed as a mineral soap.”  He also provided chemical analyses of the two clays.   In the second  paper, Knight (1897a) mentions that “Since the year 1888 Mr. William Taylor of Rock Creek Station,...  has shipped to various parts of the United States occasional carloads of a peculiar clay , which, for convenience, may be hereafter known as “Taylorite”. ... The present quarry operated by Mr. Taylor is a quarter mile north of the railroad, but at a point further to the eastward the railroad cuts through the bed. ... When taken from the quarry it has an unctuous feeling, and when water is added , it forms an emulsion . ... Inappropriately this clay has been called ‘mineral soap’ on account of its soapy feeling in water.”    In an abstract of Knight’s second paper, Spencer (1898) noted that the proposed name taylorite is “a name already in use.”  In his third  paper, Knight (1898) mentions that he had learned that “the name Taylorite is preoccupied; consequently it will henceforth be known as Bentonite.” and provided four analyses of Bentonite.

Interestingly, Knight’s (1893) paper has been largely overlooked.  Keele (1920) is the only paper that I found referring to Knight’s first paper.  
                       
Knechtel (1952), and  Hosterman  and Patterson (1992,) credit  Engelmann  (1858) with being the  first to describe the clay that we now call bentonite.   This is Engelmann’s (1858, p.  511) description of clay in the Cretaceous age strata in Carbon County, Wyoming:

“Between Medicine-Bon creek and Pass creek, south of the butte, was an exposure of sandy, argillaceous slate, and above it a layer of a yellow unctuous matter, covered on the surface with an efflorescence of salts, which seemed to be a product of the decomposition of the igneous rocks. It readily imbibes water, and thereby increases much in volume and becomes plastic. An analysis of a piece which had lost most of its soluble parts gave--
Water, 18 per cent.; silica, 51 per cent. ; alumnia, 30 per cent. ; calcia, traces.
     Nearer to camp 42 were similar layers; some, also, yellowish, some green, with a talcose structure. The specimens of this variety separated in the water into a light yellow stuff like the other, and in dark colored heavier particles. Analysis gave:
Water, 14 per cent.; silica, 55.5 per cent. ; alumina, 30.5 per cent.; calcia, traces.   
     It is, therefore, a mineral similar in its composition and properties to the bole and pimelithe. Many crystals of gypsum were disseminated through these strata, and efflorescences of salt on the surface tasted like potash or soda.”

Knechtel (1952) comments that “Engelmann's citations of bole and pimelite for comparison seem appropriate enough, in view of the stage of development of mineralogic thought in his time.  In the contemporary edition of Dana’s System of Mineralogy (1854, pp. 252, 503) bole is defined as material closely resembling halloysite both in appearance an in its large content of water; “.    Halloysite is an aluminosilicate clay mineral.  Pimelite is a light green, somewhat greasy or waxy, smectite clay.

Intriguingly, there are many earlier papers on Fuller’s Earth, edible clay and other clays that  refer to a clay that we would now call Bentonite.   Not all reports of Fuller’s earth are bentonite, but many are.  For example, Sir Roderick Murchison (1839) reported on layers of saponaceous clay/Fuller’s earth  in the Upper Silurian rocks of Herefordshire that are now identified as bentonite (Huff,  Morgan,  Rundle,  1996 ).    This is Sir Roderick Murchison’s (1839) report: “these flagstones are separated from the overlying Aymestry limestone, by courses of a saponaceous clay (in many instances a complete fuller's-earth) , of a yellowish white and grey colour, which is commonly known throughout Herefordshire and the adjacent counties under the name of “Walker's earth, or soap," and is sometimes used by the country people for cleansing purposes. Beds of this " Walker's  earth" are not infrequent in other parts of the Upper Silurian Rocks, particularly in the Wenlock shale;  and it will afterwards appear, that from their saponaceous qualities the surfaces of these beds have frequently aided the slipping of superincumbent masses of rock.”   In addition, Fitton (1847) described a Fuller’s earth bed from the Isle of Wight that has now been identified as Bentonite by Ruffell et al. (2002).  As well,  Fitton (1836) had earlier identified a number of Fuller’s earth beds in the southeast of England that are likely bentonite (see Hallam & Sellwood,  1968;  Goldring, 1999).

One of the more interesting papers that I found was by Wynne (1878), who  in a report on the geology of the Salt Range in the Punjab mentions a clay-ash/decomposed rock found with volcanic rock used as soap, commenting: “Lavender Clay. The lavender clay-ash or decomposed rock found with the volcanic rock of Nilawán, &c., is used by the natives as soap or to assist in washing.”    Ball’s (1881) and Watt’s (1889)  comments on the fire clays, fuller’s earth and edible clays of India are also intriguing, particularly Watt’s comment (at page 362) on the “The sabún mití or soap-earth of Colgong in the Bhagalpur Division”, Bengal.    Kirwan (1794) devotes pages 174 to 206 of this very early text on mineralogy to clays and earths, a few of which might be worth following up on to determine whether they can be linked to bentonite, particularly one that ‘imbibed water strongly’ and "is often of pseudo- volcanic origin, ...  and perhaps also sometimes really volcanic; but it also  frequently arises from the decomposition, or disintegration, of other stones."   Muir's (1878) paper on an edible clay eaten by sheep in New Zealand is interesting because it contains an analysis of the clay (and not just because the sheep were eating clay), and if the clay is Bentonite would be an early British analysis of Bentonite.

A number of authors  have investigated  the references to Fuller’s earth and other earths used in ancient Greece, by the Roman Empire and in the Middle Ages.   For example, the Cimolian earth mentioned by Pliny the Elder (AD 79) in Naturalis Historia is said to be bentonite (Beneke and Lagaly, 2002, page 64;  Williams,  2013, page 254; Pabst  and Koøánová,  2009, page 89) while the gray earth at Kaaden  mentioned by Agricola (1546)  “is the bentonite of the Rokle deposit type, the major Czech bentonite deposit of today”  (Pabst  and Koøánová,  2009, page 94).  Robertson (1949) mentions that Pliny the Elder recorded in Book  xxxv of his  Natural  History that the earth saxum has the property of increasing in bulk when soaked in water, and states that “the suggestion that saxum is really the first record of bentonite is strengthened by the fact that bentonite has been worked commercially in Italy on Ponza Island near Naples since 1935.”  Pittinger (1975) reviewed the mineral products of the Greek island of  Melos in antiquity, and concludes that alumen of Pliny the Elder “is the bentonited mined today” on Melos, while the Melian earth of Theophrastus (c.  372-322 B.C.)  “could describe certain bentonitic deposits of high silica content, extensive on Melos.”  Koutsopoulou , Christidis and Marantos (2016) mention that the bentonites from the Greek Island of Samos –  Samian Earth – has been utilized since ancient times, but that the bentonites are mined now only at a local scale.  Christidis  and Scott (1993) note that “Greek bentonites have been exploited since ancient times and the clays on the island of Milos and Kimolos are mentioned by Theophrastus in his work ‘About Stones’.”  However, Caley and  Richards (1956, 208-9) had different interpretations for Theophrastus’  Melian earth, Kimolian earth and Samian earth.


Christopher Brett
Ottawa

References and Suggested Reading

Agricola, Georgius, 1546
De natura fossilium. Froben, Basel.   [ 1955, De Natura Fossilium - Textbook of
Mineralogy . English translation by M.C. Bandy and J.A. Bandy for the Mineralogical Society of America, Special Paper 63), Geological Society of America, New York.
http://farlang.com/books/agricola-bandy-de-natura-fossilium    ]

Anonymous, 1898
Mineral Soap.  American Soap Journal and Perfume Gazette, volume VIII, No. 12, page 412

Anonymous, 1922
The mineral "bentonite": its occurrence and uses.  Bulletin of the Imperial Institute, vol. 20,  pages 344-349
 https://archive.org/details/bulletinofimperi20commuoft/page/344
https://books.google.com/books/about/Bulletin.html?id=xCQzAQAAMAAJ

Anonymous, 2019a       
Loxter Ashbed Quarry.   Upper Ludlow Shales over massive Aymestrey Limestone with thin bentonite horizons displaying an open anticline plunging S. [Photographs of bentonite layers.]
http://www.buildingstones.org.uk/search/nprn/quarry594

Anonymous, 2019b       
Whitman’s Hill Quarry -  Herefordshire & Worcestershire Earth Heritage Trust.   [Photographs of bentonite layers.]
http://www.earthheritagetrust.org/pub/learning-discovery/aggregates/aggregates-of-herefordshire/site-examples-hfds/whitmans-hill-quarry/

Allan, John. A. And Sanderson, J.O.G., 1945
Geology of Red Deer and Rosebud Sheets, Alberta.  Res Council Alberta Report 13, 51 pages
Bentonite at pages 49-51; clay at 52
https://ags.aer.ca/publications/REP_13.html
https://ags.aer.ca/document/REP/REP_13.pdf

Beneke, Klaus and Lagaly, Gerhard, 2002
From Fuller’s Earth to Bleaching Earth: A Historical Note.  ECGA (European Clay Group Association) Newsletter No.5, July 2002, page 57-78
http://www.uni-kiel.de/anorg/lagaly/group/klausSchiver/bleachingearth.pdf

Ball, V., 1881
A Manual of the Geology of India: Part III. Economic geology . Calcutta: Office of the Geological Survey of India. London: Trübner & Co.  663 pages.  clay at pages 561- 571
https://books.google.ca/books?id=1pvscyOHjQcC

Caley, E.R. and J.C. Richards, 1956,
Theophrastus on Stones, Columbus: Ohio State University.
https://pdfs.semanticscholar.org/6aea/1f77da14667d90a6f6464afe4f2fdde8a6f5.pdf

Carretero,  M.Isabel, 2002
Clay minerals and their beneficial effects upon human health.   Applied Clay Science, Volume 21, Issues 3–4, June 2002, Pages 155-163
https://doi.org/10.1016/S0169-1317(01)00085-0
https://www.sciencedirect.com/science/article/pii/S0169131701000850

Carrier, Maureen, 2018
Geology of the Ottawa Region with Dr. Wouter Bleeker, October 13,2018 – Macnamara Field Naturalists' Club
https://mfnc.ca/geology-of-the-ottawa-region-with-dr-wouter-bleeker-october-132018/

Christidis, George and Scott, Peter W., 1993
Laboratory evaluation of bentonites.  Industrial Minerals, August 1993, pages 51-57
https://www.researchgate.net/profile/GE_Christidis/publication/284127401_Laboratory_evaluation_of_bentonites/links/5671513508ae0d8b0cc2ebf0/Laboratory-evaluation-of-bentonites.pdf

Condra, G. E., 1908,
Geology and water resources of a portion of the Missouri River valley in Northeaster Nebraska: U.S. Geol. Survey Water-Supply Paper 215, 59 pages 
https://pubs.er.usgs.gov/publication/wsp215
https://pubs.usgs.gov/wsp/0215/report.pdf

Eisenhour, Don D. And Brown,  Richard K., 2009
Bentonite and Its Impact on Modern Life.  Elements (2009) 5 (2): 83-88.
https://doi.org/10.2113/gselements.5.2.83

Engelmann, Henry, 1858,
Report of a geological exploration from Fort Leavenworth to Bryan's Pass, made in connection with the survey of a road from Fort Riley to Bridger’s Pass, under command of Lieutenant F.T. Bryan, topographic engineer, 1856, in Report of the Secretary of War, 1857: U.S. Congress, 35th, 1st session, p. 489-517.
https://books.google.ca/books?id=0YMsAAAAIAAJ
https://books.google.ca/books?id=BlBDAQAAMAAJ

Fisher, C. A., 1905
The bentonite deposits of Wyoming. In Bulletin 260  United States  Geological  Survey, 1905, pp 559-563
https://digital.library.unt.edu/ark:/67531/metadc944632/m1/572/?q=bentonite

Fitton, William Henry,  1824
Inquiries respecting the Geological Relations of the Beds between the Chalk and the Purbeck Limestone in the Southeast of England. [Thomson's] Annals of Philosophy for 1824, New Series, vol. viii, 365-383
https://www.biodiversitylibrary.org/item/53939#page/5/mode/1up

Fitton, William Henry, 1836
 Observations on some of the Strata between the Chalk and the Oxford Oolite, in the South-east of England.  [Read June 15, 1827.]    Transactions of the Geological Society,  2nd Series, vol. iv. p. 103- 388 https://www.biodiversitylibrary.org/item/111668#page/121/mode/1up
Isle of Wight starts 182

Fitton , W.H. 1847.
A stratigraphical account of the section  from Atherfield to Rocken-End, in the Isle of Wight.
Quarterly Journal of the Geological Society of London, 3, 289-328.
https://www.biodiversitylibrary.org/item/113687#page/427/mode/1up   

Goldring, R. 1999.
Sedimentological aspects and preservation of Lower Cretaceous (Aptian) bentonites (fuller's earth) in southern England. Neues Jahrbuch fur Geologie und Palaontologie, 214, 3-24.
DOI: 10.1127/njgpa/214/1999/3

Hallam, A. & Sellwood, B.W. 1968.
 Origin of fuller's earth in the Mesozoic in southern England. Nature, 220, 1193-1195.

Hewitt, D. F.,  1917
The origin of bentonite and the geologic range of related materials in Bighorn, Wyoming. Journal fo the Washington. Academy of  Sciences, volume 7, 196-198
https://www.biodiversitylibrary.org/item/18415#page/202/mode/1up

Hosterman, John W.  and Patterson, Sam H., 1992
Bentonite and Fuller’s Earth Resources of the United States.  U.S. Geological Survey Professional Paper 1522.  45 pages
https://books.google.com/books/about/U_S_Geological_Survey_Professional_Paper.html?id=bTdSAQAAMAAJ

Huff, W.D.; Morgan, D.J.; Rundle, C.C.. 1996    
Silurian K-bentonites of the Welsh Borderlands : geochemistry, mineralogy and K-ar ages of illitization  . Nottingham, UK, British Geological Survey. (WG/96/045) (Unpublished)
http://nora.nerc.ac.uk/id/eprint/709

Jameson, Robert, 1820
A System of Mineralogy, in which Minerals are Arranged According to the Natural History Method, Third Edition, Volume 2.  Edinburgh: Archibald Constable & Co.  London: Hurst, Robinson & Co.   632 pages.  Fuller’s Earth at pages 300-304 https://books.google.com/books/about/A_System_of_Mineralogy_in_which_Minerals.html?id=Bc5aEjAY5dQC

Keele, J., 1915
Clay and Shale deposits of the western provinces, part 5; Keele, J. Geological Survey of Canada, Memoir no. 66, 1915, 74 pages, https://doi.org/10.4095/101562
http://ftp.maps.canada.ca/pub/nrcan_rncan/publications/ess_sst/101/101562/me_066_en.pdf

Keele, J., 1920
Ceramic Division, 153-, in  Summary Report of the Mines Branch for the Calendar Year Ending December 31, 1918.

Kirwan, Richard, 1794
Elements of Mineralogy, 2nd Edition, Volume 1,
Argillaceous Genus174-206, Fuller’s Earth  p. 184
https://archive.org/details/elementsmineral01kirwgoog/page/n237

Knechtel, Maxwell M., 1952
Early Ideas on Origin of Bentonite. Bulletin of the American Association of Petroleum Geologists, Volume 36, Issues 1-6, pages 884–886
https://books.google.ca/books?id=ASv0AAAAMAAJ

Knight, W. C., 1893
Geology of the Wyoming Experiment Farms, and Notes on the Mineral Resources of the State.
Bulletin No. 14  by University of Wyoming Agricultural Experiment Station, October, 1893, pages 103-211;   Fire Clays at 193-4
https://repository.uwyo.edu/ag_exp_sta_bulletins/31/

Knight, W. C., 1897a 
“Mineral Soap”.  Engineering and Mining Journal, Volume LXIII, June 12, 1897, 600-601
https://books.google.com/books/about/Engineering_and_Mining_Journal.html?id=y3VJAQAAMAAJ

Knight, W. C., 1897b 
That “Mineral Soap.”  American Soap Journal and Perfume Gazette, volume VIII, No 4, page 125, July 1, 1897

Knight, W. C. , 1898
Bentonite.  Engineering and Mining Journal, vol 66, October 22, 1898, p. 491
 https://books.google.ca/books?id=9Jg-AQAAMAAJ

Koutsopoulou, E. ; G.E. Christidis; and  I. Marantos 2016
Mineralogy, geochemistry and physical properties of bentonites from the Western Thrace Region and the islands of Samos and Chios, East Aegean, Greece. Clay Minerals (2016) 51 (4): 563-588.  https://doi.org/10.1180/claymin.2016.051.4.03

Mackenzie, R.C., 1979
Clay Mineralogy - Whence and Whither?   Developments in Sedimentology, Volume 27, 1979, Pages 1-14  https://doi.org/10.1016/S0070-4571(08)70696-4
 https://www.sciencedirect.com/science/article/pii/S0070457108706964

McConnell, R.G., 1889
Report On An Exploration in the Yukon and MacKenzie Basins, N.W.T.,  1D-161D, in Geological Survey of Canada Report of Progress 1888-89, clay at page 99D
 https://archive.org/details/vol188889reporto00geol/page/n5
https://archive.org/details/vol188889reporto00geol/page/n254

Muir, M. M. Pattison, 1878
Note on an Edible Clay from New Zealand.   Proceedings of the Manchester Literary and Philosophical Society, volume 17, pages 6-7
https://books.google.ca/books?id=oZ1GAQAAMAAJ

Murchison, Roderick Impey, 1839
The Silurian System. Part 1. London: John Murray. 576 pages
https://books.google.com/books/about/The_Silurian_System.html?id=jxBfAAAAcAAJ
https://www.biodiversitylibrary.org/item/165541#page/252/mode/1up
Walker’s Earth, Walker’s soap  at pages 204, 249

O'Shaughnessy,  W. B.,  1841
Report and Correspondence on the Manufacture of an Improved Pottery from Indian Clays. The Bengal Dispensoatory and Pharmacopoeia.  18 pages
https://books.google.com/books/about/Report_and_Correspondence_on_the_Manufac.html?id=PY9eAAAAcAAJ

Pabst, Willi and Koøánová, Renata, 2009
Prehistory of clay mineralogy – from ancient times to Agricola.  Acta Geodyn. Geomater., Vol. 6, No. 1 (153), 87–100, 2009
https://www.irsm.cas.cz › materialy › acta_content › 6_Pabst

Pittinger, Jill,  1975
The Mineral Products of Melos in Antiquity and Their Identification.  The Annual of the British School at Athens, Vol. 70 (1975), pp. 191-197     https://www.jstor.org/stable/30103322

Pliny the Elder,  written before AD 79, printed 1469
Naturalis Historia, [The Natural History, Book XXXV. An account of paintings and colours. As translated by John Bostock. 
http://www.perseus.tufts.edu/hopper/text?doc=Perseus:abo:phi,0978,001:35 ]
Also: http://perseus.uchicago.edu/perseus-cgi/citequery3.pl?dbname=PerseusLatinTexts&getid=1&query=Plin.%20Nat.%2035.56

Ries, H; and Keele, J. 1913
 Report on the clay and shale deposits of the western provinces, part II.  Geological Survey of Canada, Memoir no. 25, 1913, 136 pages,    https://doi.org/10.4095/100499

Robertson, Robert H. S., 1949
The Fuller's Earths of the Elder Pliny.  The Classical Review, Volume 63, Issue 2,    September 1949 , pp. 51-52      DOI: https://doi.org/10.1017/S0009840X00094749
https://www.cambridge.org/core/journals/classical-review/article/fullers-earths-of-the-elder-pliny/65D3CB6974EF87AADCC08EAE9DFAE543

Robertson,  R.  H.  S.,  1958.
The  earths  of  Theophrastus.  Classical  Rev.,  8:  222-223.

Ruffell, A.H.,  Hesselbo, S.P.,  Wach, G.D., Simpson, M.I. and D.S.Wray, 2002
Fuller's earth (bentonite) in the Lower Cretaceous (Upper Aptian) of Shanklin (Isle of Wight, southern England).  Proceedings of the Geologists' Association,  Volume 113, Issue 4, 2002, Pages 281-290.  https://doi.org/10.1016/S0016-7878(02)80034-7

Selwyn, A.R.C., 1874   
Observations in the North West Territory on a Journey Across the Plains from Fort Garry to Rocky Mountain House Returning by the Saskatchewan River & Lake Winnepeg. Pages 17-62, in Geological Survey of Canada Report of Progress 1873-74,
http://archive.org/stream/annualreportgeo13canagoog#page/n6/mode/2up

Spence, H. S.,  1924
Bentonite. Canada Mines Branch, Publication 626, 1924, 45 pages, https://doi.org/10.4095/307808

Spencer, L.J..,  1898        
[Abstract of]  “Mineral Soap” By Wilbur C. Knight. Journal of the Chemical Society, London,  Volume 74, Part 2, page 610
https://books.google.com/books/about/Journal_Chemical_Society_London.html?id=96MxAAAAYAAJ

Sutherland, Wayne M., 2014
Wyoming Bentonite.  Summary Report. Wyoming Geological Survey.  4 pages.
https://www.wsgs.wyo.gov/products/wsgs-2014-bentonite-summary.pdf

Theophrastus, [before] 287 BC
Περὶ λίθων  [Translation: on Stones], [see Caley, E.R. and J.C. Richards, 1956, Theophrastus on Stones,Columbus: Ohio State University
https://pdfs.semanticscholar.org/6aea/1f77da14667d90a6f6464afe4f2fdde8a6f5.pdf].

Watt, George, 1889
A Dictionary of the Economic Products of India - Volume 2. Calcutta, Government Printing Office, 689 pages. Clay at pages 360-367
https://archive.org/details/in.ernet.dli.2015.31092/page/n367

Wherry, Edgar. T., 1917
Clay Derived from volcanic dust in the Pierre in South Dakota. Journal of the Washington. Academy of  Sciences, volume 7, 576-583
https://www.biodiversitylibrary.org/item/18415#page/582/mode/1up

Williams,  Cheryll, 2013
Medicinal Plants in Australia Volume 4: An Antipodean Apothecary .  New South Wales, Australia: Rosenberg Publishing,  552 pages.   Page 254  Cimolian earth probably bentonite
https://books.google.com/books/about/Medicinal_Plants_in_Australia_Volume_4.html?id=7eVUAQAAQBAJ    

Winer, A. A., 1954
Acid Activation Of Saskatchewan Bentonites.  Saskatchewan Department of Mineral Resources. Industrial Minerals Research Branch. Report of Investigations No. 4.
8792-RPI-4_Acid_Acitvation_Of_Sask_Bentonites.pdf

Wynne, A.B., 1878
Geology of the Salt Range in the Punjab.  Memoirs of the Geological Survey of India, volume 14, 313 pages, at page 300
https://books.google.ca/books?id=x2-OcwxiS74C&dq


The additional references are provided at the end of my July 28, 2019 blog posting.

Mark Your Calendars for a Tour of the Tatlock Quarry on Saturday, August 24th

Below is an advertisement from this week’s  Perth Courier for the tour of OMYA’s Tatlock Quarry on August 24th  from 10 am to 2pm, rain or shine.

The advertisement promises a bottle of OMYA’s Maple Syrup to those that bring a non-perishable food item or make a cash donation to the Lanark Food Pantry.    The syrup produced in past years has been excellent!

The Tatlock quarry is located in Lanark County about 30 km north of Perth up Highway 511, turning right on McIlraith Road.  There is more than ample parking available in the fields opposite the quarry entrance.   Below is a photo of the quarry that I took while on the 2015 tour.  The bus is barely visible at the bottom of the quarry.

OMYA is a world leader in the production of calcium carbonate which it mines from quarries located throughout the world.    OMYA’s quarry at Tatlock, Lanark County is the largest calcium carbonate mine in Canada and is said to produce the purest calcium carbonate in the world.  OMYA mines and crushes the calcium carbonate at the Tatlock quarry and processes the product at its plant west of Perth along Highway 7.   

The Tatlock quarry is about 900 meters long, 400 meters wide and 110 meters deep.  A  Google satellite view of the quarry can be obtained  by typing   45.145370, -76.497971 into the Google search engine and searching under MAPS, and switching to SatelliteView. 

Christopher Brett

Porphyritic Volcanic Rock - When the Comment is More Interesting than the Original Post

Henri Lessard, who writes the  Géo-Outaouais blog covering the geology of the Outaouais and Ottawa area, left me a very interesting comment, that I’ve reproduced below (as I suspect most people don’t read the comments):

“A pyroxenite seems to have already been discovered in the Ordovician limestone at Hull (Gatineau), Qc....
      Drilling reports dating from 1998 for the construction of Boulevard des Allumettières at Hull (now Gatineau) reports a mafic intrusive rock (a pyroxenite) in Ordovician limestone.
     The "greenish intrusive" encountered in the upper part of a borehole, between 1.25 m and 1.50 m deep. The intrusive-limestone contact is well defined, however, the orientation of the contact is undefined.
      Drilling was carried out at the corner of Demontigny and Laramée streets (the latter today under boulevard des Allumettières). In thin section, the intrusive is equigranular (grains 0.5-1.0 mm), and consists of 75% orthopyroxene (hypersthene) and clinopyroxene (augite) in equal proportions. The remaining 25% is composed of quartz, calcite and clay minerals [weathered?] "So we are dealing with pyroxenite. (P.13)
      Link toward my blog (in french) :
http://geo-outaouais.blogspot.com/2018/06/roche-intrusive-pyroxenite-dans-le.html
Thank You,
Henri Lessard”

On his blog page he references:
Les Laboratoires Gatineau, 1998. Étude de caractérisation des sols et du roc : boulevard St-Laurent - Laramée, Hull - secteur DeMontigny au Lac-des-Fées. Projet 20-6672-8385-A - Rapport final. Gouvernement du Québec, Ministère des Transports.

Other interesting posts from Henri Lessard’s blog, in a similar vein, is his post from Wednesday, December 12, 2018 entitled “Roche porphyrique à l'Ange-Gardien, QC”   where he includes photographs of a rock rich in feldspar phenocrysts, and his post from Thursday, November 16, 2017 entitled ‘Volcanisme à L'Ange-Gardien, QC”, both of which discuss the Mesoproterozoic Robitaille igneous suite which has been assigned an age of 1060 Ma (Hogarth, 2007).   L'Ange-Gardien is a municipality in the Outaouais region of Quebec.    The Mesoproterozoic Robitaille igneous suite is found on both sides of the Rivière du Lièvre at L'Ange-Gardien.



I decided to highlight Henri Lessard's comment because it is more interesting than my original post, and the pyroxenite he mentions is worth further investigation.

Christopher Brett
Ottawa

Suggested Readings:

Hogarth, Donald D., 2007 (or more recent)
GM 63238: Rocks of the Mason -Buckingham - Mayo area, with emphasis on Mesoproterozoic Igneous Types. Ministère de l’Énergie et des Resources naturelles, Québec
http://gq.mines.gouv.qc.ca/documents/examine/GM63238/GM63238.pdf

Hogarth, Donald D., 2016
Chemical trends in the Meech Lake, Québec, carbonatites and fenites.   The Canadian Mineralogist 54(5):1105-1128  September 2016
https://www.researchgate.net/publication/318091132_Chemical_trends_in_the_Meech_Lake_Quebec_carbonatites_and_fenites

Hogarth,  Donald D.  and  van Breemen, O.,   1996:
Geology  and  age  of  the Lac  a  la Perdrix  fenite,  southern Gatineau district, Quebec; in Radiogenic Age and Isotopic Studies: Report 9; Geological Survey of Canada, Current Research  1995-F, p.  33-41
https://inis.iaea.org/collection/NCLCollectionStore/_Public/28/056/28056346.pdf

Hogarth, Donald D.  And Robin, Michel J.L., 2007
Strontium in Feldspars of High-K Proterozoic Igneous Rocks of the Robitaille Suite, Buckingham, Québec. The Canadian Mineralogist, vol. 45, p. 1293-1306.
http://dx.doi.org/10.2113/gscanmin.45.5.1293
https://pubs.geoscienceworld.org/canmin/article-abstract/45/5/1293/13682/STRONTIUM-IN-FELDSPARS-OF-HIGH-K-PROTEROZOIC?redirectedFrom=fulltext

Lafleur, Jean and Hogarth, Donald D., 1981
Cambro-Proterozoic volcanism near Buckingham, Quebec. [trachyandesit 573 +-32 Ma]  Canadian Journal of Earth Sciences, 1981, 18(12): 1817-1823,
https://doi.org/10.1139/e81-169

Sinaei-Esfahani, Fahimeh,  2013
Localized metasomatism of Grenvillian marble leading to its melting,  Autoroute 5  near  Old  Chelsea, Quebec.  Thesis submitted for the degree of Masters of Science. Department of Earth and Planetary Sciences, McGill University, Montreal, 133 pages     digitool.library.mcgill.ca › thesisfile117148
 [ Local metasomatism of regional marble by an alkaline fluid of mixed crust + mantle derivation, possibly at the end of the Ottawan orogenic phase, at approximately 1020 m.y., or the Rigolet orogenic phase, at approximately 980 m.y.]



 

Phenocrysts in a Bed of Porphyritic Volcanic Rock in the Ordovician Sedimentary Rocks of the Ottawa Embayment, Eastern Ontario

In the sedimentary rocks of the Ottawa Embayment I may have found a thin bed of a porphyritic volcanic rock.   

Finding evidence of altered volcanic ash (K-bentonite beds) in the Ordovician rocks of Eastern Ontario and the Ordovician rocks of Eastern North America would  not be unusual, as occurrences have been reported for over eighty-five years, and the K-bentonite beds have been used as Ordovician stratigraphic marker horizons over much of the eastern United States and southern Ontario.  For example, Fyon (2019) provides good photos and an explanation of the K-bentonite volcanic ash beds in Ordovician limestone  at Marmora, Ontario, while  Sharma et al. (2005a, b) reported on a 6 cm thick K-bentonite (volcanic ash) bed in the Ordovician Billings Formation shales of the Ottawa Embayment, found in logged drill core from Russell, Ontario.   Kolata, Huff  and  Bergstrom (1996) reviewed the Ordovician K-bentonites of eastern North America, reporting “at least 60 volcanic ash beds, K-bentonites” within the Ordovician stratigraphic succession, concluding that the “parental magmas consisted of a calc-alkaline suite ranging from andesite, rhyodacite, trachyandesite and rhyolite” in a “setting characterized by destructive plate-margin volcanics” where erupted volcanic ash was “carried by the prevailing ... tradewinds for hundreds of kilometers ... and were deposited in shallow cratonic seas.”  For southern Ontario they report two K-bentonites in the Ordovician Gull River Formation (citing Liberty, 1969) and one in the Ordovician Bobcaygeon succession (citing Liberty, 1969), noting that “The Millbrig occurs in the same stratigraphic interval as [K-bentonite] bed MR, described by Liberty from near the base of the Bobcageon Formation in outcrops in the Lake Simcoe region, southwestern Ontario.”   Liberty’s (1969) reports are of k-bentonite clay layers.  


Finding visible phenocrysts  in Ordovician K-bentonite beds is not the norm.   John Haynes (1989) describes the feldspars of the Ordovician Deicke and Millbrig K-bentonite Beds of the southeastern United States,  noting (page 37) that “Feldspars are the most abundant phenocrysts in the Dieke and Millbrig....Grain sizes vary greatly; the feldspars average less than .5 mm long in samples from the west-central Valley and Ridge in Virginia, and they average between 0.5 - 1 mm in samples from the Nashville Dome and the Valley and Ridge from southwestern Virginia to Alabama.”   He included a number of photomicrographs (Figs. 17-21)  of feldspar phenocrysts in his doctoral thesis, but the ones figured are less than a 2.5 mm long.  Others report even smaller crystals.  When Delano et al. (1990) examined 30 K-bentonites (altered volcanic ashes)  in the late Ordovician  Utica shale of New York State they found fragmental feldspar crystals up to 600 microns in diameter, with most crystals under 45 microns.

Haynes (1994) mentions “In the southeastern United States, identification of the Rocklandian Deicke and Millbrig K-bentonite Beds is based on differences in phenocryst mineralogy in the tuffaceous zones of each bed, and the two beds can be reliably and consistently distinguished on this basis. The common phenocrysts in the Deicke are labradorite and various Fe-Ti minerals, and in the Millbrig they are andesine, quartz, and biotite. Phenocrysts present in trace amounts are biotite and quartz in the Deicke, and apatite and zircon in both beds. The Deicke is altered dacitic or latitic ash, whereas the Millbrig is altered rhyodacitic ash. Both beds are interpreted as airfall deposits produced by huge volcanic eruptions, each of which was much larger and produced far more ash than the 1815 eruption of Tambora and even the great Toba eruption of 75 Ka.”  

Haynes (1994) notes that “Biotite, quartz, feldspars, and other clay minerals are present as primary phenocrysts and secondary phenocrysts in the Diecke and Millbrig in the study area – and in fact are so abundant and coarse grained in some zones that the material in those zones is tuffaceous rather than bentonitic – but the principal constituent of these and many other beds in Lower Paleozoic strata is mixed-layer illite/smectite (I/S) clay...”   

There are numerous other reported occurrences where K-bentonite (volcanic ash) outcrops in Ontario and the Ottawa Embayment.  Brun and Chagnon (1979) reported three occurrences of clay (volcanic ash beds) in  Black River and Trenton Group (middle Ordovician) rocks of the Ottawa Embayment, at quarries in Aylmer, Lucerne and Hull, Quebec (just across the river from Ottawa). Suarez et al. (2016) reported a late Ordovician U-Pb zircon age from K-bentonite found in the Trenton Group near Kirkfield, Ontario.  Al-Delami and Dix (2009) reported two thin (~3 cm) biotite-bearing clay beds in the Upper Ordovician Verulam Formation (Ottawa Group)  in the western portion of the Ottawa Embayment, eastern Ontario, which they interpreted as altered volcanic ash from two related eruptive events.  Cornell (2001) reviewed the K-bentonite (volcanic ash) occurrences in Ordovician rocks in Ontario and New York State,  and reported  collecting and examining K-bentonite  at localities that  included  Brechin Quarry, Brechin Ontario; Miller Paving Quarry, Dalrymple, Ontario; Provincial Route 35 road cut just south of Coboconk, Ontario; Provincial Highway 7 road cut west of Marmora, Ontario; Bethlehem Steel Mine, Marmora Ontario; Provincial Route 2 road cut just east of Napanee, Ontario (below the highway department); QEW Highway 401 road cut at Montreal Street exit, Kingston, Ontario;  Division Street Quarry, Kingston, Ontario; and Barriefield Hill, near Kingston, Ontario.  (Inserted August 12, 2019):  Kolata, Huff and Bergström (1996) briefly described the Ordovician K-bentonite bed at the quarry near Aylmer, Quebec (just across the river from Ottawa) noting that this bed is as much as 17 cm thick.   Salad Hersi (1998) reported on a Bentonite layer in a roadcut at the intersection of Tenth Line Rd. and St. Joseph Blvd. in Orleans, Ontario (now part of Ottawa),  within the Hull Formation about 1 meter below the base of the Verulam Formation.   Kierman (1999) analyzed those two K-Bentonites from the Ottawa Embayment: one at the Klock Quarry in Aylmer, Quebec, and the second near the intersection of St. Joseph Blvd. and Tenth Line Rd. in Orleans, Ontario about 1 m below the base of the Verulam Formation.  Dix and Jolicoeur ( 2011) discuss bentonite layers in the Ordovician Billings Formation and Carlsbad Formation, Eastern Ontario.
I did not find a report of a porphyritic volcanic rock from the Ordovician rocks of the Ottawa Embayment.

The potassium-rich bentonite clay formed from altered volcanic ash was originally called bentonite, then metabentonite and only later called K-bentonite (Lounsbury  and Melhorn, 1963).  Kay (1929, 1931, 1935) reported on a six inch layer of  metabentonite (now, K-bentonite) north of Kingston, Ontario at the base of the Ordovician Glenburnie shale, and that the metabentonite had been identified at Napanee, Ontario.   Kay (1931, 1935) also reported  metabentonite occurrences in a number of exposures in the Ordovician Coboconk limestone between Lake Simcoe and Georgian Bay, in Simcoe County, Ontario, with the best of the exposures at quarries  between Orillia and Coldwater.  Maddox (1930) reported a bed of  “bentonite” in Ordovician rocks in a well  2 1/2 miles southeast of Collingwood, Ontario, which Kay (1931) identified as a metabentonite (now, K-bentonite). Orr (1959) reported on samples of “metabentonite or K-bentonite” of Ordovician age from four separate quarries north of Lake Simcoe, Ontario: the first from two 1 inch seams  near the town of Medonte; the second from a 1/2 inch thick bentonite layer at the west quarry at the town of Coboconk; the third from an inch thick bentonite layer at an abandoned quarry 25 miles southwest of the town of Sebright; the fourth from the upper of two 1 inch bentonitic shale partings at a quarry north of the Longford Mills.

 K-bentonite (volcanic ash) layers within sedimentary rocks  are fairly common from the Precambrian  to the Tertiary (see Huff, 2016).   Crystal tuffs and tuffacious zones within K-bentonites layers  have been  reported from various  periods in addition to the Ordovician, but my initial online research suggests that the large size of the feldspar phenocrysts in the rock that I found is very unusual .  For example,  Dennison and Textoris (1978)  report that the Devonian Tioga K-bentonite (found in Virginia, West  Virginia, Pennsylvania, New York)  has several tuffaceous layers,  and  state that “The Tioga tuff ranges (in its original rock state) from coarse crystal tuffs rich in biotite and feldspars (Fig. 3) to tuffaceous shales. ... Up to 35 percent of some samples of the middle coarse zone consist of euhedral and fragmented K-feldspar and Na-rich plagioclase.”  They use isopach data and crystal size for biotite  and feldspar to speculate as to the location of the volcanic source of the Tioga tuffs.  Their map plotting the mean diameter of the coarsest feldspar in the middle coarse zone of Tioga Bentonite, Appalachian Basin, has feldspars ranging from .1mm to 1 mm.
   

In my January 7, 2018 blog posting I mentioned that the Ontario Geological Survey (“OGS”) had released the Summary of Field Work and Other Activities, 2017 (Open File Report 6333), in which Catherine Béland Otis reported on her project ‘Paleozoic Mapping of Eastern Ontario’ . She mentioned  that she had been looking at ages determined from zircons found in bentonite beds in Eastern Ontario and hoped to correlate strata in Eastern Ontario with adjacent jurisdictions, and that “The bentonite beds  represent Late Ordovician volcanic ash deposits from a volcanic arc, now disappeared, located hundreds of kilometres to the east.”   I thought at that time that the altered volcanic ash (K-bentonite beds) would  be an interesting blog posting.  What is surprising is the number of papers written on the beds in the Ordovician of North America.

Christopher Brett
Ottawa, Ontario

References and Suggested Reading

Adhya, Soumava,  2009
Geochemical fingerprinting of volcanic airfall deposits: A tool in stratigraphic correlation.
Ph.D. Thesis and Dissertation. Department of Earth and Atmospheric Sciences, University at Albany, State University of New York.  532 pages.
http://scholarsarchive.library.albany.edu/cas_daes_geology_etd/125

Al-Delami, M. And Dix, G.R., 2009   
Distal Limits and Composition of a Late Ordovician (Mohawkian) Biotite-Bearing Volcanic ash, Foreland Carbonate Platform (Verulam Formation), Ottawa Embayment: Helping to Define Magmatic Change in Volcanism Following Later Platform Foundering.  American Geophysical Union, Spring Meeting 2009, abstract id. V31B-10
http://adsabs.harvard.edu/abs/2009AGUSM.V31B..10A

Allen, V.T. , 1929
Altered tuffs in the Ordovician of Minnesota. Journal of Geology,  37, 239–248.
https://doi.org/10.1086/623617
https://www.jstor.org/stable/30055890
   
Allen, V.T. , 1932
Ordovician Altered Volcanic Material in Iowa, Wisconsin, and Missouri.  The Journal of Geology 40, no. 3 (Apr. - May, 1932): 259-269.
https://doi.org/10.1086/623945    https://www.jstor.org/stable/30057999

Anonymous, 2019
Deicke and Millbrig bentonite layers - Wikipedia.
https://en.wikipedia.org/wiki/Deicke_and_Millbrig_bentonite_layers

Armstrong, D.K., 2000
Paleozoic Geology of the Northern Lake Simcoe Area, South-Central Ontario. Ontario Geological Survey Open File Report 6011, at pages 18 and 23
http://www.geologyontario.mndmf.gov.on.ca/mndmfiles/pub/data/imaging/OFR6011/OFR6011.pdf

Barth, A.P.; A.D.G. Feilen; S.L. Yager; S.R. Douglas; J.L. Wooden; N.R. Riggs; J.D. Walker
2012
Petrogenetic connections between ash-flow tuffs and a granodioritic to granitic intrusive suite in the Sierra Nevada arc, California .  Geosphere (2012) 8 (2): 250-264.
https://doi.org/10.1130/GES00737.1
https://pubs.geoscienceworld.org/gsa/geosphere/article/8/2/250/132512/petrogenetic-connections-between-ash-flow-tuffs

Brett, Carlton,  McLaughlin, P. , Cornell, S., and Baird, G. 2004
Comparative sequence stratigraphy of two classic Upper Ordovician successions, Trenton Shelf (New York–Ontario) and Lexington Platform (Kentucky–Ohio): implications for eustasy and local tectonism in eastern Laurentia. Palaeo:  Palaeogeography, Palaeoclimatology, Palaeoecology, vol. 210, pages 295- 329; K-bentonites at 306-308
https://www.academia.edu/17890405/Comparative_sequence_stratigraphy_of_two_classic_Upper_Ordovician_successions_Trenton_Shelf_New_York_Ontario_and_Lexington_Platform_Kentucky_Ohio_implications_for_eustasy_and_local_tectonism_in_eastern_Laurentia

Brun J., 1974
Etude Petrograpique des formations du Black River et du Trenton du Quebec.
Ministere de Rechesses Naturelles Service des gites Mineraux. 24 pages

Brun, J.  and Chagnon, A., 1979
Rock Stratigraphy and clay mineralogy of volcanic ash beds from the Black River and Trenton Groups (middle Ordovician) of southern Quebec.  Can. Journal of Earth Sciences, vol 16, 1499–1507
https://www.nrcresearchpress.com/doi/abs/10.1139/e79-133

Carey, Adam, Samson, Scott D.,  and Bryan Sell, 2009
Utility and Limitations of Apatite Phenocryst Chemistry for Continent-Scale Correlation of Ordovician K-Bentonites.  The Journal of Geology, Vol. 117, No. 1 (January 2009), pp. 1-14
https://www.jstor.org/stable/10.1086/594368

Cornell, Sean R., 2001
 Sequence Stratigraphy and Event Correlations of Upper Black River and Lower Trenton Carbonates of Northern New York State and Southern Ontario, Canada.  Thesis, Master of Science, University of Cincinnati
 https://etd.ohiolink.edu/!etd.send_file?accession=ucin997444936&disposition...

Delano, J. W.,  Schirnick, C., Bock, B.,  W. S. F. Kidd, M. T. Heizler, G. W. Putman, S. E. De Long, M. Ohr, 1990
Petrology and Geochemistry of Ordovician K-Bentonites in New York State: Constraints on the Nature of a Volcanic Arc.  The Journal of Geology, Vol. 98, No. 2 (Mar., 1990), pp. 157-170
https://www.jstor.org/stable/30063767

Dennison , J. M. And Textoris, D. A, 1978
Tioga Bentonite Time-Marker Associated with Devonian shales in Appalachian Basin.  166-182
in  Proceedings First Eastern Gas Shales Symposium, October 17-19, 1977, Lakeview Inn and Country Club, Morgantown, West Virginia. Department of Energy, Technical Information Center, 1978 ,  783 pages
https://books.google.com/books/about/Proceedings_First_Eastern_Gas_Shales_Sym.html?id=rA8Ma1wed6QC

Dix, George R. And Jolicoeur, C. , 2011
Tectonostratigraphic framework of Upper Ordovician source rocks, Ottawa Embayment (eastern Ontario).  Bulletin of Canadian Petroleum Geology, Vol. 59, No. 1 (March, 2011), P. 7–26
https://doi.org/10.2113/gscpgbull.59.1.7

Fyon, Andy, 2019
Marmora Ash Beds — Ontario Beneath Our Feet
https://www.ontariobeneathourfeet.com/marmora-ash-beds
downloaded July 27, 2019
   
Haynes, John T., 1989
The Mineralogy And Stratigraphic Setting Of The Rocklandian (Upper Ordovician) Deicke And Millbrig K Bentonite Beds Along The Cincinnati Arch And In The Southern Valley And Ridge.
Ph.D. thesis,   University of Cincinnati
https://scholar.uc.edu/concern/etds/cn69m4153?locale=en

Haynes, John T., 1994
The Ordovician Deicke and Millbrig K-Bentonite Beds of the Cincinnati Arch and the Southern Valley and Ridge Province. Geological Society of America Special Paper Volume 290   
Doi: https://doi.org/10.1130/SPE290-p1
https://pubs.geoscienceworld.org/books/book/426/chapter/3798516/the-ordovician-deicke-and-millbrig-k-bentonite
https://books.google.com/books/about/The_Ordovician_Deicke_and_Millbrig_K_ben.html?id=MYuKAAAAQBAJ

Hewett, D. F., 1917
The origin of bentonite and the geologic range of related materials in Bighorn basin, Wyoming.  Journal Washington Academy Sciences, vol. VII, pp 196-198
https://www.biodiversitylibrary.org/item/18415#page/202/mode/1up

Huff, Warren, 2016   
K-bentonites: A review.  American Mineralogist, Volume 101(1), pages 43-70  
https://www.researchgate.net/publication/289366248_K-bentonites_A_review

Huff, W., Kolata, D.R., Bergstrom, S. M. And Zhang, Y-S., 1996
Large-magnitude Middle Ordovician volcanic ash falls in North America and Europe: dimensions, emplacement and post-emplacement characteristics. Journal of Volcanology and Geothermal Research, volume 73, 285-301
Https://www.academia.edu/27206142/Large-magnitude_Middle_Ordovician_volcanic_ash_falls_in_North_America_and_Europe_dimensions_emplacement_and_post-emplacement_characteristics

Kay, G.M., 1929,
Stratigraphy of the Decorah Formation, Journal of Geology, vol. 37, 639-671,
       
Kay, G. M., 1930
Age of the Hounsfield Metabentonite, Science, vol. 72, 365

Kay, G.M., 1931
Stratigraphy of the Ordovician Hounsfield Metabentonite, Journal of Geology, vol. , p. 361-376.
https://www.jstor.org/stable/3008078

Kay, G.M.,  1935
Distribution of Ordovician altered volcanic materials and related clays. Geological Society of America Bulletin 46: 225-244     doi:10.1130/GSAB-46-195

Kierman, Jeffrey P., 1999
Lithography, Sedimentology and Diagenesis of the Upper Ordovician Hull Beds and Verulam Formation, Upper Ottawa Group, Eastern Ontario. Thesis, Master of Science, Department of Earth Sciences, Carleton University.   262 pages.   MQ43360.pdf
https://www.collectionscanada.gc.ca/obj/s4/f2/dsk1/tape8/PQDD_0003/MQ43360.pdf

Kolata, Dennis R.,  Huff,  Warren D.  and  Bergstrom, Stig M., 1996
Ordovician K-bentonites of eastern North America.  Geological Society of America, Special Paper 313
https://books.google.com/books/about/Ordovician_K_bentonites_of_eastern_North.html?id=iTDpAgAAQBAJ
https://epdf.pub/ordovician-k-bentonites-of-eastern-north-america.html

Lafleur, Jean and Hogarth, D.,
Cambro-Proterozoic volcanism near Buckingham, Quebec. [trachyandesit 573 +-32 Ma]
Canadian Journal of Earth Sciences, 1981, 18(12): 1817-1823,
https://doi.org/10.1139/e81-169

Liberty, B.A., 1969
Paleozoic geology of the Lake Simcoe area, Ontario. Geological Survey of Canada Memoir 355,  215  pages. https://doi.org/10.4095/102319

Lounsbury , Richard W. and Melhorn Wilton N., 1963
Clay mineralogy of Paleozoic k-bentonites of the Eastern United States (part 1). Twelfth national conference on clays and clay minerals, 557-565
https://link.springer.com/article/10.1346/CCMN.1963.0120148
 “Ross (1928) proposed the term metabentonite for these altered volcanic ash deposits. Since, as Weaver (1953) points out, these materials are frequently not metamorphosed, they are not metabentonites.   He suggests use of the term  K-bentonite for these deposits.”

Maddox, D.C., 1930
Bentonite in the Ordovician near Collingwood, Ontario. Science, Vol. 72, Issue 1877, pp. 630
DOI:     10.1126/science.72.1877.630
https://science.sciencemag.org/content/72/1877/630.1

 Mitchell CE, Adhya S, Bergström SM, Joy MP, Delano JW.,  2004.
 Discovery of the Ordovician Millbrig K-bentonite bed in the Trenton Group of New York State: implications for regional correlation and sequence stratigraphy in eastern North America. Palaeogeography, Palaeoclimatology, Palaeoecology 210: 331-346
[Only Abstract looked at]
https://doi.org/10.1016/j.palaeo.2004.02.037

Orr, John Barrie Bain, 1959   
Ordovician Bentonites from Ontario.  Thesis, Master of Science, The University of Alberta. 86 pages
https://archive.org/details/Orr1959

Oruche, Nkechi E.,  Dix, George R. And  Sandra L. Kamob, 2018
Lithostratigraphy of the upper Turinian – lower Chatfieldian (Upper Ordovician) foreland succession, and a U–Pb ID–TIMS date for the Millbrig volcanic ash bed in the Ottawa Embayment. Canadian Journal of Earth Sciences, 2018, 55(9): 1079-1102,
[Only Abstract looked at]
https://doi.org/10.1139/cjes-2018-0006
https://www.nrcresearchpress.com/doi/abs/10.1139/cjes-2018-0006

Ross, C.S., 1927
Altered Paleozoic Volcanic Materials and Their Recognition., Bulletin American Association  Petroleum Geologists, Vol. XII, p. 149-164
http://archives.datapages.com/data/bulletns/1917-30/data/pg/0012/0002/0100/0143.htm

Salad Hcrsi , Osman , 1998
 Stratigraphic revision of the Upper Chazyan to Trentonian succession, and sedimentologic and diagenetic aspects of the Blackriveran strata Ottawa Embayment, Ontario, Canada. Unpub. PhD. thesis Carleton  University, Ottawa, Ontario, Canada, 370 pp.
https://www.collectionscanada.gc.ca/obj/s4/f2/dsk2/tape17/PQDD_0035/NQ26886.pdf

Samson, Scott, 1996
40Ar/39Ar and Nd-Sr isotopic characteristics of mid-Ordovician North American K-Bentonites: A test of early Paleozoic Laurentia-Gondwana interactions. Advanced Earth and Space Science.
https://doi.org/10.1029/96TC00829
https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/96TC00829

Sharma, S., Dix, G.R.  and M. Villeneuve, 2005a
Petrology and potential tectonic significance of a K-bentonite in a Taconian shale basin (eastern Ontario, Canada), northern Appalachians: Geological Magazine, v. 142, p. 145-158.
DOI: 10.1017/S001675680400041X
https://www.researchgate.net/publication/248686363_Petrology_and_potential_tectonic_significance_of_a_K-bentonite_in_a_Taconian_shale_basin_eastern_Ontario_Canada_northern_Appalachians           

Sharma , S.,  Dix. G.R., Coniglio, M.,  Achab, A. , and Riva, J. F. V., 2005b
Records of Punctuated Tectonism in Platform-Interior Graben Systems (Ontario, Canada) Far-Flung from Contemporaneous Taconic Orogenesis in the Northern Appalachians.
Poster presentation at AAPG Annual Convention, Calgary, Alberta, June 19-22, 2005. http://www.searchanddiscovery.com/documents/2005/sharma/index.htm
www.searchanddiscovery.com/documents/2005/sharma/images/poster01.pdf

Suarez, S. E.; Brookfield, M. E.; Catlos, E. J.; Stockli, D. F.; Batchelor, R. A., 2016
Precise U/Pb zircons dates of bentonites in Upper Ordovician and Lower Silurian.  American Geophysical Union, Fall Meeting 2016, abstract #V11A-2761
http://adsabs.harvard.edu/abs/2016AGUFM.V11A2761S
 3 precise U-Pb zircon ages from the Trenton Group, Ontario, Canada,   The youngest age from the top of the Kirkfield Formation in Ontario is 448.0 +/- 18 Ma, which fits with existing late Ordovician stratigraphic ages

Tweet, Justin, 2016
(former) Ash beds in St. Paul
Equatorial Minnesota: Minnesota paleontology and geology, National Park Service paleontology, the Mesozoic, and occasional distractions.   Posted Sunday, July 31, 2016
https://equatorialminnesota.blogspot.com/2016/07/former-ash-beds-in-st-paul.html

Ver Straeten, C.,  Baird, G. C.,  Karabinos, P., Samson, S. D., and Brett, Carlton E.,  2012
Silicic Appalachian Magmatism During the Ordovician and Devonian: Perspectives from the Foreland Basin, and the Hinterland.   In New York State Geological Association, 84th Annual Meeting Guidebook, Publisher: New York State Geological Association, Editors: Todd W. Rayne, pp. A7-1 to A7-59
https://www.researchgate.net/publication/281120169_Silicic_Appalachian_Magmatism_During_the_Ordovician_and_Devonian_Perspectives_from_the_Foreland_Basin_and_the_Hinterland

Wentworth, Chester K. And Williams, Howel, 1932
The Classification and Terminology of the Pyroclastic Rocks, pages 19-53,  in Report of the Committee on Sedimentation, 1930-1932, Bulletin of the National Research Council, No. 89,  National Academy of Sciences, Washington, D.C.
https://books.google.com/books/about/Bulletin_of_the_National_Research_Counci.html?id=ECMrAAAAYAAJ