Lower Ordovician Fossils in Undocumented Silicate Stone Formation

[FranzBernhard]

3 minutes ago, Al Dente said:

Most midwestern chert is formed from silica replacing limestone.

Is the vuginess of the presented specimen indicative for that kind of formation?

Franz Bernhard

[Philip Rutter 2]

5 hours ago, Al Dente said:

 

Not all chert behaves the same. Some cherts have very nice conchoidal fracture while others not so much. 

 Sorry all, a point I just didn't make, since it hasn't been on the top of my mind for years - my stone not only demonstrates emphatic rhombohedral fracture, it doesn't ever show conchoidal fracture.  Based on, oh, 10,000 or so observations.  Not ever.   Silicate rock includes a large diversity of "species" - from fibrous to crystalline - and everything in between.  My stuff is 450 million years old- there's plenty of rearrangement visible, including large chunks that were laid down as sediment- but now appears to have one single crystal conformity all the way across the piece.  The cyrstallinity of the formation varies from nano and crypto to micro to not quite micro -    I'm far more interested in how fascinatingly variable the stone is, within boundaries, rather than nailing down an exact human label for what is a highly diverse gift from our ancestors in the stone --  :-)

[Philip Rutter 2]

8 hours ago, FranzBernhard said:

"Silica rock" formed in freshwater, that means, formed in lakes?

Franz Bernhard

It is generally agreed that the formations above and below are from shallow marine, salt, water.  Fossils, e.g. nautiloids, are also compatible with salt water.

[Philip Rutter 2]

5 hours ago, FranzBernhard said:

Is the vuginess of the presented specimen indicative for that kind of formation?

Franz Bernhard

 

It's usually at least that vuggy; very often more so, lots of variation.  

[Kane]

Have you considered diagenetic reworking? 

[Philip Rutter 2]

12 hours ago, DPS Ammonite said:

Having a geology degree, I noticed that geologists include lots of cryptocrystalline and microcrystalline varieties of quartz in the term chert. That includes jasper, flint, opal, agate and chalcedony. I try to give a more specific name such as opal, chalcedony etc if the rock is distinctive, but realise that others may call it just chert. 
 

Look at Mindat for a definition chert with references:

 

https://www.mindat.org/min-994.html

Aha!  lol - exactly - somewhere on this site in the past few days I proudly announced my identity as a "Splitter" .  I cut my teeth on plant taxonomy- and animal - and just so you know, us biologists think lumping opal and chalcedony with chert - is - not useful.  To be as polite as possible.  :-)  Also, my intention announced here is to form a business based on these stones, selling partially to the Chinese scholar's rocks market - they, I guarantee- are Splitters of the first order.  Dig in there, you'll find "there are 5 main kinds of scholar's rocks.."...   or 6, or 8 - go on line to a Chinese website and you'll find them fiercely delinitating 100's that you must not ever confuse or conflate.  

 

On a deeper scholarly note, I'll gladly grant that both lumpers and splitters have their real-world uses.  Generating endless argument, however, is not among them.  :-)

 

Mindat - inhaled all that years ago; good stuff.

Edited September 6 by Philip Rutter 2
spell

[Philip Rutter 2]

10 minutes ago, Kane said:

Have you considered diagenetic reworking? 

Absolutely yes; that was my only hypothesis for the first 3 years (out of 7 so far) .   The gritty details though are elusive; and I think there has also been some plain 300 million years of very gradual crystal re-alignment - on a whimsical basis.   The chemistry of the layer, and the changes it has experienced - are not obvious, and would seem to be highly divergent from the surrounding strata.  But - ah, the unconformity!  What went on there?  I venture to hope that real investigation of this formation, exaclty (I think) in the unconformity - might start to explain that -

[digit]

5 minutes ago, Philip Rutter 2 said:

selling partially to the Chinese scholar's rocks market

A new term I had not encountered before. Always a good day when you add knowledge.

 

https://en.wikipedia.org/wiki/Gongshi

 

 

Cheers.

 

-Ken

[Philip Rutter 2]

Just now, digit said:

A new term I had not encountered before. Always a good day when you add knowledge.

 

https://en.wikipedia.org/wiki/Gongshi

 

 

Cheers.

 

-Ken

Thanks!  Also worth knowing- there are, last count,  over 2.4 million collectors of gongshi in China.  Auctions in Hong Kong and Shanghai regularly sell single stones in the $100K (US) range- and $500k happens regularly.   The image is a priceless museum piece of the "Kun stone" type - not usually listed as a "type" in first-level searches, partly because it is now hard to come by; only one mountain produced it, and for 200 years all governments have forbidden further mining as too dangerous- honeycombed the place.

[DPS Ammonite]

1 hour ago, Philip Rutter 2 said:

my stone not only demonstrates emphatic rhombohedral fracture, it doesn't ever show conchoidal fracture.

Have you tried to make a thin section and have a geologist look at it under a petrographic microscope? I may be starting to metamorphose and show planar structures thus hindering conchoidal fracturing.
 

Also, what do you think the original source of the silica was? Silicious critters, volcanic ash, hot spring deposits, replacement of limestone by silica?

 

When I was in the San Francisco Bay Area of California, there were lots of ribbon cherts that exhibited blocky fracturing on the macro level, but on a smaller scale there was conchoidal fracturing. Have you tried to flake off small corners of your chert (like you were going to flake an arrowhead) to see if there in conchoidal fracture. 
 

See this similar observation from this website:

 

https://writingfornature.wordpress.com/2013/11/13/chert-the-birthstone-of-our-species/

 

 

[DPS Ammonite]

1 hour ago, Philip Rutter 2 said:

my intention announced here is to form a business based on these stones, selling partially to the Chinese scholar's rocks market

There were lots of cool Chinese Scholar related rocks in Northern California. 
 

See an exhibit of Suiseki:

 

https://oaklandgeology.com/2011/06/19/suiseki-2011/

[DPS Ammonite]

This is fuzzy, but sort of looks like curved fracturing, conchoidal fracturing, on a small scale.

[Philip Rutter 2]

9 minutes ago, DPS Ammonite said:

Have you tried to make a thin section and have a geologist look at it under a petrographic microscope? I may be starting to metamorphose and show planar structures thus hindering conchoidal fracturing.
 

Also, what do you think the original source of the silica was? Silicious critters, volcanic ash, hot spring deposits, replacement of limestone by silica?

 

When I was in the San Francisco Bay Area of California, there were lots of ribbon cherts that exhibited blocky fracturing on the macro level, but on a smaller scale there was conchoidal fracturing. Have you tried to flake off small corners of your chert (like you were going to flake an arrowhead) to see if there in conchoidal fracture. 
 

See this similar observation from this website:

 

https://writingfornature.wordpress.com/2013/11/13/chert-the-birthstone-of-our-species/

 

 

"Have you tried to make a thin section and have a geologist look at it under a petrographic microscope? I may be starting to metamorphose and show planar structures thus hindering conchoidal fracturing." --

 

Alas I have not had the chance yet- but that's high on the list of wants.  Anybody here got the facilties and want to take a crack?  :-)   A college girlfriend was a Geology major, and was TA's the Petrology lab at the time- I have fond memories of my eye glued to the microscope while she leaned over me whispering sweet petrologies in my ear-  :-)

 

"Also, what do you think the original source of the silica was? Silicious critters, volcanic ash, hot spring deposits, replacement of limestone by silica?"

 

Excellent points!!  A) most reef formers at the time were stony sponges - sponges are usually metabolizing silicon, acquiring and depositing pretty large amounts.  I have fossils I'm confident (82% Bayesian) are stony sponges.  The kicker is the chemistry of the Ordovician oceans; our windows there are scattered; but current belief is that early in the Ordovician the atmosphere had 14-15 TIMES  higher than present.  Volcanism usually cited as the cause, so transient; but the effects on ocean chemistry arguably would have been very large, changing the metabolic availability of silca.   Diatoms only appear in the Jurassic, but some foraminfera use silicon, and are much older- 

 

Incidentally, I think the Encyclopedia Britannica has waked up and become afraid of Wikipedia- and responded explosively - to the good.  The entire Britannica entry on "Ordovican" is like an order magnitude larger than Wikipedia - with solid information and links all over: https://www.britannica.com/science/Ordovician-Period/Circulation that contains the links to the carbon dioxide research- 

 

I do have a little evidence of "hot springs" , in a couple look-alike "reef fossils" my geologists assure me are iron carbonate, pretty certainly substituted for the original whatever; but so far these are scarce, and only found in the stream bed, without context.

 

"but on a smaller scale there was conchoidal fracturing. Have you tried to flake off small corners of your chert (like you were going to flake an arrowhead) to see if there in conchoidal fracture. "

 

I have done a substantial amount of flaking/breaking , including digging a complete small nautiloid and a couple gastropods out of solid stone - a good trick with only steel to dig with.  Typically for that experience the flakes I was removing were basically chaotic; no crystalline pattern, no cleavage, nothing visibly conchoidal.  Essentially "one data point" there, though -  but note, in stone identical to the piece pictured at the top, there are hidden fossils that retain enough integrity they can be dug out of the matrix intact - though when the whole block of matrix is fractured the overwhelming tendency is to break in straight lines right through any such fossils - 

[Philip Rutter 2]

3 hours ago, DPS Ammonite said:

This is fuzzy, but sort of looks like curved fracturing, conchoidal fracturing, on a small scale.

I have since then acquired a professional level camera and lens- but still have a ton of photos in the catalog that are not quite "it"

2 things here; what my eye catches first for the bit you have circled, is how the edges of it, form really quite a good rhombus.  :-)

And, I found another photo, same rock, same set, different angle and light- a very poor photo made while learning the situation, which does however show the entire area below your circle as being exceptionally flat- it fractured that way; and I think no experienced flint or chert knapper would expect to see that fracture more than once in a thousand breaks or so- but they're common for me.

 

Edited September 6 by Philip Rutter 2
spell

[Philip Rutter 2]

DPS Ammonite - it occurs to me that being a professional, it should not be too hard for you to get ahold of this paper: JOURNAL OF SEDIMENTARY PETROLOGY, Vor.. 23, No. 3, Pp. 174-179 FIGS. 1-4, SEPTEMBER,1953 

SILICIFICATION IN THE ONEOTA DOLOMITE, N. PROIOPOVICH University of Minnesota.  

 

I dug the reference out years ago, via image search; this was the only "recent" publication with pictures that matched my fossils; and when i finally wangled a full copy of the paper, it turned out to be about 6 times more informative and extensive than any preliminaries indicated; a very good geologist - and - what he describes, as far as I can tell, is a duplicate of my own formation, stone, fossils, and all.

 

The paper was a lot of work for me to get through- it assumes the reader is a full professional geologist- in 1950.  Besides dense jargon, some out of date, I think the majority of fossil names used may be obsolete- a few I could not find at all.  It should be a little easier for you to navigate, and I think it would give you the best idea of what I'm talking about.  The author did find the silicified stratum odd- and if I recall he hinted that he was forced to suspect that the silicification was - primary.  Heresy, of course, which might be why the paper is so little known.

 

The fossil I was image searching for was originally called a Cryptozoon, around 1910 I think, and designated a "sort of stromatolite" generally from "algal mats" - and the fossils are utterly NOT from any algal mat- but just they didn't know what else to call them.  Here's one of mine below.  Typical is the top with fingers, the severe contraction in the middle, and a blooming under part basically as massive as the top.  Algal mat, you bet.  As a near-miss oceanographer, it looks to me like a reef organism of some sort, with the "undercarriage" serving for a growth base on a soft bottom, likely mud.  I've got lots of these- and others that are different, but would fit in the same world- mud bottom salt estuary, perhaps.  

 

The photo does not allow good fine detail, sadly, but you can see one of the consistent features/problems/ selling points- there is drusy quartz all over any old exposed stone, fresh breaks being clear of it.  Also lots of iron stain.

 

The Wisconsin paper shows - twins to my fossils - but I have lots of other fossils he didn't have time to find- I think-

 

I didn't do any of the breaking; this fellow was found in a feeder ravine, half way down- having been tumbled and pounded in floods causing the quite visible breaks.  The "skeletal stone" - is not dolomite, or carbonaceous; and it naturally tends to break in those straight planes.

Edited September 7 by Philip Rutter 2

[minnbuckeye]

Again, as a non professional that has hunted your area extensively, I still lean towards a geologic formation and not  stromatolite.

[DPS Ammonite]

6 minutes ago, Philip Rutter 2 said:

DPS Ammonite - it occurs to me that being a professional, it should not be too hard for you to get ahold of this paper: JOURNAL OF SEDIMENTARY PETROLOGY, Vor.. 23, No. 3, Pp. 174-179 FIGS. 1-4, SEPTEMBER,1953 

SILICIFICATION IN THE ONEOTA DOLOMITE, N. PROIOPOVICH University of Minnesota.  

Sorry, I have no access. Maybe another member does.You may also be able to get it at your local library

 

[Isotelus2883]

It might be possible it’s from a thin layer of druzy quartz on the surface of the rock?

[Philip Rutter 2]

3 minutes ago, DPS Ammonite said:

Sorry, I have no access. Maybe another member does.You may also be able to get it at your local library

 

Oh, I have a PDF, but its from behind a paywall, and technically not supposed to be handed about.  I don't want to tick anybody off.  Though... it's pretty old...  

[Philip Rutter 2]

14 minutes ago, minnbuckeye said:

Again, as a non professional that has hunted your area extensively, I still lean towards a geologic formation and not  stromatolite.

Have you found any like this?  Arguing very strongly against it being geological is the abundant repetition of specific forms - the top, the narrow center, and the broad bottom; specimens like this are known- rarely - from New York, Minneapolis, Wisconsin- and me.  Typical of animals; very, very odd for geology to be so consistent with such specific complex form.    

 

Also; I started out with the assumption/belief these were the products of karst chemistry- after 3 years - that became untenable.  :-)

 

I just went back and looked hard at the photo - forcing myself to see NOT the stone- but the flat photograph.  I can absolutely understand where you are coming from.   :-)     You're probably familiar with the frustration of trying to convey a 3 dimensional object wtih the only information for transfer being a flat photo.  They just don't cut it.  Video is slightly better; only slightly- and only takes about 20X more work than a photo...  gah.     :-)

Edited September 7 by Philip Rutter 2

[Philip Rutter 2]

7 minutes ago, Isotelus2883 said:

It might be possible it’s from a thin layer of druzy quartz on the surface of the rock?

Um- what?  what might be from the druzy?  I missed the antecedent here-   :-)

[DPS Ammonite]

8 minutes ago, Philip Rutter 2 said:

Oh, I have a PDF, but its from behind a paywall, and technically not supposed to be handed about.  I don't want to tick anybody off.  Though... it's pretty old...  

 

Do you see upward convex layering in the chert that stromatolite might have?

 

It is fair use if you want to briefly quote or use a few photos. What caused the silification? Were stromatolites involved?

 

See photo of a lucustrine Miocene stromatolite that I found near Phoenix.

 

 

[Philip Rutter 2]

8 minutes ago, DPS Ammonite said:

 

Do you see upward convex layering in the chert that stromatolite might have?

 

It is fair use if you want to briefly quote or use a few photos. What caused the silification? Were stromatolites involved?

 

See photo of a lucustrine Miocene stromatolite that I found near Phoenix.

 

 

No upward convex layering noted so far.    I'm not sure brief quotes  will have the force of the entire work.   He does not have real suggestions for the cause of the silicification - like me; it's a question.  I don't think he mentions stromatolites; I have several things I suspect are stromatolites -but the ones I've cracked open don't convinvce.

 

A question I've spent a couple hours seaching for an answer to on the internet- no luck so far - What does the bottom of a living stromatolite on soft substrate - look like?   Any paper that I though might deal with it is behind paywalls; no photos I can find-  any idea?

 

[Isotelus2883]

When you tested the rock and got back 95% silica. It may be that it came from a thin layer of druzy.

[Philip Rutter 2]

2 hours ago, Isotelus2883 said:

When you tested the rock and got back 95% silica. It may be that it came from a thin layer of druzy.

Ah.  Perfectly sensible.  3 answers; the samples I sent I think were clean of druzy- I do have photos of them somewhere.  And 2; the gentleman doing the x-ray was an emeritus professor of Geology - I'd pretty much trust him to watch out for that. 

 

And probably best, 3 - not common information but quartz is transparent to x-rays; quartz tubes are regularly used to contain material being subjected to x-ray analysis - as they don't interact.  And why I knew that, I don't know.   :-)