Lower Ordovician Fossils in Undocumented Silicate Stone Formation

[FranzBernhard]

9 hours ago, Philip Rutter 2 said:

And probably best, 3 - not common information (1) but quartz is transparent to x-rays; (2) 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.   :-)

(1) Not particularly. X-rays energetic enough will go through a given sheet of silica. X-rays not energetic enough will the absorbed by the same sheet of silica.

 

(2) Are you talking about glass capillaries for X-ray diffraction?

 

Franz Bernhard

 

 

Edited September 7 by FranzBernhard

[Isotelus2883]

This might answer:

https://www.usgs.gov/publications/origin-jasperoid-limestone#:~:text=As limestone dissolves%2C Ca ions,the precipitation of colloidal silica.

I don’t think it is stromatolite. You can easily test this by testing another fossil to see what the silica content is. 

[ynot]

On 9/5/2024 at 6:20 PM, Philip Rutter 2 said:

But - known geology below; Oneota dolostone; and above; New Richmond sandstone - are both reasonably well studied and characterized, and a pure silicate layer, which after 3 years and one broken wrist of surveying I estimate as varying from 3 m to 8 m thick - is just not mentioned anywhere.

 

My 7 year educated guess is that the silicate is IN the unconformity known to lie between the Oneota and the New Richmond.  Ain't that interesting?

 

Seems to be mentioned here....

On 9/5/2024 at 8:28 PM, Philip Rutter 2 said:

Their description of chert in the Oneota agrees with my own; there is an abundance of oolitic chert, as well as other oolites.  They refer to bands of chert some meters thick- that's new to my info, and I wanna see them.  :-)

From your description I think you are digging in one of the bands of "chert" .

 

Have you considered stress fracturing? I have seen silicate rocks that have been subjected to high stress that will have pseudo rhombohedral fracture. A mile thick ice sheet did cover that area.

Also there is the possibility of temperature change fracturing (like marbles in boiling water)

 

Regarding the "label"  put on it, at 95% silica it is a silicate rock.

Because of the environment in which it formed it is clearly not agate or chalidone. It is also clearly not jasper, chrysoprase, quartzite or keystone..

This leaves either flint or chert, take your pick.

I know of no other silicate rocks that would fit this type deposit.

 

 

 

 

 

 

 

 

[Diomedia]

Welcome Philip!  I am following this thread with much interest. The advisor on the Carleton paper is, I believe, a sedimentologist and may be able to offer an opinion on the chert controversy. (I have not read the paper). Question - would making a thin section of this rock to discern any relict structure be a possibility?  Also, isn’t chert a deep water pelagic ooze deposit? The Ordovician rocks in SE Minnesota are, I think, mostly shallow epeiric seas.