small round balls

[allen.wallace]

I collected several of these small round balls in limestone (shale?) from the Eocene Green River Formation. The location is Tucker, Spanish Fork Canyon, Utah. 

The diameter is about 13mm, about the width of my small fingernail. When these are broken open, I see that the sphere is packed with 0.2mm white "crystals".  I say "crystals" because they look like calcite to me and some have small (0.05mm) hollow spaces. The crystal density is least in the center of the sphere. FYI, the limestone does show small amounts of black organic fragments. In the field, these look very much like a fossil, but under the microscope, the cross-section looks like it is geological in origin. Any ideas?

Edited October 22, 2018 by allen.wallace
typo

[allen.wallace]

adding pictures

[ynot]

My first thought is a burow cast with fecal matter (coprolite) in it.

Let's see what @GeschWhat and @Carl think

[abyssunder]

I think, the "small round balls" might be sandstone concretions with ooids, but it's just a guess.

[Herb]

I am with abyssunder

[Rockwood]

The presence, or absence of other trace, or body, fossils in the area would seem a relevant clue in this situation.

[RJB]

From what ive just read, ooids form with wave action.  How can they form into a ball?  Very interesting though. 

 

RB

[Carl]

Wow... Very interesting. I doubt that's a mass of coprolites. It reads more like non-fossil. An interesting detail is that the white bits are more concentrated at the sphere's edge. And I certainly can't claim to know ooids very well but this doesn't look like any of the examples of that I've seen.

[abyssunder]

The Green River Formation has oolitic limestone and algal pebble beds. Below are two images which may have characters similar to the specimen in question.

 

 

" According to the writer's interpretation of the origin of calcareous oolites and of fresh-water algae reefs oolites may be intimately associated with algae reefs because the conditions favorable to the formation of oolites are in general also favorable to the growth of algal limestone deposits, though the converse is by no means true; or they may be intimately associated because the oolite grains were transported to the growing reef in the same way that clastic grains are carried to and inclosed in algae reefs. "

 

excerpts from W. H. Bradley. 1928. Algal reefs and Oolites of the Green River Formation. U.S.G.S. Professional paper 154: 203-223

[allen.wallace]

I'd like to thank you all for all the replies, specially abyssunder for the link to the USGS paper.   

[abyssunder]

You're welcome, any time! Thank you for posting here!

[supertramp]

hmm ... the white “bits” do not seem to have smoothed contours or an internal concentric structure; some seem to be packaged and interlocked as if they grew togethere;

the fact that the small white pieces are more concentrated at the edge of the sphere (is it the same for all the other little balls you find?), makes me think that the pattern originated in a diagenetic environment.

 

ciao