Exploded Calamites?

[billheim]

Hi All.

I recently had an invitation to some private property in Greenup County Kentucky to identify the fossils in the creek bed and surrounding hills. Based on the KGS, the property is in quadrangle G54 and the creek and hills are Lower and Upper Mississippian and Lower Pennsylvanian. There were definitely some Calamites and other plant fossils up on the ridge and marine invertebrate fossils down at the base of the hill beside the creek. The hills have Pennsylvanian and the road and creek sides have Mississippian. Obviously, the creek bed is a mix.

There is one large type of fossil the property owner was finding in the creek that I'm not sure is identifiable, but he found a number of these, so perhaps someone else has seen them and knows what they are.

See the attached photos. These specimens do not have a texture that leads me to identify them, and they are completely mineralized and probably exploded from the original size of the fossil. The specimens belong to the property owner and I did not find one myself, so I can't take more photos to show.

My first guess is exploded Calamites, but then again it could just be concretions or burrows that have exploded over time.

Please send your thoughts on these. All leads are useful in my research of a good identification.

Thanks!

Bill

[Raggedy Man]

I like the burrow hypothesis. They definitely resemble some I've seen in Colorado and Nebraska.

[Auspex]

To me, the undulating surface irregularity is more burrow-like than plant-like, but it's so BIG that I don't know what would have made it.

[abyssunder]

Very strange in any case. I vote for a very mineralized plant material.

[paleoflor]

Wonder whether this could be a part/segment of a (weathered) stalagmite/stalactite? Many stalagmites/stalactites have a hollow core in cross section, and would be built-up concentrically. Are there any karst/limestone cave formations in the area?

[billheim]

Wonder whether this could be a part/segment of a (weathered) stalagmite/stalactite? Many stalagmites/stalactites have a hollow core in cross section, and would be built-up concentrically. Are there any karst/limestone cave formations in the area?

That's a very insightful idea. I was told by the property owner that some of the material in that creek bed is presumed to be downstream from Carter Caves.

Kentucky is famous for its many caves and this is a decent possibility.

In looking at the surface of the specimens I've pictured, it's very rough. Can these stalagmites and/or stalacites weather to such a rough surface? (that's a real question, not rhetorical).

Thanks for the idea, Paleoflor.

Bill

Edited September 16, 2015 by billheim

[abyssunder]

Ooh, now I realize! It's a good possibility (shame on me that I have not recognised from the beginning, I was focused on other patterns). They can be stalagmites in my thinking, compared with the karst formations we have in my country.

[howard_l]

The main problem with stalagmites and/or stalacites is time. The karst formation in the northeastern Kentucky area formed much, much later than the limestone of the Slade Formation where the caves are forming. The specimen in question appears to be limestone partially replaced by chert. This formed fairly soon (geologically) after deposition, long before any karst formation. The Pennsylvanian units in this area do not have any carbonates and any plant material would be found only in clastic sediments. My guess is this would be some type of boring coming from the Slade Formation.

[paleoflor]

The main problem with stalagmites and/or stalacites is time. The karst formation in the northeastern Kentucky area formed much, much later than the limestone of the Slade Formation where the caves are forming. The specimen in question appears to be limestone partially replaced by chert. This formed fairly soon (geologically) after deposition, long before any karst formation. The Pennsylvanian units in this area do not have any carbonates and any plant material would be found only in clastic sediments. My guess is this would be some type of boring coming from the Slade Formation.

Probably I'm not following your reasoning simply because I'm completely unfamiliar with the geology in your locale, but could you perhaps explain in a bit more detail why time is such an issue here? I do get that anything found in situ should be at least as old as the formation in which it is found. The specimen here, on the other hand, was found in a creek bed and thus may constitute loose material in the creek bed (not clear to me on basis of the descriptions above). So I guess my question is: Why wouldn't such loose material in a creek postdate the formation of caves?

If the specimen is really partially chert (how do you determine this from photo?), then this would render the stalactite/stalagmite origin doubtful indeed. On the other hand, I also have trouble imaging a boring/borrow structure with such a rather prominent and quite continuous central cavity, as that displayed by the specimen here.

[howard_l]

The cave formations found in the karst areas of nothern KY. are essentially Travertine. Travertine does not last very long being tumbled in a stream. Unless this specimen was found around a mile or less from a cave deposit I doubt it would have held up. The lower part of the Slade Formation contains a unit that contains abundant chert and geodes. Do I know positively that this is chert without a hardness test, no. These rocks look much more like the chert found in that area then it does Travertine. I think that it is very poorly replaced chert from the original limestone. The time factor deal with the age of the limestone formation and when the diagenetic replacement occurred in comparison to when the karst formation occurred. Trace fossils are extremely common through out the Mississippian of this area. I have seen both burrows and chert nodules that were probably once burrows that had hollow interiors. The first photo looks like a geode vug in the side, again without a hardness test it would be just a guess. One thing I am certain of it is not a Calamites, the Pennsylvanian of that area would not have that type of replacement material.

[billheim]

Thanks to all for your insightful comments.

I particularly appreciate Howard's information on timeframes and Travertine vs chert and limestone.

It doesn't seem likely that these are stalagmites or stalactites.
The geode idea is still in play. I did not see any geodes in the area though and in the days when I was finding geodes while traveling, I was finding quite a lot of them. But creeks do mix things up.

Burrows are also still in play. They seem a bit large for burrows, but not out of the question.
I think I can rule out plant fossils in this case, because all the definite plant fossils we found In the creek and up on the ridge were molds in rock with nothing but an impression of the outer surface left. Howard_L anticipated that.

So burrows and geodes/concretions are what we have left.

Thanks so much!

Bill