Eocene Leaves

[ashcraft]

I came into possession of some leaves preserved in clay. The story is rather long, but interesting (at least to me). I want to use the leaves in an upcoming presentation, and am trying to get some info on them. They can be viewed at the following location, the entire story is listed at the end of the pictures. Any comments, questions, suggestions, identifications, speculations, or any other ions that I have left out would be most appreciated.

http://www.lakeneosho.org/Temp36.html

Thanks,

Brent Ashcraft

[Guest N.AL.hunter]

Wow, what a job ahead of you. The first pic has Ft. Union written on the fossil. Do you not trust that or do you already know that it was added at a latter date? I'll do some research to see if I can find anything out.

[ashcraft]

What I think it says is "Idalia, Fort Union Formation", which would mean it came from Missouri, but the words are so blurred at the end, it is hard to say. I am hoping that somebody has prospected the Fort Union, and can say that they have seen similar in the formation, or the mateial that they have seen is significantly different. It is a shot in the dark at best.

Thanks for your interest,

Brent Ashcraft

[Guest N.AL.hunter]

I've spent a little bit of time online this morning looking at the fossil leaves for sale at a couple of sites which are identified as coming from the Ft. Union Formation in Montana. On visual inspection alone, the ones you posted look different than the current ones available for sale. The matrix looks different, and the color is not as uniform as the ones for sale. And I know that color is not diagnostic, but it helps. However, I also looked up the geologic extent of this formation and it sure does cover a lot of area. The write-up for your Idalia says they were collected in mud and not described as having come from a shale or sandstone matrix. The matrix around the ones posted online for sale look more like a shale or sandstone, while the matrix around the specimens you have looks more like a mudstone/dried mud type matrix. Also, the ones for sale appear in a matrix that splits more along the plane, while your specimens appear to come from a matrix more prone to crumbling when split. Therefore, my visual guess, coupled with the written description for you specimens, would indicate to me that they were collected in Idalia.

I guess I am also confused about something the write-up said. Duckworth sent his specimens from Idalia away to the museum, but they sent him back specimens from Montana and not Missouri? Why? Why didn't they just send him back the duplicate specimens from Idalia?

I am totally guessing here, thanks for the fun it was trying to figure this thing out.

[ashcraft]

I surely do appreciate the gum-shoe work. The matrix that Idalia material is from is a clay that was being mined for brick manufacture around the turn of the last century, when still in situ, it appears to be a solid mass, but supposedly when it dries, it shows bedding planes. There is no rock in this formation at all, there is some unconsolidated sand. The whole formation lies on top of the Wilcox sandstone. The national museum deemed these fossils to be important because it correlated this material to the Eocene, most of the material around here of that age is particularly unfossilferous, so it was aged on physical properties only. Dan Stewart of the USGS thought this deposit was unique enough to be given a formational status, but he never published that particular work. Some believe it was a river deposit, as the Mississippi embayment moved southward. I would love to find it and collect a few of the leaves myself, and sieve a few (several) pounds of it to see if any other material is present. I can find no record of this having been done. All and all, an interesting and challenging problem.

Brent Ashcraft

[RJB]

Hey Mr. Ashcraft. Here are some pictures of some leaves that Ive found in the eastern part of Montana. Am told it is Fort Union formation. Hope this helps?

RB

[ashcraft]

Beautiful leaves- are they in mudstone or clay (or something else)?

Brent Ashcraft

[RJB]

Beautiful leaves- are they in mudstone or clay (or something else)?

Brent Ashcraft

I would say its mudstone, but thats just a guess. Its very hard rock that they are in. Thanks for the compliment.

RB