Texas Fossils

[Mike Zimmer]

Hay folks, As promised I'd put out some of what I've found here in Texas. first I had to do some research on where I found this stuff. I have a job a little ways West, North/West of Fredericksburg. Just below the Llano uplift. I'm having a good time turning a hay barn into a hunting lodge on 400 some-odd acres all by myself. If some wants to look it up it's towards the end of Live Oak Creek.

The maps say It's in Cretaceous(Comanche), though I believe it goes down much farther. There is a bluff close to the creek. from where the last rays of sun touch to the bottom of the creek is +- 125 feet in about 100 yards. That's a lot of time in layers of rock. I haven't gone and checked it out because it's on someone else's property but I think I saw granite, If it isn't it is really red and solid in the creek bed. To put it simply I'm not really sure about the age of these rocks. I was hoping to pin it with the Brachiopods but I can't find them. They seem to have a very distinctive ridge and ribs to them, and I find the every were.

What I've found has been on the surface or in the creek bed I've done no digging, except post holes and I did find one of the sponges in the dirt that way. I'm in one big flood plane where this structure is. I've not made any real effort to go looking for fossils.... YET. Not to bad for just taking a walk for an hour or two, or picking up as I see them. After all I am supposed to be working!

[TyrannosaurusRex]

Nice!

[Mike Zimmer]

Here are the sponges I found. Or sponge related, I think, don't know the names of them yet though, hoping for some help. Imagine that Me finding sponges. also is one side of the brachiopods.

[LanceH]

The bigger rock in the second picture has a cross-section of an Engonoceras ammonite.

[Mike Zimmer]

wow, I didn't expect a reply so fast. Thanks! One down. Second view of the same bunch.

[erose]

In Post #3 the shells are oysters: Ceratostreon texana. It is pretty much an index fossil for the Lower Fredericksburg Group although they do occur in the uppermost Glen Rose Formation (Trinity Group) as well. Looking at the Llano sheet and Live Oak Creek you are probably in the Fort Terrett or Segovia Formations. Not sure if those are sponges or just porous rock. Never seen sponges in those formations myself. And it is all Cretaceous Period (Comanche Series) as you noted. Keep your eyes open for sea urchins and other types of fossils as the Fredericksburg is known for them.

[Mike Zimmer]

This has got me a little confused, I found a rock with dried mud cracks and one with rain drops, go figure? One burst open in my fire pit and gave me some interesting creatures, and one that is more dolomite than lime stone had a cephalopod in it. I'm all over the board.

[Mike Zimmer]

Lance H., Thank you for your input I looked up what you suggest it was and I wish it was but it's not an Ammonite. If you click on the photo to make it larger you'll see it has no spiral what so ever. Back to the drawing board. Thanks again though.

Thanks also to Erose for the more detailed description of the area that will help me a lot. I see your in Austin as well, might have to look you up some time. Show off my collection of sponges... Tee Hee

[Auspex]

Lance H., Thank you for your input I looked up what you suggest it was and I wish it was but it's not an Ammonite. If you click on the photo to make it larger you'll see it has no spiral what so ever...

A transverse cross-section would not show a spiral.

[Mike Zimmer]

Here is another view of that piece it is not a transverse cross-section either

[Dave in Alaska]

I think there is some confusion about which pieces are being discussed. Correct me if I am wrong, but it is the picture on the right of post 7 and post 1 that has the ammonite cross section.

[Auspex]

I think there is some confusion about which pieces are being discussed. Correct me if I am wrong, but it is the picture on the right of post 7 and post 1 that has the ammonite cross section.

[Mike Zimmer]

Ahhhh, The right picture in the first post Not the first picture in the second post. OK I feel stupid! Yah, I would agree with that, but still, what's the other thing???

[Auspex]

...what's the other thing???

If you mean this:

I take it to be a concretionary structure.

[Mike Zimmer]

If you mean this:

~.JPG

I take it to be a concretionary structure.

Good thought Auspex, made me go get the rock and a glass and take a look. Don't thinks so though to many different materials in the same place. their is different lime stones, chert, ooliths and such all mixed together in different densities. a Concretion would be more uniform like a crystal.

I wonder If it is where something was growing on the sea floor, waving around, then got broken off?? Any thoughts

[Auspex]

...I wonder If it is where something was growing on the sea floor, waving around, then got broken off?? Any thoughts

To my old eyes, it has all the appearance of nested spheres; I'm sticking with concretionary structure.

[BobC]

I agree with Auspex and Erose. I don't think any of that stuff is coral. A good test to tell if something is coral is that if you magnify the round openings you will see tooth-like structures around the inside of the holes. It's easy to get fooled.

[Mike Zimmer]

My How I love a good debate! This Is what I'm after. Put all the options on the table, anything you can think of. State your reasons why you think it may be this or that. Then let every one start picking them apart and trying to figure out how to prove their point. THIS IS HOW YOU LEARN WHAT THINGS ARE. I got half a mind to saw this in half and polish it to see what's inside. trouble is I don't have a scope powerful enough to see the grains or cells. The rest I can do.

[JohnJ]

My How I love a good debate! This Is what I'm after. Put all the options on the table, anything you can think of. State your reasons why you think it may be this or that. Then let every one start picking them apart and trying to figure out how to prove their point. THIS IS HOW YOU LEARN WHAT THINGS ARE. I got half a mind to saw this in half and polish it to see what's inside. trouble is I don't have a scope powerful enough to see the grains or cells. The rest I can do.

Do it. Cut it in half and use the 'macro' or 'close-up' function on your camera to take a photo. A sharp image can reveal details when viewed on a larger screen that you might not see that well otherwise.

[Mike Zimmer]

OK experiment complete. See what you think.

[Mike Zimmer]

This is the best I could do with what I have. personally, I'm sticking with something growing there. Something soft to wave around easily like a sponge. notice the circles of shifted silt around it. It's Not any kind of plant thing, It doesn't seem to have any roots. No layers to be a stromatolites.

[Auspex]

Except for where it is weathered, it is pretty much homogeneous with the matrix. From this we at least know that it is not an embedded body fossil or burrow. Pretty curious!

[Mike Zimmer]

Here is another thought, What kind of creature would stamp a mark like that on the sea floor? That would also account for the silt rings and mound around it.