Oligocene Chadron Formation Agatized Wood And Pinecone?

[squalicorax]

Hey all I found these items in the "dazzling white" member of the Chadron Formation in Northwestern South Dakota.

I figure the wood cannot be identified although I can see some variance with the 40-50 or so specimens I collected. Was curious about the other object I have posted.

The chadron formation was a series of floodplains that were blanketed with ash fall from various volcanos in the west which replaced the wood with silica.

I mapped an area known as Slim Buttes as part of my geology field camp. Unfortunately we were not allowed to collect any vertebrate remains but I saw many!

Item in Question

full res - http://i.imgur.com/lDS7Nvq.jpg

Some wood from the site.

http://i.imgur.com/Q1mD1cq.jpg

full res http://i.imgur.com/KBGpAs8.jpg

Bonus Locality Shot

Edited August 16, 2013 by squalicorax

[Plantguy]

Looks like a great trip. Sorry I cant add anything worthwhile on the unknown....it does appear to have some radiating structure and shape suggesting a cone.

I do absolutely love the locality shot--great rocks! So were talking about a wonderful angular unconformity? So what formation/strata is on top of what in these shots. I dont know much at all about SD geology...

You do have vert pictures, right? Regards, Chris

[PRK]

That shot of the locale, makes my heart race and butterflies in my stomach. Beautiful !

I really love/miss those badlands !

Edited August 17, 2013 by PRK

[squalicorax]

Looks like a great trip. Sorry I cant add anything worthwhile on the unknown....it does appear to have some radiating structure and shape suggesting a cone.

I do absolutely love the locality shot--great rocks! So were talking about a wonderful angular unconformity? So what formation/strata is on top of what in these shots. I dont know much at all about SD geology...

You do have vert pictures, right? Regards, Chris

Hey yeah angular unconformity and multiple mile long faults cross the area. The top unit lying horizontal is a coarse grained sandstone from the Miocene from the Arikaree group. The Brule (Oligocene) sits below at about 20-30 degree dip and contains typical badlands fauna. The Chadron is below the Brule and mostly contains just petrified wood.

Ill post some vert pics soon.

Edited August 17, 2013 by squalicorax

[squalicorax]

As promised

original http://i.imgur.com/5r5UpM2.jpg

lets look closer

original http://i.imgur.com/ZYESuDG.jpg

A turtle in good shape for the Brule

orginal http://i.imgur.com/d8XwTNO.jpg

Unknown vert

Cool Fault in the Chadron

http://i.imgur.com/Clvoxuc.jpg

[AgrilusHunter]

Spectacular location! Is that a reverse fault in the last pic?

[squalicorax]

Yes

[Plantguy]

Hey yeah angular unconformity and multiple mile long faults cross the area. The top unit lying horizontal is a coarse grained sandstone from the Miocene from the Arikaree group. The Brule (Oligocene) sits below at about 20-30 degree dip and contains typical badlands fauna. The Chadron is below the Brule and mostly contains just petrified wood.

Ill post some vert pics soon.

Thanks for the additional info...vert photos and the other outcrop photo below are great. Got to be tough just walking past the vert material! Regards, Chris