Atrasado Formation

[kgbudge]

From the Atrasado Formation in San Diego Canyon, New Mexico. Took a couple of younger friends fossil hunting, and we found a good bed.

 

This one's a real beauty. My photographic equipment is primitive and doesn't do it justice.

 

 

Graptolites and something else.

 

 

Not sure what the circular structures are; I don't have the equipment for proper microphotography. There is a very clear echinoderm plate elsewhere in the sample so I'm wondering if these are some kind of echinoderm. They're very clear under the loupe and obviously fossils, not sedimentary structures.

 

Bryozoans.

 

 

This particular bed was thick with the stem bryozoans in the second photograph, as well as scads of brachiopods and a few crinoid stems.

[jpc]

the mystery pieces look like sea urchin plates

[Wrangellian]

Nice finds from an unheard-of location (for most of us, I think!) 

[kgbudge]

San Diego Canyon is a superb fossil site, as are other Pennsylvanian beds in the western Jemez Mountains. Local geologists and fossil hunters know it well, but it's not much known outside the state. From my perspective, maybe that's a good thing? 

[Wrangellian]

I would consider that a good thing

[kgbudge]

Another fun find.

[kgbudge]

This has rather poorly preserved crinoid stem segments. I'd consider it junk except for one thing: It's remarkable to find body fossils preserved at all in an arkosic sandstone like this one.

 

 

This is from the transition of the Atrasado Formation to the overlying El Cobre Canyon Formation. The transition is from a marine shelf environment to a deltaic environment; the arkosic sediments are from the Nacimiento Uplift, part of the Ancestral Rocky Mountains. This comes from the point in geologic time where sediments from the uplift are startng to engulf the marine shelf.

 

The best shelf fossil beds are just below this point stratigraphically. There the rock is still mostly limestone but is starting to have more clastic beds, and I suspect this sometimes preserved mass kills of the marine fossils.

 

[kgbudge]

Dont' think I've posted this before: A nice little spirifer in solid limestone.

 

Might benefit from more preparation, but I want to practice some more on junk first before risking ruining this one.