We went to Cannon Falls today to look for fossils! The previous trip had been a total wash because I do not do geostrata with anything approaching skill, and I ended up missing the washout we wanted and putting us on a roadcut where it was mostly st. peter sandstone with all the decorah shale scraped off the top by glaciers. Derp.

The place we went today, you literally walk on the fossils you don’t want, to get to the ones you do. Tiny tiny perfect brachiopods (platystrophia) littered the ground so we picked those up with glee. They look like this:

except the Minnesota ones are smaller, and often better preserved than you find elsewhere. They weather right out of the outcrop and scatter everywhere. The ones we were picking up were over 450,000,000 years old.

Lots of corals too. We got the usual branchy kind that looks like various twigs, and like three or four horn corals, which look like Terezi horns and were the only solitary corals until they got the Cosmic Nope. I never had any of these in my collection before, but this spot is a huge treasure trove of stuff that wasn’t showing up at Lilydale.

There were also nipple-looking Karkat horns, prasopora conoidea, which we grabbed a bunch of. I found one tiny snail shell, another first. Then we both found ticks crawling on us (not biting, though) and decided to skedaddle for the day.

I’m getting a gardener’s kneeling board and bringing a hammer and a spade and we’re going back again. Bug spray will be liberally applied.

We’ll see what happens next.

alexadventure:

Thin section of a bryozoan at 40x magnification in cross-section, showing its internal structure. You’re looking upwards through a stalk of the bryozoan, which branches out like a tree. Crystals are calcite. Non-polarized light. 

Finished polishing off my newest thin section today so I’ll throw some pictures from it up tomorrow. If anyone’s interested I might do a photoset on how to actually make a microscope-thin slide out of a rock, because it’s really fun to do. 

alexadventure:

A thin section of a Ordovician-age packstone from the Cincinnati arch, under 10x magnification in non-polarized light, showing a cross section of a bryozoan (a colonial organism like coral) and a brachiopod (think a clam).

That pointy oval near the bottom is the brachiopod. At death it popped open just a little bit, allowing water to infiltrate. That water carried dissolved calcium from the rest of the organisms, which formed the calcite crystals that you see filling up the space. The bryozoan- with a really cool view of its internal structure- is the big pillar in the middle. 

Also, some of the darker spots throughout the slide are fossilized poop. Science!