OSU Geotour Supplemental IV: From the Ancient Seas of My Birthplace


Almost halfway through our tour of OSU geology! We’re coming up on the Memorial Union now, and I hope you left yourself lots of time, because this is one of those places that a person could get completely lost in – and that’s just on the outside of the building.

Stop 11: Memorial Union, East End

Approach the black hole. It doesn’t look like a black hole, but it is sucking you in.

The Memorial Union. This is a place that could keep a geologist occupied for hours.

The Memorial Union. This is a place that could keep a geologist occupied for hours.

Walk to the east end. Put your nose up against the rock. You have now passed the event horizon…

This is the Salem Limestone. Indiana’s famous for it, ships it all over the place. Indiana, a long damned time ago (330 million years), used to be a lovely little tropical sea, with coral reefs and shellfish, and there might have been islands with white sand beaches nearby, and the only drawback to being there then is the fact that the invention of alcohol was a third of a billion years in the future… but still, I’d take lounging round there at that time over lounging round there now. Just because I was born there doesn’t mean I have to like it.

I do love its limestone, though.

Trace fossils. These look like they could be feeding traces, made by things nosing about in the carbonate muds; they could be burrows, too. Someone with expertise may be able to look upon them and say, "Ha, yes, they are X" justlikethat.

Trace fossils. These look like they could be feeding traces, made by things nosing about in the carbonate muds; they could be burrows, too. Someone with expertise may be able to look upon them and say, “Ha, yes, they are X” justlikethat.

This is quite the fossil hash. Everything's chopped up into bits and pieces, implying a high-energy environment. And indeed, this is so: the Salem Limestone comes from the sandbars and channels that followed an ancient coastline.

This is quite the fossil hash. Everything’s chopped up into bits and pieces, implying a high-energy environment. And indeed, this is so: the Salem Limestone comes from the sandbars and channels that followed an ancient coastline.

The little hatched shapes are, if memory serves, bits of coral. There's a huge range of stuff in the Salem Limestone. And a lot of it's visible without a hand lens.

The little hatched shapes are, if memory serves, bits of coral. There’s a huge range of stuff in the Salem Limestone. And a lot of it’s visible without a hand lens.

Sometimes you can see small shells like this one. Imagine taking a slice through a closed scallop or clam - that's basically what we're seeing here, I think. Of course, I know bugger-all about identifying fossils, so don't quote me until an expert confirms.

Sometimes you can see small shells like this one. Imagine taking a slice through a closed scallop or clam – that’s basically what we’re seeing here, I think. Of course, I know bugger-all about identifying fossils, so don’t quote me until an expert confirms.

Another bit of shell? Maybe? All I can say with certainty is that it is a fossil, the remains of some little critter that once lived the tropical life. it's certainly not living it now...

Another bit of shell? Maybe? All I can say with certainty is that it is a fossil, the remains of some little critter that once lived the tropical life. it’s certainly not living it now…

I have no idea. It looks sorta like a crinoid, but sorta not. I'll skip lightly over what it might be and distract you by pointing out that this stone isn't really gray-blue - that's just a matter of lighting. I was practically shooting in the dark. Shady part of the building when it's near sunset, that's for sure. Of course, that makes sense, considering it's the east.

I have no idea. It looks sorta like a crinoid, but sorta not at all. I’ll skip lightly over what it might be and distract you by pointing out that this stone isn’t really gray-blue – that’s just a matter of lighting. I was practically shooting in the dark. Shady part of the building when it’s near sunset, that’s for sure. Of course, that makes sense, considering it’s the east. That was your Profound Thought for the Day. Cherish it.

Now, this is definitely a crinoid! This is the calyx, which is a bit rarer to find than the stems. This stuff is packed with crinoids, though, and you don't need to be an expert to find them. I found dozens in just a short time.

Now, this is definitely a crinoid! This is the calyx, which is a bit rarer to find than the stems. This stuff is packed with crinoids, though, and you don’t need to be an expert to find them. I found dozens in just a short time.

The crinoid calyx again, with a ball-point pen for scale. Tiny and precious!

The crinoid calyx again, with a ball-point pen for scale. Tiny and precious!

Forams! Or foraminaferas, if you want to be formal. These little treasures are usually too tiny to see easily with the naked eye, but these are the size and shape of rice grains. Lovely! I was excited to see them, knowing how useful forams have been for dating formations, studying evolution, and a myriad of other nifty things.

Forams! Or foraminaferas, if you want to be formal. These little treasures are usually too tiny to see easily with the naked eye, but these are the size and shape of rice grains. Lovely! I was excited to see them, knowing how useful forams have been for dating formations, studying evolution, and a myriad of other nifty things.

We've been looking at very small parts of individual blocks - here's the wall.

We’ve been looking at very small parts of individual blocks – here’s the wall.

Right. So here we have very shelly limestone – practically a coquina, although not that shelly. We know that things like crinoids generally live in happy little shallow seas, so we’re suspecting a marine environment. And we know there was some vigorous, although not intense, wave action – enough it produced shell fragments, but didn’t wash away all the lovely carbonate-rich mud. All of these things point to a near-shore environment in a shallow tropical sea, but if you look up, you will find your final bit of evidence.

See? Up at the top - fossilized waves!

See? Up at the top – fossilized waves!

Ba-dum-dum. And yes, I very nearly hit Lockwood when he hit me with that, but I laughed. It’s funny. Awful, but funny.

And very nearly true. Turns out there are sedimentary structures preserved in the stone that tell us about currents and storms and tides. Pretty amazing, eh? You can read all about it in David B. Williams’s wonderful Stories in Stone.

Next comes one of the most delicious staircases I’ve ever seen, although the builders made a big mistake…

 

Back to Phase III or Ahead to Phase V

Comments

  1. Lyle says

    Actually this leads to an interesting thought about Indiana geology. If you start at New Albany on I64 you go thru progressively younger rocks all the way to Il. The Mississippian shows up in the middle of the state in a set of higher hills than east or west of it. (Around Indiana highway 37) which also goes thru Bedford which is the center of the limestone belt. Then as you go west you get into Pennsylvanian rocks at the surface and the coal belt. Finally due to the 30 foot per mile dip to the west of this part of the state, the coal area gets buried with Pennsylvanian rocks that are not as coal rich in the far west of the state.

  2. cope says

    I think that rather than feeding traces, those arcuate shapes are cross-sections of shells. The criss-crossy bits are, I believe, Fennestella bryozoans.

    Salem limestone (the official state stone of Indiana) was used in the building of many well-known structures including the Empire State Building. When I was in college in Illinois back in the day, one of our field trips was to a quarry from which the stone used on the Empire State Building came.

  3. says

    There’s a lot of similar fossil-rich ~Mississipian limestone near where I live (same formation? I don’t know these things). My siblings and I used to collect interesting bits of it on the beach every summer. We had at one point planned to make necklaces out of crinoid segments, though that never really happened. The rocks that are “practically a coquina”, bursting with shell fragments, coral, bryozoans, and crinoids, are some of my favourites. I love the way they evoke a busy, wave-roiled ancient seafloor.