Coon Creek Science Center: Collecting Cretaceous Fossils

cc-fossils-0391 — 70 million year old shell and its imprint in a clay matrix, collected at the Coon Creek Science Center.

Collecting the amazingly well-preserved Cretaceous molluscs and arthropods at the Coon Creek Science Center was an excellent way to learn about fossils and the geology of the Mississippi Embayment.

Consider: the actual shell of an actual organism that actually lived 70 million years ago; not the form of the shell, petrified in silica; not the silent imprint of ridges and grooves in the mud of some bivalve’s test, long dissolved by the silent flux of millenia of groundwater flow, although you can find those, too; but to stand in the daylight, on the gravel bar of a creek, and hold the actual shell of an actual marine organism that lived here when it was six meters under water.

When we got to Coon Creek, Pat Broadbent did her typical, excellent presentation, starting with the very basics question of, “What are fossils?” Apart from the aforementioned actual preserved shells, you can also find trace fossils, like, for example, where the imprints of the an organism is left in the mud while the shell itself has long dissolved away. They can be imprints, or molds of the shells. One of my students found the mold of a crab’s claw along the creek bed; the mud filling in the claw had solidified into rock but you could clearly see where the pincer once articulated.

Pat also talked about the Mississippi Embayment, which is the long, broad valley through which the Mississippi River flows.

Cretaceous-94Ma — The breakup of the supercontinent, Pangea. Notice how the North Atlantic Ocean is opening as North America pulls away from Europe and Africa. You can also see the flooded Mississippi Embayment. (Image from Scotese, C.R., 2002, http://www.scotese.com, (PALEOMAP website)).

When the supercontinent Pangea started to break up, North America pulled away from Europe and Africa. This created a rift that eventually became the North Atlantic Ocean. At about the same time, North America tried to split into two as a second rift was created, right where the Mississippi Embayment is today.

How the coastline of North America, has changed over the last 100 million years. The sediments at Coon Creek were deposited in the Cretaceous (black line). The current coastline is shown in blue. (Image from Wikipedia).

But the rift failed (Cox and Van Arsdale, 2007). It did, however, stretch and thin the continental crust enough to create a large inland sea running up the middle of North America. Over the 100 million years since, the rift formed, the Mississippi Embayment has filled in, first with oceanic sediment, but then with terrestrial sands and silts as the mountains to the east and west were eroded away and washed into the inland sea.

The layer of silt and glauconite clay that encases the fossils at Coon Creek is called the Coon Creek Formation. Pat was very clear that we should refer to this material surrounding the fossils as “matrix”. The “d” word was prohibited. These sediments were deposited while the sea still flooded the embayment. They formed a sand bank, several kilometers offshore.

I vaguely remember doing some research on glauconite a long time ago. Glauconite pellets are found in shallow marine waters, usually far enough away from the coastline so that sediment is deposited slowly, and it’s the finer materials, such as silts and clays, that are deposited. The water also needs to be deep enough to protect the fine sediment from the force of the waves. These are ideal conditions for clams, mussels, conchs, and their Cretaceous relatives.

A simple smear of the sediment across a microscope slide is enough to show that the matrix is has a lot of quartz. You need a microscope because the mineral grains are tiny, silt sized or smaller.

But the best part of looking at the slides is finding the microscopic fossils. They’re not as ubiquitous as you might think, but they’re there if you look. I found a couple of forams, a snail-like one and another that looks like a bolivina species.

What looks like a type of boliviana foraminfera. It's benthic, which means that it lives in the sediments not in the water. — What looks like a type of bolivina foraminfera. It's benthic, which means that it lives in the sediments not in the water. It is surrounded by silt-sized grains of quartz.

However, the smear slides came later. After Pat’s talk, she took us out to a small mound of matrix that had been excavated for sampling. Everyone grabbed chunks of matrix and pared away at them until they found something promising. These promising samples were wrapped in aluminum foil so we could clean them up under more controlled conditions.

Cleaning takes time and patience, so Pat showed us how to do it, and each student worked on a single sample. The main idea is to create a display of the fossil using the matrix as a base. The general procedure is to:

Use a small pick, paintbrush and spray-bottle of water, to wash and wipe away the matrix from the fossil.
Let it dry out well, which usually takes about five days.
Paint the entire thing with a 50-50 mix of acrylic floor wax and water. Pat recommends Future Floor Wax, but that seems to have been rebranded out of existance.
Repeat that last step three times (let it dry for about 15 minutes inbetween) to get a well preserved, robust sample.

After the instructions on cleaning, we broke for lunch. For most of us lunch could not have come early enough, not because we were particularly hungry, but because it was quite cold outside. Just the week before the temperature had been above 20 °C, t-shirt weather. Now students were clustering around a couple space heaters trying to ward off frostbite (or at least that’s what they claimed). I did offer that they could stay inside after lunch while the rest of the class walked along the creek, but no-one took me up on it. I don’t know if it’s specific to this group or just to adolescents in general, but if there a chance to walk through water, and get dirty and wet, they’ll take it no matter what the consequence.

Sandbar0389 — Students looking for fossils in gravel bar.

Walking the creek, pulling shells and molds out of the gravel bars, was the best part of the visit.

cc-group-boots-0390-b — Students standing in the creek, testing their rubber boots.

The water was shallow, not getting up above the shins, despite the rain showers of the preceding days. A few students borrowed rubber boots, which half of them proceeded to fill with water.

There were quite a lot of fossils. Some of the bivalves have really thick strong shells that not only survived the 70 million years since the Cretaceous, but being washed out of the matrix and tumbled down a stream bed with all sorts of sand and gravel. Some of the casts, like the aforementioned arthropod claw, are also pretty robust.

Shell0385 — Snail shell that's been in the ground for millions of years and then got washed out into a gravel bar.

A couple of the more interesting finds are the rather elongate tube like structures that are believed to be either fossilized burrows, or fish feces (coporolite). The material in the coporolite has been replaced by minerals, which is why it survived, but it still retains a little of the ick factor.

There’s an awful lot to learn at Coon Creek. I did not even mention the mesosaur skeletons that have been found there, but there is a nice IMAX movie, Sea Monsters, that’s a nice complement to the field trip because it’s set at the same time, and in the same marine environment as the Coon Creek Formation.

Cool and Wet, but Quiet

nt-rain-lake-0440 — Early morning rain drops fall on the lake at Natchez Trace.

It’s dawn, but the sun has not yet come up. Even when it does it won’t be able to break through the solid, low sheet of stratus clouds. Make that nimbostratus clouds, ’cause it’s raining. The light, forever-drizzle as the spring warm fronts push slowly, persistently, against the winter.

nt-cardinal-m-0446 — Male cardinal getting ready to protect his territory.

It’s cold, but the birds are out, and so am I. Impervious to the weather, two bright males compete for the attention of a female. She stands apart, as patient as the rain. The males chase each each other from tree to tree. Their intentions are overt, their challenges obvious; yet there is so much less tension than when primates interact.

nt-cardinal-0440-b — Studied indifference.

I appreciate their lack of subtlety.

I like rainy days. They bring back memories: of hard, tropical rain beating a pulsing, bass, asyncopation on a galvanized steel roof; of goalkeeping on a flooding field, where you could not even see the half-line, much less the other goal; of hiking the calmed streets of New York, dry and warm with the hood up on a bright orange raincoat.

The rain isolates and quiets the world. Though I enjoy our immersion trips, and really believe they are one of the best mediums for learning, I savor those few minutes of solitude each morning. Before the cacophony to come.

Coon Creek Immersion: Visiting the Cretaceous

Just got back from our immersion trip to collect Cretaceous fossils at the Coon Creek Science Center, and hiking in Natchez Trace State Park.

It was an excellent trip. Despite the cold, Pat Broadbent did her usual, excellent job explaining the geology of Coon Creek and showing us how to collect and preserve some wonderful specimens. Back at the cabins, we looked at some of the microfossils from the Coon Creek sediments (and some other microscopic crystals); similar fossils can tell us a lot about the Earth’s past climate.

Back at the Park, we traced a streamline from the watershed divide to its marshy estuary, and cooked an excellent seafood dinner as we learned about the major organ systems.

cc-red-snapper-01 — Dinner was delicious.

Our trip was not without difficulties, however. The group learned a bit more about self-regulation, governance and the balance of powers, as a consequence of “The Great Brownie Incident,” and the, “P.E. Fiasco.”

We were also fairly well cut off from the “cloud”: no internet, and you could only get cell reception if you were standing in the middle of the road in just the right spot in front of Cabin #3.

But more on these later. I have some sleep to catch up on.

View Coon Creek Immersion in a larger map

Trail of Tears State Park in Missouri

trail-of-tears-outlook-panorama_b — View over the Mississippi River from the scenic outlook in the Trail of Tears State Park. The outlook juts out over rocky bluffs, which allows you to see the flood plain across the river.

Driving through Missouri last week, I stopped at the Trail of Tears State Park, which may be an excellent place to study the post-colonial history of Native Americans (perhaps as part of our civil rights discussions), and observed the Mississippi River and its flood plain before it becomes engorged at its confluence with the Ohio River.

In 1830, President Andrew Jackson passed the Indian Removal Act, which called for the removal of American Indians living east of the Mississippi River to relocate west of the Mississippi River. …

While some of the Cherokees left on their own, more than 16,000 were forced out against their will. In winter 1838-39, an endless procession of wagons, horsemen and people on foot traveled 800 miles west to Indian Territory. Others traveled by boat along river routes. Most of the Cherokee detachments made their way through Cape Girardeau County, home of Trail of Tears State Park. While there, the Indians endured brutal conditions; they dealt with rain, snow, freezing cold, hunger and disease. Floating ice stopped the attempted Mississippi River crossing, so the detachments had to set up camps on both sides of the river. It is estimated that over 4,000 Cherokees lost their lives on the march, nearly a fifth of the population.

–Missouri Department of Natural Resources: Remembering an American Tragedy

The small museum at the main park building does a very good job of trying to dispassionately tell the tragic story.

View Trail of Tears State Park, MO in a larger map

trail-of-tears-nature-walk — Taking a break on the Nature Walk behind the park's museum.

There’s a short, 1 km nature walk behind the building that was nice on a beautiful, sunny day in early spring. Warm, with the trees just barely beginning to bud you can get a feel for the ridge-and-valley topography of the park, which is in stark contrast to the flat floodplain of the Mississippi on the other side of the river. The park’s roads weave up and down the ridges, and I wished I’d had my bike with me.

riverside-campground-barge — Barge going downstream on the Mississippi River, past the river-side campground.

This early in the year (mid-March) most of the campgrounds in the interior of the park seem to be closed, but there is one down on a beach of the Mississippi River that was empty but open. This one has electrical hookups which is not a bad thing if you have the place all to yourself.

The scenic outlook is a wooden platform that juts out through the trees so you can see across the Mississippi to the flat floodplain and farmland beyond. Sitting on a cliff of sedimentary rock (it looked like limestone from a distance), the outlook is high enough that you can just make out the shapes of old meander bends and ox-bow lakes.

It’s a small park, probably worth a visit for the museum, and the outlook is nice, but probably not somewhere you’ll want to spend the night unless some of the upland campgrounds are open.

The museum’s focus on the relocation of the Cherokee would be a nice followup to the pre-Columbian focus of the Chucalissa Museum in Memphis.

cape_giradeau-river-wall — Cape Girardeau River Wall.

If you’re looking at river processes, you’ll probably also want to stop in Cape Giradeau, which boasts a fromidable wall to protect the downtown from the Mississippi River’s spring floods.

Limestone Trails at Montgomery Bell State Park

View Limestone Bed Hike at Montgomery Bell in a larger map

This short hike that follows a limestone bedded creek, will likely take a while because there’s quite a bit of geology to see.

mont-bell-0214s — The start of the hike is on the eastern side of the bridge between the villas and the hotel. Head north (left in the image) toward the lake.

This year, it was on a chilly, rainy morning in February, that we started on our hike. We took a left off the concrete stairway onto the trail that runs parallel to the river flowing in the ravine just below our cabins.

We’d stayed at the villas at Montgomery Bell State Park, which is about an hour east of Nashville. The villas are quite nice. Built into the side of the valley, sitting just across a small river from the park’s hotel/conference center, and designed to be energy efficient, they’re quite comfortable with their geothermal heating and vaulted ceilings.

They’re so nice that some wanted to stay in the warm. Others, however, were eager to get outside, despite, or perhaps even because of, the rain. I gave them the choice, but everyone came.

With the rain, we soon ran into trouble. Runoff from the road and building uphill converted part of the trail into a small stream. The first few brave souls committed to wet feet, and waded through.

mont-bell-0199s — The dam and lake at Montgomery Bell.

But the stream along the trail did not last long. Pretty soon we left it behind, and coming out of the valley the lake and dam opened up to the right and left. Though it had been raining for much of the previous night, the lake was still very low after the dry autumn and winter. The line of grass that marks its usual shoreline was over a meter above the level of the water.

mont-bell-0198s — Short concrete wall that acts as the outlet level for the dam.

So we crept along the southern edge of the dam to follow the path of the overflow channel. It was quite interesting to see the sediment and debris that choked the reservoir side of the concrete wall that regulates the level of the lake. The other side of the wall, where the water must accelerate as it overtops the barrier, was clean, bare and smooth, looking a lot like concrete until you get close enough to see that it’s hard, dark, limestone bedrock.

mont-bell-0208 — Drill-hole with radial shatter pattern.

But not hard enough. Small, round holes pockmark the rock. Clearly artificial, with radial cracks diverging from the center, they remind me of Sarajevo roses.

They’re probably contemporaneous with the building of the dam. In order to have their outflow channel, the dam builders needed to blast away some of the rock, so they drilled holes and filled them with explosives. The blasts crushed the upper layers of rock, but the bedding plane, upon which we are walking, dissipated the force and remained, mostly, intact.

mont-bell-0216s — Following the reservoir outflow channel.

The bedding plane is a bit slippery with the rain and light coating of moss, so we take a bit more care with our footing. The sides of the outflow channel are steep, with nice exposures of horizontal layers of limestone rocks.

Though I don’t go into it in detail, the different layers, with their different colors, hardness, and fossils, show the changing environment in which the sediments that created these rocks were deposited. The more friable, tan-colored layers were likely formed at a time when sea-level was lower, when this area was closer to the coastline so more sand and clays could settle out of the muddy waters emerging from fecund deltas. On the other hand, the dark, dense, grey limestone rocks are much more typical of deeper seas, offshore environments.

mont-bell-0219s2 — Tree roots prying apart the bedrock: biological weathering.

I did take the time to elaborate on the topic of weathering when my students pointed out the tree growing on the side of the cliff, with its roots entwining and pulling apart the limestone rock. It’s a part of the rock cycle that we had not spent a whole lot of time talking about in the classroom so I was glad for the opportunity.

mont-bell-0224s — Joints in limestone. Notice how the layers on either side of the joint line up.

Weathering also plays a part in the widening of joints, and the joints we saw were obvious and important in shaping the course of the channel. Joints are simply breaks in the rocks. When this region was uplifted, the rocks were squeezed and fractured by tectonic forces. There was not enough tectonism to seriously deform the region, the rocks are after all still close to horizontal, but they did break, creating joints that cut right through the bed of our channel and straight through the wall.

You’ll notice that the layers on either side of the joint line up, so this is just a fracture in the rock. Often, the rock will break and one side will be pushed up relative to the other; that would be considered a fault.

mont-bell-0225s — Runnoff from the rain, flowing along and widening joint in limestone.

One of the nice things about being out in the rain, was that you could see the water in action. Gliding along the joints, picking up and eroding small pieces of debris, while slowly, imperceptibly, dissolving away the rock and enlarging the joints. It’s the same process that created the caves we saw last year at Merimec; the reprecipitation of dissolved calcium carbonate from the limestone rocks is what creates the stalactites, stalagmites and other cave formations.

mont-bell-0226s — Looking up the channel at exposed bedding planes and joints.

It took a bit of care to follow the channel down. It also took teamwork. We’ve been practicing all year and it’s under these conditions that all the teambuilding, from the challenge course onward, really pays off.

mont-bell-0229s — Committing to wet feet.

At the bottom of the bedrock traverse was a big puddle. The water from the regular outflow of the dam creates pushes up sediment that blocks the free flow of the runoff from the current rainfall. Undoubtedly, this gets washed away when the reservoir overflows through the outlet channel, but today there was just a big puddle.

Here we faced a choice. We could have taken a hard right and walked back up to the dam along the edge of the small cliff that overlooked the outlet channel we’d just come down. It’s a nice walk, through last year’s leaf litter, and the overhang is just high enough to provide a small taste of vertigo. But the students wanted to push on, past the confluence, and follow the stream downhill. A second set of students had made the full commitment to wet feet, and any initial reluctance to be outside on a rainy day had disappeared. We followed the stream.

mont-bell-0234s — Convergence of the overflow channel and the drainage stream for the reservoir.

Just a few meters downstream from our decision puddle, we ran into the confluence of the regular outflow from the dam and the ephemeral, rainfall driven stream we’d been following. It’s a good place to talk about tributaries, deltas, and sediment transport, deposition and erosion, because the channel deepens into a little pool with lots of small scale features.

Past the confluence the stream straightens out. It’s remarkably straight. If it weren’t for the fact that we’re in limestone rocks, it would be easy to assume, given the dam and all, that the lack of sinuosity is artificial. But it seemed like the stream was flowing parallel to the joints we’d seen earlier, so it’s not unlikely that the water is following a fracture in the rock. When convergent, tectonic forces fracture rocks, the rocks tend to break at an angle to the direction of the forces (somewhere around 60 degrees to the direction of the forces, if I remember correctly).

mont-bell-0255s — Climbing up to the trail that follows the ridge.

Following the stream brought us close to the picnic shelter near the entrance to the park. Just across the water is a pathway up the rocks on the side of the valley that takes you up to the trail that follows the ridge that parallels the valley.

mont-bell-0262 — Looking down at the stream and its floodplain from the top of the ridge.

It’s quite peaceful, standing on the ridge while water droplets drip through the sparse winter canopy, with last fall’s leaf litter beneath your feet.

Looking back down into the valley you could see (and talk about) the stream and its flat flood plain. It’s a chance to anthropomorphize. The stream “wants” to meander. It has to be constrained to one side for a reason.

mont-bell-0270s — Crossing the dam on the way back to the cabins (upper left).

The ridge trail takes us back to the reservoir and dam, which are quite noticeable if you’re paying attention. We traipsed down the hill and walked a narrow path between the tall, reddish-tan grass that tops the dam, and the bouldery rip-rap that protects the earthen structure from the force of the waves.

We could see the villas ahead of us.

Memories in the fire

1

I decided that we would read our memoirs, the ones my students had been working on for the last five weeks, on our immersion trip down to Mississippi. The idea of sitting around the fire, sharing memories was just too enticing to pass up.

I was a little surprised that no one objected, or even hesitated, when I made the suggestion the week before. We’d just come in from soccer and I was trying to figure out how we’d fit the projects, the tests and the presentations into the time we had left. There was a precedent. They’d read their first stories, the ones from the orientation cycle, on our first immersion and that had worked out well because it had given us an entire afternoon to have a great discussion. They seem actually to look forward to, what’s come to be called, “Teatime with Doctor.”

“What if,” I asked, a little quietly to one of the 8th graders, who’d been on the challenge course immersion the year before and happened to be walking by, “you read your memoirs around the campfire on immersion?”

“Yes.” Declarative and succinct. I raised an eyebrow, but he just continued on his way. I was a little surprised he did not have more to say. I’m always surprised when my students don’t have more to say. My students can be quite loquacious given any opportunity, and this one in particular tended to have strong opinions that he was usually more that willing to share.

The discussion with the rest of the class took barely longer. The larger the group, the more likely you are to have people who need to think out loud, but there were unanimous thumbs up in less than two minutes.

I think that there’s some primal need that gets stirred up by even the thought of sitting around a fire and sharing stories. Of course this plan of action also fulfilled that other fundamental need of the adolescent, the need to procrastinate.

II

We get to Camp H., have lunch, and an afternoon of community building games. Lamplighter’s been working with the camp leader here for years and Ms. A’s impressed by how well this group works together. No surreptitious sabotage, no subtle denigration, no stubborn unwillingness to participate.

We talk about the group, she and I, as we walk back to the cabin, red gravel crunching under our feet, oak leaves turning color overhead, and myself getting slightly out of breath on the last climb. I’m perhaps a little more impressed than she is because I can see the conflict in those by now familiar faces; glimpses of of baser instincts being overruled by the prefrontal cortex. It is a sight that is ambrosia to the middle school teacher.

I get back to our cabin and I find V., one of the two students I’d promised they could get the campfire going.

“Are you guys getting the fire started?” I ask.

“We’re just going to play football for a little while, then start on the fire,” he replies. V’s been our main supervisor for Student Run Business this cycle and it shows. He’s been breaking out his calm, clear, confident, supervisor voice on the challenges all afternoon.

“We have half an hour until dinner and it will probably be dark afterward,” I say.

He just nods, seething competence.

It’s 5:45 and they’re still playing football. I look at my watch more and more frequently. I’m not going to remind them of what they have to do. We’re Montessori after all.

Two of the girls start working on the fire pit. Aha, I think to myself, this is going to get interesting. I saunter outside and my path nonchalantly takes me down to the fire pit. I suggest more kindling, they never get enough kindling. The boys realize other people are working on “their” fire.

Dissension in the ranks. Conflict. I tell them they should work together. Harsh words are spoken. A covenant broken. The poignant cry of impassioned idealism, “injustice”. Things fall apart; the center does not hold; Bethlehem is apparently somewhere on the other side of the playing field.

Ten minutes later it’s time to go to dinner, but first it’s time to rebuild, time to remind them of the covenant they came up with that very afternoon, time to have a short, quiet talk about the use of language.

Over dinner the laughter starts up again. I’m at the other table with Ms. A and her family, all of whom work at the camp in some degree or the other. After the last fifteen minutes I’m extra impressed by the calmness of her teenagers.

When we get back to the fire pit the laughter is perhaps a bit too loud, but the group seems back together again. The fire is started without recrimination (eventually because they did not have enough kindling).

We sit around the fire, reading stories, finding issues, being helpful writing partners, and learning how important it is to be critical, brutal even, to our own work. There are some really good writers in the group, and there’s nothing better than learning from your peers.

“Can we put our memoirs in the fire when we’re done?”

“Sure,” I say. Sharing our writing is supposed to be a celebration. Something strikes me as just about right about liberating these memories in flame, letting them take on a new, ethereal life. Burning pages in dancing flame, marking the putting away of cherished, childhood things; an adolescent rite of passage.

As the last few stragglers work on putting out the fire I sit there, on a cool fall night, thinking about cycles and the seasons. I wish I was on the beach, watching the tide come in, small waves advancing and retreating, bigger waves pushing them farther from time to time, every time a little closer to where they need to be.

Classroom culture

One of the most powerful aspects of a multi-aged classroom is the institutional memory that develops and makes learning a whole lot easier than starting off, every year, from scratch. All the aches and toil of last year did not just disappear when the new crop of students started. The new kids look to the older students for cues about how to behave and it has been saving me a whole lot of time and energy.

That’s not to say that bad habits don’t persist too. But having a slew of new students mixes things up enough so that even the returning students are receptive to some change.

So now I have a bit more time and energy that I can now put into new projects and tailoring the curriculum to make life a little more interesting for one and all.

Well we’re on our first immersion now and I’m getting a little reflective. Probably because it’s close to 2 am and they’re still not asleep.