Tampa Fossilized Coral

I have in my lab some fossilized coral from the area of the Wetherington Island site, which is located  just east of Tampa, Florida. The site is a major Paleoindian and Archaic quarry site that runs back from the north bank of an abandoned channel of the Hillsborough River. There are ancient quarry pits dug through a buried gleyed A horizon into the limestone marl, chert workshops where they heat treated the chert, and megafauna bones in the Paleoindian strata. The deposits of chert and chalcedony at the site are very rich. When the water in the creek is low, you can see a large chunk of modified bedrock chert sticking out of the riverbed. By modified, I mean it has been partly chipped away; it is covered in flake scars from knapping. Excavations at the site have produced literally tons of debitage (See Brown 2001 and references therein). A fair portion of the debitage is fossilized coral, which is presumably what archaeologists in the region call "Tampa Fossil Coral." The quarrying apparently intersected a fossil reef embedded in the Tampa Limestone Member of the Hawthorne formation.

Early today, I was showing some flakes of the fossilized coral to a colleague and, as always, it was difficult to see the skeletons of the coral animals in the rock. You can only see them when the flake or chunk has fractured perpendicular to the axis of the coral animals; then they appears as stars or asterisks in the chert. Out of frustration, I took some pictures of the flake with my digital microscope, and they came out surprisingly well, so I thought I would share them with the world.

First are a couple of pictures of the flake (ventral and dorsal) and then a few closeups of the ventral face. You will probably need to enlarge the photographs (by clicking on the thumbnails) to see what I'm describing.

Low magnification microphotograph of the ventral face of a fossilized coral flake. The skeletons of the coral animals are visible as star- or asterisk-shaped shadows embedded in the stone. This is not an archaeological specimen, but rather a modern, experimental one.

Low magnification microphotograph of the dorsal face of a fossilized coral flake. The skeletons of the coral animals are visible as star- or asterisk-shaped shadows embedded in the stone. This is not an archaeological specimen, but rather a modern, experimental one.

Close-up of the dorsal face of the specimen above.

Close-up of the dorsal face of the specimen above.

Close-up of the dorsal face of the specimen above.

Close-up of the dorsal face of the specimen above.

It is very lovely rock, which turns bright colors--red and orange--when heat treated. I think the coral animals are clearer in these microphotographs than in real life not only because of the magnification but also because I used polarized light. The flake was resting on a shiny white surface and it is possible that it reflected some of the incident light back through the specimen, which is translucent, creating enhanced visibility.

At least in North America, ancient lithic artifacts are made out of fossilized material, including fossilized (or petrified) wood, more often than one might imagine. 


Reference cited

Brown, Clifford (2001). The Fractal Dimensions of Lithic Reduction. Journal of Archaeological Science Vol. 28, No. 6, pp. 619-631. 

Knap-in

I took a couple of graduate students to a knap-in last weekend and my hands have almost recovered, but the shoulder I injured digging in Nicaragua last summer is still aching.

The Stone Age and Primitive Arts Festival was held in Ochlockonee River State Park, which is a pretty little park located in the Apalachicola River delta, southwest of Tallahassee in the eastern part of the Florida panhandle.

Ochlockonee State Park

It was a heck of a drive. Google Maps said it would be about 6 hours and 49 minutes driving time, but it took us much more--it seemed like 8 hours--even though there were no detours, construction zones, or traffic jams.

The nearest town, between our hotel and the park, was Sopchoppy. It's a small town that looks like it's down on its luck: a lot of stores are closed, some houses are abandoned, and some structures are collapsing. The town used to be a stop on a long-abandoned rail line that served the logging and turpentine industries. Since they dried up a century ago, Sopchoppy has been struggling. That why we were shocked but delighted to find that the only restaurant in town was superb. The Sopchoppy Pizza Company serves not only really excellent pizza but a variety of other tasty and creative dishes. It's housed in a nicely maintained historic building and the decor is fun and charming. It's immaculate and homey. Ironically, it is a far better restaurant than most of those in the affluent and sophisticated area where I live in Palm Beach County.

The two students I brought, Lana Ruck and Justin Colon, are both interested in lithic analysis. Lana's research focuses on determining handedness from debitage attributes. The evolution of handedness is important because it may be related to the evolution of language. Both are related to brain laterality and they are processed in similar and unusual ways in the brain. To test her hypotheses, which include attempts to replicate the results of previous studies that have claimed to identify handedness from debitage, she needs debitage from left-handed knappers. As it happens, left-handed knappers turn out to be as rare as Tea Party Communists. But there were several at the knap-in, and so Lana was able to collect some critical data.

Lana and Justin

Here's a sight you won't often see: two left-handed knappers.

Two left-handed knappers

Here's one of them actually knapping, with the copper billet in his left hand.

Left-handed knapping in progress

We spent most of our time just practicing. The many experienced knappers there were very generous in sharing their knowledge and experience with amateurs like us. I bought a couple of hundred pounds of nice chert from a vendor.  That was a significant motivation for attending, for me, because it's really hard to buy chert sight-unseen on the Internet and the shipping costs are prohibitive anyway. Because I drove up in a big SUV, I could carry back as much chert as I could afford to buy. I spent $500 on chert at $3/lb, which seemed to be the going rate. It's nice material: Georgetown flint from Texas, smooth as butter. I also picked up some useful knapping tools, such as pressure flakers. I have made these by hand in the past, but the ones on sale were nice.  It is difficult to assemble a good collection of tools, such as billets, flakers, and hammerstones, but the largest impediment to learning how to knap is obtaining a sufficient supply of good raw material to practice on. So, being able to buy a pile of chert was very important to me.

Here's our tarp with our knapping stuff on it, with and without grad students:

The tarp we bought for knapping

Justin and Lana preparing to knap

The weather was beautiful, cool, dry, and crisp. There were knapping contests (we only observed), demonstrations, and folk music. A fun time was had by all.

Interesting article on Lower Paleolithic Stone Toolmaking

Faisal, Aldo, Dietrich Stout, Jan Apel, and Bruce Bradley (2010). The Manipulative Complexity of Lower Paleolithic Stone Toolmaking. PLoSOne 5(11): e13718. doi:10.1371/journal.pone.0013718.

Related news release with a nice video.