Mayfield, KY Field Trip

Bald Cypress leaf

The KPS took a field trip to far western KY near the Mayfield area. The purpose of this trip was to visit several quarries which mined clay and learn a little about the ball clay industry. This clay is used in many ceramic products such as toilet bowls and tanks, sinks, refractory materials, floor tiles, ceiling tiles, etc. Also, potters clay is made from these deposits. Almost none of the clay mined is used "as is". It is blended with other materials (such as kaolin and talc) before it is made into the final products. We got to see core samples and test equipment in a modern clay testing lab at one of the sites (Old Hickory). These facilities test core samples for all the required properties before any of the clay is actually mined.

The clay mined is from the Claiborne Formation, which is Middle Eocene in age. These are not marine deposits. In fact, any marine influence on the clay destroys the chemistry of the material, and makes it unsuitable for mining! Some of this clay is quite fossiliferous. Plant fossils are exquisitely preserved in the clay. A particular clay called the "Lamkin Clay" has the best fossils. We collected clay fossils in a clay barn, where different types of clay from different deposits are stored in big piles out of the rain, and then processed. The processing included a grinder that reduced the clay chunk size to about 1.5 inches, a powdering operation, a slurry making tank, and a bagging operation. Almost any piece of Lamkin Clay split in half had plant fossils. They were exquisitely preserved, but after a short time, as the clay dried out, the fossil leaves would crumble to dust! We tried to spray the fresh leaves with hair spray. This was only marginally helpful. If a fossil was sprayed with many coats, and the hair spray could soak into the clay, then the leaf was stabilized pretty well. Probably the best way would be to dip the specimen in some sort of solution that would soak in to the clay and prevent it from shrinking as it dried out (in addition to bonding the leaf to the clay). Of course, we were not prepared for this! A second trip on the same day was to a quarry mining the same types of clay. They had to remove an Eocene overburden layer of waste clay that was loaded with lignitized wood pieces and logs. This material looked remarkably like fresh wood (and has even been known to catch on fire spontaneously in the quarry). All in all, this was a very enjoyable trip, and the collecting was very different from our usual Paleozoic expeditions.

Big Hill


The KPS took a field trip to the giant roadcut in Big Hill, KY. It is located on Rt. 421 in extreme southern Madison county. It exposes Mississippian strata with the Borden Formation at the bottom (Early Mississippian) and the Paragon Formation at the top (Late Mississippian). Typical Mississippian fossils can be found including partial crinoid calyxes, ammonoids (and even an occasional fish bone) in ironstone nodules, blastoids, Archimedes bryozoans, horn coral, brachiopods, shark teeth, and gastropods.