Driving County Roads

An on line journal sharing my views. The content reflects my background as a rural person employed in agriculture and as a retired elected official of local government.

Sunday, April 20, 2008

OLDER THAN DIRT

Well almost! In a Kaolin Mine near Courtland, Minnesota lie fossil leaf specimens 95 to 97 million years old. Minnesota Valley Minerals operates the mine, which produces Kaolinitic clays, which are shipped to Springfield, Minnesota to the former Ochs Brick Company. (The company has recently changed hands and I am not sure of the name of the new owner.) Other clays from the mine are used by the Courtland Clay Company and are processed to produce ceramic and pottery clays.

In 1995 the fossil leaves were discovered at the mine site. The basal portion of the clay deposit at the mine is believed to be the Paleozoic “Eau Claire” formation, made up of red-green shales. This is overlain by an “unconformity” sand, which is possibly derived from the weathering of local sandstones and the near-by Sioux Quartzite. The cretaceous Kaolinitic clays overlay the “unconformity” sands. They are assumed to have been deposited at the margins of epicontinental seas or in deltaic systems related to low energy streams draining a continental landmass.

The fossil leaf specimens are imbedded in the kaolin clay. Dr. David Dilcher is a paleobotanist and fossil leaf expert at the Florida Museum of Natural History. He has placed the age of the fossil leaves to be approximately 95 million years old. This is near the time of the origin of flowering plants in Minnesota. The fossil leaves are found in “channel-like” structures in the kaolin clay deposit. Most are deciduous species belonging to the “angiosperms”, the highest order of the plant kingdom. Among the leaves found in the specimens are “Andromeda snowi” a relative of the rhododendrons; “Salix lesquereuxi”, a willow; Populilies elegans”, a populus; “Sassafras parvifolium”, a sassafras; and numerous others. Specimens of the “Pinus” species, the first known conifer or pine tree have been found.

In late 1999 Minnesota Valley Minerals, Inc. made the discovery of the first “shelled” creature, a clam, in the cretaceous strata on the site. This is a very important discovery, as it will help scientists learn more about the overall cretaceous environment. Dr. Dilcher continues to study this site. Minnesota Valley Minerals gives tours every year to schools and other groups. end

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