FarWest Geoscience Foundation

Paleobotanical Field Trip To Sailor Flat, California

David Lawler (upper center, with back to camera) and Dr. Diane Erwin (along slopes, bending to examine a fossil specimen), Collections Manager of Fossil Plants at the University California Museum of Paleontology, show the group what they're especially after--fossilized plants that reveal most if not all of the leaf margin, with excellent venation; other prized items from the chocolate shale deposits include beautiful examples of the original cuticle, which is that thin wax coating on the upper epidermis of leaves that helps protect against excessive water loss, mechanical injury, and fungal attack. In the Middle Eocene chocolate shales, exposed by hydraulicking methods during gold recovery, the original cuticle is locally quite abundant, appearing as a thin wax paper-like material that easily peels off the matrix upon direct exposure to the air; for this reason we were instructed to wrap it with urgent immediacy in tissue paper to prevent any loss of the invaluable substance--a genuine rarity in the fossil record. The fossil-bearing chocolate shales at the Sailor Flat locality are roughly 10 feet thick--anywhere from twice to three times the usual thickness observed at many of the abandoned hydraulic mines in the northern Gold Country of California.

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