Woods of the Eocene Nut Beds Flora, Clarno Formation, Oregon, USA

Abstract

E.A. Wheeler and S.R. Manchester, 2002, International Association of Wood Anatomists Journal Supplement 3, 188 p. (Softcover, US $45.00) ISBN: 90-71236-52-8. Although commonly called “petrified wood,” only in a few cases, such as the jasper-replaced Triassic fossil wood of Arizona, has wood literally been turned into stone. A better term is permineralized wood, because cell walls visible in thin section are the original cellulose and lignin of the plant, and it is only the space left by the decayed cell that is filled with preservative minerals, such as silica, calcite and pyrite. Well-preserved microscopic cell-wall structure is used as the basis for identification of different woods. More often than I would like, enthusiastic rockhounds have urged me to identify fossil wood for them. Like the nodule and thunderegg collectors convinced that they have found dinosaur eggs, usually permineralized wood collectors also are disappointed, sometimes annoyed, when I confess that I am unwilling to identify fossil wood specimens for them. Not only is the preparation of the requisite thin sections an unreasonable financial and physical effort for casual inquiries, but identification of woods is difficult and not for the faint of heart. Nevertheless several of my students and visitors have persisted with thin section preparation and computer keys (using Wheeler et al., 1986) to find a treasure trove …