WHEELER, E.A.* AND T.M. LEHMAN. Department of Wood and Paper Science, Box 8005, N.C. State University, Raleigh, N.C. 27695-8005. Department of Geosciences, Texas Tech University, Box 4109, Lubbock, TX 79409. - Woody dicots of the Cretaceous-Paleocene of Big Bend National Park, Texas.
Angiospermous woods occur throughout the Campanian Aguja Formation and
the Maastrichtian Javelina Formation. Dicotyledonous trees are most
abundant at the top of the Aguja and the lower part of the Javelina
Formations. One locality has logs and in situ stumps, with an average
spacing of 40 feet between each tree, and trees nearly 1 meter in
diameter. The Lower Shale Member of the Aguja contains platanoids,
Bombacoxylon, and a wood with generalized structure. In contrast to
other Cretaceous localities with dicot wood, Paraphyllanthoxylon is
not common. The phyllanthoid wood found at Big Bend is similar to a
species that occurs in the San Juan Basin, New Mexico. The vertebrate
faunas of the Fruitland and Kirkland Formations, New Mexico and of
Aguja Formation are said to comprise a “southern” fauna distinct from
the “northern fuana” of Alberta and Montana. The wood remains are
consistent with such provincialism. Most of the dicot wood types are
characterized by high proportions of parenchyma; close to 50% ray
parenchyma in one. Such high proportions would affect the mechanical
behavior of the wood. Javelinoxylon (a Malvalean-like wood) is the
dominant wood type of the Javelina Formation. Wood is very rare in
the lower part of the Paleocene Black Peaks Formation, but in the
middle and upper parts of the Black Peaks, Paraphyllanthoxylon
abbottii is common, and is the only wood type found.
Key words: Big Bend National Park, Cretaceous, Paleocene, wood