Abstract Detail


Allen, Sarah [1], Jud, Nathan [2], Hatch, Haley [1], Berry, Keith [3].

Laramidian forests: New fossil wood data from the late Maastrichtian of Colorado.

The Vermejo Formation in the Raton Basin in Colorado and New Mexico preserves a diverse Late Cretaceous (~68 Ma) flora that grew near the margin of the Western Interior Seaway. Plant remains found in this delta-plain or coastal deposit include palynomorphs, leaves, and fossil woods. Previous investigations in the Vermejo Formation have revealed high angiosperm diversity based on fossil pollen and leaves; however only two species have been described from fossil woods and both are conifers. To better understand the canopy forming component of the flora, samples of permineralized woods that occur in situ (largest ~0.5 m in diameter) or as float were collected from the Vermejo Formation at Berwind Canyon in south-central Colorado. Thin sections were prepared of nineteen specimens using both standard ground thin sectioning and the cellulose acetate peel technique. Of the 19 specimens, 13 are conifers and six are dicotyledonous angiosperms. Growth interruptions are visible in the conifer specimens, but a clear distinction between earlywood and latewood is lacking. None of the angiosperm woods have distinct growth rings, which indicates limited seasonality. There are at least three angiosperm wood types. One is distinguished by mostly solitary vessels, scalariform perforation plates, and sizable rays with many over 1 mm high and more than 10 cells wide. Another type also has solitary vessels common with some groups of two, scalariform perforation plates, but rays are commonly 1–3 cells wide (rarely 5–6 seriate), and the fibers are very thick-walled. The third dicotyledonous wood type has vessels most commonly in short (2–3) radial multiples, simple perforation plates, heterocellular rays that are 1–3 cells wide, and abundant diffuse axial parenchyma. Fossil leaves (e.g., "Ficus" planicostata) also preserved in the Vermejo Formation will provide additional information about the taxonomic richness of the flora. Reports of angiosperm woods from Cretaceous deposits are sparse relative to Paleogene deposits, so new localities like Berwind Canyon provide important opportunities to expand our understanding of Cretaceous plant communities with woody taxa. Most records of Upper Cretaceous angiosperm woods in the Western Interior are from further south, both in the Raton Basin and beyond, including wood assemblages in Texas (Big Bend National Park) and New Mexico, U.S.A., and Mexico. The Berwind Canyon wood assemblage provides an opportunity to expand our knowledge of woody taxa during the Maastrichtian in the Western Interior, U.S.A.

1 - Penn State Altoona, 3000 Ivyside Park, Altoona, PA, 16601, USA
2 - William Jewell College, 500 College Hill, Liberty, MO, 64068, USA
3 - Hoehne School District, Hoehne, CO, 81046, USA

Raton Basin
wood anatomy
Vermejo Formation.

Presentation Type: Poster
Number: PPB003
Abstract ID:731
Candidate for Awards:None

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