- UW Department of Geology and Geophysics
Silicified woods are common in the upper D1 (Paleocene – Puercan and Torrejonian) and D2 (Eocene – Wasatchian) sequences of the Denver Basin. Almost all derive from angiosperms. Woods from the upper D1 sequence are the second set of angiosperm woods described from Paleocene strata of the Rocky Mountain region. Wood assemblages from the upper D1 sequence differ from Paleocene wood assemblages of the San Juan Basin, New Mexico and the Big Bend region of Texas, indicating variation within the Western Interior. Lauraceous woods with oil cells are common in the Denver Basin assemblages while they are not known from the San Juan Basin or Big Bend. This initial survey suggests that the early Paleocene D1 (7 wood types) and early Eocene D2 (5 wood types) wood assemblages differ. Lauraceous woods with oil cells apparently are not common in the D2 sequence. The early Eocene Denver Basin wood assemblages differ from the early Eocene Yellowstone Fossil Forest wood assemblages in which conifers are common and phyllanthoid woods are rare. Growth rings are present but not well defined in the D1 and D2 sequence woods. The Denver Basin angiosperm woods are neither semi-ring porous nor ring porous, features that are common in present-day northern temperate forests and in angiosperm woods from the late Eocene Florissant Fossil Beds.