Gregory, K.M., 1997, The late Eocene House Range Flora, Sevier Desert,
Utah: Paleoclimate and paleoelevation: PALAIOS, v. 12, p. 552-567.
Abstract.-- The late Eocene House Range flora is preserved
in a lacustrine limestone on the east flank of the House Range, located
at the western edge of the Sevier Desert, Utah. This flora is of special
interest because it is the first documented from the middle Tertiary of
western Utah, and it grew in the hanging wall of the proposed Sevier Desert
Detachment. The flora is dated as Chadronian on the basis of an associated
gastropod. This age determination is consistent with a single-crystal 40Ar/39Ar
date of 31.4 ± 0.5 Ma from a nearby outcrop of the Windous Butte
tuff which contains clasts of the limestone. Physiognomic analysis of the
fossil angiosperm leaves implies a mean annual temperature (MAT) of 13.2
± 1.5 °C and a growing season precipitation of 85 ± 16
cm. The vegetation was either notophyllous broadleaved evergreen or mixed
broadleaved evergreen; it is most similar to modern warm-temperate floras
from Japan. If the estimated MAT is compared to the coeval MAT at the coast
and a terrestrial lapse rate is applied, a paleoelevation of 2.8 ±
0.8 km is implied, compared to a modern elevation of 1.7 km. This paleoelevation,
if taken to be representative of regional paleoelevation, implies that western
Utah was higher than western Nevada and as high as central Colorado in the
late Eocene, but then collapsed to modern elevations during later extension.