Canyon of Lodore, Green River. Dinosaur National Monument.
Moffat County, Colorado. 1871.
USGS Earth Science Photographic Archive digital files: hjk00500 and hjk0500a
The Canyon of Lodore cuts through an uplifted plateau, exposing strata of
the Uinta Mountain Group (dense sandstone and quartzite of late Precambrian
age, about 1 billion years). Downstream the river canyon cuts through progressively
younger strata including the Lodore Formation (Cambrian sandstone, about
525 to 505 million years) and strata consisting of limestone, sandstone,
and shale of late Paleozoic Age (about 350 to 250 million years). The dinosaur-fossil
bearing strata of Mesozoic age (250 to 65 million years) crop out along
the southern and western margins of this uplifted region and along the Yampa
River (but not in the vicinity of Canyon of Lodore). The mountain ranges
of the Rocky Mountain region (including the uplift of the Uinta Arch) occurred
in multiple stages of Laramide Orogeny (roughly 70 to 20 million years ago),
and uplift is still proceeding in the region. Younger sedimentary deposits
derived from the surrounding Laramide uplifts cap many of the mesas and
uplifted areas throughout the park region. |