Weber Sandstone
The pale, cross-bedded Pennsylvanian-Permian eolian sandstone that forms the great walls of Split Mountain and Whirlpool Canyon — the cliff-former of Dinosaur country.
Also known as: Weber, Weber Quartzite
Paleozoic — ancient sea life, from the first shells to the first forests
The world back then
Late Pennsylvanian into Permian, about 305 million years ago. Another great sand sea, this one with ponds trapped between the dunes — pale, cross-bedded desert deposited as the sea drew back, wind stacking it thousands of feet deep. Hot, dry, and endless, with the occasional lime-crusted pool. A frozen erg in the making, up in Dinosaur country.
That desert is the pale wall of Split Mountain, and the Green River saws right through it while you ride along. The dunes went on for ages; the river cuts them like they're nothing and hands you the tour. More petrified dunes, more absurd luck — it never stops being a good deal.
Recognize it in the field
- Typical color
- white to light-gray or buff
- Weathers as
- The principal cliff-former of Dinosaur NM — massive cross-bedded walls (Split Mountain, Whirlpool Canyon).
- Grain
- fine- to medium-grained, well-sorted quartz arenite
Look for
- large-scale eolian cross-bedding
- white/buff quartz arenite (quartzite where indurated)
- interdune-pond carbonates and marine interbeds at the base
- the big cliff-former of the Uinta canyons
- vertebrate trackways reported
How this rock was made
A Pennsylvanian-to-Early-Permian sand sea deposited as the sea receded.
The setting: wind-blown dune sea (eolian erg) (sand sea) with interdune-pond carbonates
~1,000 ft as the cross-bedded quartz-arenite body at Dinosaur; ~3,000 ft at the type section (upper Weber Canyon).
In the rock record
↑ Younger — rests above
↓ Older — sits beneath
Where to see it
Regions: Uinta Mountains (Middle Rocky Mountains province; NPS files Dinosaur NM under Colorado Plateaus)
- Split Mountain and Whirlpool Canyon walls (Green River, Dinosaur NM)
Float past it: Split Mountain · Whirlpool Canyon