The Book Cliffs of Utah cover a huge portion of East/Central Utah. The depositional period is in the Cretaceous, but time periods vary widely depending on your location. We entered Utah from the east and exited near Harley Dome (just west of rest area). From there, we headed north to old highway 6 which heads back to the east. The second dirt road leading north goes through miles of Mancos Shale. Some of the mesas in this area are capped by sandstones of the Mesa Verde Group. The fossils we found in the Mancos were poorly preserved, yet this is not the case further towards the sheer walls of the Book Cliffs where concretions and simple weather reveal fine specimens.
As we headed further north up Middle Canyon Rd., we entered the complex sandstones, coals and shales of the Mesa Verde Group. Our excavation efforts were focused on a fossil plant bench at a locality believed to be the Nelsen or Sego Sandstone Formations. (GPS coordinates: N 39*18.030'; W 109*17.859'; Elev. 5323'. - see map in Mesa Verde Group images below.) Analysis of the sedimentary structure at this fossil plant bench revealed a very fine- to fine sandstone, thinly laminated with finely-truncated cross-beds, subrounded, mostly beige/tan-to light gray material (with Araucaria & palm fronds mostly occurring in the tan/beige material; with some palm fronds being in the lighter gray material).
Mancos Shale is the prevalent formation just north of I-70 in the eastern
portion of the state. Vast square miles of the Cretaceous shale are
visible from I-70 up to the base of the Book Cliffs to the north.
We walked a creekbed in the Mancos, but our finds were limited to some
poorly-preserved & unidentified clams and other invertebrates.
Shale" for more images.
MESA VERDE GROUP
you head further north on dirt roads, the Mancos mesas are capped with
sandstones of the Mesa Verde Group. Continuing further north into
canyons such as Middle Canyon or East Canyon, you enter the complex Mesa
Verde Group. Based on preliminary research, we believe our 2nd excavation
locality on Middle Canyon Rd. is in either the Nelsen or Sego Sandstone
Formations. The bench quarry was 3-5 meters to the west of Middle
Canyon Rd and approx. 5-8 meters above the road on a distinct outcrop.
We immediately found many palm fronds here, then many specimens of Araucaria
(?) and other unidentified leaves. Little research or organized collecting
of fossil plants has been done in these formations of the Mesa Verde Group.
Most leaves or poorly preserved which makes identification nearly impossible.
And, unfortunately, species of Araucaria is very hard to differentiate.
However, we did find one well-preserved specimen which is now in the collections
at the Denver Museum of Nature & Science (DMNS). See "Mesa
Verde Group" for more images of our finds.
MESA VERDE GROUP
we arrived at the fossil plant locality in the Mesa Verde Group, we traveled
on the Middle Canyon dirt road through a private ranch. Just north
of the ranch, we observed many petroglyphs in the sandstone canyons.
Most appear to be authentic petroglyphs, yet others have been altered by
more "recent" graffiti. See "Petroglyphs
in Mesa Verde Group".
MESA VERDE GROUP
other images in the Mesa Verde Group, such as concretions and cliffs, see