Geology Reference
In-Depth Information
over 1,500 feet long. Underground channels follow the
east-west direction of nearby Officer's Cave Ridge. As
the cave erodes, large slabs drop from the roof creating
an unusual display of rockfalls.
John Day Fossil Beds National Monument
The 14,012 acres of the John Day Fossil Beds
National Monument record the Cenozoic history of the
southwestern edge of the Blue Mountains. Travelling
to three different national park locations in Grant and
Wheeler counties, the visitor is treated to a fascinating
view of extinct animals and plants as well as a colorful
eroded landscape of volcanic and sedimentary deposits
of both the Clarno and John Day formations. Oxida-
tion of layers of ancient soils gives them a highly
varigated or multi-colored appearance.
The story told in the rocks here began when
volcanic eruptions of the Clarno entombed plants from
a tropical environment 44 million years ago. Only a few
large animals have been found from this period,
however. Beginning 36 million years ago, renewed,
explosive volcanic activity of the John Day episode
released great volumes of ash which covered and
preserved both plants and animals living in the ancient
grasslands and along waterways. The John Day beds of
the National Monument are famous for the many types
of cats, dogs, camels, rodents, and cow-sized rhinocer-
oses. Among these were the small, 3-toed horse and
the common oreodon. This was a sheep-like animal
whose skulls were collected by early Oregon pioneers.
The Metasequoia, or dawn redwood, was one of the
most prevalent plants encountered during the temper-
The pig-like entelodont, the delicate and deer-like
Hypertragulid, and the oreodons, the size of a
sheep, are among the fossil mammals found in the
John Day beds of eastern Oregon.
