Skip to main content

Morrison Formation

Commonly cliff-forming, cross-bedded sandstone lenses alternating with slope-forming siltstone, mudstone and shale. Colors are highly variable, and include greenish gray, reddish brown, pink, white, and purple. Sands were deposited by braided streams with finer sediment representing overbank or lacustrine deposits. (145-160 Ma)
State Arizona
Name Morrison Formation
Geologic age Late Jurassic
Primary rock type mudstone
Secondary rock type sandstone
Other rock types siltstone; conglomerate
Lithologic constituents
Minor
Sedimentary > Clastic > Mudstone (Bed)
Sedimentary > Clastic > Sandstone (Bed)
Sedimentary > Clastic > Siltstone (Bed)
Incidental
Sedimentary > Clastic > Conglomerate (Bed)
Sedimentary > Chemical > Chert (Bed)
Sedimentary > Carbonate > Marlstone (Bed)
Sedimentary > Clastic > Mudstone > Claystone > Bentonite (Bed)
Sedimentary > Clastic > Mudstone (Tuffaceous)
Sedimentary > Clastic > Sandstone (Tuffaceous)
Sedimentary > Clastic > Siltstone (Tuffaceous)
Map references
Richard, S. M., Reynolds, S.J., Spencer, J. E., and Pearthree, P. A., 2000, Geologic Map of Arizona: Arizona Geological Survey Map 35, 1 sheet, scale 1:1,000,000.
Unit references
Richard, S. M., Reynolds, S.J., Spencer, J. E., and Pearthree, P. A., 2000, Geologic Map of Arizona: Arizona Geological Survey Map 35, 1 sheet, scale 1:1,000,000.
Blakey, R.C., 1989, Triassic and Jurassic geology of the southern Colorado Plateau, in Jenney, J.P., and Reynolds, S.J., editors, Geologic evolution of Arizona: Arizona Geological Society Digest 17, p. 369-396.
Counties Apache - Coconino - Navajo