Friday, June 22, 2018


Panoramic view of Monument valley taken from the Visitor Center by Moritz Zimmermann.  Public Domain photo. 

I recently had the opportunity to visit one of the most fascinating places in the United States---the Red Rock Country along highways U.S. 163 and U.S. 191 in extreme southeastern Utah (but extending into northern Arizona).  At the time of my visit tourists were sparse and roads almost deserted.  However, the geology was well-exposed and landscapes were spectacular.  Although I had roamed the area in the late 1960s with a paleontologist friend looking for fossils, I had not returned until this year.  During this trip, time was not important and that fact allowed us to camp and travel at our leisure.

Originally, we entered Utah from the south via the roads crossing the lands governed by the Navajo Nation (Naabeehó Bináhásdzo).  The territory is a massive hunk of land (nearly 18 million acres) in southeastern Utah, northwestern New Mexico and northeastern Arizona.  Since I am a big fan of authors Tony and Anne Hillerman I was constantly on the lookout for "heros" and crime solvers Joe Leaphorn and Jim Chee.
Book cover courtesy of Cover artist Gail Burwen and Harper and Row, Publishers 1093
We actually entered the Navajo Nation on U.S. 89 near Cameron after traveling north from Flagstaff, Arizona. Near Tuba City US 89 continues on to Page and Lake Powell while U.S. 160 branches off and heads northeast to Kayenta where US 163 heads north into Monument Valley Navajo Tribal Park and Utah.  In fact, the Park encompasses parts of both Utah and Arizona with the information and visitor center in Arizona (although the Route 42 “turnoff” is in Utah). Visitor traffic is restricted in the park to specific roads, both paved and unpaved, so travelers should not go wandering off into well-marked restricted roads and trails.  There is a $20 fee to enter the main Park area and visitor center although travel on US 163 through the Park is free.  Campgrounds are available at the Visitor Center or along US 163.
Movie poster courtesy of Warner Bros. Pictures 1956.
As a boy growing up in the late 1940s and 1950s I was enthralled with western/cowboy movies especially those $.10 Saturday afternoon matinees. And my favorite actor was the Duke, John Wayne, a man who uttered my favorite quotes: Life is tough, but it’s tougher if your stupid.  My imagination of the “west” was inspired by scenes from the red rocks at Monument Valley and Kanab, Utah (southwestern Utah) or the forests and jumbled boulders in the Sierra Nevada mountains.  But perhaps Monument Valley scenes were the most deeply imprinted in my young mind!

The first major movie filmed in the Park was the iconic Stagecoach staring a then unknown actor by the name of John Wayne (1939) and directed by John Ford.  The movie cemented Wayne’s fame, and the scenery so impressed Ford that he filmed nine more movies in the red rocks with Wayne starring in four of these.  Although Stagecoach was filmed before my birth, the Black and White feature was a staple in the Saturday presentations.  By the 1950s color had arrived in the movies and I vividly remember Wayne riding through Monument Valley in the Searchers—filmed in wonderful Technicolor.

Here we go, the "stagecoach" traveling through "Apache Country." The Ringo Kid's (Wayne) rifle is big-looped Winchester Model 92 Trapper with the barrel chopped short.  In the real world, both Winchester and Remington chambered the gun for smokeless and high powered .44-40 ammunition.
Although I did not see the Duke on scene, I did observe some great geology.  The Monument is part of the Colorado Plateau Physiographic Province, an area or block of rather undeformed (not affected by major mountain building events) rocks.  In Arizona the block drops off (Mogollon Rim) into the mountains and valleys of the Basin and Range Province.  On the west in Utah and northwestern Arizona there is a Transition Zone that separates the Plateau from the Basin and Range.  The eastern boundary is defined by the Rio Grande Rift Zone to the south and features of the Rocky Mountains in the north.  The Uinta Mountains, part of the Rocky Mountains, represents the northern boundary.  It is interesting to note that the eastern, southern and western boundaries have huge accumulations of Cenozoic volcanic rocks.  More than anything else the Colorado Plateau exposes a great stratigraphic section of Pennsylvanian, Permian, Triassic and Jurassic “red rocks.”  The vast array of colors are due to iron oxides (red, yellow and pink), manganese (mostly lavender although black coatings), and unoxidized iron minerals (green and “purple”). Many of the country’s more famous national parks and monuments are in the Colorado Plateau. Monument Valley sits about in the center of the Plateau in a subsection named the Navajo Section.

Public Domain diagram, USGS.
Geologists are fond of referring to the rocks of the Colorado Plateau as “layer cake geology” since generally flat-lying sedimentary rocks are well exposed along the erosional streams and their large to small tributaries.  Sandstones often form cliffs and escarpments while the more easily erodible shales form valleys and “flat lands.”  This sort of landscape is quite observable in Monument Valley—but there are exceptions!  A few miles south of the Utah-Arizona border, and north of Kayenta, is a large and impressive landmark—Agathla Peak. The Peak is an erosional remnant of the throat of a volcano and the resulting igneous rock (minette) is composed of fractured volcanic breccia.  The igneous rock also welds together fractured sedimentary rocks of the Triassic Chinle Formation.  The Peak is a classic example of a diatreme, a volcanic pipe formed by a gaseous explosion that “shoots” the magma toward the surface.  In this case, the magma flew through the overlying Chinle Formation encasing fractured pieces of the sedimentary rock.  Geologists believe minette magmas originated in the upper mantle.  The igneous rocks probably solidified about 27 Ma and the Peak is part of the larger Navajo Volcanic Field of which Shiprock is the best-known structure.
Agathla Peak rises about 1500 feet above the desert floor.
Monument Valley is famous for its namesake monuments---spires and buttes and mesas with a common stratigraphic section.  The floor of the valley/park and the lower slope of the monuments is composed of the Lower Permian Organ Rock Formation.  The unit “consists primarily of pale-red, very fine-grained sandstones, siltstones, and limestone nodule conglomerates deposited in fluvial [stream] channels and on floodplains associated with north to southwest-flowing, meandering streams” (Stanesco and others, 2000).  Conformably overlying the Organ Rock, and forming the massive cliffs of the monuments, is the Permian DeChelly Sandstone, an aeolian (wind-blown) red sandstone composed of hematite-covered quartz grains.  The DeChelly erg (large area of dunes and sand sheets) was extensive and covered large parts of the Four Corners region extending from southeastern Utah into New Mexico and Arizona.  The end of the Paleozoic Era is represented by a slight unconformity between the DeChelly and the overlying Early Triassic Moenkopi Formation.  The latter caps most of the buttes and mesas and is composed of brick-red, fine-grained fluvial siltstone and sandstone. The Moenkopi also forms a slight slope that distinguishes it from the Shinarump Member of the Triassic Chinle Formation.  The fluvial conglomerate and sandstone is channeled into the Moenkopi on some of the monuments.  More “hidden” areas of the Park expose Permian rocks older than the Organ Rock and younger members of the Chinle Formation.  
Mitchell Meas near the Visitor Center.
The iconic West Mitten.
This is about the only road visitors may travel in the Park without a Native guide.  It starts at the Visitor Center, heads southeast around Rain God Mesa (not shown) and back to the Center. The three structures are West Mitten, East Mitten and Merrick Butte.

Monument Valley is a great place to stand on the balcony of the Visitor Center and easily identify geologic formations on the monuments---impress your friends! 

This Blog posting is about a month or so late. I don't have many excuses, and probably don't need any since I write for fun.  But, since my friends insisted: I was traveling across the west, writing four articles for the Rocky Mountain Federation Newsletter, spending over two weeks visiting friends and relatives in the Midwest, giving three presentations at an out-of-state rock and mineral show, hosting long-time friends at our home, cleaning up the yard, watching my grandson play rugby, watching my granddaughter smoke them in the 100 m, 200 m and 400 m, and getting knee and back injections.  As I noted in a previous offering, for this posting, I was camped at one of the most beautiful place in the U.S., Monument Valley in Navajo Tribal Park (southeastern Utah).  Not only is civilization unavailable, so are newspapers, television stations, internet service, telephone service and noisy railroads.  What is available are fantastic sunsets and sunrises, amazing red rock scenery, crystal clear night skies with a full moon, and a real quietness.  Life is good.


Stanesco, J.D., R.F. Dubiel, J.E. Huntoon, 2000, Depositional environments and paleotectonics of the Organ Rock Formation of the Permian Cutler Group, southeastern Utah in Geology of Utah's Parks and Monuments, D.A Sprinkel, T.C. Chidsey, Jr., P.B. Anderson, Eds.: Utah Geological Association Publication 28.