Lockwood has come up with a sexy topic for this month's Accretionary Wedge — yes, you guessed it (or already knew): Sexy Geology. For the record, Lockwood has defined "sexy" as:
I mean geology that makes your heart race, your pupils dilate. Rocks and exposures that make you feel woozy and warm. Structures and concepts that make your skin alternately sweaty and covered with goosebumps. Places you've visited, read about, or seen photos of that make you feel weak-kneed, and induce a pit in your stomach.
I'm in a bit of a rush these days it seems, and so I'm just going to post a couple photos of some geology that always turns me on, and two links to related posts from earlier this year. Beds and bedding are always of interest to geologists; cross-bedding is best.
I didn't know we were going in search of cross bedding the day we decided to circumvent downtown Zion Canyon (a place you can get to via shuttle, a Red Pass, by bicycle, or on foot), to take the side road under and over the mountain: the Zion–Mount Carmel Highway. I remembered from long ago, and indeed the Zion Canyon Map confirmed, that an overlook trail takes off back towards the canyon just past the main tunnel, a tunnel that is 1.1 miles long and was built in 1930 (Google Maps Street View of the tunnel near the first window). I had very little memory of the trail, other than that it provided an overlook of the lower part of Zion Canyon.
The trail is entirely in (or on) the Jurassic Navajo Sandstone, a thick dune sand recognizable in cliffs from miles away. I smiled the entire length of the trail and back: I think it was the cross-bedding. The hike may have stirred some sentimentalsentiments (about these cross-bedded sediments), but if so, the stirred memories are buried too deep to make a difference to me today.
The trail is a 1 mile round trip with a total change in elevation of 163 feet. It's rated as moderate, mostly because of some narrow passageways and long drop-offs. Handrails are provided in particularly steep parts and where drop-offs are particularly dangerous or where the trail is narrow or slippery. At least one person has died after falling 400 feet from the end-of-trail overlook. The trail begins in a set of steep stairs carved into a pale orange part of the Navajo. Views are everywhere stunning. A leaning tree frames the fore trail. Looking back under the leaning tree provides a view of the ever-present cross bedding. A somewhat narrow part of the trail has a small seep near the base of a sandstone cliff. Cross bedding! The trail, hidden by trees at the base of the cliff, goes on beyond a little embayment in the canyon. More cross bedding, a little below the previous shot. Rocks are perched in a manganese-stained gully. The trail — becoming a boardwalk hung over a hundred to two hundred feet of air — is about to enter a small alcove or cave. Water seeps all along the base of the overhang, drips down the back wall, and drips from the ceiling. The air was already cool before we entered the cave, possibly not quite 70° F; inside the cave it was cooler and damper, probably a great place to hang out in the heat of summer. For scale, you can see footprints in the foreground on the sandy floor; the height near the farthest shade-sun boundary (with tree to the left and rocks to the right) is about 12 feet. An inset arch can be seen from the cave, across a slot-canyon portion of Pine Creek. The trail is still hidden by trees. Now we're walking along a narrow ledge cut in sandstone, just above this Indian paintbrush. Looking back toward the trailhead and the bridge coming out of the mile-long tunnel, we can see the slot-canyon portion of Pine Creek. MOH said he could see the bottom of the canyon with binocs. The rocks on the bare sandstone in the lower part of this photo are the same rocks perched on cross beds from six shots back (second of two cross bedding photos before the cave). The rocks will someday plunge into the slot canyon below. While taking a little side trail, we came upon a small herd of six to ten Bighorn Sheep, ewes with at least two lambs. A lamb amongst the cross beds. After a little less than an hour of moseying along, we arrived at our destination, the canyon overlook above The Great Arch (MSRMaps location, Google Maps photo).
NOTE: This post is part of a slow-to-develop geoblogospheric meme: SentimentalSediments, started bravely by Dana over at En Tequila Es Verdad. Entries are supposed to be about your favorite sedimentary rock or sedimentary structure. As a hard rocker, I had a hard time thinking of any particular sed rock I'm actually sentimental about, but the whole of red rock and canyon country in the southwest contains my favorite sedimentary rocks and favorite stratigraphy, with any sentimentality on my part dating back to 1971 or 1973. At first I didn't think I had any digital photos from the area, but I have some from Fisher Towers and the San Rafael Swell. Now I also have some from Zion. :)
Stewart, Michael, 2006, Zion National Park: University of Illinois, Geology 104, Geology of National Parks and Monuments, Course Lecture Material (web only).
You can camp at Fisher Towers, and I have camped there, although maybe not in winter. They have a campground up near the cliffs, just below the trailhead parking lot. I've camped there, a long time ago, not alone, maybe just once. I've camped at Fisher Towers since that long ago time, at least once, maybe more than once, alone or with one dog. When camping, I don't always like to camp in set-up campgrounds where other people are nearby, almost hovering. It depends on the campground; it depends on my frame of mind.
The main time I remember camping outside the campground, that time with one dog [link not accessible on 11Feb2012], I camped on the small hill you see in the photo above and below. I camped inside the back of my truck, a different truck than the one I have now, a light green Ford with a nice Caravan camper and good setup in the back for sleeping and storing things. The dog liked to sleep on the floor of the truck bed; I slept above in a raised plywood bed. Here's the little two-track road to the top of the hill upon which I once, at least once, camped. The view from the top of the hill was 360, with cliffs and sky all around, the towers behind. The road to said former campsite is now closed. That is the way of the west at present. I can see closing this road to vehicular travel, but don't really get closing it to camping. No tents, the sign says! Probably one can just walk off around the hill to another hill and find another site, if one does not want to camp in the company of strangers. I, myself, will probably drive up some other side road the next time I come here, but will also consider camping in the maintained campsite if it is not too crowded and not too noisy. The road in and out of Fisher Towers is made of red dirt, which can get mucky or slippery in the snow and mud of winter. Here, it crosses a red sand wash on the way out from the towers. As you can see, the sand wash to the right is also closed, this time specifically to motor vehicles of all kinds. I recommend paying attention to this sign. Walk, if You want to Go Down There! [It reminds me of Little Big Man: "You go down there," he says to Custer.] The sand wash to the left, more or less back towards the towers, does not have the same sign, and shows at least one set of tracks. Someone probably removed the warning sign, or maybe this is supposed to be a travelway. Again, I recommend walking, unless you happen to have an actual road map. What I find more interesting than the truck tracks, however, is the patterns made by the red sediment - clay, silt, sand, and gravel - when it was deposited by snowmelt water, a rainshower, or a tiny flash flood: mini-alluvial fan-type deposits, little eroded stream channels, and an overall braided to rippled texture.
The Carnival of the Arid is now scheduled to be a monthly thing, to be published on the first day of every month, so consider contributing in the future, if you haven't already. A fewothers from the GeoBlogosphere, alsohereandhere, were included this month.
The photo above, is from Utah Route 28 south of I-70 on the way into Fisher Towers. The rock formation is probably Navajo Sandstone or possibly Entrada Sandstone.
If you'll go back to one of my earlier aerial views of the Fisher Towers and Professor Valley areas on the Colorado River, you'll see that I've enlarged one corner - and added in a couple lines indicating two faults that cut through the area. The faults, also seen on the geologic maps of the area, here and here, appear to be closely related to the northwest-trending Arches National Park uplift or anticline. The photo above shows the dropped down and possibly folded or slumped graben, as seen from the dirt road just below Fisher Towers. The camera was looking just a little bit south of west (WSW). And here's a little field sketch of the same faulted area, as drawn in 1997 from a slightly different angle, showing how all units in the center of the two faults have been dropped down. The cliff-forming, Jurassic Wingate Sandstone is a good marker bed to follow in the photos and in the cartoon-like field sketch.
If you drive Utah Route 128 from I-70 to Moab, you will pass right by these structures. And actually, because they cross the river and the road, you will drive right over them.
View of Fisher Towers from the trail-head parking lot.
After driving down Utah Route 128 from I-70 about 20 miles, you will come to a red dirt road and a sign pointing left toward Fisher Towers. As you probably recall, Fisher Towers is in the Richardson Ampitheater, in Professor Valley, within view of the red Colorado River. Fisher Towers and all the Permian and Triassic rocks making up the Richardson Ampitheater are very good examples of why the Colorado River sometimes runs red.
Follow the dirt road - this time of year I strongly recommend 4WD and caution - to the parking lot below the towers. A nice campground sits in the shadow of the towers, in case you want to spend the night. I thought it was a little chilly for that, however, and didn't stay. Above, an excellent view of one of the towers looming overhead, with its dark red Moenkopi cap (Triassic), and red to dark purplish red Cutler Formation walls and base (Permian). If you follow the trail from the parking lot, you can walk beneath the towers, cross gullies and drainages, and generally have a good time. Another close-up view of the towers behind a cliff in the Cutler Formation. Above, a detail of mini-towers in the Cutler Formation. In this photo, above, you can see what the Permian Cutler Formation looks like: the irregularly-bedded, orange-red to pinkish to purplish-red red beds below the red cliff of the Triassic Moenkopi, below the slope-forming Triassic Chinle Formation, which is below the Triassic Wingate Sandstone cliff at the very top of the slope. The Moenkopi Formation does not appear to be very thick at Fisher Towers. In this last photo, it consists of just the dark red cliff in the center of the view, along with the medium red cliff just below that. The Cutler Formation starts at the first sign of the slope-forming, mostly talus-covered lighter purplish or pinkish red rocks below the cliff of Moenkopi. I think that the little ledge above the dark red Moenkopi cliff is part of the Chinle Formation, but am not entirely sure of where the upper Moenkopi contact lies. Individual ledges in the Chinle can be used as local marker beds, because they can be followed for some distance. Here, the Chinle is mostly reddish, but it can be various colors, as in the Painted Desert and Petrified Forest of Arizona.
David B. Williams of Stories in Stone correctly identified the mystery area in the January-09 WITW as the Professor and Castle valleys, which are located along the Colorado River about 20 miles northeast of Moab, Utah, on backroad Route 128, which heads south from I-70 at exit 204, the westernmost of the Cisco exits. See the topographic map area here.
I've shown the original photo again, below, with major geologic units and contacts added to the duplicate photo below that. It turns out that the central portion of the area, which is the somewhat bowl-shaped Richardson Ampitheater, is underlain by the dark red Permian Cutler Formation, and that red and red-orange Triassic to Jurassic formations make up most of the rest of the picture back to about where I've drawn the Dakota Sandstone, which is Cretaceous.
Please note that the contacts between formations, especially between the Permian Cutler Formation and the Triassic Moenkopi Formation, are inexact. Additionally, the contacts between the Wingate Sandstone, Kayenta Formation, Navajo Sandstone, and Entrada Sandstone are inexact, possibly mislocated in some places on the photo, and more complex than shown. Generally speaking, I've left out the Kayenta Formation between the Wingate and Navajo formations, and have only shown a few formations above the Entrada Sandstone for some semblance of simplicity. Do not rely on my lines for any kind of mapping in the area other than crude, for-fun stuff; instead, go to the original sources!
For precise geologic details, please see the three geologic quadrangle maps of the area, the Fisher Towers quadrangle, the Big Bend quadrangle, and the Dewey quadrangle, also referenced below. Other nearby geologic maps can be found here. I noticed geologic explanations and descriptions of map units (map legends) only on the second and third of the above quadrangles. Another, smaller-scale map, covers the entire area, the geologic map of the Moab and eastern part of the San Rafael Desert 30' x 60' quadrangles. To follow along with the general stratigraphy of the area, see the strat column below for nearby Arches National Park.
If you go to the original strat column page linked to above, you can click on any formation to find out more - possibly more info than you ever wanted to know - with lots of references and some nice photos! Also check out the ongoing series on the Colorado Plateau at Geotripper.
And hey, now for some photos! Above you can see the famous Fisher Towers, with the semi-frozen Colorado River in the foreground and the La Sal Mountains in the background. The photo was taken from Route 128 looking almost directly south, before getting into Professor Valley and the Richardson Ampitheater. For another excellent and similar view of the towers - without snow - see this post at Geotripper, which also describes the Moenkopi Formation. Fisher Towers is an awesome place, in my opinion, located on the east side of the Richardson Ampitheater. The towers are capped by the lower part of the Triassic Moenkopi Formation above the Permian Cutler Formation, which forms almost everything you see in the above photo, from the Moenkopi cap down. This view of the towers was taken from the red-dirt access road to Fisher Towers, looking more-or-less to the east.
From the towers, you can look all around the area, with the cliffs and towers behind you, and a grand 180-degree plus view in every other direction.
To the southeast, looking in the direction of Moab, which you can't actually see, you will have a great view of some mesas and spires. The mesas and spires are formed in the Wingate Sandstone, above the slope-forming Chinle and Moenkopi Formations. This mesa, with its several spires or pillars, is part of a series of mesas that separate Professor Valley from Castle Valley (see topo map). A closeup of part of the mesa shows the unusual rock formations in more detail. The pillars to the right of the central Wingate Sandstone cliff are called the Priest and Nuns, with the large man-like figure presumably being the priest. The larger pillar to the left of the Wingate cliff is called Castle Rock, and sometimes called Castleton or Castleton Tower. Perry, of Robert Perry Hooker, provided a link to a fabulous panorama taken from the top of Castle Rock.
Also, as mentioned in earlier comments, Jon Bon Jovi shot a video from the central Wingate mesa seen in the previous photo (and from Castle Rock?). The video is for his song Blaze of Glory. Castle Rock, the Priest and Nuns, and Fisher Towers can occasionally be seen in the video, along with other panoramas of the area.
Some References: Doelling, H. H., 1996, Geologic map of the Dewey quadrangle, Grand County: Utah Geological Survey, M-169, scale 1:24,000.
Doelling, H. H., and Ross, M. L., 1998, Geologic map of the Big Bend quadrangle, Grand County, Utah: Utah Geological Survey, M-171, scale 1:24,000.
Doelling, H. H., 2001, Geologic map of the Moab and eastern part of the San Rafael Desert 30' x 60' quadrangles, Grand and Emery Counties, Utah, and Mesa County, Colorado: Utah Geological Survey M-180, scale 1:100,000.
Doelling, H. H., 2002, Geologic map of the Fisher Towers quadrangle, Grand County, Utah: Utah Geological Survey, M-183, scale 1:24,000.
The Where in the West series was started here one year ago, in January of 08, when this LFD blog was in its infancy and in a different, unpublished format. Today's January-09 posting is the 8th posting of WITW (not counting one Where in the North in December). WITW is, therefore, a somewhat irregular quasi-monthly thing.
Once again, the unknown area, shown in two photos below, is somewhere in the western part of the United States. Where could it be? Why are some of the rocks so red (besides a slight bit of color enhancement to cancel out the haze)? What is the white unit? What is the basic geology of the area, what are some of the major rock formations, or what is the area known for? Damn, it looks like a river runs through it!
Photo One
Photo Two
The two photos were taken from an unknown altitude, looking northward, almost exactly two years ago. They could almost form stereo pairs, but don't. This is one of my favorite places in the entire world. (Uh, oh! Did I give it away?)
Btw, if you had to pick one geologic time period for the area, what would you pick?
Lockwood has come up with a sexy topic for this month's Accretionary Wedge — yes, you guessed it (or already knew): Sexy Geology. For the record, Lockwood has defined "sexy" as:
Beds and bedding are always of interest to geologists; cross-bedding is best.
Photos are of the Jurassic Navajo Sandstone in Zion National Park, on Utah route 9, the Zion–Mount Carmel Highway, a few miles east of the Canyon Overlook Trailhead.
