Tom Schweich  

Montana

Sweetgrass

Exit: 363, for Shelby, Montana.

Cross Marias River.

Great Falls

Exit 278: US I-15 Business, into Great Falls.

Butte

Exit 121

Exit 111: MT Highway 91, Divide Creek Road, south to Dillon.

Exit 99: MT Highway 91, Moose Creek Road

Exit 85: MT Highway 91, Brownes Bridge Road., north of Glen and Burma Road.

Exit 63: US Interstate 15 Busines, North, to Dillon, north.

Dillon

Exit 62: US Interstate 15 Business, South, to Dillon, south.

Exit 0: South Valley Road, to Monida.

Junction: US Highway 20, east to Yellowstone.

Idaho

Idaho Falls

Exit 116: I-15 Bus., US Highway 26, W. Sunnyside Road, business route through downtown Idaho Falls.

Blackfoot

Chubbuck

Pocatello

Exit 47: US Highway 30, east and south to US I-80 at its Exit 66, just west of Little America.

Utah

Tremonton

Brigham City

A reason to take US Highway 91 as an alternate to Interstate 15 would be to see the spillway of Pleistocene Lake Bonneville into the Snake River drainage. The bedrock threshold that established the Provo shoreline is at Red Rock Pass, while an earlier failed alluvial dam is placed at Zenda.

Layton

Junction:

• W. Antelope Drive, the road to Antelope Island. Also known variously as W 1700 S, Antelope Island Road, W Antelope Island Causeway, and East Side Road, all the way to Fielding Garr Ranch.
• Utah State Route 127, part way to the causeway, to intersection with S 4500W, Utah SR 110.

Salt Lake City

American Fork

The approximate south end of Salt Lake Valley

Spanish Fork

Santaquin

Scipio

Holden

Beaver

Parowan Valley

Paragonah

Red Creek exits through the Hurricane Cliffs into Paragonah. On Red Creek, S. L. Welsh made a collection of Frasera albomarginata.

Parowan

Cedar City

Anderson Junction

Exit 27: Utah Highway 17, South to Toquerville, and UT Highway 9 to Zion National Park, or to UT Highway 59, AZ Highway 389, to Kanab, Utah, Page, Arizona, and points east.

Grapevine Wash drains Italian Wash, which drains Italian Spring.

There is a collection of Frasera albomarginata from Italian Spring.

Leeds

Exit 16: Utah Highway 9,

• East: to Hurricane and Zion National Park.
• Also to Fredonia, AZ, and Kanab, UT, by way of Utah Highway 59 and Arizona Highway 389.

Saint George

• Bluff Street, UT Hwy18, west side of St. George.
• Riverside Drive, to southeastern Saint George.

Exit 2: Southern Parkway, Sun River Parkway.

This is the approximate location of the crossing of the Old Spanish Trail from east to west. To the west the trail skirted the south side of Bloomington Hill and ascended Curly Hollow Wash. From the east the trail descended Fort Pearce Wash.

We stopped here for lunch one time and watched some rafters launch their raft, and drift downstream into the gorge.

As an application of their criteria-based methodology for determining the mechanism of transverse drainage development, Douglass, et al. (2009) determined antecedence as the mechanism for transverse drainage through Virgin River Gorge.

Littlefield

Nevada

Mesquite

Glendale

• U. S. Interstate 515, southeast through Las Vegas to Henderson, Nevada.
• U. S. Highway 93, south to Kingman, Wickenburg and Phoenix.
• U. S. Highway 95, north, to Beatty, Tonopah, Fallon, etc., south to Searchlight.

Las Vegas

Jean

Sheep Mountain, type locality of the Goodsprings Dolomite, is across the valley to the southeast.

Devil Peak at the south end of the Mesquite Valley

Devil Peak is a small (~2.5 km diameter) hypabyssal rhyolite dome that intruded into Paleozoic carbonate strata of the southern Spring Mountains (Guest, et al., 2007). It is also the probable source for megabreccia sheets, pyroclastic deposits, and obsidian rock avalanche deposits that make up the crest of Black Butte. These deposits are evidence for about 30 km of dextral slip along the Stateline Fault System.

Primm

California

The Ivanpah Bird Fryer in operation.	Primm at Stateline.

This is the former location of Lakeview, California. Annie Alexander and Louise Kellogg collected here on May 17, 1940. I found the location indicated on a 1939 edition of a AAA highway map.

Mountain Pass

View of the Unocal processing plant at the Mountain Pass Rare Earth Mine

Prior to 1924, an unpaved road known as Arrowhead Trail, which was oil-treated shortly thereafter, generally followed meandering "dry" streambeds through Mountain Pass and Wheaton Canyon. Between 1933 and 1937, a greatly improved two-lane highway was constructed, which served as U.S. Highway 91 and 466 until 1963.

Clark Mountain Station

Valley Wells

Junction:

• Kingston Road, north, leads to Excelsior Mine Road and the Kingston Range. This is a good road that ultimately leads to Tecopa Hot Springs on California Highway 127.
• Kessler Springs Road, south, is one gateway road into the Mojave National Preserve.

Halloran Summit

Halloran Springs

Junction: Halloran Springs Road, west to Silver Lake on California Highway 127.

Baker

The Mad Greek Restaurant in Baker, California.

• Kelbaker Road, south is one gateway road into Mojave National Preserve, leading through the Cima Volcanoc Field to Kelso, and then to U. S. Interstate 40.
• California Highway 127, the southern gateway to Death Valley, north to Shoshone and Death Valley Junction.

The photo is taken from Zzyzx Road, but a similar view can be had from US I-15.

Ventifact Hill

U. S. Interstate 15 looking east toward Baker and Las Vegas from Ventifact Hill

Field trip stop on the shore of Lake Manix

The history of lakes in the eastern Afton basin is very short compared with most Mojave Desert basins. The basin apparently did not exist prior to the rapid rise of the Cady Mountains in the Middle Pleistocene, as the oldest lacustrine evidence in eastern Afton basin is no older than about 300 ka. Afton area lacustrine sections provide evidence for three major lake events.

The most prominent lake stand occurred during OIS 6 (Illinoian). All of the thick green clays visible in the Afton area are from this lake stand. Some of the clays have gypsum crystals, suggesting that this lake eventually dessicated. The Illinoian lake was followed by a lengthy dry interval probably starting in the Sangamon (OIS 5e).

Next a tufa deposit dated at 80 ka, suggests that an OIS 4 lake reached an elevation of 525 m. Correlable strata are located near Camp Cady.

Finally, there are several beach ridges and tufas at elevation of 542.5 m, show in the photograph at left, that have been reliably dated by radiocarbon methods to between 21.5 and 18 ka. This is slightly above the approximate elevation of the topographic divide into Coyote Basin, suggesting the maximum level of Lake Manix was maintained internally by overflows into Coyote Basin.

Sometime about 18 ka., water overtopped the lowest rim of the Manix basin immediately above Afton Canyon and the water spilled out, removing that part of the canyon above the lake floor in a matter of hours. Since that time the Mojave River has continued to cut Afton Canyon, and the landscape is still adjusting to the rapid base level drop (Meek, 2000)

There is no freeway exit here. The nearest exits are Harvard Road to the west and Field Road to the east.

Former military fort, guarding the Mojave Road, on the Mojave River about 1 1/2 miles south of US I-15.

Field discussion of the geology in today's field trip.

Lime Hill is made up of Miocene Barstow Formation sediments overlain by a thick gravel sequence.

Barstow

• Barstow Road,
• California Highway 247

Victorville

Cajon Pass

San Diego