Geology of the Mojave National Desert Preserve 23Sept2016

and deposits, the principal faults and folds, Mesozoic structural events, and the geologic and tectonic history of the Cima Dome, Mescal Range, Ivanpah Mountains, Mid-Hills, Hole-in-the-

Field trip leaders

Thom Davis, Thomas L Davis Consulting Geologist, Ventura, CA, and

the Geologic Maps Foundation, Inc

Yannick Wirtz, Department of Geological Sciences

California State University Long Beach

Geologic field trip to the Mojave National Preserve, California

October 5-7, 2016 PS-RMS AAPG Field trip #5

Geologic field trip to the Mojave National Preserve

Coordinator: Dan Sturmer (sturmer.dan@gmail.com )

Meeting Point (35.441001°,-115.673135°): The group will meet at 2:00 pm, 10/5 at the

Cima Road exit (also Excelsior Mine Road) off I-15; this exit is about 25 miles from Primm that’s at the Nevada/California border, and Primm is about 40 miles south of Las Vegas Late arrivals can meet the group at the Mid Hills Campground (35.133237°,- 115.434817°) in the Mojave National Preserve (MNP) Yes, this is a change from the original posted time and meeting place and campground Please top-off your vehicle’s gas tank at the station at the Cima Road exit There are no gas stations or stores within the MNP, we will be doing a fair amount of driving within the MNP (200-250 miles), and the trip ends near I-40 and there the nearest gas station is about one hour drive In addition make sure you have food for 2.5 days camping and hiking; water is available at the campgrounds

End of the trip: The trip will end at 4:00 PM (10/7) at the intersection of the Essex

Road and I-40 The field trip does not return to Las Vegas, and from the intersection it’s 1.5 hours drive to Barstow and I-15, and it’s about a 4 hours drive to Los Angeles from the intersection If you wish to return to Las Vegas then take 1-40 west to Kelbaker Road, go north (right) on that road to Kelso, take the Kelso-Cima Road to Cima, and take the Cima Road to I-15

Vehicles and camping: Participants must provide their own transportation (high

clearance vehicles recommended), all meals (including lunches), and camping gear

Camping the first night is at the Mid Hills Campground (MNP), and we will move to the Hole-in-the-Wall Campground (MNP) for the second night Both campgrounds have water, fire pits, tables, and bathrooms Campground costs are included in the field trip fee

Trip summary: This will be “very old school” geology where we will hike to the best

outcrops and panoramic view locations Moderate to good level hiking ability is required

of the participants (5-7 miles per hike, with about 1,000 feet elevation gains) We will use published geologic maps and our own observational skills to discuss the principal geologic units of the area (Proterozoic gneissic terrane, Paleozoic strata, Jurassic and Cretaceous granitic plutons, Miocene ash and flow deposits, and Quaternary land forms

and deposits), the principal faults and folds, Mesozoic structural events, and the

geologic and tectonic history of the Cima Dome, Mescal Range, Ivanpah Mountains, Mid-Hills, Hole-in-the-Wall area, and the Providence Mountains

Weather and clothing: For this time of year it will be, most likely, warm by midday

(upper 80s to lower 90s) but it can be very cool at night (into the 30s or 40s) Mid Hills campground is at 4400 ft and the Hole-in-the-Wall campground is at 5600 ft This area can be windy too Please check the weather forecast before the trip and bring what you need to be comfortable Bring sunscreen, a hat, and sunglasses Long pants and long sleeve shirts are best to avoid too much sunshine and the numerous plants that will stick you

Recommended for camping and hiking: This is classic car camping so bring

firewood, stove, lantern, flashlight, tent (optional), sleeping bags, coolers (with your favorite beverages inside), cooking gear and eating utensils, and food for 2 dinners, 2 breakfasts, and 2 lunches For hiking bring canteens (several), leather boots or scree gators are recommended, windbreaker, and a day pack to carry your lunch Note: alcoholic beverages can only be consumed in the campgrounds and after the day

portion of the trip is completed

Food and Beverages: Snacks and nonalcoholic refreshments will be provided on the

trip, but not meals

Guidebook: Paper copies will be provided at the meet-up area

Emergency: Should an emergency occur, inform the leaders immediately They will

coordinate a response to the appropriate authorities, if needed If you have a medical condition that should be known, please tell us in advance! Be sure to bring all

necessary medications

Liability Waiver: Due to insurance requirements, you must sign the liability waivers

before the trip Please return the Pacific Section and Rocky Mountain Sections of the American Association of Petroleum Geologists (“AAPG PS-RMS ”) liability waivers to Dan Sturmer via email and cc me If you do not sign the waivers, you will not

be allowed to go on the trip

Geologic information on the MNP: A large amount of information and data about the

geology of the Mojave National Preserve are available at various web sites:

Regional tectonic map showing the Mojave National Preserve (MNP); formerly the East Mojave National Scenic Area (from USGS Bulletin 2160) Note the eastern limits of various rock provinces and the

abundance of east vergent thrust faults

1st Day (Wednesday, October 5, 2016)

From meet-up location drive 11.3 miles south along the Cima Road to Stop

1 Please fill-up your vehicles with gas before leaving the meet-up location

Stop 1, Teutonia Peak view stop and Cima Dome

View stop from the Cima Road, and depending on the time we will do a 2.5 mile round trip hike to Teutonia Peak area We need to leave Stop 1 at 4:30

PM in order to be at the Mid-Hills campground by 5:30 PM; sunset is at

of Cretaceous Teutonia quartz monzonite (adamellite)

 View to the east of Kessler Peak (elev=6163’), Ivanpah Mountains, and New York Mountains; Kessler Peak consists of Jurassic Ivanpah granite

 Late Cretaceous extension and uplift, and the East Mojave fault (Miller,

et al, 1996; Wells, et al., 2005)

 View to the north of the Shadow Valley, Clark Mountain, and the

Kingston Range; east vergent Clark Mountain thrust complex (Nelson and Burchfiel, 1979)

 View to the west of the Cima Dome, and beyond the Cinder Cone Lava Beds

 View to the south of the Providence, Granite and Kelso Mountains, and Kelso Dunes

 Cima Dome and pediment formation: A pediment is a gently sloping erosion surface or plain of low relief formed by running water in arid or semiarid region at the base of a receding mountain front A pediment is underlain by bedrock that is

typically covered by a thin, discontinuous veneer of soil and alluvium derived from upland areas Much of this alluvial material is in transit across the surface, moving

during episodic storm events or blown by wind Pediment-forming processes are much-debated, but it is clear that rocks such as granite and coarse sandstone (and Tertiary conglomerate made up of boulders of these rocks) form virtually all

pediments in the Mojave Desert These rocks disintegrate grain-by-grain, rather than fracturing and then being reduced in grain size by alluvial transport processes Large areas within the Mojave Desert are pediment surfaces These pediments reflect both the antiquity of some mountain structures in the region and the persistent arid

climatic conditions in the region Perhaps the most notable pediment in the region

is Cima Dome , a very broad, shield-shaped upland area within the Mojave National Preserve (below) This great, gently-sloped upland area represent a region where desert-style weathering and erosion has stripped away most of the relief to the point that the erosion keeps pace with surface weathering and that surface gradient is gentle enough to prevent gully-style downcutting Isolated rocky hills or knobs that

rise abruptly from an erosional surface in desert regions are called inselbergs The

development of pediments and alluvial fans is progressive with the uplift of

mountains and subsidence of adjacent basins Pediments reflect a relative "static equilibrium" between erosion of materials from upland areas and deposition within

an adjacent basin The slope of the landscape is gentle enough that weathering and transport of sediments from upland areas and the pediment that no significant

stream incision occurs In many areas throughout the Mojave region it is nearly impossible to see where a pediment ends and alluvial fans begin, however,

geophysical data and water-well drilling shows that in many places sediment filled basins do occur adjacent to pediment areas

The impact of climate change on alluvial fans has been the focus of much research Studies show that a period of elevated alluvial fan deposition occurred between the time of the Last Glacial Maximum (about 15,000 years ago) and the beginning of

arid conditions in the early Holocene (about 9,400 years ago) McDonald et al,

(2003) suggest that the climatic transition from seasonable wet conditions to arid conditions, punctuated by extreme storm event (possibly associated with tropical cyclones) may be responsible for this change Today, heavy rainfalls rarely provide enough precipitation to allow enough surface runoff to occur on highly porous soils and colluvium Only during major stream event will water discharge in volume and intensity to move material from mountain source areas to lower fan areas In addition

to extreme storm events, the buildup of alluvial fan deposits at this

Pleistocene/Holocene time transition may be linked with the transition from

widespread plant cover to the more barren character of the modern Mojave

landscape Die-back of plants would decrease rooting, making more mountain-side material available for erosion and transport to alluvial fans

The full version of the above discussion on pediments, with photos, can be found at http://digital-desert.com/mojave-preserve/geology/10.html

From USGS Bulletin 2160

Cima Dome from the Mid Hills Teutonia Peak is barely visible just right of the crest of the Dome, and the Ivanpah Mountains are just right of the Peak

Teutonia Peak, an inselberg of Jurassic Ivanpah granite

From: USGS Geology in the Parks, MESOZOIC ROCKS, by Gordon B Haxel and David M Miller, http://geomaps.wr.usgs.gov/parks/mojave/MESOmoja.html

Jurassic Plutonic Rocks: The Ivanpah Granite of Beckerman and others

(1982) is 150 to 145 Ma (J.D Walker, 1992, oral commun.) It consists of biotite monzogranite that is strongly porphyritic The pluton is moderately peraluminous and potassic

Cretaceous Plutonic Rocks: Most Cretaceous plutonic rocks of the EMNSA

belong to the Early and Late Cretaceous Teutonia batholith (Beckerman and others, 1982Preliminary U-Pb zircon ages for major plutons of the batholith range from 93 to 100 Ma (determined by E DeWitt, 1990) The six major plutons that constitute the eastern Teutonia batholith crop out chiefly in the New York Mountains, Mid Hills, and the Cima Dome-Wildcat Butte-Marl

Mountains area (pl 1) Five of the six plutons are fairly large, with exposed areas §50 to 200 km2 These plutons are intermediate to felsic in

composition The sixth, mafic pluton forms a subcircular outcrop area §2 km

in diameter; correlative bodies are yet smaller The five relatively large plutons of the Teutonia batholith principally range in composition from

quartz monzodiorite to syenogranite, with granodiorite and monzogranite as the principal compositional types; monzodiorite is a minor phase of one pluton Despite this compositional range, granite constitutes most of the exposed rock Three of the five plutons are leucocratic Teutonia Adamellite, Mid Hills Adamellite, and Kessler Springs Adamellite of Beckerman and

shortening shown by brittle-style thrust plates developed in the foreland of the

Cordilleran thrust belt and ductile-style nappes in southeastern California and Arizona (Burchfiel and Davis, 1971, 1977, 1981; Howard and others, 1980; Snoke and Miller, 1988; Miller and Barton, 1990) Generally east-directed thrust faults, present in the Cowhole Mountains and the Clark Mountain Range areas, may be Middle Triassic(?) through Early Jurassic (Burchfiel and Davis, 1981)

From Stop 1 drive 6 miles south to the road intersection at Cima and take the Kelso-Cima Road south 5 miles Turn left on to the Mojave Road and continue 6 miles east on the Mojave Road Turn right on to the Black

Canyon Road and from there go 3 miles south Make a right on to the Wild Horse Canyon Road and follow for 2 miles to the entrance to the Mid-Hills Campground We will camp the first night at Mid Hills

Portion of the geologic map from USGS Bulletin 2160 showing the Mid Hills The East Providence fault (Hazzard, 1954) is now

considered a segment of the regional East Mojave fault (Miller, et al., 1996; Wells, et al., 2005)

A Mid Hills Campground site

2d Day (Thursday, October 6, 2016)

We will depart Mid-Hills campground by 7:30 AM; sunrise is ~6:30 AM From Mid Hills Campground return to Cima via same road we used

yesterday From Cima take the Cima Road 10.5 miles north to a dirt road, turn off on the right, and head 2.0 miles east to reach the south side of Striped Mountain

Map showing various roads in the Ivanpah Mountains and Mescal Range (from Digonnet, 2013)

Stop 2, Striped Mountain loop and hike We will investigate the

geology around Striped Mountain (elev=5954’), the west flank of the

Ivanpah Mountains, and south side of the Mescal Range This will require

a driving loop around the mountain and taking short hikes to key locations

Present and discuss:

 Mesozoic deformation: Structural elements from Sevier and Laramide events are present in this area (Nelson and Burchfiel, 1979)

 Late Cretaceous deformation (Laramide) in the southern Cordillera was different from the northern segment as it is now believed that it was

affected primarily by extensional, and possibly strike-slip deformational events (Burchfiel, et al., 1992)

 Early Cretaceous thrust faults in the Clark and New York Mountains may have several tens of kilometers of eastward directed overthrusting with some of the thrusts having hanging-walls of crystalline basement and the convergent structures may represent the southernmost extent of the Sevier event (Burchfiel, et al., 1992)

Striped Mountain, Ivanpah Mountains

Cross section I-I’ from USGS Professional Paper 275 showing a portion of the east vergent Clark Mountain thrust complex (Nelson and Burchfiel, 1979)

A portion of the geologic map from USGS Professional Paper 275 (Hewett, 1956) showing Cima Dome, Ivanpah Mountains, and Mescal Range The Clark Mountain fault is now called the Kokoweef fault (Nelson and Burchfiel, 1979) The Mescal fault is part of the Clark Mtn thrust complex

The East Mojave fault (EMF) is a proposed regional structure that

combines several previously mapped faults (East Providence fault, Pinto shear zone of the New York Mountains, and Cima faults) (Miller, et al.,

1996) The EMF has down on the west separation and is offset by Miocene and younger faults During the late Cretaceous the EMF connected areas

of extension from Death Valley southward to the Old Woman Mountains and provide further support for regional extension in the North American Cordillera at about 70 Ma Mapping suggests that the Kokoweef fault might

be another splay of the EMF

Portion of the geologic map from USGS Bulletin 2160 showing the Ivanpah Mountains and southern Mescal Range Note the numerous east vergent thrust faults South of the red boundary is Mojave National Preserve

(MNP) land See the end of this guidebook for the map explanation