Week 6 - Geological Interpretations

Inyo County, California

Inyo County, California map, courtesy of Compare Infobase Limited, retrieved from http://thisweekincaliforniahistory.com/california-history-timeline-march-16-to-march-23/

Mount Whitney, courtesy of Marli Miller

Badwater Basin, courtesy of “Adventure Never Ends”, retrieved from https://www.trover.com/d/m9yG-badwater-basin-inyo-county-california

 Traveling across Inyo County only gives me a small snapshot of the geologic complexities of California. The county was formed in 1866, but the landscape shows a much deeper history. Inyo County was formed from parts of Mono, Tulare, Kern and San Bernardino Counties, and it includes Mount Whitney, the highest peak in the U.S. at 14,505 feet in elevation, as well as Badwater Basin, the lowest point in North America. 

Black Mountains, courtesy of Ray Nordeen, retrieved from https://geomaps.wr.usgs.gov/parks/deva/ftbad1.html

 The Black Mountains’ steep face ascends from the valley floor and are made up of some of the oldest rocks in Death Valley at approximately 1.7 billion years old. These Precambrian rocks are remnants of an ancient volcanic mountain belt with flanking deposits of sand and mud. These volcanic rocks were metamorphosed severely between 1.7 and 1.8 billion years ago. They were altered, recrystallized, then partially remelted by the internal heat of the earth and the weight of the overlapping younger rocks. The original rocks were distorted to contorted gneiss, making it almost impossible to recognize their original parentage. These vulnerable rocks were then injected with magma 11 million years ago, causing them to solidify and form the Willow Spring pluton (Frank, 2016).

Sinuous, water-sculpted curves of Mosaic Canyon marble, courtesy of Marli Miller, retrieved from https://geomaps.wr.usgs.gov/parks/deva/ftmos1.html 

About a quarter mile into the entrance of Mosaic Canyon, it narrows significantly to a deep slot cut into the Tucki Mountain face. The trail is enclosed by smooth, polished marble walls as the sinuous curves continue. The canyon follows faults that when the rocky crust of Death Valley region began stretching, it formed, a few million years ago. The water carved out the canyon by scrubbing away the rock weakened by the fault (Frank, 2016).

Marble from the canyon displays intricately folded layers, courtesy of USGS, retrieved from https://geomaps.wr.usgs.gov/parks/deva/ftmos1.html

The polished marble walls of the canyon have been carved from Noonday Dolomite as well as other Precambrian carbonite rocks. The formation began as limestone that was deposited nearly 700-850 million years ago during the late Precambrian. Later magnesium deposits altered the limestone from calcium carbonate to dolomite, a calcium-magnesium carbonate. Younger sediment deeply buried the dolomite where high pressure and temperature morphed it into to metamorphic marble rock. These metamorphic rocks have been exposed by the uplift of the nearby mountain ranges (Frank, 2016).

Titus Canyon, courtesy of Mari Miller, retrieved from https://geomaps.wr.usgs.gov/parks/deva/fttit1.html

Titus Canyon is a deep and narrow gorge that cuts into the steep Grapevine Mountains face. The rocks that make up the range are approximately half a billion years old, however, the range itself was uplifted more recently. Cambrian age limestone around 505-570 million years old are the grey rocks lining the western end walls of the canyon. The Paleozoic rocks formed when Death Valley was submerged beneath tropical sea water, draining in the Precambrian and exposing the limestone.

Titus Canyon Cambrian limestone, courtesy of M. Moreno, USGS, retrieved from https://geomaps.wr.usgs.gov/parks/deva/fttit1.html

 Amargosa Chaos was named by L.F. Noble, a geologist, because he found the region so complexly folded and faulted. Later, geologists discovered that intense pressure had pulled large crust blocks apart, causing the intricate structure.

Amargosa Chaos, courtesy of Marli Miller, retrieved from https://geomaps.wr.usgs.gov/parks/deva/ftchaos1.html

Four major events have been documented that helped form Amargosa Chaos: As long as 1,700 million years ago, the first event metamorphosed the Precambrian basement rocks of Death Valley. While layered younger Precambrian sediments deposited on top of the beveled surface of older metamorphic basement rocks, the second event began. Approximately half a billion years following, during the Mesozoic or Tertiary time, the third event folded Cambrian and Precambrian sedimentary rocks. The fourth and most recent event, involved crustal stretching that created high mountains and deep valleys of this portion of the Basin and Range Province. Older rocks were intensely sheared and faulted between the Late Miocene and Pliocene time, in some areas only lens-shaped pods of thick rock layers bounded on all sides from faults remain and other layers have been cut carved out of their original sequence completely (Frank, 2016). 

Deep vibrant colors make up the face of the Black Mountains along Artist’s Drive. It is a curvy, one-lane, one-way road that leads to the edge of the Black Mountains and ascends to the top of an alluvial fan fed by a deep canyon that cuts through the mountains.

Artist’s Drive, courtesy of Tom Bean, NPS, retrieved from https://geomaps.wr.usgs.gov/parks/deva/ftart1.html

As the road winds, it dips into ravines carved into the fan by sporadic flash floods, it also rises high up onto the fan as well. The formation is Miocene and consists of gravel, playa deposits and a great amount of volcanic debris, possibly 5,000 feet thick. Hydrothermal alteration and chemical weathering are partially responsible for the displayed colors (Frank, 2016).

Rocks, fossils, and landscape characteristics serve as evidence for interpreting the geologic history of any area. The differences in this county alone are spectacular, to help interpret these multiple landscapes, I would request samples of different layers in each formation to determine a rough timeline and compare samples from the different areas to establish if there are matches, assisting in historical placement. I would use the principle of original horizontality to develop a timeline of plate collision causing the mountain ranges and other rock formations to develop in the area. I would look for unconformities in the formations. I would request reports on the superposition of the sights to assist me as well (Lutgens, 2016, pp. 471-491).

References

Frank, D. (2016). Death valley geology field trip: Amargosa Chaos. United States Geological Survey. Retrieved from https://geomaps.wr.usgs.gov/parks/deva/ftchaos1.html

Frank, D. (2016). Death valley geology field trip: Artist’s Drive. United States Geological Survey. Retrieved from https://geomaps.wr.usgs.gov/parks/deva/ftart1.html

Frank, D. (2016). Death valley geology field trip: Badlands. United States Geological Survey. Retrieved from https://geomaps.wr.usgs.gov/parks/deva/ftbad1.html

Frank, D. (2016). Death valley geology field trip: Mosaic canyon. United States Geological Survey. Retrieved from https://geomaps.wr.usgs.gov/parks/deva/ftmos1.html

Lutgens, F. K, Tarbuck, E. J., & Tasa, D. (2016). Essentials of geology. (13th ed.). Upper Saddle River, NJ: Prentice Hall (Pearson). ISBN-10: 0134446623; ISBN-13: 9780134446622