Geology of Yosemite Lakes Park (YLP) in Coarsegold, California

Yosemite Lakes Park (YLP) is

located in the Sierra Nevada

foothills about half way between

Fresno, California and Yosemite

National Park alone California

Highway 41.

Photo Courtesy of www.city-data.com

The geological processes that have created the beautiful landscape of YLP are just a small part of much larger system. Mainly, the Sierra Nevada Mountain Range.

Shuteye Peak in the Sierra Nevada

The Sierra Nevada stretches for 400 miles

(646 kilometers) along the eastern side of

California. It is the longest and highest

continuous mountain range in the lower forty-

eight states. It is a well-pronounced

asymmetrical mountain range with a steep east

escapement and a gradual westward sloping side

that extends into the broad San Joaquin Valley. A

large normal system fault along the eastern edge

of the Sierra Nevada, called the Sierra Nevada

Fault, began to uplift about 25 million years ago

at the end of the Oligocene epoch. The uplift

was due to a major change in the motion of the

North American plate. The Farallon oceanic

plate, that was being subducted under what

would become the Sierra Nevada Mountain

Range, was totally consumed into the subduction

zone.

The Pacific plate that moved into its place

was moving in a different direction

(northwest). The new boundary between the

North American plate and the Pacific plate

became a strike-slip fault system known

today as the San Andreas. The change in

motion from a convergent to a lateral

movement produced a different stress on the

Sierra Nevada region. Since the Sierra

Nevada initial begin, the uplift has

accelerated. It is estimated that the Sierra

Nevada uplifts at a rate of 4 centimeters for

every 100 years. The continental crust east

of the region began to expand and the Sierra

Nevada region began to rise. Below is a

picture of the uplift and tilt of the Sierran

Block with the east escarpment formed along

the fault and the gently sloping western side.

The Sierran Block is in the center of a

highly active geological area. To the

north is the very volcanically active

Cascade Mountain range; to the south

the Garlock Fault system running east

to west; to the east is the Basin &

Range province with many active fault

systems such as Eastern California

Shear Zone & Sierra Nevada Seismic

Belt; and, of course, the world famous

San Andreas Fault.

The San Andreas is a major fault

of an intricate fault network that

cuts through the California coastal

region. The entire San Andreas

Fault system is more than 800

miles long and extends to depths

of at least 10 miles. The fault is a

complex zone of crushed and

broken rock from a few hundred

feet to a mile wide. Many smaller

faults branch from and join the

San Andreas Fault zone .

The Sierran Block is a large batholith that forms the core of the Sierra Nevada Mountain Range.

The batholith is composed of plutons that formed

deep underground during a magma intrusion event

many millions of years before the Sierra Block

began to rise. The extremely hot more buoyant

plutons called diapirs intruded through denser

country rock and sediments, but never reaching the

surface. Additionally during the magma intrusion,

some magma reached the surface as lava flows, but

most of it cooled and hardened below the surface

and remained buried for millions of years. As the

mountains rose, erosion wore down the material

that had covered the batholith. The exposed

portions are the familiar granite peaks of the Sierra

Nevada mountain range, but most of the batholith

remains below the surface.

The Sierra Batholith, containing plutonic rocks (igneous rock), ranging from granite to granodiorite to diorite.

Granite

Granodiorite

DioriteThis chart illustrates the generalized mineral composition of igneous rocks. Granite, compositionally equivalent to granite but of a fine grain size, are composed mainly of orthoclase feldspar, quartz, plagioclase feldspar, mica and amphibole.

In the Sierra Nevada Mountains a process known as sheeting is taking place. Sheeting occurs

when large masses of igneous rock are exposed by erosion resulting in concentric slabs breaking

loose of the main structure. This breaking loose or sheeting is caused by the reduction of pressure

when the overlying rock is eroded away, a process known as unloading. As the rock unloads, the

upper outer layer expands more than the lower rock that causes separation from the Batholith. As

this process continues weathering eventually causes slabs to separate creating exfoliation domes.

Half Dome Yosemite National Park California

The best-known example of an exfoliation dome is Half Dome in Yosemite National Park.

Geology of Yosemite Lakes Park, Ca

Revis MountainRevis Mountain is a mountain summit in Madera County in California.

Latitude: N 37.194392 Longitude: W -119.745985

Facing East. This is a view of Granite Mountain from Revis Mountain Summit. Revis Mountain Summit is 2,162 feet (658.98 meters).

Revis Mountain

Southern View of Revis Mountain in Yosemite Lakes Park, California.

Distant Northern View of Revis Mountain taken from Chukchansi Gold Resort & Casino, Coarsegold, California

Exfoliation is evident all over the YLP area. Below pictures are locations of exfoliation on Revis Mountain .

Igneous Material Intrusion Tabular Intrusion

I. Intrusive rocks are classified according to their shape and orientation. A. The two general types are tabular and massive. 1. Tabular describes a feature having two dimensions that are much longer than the third. 2. Massive is an igneous pluton not tabular in shape. B. Intrusive igneous material that cuts across existing sedimentary beds are discordant and those that form parallel to the existing sedimentary beds are concordant.

GraniteGranite comes from the Latin word "granum" (or grain) because of it granular texture. Sometimes members of this group are also called granitiods or quartz-feldspar-plutonic rocks. These are the most widely distributed plutonic rocks. Light colored mineral that is 20-60 % quartz, 40-80% feldspar and 0-20% dark minerals such as biotite, augite, hornblende, muscovite, apatite, zircon and/or magnetite. Feldspar, quartz and biotite (mica) are popularly considered to be the essential constituents of granite.

Quartz is the second most abundant mineral in the Earth's continental crust is made up of a continuous framework of SiO4 silicon–oxygen tetrahedral, with each oxygen being shared between two tetrahedral, giving an overall formula SiO2.

Feldspars , the most abundant mineral in the Earth’s continental crust (KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8) are a group of rock-forming tectosilicate minerals which make up as much as 60% of the Earth's crust. A mineral composed largely of linked chain of silica, aluminum and oxygen elements. Feldspar means "field crystal."

Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula (Mg,Fe)3AlSi3O10(F,OH)2.

Granite of Yosemite Lakes ParkOn the left are three views of a same granite formation. Granite formation is located on Revis Mountain

Weathered Not Weathered

Hydrology of YLP

One fourth of the Earth's continents is composed of mountainous terrain and mountain rivers.

Hydrology is the study of water and its interactions with the landscape.

Water. Water, everywhere.Water run off near top of Revis Mt.

Yosemite Lakes Park received over 8 inches of rain during the month of March, 2011

Spectacular Water Fall in YLPHydrology seeks to understand the processes that control the flow of water.

Coarsegold CreekSwollen with much run off from YLP, Coarsegold and Oakdale area.

Coarsegold Creek exhibits evidence of some meandering.

No Oxbow Lakes have been observed in the YLP area.

Coarsegold Creek exhibits some evidence of erosion.

Quartz Mountain in background

The Hydrology of YLP is fascinating to examine because the park lies at the center of one of the most extreme Mediterranean type climates on the Earth. Such climates are characterized by cool, wet winters and long, dry summers. During the winters, large Pacific storms bring high amounts of moisture into California. As this warm moist air encounters the Sierra Nevada Mountains, it is forced up and over a crest. As the air moves up and over the mountains, it cools causing water to condense and precipitate as rain and/or snow. This is the reason why 50 percent of California’s water comes solely from the Sierra Nevada. It is referred to as the Orographic Effect.

GOLD! The Mother Lode!

Coarsegold, California and YLP lay at the southern end of California gold country. Coarsegold Creek is an excellent source of placer gold.

Young mountain ranges are ideal locations for gold mining. The Sierra Nevada is a very young mountain range being less than 30 million years old.

Quartz Gold California highway 49 The Golden Chain

SUMMARY• Sierra Nevada Uplift is due to the Farallon Plate subducting under the North American Plate.• It is estimated that the Sierra Nevada uplifts at a rate of 4 centimeters for every 100 years.• The Sierran Block is a large batholith that forms the core of the Sierra Nevada .• The Sierra Batholith, containing plutonic rocks (igneous rock), ranging from granite to

granodiorite to diorite. • Sierra Nevada Mountain Range is dominated by exfoliating granite domes, i.e. Half Dome.

• YLP’s largest exfoliating dome is Revis Mountain with an elevation of 2,162 feet (658.98 meters).

• Revis Mountain is an exfoliating dome.• Granite in YLP is composed of quartz, feldspar and biotite (mica).• Granite on Revis Mountain displays much igneous intrusions. • The Hydrology of YLP is fascinating to examine because the park lies at the

center of one of the most extreme Mediterranean type climates on the Earth. • Coarsegold Creek is an excellent location to prospect for placer gold.

Following pictures displays the natural beauty of Yosemite lakes Park, California.

The End