Bristol Lake is a

dry lake A dry lake bed, also known as a playa, is a basin or depression that formerly contained a standing surface water body, which disappears when evaporation processes exceeds recharge. If the floor of a dry lake is covered by deposits of alkaline c ...

in the

Mojave Desert The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily in ...

San Bernardino County, California San Bernardino County (), officially the County of San Bernardino, is a County (United States), county located in the Southern California, southern portion of the U.S. state of California, and is located within the Inland Empire area. As of the ...

, northeast of

Twentynine Palms Twentynine Palms (also known as 29 Palms) is a city in San Bernardino County, California. Twentynine Palms serves as one of the entry points to Joshua Tree National Park. History Twentynine Palms was named for the palm trees found there in ...

. Bristol Lake is located southeast of

Amboy Amboy may refer to: Places * Amboy, Córdoba, village in Calamuchita Department, Córdoba province, Argentina United States * Amboy Crater, feature in Mojave National Preserve, California Settled U.S. places * Amboy, California * Amboy, Ge ...

and

U.S. Route 66 U.S. Route 66 or U.S. Highway 66 (US 66 or Route 66) was one of the original highways in the United States Numbered Highway System. It was established on November 11, 1926, with road signs erected the following year. The h ...

, and is also south of Cadiz.

Amboy Crater Amboy Crater is a dormant cinder cone volcano that rises above a lava field in the eastern Mojave Desert of southern California, within Mojave Trails National Monument. It is about equidistant from Barstow to the west and Needles to the e ...

and the

Bullion Mountains The Bullion Mountains are located in the Mojave Desert of California southeast of the city of Barstow. The mountain range stretches for approximately 50 miles in a northwest-southeasterly direction north of Joshua Tree and Twentynine Palms. Sinc ...

are to the west, and

Old Woman Mountains The Old Woman Mountains are located south of the town of Essex, California, and north of Danby Dry Lake. The range reaches an elevation of at the west end (Old Woman Mountain), and lies in San Bernardino County in the Mojave Desert. Geography Th ...

to the east. The lake is approximately long and at its widest point.

Geological setting

Bristol Lake is located in San Bernardino County's Mojave Desert. It is a playa lake in the

Basin and Range Province The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternating ...

and is the northernmost member of a northwest-southeast trending playa lake system that includes Cadiz Lake and Danby Lake.Hanford, C. Robertson. "Sedimentology and Evaporite Genesis in a Holocene Continental-sabkha Playa Basin-Bristol Dry Lake, California." Sedimentology, 29.2 (1982): 239–253.

Mineralogy

Bristol Lake's mineralogy is described as having a bullseye pattern of minerals with lithofacies consisting of

halite Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...

at the center surrounded by mud,

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywall. ...

, and finally a sand flat playa margin. These minerals also have vertical lithofacies which resemble the horizontal facies stratification with gypsum occurring deeper in the playa followed by mud-halite and halite on top.Rosen, Michael R, and John K Warren, "The Origin and Significance of Groundwater-seepage Gypsum from Bristol Dry Lake, California, USA." ''Sedimentology'', 37.6 (1990): 983–996. The mud lithofacies consists of thick detrital mud, and the halite lithofacies is defined by giant hopper shaped crystals. Gypsum occurs in large lenticular crystals throughout the playa but is mostly concentrated around the mud lithofacies. Gypsum crystal sizes increase toward the center of the playa.

Interpretation

Gypsum

Past studies have determined that the gypsum occurring in Bristol Lake precipitated displacively within the sediment where groundwater saturated with gypsum recharges around the mud lithofacies. This is supported by the geometry of the deposit and by chemical data, which suggests that water precipitating gypsum in the playa is more associated with groundwater than the brine at the basin center. The large size of the gypsum crystals may be due to several reasons; inflow waters containing low Ca/ SO₄ ratios may result in large lenticular crystals, microorganisms have the potential to rework large lenticular crystals, high concentrations of

NaCl Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...

in inflow waters can decrease nucleation density of minerals resulting in larger crystal sizes. It is likely that a combination of these processes was needed in order to form the gypsum crystals mentioned because gypsum crystals formed from low Ca/SO₄ ratios or from microbial activity alone would not result in gypsum crystals large enough, and because gypsum crystal size increases toward the center of the playa where sodium chloride concentrations are greatest.

Halite

Thin crusts and hopper-shaped halite crystals that occur in the sediment are caused by evaporative growth from capillary brines discharging at the surface.

Mud

Sediment mineral composition found in the desert saline sediments of southern California are predominantly influenced by the composition of the source rock, this is true for Bristol Lake as well.

Possible magma chamber

The brine chemistries at Bristol Lake are different from those predicted to form by the evaporative concentrations of the two inflow waters currently accounted for. # Na-HCO₃-SO₄ will precipitate CaCO₃ which will deplete the water in calcium. These waters evolve into Na-HCO₃-CO₃-Cl-SO₄ brines with minor magnesium and potassium. They will precipitate halite, Na-Sulfate, and Na-carbonate mineral upon further evaporation. # Cl-SO₄ is predicted to precipitate calcite and then gypsum and form neutral Na-SO₄-Cl brines with subordinate K and Mg. These brines are predicted to precipitate halite and sodium-sulfate salts during further evaporative concentration. The basin center brines of BDL (saline mudflats and saline pan areas) are Na-Ca-Cl rich with lower concentrations of potassium and magnesium and little sulfate and

bicarbonate In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula . Bicarbonate serves a crucial biochemic ...

. Differing from their predicted chemical composition mostly by lacking sulfate, carbonate and bicarbonate and having high levels of chlorine. Rosen 1991 attributed increased concentration of chlorine to be from atmospheric precipitation, however the Ca-Cl concentrations present at Bristol Lake are not compatible with normal low temperature surface weathering and evaporative concentration processes. It is speculated that a magma chamber drives the formation of Ca-Cl brines at elevated temperatures and drives the transportation of these brines to the surface. Other evidence of a magma chamber in the area is the

and its associated lava flows, which occur directly North of Bristol Lake.Lowenstein, Tim, and François Risacher. "Closed Basin Brine Evolution and the Influence of Ca–Cl Inflow Waters: Death Valley and Bristol Dry Lake California, Qaidam Basin, China, and Salar De Atacama, Chile." ''Aquatic Geochemistry'', 15.1 (2009): 71–94.

Industry

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quantitie ...

evaporator operation is situated on the dry lake bed just east of Amboy Road. File:CadizSalt.jpg, Salt evaporators in Bristol Dry Lake File:Bristol Lake.JPG, Bristol Dry Lake after a rainfall

References

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External links

Satellite Photo (Google Maps)
{{authority control Endorheic lakes of California Salt flats of California Lakes of the Mojave Desert Lakes of San Bernardino County, California Lakes of California Landforms of San Bernardino County, California Lakes of Southern California