Death Valley, Badwater pan

Geologically, Death Valley, California, is probably the best-known playa of the Basin and Range setting in the USA, yet Death Valley is a very steep-sided and unusual lacustrine depression. Located in the lowest part of the Mojave Desert, its floor is some 86 m below sea level, making it the lowest continental locality in the Western Hemisphere. It has an area around 7,800 km2, while the highest point in Death Valley itself is Telescope Peak in the Panamint Range, with an elevation of 3,366 m.

Climatically, at 56.7°C, one of the world’s highest air temperatures was recorded at Furnace Creek in Death Valley on July 10, 1913. The highest surface temperature ever recorded in Death Valley was 93.9 °C on July 15, 1972, at Furnace Creek, which remains the highest ground surface temperature ever recorded on earth, as well as the only recorded surface temperature of above 200 °F (93.3 °C).

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Death Valley drainage sump showing the salt-encrusted Badwater Pan

With its current hydrology, the lowest part of the Death Valley sump is a saline pan rather than a perennial halite-accumulating lake. But in the Late Pleistocene, it was a deep perennial saline system. Although well studied, the volume of salts accumulating in Death Valley is relatively minor in terms of the total amount of salt in saline lacustrine settings of the world. The steep valley sides mean the [pan sump can become a perennial saline lake with relatively minor changes in climate. In many areas of Death Valley, the coarse-grained debris flows of the alluvial fan directly abut the salt crusts of the sabkha and the saline pan. San flats and dry mudflats, so evident in most Basin and Range playas, are poorly developed or absent in Death Valley. This too, reflects the steep valley walls and its relatively high watertable, in relation to the lake surface. It is a rapidly subsiding saline lacustrine system in which more than 50% of the Quaternary sediment fill beneath the lowest parts of the lake floor, as at Badwater Pan, are dominated by saline lake and pan halite rather than matrix-rich evaporitic mudflat sediment (sabkha).


Landsat image of the Badwater region of Death Valley, California, showing the saline pan in lowest part of sump and the stratigraphic column of upper 90 metres of core DV-93-1 from within the pan, (after Li et al., 1997). Lake levels and watertable fluctuations are shown ranging from driest (sabkha) through saline pan (SP) to the wettest lacustrine phases of saline lake (SL) and deepest lake (DL). The dominant evaporite mineral is halite and the position of the sulphate evaporites in the core, as well as the weight percent CaCO3 in the > 1µm fraction, are also shown.

Core intervals through saline pan sediments at Badwater are composed of interbedded halite, chaotic muddy halite, and mud. The halite contains abundant vertical dissolution pipes, cemented with clear halite, indicating the watertable periodically dropped below the surface of the stacking halite crusts. These sediments record repeated flooding by dilute waters, dissolution of subaerially exposed surface salt crusts, deposition of mud from suspension, precipitation of halite during the saline lake phase, and cementation by diagenetic halite. Such deposits document a relatively wet climate with a high ratio of water inflow to evaporation compared to today.

Ostracods in calcitic mud layers represent the least saline, deepest lake phases when, based on the position of beach deposits in the valley walls, water depths in the deepest part of the lake were as much as 90 m above the current water table. Halite layers are made of fine-grained cumulates and clear, vertically-oriented crystals precipitated during shallower, perennial lake stages. The near-complete absence of syndepositional dissolution textures in saline minerals precipitated in the perennial saline lake interval, imply that the accumulating salts were permanently protected from dissolution by an overlying perennially-saline at times holomictic water column. (see Warren, 2016, Chapter 3 for detailed literature synthesis).


Economic history of Death Valley

The valley received its English name in 1849 during the California Gold Rush. It came from a party of travelers who, after leaving Salt Lake City, made a disastrous short-cut across the region on their way to the California gold fields. Before departing the valley, the survivors (13 of the party died) cursed the valley and gave it a name, saying: "We took off our hats, and then, overlooking the scene of so much trial, suffering, and death, spoke the thought uppermost in our minds, saying, 'Good-bye, Death Valley.’

During the 1850s, gold and silver were extracted in the valley. In the 1880s, borax was discovered and extracted by mule-drawn wagons. The borax  ore(mostly colemanite) occurs in the saline lacustrine Furnace Creek Formation (Miocene).

In the early 1870’s, a band of outlaws hiding out in the Panamint Mountains unexpectedly discovered silver in Surprise Canyon. By 1874, Panamint City was a booming mining town with a population of 2,000. Two years later, a flash flood wiped out most of the town. There are similar "boom and bust" stories for the many ghost towns scattered throughout the valley such as Ballorat, Chloride City, Leadfield, Harrisburg, Greenwater, Rhyolite and Skidoo. In the 1880s, borax was discovered and extracted by mule-drawn wagons 

Badwater, Death Vallay (image from Wikipedia)
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