Salar De Uyuni Research Articles

The World's Most Dangerous Road (A Bolivian Detour)

The World's Most Dangerous Road (A Bolivian Detour) Jenny Browne (bio) 1 Two roads diverged in a yellow wood, And sorry I could not travel both My husband, Scott, and I have this single month in South America, which means we have to make choices, cut out ruins, islands, entire countries. We've met the long haulers: packs of Israelis just out of military service with nine months to travel; the German couple who quit their jobs, sold their houses, and hit the road; the Oregon hippy with his camera and Kerouac. Happy hour at the Irish bar in Cuzco, he crows, "You only have a month?" then grows solemn with purpose. "I'll be in China in a month. You've got to do the Yangtze before it is too late, before everything is ruined." Everything. Ruined. I used to be one of them. I'm not sure what I am now. We're heading to the Salar de Uyuni, the salt flat remains of a prehistoric lake along the Bolivian border with Chile. We've seen pictures of Daliesque landforms, purple mineral-rich mountains, blood red lakes. First stop is La Paz, the highest capital city in the world at nearly 12,000 feet above sea level. The city named for peace is a lung-busting maze of cobbled streets. If something exists, it's for sale in Bolivia. You can buy cell phone minutes from a phone chained to a person who then looks discretely in the other direction. Llama fetuses and little stone fertility statues with huge penises pack the Mercado de Brujas. A fried Spam stand sizzles next to a cart of bootlegged Freddy Mercury CDs next to an open suitcase full of pantyhose. Cries of "You want? You want?" Every square inch along the main promenade of El Prado is packed. One guy followed us for blocks hissing, smokesnortInternet? smokesnortInternet? [End Page 9] We have tickets out. We have film. We have peanut butter. We have Chifa the night before leaving at a place called Discoteca Jackie Chan. Chinese food, Jackie Chan movies, disco dancing, and Bolivia all in one bite? I know but who could resist? I got up early and headed out to find coffee. When I return, Scott is curled into a ball on the bed. He has already thrown up three times. His lips are gray, dry. He is breathing slowly through his mouth. But we have plans. "Do you want some Sprite?" "Uhhhh." "I'll go buy some crackers." "Nuhhhh." "We have to check out in a half hour." "Whuhh." Why do I say stuff like that? Do we really have to check out in a half hour? Did I mention that I had stir-fried vegetables and rice at the Discoteca? Scott had stir-fried vegetables with the fermented black bean sauce. I know. I sit on the lumpy bed in the Hotel Happy Days and watch a badly dubbed and very fuzzy Pulp Fiction on the television in the corner. Eventually, Scott sits up, presses his hands hard into his thighs, and rises to his feet. He leans against the wall carefully and mumbles, "Let's go, I'll be alright." We shuffle downstairs and I hail a cab to get us to the bus station in time for our overnight bus to Uyuni. The gold shag dashboard of the little Rabbit has a bobbling-head pink plastic alien glued to it. The driver grunts and slams the car into gear. Scott presses his cheek against the glass and grips my thigh. The grayness has spread to his hands. We make it about ten blocks of start-screech-stop-honk-grunt. As one prone to motion sickness when he feels fine, Scott's glassy eyes grow panic-stricken, wild. "Tell him to stop now, right now!" "Señor, por favor, mi esposo es enfermo. Aquí es bueno." "No Señora, aquí es peligroso. Esta cerca." "He says it's dangerous here. We're almost there." Scott is clutching his gut, nearly convulsing. I shout at the driver, "Aquí, aquí por favor!" "Esta aquí, aquí." he shouts back. We are there, and to prove it he wildly...

The effect of filtration on analyses of surface water samples. A study from the Salars of Coipasa and Uyuni, Bolivian Altiplano

Analyses by inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS) and cold vapour atomic absorption (for Hg, CVAA) of a wide range of elements in some 300 surface water samples from the Salar de Uyuni and Salar de Coipasa catchments of the Bolivian Altiplano have been undertaken. Comparison of analyses of acidified aliquots of unfiltered sample water with water filtered at 0.45 μm reveals that the following elements are not affected significantly by filtration in this high-pH environment: B, Ca, Li, Mg, K, Si, Na, Sr, S. The following elements appear to experience significantly elevated concentrations in unfiltered samples, relative to filtered: Al, (As to a minor extent), Ba, Be, Cd, Cr, Co, Cu, Fe, Pb, Mn, Hg, Ni, P, Ag, Tl, Ti, V. The effect appears to be related to the presence, and subsequent dissolution in acid preservative, of Fe-, Al-or Mn-oxyhydroxide flocs (or coatings on silicate particles) in unfiltered samples, and their retention or precipitation on filters.

In-flight absolute calibration of the Landsat-5 TM on the test site Salar de Uyuni

In Brazil, the increase of the application of quantitative approaches in the natural resources studies using remote sensing technology has required knowledge about the radiometric conditions of remote sensors as the Thematic Mapper (TM) and the Enhanced TM Plus, for instance. The establishment of a correlation between radiometric data and biophysical and geophysical ones has become a frequent need in the Brazilian remote sensing community, and it has increased the demand of calibration coefficients in order to transform digital numbers to physical values like radiance and reflectance. Since the China-Brazil Environmental Remote Sensing Satellite became a reality, the necessity to perform calibration campaigns increased significantly. Following Price and other researcher's suggestions, an in-flight absolute calibration of the Landsat-5 data was carried out in the Salar de Uyuni, Bolivia. It was only possible to determine calibration coefficients for bands TM2, TM3, and TM4 due to the saturation of band TM1 and surface moisture conditions that impacted the TM5 and TM7. The methodology applied here seemed to be sufficient to determine valid calibration coefficients for orbital sensors.

Vegetation and climate change on the Bolivian Altiplano between 108,000 and 18,000 yr ago

A 90,000-yr record of environmental change before 18,000 cal yr B.P. has been constructed using pollen analyses from a sediment core obtained from Salar de Uyuni (3653 m above sea level) on the Bolivian Altiplano. The sequence consists of alternating mud and salt, which reflect shifts between wet and dry periods. Low abundances of aquatic species between 108,000 and 50,000 yr ago (such as Myriophyllum and Isoëtes) and marked fluctuations in Pediastrum suggest generally dry conditions dominated by saltpans. Between 50,000 yr ago and 36,000 cal yr B.P., lacustrine sediments become increasingly dominant. The transition to the formation of paleolake “Minchin” begins with marked rises in Isoëtes and Myriophyllum, suggesting a lake of moderate depth. Similarly, between 36,000 and 26,000 cal yr B.P., the transition to paleolake Tauca is also initiated by rises in Isoëtes and Myriophyllum; the sustained presence of Isoëtes indicates the development of flooded littoral communities associated with a lake maintained at a higher water level. Polylepis tarapacana-dominated communities were probably an important component of the Altiplano terrestrial vegetation during much of the Last Glacial Maximum (LGM) and previous wet phases.

Reactive bromine and sulfur emissions at Salar de Uyuni, Bolivia

Field measurements of reactive halogen and sulfur gas emissions were performed at the world's largest salt pan, the Salar de Uyuni, Southern Altiplano, Bolivia (19.8°–20.7°S, 67.0°–68.2°W), during the dry season in October/November 2002. Bromine monoxide (BrO) and sulfur dioxide (SO2) were studied by ground‐based scattered light Multi Axis Differential Optical Absorption Spectroscopy (MAX‐DOAS) at various locations upwind and inside the salar. Significant amounts of BrO were found at all locations with the lowest levels at the northern edge of the salar (upwind), while BrO slant column densities (differential with respect to zenith) of up to 3.7 × 1014 molec/cm2 were observed inside the salar. Using the MAX‐DOAS vertical profile information BrO mixing ratios of >20 ppt are calculated, which can have significant impact on tropospheric ozone chemistry both locally and regionally. SO2 slant column densities of >5 × 1016 molec/cm2 were found around the salar, suggesting emissions from volcanic activity.

Hydrologic variation during the last 170,000 years in the southern hemisphere tropics of South America

Despite the hypothesized importance of the tropics in the global climate system, few tropical paleoclimatic records extend to periods earlier than the last glacial maximum (LGM), about 20,000 years before present. We present a well-dated 170,000-year time series of hydrologic variation from the southern hemisphere tropics of South America that extends from modern times through most of the penultimate glacial period. Alternating mud and salt units in a core from Salar de Uyuni, Bolivia reflect alternations between wet and dry periods. The most striking feature of the sequence is that the duration of paleolakes increased in the late Quaternary. This change may reflect increased precipitation, geomorphic or tectonic processes that affected basin hydrology, or some combination of both. The dominance of salt between 170,000 and 140,000 yr ago indicates that much of the penultimate glacial period was dry, in contrast to wet conditions in the LGM. Our analyses also suggest that the relative influence of insolation forcing on regional moisture budgets may have been stronger during the past 50,000 years than in earlier times.

Dust-Storm Source Areas Determined by the Total Ozone Monitoring Spectrometer and Surface Observations

Dust storms are recognized as having a very wide range of environmental impacts. Their geomorphological interest lies in the amount of deflation and wind erosion they indicate and their role in loess formation. Atmospheric mineral-dust loading is one of the largest uncertainties in global climate-change modeling and is known to have an important impact on the radiation budget and atmospheric instability. Major gaps remain in our understanding of the geomorphological context of terrestrial sources and the transport mechanisms responsible for the production and distribution of atmospheric dust, all of which are important in reducing uncertainties in the modeling of past and future climate. Using meteorological data from ground stations, from the space-borne Total Ozone Monitoring Spectrometer (TOMS), and from the National Center for Environmental Prediction–National Center for Atmospheric Research reanalysis project, we illustrate the key source regions of dust and demonstrate the primacy of the Sahara. Objectively defined source regions for the Sahara are determined from eigenvector techniques applied to the TOMS data. Other key regions include the Middle East, Taklamakan, southwest Asia, central Australia, the Etosha and Mkgadikgadi basins of southern Africa, the Salar de Uyuni (Bolivia), and the Great Basin (United States). In most of these regions, large basins of internal drainage, as defined from a digital elevation model, are dust sources where the near-surface atmospheric circulation (determined by calculated means of potential sand flux) is favorable for dust mobilization. Surface observations indicate some regions as being important that do not appear on the TOMS maps. Possible reasons for these discrepancies are explored.

Characterization of the salar de uyuni for in-orbit satellite calibration

Field work was carried out on June 8 and 9, 1999 to evaluate the use of the Salar de Uyuni as a test site for in-orbit satellite calibration. A dataset of ten Thematic Mapper (TM) images, from 1988-1997, was used to select three test points based on the analysis of the temporal stability of the reflectance of Salar's surface. Bidirectional reflectance factor (BRF) values of Salar's surface within the precision suitable for vicarious calibration procedures were obtained using a CE313-2/CIMEL radiometer. In spite of seeming visually homogeneous, the BRF values of one test point have presented significative statistical differences with the two others. Atmospheric characterization was possible with a sunphotometer CE317/CIMEL showing the low importance of the atmospheric effects in the image acquisition. The results confirm that the Salar de Uyuni has the characteristics pointed out by many authors as suitable for a vicarious calibration site, specially from April to November because of the reduced rainfall occurrence. The main disadvantages are the difficult access and the critical period for data collecting in the rainy season from November to March. An angular reflectance variation study is recommended in order to evaluate its Lambertian properties.

Parabolic halite dunes on the Salar de Uyuni, Bolivia

Palaeoenvironmental interpretation in desert and evaporitic sediments is often ambiguous. Consequently, the recognition of primary sedimentary structures that indicate subaerial exposure or shallow marine conditions are therefore of crucial importance when interpreting marginal sedimentary evaporite facies. Parabolic halite dunes, described here for the first time, are observed on the salt crust of the largest salt flat in the world, the Salar de Uyuni in Bolivia. The halite dunes are relatively small (0.7–1.3 m in width and length), well-defined lobate to hemicyclic parabolic dunes, and are formed directly on the salt crust. A model describing the formation and migration of the dunes in relation to brine level and climatic conditions is presented.

A 106 ka paleoclimate record from drill core of the Salar de Atacama, northern Chile

A 100 m long salt core (SQM #2005) from the Salar de Atacama, northern Chile (23°S, 68°W), a dry lake bed, contains a 106 kyr paleoclimate record of hydrologic balances on the western slopes of the central Andes of South America. Six U-series disequilibrium dates range sequentially from 106.1±6.4 to 5.4±2.7 ka. Based on sedimentary structures and petrographic textures of salts and associated siliciclastic sediments, interpretations of paleoenvironments and net hydrologic balance suggest that relatively wet periods (saline lakes and expanded mudflats) existed in the Salar de Atacama from 75.7 to 60.7 ka and from 53.4 to 15.3 ka, with the wettest perennial lake interval from 26.7 to 16.5 ka. Short relatively wet periods also occurred in the Holocene from 11.4 to 10.2 ka and from 6.2 to 3.5 ka. These wet periods at Salar de Atacama correspond well with other late Pleistocene climate records from the central Andes that are a function of the net hydrologic budget. The Minchin–Tauca lake sequence from Salar de Uyuni, Bolivia, is synchronous with the 53.4–15.3 ka saline lake wet period at Salar de Atacama. The Tauca phase coincided with the wettest perennial lake interval at Salar de Atacama from 26.7 to 16.5 ka. The Coipasa lake phase from Uyuni was probably contemporaneous with the early Holocene wet period at Salar de Atacama from 11.4 to 10.2 ka. The early Holocene wet interval at Salar de Atacama was also synchronous with the maximum Holocene lake levels of the Chilean Altiplano lakes to the east and with grass-rich rodent middens between 11.8 and 10.5 ka in age from the Atacama basin. The lake period at Salar de Atacama between 26.7 and 15.3 ka compares closely with low δ 18O values, low anion concentrations and high accumulation rates from the Sajama glacial ice core, southwestern Bolivia between 25 and 15.5 ka. It is concluded that wet and dry phases were synchronous in the central Andean plateau of southwestern Bolivia and along the western flank of the Andes of northern Chile over the past 50 kyr. This region, which today receives its moisture from the Amazon Basin to the east, probably also did so in the past. The wet periods at Salar de Atacama are in phase with January insolation maxima at 15°S at 70, 45, and 20 ka, which suggests that past changes in summer insolation influenced precipitation patterns in the central Andes. However, there are no major wet periods linked to the January insolation maximum at 93 ka and the present-day extremely dry climate in the Atacama Desert is associated with a peak in summer insolation. Therefore there must be other important influences over precipitation in the central Andes which modify the first order insolation controls.

Dating of paleolakes in the central Altiplano of Bolivia

The deposits of the extensive paleolakes of the Bolivian Altiplano correspond to an alternation of lacustrine episodes and dry periods, a phenomenon commonly explained by climatic changes. The lack of precise dating of the deposits has prevented detailed reconstruction of the evolution of paleolakes that would allow a determination of the relative influence of interconnections between neighboring basins and local climatic conditions. Among the five paleolakes of the northern Altiplano (Titicaca basin) and the three of the central Altiplano (Poopó, Coipasa and Uyuni basins) only the two most recent paleolakes have been dated.A 121m long sediment core recovered from the Salar de Uyuni contained 11 lacustrine layers (L1–L11) separated by 12 salt crusts. Radiocarbon dating shows that the younger layers L1 and L2 are related to the Tauca lacustrine phase (12 000–16 000calyrbp) and layers L3 and L4 to the Minchin lacustrine phase (30 000–73 000calyrbp). Layer L5, located at 46m below the surface, contains a volcanic ash with well-preserved biotites is here dated by the 40Ar/39Ar method. The measured age of 191 000±5000y is the first date ever obtained from a pre-Minchin paleolake (Lake Escara). This result combined with 14C and U/Th data obtained on lakes Tauca and Minchin from various authors suggests that the duration of the lacustrine events increased regularly during the Pleistocene. In contrast, paleolake levels in the northern Altiplano decreased from the oldest known (Lake Mataro, 3950m) to the present Titicaca level (3806m). A progressive erosion of the threshold between the northern and central Altiplano may have allowed important volumes of water to overflow from the northern basin into the central Altiplano. The existence of large paleolakes in the central Altiplano was thus not only dependent on local climatic conditions but also on additional inputs from the north, where climatic conditions could have been quite different from those prevailing in the south.

Tropical climate changes at millennial and orbital timescales on the Bolivian Altiplano.

Tropical South America is one of the three main centres of the global, zonal overturning circulation of the equatorial atmosphere (generally termed the 'Walker' circulation). Although this area plays a key role in global climate cycles, little is known about South American climate history. Here we describe sediment cores and down-hole logging results of deep drilling in the Salar de Uyuni, on the Bolivian Altiplano, located in the tropical Andes. We demonstrate that during the past 50,000 years the Altiplano underwent important changes in effective moisture at both orbital (20,000-year) and millennial timescales. Long-duration wet periods, such as the Last Glacial Maximum--marked in the drill core by continuous deposition of lacustrine sediments--appear to have occurred in phase with summer insolation maxima produced by the Earth's precessional cycle. Short-duration, millennial events correlate well with North Atlantic cold events, including Heinrich events 1 and 2, as well as the Younger Dryas episode. At both millennial and orbital timescales, cold sea surface temperatures in the high-latitude North Atlantic were coeval with wet conditions in tropical South America, suggesting a common forcing.

Tectonic rotations within the Bolivian Altiplano: Implications for the geodynamic evolution of the central Andes during the late Tertiary

Paleomagnetic results from 61 sites in Tertiary red beds and volcanic rocks from the Bolivian Andes allow quantification of tectonic rotations within the Altiplano domain. A total of 16 sites were also obtained in lower Miocene ignimbrites that cover the forearc of the north Chilean Andes near Arica. In the southern Altiplano (Lipez region) a local clockwise rotation of up to 38° is recorded in lower Miocene volcanic rocks. Farther north, near the Salar de Uyuni, there is no evidence of significant rotations. Counterclockwise rotations are observed in the Northern Altiplano. The largest counterclockwise rotation (28°) is found in Eocene‐Oligocene red beds (Tiwanaku Formation) along the eastern border of the Corque syncline. Middle Miocene sediments located within the center of the Corque basin record a counterclockwise rotation of only 10°. About 200 km north of the Corque basin, Eocene‐Oligocene sedimentary rocks near the locality of Viacha record only 10° counterclockwise rotation. Paleomagnetic results in lower Miocene ignimbrites from the forearc near the Arica bend do not show evidence for late Cenozoic rotation of the forearc. These new results suggest that the 20° to 25° counterclockwise rotation of the southern Peruvian forearc occurred prior to the Miocene. Anisotropy of magnetic susceptibility (AMS) data show a magnetic fabric mostly controlled by bedding, but slight AMS lineations are found almost parallel to the major regional structural trends such as fold axes. The apparent relationship between tectonic rotations, AMS lineations, and structural trends suggests that rotations occured after or during the final stage of folding. Paleomagnetic data obtained in Paleozoic rocks show evidence of clockwise rotation of the southern sub‐Andean ranges. Tectonic rotations during the Neogene are mostly localized on the eastern side of the central Andes. The curvature of the occidental margin near Arica was likely acquired prior to the last stage of Andean deformation. Although the magnitude of the rotations may vary from one locality to the other, there is a consistent pattern showing counterclockwise rotations to the north and clockwise to the south. A large‐scale regional mechanism is needed to explain this pattern of tectonic rotations within the central Andes. We propose a model in which along‐strike segmentation of the Andean foreland and indentation of the Altiplano by a curved forearc are the major factors controlling tectonic rotations within the Altiplano, Eastern Cordillera, and sub‐Andean ranges.

Miocene to recent history of the western Altiplano in northern Chile revealed by lacustrine sediments of the Lauca basin (18�15??18�40? S/69�30??69�05?W)

The intramontane Lauca Basin at the western margin of the northern Chilean Altiplano lies to the west of and is topographically isolated from the well-known Plio-Pleistocene lake system of fluvio-lacustrine origin that covers the Bolivian Altiplano from Lake Titicaca to the north for more than 800 km to the Salar de Uyuni in the south. The Lauca Basin is filled by a sequence of some 120 m of mainly upper Miocene to Pliocene elastic and volcaniclastic sediments of lacustrine and alluvial origin. Volcanic rocks, partly pyroelastic, provide useful marker horizons. In the first period (6–4 Ma) of its evolution, the ‘Lago Lauca’ was a shallow ephemeral lake. Evaporites indicate temporarily closed conditions. After 4 Ma the lake changed to a perennial water body surrounded by alluvial plains. In the late Pleistocene and Holocene (2-0 Ma) there was only marginal deposition of alluvial and glacial sediments. The basin formed as a half-graben or by pull-apart between 10 and 15 Ma (tectonic displacement of the basal ignimbrite sequence during the ‘Quechua Phase’) and 6.2 Ma (maximum K/Ar ages of biotites of tuff horizons in the deepest part of the basin). Apart from this early basin formation, there has been surprisingly little displacement during the past 6 Ma close to the Western Cordillera of the Altiplano. Also, climate indicators (pollen, evaporites, sedimentary facies) suggest that an arid climate has existed for the past 6 Ma on the Altiplano. Together, these pieces of evidence indicate the absence of large scale block-faulting, tilt and major uplift during the past 5–6 Ma in this area.

Crustal modification during subduction-zone magmatism: Evidence from the southern Salar de Uyuni region (20°-22°S), central Andes

Late Cenozoic volcanic rocks erupted in the southern Salar de Uyuni region of the central Andes provide evidence for recent modification of both the lower and upper continental crust during subduction-zone magmatism. At a given SiO 2 content, K 2 O and related incompatible trace element concentrations increase eastward in basaltic andesite samples and are associated with increasing Sr isotopic ratios and decreasing Sr concentrations. These data favor a model in which basaltic andesite magmas are contaminated by lower continental crust that becomes increasingly more mafic toward the active volcanic front because of relatively recent intrusion and hybridization by primary basaltic magmas. Compositions of andesitic lavas continue the geochemical trends established by the basaltic andesite samples except that Sr isotopic ratios of lavas erupted at the arc front are constant to slightly decreasing with increasing SiO 2 contents. Assimilation of upper-crustal rocks that also vary in composition across the strike of the arc is the most plausible mechanism to produce the distinct Sr isotopic trends of the andesitic lavas. At the volcanic front, the magmas producing the andesitic lavas assimilated rocks within the Quaternary volcanic and plutonic complex of the Andean arc itself. Toward the east, the magmas assimilated basement rocks that become progressively older with distance from the volcanic front because of diminishing modification by late Cenozoic arc magmatism. Thus, the across-arc geochemical trends in the southern Salar de Uyuni region are consequences of spatial variations in the composition of the lower and upper continental crust, and these variations appear to be linked to the subduction process itself.

Chemical composition and distribution of lithium-rich brines in salar de Uyuni and nearby salars in southwestern Bolivia

Preliminary investigations at Salar de Uyuni and the nearby salars (salt pans) of Coipasa and Empexa in the southern part of the Bolivian Altiplano show the presence of widespread lithium-rich brines. Widely scattered brine samples from Salar de Uyuni, which has an area of about 9000 km2 and is the largest salt pan on earth, show lithium values ranging from 80 to 1500 ppm. High values of 300–700 ppm are most prevalent in an area of about 2500 km2 in the east-central and southeastern part of the salar. A few brine samples in small areas in Coipasa and Empexa Salars have values ranging from 170 to 580 ppm Li. All the brines are essentially saturated with halite and are moderately high in sulfate (5000–15,000 ppm SO4) but low in carbonate (<500 ppm HCO3). Potassium and magnesium values are relatively high, chiefly in the range of 2000–20,000 ppm, and the KMg ratio is about 1:1. The LiK and LiMg ratios are relatively constant at about 1:20.The crystalline saline material and brines in these salars are residual from a former large lake, Lago Minchin, that occupied much of the southern Bolivian Altiplano during late Pleistocene time, augmented by saline material carried to the salars by streams since final drying of this lake. Thermal springs associated with rhyolitic volcanic rocks of Quaternary age may have been a major source of the lithium.