Pampa Del Tamarugal Research Articles

Food habits of the barn owl Tyto alba in the National Reserve Pampa del Tamarugal, Atacama Desert, North Chile

In the present study the diet of the barn owl Tyto alba was analysed in the ecosystem of Pampa del Tamarugal, in the Atacama Desert, northern Chile. The area is characterised by extremely dry conditions, and relatively homogeneous and poor vegetation, dominated mainly by tamarugo forests (Prosopis tamarugo). The results indicated that small mammals were the greatest proportion (76.2%) in the diet of the barn owl, which predated only four species, of which the rodent Phyllotis darwini (approximately 62%) represented the major proportion. Nevertheless, reptiles and arthropods were also relevant prey for the barn owl, with a proportion of 5% and 15.1%, respectively. The general dietary composition of the tamarugos barn owl showed a wide‐ranging diet pattern, characterised mainly by a poor diversity of small mammals and a significant consumption of reptiles and arthropods, in contrast to the sites in the central region and south Chile, where the diet included a greater diversity of small mammals, especially rodents. This pattern might reflect the conditions of extreme aridity, and low primary productivity in the ecosystem of Pampa del Tamarugal, restricting the abundance and diversity of the preferential prey (e.g. rodents). Hence, T. alba tends to increase its trophic diversity, adding other kinds of alternative prey to compensate for the low proportion of preferential prey available in the field. Present address: Marcelo M. Rivadeneira, Section of Ecology, Behavior & Evolution, Division of Biology, University of California, San Diego, La Jolla, CA92093–0116 California, USA

Descripción de una nueva especie de Eupithecia Curtis (Lepidoptera: Geometridae) de la Pampa del Tamarugal, Chile

Se describe el adulto de una nueva especie de Eupithecia Curtis, aparentemente endemica de la Pampa del Tamarugal, Chile. Sus larvas son antofagas sobre Prosopis tamarugo Phil. (Fabaceae). Se ilustra el adulto, VIII segmento abdominal del macho y la gentalia del macho y de la hembra.

Advective, orographic and radiation fog in the Tarapacá region, Chile

A project in northern Chile was undertaken to determine the origin and behaviour of fog in the coastal and inland locations of the Tarapacá Region. In the Pampa del Tamarugal, 50 km from the sea, conditions exist for the formation of radiation fog. Advective fog has been studied on the coast and orographic fog was observed at a few coastal sites near mountain ranges with elevations above 1000 m. Fog water collected by two standard fog collectors (SFC) for 3 1/2 years showed an average flux of 8.5 l m −2 day −1 on the coast and 1.1 l m −2 day −1 inland 12 km from the coastline. On only a few days in 10 months was water collected at the inland site of Pampa del Tamarugal. GOES satellite images are shown to illustrate the pattern of formation of the stratocumuli cloud over the sea, its approach to the coastline, the entrance of fog by corridors through the coastal range and the presence of radiation fog inland. The results are important for the understanding of fog formation and dissipation along the coastal mountain range and for the recognition of potential sites for the installation of fog water collectors, which can be used as a water source in the Atacama Desert. The results also provide vital information for use in the preservation of the unique ecosystems of the most arid desert of the world.

Tectonic signatures in arid continental basins: an example from the Upper Miocene–Pleistocene, Calama Basin, Andean forearc, northern Chile

The Calama Basin, a transtensional basin situated within the Andean forearc, and its extension to the Pampa del Tamarugal (Central Depression), is filled with 700 m of sediments. Detailed sedimentary logging and 40Ar/ 39Ar dates from interbedded volcanic deposits have established a lithostratigraphic and chronostratigraphic framework for the upper 95 m thick Upper Miocene–Pleistocene succession. Five facies associations, fluvio-lacustrine diatomite, palustrine carbonate, massive anhydrite, fluvial and alluvial fan, have been identified within this part of the basin-fill. The following events are recognised in the basin evolution: (1) deposition of diatomaceous lacustrine sediments in two separate depocentres in the Pampa del Tamarugal and the central Calama Basin, with alluvial fan accumulation along the basin margins at 8 Ma; (2) localised deformation within the central Calama Basin between 7 and 6 Ma but continuous sedimentation elsewhere; (3) palustrine carbonate deposition across the entire area from 6 to 3 Ma except in the Pampa del Tamarugal where diatomaceous sedimentation continued until 5 Ma before being replaced by palustrine carbonate deposition; (4) widespread folding after 3 Ma and entrenchment as the drainage system cut down to reach a new base level caused by the Rio Loa breaching the Coastal Cordillera and reaching the sea. Localised lacustrine deposition in topographic lows or tectonically created dams also occurred during this period. Comparison with similar age facies elsewhere in northern Chile has shown changes such as these to be localised and diachronous, indicating that tectonic controls on accommodation space and drainage patterns are the primary influence on sedimentation in this tectonic setting. The lacustrine deposits do not appear to be a reliable recorder of low-frequency climatic change. This is exemplified by the change from lacustrine to palustrine deposition at 6–5 Ma which would appear to record a drying of the climate. However, a synchronous change from ephemeral alluvial fan deposition to more permanent fluvial deposition at the basin margins indicates increased run-off.

A preliminary petrographic study of the Chilean nitrates

AbstractThe nitrate deposits of the northern Atacama Desert occurin a narrow zone between the low-lying Pampa del Tamarugal to the east and the hills of the Coastal Range to the west. High purity nitrate ore occurs as stratiform seams about 20 cm thick, present at depths of 3–7 m below thedesert surface. The ore is hosted by a variety of lithologies and overlain by salt-cemented regolith. The ore is largely composed of nitratite (= sodanitre or Chilean salt peter) and halite with locally abundant humberstonite, polyhalite and mirabilite. Other salts present include Ca iodates and a variety of sulphate, borate and chromate minerals. Textural relationships can be used to deduce paragenetic sequences for individual salt samples and these combined to produce a generalized paragenetic web for the nitrate ore.These textural data can be combined with published solubility data to investigate the course of fluid evolution during ore genesis. The multiplicity of paragenetic relationships within the ore reflects the derivation of precipitating fluids from a variety of sources: westwards flowing Andean groundwater, coastal fogs, occasional rainfall and Andean-derived surface floodwaters. The unusual mineralogy of the nitrate ore reflects the extreme chemical evolution of the precipitating brines through multiple episodes of salt precipitation and remobilization during transport to the nitrate horizons. The formation of high purity nitrate ore appears to be the result of multiple phases of dissolution, reprecipitation and recrystallization, that have separated the highly soluble nitrate salts from less soluble salts in the overlying profile. Salts have largely accumulated through displacive growth, but some of the host silicate and carbonate lithologies have also undergonea small degree of salt replacement.

Silvopastoral systems in arid and semiarid zones of northern Chile

The main silvopastoral systems carried out in arid and semiarid zones of northern Chile are presented. Plantations with quenoa (Polylepis besseri) in the Precordillera (3,000–4,000 meters above sea level) and with ‘quenoa de altura’ (Polylepis tarapacana) in the High Plateau (over 4,000 m.a.s.l.) are described. For extremely arid zones (2 mm/yr), tamarugo (Prosopis tamarugo) and algarrobo (Prosopis chilensis) plantations in Pampa del Tamarugal are reviewed. In this zone 20,483 ha have been planted, 88% with P. tamarugo. These plantations feed a variable herd of 7,000–9,000 sheep and goats per yr. The forage produced per tree varies from 20 to 70 kg/yr for 14 to 22 yr old trees, planted in densities of 100/ha. For the semiarid zone, plantations with forage shrubs of the genus Atriplex are described. Between 1975 and 1989, about 37,000 ha were planted in the coastal zone of Coquimbo region, 60% of them with A. nummularia and the rest with A. repanda. Productivity varies widely in both species. It depends on management techniques and environmental variables. Afforestation with such species offers green forage during periods of scarcity of natural grasses, especially during long droughts. The rate of afforestation is declining because the government has stopped planting, and the private sector is planting less than expected. This is because often yields have been low, due to either natural causes or deficient management.

Reforestation of arid and semi-arid zones in Chile

The paper describes past experience and the present state of reforestation in the arid and semi-arid zones of Chile. Some edaphoclimatic reference information is given for the areas. A summary is given of species introduction trials carried out to date with their initial results and indications of the experimental designs employed. Information is included concerning silvicultural experience with Atriplex nummularia Lindl. in the areas where it is extensively planted. Some important results obtained with the species Simmondsia chinensis (Link.) Schneider are presented. This species is currently being planted on a commercial scale in Chile. Information is also included on experience with Prosopis tamarugo Phil, a species growing in the Pampa del Tamarugal, one of the most inhospitable deserts in the world. Information is presented on nursery techniques and planting of this species, with results on yield and technical coefficients used. Finally, a summary is given of the policy that Chile is applying in the development of land in the arid and semi-arid zones.

Source of Ground Water in the Deserts of Northern Chile: Evidence of Deep Circulation of Ground Water from the Andes

AbstractGround water in the Pampa del Tamarugal basin part of the desert of Northern Chile is the main water resource for cities and agricultural activities in the region. As the area received virtually no precipitation, the source of the ground water is rains in the high Andes. Aquifer recharge has been linked to a drainage system associated with this part of the Andes. Ground‐water flow is from northeast to southwest, and a flow component from east to west is also observed in some parts of the basin. In general, the water becomes very saline towards the western part of the basin, giving rise to salt lakes (salares) in ground‐water discharge areas. However, isotopic, chemical, and geological evidence plus ground‐water temperatures distribution, suggest the existence of a different recharge mechanism linked to a regional ground‐water flow system. It is suggested that low‐salinity water emerges from ground water recharged in the high Andes through a basement fault system underneath the basin. This model has implications for the future exploration for new fresh‐water resources.

Rôle du volcanisme explosif et du vent dans la formation des précipités calcaires quaternaires («tosea») de la Pampa argentine

Calcretes have been a traditional subject of polemics between edafologists considering them as generated by pedogenic processes, and geomorphologists who attributed the transportation of their calcium carbonate to surficial run-off. Recently, some english-speaking Authors have gathered evidence of the role of wind in dust transport and on the contribution of this dust for the formation of soils. J. Tncart, in 1968, demonstrated that the alcalis which turn rural development very difficult in the pampa Deprimida of Argentine, has been transported by westerly winds and has probably a volcanic origin. The present paper treats of the regions which form half a circle from the NW to the SW of the pampa Deprimida They are characterized by limestone deposits, indurated ("tosca", equivalent of the mexican "caliche"), or not The following results have been obtained from field observations, as unfortunately no laboratory investigations have been possible. 1) The calcium carbonate, which predominates in the area, and the alcalis of the "sahtrales" are wind transported. 2) In some places, calcium carbonate is mixed with volcanic ashes and small pyroclastic debris. It is therefore presumed of volcanic origin. 3) Rainfalls, presumably resulting for a part of the volcanic explosions themselves, have partially dissolved the limestone dust and precipitated the carbonate when water evaporated It resulted in a diagenesis of the carbonate into laminated calcrete and, underneath, when water was abundant enough, into veins and concretions along the water paths, amist the unconsohdated silty carbonate Regional differences can be noted according to the amount of precipitations, which is lower westwards, and which have changed during the pleistocene with alternating dry and wet periods, as demonstrated in the Pampa Deprimida. 4) "Tosca" does not result from pedogenic processes : it crops frequently, without any cover, on the highest points of the landscape, so that it cannot be an exhumed BCa horizon. Presently, in the wetter parts of the area investigated, i.e. around Sta Rosa, calcrete suffers a destruction by pedogenesis and rendzina soils are forming In the West of La Pampa Province, alcalis have been deposited on solid basalt, contained in aeohan sandy loams. Their lixiviation by throughflow feeds extensive "sahtrales" which seem to be the equivalent of the closed basins of the western side of the Andes, in the Chilean Pampa del Tamarugal, where nitrate has been mined and still is in decreasing quantities. 5) The volcanic dust, both calcarous and alcaline, has been transported by westerly winds, as formerly established by investigations in the Pampa Deprimida. Sedimentation decreases eastwards. Calcareous dust, probably coarser than alcaline dust, has been deposited first and has not reached the Pampa Deprimida when alcali aerosols did Alcaline dust is found along a kind of beam from Corral de Piedra to the Pampa Deprimida, passing through the extensive "sahtrales" near Puelén (Salitral de la Perra). The distribution of both calcareous and alcaline wind-born products suggests that they come from the South of Neuquén Provinc but from volcanoes, not yet precisely identified. 6) Calcareous dust have been deposited from the North of the Rio Negro Province to the South of Cordoba Province, during at least 3, more probably 4 paroxysmal periods during the Pleistocene.

Isotope hydrology of groundwaters in the Pampa del Tamarugal, Chile

The water resources in northern Chile are extremely scarce and development is limited by this. This paper discusses the isotope hydrology of groundwaters in the Pampa del Tamarugal — an area of extreme aridity (rainfall < 1 mm/yr.) — whose groundwater resources are mined for the town of Iquique, as well as for industrial and agricultural purposes. The aim of the project was to obtain information on modern recharge and to delineate, if possible recharge environments. To obtain the necessary background information a precipitation survey in the high Andes, as well as spring- and surface-water studies were carried out. The results show that a well-defined meteoric water line exists where σ 2 H = (7.8 σ 18 O + 10.3)% , and altitude effects depend on air-mass movements and cannot be defined without a broader regional and detailed sampling programme. However, it is still possible to assign maximum altitudes of recharge to springs in the Andes and at the eastern border of the Pampa del Tamarugal. Comparison of these data with groundwater compositions show, that these groundwaters originate from infiltrating surface water rather than directly infiltrated precipitation. A dependence of individual groundwater systems on specific quebradas (river valleys) is recognized. However, low 14C activities indicate that most of the waters pumped today are fossil and at least several hundreds if not thousands of years old. Some minor subsurface recharge does occur at the foot of the Andes, especially at Pica where high-altitude waters discharge, but even there groundwater appears to be a diminishing resource.