North-central Andes Research Articles

Densities and habitat preferences of Andean cloud-forest birds in pristine and degraded habitats in north-eastern Ecuador

SummaryThe montane cloud-forests of the north-central Andes and the montane grassland and transitional elfin forest of the central Andean páramo contain a high diversity of bird species including several restricted range and uncommon species. Little is known of how densities of Andean cloud-forest species are affected by habitat degradation. Bird densities within pristine and degraded habitats at the Guandera Biological Reserve, Carchi province, Ecuador were recorded over a 10-week period. Densities were calculated for 48 species; where densities could be compared, 69% of species occurred at a higher density in pristine habitats. Pristine forest had the highest species richness with 72 species and páramo contained 44 species. In total, 26% of pristine forest species were only found in pristine forest, 39% of páramo species only in páramo, 13% of farmland species only in farmland and there were no exclusively secondary scrub species; 47% of species found in pristine forest, and 50% found in páramo were found in both secondary scrub and farmland. Restricted range species recorded at Guandera included the Carunculated Caracara Phalcobenus carunculatus, Black-thighed Puffleg Eriocnemis derbyi, Chestnut-bellied Cotinga Doliornis remseni, Crescent-faced Antpitta Grallaricula lineifrons, Masked Mountain-tanager Buthraupis wetmorei and Black-backed Bush-tanager Urothraupis stolzmanni. Three further species that occurred at Guandera of relatively local occurrence were the Grey-breasted Mountain Toucan Andigena hypoglauca, Golden-breasted Puffleg Eriocnemis mosquera and Mountain Avocetbill Opisthoprora euryptera. Of these nine species at least five used degraded habitats, while three occurred only in pristine treeline habitats.

Reliability analysis for design of stake networks to measure glacier surface velocity

AbstractMeasurement of glacier surface velocity provides some constraint on glacier flow models used to date ice cores recovered near the flow divide of remote high-altitude ice caps. The surface velocity is inferred from the change in position of a network of stakes estimated from the least-squares adjustment of geodetic observations – terrestrial and/or spaced-based – collected approximately 1 year apart. The lack of outliers in and the random distribution of the post-fit observation residuals are regarded as evidence that the observations contain no blunders. However, if the network lacks sufficient geometric redundancy, the estimated stake positions can shift to fit erroneous observations. To determine the maximum size of these potential undetected shifts, given the covariance of the observations and the approximate network geometry, expressions are developed to analyze a network for redundancy number and marginally detectable blunders (internal reliability), and the position shifts from marginally detectable blunders (external reliability). Two stake networks, one on the col of Huascar–n (9°–07'S, 77°–37'W; 6050 m a.s.l.) in the north-central Andes of Peru and one on the Guliya ice cap (35°–17'N, 81°–29'E; 6200 m a.s.l.) on the Qinghai–Tibetan Plateau in China, are examined for precision and internal and external reliability.

Reliability analysis for design of stake networks to measure glacier surface velocity

AbstractMeasurement of glacier surface velocity provides some constraint on glacier flow models used to date ice cores recovered near the flow divide of remote high-altitude ice caps. The surface velocity is inferred from the change in position of a network of stakes estimated from the least-squares adjustment of geodetic observations – terrestrial and/or spaced-based – collected approximately 1 year apart. The lack of outliers in and the random distribution of the post-fit observation residuals are regarded as evidence that the observations contain no blunders. However, if the network lacks sufficient geometric redundancy, the estimated stake positions can shift to fit erroneous observations. To determine the maximum size of these potential undetected shifts, given the covariance of the observations and the approximate network geometry, expressions are developed to analyze a network for redundancy number and marginally detectable blunders (internal reliability), and the position shifts from marginally detectable blunders (external reliability). Two stake networks, one on the col of Huascar–n (9°–07'S, 77°–37'W; 6050 m a.s.l.) in the north-central Andes of Peru and one on the Guliya ice cap (35°–17'N, 81°–29'E; 6200 m a.s.l.) on the Qinghai–Tibetan Plateau in China, are examined for precision and internal and external reliability.

From Clay to Pots: A Petrographical Analysis of Ceramic Production in the Callejón de Huaylas, North-Central Andes, Peru

At the cross-roads of ethnoarchaeology and ceramic studies, this article investigates the compositional relationship between the different constituents of ceramic paste. The question related to provenance and technical studies is how one can recognize the different raw materials in the ceramic, when both are soils. The context of study is the ceramic production of three potters of the Callejón de Huaylas in the Peruvian Andes. Detailed petrographical analysis of unfired earths, and of the pot produced, shows mineral differences between the raw materials. These can be identified within the ceramic fragment. Variability in granulometry and composition is introduced during the manufacturing process as a result of the preparation and mixing of the constituents. Differences between manufacturing centres and clay sources are even more obvious with X-ray fluorescence analysis. The different raw materials used can be identified in the pot if raw materials are sampled around the centre of production. Analysis of traditional ceramics is essential in appreciating ceramic technology and its influence upon the mineral and chemical composition of ceramic paste. This will enable a richer analysis of prehistoric ceramic production and distribution.

Late Glacial Stage and Holocene Tropical Ice Core Records from Huascarán, Peru

Two ice cores from the col of Huascarán in the north-central Andes of Peru contain a paleoclimatic history extending well into the Wisconsinan (Würm) Glacial Stage and include evidence of the Younger Dryas cool phase. Glacial stage conditions at high elevations in the tropics appear to have been as much as 8 degrees to 12 degrees C cooler than today, the atmosphere contained about 200 times as much dust, and the Amazon Basin forest cover may have been much less extensive. Differences in both the oxygen isotope ratio zeta(18)O (8 per mil) and the deuterium excess (4.5 per mil) from the Late Glacial Stage to the Holocene are comparable with polar ice core records. These data imply that the tropical Atlantic was possibly 5 degrees to 6 degrees C cooler during the Late Glacial Stage, that the climate was warmest from 8400 to 5200 years before present, and that it cooled gradually, culminating with the Little Ice Age (200 to 500 years before present). A strong warming has dominated the last two centuries.

Tomato-like nightshades: Affinities, autoecology, and breeders’ opportunities

The group of nightshades I would like to discuss consists of four species: Solahum juglandifolium Dun., S. lycopersicoides Dun., S. ochranthum Dun., and S. rickii Corr. (Solanaceae). Belonging to section Petota, subsection Potatoe, series Juglandifolia, they differ from other species in Potatoe and resemble Lycopersicon in respect to absence of tubers and presence of yellow corolla. Other tomato-like features that distinguish them from the great majority of Solanum species are articulated pedicels and pinnately segmented leaves. In the aggregate, the association of all of these traits in the four species renders them unique amongst the myriad Solarium species. They nevertheless differ from Lycopersicon in several important features to be considered below and are reproductively isolated from them by formidable reproductive barriers, which have been circumvented only in crosses with S. lycopersicoides, and even in this instance, only as a consequence of experimental manipulations. All of these species are diploids (2n = 24). My interest in this group was stimulated in the 1940s by a collection of S. lycopersicoides provided by Professor T. H. Goodspeed, collected by R. D. Metcalf in 1942 (his No. 30382) near Candarave, Dept. Tacna, Peril, under the auspices of the third University of California Botanical Garden Expedition to the Andes. Of the seed collected, only a few germinated at the UC-Berkeley Botanical Garden, but we were able to maintain a clone therefrom and utilize it in experiments to which I shall refer later. Since that time it has been my good fortune to visit populations of all four species in their native habitats, to make many collections of them, and to culture them for seed increase and various studies. This group is important for several reasons. Breeders constantly probe new sources of germplasm for purposes of plant improvement. The cultivated tomato (L. esculentum L.) is one of a large group of crop species whose genetic variability is so greatly reduced that they lack many genes needed for breeding purposes. In the case of the tomato, this depletion evidently resulted from events that ensued prior to, during, and subsequent to domestication (Rick 1976). The generally accepted immediate ancestor of the tomato is var. cerasiforme of the cultivated species--a largely self-pollinated taxon that evidently migrated from its ancestral area in the north central Andes to its area of domestication in Mesoamerica. Founder events during this migration (doubtlessly often in small populations) would have tended to diminish genetic variability existing in the original source(s), a situation verified by comparisons of genetic content of monogenically determined isozymes (Rick et al. 1974; Rick and Fobes 1975). The domestication process itself in a self-pollinator would have tended to further reduce reserves as a result of selection for desired types. Finally, transport to Europe, further mi

Geologic, Fluid Inclusion, and Stable Isotope Studies of the Pasto Buena Tungsten-Base Metal Ore Deposit, Northern Peru

The Pasto Bueno tungsten-base metal ore deposit is situated at an elevation of nearly equal 4,000 meters in the north-central Andes of Peru. Mineralization occurs in near-vertical quartz vein systems that span several hundred meters on either side of the upper intrusive contact of a 9.5-m.y.-old quartz monzonite stock emplaced in a Jurassic-Cretaceous shale and quartzite sequence. The stock exhibits four pervasive and roughly zoned alteration assemblages from core to periphery: (1) alkalic, (2) phyllic-sericitic, (3) argillic, and (4) propylitic. Greisen assemblages of zinnwaldite, fluorite, pyrite, and minor topaz and tourmaline occur within the phyllic zone.The principal vein minerals are wolframite, tetrahedrite/tennantite, sphalerite, galena, and pyrite in a gangue of quartz, fluorite, sericite, and carbonate. Detailed studies of the hydrothermal mineral paragenesis established three major recognizable divisions: Greisen (60 to 70 percent of deposition), Vein (25 to 35 percent of deposition), and Vug ( 40 equivalent weight percent NaCl), high-temperature (400 degrees to 500 degrees C) solutions of magmatic derivation. The subsequent main Vein stage ore fluids attained a temperature range of 175 degrees to 290 degrees C and a salinity range of 2 to 17 equivalent weight percent NaCl. Boiling of the ore solutions is indicated only for the Greisen and early Vein stages of hydrothermal activity.The results of stable isotope studies on water in primary fluid inclusions indicate that the delta D (sub H 2 O) of the ore fluids varied from -29 per mil to -88 per mil (SMOW). Analyses of water contained in secondary inclusions indicate the delta D (sub H 2 O) of the fluids attained values as low as -145 per mil prior to the cessation of hydrothermal activity. The delta 18 O (sub H 2 O) of the hydrothermal fluids, as calculated from the delta 18 O quartz and carbonate data and the temperature data, range from +7.8 per mil to +0.0 per mil (SMOW). The delta D value of present-day meteoric water is --96 per mil.The patterns for delta D (sub H 2 O) and delta 18 O (sub H 2 O) values of the hydrothermal fluids indicate that mixing of a meteoric and possibly a metamorphic or other water component with water of magmatic derivation occurred during Vein stage deposition. Major variations in the deuterium content of the ore solutions are not reflected by fluctuations in the 18 O content, indicating that meteoric water circulated deep into the hydrothermal plumbing system. Wolframite deposition was associated with episodes of meteoric water influx that are reflected in the temperature, salinity, and delta D values of the water in fluid inclusions. Sulfide mineralization, on the other hand, was associated with water of magmatic derivation.The delta 13 C data for hydrothermal CO 2 range from --4.1 per mil to -11.9 per mil (PDB) and are interpreted to indicate that the carbon in the ore fluids was derived from both sedimentary and deep-seated sources. delta 34 S values of pyrite data exhibit a narrow range of values (-2.5 per mil to +3.9 per mil) with an average of +0.6 per mil, indicating that the sulfur was derived from a deep-seated or mantle source.Most of the components present in the Pasto Bueno ore deposits appear to be of magmatic origin. Clearly however, significant volumes of meteoric water and possibly other water were involved in some stages of the ore deposition process.

Mineral Resources of Ecuador-Development and Prospects: ABSTRACT

Mineral deposits in Ecuador are many but only one metalliferous mine, the Portovelo gold mine, now is operating. It was worked in colonial times but on a systematic basis only since 1904. Gold was the principal product together with silver, copper, lead, and zinc. At present, copper is more important but the ore reserves are virtually exhausted. The Macuchi mine was worked for copper, gold, and silver in the 1940s and prospects containing various combinations of copper, silver, lead, and zinc were discovered at La Plata, Sigchos, Molleturo, and Pilshum. In 1965 the United Nations in cooperation with the newly established Servicio Nacional de Geologia y Mineria began a seven-year mineral resources survey. The principal discovery was the Chaucha porphyry copper-molybdenum deposit where 55 million tons of 0.7-percent copper were proved. Other porphyry copper-molybdenum deposits were discovered at Los Linderos, Rio Playas, and Fierro Urco. At Fierro Urco 50 million tons of ore with low-gold values was indicated. Vein-type mineralization at Angas (copper, lead, zinc, silver, and gold), San Bartolome (silver and lead), and Uritohuaser (zinc, lead, and silver) also were discovered. Anomalies in tin and tungsten minerals were found near Saraguro. Most surveys have been in the southern Andes where exposed Tertiary and older rocks are intruded by granitic bodies. The flanks of the Andes have not been explored thoroughly because of difficult access and dense forest. Much of the north-central Andes has a cover of Quaternary volcanic rocks mantling the older rocks, but until there are methods to probe through this thick mantle for possible mineralization the potential is unknown. The prospects however must be good because the Ecuadorian Sierra is part of the great mineralized mountain belt extending through the western Americas. End_of_Article - Last_Page 1451------------

Native Pastoralism in the South Andes

Although it has usually been recognized that the Andean llama and alpaca (Lama glama and Lama pacos, respectively; Gilmore I950) were aboriginal domestic herd animals, it has been widely assumed that pastoralism never became a primary mode of adaptation in the New World, and that even subsequent to the conquests it was anomalous and restricted to European animals. Ethnographers of the Central Andes have considered the herding of lamoids a subsidiary enterprise undertaken by communities based primarily on cultivation. The early chronicler Poma asserted that it was invariably a task of age-grades, and in I93I Troll was sure that no pastoral economy had developed anywhere in the Andes apart from tuber cultivation (Murra I965: I88-I89). Murra's research has revealed the important role of alpacas and llamas in the economy, social stratification, and ritual of the aboriginal Andean states, but he too concludes that herding was always carried out in upland grazing stations by kin, retainers, or a social class based in agricultural communities. However, because control of herds was a key basis of wealth and prestige in the south central Andean plateau and Titicaca basin, such hierarchical situations were likely to develop under the centralized regimes of this area whether or not pastoralism was previously an independent enterprise in some communities. Even under these regimes independent pastoral communities could have continued in the harsh puna uplands or remote cordillera flanks, jurally subservient but in de facto control of their herds. The elitist bias of most colonial reports, usually overlooking provincial situations, could have continued to obscure the existence of such communities. I suspect that a similar research bias has perpetuated our ignorance until recently. Gade (I969) has reconsidered several misconceptions regarding the Andean lamoids, but does not directly consider the question of pastoralism. This matter remains to be resolved by ethnography and ethnohistory. Recent evidence in Andean ethnography substantiates the contemporary existence of pastoral communities based on herding of native lamoids, and strongly suggests that similar adaptations were ancient. Lynch (I97I ) has analyzed archeological data from the Callejon de Huaylas of the north central Andes which suggests that pastoral transumance may have developed in preceramic times and furnished an appropriate human ecosystem for the domestication of cultigens. Insofar as this area is peripheral for the distribution of the llama and probably outside the range of the alpaca one suspects that these lamoids were neither late domesticates nor nec-

Structural Evolution of the Cordillera Huayhuash, Andes of Peru

An expedition to the Cordillera Huayhuash in the north-central Andes of Peru has shown the range consists of complexly folded and thrust-faulted Cretaceous sedimentary rocks, and less deformed early to middle Tertiary(?) andesitic volcanic rocks, all intruded by granitic plutons thought to be as young as 9 m. y. B.P. A younger sequence of felsic ash flows has escaped folding and intrusion. Unlike the Cordillera Blanca to the north (a batholith), the major 6,000 m summits of the Cordillera Huayhuash are carved from a complex synclinorium of Upper Cretaceous Jumasha Formation carbonates. The region has suffered two deformations. The first deformation was the most severe, producing tight flexural-slip and flexural-flow folds and east-directed thrust faults between Late Cretaceous and middle(?) Tertiary. During deformation, detachment of the Cretaceous prism from some unexposed basement occurred at the horizon of basal Cretaceous Oyon Formation shale. Less severe middle(?) Tertiary deformation warped andesitic volcanic rocks into broad gentle folds, and may have either reactivated or initiated thrust faults. Field data and hypsometric (area altitude) analysis suggest the middle to late Tertiary Puna erosion surface is represented in the Cordillera Huayhuash by accordant flanking ridge-tops and a landmass concentration below 5,000 m. The 6,000 m axial ridge stood above this surface as a residual mass around which ash flows were deposited. Latest Tertiary to Quaternary orogenic uplift, perhaps during the last 6 m.y., incised drainage and represents the most recent deformation of the region.