Ojo De Agua Research Articles

Human burials during the hunter‐gathering/farming transition in Ojo de Agua, Northern Patagonia, Argentina

AbstractThis paper explores the implications of the conformation of formal burial areas in the southernmost limit of agricultural dispersion in South America. Previous research proposed the development of cemeteries or formal burial areas due to specialization in using specific habitats and the development of territorial ownership. From a paleoecological background, we hypothesize that hunter‐gatherers intensified resource exploitation and develop territoriality in population growth and pressure over resources. The expectation is that formal burial areas emerged in this context to legitimize the ties with the territory and ensure exclusive access to the land and its resources. To evaluate this hypothesis, we analyzed a mortuary context from southern Mendoza (Central Western Argentina), named Ojo de Agua, by describing the site's characteristics, burial modality, presence of grave goods, age at death profile, and evidence of violence. This site has two main conditions for handling our hypothesis: (1) the chronology and spatial localization coincide with the temporal and geographic dispersion of pre‐Hispanic cultigens; (2) systematic procedures during fieldwork led us to access a significant amount of information not available in other mortuary contexts of the area. Our results point to Ojo de Agua as a cemetery that emerged in the frame of increasing territoriality and conflict with neighboring groups and permitted us to improve our knowledge about the dynamic relationship between human population, environment, and cultural responses in the context of intensification and contact with food production. These results deepen recent studies in the same line but with a greater resolution.

Ancient mitochondrial genome diversity in South America: Contributions from Quebrada del Toro, Northwestern Argentina.

The objective of this study was to enhance our understanding of the population history in South America, specifically Northwestern Argentina, by analyzing complete ancient mitogenomes of individuals from the Ojo de Agua archeological site (970 BP) in Quebrada del Toro (Salta, Argentina). We analyzed teeth from four individuals from the site Ojo de Agua (970 ± 60 BP), located in Quebrada del Toro (Andean region of Northwestern Argentina). DNA extracts were converted to double-stranded DNA libraries and indexed using unique dual-indexing primer combinations. DNA libraries were then enriched for the complete mitochondrial genome, pooled at equimolar concentrations, and sequenced on an Illumina® MiSeq™ platform. Reads from high quality libraries were trimmed, merged, and then mapped to the revised Cambridge Reference Sequence. The aDNA damage patterns were assessed and contamination estimated. Finally, variants were called, filtered, and the consensus mitogenome was constructed and used for haplogroup assignment. We also compiled available mitogenome sequences from ancient and present-day populations from the Southcentral Andes and other surrounding regions in Argentina. Maximum Likelihood and Bayesian phylogenetic reconstructions were obtained using the generated dataset. We successfully obtained the complete mitogenome sequence from one individual with an average depth coverage of 102X. We discovered a novel haplotype that was assigned to haplogroup D1. Phylogenetic reconstructions suggests that this haplotype falls within the sister branches of the D1j lineage, forming a well-supported clade. The estimate TMRCA of this clade that includes D1j and its sister branches ranged between 12,535 and 18,669 ya. The sequence analyzed in this study represents the first ancient mitogenome from within the valley region in Northwestern Argentina. We found that a representative of a lineage highly associated with D1j was already present approximately 1000 BP in the region. Our results agree with the proposed origin of D1j in other regions north of Patagonia and independent of the Pacific coast fast migratory route, contrary to what was originally hypothesized. This study highlights the lack of information regarding pre-Hispanic genetic diversity and contributes to the knowledge about the peopling process in South America.

Inequality on the southwest Maya frontier: House size variations in three polities of the Rosario Valley, Chiapas

AbstractBeing a form of labor investment, house size is frequently analyzed as an index of socioeconomic inequality. However, datasets that lack wide-ranging residential stratigraphic information are not reliable sources of labor investment estimates. This is the case for Late Classic domestic architecture data from three polities in the Rosario Valley (modern-day Chiapas) on the southwest Maya frontier: Rosario, Ojo de Agua, and Los Encuentros. Although the sample's house size inequality generally cannot index period-specific labor investment, it may signify prestige differentiation. For each polity we generated Lorenz curves and calculated Gini coefficients for five variables representing house size (area and volume). Results resemble inequality data from lowland Classic Maya centers. We also demonstrate that the smallest, shortest-lived polity had more equal house size values, likely due to the modesty of its apical elite architecture. In contrast, the two larger, older polities were more unequal because they had substantial palaces.

Crustal focal mechanisms in the NW sierras de cordoba, and connections with mio-pliocene basement thrusting of the easternmost Sierras Pampeanas, south-Central Andes

The seismicity studied in this paper is located along the back arc region, between 30°35′ and 31°52’ S latitude, in the morphostructural unit known as Eastern Sierras Pampeanas. Seventeen crustal earthquakes could be identified and located, between June 2004 and March 2018, using seismic data recorded by the broadband seismological network of National Institute for Seismic Prevention (INPRES), combined with free seismic data from the Incorporated Research Institutions for Seismology (IRIS). Focal mechanisms were calculated from localized seismicity using the P-wave first motions and interpreted as a strain style on the western portion of Sierras de Córdoba. Overall, the seismicity in this region during the study period was constrained to the upper ∼25 km of the crust and is mostly concentrated along minor structures and not along the major range-bounding faults. Although there is evidence of quaternary activity along the larger structures, the relationship between these displacements and modern deformations is not well developed due to the lack of local seismic stations in the area and the long recurrence interval between earthquakes of significant magnitudes. However, very recent morphometric studies in the Sierras Pampeanas have analyzed the main topography controls and suggested relatively higher uplift rates in the central sectors of the Sierra de Pocho, and a balance between tectonic uplift and erosion rates. Nevertheless, three seismic events showed greater depths around 36 km according to previously proposed geological and geophysical models of crustal thickness and mohorovicic depth. Although focal mechanism solutions show varied results, distributed throughout all the region, it is possible to determine an inverse deformation with an oblique component assigned to regional faults and an area where a normal deformation with an oblique component predominates, near to the Ojo de Agua Lineament. Accordingly with seismological observations, we proposed a model in which the seismogenic structures seem to have detached from deep horizontal intra-crustal interfaces that affects the faults and brittle structures, which document that the Eastern Sierras Pampeanas are actively deforming in response to compression from the convergent margin.

Ore Mineralogy, Geochemistry, and Dating (Re-Os, Ar-Ar) of the El Volcán Porphyry/Epithermal System, Maricunga Gold Belt, Northern Chile

Abstract The El Volcán gold project (8.9 Moz Au @ 0.71 g/t Au) is located in the Maricunga gold belt in northern Chile, on the flank of the large Cenozoic Copiapó Volcanic Complex. Precious metal mineralization is hosted in two zones (Dorado and Ojo de Agua) of (pervasively) altered Miocene porphyry intrusions and lava flows of andesitic to rhyolitic composition, and in breccias. The ore zones reflect an evolving magmatic-hydrothermal system with mineral assemblages of magnetite-ilmenite-pyrite-molybdenite (early), bornite-chalcopyrite-pyrite-rutile (stage I), chalcocite-chalcopyrite-enargite-fahlore-pyrite (stage II), and chalcopyrite-covellite-pyrite (stage III). Alteration is dominantly of Maricunga-style (illite-smectite-chlorite ± kaolinite), partly obscured by quartz-kaolinite-alunite ± illite ± smectite alteration. Powdery quartz-alunite-kaolinite alteration with native sulfur and cinnabar forms shallow steam-heated zones. Early K-feldspar ± biotite alteration is preserved only in small porphyry cores and in deep drill holes. Most gold is submicrometer size and is in banded quartz veinlets, which are characteristic of the Maricunga gold belt. However, some gold is disseminated in zones of pervasive quartz-kaolinite-alunite alteration, with and without banded quartz veinlets. Minor visible gold is related to disseminated chalcocite-chalcopyrite-enargite-fahlore-pyrite. The lithogeochemical database identifies a pronounced Au-Te-Re signature (>100× bulk crust) of the hydrothermal system. Molybdenum-rich bulk rock (100–400 ppm Mo) has an Re-Os age of 10.94 ± 0.17 Ma (2σ). 40Ar-39Ar ages on deep K-feldspar alteration and on alunite altered rock have the same age within error and yield a combined age of 11.20 ± 0.25 Ma (2σ). The formation of the El Volcán gold deposit took place during the establishment of the Chilean flat-slab setting in a time of increasing crustal thickness when hydrous magmas were formed in a mature arc setting. The vigorous nature of the hydrothermal system is expressed by abundant one-phase vapor fluid inclusions recording magmatic vapor streaming through a large rock column with a vertical extent of ≥1,500 m.

Presence of Arsenic in Potential Sources of Drinking Water Supply Located in a Mineralized and Mined Area of the Sierra Madre Oriental in Mexico.

Mine wastes from the La Aurora mine in the state of Guanajuato were generated by the flotation process and placed in four tailing dumps on the local stream while the plant operated. Given that these wastes contain toxic elements, it is important to establish their impact on the quality of several surrounding natural sources of water that are considered potential drinking water supplies. This study identified four water source types, in which the contents of arsenic (As), mercury (Hg), and thallium (Tl) were exceeded, according to international guideline values for drinking water quality. The first type of aqueous sample corresponded to leachates produced by rainwater infiltration in tailings and water–mineral waste interactions. The second type corresponded to surface water along the Xichú and La Laja Streams, and the third and fourth types involved two groundwater well samples and spring samples, respectively. The Chiquito Stream was used as a reference area that had not been impacted by the mine wastes. The isotopic signatures associated with δ34Ssulfate and δ18Osulfate compositions from the El Ojo de Agua spring are similar to those of the Santa María River and are different from those of the mine waste leachates. This study shows evidence of the presence of As in the El Ojo de Agua spring, which results from dissolution of secondary mineral phases that were produced by alteration of the mine wastes, which then migrated along the Xichú Stream system until reaching the spring. These As-bearing fine particles are prone to dissolution when in contact with this water source. Principal component analysis revealed that the observed As, Tl, and Hg can be attributed to weathering of the mine wastes. However, the results suggest that a natural contribution of these elements could be associated with rainwater–igneous rock interactions.

The sauropod record of Salitral Ojo del Agua: An Upper Cretaceous (Allen Formation) fossiliferous locality from northern Patagonia, Argentina

The record of sauropods in the Upper Cretaceous of Patagonia is rich. However, there are still several blanks on this record. Here it is described a new sauropod assemblage coming from the Salitral Ojo de Agua Area, Río Negro province, northern Patagonia, Argentina (Allen Formation; Maastrichtian). Remains of indeterminate saltasaurines, aeolosaurines, as well as new specimens of the small saltasaurine Rocasaurus muniozi and the new eutitanosaur Menucocelsior arriagadai gen. et sp. nov., are described. The new eutitanosaur is represented by an incomplete caudal series and some appendicular bones that indicate that it does not belong to any previously recognized eutitanosaur clade (e.g, Colossosauria, Saltasaurinae, Aeolosaurini). The co-occurrence of several roughly coeval titanosaurs in a restricted area (as occur in Bajo de Santa Rosa, Salitral Moreno and Salitral Ojo de Agua sites) with different body plans, indicates that they probably occupied particular ecological niches and that probably competition for resources was limited, allowing the connivance of several taxa in a single locality and age. This pattern is not observed in other sites of the world. Based on these records and on the high diversity of osteoderm morphotypes recovered, it appears to be certain that palaeoecological conditions in the area were able to sustain and promote the flourishing of many species of titanosaurs.

Crecimiento demográfico y degradación de los recursos: El caso del agua en las comunidades Ojo de Agua y Crun Shurin, de los territorios indígenas Boruca y Térraba del Pacífico de Costa Rica (2000-2019)

En el presente artículo se investiga la gestión social del recurso hídrico en las comunidades indígenas Ojo de Agua y Crun Shurin, del Pacífico de Costa Rica, con la intención de identificar a los actores sociales e institucionales involucrados, así como las relaciones entre ellos. Específicamente, se exploran los retos en materia de acceso al agua manifestados por personas indígenas de ambas comunidades, así como el papel de las instituciones estatales en la búsqueda de soluciones a dichas problemáticas. Se hizo uso de entrevistas grupales, estadísticas sobre el crecimiento demográfico en los dos territorios y se evaluó, mediante análisis de laboratorio, la calidad del agua que consumen diariamente, para señalar posibles fuentes de contaminación.

<p class="Body"><strong>Mites associated to chile piquín (<em>Capsicum annuum</em> L. var. <em>glabriusculum</em>) in two Protect Natural Areas in Northeastern México</strong></p>

The conservation status of an ecosystem is checked by studying the composition and diversity of the organisms that interact in trophic chains. The aim of this study was to evaluate the biodiversity of mites associated to Capsicum annuum L. var glabriusculum (Solanaceae) at three sampling sites corresponding to two Protected Natural Areas (PNA) in Tamaulipas state, Mexico. Samplings were carried out in “Cañón de la Peregrina” and “Altas Cumbres” situated in the PNA "Altas Cumbres" and “Ojo de Agua”, located in the "El Cielo" Biosphere Reserve. Mite diversity was H = 1.09 ± 0.14 in Ojo de Agua, and it was H = 1.08 ± 0.08 and H = 1.11 ± 0.06 in Altas Cumbres and Cañón de la Peregrina, respectively. A total of 47 species were identified belonging to 35 genera of 18 families associated to C. annuum L. var glabriusculum in Mexico. Predatory mite richness was higher than that of generalist and phytophagous mites (31, 11 and 5 species, respectively) for the two ANP. The similarity index of Jaccard between OA–AC (IJ = 0.257; P < 0.05), CP–AC (IJ = 0.293; P < 0.05) and AC–CP (IJ = 0.324; P < 0.05) was low. Pseudopronematalus sp. 4 (Iolinidae) was predatory mite most abundant in both ANP (Pi = 9.311); followed by Metaseiulus (Metaseiulus) negundinis (Denmark) (Phytoseiidae) only for ANP “Altas Cumbres” (Pi = 1.004). While for phytophagus mite, Aculops lycopersici (Tryon) (Eriophyidae) and Tetranychus merganser Boudreaux (Tetranychidae) presented the highest abundances in all sites (Pi = 79.919 and 5.142, respectively). The high number of mites species associated to chile piquín suggests stability in the PNA despite anthropogenic activities, and that the PNA works as a mite reservoir.

The role of sheep production in the livelihoods of Mexican smallholders: Evidence from a park-adjacent community

Traditional sheep production is part of the livelihood activities of natural resources' users in some protected areas. The aim of this study was to identify livelihood profiles of sheep producing households, in a park-adjacent community of central Mexico, using both production orientation and households’ strategies for access to sheep as key analytical categories. Data were collected through a questionnaire administered to a total of 62 sheep producing households, a hierarchical cluster analysis was performed and four household profiles were identified and described including additional socio-economic and sheep production-related characteristics: “Fatteners”, “Small breeders”, “Shepherd breeders” and “Non-shepherd breeders”. The "shepherd breeders" were highly linked to sheep farming in terms of the human capital engaged in this activity, the income they obtained from it and the way they used it. The “non-shepherd breeders” seemed to be mainly farmers linked to sheep production through joint livestock ventures. “Fatteners” complemented sheep production with non-agricultural activities, under a production system that tends to be more intensive, and “small breeders” combined the extensive management of animals with non-agricultural employment. Shepherding was more frequently performed by the groups of breeders compared with the fatteners. The case of the Ojo de Agua community provides new insights for the analysis of the role of livestock in rural livelihoods and the implications of protected areas' management on the wellbeing of their inhabitants and users.

Fertilización orgánica con tres niveles de gallinaza en cuatro cultivares de papa

El presente trabajo se realizó en el ciclo primavera-verano de 2017 en Ojo de Agua, municipio de Zinacantepec, Estado de México, para evaluar la respuesta de tres niveles de gallinaza y un tratamiento de fertilización químico en cuatro cultivares de papa. Los 16 tratamientos se evaluaron en un diseño experimental de bloques completos al azar en arreglo factorial 4x4 con tres repeticiones. El tamaño de la parcela experimental se integró con tres surcos de 4 m de largo y 0.90 m de ancho. Las variables registradas fueron altura de planta, número de tallos y de tubérculos por planta, pesos de tubérculo por planta, de follaje en fresco, índice de cosecha, rendimiento por hectárea, diámetro (DT) y longitud de tubérculo (LT). Los resultados mostraron que los cv. Rosita (24.38 t ha-1) y Ágata (23.85 t ha-1), en 4 t ha-1 de gallinaza, produjeron los mayores rendimientos de tubérculo. Los componentes principales 1 y 2 explicaron el 69.19% de la variación total original. En 4 t ha-1 de gallinaza hubo más tallos y mayores pesos de tubérculo, follaje en fresco y producción de tubérculo. Los cv. Rosita y Ágata sobresalieron en tallos por planta, así como en pesos de tubérculo y de follaje en fresco; la primera tuvo más tubérculos por planta. En los cv. Fianna, Ágata y Lucero se registraron los mayores índices de cosecha.

New Species of Gyrodactylus von Nordmann, 1832 from Native Fish from Chiapas, Mexico, Studied by Morphology and Molecular Analyses.

Three new species of Gyrodactylus von Nordmann, 1832 are described from Poeciliopsis hnilickai and Tlaloc labialis (syn. Profundulus candalarius and Profundulus labialis) from the state of Chiapas, Mexico. Gyrodactylus chiapaneco n. sp. is described from T. labialis. Gyrodactylus guatopotei n. sp. was found to infect P. hnilickai. Gyrodactylus tlaloci n. sp. is described from T. labialis. The new species were characterised morphologically (haptoral hooks) and molecularly (sequences of the Internal Transcribed Spacer region (ITS1-5.8S-ITS2) of rDNA). During a survey in March 2017 in the state of Chiapas, individuals of Tlaloc labialis were collected by electrofishing from Arroyo Ojo de Agua and from Río Hondo, Ixtapa, Río Las Lajas and Poeciliopsis hnilickai from Río Hondo, Ixtapa and Río Cacao. Three new species of Gyrodactylus were found and are described herein based on morphological and genetic analysis. Attachment hooks were excised and partially digested with a proteolytic solution to remove tissue enclosing the haptoral armature. Measurements and pictures of the haptoral hard structures were taken and were compared with other Gyrodactylus species found on poeciliids and profundulids. The bodies from which haptoral hook were removed were stored individually in 95% ethanol at -20 °C for molecular analyses. Sequences of the Internal Transcribed Spacer region of rDNA were obtained for each species and were compared with 26 Gyrodactylus spp. The genetic divergence among species of Gyrodactylus was estimated using uncorrected "p" distances with the program MEGA. The haptoral hook of Gyrodactylus chiapaneco n. sp. are similar to G. poeciliae from Venezuela; those from Gyrodactylus guatopotei n. sp. resemble the sclerites of G. turnbulli from Singapore and G. pictae from Trinidad, and the haptoral hooks of Gyrodactylus tlaloci n. sp. are comparable to those of G. pseudobullatarudis and G. zapoteco from Mexico; most of these parasites were described from poeciliid fishes, except G. zapoteco which was recently described from Profundulus oxacae from Oxaca, Mexico. The sequences of the three new species were aligned with sequences of 26 other Gyrodactylus spp. Maximum likelihood and Bayesian inference analyses indicated that the three new taxa are members with well-supported lineages-the new taxa are the first species of Gyrodactylus to be described from Poeciliopsis hnilickai and Tlaloc labialis from Chiapas. Gyrodactylus chiapaneco n. sp., Gyrodactylus guatopotei n. sp. and Gyrodactylus tlaloci n. sp. are described based on morphological and molecular analyses. Two of the three new species of Gyrodactylus described here, and both roughly fall morphologically and molecularly into the group of parasites harbouring slender marginal hooks: G. chiapaneco n. sp. and G. tlaloci n. sp. both possess marginal sclerites with slim shafts and group phylogenetically with other gyrodactylids of similar marginal hook morphology. Gyrodactylus guatopotei n. sp. groups with gyrodactylids possessing marginal hooks with quite elongated shafts, most of which have been found infecting poeciliids in the Antilles (e.g. G. pictae and G. turnbulli). Poeciliid, profundulid and goodeid fishes are morphologically and ecologically similar and nowadays live in sympatry or close geographical distance in Mesoamerica.

La construcción de las identidades en el “documental indígena”

<p class="p1">En el ensayo se analizan diversas formas de representar las identidades étnicas en las películas documentales producidas entre 1992 y 2011 por Ojo de Agua Comunicación, una organización de comunicadores de Oaxaca. Dicho análisis se basa en la problematización de los conceptos del cine documental y del video indígena, y de su capacidad de relacionarse con el otro, para que éste pueda autorrepresentarse en una narrativa audiovisual. Se argumenta que el uso del lenguaje de los documentales observacionales (Bill Nichols) impide la emergencia del otro, debido a que apuesta por una fuente única del discurso y una evaluación del otro en que éste no participa. Además la organización del montaje y la selección de los hechos y de las ideas es siempre responsabilidad del cineasta. </p>

Initial limnological observations at five small lakes in southern Pacific Costa Rica

Costa Rica has hundreds of lakes, many of which have never been described or sampled by limnologists. Here we summarize initial observations of five small (0.2–1.7ha) lakes located at low elevation (365–490m) in the cantón of Buenos Aries. We collected basic limnological data and samples during visits in 2013 and 2014, and compiled environmental and archaeological data for their surroundings as a contribution to the documentation of lake diversity in Costa Rica, and to support parallel investigations of indicators of environmental history preserved in the sediments of the lakes. Lagunas Carse, Los Mangos, Danta, and Ojo de Agua all appear to owe their origin to landslide events, while Laguna Junquillo is an artificial impoundment. Radiocarbon dates on plant macrofossils near the bases of sediment cores from three of the natural lakes provide minimum ages for lake formation; results indicate that Laguna Los Mangos formed over 4 100 years ago, while Laguna Danta formed prior to 1 320 CE and Laguna Carse formed ca. 1 550 CE, near the time of the Spanish Conquest. More than two dozen archaeological sites are located within 1–3Km of the natural lakes, documenting pre-Columbian human occupation and likely use of lake resources. Lake water temperatures and water chemistry were in keeping with observations at lakes throughout Costa Rica. All five lakes are probably polymictic lakes that turn over frequently; none evinced stratification. The surface lake sediments showed similar organic matter content (22,1–28,8%), with values falling near the middle of the range of lakes previously sampled in Costa Rica. Phytoplankton samples included taxa previously reported from small lowland lakes, but differed between lakes and included dominant taxa that were subdominant or uncommon at other lakes surveyed. Our investigation adds to knowledge of lake characteristics and diversity in Costa Rica, and provides benchmarks for assessing future changes in these lakes and their watersheds resulting from human activity, natural disturbances, and regional and global climate change.

Distorting the utopia of sustainability and eco-tourism: defense from the indigeneous perspective

The world should no longer postpone the renewal of paradigms. The urgency is oriented to serve two of the priority issues of worldwide interest: environmental deterioration and the civilization/dehumanization crisis, where greater interest is put in recovering the harmony with nature, in order to promote life and ensure its reproduction. Paraphrasing Houtart (2011), it is about achieving the Well-Being of the humankind, which implies, as a first step, the respect for the integrity of Nature, as a source of life. In this orientation and as an effort to add to this movement, the aim of this paper focuses on the resistance and protecting expressions witnessed in the ecological ejidal Ojo de Agua de Ballesteros, Salvatierra, Guanajuato, which by promoting the ejidal ecological tourism, is actually doing no more than preserving its property and natural patrimony and thus the sustainability of its environmental offer. The research methodology is based on the Participative Action Research, through the application of guided in-depth interviews, case studies, elaboration of diagnostics and participative observation. As one of the main result of this survey, we show how the collective action among his actors is fundamental to build a rural sustainability, as a mean of assuming a global ecological mission.

Anomalously deep earthquakes related to the Ojo de Agua Lineament and its tectonic significance, Sierras Pampeanas of Córdoba, Central Argentina

The Sierras de Córdoba are the easternmost uplifted ranges of the Sierras Pampeanas geological province of Argentina. They are composed of a Neoproterozoic–Paleozoic basement arranged in north–south aligned mountain ranges, limited by west-vergent reverse faults, reactivated or formed by compressive tectonics during the Andean orogeny. The ranges are also affected by oblique subvertical lineaments, probably related to pan-Gondwanan structures. The recorded seismicity shows anomalously deep earthquakes (up to 80 km depth) concentrated in the northwestern area. We attribute this seismicity to the current tectonic activity of the Ojo de Agua Lineament. This lineament is a N130º–135° strike, 70º–80° NE dip, macrostructure with more than 80 km depth and 160 km length. A sinistral transcompressional kinematics (convergent oblique shear) is deduced by the focal mechanism of a deep earthquake, together with hydrological and geomorphological features strongly modified. The continental lithosphere under the Sierras de Córdoba would be colder and more rigid than in a normal subduction area, due to the retraction of the asthenospheric wedge to the foreland, causing seismicity to depths greater than 40 km, below the Mohorovičić discontinuity. Neogene volcanism would be closely related to this lineament, allowing the rapid ascent of melts from the mantle.

Environmental and zooplankton parameter changes during the drying of a saline shallow temporary lake in central Argentina

Central Argentina has numerous saline lakes sustained by groundwater sources and rainfall. These lakes are temporary and experience significant changes in water level and salinity, depending on wet and dry climate cycles. This study aims to investigate the scarcely known dynamics of environmental and zooplankton parameters during the drying phase of one of these lakes. Monthly samples were taken from December 2 012<br />to July 2 013 in the Ojo de Agua Uriburu lake, previous to its drying. At the beginning of the study, the lake’s depth was 0.7 m and its salinity was 16.65 g/L, later, in July, its depth decreased to 0.06 m and its salinity increased to 92.9 g/L. Zooplankton species richness was low (three crustaceans and three rotifers), with <em>Boeckella poopoensis</em> and <em>Moina eugeniae</em> dominating in the system. Maximum density and biomass were attained<br />by the two dominant species in April (318.5 ind/L and 3 029.1 g /L dry weight; and 242.4 ind/L and 1 530.4 g/L dry weight, for <em>B. poopoensis</em> and <em>M. eugeniae</em>, respectively), and no correlation was found between these parameters and salinity. Maximum average body lengths for both species were observed in the last months of sampling (<em>M. eugeniae</em>: 1 020 84.2 m and<em> B. poopoensis</em>: 1 348.8 89.0 m). At this point of the study, neither juvenile nor larval stages were found. The increase in average body size is, arguably, the result of increased salinity in the system through a negative<br />effect on reproduction. Because this lake reached hypersalinity, its ecological dynamics are unique among those of other temporary, saline lakes that dried in central Argentina. Similar studies on other temporary ecosystems are needed to increase the information on these little known ecological aspects.

The Younger Dryas black mat from Ojo de Agua, a geoarchaeological site in Northeastern Zacatecas, Mexico

New explorations in the desert of northeastern Zacatecas, in central-northern Mexico, revealed dozens of archaeological and geoarchaeological sites. One of them, Ojo de Agua, contains the remains of a Pleistocene spring-fed hydrographic system located at the southeastern end of a large elongated endorheic basin. The locality yielded a particularly dark, highly organic stratigraphic layer commonly known in the Americas as Black Mat (BM), exposed on the natural profiles of a creek, but not associated with cultural materials. Several radiocarbon assessments confirmed the formation of the Ojo de Agua Black Mat during the Younger Dryas chronozone, with ten calibrated results clustering between 12,700–12,100 cal BP. This multi-proxy study confirmed the peculiarity of the deposit and found similarities and differences with other contexts of Younger Dryas age. The Ojo de Agua Black Mat (stratum C2) is far richer in charcoal specks than the related strata, but lacks phytoliths, diatoms or ostracods. No further biological remains were found in it, except for intrusive capillary roots. Clearly water-lain in a shallow pond, the stratum qualifies as a clayey silt with an acidic-to-neutral pH. Rich in heavy metals and with high contents of titanium, the Ojo de Agua Black Mat yielded significant indicators of intense wildfires during the Younger Dryas, but produced no carbon spherules or nanodiamonds supposedly linked to the impact theory.

Modeling Agricultural Potential Near the Ocampo Caves, Tamaulipas: Integrating Archaeological and Geospatial Applications

The Ocampo Caves of Tamaulipas, Mexico are well-known for archaeological evidence of early domesticated plants and the development of prehistoric food production. Richard S. MacNeish's 1953–1954 investigations in Romero's, Valenzuela's, and Ojo de Agua Caves yielded important insights into local prehistoric societies, the adoption of domesticated plants, and the use of caves as temporary campsites. Our research approaches the broader context of landuse by the occasional occupants of the caves through a geospatial analysis of the agricultural potential of the surrounding landscape. A recent archaeological survey revealed additional cave sites, as well as open-air settlements in the vicinity of the Ocampo Caves. The distribution of open settlements with architecture in a wide range of topographic settings raises the question of how this very rugged landscape might have been cultivated on a sufficient scale to support village populations. To address this issue, we developed a suitability raster using a geogr...

Caracterización del peligro por inundaciones en el oasis La Purísima, Baja California Sur, México

In the Mexican state of Baja California Sur there are only four oasis of more than 2.0 km2; La Purísima (2.25 km2) is the third largest of them. In the past this oasis was frequently affected by flooding, resulting from extreme rainfall events, which in several occasions generated severe destruction in the oasis. The first permanent settlement in the oasis of La Purísima was the foundation of a Jesuit mission at Cadegomó River in 1720. Since then the oasis repeatedly has been affected by floods; for example hurricanes caused severe damages in 1770 and in 1828, when finally the mission was abandoned. It took ten years to revive the mission, which remained in operation for several years after independence of Mexico. After its secularization, La Purísima became village in 1858. Major inundations occurred in 1957 and 1959, as well as in 2008 and 2009 which affected all farmers in the oasis. Parts of garden areas were lost, many fields covered with sand and the irrigation channels were severely damaged. The destruction included plantations of avocado, mango, guava, banana, plum, apple, black fig, orange trees, sugar cane and severe livestock losses.The mayor part of the La Purísima watershed, with a total area of 1,728.6 km2 is dominated by a very arid, warm climate (BWh (x’) after Köppen), with an average annual temperature between 18° and 20° C, whereas the lowlands, near the Pacific Ocean are influenced by a very dry and warm weather (BW (h>) (x>)), with a higher annual average temperature of 22° C.The main extreme weather events that aífect the area are the tropical cyclones that originate in the Northeast Pacific, and aífect the peninsula of Baja California during the months May to November. In the last decade there has been an increase of extreme rain events in the area, caused by tropical cyclones.A hydrological analysis was conducted, regarding to possible flooding levels, caused by extreme rainfall events. This included a statistical analysis of precipitation data in order to define the relation between rainfall intensity and return period. The data were entered into hydrologic and hydraulic models, using HEC-1 and HEC-RAS software in combination, which permitted to calculate the volume and impact of floods in the Cadegomo River under diíferent scenarios of extreme rainfall events. According to the evaluated scenarios of extreme runoíf events, a hazard map of flooding areas under diíferent return periods was elaborated.The results indicate a significant rise in the water levels of the drainage basin, caused from extreme rainfall events with an increase in the flooded area by 14%, estimated for the return period of 20 years and a 1 000 year event would generate an increase in the flooded area by 67%, which would aífect important areas of the urban region, as well as nearly all gardens of the oasis.The occurrence of floods in the past and their eífects on the oasis La Purísima were analyzed through historical evidences which permitted to verify the scenarios and calibrate the models. In three occasions runoíf volumes of higher magnitude were documented at the hydrological station ”Ojo de Agua”, run by the National Water Commission (CONAGUA): in September 1962, December 1972 and September 1974. The rainfall recorded in 1972 was 69 mm, which caused a total runoíf of 29.48 million cubic meters, observed during the next 230 hours; this is comparable to a model event with a return period of 10 years.In Baja California Sur, due to the lack of direct runoíf measurements, it is of utmost importance to continue ela-borating climate and hydraulic models to quantify the local eífects that could be expected before the end phenomenon of runoíf, in order to install measures to limit the economic damage and impacts on society.