Science.gov

Sample records for bajas cuboidales utilizando

  1. Baja California, Mexico

    NASA Technical Reports Server (NTRS)

    1989-01-01

    Sunglint on the surface of the Sea of Cortez near the island of Tiburon (28.5 N, 112.5W) reveals intricate patterns of internal waves under the placid surface. Mexico's state of Sonora and the Sonora Desert is on the mainland and the state of Baja California consists of the entire peninsula. The large bay on the Pacific side of Baja is Laguna Ojo de Libre (Bay of Whales) which is a breeding area for the Pacific Grey Whales.

  2. Baja Earthquake Perspective View

    NASA Image and Video Library

    2010-04-05

    The topography surrounding the Laguna Salada Fault in the Mexican state of Baja, California, is shown in this combined radar image and topographic view with data from NASA Shuttle Radar Topography Mission where a 7.2 earthquake struck on April 4, 2010.

  3. Baja California, Mexico

    NASA Technical Reports Server (NTRS)

    1981-01-01

    An interesting view down the axis of Baja California, Mexico (26.5N, 113.0W). At the center of the Scene is Laguna Ojo de Liebre (Bay of Whales) which is a breeding area for the Pacific Grey Whale. The Sea of Cortez, also known as the Gulf of California, is to the left and the Pacific Ocean is to the right.

  4. Lecturas de Baja California (Readings from Baja California).

    ERIC Educational Resources Information Center

    Munoz, Gabriel Trujillo, Ed.

    This anthology/textbook is part of a Mexican series of instructional materials designed for Spanish speaking adults who are in the process of becoming literate or have recently become literate in their native language. This document presents a collection of works from important writers directed to the population of Baja California, especially to…

  5. Lecturas de Baja California (Readings from Baja California).

    ERIC Educational Resources Information Center

    Munoz, Gabriel Trujillo, Ed.

    This anthology/textbook is part of a Mexican series of instructional materials designed for Spanish speaking adults who are in the process of becoming literate or have recently become literate in their native language. This document presents a collection of works from important writers directed to the population of Baja California, especially to…

  6. Baja Earthquake, Radar Image and Colored Height

    NASA Image and Video Library

    2010-04-05

    The topography surrounding the Laguna Salada Fault in the Mexican state of Baja, California, is shown in this perspective view with data from NASA Shuttle Radar Topography Mission where a 7.2 earthquake struck on April 4, 2010.

  7. Deforestation in Tierras Bajas, Bolivia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This false-color image shows the gradual conversion of forest lands for agricultural use in the Tierras Bajas region of Santa Cruz, Bolivia, as observed by the Enhanced Thematic Mapper Plus (ETM+) flying aboard Landsat 5. Forest and woodland are represented as grey tones from Channel 5 in this ETM+ scene, collected in 1998. Other colors indicate the first year in which a site was developed for agriculture (see color scale in the image, which corresponds to years of development). In this scene, land use types are delineated with lines. Solid white lines show the locations of planned colonies, dashed white lines show spontaneous colonies, and dotted white lines show Mennonite colonies. All other regions of development are non-Mennonite industrial soybean farms. Natural vegetation formations in this image are delineated with black lines. Solid black lines show the locations of Northern Chaco Woodlands and dashed black lines show Cerrado regions. For more information, see this previous Image of the Day regarding Bolivian deforestation. Image courtesy Marc Steininger, NASA GSFC

  8. Louse flies on birds of Baja California.

    PubMed

    Tella, J L; Rodríguez-Estrella, R; Blanco, G

    2000-01-01

    Louse flies were collected from 401 birds of 32 species captured in autumn of 1996 in Baja California Sur (Mexico). Only one louse fly species (Microlynchia pusilla) was found. It occurred in four of the 164 common ground doves (Columbina passerina) collected. This is a new a host species for this louse fly.

  9. Hurricane Linda Off the Baja Coast

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This Quick Time movie captures Hurricane Linda moving off the Baja California coast in September 1997. The strongest hurricane on record for the eastern Pacific at that time, Hurricane Linda invaded Southern California with winds that had gusted to 105 mph (174 kph). While off the coast of Mexico, her winds gusted up to 220 mph (354 kph). Earth science and weather studies are an important ongoing function of NASA and its affiliates.

  10. Hurricane Douglas south of Baja California

    NASA Technical Reports Server (NTRS)

    2002-01-01

    As recently as July 23, 2002, Hurricane Douglas was a category 2 hurricane, with winds as high as 90 knots (over 100 miles per hour). As of July 24, Douglas had dropped back to category 1 status as it moved away from the Baja California Peninsula in the eastern Pacific Ocean. The storm is predicted to continue moving westward over the next 24 hours and should weaken as it moves over cooler waters. This image was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite on July 23, 2002.

  11. A Guide to the Baja California Field Studies Program.

    ERIC Educational Resources Information Center

    Mercade, Jose A.

    Since 1974, Glendale Community College (GCC) has offered a variety of biology, social science, and language classes at a field station located on the Baja California peninsula, Republic of Mexico. This guide to GCC's Baja California Field Studies Program (BCFSP) provides manuals, forms, job descriptions, contracts with participating organizations,…

  12. NASA Radar Captures Earth Deformation from 2010 Baja Calif. Quake

    NASA Image and Video Library

    2011-03-04

    This radar image from NASA Uninhabited Aerial Vehicle Synthetic Aperture Radar UAVSAR shows the deformed Earth caused by a 7.2 earthquake in Mexico state of Baja California and parts of the American Southwest on April 4, 2010.

  13. GOES Video of Odile Making Landfall in Baja

    NASA Image and Video Library

    Satellite Movie Shows Hurricane Odile Make Landfall in Baja California This animation of NOAA's GOES-West satellite imagery from September 13 through September 15 shows Hurricane Odile's movement a...

  14. Energy, the Environment, and the California - Baja California Border Region

    SciTech Connect

    Powers, Bill

    2005-07-01

    The continued development of Baja California as an electricity and natural gas supply source for California is not in the best public interest of the citizens of Baja California or California. Siting power plants in the badly contaminated Imperial County - Mexicali air basin to serve Southern California load center raises serious environmental justice issues on both sides of the border that are not adequately addressed by existing environmental protection regulations.

  15. Geochronology of Early Eocene strata, Baja California

    SciTech Connect

    Flynn, J.J.; Cipolletti, R.M.

    1985-01-01

    Recent discoveries clearly indicate a Wasatchian (Early Eocene) land mammal age for fossil vertebrates from the Punta Prieta area, Baja California North, Mexico. This fauna provides a rare test for discriminating the temporal significance of mammalian faunas over a broad geographic area. The authors sampled intertonguing, fossiliferous terrestrial and marine strata for paleomagnetic and biostratigraphic analyses to provide an independent age determination for the Punta Prieta area mammal fauna. The marine macroinvertebrate assemblage is most likely upper Meganos to lower Capay West Coast Molluscan Stage based on the temporal ranges of all the taxa; also, none of the taxa occur in pre-Meganos stages. Two genera of planktonic forams indicate a probably Eocene age. They sampled seventeen paleomagnetic sites over 50 meters in the terrestrial mammal-bearing section, and thirteen sites over 25 meters in the marine section. The entire terrestrial sequence is reversely magnetized; initial results indicate the marine sequence probably also is reversely magnetized. Based on all the available biochronologic evidence this reversed sequence most likely should be correlated with the long reversed polarity Chron C24R. Clarkforkian to Early Wasatchian faunas in Wyoming also are associated with Chron C24R. All the available biostratigraphic and magnetostratigraphic evidence strongly supports an Early Eocene age for the Punta Prieta mammalian fauna and temporal equivalence of the Punta Prieta Wasatchian fauna with Wasatchian faunas from the Western United States. Land mammal ages are synchronous and applicable across broad geographic areas.

  16. Glory, Vortex Street off Baja California

    NASA Technical Reports Server (NTRS)

    2007-01-01

    On June 19, 2007, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured both a vortex street and a glory visible amid the lattice of clouds over the Pacific Ocean off Baja California. In this image, the swirling clouds known as vortex streets appear along the left edge of the image, stretching southward from Isla Guadalupe. Another NASA satellite captured an earlier example of vortex streets in June 2000. These atmospheric vortices, known as Von Karman vortex streets, often occur in the wake of an obstacle to air flow, such as an island. Stratocumulus clouds--low-lying, sheets of puffy clouds-- over the ocean show the impact of the island on air flow visible though their alternating pattern of clockwise and counter-clockwise swirls. Southeast of the vortex street, a glory, which resembles a rainbow, hovers above the cloud cover. The glory is faint but large, 200 to 300 kilometers long, along a north-south orientation. This phenomenon can occur when the satellite passes directly between the Sun and a bank of clouds below. (People also observe them while looking down on clouds from airplanes.) Not just any kind of cloud can produce a glory; only clouds composed entirely of water droplets (as opposed to ice crystals) can make them. The droplets that form glories generally have diameters of less than 50 micrometers (a micrometers is a millionth of a meter). The water droplets bend the light, showing its different wavelengths, or colors. In this glory, reds and oranges are most visible. NASA image by Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center.

  17. Glory, Vortex Street off Baja California

    NASA Technical Reports Server (NTRS)

    2007-01-01

    On June 19, 2007, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured both a vortex street and a glory visible amid the lattice of clouds over the Pacific Ocean off Baja California. In this image, the swirling clouds known as vortex streets appear along the left edge of the image, stretching southward from Isla Guadalupe. Another NASA satellite captured an earlier example of vortex streets in June 2000. These atmospheric vortices, known as Von Karman vortex streets, often occur in the wake of an obstacle to air flow, such as an island. Stratocumulus clouds--low-lying, sheets of puffy clouds-- over the ocean show the impact of the island on air flow visible though their alternating pattern of clockwise and counter-clockwise swirls. Southeast of the vortex street, a glory, which resembles a rainbow, hovers above the cloud cover. The glory is faint but large, 200 to 300 kilometers long, along a north-south orientation. This phenomenon can occur when the satellite passes directly between the Sun and a bank of clouds below. (People also observe them while looking down on clouds from airplanes.) Not just any kind of cloud can produce a glory; only clouds composed entirely of water droplets (as opposed to ice crystals) can make them. The droplets that form glories generally have diameters of less than 50 micrometers (a micrometers is a millionth of a meter). The water droplets bend the light, showing its different wavelengths, or colors. In this glory, reds and oranges are most visible. NASA image by Jeff Schmaltz, MODIS Rapid Response Team, Goddard Space Flight Center.

  18. Does Patellar Eversion in Total Knee Arthroplasty Cause Patella Baja?

    PubMed Central

    Sharma, Vineet; Tsailas, Panagiotis G.; Maheshwari, Aditya V.; Ranawat, Chitranjan S.

    2008-01-01

    Several proponents of minimally invasive surgery-total knee arthroplasty (MIS-TKA) have suggested patellar eversion during a standard exposure of the knee may cause shortening of the patellar tendon and poorer outcomes secondary to acquired patella baja. To explore this suggestion, we retrospectively reviewed 135 consecutive TKAs in 110 patients to ascertain the effect of TKA on the postoperative Insall-Salvati ratio. All surgeries were performed using standard TKA techniques with a midline incision, medial parapatellar arthrotomy, partial excision of the fat pad, and routine eversion of the patella. One patient developed a postoperative patella baja, defined as an Insall-Salvati ratio of less than 0.8. The Knee Society score for knee and function in this patient was 75 and 70, respectively. Five additional patients had a decrease in Insall-Salvati ratio by 10% or more but without patella baja. Mean Knee Society score for knee and function in these five patients was 94 (range, 73–99) and 96 (range, 90–100), respectively, as compared with 93 (range, 37–99) and 94 (range, 40–100) in the remaining 104 patients. Our data suggest the incidence of patella baja is low after TKA despite routine patellar eversion. Furthermore, a 10% or more decrease in the Insall-Salvati ratio without patella baja was not associated with a worse clinical outcome. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence. PMID:18568378

  19. Coastal management at Ojo de Liebre, Baja California Sur

    Treesearch

    Frederico Salinas-Zavala; Alfredo Ortega-Rubio; Diego Valez-Zamudio; Aradit. Castelanos-Vera

    2000-01-01

    We analyzed the biotic, abiotic, and human components interacting at the coastal zone of the Ojo de Liebre Lagoon, Baja California Sur, Mexico. Using geographic information systems, satellite images, and the main biological, physical, and socioeconomic components, we developed an environmental characterization of the zone. According with the natural features of the...

  20. Mining activities and arsenic in a Baja California Sur watershed

    Treesearch

    Alejandro Naranjo-Pulido; Alfredo Ortega-Rubio; Baudillo Acost-Vargas; Lia Rodriguez-Mendez; Marcos Acevedo-Beltran; Cerafina Arguelles-Mendez

    2000-01-01

    Mining is one of the most important sources of income for the Baja California Sur state. This state is the second most important area for mineral (gold, silver, copper) and non-mineral (salt) mining activities in the Mexican Republic. In the San Antonio-El Triunfo region, mineral-mining activities flourished during the 19th century. Tons of debris containing a high...

  1. Terrestrial Birds and Conservation Priorities in Baja California Peninsula

    Treesearch

    Ricardo Rodriguez-Estrella

    2005-01-01

    The Baja California peninsula has been categorized as an Endemic Bird Area of the world and it is an important wintering area for a number of aquatic, wading and migratory landbird species. It is an important area for conservation of bird diversity in northwestern México. In spite of this importance, only few, scattered studies have been done on the ecology...

  2. Traditional medicine of Baja California Sur (Mexico). I.

    PubMed

    Dimayuga, R E; Agundez, J

    1986-08-01

    This study deals with the medicinal use of 30 plants collected in the Municipio de Los Cabos and part of the Municipio de la Paz, Baja California Sur, Mexico. The plants were all taxonomically identified at least to genus level, and their medicinal use, as described to us by elder people, is discussed.

  3. Antimicrobial screening of medicinal plants from Baja California Sur, Mexico.

    PubMed

    Encarnación Dimayuga, R; Keer Garcia, S

    1991-02-01

    The ethanolic extracts of 72 plants belonging to 35 different families, and used in traditional medicine in Baja California Sur (México), were tested for antimicrobial activity in vitro using the filter paper disk assay method. Activity against Staphylococcus aureus, Bacillus subtilis, Streptococcus faecalis (Gram-positive microorganisms), Escherichia coli (Gram-negative microorganisms) and Candida albicans (yeast) is discussed.

  4. Deformation and rotation in southern Baja California, MX

    NASA Astrophysics Data System (ADS)

    Malservisi, R.; Plattner, C.; Hackl, M.; Weber, J.; Bachtadse, V.; Umhoefer, P.

    2008-12-01

    We use velocity data from 16 campaign GPS stations to study the motion and deformation in southern Baja California. The GPS timeseries span a total time of eight years and have four data collection periods with each more than two days. Due to the campaign mode GPS uncertainties are relatively large with respect to the estimated deformation signal of ~2 mm/yr. Therefore we choose robust analysis of the regional and local strain. We calculate the rigid block motion, its residuals, and relative motions. We use triangulation for local estimates of rotations and strain rates. To better estimate the deformations within the Southern Baja rigid block, we calculate a local GPS reference frame. The residual motion within this block is of the order of 0.5 mm/yr. Due to the small extent and small number of station within the rigid Southern Baja block, the errors associated with the regional velocity field is comparable with studied signal. Nevertheless, the direction of the residual w.r.t the local reference frame is in good agreement with the observed slip motion of the local known faults (Busch et al., 2006; 2007; and P. Umhoefer, personal communications) with significant extension between the Baja California peninsula and islands in the Gulf of California. In accordance to results from geological mapping, a strain analysis of the data shows significant deformation in the southeastern region of Baja California. The rotations induced by this deformation are also compared with long-term paleomagnetic reconstructions to evaluate the history of deformation of the region.

  5. Identifying recharge from tropical cyclonic storms, Baja California Sur, Mexico.

    PubMed

    Eastoe, Christopher J; Hess, Greg; Mahieux, Susana

    2015-04-01

    Groundwater in the Todos Santos watershed in southern Baja California, and throughout the peninsula south of latitude 28°N, has values of (δ18 O‰, δD‰) ranging between (-8.3, -57) and (-10.9, -78). Such negative values are uncharacteristic of the site latitude near the sea level. Altitude effects do not explain the isotope data. Tropical depressions originating along the Pacific coast of North America yield rain with isotopic depletion; rain from these weather systems in southern Arizona commonly has δ18O values<-10‰ in comparison with amount-weighted mean summer and fall rain at -6‰. Isotope data indicate hurricane rain as the predominant source of recharge in southern Baja California, where named tropical depressions bring large rains (>50 mm) at least once every 2 to 3 years, and along the Pacific coast between Jalisco and Oaxaca.

  6. A new species of Ceanothus from northern Baja California

    USGS Publications Warehouse

    Boyd, Steve; Keeley, Jon E.

    2002-01-01

    Ceanothus bolensis S. Boyd & J. Keeley is a new species in the subgenus Cerastes from northwestern Baja California, Mexico. It is well represented at elevations above 1000 m on Cerro Bola, a basaltic peak approximately 35 km south of the U.S./Mexican border. It is characterized by small, obovate to oblanceolate, cupped, essentially glabrous leaves with sparsely toothed margins, pale blue flowers, and globose fruits lacking horns. Principal components analysis on morphological traits shows it to be distinct from other members of Cerastes which are distributed away from the coast in southern California and Baja California, Mexico. These phenetic comparisons also suggest that Ceanothus otayensis should not be subsumed under C. crassifolius, as treated in the Jepson Manual, but rather should be retained at specific rank as well.

  7. [Marine algae of Baja California Sur, Mexico: nutritional value].

    PubMed

    Carrillo Domínguez, Silvia; Casas Valdez, Margarita; Ramos Ramos, Felipe; Pérez-Gil, Fernando; Sánchez Rodríguez, Ignacio

    2002-12-01

    The Baja California Peninsula is one of the richest regions of seaweed resources in México. The objective of this study was to determine the chemical composition of some marine algae species of Baja California Sur, with an economical potential due to their abundance and distribution, and to promote their use as food for human consumption and animal feeding. The algae studied were Green (Ulva spp., Enteromorpha intestinalis, Caulerpa sertularoides, Bryopsis hypnoides), Red (Laurencia johnstonii, Spyridia filamentosa, Hypnea valentiae) and Brown (Sargassum herporizum, S. sinicola, Padina durvillaei, Hydroclathrus clathrathus, Colpomenia sinuosa). The algae were dried and ground before analysis. In general, the results showed that algae had a protein level less than 11%, except L. johnstonii with 18% and low energy content. The ether extract content was lower than 1%. However, the algae were a good source of carbohydrates and inorganic matter.

  8. Densidad de desarrollo alta y baja en Puerto Rico

    Treesearch

    William A. Gould; Sebastian Martinuzzi; Olga M. Ramos Gonzalez

    2008-01-01

    Este mapa demuestra la distribución de terrenos de alta y baja densidad de desarrollo urbano en Puerto Rico (Martinuzzi et al. 2007). El mapa fue creado mediante el analisis de un mosaico de imagenes de satelite Landsat ETM+ de los años 2000 – 2003. La clasificacion no supervisada ISODATA (“Iterative Self-Organizing Data Analysis Technique”) (ERDAS 2003) fue utilizada...

  9. Traditional medicine of Baja California Sur (Mexico). II.

    PubMed

    Encarnacion Dimayuga, R; Fort Murillo, R; Luis Pantoja, M

    1987-08-01

    Continuing our studies of traditional medicine, as used in rural areas of Baja California Sur, now we wish to report on the medicinal uses of 49 more plants. Some of the more complex recipes of these medicinal plants, are discussed in the present paper. The information presented here was collected in the Municipio of Los Cabos and part of the Municipio of La Paz, B.C.S., Mexico.

  10. Miocene detachment faulting predating EPR propagation: Southern Baja California

    NASA Astrophysics Data System (ADS)

    Bot, Anna; Geoffroy, Laurent; Authemayou, Christine; Bellon, Hervé; Graindorge, David; Pik, Raphaël.

    2016-05-01

    At the southern tip of the Baja California peninsula, we characterize the onshore structures and kinematics associated with crustal necking leading up to the Pliocene breakup and early East Pacific Rise seafloor spreading. From a combination of tectonic field investigations, K-Ar and cosmogenic isotope dating and geomorphology, we propose that the Los Cabos block represents the exhumed footwall of a major detachment fault. This north trending detachment fault is marked by a conspicuous low-dipping brittle-ductile shear zone showing a finite displacement with top to the SE ending to the ESE. This major feature is associated with fluid circulations which led to rejuvenation of the deformed Cretaceous magmatic rocks at a maximum of 17.5 Ma. The detachment footwall displays kilometer-scale corrugations controlling the present-day drainage pattern. This major detachment is synchronous with the development of the San José del Cabo Basin where syntectonic sedimentation took place from the middle Miocene to probably the early Pliocene. We propose that this seaward dipping detachment fault accommodates the proximal crustal necking of the Baja California passive margin, which predates the onset of formation of the East Pacific Rise spreading axis in the Cabo-Puerto Vallarta segment. Our data illustrate an apparent anticlockwise rotation of the stretching direction in Baja California Sur from ~17 Ma to the Pliocene.

  11. Virtues of simple hydro-economic optimization: Baja California, Mexico.

    PubMed

    Medellín-Azuara, J; Mendoza-Espinosa, L G; Lund, J R; Harou, J J; Howitt, R E

    2009-08-01

    This paper uses simple hydro-economic optimization to investigate a wide range of regional water system management options for northern Baja California, Mexico. Hydro-economic optimization models, even with parsimonious model formulations, enable investigation of promising water management portfolios for supplying water to agricultural, environmental and urban users. CALVIN, a generalized hydro-economic model, is used in a case study of Baja California. This drought-prone region faces significant challenges to supply water to agriculture and its fast growing border cities. Water management portfolios include water markets, wastewater reuse, seawater desalination and infrastructure expansions. Water markets provide the flexibility to meet future urban demands; however conveyance capacity limits their use. Wastewater reuse and conveyance expansions are economically promising. At current costs desalination is currently uneconomical for Baja California compared to other alternatives. Even simple hydro-economic models suggest ways to increase efficiency of water management in water scarce areas, and provide an economic basis for evaluating long-term water management solutions.

  12. Treatment of patella baja by a modified Z-plasty.

    PubMed

    Guido, Wierer; Christian, Hoser; Elmar, Herbst; Elisabeth, Abermann; Christian, Fink

    2016-09-01

    The purpose of this study was to evaluate the efficiency of a modified Z-plasty for patellar tendon lengthening for the treatment of patella baja. Rather than adapting only two tendon reins according to the conventional Z-plasty method, the modified Z-plasty provides four reins to enable multifold overlapping of the tendon tissue. Between 2010 and 2012, a modified Z-plasty procedure was performed in four patients suffering from patella baja. Physical examinations and standardized scoring instruments served as the evaluation measures. The median preoperative CD ratio of 0.53 (range 0.43-0.62) was corrected to 1.03 (range 1-1.06) after a median follow-up of 34 months (range 23-41 months). The median preoperative flexion of 108° (range 80-135°) improved to 143° (range 110-145°) compared with the flexion of 145° (range 140-145°) of the unaffected knee. No patients showed any signs of extension lag. The median Lysholm score improved from 49 (range 22-80) to 91 (range 67-95), and the Tegner activity level improved from 2 (range 0-6) to 6 (range 2-6). The median VAS status for pain decreased from an average of 8.5 (range 4-10) to 1 (range 0-2). No complications were observed. The modified Z-plasty procedure is a valuable technique for the treatment of patella baja, especially if allografts are not available. This procedure allowed for early mobilization and achieved excellent clinical results. IV.

  13. GEMINI-9 - EARTH SKY - NORTHWESTERN MEXICO, BAJA CALIFORNIA

    NASA Image and Video Library

    1966-06-05

    S66-38070 (5 June 1966) --- Northwestern Mexico as seen from the Gemini-9A spacecraft during its 32nd revolution of Earth. The large penisula is Baja California. The body of water at lower right is the Pacific Ocean. The land mass at upper left is the State of Sonora. The Gulf of California separates Sonora from the peninsula. The nose of the spacecraft is at left; and at right is the open hatch of the spacecraft. Astronaut Eugene A. Cernan, pilot, took this picture with his modified 70mm Hasselblad EVA camera, using Eastman Kodak, Ektachrome, MS (S.O. 217) color film. Photo credit: NASA

  14. Frequently used medicinal plants in Baja California Norte.

    PubMed

    Winkelman, M

    1986-11-01

    Herbalists in Baja California Norte, Mexico, were interviewed to determine the ailments and diseases most frequently treated with 22 commonly used medicinal plants. Those diseases which were most frequently mentioned by the herbalists provided the focus for initial assessments. The phytochemistry of the medicinal plants was determined from published research, and the likelihood of successful treatment of diseases was assessed by determining the known pharmacological actions of the plant constituents. Most of the plants contained substances which had recognized pharmacological effects in the treatment of the diseases being treated by the herbalists.

  15. Pseudo-patella baja after total knee arthroplasty.

    PubMed

    Kazemi, Seyyed Morteza; Daftari Besheli, Laleh; Eajazi, Alireza; Miniator Sajadi, Mohammad Reza; Okhovatpoor, Mohammad Ali; Farhang Zanganeh, Ramin; Minaei, Reza

    2011-05-01

    One of the complications of total knee arthroplasty (TKA) which has not yet been directly addressed is pseudo-patella baja (PPB). True patella baja (PB) is present when the length of the patellar tendon becomes shorter. PPB is present when the patella tendon is not shortened, but the level of the joint line is elevated. This study was conducted to assess PPB in TKA. Sixty patients who had had a primary TKA at our center between 1995 and 2005 were included. The average follow-up was 27.5 months. The Knee Society Scoring (KSS), lateral knee x-rays and the Blackburne-Peel index were used for assessments. Out of the 60 patients, 43 (72%) demonstrated no joint line elevation or patellar tendon shortening (group A). Fifteen patients (25%) had joint line elevation (group B), and both PB and PPB were present in 2 (3%) patients (group C). KSS was lower in groups B and C compared with group A, but this difference was not statistically significant. The average range of motion (ROM) in group A was significantly higher compared with either group B or C, and patients in groups B and C showed significantly more severe pain compared with group A (P<0.001). PPB is not an uncommon finding after TKA and is associated with a statistically significant decrease in ROM and an increase in pain. Furthermore, KSS in the PPB group was less than in patients without PPB, although the difference was not statistically meaningful.

  16. Holocene plinian eruption of La Virgen volcano, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Capra, L.; Macías, J. L.; Espíndola, J. M.; Siebe, C.

    1998-02-01

    A plinian eruption occurred approximately 6500 yr ago at La Virgen Volcano, the youngest volcano of the Tres Virgenes Volcanic Complex (TVVC), located in Baja California, Mexico. Deposits of the eruption suggest a sequence of events that started with the opening of the volcanic conduit, and development of a plinian eruption column up to 18 km in height. This eruption column produced a fallout deposit with a dispersal axis toward the southwest, an areal extent of about 500 km 2, and a minimum volume of 1.14 km 3. Vulcanian activity (hydromagmatic) followed the plinian phase, producing pyroclastic surge and fallout deposits. The eruptive activity ceased after a basaltic-andesite lava flow was emplaced closing the eruptive activity. Petrological and geochemical evidence indicates that the eruption was triggered by magma mixing processes. Our studies confirm that La Virgen is a dormant volcano with the potential for future violent eruptions. The present study provides important information for the construction of a volcanic hazards map. Significant hazards are presented to the population living within a distance of 30 km from the volcano, together with the interstate road connecting the entire peninsula of Baja California, which runs at a distance of only 3 km from the volcano.

  17. Ethnobotanical treatments of diabetes in Baja California Norte.

    PubMed

    Winkelman, M

    1989-06-01

    This paper provides a brief review of the current biomedical knowledge on some of the medicinal plants used in the treatment of diabetes in Baja California Norte. In general there is very little biochemical knowledge of the specific modes of action in the treatment of diabetes, but most of the plants have been found to contain substances (e.g., glucosides, alkaloids) frequently implicated as having anti-diabetic effects. Furthermore, clinical studies with animals indicate that most of these plants do have hypoglycemic properties. This paper calls attention to the need for further biochemical investigations into the plant constituents and invites collaboration in the development of clinical field studies to assess the efficacy of herbalists' use of medicinal plants in the treatment of diabetes in Baja California Norte or other U.S.-Mexico border areas. Such research can make an important contribution to the World Health Organization's plan of "Health for All by the Year 2000" through establishing a scientific basis for traditional medicine.

  18. Recognition on space photographs of structural elements of Baja California

    NASA Technical Reports Server (NTRS)

    Hamilton, W.

    1971-01-01

    Gemini and Apollo photographs provide illustrations of known structural features of the peninsula and some structures not recognized previously. An apparent transform relationship between strike-slip and normal faulting is illustrated by the overlapping vertical photographs of northern Baja California. The active Agua Blanca right-lateral strike-slip fault trends east-southeastward to end at the north end of the Valle San Felipe and Valle Chico. The uplands of the high Sierra San Pedro Martir are a low-relief surface deformed by young faults, monoclines, and warps, which mostly produce west-facing steps and slopes; the topography is basically structural. The Sierra Cucapas of northeasternmost Baja California and the Colorado River delta of northwesternmost Sonora are broken by northwest-trending strike-slip faults. A strike-slip fault is inferred to trend northward obliquely from near Cabo San Lucas to La Paz, thence offshore until it comes ashore again as the Bahia Concepcion strike-slip fault.

  19. Crustal thickness estimates for Baja California, Sonora, and Sinaloa, Mexico, using disperse surface waves

    NASA Astrophysics Data System (ADS)

    López-Pineda, Leobardo; Rebollar, Cecilio J.; Quintanar, Luis

    2007-04-01

    Dispersed surface waves of regional events recorded at Network of Autonomously Recording Seismographs (NARS)-Baja and Red Sísmica de Banda Ancha (RESBAN) networks located over the Baja California Peninsula, Sonora, and Sinaloa, Mexico, were used to estimate shear wave elastic models and crustal thickness. We analyzed fundamental modes of surface waves with period between 10 and 40 s. Multiple filter analysis and the inversion method described by Herrmann and Ammon (2003) was used. Crustal thickness estimates for the Peninsular Ranges of Northern Baja California agree with those obtained by previous studies in the Peninsular Ranges of Northern Baja California. We analyzed dispersion of surface waves with northwest-southeast travel paths along the east and west sides of the Baja California Peninsula as well as a northwest-southeast travel path along the western sides of the Mexican states of Sonora and Sinaloa. It was found that the crustal structure east of the Baja California Peninsula is similar to the structure of Sonora and Sinaloa. The correlation between those two structures suggests dextral offset of the order of 275 ± 25 km if we consider Baja California Peninsula as a rigid body moving toward the northwest relative to the North America plate. This displacement between the structures is in agreement with the displacement determined by the dating of Miocene deposits located in San Felipe on the Baja California Peninsula (Pacific plate), and Isle Tiburon located west of Sonora (North America plate).

  20. Pseudo-Patella Baja after total knee arthroplasty

    PubMed Central

    Kazemi, Seyyed Morteza; Besheli, Laleh Daftari; Eajazi, Alireza; Sajadi, Mohammad Reza Miniator; Okhovatpoor, Mohammad Ali; Zanganeh, Ramin Farhang; Minaei, Reza

    2011-01-01

    Summary Background One of the complications of total knee arthroplasty (TKA) which has not yet been directly addressed is pseudo-patella baja (PPB). True patella baja (PB) is present when the length of the patellar tendon becomes shorter. PPB is present when the patella tendon is not shortened, but the level of the joint line is elevated. This study was conducted to assess PPB in TKA. Material/Methods Sixty patients who had had a primary TKA at our center between 1995 and 2005 were included. The average follow-up was 27.5 months. The Knee Society Scoring (KSS), lateral knee x-rays and the Blackburne-Peel index were used for assessments. Results Out of the 60 patients, 43 (72%) demonstrated no joint line elevation or patellar tendon shortening (group A). Fifteen patients (25%) had joint line elevation (group B), and both PB and PPB were present in 2 (3%) patients (group C). KSS was lower in groups B and C compared with group A, but this difference was not statistically significant. The average range of motion (ROM) in group A was significantly higher compared with either group B or C, and patients in groups B and C showed significantly more severe pain compared with group A (P<0.001). Conclusions PPB is not an uncommon finding after TKA and is associated with a statistically significant decrease in ROM and an increase in pain. Furthermore, KSS in the PPB group was less than in patients without PPB, although the difference was not statistically meaningful. PMID:21525812

  1. A Weather Analysis and Forecasting System for Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Farfan, L. M.

    2006-05-01

    The weather of the Baja California Peninsula, part of northwestern Mexico, is mild and dry most of the year. However, during the summer, humid air masses associated with tropical cyclones move northward in the eastern Pacific Ocean. Added features that create a unique meteorological situation include mountain ranges along the spine of the peninsula, warm water in the Gulf of California, and the cold California Current in the Pacific. These features interact with the environmental flow to induce conditions that play a role in the occurrence of localized, convective systems during the approach of tropical cyclones. Most of these events occur late in the summer, generating heavy precipitation, strong winds, lightning, and are associated with significant property damage to the local populations. Our goal is to provide information on the characteristics of these weather systems by performing an analysis of observations derived from a regional network. This includes imagery from radar and geostationary satellite, and data from surface stations. A set of real-time products are generated in our research center and are made available to a broad audience (researchers, students, and business employees) by using an internet site. Graphical products are updated anywhere from one to 24 hours and includes predictions from numerical models. Forecasts are derived from an operational model (GFS) and locally generated simulations based on a mesoscale model (MM5). Our analysis and forecasting system has been in operation since the summer of 2005 and was used as a reference for a set of discussions during the development of eastern Pacific tropical cyclones. This basin had 15 named storms and none of them made landfall on the west coast of Mexico; however, four systems were within 800 km from the area of interest, resulting in some convective activity. During the whole season, a group of 30 users from our institution, government offices, and local businesses received daily information

  2. NASA Satellite Imagery Shows Sparse Population of Region Near Baja, California Earthquake

    NASA Image and Video Library

    2010-04-09

    This image from NASA Terra spacecraft shows where a magnitude 7.2 earthquake struck in Mexico Baja, California at shallow depth along the principal plate boundary between the North American and Pacific plates on April 4, 2010.

  3. Craniometric evidence for Palaeoamerican survival in Baja California.

    PubMed

    González-José, Rolando; González-Martín, Antonio; Hernández, Miquel; Pucciarelli, Héctor M; Sardi, Marina; Rosales, Alfonso; Van Der Molen, Silvina

    2003-09-04

    A current issue on the settlement of the Americas refers to the lack of morphological affinities between early Holocene human remains (Palaeoamericans) and modern Amerindian groups, as well as the degree of contribution of the former to the gene pool of the latter. A different origin for Palaeoamericans and Amerindians is invoked to explain such a phenomenon. Under this hypothesis, the origin of Palaeoamericans must be traced back to a common ancestor for Palaeoamericans and Australians, which departed from somewhere in southern Asia and arrived in the Australian continent and the Americas around 40,000 and 12,000 years before present, respectively. Most modern Amerindians are believed to be part of a second, morphologically differentiated migration. Here we present evidence of a modern Amerindian group from the Baja California Peninsula in Mexico, showing clearer affinities with Palaeoamerican remains than with modern Amerindians. Climatic changes during the Middle Holocene probably generated the conditions for isolation from the continent, restricting the gene flow of the original group with northern populations, which resulted in the temporal continuity of the Palaeoamerican morphological pattern to the present.

  4. Strain accumulation along the Laguna Salada fault, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Savage, J. C.; Lisowski, M.; King, N. E.; Gross, W. K.

    1994-09-01

    Strain accumulation observed over the 1978-1991 interval in a 30 x 100 km aperture trilateration network spanning the Laguna Salada fault is described by the principal strain rates 0.101 +/- 0.012 microstrain/yr N80 deg E +/- 2 deg and -0.021 +/- 0.012 microstrain/yr N 10 deg W +/- 2 deg, extension reckoned coseismic effects of the nearby 1979 Imperial Valley (M = 6.5), 1980 Vistoria (Baja California) (M = 6.4), 1987 Superstition Hills (M = 6.5), and 1987 Elmore Ranch (M = 5.9) earthquakes. The observed strain rates indicate extension at a rate of about 0.08 microstrain/yr perpendicular to the trend (N 35 deg W) of the Salton trough as well as a right-lateral tensor shear strain rate 0.05 microstrain/yr across it. The extension perpendicular to the trough is observed neither farther north near the Salton Sea nor farther south across the Gulf of California. However, Holocene slip on the Laguna Salada fault, about equal parts right-lateral and normal slip, is consistent with the observed strain accumulation. A simple dislocation model intended to explain the observed strain accumulation as a product of slip at depth on the Laguna Salada Fault would require that the fault be listric.

  5. Microfossils from Cerro Prieto geothermal wells, Baja California, Mexico

    SciTech Connect

    Cotton, M.L.; Haar, S.V.

    1982-08-10

    To aid in a paleonenvironmental and age reconstruction of the Cerro Prieto reservoir system, 59 samples of well cuttings were analyzed for microfossils. The cuttings were obtained at depths from 351 to 3495m in 14 geothermal wells in the Cerro Prieto field, Baja California, Mexico. Foraminifera was found in 6 samples, ostracodes in 19 samples and mannoplankton as coccoliths in 24 samples. Other groups, such as molluscus, insects, fish skeletal parts, and plant material were occasionally present. Detailed interpretations at this time cannot be made because of poor preservation of samples. This is primarily due to causes: dissolution by geothermal fluids that reach 350/sup 0/C, and the extensive mixing of filled Cretaceous forms (reworked from the Colorado Plateau region) with Tertiary species during drilling. Further studies of ostracodes and foraminifera from colder portions of the wells are needed. The abundant and well-preserved ostracodes indicate marine to backish water inviroments that correspond in part, to lagoonal or estuarine facies. The presence of the mid-Tertiary (15-m.y.-old) marine foraminifera, Cassigerinela chipolensis, in wells M-11 and M-38, 350 to 500m deep, is perplexing. These are not laboratory contaminates and, as yet have not been found in the drilling mud. If further studies confirm their presence at Cerro Prieto, established ideas about the opening of the Gulf of California and about Pacific Coast mid-Tertiary history will need to be rewritten.

  6. Microfossils from Cerro Prieto geothermal wells, Baja California, Mexico

    SciTech Connect

    Cotton, M.L.; Vonder Haar, S.

    1980-01-01

    To aid in a paleoenvironmental and age reconstruction of the Cerro Prieto reservoir system, 59 samples of well cuttings were analyzed for microfossils. The cuttings were obtained at depths from 351 to 3495 m in 14 geothermal wells in the Cerro Prieto field, Baja California, Mexico. We found foraminifera in 6 samples, ostracodes in 19 samples, and nannoplankton as coccoliths in 24 samples. Other groups, such as molluscs, insects, fish skeletal parts, and plant material were occasionally present. Detailed interpretations are not possible at this time because of poor preservation of samples. This is primarily due to causes: dissolution by geothermal fluids that reach 350{sup 0}C, and the extensive mixing of filled Cretaceous forms (reworked from the Colorado Plateau region) with Tertiary species during drilling. Further studies of ostracodes and foraminifera from colder portions of the wells are needed. The abundant and well-preserved ostracodes indicate marine to brackish water environments that correspond, in part, to lagoonal or estuarine facies. The presence of the mid-Tertiary (15-My-old) marine foraminifera, Cassigerinela chipolensis, in wells M-11 and M-38, 350 to 500 m deep, is perplexing. These are not laboratory contaminates and, as yet, have not been found in the drilling mud. If further studies confirm their presence at Cerro Prieto, established ideas about the opening of the Gulf of California and about Pacific Coast mid-Tertiary history will need to be rewritten.

  7. [Main causes of maternal mortality in Mexicali, Baja California (Mexico)].

    PubMed

    Medina-Ramírez', Maria Concepción; Leal-Anaya, Paula; Aguilera-Romero, Tricia Nohemí; Leyva-Quintero, Elizabeth

    2015-11-01

    The objective of this study is to determine the main causes of maternal mortality in the period 2009 to 2013 in Mexicali, Baja California, Mexico. Epidemiological, observational, descriptive, cross-sectional, and retrospective study was conducted with a universe of 30 cases of maternal death. The information was collected from death certificates and records of cases obtained from the Institute of State Public Service Health of University Xochicalco. The average age of patients were 26.6 ± 5.6 years. Educational level and marital status was with junior school 15 (50%) and free union 12 (40%) respectively, 21 (70%) had no prenatal care. The mean gestational age was 28.8 ± 3.72 weeks, there was no difference in the place of residence, urban and rural, 15(50%). The main cause of death was hemorrhage 9(30%). The highest mortality was during the postpartum period 23 (77%). During the study period, the mortality rate was 36.8 x 100,000 live births. The increased frequency of maternal mortality was in young women, 70% had no prenatal care. Bleeding from ectopic pregnancy was the leading cause of death.

  8. Geochemical characteristics of the San Miguel aquifer, Baja California, Mexico.

    NASA Astrophysics Data System (ADS)

    Tostado-Plascencia, Miriam; Rosas-Elguera, Jose; Kretzschmar, Thomas

    2010-05-01

    The valley of San Miguel, located in the state of Baja California, Mexico, is an important region because of the wine industry. It is therefore important to know groundwater characteristics. Two aquifers can be recognized in the San Miguel basin, first one is in fractured granitic rocks (in the upper part of the basin, called UB) and other is free-type in detritc sediments (in the lower part of the basin, close to the sea, called LB). The water temperature ranges between 25°C y 11°C without significant variations along the year. The conductivity increases with the water temperature and decreases in February when the temperature is lower. The pH of the waters in UB is between 8.5 and 6.5 but in the LB is in the range of 6.8 to 7.3. Our data show that Na, Mg, and HCO3- concentrations decrease during the rainy season due to ion exchange. According to the Stiff diagrams the waters of the LB are classified as sodium chloride. In the UB the water classification includes calcium and magnesium bicarbonate, magnesium chloride, and few calcium chloride and sodium chloride. The saturation indexes of the waters suggest that the mineral phases which can be present are: K-feldspar, gibbsite, albite, quartz, calcite, aragonite, gypsum, and magnesite. Because of SI>0 then the first four phases can precipitate but the SI of magnesite and gypsum is negative thus the can be dissolved. Finally, calcite and aragonite are in equilibrium due to they are close to zero. Our results suggest that the aquifers of the San Miguel basin do not show evidence of saline intrusion.

  9. Prevention of pseudo-patella baja during total knee arthroplasty.

    PubMed

    Seo, Jai-Gon; Moon, Young-Wan; Kim, Sang-Min; Park, Sang-Hoon; Lee, Byung-Hoon; Chang, Moon-Jong; Jo, Byung-Chul

    2015-12-01

    Pseudo-patella baja (PPB) is a surgical complication that can arise from total knee arthroplasty and occurs when the patella tendon is not shortened but the level of the femorotibial joint line is elevated. The goal of this study was to assess the performance of a technique specifically designed to prevent the occurrence of PPB and its radiological results. Ninety-nine patients undergoing total knee arthroplasty were included. Patients were divided into a non-correction group and a correction group. The correction group were applied an additional metal block in order to reduce the excess resection of the distal femur. To evaluate PPB, the change in the pre- and postoperative joint line was measured using the modified Blackburne-Peel Index (BPI). In the non-correction group, 68 of 74 cases showed an occurrence of PPB (92 %), in the correction group, 6 of 57 cases showed an occurrence of PPB (11 %). The preoperative-modified BPI of the non-correction group was not significantly different from that of the correction group (0.6 ± 0.1 vs. 0.6 ± 0.2). The modified BPI decreased significantly in the non-correction group after TKA (0.6 ± 0.1 vs. 0.2 ± 0.1, p < 0.05). However, the modified BPI did not change significantly in the correction group after TKA (0.6 ± 0.2 vs. 0.6 ± 0.2). The comparison of preoperative and postoperative radiological results showed that our intervention maintained the joint line without elevation. We proposed an effective method to prevent various complications due to the joint line elevation that occur in PPB. III.

  10. Microseismicity Studies in Northern Baja California: General Results.

    NASA Astrophysics Data System (ADS)

    Frez, J.; Acosta, J.; Gonzalez, J.; Nava, F.; Suarez, F.

    2005-12-01

    Between 1997 and 2003, we installed local seismological networks in northern Baja California with digital, three-component, Reftek instruments, and with 100-125 Hz sampling. Each local network had from 15 to 40 stations over an area approximately of 50 x 50 km2. Surveys have been carried out for the Mexicali seismic zone and the Ojos Negros region (1997), the San Miguel fault system (1998), the Pacific coast between Tijuana and Ensenada (1999), the Agua Blanca and Vallecito fault systems (2001), the Sierra Juarez fault system (2002), and other smaller areas (2001 and 2003). These detailed microseismicity surveys are complemented with seismograms and arrival times from regional networks (RESNOM and SCSN). Selected locations presented here have errors (formal errors from HYPO71) less than 1 km. Phase reading errors are estimated at less than or about 0.03 s. Most of the activity is located between mapped fault traces, along alignments which do not follow the fault traces, and where tectonic alignments intersect. The results suggests an orthogonal pattern at various scales. Depth distributions generally have two maxima, one secondary maximum, at about 5 km; the other, located at 12-17 km. The Agua Blanca fault is essentially inactive for earthquakes with ML > 1.7. Most focal mechanisms are strike-slip with a minor normal component; the others are dominantly normal; the resulting pattern indicates a regional extensional regime for all the regions with an average NS azimuth for the P-axes. Fracture directions, obtained from directivity measurements, show orthogonal directions, one of which approximately coincides with the azimuth of mapped fault traces. These results indicate that the Pacific-North American interplate motion is not being entirely accommodated by the NW trending faults, but rather is creating a complex system of conjugate faults.

  11. Stratigraphy of Reforma Caldera, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    García Sánchez, L.; Macias, J. L.; Osorio, L. S.; Pola, A.; Avellán, D. R.; Arce, J. L.; Saucedo, R.; Sánchez, J. M.; García-Tenorio, F.; Cisneros, G.; Reyes-Agustín, G.; Cardona, S.; Jimenez, A.

    2015-12-01

    The Reforma caldera is located at ~35 km to the northwest of Santa Rosalía in the central part of the Baja California peninsula. It has 10 km in diameter and a maximum height of 1200 masl in the center and between 100 and 500 masl in its slopes. Reforma is within a tectonic zone affected by two fault systems: A NW-SE normal fault system linked to the opening of the Gulf of California, and a NNW-SSE and NW-SE strike-slip fault system associated with an active Riedel system. Reforma was built upon Cretaceous granites that outcrop at the caldera center, Miocene to Pliocene volcano-sedimentary rocks of the Comondú group, and Miocene marine sediments of the Santa Rosalía basin. On top of these rocks outcrop at least four submarine to subaerial ignimbrites interbedded with marine fossiliferous beds and the lower Pleistocene deposits associated to the Reforma caldera. These deposits are formed by a ignimbrite that shifts to different lithofacies that change gradually their welding, here dubbed basal, transitional, intermediate, and upper (all of then enriched in black fiammes), followed by a pumice-rich, white fiammes, and vitrophyre lithofacies, which are distributed around the 9 km wide caldera and have been associated to the caldera formation episode. Deposits related to post-caldera volcanism are andesite-basaltic lava flows erupted along the caldera rim through localized feeding dikes and andesitic and rhyolitic domes, and scoria cinder cones exposed inside and outside the caldera. On top of these deposits rest the middle Pleistocene Aguajito caldera deposits.

  12. 2-D tomographic imaging of continental crust and relic slab beneath Baja California

    NASA Astrophysics Data System (ADS)

    Brothers, D. S.; Harding, A. J.; Kent, G.; Driscoll, N.

    2009-12-01

    Rifting of Baja California from the margin of North America began as, or sometime before, subduction of the Farallon plate ceased (~12 Ma). Many have speculated that increased coupling between the subducted Farallon slab and overriding plate caused the young upper part of the subducted plate to detach from the older, colder, sinking slab. Then as the fragments of the Farallon plate took on Pacific plate motion, traction forces between the relic slab and Baja influenced rift localization in the Gulf of California. To better understand the processes that led to rifting of the Baja peninsula a 350 km seismic refraction/reflection profile was collected in 2002 in an effort to constrain the crustal thickness, the extent of relic slab beneath Baja California and the upper mantle P-wave velocities. The line spans the Baja Peninsula from the paleo-trench to the central Gulf of California, between the Farallon and Pescadero basins. 13 Ocean-Bottom Seismometers and 8 onshore Ref-Tek portable seismometers recorded 35,504 airgun shots from the R/V Ewing. Multichannel seismic (MCS) reflection profiles were collected on either side of the peninsula, providing information on the upper crustal structure and style of post-subduction deformation, particularly along the Tosco-Abreojos and Santa Margarita-San Lazaro fault systems. Here we present the integrated results of the MCS profiles and 2-D travel time tomography. Ray tracing was performed on 13,388 arrival picks, including Pg, Pn and PmP arrivals. Initial tomographic inversions reveal a crustal root beneath Baja California with an average velocity of 6.0 km/s. Continental crust thins to the east into the Gulf of California and has a velocity structure consistent with that of the Alarcon segment of the PESCADOR experiment. Perhaps the most significant observation is an ~6 km thick, 8° east-dipping high velocity zone (mean of 6.7 km/s) that underplates the western Baja margin and extends at least 60 km from the former trench

  13. Geochemistry of Holocene volcanic rocks associated with ridge subduction in Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Rogers, G.; Saunders, A. D.; Terrell, D. J.; Verma, S. P.; Marriner, G. F.

    1985-05-01

    Although the geochemistry of magmatism associated with the subduction of oceanic lithosphere is well understood1-6, the geochemical signature of lavas produced shortly after subduction of an oceanic spreading centre has not been characterized. The Baja California peninsula in Mexico provides an ideal scenario to study the latter process. Geophysical models indicate that, in response to oblique collision of the ancestral East Pacific Rise (EPR) with the western seaboard of North America at ~29 Myr, subduction of the Farallon plate was succeeded by the progressive southwards development of a transform fault system7-9. At 12.5 Myr a considerable length of the EPR was simultaneously subducted beneath Baja, thus terminating subduction processes along this segment10. By 3.5 Myr the locus of transcurrent faulting had switched from the west of Baja to within the developing Gulf of California, coupling Baja to the Pacific plate11-13. We present here data for Holocene volcanic rocks from Baja California Norte which show that post-ridge subduction volcanism has a distinctive geochemistry. These results have important consequences for the interpretation of ancient orogenic belts.

  14. Increased incidence of patella baja after total knee arthroplasty revision for infection.

    PubMed

    Chen, Antonia F; Tetreault, Matthew W; Levicoff, Eric A; Fedorka, Catherine J; Rothenberg, Adam C; Klatt, Brian A

    2014-12-01

    The incidence of patella baja in total knee arthroplasty (TKA) revisions for aseptic and septic causes is not well defined. We retrospectively reviewed 101 mobile-bearing TKA revisions performed between 2003 and 2009. Aseptic (n=67) and septic (n=34) revisions were compared for patella baja. A nonarticulating spacer was used as the initial treatment for infected cases. The Insall-Salvati ratio was radiographically measured before surgery (preexplant for septic revisions) and at latest follow-up (postreplant for septic revisions). Mean (SD) Insall-Salvati ratio did not differ between groups before surgery, 1.00 (0.25) for aseptic and 0.96 (0.22) for septic, but differed significantly after surgery, 0.99 (0.23) for aseptic and 0.77 (0.24) for septic. After correcting for preoperative patellar height, there was a statistically significant postoperative difference between aseptic cases, 1.09 (0.19), and septic cases, 0.82 (0.21). There was also a significant difference in mean (SD) postoperative range of motion (ROM) between aseptic cases, 108.0° (20.7°), and septic cases, 92.2° (34.6°), and decreased ROM between cases with patella baja, 95.1° (31.6°) and cases without patella baja, 106.8° (23.6°). TKA revisions done for septic causes using a nonarticulating spacer resulted in a higher incidence of patella baja and decreased ROM.

  15. Impact of patellar height on unicompartment knee arthroplasty: does patella baja lead to an inferior outcome?

    PubMed

    Neogi, Devdatta Suhas; Bae, Ji Hoon; Seok, Chang Woo; Lim, Hong Chul

    2014-03-01

    Though a number of series with long-term results have been published, there is still a paucity of literature on the role of patellar height after unicompartment knee arthroplasty (UKA). The present study was conducted with a hypothesis that patella baja may lead to a poor outcome at follow-up. A retrospective review of 134 knees was performed and patellar height calculated before and after UKA by Blackburne-Peel index (BPI) and the Insall-Salvati ratio (ISR) on true lateral radiographs of the patients in 30° of flexion taken pre-operatively and at 1 year, 2 years and final follow-up (minimum 5 years). Statistical analysis was performed to evaluate the outcomes. There was a decrease in ISR in 14.18 % and in BPI in 19.4 % at final follow-up. There was a significant decrease in BPI values while the decrease was not significant for ISR. After eliminating the pre-operative patella baja, 7.3 % developed post-operative patella baja, according to ISR, while 11.5 % developed patella baja as per BPI. At final follow-up there was a statistically significant decrease in stair climbing scores in patients with patella baja when compared to patients with normal ISR. Patients with a decrease in patellar height as per ISR have a decrease in stair climbing score at mid-term follow-up while the overall KSS, and pain scores are not affected by a change in patellar height and neither is there a significant progress in patellofemoral osteoarthritis among patients with patella baja compared to normal patella.

  16. Paleontology of the Toa Baja. number sign. 1 well, Puerto Rico

    SciTech Connect

    Montgomery, H. ); Robinson, E. ); Saunders, J. ); Van den Bold, W. )

    1991-03-01

    The Toa Baja well penetrated 585.2 m of fossiliferous Oligocene and Miocene limestone, sandstone, and shale above 2119 m of Eocene, dominantly volcaniclastic strata. Oligocene and Miocene rocks were deposited on a broad, shallow shelf. The unconformity between Eocene and Oligocene strata spans at least the Late Eocene, and probably part of the Early Oligocene at Toa Baja. Below the unconformity, unfossiliferous volcaniclastic and igneous rocks are interstratified with fossiliferous limestone beds containing Middle and possibly late Early Eocene planktic foraminifera probably deposited in deep water. No Paleocene or Cretaceous fossils were recovered.

  17. Tibio-calcaneo-naviculo-cuboidale arthrodesis: 6 patients followed for 1-8 years.

    PubMed

    Weber, Michael; Schwer, Helmut; Zilkens, Karl W; Siebert, Christian H

    2002-01-01

    As a salvage procedure for patients with irreparable damage to the peritalar anatomy, we used a new method, the Ilizarov ring fixator, to stabilize a tibio-calcaneo-naviculo-cuboideal (TCNC) arthrodesis after resecting the talus in 6 patients with an average follow-up of 3 years. The tibia was lengthened by callus distraction, mean 6 (3.5-10) cm. Patients with exacerbation of a chronic talar osteomyelitis, symptomatic posttraumatic changes, and those with extremely unstable club feet and talar deformity preventing an adequate reduction of the joint, were successfully treated with the TCNC-fusion. The method permits early weight bearing, while providing stability and compression of the fusion, thereby avoiding further loss of bone stock.

  18. Stratigraphy, geochemistry and mineralogy of Eocene rocks from the Toa Baja drillhole

    SciTech Connect

    Smith, A.L.; Severin, K.; Larue, D.K. )

    1991-03-01

    The stratigraphy of the Eocene rocks of the Toa Baja drillhole is dominated by volcaniclastic sediments which are interbedded with marly pelagic limestones, especially in the lower part of the hole, and lava flows. Petrological, geochemical and paleontological evidence suggest that the site of deposition was a deep marine basin and the source of the volcanics were subaerial or shallow submarine island arc volcanoes.

  19. Health Care among the Kumiai Indians of Baja California, Mexico: Structural and Social Barriers

    ERIC Educational Resources Information Center

    Fleuriet, K. Jill

    2009-01-01

    In this article, the author documents the illness and health care problems facing indigenous communities in Baja California, Mexico, by using ethnographic data from research she conducted from 1999 to 2001 with rural, indigenous Kumiai and with their primary health care providers in urban Ensenada. The author contends that barriers to care are…

  20. Herpetofauna associated with palm oases across the Californian-Sonoran transition in northern Baja California, Mexico

    Treesearch

    Hart Welsh; W. H. Clark; E. Franco-Vizcaíno; J. H. Valdéz-Villavicencio

    2010-01-01

    Ecological boundaries have been of interest to naturalists since the time of Darwin and Wallace because they are transitional zones on the landscape across which distinct changes occur in constitution of plant and animal communities. In the xeric landscapes of the central Baja California Peninsula, fan palm (Erythea armata and ...

  1. Mission and modern citrus species diversity of Baja California Peninsula cases

    USDA-ARS?s Scientific Manuscript database

    The spring-fed mission oases of the Baja California peninsula, Mexico, hold several species, varieties and unique hybrids of heritage citrus, which may represent valuable genetic resources. Citrus species first arrived to the peninsula with the Jesuit missionaries (1697-1768), and new varieties were...

  2. Health Care among the Kumiai Indians of Baja California, Mexico: Structural and Social Barriers

    ERIC Educational Resources Information Center

    Fleuriet, K. Jill

    2009-01-01

    In this article, the author documents the illness and health care problems facing indigenous communities in Baja California, Mexico, by using ethnographic data from research she conducted from 1999 to 2001 with rural, indigenous Kumiai and with their primary health care providers in urban Ensenada. The author contends that barriers to care are…

  3. Islas Marias Archipelago, Mexico. A Missing Piece to Reconstruct the Paleoposition of Baja California

    NASA Astrophysics Data System (ADS)

    Schaaf, P. E.; Pompa, V.; Hernandez, T.; Weber, B.; Solis, G.; Villanueva, D.; Perez-Venzor, J.

    2011-12-01

    Paleopositions for southern Baja California peninsula have yielded controversial models over the past 30 years. Mainly based on paleomagnetic data many hypotheses place Baja at lower paleolatitudes in front of southern Mexico or Central America with subsequent northward translations. Other models suggest minor, if any, northward displacements with respect to continental Mexico combined with clockwise rotations. Lithological, geochemical, and geochronological similarities for southern Baja California and Puerto Vallarta (western Mexico Pacific margin) igneous rocks seem to confirm the latter model. To further prove this model we have mapped and collected rocks from Maria Madre, the largest island of the Islas Marias archipelago, located in the mouth of the Gulf of California. In an area of only 145 square kilometers, metamorphic basements rocks (ortho and migmatitic gneisses), highly deformed metasediments, granitoids, acid to intermediate volcanic sequences, and a cover with gently folded marine sediments are exposed. The basement complex with gneisses and metasediments, including garnet-bearing paragneiss and calc silicates, as well as the granodioritic-tonalitic intrusives display an extraordinary accordance with similar units observed in the Los Cabos Block (LCB) of Baja California Sur. Furthermore, U-Pb zircon ages of 162 and 170 Ma for the basement gneisses and of 80 Ma for the granitoids have been reported also from the LCB. Additionally, upper Cretaceous intrusive ages are well known from the Puerto Vallarta batholith in Jalisco and Nayarit, mainland Mexico. Geochemical and isotopic data as well as Nd model ages confirm a magmatic consanguinity of LCB, Islas Marias, and Puerto Vallarta granitoids. The volcanic units of Maria Madre Island include ignimbrites and effusive dacitic-rhyolithic rocks, which can be correlated to the Sierra Madre Occidental province and the Comundú Formation of Baja California. Age determinations are under work to confirm this

  4. Behaviours and opinions towards outdoor smoking bans and cigarette littering in Baja California, Mexico.

    PubMed

    Basto-Abreu, Ana C; Christine, Paul J; Zepeda-Tello, Rodrigo; Romero-Martínez, Martín; Aguilar Duque, Julian I; Reynales-Shigematsu, Luz M; Barrientos-Gutierrez, Tonatiuh

    2016-04-01

    Outdoor smoking bans have been implemented to reduce secondhand smoke exposure and cigarette littering. We aimed to explore outdoor smoking behaviours, cigarette littering, and support towards a recently enacted outdoor smoking ban in Baja California, Mexico. From October 2013 to April 2014 a representative sample of 800 adults from urban areas of Baja California was surveyed to obtain information on demographics, smoking status, opinion towards outdoor smoking bans in general and in specific locations, and perceptions and habits regarding cigarette littering. Descriptive statistics and Poisson regression analyses were conducted to estimate prevalence ratios and corresponding 95% CI taking into account the complex survey design. Outdoor smoking was frequently observed, as 86.8% of the population reported having seen people smoking in parks and beaches and 94.4% in open venues such as concerts or stadiums. A smoking ban in all outdoor areas was supported by 71.8% of Baja California residents. Site-specific support ranged from 80% (stadiums) to 89% (public parks). Support for the ban was higher among never and ex-smokers than in current smokers. Cigarette littering was negatively perceived by 98% of the participants, yet 45% of all cigarettes smoked were thrown on the ground. Based on cigarette consumption and butt littering reported in the survey, we estimated that 27 million cigarette butts become litter every month in urban areas of Baja California. Outdoor smoking is still frequent in outdoor areas where people gather, and an important source of littering. We found substantial public support towards the outdoor smoking ban, which should translate into easier implementation and compliance in Baja California, Mexico. © The Author 2015. Published by Oxford University Press. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  5. Crustal Structure of Southern Baja California Peninsula, Mexico, and its Margins

    NASA Astrophysics Data System (ADS)

    Gonzalez, A.; Robles-Vazquez, L. N.; Requena-Gonzalez, N. A.; Fletcher, J.; Lizarralde, D.; Kent, G.; Harding, A.; Holbrook, S.; Umhoefer, P.; Axen, G.

    2007-05-01

    Data from 6 deep 2D multichannel seismic (MCS) lines, 1 wide-angle seismic transect and gravity were used to investigate the crustal structure and stratigraphy of the southern Baja California peninsula and its margins. An array of air guns was used as seismic source shooting each 50 m. Each signal was recorded during 16 s by a 6 km long streamer with 480 channels and a spacing of 12.5 m. Seismic waves were also recorded by Ocean Bottom Seismometers (OBS) in the Pacific and the Gulf of California and by portable seismic instruments onshore southern Baja California. MCS data were conventionally processed, to obtain post-stack time-migrated seismic sections. We used a direct method for the interpretation of the wide-angle data, including ray tracing and travel times calculation. In addition to the gravity data recorded onboard, satellite and land public domain data were also used in the gravity modeling. The combined MCS, wide-angle and gravity transect between the Magdalena microplate to the center of Farallon basin in the Gulf of California, crossing the southern Baja California Peninsula to the north of La Paz, allows to verify the existence of the Magdalena microplate under Baja California. We have also confirmed an extensional component of the Tosco-Abreojos fault zone and we have calculated crustal thicknesses. We have also observed the continuation to the south of the Santa Margarita detachment. The MCS seismic sections show a number of fault scarps, submarine canyons and grabens and horsts associated to normal faults offshore southern Baja California peninsula. The normal displacement observed in the Tosco-Abreojos fault zone and some basins in the continental platform, as well as the presence of faulted acoustic basement blocks, evidence that not all extension was accommodated by the Gulf Extensional Province during the middle to late Miocene. Part of the extension was (and is) accommodated in the Baja California Pacific margin. This confirms the observations

  6. Remote sensing exploration for metallic mineral resources in central Baja California

    NASA Technical Reports Server (NTRS)

    Baker, R. N.

    1977-01-01

    Remote sensor data (primarily LANDSAT) was analyzed by photogeologic and computer-assisted enhancement techniques to evaluate the metallic mineral potential of Baja California. Overlays were prepared at 1:1,000,000 and 1:500,000 and included known geologic relationships and mineral occurrences, lineament, drainage and structural patterns, tonal anomalies, and enhancement results. Computer-assisted enhancement and classification of the test sites was performed using the IMAGE 100 system to identify subtle tonal anomalies thought related to mineralization using known sites as analysis guides. Mineral potential maps of Baja California were generated from these analyses and the ten highest priority targets visited. Preliminary assay results (atomic absorption analysis) for the samples recovered showed moderate to high geochemical anomalies for Copper (10 of 12 samples), Zinc (3 of 12 samples) and Lead (4 of 12 samples).

  7. Uranium series ages of corals from the upper Pleistocene Mulege terrace, Baja California Sur, Mexico

    SciTech Connect

    Ashby, J.R.; Ku, T.L.; Minch, J.A.

    1987-02-01

    Specimens of Porites californica contained in the sediments of upper Pleistocene, +12-m marine terrace deposits developed on the east coast of the Baja California (Mexico) peninsula at Mulege have yielded /sup 239/Th//sup 234/U dates of 124 +/- 5 and 144 +/- 7 ka (+/- 1 sigma). These dates can be assigned to the well-documented late Pleistocene oxygen-isotope stage 5e high sea stand. Differences between the eustatic and present elevations of this terrace indicate average uplift rates since terrace formation of approximately 4 to 5 cm/1000 yr, indicating a relative stability and lack of major vertical deformation since the late Pleistocene. This terrace in the Mulege area can now be correlated with other marine terraces throughout the Baja California peninsula and southern California.

  8. Assessing neuropsychological performance in a migrant farm working Colonia in Baja California, Mexico: a feasibility study.

    PubMed

    Bousman, Chad A; Salgado, Hugo; Hendrix, Terence; Fraga, Miguel; Cherner, Mariana

    2011-08-01

    Neuropsychological impairments (NPI) can lead to difficulties in daily functioning and ultimately contribute to poor health outcomes. However, evidence for the feasibility of NPI assessment in resource-limited settings using tests developed in high literacy/high education cultures is sparse. The main objectives were to: (1) determine the feasibility and appropriateness of conducting neuropsychological assessments among a migrant farm worker population in Baja California, Mexico and (2) preliminary describe neuropsychological test performance in this unique population. A neuropsychological test battery was administered to 21 presumably healthy adults (8 men, 13 women) during a two-day international health services and research collaboration. All but one neuropsychological test (i.e. figure learning) was feasible and appropriate to administer to the study population. Contrary to expectations, participants performed better on verbal rather than nonverbal neuropsychological tests. Results support inclusion of neuropsychological tests into future studies among migrant farm worker populations in Baja California, Mexico.

  9. Recent distribution and status of nesting bald eagles in Baja California, Mexico

    USGS Publications Warehouse

    Henny, C.J.; Conant, B.; Anderson, D.W.

    1993-01-01

    We studied Bald Eagles(Haliaeetus leucocephalus) nesting in Baja California, Mexico, and vicinity from 1983-1993. The range of nesting Bald Eagles in Baja California has been reduced from a scattering of pairs along both the Pacific and Gulf sides to a remnant population in Magdalena Bay where no more than three pairs were found annually. Low numbers and a restricted distribution make this disjunct population especially vulnerable to human disturbance. Additional protection of present nesting localities and a reintroduction program on remote islands in the Gulf of California where eagles historically nested, are proposed. Limited data on nesting success indicate that the Magdalena Bay population is reproducing successfully with young probably dispersing north following fledging. The Bald Eagles found wintering along the Colorado River Delta in January apparently nest farther north in the United States or Canada.

  10. Case for northward transport of Baja and coastal southern California: Paleomagnetic data, analysis, and alternatives

    SciTech Connect

    Beck, M.E. Jr. )

    1991-05-01

    This paper reviews Cretaceous paleomagnetic evidence for Baja and coastal southern California as a whole, results from Baja and southern California require transport of 1,000 km or more, relative to interior North America. Agreement between independent results, for different rock types and experimental techniques is overwhelming. Dextral shear driven by right-oblique subduction readily accounts for the paleomagnetic results. Alternative explanations such as experimental errors, rock-magnetic effects, anomalous geomagnetic behavior, errors in dating, or local structure are inadequate, improbable, or both. Some geologists have difficulty reconciling the findings of paleomagnetism with their own results; hence, as emphasized by Gastil, a conflict and enigma exist. To resolve them will require a willingness on both sides to honestly scrutinize basic assumptions.

  11. The origin of bajaites from the San Borja Volcanic Field in Baja California Norte, Mexico

    NASA Astrophysics Data System (ADS)

    Bibbins, M.; Castillo, P.; Negrete-Aranda, R.; Canon-Tapia, E.; Alva-Valdivia, L. M.; Garcia-Amador, B. I.

    2014-12-01

    Baja California is a peninsula in western Mexico that was formed through a dynamic tectonic history of convergence, rifting and strike slip motion. At approximately 13 Ma, subduction along the northwestern coast of Mexico stopped, subsequently the Gulf of California opened and strike slip faults formed parallel to the ancient trench. After subduction ended, arc-related magmatism continued as the Baja peninsula was forming until about 2 Ma. The lavas erupting in the peninsula have variable compositions including calc-alkalic and tholeiitic arc basalts and bajaites. The term bajaite is a collective term for the high magnesian andesites and basaltic andesites in Baja California that have adakitic characteristics. Adakites, on the other hand, are arc lavas characterized by high silica content and Sr/Y and La/Yb ratios; these are generally believed to have formed through melting of subducted basaltic crust. The origin of bajaite is controversial. It has been proposed as product of melting of either subducted basaltic crust primarily because of its adakitic characteristics (Saunders et al, 1987) or metasomatized mantle wedge because of its arc lava-like geochemical features (Castillo, 2008); it has also been proposed as a mixture of differentiated and mafic arc lavas (Streck et al, 2007). The composition of bajaite is similar to that of the bulk continental crust and, thus, its true origin can shed light on the mechanism for continental growth. In this study, we use geochemical techniques to resolve some of the controversies surrounding the origin of bajaite. We analyze the petrographic, major element, trace element, and Sr-Nd-Pb isotopic compositions of bajaites from the San Borja Volcanic Field in Baja California Norte, Mexico to better constrain their petrogenetic history and origin.

  12. A tree-ring reconstruction of past precipitation for Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Díaz, Sara C.; Touchan, Ramzi; Swetnam, Thomas W.

    2001-06-01

    There is great interest in the climatic variability of Baja California and the Sea of Cortes, but long-term information is limited because instrumental climate records begin in the 1940s or 1960s. The first tree-ring chronology of Pinus lagunae was developed from the southern part of the Baja California Peninsula and the chronology is used to reconstruct the history of precipitation variations. A September-July precipitation reconstruction is developed for the period AD 1862-1996 (R=0.71, p<0.0001, n=56, cross-validation=0.68). This reconstruction is used to assess precipitation variability over the past two centuries, including the relationship with ENSO events. The reconstructed precipitation series indicates a long drought period from 1939 to 1958. It also shows that 1983, one of the strongest El Niño events of the 20th century, is the wettest year. El Niño events during the 20th century are associated with above-normal precipitation, whereas La Niña events are characterized by below-normal precipitation. Four of the most extreme wet years occurred in association with these warm events (1905, 1912, 1919 and 1983). Seventy-one percent of La Niña events are characterized by below-normal precipitation. Sixty-two percent of El Niño events are characterized by above-normal precipitation. Tree-ring growth of P. lagunae is most strongly correlated with winter precipitation in Sonora, Sinaloa and southern Baja California Sur. Precipitation data from meteorological stations in northern Baja California do not correlate well with the tree-ring chronology because this zone has a Mediterranean climate, which differs from the rest of northwest Mexico.

  13. [Polyplacophoran communities (Mollusca: Polyplacophora) at Bahia de La Paz, Baja California Sur, México].

    PubMed

    García Ríos, Cedar I; Alvarez Ruiz, Migdalia

    2007-03-01

    Eight species of polyplacophorans have been reported from La Bahia de la Paz, Baja California Sur, Mexico. We add Lepidochitona beanii, Chaetopleura lurida, Stenoplax limaciformis, S. mariposa, Lepidozona clathrata, L. serrata and Acanthochitona arragonites, increasing the known number of species to 15. Ordination analysis of five chiton communities at the site suggests a correlation of wave exposure to species composition and diversity: communities with intermediate wave exposure have more species (richness) and higher diversity (Shannon's index).

  14. DDT in Mytilus edulis: Spatio-temporal variations in the Punta Banda estuary, Baja California, Mexico

    SciTech Connect

    Galindo-Bect, M.S.; Flores-Baez, B.P. )

    1991-02-01

    The mussel Mytilus sp. has been widely used as a sentinel organism or biological indicator of organic pollutants in the marine environment. In studies recently carried out in Baja California, Mexico, it was found that the spatial and temporal variations of DDT in samples of the mussel Mytilus californianus collected from the area exposed to the ocean do not follow a defined pattern and that the highest values of DDT are found at the border with the US. The Maneadero Valley in Baja California, Mexico, is an agricultural area where important volumes of pesticides are applied, part of which are transported to the Punta Banda Estuary where they remain for an undetermined period of time during which they are consumed and bioaccumulated by organisms. The main objective of the present work is to determine the levels and temporal variation of DDT in the mussel Mytilus edulis in the Punta Banda Estuary, Baja California. With the results, the authors will define the dynamics of this pollutant in the estuary.

  15. Uranium-series ages of marine terraces, La Paz Peninsula, Baja California Sur, Mexico

    USGS Publications Warehouse

    Sirkin, L.; Szabo, B. J.; Padilla, G.A.; Pedrin, S.A.; Diaz, E.R.

    1990-01-01

    Uranium-series dating of coral samples from raised marine terrace deposits between 1.5 and 10 m above sea level in the La Paz Peninsula area, Baja California Sur, yielded ages between 123 ka and 138 ka that are in agreement with previously reported results. The stratigraphy and ages of marine units near the El Coyote Arroyo indicate the presence of two high stands of the sea during the last interglacial or oxygen isotope substage 5e at about 140 ka and 123 ka. Accepting 5 m for the sea level during the last interglacial transgression, we calculate average uplift rates for the marine terraces of about ???70 mm/ka and 40 mm/ka. These slow rates of uplift indicate a relative stability of the La Paz peninsula area for the past 140 000 years. In contrast, areas of Baja California affected by major faultf experienced higher rates of uplift. Rockwell et al. (1987) reported vertical uplift rates of 180 to 300 mm/ka at Punta Banda within the Aqua Blanea fault zone in northern Baja California. ?? 1990 Springer-Verlag.

  16. Heavy metal accumulation in four species of sea turtles from the Baja California peninsula, Mexico.

    PubMed

    Gardner, Susan C; Fitzgerald, Sionnan L; Vargas, Baudilio Acosta; Rodríguez, Lia Méndez

    2006-02-01

    Heavy metals were assessed in four species of sea turtles from the Baja California Peninsula, Mexico, representing the first report of heavy metal concentrations in tissues of post-yearling sea turtles from the Eastern Pacific. Concentrations of Cd measured in C. mydas kidney (653 microg/g dry wt) were the highest ever reported for any sea turtle species. Cd accumulated preferentially in kidney and the ratios of kidney to liver Cd in Baja California turtles were among the highest reported for sea turtles globally. Zn, Ni, and Mn concentrations were also significantly higher in kidney than other tissues, while Cu and Fe were greatest in liver, and all metals were lowest in muscle. With the exception of one value (69.9 microg/g in kidney of C. caretta), Pb was low in all tissues from Baja California. In comparisons across species, kidney of C. mydas had greater Zn and Ni concentrations as compared to other species, although there was no difference in liver metal levels among the species. Positive correlations were detected in the concentrations of Cd, Cu and Ni with the straight carapace length of C. caretta.

  17. Multidrug-resistant tuberculosis among patients in Baja California, Mexico, and Hispanic patients in California.

    PubMed

    Bojorquez, Ietza; Barnes, Richard F W; Flood, Jennifer; López-Gatell, Hugo; Garfein, Richard S; Bäcker, Claudia E; Alpuche, Celia; Vinetz, Joseph M; Catanzaro, Antonino; Kato-Maeda, Midori; Rodwell, Timothy C

    2013-07-01

    We sought to compare prevalence and determinants of multidrug-resistant tuberculosis (MDR-TB) between tuberculosis patients in Baja California, Mexico, and Hispanic patients in California. Using data from Mexico's National TB Drug Resistance Survey (2008-2009) and California Department of Public Health TB case registry (2004-2009), we assessed differences in MDR-TB prevalence comparing (1) Mexicans in Baja California, (2) Mexico-born Hispanics in California, (3) US-born Hispanics in California, and (4) California Hispanics born elsewhere. MDR-TB prevalence was 2.1% in Baja California patients, 1.6% in Mexico-born California patients, 0.4% in US-born California patients, and 2.7% in Hispanic California patients born elsewhere. In multivariate analysis, previous antituberculosis treatment was associated with MDR-TB (odds ratio [OR] = 6.57; 95% confidence interval [CI] = 3.34, 12.96); Mexico-born TB patients in California (OR = 5.08; 95% CI = 1.19, 21.75) and those born elsewhere (OR = 7.69; 95% CI = 1.71, 34.67) had greater odds of MDR-TB compared with US-born patients (reference category). Hispanic patients born outside the US or Mexico were more likely to have MDR-TB than were those born within these countries. Possible explanations include different levels of exposure to resistant strains and inadequate treatment.

  18. Electrical structure of the Baja California lithosphere beneath Vizcaíno region

    NASA Astrophysics Data System (ADS)

    Romo, J. M.; Gomez-Trevino, E.; Perez-Flores, M. A.; Garcia-Abdeslem, J.; Esparza, F. J.; Flores-Luna, C. F.

    2001-12-01

    Understanding the lithosphere physical properties beneath the central part of the Baja California peninsula, in northwest Mexico, is critical to substantiate some of the theories about the tectonic evolution of this segment of the Pacific-North American plate boundary. We present results from a geophysical survey designed to investigate the electrical conductivity, the mass density and the magnetic susceptibility in a cross section through the Vizcaíno National Park region. Magnetotelluric, gravity and magnetic measurements were taken along a 200 km NE-SW profile from the Gulf of California coast to the Pacific Ocean coast, at the peninsula middle latitude. We use two-dimensional numerical models to interpret the different data sets. The magnetotelluric model shows two conductive features of tectonic interest. One is a 15º dipping conductor that extends from the Pacific coast to about 100 km westwards, where the dip increases to 45º, reaching a depth of over 100 km beneath the Baja California eastern coast. This conductor supports the hypothesis that a captured microplate remains beneath the Baja continental crust. The other feature is a shallow conductor, no deeper than 20 km, which rises near the surface and extends horizontally overlapping for about 40 km the 15º dipping conductor. According to prevailing views of the tectonic evolution of the area, this conductor could be associated to the complex interaction between adjacent microplates. The gravity and magnetic interpretations further support the magnetotelluric model.

  19. Geophysical characterization of subaerial hydrothermal manifestations in Punta Banda, Baja California, Mexico.

    NASA Astrophysics Data System (ADS)

    Flores-Marquez, L.; Prol-Ledesma, R. M.; Arango, C.; Canet, C.

    2009-04-01

    Important growth of population in Baja California Peninsula has triggered the need for energy and fresh water. The most sustainable possibility for increasing the availability of fresh water is the use of renewable energy sources in desalination plants. The abundance of geothermal manifestations in the peninsula provides a reliable energy source for desalination purposes. Geothermal development of the Baja California Peninsula dates from the 70's, when the Cerro Prieto geothermal field started producing electricity. Two important cities, Tijuana and Ensenada, are located in the north-western area of Baja California. The city of Ensenada has a desalination plant that is due to be replaced and the geothermal resources of the area could be an option for the new desalination plant. Punta Banda, a region near Ensenada, was specially investigated to determine its geothermal potential. Subaerial springs and the submarine vents were sampled and studied in this work, also geological and geochemical studies were performed, moreover geoelectrical surveys were accomplished to characterize the hydrothermal system at depth. Even though saline intrusion is a severe problem in Ensenada (TDS higher than 3000), thermal springs away from the coast and coastal springs have salinities lower than sea water. According to the geoelectrical models obtained from profiles, the inferred conductive features can be related to thermal anomalies. The existence of hot springs located along a trend suggests that the dynamic of the thermal fluid is restricted by secondary faults.

  20. Public health assessment for Vega Baja Solid Waste Disposal, Rio Abajo Ward/La Trocha, Vega Baja County, Puerto Rico, Region 2: CERCLIS Number PRD980512669. Final report

    SciTech Connect

    1998-11-30

    The Vega Baja Waste Disposal Site is a public health hazard because long-term exposure to lead in soil in some yards cause harmful effects in children. Children and especially preschool children who live in yards with elevated levels of soil lead might be exposed to small amounts of lead when they accidentally swallow soil and dust that cling to their hands. The level of lead in garden vegetables from the site is not a public health threat. It is safe for residents to grow and eat garden vegetables. ATSDR recommends that EPA prevent long-term exposure to lead-contaminated soil where lead levels are consistently elevated. ATSDR also recommends that EPA consult with ATSDR officials to ensure that Superfund activities to stop exposure to lead-contaminated soil at the site continues to be protective of public health.

  1. Geologic and geomorphic evidence for the magnitude of rift-related subsidence of northeastern Baja California

    NASA Astrophysics Data System (ADS)

    Oskin, M.

    2001-12-01

    Present elevation of the eastern Peninsular Ranges of northern Baja California is 1 to 2.5 km higher than the adjacent Gulf of California Extensional Province. A pre-rift erosion surface and the distribution and facies of pre-rift sedimentary and volcaniclastic rocks indicate that prior to rifting, elevation was similar across northeastern Baja California. Eocene(?) through Miocene fluvial systems and volcaniclastic deposits of an Early to Middle Miocene volcanic arc flowed from what is now the Gulf Extensional Province westward across the southern Sierra San Pedro Mártir. These drainage systems were later occupied by a welded ash-flow tuff, the ~12.6 Ma Tuff of San Felipe, which erupted from a vent in western Sonora prior to opening of the Gulf of California. Approximately (1)/(3) of the elevation of a pre-rift erosion surface on the eastern Peninsular Ranges closely follows the structure of adjacent rift basins, suggesting that this topography is supported by flexure of the upper continental crust with an effective elastic thickness, Tc≈ 5 km. After removing these local topographic anomalies, a regional 1 to 1.5 km elevation difference remains between the Peninsular Ranges and the Gulf of California. Recently published geophysical studies indicate that northeastern Baja California is comprised of 33--40 km-thick crust beneath the Sierra San Pedro Mártir and 15--18 km-thick crust beneath the rifted margin of the Gulf of California. Elevation differences between these areas are consistent with regional Airy-type isostatic compensation of rift-related crustal thickness changes with support of locally high topography of the eastern Peninsular Ranges by flexure of the upper continental crust.

  2. Tectonic controls on sedimentation in Mesozoic convergent margin basin of Baja California (Mexico)

    SciTech Connect

    Busby-Spera, C.J.; Smith, D.P.; Morris, W.R. )

    1990-05-01

    Mesozoic rocks of the Baja California peninsula form one of the most extensive, best exposed, oldest (160 m.y.), and least-tectonized and metamorphosed convergent margin basin complexes in the world. Much of the fill of these basins consist of coarse-grained volcaniclastic and epiclastic sequences that directly reflect the tectonic evolution of the region. The early history of the convergent margin was dominated by sedimentation in small, steep-sided basins within oceanic island arc systems. The Triassic and Jurassic convergent margin basins probably represent proto-Pacific terranes that traveled from another area. These terranes were assembled by the Late Jurassic to Early Cretaceous, and underlie the forearc region of a medial Cretaceous oceanic island arc system. Tbis system fringed the Mesoamerican continental margin and underwent regional-scale extension during subduction of old, dense lithosphere. The latest phases of sedimentation in the convergent margin occurred in broad, relatively stable forearc basins of a mature continental arc, during the Late Cretaceous to Paleocene. Nonetheless, intrabasinal faults provided some controls on depositional systems and bathymetry. The authors speculate that these faults formed in response to oblique convergence which ultimately resulted in 10-19{degree} northward displacement of Baja California relative to the North American craton, from the latitude of Central America to northern Mexico. The fill of oceanic island arc basins in Baja California is dominated by coarse-grained marine wedges including (1) arc apron deposits, consisting of pyroclastic and/or volcanic epiclastic debris deposited in intra-arc or back-arc basins, and (2) slope apron deposits, consisting of epiclastic debris shed from local fault scarps and more distally derived arc volcaniclastics, deposited in forearc basins.

  3. Multidrug-Resistant Tuberculosis Among Patients in Baja California, Mexico, and Hispanic Patients in California

    PubMed Central

    Bojorquez, Ietza; Barnes, Richard F. W.; Flood, Jennifer; López-Gatell, Hugo; Garfein, Richard S.; Bäcker, Claudia E.; Alpuche, Celia; Vinetz, Joseph M.; Catanzaro, Antonino; Kato-Maeda, Midori

    2013-01-01

    Objectives. We sought to compare prevalence and determinants of multidrug-resistant tuberculosis (MDR-TB) between tuberculosis patients in Baja California, Mexico, and Hispanic patients in California. Methods. Using data from Mexico’s National TB Drug Resistance Survey (2008–2009) and California Department of Public Health TB case registry (2004–2009), we assessed differences in MDR-TB prevalence comparing (1) Mexicans in Baja California, (2) Mexico-born Hispanics in California, (3) US-born Hispanics in California, and (4) California Hispanics born elsewhere. Results. MDR-TB prevalence was 2.1% in Baja California patients, 1.6% in Mexico-born California patients, 0.4% in US-born California patients, and 2.7% in Hispanic California patients born elsewhere. In multivariate analysis, previous antituberculosis treatment was associated with MDR-TB (odds ratio [OR] = 6.57; 95% confidence interval [CI] = 3.34, 12.96); Mexico-born TB patients in California (OR = 5.08; 95% CI = 1.19, 21.75) and those born elsewhere (OR = 7.69; 95% CI = 1.71, 34.67) had greater odds of MDR-TB compared with US-born patients (reference category). Conclusions. Hispanic patients born outside the US or Mexico were more likely to have MDR-TB than were those born within these countries. Possible explanations include different levels of exposure to resistant strains and inadequate treatment. PMID:23678924

  4. The Tuff of San Felipe: an extensive middle Miocene pyroclastic flow deposit in Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Stock, Joann M.; Lewis, Claudia J.; Nagy, Elizabeth A.

    1999-11-01

    We document the existence of a widespread Miocene ash-flow tuff sheet in northeastern Baja California, Mexico. The Tuff of San Felipe (new name) was erupted from a vent east of the Sierra San Felipe of NE Baja California at ca. 12.6 Ma. This is the only widespread middle Miocene pyroclastic flow deposit identified in northeastern Baja California. Its distinctive age and widespread distribution make it an important marker horizon for structural reconstruction of this part of the Gulf Extensional Province, which is on the Pacific plate. The vent position, near the modern Gulf of California coast, allows the possibility that exposures of the Tuff of San Felipe may be preserved east of the Gulf on the North America plate in Sonora, yielding a tie point for the past relative position of the two plates. This paper summarizes all known information including petrography, geochemistry, geochronology, paleomagnetics, geographic distribution, and field appearance of this important tuff. It is a densely welded, crystal-rich, lithic-lapilli pyroclastic flow deposit, with 5-15% alkali feldspar, and can be 180 m thick in some locations near the vent. The Tuff of San Felipe is >40 m thick up to 40 km SW of the vent and >10 m thick at least 25 km NNW of the vent. A minimum volume estimate for the deposit is 54 km 3. Some recent 40Ar/ 39Ar age determinations suggest that the tuff is about 12.6 Ma in age. In all locations studied, the Tuff of San Felipe has a unique, low-inclination, reversed magnetization, which may record a field transition or a geomagnetic excursion within reversed polarity subchron C5Ar.2r (12.401 to 12.678 Ma). This low-inclination magnetization, as well as the mineralogy and age, is key to correlating the tuff across the region, because deposits are highly disrupted by subsequent normal faulting and outcrops are sparse and discontinuous away from the vent. The documentation of these characteristics is important because the Tuff of San Felipe is a key structural

  5. Coast of Isla Cerralvo, Baja, California as seen from STS-62

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Though it did not reproduce well, this photo gives scientific information to aid in studying all types of Earth's processes. It documents ocean features in the sunglint in the Gulf of California, off the Isla Cerralvo, southern Baja, California. Biological oils collect on the surface of the water and take the form of the currents. The sun reflects off the oily surface and shows current patterns, eddies and ship wakes. The small bright spot on the edge of the eddy is a ship dumping oily water from its bilges. The line in the brighter area is a light wind gust roughening the surface.

  6. The Southern Baja - Islas Marías - Sinaloa Transect: What is common? What was moving?

    NASA Astrophysics Data System (ADS)

    Schaaf, P. E.; Perez-Venzor, J.; Solis, G.; Hernandez, T.; Arrieta, G. F.; Pompa, V.; Villanueva, D.

    2013-12-01

    The Gulf of California extensional province constitutes an issue of ongoing multidiscipline investigations. It is considered as a result of late Miocene to Pliocene faulting and 'Comondu-type' magmatism related to Pacific-North America plate boundary motions. Transtensional faulting has rifted Baja California obliquely away from mainland Mexico over the past 12 Ma. To understand these processes and to reconstruct transportation distances, it is helpful to look back into the past. In this contribution we present a V-shaped lithological and geochronological profile, starting from the Los Cabos Block, Baja California Sur to the west, passing southerly Islas Marias Islands in the mouth of the Gulf and ending in south-central Sinaloa (Mazatlan region) to the east. All three locations display 80 Ma plutonic rocks of granodioritic to tonalitic compositions with similar Sr and Nd isotope signatures. Voluminous to minor shaped early Cretaceous gabbro outcrops are found south of La Paz (Novillo Massif) and ca. 30 km N of Mazatlan. The basement of the three sites is composed of 160-170 Ma (+/- migmatitic) orthogneisses, covered by schists and paragneisses with detrital zircon peaks at ca. 260, 520, and 1000 Ma. Abundant calc-silicates are found in the southern Los Cabos Block as well as on Maria Madre Island. Sandstones and shales from Islas Marias can be divided into two units with minimum detrital zircon ages of 80 Ma and 21 Ma, respectively. The micropaleontological record in these sediments indicates repeated uplift and subsidence events, related to the opening of the Gulf of California. In Maria Magdalena island, the sedimentary sequence is intruded in sills by < 21 Ma MORB-type gabbros. The overwhelming lithological and geochronological similarities of the Los Cabos Block and Islas Marias rock units give strong evidence for their common and continuous magmatic and metamorphic evolution and confirm a 400-450 km NW displacement of southern Baja. Larger offsets are

  7. Coast of Isla Cerralvo, Baja, California as seen from STS-62

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Though it did not reproduce well, this photo gives scientific information to aid in studying all types of Earth's processes. It documents ocean features in the sunglint in the Gulf of California, off the Isla Cerralvo, southern Baja, California. Biological oils collect on the surface of the water and take the form of the currents. The sun reflects off the oily surface and shows current patterns, eddies and ship wakes. The small bright spot on the edge of the eddy is a ship dumping oily water from its bilges. The line in the brighter area is a light wind gust roughening the surface.

  8. Caries prevalence of preschoolchildren in Baja, Hungary in 1955 and 1975.

    PubMed

    Bruszt, P; Bánóczy, J; Esztáry, I; Hadas, E; Marosi, I; Nemes, J; Albrecht, M

    1977-05-01

    In 1975 caries epidemiologic investigations were performed in 1,017 preschoolchildren of Baja, aged 3--6 years. The data were analyzed and compared with those of 620 preschoolchildren of the same city in 1955. A mean increase of 10.9% of the caries frequency (percentage of examinees with caries), and a mean increase of 43.5% of the caries intensity(dmft count per examinee) could be observed in spite of a better vitamin D prophylaxis. The possible cariogenic role of the increased surgar consumption (37.5 kg from 24.4 kg per individual during 20 years) is discussed.

  9. Use of a TTA plate for correction of severe patella baja in a Chihuahua.

    PubMed

    Edwards, George A; Jackson, Andrew H

    2012-01-01

    A 7 yr old spayed female Chihuahua presented for right hind limb lameness and reduced stifle range of motion. Radiographs showed a marked patella baja of the right stifle and evidence of a previous surgery to correct a medial patellar luxation. A tibial tuberosity osteotomy was performed to allow proximal translation of the tibial tuberosity, which was stabilized with a tibial tuberosity advancement plate. Four weeks postoperatively, lameness and articular range of motion were improved, and the use of anti-inflammatory and analgesic medications was discontinued. The dog was still ambulating well and had no lameness 12 mo postsurgically.

  10. Coast of Isla Cerralvo, Baja, California as seen from STS-62

    NASA Image and Video Library

    1994-03-05

    STS062-153-226 (4-18 March 1994) --- Though it did not reproduce well, this photo gives scientific information to aid in studying all types of earth's processes. It documents ocean features in the sunglint in the Gulf of California, off the Isla Cerralvo, souther Baja, California. Biological oils collect on the surface and shows current patterns, eddies and ship wakes. The small bright spot on the edge of the eddy is a ship dumping oily water from its bilges. The line in the brighter area is a light wind gust roughening the surface.

  11. Identification of hydrothermal mineralization in Baja California, Mexico from orbit using the Shuttle multispectral infrared radiometer

    NASA Technical Reports Server (NTRS)

    Rowan, L. C.; Crowley, J. K.; Kingston, M. J.; Goetz, A. F. H.

    1983-01-01

    Data from the Space Shuttle Multispectral IR Radiometer (SMIRR), which is a 10-channel remote sensor designed to record narrow band spectral data in the 0.5-2.4 micron wavelength range, were used to identify and study a previously unreported area of hydrothermal alteration on the Baja California peninsula. Absorption at 2.17 microns, which is diagnostic of the minerals pyrophyllite, dickite, and alunite, was observed in many spectra and the presence of pyrophyllite and dickite was confirmed by X-ray diffraction analysis of field samples. Anomalously high Mo, B, Sn, Zr, and Ag were found in three samples.

  12. Whole genome sequencing of Mycobacterium bovis to obtain molecular fingerprints in human and cattle isolates from Baja California, Mexico.

    PubMed

    Sandoval-Azuara, Sarai Estrella; Muñiz-Salazar, Raquel; Perea-Jacobo, Ricardo; Robbe-Austerman, Suelee; Perera-Ortiz, Alejandro; López-Valencia, Gilberto; Bravo, Doris M; Sanchez-Flores, Alejandro; Miranda-Guzmán, Daniela; Flores-López, Carlos Alberto; Zenteno-Cuevas, Roberto; Laniado-Laborín, Rafael; de la Cruz, Fabiola Lafarga; Stuber, Tod P

    2017-10-01

    To determine genetic diversity by comparing the whole genome sequences of cattle and human Mycobacterium bovis isolates from Baja California. A whole genome sequencing strategy was used to obtain the molecular fingerprints of 172 isolates of M. bovis obtained from Baja California, Mexico; 155 isolates were from cattle and 17 isolates were from humans. Spoligotypes were characterized in silico and single nucleotide polymorphism (SNP) differences between the isolates were evaluated. A total of 12 M. bovis spoligotype patterns were identified in cattle and humans. Two predominant spoligotypes patterns were seen in both cattle and humans: SB0145 and SB1040. The SB0145 spoligotype represented 59% of cattle isolates (n=91) and 65% of human isolates (n=11), while the SB1040 spoligotype represented 30% of cattle isolates (n=47) and 30% of human isolates (n=5). When evaluating SNP differences, the human isolates were intimately intertwined with the cattle isolates. All isolates from humans had spoligotype patterns that matched those observed in the cattle isolates, and all human isolates shared common ancestors with cattle in Baja California based on SNP analysis. This suggests that most human tuberculosis caused by M. bovis in Baja California is derived from M. bovis circulating in Baja California cattle. These results reinforce the importance of bovine tuberculosis surveillance and control in this region. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  13. A Weather Analysis System for the Baja California Peninsula: Tropical Cyclone Season of 2008

    NASA Astrophysics Data System (ADS)

    Farfán, L. M.

    2009-05-01

    General characteristics of tropical weather systems are documented on a real-time basis. This study covers the warm season of 2008, from May through November, and includes observations from satellite imagery as well as reports from a rain-gauge network. During this season, the basin had 16 tropical storms and three of them made landfall in the Baja California peninsula, in northwestern Mexico. Tropical storm Julio developed in August and tropical storm Lowell made landfall in mid-September. Norbert, in early October, was the most intense hurricane of the season with strong winds and heavy rainfall that caused significant damage to the infrastructure in the southern peninsula. By the next day, the system moved over the mainland, causing major flooding in Sinaloa, Sonora, and Chihuahua. By request of the Baja California government, a meteorological perspective associated with the structure, intensity, and motion of Hurricane Norbert was presented. This consisted of high-resolution satellite imagery used to explain the spatial and temporal patterns of convection. This material provided an integral analysis of Norbert's behavior during its approach and passage over land, and it was one element, used by emergency managers, to determine the extent of the affected areas.

  14. A weather analysis system for the Baja California peninsula: tropical cyclone season of 2007

    NASA Astrophysics Data System (ADS)

    Farfan, L. M.; Cosio, M. A.

    2008-05-01

    General characteristics of tropical weather systems were documented on a real-time basis. The geographical area of interest is the Baja California peninsula, located in northwestern Mexico. This study covers the warm season of 2007, from May through October, and includes observations derived from radar and satellite imagery as well as reports from a network of rain gauges. A set of graphical products were generated and they were available to the public through the internet. The analysis system has been in operation since the summer of 2005 and it is focused to document the development of tropical cyclones in eastern Pacific Ocean. During the season of 2007, this basin had a total of 11 tropical storms and four of them were within 800 km from the west coast of Mexico (Dalila, Ivo, Juliette and Kiko). Only one system made landfall in the area of interest: Hurricane Henriette which moved across Baja California, the Gulf of California and a portion of the state of Sonora. This presentation provides an overview of the graphical products along with lessons learned from the season studied, collaborations with local emergency managers and plans for the upcoming season of 2008.

  15. Crustal Structure of Southern Baja California Peninsula, Mexico, From Magdalena Microplate to Farallon Basin

    NASA Astrophysics Data System (ADS)

    Robles, L. N.; Gonzalez-Fernandez, A.; Fletcher, J. M.; Lizarralde, D.; Kent, G. M.; Harding, A. J.; Holbrook, W. S.; Umhoefer, P. J.; Axen, G. J.

    2004-12-01

    Wide-angle seismic data were used to investigate the crustal structure of a transect between the Magdalena Microplate to the Farallon Basin in the Gulf of California, crossing the southern Baja California Peninsula to the north of La Paz (Mexico). This is the first deep seismic study in the area, providing information of the fossil subduction zone of the Magdalena Microplate under Baja California. We have also obtained results of the seismic structure of major fault zones in the area such as Tosco-Abreojos and Santa Margarita. Seismic data were recorded by Ocean Bottom Seismometers (OBS) in the Pacific and the Gulf of California and by portable seismic instruments onshore. More than 5000 offshore high-volume air gun shots were used as energy source in both sides of the Peninsula. Wide-angle data were processed to enhance the signal to noise ratio to help in the identification of the seismic energy arrivals. We used a direct method of interpretation, including ray tracing, travel times and synthetic seismograms calculation. The availability of a number of recording instruments allows multiple coverage of the crustal structure.

  16. Paleoenvironmental interpretation of section of Rosario Formation in Ensenada, Baja California, Mexico

    SciTech Connect

    Tellez-Duarte, M.A.; Ferman-Almada, J.L.

    1986-07-01

    In contrast to previous interpretations of the Rosario Formation in other parts of Baja California, a stratigraphic section 6 km north of Ensenada, Baja California, Mexico, contains evidences for deposition in shallow waters during a regressive event in a steep slope basin. Among the sedimentary evidence, the section shows a coarse, shoaling-upward sequence, with high-angle cross-stratification and planar bed lamination. Load structures with a westward orientation were found only at the base. The fossils assemblages support the same shoaling-upward interpretation as the sedimentary evidence, with ammonoids and deposit feeder trace fossils (such as Chondrites) at the bottom to mollusks and suspension feeder trace fossils (such as Scolicia and Ophiomorpha, characteristic of shallower waters) at the top. This sedimentologic and paleontologic evidence suggests nearshore to beach coastal deposits. The contact between the section and a discontinuous thin limestone bed at the top of the section shows an unconformity. The absence of well-preserved fossils makes this limestone difficult to date, but the lithology is similar to that of Paleocene Sepultura Formation limestones.

  17. Dynamics of mesoscale anticyclones in the California Current System off the Northern Baja California Coast

    NASA Astrophysics Data System (ADS)

    Gomez-Valdes, J.; Torres, H. S.

    2015-12-01

    Subsurface eddies are ubiquitous features in eastern boundary current systems. They tend to modulate the across-shore transport of heat and tracers. In the California Current System they have been observed using different field techniques. Using shipboard measurements, an anticyclonic subsurface eddy was observed in October 2009 off the northern Baja California coast. The genesis, evolution, and turbulent heat transport of the anticyclonic eddy are addressed in this study using a realistic regional model. The oceanic response to the synoptic wind variations acts as finite amplitude perturbation. The hydrodynamic stability of the California Undercurrent is compromised, through baroclinic instability, this lead to the formation of subthermocline eddy that detach from the coast and move out toward the open ocean. The potential vorticity associated to the eddy is eroded by the irregularities of the bottom topography and it is dissipated in the northern Baja California offshore. Once the anticyclonic eddy is weakened, the eddy heat anomaly is reincorporated into the transitional zone by the mean flow. This study shows evidence of reinstatement of the thermal anomalies toward the transitional zone of the southern region of the California Current, helping to keep its water mass relatively warmer than the adjacent sea.

  18. Reinterpretation of Mesozoic ophiolite arc, and blueschist terranes in southwestern Baja California

    SciTech Connect

    Sedlock, R.L. . Geology Dept.)

    1993-04-01

    The nature and significance of disrupted Mesozoic oceanic rocks on Isla Santa Margarita and Isla Magdalena, western Baja California Sur, have been reinterpreted on the basis of detailed mapping and petrologic studies. Three structural units are recognized. (1) The upper plate consists of ophiolitic, arc, and forearc basin rocks. Ophiolitic rocks, including metamorphosed ultramafic rocks, gabbro, dikes, volcanic rocks, and chert, underwent strong contractional deformation and penetrative greenschist-facies metamorphism. Arc rocks, including gabbro, a dike and sill complex, compositionally diverse volcanic rocks, lahars, and volcaniclastic strata, lack a penetrative fabric and are weakly metamorphosed. Forearc basin rocks consist of unmetamorphosed conglomerated and rhythmically bedded siliciclastic turbidites. (2) The lower plate is a subduction complex consisting of weakly to moderately foliated and metamorphosed pillow and massive lavas, breccia, and tuff( ), interbedded red and green siliceous argillite, and rare radiolarian ribbon chert and limestone. Blueschist-facies metamorphism is indicated by lawsonite, aragonite, sodic amphibole, and sodic clino-pyroxene. (3) Serpentine-matrix melange crops out in shallowly dipping fault zones between the upper and lower plates. The structural and petrologic characteristics of the Mesozoic units, the geometry of contacts between them, and the age of extension are similar to those in the Isla Cedros-Vizcalno Peninsula region, 400 km to the northwest. The author infers that syn-subduction extension was a regional event that affected much of the western Baja forearc during the Late Cretaceous and Paleogene.

  19. Tectonic analysis of Baja California and Parras shear belt in Mexico

    NASA Technical Reports Server (NTRS)

    Abdel-Gawad, M. (Principal Investigator); Tubbesing, L.

    1974-01-01

    The author has identified the following significant results. Geological correlation of terrain across the Gulf of California using ERTS-1 imagery revealed significant similarities between Isla Tiburon, Isla Angel de la Guarda, and the San Carlos Range in mainland Mexico. ERTS-1 imagery was used to check the validity of the existence of major trans-Baja fault zones. ERTS-1 imagery also shows that high albedo sediments similar to known late Tertiary marine sediments are widespread in southern and middle Baja and extend in places to the eastern side of the Peninsula. Major faults in northern Mexico and across the border in the United States were mapped, and ample evidence was found that the Parras and parts of the Texas lineament are belts of major transverse shear faults in areas outside the supposed limit of the Texas and Parras lineaments. A fundamental concept which may help explain many complexities in the tectonic development is beginning to emerge: The southwestern part of North America was torn by massive left-lateral shear of transverse trend (east-west) during the compressive stage of the late Mesozoic and early Cenozoic. This tectonic style has changed into tensional rifting (Basin and Range) and right-lateral shear later in the Cenozoic and Quaternary.

  20. Persistent marine debris in the North Sea, Northwest Atlantic Ocean, Wider Caribbean Area, and the West Coast of Baja California. Final report

    SciTech Connect

    Heneman, B.

    1988-07-01

    Information on persistent marine debris (including plastics, glass, metal, and tar) in four study areas (North Sea, northwest Atlantic Ocean, Wider Caribbean Area, and the west coast of Baja California) was obtained through literature searches, a mailed survey, correspondence, interviews, and personal observations. All of the study areas except Baja California were found to have severe marine debris problems.

  1. Proceedings of the Binational Conference on Libraries in California and Baja California (1st, Tijuana, Baja California, Mexico, January 13-14, 1984) = Memorias de la Primera Conferencia Binacional de Bibliotecas de las Californias.

    ERIC Educational Resources Information Center

    Ayala, Marta Stiefel, Ed.; And Others

    This document includes the text of presentations given at the First Binational Conference on Libraries in California and Baja California, as well as minutes from four roundtables held at the conference. Following a prologue and a brief background on the conference, the following presentations are included: (1) "State Support for Public…

  2. The surface expression of radiocarbon anomalies near Baja California during deglaciation

    NASA Astrophysics Data System (ADS)

    Lindsay, Colin M.; Lehman, Scott J.; Marchitto, Thomas M.; Ortiz, Joseph D.

    2015-07-01

    Periods of declining atmospheric radiocarbon activity (Δ14C) during the Heinrich 1 (∼17.8-14.6 ka) and Younger Dryas (∼12.8-11.5 ka) stadials of the last deglaciation coincide with intervals of rising atmospheric CO2, as well as evidence of 14C-depleted carbon at intermediate ocean depths near Baja California, Mexico and in the Arabian Sea. The latter has been interpreted as the signature of aged carbon emerging through the intermediate ocean to the atmosphere from a previously isolated deep ocean reservoir. Here we report measurements from near Baja California that enable us to reconstruct the Δ14 C of surface waters as recorded by three different species of planktonic foraminifera. We find that surface ocean Δ14 C recorded by planktonic foraminifera was anomalously low relative to the coeval atmosphere during previously documented periods of low benthic Δ14 C, consistent with upwelling and subsequent mixing and/or partial atmospheric equilibration of the intermediate-depth benthic signal. We also propose an oceanographic explanation for observed Δ14 C differences between individual planktonic species during deglaciation at this location, based on seasonal growth habitats and a seasonal change in the source of coastal upwelling waters: from northern in the spring to southern in late summer, as the shelf-trapped poleward California Undercurrent strengthens. An analysis of the contemporary hydrography and planktic habitat preferences suggests that G. bulloides and G. sacculifer record primarily springtime conditions off Baja California, when the local influence of waters sourced from the surface of the North Pacific is greatest. This is supported by the strong resemblance of the Δ14 C of those species and a recent record of planktic Δ14 C from the Northeast Pacific during deglaciation. Lower Δ14 C recorded by the late-summer species G. ruber suggests that locally upwelling waters carried 14C-depleted carbon that was proximately sourced from equatorial

  3. Statistical analysis of eruptive vent distribution from post-subduction monogenetic fields in Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Germa, A.; Cañon-Tapia, E.; Connor, L.; Le Corvec, N.

    2012-04-01

    Volcanism in Baja California (BC, Mexico) was active from the end of the subduction of the Farallon plate (12.5Ma) until recently (< 1Ma). Most of this volcanism formed twelve volcanic fields, seven of them being monogenetic, delineating a ~600-km-long array parallel to the Gulf of California. Previous studies on these fields have focused on the compositional diversity of magmatic products. Although geochemistry and ages of few lava flows are constrained, only two studies investigated the spatial distribution of the eruptive vents of San Borja. Within a monogenetic volcanic field, cone alignments and linear arrays are considered to reflect the geometry of feeder dikes formed either parallel to the maximum principal stress (σ1) in the lithosphere or using pre-existing crustal fractures. These intrinsic local structures will be compared with the shape of the field, which could reflect the shape of the source at depth. Using satellite imagery to define the location of eruptive centres on four monogenetic volcanic fields from central Baja California (Jaraguay, San Borja, Santa Clara, and San Ignacio), we completed statistical analyses of their spatial distribution. Using commercially available GIS software, spatial density analysis, and statistical scripts, each volcanic field was analysed for the number and density of vents, clustering, vent spacing and alignment azimuths. Our preliminary results reveal that vent densities are within the range of 0.001 to 0.2 vents / 100 km2. Eruptive vents are generally clustered, with density higher than 0.1 vents/100 km2. A common elongation direction trends N135° to N152° in most clusters and fields. We thus propose a NW-SE direction as the preferred orientation of the maximum principal stress (σ1), direction that needs to be confirmed by azimuths of the vents alignments. Using a combination of different computational methods, this study allows to quantify the influence of tectonic stresses at the deep and shallow level within

  4. Morphological Study of Jaraguay and San Borja Volcanic Fields, Baja California, Mexico.

    NASA Astrophysics Data System (ADS)

    Negrete-Aranda, R.; Canon-Tapia, E.

    2005-12-01

    Volcanism younger than 12.5 Ma has occurred mainly as monogenetic volcanic fields along the Baja California Peninsula, but until now very little attention has been given to the morphological description of this type of volcanism. In this study we present the preliminary results of the first stage of elaboration of a Geographical Information System (GIS) of the northernmost volcanic fields of the Peninsula; Jaraguay and San Borja, which are among the less studied fields in the region. The present status of the GIS includes the main morphological characteristics and localization of over 350 eruptive centers identified in both volcanic fields. Our data show that over 90% of the eruptive centers are cinder cones, whereas the rest of volcanic structures include some stratovolcanos, shield volcanoes and calderas. Detailed analysis of digital elevation models and 14 m resolution Landsat TM images show a remarkable diversity of the size of reported eruptive centers: the average height lies around 720 m with peaks that reaches 1,412 m asl. Preliminary graphic analyses show local concentrations of the biggest volcanic structures in some areas in both fields. This spatial distribution is more evident at the San Borja volcanic field where the biggest volcanic centers are systematically located in its south and north-western boundaries. A similar concentration of bigger volcanic structures is found at the western edge of Jaraguay volcanic field where cinder cones are largely confined to its eastern most edge. The observed morphological changes of volcanic structures occur in both cases within a distance of less than 100 km. We interpret such variations as the result of heterogeneities of the low velocity zone below this particular area of the Baja California Peninsula, although the final evaluation of the distribution of the regional stress field and its relationship with the actual spatial distribution of eruptive centers must wait until more information becomes available. In

  5. Geomagnetic Paleosecular Variation and Tectonic Correction for the Past 12 Ma in Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Garcia-Amador, B. I.; Alva-Valdivia, L. M.; Canon-Tapia, E.

    2014-12-01

    During the last 30 years, study of Paleosecular Variation (PSV) has been analyzed within specific timescales (e.g. 0-5 Ma; 5-22.5 Ma; etc.), considering the main criteria variation in directions of paleomagnetic data due to displacement of tectonic plates, and the scarcity of spatial and temporal distribution of rock outcrops, we propose using the previous geological and geophysical studies comprising the tectonic displacement of Baja California for the last 12 Ma, a method (working in space and time) to precise the PSV of our paleomagnetic sites (assuming a thermoremanent magnetization). We completed two paleomagnetic rock field sampling works: Loreto-Santa Rosalia-Punta Abreojos (between 26° and 27.4° N), with 156 cores from 16 sites; and San Borja and Jaraguay volcanic fields (between 28° and 30° N), with 230 cores from 27 sites. These sites are mainly volcanic rocks (andesite-basalt) with radiometric ages previously reported. We selected those younger than 12 Ma age without effect of rotation or flattening within the peninsula. Rock magnetic experiments were done to characterize the magnetic carrier of the remanence, such as susceptibility vs. low and high temperature, hysteresis, FORC, Koenigsberger ratio determination and directional analysis. Our results suggest that in most of the cases (80%) we have a contribution of TM0 to TM20, and magnetic domain of PSD + SP. In addition to our data, we gathered all paleomagnetic works in volcanic rocks younger than 12 Ma along Baja California. For the PSV, we calculated the angular standard deviation (SB) of the VGPs with respect to its mean average and also to the geographic axis. Both results were compared with the calculation of the SB once the correction of paleomagnetic sites based on the tectonic displacement was applied. Finally, all results (with and without correction) were compared with Model G and TK03.GAD, finding that data of the SB with tectonic correction are the best fit models, suggesting a

  6. The Palaeodiet of the Pericue Indians of the Cape Region of Baja California Sur, Mexico.

    NASA Astrophysics Data System (ADS)

    Beer, N.; Gonzalez, S.; Huddart, D.; Rosales-Lopez, A.; Lamb, A.

    2008-05-01

    The archaeology of the Pericue Indians inhabiting the Cape region of Baja California has long been an area of interest. The dolichocranic traits exhibited by this population have lead to suggestions that these people were a relic population of an early coastal migration into North America. The antiquity of directly dated Pericue human remains only reaches 3,000 B.P. with occupation sites dating back to 9,000 B.P. The site of Babisuri cave in Isla Espiritu Santo may demonstrate a very early human presence in Baja California Sur between 36,000 to 45,000 B.P. although the exact nature of this evidence is unclear. Increasing tourist development within this region threatens many archaeological sites particularly coastal shell middens and rock shelters. Current rescue excavations are yielding important information regarding many aspects of the culture of the Pericue Indians. Geochemical evidence of diet {d13C and d15N} taken from Pericue bone samples, modern and archaeological animals and modern plants is helping us to understand the complicated subsistence strategies of this group. Initial results highlight a complicated and diverse diet including marine and terrestrial resources, most likely exploited seasonally. Similarities between the diet of the Pericue and other nearby coastal Indian groups are clear and will be discussed. Pericue Indian material culture, combined with the exploitation of marine mammals and the construction of enormous shell mounds display parallels with other central and North American groups. The exploitation of marine mammals and the associated stone tools display striking similarities to the Chumash people of the Channel Islands of Coastal Southern California. Some of these cultural similarities will be highlighted in this presentation. Current genetic work is attempting to discover the nature of the similarities between the Chumash and Pericue groups as some cultural elements of each group have parallels with the other. Initial genetic

  7. The Surface Expression of Radiocarbon Anomalies near Baja California during Deglaciation

    NASA Astrophysics Data System (ADS)

    Lindsay, C. M.; Lehman, S.; Marchitto, T. M.; Ortiz, J. D.; van Geen, A.

    2013-12-01

    In 2007, Marchitto et al. noted that periods of declining atmospheric radiocarbon activity (Δ14C) during the Heinrich 1 and Younger Dryas stadials coincided with intervals of rising atmospheric CO2, as well as extremely 14C-depleted carbon at intermediate depths near Baja California, Mexico. They interpreted this as evidence of aged carbon emerging through the intermediate ocean to the atmosphere from an isolated deep marine reservoir, and proposed that the signal was transported to Baja from the Southern Ocean via Antarctic Intermediate Water. Here we report on measurements from the same core used by Marchitto et al. (2007) that enable us to reconstruct the Δ14C of surface waters. 14C was measured in mono-specific samples of G. ruber, G. sacculifer and G. bulloides planktonic foraminifera. Independent calendar ages were provided by the published age model, which tied diffuse spectral reflectance to the layer-counted GISP2 oxygen isotope record. Preliminary results reveal that surface ocean Δ14C relative to the coeval atmosphere was lower during periods of low benthic Δ14C, consistent with upwelling and subsequent mixing and/or partial atmospheric equilibration of the intermediate-depth signal. Planktic Δ14C was higher during the Bølling-Allerød/Antarctic Climate Reversal (BA/ACR), reflecting upwelling of better-ventilated waters at a time when benthic Δ14C had a modern-like offset from the atmosphere. G. ruber Δ14C is lower than in other planktonic species during deglaciation. We propose that this offset arises from a late summer G. ruber calcification habitat and a spring G. bulloides and G. sacculifer habitat, combined with a seasonal change in the source of coastal upwelling waters from northern in the spring to southern in late summer, as the shelf-trapped poleward California Undercurrent strengthens. This interpretation invokes a southern hemisphere source for depleted carbon at the Baja surface, via northward, coastal advection of southern

  8. Regime Shifts in Productivity off Baja California During the Late Pleistocene?

    NASA Astrophysics Data System (ADS)

    Ortiz, J. D.; O'Connell, S. E.; Delviscio, J.; van Geen, A.; Beaufort, L.

    2003-12-01

    The eastern subtropical Pacific is a region of the surface ocean influenced strongly by ENSO but characterized by generally low sedimentation rates. Core MD02-2508 raised from ~700m depth on the Magdelana Margin near the southern tip of Baja California during the IMAGES VIII MONA cruise exhibits high sedimentation rates and appears to extend beyond 100 ka based on a preliminary age model. Work on a piston core collected during a prior cruise to the same location (MV99-PC08) demonstrates a clear correlation between the GISP-2 d18O record, and sedimentary records of diffuse spectral reflectance, organic carbon, calcium carbonate, and benthic foraminifers per gram sediment during the past 52 kyrs. Peaks in organic carbon content, which occur during warm interstadial events, correspond to maxima in benthic foraminiferal absolute abundance that are as much as two order of magnitude greater than those observed during cool stadial events. Although the age model of the core MD02-2508 is preliminary, data from this new core appears to extend this correlation back beyond 100 ka. From 2400 cm to 0 cm, sediment in core MD02-2508, is only laminated during the strongest of the interstadial events and exhibits an inverse linear correlation between calcium carbonate content and organic carbon content. Sediment deposited below 2400 cm are radically different. The base of core MD02-2508 is more distinctly and continuously laminated, exhibiting greater variance in organic carbon and calcium carbonate content. Of perhaps greater significance, there is a positive, exponential relationship between calcium carbonate and organic carbon content off Baja California during this interval, except for brief periods of lower organic carbon and calcium carbonate that exhibit the negative correlation which dominates at the site from 2400-0 cm. These results suggest greatly enhanced marine productivity prior to 100 ka off Baja California than at any time in the past 100 kyrs. One potential way to

  9. A Crustal Velocity Model for South Mexicali Valley, Baja California, México.

    NASA Astrophysics Data System (ADS)

    Ramirez, E.; Vidal-Villegas, A.; Stock, J. M.; Gonzalez-Fernandez, A.

    2016-12-01

    The northern Baja California region consists of two subregions of different geological features: the Peninsular Ranges of Baja California, of granitic composition, and the Mexicali Valley region, characterized by a series of sedimentary basins: the Laguna Salada and the Mexicali Valley. Due to the lack of an appropriate crust model for South Mexicali Valley, a refraction study was conducted. We installed 16 three-component short period stations (2 Hz) and one broadband station (100 s - 50 Hz). The stations, spaced 6 km along a refraction profile, recorded a blast performed in the southwest Arizona near the border with Sonora, Mexico. Records gathered were used to estimate a crust velocity structure model for South Mexicali Valley. The beginning of the profile is at San Luis Rio Colorado (SLRC), Sonora and its ending is at the middle of Sierra Juarez, Baja California. As a "reverse shot", for a 47 km section between SLRC and El Mayor Mountain, we used an aftershock M 3.4 of the 2010 M 7.2 El Mayor - Cucapah earthquake. Record sections show seismograms with impulsive P arrivals for nearby stations. The arrival Pn wave is observed at three stations located in Laguna Salada and Sierra Juarez. From the first arrivals of refractions and reflections of the P wave we performed direct modeling of travel times and relative amplitudes (normalized synthetic seismograms). Method based on asymptotic ray theory programed in the RAYINVR software (Zelt and Smith, 1992). We propose an average-three-layer velocity structure model: 2.9, 5.6 and 6.9 km/s, with thicknesses of 1.2, 4.4 and 9.6 km, respectively. Velocities of our model for the region under study are about 1 km/s higher than the model proposed by McMechan and Mooney (1984) for the Imperial Valley. The preliminary interpretation using the "reverse shot" indicates a crust of 15 km depth beneath the Mexicali Valley and 19 km under the El Mayor Mountain and Laguna Salada basin. On the eastern side of the El Mayor Mountain we

  10. Preliminary Analysis of Remote Triggered Seismicity in Northern Baja California Generated by the 2011, Tohoku-Oki, Japan Earthquake

    NASA Astrophysics Data System (ADS)

    Wong-Ortega, V.; Castro, R. R.; Gonzalez-Huizar, H.; Velasco, A. A.

    2013-05-01

    We analyze possible variations of seismicity in the northern Baja California due to the passage of seismic waves from the 2011, M9.0, Tohoku-Oki, Japan earthquake. The northwestern area of Baja California is characterized by a mountain range composed of crystalline rocks. These Peninsular Ranges of Baja California exhibits high microseismic activity and moderate size earthquakes. In the eastern region of Baja California shearing between the Pacific and the North American plates takes place and the Imperial and Cerro-Prieto faults generate most of the seismicity. The seismicity in these regions is monitored by the seismic network RESNOM operated by the Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE). This network consists of 13 three-component seismic stations. We use the seismic catalog of RESNOM to search for changes in local seismic rates occurred after the passing of surface waves generated by the Tohoku-Oki, Japan earthquake. When we compare one month of seismicity before and after the M9.0 earthquake, the preliminary analysis shows absence of triggered seismicity in the northern Peninsular Ranges and an increase of seismicity south of the Mexicali valley where the Imperial fault jumps southwest and the Cerro Prieto fault continues.

  11. Prevalence of infection with Toxoplasma gondii in landrace and mixed breed pigs slaughtered in Baja California Sur state, Mexico

    USDA-ARS?s Scientific Manuscript database

    Purpose We performed a cross-sectional study to determine the seroprevalence of Toxoplasma gondii infection in 308 domestic pigs slaughtered in La Paz, Baja California Sur State, Mexico using the modified agglutination test (MAT, cut off 1:25). Results Forty (13%) of the 308 pigs were seropositive ...

  12. 78 FR 20887 - Approval of Subzone Status; Pepsi Cola Puerto Rico Distributing, LLC, Toa Baja, Puerto Rico

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-08

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE Foreign-Trade Zones Board Approval of Subzone Status; Pepsi Cola Puerto Rico Distributing, LLC, Toa Baja..., requesting subzone status subject to the existing activation limit of FTZ 7, on ] behalf of Pepsi Cola Puerto...

  13. Phylogeography and Ecological Niche Modeling of the Desert Iguana (Dipsosaurus dorsalis, Baird & Girard 1852) in the Baja California Peninsula.

    PubMed

    Valdivia-Carrillo, Tania; García-De León, Francisco J; Blázquez, Ma Carmen; Gutiérrez-Flores, Carina; González Zamorano, Patricia

    2017-09-01

    Understanding the factors that explain the patterns of genetic structure or phylogeographic breaks at an intraspecific level is key to inferring the mechanisms of population differentiation in its early stages. These topics have been well studied in the Baja California region, with vicariance and the dispersal ability of individuals being the prevailing hypothesis for phylogeographic breaks. In this study, we evaluated the phylogeographic patterns in the desert iguana (Dipsosaurus dorsalis), a species with a recent history in the region and spatial variation in life history traits. We analyzed a total of 307 individuals collected throughout 19 localities across the Baja California Peninsula with 15 microsatellite DNA markers. Our data reveal the existence of 3 geographically discrete genetic populations with moderate gene flow and an isolation-by-distance pattern presumably produced by the occurrence of a refugium in the Cape region during the Pleistocene Last Glacial Maximum. Bayesian methods and ecological niche modeling were used to assess the relationship between population genetic structure and present and past climatic preferences of the desert iguana. We found that the present climatic heterogeneity of the Baja California Peninsula has a marked influence on the population genetic structure of the species, suggesting that there are alternative explanations besides vicariance. The information obtained in this study provides data allowing a better understanding of how historical population processes in the Baja California Peninsula can be understood from an ecological perspective. © The American Genetic Association 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  14. The microbial community at Laguna Figueroa, Baja California Mexico - From miles to microns

    NASA Technical Reports Server (NTRS)

    Stolz, J. F.

    1985-01-01

    The changes in the composition of the stratified microbial community in the sediments at Laguna Figeroa following floods are studied. The laguna which is located on the Pacific coast of the Baja California peninsula 200 km south of the Mexican-U.S. border is comprised of an evaporite flat and a salt marsh. Data collected from 1979-1983 using Landsat imagery, Skylab photographs, and light and transmission electron microscopy are presented. The flood conditions, which included 1-3 m of meteoric water covering the area and a remanent of 5-10 cm of siliciclastic and clay sediment, are described. The composition of the community prior to the flooding consisted of Microcoleus, Phormidium sp., a coccoid cynanobacteria, Phloroflexus, Ectothiorhodospira, Chloroflexus, Thiocapsa sp., and Chromatium. Following the floods Thiocapsa, Chromatium, Oscillatora sp., Spirulina sp., and Microcoleus are observed in the sediments.

  15. Miocene to Recent Volcanism in NE Baja California and its Correlation to Adjacent Regions

    NASA Astrophysics Data System (ADS)

    Stock, J. M.

    2007-05-01

    This paper reviews the status of knowledge of volcanic rocks from part of NW Mexico. Rocks of the Puertecitos Volcanic Province, NE Baja California, span the time period from subduction-related volcanism (the "early to middle Miocene arc" of Gastil et al.) through to modern rift-related volcanism. Ages and major element geochemistry of the principal rock packages were summarized by Martin-Barajas and colleagues in various publications. Additional geochronology and paleomagnetic studies were done by Lewis (1994) and Nagy (1997) to characterize the ages, magnetic polarities, and distributions of the major pyroclastic flow deposits and lavas. The arc-related rocks consist of voluminous epiclastic material of 20-17 Ma and local vents of mafic to intermediate lavas as young as 15.5 Ma. These were eroded prior to deposition of the ca. 12.5 Ma Tuff of San Felipe, a peralkaline high-Si rhyolite pyroclastic flow deposit that is inferred to indicate post-subduction volcanism. Intermediate lavas were erupted in this region ca 9 Ma, followed by a 6.4-6.1 Ma sequence of rhyolite domes and ignimbrites. In the southern Puertecitos Volcanic Province, another pulse of volcanism from 3.3 to 2.7 Ma produced a series of at least 20 thin, high-temperature pyroclastic flow deposits. Volcanism continued with Pliocene and Quaternary andesites and more evolved lavas. This volcanic history is compared to that of surrounding regions. The 20-15 Ma arc rocks are partly younger than similar rocks farther north in the Baja California peninsula and are coeval with volcanic arc rocks farther south. Northward, the centers decrease in frequency in map view; volumes decrease and the relationship of these lavas to coeval lavas near the border (e.g., Alverson Fm in S. California) is not clear. This may be an effect of the northern limit of the corresponding subduction zone. The ca. 6 Ma volcanism is related to rifting of the northern Gulf of California, particularly due to its structurally controlled

  16. Chemically diverse, sporadic volcanism at seamounts offshore southern and Baja California

    USGS Publications Warehouse

    Davis, A.S.; Gunn, S.H.; Bohrson, W.A.; Gray, L.-B.; Hein, J.R.

    1995-01-01

    Compositions of lavas from seven small to medium-sized seamounts offshore southern and Baja California, include low-K2O tholeiitic, transitional, and mildly to moderately alkalic basalt and their differentiates. The seamounts with these MORB-like lavas are inferred to have formed at or near the spreading center. Based on 40Ar/39Ar laser fusion techniques, MORB-like lava from one of the northern edifices is as old as the underlying oceanic crust (>20 Ma), indicating that it originated at a spreading center. Other seamount lava ages are much younger than the oceanic crust on which they reside. Some of the seamounts with transitional and alkalic lavas may have formed as part of a short, age-progressive chain formed by a short-lived mantle plume. Many others, may have resulted from upwelling mantle diapirs in response to localized extension. -from Authors

  17. Precipitation forecast using artificial neural networks. An application to the Guadalupe Valley, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Herrera-Oliva, C. S.

    2013-05-01

    In this work we design and implement a method for the determination of precipitation forecast through the application of an elementary neuronal network (perceptron) to the statistical analysis of the precipitation reported in catalogues. The method is limited mainly by the catalogue length (and, in a smaller degree, by its accuracy). The method performance is measured using grading functions that evaluate a tradeoff between positive and negative aspects of performance. The method is applied to the Guadalupe Valley, Baja California, Mexico. Using consecutive intervals of dt=0.1 year, employing the data of several climatological stations situated in and surrounding this important wine industries zone. We evaluated the performance of different models of ANN, whose variables of entrance are the heights of precipitation. The results obtained were satisfactory, except for exceptional values of rain. Key words: precipitation forecast, artificial neural networks, statistical analysis

  18. Numerical simulation of the sea breeze, ideal and realistic: Baja California, Mexico case

    NASA Astrophysics Data System (ADS)

    Colorado, G.; Mateos, E.; Ayala, R.

    2016-12-01

    In studies, with data from weather stations in Bahia de Todos Santos, Baja California, Mexico, was found that the sea-land breeze is an important component of the wind circulation. Therefore, its behaviour was simulated numerically with the WRF model to identify not only the surface field, but the vertical component of this phenomenon, in addition to quantifying the number of events during the year 2010. The model was forced with NARR data, and triple nested meshes were defined, whose smallest nest has a horizontal resolution of 2 km. In parallel to realistic simulation, an idealized numerical experiment was done with the WRF-idealize sea breeze example to verify whether the WRF model can reproduce the sea breeze. In order to do this, three variables were analyzed: temperature, relative humidity and the U component of the wind.

  19. Seasonal variability shapes resilience of small-scale fisheries in Baja California Sur, Mexico

    PubMed Central

    Leslie, Heather M.

    2017-01-01

    Small-scale fisheries are an important source of food and livelihoods to coastal communities around the world. Understanding the seasonality of fisheries catch and composition is crucial to fisheries management, particularly in the context of changing environmental and socioeconomic conditions. While seasonal variability directly impacts the lives of fishers, most fisheries studies focus on longer-term change. Here we examine seasonal variability in the small-scale fisheries of Baja California Sur, Mexico based on 13 years of government fisheries data. We investigate how four fisheries indicators with direct relevance to ecological resilience–magnitude and variance of landed fish biomass, taxon richness and the proportion of top-trophic-level taxa in total catch–vary within and among years and at multiple spatial scales. We find that these resilience indicators vary both seasonally and spatially. These results highlight the value of finer-scale monitoring and management, particularly for data-poor fisheries. PMID:28783740

  20. Metal concentrations in demersal fish species from Santa Maria Bay, Baja California Sur, Mexico (Pacific coast).

    PubMed

    Jonathan, M P; Aurioles-Gamboa, David; Villegas, Lorena Elizabeth Campos; Bohórquez-Herrera, Jimena; Hernández-Camacho, Claudia J; Sujitha, S B

    2015-10-15

    Concentrations of 11 trace metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd, As, Hg) in 40 fish species from Santa Maria Bay, Baja California Sur, Mexico, the strategically important area for marine mammals and organisms were analyzed. Based on their concentrations the ranking of metals Fe>Zn>Ni>Cr>Mn>Pb>Cu>Co>As>Cd>Hg suggests that organism size, metabolism and feeding habits are correlated with metal concentrations. Local geological formations affect the concentrations of different metals in the aquatic environment and are subsequently transferred to fishes. The correlation analysis suggests that metabolism and nurturing habits impact the concentration of metals. Concentrations of Fe and Mn appear to be influenced by scavenging and absorption processes, which vary by species. The considerable variability in the metal concentrations obtained in different species underscores the importance of regular monitoring.

  1. Agave turneri (Agavaceae), a new species from northeastern Baja California, Mexico

    USGS Publications Warehouse

    Webb, R.H.; Salazar-Cesena, J. M.

    2011-01-01

    Agave turneri, a new species of Agave from the Sierras Cucap?? and El Mayor in northeastern Baja California, Mexico, is a medium-sized species that does not produce offsets, has a relatively short and narrow panicle, and has a distinctive flower structure. The closest relatives to this new species are Agave moranii, which occurs approximately 200 km to the south of the type locality, and A. deserti var. simplex, which occurs in Arizona and California. This new species is a narrow endemic restricted to specific granodiorite and tonalite habitats in a hyperarid environment. Agave turneri appears to be a critically endangered owing to its habitat preference for specific types of granite in the Sierra Cucap??, threats due to prolonged drought and global change, and its close proximity to the Mexicali metropolitan area. ?? 2010 The New York Botanical Garden.

  2. Agave turneri (Agavaceae), a new species from northeastern Baja California, Mexico

    USGS Publications Warehouse

    Webb, Robert H.; Salazar-Ceseña, J. Mario

    2011-01-01

    Agave turneri, a new species of Agave from the Sierras Cucapá and El Mayor in northeastern Baja California, Mexico, is a medium-sized species that does not produce offsets, has a relatively short and narrow panicle, and has a distinctive flower structure. The closest relatives to this new species are Agave moranii, which occurs approximately 200 km to the south of the type locality, and A. deserti var. simplex, which occurs in Arizona and California. This new species is a narrow endemic restricted to specific granodiorite and tonalite habitats in a hyperarid environment. Agave turneri appears to be a critically endangered owing to its habitat preference for specific types of granite in the Sierra Cucapá, threats due to prolonged drought and global change, and its close proximity to the Mexicali metropolitan area.

  3. Experiential environmental learning: A case study of innovative pedagogy in Baja Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Schneller, Andrew Jon

    This mixed methods case study describes an innovative two-semester middle school environmental learning course that departs from traditional Mexican expository pedagogy through the incorporation of experiential and service learning. This research takes place in a small middle school in Pescadero, Baja California Sur, Mexico. The research approach utilized in the study adds to the handful of studies in this cross-disciplinary field by employing quantitative methodologies to measure course outcomes on student environmental knowledge, perceptions, and actions, while simultaneously qualitatively describing the behavioral, educational, environmental, and social experiences of students. This research employs Dewey's theories of experience---as well as those of more contemporary authenticity theorists---in order to identify the philosophies that advocate incorporating experiential pedagogy within the curriculum. Implications for Mexican educational policy, practical pedagogical applications, and theory are discussed.

  4. Hydrodynamic properties of San Quintin Bay, Baja California: Merging models and observations.

    PubMed

    Melaku Canu, Donata; Aveytua-Alcázar, Leslie; Camacho-Ibar, Victor F; Querin, Stefano; Solidoro, Cosimo

    2016-07-15

    We investigated the physical dynamics of San Quintin Bay, a coastal lagoon located on the Pacific coast of northern Baja California, Mexico. We implemented, validated and used a finite element 2-D hydrodynamic model to characterize the spatial and temporal variability of the hydrodynamic of the bay in response to variability in the tidal regime and in meteorological forcing patterns. Our analysis of general circulation, residual currents, residence times, and tidal propagation delays allowed us to characterize spatial variability in the hydrodynamic basin features. The eulerian water residence time is -on average and under reference conditions- approximately 7days, although this can change significantly by region and season and under different tidal and meteorological conditions. Ocean upwelling events that bring colder waters into the bay mouth affect hydrodynamic properties in all areas of the lagoon and may affect ecological dynamics. A return to pre-upwelling conditions would take approximately 10days. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Volcanic materials superconductivity in desert areas of the states of Sonora and Baja California

    NASA Astrophysics Data System (ADS)

    Holguín, Aldo

    2017-01-01

    Research was conducted to find materials in their natural state at room temperature and exhibit the effects of superconductivity in the volcanic region of deserts Altar in Sonora and Baja California Norte. 100 were collected at random samples of materials from different parts of the region and underwent tests to determine their electromagnetic parameters of electrical resistance, magnetism, temperature and conductivity. Only it has been found that the effects of superconductivity in them is only present at very low temperatures corroborating what has been done in other investigations, however no indication that there is a material or combination of materials that can produce the effects of superconductivity other temperatures so it is suggested to continue the search for such materials and / or develop a technique at room temperature to allow mimic the behavior of atoms when superconductivity occurs at.

  6. Bacteriological water quality along the Tijuana-Ensenada, Baja California, México shoreline.

    PubMed

    Orozco-Borbón, Ma Victoria; Rico-Mora, Roxana; Weisberg, Stephen B; Noble, Rachel T; Dorsey, John H; Leecaster, Molly K; McGee, Charles D

    2006-10-01

    This survey was part of a Binational Program (Mexico-United States) in microbiological water quality, with a goal to assess the shoreline bacteriological water quality from Tijuana to Ensenada, Mexico. Samples were collected at 29 sites (19 beaches and 10 outfalls), from the United States border to Punta Banda, Baja California, during summer (1998) and winter (1999). Total coliforms, fecal coliforms and enterococci were used as bacterial indicators. Standard methods were used for total and fecal coliforms, while the Enterolert quick method (IDEXX) was used for the enterococci. Compared with outfalls, the beaches exceeded water quality standards by a small percent, 25.3% in summer and 17% in winter. For outfalls, the percentage of shoreline that exceeded bacterial indicator thresholds had a minor value in summer (32.7%) than in winter (50%). Sites near wastewater discharges had the lowest quality and did not meet the microbiological water quality criteria for recreational use.

  7. Assessment of active faults for maximum credible earthquakes of the southern California-northern Baja region

    NASA Astrophysics Data System (ADS)

    Slemmons, D. B.; Omalley, P.; Whitney, R. A.; Chung, D. H.; Bernreuter, D. L.

    1982-06-01

    Compilation of a data base is presented for maximum or maximum credible earthquakes that can be used to compute seismic hazard spectra at the San Onofre Nuclear Generating Stations in southern California. Estimates of fault slip rate and estimated recurrence - northern Baja California region are given. According to a direct relationship between the total fault length and the earthquake magnitude, the maximum earthquake for the Offshore Zone of Deformation (OZD) is estimated to be of about 6.8 or 6.9 surface wave magnitude. Another empirical relationship relating the fractional fault length and earthquake magnitude for strike slip faults results in an estimated maximum earthquake of about M/sub S/ = 6.8 for the OZD.

  8. Porosity of coastal deltaic sandstones, Cerro Prieto geothermal field, Baja California, Mexico

    SciTech Connect

    Vonder Haar, S.P.

    1984-04-01

    Core porosity values for sandstones and density log-derived porosities for sandstone-siltstone-shale sequences indicate a range from less than 1% to 40% at the Cerro Prieto geothermal field, Baja California, Mexico. Mean porosity values indicate that a general trend of decreasing porosities with increasing depth from 35% at 600 m to 10% at 2300 m is complicated by the 15 to 30% porosities in the 350/sup 0/C hot water zone at about 2700 m depth. Scanning electron microscopy documents secondary dissolution porosity, mineral overgrowths, and abundant clay minerals. Core permeability ranges from 0.1 to 1000 millidarcies for the more than 50 cores studied. The porosity variability indicates that geothermal systems provide an ideal setting for testing concepts of dissolution porosity and increased secondary dissolution permeability that could be useful for nuclear waste storage as well as petroleum reservoir engineering.

  9. Farallon slab detachment and deformation of the Magdalena Shelf, southern Baja California

    USGS Publications Warehouse

    Brothers, Daniel S.; Harding, Alistair J.; Gonzalez-Fernandez, Antonio; Holbrook, W.S. Steven; Kent, Graham M.; Driscoll, Neal W.; Fletcher, John M.; Lizarralde, Daniel; Umhoefer, Paul J.; Axen, Gary

    2012-01-01

    Subduction of the Farallon plate beneath northwestern Mexico stalled by ~12 Ma when the Pacific-Farallon spreading-ridge approached the subduction zone. Coupling between remnant slab and the overriding North American plate played an important role in the capture of the Baja California (BC) microplate by the Pacific Plate. Active-source seismic reflection and wide-angle seismic refraction profiles across southwestern BC (~24.5°N) are used to image the extent of remnant slab and study its impact on the overriding plate. We infer that the hot, buoyant slab detached ~40 km landward of the fossil trench. Isostatic rebound following slab detachment uplifted the margin and exposed the Magdalena Shelf to wave-base erosion. Subsequent cooling, subsidence and transtensional opening along the shelf (starting ~8 Ma) starved the fossil trench of terrigenous sediment input. Slab detachment and the resultant rebound of the margin provide a mechanism for rapid uplift and exhumation of forearc subduction complexes.

  10. Preliminary geologic studies of Sierra El Aguajito (Baja California, Mexico): a resurgent-type caldera

    NASA Astrophysics Data System (ADS)

    Garduño-Monroy, V. H.; Vargas-Ledezma, H.; Campos-Enriquez, J. O.

    1993-12-01

    Geologic field studies conducted in the Quaternary volcanic field of Tres Virgenes (State of Baja California Sur, Mexico) revealed the existence of a resurgent caldera. The caldera's eruptive products, the Aguajito sequence, overlie the products of the nearby Reforma caldera (Reforma sequence) whose youngest products have already been dated as Quaternary. The rim of the Aguajito caldera is inferred by the existence of an arcuate alignment of rhyolitic domes. The mean diameter of this subcircular feature is 10 km. The volume of its mapped acidic products is a minimum of 10 km 3. Several horizons within the sequence contain shells. K/Ar dates of the ignimbrites and domes of El Aguajito formation confirm that the unit are Pleistocene. The detailed stratigraphy also shows the evolution of a marine regression partly related to the caldera.

  11. The Baja California Borderland and the Neogene Evolution of the Pacific-North American Plate Boundary

    NASA Astrophysics Data System (ADS)

    Fletcher, J. M.; Eakins, B. W.

    2001-12-01

    New observational data on Neogene faulting in the borderland of Baja California places important constraints on tectonic models for the evolution of the Pacific-North American (P-NA) plate boundary and rifting in the Gulf of California. Neogene faults in the borderland range from strike slip to normal slip and accommodate integrated transtension. Most have east-facing escarpments and likely reactivate the former east-dipping accretionary complex. Numerous lines of evidence indicate that Neogene faults are still active and accomplish a significant component ( ~1-5 mm/yr) of Pacific-North American shearing. Quaternary volcanoes are found offshore and along the Pacific coastal margin, Quaternary marine terraces are warped and uplifted as high as 200 masl. Many of the offshore faults have fresh escarpments and cut Holocene sediments. Extensive arrays of Quaternary fault scarps are found throughout the coastal region and in Bahia Magdalena they are clearly associated with major faults that bound recently uplifted islands. A prominent band of seismicity follows the coast and eight earthquakes (Ms>5.0) were teleseismically recorded between 1973 and 1998. This evidence for active shearing indicates that the Baja microplate has not yet been completely transferred to the Pacific plate. The best lithologic correlation that can be used to define the total Neogene slip across the borderland faults is the offset between the Magdalena submarine fan and its Baja source terrane. The distal facies of the fan drilled during DSDP leg 63 is dominated by mudstone and siltstone that contain reworked Paleogene cocoliths derived from strata correlative with the Tepetate formation found throughout the borderland and fine-grained sandstone derived from a source terrane of granitoid basement. The Middle Miocene La Calera formation of the Cabo trough is one of many granitoid-clast syn-rift alluvial deposits that could form the continental counterpart of the submarine fan near the mouth of the

  12. New constraints on deglacial marine radiocarbon anomalies from a depth transect near Baja California

    NASA Astrophysics Data System (ADS)

    Lindsay, Colin M.; Lehman, Scott J.; Marchitto, Thomas M.; Carriquiry, José D.; Ortiz, Joseph D.

    2016-08-01

    Previous studies have shown that radiocarbon activities (Δ14C) in the low-latitude, middepth Pacific and Indian Oceans were anomalously low during Heinrich Stadial 1 (HS1, ~17.8-14.6 ka) and the Younger Dryas (YD, ~12.8-11.5 ka), coincident with intervals of rising atmospheric CO2 concentration and declining atmospheric Δ14C. However, a full explanation of these events remains elusive due to sparse and sometimes conflicting data. Here we present new 14C measurements on benthic and planktic foraminifera that, in combination with previously published measurements, enable us to reconstruct the Δ14C depth gradient near Baja California. Vertical profiles were similar to present during the Last Glacial Maximum and Bølling/Allerod (14.6-12.8 ka) but display a pronounced middepth (~700 m) Δ14C minimum during HS1 and the YD. The latter observation, along with a comparison to other regional reconstructions, appears to rule out intermediate waters from the north or from directly below as proximate sources of aged 14C-depleted ocean carbon during deglaciation and point instead to changes in the composition of Equatorial Pacific intermediate waters. Simple mixing constraints require Equatorial Pacific intermediate waters to be only slightly lower in Δ14C than at Baja California, in contrast with previous observations of extremely low Δ14C at Galapagos Rise. While the latter may have been influenced by localized releases of geologic (14C-dead) CO2, the smaller and more widespread deglacial Δ14C anomalies in the Arabian Sea and North Pacific seem to require a source of aged carbon in the glacial deep Southern and Pacific Oceans for which there is growing evidence.

  13. Modern carbonate sediments and environments of the LaPaz region, Baja California Sur, Mexico

    SciTech Connect

    Halfar, J.; Ingle, J.C. Jr.; Cruz-Orozco, R.; Godinez-Orta, L.

    1996-12-31

    The Gulf of California represents one of the most productive and unique marginal seas in the world. The mouth of the Gulf captures warm equatorial water while annual wind patterns assure major upwelling of nutrient-rich water leading to a rich marine biota. These conditions have created a wide array of tropical through warm temperate carbonate environments. The most unusual of these environments is located in the La Paz region of Baja California Sur where tropical-subtropical water temperatures and low rainfall have allowed growth of corals, calcareous red algae, and other shelled invertebrates to form a carbonate bank environment. Sampling and mapping transacts in shallow bays north of La Paz and on the adjacent Espiritu Santo island have revealed a full spectrum of subenvironments including mangrove bordered, terrigenous mud dominated coastal zones, which grade into carbonate tidal flats. In addition, single coral heads as well as incipient reef structures constructed by Porites and Pocillopora coral are present in deeper water areas. Coralline red algae, which are increasingly utilized for paleoenvironmental reconstructions, grow in high abundance on coral debris and in soft sediments and turn out to be main contributors to the La Paz carbonates. Analysis of siliciclastic admixtures, grain size and organic carbon content allow a classification of distinct environments. These data are supplemented by an evaluation of benthic foraminiferal zonations and the varying abundance of biogenic constituents. This Baja California Sur carbonate environment holds special relevance for the interpretation of analogous Neogene and Paleogene paleoenvironments marking major paleoclimatic and paleoceanographic events along the Pacific Coast of North America.

  14. Modern carbonate sediments and environments of the LaPaz region, Baja California Sur, Mexico

    SciTech Connect

    Halfar, J.; Ingle, J.C. Jr. ); Cruz-Orozco, R. ); Godinez-Orta, L. )

    1996-01-01

    The Gulf of California represents one of the most productive and unique marginal seas in the world. The mouth of the Gulf captures warm equatorial water while annual wind patterns assure major upwelling of nutrient-rich water leading to a rich marine biota. These conditions have created a wide array of tropical through warm temperate carbonate environments. The most unusual of these environments is located in the La Paz region of Baja California Sur where tropical-subtropical water temperatures and low rainfall have allowed growth of corals, calcareous red algae, and other shelled invertebrates to form a carbonate bank environment. Sampling and mapping transacts in shallow bays north of La Paz and on the adjacent Espiritu Santo island have revealed a full spectrum of subenvironments including mangrove bordered, terrigenous mud dominated coastal zones, which grade into carbonate tidal flats. In addition, single coral heads as well as incipient reef structures constructed by Porites and Pocillopora coral are present in deeper water areas. Coralline red algae, which are increasingly utilized for paleoenvironmental reconstructions, grow in high abundance on coral debris and in soft sediments and turn out to be main contributors to the La Paz carbonates. Analysis of siliciclastic admixtures, grain size and organic carbon content allow a classification of distinct environments. These data are supplemented by an evaluation of benthic foraminiferal zonations and the varying abundance of biogenic constituents. This Baja California Sur carbonate environment holds special relevance for the interpretation of analogous Neogene and Paleogene paleoenvironments marking major paleoclimatic and paleoceanographic events along the Pacific Coast of North America.

  15. 2D Numerical Models of Ridge-Trench Collision: Implications for Slab Detachment Beneath Baja California

    NASA Astrophysics Data System (ADS)

    Burkett, E. R.; Billen, M. I.

    2008-12-01

    The approach of a buoyant spreading ridge to a subduction zone is a scenario that may lead to detachment of a subducted slab. Previous work has called upon the detachment process as a possible explanation for observed ridge abandonment and slab-window related magmatism in Baja CA/western Mexico, but such a scenario has not previously been tested using fully-dynamic numerical models. We use two-dimensional fully- dynamic models of ridge approach to a subduction zone to explore the dependence of detachment and resultant surface effects on subducted slab length, ridge-trench distance, spreading rate, and lithospheric yield strength. We find that our models, which include non-Newtonian rheology, demonstrate the following dynamics of ridge approach: (a) a decrease in subduction velocity as the ridge approaches the trench, (b) a shrinking surface plate that maintains a uniform subduction velocity, (c) rapid slab detachment at depths ranging from 55-95 km depth depending on the slab age (7-12 My) and (d) ridge abandonment distances of 125-225 km from the trench, and slab gap distances of 200-270 km from the trench. Slab gap distance is used as a proxy for the distance to a possible slab-window related magmatism. These results are consistent with observations in Baja CA, where detachment of the Cocos slab may explain abandonment of observed segments of the East Pacific Rise 50-200 km outboard of the trench and the presence of a non-arc magmatic pulse 100-250 km inboard of the trench, with geochemical signatures separate from that associated with the normal subduction history for the Farallon plate.

  16. The Toa Baja Drilling Project and current studies in Puerto Rican geology: Introduction and summary

    SciTech Connect

    Larue, D.K. )

    1991-03-01

    This volume concerns information learned by drilling the Toa Baja well on the north coast of Puerto Rico, and current studies of Puerto Rican geology and tectonics. The Toa Baja Drillsite is located in the North Coast basin of Puerto Rico about 10 km west of San Juan. The hole was spudded on August 23, 1989, and plugged and abandoned on November 7, 1989 at a total depth of 2,704m. Two lithologies were encountered during drilling: an upper series consisting of Oligocene-Miocene shallow-water limestone and sandstone facies, and a lower series consisting of Eocene deep-water volcaniclastic strata, including some lava flows or shallow intrusions, pelagic marls, and altered igneous rocks or coarse-grained sandstones. Principal findings made during drilling include: (1) the important unconformity separating the upper and lower series at about 579 m; (2) 8 faults defined clearly by dipmeter log; (3) changes in rock type probably associated with reflection events in seismic reflection profiles crossing the drillsite; (4) confirmation of overall low geothermal gradients and heat flow, but presence of a thermal anomaly near 2683 m; (5) documentation of high paleogeothermal gradients using petrographic, isotopic, X-Ray diffraction and electron microprobe studies; (6) presence of fractures indicating a current extensional tectonic setting. Current studies in the Puerto Rico region include: (1) paleomagnetic evidence for late Miocene counterclockwise rotation; (2) geochemical evolution of Cretaceous and Eocene igneous rocks; (3) evidence of transtension in the northeast Caribbean plate boundary zone; (4) results of studies of ancient fault zones on Puerto Rico; and (5) stratigraphic studies of the Tertiary of Puerto Rico.

  17. Población de galaxias de baja luminosidad en cúmulos

    NASA Astrophysics Data System (ADS)

    Valotto, C. A.; Muriel, H.; Moore, B.; García Lambas, D.

    En este trabajo se discute sobre la presencia de un exceso de galaxias de baja luminosidad en medios de alta densidad de galaxias y la posibilidad de que los halos de galaxias cD puedan ser formados a partir de galaxias en cúmulos ricos, los cuales muestran una función de luminosidad (FL) con el extremo débil plano. Se analizaron muestras de cúmulos cercanos obtenidas a partir de los catálogos de Abell y X-ray Sample of Bright Clusters. Los resultados obtenidos muestran que los cúmulos de galaxias que tienen emisión en rayos X detectada poseen una FL plana (α ≈ -1.2), consistente con los valores encontrados para las galaxias de campo. En cambio, los cúmulos de galaxias identificados a partir de distribuciones bidimensionales de galaxias que no tienen su contraparte en rayos X, muestran una FL con una pendiente pronunciada en el extremo débil (α ≈ -1.6). Se examinaron además, los posibles efectos debido a la presencia de una galaxia central dominante sobre el extremo débil de la FL. Se analizaron muestras de acuerdo a la clasificación Bautz-Morgan dividiendo en las submuestras I,I-II y II, II- III, III. Las FL resultantes para ambas muestras son indistinguibles. Nuestros resultados son consistentes con la hipótesis de que los efectos de proyección en cúmulos identificados en dos dimensiones pueden producir un exceso artificial de galaxias de baja luminosidad.

  18. Discordant paleomagnetic data for middle-Cretaceous intrusive rocks from northern Baja California: Latitude displacement, tilt, or vertical axis rotation?

    NASA Astrophysics Data System (ADS)

    BöHnel, Harald; Delgado-Argote, Luis A.; Kimbrough, David L.

    2002-10-01

    Paleomagnetic results and U/Pb zircon dating from the San Marcos dike swarm and the El Testerazo pluton in the Cretaceous Peninsular Ranges batholith of northern Baja California are used to evaluate alternative pre-Neogene paleogeographic reconstructions of the Baja California peninsula. The San Marcos dike swarm is a dense, northwest striking, regional dike swarm that is exposed over an ˜100 km long segment of the batholith and has yielded a U/Pb zircon crystallization age of 120 ± 1 Ma. Dike attitudes from the swarm suggest a regionally consistent average ˜320°E strike and ˜79°NE dip. The El Testerazo pluton is a younger tonalite intrusion that truncates the northern end of the dike swarm. All but one of 36 sites sampled in this study show remanence of normal polarity. Paleopoles for the San Marcos dike swarm and El Testerazo pluton are indistinguishable and were combined into a paleopole at 248.1°E, 86.6°N, A95 = 4.8°, which is displaced with respect to the 122 Ma reference pole for stable North America at 198.2°E, 72.3°N, A95 = 3.3°. The displacement may be described by an apparent clockwise rotation of 18° ± 6° and an apparent northward shift of 8° ± 5°. Restoring a northward shift of about 3°, related to the separation of Baja California from North America since 10 Ma, only a marginal northward displacement of 5° ± 5° is left. The clockwise rotation may be the result of crustal block rotations within the right-lateral shear systems in northern Baja California, although there is no geological evidence that supports this possibility. Alternatively, the difference between paleopole and reference pole may be due to tilting of the study area. Restoring a northeastward tilt of 11°, based on the mean dip measured for the San Marcos dike swarm in the study area, yields a paleopole at 187.6°E, 70.8°N, A95 = 5.6°, which is indistinguishable from the 122 Ma North American reference pole. The tilting hypothesis suggested previously as a

  19. Late Quaternary Faulting along the San Juan de los Planes Fault Zone, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Busch, M. M.; Coyan, J. A.; Arrowsmith, J.; Maloney, S. J.; Gutierrez, G.; Umhoefer, P. J.

    2007-12-01

    As a result of continued distributed deformation in the Gulf Extensional Province along an oblique-divergent plate margin, active normal faulting is well manifest in southeastern Baja California. By characterizing normal-fault related deformation along the San Juan de los Planes fault zone (SJPFZ) southwest of La Paz, Baja California Sur we contribute to understanding the patterns and rates of faulting along the southwest gulf-margin fault system. The geometry, history, and rate of faulting provide constraints on the relative significance of gulf-margin deformation as compared to axial system deformation. The SJPFZ is a major north-trending structure in the southern Baja margin along which we focused our field efforts. These investigations included: a detailed strip map of the active fault zone, including delineation of active scarp traces and geomorphic surfaces on the hanging wall and footwall; fault scarp profiles; analysis of bedrock structures to better understand how the pattern and rate of strain varied during the development of this fault zone; and a gravity survey across the San Juan de los Planes basin to determine basin geometry and fault behavior. The map covers a N-S swath from the Gulf of California in the north to San Antonio in the south, an area ~45km long and ~1-4km wide. Bedrock along the SJPFZ varies from Cretaceous Las Cruces Granite in the north to Cretaceous Buena Mujer Tonalite in the south and is scarred by shear zones and brittle faults. The active scarp-forming fault juxtaposes bedrock in the footwall against Late Quaternary sandstone-conglomerate. This ~20m wide zone is highly fractured bedrock infused with carbonate. The northern ~12km of the SJPFZ, trending 200°, preserves discontinuous scarps 1-2km long and 1-3m high in Quaternary units. The scarps are separated by stretches of bedrock embayed by hundreds of meters-wide tongues of Quaternary sandstone-conglomerate, implying low Quaternary slip rate. Further south, ~2 km north of the

  20. Reconstructing the Vertical 14C Gradient of the Baja Margin during the Last Deglaciation

    NASA Astrophysics Data System (ADS)

    Lindsay, C. M.; Lehman, S. J.; Marchitto, T. M.; Ortiz, J. D.; van Geen, A.

    2011-12-01

    The radiocarbon activity (Δ14C) of the atmosphere decreased in two steps during the last deglaciation, coinciding with the well-known Heinrich 1 (H1) and Younger Dryas (YD) stadials. A leading explanation for these periods of decline involves the release of 14C-depleted carbon from a deep, isolated ocean reservoir- a mechanism that may also help to explain the deglacial rise in atmospheric CO2. Reconstructions of intermediate water Δ14C near Baja California, Mexico (Marchitto et al., 2007 Science) and in the Arabian Sea (Bryan et al., 2010 Earth Planet. Sci. Lett.) document two intervals of extreme depletion relative to the coeval atmosphere during H1 and the YD that are interpreted as evidence of the return of this aged carbon from the deep reservoir to the upper ocean and atmosphere. Here we report on 14C measurements in additional cores from the Baja margin that expand the depth range of our observations and enable reconstruction of the vertical Δ14C gradient. Calendar ages were determined by (1) correlation of diffuse spectral reflectance (DSR, a proxy related to local productivity) with the layer-counted age model in the GISP2 ice core and (2) correlation of raw planktic G. ruber 14C ages to new measurements in core PC08 previously studied by Marchitto et al. (2007). Together these provide a common and consistent calendar age model for margin core PCO8 (depth 705 m), core PC13 from Soledad Basin (sill depth 290 m) and margin core GC38 (depth 1270 m). In preliminary results, G. ruber Δ14C data from PC08 exhibit a record of deglacial depletion events that is consistent with partial upward mixing of the intermediate-depth signal to the surface. Δ14C at 1270 meters showed relatively little change during H1 and YD, indicating that anomalously depleted water did not penetrate to this depth. The vertical gradient collapsed to within observational uncertainties at the start of the Bølling-Allerød/Antarctic Climate Reversal. Taken together the results support

  1. Late Pleistocene-Holocene alluvial stratigraphy of southern Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Antinao, José Luis; McDonald, Eric; Rhodes, Edward J.; Brown, Nathan; Barrera, Wendy; Gosse, John C.; Zimmermann, Susan

    2016-08-01

    A late Pleistocene to Holocene alluvial stratigraphy has been established for the basins of La Paz and San José del Cabo, in the southern tip of the Baja California peninsula, Mexico. Six discrete alluvial units (Qt1 through Qt6) were differentiated across the region using a combination of geomorphologic mapping, sedimentological analysis, and soil development. These criteria were supported using radiocarbon, optically stimulated luminescence and cosmogenic depth-profile geochronology. Major aggradation started shortly after ∼70 ka (Qt2), and buildup of the main depositional units ended at ∼10 ka (Qt4). After deposition of Qt4, increasing regional incision of older units and the progressive development of a channelized alluvial landscape coincide with deposition of Qt5 and Qt6 units in a second, incisional phase. All units consist of multiple 1-3 m thick alluvial packages deposited as upper-flow stage beds that represent individual storms. Main aggradational units (Qt2-Qt4) occurred across broad (>2 km) channels in the form of sheetflood deposition while incisional stage deposits are confined to channels of ∼0.5-2 km width. Continuous deposition inside the thicker (>10 m) pre-Qt5 units is demonstrated by closely spaced dates in vertical profiles. In a few places, disconformities between these major units are nevertheless evident and indicated by partly eroded buried soils. The described units feature sedimentological traits similar to historical deposits formed by large tropical cyclone events, but also include characteristics of upper-regime flow sedimentation not shown by historical sediments, like long (>10 m) wavelength antidunes and transverse ribs. We interpret the whole sequence as indicating discrete periods during the late Pleistocene and Holocene when climatic conditions allowed larger and more frequent tropical cyclone events than those observed historically. These discrete periods are associated with times when insolation at the tropics was

  2. New geologic slip rates for the Agua Blanca Fault, northern Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Gold, P. O.; Behr, W. M.; Fletcher, J. M.; Hinojosa-Corona, A.; Rockwell, T. K.

    2015-12-01

    Within the southern San Andreas transform plate boundary system, relatively little is known regarding active faulting in northern Baja California, Mexico, or offshore along the Inner Continental Borderland. The inner offshore system appears to be fed from the south by the Agua Blanca Fault (ABF), which strikes northwest across the Peninsular Ranges of northern Baja California. Therefore, the geologic slip rate for the ABF also provides a minimum slip rate estimate for the offshore system, which is connected to the north to faults in the Los Angeles region. Previous studies along the ABF determined slip rates of ~4-6 mm/yr (~10% of relative plate motion). However, these rates relied on imprecise age estimates and offset geomorphic features of a type that require these rates to be interpreted as minima, allowing for the possibility that the slip rate for the ABF may be greater. Although seismically quiescent, the surface trace of the ABF clearly reflects Holocene activity, and given its connectivity with the offshore fault system, more quantitative slip rates for the ABF are needed to better understand earthquake hazard for both US and Mexican coastal populations. Using newly acquired airborne LiDAR, we have mapped primary and secondary fault strands along the segmented western 70 km of the ABF. Minimal development has left the geomorphic record of surface slip remarkably well preserved, and we have identified abundant evidence meter to km scale right-lateral displacement, including new Late Quaternary slip rate sites. We verified potential reconstructions at each site during summer 2015 fieldwork, and selected an initial group of three high potential slip rate sites for detailed mapping and geochronologic analyses. Offset landforms, including fluvial terrace risers, alluvial fans, and incised channel fill deposits, record displacements of ~5-80 m, and based on minimal soil development, none appear older than early Holocene. To quantitatively constrain landform ages

  3. Plio-pleistocene volcano-tectonic evolution of la Reforma Caldera, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Demant, Alain; Ortlieb, Luc

    1981-01-01

    La Reforma volcanic complex, in east-central Baja California, shows a characteristic caldera structure, 10 km in diameter. The first eruptive stage, during the Pliocene, was manifested by ash and pumice falls and by subaqueous pumitic flows. In a second stage basic flows were deposited in a near-shore environment (subaerial and pillow lavas). During the early Pleistocene a large ignimbritic eruption, producing mainly pantelleritic tuffs, immediately predated the formation of the caldera itself. Afterwards, along marginal fractures of the caldera, some rhyolitic domes and flows partially covered the thick ignimbritic sheet. A block of Miocene substratum, in the center of the caldera, has been uplifted, nearly 1 km, by "resurgent doming". Small outcrops of diorite might constitute the top of coarse-grained crystallized magmatic bodies, and thus support the "resurgent doming" interpretation. A few basaltic cones were finally built on the flanks of the caldera complex; the latter are not related to the caldera history but to the extension tectonics of the Gulf of California which are also responsible for the Tortuga Island and the Holocene Tres Virgenes tholeiitic cones. South of la Reforma are found the highest (+300 m) Pleistocene marine deposits of the Gulf coast of Baja California. The uplift of this area is due in part to the positive epeirogenic movements of the whole peninsular crustal block, and also to the late doming of the caldera. On the coastal (eastern) flank of La Reforma complex up to seven stepped wave-cut terraces have been preserved, the highest reaching more than +150 m and the lowest ones +25 m. Lateral correlations of the marine terraces along the whole Gulf of California suggest that this volcano-tectonic uplift, that is still active, is of the order of 240 mm/10 3 y. The set of terraces is interpreted to be Middle (700-125 × 10 3y) to Upper (125-80 × 10 3y) Pleistocene, and is tentatively correlated with the paleoclimatic chronology of deep

  4. Osprey distribution, abundance, and status in western North America: III. The Baja California and Gulf of California population

    USGS Publications Warehouse

    Henny, C.J.; Anderson, D.W.

    1979-01-01

    -An estimated 810 ? 55 pairs (minimum estimate) of ospreys (Pandion haliaetus) were nesting in the study area during our survey (24 March-l April 1977). Approximately 174 pairs nested along the Pacific side of Baja California, 255 pairs along the gulf side, 187 pairs on the Midriff Islands, and 194 pairs in coastal Sonora and Sinaloa. Most nested on cliffs adjacent to the sea (59%); some nested on cactus in flat terrain (26%). Seven per cent nested on the ground, three percent nested in mangroves and other trees in the southern portion of the study area,.and four percent nested on man-made structures. The extreme northwestern Baja California population that was extirpated early in this century has not recovered. However, several populations immediately to the south along the Pacific Coast now appear stationary. Pesticide residues in osprey eggs from Mexico were among the lowest reported for the species in North America.

  5. Current Status of Research on the Shorebirds, Marsh Birds, and Waders of the Peninsula of Baja California

    Treesearch

    Eric Mellink

    2005-01-01

    Regarding the information on its birds, the peninsula of Baja California has a luxury status, compared to other regions of México. In this sense, it is useful to compare it with its nearest states: Sonora and Sinaloa. While the peninsula measures 143,790 km², Sonora is 184,937 km². Sinaloa (58,092 km²), although much smaller, has a...

  6. Mid- to Late-Wisconsin Pollen Record of San Felipe Basin, Baja California

    NASA Astrophysics Data System (ADS)

    Lozano-García, María. Socorro; Ortega-Guerrero, Beatriz; Sosa-Nájera, Susana

    2002-07-01

    A lacustrine sequence from Laguna Seca San Felipe, Baja California, in the southwestern Sonoran Desert, provides the first record of mid- to late-Wisconsin vegetation in one of the driest regions of North America. Pollen analysis was performed in the intermediate part of the sequence from ca. 44,000 to ca. 13,000 14C yr B.P. according to six 14C radiocarbon dates. Sedimentation of eolian sands prior to 44,000 14C yr B.P. indicates dry conditions. High pollen concentration of montane and chaparral species in the pollen assemblages contrast with the modern desert vegetation. Sixty-four pollen types were identified. The source of mid- to late-Wisconsin sedimentation must have been the plant communities in the surrounding highlands of the basin. Mid-Wisconsin pollen assemblages dominated by pines, junipers, and Artemisia reflect humid conditions in the area. By late Wisconsin time, a significant increment in junipers indicates a lowering in the altitudinal ranges of woodlands/chaparral. Pollen from wind-pollinated species is abundant while desert plants, specifically animal or insect pollinated species, are poorly represented. The San Felipe record does not identify the Last Glacial Maximum as the time of greatest effective moisture, as suggested by pluvial lake levels and other paleoclimatic evidence in the soutwestern United States.

  7. Geologic implications of the oxygen isotope profile of the Toa Baja drill hole, Puerto Rico

    SciTech Connect

    Smith, B.M. )

    1991-03-01

    The whole-rock O-isotopic compositions of volcanic and volcaniclastic samples from the Toa Baja drill hole demonstrate that low-temperature (< 200C) processes have strongly enriched the island arc materials in {sup 18}O. Subsequent to eruption, processes such as subaerial weathering, alteration during transport and deposition in volcaniclastic aprons, submarine weathering, burial diagenesis, and prograde regional metamorphism through the beginning of the prehnite-pumpellyite facies have raised average whole-rock {delta}{sup 18}O values by {approximately}4% for basalt and andesite lava flows, and by {approximately}8% for volcaniclastic sandstones. These O-isotopic disturbances were probably caused by oxygen exchange with regionally circulating seawater under rather high-water/rock conditions. The processes associated with ageing' of volcanic and volcaniclastic materials in the oceanic environment are probably more important to the global budgets of the oxygen isotopes than has been assumed in the past. Integration of these results into global models for the oxygen isotopes awaits analysis of more varied oceanic terranes, to determine the generality of the O-isotopic conclusions proferred here, and to more carefully evaluate the relative sizes of volcanic, volcaniclastic, and oceanic oxygen reservoirs and their variabilities in time.

  8. Dynamics of Late Cretaceous rocky shores (Rosario Formation) from Baja California, Mexico

    SciTech Connect

    Lescinsky, H.L. ); Ledesma-Vazquez, J. ); Johnson, M.E. )

    1991-04-01

    Two rocky-shore deposits are described at localities of Late Cretaceous age in Baja California, Mexico. The main locality, at Las Minas, is characterized by a carbonate matrix containing clasts derived from an underlying andesite flow. Basal boulders give way up section to smaller cobbles and silt, indicating a transgression. The biotas from the sites include encrusting forms (coralline algae, bryozoans, serpulids, ostreids, spondylids), pholadid bivalve borings, and several nestling and mobile taxa. The well exposed boulder zone contains clusters of nestling pectinids preserved in growth position. This is the first such observation from an ancient rocky shore. Echinoids also lived within the relatively stable boulder interstices. Rocky-shore biotas of Late Cretaceous age from around the world contain many elements in common, including large encrusting oysters, spondylids, serpulids, rhynconellid brachiopods, and echinoids. Other groups common to rocky shores today are found at only some Cretaceous localities (e.g., barnacles, trochid and cerithiid gastropods, limpets, chitons). More archaic taxa, such as crinoids and large inarticulate brachiopods, are rarely represented at the known Cretaceous localities. Reconstructions of the biotas of ancient rocky shores offer a new avenue for the study of evolution on hard substrates. As the number and quality of described rocky-shore localities increases, it will be possible to put into a broader context evolutionary trends derived strictly from hard-grounds or other hard-substrate types.

  9. The Endemic Insular and Peninsular Species Chaetodipus spinatus (Mammalia, Heteromyidae) Breaks Patterns for Baja California

    PubMed Central

    Álvarez-Castañeda, Sergio Ticul; Murphy, Robert W.

    2014-01-01

    The Baja California peninsula is the second longest, most geographically isolated peninsula on Earth. Its physiography and the presence of many surrounding islands has facilitated studies of the underlying patterns and drivers of genetic structuring for a wide spectrum of organisms. Chaetodipus spinatus is endemic to the region and occurs on 12 associated islands, including 10 in the Gulf of California and two in the Pacific Ocean. This distribution makes it a model species for evaluating natural historical barriers. We test hypotheses associated with the relationship between the range of the species, patterns in other species, and its relationship to Pleistocene-Holocene climatic changes. We analyzed sequence data from mtDNA genes encoding cytochrome b (Cytb) and cytochrome c oxidase subunits I (COI) and III (COIII) in 26 populations including all 12 islands. The matrilineal genealogy, statistical parsimony network and Bayesian skyline plot indicated an origin of C. spinatus in the southern part of the peninsula. Our analyses detected several differences from the common pattern of peninsular animals: no mid-peninsula break exists, Isla Carmen hosts the most divergent population, the population on an ancient southern Midriff island does not differ from peninsular populations, and a mtDNA peninsular discordance occurs near Loreto. PMID:25542029

  10. First Record of Fibropapillomatosis in a Green Turtle Chelonia mydas from the Baja California Peninsula.

    PubMed

    Reséndiz, Eduardo; Flores-Ramírez, Sergio; Koch, Volker; Cordero-Tapia, Amaury

    2016-12-01

    Fibropapillomatosis (FP) is characterized by multiple fibroepithelial tumors in all parts of the skin and has been reported in sea turtles worldwide. Clinically infected individuals are often emaciated and anemic. In Mexico, however, there are few records of this disease. In this study of green turtles Chelonia mydas in Laguna San Ignacio in Baja California Sur (BCS), we noted one juvenile with multifocal fibropapilloma lesions on the external upper surface of its eyes and hind flippers. Light microscopy revealed hyperkeratosis, epidermal hyperplasia, dermal papillary projections, and fibroblast proliferation. Electron microscopy revealed viral particles. Biopsies of normal skin were done to determine the origin of the turtle through genetic analysis. Its mitochondrial DNA matched that of a haplotype (CMP2) from a Hawaiian green turtle population. Finding FP in a turtle captured in BCS elucidates the need for further monitoring along the west coast of Mexico. Further investigation should include testing tumors to detect and characterize any chelonid herpesviruses and explore any association with FP and other diseases that pose a health risk to other sea turtle species. Received March 26, 2016; accepted August 3, 2016.

  11. Prevalence of Diabetes and Metabolic Syndrome in a Migrant Mixtec Population, Baja California, Mexico

    PubMed Central

    Goodman, David; Fraga, Miguel A.; Brodine, Stephanie; Ibarra, Maria-de-la-Luz; Garfein, Richard S.

    2016-01-01

    This study was conducted to determine the prevalence and correlates of metabolic syndrome (MS) and diabetes among a migrant Mixtec population residing in San Quintin, Baja California, Mexico. A cross-sectional study utilizing data collected during a 2-day clinic in 2008 in a rural farming community with a high prevalence of Mixtec Indians. Interviews and clinical examinations were performed to assess sociodemographic data, medical history and anthropometric measures. Blood samples were obtained to measure glycated hemoglobin, fasting glucose, triglycerides, total cholesterol, HDL and LDL. Of the 107 patients surveyed, 56 % were female and mean age was 38.5 (range: 18–74, SD = 12.6) years. Overall, 41.1 % had MS and 26.2 % had diabetes. Drinking alcohol more than once a week [adjusted OR (AOR) = 16.0, p = 0.008] and being literate (AOR = 0.38, p = 0.035) were independently associated with MS. Only female gender was significantly associated with diabetes (OR = 3.95, p = 0.005). The high prevalence of MS, diabetes and other metabolic abnormalities among migrant farm workers in San Quintin suggest the need for interventions to reduce the risk for these conditions. PMID:22961334

  12. Contrasts between source parameters of M [>=] 5. 5 earthquakes in northern Baja California and southern California

    SciTech Connect

    Doser, D.I. . Dept. of Geological Sciences)

    1993-04-01

    Source parameters determined from the body waveform modeling of large (M [>=] 5.5) historic earthquakes occurring between 1915 and 1956 along the San Jacinto and Imperial fault zones of southern California and the Cerro Prieto, Tres Hermanas and San Miguel fault zones of Baja California have been combined with information from post-1960's events to study regional variations in source parameters. The results suggest that large earthquakes along the relatively young San Miguel and Tres Hermanas fault zones have complex rupture histories, small source dimensions (< 25 km), high stress drops (60 bar average), and a high incidence of foreshock activity. This may be a reflection of the rough, highly segmented nature of the young faults. In contrast, Imperial-Cerro Prieto events of similar magnitude have low stress drops (16 bar average) and longer rupture lengths (42 km average), reflecting rupture along older, smoother fault planes. Events along the San Jacinto fault zone appear to lie in between these two groups. These results suggest a relationship between the structural and seismological properties of strike-slip faults that should be considered during seismic risk studies.

  13. Prevalence of diabetes and metabolic syndrome in a migrant Mixtec population, Baja California, Mexico.

    PubMed

    Goodman, David; Fraga, Miguel A; Brodine, Stephanie; Ibarra, Maria-de-la-Luz; Garfein, Richard S

    2013-02-01

    This study was conducted to determine the prevalence and correlates of metabolic syndrome (MS) and diabetes among a migrant Mixtec population residing in San Quintin, Baja California, Mexico. A cross-sectional study utilizing data collected during a 2-day clinic in 2008 in a rural farming community with a high prevalence of Mixtec Indians. Interviews and clinical examinations were performed to assess sociodemographic data, medical history and anthropometric measures. Blood samples were obtained to measure glycated hemoglobin, fasting glucose, triglycerides, total cholesterol, HDL and LDL. Of the 107 patients surveyed, 56 % were female and mean age was 38.5 (range: 18-74, SD = 12.6) years. Overall, 41.1 % had MS and 26.2 % had diabetes. Drinking alcohol more than once a week [adjusted OR (AOR) = 16.0, p = 0.008] and being literate (AOR = 0.38, p = 0.035) were independently associated with MS. Only female gender was significantly associated with diabetes (OR = 3.95, p = 0.005). The high prevalence of MS, diabetes and other metabolic abnormalities among migrant farm workers in San Quintin suggest the need for interventions to reduce the risk for these conditions.

  14. Geothermal Exploration Using Remote Sensing in the South of Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Báncora, Cristina; Prol-Ledesma, Rosa María

    2008-05-01

    The area from Ciudad Constitución to Los Cabos in Baja California Sur was studied using a mosaic of four Landsat ETM+images. The main objective was to define favorable areas for utilization and exploitation of geothermal energy. The approach was to spectrally and spatially enhance the images to define characteristics related with geothermal activity, as are the presence of altered rock and main geological structures. The products of hydrothermal alteration are minerals that belong to two main groups: oxides and hydroxyls. Therefore, image processing is necessary to enhance oxides and hydroxyls spectral features and subdue the vegetation spectral characteristics. The band subtraction (4-3, 3-1, 5-7) gave the finest results due to the fact that it is a linear equation that does not cause loss of information when it is stretched. A color composite was done with these three layers and after a detailed visual analysis three areas were point out to be prospective to contain hydrothermal activity.

  15. Mobile colposcopy in urban and underserved suburban areas in Baja California

    NASA Astrophysics Data System (ADS)

    Madiedo, Marta; Contreras, Sonia; Villalobos, Octavio; Kahn, Bruce S.; Safir, Amit; Levitz, David

    2016-03-01

    Cervical cancer is the leading cause of cancer death for women in low resource settings, often affecting the most economically disenfranchised segment of the population. The key challenge with cervical cancer is the lack of an effective screening program for many of the at-risk, difficult-to-reach women. Outreach programs that utilize mobile clinics to increase access to screening and care in Baja California have been developed. However, many barriers such as quality assurance, efficient referral remained a challenge in this region. Visualization-based co-tests together with cytology (Pap smears) as a primary screen have been proposed. Here, the mobile colposcope of the enhanced visual assessment (EVA) is used to capture an image immediately following a Pap smear. EVA images were reviewed by expert colposcopists. Initial or preliminary data from pilot services showed that Pap false positives and Pap false negatives maybe reduced by expert review of EVA images. This suggests that reviewing of EVA images may be instrumental in catching inaccurate Pap results, thereby improving care. Thus, there is a need to further explore the benefits of using EVA as additional information when conducting Pap smear screenings.

  16. Urinary arsenic levels influenced by abandoned mine tailings in the Southernmost Baja California Peninsula, Mexico.

    PubMed

    Colín-Torres, Carlos G; Murillo-Jiménez, Janette M; Del Razo, Luz M; Sánchez-Peña, Luz C; Becerra-Rueda, Oscar F; Marmolejo-Rodríguez, Ana J

    2014-10-01

    Gold has been mined at San Antonio-El Triunfo, (Baja California Sur, Mexico) since the 18th century. This area has approximately 5,700 inhabitants living in the San Juan de Los Planes and El Carrizal hydrographic basins, close to more than 100 abandoned mining sites containing tailings contaminated with potentially toxic elements such as arsenic. To evaluate the arsenic exposure of humans living in the surrounding areas, urinary arsenic species, such as inorganic arsenic (iAs) and the metabolites mono-methylated (MMA) and di-methylated arsenic acids (DMA), were evaluated in 275 residents (18-84 years of age). Arsenic species in urine were analyzed by hydride generation-cryotrapping-atomic absorption spectrometry, which excludes the non-toxic forms of arsenic such as those found in seafood. Urinary samples contained a total arsenic concentration (sum of arsenical species) which ranged from 1.3 to 398.7 ng mL(-1), indicating 33% of the inhabitants exceeded the biological exposition index (BEI = 35 ng mL(-1)), the permissible limit for occupational exposure. The mean relative urinary arsenic species were 9, 11 and 80% for iAs, MMA and DMA, respectively, in the Los Planes basin, and 17, 10 and 73%, respectively, in the El Carrizal basin. These data indicated that environmental intervention is required to address potential health issues in this area.

  17. Parasite structure of the Ocean Whitefish Caulolatilus princeps from Baja California, México (East Pacific)

    NASA Astrophysics Data System (ADS)

    Rodríguez-Santiago, M. A.; Rosales-Casián, J. A.

    2011-06-01

    The metazoan parasite fauna of Caulolatilus princeps from northern Baja California, Mexico is quantitatively described for the first time. Further, the ecological aspects of prevalence, abundance, and intensity of infection are examined through an annual cycle. Six parasite species were recorded; 2 ectoparasites (1 monogenean and 1 copepod) and 4 endoparasites (2 digeneans and 2 nematodes). The digeneans Choanodera caulolatili and Bianium plicitum, the nematodes Anisakis sp. and Hysterothylacium sp., and the copepod Hatschekia sp. set new geographical and host records. The highest values of prevalence and abundance were in Anisakis sp. (prevalence = 93.3%, abundance = 12.4 ± 4.7 ind/host) and in Hysterothylacium sp. (prevalence = 86.6%, abundance = 16.5 ± 3.4 ind/host). The mean intensity of infection showed maximum values in summer (August = 14.2) and minimums in winter (February = 4.2). The mean intensity was higher in Hatschekia sp. (20.3 ± 7.8) followed by Hysterothylacium sp. (18.6 ± 1.4) and Anisakis sp. (12.9 ± 2.2). Larval stages of Anisakis and Hysterothylacium were particularly important due to their high abundance and prevalence, because they represent a human health risk (anisakiasis). In addition, the relationships between the metazoan parasites of C. princeps and host size and weight, fish condition and water temperature (bottom) are discussed.

  18. Paleomagnetic study of the monogenetic volcanism in San Borja and Jaraguay, Baja California Norte, Mexico

    NASA Astrophysics Data System (ADS)

    Garcia-Amador, B. I.; Alva-Valdivia, L. M.; Canon-Tapia, E.

    2012-12-01

    The volcanic fields of San Borja and Jaraguay, Baja California Norte; include monogenetic, composite and ignimbrite volcanism, distributed between 30° and 28° north latitude, product of the stages of tecto-magmatic activity of the last 23 Ma. This study reports the results of 230 cores from 27 sites, mainly in lava flows of magnesium andesite composition and all with radiometric ages known. The results of rock magnetic experiments as susceptibility vs. temperature, hysteresis and demagnetization processes, suggest the presence of only one mineralogical phase (reversibility) present with slight changes, PSD magnetic domain type and just one component of magnetization (univectorial diagram). This makes paleointensity experiments have a high probability of success, which we will present at the meeting. The temporal distribution of sites sampled was divided into two main periods: 2.6 - 6.3 Ma (19 sites) and 8.12 - 14.64 Ma (8 sites), which will be used for the analysis of paleosecular variation of the geomagnetic field.

  19. Lipophilic toxins in cultivated mussels (Mytilus galloprovincialis) from Baja California, Mexico.

    PubMed

    García-Mendoza, Ernesto; Sánchez-Bravo, Yaireb A; Turner, Andrew; Blanco, Juan; O'Neil, Alison; Mancera-Flores, Jennifer; Pérez-Brunius, Paula; Rivas, David; Almazán-Becerril, Antonio; Peña-Manjarrez, José Luis

    2014-11-01

    Here, we report different lipophilic toxins (LTs) detected by LC-MS/MS in Mediterranean mussels (Mytilus galloprovincialis) collected through 2012 in Todos Santos Bay, northwest Baja California, Mexico. The concentration of okadaic acid (OA), dinophysistoxin 2 (DTX2), and pectenotoxin 2 (PTX2) reached 500 μg kg(-1) during July and increased to 1647 μg kg(-1) in October. These toxins were associated with the presence of Dinophysis fortii and Dinophysis acuminata and a strong stratification of the water column. Other LTs present were yessotoxins, with a maximum concentration of 1080 μg kg(-1) in June. Cyclic imines (13-desmethyl spirolide and gymnodimine) and azaspiracid 1 were also detected in the mussels but at low concentrations. Diarrhetic toxins concentrations evaluated by LC-MS/MS were compared with the results of two mouse bioassay protocols. Positive results were obtained with both MBA protocols in several samples that presented toxicities below 160 μg OA-eq kg(-1), as estimated by LC-MS/MS results whereas other samples returned negative MBA results in samples with concentrations above this level. Therefore, analytical methods need to be applied to confirm the presence of regulated LTs. This is the first report of LTs in mussels cultivated in Mexico. The occurrence of these toxins represents an emerging problem in the region.

  20. Bioavailability and Natural Pollution of Heavy Metals in Bahia de Magdalena, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Lee, W.; O'Shea, B.

    2012-12-01

    In the pristine environment of Bahia de Magdalena, Baja California, elevated concentrations of heavy metals have been reported in the biota within the bay, such as sea grasses, blue crabs, and marine turtles. While the hypothesized source of these metals has emphasized anthropogenic inputs from a local fish cannery, geologic enrichment of metals from natural ophiolite formations in the Puerto Magdalena region may be an increasingly feasible source. Total (XRF) chromium and nickel concentrations (max 4,450 ppm and 2,396 ppm, respectively) in rock and soil are orders of magnitude higher than average concentrations in the crust and the beach sands directly impacted by waste discharge from the cannery (mean Cr, 55ppm and mean Ni 17ppm at cannery). Bioavailable (HNO3 acid extracted) metals differ between rock and soil versus cannery-impacted sites. Most notably, Ni is very bioavailable (mean 70% total Ni extracted) in pristine ophiolite areas, but almost completely unavailable at cannery-impacted sites. In contrast, Zn is slightly more bioavailable at the impacted cannery site (mean 55% Zn extracted) than the ophiolite rocks (mean 45% Zn extracted). In addition, these results suggest that while metals, such as Cu, Fe, and Mn, have been previously studied in the biota of the bay, other heavy metals such as Ni and Cr should be included in future biological studies within Bahia de Magdalena.

  1. Two waves of diversification in mammals and reptiles of Baja California revealed by hierarchical Bayesian analysis.

    PubMed

    Leaché, Adam D; Crews, Sarah C; Hickerson, Michael J

    2007-12-22

    Many species inhabiting the Peninsular Desert of Baja California demonstrate a phylogeographic break at the mid-peninsula, and previous researchers have attributed this shared pattern to a single vicariant event, a mid-peninsular seaway. However, previous studies have not explicitly considered the inherent stochasticity associated with the gene-tree coalescence for species preceding the time of the putative mid-peninsular divergence. We use a Bayesian analysis of a hierarchical model to test for simultaneous vicariance across co-distributed sister lineages sharing a genealogical break at the mid-peninsula. This Bayesian method is advantageous over traditional phylogenetic interpretations of biogeography because it considers the genetic variance associated with the coalescent and mutational processes, as well as the among-lineage demographic differences that affect gene-tree coalescent patterns. Mitochondrial DNA data from six small mammals and six squamate reptiles do not support the perception of a shared vicariant history among lineages exhibiting a north-south divergence at the mid-peninsula, and instead support two events differentially structuring genetic diversity in this region.

  2. Geologic interpretation of Apollo 6 stereophotography from Baja California to west Texas

    NASA Technical Reports Server (NTRS)

    Gawarecki, S. J.

    1970-01-01

    Excellent space photography of parts of the southwestern United States and northwestern Mexico was obtained during the unmanned Apollo 6 spaceflight. Two features of this photography made it useful for geologic interpretations: its vertical stereocoverage and its exposure under a relatively low angle of solar illumination through an unusually cloud-free and clear atmosphere. The structural patterns, which were topographically enhanced by the longer shadows, were annotated on the photographs, in order to analyze their trends with respect to the continental tectonic framework, and to attempt to correlate the pattern with known copper or other base metal deposits. The annotated fracture patterns showed the regional trends and their distribution. The area studied was a 100- to 105-mile swath of terrain covering a total land area of approximately 60,000 square statute miles. The coverage began from a point centered on Punta Colnett on the Pacific coast of Baja California and extended to the Sacramento Mountains of New Mexico and west Texas.

  3. Characterization of halophiles isolated from solar salterns in Baja California, Mexico.

    PubMed

    Sabet, Shereen; Diallo, Lamine; Hays, Lauren; Jung, Woosung; Dillon, Jesse G

    2009-07-01

    Solar salterns are extreme hypersaline environments that are five to ten times saltier than seawater (150-300 g L(-1) salt concentration) and typically contain high numbers of halophiles adapted to tolerate such extreme hypersalinity. Thirty-five halophile cultures of both Bacteria and Archaea were isolated from the Exportadora de Sal saltworks in Guerrero Negro, Baja California, Mexico. 16S rRNA sequence analysis showed that these cultured isolates included members belonging to the Halorubrum, Haloarcula, Halomonas, Halovibrio, Salicola, and Salinibacter genera and what may represent a new archaeal genus. For the first time, metabolic substrate usage of halophile isolates was evaluated using the non-colorimetric BIOLOG Phenotype MicroArray plates. Unique carbon substrate usage profiles were observed, even for closely related Halorubrum species, with bacterial isolates using more substrates than archaeal cultures. Characterization of these isolates also included morphology and pigmentation analyses, as well as salinity tolerance over a range of 50-300 g L(-1) salt concentration. Salinity optima varied between 50 and 250 g L(-1) and doubling times varied between 1 and 12 h.

  4. Norrisiella sphaerica gen. et sp. nov., a new coccoid chlorarachniophyte from Baja California, Mexico.

    PubMed

    Ota, Shuhei; Ueda, Kunihiko; Ishida, Ken-Ichiro

    2007-11-01

    A new chlorarachniophyte, Norrisiella sphaerica S. Ota et K. Ishida gen. et sp. nov., from the coast of Baja California, Mexico is described. We examined its morphology, ultrastructure, and life cycle in detail, using light microscopy, transmission electron microscopy, and time-lapse videomicroscopy. We found that this chlorarachniophyte possessed the following characteristics: (1) vegetative cells were coccoid and possessed a cell wall, (2) a pyrenoid was slightly invaded by plate-like periplastidial compartment from the tip of the pyrenoid, (3) a nucleomorph was located near the pyrenoid base in the periplastidial compartment, (4) cells reproduced vegetatively via autospores, and (5) a flagellate stage was present in the life cycle. This combination of characteristics differs from any of the described chlorarachniophyte genera, and therefore a new genus is established. Fluorescent microscopic observations suggested that the alga formed multinucleate cells prior to forming autospores. Time-lapse observations during autospore formation showed that cytokinesis occurred simultaneously in the multinucleate cells. Zoospores were also produced, and video sequences captured the release of zoospores from coccoid cells.

  5. Geologic structure and tectonics of inner continental borderland of northern Baja California

    SciTech Connect

    Legg, M.R.; Victor, W.O.; Francisco, S.V.

    1987-05-01

    Detailed marine geophysical surveys of the inner California continental borderland west of northern Baja California show that the region is underlain by two major, northwest-trending, Quaternary, dextral wrench fault systems. The San Clemente fault system lies along the western part of the inner borderland and is delineated by the San Clemente and San Isidro fault zones. Together, these fault zones connect to form a long (300 km), narrow (5-10 km), continuous zone of faulting that is very similar to the larger San Andreas fault system onshore. The Agua Blanca fault system is a complex zone of shear delineated by three or more subparallel wrench fault zones in the eastern part of the inner borderland. The westernmost San Diego Trough-Bahia Soledad fault zone consists of relatively long (50 km), continuous, main fault traces which cut the Quaternary sediments of the nearshore basin trough. The Coronado Bank-Agua Blanca fault zone is more complicated, with numerous discontinuous, subparallel, right- and left-stepping, anastomosing fault traces which are associated with significant structural relief. A nearshore zone of faults, marked by the Newport-Inglewood-Rose Canyon fault zone in the north and the Estero-Descanso fault zone in the south, parallels the coast and defines the eastern boundary of the California continental borderland structural province. All of these eastern fault zones merge into the transpeninsular Agua Blanca fault, and their N30/sup 0/W trend differs substantially from the trend of the major peninsular ranges fault zones.

  6. Seismic expression of Late Quaternary Banda submarine canyon and fan offshore northern Baja California

    SciTech Connect

    Legg, M.R.

    1987-05-01

    High-resolution seismic reflection profiles obtained throughout the inner California continental borderland offshore northwestern Baja California, Mexico, show the presence of numerous modern submarine canyons and associated fans. One set of these, the Banda submarine canyon/fan, is of relatively recent origin, as demonstrated by onlap of the basal fan sediments against an acoustically transparent, presumably hemipelagic deposit. Late Quaternary sedimentation rates inferred from isotopically dated piston core samples place the age of the postulated hemipelagic unit at approximately 650,000 years ago. The Banda submarine canyon heads within the Bahia Todos Santo and passes through a narrow gorge between Punta Banda and Islas Todos Santos. It is proposed that this submarine canyon and fan system formed entirely during late Quaternary time, following the breach of the Punta Banda ridge during a late Pleistocene high sea level stand. The presence of an ancient, buried channel exiting to the north out of Bahia Todos Santos probably marks the head of an earlier submarine canyon which acted as the conduit of clastic sediments from Valle Maneadero to the deep borderland basins. The now active Banda submarine canyon pirated the supply of terrigenous clastics from this older canyon. The active Agua Blanca fault zone cuts across the head of Banda submarine canyon, suggesting that tectonic movements may have played a role in the development of the Banda submarine canyon and fan system.

  7. [Distribution of aquatic and raptor birds in a freshwater artificial pond of Baja California Sur, Mexico].

    PubMed

    Castillo-Guerrero, J A; Carmona, R

    2001-01-01

    We determined the taxonomic composition and spatial-temporal distribution of aquatic and raptor birds in a freshwater artificial pond of El Centenario, Baja California Sur, México, during 24 biweekly censuses (April, 1998 to March, 1999). The pond is particularly attractive for birds because of its variety of food items. A total 25,563 records of 69 species were done, among them the first report of Chlidonias niger and Phalaropus tricolor for the region. Species richness and abundance were determined for the migrant component, mostly Anatidae (16 species and 55.6% of the total abundance) and shorebirds (18 species and 13.3%). The greater number of species and individuals was in C the deepest and more heterogeneous section of the pond. The most important species was Oxyura jamaicensis (30% of the total observed individuals), with highest abundance in the peninsula. The artificial pond presented an atypical and distinct ornithological composition because it is located in an arid region, and acts as a resting site for migrant birds. The site included species that usually live in freshwater and coastal areas, a characteristic reflected in their high richness. It contributes noticeably to the local avian biodiversity.

  8. [Distribution of aquatic birds in oxidation lagoons of La Paz city in South Baja California, Mexico].

    PubMed

    Zamora-Orozco, Elvia Margarita; Carmona, Roberto; Brabata, Georgina

    2007-06-01

    Taxonomic composition, spatial and temporal distribution of aquatic birds in oxidation lagoons (LO) of La Paz city in south Baja California, Mexico, were determined during 24 censuses realized in two-week intervals (April/98-March/99). There are five lagoons of5 Ha each and 17 ha of terrains constantly flooded that serve as feeding areas for cattle and birds. One hundred twenty three species were observed, 75 of which were aquatic birds. A total of 46 041 observations were made (average 1 918 birds/census). Richness and abundance of aquatic birds were influenced mainly by migration of anatids and sandpipers. The first group had the greatest abundance due to its affinity towards fresh water bodies. The terrains were the favorite sites of dabbling ducks (Anas) and sandpipers. In contrast, two of the most abundant species (Oxyura jamaicensis, 12.5% of all species, and Fulica americana, 8.8 %) restricted their presence to the oxidation lagoons. LO presented a bird structure of its own and atypical, according to the dryness of the region.

  9. A weather analysis system for Baja California: tropical cyclone season of 2006

    NASA Astrophysics Data System (ADS)

    Farfan, L. M.

    2007-05-01

    During the warm season of 2006, general characteristics of tropical weather systems were documented on a real-time basis. This study covered the period July-October and included an analysis of observations derived from a regional network: imagery from radar and geostationary satellite, and data from surface stations. A set of graphical products were generated and were available to a broad audience by using the internet address http:met-bcs.cicese.mx. Products were updated anywhere from one to 24 hours and included displays from numerical models. The analysis system has been in operation since the summer of 2005 and it is concentrated in the development of eastern Pacific tropical cyclones. In 2006 this basin had 18 tropical storms and 10 hurricanes, which are slightly above the corresponding normals. Three cyclones (John, Lane, and Paul) made landfall on the northwest coast of Mexico and four other systems developed within 800 km from the area of interest, resulting in additional events of convective activity over southern Baja California. This presentation is intended to provide a summary of the tropical cyclone activity, lessons learned from the application of the analysis system, and plans for the upcoming season of 2007.

  10. Pelagic amphipod assemblage associated with subarctic water off the West Coast of the Baja California peninsula

    NASA Astrophysics Data System (ADS)

    Lavaniegos, Bertha E.

    2014-04-01

    The California Current system is a large marine ecosystem with transition gradients between subarctic and tropical biomes containing diverse habitats. Biogeographic species groups must be carefully analyzed in order to detect tendencies shifting the ecosystem toward a more temperate or tropical state. Species composition of hyperiid amphipods was analyzed in July 2002 for evidence of subarctic water intrusion and for signals of the El Niño event developing in the equatorial Pacific. Multivariate analysis showed a dominance of “transition zone” species typical of the California Current. The main evidence of subarctic water intrusion was the extended distribution of Themisto pacifica, which reached as far south as 27°N, with particularly high abundances at 30-32°N. The intrusion of subarctic water took place despite evidence that an El Niño event was in progress. The zonal advection due to El Niño intersected the equatorward flow of the subarctic intrusion and probably produced a large cyclonic eddy off Baja California. This eddy maintained a limited El Niño influence at a few offshore stations near its southern boundary. The main environmental variables influencing the amphipod assemblage structure were water temperature and the abundance of salps. T. pacifica, a species with cool water affinity, was more sensitive to temperature, whereas subtropical species, such as Vibilia armata, were strongly correlated with the availability of salps.

  11. Relationships between eastern Pacific tropical cyclones and convective rainfall in Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Farfan, L. M.; Cosio, M. A.

    2007-05-01

    The influence of tropical cyclones in rainfall patterns over the Baja California peninsula is examined. The impact of these systems, over the southern portion of the peninsula, is analyzed and the study period is limited to the summer of 2004. This is associated with the field phase of the North American Monsoon Experiment (NAME), which is intended to improve predictions of warm season precipitation over North America. We used the best-track dataset from the U.S. National Hurricane Center to classify, based on distance from the circulation center, systems that approached the peninsula at ranges of 400-, 800- and 1200-km. During the season of 2004, activity was below the long-term annual mean with nine systems developing between July and September. Four cases were selected for subsequent analysis: Tropical Storm Blas, Hurricane Frank, Hurricane Howard, and Hurricane Javier. Data from the upper-air station at La Paz were used to evaluate humidity changes during the storm approach and rain gauge reports provided information to determine the spatial distribution of the convective precipitation. Our analysis shows that, when compared with a base period of 15 years, 2004 resulted in below normal precipitation over the southern peninsula. In contrast, above normal conditions occurred in the central peninsula.

  12. Latent tuberculosis infection in a migrant agricultural community in Baja California, Mexico.

    PubMed

    Garfein, Richard S; Burgos, Jose Luis; Rodriquez-Lainz, Alfonso; Brodine, Stephanie; Pietrucha, Amanda; Rondinelli, Amanda; Laniado-Laborin, Rafael; Ibarra, Elvira; Cañez, Alejandro; Fraga, Miguel

    2011-10-01

    The objectives were to estimate the prevalence and identify correlates of latent tuberculosis infection (LTBI) among residents of a migrant agricultural community in San Quintín, Baja-California, Mexico. Residents completed a questionnaire and had their blood tested for LTBI using the QuantiFERON(®)-TB Gold In-Tube (QFT) assay. Among 133 participants, 39.8% (95% CI 31.5-48.7%) tested QFT-positive. Having crossed the U.S.-Mexican border since living in San Quintin (P = 0.03), consuming unpasteurized milk (P = 0.02) and receiving health care at IMSS-Oportunidades in the last 6 months (P = 0.03) were independently associated with QFT-positivity. High LTBI prevalence in this community emphasizes the need for TB education and LTBI treatment for its residents. Association with travel to the U.S. suggests the potential for TB transmission across borders. Higher QFT-positivity among those consuming unpasteurized milk could indicate M. bovis infection, previously reported among Mexican migrants living in U.S. border cities.

  13. Drug-resistant pulmonary tuberculosis in the Baja California-San Diego County border population.

    PubMed Central

    Peter, C R; Schultz, E; Moser, K; Cox, M; Freeman, R; Ramirez-Zetina, M; Lomeli, M R

    1998-01-01

    A study was conducted to determine the frequency of, and risk factors for, drug-resistant pulmonary tuberculosis (TB) among Baja California (BC) and San Diego County (SDC) residents. Another purpose was to document the amount of contact between pulmonary TB patients and residents of the opposite side of the the border. During the period from February 1995 to May 1996, pulmonary TB patients from BC (n = 427) and SDC (n = 331) were evaluated with cultures, drug susceptibility tests, and questionnaires. Drug resistance was found in 41% of the BC Mycobacterium tuberculosis complex (MTB) isolates and 20% of the SDC isolates. Resistance to both isoniazid (INH) and rifampin (RIF) varied from 1% of isolates from SDC patients to 17% of isolates from BC patients. Patients with a history of previous treatment had increased odds of drug-resistant disease. Older BC patients were more likely to have INH- or RIF-resistant TB. Although 42% of Tijuana TB patients reported recent contact with residents from SDC, travel to Mexico and contact with residents from Mexico were not significant risk factors for drug-resistant TB among SDC residents. However, the demonstrated contact between TB patients and residents on opposite sides of the border indicates the importance of coordinating efforts internationally to control TB. PMID:9795580

  14. El Niño controls Holocene rabbit and hare populations in Baja California

    NASA Astrophysics Data System (ADS)

    Hart, Isaac A.; Broughton, Jack M.; Gruhn, Ruth

    2015-07-01

    The El Niño/Southern Oscillation (ENSO) is a major source of climatic variation worldwide, with significant impacts on modern human and animal populations. However, few detailed records exist on the long-term effects of ENSO on prehistoric vertebrate populations. Here we examine how lagomorph (rabbit and hare) deposition rate, population age structure and taxonomic composition from Abrigo de los Escorpiones, a well-dated, trans-Holocene vertebrate fauna from northern Baja California, Mexico, vary as a function of the frequency of wet El Niño events and eastern Pacific sea-surface temperatures (SSTs) derived from eastern Pacific geological records. Faunal indices vary significantly in response to El Niño-based precipitation and SST, with substantial moisture-driven variability in the middle and late Holocene. The late Holocene moisture pulse is coincident with previously documented changes in the population dynamics of other vertebrates, including humans. As the frequency and intensity of ENSO is anticipated to vary in the future, these results have important implications for change in future vertebrate populations.

  15. The application of economic-engineering optimisation for water management in Ensenada, Baja California, Mexico.

    PubMed

    Medellín-Azuara, J; Mendoza-Espinosa, L G; Lund, J R; Ramírez-Acosta, R J

    2007-01-01

    Mathematical optimisation is used to integrate and economically evaluate wastewater reuse, desalination and other water management options for water supply in Ensenada, Baja California Mexico with future levels of population and water demand. The optimisation model (CALVIN) is used to explore and integrate water management alternatives such as water markets, reuse and seawater desalination, within physical capacity constraints and the region's water availability, minimising the sum of economic costs of water scarcity and operating costs within a region. The modelling approach integrates economic inputs from agricultural and urban water demand models with infrastructure and hydrological information, to identify an economically optimal water allocation between water users in Ensenada. Estimates of agricultural and urban economic water demands for year 2020 were used. The optimisation results indicate that wastewater reclamation and reuse for the city of Ensenada is the most economically promising alternative option to meet future water needs and make water imports less attractive. Seawater desalination and other options are not economically viable alone, but may have some utility if combined with other options for the Ensenada region.

  16. Paleomagnetic Reconstruction of Post-Paleozoic Tectonic Motions for the Intermontane and Yukon-Tanana Terranes of Baja British Columbia

    NASA Astrophysics Data System (ADS)

    Symons, D. T.; Harris, M. J.; McCausland, P. J.; Blackburn, W. H.; Hart, C. J.

    2004-05-01

    Paleopoles from 42 Mesozoic and Cenozoic rock units in the Intermontane Belt (IMB) and Yukon-Tanana (YT) terranes are deemed to be sufficiently represented paleomagnetically and well dated radiometrically to merit consideration. Unlike previous analyses based on paleoinclination only that have led to estimates up to ˜3500 Km for northward (poleward) displacement of Baja BC relative to the North American craton, the pattern of both paleoinclination and paleodeclination are used to assess the reliability of each paleopole. The analysis indicates that: 1) the YT terrane is autochthonous or parautochthonous; 2) the IMB terranes rotated steadily atop the craton by 16° ±6° between 54 Ma and the present, accomodated by extension in the south and compression in the north; 3) the IMB terranes were rotated a further 35° ±14° and translated northward by 8° ±7° (900 Km) from 102 to 54 Ma, consistent with geological estimates for the northward displacement of interior Baja BC; and, 4) the Cache Creek, Quesnel and probably Stikine terranes were part of Baja BC since Early Jurassic.

  17. Cryptic vicariance in Gulf of California fishes parallels vicariant patterns found in Baja California mammals and reptiles.

    PubMed

    Riginos, Cynthia

    2005-12-01

    Comparisons across multiple taxa can often clarify the histories of biogeographic regions. In particular, historic barriers to movement should have affected multiple species and, thus, result in a pattern of concordant intraspecific genetic divisions among species. A striking example of such comparative phylogeography is the recent observation that populations of many small mammals and reptiles living on the Baja California peninsula have a large genetic break between northern and southern peninsular populations. In the present study, I demonstrate that five species of near-shore fishes living on the Baja coastline of the Gulf of California share this genetic pattern. The simplest explanation for this concordant genetic division within both terrestrial and marine vertebrates is that the Baja Peninsula was fragmented by a Plio-Pleistocene marine seaway and that this seaway posed a substantial barrier to movement for near-shore fishes. For some fish species, the signal of this vicariance in mtDNA has been eroded by gene flow and is not evident with classic, equilibrium measures of population structure. Yet, significant divisions are apparent in coalescent analyses that jointly estimate divergence with gene flow. The genetic divisions within Gulf of California fishes also coincide with recognized biogeographic regions based on fish community composition and several environmental factors. It is likely that adaptation to regional environments and present-day oceanographic circulation limit gene exchange between biogeographic regions and help maintain evidence of past vicariance.

  18. New Constraints on Baja California-North America Relative Plate Motion Since 11 Ma

    NASA Astrophysics Data System (ADS)

    Bennett, S. E.; Skinner, L. A.; Darin, M. H.; Umhoefer, P. J.; Oskin, M. E.; Dorsey, R. J.

    2013-12-01

    Tectonic reconstructions of the Pacific-North America (PAC-NAM) plate boundary across the Gulf of California and Salton Trough (GCAST) constrain the controversial magnitude of Baja California microplate-North America (BCM-NAM) relative motion since middle Miocene time. We use estimates of total PAC-NAM relative dextral-oblique motion from the updated global plate-circuit model (Atwater and Stock, 2013; GSA Cordilleran Mtg) to resolve the proportion of this motion on faults east of the BCM. Modern GPS studies and offset of late Miocene cross-gulf geologic tie points both suggest that BCM has never been completely coupled to the Pacific plate. Thus, our preferred GCAST reconstruction uses 93% BCM-PAC coupling from the present back to 6 Ma. We assume BCM-PAC coupling of 60% between 6 and 7 Ma, and 25% between 7 and 11 Ma, to avoid unacceptable overlap of continental crustal blocks between Baja California and the Sierra Madre Occidental (on stable NAM). Using these coupling ratios and PAC-NAM stage Euler poles, we determine the azimuth and velocity of individual points on the BCM in 1 million year increments back to 11 Ma. This procedure accounts for minor clockwise rotation of BCM that occurred during oblique rifting, and shows how total BCM-NAM relative motion increases from north to south due to greater distance from the Euler pole. Finer-scale restoration of tectonic blocks along significant (>1 km offset) faults, across extensional (e.g. pull-apart and half-graben) basins, and by vertical-axis rotation is constrained by local geologic and marine-geophysical datasets and accomplished via the open-source Tectonic Reconstruct ArcGIS tool. We find that restoration across the Gulf of California completely closes marine basins and their terrestrial predecessors between 6 and 9 Ma. Latest Miocene opening of these basins was coincident with a ~10° clockwise azimuthal change from 8 to 6 Ma in PAC-NAM relative motion, as revealed by the global plate circuit model. The

  19. Influence of anomalous subarctic water intrusion on phytoplankton production off Baja California

    NASA Astrophysics Data System (ADS)

    Espinosa-Carreón, T. L.; Gaxiola-Castro, G.; Durazo, R.; De la Cruz-Orozco, M. E.; Norzagaray-Campos, M.; Solana-Arellano, E.

    2015-01-01

    The southern region of the California Current (CC) off Baja California represents a transitional environment, with the influence of low temperature and less saline CC water during spring and summer, and warm and salty tropical and subtropical conditions through the end of summer and autumn. From 2002 to 2006, an anomalous subarctic water (SAW) intrusion generated changes in the epipelagic ecosystem dynamics, affecting phytoplankton biomass and primary production. The goal of the present work is to show the effects of the SAW intrusion off Baja California in the phytoplankton production during the two contrasting years 2002 and 2005. Our results show that the minimum water salinity was associated with density levels of 24.6-25.5 kg m-3 in 2002 and 24.3-25.2 kg m-3 in 2005, indicating that the anomalous SAW intrusion was more pronounced in 2005. In 2005, the mean chlorophyll concentration was low (<0.4 mg m-3) and associated with negative salinity anomalies (<-0.02). The mean satellite-derived chlorophyll (CHL) values were 0.25 and 0.26 mg m-3 in 2002 and 2005, although in the coastal zone they were >1.0 mg m-3 in some months. CHL values were significantly different between the north and south zone and among months (p<0.01). The mean values of the photosynthetic parameters (maximum light utilization coefficient (αB) and maximum photosynthesis rate (PBm)) were one order of magnitude higher in 2005 compared to 2002 (p<0.01). The primary production estimated by the Herman and Platt model and the Carr model was very different in 2002 (mean values of 907 and 143 mgC m-2 d-1 respectively), but similar in 2005 (750 and 1006 mgC m-2 d-1 respectively). The differences between models may be due to the diverse chlorophyll data used in the singular models (in situ vs. satellite-derived), and to the weight of the phytoplankton photosynthetic parameters in each algorithm. We conclude that for the present data set the Herman and Platt model is more suitable. To assess the relative

  20. Stratigraphy and geochronology of the Comondú Group near Loreto, Baja California sur, Mexico

    NASA Astrophysics Data System (ADS)

    Umhoefer, Paul J.; Dorsey, Rebecca J.; Willsey, Shawn; Mayer, Larry; Renne, Paul

    2001-10-01

    Upper Oligocene to Middle Miocene volcanic and sedimentary rocks in the Loreto region, Baja California Sur, are widely exposed and make up the Comondú Group as redefined here following McFall. The Comondú Group is part of a volcanic arc and forearc basin that formed along the northwestern margin of Mexico. Regional to detailed scale mapping, stratigraphic analysis, and geochronology in a 10-20-km-wide and 70-km-long belt from the gulf escarpment to the coast near Loreto reveal three main units in the Comondú Group and a composite thickness of ˜1.5-2 km. (1) The lower clastic unit (˜30-19 Ma) contains 200-300 m of fluvial sandstone and conglomerate with probable local eolian deposits and numerous felsic tuffs and basalt flows that accumulated in a forearc basin. (2) The middle breccia and lava flow unit (˜19-15 Ma) is up to 750 m thick and consists of massive andesite breccia that was deposited as proximal debris flows interbedded with minor andesite lava flows. (3) The upper lava flow and breccia unit (˜15-12 Ma) consists almost entirely of up to ˜600 meters of andesite lava flows a few kilometers west of Loreto that are part of a composite volcano. North and south of Loreto for up to 25 km, the unit is composed of andesite lava flows and massive andesite breccia that formed from thick debris flows near that and other volcanic centers. The three units of the Comondú Group in the Loreto area correlated with the Salto, Pelones, and Ricasón formations of the Bahı´a Concepción area. The lower clastic unit of this study is time equivalent to the marine San Gregorio, El Cien, and Isidro formations on the western and southern Baja California peninsula. The middle and upper units of the Loreto area are the proximal equivalent to the type section of the Comondú Group near the village of Comondú. During deposition of the lower part of the Comondú Group, the arc lay to the east on mainland Mexico in the Sierra Madre Occidental, and then migrated to the

  1. Petrology and Geochronology of High-Grade Metamorphic Rocks from Cedros Island, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Gonzales, D.; Leech, M. L.

    2014-12-01

    High-grade metamorphic rocks exposed on Cedros Island, Baja California, Mexico, record the Mesozoic subduction history of western North America. Blocks of amphibolite, blueschist, and eclogite crop out in a serpentinite-matrix mélange on the southeast and southwestern parts of Cedros Island. Amphibolite blocks contain Amp + Ep + Ab + Chl ± Ms ± Grt ± Ttn ± Qz; blueschist blocks have the assemblage Na-Amp + Ms + Lw + Qz ± Ttn ± Grt ± Jd ± Chl; and eclogite blocks are comprised primarily of Omp + Grt with retrograde Na-Amp + Ms + Lw. Blueschists from Cedros have been dated using 40Ar/39Ar step-heating of white mica and sodic amphiboles that yield ages from 103 ± 4 Ma to 94.9 ± 1.1 Ma, respectively, that represent cooling during exhumation. Apatite fission-track dating gives ages from 32 ± 4 Ma to 22 ± 3 Ma that record exhumation through the upper crust. Related Mesozoic subduction zone rocks of the Franciscan Complex crop out in a serpentinite-matrix mélange along coastal northern California. The Franciscan rocks are older, yielding 40Ar/39Ar step-heating ages of hornblende from amphibolite ranging from 159 to 156 Ma and represent an older part of the subduction history of the oceanic Farallon plate along western North America. I will determine the prograde and peak metamorphic P-T conditions for these high-grade rocks using petrography, mineral chemistries, and isochemical phase diagram modeling with Perple_X to generate complete P-T paths. I will then supplement these data with Sm-Nd and Lu-Hf geochronology for these high-grade Cedros rocks to evaluate their subduction/exhumation history, and develop a tectonic model for these southernmost Franciscan-type rocks. Ultimately, I will compare my results to Franciscan rocks in northern California to better understand the Mesozoic subduction margin of western North America.

  2. ENSO-Influenced Upwelling off of Southern Baja California Since the Last Glaciation

    NASA Astrophysics Data System (ADS)

    Marchitto, T.; Ortiz, J.; Carriquiry, J.; Sanchez, A.; Dean, W.; Zheng, Y.; Levi, C.; van Geen, L.

    2004-12-01

    During modern El Nino events, upwelled nutrients off of southern Baja California are sharply reduced due to a regionally deeper nutricline. We use two rapidly accumulating sediment cores from this region to reconstruct upwelling and productivity during the past 52 kyr. By doing so, we test hypotheses regarding ENSO system behavior on both orbital and millennial time scales. One of our cores, recovered near the core of the regional oxygen minimum zone (OMZ, 705 m), exhibits fluctuations in organic matter content and sediment color that bear a striking resemblance to Greenland oxygen isotope records. Specifically, organic matter was lower (suggesting a weaker OMZ) during Dansgaard-Oeschger stadial events. As noted previously at Santa Barbara Basin, OMZ weakening could have been due to reduced productivity or to increased ventilation from the North Pacific. Several lines of evidence point to the dominance of productivity over ventilation. First, benthic foraminiferal Mg/Ca and d18O are inconsistent with cooler (North Pacific derived) intermediate waters during stadials. Second, benthic radiocarbon ventilation ages suggest significant changes in intermediate depth circulation that appear to be unrelated to the OMZ fluctuations. Finally, benthic foraminiferal fluxes decrease dramatically during stadials, indicative of lower productivity. The productivity record is consistent with El Nino-like conditions during stadials, though other mechanisms cannot be ruled out. Our second core is from nearby Soledad Basin, which has an effective sill depth of 290 m. In contrast to the deeper core, planktonic foraminiferal preservation is excellent in Soledad Basin. We are currently analyzing planktonic Mg/Ca, Cd/Ca, and Zn/Ca in an attempt to reconstruct the upwelling history of this site since the Bolling/Allerod. We will test model results that suggest ENSO has varied with orbital forcing, and search for millennial-scale variability within the Holocene.

  3. Diversity of free-living marine nematodes (Enoplida) from Baja California assessed by integrative taxonomy.

    PubMed

    Pereira, Tiago José; Fonseca, Gustavo; Mundo-Ocampo, Manuel; Guilherme, Betânia Cristina; Rocha-Olivares, Axayácatl

    2010-01-01

    We used morphological and molecular approaches to evaluate the diversity of free-living marine nematodes (order Enoplida) at four coastal sites in the Gulf of California and three on the Pacific coast of Baja California, Mexico. We identified 22 morphological species belonging to six families, of which Thoracostomopsidae and Oncholaimidae were the most diverse. The genus Mesacanthion (Thoracostomopsidae) was the most widespread and diverse. Five allopatric species, genetically and morphologically differentiated, were found in two localities in the Gulf of California (M. sp1 and M. sp2) and three in the Pacific coast (M. sp3, M. sp4 and M. sp5). Overall, we produced 19 and 20 sequences for the 18S and 28S genes, respectively. Neither gene displayed intraspecific polymorphisms, which allowed us to establish that some morphological variation was likely either ontogenetic or due to phenotypic plasticity. Although 18S and 28S phylogenies were topologically congruent (incongruence length difference test, P > 0.05), divergences between species were much higher in the 28S gene. Moreover, this gene possessed a stronger phylogenetic signal to resolve relationships involving Rhabdodemania and Bathylaimus. On the other hand, the close relationship of Pareurystomina (Enchilidiidae) with oncholaimids warrants further study. The 28S sequences (D2D3 domain) may be better suited for DNA barcoding of marine nematodes than those from the 18S rDNA, particularly for differentiating closely related or cryptic species. Finally, our results underline the relevance of adopting an integrative approach encompassing morphological and molecular analyses to improve the assessment of marine nematode diversity and advance their taxonomy.

  4. Parallel rapid HIV testing in pregnant women at Tijuana General Hospital, Baja California, Mexico.

    PubMed

    Viani, Rolando M; Araneta, Maria Rosario G; Spector, Stephen A

    2013-03-01

    The objectives of this study were to evaluate the performance of parallel rapid HIV testing and the presence of HIV-associated risk factors in pregnant women with unknown HIV status in Baja California, Mexico. Pregnant women attending the delivery unit or the prenatal clinic at Tijuana General Hospital had blood drawn for parallel rapid HIV testing with Determine™ HIV-1/2 and Uni-Gold™ Recombigen(®) HIV. The parallel rapid HIV test performance was compared to the enzyme immunoassay (EIA) and western blot. From September 2007 to July 2008, 1,383 (94%) of 1,464 women in labor and 1,992 (96%) of 2,075 women in prenatal care were enrolled. The HIV seroprevalence among women screened during labor (19/1,383, 1.37%, 95% CI: 0.85-2.18%) was significantly higher compared to those seeking prenatal care (5/1,992, 0.25%, 95% CI: 0.09-0.62%; p<0.001). Of 25 pregnant women testing positive by parallel rapid HIV testing 24 had a positive confirmatory western blot and one (0.03%) was confirmed as false positive. Additionally, two (0.06%) women had parallel rapid HIV discordant testing results; both tested negative by western blot. All women who tested negative by rapid testing had negative results on pooled EIA antibody testing. The overall sensitivity, specificity, and positive and negative predictive values of parallel rapid HIV testing were 100%, 99.9%, 96%, and 100%, respectively. These findings document a very high acceptance rate and an excellent performance of the parallel rapid HIV testing strategy during pregnancy.

  5. Oxygen history off Baja California over the last 80 kyr: A new foraminiferal-based record

    NASA Astrophysics Data System (ADS)

    Tetard, Martin; Licari, Laetitia; Beaufort, Luc

    2017-03-01

    The intensity of the Oxygen minimum zone (OMZ) of the eastern North Pacific (ENP) experienced strong variations during the last glacial, mirroring changes in the balance between export production (O2 consumption) and water mass ventilation (O2 renewal). In this paper we present a new benthic foraminiferal assemblages record from Core MD02-2508, recovered from the Pacific slope off Baja California, Mexico. The record reflects oxygen conditions at the northern limit of the OMZ during the last 80 kyr. We statistically identified three assemblages, characteristic of dysoxic, suboxic, and oxic conditions, which we used to produce the first semiquantitative reconstruction of [O2] for the northeastern Pacific Ocean. Our results show that the estimated [O2] covaries with δ18O records from the North Greenland Ice Core Project. Oxygen concentrations overall exhibit moderate values ( 1 mL.L-1) during stadials, reaching 2 mL.L-1 during stadials corresponding to Heinrich events in the Atlantic Ocean. Conversely, bottom waters at the core location were strongly depleted in oxygen (<0.5 mL.L-1) during interstadials. Benthic foraminiferal abundance increased with higher export production as recorded by geochemical tracers (Cd/Al ratio). This export production signal increases (decreases) with a fall (rise) in [O2] during interstadials (stadials), suggesting a relationship between both parameters during these intervals. The influence of ventilation on oxygenation is also a key player. O2 pulses suggested by the downcore records of serial/spiral test ratio and abundance of oxic species may be explained by enhanced ventilation during Heinrich stadials, in agreement with latest modeling-based oceanic circulation reconstructions.

  6. Molecular epidemiology of Mycobacterium tuberculosis in Baja California, Mexico: A result of human migration?

    PubMed

    Flores-López, Carlos A; Zenteno-Cuevas, Roberto; Laniado-Laborín, Rafael; Reynaud, Yann; García-Ortiz, Rosa Alejandra; González-Y-Merchand, Jorge A; Rivera, Sandra; Vázquez-Chacón, Carlos A; Vaughan, Gilberto; Martínez-Guarneros, José Armando; Victoria-Cota, Nelva Lorena; Cruz-Rivera, Mayra; Rastogi, Nalin; Muñiz-Salazar, Raquel

    2016-07-11

    The State of Baja California (BC) exhibits the highest incidence and prevalence rates of tuberculosis (TB), and multidrug-resistant TB (MDR-TB) in Mexico. However information about the circulation of M. tuberculosis lineages in BC and Mexico as a whole is limited. Here, we describe the genetic relationship and genetic diversity among M. tuberculosis clinical isolates (n=140) collected in BC between October 2009 and April 2011 with other regions of Mexico, the United States, and Latin America. All specimens were genotyped based on 24 mycobacterial interspersed repetitive units (MIRU)-variable number of tandem repeats (VNTR) loci. Population structure and minimum spanning tree (MST) analyses were used to assess the genetic diversity and distribution of BC isolates in comparison to USA and South America strains. Among the nine lineages observed, LAM, Haarlem and S were the most frequent identified in BC. Population structure analysis clustered most BC isolates (41%) into three distinctive groups that included strains from San Diego and South America, whereas other BC strains (22%) clustered with other Mexican strains. A subset of isolates (12%) seemed to be autochthonous of BC, while 25% were cosmopolitan and grouped into multiple clusters. It is highly likely that the TB genetic structure observed in BC is due to human migration. Additional studies are required to determine the mechanism involved in the phylogeographic distribution of M. tuberculosis in Mexico. Implementation of domestic molecular TB surveillance programs is required to better understand the molecular epidemiology of TB not only in the region but at the national level.

  7. Mountain-Block Recharge in the Santo Tomas Valley, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Thomas, W. M.; Kretzschmar, T.

    2009-12-01

    Mountain block recharge (MBR) to adjacent basin aquifers can be a significant source of groundwater in arid and semi-arid regions. Unfortunately, geologic complexities within the mountain block often limit our understanding of this indirect form of recharge. Secondary permeability, resulting from faults and fractures, allows rainwater to infiltrate crystalline mountain rock, ultimately recharging the basin aquifer. Therefore, it is essential to consider mountain block geological features, especially faults, in recharge studies. We attempt to better understand MBR by creating a detailed fracture-trace map and by sampling springs and groundwater throughout the Santo Tomas valley, located in Northern Baja California, Mexico. Bounded by active faults, the valley is heavily fractured. These fractures enable fluid flow within the mountain block. Stable isotope (δ18O and δ2H) data show two distinct types of spring water within the watershed, possibly representing local and regional flow paths. Thermal springs, believed to be regional flow, display a -1.9‰ δ18O depletion when compared to all other spring water, indicative of recharge from higher elevations or older waters; both of the latter would be less affected under local drought conditions. This distinct isotopic signal was found 15 km downstream in the alluvial aquifer, indicating a significant amount of water is recharging the basin aquifer via the mountain block along this flow regime. A quantitative permeability value for the faults and fracture zones is difficult to attain due to their heterogeneous nature. However, the thermal system and most cold-water springs surface along active faults, which appear to transmit more water than undifferentiated fractures. Stable isotope (O and H) data. An isotopic distinction can be seen between the hot and cold springs within the watershed. Note that all the spring samples are taken between 400 - 550 m elevation, which includes the hot springs.

  8. Seismic Images of Faulting and Fossil Subduction of the Southern Baja California Margins

    NASA Astrophysics Data System (ADS)

    Gonzalez, A.; Fletcher, J. M.; Lizarralde, D.; Kent, G. M.; Harding, A. J.; Holbrook, S.; Umhoefer, P. J.; Axen, G. J.; Gorman, A. R.

    2003-12-01

    From September to November 2002, a marine geophysics experiment was carried out, using 2 ships and onshore personell, recording deep MCS (Multichannel Seismics), wide angle, gravity, magnetic and bathymetric data. The main objective of this experiment is to better understand the continental breakup processes and the rifting of the Baja California Peninsula from Mexico mainland. An array of airguns with a total air volume of 8000 cu.in. was the seismic source and a 6000 km-long, 480-channel streamer was used to record the deep MCS data. This equipment was towed by the R/V Maurice Ewing. A series of stacked and migrated sections have been obtained, showing a number of noticeable structures. To the W of the line corresponding to the Pacific margin, the fossil trench is covered by recent sediments, that are part of the Magdalena Fan. Towards the E, near the slope break, the Tosco-Abreojos fault zone is clearly imaged, showing some extensional component. Further to the E, an old syncline is covered in erosive unconformity by recent sediments. In the eastern part of the section, a half-graben structure can be observed. Under this structure, a reflective zone can be interpreted as the mylonitic zone corresponding to a detachment. Some basement scarpments seem to be parallel faults to the semigraben master fault. Other normal faults in the sediments of the basin are synthetic and antithetic with it. The master fault probably is the continuation to the S of the Santa Margarita-San Lazaro fault, reported previously as a detachment in Santa Margarita and Magdalena islands. The seismic line in the Gulf of California margin begins at a conspicuous slope at the mouth of the La Paz Bay, and corresponds to the same strike-slip fault observed in Partida and Espiritu Santo islands. The rest of the line is characterized by numerous strike-slip and normal faults, producing strong bathymetric variations.

  9. Comparison of Upwelling Indices Off Baja California derived from three different wind data sources

    NASA Astrophysics Data System (ADS)

    Pérez-Brunius, P.; López, M.; Parés-Sierra, A.; Pineda, J.

    2007-05-01

    Coastal upwelling indices (i.e. offshore Ekman transport) along the western coast of North America have been produced since 1945 by the Pacific Fisheries Environmental Laboratory (PFEL), a division of the U.S. National Oceanic and Atmospheric Administration. They have been widely used for topics ranging from description of coastal circulation patterns, climate change, and linkage between environmental and biological variability. In this study, we evaluate the PFEL indices along the northern Baja California Pacific coast (27°-33°N) by comparing them with those derived from winds measured by the QuikSCAT satellite and by coastal meteorological stations. With the exception of the PFEL series off San Diego, CA (33°N), the three datasets compare reasonably well, having similar typical year patterns, correlations >0.6, and significant coherences for periods 3-5 days or longer. By contrast, the seasonal variations, the timing and magnitude of maximum upwelling, and the variability of the PFEL indices at 33°N are significantly different compared to all the other time series, including QuikSCAT at that location. Hence, caution is suggested in using the PFEL indices as estimates of upwelling in the coastal region around the U.S.-Mexico border. The performance of the QuikSCAT winds close to shore is evaluated using the coastal meteorological station data. Although large RMS errors in direction were found for the QuikSCAT winds, they reproduce well the typical year observed by the meteorological stations, and show reasonable coherences for frequencies in the weather band and lower.

  10. [Growth and mortality of the mollusk Pteria sterna in wild banks of Southern Baja California, Mexico].

    PubMed

    Wright-López, Humberto; Holguín-Quiñones, Oscar; Arreguín-Sánchez, Francisco; Roque-Villada, Irene

    2009-09-01

    The Gulf of California nacre shell Pteria sterna is an important marine resource in Mexico, and the main species for "half" and round pearl production in the American continent. Wild spat can only be extracted legally for research or culture activities. This study calculates growth and mortality parameters for wild stocks in the eastern coast of Southern Baja California. Height's data (353 dorso-ventral measurements) were taken from 1997 to 1999 at Santa Rosalia, Mulegé and Loreto Bay coast. The maximum length was estimated at 130.35 mm (124.22-136.48 mm, p>0.95). The length frequency data were set in a "virtual year". Seasonal von Bertalanffy growth parameters were calculated in the ELEFAN I routine, the values are: L(infinity) = 156.02 mm, k = 0.48 year(-1), t0 = -0.216 years, C = 0.43, WP = 0.73. and t(s) = 0.5. The growth performance index was phi' = 4.068. The total mortality was calculated from length-converted catch curve Z = 3.34 year(-1). The length-weight relationship was fixed for the equation W = 0.000756 * L(i)(2.7075) (r2 = 0.90, n = 233). The growth parameters values in experimental repopulation conditions are quite different, in contrast with the growth estimated in wild stocks oysters. The value of total mortality is similar to the estimations for Pinctada fucata populations from the Red Sea and P. radiata from the Mediterranean Sea.

  11. [Temporal and spatial distribution of shorebirds (Charadriiformes) at San Ignacio Lagoon, Baja California Sur, Mexico].

    PubMed

    Mendoza, Luis Francisco; Carmona, Roberto

    2013-03-01

    Baja California Peninsula has several wetlands that represent important ecosystems for shorebirds. San Ignacio Lagoon is one of these sites, and supports 10% of the total abundance of shorebirds reported in this Peninsula. Since there is few information about this group in this area, we studied spatial and temporal changes in abundance and distribution of shorebirds in San Ignacio Lagoon. For this, we conducted twelve monthly censuses (October 2007-September 2008) on the entire internal perimeter of the lagoon, which we divided into four areas: two at the North and two at the South. We observed a seasonal pattern, with the lowest abundance in May (1 585 birds) and the highest in October (47 410). The most abundant species were Marbled Godwits (Limosa fedoa; 55% of the total records), Western Sandpipers (Calidris mauri; 23%), and Willet (Tringa semipalmata; 10%). All three species were more abundant in autumn; for both, the Marbled Godwit and Willet, we observed their highest numbers in winter and spring, while the Western Sandpiper showed noticeable oscillations, reaching a maximum in early winter (December). In summer, Marbled Godwit and Willet were the only birds present but in lower numbers. Here present the first records of the Pacific Red Knot (Calidris canutus roselaari) in the area. Bird abundance and species richness were influenced seasonally by migration and spatially by sites in the lagoon. The greatest shorebird abundance was in the South area of the lagoon, probably because of better accessibility to food. Our results allowed the inclusion of San Ignacio Lagoon in the Western Hemisphere Shorebirds Reserve Network (WHSRN) as a site of international importance.

  12. Occurrence of Landslides during the Approach of Tropical Cyclone Juliette (2001) to Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Antinao, J.; Farfan, L.

    2012-12-01

    The approach of Tropical Cyclone Juliette to the Baja California Peninsula in September 2001 triggered at least 419 landslides. Most of the landslides were shallow slips and debris slides, of limited areal extent, which were converted rapidly into debris flows to be exported quickly out of the mountain areas towards the lowlands. Main factors affecting landslide occurrence were total storm rainfall and intensity, aspect, geology and vegetation association. Two processes can be distinguished as initiating slope failure. The first process is linked to failures in concave topography, where accumulation of rainfall from exposed bedrock slopes generated excess overland flow that aggregated to generate a 'fire hose' effect on the base of slopes, mobilizing regolith. A second process involved a combination of wind and excess overland flow developed in the more convex or planar upper slopes, where heterogeneous regolith has formed in time following successional changes in vegetation associations along the oak-dry tropical forest ecotone. In this area, wind uprooted trees that dislodged large regolith and bedrock blocks, priming hillslopes for further runoff concentration. From the analysis of historical information, an estimative threshold curve for triggering landslides in this region is sketched. It was also determined that storms like Juliette approach the southern peninsula on average once every 100 years. Denudation estimates are in the higher end of the spectrum for a tectonically passive margin. These estimates should be considered when taking decisions regarding management of water resources in this area through damming of streams. The results emphasize the need for a more detailed representation of the spatial distribution of the rainfall and winds for this mountainous region frequently affected by the passage of tropical cyclones.

  13. Climate and upper ocean variability off Baja California, Mexico: 1997-2008

    NASA Astrophysics Data System (ADS)

    Durazo, Reginaldo

    2009-12-01

    Temperature and salinity anomalies derived from observations obtained in the period 1997-2008 are used to study the changes in physical properties off the Baja California west coast (24-31 N). Near surface anomalies were used to characterize four periods of distinctive variability: (1) a warm and saline phase of El Niño 1997-1998, (2) a saline period from 1999 to 2002, (3) fresh subarctic water in 2002-2006, and (4) a saline-fresh (El Niño-La Niña) phase in late 2006 to early 2008. Subsurface (200 m) salinity anomalies depicted a trend towards saltier conditions (ΔS ∼ 0.1) from 2001 onwards, and did not show the four periods discernible near surface. EOF analysis of sea surface wind stress and wind stress curl suggested that after the intense westerly winds in late 2001, freshening during late 2002-2006 was due to the weakening (strengthening) of the North Pacific Current (Aleutian Low), and to a decrease of wind stress curl produced upwelling. Data also showed differences in the timing and magnitude of anomalies observed between the north (poleward of 28 N) and the south (equatorward of 28 N). Subsurface geostrophic currents demonstrated the existence of two large scale cyclonic gyres, one associated with a subarctic domain in the northern region, and another having tropical characteristics. The likely role of subsurface cyclonic pairs in the definition of a provincial boundary, and the importance in influencing the CCS ecosystem, are discussed.

  14. Variability on the Hypoxic Conditions in the Northwestern Region of the Baja California Peninsula

    NASA Astrophysics Data System (ADS)

    Bustos-Serrano, H.

    2015-12-01

    The NW region of the Baja California peninsula in México is dominated by the California Current System (CCS). Dissolved oxygen (DO) is a key variable in water bodies because it is considered as a health in biological processes. Hypoxic conditions (DO 60 to 120 μmol kg-1) occur naturally in large areas of the ocean. In the Eastern Pacific, the DO can be altered by eutrophication, derived from anthropogenic activity, especially in shallow and enclosed seas. Fluctuations in the conditions of hypoxia zones may have significant ecological and economic impact. It is of interest in assessing whether hypoxic conditions in the vicinity of Bahia de Todos Santos (BTS) and Coronado Islands in México are altered by anthropogenic activity (Figs. 1 and 2 respectively). For the present study, we worked with data collected from oceanographic expeditions during the period October 2010 to June 2015. The DO was determined using a CTD (SBE Model 25) and by sea water collection with hydrographic bottles using a modification of the Winkler method. The signs of hypoxia are evident in the area near BTS and in the vicinity of Coronado´s Islands, mainly on locations between the Todos Santos Islands and the peninsula of Punta Banda, which shows that the hypoxic zone begins to occur in shallow water between 50-200 m depth. This particular area corresponds to the point where the Mexican Navy determined as a site for dredging materials from the ports of Ensenada and El Sauzal, it is possible that the anthropogenic activity alters the natural conditions of hypoxia in the area to enlarge. In June 2012 for the first time in that region we obtained sediment samples below 700 m depth, which are mixed terrigenous clastic and oceanic sediments.

  15. Terrain complexity characterization in the eastern coast of Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Martínez Flores, G.; Nava-Sanchez, E. H.; Segovia Zavala, J. A.

    2013-05-01

    Terrain complexity is an important feature for geomorphological analysis and characterization, since it is associated with processes that control the landscape evolution, giving rise to geological formations of varying topographic complexity. In the geometrical sense, the terrain complexity depicts the shape of the landform surface or cross section, such as rugosity, curvature, fractal dimension, slope, aspect, etc. Moreover, the coastline complexity or indentation index has been used as an auxiliary parameter in coastline characterization. Currently, there are a variety of terrain and shoreline complexity indexes, derived from digital elevation models and digital coastlines, respectively, which usually are evaluated and interpreted independently. In this work the evaluation of these indexes was implemented in twenty watersheds of the eastern coast of the Mexican state of Baja California Sur. To evaluate the terrain complexity index, the slope, profile curvature and roughness were computed and weighted. For this purpose the digital elevation model of 30 m resolution, obtained from the National Institute of Statistics and Geography (INEGI) was used. The coastline complexity was assessed based on the variability of angles of coastline segments, as are defined in the Global Self-consistent, Hierarchical, High-resolution Geography Database (GSHHG). Five classes were identified for each index, whose distribution was represented by digital cartography. In general, the gullies have the highest terrain complexity, while the lower values correspond to areas of alluvial fans and other areas of sedimentation close to the shoreline. The spatial distribution of these indexes could be useful to mapping terrain classification and as support to analyze geological and oceanographic processes that influence this region.

  16. Stratigraphy of Pyroclastic Deposits of EL Aguajito Caldera, Baja California Sur, MÉXICO

    NASA Astrophysics Data System (ADS)

    Osorio Ocampo, L. S.; Macias, J. L.; García Sánchez, L.; Pola, A.; Saucedo, R.; Sánchez, J. M.; Avellán, D. R.; Cardona, S.; Reyes-Agustín, G.; Arce, J. L.

    2015-12-01

    El Aguajito caldera is located in the State of Baja California Sur, it comprises an area of 450 km2 and sits within the Santa Rosalía Basin which is controlled by NE-SW extensional structures and the NW-SE Cimarron Fault that transects the caldera structure. The oldest rocks are ~90 Ma granodiorites covered by an Oligocene-Miocene volcano-sedimentary sequence, the Miocene Santa Lucia Formation and La Esperanza basalt. Pliocene volcanism is represented by La Reforma caldera, El Aguajito caldera, and the Tres Vírgenes Volcanic complex. This study focuses on the cartography and stratigraphy of area in order to understand the evolution of the volcanic system. The stratigraphy from base to top consists of a series of shallow marine sediments (fossiliferous sandstones) covered by a thick sequence of ignimbrites and pyroclastic flows interbedded with volcaniclastic deposits (Gloria and El Infierno Formations). On top of these deposits is El Aguajito caldera, it consists of a 2 m thick pumice fallout followed by an ignimbrite with three transitional lithofacies: a ≤30-m thick light-pink pyroclastic flow enriched in pumice at the base that gradually becomes enrich in lithics towards the top with the occurrence of degasing pipes. On top rests a 15 m-thick light-purple ignimbrite slightly welded with fiammes and a sequence of pumiceous pyroclastic flows and fallouts. These deposits have been associate to the caldera formation with a collapse diameter of ~8 km marked by rhyolitic domes exposed along a ring collapse crowned the sequence as well as NW-SE aligned rhyolitic domes parallel to the seashore. This cartography allowed to present a preliminary new geological map with four stratigraphic units recognized so far, that were emplaced under subaerial conditions beginning with a Plinian column followed by the emplacement of El Aguajito ignimbrite with its subsequent caldera collapse and finally the extrusion of resurgent domes.

  17. Ostracode Paleoecology and Trace Element Shell Chemistry: A case study from Laguna Salada, Baja California, Mexico.

    NASA Astrophysics Data System (ADS)

    Romero-Mayen, V.; Bernal, J.; Palacios-Fest, M.; Carreno, A.

    2007-05-01

    The Laguna Salada Basin in northeastern Baja California constitutes the southwestern limit of the Salton Trough and provides insights into the evolution of marine and non-marine sedimentary basins during the latest Neogene at the head of the Gulf of California. A 43 m long core (LS04-1) recovered from the Basin consisted of alternating clay, silt and sand beds with gypsum lenses. Three radiocarbon dates provided the age control: 41,520±790 cal years BP at 30.21 m, 25,590±320 cal years BP at 26.60 m and 15,150±70 cal years BP at 7.50 m. A total of 103 samples were analyzed for taxonomy, taphonomy and geochemistry. Eighteen marine and brackish- water ostracode species and nine benthic foraminifera species were identified. Faunal changes suggest variations in the water source with the opening of the basin to the Gulf of California. The Mg/Ca and Sr/Ca ratios of valves of two ostracode species (Limnocythere staplini and Cyprideis castus) were measured using ICPMS. Based on the Mg/Ca ratios, water paleotemperatures were estimated using a regression model. Shell chemistry shows mixed results. Some intervals fit an acceptable range, whereas other are unrealistic. Analysis of Sr/Ca ratios ostracode valves from the conflicting horizons show evidence of diagenetic effects. The fossil assemblages indicate two dry periods: prior to the 41,520 cal years BP and after the 15 ,150 cal years BP, with the maximum highstand of the basin between 25,590 and 15,150 cal years BP. Given the diagenetic effects at Laguna Salada, ostracode shell chemistry paleotemperature estimates may not be warranted in attempting to determine this parameter from the dry periods shown by faunal assemblages.

  18. History and status of introduced mammals and impacts to breeding seabirds on the California channel and Northwestern Baja California Islands

    USGS Publications Warehouse

    McChesney, G.J.; Tershy, B.R.

    1998-01-01

    The California Channel Islands, U.S.A., and Northwestern Baja California Islands, Mexico, host important breeding populations of several seabird species, including the endemic Black-vented Shearwater (Puffinus opisthomelas) and Xantus' Murrelet (Synthliboramphus hypoleucus). Mammals introduced to nearly all of the islands beginning in the late 1800s to early 1900s include: cats (Felis catus), dogs (Canis familiaris), Black Rats (Rattus rattus), rabbits and hares (Leporidae), goats (Capra hirca), sheep (Ovis ones), and other grazers. Cats, dogs and rats are seabird predators, grazers such as goats and sheep cause habitat degredation, and rabbits destroy habitat and compete with hole-nesting seabirds. Cats, which were introduced to at least 19 islands and currently occur on ten islands, have had the greatest impacts on seabirds, including the extinction of the endemic Guadalupe Storm-Petrel (Oceanodroma macrodactyla). Cats are known to have eliminated or severely reduced colonies of Black-vented Shearwaters, Cassin's Auklets (Ptychoramphus aleuticus) and Xantus' Murrelets. Black Rats have occurred on a minimum of seven islands and have reduced numbers of small, hole-nesting alcids on at least one island. At many islands, defoliation and erosion caused by rabbits and large grazing mammals has been severe. Their effects on seabirds are not well documented but potentially are serious. Impacts from introduced mammals have been most severe on islands with no native mammalian predators. On the Northwestern Baja California Islands, temporary and permanent human settlements have led to a greater diversity and source of introductions. Programs to remove introduced mammals and to reduce the possibility of future introductions are needed to restore seabird populations and to preserve the biodiversity of the region. Surveys are needed particularly on the Northwestern Baja California Islands to update the status and distribution of seabirds and to further assess impacts from

  19. Using leaf margin analysis to estimate the mid-Cretaceous (Albian) paleolatitude of the Baja BC block

    NASA Astrophysics Data System (ADS)

    Miller, Ian M.; Brandon, Mark T.; Hickey, Leo J.

    2006-05-01

    The "Baja BC hypothesis", which postulates that western Washington State, British Columbia and southern Alaska originated at the latitude of Mexico, has pitted paleomagnetic results against long-held interpretations about the tectonic evolution of western North America. In this paper we develop a new paleobotanical method for estimating paleolatitude and apply it to this problem. We start by showing that the modern MAT field for North America is well correlated with latitude, demonstrating the feasibility of using MAT to estimate paleolatitude. A compilation of MAT and floral data from 84 modern sites in Central and North America is used to establish a new prediction relationship, MAT = 1.32 + 28.99 P, where P is the proportion of smooth-margined species within a floral sample at a site. Our analysis also includes a more complete estimate of the uncertainties associated with estimating MAT from a measurement of P. Using modern data, we show that MAT and P can be used to estimate latitude as well. We then apply this approach to resolve the paleolatitude of Baja BC. Eleven floral sites from stable North America are used to establish the latitudinal MAT profile for North America during the Albian and Cenomanian. A floral site from the Winthrop Formation, a mid-Cretaceous (110-100 Ma) fluvial unit in the Methow basin of northern Washington State, is linked to the Baja BC block and predates its proposed northward offset. Forty-three morphospecies of dicotyledonous angiosperm leaves from the Winthrop Formation give P = 0.76, which is equivalent to a MAT of 23.4 °C, indicating a subtropical to tropical climate. We use the North American MAT profile to estimate a paleolatitude of 38.4°N for the Winthrop flora, indicating ˜ 2200 km of northward offset relative to stable North America.

  20. Spatial and temporal evolution of basalts and magnesian andesites (``bajaites'') from Baja California, Mexico: the role of slab melts

    NASA Astrophysics Data System (ADS)

    Calmus, T.; Aguillón-Robles, A.; Maury, R. C.; Bellon, H.; Benoit, M.; Cotten, J.; Bourgois, J.; Michaud, F.

    2003-01-01

    Late Miocene to Quaternary basalts and associated magnesian basaltic andesites and andesites, locally referred to as "bajaites", occur in the central part of the Baja California (BC) Peninsula. They form five volcanic fields (Jaraguay, San Borja, San Ignacio, Santa Rosalia, La Purisima) delineating a 600-km-long array parallel to the Gulf of California. They range in age from Late Miocene to Pleistocene, and display very specific geochemical characteristics: SiO 2=50% to 58%, high MgO contents, very low FeO*/MgO ratios usually less than 1.5, highly fractionated rare earth element patterns with low Y and heavy rare earth element, very high Sr (commonly between 2000 and 3000 ppm) and Ba (up to 2300 ppm) contents. The geochemical study and K-Ar dating of ca. 50 samples of these rocks allow us to show that most of their incompatible element ratios, which vary significantly in space and time, reflect source heterogeneities rather than partial melting, fractional crystallisation or crustal contamination effects. Their slab melt imprint increases from northwest to southeast and with time. It is best expressed in the geochemical signatures of Quaternary lavas from La Purisima volcanic field. These features reflect the origin of the "bajaites" by melting of mantle peridotites previously metasomatised by slab melts, in connection with the opening of an asthenospheric window below the Baja California Peninsula during Early and Middle Miocene in northern Baja California, and during Late Miocene in southern Baja California. Melting was initiated by the high thermal regime accompanying ridge subduction or slab tearing/breakoff, and later by Plio-Pleistocene thermal pulses linked to the opening of the Gulf of California. We show that the incongruent melting of metasomatic pargasitic amphibole, leaving a garnet-rich residue, accounts for most of the specific geochemical features of the magnesian andesite suite. This breakdown started at ca. 1000 °C at depths of 70-110 km, and

  1. Mercury dispersal to arroyo and coastal sediments from abandoned copper mine operations, el Boléo, Baja California.

    PubMed

    Kot, Fyodor; Shumilin, Evgueni; Rodríguez-Figueroa, Griselda Margarita; Mirlean, Nicolai

    2009-01-01

    Evidence for mercury dispersal in an arid coastal region of central Baja California (Mexico) suggests that abandoned copper mining operations are a noticeable source of mercury in the environment. There is a generally elevated level of mercury in alluvium of arroyos throughout the mining district (0.14-0.18 mg kg(-1)). In the first several dozen meters surrounding two of the biggest mines, mercury levels range from 0.26 to 3.16 mg kg(-1), forming a halo of anomalously high concentrations. The coastal marine sediments, particularly those close to the copper smelter in the town of Santa Rosalía, also display some mercury enrichment.

  2. Epiphytic diatoms associated with red mangrove (Rhizophora mangle) prop roots in Bahía Magdalena, Baja California Sur, Mexico.

    PubMed

    Siqueiros Beltrones, D A; López Fuerte, F O

    2006-06-01

    The first floristic inventory of benthic diatoms is provided for the Bahia Magdalena-Bahia Almejas lagoon system. Samplings were carried out during November of 1999. The oxydized samples were mounted permanently. Eighty six diatom taxa were identified, out of which 59 are new records for the Bahia Magdalena area, and 12 taxa are new for the Baja California peninsula. Taxa recorded previously as rare in other substrata are common or abundant on the epiphytic macroalgae of mangrove prop roots. Other species are mainly epipelic forms, while 24 are commonly found as tychoplankton in the area. Certain taxa appear to be characteristic of mangrove systems in general.

  3. Helminth parasites of Pseudacris hypochondriaca (Anura: Hylidae) from Baja California, Mexico, with the description of two new species of nematodes.

    PubMed

    Martínez-Salazar, Elizabeth A; Falcón-Ordaz, Jorge; González-Bernal, Edna; Parra-Olea, Gabriela; de León, Gerardo Pérez-Ponce

    2013-12-01

    The helminth parasite fauna of the hylid frog Pseudacris hypochondriaca in several localities along the Baja California Peninsula in northwestern Mexico is presented. The helminth fauna consists of 4 species of nematodes (Oswaldocruzia pipiens, a larval form of an Ascaridid, 2 new species belonging to the genera Rhabdias and Cosmocercoides), and 1 species of digenean ( Gorgoderina sp.). The new species of Rhabdias represents the 88th species assigned to the genus and the third species described from Mexican anurans. Also, the species of Cosmocercoides represents the 20th species assigned to the genus and the first representative of this genus described from Mexico.

  4. The geothermal diploma program at the Universidad Autonoma De Baja, California a review from 1983 to 1994

    SciTech Connect

    Alpirez, G.M.

    1995-12-31

    Since 1983, the Engineering Institute at the Universidad Autonoma de Baja California (UABC) has offered a Geothermal Diploma Program. Sixty three students coming from different disciplines, have successfully completed the Program . This Program was offered by the UABC in collaboration with the Instituto de Investigaciones Electricas (IIE) and the Consejo Nacional de Ciencia y Tecnologia. A year later (1984), the Comision Federal de Electricidad joined in strengthening the program. Many trainees were sponsored by IIE and CONACYT. Since 1993, the program is not supported by them. They now only support Master and Ph.D. programs. This paper presents a review of the geothermal program from 1983 to 1994.

  5. Lanthanide behavior in hypersaline evaporation ponds at Guerrero Negro, Baja California, Mexico - an environment with halophiles

    NASA Astrophysics Data System (ADS)

    Choumiline, K.; López-Cortés, A.; Grajeda-Muñoz, M.; Shumilin, E.; Sapozhnikov, D.

    2013-12-01

    Lanthanides are known, in some cases, to be sensitive to changes in water column or sediment chemistry, a fact that allows them to be used as environmental fingerprints. Nevertheless, the behavior of these elements in hypersaline environments is insufficiently understood, especially in those colonized by bacteria, archaea and eukarya halophiles. Extreme environments like the mentioned exist in the artificially-controlled ponds of the 'Exportadora de Sal' salt-producing enterprise located in Guerrero Negro (Baja California, Mexico). Sediment cores from various ponds were collected, subsampled and measured by ICP-MS and INAA. This allowed differencing the behavior of lanthanides and trace elements under a water column salinity gradient along the evaporation sequence of ponds. Sediment profiles (30 mm long), obtained in Pond 5, dominated by Ca and Mg precipitation and at the same time rich in organic matter due to bacterial mat presence, showed highs and lows of the shale-normalized patterns along different in-core depths. Two groups of elements could be distinguished with similar trends: set A (La, Ce, Pr and Nd) and set B (Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu). The first 'group A' had two prominent peaks at 15 mm and around 22 mm, whereas the 'group B' showed only slight increase at 15 mm and none at 22 mm. Microscopic analyses of prokaryotic cells of a stratified mat in Pond 5 (collected in 2004) showed filamentous bacteria and cyanobacteria with a cell abundance and morphotype richness maxima of prokaryotic cells in a chemocline from 3 mm to 7 mm depth which co-exists nine morphotypes of aerobic and anaerobic prokaryotes Microcoleus chthonoplastes, Leptolyngbya, Cyanothece, Geitlerinema, Spirulina, Chloroflexus, Beggiatoa, Chromatium and Thioploca. Below the 7 mm depth, oxygenic photosynthesis depletes and sulfur reducing compounds increase. The highs of the shale-normalized lanthanide contents of the 'group A' (at 15 mm depth) seem to correlate with the

  6. Detachment Faulting and Hanging-wall Segmentation in the Gulf Extensional Province, Baja California

    NASA Astrophysics Data System (ADS)

    Seiler, C.; Fletcher, J. M.; Quigley, M. C.; Gleadow, A. J.; Kohn, B. P.

    2007-12-01

    The opening of the Gulf of California, caused by the re-localization of the Pacific -- North America plate boundary, is a premier example of an incipient passive margin. The San Felipe area in northern Baja California comprises a typical basin and range-style topography, produced by Neogene extension affecting the Gulf Extensional Province (GEP). The > 100 km long Sierra San Pedro Mártir (SSPM) escarpment is defined by an east-down normal fault system, separating the unextended western part of the peninsula from the GEP. The hanging-wall of the SSPM fault is characterized by several fault-bound blocks that have been rotated around both vertical and horizontal axes. The Las Cuevitas and the Santa Rosa detachments are two major fault systems in the Sierra San Felipe that are responsible for segmentation of the hanging-wall of the SSPM fault. The curvilinear, NE to NNW striking Las Cuevitas Detachment extends for more than 43 km and brings Neogene volcanics and sediments in contact with the Mesozoic basement of the footwall. The detachment dips at 15-50° and accommodates more than 4-6 km of east-down displacement. Faulting appears to preferentially occur at the contact of Mesozoic metamorphics to granitoid intrusives with transfer faults translating deformation between the faulted contacts. Fission track and (U-Th)/He thermochronology constrain the initiation of deformation on the Las Cuevitas detachment to the latest Miocene. The > 45 km long and equally curvilinear Santa Rosa Detachment system consists of a low-angle normal fault system (15-35° dip) with transfer zones facilitating the transfer of strain between individual segments of the detachment fault. The slip direction varies between top-to-the-east and top-to-the-south, a possible explanation for the change in strike from NW to NE to NW. The roughly 4-5 km offset of Neogene volcanic and sedimentary deposits has created the necessary space for syntectonic deposition in the Santa Rosa Basin. The onset of

  7. Decadal-Scale Variations in Eastern Pacific Thermocline Structure from Soledad Basin, Baja California

    NASA Astrophysics Data System (ADS)

    Levi, C.; van Geen, A.; Ortiz, J. D.; Zheng, Y.; Marchitto, T. M.; Dean, W. E.; Carriquiry, J.

    2004-12-01

    Soledad Basin, a semi-enclosed basin on the Pacific margin of southern Baja California at 25oN, is ideally located to document past variations of ocean/atmosphere interactions responding to the Pacific Decadal Oscillation (PDO) and the El Nino-Southern Oscillation (ENSO). Very high sedimentation rates (~108 cm/kyr; van Geen et al., Paleoceanography, v. 8, no. 4, 2003) combined with low bottow-water oxygen levels have prevented sediment bioturbation throughout the Holocene, setting the stage for high-resolution paleoclimatic reconstructions in this key climatic area. Current studies of this site focus on the combination of a 210Pb-dated multicore and 14C-dated gravity and piston cores. Available data include a 1-cm resolution diffuse spectral reflectance record, indicative of diagenetic processes linked to productivity (Ortiz et al., Geology, v. 32, no. 6, 2004) and Mg/Ca ratios for several planktonic foraminifera species. Mg/Ca results for two shallow-dwelling species in the multicore indicate little change in sea surface temperature (+/-1.1 deg C) over the mean value of 23 deg C observed over the past two centuries. In contrast, variations of Mg/Ca ratios for a deeper-dwelling species suggest considerably larger temperature variations of +/-1.8 deg C with respect to the mean value of 17.5 deg C at the depth habitat of this species. This suggests fluctuations in the temperature, and therefore nutrient content, of thermocline waters upwelling toward the surface at this site without any appreciable changes in upwelling. Periods of low subsurface temperatures in the water column inferred from Mg/Ca correspond to darker sediment bands, suggesting a connection between the structure of the thermocline, the supply of nutrients to the photic zone, and surface productivity. This interpretation is supported by elevated authigenic Mo concentrations in those same dark bands of 30-40 mg/kg. The presentation will include a comparison of these results with instrumental and other

  8. Geochemistry of a Tertiary sedimentary phosphate deposit: Baja California Sur, Mexico

    USGS Publications Warehouse

    Piper, D.Z.

    1991-01-01

    The San Gregorio Formation in Baja California Sur, a phosphate-enriched sedimentary unit of late Oligocene to early Miocene age, has been analyzed in two areas (La Purisima and San Hilario) for its chemical composition (major oxides, Cu, Cd, Cr, Co, V, and rare-earth elements - REE) and isotopic composition (??18O and ??13C). A detrital and a marine component were determined from major oxides. The detrital component consists of an unaltered volcanic-ash fraction and a terrigenous clay-silt fraction. The marine component, which accumulated initially as biogenic and hydrogenous material, is now present as opal-A, opal-CT, CaCO3, organic matter, and an authigenic phosphate fraction, mostly pelletal and composed of the carbonate-fluorapatite mineral francolite. The minor elements have been partitioned into these components by assuming a constant composition for the two detrital fractions. The composition of the marine component of minor elements can then be interpreted by assuming that the stoichiometry of the original accumulating organic matter was equal to that of modern plankton. The Cu and Cd contents in the marine component of all rocks require that the seawater-derived fractions of these two metals were supplied to the seafloor solely by organic matter. Enrichments of Cr and V at both sites required an additional marine input. On the basis of their geochemistry in the modern ocean, Cr and V could have precipitated, or been adsorbed, onto settling particles from an O2 minimum zone in which the O2 content was low enough to promote denitrification rather than oxygen respiration. An enrichment of the REE, now within the apatite fraction, resulted from their adsorption onto particulates also in the O2 minimum zone and to the dissolution and alteration of biogenic phases (predominantly silica) within the sediment. Co and Fe2O3 show no enrichment above a detrital contribution. The ??18O-values of apatites from the La Purisima site are heavier than those of apatites

  9. Challenges and opportunities for implementing sustainable energy strategies in coastal communities of Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Etcheverry, Jose R.

    This dissertation explores the potential of renewable energy and efficiency strategies to solve the energy challenges faced by the people living in the biosphere reserve of El Vizcaino, which is located in the North Pacific region of the Mexican state of Baja California Sur. This research setting provides a practical analytical milieu to understand better the multiple problems faced by practitioners and agencies trying to implement sustainable energy solutions in Mexico. The thesis starts with a literature review (chapter two) that examines accumulated international experience regarding the development of renewable energy projects as a prelude to identifying the most salient implementation barriers impeding this type of initiatives. Two particularly salient findings from the literature review include the importance of considering gender issues in energy analysis and the value of using participatory research methods. These findings informed fieldwork design and the analytical framework of the dissertation. Chapter three surveys electricity generation as well as residential and commercial electricity use in nine coastal communities located in El Vizcaino. Chapter three summarizes the fieldwork methodology used, which relies on a mix of qualitative and quantitative research methods that aim at enabling a gender-disaggregated analysis to describe more accurately local energy uses, needs, and barriers. Chapter four describes the current plans of the state government, which are focused in expanding one of the state's diesel-powered electricity grids to El Vizcaino. The Chapter also examines the potential for replacing diesel generators with a combination of renewable energy systems and efficiency measures in the coastal communities sampled. Chapter five analyzes strategies to enable the implementation of sustainable energy approaches in El Vizcaino. Chapter five highlights several international examples that could be useful to inform organizational changes at the federal

  10. Evolución de estrellas enanas blancas de Helio de masa baja e intermedia

    NASA Astrophysics Data System (ADS)

    Althaus, L. G.; Benvenuto, O. G.

    Numerosas observaciones realizadas particularmente en los últimos dos años parecen confirmar que las enanas blancas (EB) de helio de masa baja e intermedia son el resultado de la evolución de sistemas binarios cercanos. Con el objeto de realizar una adecuada interpretación de estos objetos son necesarios modelos de EBs de helio lo más detallado posibles. En este estudio presentamos cálculos detallados de la evolución de EBs de helio con masas entre M=0.1Msolar y M=0.5Msolar a intervalos de 0.05Msolar . Para ello, hemos tenido en cuenta los efectos de temperatura finita mediante un código de evolución estelar lo más actualizado posible. En particular, el transporte de energía es descripto en el marco del nuevo modelo para la convección turbulenta desarrollado por Canuto - Mazzitelli. Además hemos considerado la nueva ecuación de estado para plasmas de helio de Saumon et al. y nuevas opacidades radiativas OPAL. Las pérdidas por neutrinos fueron asimismo tenidas en cuenta. Excepto para las EBs más masivas, nuestros modelos iniciales están ubicados en las cercanías de la correspondiente línea de Hayashi para configuraciones de helio. Nuestros resultados muestran que existe una región prohibida en el diagrama observacional HR donde ninguna EB de helio puede encontrarse. Dicha región es para log{(L/Lsolar )}>= -0.25 and log{Teff} >= 4.45. Hemos encontrado también que los tracks evolutivos en el diagrama HR en el dominio de alta luminosidad (pre - EB) son fuertemente afectados por la eficiencia convectiva y que las pérdidas por neutrinos son importantes en los modelos más masivos. Finalmente hemos analizado la estructura de la zona convectiva externa encontrando que la teoría de Canuto - Mazzitelli conduce a un perfil convectivo muy diferente del dado por cualquier versión de la popular teoría de la mixing length. Si bién este comportamiento es decisivo en el contexto de las inestabilides pulsacionales, los radios y gravedades superficiales de

  11. Evidence for a second impactor at the K-Pg Boundary in Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Santa Catharina, Amanda; Kneller, Benjamin Charles; Charao Marques, Juliana; McArthur, Adam Daniel; Kane, Ian Antony; Silvestre Cevallos Ferriz, Sergio Rafael

    2017-04-01

    Controversies remain regarding the trigger, or triggers, of the Cretaceous/Paleogene Mass Extinction. The Chicxulub Impact and the Deccan Volcanism are the main candidates, but discussions about the timing of these events and the magnitude of their effects on the biota are ongoing. Data collected around the globe suggests that profound alterations in the biosphere occurred at this interval, and locations in the Northeastern Atlantic margin and the Gulf of Mexico show evidences of tsunamis and mass waste deposits directly associated with the Chicxulub Impact. Close to El Rosario, Baja California, an enigmatic stratigraphic succession spanning this interval occurs. The succession is distinct from the normal submarine slope deposits in this region and consists of (1) 30 m thick muddy debrites, rich in terrestrial material including fossilized tree trunks up to 2m long and with evidence of exposure to fires, glassy tektites and a horizon rich in gastropods, bivalves, and fragments of corals; (2) an up to 20 m thick coarse grained tuffaceous interval, andesitic in composition, within a channel-like geometry cutting into the debrites, with lapilli (ranging from 1 to 15 cm in size) in discrete sets, fossilized tree trunks close to the base, tektites and shocked quartz; and (3) muddy debrites interbedded with tuffaceous lenses that become less frequent up section. This succession sits between hemipelagic slope deposits, with an abrupt basal contact onto Upper Maastrichtian mudstones and a gradational top, which represents a stabilisation and return to the typical sedimentation environment, with Danian fauna and flora. We believe unit 1 represents material transported onto the slope by the seismic activity caused by the impact of a bolide, which destabilised the coastal region. The tuffaceous channelized unit has been dated (SHRIMP U-Pb in zircons), and its age is indistinguishable from the proposed ages for the K-Pg Boundary. No volcanic activity of this age has been

  12. Mapping mantle-melting anomalies in Baja California: a combined helium-seismology approach

    NASA Astrophysics Data System (ADS)

    Negrete-Aranda, R.; Spelz, R. M.; Hilton, D. R.; Tellez, M.; González-Yahimovich, O.

    2015-12-01

    In active tectonic settings, the presence of helium in aqueous fluids with 3He/4He ratios greater than in-situ production values (~0.05 RA where RA = air He or 1.4 x 10-6) indicates the contribution of mantle-derived volatiles to the total volatile inventory. This is an indicative of the presence of mantle-derived melts, which act to transfer volatiles from the solid Earth towards the surface. Thus, He has the potential to map regions of the underlying mantle which are undergoing partial melting - a phenomenon which should also be evident in the seismic record. Reports of high 3He/4He in hot springs in Baja California (BC) has prompted us to initiate a survey of the region to assess relationship(s) between He isotopes and geophysical images of the underlying mantle. Previous studies report 3He/4He ratios of 0.54 RA for submarine hot springs (Punta Banda 108oC; Vidal, 1982) and 1.3 RA for spring waters (81oC) at Bahia Concepcion (Forrest et al.,2005). Our new survey of hot springs in northern BC has revealed that all 6 localities sampled to date, show the presence of mantle He with the highest ratio being 1.74RA (21% mantle-derived) at Puertecitos on the Gulf coast. He ratios are generally lower on the Pacific coast with the minimum mantle He contribution being 5% at Sierra Juárez (0.11RA). Thus, preliminary trends are of a west-to-east increase in the mantle He signal across the peninsula. He results presented in this study correlate well with high resolution Rayleigh wave tomography images by Forsythe et al. (2007). Shear velocity variations in the BC crust and upper mantle have been interpreted as low velocity anomalies associated with dynamic upwelling and active melt production. More extensive sampling throughout BC coupled with analysis of other geochemical indicators of mantle degassing (e.g. CO2) will allow more detailed characterization of the extent and distribution of mantle melts in the region, facilitating assessment of the region's geothermal

  13. Spatial and Temporal Examination of Bivalve Communities in Several Estuaries of Southern California and Northern Baja California, MX

    PubMed Central

    Crooks, Jeffrey A.; Reyns, Nathalie B.

    2016-01-01

    A combination of historical bivalve surveys spanning 30–50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration. PMID:26840744

  14. Novel patterns of historical isolation, dispersal, and secondary contact across Baja California in the Rosy Boa (Lichanura trivirgata).

    PubMed

    Wood, Dustin A; Fisher, Robert N; Reeder, Tod W

    2008-02-01

    Mitochondrial DNA (mtDNA) sequence variation was examined in 131 individuals of the Rosy Boa (Lichanura trivirgata) from across the species range in southwestern North America. Bayesian inference and nested clade phylogeographic analyses (NCPA) were used to estimate relationships and infer evolutionary processes. These patterns were evaluated as they relate to previously hypothesized vicariant events and new insights are provided into the biogeographic and evolutionary processes important in Baja California and surrounding North American deserts. Three major lineages (Lineages A, B, and C) are revealed with very little overlap. Lineage A and B are predominately separated along the Colorado River and are found primarily within California and Arizona (respectively), while Lineage C consists of disjunct groups distributed along the Baja California peninsula as well as south-central Arizona, southward along the coastal regions of Sonora, Mexico. Estimated divergence time points (using a Bayesian relaxed molecular clock) and geographic congruence with postulated vicariant events suggest early extensions of the Gulf of California and subsequent development of the Colorado River during the Late Miocene-Pliocene led to the formation of these mtDNA lineages. Our results also suggest that vicariance hypotheses alone do not fully explain patterns of genetic variation. Therefore, we highlight the importance of dispersal to explain these patterns and current distribution of populations. We also compare the mtDNA lineages with those based on morphological variation and evaluate their implications for taxonomy.

  15. Environmental impact of bleufin tuna aquaculture on benthic assemblages in the western coast of Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Diaz-Castaneda, V.

    2013-05-01

    Sea-cage farming results in a constant rain of organic waste onto the surrounding benthos. In Baja California there is growing concern over the effects of sea-cages on the local environment: sediment chemistry and benthic communities. Samples were taken in 18 stations using a Van veen grab (0.1 m2) in Bahía Salsipuedes, Baja California in 2003, 2004, 2006 and 2008. Organisms belonging to 7 Phyla were collected: Polychaeta, Mollusca, Crustacea, Echinodermata, Cnidaria, Sipuncula and Bryozoa. Polychaetes were the dominant group followed by crustaceans and mollusks. Polychaetes were represented by 37 families and 157 species. Best represented families were Paraonidae, Cirratulidae, Spionidae, Glyceridae and Maldanidae. This study shows that in the NW area of the bay organic carbon (2.54%) and organic nitrogen (0.95%) are being accumulated (higher concentrations and lower Eh values) and smaller opportunistic species are increasing rapidly near the tuna pens. It is crucial to maintain "healthy" macrofaunal populations in order to enhance decomposition of organic matter and to prevent its excessive accumulation. The most abundant polychaete species were Aphelochaeta multifinis, Mediomastus ambiseta, Prionospio steenstrupi Spiophanes bombyx, Apoprionospio pygnaea, Paraonella sp, Monticellina sp, Aricidea (Allia) ramosa, Spiophanes bombyx and Levinsenia gracilis. The dominant trophic groups were deposit-feeders and carnivores. The buildup of organic matter on the seafloor has attracted scavenger species particularly peracarid crustaceans. Non-metric multidimensional scaling (MDS) separated stations depending of the distance to the tuna pens.

  16. Dynamics of a parasite assemblage of the Vermilion Rockfish Sebastes miniatus from northwestern Baja California, México

    NASA Astrophysics Data System (ADS)

    Rodríguez-Santiago, M. A.; Rosales-Casián, J. A.; Grano-Maldonado, M. I.

    2014-06-01

    A parasite assemblage of Sebastes miniatus from northwestern Baja California, México, was composed of a total of 12 species: five ectoparasites (two monogeneans and three parasitic copepods) and seven endoparasites (two digeneans, one cestode, three nematodes, and one acanthocephala). Five of these parasites constituted new genera records to the genus Sebastes, and nine were new geographic records. The most abundant species were the endoparasites Parabothriocephalus sagitticeps, Hysterothylacium sp., and Anisakis sp., and the specific richness ranged from 1 to 8 parasite species per host. The most important parasite species in terms of prevalence were Microcotyle sebastis (93 %) and Anisakis sp. (92 %). The mean abundance of parasites found in S. miniatus showed significant variations over the year, with maximum values (31.7 individuals/host) in August, and minimum (0.39 individuals/host) in February. P. sagitticeps showed the highest mean intensity of infection (190.4 parasites/host), followed by Anisakis sp. (127.2 parasites/host) and Hysterothylacium sp. (46.6 parasites/host). The presence of larval stages of the nematodes Anisakis, Pseudoterranova, and Hysterothylacium is particularly important due to their high abundance and prevalence and because they may represent a human health risk (anisakiasis). Rockfishes (family Scorpaenidae) of the genus Sebastes constitute one of the most important groundfish resources in the American and Mexican northern Pacific Ocean, both for recreational and for the commercial fisheries of California and Baja California. These rockfish species makes up a substantial part of the Mexican cuisine.

  17. Status of the California Red-legged Frog (Rana draytonii) in the State of Baja California, México

    USGS Publications Warehouse

    Peralta-Garcia, Anny; Hellingsworth, Bradford D.; Richmond, Jonathan Q.; Valdez-Villavicencio, Jorge H.; Ruiz-Campos, Gorgonio; Fisher, Robert N.; Cruz-Hernandez, Pedro; Galina-Tessaro, Patricia

    2016-01-01

    The California Red-legged Frog (Rana draytonii) is a threatened species in the United States that has undergone population declines, especially in southern California. Due to the lack of information on the status of Mexican populations, we surveyed for the presence of R. draytonii in Baja California and assessed possible threats to population persistence. Our study area extended from the U.S.-Mexican border to the southern end of the distribution of the species in the Sierra San Pedro Mártir. We found R. draytonii at six of 15 historical sites, none at five proxy sites (i.e., alternative sites chosen because the historical record lacked precise locality data), and four at 24 additional sites. The 10 occupied sites are within three watersheds in the Sierra San Pedro Mártir (two sites at Arroyo San Rafael, two sites at Arroyo San Telmo, and six sites at Arroyo Santo Domingo). We did not detect R. draytonii at 60% of historical sites, including the highest elevation site at La Encantada and multiple low-elevation coastal drainages, suggesting the species has declined in Baja California. The threats we noted most frequently were presence of exotic aquatic animal species, water diversion, and cattle grazing. Management of remaining populations and local education is needed to prevent further declines.

  18. Prevalence of infection with Toxoplasma gondii in landrace and mixed breed pigs slaughtered in Baja California Sur State, Mexico.

    PubMed

    Alvarado-Esquivel, Cosme; Vazquez-Morales, Renata Fabiola; Colado-Romero, Edgar Eusebio; Guzmán-Sánchez, Ramiro; Liesenfeld, Oliver; Dubey, Jitender P

    2015-03-01

    We performed a cross-sectional study to determine the seroprevalence of Toxoplasma gondii infection in 308 domestic pigs slaughtered in La Paz, Baja California Sur State, Mexico using the modified agglutination test (MAT, cut off 1:25). Forty (13%) of the 308 pigs were seropositive with MAT titers of 1:25 in 16, 1:50 in 5, 1:100 in 4, 1:200 in 5, 1:400 in 3, 1:800 in 3, 1:1600 in 2, and 1:3200 in 2. Multivariate analysis of pigs' characteristics showed that seropositivity to T. gondii was negatively associated with mixed breed (OR = 0.02; 95% CI: 0.003-0.26; P = 0.001). Other variables including sex, type of raising, and municipality did not show an association with T. gondii seropositivity by multivariate analysis. The frequency of high antibody titers (≥1:400) was significantly higher (P < 0.001) in Landrace pigs than mixed breed pigs. The seroprevalence of T. gondii infection in pigs for slaughter in Baja California Sur State is low compared with seroprevalences reported in pigs in other Mexican states. Landrace pigs demonstrated higher seroprevalence rates and antibody levels than mixed breed pigs. This is the first report of T. gondii infection in pigs raised in a desert climate.

  19. Novel patterns of historical isolation, dispersal, and secondary contact across Baja California in the Rosy Boa (Lichanura trivirgata)

    USGS Publications Warehouse

    Wood, D.A.; Fisher, R.N.; Reeder, T.W.

    2008-01-01

    Mitochondrial DNA (mtDNA) sequence variation was examined in 131 individuals of the Rosy Boa (Lichanura trivirgata) from across the species range in southwestern North America. Bayesian inference and nested clade phylogeographic analyses (NCPA) were used to estimate relationships and infer evolutionary processes. These patterns were evaluated as they relate to previously hypothesized vicariant events and new insights are provided into the biogeographic and evolutionary processes important in Baja California and surrounding North American deserts. Three major lineages (Lineages A, B, and C) are revealed with very little overlap. Lineage A and B are predominately separated along the Colorado River and are found primarily within California and Arizona (respectively), while Lineage C consists of disjunct groups distributed along the Baja California peninsula as well as south-central Arizona, southward along the coastal regions of Sonora, Mexico. Estimated divergence time points (using a Bayesian relaxed molecular clock) and geographic congruence with postulated vicariant events suggest early extensions of the Gulf of California and subsequent development of the Colorado River during the Late Miocene-Pliocene led to the formation of these mtDNA lineages. Our results also suggest that vicariance hypotheses alone do not fully explain patterns of genetic variation. Therefore, we highlight the importance of dispersal to explain these patterns and current distribution of populations. We also compare the mtDNA lineages with those based on morphological variation and evaluate their implications for taxonomy. ?? 2007 Elsevier Inc. All rights reserved.

  20. Spatial and Temporal Examination of Bivalve Communities in Several Estuaries of Southern California and Northern Baja California, MX.

    PubMed

    Novoa, Anai; Talley, Theresa S; Talley, Drew M; Crooks, Jeffrey A; Reyns, Nathalie B

    2016-01-01

    A combination of historical bivalve surveys spanning 30-50 years and contemporary sampling were used to document the changes in bivalve community structure over time at four southern California and one northern Baja California estuaries. While there are limitations to the interpretation of historic data, we observed generally similar trends of reduced total bivalve species richness, losses of relatively large and/or deeper-dwelling natives, and gains of relatively small, surface dwelling introduced species across the southern California estuaries, despite fairly distinct bivalve communities. A nearly 50-year absence of bivalves from two wetlands surveyed in a Baja California estuary continued. A combination of site history and current characteristics (e.g., location, depth) likely contributes to maintenance of distinct communities, and both episodic and gradual environmental changes likely contribute to within-estuary temporal shifts (or absences). We highlight future research needed to determine mechanisms underlying patterns so that we can better predict responses of bivalve communities to future scenarios, including climate change and restoration.

  1. Lipid Biomarkers for Methanogens in Hypersaline Cyanobacterial Mats for Guerrero Negro, Baja California Sur

    NASA Technical Reports Server (NTRS)

    Jahnke, Linda L.; Embaye, Tsegereda; Summons, Roger E.; Fonda, Mark (Technical Monitor)

    2002-01-01

    Analyses of sediments from the vicinity of active methane seeps have uncovered a particular suite of lipid biomarker patterns that characterize methane consuming archaea and their syntrophic, sulfate reducing partners. These isoprenoid biomarkers, largely identified by their anomalously light carbon isotopic signatures, have been a topic of intense research activity and are recorded in numerous methane-rich environments from Holocene to Cenozoic. This phenomenon has implications for depleted kerogens at 2.7 Ga on early Earth (Hinrichs 2002). In contrast, the lipid biosignatures of methane producing archaea are not readily identified through distinct isotopic labels and have received comparably little attention in analyses of archaea in environmental samples. Indeed, environmental analyses generally detect only free archaeal lipids, not the intact, polar molecules found in the membrane of living organisms. As part of the Ames NAI, the 'Early Microbial Ecosystem Research Group' (EMERG) is working to understand microbial processes in the hypersaline cyanobacterial mats growing in the salt evaporation ponds of the Exportadora de Sal at Guerrero Negro, Baja California Sur, Mexico. The aim of this study was to develop methods by which we could identify the organisms responsible for methane generation in this environment. While the ester-bound fatty acids, hopanoids and wax esters provide a means to identify most of the bacterial components of these mats, the archaea which Ere evidently present through genomic assays and the fact of intense methane production (Hoehler et al. 200l), have not been identified through their corresponding lipid signatures. Archaeal core lipids present a number of analytical challenges. The core lipids of methanogens comprise C20, C40 and sometimes C25 isoprenoid chains, linked through ether bonds to glycerol. As well as archaeal (C20), sn-2- and sn-3-hydroxyarchaeol are associated particularly with methylotrophic methanogens. Recently, we have

  2. Magnetic Fabric and Paleomagnetism of the Peninsular Ranges Batholith, Sierra San Pedro M rtir, Baja California.

    NASA Astrophysics Data System (ADS)

    Knight, M.; Herrero-Bervera, E.; Molina-Garza, R. S.; Böhnel, H. N.

    2003-12-01

    We summarize results of recent paleomagnetic, structural, petrologic and magnetic fabric studies along an east-west (60 km long) transect across the Peninsular Ranges Batholith (PRB) in north-central Baja California. The transect includes both magnetite rich plutons from the western sector of the PRB, and ilmenite rich plutons from the eastern sector, as well as plutons on the eastern and western side of major tectonic discontinuities. We include results for 8 plutons, included well-characterized bodies such as San Pedro M rtir (SP), San José (SJ) and La Zarza (LZ), and relatively little known plutons such as Potrero (PO), Aguaje del Burro (AB), El Milagro (MI), and San Telmo (ST). Plutons on the western sector of the PRB yield a paleomagnetic pole at 82° N-186.4° E (A95=4.8° ). When rotated into a pre- Gulf of California position, the pole (79.2° -188.2° ) is statistically undistinguishable from the North American reference pole. In contrast, SP, SJ and PO plutons, on either side of the NW trending Main Martir Thrust yield clearly discordant direction that can only be reconciled with results for the western plutons assuming southwestward tilt of ˜ 25° for SP and greater than 45° for SJ and PO. We find strong evidence in support of tilt of the plutons from thermochronological, structural, and geobarometric data. These data will be discussed elsewhere. Here we focus on magnetic fabric data. AMS for SJ is strongly developed with high values for degree of anisotropy (P= 1.14 a 1.40), but marked east-west asymmetry that contrasts with the general symmetry of the pluton along a north-south axis. Oblate fabrics (T ˜ +0.4) with dispersed lineation directions dominate the west side of the pluton and prolate fabrics (T ˜ -0.15) with steep to vertical lineations dominate on its eastern side. This fabric is interpreted to result from magma flow. SP, a much larger pluton and sensibly asymmetric, displays high degrees of anisotropy (P ˜1.2) on its western side but

  3. Twentieth century demographic changes in cirio and cardón in Baja California, Mexico

    USGS Publications Warehouse

    Bullock, Stephen H.; Martijena, Nora E.; Webb, Robert H.; Turner, Raymond M.

    2005-01-01

    Aim  Our purpose was to discern long-term large-scale patterns of survivorship and recruitment of two dominant, charismatic and useful desert plants, cirio [Fouquieriaceae; Fouquieria columnaris (Kell.) Kell. ex Curran] and cardón [Cactaceae; Pachycereus pringlei(S.Watson) Britton & Rose], and to evaluate the effects of physical and human factors. Location  The study included 77 sites distributed over c. 13,200 km2 in the northern Vizcaíno Region of the Sonoran Desert, state of Baja California, México. Method  Censuses used identified individuals (n = 3780 cirio and 2246 cardón) and were based on repeat photography. Time intervals between censuses ranged from 29 to 96 years, ending in 1996–2002. Earlier repetition (1963) of old photographs at 14 sites allowed analysis of temporal variation. The effect of elapsed time was modelled with Weibull functions for survivorship and linear functions for recruitment. To explain the residual variations, we tested categorical and continuous variables related to substrate, geomorphology, climate and geography. Human impacts were weighed with historical and quantitative analysis. Results  Elapsed time accounted for 45% of the variation of survivorship in cirio but only 35% in cardón. The fitted Weibull curves were used to estimate longevity: all-size cohorts of 1000 individuals would die out in 388 (cirio) and 723 years (cardón). Recruitment in cirio was linearly related to time (r2 = 0.71) and averaged < 0.003 year−1 but was less than mortality at 90% of the sites. For cardón, recruitment averaged > 0.005 year−1, was linearly related to time (r2 = 0.66) and was less than mortality at only 33% of the sites. Vital rates were not strongly correlated between mid- and late-century but were mostly similar to the long-term regional rates. Removing the factor of elapsed time, the residual variations showed that survivorship was greater on sites protected from winds for cirio and was less on

  4. Hurricane effects on the coastline from Cabo San Lucas Bay, Baja California Peninsula, Mexico

    NASA Astrophysics Data System (ADS)

    Nava-Sanchez, Enrique; Navarro-Lozano, Octavio; Murillo-Jimenez, Janette; Godinez-Orta, Lucio

    2010-05-01

    Cabo San Lucas, located on the southern tip of the Baja California Peninsula, is on the track of two to five hurricanes per year. Thus the purpose of this work was to evaluate the effects of hurricanes on the stability of the coastline of San Lucas Bay. We apply GIS for determining inland geomorphology and conducted bathymetric surveys for the marine area. Results from previous sedimentological researches of fluvial, littoral and shallow marine environments were reanalyzed to determine the sedimentary processes responsible for the stability of the coastline. Also, we were monitoring beach profiles in the bay and also other beaches from the tip of the peninsula from 1997 to 2004 and recorded the effects of Hurricane Juliette in 2001 (category 3 in the Saffir-Simpson scale), which left an accumulative precipitation of 850 mm and formed waves of 8 m in height during the four days of maximum impact. We found out that inland and marine geomorphology, as well as littoral and alluvial sediment transport play a major role to keep the coastline relatively stable for at least the last 3,000 years. Geomorphology of the drainage basin is steep favoring the formation of flash floods that feed an alluvial fan to finally discharge sediments to the San Lucas Bay where a temporal fan-delta is developed during catastrophic rains. Marine morphology is dominated by the San Lucas submarine canyon, located on the southern half of the bay, whose canyon head is just at the foot of the beach (4 to 6 m in depth). On the northern half, there is a narrow submarine terrace with a break 40 m deep, covered mostly by fluvial sediments. At the littoral, there is only one dune ridge which is almost continuous and only cut by the arroyo. The dune ridge was dated at two levels; at the bottom, just above Pleistocene fluvial sediments and at the top, giving dates of 3200 and 800 years respectively. These dates are interpreted as an evidence for the stability of the dune ridge. The sand from the beach

  5. Geochemical survey of medium temperature geothermal resources from the Baja California Peninsula and Sonora, México

    NASA Astrophysics Data System (ADS)

    Barragán R, R. M.; Birkle, P.; Portugal M, E.; Arellano G, V. M.; Alvarez R, J.

    2001-09-01

    Waters from hot springs and deep wells from Cerritos in the northern Baja California Peninsula and deep wells from the Riı´to zone (Sonora state) were studied in order to classify medium temperature geothermal resources to be exploited in NW-Mexico. Geochemical characteristics of San Felipe and Punta Estrella coastal springs indicate the mixing of seawater and meteoric components with secondary leaching of evaporates. Reservoir temperatures for both zones were estimated up to 225°C. Mixing of high portions of seawater (>80 wt%) with local waters could be the origin for the Puertecitos coastal spring, with a reservoir temperature estimation of 195°C. The El Coloradito coastal spring is composed of meteoric water with a reservoir temperature of 127°C. The formation of thermal manifestations along the Baja California coast could be related to the heating up of convecting seawater along extensional tectonic structures, as observed for submarine hydrothermal vents at the Gulf of California and along the East Pacific Rise. Volcanic steam-heated waters with a reservoir temperature of 135°C were found at the Valle Chico inland springs from the Baja California Peninsula. Deep fluids from the Riı´to zone originated by evaporation of infiltrated waters with similar characteristics to those located in the Mexicali Valley. Reservoir temperature of 192 and 126°C are estimated for the Riı´to deep wells ER-1B (ER) and R-1, respectively. The Riı´to artesian wells M-1, M-2 and M-4 indicate reservoir temperatures from 109 to 118°C. Isotopic data define the artesian wells as typical surface water or shallow groundwater from the Mexicali Valley. The Cerritos deep fluids of the Mexicali Valley show a close chemical and isotopic relationship to the adjacent Cerro Prieto reservoir fluids suggesting a similar origin and a possible connection of both aquifer systems. Conductive cooling of Cerro Prieto discharge fluids could originate the cooler Cerritos system (130

  6. A High-Resolution Mid- to Late-Holocene Sea-Surface Temperature Record from the Subtropics, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Coombs, M.; Herguera, J. C.; Lea, D. W.

    2004-12-01

    San Lazaro basin provides a unique environment in which to study paleoclimate because it lies at the intersection of the cooler California Current that originates to the north and the warmer Pacific tropical current that originates to the south. Studies in this basin will provide insight into the varying strength of these currents at decadal and centennial resolutions. In addition, the present-day basin is suboxic (<3 uM/kg), and laminations throughout the top ˜6 m of ocean floor sediments indicate that it may have been suboxic for the past ˜6.5 ky. Suboxia is advantageous in the study of high-resolution paleoclimate records, as lower levels of oxygen inhibit the activity of sediment-disturbing organisms that might smooth climate records. We will present parts of a new decadal-resolution sea-surface temperature (SST) record from San Lazaro (AKA Soledad) basin, Baja California, Mexico. We estimate SST using Mg/Ca and d18O data measured on surface-dwelling planktonic foraminifera Globigerinoides ruber and Globigerina bulloides from ocean-sediment giant box core MD02-2506C2. This 4.6-m core exhibits an ˜0.8 mm/yr sedimentation rate (van Geen et al., 2003) and represents the period ˜5,000 to ˜500 years BP. We sampled the core at 1-cm continuous (i.e., approximately decadal) resolution. Preliminary results indicate that Mg/Ca values for G. ruber range between 2.3 and 3.3 mmol/mol ( ˜20 and ˜24 deg C), with higher values characteristic of the mid-Holocene. Annual sea-surface temperatures for the period 1950 to 1990 ranged between ˜19 and ˜23 deg C (CalCOFI, COADS), suggesting that mid- to late-Holocene SST values were ˜1 deg C higher than the those of the last half century. We will compare our SST proxy results with d18O records from Santa Barbara basin (e.g., Kennett and Kennett, 2000); tree-ring records from Baja California (Bullock, 2003) and Southern California (De Nava et al., 1999); and pluvial (Davis, 2003) and packrat midden (Clark and Sankey, 1999

  7. A Study on the Attitudes and Opinions of Engineering Students from the University of Baja California, Mexico, on Science, Technology, and Society

    ERIC Educational Resources Information Center

    Oliveros Ruiz, Maria Amparo; Sevilla Garcia, Juan Jose; Schorr, Michael

    2010-01-01

    A proposal is presented for the incorporation of the concepts of STS into the teaching of science and technology at the Faculty of Engineering, Mexicali Campus, of the University of Baja California. The method outlined for the development of research and the application of the "Opinions Questionnaire on Science, Technology and Society"…

  8. A Study on the Attitudes and Opinions of Engineering Students from the University of Baja California, Mexico, on Science, Technology, and Society

    ERIC Educational Resources Information Center

    Oliveros Ruiz, Maria Amparo; Sevilla Garcia, Juan Jose; Schorr, Michael

    2010-01-01

    A proposal is presented for the incorporation of the concepts of STS into the teaching of science and technology at the Faculty of Engineering, Mexicali Campus, of the University of Baja California. The method outlined for the development of research and the application of the "Opinions Questionnaire on Science, Technology and Society"…

  9. Funding and Administrative Coordination of the Baja Field Studies Program at Glendale Community College during the Years 1974 to 1983: A Historical Investigation.

    ERIC Educational Resources Information Center

    Mercade, Jose A.

    Glendale Community College's (GCC's) Baja Field Studies Program began in 1974 as a faculty-initiated overseas field program in marine biology and developed into a college-wide, interdisciplinary program offering different courses under the leadership of a program coordinator. As changes in funding and administration took place due to the altered…

  10. The Social-Action Role of the University: San Juan, Puerto Rico. A Study of the Torrecilla Baja (Pinones) Community. Final Report.

    ERIC Educational Resources Information Center

    Cataura, Osvaldo; Terrassa, Juan A.

    This document presents a report of an experimental community service program that took place in Torrecilla Baja (Pinones), a suburban sector of San Juan, Puerto Rico, from June 30, 1971 through May 30, 1972. Students and faculty alike participated in the program, trying to develop recreational and other programs for the 1,300 underprivileged…

  11. Proximalisation of the tibial tubercle gives a good outcome in patients undergoing revision total knee arthroplasty who have pseudo patella baja.

    PubMed

    Vandeputte, F-J; Vandenneucker, H

    2017-07-01

    The aim of this study was to compare the outcome of revision total knee arthroplasty (TKA) with and without proximalisation of the tibial tubercle in patients with a failed primary TKA who have pseudo patella baja. All revision TKAs, performed between January 2008 and November 2013 at a tertiary referral University Orthopaedic Department were retrospectively reviewed. Pseudo patella baja was defined using the modified Insall-Salvati and the Blackburne-Peel ratios. A proximalisation of the tibial tubercle was performed in 13 patients with pseudo patella baja who were matched with a control group of 13 patients for gender, age, height, weight, body mass index, length of surgery and Blackburne-Peel ratio. Outcome was assessed two years post-operatively using the Knee Society Score (KSS). The increase in KSS was significantly higher in the osteotomy group compared with the control group. The outcome was statistically better in patients in whom proximalisation of > 1 cm had been achieved compared with those in whom the proximalisation was < 1 cm. In this retrospective case-control study, a proximal transfer of the tibial tubercle at revision TKA in patients with pseudo patella baja gives good outcomes without major complications. Cite this article: Bone Joint J 2017;99-B:912-16. ©2017 The British Editorial Society of Bone & Joint Surgery.

  12. Interactions between western gall rust and its Pinus hosts, P. jeffreyi and P. contorta, in Sierra De San Pedro Martir National Park, Northern Baja California, Mexico

    Treesearch

    Detlev R. Vogler; Brian W. Geils

    2008-01-01

    The Sierra de San Pedro Martir is a mountain range in north-central Baja that comprises the southern-most extension of the Californian coniferous flora, including Pinus jeffreyi, P. contorta, P. lambertiana, Abies concolor, and Calocedrus decurrens. These forests are similar...

  13. Reconnaissance geologic map of the Loreto and part of the San Janier quadrangles, Baja California Sur, Mexico

    USGS Publications Warehouse

    McLean, Hugh

    1988-01-01

    The Loreto area of Baja California Sur, Mexico, contains a diverse association of igneous, sedimentary, and metasedimentary rocks exposed in the foothills and arroyos between the Sierra La Giganta and Gulf of California. The Loreto area was selected for this study to examine the possible relation of the marine rocks to the opening of the Gulf of California, and to determine the stratigraphic and structural relations between basement rocks composed of granitic and prebatholithic rocks and overlying Tertiary (mainly Miocene) sedimentary and volcanic rocks, and by a sequence of Pliocene marine and nonmarine sedimentary rocks. The Pliocene marine rocks lie in a structural depression informally called here, the Loreto embayment. This geologic map and report stem from a cooperative agreement between the U.S. Geological Survey and the Consejo de Recursos Minerales of Mexico that was initiated in 1982.

  14. Effects of abnormal flooding events on microbial mat communities and aragonitic stromatolites, Laguna Mormona, Baja California, Mexico

    SciTech Connect

    Horodyski, R.J.

    1985-02-01

    Laguna Mormona (Baja California, Mexico) is a coastal sabkha that contains a variety of microbial (cyanophycean and bacterial) mat communities. Studies conducted during 1971-76 concentrated on the microstructure, macrostructure, and degradation of these microbial mats and aragonitic stromatolites and the information they provide that is relevant to the interpretation of Proterozoic stromatolites, silicified microbial mats, and their contained microfossils. Abnormally high rainfall in 1979-80 flooded the sabkha to depths exceeding 1 m and profoundly affected these microbial communities by lowering the salinity of the water and depositing 5-10 cm of very fine grained, organic-rich mud over most of the microbial mats. The water level has returned to normal, and diatoms, cyanophytes, and bacteria locally form millimeter-thick mats upon this mud in areas that previously contained well-developed mats; however, it is unclear whether these mats will eventually attain the thickness (up to 30 cm) of their predecessors.

  15. Bioaccumulation and biomagnification of total mercury in four exploited shark species in the Baja California Peninsula, Mexico.

    PubMed

    Maz-Courrau, A; López-Vera, C; Galván-Magaña, F; Escobar-Sánchez, O; Rosíles-Martínez, R; Sanjuán-Muñoz, A

    2012-02-01

    The present study determined the average mercury bioaccumulation in the muscle tissue of four shark species (Carcharhinus falciformis, Prionace glauca, Sphyrna zygaena and Isurus oxyrinchus) captured in the Baja California Peninsula. We also evaluated biomagnification of some prey consumed by sharks. All sharks' species had mercury levels over the limit specified by the Mexican government for human consumption. Blue shark (P. glauca) presented highest mercury values (1.96 ± 1.48 μg/g Hg d.w.) and it was the unique specie that showed a negative correlation with mercury content (Rs = -0.035, p = 0.91). Scomber japonicus was the prey with high content of mercury (0.57 ± 0.02 μg/g).

  16. Key species and impact of fishery through food web analysis: A case study from Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Rocchi, Marta; Scotti, Marco; Micheli, Fiorenza; Bodini, Antonio

    2017-01-01

    Ecosystem-Based Management (EBM) aims to support the protection of natural ecosystems and to improve economic activities. It requires considering all of the actors interacting in social-ecological systems (e.g., fish and fishers) in the understanding that their interplay determines the dynamic behavior of the single actors as well as that of the system as a whole. Connections are thus central to EBM. Within the ecological dimension of socio-ecological systems, interactions between species define such connections. Understanding how connections affect ecosystem and species dynamics is often impaired by a lack of data. We propose food web network analysis as a tool to help bridge the gap between EBM theory and practice in data-poor contexts, and illustrate this approach through its application to a coastal marine ecosystem in Baja California Sur, Mexico. First, we calculated centrality indices to identify which key (i.e., most central) species must be considered when designing strategies for sustainable resource management. Second, we analyzed the resilience of the system by measuring changes in food web structure due to the local extinction of vulnerable species (i.e., by mimicking the possible effect of excessive fishing pressure). The consequences of species removals were quantified in terms of impacts on global structural indices and species' centrality indices. Overall, we found that this coastal ecosystem shows high resilience to species loss. We identified species (e.g., Octopus sp. and the kelp bass, Paralabrax clathratus) whose protection could further decrease the risk of potential negative impacts of fishing activities on the Baja California Sur food web. This work introduces an approach that can be applied to other ecosystems to aid the implementation of EBM in data-poor contexts.

  17. Active Pacific North America Plate boundary tectonics as evidenced by seismicity in the oceanic lithosphere offshore Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Hauksson, Egill; Kanamori, Hiroo; Stock, Joann; Cormier, Marie-Helene; Legg, Mark

    2014-03-01

    Pacific Ocean crust west of southwest North America was formed by Cenozoic seafloor spreading between the large Pacific Plate and smaller microplates. The eastern limit of this seafloor, the continent-ocean boundary, is the fossil trench along which the microplates subducted and were mostly destroyed in Miocene time. The Pacific-North America Plate boundary motion today is concentrated on continental fault systems well to the east, and this region of oceanic crust is generally thought to be within the rigid Pacific Plate. Yet, the 2012 December 14 Mw 6.3 earthquake that occurred about 275 km west of Ensenada, Baja California, Mexico, is evidence for continued tectonism in this oceanic part of the Pacific Plate. The preferred main shock centroid depth of 20 km was located close to the bottom of the seismogenic thickness of the young oceanic lithosphere. The focal mechanism, derived from both teleseismic P-wave inversion and W-phase analysis of the main shock waveforms, and the 12 aftershocks of M ˜3-4 are consistent with normal faulting on northeast striking nodal planes, which align with surface mapped extensional tectonic trends such as volcanic features in the region. Previous Global Positioning System (GPS) measurements on offshore islands in the California Continental Borderland had detected some distributed Pacific and North America relative plate motion strain that could extend into the epicentral region. The release of this lithospheric strain along existing zones of weakness is a more likely cause of this seismicity than current thermal contraction of the oceanic lithosphere or volcanism. The main shock caused weak to moderate ground shaking in the coastal zones of southern California, USA, and Baja California, Mexico, but the tsunami was negligible.

  18. Studies of morphological and molecular phylogenetic divergence in spiders (Araneae: Homalonychus) from the American southwest, including divergence along the Baja California Peninsula.

    PubMed

    Crews, Sarah C; Hedin, Marshal

    2006-02-01

    Comparative phylogenetic and phylogeographic analyses have revealed a pervasive midpeninsular divergence in the mitochondrial genealogies of numerous vertebrate taxa distributed on the Baja California Peninsula. In this study, we extend the investigation of regional vicariance in Baja California to an arthropod taxon by examining patterns of phylogenetic and morphological divergence in the spider genus Homalonychus (Araneae, Homalonychidae). We analyzed data from two mtDNA genes (16S rRNA and NADH dehydrogenase subunit (1) and a nuclear gene (28S rRNA) using maximum parsimony and Bayesian phylogenetic analyses, and also conducted geometric morphometric analyses employing landmark data on male and female genitalia. Genes and morphology both reveal a deep split across the Colorado River and Gulf of California, separating Homalonychus selenopoides on the east side of river from its congener Homalonychus theologus on the west side of the river, including the Baja California Peninsula. Along the north-south axis of the Baja Peninsula, an apparently more recent midpeninsular phylogenetic break is evident within H. theologus in the mitochondrial genome and in female genitalia. However, there is no measurable divergence between northern and southern populations in either nuclear DNA or male genitalia. We suggest that this discordance between datasets reflects either a difference in rates of evolution between male versus female systems, or that male-based nuclear gene flow is obscuring a phylogenetic split that is fixed in the female-based systems. Our findings provide additional support for a midpeninsular Baja divergence event, although the timing and geological evidence for such an event remain elusive.

  19. Strain Localisation at Rift Segment Boundaries: An Example from the Bocana Transfer Zone in Central Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Seiler, C.; Gleadow, A. J.; Kohn, B. P.

    2012-12-01

    Rifts are commonly segmented into several hundred kilometre long zones of opposing upper-plate transport direction with boundaries defined by accommodation and transfer zones. A number of such rift segments have been recognized in the northern Gulf of California, a youthful oceanic basin that is currently undergoing the rift-drift transition. However, detailed field studies have so far failed to identify suitable structures that could accommodate the obvious deformation gradients between different rift segments, and the nature of strain transfer at segment boundaries remains enigmatic. The situation is even less clear in central and southern Baja California, where a number of rift segments have been hypothesized but it is unknown whether the intervening segment boundaries facilitate true reversals in the upper-plate transport direction, or whether they simply accommodate differences in the timing, style or magnitude of deformation. The Bocana transfer zone (BTZ) in central Baja California is a linear, WNW-ESE striking structural discontinuity separating two rift segments with different magnitudes and styles of extensional deformation. North of the BTZ, the Libertad fault is part of the Main Gulf Escarpment, which represents the breakaway fault that separates the Gulf of California rift to the east from the relatively stable western portion of the Baja peninsula. The N-striking Libertad escarpment developed during the Late Miocene (~10-8Ma) and exhibits a topographic relief of ca. 1,000m along a strike-length of ca. 50km. Finite displacement decreases from ~1000m in the central fault segment to ~500m further south, where the fault bends SE and merges with the BTZ. In the hanging wall of the Libertad fault, a series of W-tilted horsts are bound along their eastern margins by two moderate-displacement E-dipping normal faults. South of the BTZ, extension was much less than further north, which explains the comparatively subdued relief and generally shallower tilt of

  20. Hypoxic cyclicity in sediments of Soledad Basin, Baja Mexico: A record of high-frequency climate fluctuations?

    NASA Astrophysics Data System (ADS)

    Westman, A. E.; Brooks, G. R.; Lea, C.

    2007-05-01

    The sedimentary record in Soledad Basin, 45 km west of Baja, Mexico, shows high-frequency oscillations in hypoxia, which can be linked to fluctuations in climate. Soledad Basin, a semi-enclosed basin with a sill depth of 290m, has been shown to exhibit variable levels of hypoxia throughout the geologic past. Located at the intersection of the California Current and California Undercurrent, Soledad Basin is highly responsive to changes in current strength and upwelling, the combination of which creates fluctuations in hypoxia. During climatic cool periods, the California Current is weakened decreasing upwelling and biologic productivity along the Baja Borderland. This causes increased hypoxia in Soledad Basin. The California Undercurrent is also weakened during these cooler periods and brings less nutrients and oxygen to the basin further increasing hypoxia. Since Soledad Basin sediments are undisturbed and have accumulated rapidly, this is a prime location to study high frequency variations in hypoxia in the sedimentary record. The objective of this study was to examine how and to what extent hypoxic events have been recorded in the sedimentary record of Soledad Basin, and gain insight into what controls these events. Surface sediment samples and a single 1.1m gravity core were collected aboard the S.S.V. Robert C. Seamans on a SEA Semester cruise in October 2005. The core was taken at a depth of 490 m near the deepest point of the basin. The core contained laminated sediments consisting of >95% mud. Using 210Pb analysis, a sedimentation rate of 15 cm over the past 100 years was determined, which is consistent with previous research. Trace metal analyses were performed at the cm-scale on selected intervals between 0.34-0.44m and 0.78-0.92m. These intervals correspond to dark organic-rich (>15% organic content) laminations alternating with lighter layers containing less organic material (<15% organic content). All sediments were found to be enriched in Molybdenum

  1. Food webs including parasites, biomass, body sizes, and life stages for three California/Baja California estuaries

    USGS Publications Warehouse

    Hechinger, Ryan F.; Lafferty, Kevin D.; McLaughlin, John P.; Fredensborg, Brian L.; Huspeni, Todd C.; Lorda, Julio; Sandhu, Parwant K.; Shaw, Jenny C.; Torchin, Mark E.; Whitney, Kathleen L.; Kuris, Armand M.

    2001-01-01

    This data set presents food webs for three North American Pacific coast estuaries and a “Metaweb” composed of the species/stages compiled from all three estuaries. The webs have four noteworthy attributes: (1) parasites (infectious agents), (2) body-size information, (3) biomass information, and (4) ontogenetic stages of many animals with complex life cycles. The estuaries are Carpinteria Salt Marsh, California (CSM); Estero de Punta Banda, Baja California (EPB); and Bahía Falsa in Bahía San Quintín, Baja California (BSQ). Most data on species assemblages and parasitism were gathered via consistent sampling that acquired body size and biomass information for plants and animals larger than ∼1 mm, and for many infectious agents (mostly metazoan parasites, but also some microbes). We augmented this with information from additional published sources and by sampling unrepresented groups (e.g., plankton). We estimated free-living consumer–resource links primarily by extending a previously published version of the CSM web (which the current CSM web supplants) and determined most parasite consumer–resource links from direct observation. We recognize 21 possible link types including four general interactions: predators consuming prey, parasites consuming hosts, predators consuming parasites, and parasites consuming parasites. While generally resolved to the species level, we report stage-specific nodes for many animals with complex life cycles. We include additional biological information for each node, such as taxonomy, lifestyle (free-living, infectious, commensal, mutualist), mobility, and residency. The Metaweb includes 500 nodes, 314 species, and 11 270 links projected to be present given appropriate species' co-occurrences. Of these, 9247 links were present in one or more of the estuarine webs. The remaining 2023 links were not present in the estuaries but are included here because they may occur in other places or times. Initial analyses have examined

  2. [Length, body weight and sex of the golden Coryphaena hippurus (Perciformes: Coryphaenidae), of the littoral of Sinaloa, Nayarit and Baja California Sur, Mexico].

    PubMed

    Madrid, J V; Beltrán-Pimienta, R

    2001-01-01

    Dolphin fish population data were recorded from landings in Sinaloa, Nayarit and Baja Califonia Sur, Mexico, in 1997. Of 3,211 organisms, only 2,812 produced complete biometric data. The maximal length and weight were 192 cm and 30 kg. The three sampling sites and the climatic periods also were associated with different size (P < 0.05). The covariate analysis of weight and length relationships indicated significative differences (P < 0.05) for total data and by sex. Condition factor was higher throughout the study period in Mazatlán, and the variation was higher, in the spring. The sexual ratio was in Mazatlán constant, while there were more males in Nayarit in the fall and the spring and in Los Cabos in the spring. There may be population differences, between the central mexican Pacific Coast and the Peninsula of Baja data.

  3. Relative inactivity during the last 140,000 years of a portion of the La Paz fault, southern Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Szabo, B. J.; Hausback, B. P.; Smith, J. T.

    1990-03-01

    Uranium-series dating of corals overlying the undeformed Punta Coyote gravels indicates that the underlying La Paz fault zone has been relatively inactive in this part of the Baja California peninsula during the last 140,000 years, and possibly for a significantly longer period. However, Holocene seismic activities along extensions of the fault zone north of Cabo San Lucas suggest potential seismic hazards for the city of La Paz (population 200,000), which lies about 6 km from the fault.

  4. Late Miocene to Recent transtensional tectonics in the Sierra San Fermı´n, northeastern Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Lewis, Claudia J.; Stock, Joann M.

    1998-08-01

    Basins and ranges within part of the Gulf of California Extensional Province (Mexico) have experienced complex distributed deformation, including normal and strike-slip faulting and block rotations, linked to dextral shear at the Pacific-North America plate boundary. In the Sierra San Fermı´n and southern Sierra San Felipe (northeastern Baja California), normal faulting began between 12.5 and 6 Ma, although most extension occurred between about 6 and 3 Ma, strongly influencing thickness and distribution of ash-flow tuffs and sedimentary deposits. Extension is generally <10% in 6 Ma rocks and somewhat more in 12.5 Ma rocks. Inversion of kinematic data, interpreted together with published paleomagnetic data, suggests that the axis of least principal stress was oriented between W-E and SW-NE in late Miocene time. Our data indicate an important change in the amount of dextral shear, but not necessarily the least principal stress direction (WSW-ENE), at about 3 Ma. Structural constraints limit significant sinistral strike-slip faulting, conjugate to the dextral plate boundary, to the last ˜3 My. Progressive changes in the geometry of faulting through time are consistent with regional strain partitioning within the Pacific-North America plate boundary zone, and are predicted by physical and analytical models of oblique divergence as the orientation of the stretching vector α changes to lower and lower values.

  5. Marine diet and tobacco exposure affects mercury concentrations in pregnant women (I) from Baja California Sur, Mexico

    PubMed Central

    Gaxiola-Robles, Ramón; Bentzen, Rebecca; Zenteno-Savín, Tania; Labrada-Martagón, Vanessa; Castellini, J. Margaret; Celis, Alfredo; O’Hara, Todd; Celina Méndez-Rodríguez, Lía

    2017-01-01

    Seafood provides essential polyunsaturated fatty acids (PUFA) and other nutrients to pregnant women and their fetus(es) while a diet rich in finfish can be a major pathway of monomethyl mercury (MeHg+) exposure. We measured total mercury concentration ([THg]) in hair samples provided by 75 women in Baja California Sur (BCS) to assess its relationship with age, parity, tobacco smoke exposure, and diet based on survey methodologies. Generalized linear models (GLM) were used to explain the possible association of the different variables with [THg] in hair. Median [THg] in hair was 1.52 µgg−1, ranging from 0.12 to 24.19 µgg−1 and varied significantly by segment. Approximately 72% (54/75) of those evaluated exceed 1 µgg−1 [THg] and 8% (6/75) exceed 5 µgg−1 [THg] in hair. Although frequency of fish consumption contributed significantly to explaining hair [THg], fish consumption only explained 43% of [THg] in a GLM incorporating tobacco exposure and body mass index. This study establishes possible relationships among multiple potential sources of exposure and other factors related to [THg] in hair of women in the prenatal period. A more detailed examination of other sources of exposure and factors contributing to [THg] is warranted. PMID:28203532

  6. The turbellarian urastoma cyprinae from edible mussels mytilus galloprovincialis and mytilus californianus in baja california, NW Mexico

    PubMed

    Caceres-martinez; Vasquez-yeomans; Sluys

    1998-11-01

    The turbellarian Urastoma cyprinae (Graff, 1913) was found in the mantle cavity of Mytilus galloprovincialis Lamarck and Mytilus californianus Conrad, on the Pacific coast of Baja California NW Mexico. This is the first record of this turbellarian for bivalves from the Pacific coast of North America. In M. galloprovincialis from an exposed rocky shore, prevalence ranged from 10 to 87% and mean number of turbellarians per infested mussel was 1.9; in a culture area prevalence ranged from 57 to 100% and the mean number of turbellarians per infested mussel was 7.4. In the protected and polluted areas U. cyprinae was scarce or absent, prevalence ranging from 0 to 15% and the mean number of turbellarian per infested mussel being 0.07. The prevalence and the mean number of turbellarians per M. californianus in the exposed rocky shore ranged from 20 to 100% and 5.1, respectively. There were more worms in the larger mussels. Demibranches of M. galloprovincialis and M. californianus may be injured by the presence of turbellarians. An infiltration of hemocyte cells around the turbellarians was observed in both species and the blood sinuses in the infected area were engorged. Recorded damage was not related to a negative effect on the condition index of mussels. Copyright 1998 Academic Press.

  7. Tropical-Depression Precipitation In Southwestern North America: An Isotope Record From Arizona, And Isotope Signatures In Baja California Groundwater

    NASA Astrophysics Data System (ADS)

    Eastoe, C. J.; Hess, G.; Mahieux, S.

    2011-12-01

    A 30-year data set of O and H isotopes in individual precipitation events in Tucson, Arizona, includes entries identified with rainfall associated with tropical depressions, which occasionally pass through southern Arizona. Tropical-depression rain events yielding > 7 mm have a δ18O range -9 to -16 per mil, compared to volume-weighted average summer rainfall with δ18O = -6 per mil, a set of isotope effects similar to those observed in south Texas. The isotope signature of tropical-depression rain is present in groundwater of central and southern Baja California (BC), where summer and fall rain make up at least 50% of annual precipitation. Tritium-bearing groundwater at Todos los Santos (southern BC) has a δ18O range of -8 to -11 per mil and d-parameters near 10. Altitude effects related to adjacent, 1800 m mountains do not explain the isotope data. Groundwater of similar isotope character is present near the Tres Virgenes geothermal field (central BC), but not at Santo Tomas (northern BC). Large deuterium excess (d > 15) is not observed in any of the data.

  8. Vegetation history along the eastern, desert escarpment of the Sierra San Pedro Mártir, Baja California, Mexico

    USGS Publications Warehouse

    Holmgren, Camille A.; Betancourt, Julio L.; Rylander, Kate A.

    2011-01-01

    Plant macrofossils from 38 packrat middens spanning the last ~ 33,000 cal yr BP record vegetation between ~ 650 and 900 m elevation along the eastern escarpment of the Sierra San Pedro Mártir, northern Baja California. The middens span most of the Holocene, with a gap between ~ 4600 and 1800 cal yr BP, but coverage in the Pleistocene is uneven with a larger hiatus between 23,100 and 14,400 cal yr BP. The midden flora is relatively stable from the Pleistocene to Holocene. Exceptions include Pinus californiarum, Juniperus californica and other chaparral elements that were most abundant > 23,100 cal yr BP and declined after 14,400 cal yr BP. Despite being near the chaparral/woodland-desertscrub ecotone during glacial times, the midden assemblages reflect none of the climatic reversals evident in the glacial or marine record, and this is corroborated by a nearby semi-continuous pollen stratigraphy from lake sediments. Regular appearance of C4 grasses and summer-flowering annuals since 13,600 cal yr BP indicates occurrence of summer rainfall equivalent to modern (JAS average of ~ 80–90 mm). This casts doubt on the claim, based on temperature proxies from marine sediments in the Guaymas Basin, that monsoonal development in the northern Gulf and Arizona was delayed until after 6200 cal yr BP.

  9. Biological influences on modern sulfates: Textures and composition of gypsum deposits from Guerrero Negro, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Vogel, Marilyn B.; Des Marais, David J.; Parenteau, Mary N.; Jahnke, Linda L.; Turk, Kendra A.; Kubo, Michael D. Y.

    2010-01-01

    Gypsum (CaSO 4·2H 2O) deposits from a range of sedimentary environments at Guerrero Negro, Baja California Sur, Mexico were investigated for microscale texture and composition in order to differentiate features formed under substantial microbial influence from those for which microbial effects were relatively minor or absent. Gypsum deposits were classified according to their sedimentary environment, textures, crystal habit, brine composition and other geochemical factors. The environments studied included subaqueous sediments in anchialine pools and in solar salterns, as well as subsurface sediments of mudflats and saltpans. Gypsum that developed in the apparent absence of biofilms included crystals precipitated in the water column and subsedimentary discs that precipitated from phreatic brines. Subsedimentary gypsum developed in sabkha environments exhibited a sinuous microtexture and poikilitically enclosed detrital particles. Water column precipitates had euhedral prismatic habits and extensive penetrative twinning. Gypsum deposits influenced by biofilms included bottom nucleated crusts and gypsolites developing in anchialine pools and saltern ponds. Gypsum precipitating within benthic biofilms, and in biofilms within subaerial sediment surfaces provided compelling evidence of biological influences on crystal textures and habits. This evidence included irregular, high relief surface textures, accessory minerals (S°, Ca-carbonate, Sr/Ca-sulfate and Mg-hydroxide) and distinctive crystal habits such as equant forms and crystals having distorted prism faces.

  10. Potential toxicity of chemical elements in beach sediments near Santa Rosalía copper mine, Baja California Peninsula, Mexico

    NASA Astrophysics Data System (ADS)

    Jonathan, M. P.; Shumilin, E.; Rodríguez-Figueroa, G. M.; Rodriguez-Espinosa, P. F.; Sujitha, S. B.

    2016-10-01

    A total of 17 beach sediment samples were analyzed for the determination of thirty-one chemical elements to generate a geochemical data set from the Santa Rosalía mining area in the State of Baja California Sur (south), Mexico. Results indicate that the beach sediments were enriched in Cu, Zn, Co, Pb, Cd (3856, 2599, 635, 236, 240 mg kg-1, respectively) and in Mn (2.01%) due to a century of mining and smelting activities. Comparison of these concentration with ecotoxicological sediment quality criteria (ERL, ERM, LEL, SEL) indicated the values of As, Cd, Co, Cr, Cu, Ni, Pb, Sr, Zn and Mn were higher than the permissible limits. Average values of the calculated geoaccumulation index (Igeo) suggest that the key elements such as Mn, Ba, Cd, Co, Mo, Pb, Sr, Zn are categorized in class 4 to 6 encompassing the strongly polluted to extremely polluted groups. The association and enrichment of the above elements are also well supported statistically (factor analysis) which points to the role of Fe-Mn oxides as the main scavengers for retaining these chemical elements.

  11. Screening of extracts of algae from Baja California sur, Mexico as reversers of the antibiotic resistance of some pathogenic bacteria.

    PubMed

    Muñoz-Ochoa, M; Murillo-Alvarez, J I; Zermeño-Cervantes, L A; Martínez-Diaz, S; Rodríguez-Riosmena, R

    2010-09-01

    Sixty ethanol extracts of marine flora of Baja California Sur (Mexico) were screened to evaluate the reversing effect of the bacterial resistance to antibiotics in combination with a sublethal concentration of ampicillin or erythromycin. The activity was assayed by using a modification of the classical agar-diffusion method against 3 resistant, pathogenic bacteria; Escherichia coil (ATCC BAA196), Staphylococcus aureus (ATCC BAA42), and Streptococcus pyogenes (ATCC BAA946). From the 60 ethanolic extracts, 12 (20%) of them in combination with ampicillin were able to reverse the resistance of Staphylococcus aureus and 8 (13%) with erythromycin yielded the same reversal with Streptococcus pyogenes. An extract from Sargassum horridum was the only one that reversed the resistance to antibiotics against both Staphylococcus aureus and Streptococcus pyogenes. Our findings suggest that some algae may be source of compounds with the potential to reverse the antibiotic resistance of some bacteria. In addition, of the assayed extracts, 35 (57%) showed inhibitory activity against Staphylococcus aureus, 48 (78%) were active against Streptococcus pyogenes, but none was active against Escherichia coil. The most active extracts were from Laurencia spp., Gelidium robustum, Chnoospora implexa, Padina mexicana, Gracilaria subsecundata, and Dictyopteris undulata.

  12. Vegetation history along the eastern, desert escarpment of the Sierra San Pedro Mártir, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Holmgren, Camille A.; Betancourt, Julio L.; Rylander, Kate A.

    2011-05-01

    Plant macrofossils from 38 packrat middens spanning the last ~ 33,000 cal yr BP record vegetation between ~ 650 and 900 m elevation along the eastern escarpment of the Sierra San Pedro Mártir, northern Baja California. The middens span most of the Holocene, with a gap between ~ 4600 and 1800 cal yr BP, but coverage in the Pleistocene is uneven with a larger hiatus between 23,100 and 14,400 cal yr BP. The midden flora is relatively stable from the Pleistocene to Holocene. Exceptions include Pinus californiarum, Juniperus californica and other chaparral elements that were most abundant > 23,100 cal yr BP and declined after 14,400 cal yr BP. Despite being near the chaparral/woodland-desertscrub ecotone during glacial times, the midden assemblages reflect none of the climatic reversals evident in the glacial or marine record, and this is corroborated by a nearby semi-continuous pollen stratigraphy from lake sediments. Regular appearance of C 4 grasses and summer-flowering annuals since 13,600 cal yr BP indicates occurrence of summer rainfall equivalent to modern (JAS average of ~ 80-90 mm). This casts doubt on the claim, based on temperature proxies from marine sediments in the Guaymas Basin, that monsoonal development in the northern Gulf and Arizona was delayed until after 6200 cal yr BP.

  13. Marine diet and tobacco exposure affects mercury concentrations in pregnant women (I) from Baja California Sur, Mexico.

    PubMed

    Gaxiola-Robles, Ramón; Bentzen, Rebecca; Zenteno-Savín, Tania; Labrada-Martagón, Vanessa; Castellini, J Margaret; Celis, Alfredo; O'Hara, Todd; Celina Méndez-Rodríguez, Lía

    2014-01-01

    Seafood provides essential polyunsaturated fatty acids (PUFA) and other nutrients to pregnant women and their fetus(es) while a diet rich in finfish can be a major pathway of monomethyl mercury (MeHg(+)) exposure. We measured total mercury concentration ([THg]) in hair samples provided by 75 women in Baja California Sur (BCS) to assess its relationship with age, parity, tobacco smoke exposure, and diet based on survey methodologies. Generalized linear models (GLM) were used to explain the possible association of the different variables with [THg] in hair. Median [THg] in hair was 1.52 µgg(-1), ranging from 0.12 to 24.19 µgg(-1) and varied significantly by segment. Approximately 72% (54/75) of those evaluated exceed 1 µgg(-1) [THg] and 8% (6/75) exceed 5 µgg(-1) [THg] in hair. Although frequency of fish consumption contributed significantly to explaining hair [THg], fish consumption only explained 43% of [THg] in a GLM incorporating tobacco exposure and body mass index. This study establishes possible relationships among multiple potential sources of exposure and other factors related to [THg] in hair of women in the prenatal period. A more detailed examination of other sources of exposure and factors contributing to [THg] is warranted.

  14. [Cholelithiasis during pregnancy and postpartum: prevalence, presentation and consequences in a Referral Hospital in Baja California Sur].

    PubMed

    Álvarez-Villaseñor, Andrea Socorro; Mascareño-Franco, Héctor Luis; Agundez-Meza, José Juan; Cardoza-Macías, Francisco; Fuentes-Orozco, Clotilde; Rendón-Félix, Jorge; Chávez-Tostado, Mariana; Irusteta-Jiménez, Leire; García-Rentería, Jesús; Contreras-Hernández, Guadalupe Ivette; González-Ojeda, Alejandro

    Pregnancy and the postpartum period are risk factors for developing biliary sludge, gallstones, and any of their complications. To determine the prevalence, presentation, and consequences of cholestasis during pregnancy and postpartum in a referral hospital of Baja California Sur. This was a retrospective, observational study that enrolled pregnant or postpartum patients diagnosed with gallstones with any presentation. 137 patients were included, with 22 ± 4 years of age; 33 were pregnant and 104 in the postpartum period. Only 14% of the group had a history of cholelithiasis, and overweight/obesity was observed in 66.7 and 66.3% of pregnant and postpartum patients, respectively (p = 0.94). Of pregnant patients, 33.3% presented with acute cholecystitis, a condition observed in 16.3% of the postpartum patients (p = 0.04). Pancreatitis and choledocholithiasis were slightly more common in pregnant women (21.23% vs. 19.2%; p = 0.56). There was no maternal mortality and one case of spontaneous abortion was exclusively observed. It is a priority to diagnose and monitor cholelithiasis in pregnant women because the acute cases observed occurred more frequently, but choledocholithiasis and pancreatitis occurred similarly in both groups.

  15. Drug-scene familiarity and exposure to gang violence among residents in a rural farming community in Baja California, Mexico

    PubMed Central

    Volkmann, Tyson; Fraga, Miguel A.; Brodine, Stephanie K.; Iñiguez-Stevens, Esmeralda; Cepeda, Alice; Elder, John P.; Garfein, Richard S.

    2012-01-01

    We examined drug-scene familiarity and exposure to gang violence among residents of a migrant farming community in rural Baja California, Mexico. In October 2010, 164 members of a single colonia (community) underwent an interviewer-administered survey to assess ‘exposure to gang violence’ and ‘drug-scene familiarity’, as well as other health indicators. Logistic regression was used to identify correlates of exposure to gang violence. Overall, 20% of participants were male, the median age was 27 years, 24% spoke an indigenous language, 42% reported exposure to gang violence, and 39% reported drug-scene familiarity. Factors independently associated with exposure to gang violence included being younger (AOR=0.80 per 5-year increase, 95% CI=0.67–0.96), living in the community longer (AOR=1.47 per 5-year increase, 95% CI=1.11–1.72), higher educational attainment (AOR=1.70 per 5-year increase, 95% CI=1.07–1.12), and drug-scene familiarity (AOR=5.10, 95%CI=2.39–10.89). Exposure to gang violence was very common in this community and was associated with drug-scene familiarity, suggesting a close relationship between drugs and gang violence in this rural community. In a region characterised by mass migration from poorer parts of Mexico, where drugs and gangs have not been previously reported, emerging social harms may affect these communities unless interventions are implemented. PMID:23072623

  16. Annual variation of biomass and photosynthesis in Zostera marina L. along the Pacific Coast of Baja California, Mexico

    USGS Publications Warehouse

    Cabello-Pasini, Alejandro; Munoz-Salazar, R.; Ward, D.H.

    2003-01-01

    Density, biomass, morphology, phenology and photosynthetic characteristics of Zostera marina were related to continuous measurements of in situ irradiance, attenuation coefficient and temperature at three coastal lagoons in Baja California, Mexico. In situ irradiance was approximately two-fold lower at San Quintin Bay (SQ) than at Ojo de Liebre Lagoon (OL) and San Ignacio Lagoon (SI). As a consequence of the greater irradiance plants at OL and SI were established 1 m deeper within the water column than those at SQ. At SQ, there was a four-fold variation in biomass of Z. marina caused by changes on shoot length and not shoot density, while at OL and SI biomass and shoot length did not fluctuate significantly throughout the year. Reproductive shoot density reached maximum values concomitantly with the greater irradiance during spring-summer, however, the density was approximately three-fold greater at SQ than at the southern coastal lagoons. While irradiance levels were two-fold greater at the southern lagoons, in general, photosynthetic characteristics were similar among all three lagoons. The hours of light saturated photosynthesis, calculated from their photosynthetic characteristics and irradiance measurements, suggest that photosynthesis of shoots from OL and SI are saturated for more than 6 h per day throughout the year, while shoots from SQ are likely light limited during approximately 15% of the year. Consequently, an increase in attenuation coefficient values in the water column will likely decrease light availability to Z. marina plants at SQ, potentially decreasing their survival.

  17. Late cretaceous foraminifera, paleoenvironments, and paleoceanography of the rosario formation, San Antonio del Mar, Baja California, Mexico

    USGS Publications Warehouse

    Maestas, Y.; MacLeod, K.G.; Douglas, R.; Self-Trail, J.; Ward, P.D.

    2003-01-01

    The 315 m of Rosario Formation exposed at the San Antonio del Mar (SADM) section (Baja California, Mexico) contains moderately-to-well preserved benthic and planktic foraminifera, calcareous nannofossils, and molluscs. Nannofossils suggest most of the SADM section was deposited within a narrow interval of the late Campanian (CC21-CC22), whereas foraminifera and molluscs suggest a younger maximum age (younger than the Globotruncana ventricosa Zone) and allow deposition over a longer interval of time. Planktic foraminifera at SADM represent common Tethyan taxa. They are largely restricted to the lower and middle portions of the section and comprise 0-???40% of foraminiferal assemblages. Stable isotopic analyses of Rugoglobigerina rugosa yield ??18OV-PDB values from -2.27%, to -2.82%, corresponding to salinity-corrected paleotemperature estimates of 26-30??C for the Late Cretaceous eastern Pacific. These estimates are as warm as modern tropical temperatures and are similar to tropical paleotemperature estimates from ??18O analyses of exceptionally preserved Maastrichtian samples; however, they are considerably warmer than most tropical Campanian-Maastrichtian estimates. Benthic foraminifera indicate outer shelf paleodepths with a slight increase in depth or decrease in benthic oxygen levels in the upper parts of the interval studied. The change in the benthic assemblage corresponds to an ???1??? positive shift in benthic ??O18, suggesting a relationship between benthic assemblages and an inferred increase in the local intensity of upwelling.

  18. Geology, petrology and tectonic significance of the Mesozoic Paleoceanic terranes of the Vizcaino Peninsula, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Moore, T. E.

    The Viscaino Terrane, which is the most outboard terrane of mainland Baja California, can be divided into three principal terranes on the Vizcaino Peninsula. The structurally lowest is the disrupted composite Puerto Nuevo terrane which is represented by metamorphosed blocks in a serpentinite-matrix melange. The Viscaino Norte terrane structurally overlies the Puerto Nuevo terrane along a low-angle contact. To the south, the Vizcaino Sur terrane exposes a sequence consisting of ophiolite, tuffaceous chart and limestone of the San Hipolito Formation of Late Triassic age. Based on the petrologic, geochemical, and stratigraphic characteristics, the ophiolites of the Vizcaino Norte and Vizcaino Sur terranes are interpreted to have been formed in one or more marginal basin island arc systems during the Late Triassic whereas the ophiolitic rocks of the Puerto Nuevo terrane most likely formed at a midocean ridge. The subsequent pre-Upper Jurassic island arc deposits of the terranes are entirely volcanogenic and biogenic and contain no evidence of close proximity to a cratonal source. It is suggested that for as much as 80 my, the terranes were probably not associated with a continental margin as a fringing island arc, but instead represent allochthonous fragments of a paleogeographically complex paleo-Pacific Ocean.

  19. Vegetation history along the eastern, desert escarpment of the Sierra San Pedro Mártir, Baja California, Mexico

    USGS Publications Warehouse

    Holmgren, Camille A.; Betancourt, Julio L.; Rylander, Kate A.

    2011-01-01

    Plant macrofossils from 38 packrat middens spanning the last ~ 33,000 cal yr BP record vegetation between ~ 650 and 900 m elevation along the eastern escarpment of the Sierra San Pedro Mártir, northern Baja California. The middens span most of the Holocene, with a gap between ~ 4600 and 1800 cal yr BP, but coverage in the Pleistocene is uneven with a larger hiatus between 23,100 and 14,400 cal yr BP. The midden flora is relatively stable from the Pleistocene to Holocene. Exceptions include Pinus californiarum, Juniperus californica and other chaparral elements that were most abundant > 23,100 cal yr BP and declined after 14,400 cal yr BP. Despite being near the chaparral/woodland-desertscrub ecotone during glacial times, the midden assemblages reflect none of the climatic reversals evident in the glacial or marine record, and this is corroborated by a nearby semi-continuous pollen stratigraphy from lake sediments. Regular appearance of C4 grasses and summer-flowering annuals since 13,600 cal yr BP indicates occurrence of summer rainfall equivalent to modern (JAS average of ~ 80–90 mm). This casts doubt on the claim, based on temperature proxies from marine sediments in the Guaymas Basin, that monsoonal development in the northern Gulf and Arizona was delayed until after 6200 cal yr BP.

  20. Characterisation of an enamelled metallic object found in Guerrero Negro (Baja California) by PIXE and RBS techniques

    NASA Astrophysics Data System (ADS)

    Calvo del Castillo, H.; Ruvalcaba, J. L.; Calderón, T.; Salinas Nolasco, M. F.; Mejía, L. M.; Perdigón, K.

    2008-05-01

    The coast of Guerrero Negro (Baja California) has been known for a long time by archaeologists for its shipwrecks. Archaeologists are recovering objects that come from sunken Spanish galleons in the colonial period, and reach the American coast in the frontier of the USA with Mexico. An enamelled metallic object was found next to the beach in Guerrero Negro. We have analysed the piece with proton induced X-ray emission (PIXE) and Rutherford backscattering (RBS) in an attempt to establish whether the object could come from one of the colonial shipwrecks and to valuate its cleaning process. Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) have been also performed in three samples taken from the object in order to observe the heterogeneity of the material. The materials found revealed the presence of typical lead-glass enamels from with pigments such as cuprite (red), or lead-tin yellow used in colonial times. The metallic part consisted of brass. As for the cleaning process, the average efficiency considered as the weight% of chlorine removed, was of 83.4% for brass and 100% for enamels.

  1. Surgical treatment of a proximal diaphyseal tibial deformity associated with partial caudal and cranial cruciate ligament deficiency and patella baja.

    PubMed

    Vincenti, S; Knell, S; Pozzi, A

    2017-04-01

    Caudal cruciate ligament injury can be a complication following tibial plateau leveling osteotomy (TPLO) (Slocum und Slocum, 1993) especially if the post-operative Tibial Plateau Angle (TPA) is less than 5 degree. We describe a case of negative TPA associated with partial cranial and caudal ligament rupture treated with a center of rotation of angulation (CORA) based cranial tibial opening wedge osteotomy and tibial tuberosity transposition. A 13 kg, mixed breed dog was presented for right pelvic limb lameness. Radiographically a bilateral patella baja and a malformed tibia tuberosity along with a bilateral TPA of -8 degree were detected. Arthroscopically a partial rupture of the cranial and caudal cruciate ligaments were found. A cranial tibial opening wedge osteotomy of 23 degree and a fibular ostectomy were performed. The osteotomy was fixed with a 8 holes ALPS 9 (KYON, Switzerland) and a 3-holes 2.0mm UniLock plate (Synthes, Switzerland). Then a proximal tibial tuberosity transposition of 10mm was performed and fixed with a pin and tension band construct. The postoperative TPA was 15 degree. The radiographic controls at 6, 10 weeks, 6 months and 1 year after surgery revealed an unchanged position of the implants and progressive healing of the osteotomies. At the 6 and 12 months recheck evaluation the dog had no evidence of lameness or stifle pain and radiographs revealed complete healing of the osteotomy site and no implant failure. The diaphyseal CORA based osteotomy allowed accurate correction of a proximal tibial deformity associated with negative TPA.

  2. Quality assessment of reclaimed water for its possible use for crop irrigation and aquifer recharge in Ensenada, Baja California, Mexico.

    PubMed

    Mendoza-Espinosa, L; Orozco-Borbón, M Victoria; Silva-Nava, Patricia

    2004-01-01

    The city of Ensenada, Baja California, has three wastewater treatment plants and is one of the few cities in Mexico that treats all the wastewater that it generates. The largest wastewater treatment plant, called El Naranjo, treats on average 316 liters per second and complies with even the most stringent Mexican standards although a stricter control has to be achieved in order to avoid environmental and health problems At the moment, only 2% of the treated wastewater is used for the irrigation of sports fields and public landscape. The reclaimed water could be reused for the irrigation of crops for non-human consumption or ornamental products and/or for aquifer recharge. For reuse practices, two facts must be considered: a) an important part of the valley's production is exported to the USA and b) 30% of the city of Ensenada's water supply is obtained from the Maneadero aquifer. There is currently no Mexican legislation to stipulate adequate standards for aquifer recharge and decisions should be based on legislation from other places. Therefore, at the moment there is still a lack of technical and scientific elements to be able to make the best decision about the reuse of the wastewater.

  3. Geochemistry of Dissolved Trace Metals in the Waters of Bahia Magdalena, Baja California Sur, Pacific Coast, Mexico

    NASA Astrophysics Data System (ADS)

    Suresh Babu, S.

    2016-12-01

    Forty two samples were acquired from the surface and bottom water profiles along 5 transects spread over Bahia Magdalena lagoon, Baja California Sur to assess the behavior of trace metals in a high influenced upwelling region on the Pacific coast. To elaborate the fate of metals, also the physico-chemical parameters (pH, temperature, salinity, conductivity, dissolved oxygen). Determination of the concentrations of trace metals (Fe, Mn, Cr, Cu, Co, Pb, Ni, Zn, Cd As, Hg) were measured using Atomic absorption spectrometry. The results demonstrated high values of As, Ni and Co which is attributed to the local geology and phosphate deposits. Low values of Fe and Mn are attested to the oxic conditions of the lagoon which are responsible for the oxidation of Fe and Mn. The region witnesses raised temperatures (28.92ºC) and salinities of 35.2 PSU for its arid climatic conditions and high rates of evaporation. In general, the region presented minor quantities of dissolved trace metals due to dispersion and high intense interaction with the open sea. The results were also compared with other studies to understand the enrichment pattern in this side of the pacific coast which experiences various geothermal activities and upwelling phenomenon.

  4. Infection rates in Dipetalogaster maximus (Reduviidae: Triatominae) by Trypanosoma cruzi in the Cape Region, Baja California Sur, México.

    PubMed

    Jiménez, María-Luisa; Llinas, Jorge; Palacios, Carlos

    2003-01-01

    Infection rates of Trypanosoma cruzi Chagas (in the blood-sucking bug Dipetalogaster maximus [Uhler]) were determined from specimens collected at 12 localities in the Cape Region of Baja California Sur, Mexico. Eight collection sites were located in the tropical dry forest, two in desert shrub, and two in the ecotone between these two communities. Of the 245 D. maximus collected, 65% were first and second instar nymphs; 32.6% were third, fourth, and fifth instar nymphs; and 2.4% were adults. The highest proportion of specimens came from El Fandango (30%) and San Bartolo (23%) canyons and La Cruz hill (12%) in the mountain slopes facing the Gulf of California. In feces from individual bugs analyzed for T. cruzi, we found an overall infection rate of 7.0%. Infection rates increased from 4.1% in second instars to 42.% in fifth instars. High infection rates were found in bugs collected from La Poza (38.4%), El Gato (27.2%), and El Pedregoso (25%) hills; low infection rates were found in specimens from La Cruz hill and San Bartolo canyon. Specimens from some collection sites were not infected with T. cruzi.

  5. Fluoride, nitrate and water hardness in groundwater supplied to the rural communities of Ensenada County, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Daesslé, L. W.; Ruiz-Montoya, L.; Tobschall, H. J.; Chandrajith, R.; Camacho-Ibar, V. F.; Mendoza-Espinosa, L. G.; Quintanilla-Montoya, A. L.; Lugo-Ibarra, K. C.

    2009-07-01

    The hydrogeochemistry of 26 wells belonging to ten different aquifers in the county of Ensenada, Baja California, is studied. These wells are all used to supply the rural communities in the region, which comprise ~37,000 inhabitants, excluding the city of Ensenada. High total dissolved solids (TDS) concentrations (maximum 7.35 g l-1) indicate that salt is a ubiquitous contaminant in the aquifers due to seawater intrusion. The aquifers that support extensive agriculture activities (Maneadero, San Quintín, San Simón and El Rosario) are characterized by higher N-NO3 concentrations (maximum 20 mg l-1) derived from fertilizers. Fluoride concentrations exceed the 1.5 mg l-1 Mexican official limit in only four wells. The enrichments of F- in the southern aquifers are thought to be associated to water-rock interactions controlled mainly by Na-Ca equilibrium reactions with fluorite, as suggested from high dissolved Na concentrations in these waters. In the northern aquifer of Maneadero, no enrichment of Na is found and a geothermal source for F- is likely. Water is hard to moderately hard, with Ca/Mg ratios >1. Although drinking water directly from the tap is not a common practice in these localities, most sources have concentrations of major ions and TDS that exceed the Mexican official limits.

  6. Drug-scene familiarity and exposure to gang violence among residents in a rural farming community in Baja California, Mexico.

    PubMed

    Volkmann, Tyson; Fraga, Miguel A; Brodine, Stephanie K; Iñiguez-Stevens, Esmeralda; Cepeda, Alice; Elder, John P; Garfein, Richard S; Viidai Team

    2013-01-01

    We examined drug-scene familiarity and exposure to gang violence among residents of a migrant farming community in rural Baja California, Mexico. In October 2010, 164 members of a single colonia (community) underwent an interviewer-administered survey to assess 'exposure to gang violence' and 'drug-scene familiarity', as well as other health indicators. Logistic regression was used to identify correlates of exposure to gang violence. Overall, 20% of participants were male, the median age was 27 years, 24% spoke an indigenous language, 42% reported exposure to gang violence and 39% reported drug-scene familiarity. Factors independently associated with exposure to gang violence included being younger (adjusted odds ratio [AOR] =0.80 per 5-year increase, 95% confidence interval [CI]=0.67-0.96), living in the community longer (AOR=1.47 per 5-year increase, 95% CI=1.11-1.72), higher educational attainment (AOR=1.70 per 5-year increase, 95% CI=1.07-1.12) and drug-scene familiarity (AOR=5.10, 95% CI=2.39-10.89). Exposure to gang violence was very common in this community and was associated with drug-scene familiarity, suggesting a close relationship between drugs and gang violence in this rural community. In a region characterised by mass migration from poorer parts of Mexico, where drugs and gangs have not been previously reported, emerging social harms may affect these communities unless interventions are implemented.

  7. Baseline heavy metals and metalloid values in blood of loggerhead turtles (Caretta caretta) from Baja California Sur, Mexico.

    PubMed

    Ley-Quiñónez, C; Zavala-Norzagaray, A A; Espinosa-Carreón, T L; Peckham, H; Marquez-Herrera, C; Campos-Villegas, L; Aguirre, A A

    2011-09-01

    Environmental pollution due to heavy metals is having an increased impact on marine wildlife accentuated by anthropogenic changes in the planet including overfishing, agricultural runoff and marine emerging infectious diseases. Sea turtles are considered sentinels of ecological health in marine ecosystems. The objective of this study was to determine baseline concentrations of zinc, cadmium, copper, nickel, selenium, manganese, mercury and lead in blood of 22 clinically healthy, loggerhead turtles (Caretta caretta), captured for several reasons in Puerto López Mateos, Baja California Sur, Mexico. Zinc was the most prevalent metal in blood (41.89 μg g⁻¹), followed by Selenium (10.92 μg g⁻¹). The mean concentration of toxic metal Cadmium was 6.12 μg g⁻¹ and 1.01μg g⁻¹ respectively. Mean concentrations of metals followed this pattern: Zn>Se>Ni>Cu>Mn>Cd>Pb and Hg. We can conclude that blood is an excellent tissue to measure in relatively non-invasive way baseline values of heavy metals in Caretta caretta.

  8. A numerical modeling analysis of the phytoplankton and nutrients dynamics for Todos Santos Bay and northwestern Baja California

    NASA Astrophysics Data System (ADS)

    Cruz Rico, J. E., Sr.; Rivas, D.

    2015-12-01

    A tridimensional physical-biological numerical model is implemented for the Todos Santos Bay and the northwest of Baja California to investigate the mechanics and ecological processes associated with the regional plankton dynamics. An NPZD (Nitrate, Phytoplankton, Zooplankton, and Detritus) ecosystem simple model is used to describe the distribution and evolution of the lower trophic levels in the area of study. The model adequately reproduces the spatial distribution of the concentration of chlorophyll for the different seasons of the year. In general, the distribution of the subsurface chlorophyll maximum (SCM) depends primarily on the seasonal circulation patterns, the total solar irradiance, and the vertical flux of nutrients. Interannual variability shows two extreme years in the analyzed period: 2006 and 2007. Year 2006 was an anomalous warm year, with a weak upwelling activity and low chlorophyll concentrations compared to year 2011. These anomalies are related to the activity of the Pacific Decadal Oscillation, the El Niño+3, and the regional Outgoing Longwave Radiation. Thus, in spite of the simplicity of the NPZD model, both temporal and spatial patterns of distribution of chlorophyll and nutrients are generally reproduced.

  9. Simulation of flow in the upper North Coast Limestone Aquifer, Manati-Vega Baja area, Puerto Rico

    USGS Publications Warehouse

    Cherry, Gregory S.

    2001-01-01

    A two-dimensional computer ground-water model was constructed of the Manati-Vega Baja area to improve the understanding of the unconfined upper aquifer within the North Coast Province of Puerto Rico. The modeled area covers approximately 79 square miles within the municipios of Manati and Vega Baja and small portions of Vega Alta and Barceloneta. Steady-state two-dimensional ground-water simulations were correlated to conditions prior to construction of the Laguna Tortuguero outlet channel in 1940 and calibrated to the observed potentiometric surface in March 1995. At the regional scale, the unconfined Upper North Coast Limestone aquifer is a diffuse ground-water flow system through the Aguada and Aymamon limestone units. The calibrated model input parameters for aquifer recharge varied from 2 inches per year in coastal areas to 18 inches per year in the upland areas south of Manati and Vega Baja. The calibrated transmissivity values ranged from less than 500 feet squared per day in the upland areas near the southern boundary to 70,000 feet squared per day in the areas west of Vega Baja. Increased ground-water withdrawals from 1.0 cubic foot per second for 1940 conditions to 26.3 cubic feet per second in 1995, has reduced the natural ground-water discharge to springs and wetland areas, and induced additional recharge from the rivers. The most important regional drainage feature is Laguna Tortuguero, which is the major ground-water discharge body for the upper aquifer, and has a drainage area of approximately 17 square miles. The discharge to the sea from Laguna Tortuguero through the outlet channel has been measured on a bi-monthly basis since 1974. The outflow represents a combination of ground- and surface-water discharge over the drainage area. Hydrologic conditions, prior to construction of the Laguna Tortuguero outlet channel in 1943, can be considered natural conditions with minimal ground-water pumpage (1.0 cubic foot per second), and heads in the lagoon

  10. The shoaling of nutrient-enriched subsurface waters as a mechanism to sustain primary productivity off Central Baja California during El Niño winters

    NASA Astrophysics Data System (ADS)

    Ladah, Lydia B.

    2003-08-01

    Using CalCOFI data for coastal shallow stations (above 100 m depth), higher than expected nitrate concentrations were detected in near-surface high-temperature waters off of Central Baja California during some El Niño winters. Though recent data are not available for Central Baja California, past El Niño data, though limited, showed nitrate concentrations above 16 μM at temperatures above 16 °C, and nitrate concentrations between 1 and 2 μM at 19 °C, while the previously established relationship of temperature and nitrate for California Current waters predicts nitrate depletion above 14 or 15 °C. The anomalous, high temperature-high nitrate enrichment events documented in Central Baja California were detected as shallow as 9 m and as deep as 73 m, were associated with low-oxygen (between 2 and 4 ml/l) and high-salinity (between 33.8 and 34.3 psu) waters, and occurred during the winter months of an El Niño year. Using recent data for San Diego, CA, similar but weaker enrichment events were detected for the El Niño winter of 1997-1998. The periodic shoaling of a subsurface subtropical water mass of high temperature, high salinity, low oxygen and high nutrients during some El Niño winters is proposed to cause periodic enrichment and to maintain productivity during warming events in this area. Enrichment events were not detected off Ensenada, in Northern Baja California, possibly due to the amplification of the onshore flow during El Niño there, or due to the Ensenada front. The proposed mechanism of periodic enrichment of nutrient-depleted surface waters during some El Niño winters by subsurface waters from the California Undercurrent may explain the following: (1) survival of giant kelp forests at their southern limit in Central Baja California documented during past El Niño events in warm waters, (2) the rapid recovery and high carrying capacity of giant kelp documented after the mass disappearance during El Niño 1997-1998, and (3) the increase in the

  11. Testing Pixel Translation Digital Elevation Models to Reconstruct Slip Histories: An Example from the Agua Blanca Fault, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Wilson, J.; Wetmore, P. H.; Malservisi, R.; Ferwerda, B. P.; Teran, O.

    2012-12-01

    We use recently collected slip vector and total offset data from the Agua Blanca fault (ABF) to constrain a pixel translation digital elevation model (DEM) to reconstruct the slip history of this fault. This model was constructed using a Perl script that reads a DEM file (Easting, Northing, Elevation) and a configuration file with coordinates that define the boundary of each fault segment. A pixel translation vector is defined as a magnitude of lateral offset in an azimuthal direction. The program translates pixels north of the fault and prints their pre-faulting position to a new DEM file that can be gridded and displayed. This analysis, where multiple DEMs are created with different translation vectors, allows us to identify areas of transtension or transpression while seeing the topographic expression in these areas. The benefit of this technique, in contrast to a simple block model, is that the DEM gives us a valuable graphic which can be used to pose new research questions. We have found that many topographic features correlate across the fault, i.e. valleys and ridges, which likely have implications for the age of the ABF, long term landscape evolution rates, and potentially provide conformation for total slip assessments The ABF of northern Baja California, Mexico is an active, dextral strike slip fault that transfers Pacific-North American plate boundary strain out of the Gulf of California and around the "Big Bend" of the San Andreas Fault. Total displacement on the ABF in the central and eastern parts of the fault is 10 +/- 2 km based on offset Early-Cretaceous features such as terrane boundaries and intrusive bodies (plutons and dike swarms). Where the fault bifurcates to the west, the northern strand (northern Agua Blanca fault or NABF) is constrained to 7 +/- 1 km. We have not yet identified piercing points on the southern strand, the Santo Tomas fault (STF), but displacement is inferred to be ~4 km assuming that the sum of slip on the NABF and STF is

  12. Slab-tearing following ridge-trench collision: Evidence from Miocene volcanism in Baja California, México

    NASA Astrophysics Data System (ADS)

    Pallares, Carlos; Maury, René C.; Bellon, Hervé; Royer, Jean-Yves; Calmus, Thierry; Aguillón-Robles, Alfredo; Cotten, Joseph; Benoit, Mathieu; Michaud, François; Bourgois, Jacques

    2007-03-01

    Neogene magmatic activity in Central Baja California underwent a major change at ca. 12.5 Ma, when the Pacific-Farallon active oceanic ridge collided with the trench east of Vizcaíno Peninsula. The calc-alkaline magmatism which built the Comondú volcanic arc vanished and was replaced by unusual volcanic associations, which were erupted within six Late Miocene to Quaternary volcanic fields (Jaraguay, San Borja, San Ignacio, Santa Rosalía, Santa Clara, La Purísima), delineating a 600 km array along the Baja California Peninsula. New fieldwork, K-Ar datings and geochemical analyses on Jaraguay and San Borja lavas, combined with previous data, allow us to show that these associations include: (1) adakites emplaced between 12.5 and 8.2 Ma in the Santa Clara, Santa Rosalía and Jaraguay volcanic fields; (2) niobium-enriched basalts (NEB) in Santa Clara and Santa Rosalía (11.2 to 7.4 Ma); (3) tholeiitic basalts and basaltic andesites (11.3 to 7.2 Ma) displaying a very weak subduction imprint in La Purísima and San Ignacio; (4) alkali trachybasalts in Mesas San Carlos and Santa Catarina, northwest of Jaraguay (9.3 to 7.5 Ma), and finally (5) basalts and associated magnesian basaltic andesites and andesites. Locally referred to as "bajaites", the latter lavas display very specific geochemical characteristics, including very high Sr and Ba contents. They were emplaced in all the above-mentioned volcanic fields between 14.6 and 5.3 Ma. The origin of these Late Miocene volcanics has been considered linked either to the opening of an asthenospheric window through which they ascended (tholeiites and alkali trachybasalts), or to the melting of its edges due to thermal erosion (adakites) and the subsequent reaction between adakitic melts and the supraslab mantle (NEB and "bajaites"). However, the identification of the remnants of the Pacific-Farallon fossil ridge south of Vizcaíno Peninsula indicates that active ridge subduction was not responsible for the opening of the

  13. Geochemistry of Cenezoic volcanic rocks, Baja California, Mexico: Implications for the petrogenesis of post-subduction magmas

    NASA Astrophysics Data System (ADS)

    Saunders, A. D.; Rogers, G.; Marriner, G. F.; Terrell, D. J.; Verma, S. P.

    1987-06-01

    Late Cenozoic volcanism in Baja California records the effects of cessation of subduction at a previously convergent, plate margin. Prior to 12.5 m.y., when subduction along the margin of Baja ceased, the predominant volcanic activity had a calc-alkaline signature, ranging in composition from basalt to rhyolite. Acidic pyroclastic activity was common, and possibly represented the westermost, distal edge of the Sierra Madre Occidental province. After 12.5 m.y., however, the style and composition of the magmatic products changed dramatically. The dominant rock type within the Jaraguay and San Borja volcanic fields is a magnesian andesite, with up to 8% MgO at 57% SiO 2, low Fe/Mg ratios, and high Na/K ratios. These rocks have unusual trace-element characteristics, with high abundances of Sr (up to 3000 ppm), low contents of Rb; K/Rb ratios are very high (usually over 1000, and up to 2500), and Rb/Sr ratios are low (less than 0.01). Furthermore, La n/Yb n ratios are high, consistent with derivation from a mantle source with fractionated REE patterns. 87Sr/ 86Sr ratios are less than 0.7048, and usually less than 0.7040, whereas the pre-12.5 m.y. lavas have 87Sr/ 86Sr ratios between 0.7038 and 0.7063. We have previously termed these rocks bajaites, in order to distinguish them from other magnesian andesites. Bajaites also occur in southernmost Chile and the Aleutian Islands, areas which also have histories of attempted or successful ridge subduction. It is proposed that the bajaite series is produced during the unusual physico-chemical conditions operating during the subduction of young oceanic lithosphere, or subduction of a spreading centre. During normal subduction, the oceanic crust dehydrates, releasing volatiles (water, Rb and other large-ion lithophile elements) into the overlying wedge. Subduction of younger crust will result in a progressive decrease, and eventual cessation of the transfer of volatiles when subduction stops. Thermal rebound of the mantle may

  14. New insights into North America-Pacific Plate boundary deformation from Lake Tahoe, Salton Sea and southern Baja California

    NASA Astrophysics Data System (ADS)

    Brothers, Daniel Stephen

    three offshore faults are synchronous with Colorado River diversions into the basin. The final study was used coincident wide-angle seismic refraction and multichannel seismic reflection surveys that spanned the width of the of the southern Baja California (BC) Peninsula. The data provide insight into the spatial and temporal evolution of the BC microplate capture by the Pacific Plate. Seismic reflection profiles constrain the upper crustal structure and deformation history along fault zone on the western Baja margin and in the Gulf of California. Stratal divergence in two transtensional basins along the Magdalena Shelf records the onset of extension across the Tosco-Abreojos and Santa Margarita faults. We define an upper bound of 12 Ma on the age of the pre-rift sediments and an age of ˜8 Ma for the onset of extension. Tomographic imaging reveals a very heterogeneous upper crust and a narrow, high velocity zone that extends ˜40 km east of the paleotrench and is interpreted to be remnant oceanic crust.

  15. Candida species diversity and antifungal susceptibility patterns in oral samples of HIV/AIDS patients in Baja California, Mexico.

    PubMed

    Clark-Ordóñez, Isadora; Callejas-Negrete, Olga A; Aréchiga-Carvajal, Elva T; Mouriño-Pérez, Rosa R

    2017-04-01

    Candidiasis is the most common opportunistic fungal infection in HIV patients. The aims of this study were to identify the prevalence of carriers of Candida, Candida species diversity, and in vitro susceptibility to antifungal drugs. In 297 HIV/AIDS patients in Baja California, Mexico, Candida strains were identified by molecular methods (PCR-RFLP) from isolates of oral rinses of patients in Tijuana, Mexicali, and Ensenada. 56.3% of patients were colonized or infected with Candida. In Tijuana, there was a significantly higher percentage of carriers (75.5%). Out of the 181 strains that were isolated, 71.8% were Candida albicans and 28.2% were non-albicans species. The most common non-albicans species was Candida tropicalis (12.2%), followed by Candida glabrata (8.3%), Candida parapsilosis (2.2%), Candida krusei (1.7%), and Candida guilliermondii (1.1%). Candida dubliniensis was not isolated. Two associated species were found in 11 patients. In Mexicali and Ensenada, there was a lower proportion of Candida carriers compared to other regions in Mexico and worldwide, however, in Tijuana, a border town with many peculiarities, a higher carrier rate was found. In this population, only a high viral load was associated with oral Candida carriers. Other factors such as gender, use of antiretroviral therapy, CD4+ T-lymphocyte levels, time since diagnosis, and alcohol/ tobacco consumption, were not associated with Candida carriers. © The Author 2016. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  16. K-Ar ages confirm Pliocene age for oldest Neogene marine strata near Loreto, Baja California Sur, Mexico

    SciTech Connect

    McLean, H.

    1987-05-01

    Beds of pumiceous tuff interbedded with mollusk-rich sedimentary rocks provide new age constraints on the timing of the late Neogene subsidence and marine transgression a few kilometers north of Loreto, Baja California Sur, Mexico. The lower part of the Neogene section consists of approximately 1500 m of early to middle Miocene nonmarine volcanic-derived sandstone, breccia, and porphyritic andesite and dacite lavas, called the Comondu Formation or Comondu Group by previous workers. The Miocene rocks are unconformably overlain by nearly 1000 m of predominantly marine sandstone, siltstone, conglomerate, coquina, and tuff of Pliocene age. This 1000-m section grades upward from unfossiliferous fanglomerate, sandstone, and pelitic red beds that are interpreted to be nonmarine into mollusk-rich marine strata; this sequence indicates that marine transgression occurred within the Pliocene section. Plagioclase and hornblende from three pumiceous tuff beds stratigraphically located near the base, middle, and top of the marine section yield K-Ar ages of 3.2, 1.9, and 1.8 Ma, respectively; these ages are similar to Pliocene ages indicated by reconnaissance studies of ostracods, diatoms, and foraminifers. The diatoms indicate open-ocean waters and the foraminifers indicate outer shelf depth. Ostracods, oysters, pectens, and other fossil bivalves seem to indicate a shallow-water embayment. Lateral distribution of nonmarine and marine facies suggests a paleoenvironment in which alluvial fans fed coarse debris into a series of coastal fan deltas. The Pliocene basin may have been a largely landlocked embayment similar to the modern Bahia Concepcion, located 70 km north of Loreto. Marine and volcanic rocks are assumed to be associated with the opening of the Gulf of California. If this assumption is correct, the beds near Loreto suggest that the opening occurred during the Pliocene.

  17. A 14,000 Year Foraminiferal Trace Metal Record of ENSO-Influenced Upwelling Near Southern Baja California

    NASA Astrophysics Data System (ADS)

    Marchitto, T. M.; Ortiz, J.; Carriquiry, J.; Levi, C.; van Geen, A.

    2005-12-01

    A number of numerical modeling studies predict that the early to mid Holocene tropical Pacific should have been characterized by more La Niña-like conditions than today, with generally more vigorous trade winds and a steeper zonal tilt of the thermocline. The primary driver of this change is orbital, but various models differ in the exact mechanisms and hence timing of the change. Existing paleoclimate records offer a sometimes contradictory picture of the Holocene development of the tropical Pacific. Additional high quality records could help to resolve the true pattern of change, including its timing, and thus constrain the important climate mechanisms at work. Here we present new data from a sediment core collected in Soledad Basin, which is located off of southern Baja California (25°N) and has an effective sill depth of 290 m. Sedimentation rates are relatively constant at about 1 m/kyr, bioturbation is negligible, and foraminiferal preservation is excellent. Today the primary productivity in this region is strongly impacted by ENSO: during springs following El Niño events, upwelled waters are anomalously warm and poor in nutrients because of the deepened thermocline and nutricline. The actual intensity of upwelling, controlled by local winds, is of much less importance. Hence records of planktonic foraminiferal paleotemperatures (Mg/Ca) and paleonutrients (Cd/Ca and Zn/Ca) should mainly reflect the depth of the regional thermocline and nutricline. Preliminary Globigerina bulloides measurements appear to follow an orbital pattern and suggest that conditions were most La Niña-like (cool temperatures and high nutrients) around 6 ka. We suggest that measurements on individual tests of G. bulloides and Globigerinoides ruber may help to constrain changes in interannual ENSO variability. We will also present data spanning the Younger Dryas oscillation to determine if millennial scale climate change is reflected in the depth of the thermocline and nutricline.

  18. Soledad Basin, Baja California: a Twin to Cariaco Basin for Monitoring the Eastern Tropical Pacific Today and the Past?

    NASA Astrophysics Data System (ADS)

    Carriquiry, J.; van Geen, A.; Levi, C.; Ortiz, J. D.; Zheng, Y.; Marchitto, T. M.; Dean, W. E.

    2004-12-01

    Soledad Basin, a semi-enclosed basin on the Pacific margin of southern Baja California at 25oN, is ideally located to document past variations of ocean/atmosphere interactions responding to the Pacific Decadal Oscillation (PDO) and the El Nino-Southern Oscillation (ENSO). This presentation focuses on the hydrography and geochemistry of the basin in the context of a potential monitoring program that could reach the scale of current activities in Cariaco Basin. Soledad Basin (sometimes referred to as Magdalena Basin or San Lazaro Basin) has been studied intermittently since the 1970's although detailed studies to exploit its paleoceanographic potential have started only recently. A very flat bottom with a maximum depth of 540 m was mapped with SeaBeam. A comparison of hydrographic profiles collected inside and outside the basin indicates a sill depth of 290 m. Bioturbation is currently inhibited within the basin primarily because of low oxygen concentration in adjacent source waters, rather than oxygen consumption within the basin as is the case for Cariaco and Santa Barbara Basins. Radiocarbon dating of planktonic foraminifera indicates a very high sedimentation rates of ~108 cm/kyr up through the end of the Bolling/Allerod 13 kyr ago (van Geen et al., Paleoceanography, v. 8, no. 4, 2003). A non-bioturbated section, characterized by sub-cm dark brown to black, coarse, mm- to cm-scale laminations rather than by mm-scale fine laminations, extends almost continuously from the top of a piston core to ~9 m depth, an interval dated at 10.0 ka. In addition, thin white mm-scale laminae composed almost entirely of coccoliths packed in faecal pellets extend to a depth of ~11 m (11.3 ka). A selection of promising results based on diffuse spectral reflectance records obtained at 1-cm resolution, planktonic Mg/Ca data, and the acccumulation of authigenic Mo will be presented.

  19. Boron and strontium isotope compositions of groundwater from the La Paz arid coastal aquifer, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Mahlknecht, Jürgen; Rosner, Martin; Meixner, Anette

    2016-04-01

    In groundwater studies boron and strontium isotopic compositions can be used to identify natural and anthropogenic sources as well as processes related to groundwater recharge, flow and mixing. The La Paz arid costal aquifer in Baja California Sur, Mexico, is the most important source of drinking and irrigation water for La Paz area and suffers from anthropogenic contamination and intensive exploitation of the aquifer causing seawater intrusion and general groundwater abatement. The relatively un-radiogenic 87Sr/86Sr isotope ratios of the La Paz groundwater range in a narrow field between 0.7054 and 0.7062. In contrast to strontium the boron isotope composition displays a large variability between +27 and +55 permil d11B. The relatively low 87Sr/86Sr ratios of the La Paz groundwater highlight a significant contribution of strontium derived from local terrestrial sediments and igneous rocks with known 87Sr/86Sr ratios between 0.705 and 0.7035. The large variability of d11B values indicate that multiple sources and processes determine the boron isotope composition of La Paz groundwater. Rainwater (high d11B), seawater (~+40 permil) due to seawater intrusions, wastewater (low to medium d11B) and boron derived from the local geology (low to medium d11B) explain most of the observed groundwater d11B variability. However, d11B values higher than modern seawater point to significant boron isotope fractionation by preferential absorption of 10B onto clay minerals during the evolution of some groundwater samples. Due to low boron concentrations in rainwater a significant contribution of 11B-rich rainwater (>+40 permil) on the La Paz groundwater is unlikely.

  20. Decreased Anemia Prevalence Among Women and Children in Rural Baja California, Mexico: A 6-Year Comparative Study.

    PubMed

    Moor, Molly A; Fraga, Miguel A; Garfein, Richard S; Harbertson, Judith; Rodriguez-Lainz, Alfonso; Rashidi, Hooman H; Elder, John P; Brodine, Stephanie K

    2016-08-01

    Anemia is a public health problem in Mexico. This study sought to determine the prevalence and correlates of anemia among women and children residing in a rural farming region of Baja California, Mexico. An existing partnership between universities, non-governmental organizations, and an underserved Mexican community was utilized to perform cross-sectional data collection in 2004-2005 (Wave 1) and in 2011-2012 (Wave 2) among women (15-49 years) and their children (6-59 months). All participants completed a survey and underwent anemia testing. Blood smears were obtained to identify etiology. Nutrition education interventions and clinical health evaluations were offered between waves. Participants included 201 women and 99 children in Wave 1, and 146 women and 77 children in Wave 2. Prevalence of anemia significantly decreased from 42.3 to 23.3 % between Waves 1 and 2 in women (p < 0.001), from 46.5 to 30.2 % in children 24-59 months (p = 0.066), and from 71.4 to 45.8 % in children 6-23 months (p = 0.061). Among women in Wave 1, consumption of iron absorption enhancing foods (green vegetables and fruits high in vitamin C) was protective against anemia (p = 0.043). Women in Wave 2 who ate ≥4 servings of green, leafy vegetables per week were less likely to be anemic (p = 0.034). Microscopic examination of blood smears revealed microcytic, hypochromic red blood cells in 90 % of anemic children and 68.8 % of anemic women, consistent with iron deficiency anemia.

  1. Seasonal diet composition of Fundulus lima (Cyprinodontiformes: Fundulidae) in two oasis systems of Baja California Sur, Mexico.

    PubMed

    Acosta Zamorano, Dinora; Ruiz Campos, Gorgonio; Andreu Soler, Asunción; Reyes Valdez, Claudia Alejandra

    2011-12-01

    Fundulus lima inhabits river drainage systems and is threatened after the introduction of cichlids in the area. To support conservation programs, the spatial and temporal variation of the diet composition of this endangered killifish, was determined in two oasis systems of Baja California Sur, Mexico (San Ignacio and La Purisima river drainages), during rainy and dry seasons. F. lima was captured by using passive and active capture techniques. A total of 192 stomach contents of F. lima was analyzed. The contribution of each prey item in the diet composition was quantified by means of the indices of occurrence frequency (% OF), numerical (% N) and volume (% V) percentages. The relative importance of each prey item was determined according to the percentage of the Relative Importance Index (% RII). The similarity of the diet was calculated between hydrological basins (populations combined by basin), seasons (rainy versus dry months), sexes and size classes, by using Schoener's resource overlap index. We used two ecological indices to determine the type of feeding strategy exhibited by the fish: (1) niche breadth of Levins and (2) proportional similarity of Feisinger. Sand was the most abundant item in the stomach content of killifishes from both drainages (39% and 47%, respectively). Diet composition was similar for both drainages (74%) as well as among their respective size classes; however, it was different between sexes. In both drainages, F. lima predated mainly on diatom algae, dipterous and trichopteran larvae, and fish scales during the dry season; while it preferred dipterous larvae, filamentous algae and ostracods in the rainy season. A feeding strategy of opportunist type was exhibited by F. lima during the rainy season, changing to specialist type during the dry season. This information will be the basis for future investigations related to the conservation of this endangered species and its habitat.

  2. Petrology and Geochemistry of Abandoned Spreading Center Lavas Off Baja California: Implications for Intraplate Magmatism in Eastern Pacific

    NASA Astrophysics Data System (ADS)

    Tian, L.; Castillo, P. R.; Lonsdale, P. F.

    2008-12-01

    Abundant volcanism at active spreading centers is caused by adiabatic decompression melting of the upper mantle, but the origin of volcanism at abandoned spreading centers is an enigma. Guadalupe Island and Sara, Rosana, Rosa, and Nithya seamounts are volcanoes built on abandoned spreading centers between 26°N and 29°N in the eastern Pacific offshore Baja California. Lava samples from these volcanoes comprise predominantly of mildly to moderately alkalic basalts and their differentiates. Relative to mid-ocean ridge basalts (MORB) from the East Pacific Rise (EPR), they have higher abundances of incompatible elements and higher highly/moderately incompatible trace element ratios (e.g., Ba/Zr ~1.3). These lavas have enriched REECH patterns, with light REE enrichment up to 300X chondrites. These trace element characteristics combined with their moderately radiogenic Sr, Nd and Pb isotopic compositions indicate they originated from a geochemically enriched mantle source. In detail, the lavas have a moderate range of composition that overlaps with those of lavas from another spreading center (Davidson Seamount) and nearby seamounts (e.g., Pioneer, Rodriguez) offshore southern California and tholeiitic to alkalic seamounts near the EPR. Together, these intraplate lavas define a compositional continuum ranging from MORB-like to ocean island basalt (OIB)-like. In the case of abandoned spreading centers, the 87Sr/86Sr and 143Nd/144Nd compositions of Sara, Rosana and Nithya seamount lavas greatly overlap with those of EPR seamount lavas, but those of Rosa seamount and Guadalupe Island lavas are within the HIMU field for OIB. Thus our results suggest that volcanism at abandoned spreading centers and intraplate volcanism in eastern Pacific as a whole result from a complex interplay between mantle melting dynamics and lithospheric tectonic processes.

  3. Late Neogene stratigraphy and tectonic control on facies evolution in the Laguna Salada Basin, northern Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Martín-Barajas, A.; Vázquez-Hernández, S.; Carreño, A. L.; Helenes, J.; Suárez-Vidal, F.; Alvarez-Rosales, J.

    2001-10-01

    The Laguna Salada Basin (LSB) in northeastern Baja California records late-Neogene marine incursions in the Salton Trough and progradation of the Colorado River delta. Early subsidence and subsequent tectonic erosion are related to evolution of the Sierra El Mayor detachment fault during late Miocene time (<12 Ma). The stratigraphy of uplifted blocks on the east-central margin of the Laguna Salada Basin and from three exploratory wells allows reconstruction of the main sedimentary and tectonic events. Marine mudstone and sandstone, and subordinate conglomerate of the Imperial Formation tectonically overlie metamorphic and granitic basement. Microfossils, lithology, and sedimentary structures in the Imperial Formation define Upper Miocene (<6 Ma) outer-shelf facies that grade up-section into inner-shelf and tide-dominated delta plain deposits of the ancient Colorado River. Lower Pliocene (˜4-2 Ma) reddish, sub-arkosic fluvial sandstone and siltstone of the Palm Spring Formation defines progradation of non-marine fluvio-deltaic deposits over the marine Imperial Formation. Continuous outcrops of the Palm Spring are less than 170-m thick, but correlative deposits are more than 570 m thick in the lower part of a 2400-m deep geothermal exploratory well on the eastern margin of LSB. Interfingering fluvial-sandstone deposits and prograding alluvial fanglomerates with coarse debris-flow and rock-avalanche deposits crudely mark the onset of vertical slip along the Laguna Salada fault and rapid uplift of Sierra Cucapa and Sierra El Mayor. Up to 2 km of Quaternary alluvial-fan and lacustrine deposits accumulated along the eastern margin of LSB, whereas lower subsidence rates produced a thinner sedimentary wedge over a ramp-like crystalline basement along the western margin. In early Pleistocene time (˜2-1 Ma), the Laguna Salada became progressively isolated from the Colorado River delta complex, and the Salton Trough by activity on the Elsinore and Laguna Salada fault zones.

  4. Phylogeography of endemic Xantus' hummingbird (Hylocharis xantusii) shows a different history of vicariance in the Baja California Peninsula.

    PubMed

    González-Rubio, Cristina; García-De León, Francisco J; Rodríguez-Estrella, Ricardo

    2016-09-01

    Studies of phylogeographic patterns provide insight into the processes driving lineage divergence in a particular region. To identify the processes that caused phylogeographic breaks, it is necessary to use historical information and a set of appropriate molecular data to explain current patterns. To understand the influence of geological or ecological processes on the phylogeography of the only species of hummingbird endemic to the Baja California Peninsula, Hylocharis xantusii, mitochondrial DNA sequences of three concatenated genes (Cyt-b, COI and ND2; 2297bp in total) in 100 individuals were analyzed. The spatial analyses of genetic variation showed phylogeographic structure consisting of a north, central and south regions. According to estimated divergence times, two vicariant events are supported, permanent separation of the peninsula and formation of the Gulf of California at 5mya and temporary isolation of the southern region at the Isthmus of La Paz at 3mya. The temporal frame of genetic differentiation of intraspecific haplotypes indicates that 90% of haplotypes diverged within the last 500,000years, with a population expansion 80,000years ago. Only four haplotypes diverged ∼2.2 my and occurred in the south (Hxan_36, 38 and 45), and north (Hxan_45 and 56) regions; only haplotype 45 is shared between south and north populations. These regions also have the most recent haplotypes from 12,500 to 16,200years ago, and together with high levels of genetic diversity, we suggest two refuge areas, the Northern and Southern regions. Our results indicate that the phylogeographic pattern first results from vicariance processes, then is followed by historical and recent climate fluctuations that influenced conditions on the peninsula, and it is also related to oases distribution. This study presents the first investigation of phylogeography of the peninsular' endemic Xantus' hummingbird. Copyright © 2016 Elsevier Inc. All rights reserved.

  5. Patterns of microbial diversity along a salinity gradient in the Guerrero Negro solar saltern, Baja CA Sur, Mexico.

    PubMed

    Dillon, Jesse G; Carlin, Mark; Gutierrez, Abraham; Nguyen, Vivian; McLain, Nathan

    2013-01-01

    The goal of this study was to use environmental sequencing of 16S rRNA and bop genes to compare the diversity of planktonic bacteria and archaea across ponds with increasing salinity in the Exportadora de Sal (ESSA) evaporative saltern in Guerrero Negro, Baja CA S., Mexico. We hypothesized that diverse communities of heterotrophic bacteria and archaea would be found in the ESSA ponds, but that bacterial diversity would decrease relative to archaea at the highest salinities. Archaeal 16S rRNA diversity was higher in Ponds 11 and 12 (370 and 380 g l(-1) total salts, respectively) compared to Pond 9 (180 g l(-1) total salts). Both Pond 11 and 12 communities had high representation (47 and 45% of clones, respectively) by Haloquadratum walsbyi-like (99% similarity) lineages. The archaeal community in Pond 9 was dominated (79%) by a single uncultured phylotype with 99% similarity to sequences recovered from the Sfax saltern in Tunisia. This pattern was mirrored in bop gene diversity with greater numbers of highly supported phylotypes including many Haloquadratum-like sequences from the two highest salinity ponds. In Pond 9, most bop sequences, were not closely related to sequences in databases. Bacterial 16S rRNA diversity was higher than archaeal in both Pond 9 and Pond 12 samples, but not Pond 11, where a non-Salinibacter lineage within the Bacteroidetes >98% similar to environmental clones recovered from Lake Tuz in Turkey and a saltern in Chula Vista, CA was most abundant (69% of community). This OTU was also the most abundant in Pond 12, but only represented 14% of clones in the more diverse pond. The most abundant OTU in Pond 9 (33% of community) was 99% similar to an uncultured gammaproteobacterial clone from the Salton Sea. Results suggest that the communities of saltern bacteria and archaea vary even in ponds with similar salinity and further investigation into the ecology of diverse, uncultured halophile communities is warranted.

  6. Comparison of diazotroph community structure in Lyngbya sp. and Microcoleus chthonoplastes dominated microbial mats from Guerrero Negro, Baja, Mexico.

    PubMed

    Omoregie, Enoma O; Crumbliss, Lori L; Bebout, Brad M; Zehr, Jonathan P

    2004-03-01

    The nitrogenase activity and phylogenetic diversity of nitrogen fixing microorganisms in several different cyanobacterial mat types from Guerrero Negro, Baja California, Mexico were investigated by acetylene reduction assay, and by amplification and sequencing of the nitrogenase nifH gene. Acetylene reduction assays performed on a Lyngbya sp. and two Microcoleus chthonoplastes dominated microbial mats showed a typical diel pattern of nitrogenase activity in these mats. The highest rates of activity were found at night, with 40 and 37 micromol C(2)H(4) m(-2) h(-1) measured in the Microcoleus mats, and 9 micromol C(2)H(4) m(-2) h(-1) in the Lyngbya mat. Nitrogenase sequences were obtained that clustered with sequences from cyanobacteria, gamma-Proteobacteria, and cluster 3 of nifH. In addition, novel and divergent sequences were also recovered. The composition of nifH sequence types recovered differed between the Lyngbya and Microcoleus mats. Interestingly, nifH sequences belonging to filamentous cyanobacteria were absent in most mat samples even though both mats were dominated by filamentous cyanobacteria. nifH sequences clustering with those of unicellular cyanobacteria were found, some of which were virtually identical to the nifH sequence from Halothece sp. MPI96P605, which had previously been isolated from the mat. In manipulation experiments, the Lyngbya and Microcoleus mats were allowed to re-colonize a cleared surface. In these developing mats, nifH sequences not previously observed in the mats were discovered. Our results showed that organisms capable of N(2) fixation were present in N(2) fixing mats, that the composition of the N(2) fixing communities differs between mats, and that filamentous cyanobacterial diazotrophs may not have a large role in the early stages of mat development.

  7. Millimeter-scale resolution of trace metal distributions in microbial mats from a hypersaline environment in Baja California, Mexico.

    PubMed

    Huerta-Diaz, M A; Delgadillo-Hinojosa, F; Siqueiros-Valencia, A; Valdivieso-Ojeda, J; Reimer, J J; Segovia-Zavala, J A

    2012-11-01

    Microbial mats from two ponds with different salinities from the saltern of Guerrero Negro (Mexico) points toward millimeter-scale coherent variations in trace metal (Me) concentrations (Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn). Total, HCl-leachable and pyrite-associated Me showed a trend of increasing concentrations with increasing depth suggesting gradual addition of reactive Me probably as a result of metal sulfide precipitation at depth. The trends in Me profiles can be ascribed to the establishment and maintenance of microzones that promote geochemical processes, bacterial population distributions, and differential mass transport within the mats. Degrees of trace metal pyritization (1 ± 1% for Zn to 24 ± 7% for Cd) as well as metals associated with the pyrite fraction (<1.4-36 ± 18 nmol g(-1) for Zn and Mn, respectively) were low, as expected from a reactive Fe-limited system like Guerrero Negro. Calculated enrichment factors showed that Ni (2.6 ± 2.1), Co (5.5 ± 4.0), Pb (9.4 ± 7.4), and Cd (57 ± 39) were, on average, enriched in the microbial mats of Guerrero Negro. Natural enrichments of Cd, Pb, and Co in sediments along the coast of Baja California and metabolical requirements of Co and Ni by the predominant cyanobacteria in the Guerrero Negro mats may explain these enrichments. Metal characteristics in microbial mats could be advantageously used as biosignatures to identify their presence in the geological record or in other planetary systems. © 2012 Blackwell Publishing Ltd.

  8. Patterns of microbial diversity along a salinity gradient in the Guerrero Negro solar saltern, Baja CA Sur, Mexico

    PubMed Central

    Dillon, Jesse G.; Carlin, Mark; Gutierrez, Abraham; Nguyen, Vivian; McLain, Nathan

    2013-01-01

    The goal of this study was to use environmental sequencing of 16S rRNA and bop genes to compare the diversity of planktonic bacteria and archaea across ponds with increasing salinity in the Exportadora de Sal (ESSA) evaporative saltern in Guerrero Negro, Baja CA S., Mexico. We hypothesized that diverse communities of heterotrophic bacteria and archaea would be found in the ESSA ponds, but that bacterial diversity would decrease relative to archaea at the highest salinities. Archaeal 16S rRNA diversity was higher in Ponds 11 and 12 (370 and 380 g l−1 total salts, respectively) compared to Pond 9 (180 g l−1 total salts). Both Pond 11 and 12 communities had high representation (47 and 45% of clones, respectively) by Haloquadratum walsbyi-like (99% similarity) lineages. The archaeal community in Pond 9 was dominated (79%) by a single uncultured phylotype with 99% similarity to sequences recovered from the Sfax saltern in Tunisia. This pattern was mirrored in bop gene diversity with greater numbers of highly supported phylotypes including many Haloquadratum-like sequences from the two highest salinity ponds. In Pond 9, most bop sequences, were not closely related to sequences in databases. Bacterial 16S rRNA diversity was higher than archaeal in both Pond 9 and Pond 12 samples, but not Pond 11, where a non-Salinibacter lineage within the Bacteroidetes >98% similar to environmental clones recovered from Lake Tuz in Turkey and a saltern in Chula Vista, CA was most abundant (69% of community). This OTU was also the most abundant in Pond 12, but only represented 14% of clones in the more diverse pond. The most abundant OTU in Pond 9 (33% of community) was 99% similar to an uncultured gammaproteobacterial clone from the Salton Sea. Results suggest that the communities of saltern bacteria and archaea vary even in ponds with similar salinity and further investigation into the ecology of diverse, uncultured halophile communities is warranted. PMID:24391633

  9. Sea-surface temperature gradients across blue whale and sea turtle foraging trajectories off the Baja California Peninsula, Mexico

    NASA Astrophysics Data System (ADS)

    Etnoyer, Peter; Canny, David; Mate, Bruce R.; Morgan, Lance E.; Ortega-Ortiz, Joel G.; Nichols, Wallace J.

    2006-02-01

    Sea-surface temperature (SST) fronts are integral to pelagic ecology in the North Pacific Ocean, so it is necessary to understand their character and distribution, and the way these features influence the behavior of endangered and highly migratory species. Here, telemetry data from sixteen satellite-tagged blue whales ( Balaenoptera musculus) and sea turtles ( Caretta caretta, Chelonia mydas, and Lepidochelys olivacea) are employed to characterize 'biologically relevant' SST fronts off Baja California Sur. High residence times are used to identify presumed foraging areas, and SST gradients are calculated across advanced very high resolution radiometer (AVHRR) images of these regions. The resulting values are compared to classic definitions of SST fronts in the oceanographic literature. We find subtle changes in surface temperature (between 0.01 and 0.10 °C/km) across the foraging trajectories, near the lowest end of the oceanographic scale (between 0.03 and 0.3 °C/km), suggesting that edge-detection algorithms using gradient thresholds >0.10 °C/km may overlook pelagic habitats in tropical waters. We use this information to sensitize our edge-detection algorithm, and to identify persistent concentrations of subtle SST fronts in the Northeast Pacific Ocean between 2002 and 2004. The lower-gradient threshold increases the number of fronts detected, revealing more potential habitats in different places than we find with a higher-gradient threshold. This is the expected result, but it confirms that pelagic habitat can be overlooked, and that the temperature gradient parameter is an important one.

  10. Halorubrum chaoviator sp. nov., a haloarchaeon isolated from sea salt in Baja California, Mexico, Western Australia and Naxos, Greece

    PubMed Central

    Mancinelli, Rocco L.; Landheim, Ragnhild; Sanchez-Porro, Cristina; Dornmayr-Pfaffenhuemer, Marion; Gruber, Claudia; Legat, Andrea; Ventosa, Antonio; Radax, Christian; Ihara, Kunio; White, Melisa R.; Stan-Lotter, Helga

    2011-01-01

    Three halophilic isolates, strains Halo-G*T, AUS-1 and Naxos II, were compared. Halo-G* was isolated from an evaporitic salt crystal from Baja California, Mexico, whereas AUS-1 and Naxos II were isolated from salt pools in Western Australia and the Greek island of Naxos, respectively. Halo-G*T had been exposed previously to conditions of outer space and survived 2 weeks on the Biopan facility. Chemotaxonomic and molecular comparisons suggested high similarity between the three strains. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the strains clustered with Halorubrum species, showing sequence similarities of 99.2–97.1 %. The DNA–DNA hybridization values of strain Halo-G*T and strains AUS-1 and Naxos II are 73 and 75 %, respectively, indicating that they constitute a single species. The DNA relatedness between strain Halo-G*T and the type strains of 13 closely related species of the genus Halorubrum ranged from 39 to 2 %, suggesting that the three isolates constitute a different genospecies. The G+C content of the DNA of the three strains was 65.5–66.5 mol%. All three strains contained C20C20 derivatives of diethers of phosphatidylglycerol, phosphatidylglyceromethylphosphate and phosphatidylglycerolsulfate, together with a sulfated glycolipid. On the basis of these results, a novel species that includes the three strains is proposed, with the name Halorubrum chaoviator sp. nov. The type strain is strain Halo-G*T (=DSM 19316T =NCIMB 14426T =ATCC BAA-1602T). PMID:19567575

  11. Application of MODIS-ASTER (MASTER) simulator data to geological mapping of young volcanic regions in Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Dmochowski, Jane Ellen

    Visible, near infrared, short-wave infrared, and thermal infrared multi-channel remote sensing data, MODIS-ASTER (MASTER), are used to extract geologic information from two volcanic regions in Baja California, Mexico: Tres Virgenes-La Reforma Volcanic Region and the volcanic island of Isla San Luis. The visible and near infrared and short-wave infrared data were atmospherically corrected and classified. The resulting classification roughly delineates surfaces that vary in their secondary minerals. Attempts to identify these minerals using ENVI's Spectral Analyst(TM) were moderately successful. The analysis of the thermal infrared data utilizes the shift to longer wavelengths in the Reststrahlen band as the mineralogy changes from felsic to mafic to translate the data into values of weight percent SiO2. The results indicate that the general approach tends to underestimate the weight percent SiO2 in the image. This discrepancy is removed with a "site calibration," which provides good results in the calculated weight percent SiO2 with errors of a few percent. However, errors become larger with rugged topography or low solar angle at the time of image acquisition. Analysis of bathymetric data around Isla San Luis, and consideration of the island's alignment with the Ballenas transform fault zone to the south and volcanic seamounts nearby, suggest Isla San Luis is potentially volcanically active and could be the product of a "leaky" transform fault. The results from the image analysis in the Tres Virgenes-La Reforma Volcanic Region show the La Reforma and El Aguajito volcanic centers to be bimodal in composition and verify the most recent volcanism in the Tres Virgenes region to be basaltic-andesite. The results of fieldwork and image analysis indicate that the volcanic products of the central dome of La Reforma are likely a sequence of welded ash flow tuffs and lavas of varied composition, evidence of its origin as a caldera.

  12. Lithosphere and asthenosphere structure beneath the Gulf of California from SCOOBA and NARS-Baja surface wave data

    NASA Astrophysics Data System (ADS)

    Carriero, N.; Forsyth, D. W.; Gaherty, J. B.; Wang, Y.

    2010-12-01

    The Pacific-North America plate boundary, a young oblique rift system running lengthwise along the Gulf of California (GoC), is an excellent modern example of continental breakup and drifting. Because of the high concentration of seismometers surrounding the gulf, research in this region may answer the question of whether upwelling centers are characteristic of rift systems, and, if so, related questions about the cause of upwelling centers and the role they play in seafloor spreading. Wang et al. (2009) suggests that there is mantle upwelling in three, and possibly four, locations along the GoC. Our purpose is to obtain better resolution of the hypothesized low-velocity anomalies in the gulf, and to test whether a fourth upwelling center (located at the mouth of the gulf) exists. We use the data from eight ocean-bottom seismometers (OBS), part of the 12-month deployment of the Sea of Cortez Ocean-Bottom Array (SCOOBA) seismic experiment, and the data from onshore seismometers of the NARS-Baja experiment, to estimate the phase velocities of Rayleigh surface waves propagating through the crust and upper mantle beneath the GoC. For the larger teleseismic events, the OBS stations provide good data to periods of ~150 seconds or more, but in general have a signal-to-noise ratio that is slightly lower than the land stations. A tomographical inversion, using the two-plane wave method, is then performed on the Rayleigh waves to create a shear velocity structure of the upper 200 km of the mantle.

  13. Transformations of Mangrove Forests in Bahia Magdalena, Baja California Sur, Mexico: Two Decade Results Based on Landsat Imageries

    NASA Astrophysics Data System (ADS)

    Suresh Babu, S.; Abdul Rahaman, S.; Muthushankar, G.; Jonathan, M. P.

    2014-12-01

    Mangrove forests which thrive along the tropical and subtropical regions are the most productive ecosystems in the world with a wide range of ecological and economical services to mankind. With the rapid urbanization across the globe, these forests tend to be destroying at an alarming rate. The area of concern for this study, Bahia Magdalena is very important for the economy of the state as nearly 50% of the artisan fisheries are established in the mangrove zone. Henceforth this study is an attempt for a regional assessment and to accurately quantify the mangroves using LANDSAT imageries for over two decades in Bahia Magdalena, Baja California. Satellite imageries from the year 1986 through 2014 were analysed to assess the prolonged changes taking place in and around the mangrove reserve. Using the estimates of land use/cover for all the years, the spatio - temporal data was validated using ArcGIS software. The results revealed that the spatial extent of mangroves are decreasing until 2005 due to the developmental plans such as tourism, shrimp farming and establishment of industries in this part of the country. During the past 10 years (~ after 2005) there is no much change in the area extent of mangrove reserves due to afforestation and conservation efforts. Thus the unbiased dataset generated may be widely used for an improved understanding of the role of mangrove forests in the socio economic aspects, protection from natural disasters, identify possible areas for conservation, restoration and rehabilitation; and improve estimates of the amount of carbon stored in mangrove vegetation and the associated marine environment. Keywords: Mangroves, LANDSAT, Bahia Magdalena, México.

  14. Hydrogeochemical characterization of the thermal springs in northeastern of Los Cabos Block, Baja California Sur, México.

    PubMed

    Hernández-Morales, Pablo; Wurl, Jobst

    2016-11-19

    The existence of hot springs in the northeastern part of Los Cabos Baja California Sur (BCS), is known from pre-Hispanic times, but their hydrochemical composition had not been previously described. Several springs are located within the watershed of Santiago, and the objective of this study was to define the hydrogeochemical composition of the thermal springs and to characterize the geothermal reservoir. A total of 16 water samples were taken in 11 geothermal manifestations under dry (June 2014) and humid (March 2015) conditions. A geothermal system of low enthalpy and low mineralization was found along the San José del Cabo Fault (FSJC), with an average salinity (TDS) of 261 mg/L and an alkaline pH (8.5-9.5). The hydrogeochemical composition corresponds to the sodium-bicarbonate type, and geothermometers (silica and Na-K) indicate temperatures ranging from 70 to 115 °C for the deep thermal reservoir in conditions of equilibrium. The thermal springs with these hydrogeochemical characteristics differ in respect to the hydrochemical composition of the springs, formally described on several sites of BCS. Br/Cl and B/Cl ratios as well as the enrichment factor (EF) indicate that rainwater with a seawater component represents the source of the thermal spring water. In the springs, a mixture between thermal water and surface water is observed, combined with a relatively deep water circulation, allowing a calcium-sodium exchange, according to the host rock geochemistry. The higher temperatures found at some hot springs are related to the main trace of the San José del Cabo Fault.

  15. A geochemical comparison of alkalic lavas in the Trans-Mexican Volcanic Belt, peninsular Baja California and intraplate volcanoes in the eastern Pacific

    NASA Astrophysics Data System (ADS)

    Tian, L.; Castillo, P. R.

    2011-12-01

    The Trans-Mexican Volcanic Belt (TMVB) is a continental volcanic arc built along the southern edge of the North American plate. The volcanic rocks along TMVB are compositionally diverse and the origin of its alkalic lavas with ocean island basalt (OIB)-like composition is highly controversial. Alkalic lavas from four regions in the western, central, and eastern TMVB [e.g., Verma and Hasenaka, Geochem. J., 58, 2004; Petrone et al., Geol. S. Am. S., 402, 2006; Orozco-Esquivel et al., Geol. Soc. Amer. Bull., 93, 2007] are compared with similar OIB-like alkalic lavas from peninsular Baja California [e.g., Storey et al., Terra Nova, 1, 1989; Castillo, Geol. Soc. Amer. Bull., 120, 2008] and intraplate volcanoes in the eastern Pacific [Tian et al., Geochem. Geophys. Geosyst., 12, 2011] in order to ascertain their geochemical similarities and differences and to constrain the compositions of their respective magma sources. A few of the alkalic lavas from TMVB have very similar trace element and isotopic compositions as the OIB-like alkalic lavas from peninsular Baja California and intraplate volcanoes in the eastern Pacific. Majority of the TMVB alkalic lavas, however, are compositionally more heterogeneous, similar to the less-alkalic Nb-enriched basalts in peninsular Baja California representing OIB-like alkalic lavas that had been contaminated by other mantle components and/or crustal materials. Thus, data seem to indicate that all the OIB-like alkalic lavas can be traced to a similar source, the compositionally heterogeneous Pacific asthenosphere.

  16. Phylogeny, divergence times and species limits of spiny lizards (Sceloporus magister species group) in western North American deserts and Baja California.

    PubMed

    Leaché, Adam D; Mulcahy, Daniel G

    2007-12-01

    The broad distribution of the Sceloporus magister species group (squamata: phrynosomatidae) throughout western North America provides an appropriate model for testing biogeographical hypotheses explaining the timing and origins of diversity across mainland deserts and the Baja California Peninsula. We inferred concordant phylogenetic trees describing the higher-level relationships within the magister group using 1.6 kb of mitochondrial DNA (mtDNA) and 1.7 kb of nuclear DNA data. These data provide strong support for the parallel divergence of lineages endemic to the Baja California Peninsula (S. zosteromus and the orcutti complex) in the form of two sequential divergence events at the base of the magister group phylogeny. A relaxed phylogenetic analysis of the mtDNA data using one fossil and one biogeographical constraint provides a chronology of these divergence events and evidence that further diversification within the Baja California clades occurred simultaneously, although patterns of geographical variation and speciation between clades differ. We resolved four major phylogeographical clades within S. magister that (i) provide a novel phylogenetic placement of the Chihuahuan Desert populations sister to the Mojave Desert; (ii) illustrate a mixed history for the Colorado Plateau that includes Mojave and Sonoran Desert components; and (iii) identify an area of overlap between the Mojave and Sonoran Desert clades near Yuma, Arizona. Estimates of bidirectional migration rates among populations of S. magister using four nuclear loci support strong asymmetries in gene flow among the major mtDNA clades. Based on the nonexclusivity of mtDNA haplotypes, nuclear gene flow among populations and wide zones of phenotypic intergradation, S. magister appears to represent a single geographically variable and widespread species.

  17. Sediment Cd and Mo accumulation in the oxygen-minimum zone off western Baja California linked to global climate over the past 52 kyr

    USGS Publications Warehouse

    Dean, W.E.; Zheng, Yen; Ortiz, J.D.; VanGeen, A.

    2006-01-01

    Concentrations of organic carbon (orgC), cadmium (Cd), and molybdenum (Mo) were measured in two sediment cores raised from depths of 430 and 700 m within the oxygen-minimum zone (OMZ) off southern Baja California at a temporal resolution of e10.5 kyr over the past 52 kyr. These records are supplemented with diffuse spectral reflectance (DSR) measurements obtained on board ship soon after collection at a resolution of e10.05 kyr. In the core from 700 m depth, a component extracted from the DSR data and the three geochemical proxies generally vary in concert with each other and over a wide range (4-22% orgC; 1-40 mg/kg Cd; 5-120 mg/kg Mo). Intervals of increased orgC, Cd, and Mo accumulation generally correspond to warm periods recorded in the oxygen-isotopic composition of Greenland ice, with the exception of the Bolling/Allerod which is only weakly expressed off Baja California. Concentrations of the biogenic proxies are higher in the core from 430 m depth, but erratic sediment accumulation before 15 ka precludes dating of the older intervals that are laminated and contain elevated orgC, Cd, and Mo concentrations. The new data provide further evidence of an intimate teleconnection between global climate and the intensity of the OMZ and/or productivity along the western margin of North America. On the basis of a comparison with Cd and Mo records collected elsewhere in the region, we conclude that productivity may actually have varied off southern Baja California by no more than a factor of 2 over the past 52 kyr. Copyright 2006 by the American Geophysical Union.

  18. Remagnetization of Cretaceous forearc strata on Santa Margarita and Magdalena Islands, Baja California Sur: Implications for northward transport along the California margin

    NASA Astrophysics Data System (ADS)

    Hagstrum, Jonathan T.; Sedlock, Richard L.

    1998-12-01

    Paleomagnetic data for two sections of Cretaceous forearc strata with different structural attitudes on Santa Margarita and Magdalena Islands in Baja California Sur, Mexico, indicate that these rocks have been remagnetized, probably during the late Cenozoic. The in situ paleomagnetic directions, however, are similar to data from other Cretaceous rocks on peninsular California with unexpectedly shallow inclinations and easterly declinations. These data have been interpreted as indicating either northward tectonic transport (10°-15° of latitude) and clockwise rotation (>20°) or compaction shallowing of magnetic inclinations in sedimentary rocks combined with southwestward tilting of plutonic rocks. The available paleomagnetic data for Cretaceous forearc strata in southern and Baja California can be divided into three groups: (1) sections with normal-polarity magnetizations that fail fold tests and are remagnetized, (2) sections with normal-polarity magnetizations with no or inconclusive fold tests that may or may not be remagnetized, and (3) sections with both normal-and reversed-polarity intervals where pervasive remagnetization has not occurred. Other rocks of the Mesozoic Great Valley Group, Coast Range ophiolite, and Franciscan Complex in California also have secondary magnetizations with directions similar to younger geomagnetic field directions. Although these widespread remagnetizations could have variable local causes, we propose regional burial and uplift, related to changes in subduction parameters, as a possible explanation. Two episodes of remagnetization are apparent: one in the Late Cretaceous and a second in the late Cenozoic. On the other hand, the unremagnetized and apparently reliable data from sedimentary and plutonic rocks on the Baja Peninsula consistently indicate northward translation (14° ± 3°) and clockwise rotation (29° ± 8°) with respect to North America since the Late Cretaceous.

  19. Review of Neopalpa Povolný, 1998 with description of a new species from California and Baja California, Mexico (Lepidoptera, Gelechiidae)

    PubMed Central

    Nazari, Vazrick

    2017-01-01

    Abstract The monotypic genus Neopalpa was described in 1998 by Czech entomologist Dalibor Povolný based on two male specimens from Santa Catalina Island, California, which he named Neopalpa neonata. The female of this species was discovered recently based on a DNA barcode match and is described. In addition, a new species with marked differences in morphology and DNA barcodes from southern California and Baja California Mexico is described as Neopalpa donaldtrumpi sp. n. Adults and genitalia of both species are illustrated, new diagnosis for the genus Neopalpa is provided, and its position within Gelechiidae is briefly discussed. PMID:28228677

  20. Relative inactivity during the last 140,000 years of a portion of the La Paz fault, southern Baja California Sur, Mexico

    USGS Publications Warehouse

    Szabo, B. J.; Hausback, B.P.; Smith, Joe T.

    1990-01-01

    Uranium-series dating of corals overlying the undeformed Punta Coyote gravels indicates that the underlying La Paz fault zone has been relatively inactive in this part of the Baja California peninsula during the last 140,000 years, and possibly for a significantly longer period. However, Holocene seismic activities along extensions of the fault zone north of Cabo San Lucas suggest potential seismic hazards for the city of La Paz (population 200,000), which lies about 6 km from the fault. ?? 1990 Springer-Verlag New York Inc.

  1. Lithospheric strength in the active boundary between the Pacific Plate and Baja California microplate constrained from lower crustal and upper mantle xenoliths

    NASA Astrophysics Data System (ADS)

    Chatzaras, Vasileios; van der Werf, Thomas; Kriegsman, Leo M.; Kronenberg, Andreas; Tikoff, Basil; Drury, Martyn R.

    2017-04-01

    The lower crust is the most poorly understood of the lithospheric layers in terms of its rheology, particularly at active plate boundaries. We studied naturally deformed lower crustal xenoliths within an active plate boundary, in order to link their microstructures and rheological parameters to the well-defined active tectonic context. The Baja California shear zone (BCSZ), located at the western boundary of the Baja California microplate, comprises the active boundary accommodating the relative motion between the Pacific plate and Baja California microplate. The basalts of the Holocene San Quintin volcanic field carry lower crustal and upper mantle xenoliths, which sample the Baja California microplate lithosphere in the vicinity of the BCSZ. The lower crustal xenoliths range from undeformed gabbros to granoblastic two-pyroxene granulites. Two-pyroxene geothermometry shows that the granulites equilibrated at temperatures of 690-920 oC. Phase equilibria (P-T pseudosections using Perple_X) indicate that symplectites with intergrown pyroxenes, plagioclase, olivine and spinel formed at 3.6-5.4 kbar, following decompression from pressures exceeding 6 kbar. FTIR spectroscopy shows that the water content of plagioclase varies among the analyzed xenoliths; plagioclase is relatively dry in two xenoliths while one xenolith contains hydrated plagioclase grains. Microstructural observations and analysis of the crystallographic texture provide evidence for deformation of plagioclase by a combination of dislocation creep and grain boundary sliding. To constrain the strength of the lower crust and upper mantle near the BCSZ we estimated the differential stress using plagioclase and olivine grain size paleopiezomtery, respectively. Differential stress estimates for plagioclase range from 10 to 32 MPa and for olivine are 30 MPa. Thus the active microplate boundary records elevated crustal temperatures, heterogeneous levels of hydration, and low strength in both the lower crust and

  2. Review of Neopalpa Povolný, 1998 with description of a new species from California and Baja California, Mexico (Lepidoptera, Gelechiidae).

    PubMed

    Nazari, Vazrick

    2017-01-01

    The monotypic genus Neopalpa was described in 1998 by Czech entomologist Dalibor Povolný based on two male specimens from Santa Catalina Island, California, which he named Neopalpa neonata. The female of this species was discovered recently based on a DNA barcode match and is described. In addition, a new species with marked differences in morphology and DNA barcodes from southern California and Baja California Mexico is described as Neopalpa donaldtrumpisp. n. Adults and genitalia of both species are illustrated, new diagnosis for the genus Neopalpa is provided, and its position within Gelechiidae is briefly discussed.

  3. AUV Mapping and ROV Exploration of Los Frailes Submarine Canyon, Cabo Pulmo National Marine Park, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Troni, G.; Caress, D. W.; Graves, D.; Thomas, H. J.; Thompson, D.; Barry, J. P.; Aburto-Oropeza, O.; Johnson, A. F.; Lundsten, L.

    2015-12-01

    Los Frailes submarine canyon is located at the south boundary of the Cabo Pulmo National Marine Park on the southeast tip of the Baja California Peninsula. During the Monterey Bay Aquarium Research Institute (MBARI) 2015 Gulf of California expedition we used an autonomous underwater vehicle (AUV) to map this canyon from 50 m to 450 m depths, and then explored the canyon with a small remotely operated vehicle (ROV). This three day R/V Rachel Carson cruise was a collaboration with the Center for Marine Biodiversity and Conservation at Scripps Institution of Oceanography and the Centro para la Biodiversidad Marina y la Conservación in La Paz. The MBARI AUV D. Allan B. collected high resolution bathymetry, sidescan, and subbottom profiles of Los Frailes submarine canyon and part of the north Cabo Pulmo deep reef. In order to safely generate a 1-m lateral resolution multibeam bathymetry map in the nearshore high relief terrain, the mapping operations consisted of an initial short survey following the 100-m isobath followed by a series of short, incremental AUV missions located on the deep edge of the new AUV bathymetry. The MBARI Mini-ROV was used to explore the submarine canyon within the detailed map created by the MBARI AUV. The Mini-ROV is a 1.2-m-long, 350 kg, 1,500-m-depth-rated ROV designed and constructed by MBARI. It is controlled by six 600-watt thrusters and is equipped with a high-definition video camera and navigation sensors. This small ROV carries less accurate, lower cost navigation sensors than larger vehicles. We implemented new algorithms to localize combining Doppler velocity log sensor data and low-cost MEMS-based inertial sensor data with sporadic ultra-short baseline position measurements to provide a high accuracy position estimation. The navigation performance allowed us to colocate the ROV video imagery with the 1-m resolution bathymetric map of the submarine canyon. Upper Los Frailes Canyon is rugged and, aside from small sand pockets along

  4. Conceptualization of groundwater flow of a coastal arid aquifer using isotopic and chemical tools: La Paz, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Tamez-Melendez, Carol; Hernández-Antonio, Arturo; Mahlknecht, Jürgen

    2016-04-01

    Groundwater from the La Paz coastal aquifer in Baja California Sur, Mexico, is the main source of drinking water for the local population. Due to its proximity to the coast, sea water intrusion is the main factor of salinization of groundwater. Other geochemical processes also affect the quality of the aquifer threating its vulnerability. Forty-seven samples were analyzed for ion chemistry and isotopes. A hierarchical cluster analysis was performed for a better interpretation resulting in three main groups and proved for geographical correspondence. Deuterium and d18O ranged from -82 to -52.1 and from -11.6 to -7 permil, respectively, showing that the main recharge originates in the Sierra el Novillo, flowing toward SE-NW direction and in accordance to deuterium excess (d) high evaporation effects (d>10‰) are mostly in the middle portion of the study area and in El Centenario due to high kinetic isotope fractioning related to elevated temperatures. Hydrogeochemistry analyses demonstrated salinization mainly due to sea water intrusion and in second instance due water-rock interaction, where enrichment of Na+ (ranges from 35.7 to 1089 mg/L-1) was present in some samples probably due to weathering of silicates and/or cation exchange in soils with Ca2+ (27.7 to 658 mg/L-1) at clay-surfaces. High concentrations of NO3-2 (ranges from 1.4 to 48.8 mg/L-1), Cl- (ranges from 54.4 to 2960 mg/L-1) and Na+ show that anthropogenic input is mainly coming from an agricultural area (El Centenario-Chametla) where heavy groundwater extractions are made for irrigational purposes, lowering the groundwater table up to 10 m and consequently promoting upconing and salinity concentrations (NaCl). Carbon-13 and radiocarbon ranged from -12.3 to -9.1‰ and from 29.5 to 100.4 pmC, respectively. Distribution of ages (up to ~5000 years) indicates two flow trends (E-W and SE-NW).

  5. Vent fluid chemistry in Bahía Concepción coastal submarine hydrothermal system, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Prol-Ledesma, R. M.; Canet, C.; Torres-Vera, M. A.; Forrest, M. J.; Armienta, M. A.

    2004-10-01

    Shallow submarine hydrothermal activity has been observed in the Bahía Concepción bay, located at the Gulf coast of the Baja California Peninsula, along faults probably related to the extensional tectonics of the Gulf of California region. Diffuse and focused venting of hydrothermal water and gas occurs in the intertidal and shallow subtidal areas down to 15 m along a NW-SE-trending onshore-offshore fault. Temperatures in the fluid discharge area vary from 50 °C at the sea bottom up to 87 °C at a depth of 10 cm in the sediments. Chemical analyses revealed that thermal water is enriched in Ca, As, Hg, Mn, Ba, HCO 3, Li, Sr, B, I, Cs, Fe and Si, and it has lower concentrations of Cl, Na, SO 4 and Br than seawater. The chemical characteristics of the water samples indicate the occurrence of mixing between seawater and a thermal end-member. Stable isotopic oxygen and hydrogen composition of thermal samples plot close to the Local Meteoric Water Line on a mixing trend between a thermal end-member and seawater. The composition of the thermal end-member was calculated from the chemistry of the submarine samples data by assuming a negligible amount of Mg for the thermal end-member. The results of the mixing model based on the chemical and isotopic composition indicate a maximum of 40% of the thermal end-member in the submarine vent fluid. Chemical geothermometers (Na/Li, Na-K-Ca and Si) were applied to the thermal end-member concentration and indicate a reservoir temperature of approximately 200 °C. The application of K-Mg and Na/Li geothermometers for vent fluids points to a shallow equilibrium temperature of about 120 °C. Results were integrated in a hydrogeological conceptual model that describes formation of thermal fluids by infiltration and subsequent heating of meteoric water. Vent fluid is generated by further mixing with seawater.

  6. Cadmium and phosphate variability during algal blooms of the dinoflagellate Lingulodinium polyedrum in Todos Santos Bay, Baja California, Mexico.

    PubMed

    Gutierrez-Mejia, E; Lares, M L; Huerta-Diaz, M A; Delgadillo-Hinojosa, F

    2016-01-15

    Dinoflagellate algal blooms (DABs), with Lingulodinium polyedrum as the dominant species, have increased over the past few years in coastal areas off Baja California, Mexico. Vertical and temporal variability of particulate cadmium (Cdp), dissolved Cd (Cdd), PO4(3-) and Cdd/PO4(3-) were investigated during two intense DABs of L. polyedrum that occurred during the fall of 2011 and 2012 in Todos Santos Bay. Results were then, compared with data gathered in the absence of algal blooms during the autumn of 2013. In both algal blooms, L. polyedrum tended to be concentrated near the surface throughout the duration; however, during DAB 2011 the number of cells was twice as abundant ([10.0 ± 8.0] × 10(5) cells L(-1)) as in DAB 2012 ([5.0 ± 4.4] × 10(5) cells L(-1)). During DAB 2011, Cdp increased significantly (up to 1.02 ± 0.99 nmol kg(-1)) and was positively correlated with the cell abundance of L. polyedrum, suggesting that this dinoflagellate is able to assimilate and concentrate Cdd. Likewise, Cdd (up to 0.71 ± 0.17 nM) increased in the days of highest cell abundance, which could be attributed to uptake and subsequent regeneration of Cdd resulting from the remineralization of organic particulate matter produced during the bloom, as well as with the presence of organic ligands secreted by L. polyedrum that could keep Cdd in solution. During DAB 2011, dissolved Cdd/PO4(3-) ratios exhibited high vertical and temporal variability in the upper 5 m of the water column, but remained virtually constant near the bottom, suggesting a depth-dependent decoupling between these two dissolved components during the bloom development. Given the observed differences in the vertical and temporal variability of Cdd, Cdp, and PO4(3-) between these two intense DABs, we propose the existence of an abundance threshold of approximately 10(6) cells L(-1) of L. polyedrum above which Cd and PO4(3-) significantly increased due to remineralization in coastal waters during the bloom

  7. A Re-examination of Shallow Paleomagnetic Inclinations From the Cretaceous Valle Group Sedimentary Rocks, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Li, Y.; Kodama, K. P.; Smith, D. P.

    2001-05-01

    A paleomagnetic, rock magnetic, and sedimentological study was conducted in order to determine whether depositional/compactional processes have caused the shallow inclinations observed in the Valle Group sedimentary rocks. A total of 126 samples (14 sites) were collected from the middle Cenomanian section of the Valle along the northern coast of the Vizcaino Peninsula, Baja California, approximately 20 km east of Punta Eugenia at Campito. Samples were subjected to detailed thermal and alternating field (af) demagnetization, typically in 14 steps to 610° C for thermal demagnetization and ~24 steps to 130 mT for af demagnetization. NRMs were strong for marine sedimentary rocks, typically 10 mA/m. The mean of the site means for the demagnetized data was Inc=54.2° , Dec=306° , α 95=4.8° , N=12, in geographic coordinates, and Inc=20.5° , Dec=341.3° , α 95=4° , N=12 in stratigraphic coordinates. AMS fabrics have minimum axes clustered nearly perpendicular to bedding, typical of primary depositional/compactional fabrics. Some sites exhibited minimum axes clustering about 10° from the vertical and maximum axes clustered about 10° from the horizontal suggesting that currents and/or initial bedding dip affected the magnetization of these samples at deposition. Since the stratigraphy of the Valle Group dips consistently to the NE at approximately 50° , we sampled a tight slump fold at one site in order to constrain the age of magnetization. Both the AMS fabric and the characteristic remanence (ChRM) fail the fold test at the 95% confidence level. At another site, we sampled adjacent beds each approximately 5 cm thick composed of coarse, medium, or fine-grained sandstone. The directions of these beds are within 2° of each other. These results can be interpreted to indicate either a late remagnetization of the Valle group or an acquisition of the Valle's detrital remanence after slumping, but early in the rock's post-depositional history. Smith and Busby's (1993

  8. Submarine Neotectonic Investigations of the Bahia Soledad Fault, off Northern Baja California Near the US - Mexico Border

    NASA Astrophysics Data System (ADS)

    Anderson, K.; Lundsten, E. M.; Paull, C. K.; Caress, D. W.; Thomas, H. J.; Maier, K. L.; McGann, M.; Herguera, J. C.; Gwiazda, R.; Arregui, S.; Barrientos, L. A.

    2015-12-01

    The Monterey Bay Aquarium Research Institute (MBARI) conducted detailed surveys at selected sites on the seafloor along the Bahia Soledad Fault offshore of Northern Baja California, Mexico, during a two-ship expedition in the spring of 2015. The Bahia Soledad Fault is a NNW-trending strike-slip fault that is likely continuous with the San Diego Trough Fault offshore of San Diego, California. Constraining the style of deformation, continuity, and slip rate along this fault system is critical to characterizing the seismic hazards to the adjacent coastal areas extending from Los Angeles to Ensenada. Detailed morphologic surveys were conducted using an autonomous underwater vehicle (AUV) to provide ultra high-resolution multibeam bathymetry (vertical precision of 0.15 m and horizontal resolution of 1.0 m). The AUV also carried a 2-10 kHz chirp sub-bottom profiler and an Edgetech 110kHz and 410kHz sidescan. The two sites along the Bahia Soledad Fault each run ~6 km along the fault with ~1.8 km wide footprint. The resulting bathymetry shows these fault zones are marked with distinct lineations that are flanked by ~1 km long elongated ridges and depressions which are interpreted to be transpressional pop-up structures and transtensional pull-apart basins up to 100 m of relief. Offset seismic reflectors that extend to near the seafloor confirm that these lineations are fault scarps. The detailed bathymetric maps and sub-bottom profiles were used to locate key sites where deformed stratigraphic horizons along the fault are within 1.5 m of the seafloor. These areas were sampled using a remotely operated vehicle (ROV) equipped with a vibracoring system capable of collecting precisely located cores that are up to 1.5 m long. The coupled use of multibeam imagery and surgically-collected stratigraphic samples will enable to constrain the frequency and timing of recent movements on this fault which will be useful to incorporated into future seismic hazard assessment.

  9. San Quintín Volcanic Field, Baja California Norte, México: Geology, petrology, and geochemistry

    NASA Astrophysics Data System (ADS)

    Luhr, James F.; Aranda-Gómez, Jose J.; Housh, Todd B.

    1995-06-01

    The San Quintin Volcanic Field (SQVF) is unique for the Baja California peninsula as the only known location of intraplate-type mafic alkalic volcanism and the only known source of peridotitic and granulitic xenoliths. It consists of 10 distinct Quaternary volcanic complexes. The oldest cones mainly erupted primitive magmas (Mg # > 64)(Mg # = 100 × Mg/(Mg + (0.85 × FeTotal))), which carried occasional small xenoliths. As the SQVF evolved with time, differentiated magmas (Mg # < 64) became increasingly common, but primitive magmas, virtually devoid of xenoliths and unusually rich in olivine phenocrysts, dominanted at the youngest cones. Abundances of incompatible elements declined during evolution of the SQVF, implying a temporal increase in the extent of partial melting in the mantle, or progressive exhaustion of these elements in the source. Samples from two cones, Mazo and Ceniza, show relatively low Ce/Pb, ɛNd, and 206Pb/204Pb and high 87Sr/86Sr, which we interpret as evidence for crustal contamination of these magmas. Small isotopic variations for the other cones are collectively interpreted to reflect involvement of at least three mantle components beneath the SQVF. Ranges in isotopic composition overlap for primitive and differentiated rocks, supporting fractional crystallization as the mechanism for deriving the latter from the former. Most differentiated rocks can be successfully modeled by fractional crystallization of olivine, plagioclase, clinopyroxene, and spinel from primitive parents. The largest and most abundant xenoliths were carried by differentiated magmas, indicating that fractional crystallization took place within the mantle, below the level of peridotite entrainment, and reflecting the importance of fractionation-elevated volatile contents for driving these differentiated magmas rapidly to the surface. Primitive rocks of the SQVF are unusual compared to other reported intraplate-type mafic alkalic suites from around the world in having

  10. A Compaction-Corrected Inclination for the Middle Cretaceous Valle Group in Vizcaino Terrane, Baja California, Mexico: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Li, Y.; Kodama, K. P.; Smith, D. P.

    2001-12-01

    A recent paleomagnetic re-study of the middle-Cretaceous Valle Group of Baja California, Mexico has observed inclinations about 15° shallower than previously reported anomalously shallow inclinations. We have conducted compaction experiments and made remanence anisotropy measurements to determine if burial compaction is a cause of the shallowing. In the laboratory compaction experiments, one sample of coarse-grained sandstone was carefully disaggregated and made into a slurry with an initial water content of 82%. The sediment slurry was then compacted in our water tank consolidometer in the Earth's field which has an inclination of 60° in the laboratory. This inclination is close to the expected Cretaceous geomagnetic field direction for the Valle Group at its present position with respect to North America. The experiments indicated that the inclination of the Valle Group sandstone shallowed by 9.6° corresponding to a volume loss of 16.6% during compaction. The experiment was also used to determine the individual magnetic particle anisotropy, a, of 1.494, which allows us to use Jackson et al.'s (1991) model for correcting inclination. Eleven samples lithologically similar to the one disaggregated were chosen for a preliminary inclination correction. A sample by sample correction yielded corrected inclinations (Inc =24.5° , Dec=347.1° , \\alpha95=5.7° ) higher than the uncorrected 11 sample mean (Inc=19° , Dec=347.2° , \\alpha95=5.7° ), but statistically indistinguishable from the uncorrected site mean (Inc=20.5° , Dec=341.3° , \\alpha95=4° ) for all 12 sites of our samples from the middle Cenomanian section of Valle Fm.. Therefore, burial compaction could account for only about 6° of inclination shallowing of the coarse-grained samples. The compaction-corrected inclinations for these samples are still about 30° shallower than the expected inclination for Cretaceous North America. However, given the small number of samples and limited lithology of

  11. Numerical Simulation of Fault Interaction in a Trans-Tensional Setting, the La Paz Los Cabos Region, Baja California, Mexico.

    NASA Astrophysics Data System (ADS)

    Zielke, O.; Arrowsmith, R. J.

    2006-12-01

    A number of medium to large normal faulting earthquakes occurred in the La Paz-Los Cabos region, at the tip of Baja California, within the last four decades. They (along with the tectonic geomorphology of the fault zones on the Peninsula) demonstrate that the existing structures in the area are active and capable of hazardous earthquakes. The goal of this study is to understand how the individual active faults in this region affect the behavior of the fault system as a whole. What role does fault interaction (i.e., stress transfer) and earthquake triggering play in the La Paz-Los Cabos region? Do we know all the significant, active and therefore hazardous structures that are part of the fault system? Are these structures capable of releasing the tectonically accumulated strain? What role does that fault system play in the regional, trans-tensional setting? To approach these questions we utilize a numerical model, based on derivations by Okada (1992), with which we compute the strain distribution and Coulomb failure stress for a given (frictionless) displacement along a rectangular fault patch and its interactions with other faults of the fault array. Beginning with simple geometric models of the fault system in the La Paz-Los Cabos region, we investigate under what conditions individual earthquakes may have triggered subsequent events. We focused on the M =5.6 event on April 4th 1969 that may have had an effect on the timing of the M=6.2 event on June 30th 1995. The proximity of these two earthquakes (epicenters only 60km apart) supports the idea that stress transfer caused by the 1969 event may have altered the seismic cycle of the fault activated in 1995. Because fault geometry and slip distribution during these two events are not well known, we explore the parameter space to learn under what conditions the 1969 event may have triggered the 1995 event. We apply the empirical relations among magnitude, fault geometry, and displacement, derived by Wells

  12. Baja California: Field Study

    ERIC Educational Resources Information Center

    Frey, John; Stewart, Jack

    1974-01-01

    Describes how to plan and execute an extended field trip which provides first hand observation of biological and cultural systems. Socialization of the participants was achieved through common planning and goal achievement. (BR)

  13. Population genetic structure of annual and perennial populations of Zostera marina L. along the Pacific coast of Baja California and the Gulf of California

    USGS Publications Warehouse

    Munoz-Salazar, R.; Talbot, S.L.; Sage, G.K.; Ward, D.H.; Cabello-Pasini, Alejandro

    2005-01-01

    The Baja California peninsula represents a biogeographical boundary contributing to regional differentiation among populations of marine animals. We investigated the genetic characteristics of perennial and annual populations of the marine angiosperm, Zostera marina, along the Pacific coast of Baja California and in the Gulf of California, respectively. Populations of Z. marina from five coastal lagoons along the Pacific coast and four sites in the Gulf of California were studied using nine microsatellite loci. Analyses of variance revealed significant interregional differentiation, but no subregional differentiation. Significant spatial differentiation, assessed using θ values, was observed among all populations within the two regions. Z. marina populations along the Pacific coast are separated by more than 220 km and had the greatest θ (0.13-0.28) values, suggesting restricted gene flow. In contrast, lower but still significant genetic differentiation was observed among populations within the Gulf of California (θ = 0.04-0.18), even though populations are separated by more than 250 km. This suggests higher levels of gene flow among Gulf of California populations relative to Pacific coast populations. Direction of gene flow was predominantly southward among Pacific coast populations, whereas no dominant polarity in the Gulf of California populations was observed. The test for isolation by distance (IBD) showed a significant correlation between genetic and geographical distances in Gulf of California populations, but not in Pacific coast populations, perhaps because of shifts in currents during El Nino Southern Oscillation (ENSO) events along the Pacific coast.

  14. Population genetic structure of annual and perennial populations of Zostera marina L. along the Pacific coast of Baja California and the Gulf of California.

    PubMed

    Muñiz-Salazar, Raquel; Talbot, Sandra L; Sage, George K; Ward, David H; Cabello-Pasini, Alejandro

    2005-03-01

    The Baja California peninsula represents a biogeographical boundary contributing to regional differentiation among populations of marine animals. We investigated the genetic characteristics of perennial and annual populations of the marine angiosperm, Zostera marina, along the Pacific coast of Baja California and in the Gulf of California, respectively. Populations of Z. marina from five coastal lagoons along the Pacific coast and four sites in the Gulf of California were studied using nine microsatellite loci. Analyses of variance revealed significant interregional differentiation, but no subregional differentiation. Significant spatial differentiation, assessed using theta(ST) values, was observed among all populations within the two regions. Z. marina populations along the Pacific coast are separated by more than 220 km and had the greatest theta(ST) (0.13-0.28) values, suggesting restricted gene flow. In contrast, lower but still significant genetic differentiation was observed among populations within the Gulf of California (theta(ST) = 0.04-0.18), even though populations are separated by more than 250 km. This suggests higher levels of gene flow among Gulf of California populations relative to Pacific coast populations. Direction of gene flow was predominantly southward among Pacific coast populations, whereas no dominant polarity in the Gulf of California populations was observed. The test for isolation by distance (IBD) showed a significant correlation between genetic and geographical distances in Gulf of California populations, but not in Pacific coast populations, perhaps because of shifts in currents during El Niño Southern Oscillation (ENSO) events along the Pacific coast.

  15. California sea lions (Zalophus californianus californianus) have lower chlorinated hydrocarbon contents in northern Baja California, México, than in California, USA.

    PubMed

    Del Toro, Ligeia; Heckel, Gisela; Camacho-Ibar, Víctor F; Schramm, Yolanda

    2006-07-01

    Chlorinated hydrocarbons (CHs) were determined in blubber samples of 18 California sea lions (Zalophus californianus californianus) that stranded dead along Todos Santos Bay, Ensenada, Baja California, México, January 2000-November 2001. Summation operatorDDTs were the dominant group (geometric mean 3.8 microg/g lipid weight), followed by polychlorinated biphenyls ( summation operatorPCBs, 2.96 microg/g), chlordanes (0.12 microg/g) and hexachlorocyclohexanes (0.06 microg/g). The summation operatorDDTs/ summation operatorPCBs ratio was 1.3. We found CH levels more than one order of magnitude lower than those reported for California sea lion samples collected along the California coast, USA, during the same period as our study. This sharp north-south gradient suggests that Z. californianus stranded in Ensenada (most of them males) would probably have foraged during the summer near rookeries 500-1000 km south of Ensenada and the rest of the year migrate northwards, foraging along the Baja California peninsula, including Ensenada, and probably farther north.

  16. Mycorrhizal perennials of the "matorral xerófilo" and the "selva baja caducifolia" communities in the semiarid Tehuacán-Cuicatlán Valley, Mexico.

    PubMed

    Camargo-Ricalde, Sara Lucía; Dhillion, Shivcharn S; Jiménez-González, Carolina

    2003-04-01

    We investigated the mycorrhizal status of perennial xeric plant species occurring in the "matorral xerófilo" (arid tropical scrub) and the ecotone of the "selva baja caducifolia" (tropical deciduous forest) communities in the semiarid valley of Tehuacán-Cuicatlán, south-central Mexico. The perennial species examined are dominant/codominant elements within the "matorral xerófilo" and the "selva baja caducifolia", both endangered communities in the Biosphere Reserve Tehuacán-Cuicatlán Valley. Of the 50 sampled species, 45 were mycorrhizal. To our knowledge, we report arbuscular mycorrhizae (AM) for the first time in 37 species, of which 21 are endemic to Mexico and nine are endemic to the Valley. We also report AM for the first time in three genera, Buddleja, Hechtia and Zornia, and in one plant family, Buddlejaceae. Beaucarnea gracilis, a threatened species, and Mimosa purpusii, a potentially rare species, are both mycorrhizal. This is the first study of the mycorrhizal status of plant species within the Valley.

  17. Associations between trace elements and clinical health parameters in the North Pacific loggerhead sea turtle (Caretta caretta) from Baja California Sur, Mexico.

    PubMed

    Ley-Quiñónez, César Paúl; Rossi-Lafferriere, Natalia Alejandra; Espinoza-Carreon, Teresa Leticia; Hart, Catherine Edwina; Peckham, Sherwood Hoyt; Aguirre, Alfredo Alonso; Zavala-Norzagaray, Alan Alfredo

    2017-04-01

    This study investigated selected trace elements toxicity in sea turtles Caretta caretta population from Baja California Sur (BCS), Mexico, by analyzing associations among Zn, Se, Cu, As, Cd, Ni, Mn, Pb, and Hg with various biochemical parameters (packed cell volume, leukocytes, and selected blood parameters), and whether their concentrations could have an impact on the health status of sea turtles. Blood samples from 22 loggerhead (C. caretta) sea turtles from BCS, Mexico, were collected for trace elements on biochemistry parameter analyses. Significant associations among trace element levels and the biochemistry parameters were found: Cd vs ALP (R (2) = 0.874, p ˂ 0.001), As vs ALP (R (2) = 0.656, p ˂ 0.001), Mn vs ALP (R (2) = 0.834, p ˂ 0.001), and Ni vs LDH (R (2) = 0.587, p ˂ 0.001). This study is the first report of the biochemical parameters of the North Pacific loggerhead sea turtle (C. caretta) from Baja California Sur, Mexico, and it is the first to observe several associations with toxic and essential trace elements. Our study reinforces the usefulness of blood for the monitoring of the levels of contaminating elements and the results suggest that, based on the associations with health clinical parameters, high levels of Cd and As could be representing a risk to the North Pacific loggerhead population health.

  18. Active Crustal Deformation in the Area of San Carlos, Baja California Sur, Mexico as Shown by Data of Local Earthquake Sequences

    NASA Astrophysics Data System (ADS)

    Munguía, Luis; González-Escobar, Mario; Navarro, Miguel; Valdez, Tito; Mayer, Sergio; Aguirre, Alfredo; Wong, Victor; Luna, Manuel

    2016-10-01

    We analyzed earthquakes of sequences that occurred at different times near San Carlos, a town of approximately 5000 inhabitants. The seismic sequences happened during March-April 1989, October 2000-June 2001, and 5-15 February 2004 at about 200 km west of the Pacific-North America plate boundary. The strong shaking from initial earthquakes of the first two sequences prompted the installation of temporary seismic stations in the area. With data recorded by these stations, we found an earthquake distribution that is consistent with the northwest segment of the Santa Margarita fault. Both the focal depth, that seemed to increase in E-NE direction, and a composite fault-plane solution, obtained from polarity data of the small earthquakes, were also consistent with the main characteristics of that fault. We also found that our normal-faulting mechanism (east side down) was quite similar to centroid moment tensor solutions for earthquakes with M w 5.4 and 5.3 that occurred in the area in February 2004. It is likely, then, that these larger earthquakes also occurred along the Santa Margarita Fault. To get some insight into the regional stress pattern, we compared the above mechanisms with mechanisms reported for other earthquakes of the Pacific margin of Baja California Sur and the Gulf of California regions. We observed that focal mechanisms of the two regions have T axes of stress that plunge sub horizontally in E-NE average direction. The corresponding P axes have N-NW average trend, but for the Pacific earthquakes these axes plunge at angles that are ~35° larger than those for the Gulf earthquakes. These more vertically inclined P axes of compressive stress mean substantial oblique fault motions. The mixture of oblique and strike-slip components of fault motions, as the focal mechanisms show, confirms a transtensional stress regime for the region. Before this research, we knew little about the seismicity and styles of faulting in the area. Now we know that

  19. Primary colonization and breakdown of igneous rocks by endemic, succulent elephant trees (Pachycormus discolor) of the deserts in Baja California, Mexico.

    PubMed

    Bashan, Yoav; Vierheilig, Horst; Salazar, Bernardo G; de-Bashan, Luz E

    2006-07-01

    Trees growing in rocks without soil are uncommon. In two arid regions in Baja California, Mexico, field surveys found large numbers of rock-colonizing elephant trees (Pachycormus discolor (Benth.) Coville ex Standl. (Mexican name: copalquin) growing in igneous rocks (granite and basalt) as primary colonizers without the benefit of soil or with a very small amount of soil generated by their own growth. Many adult trees broke large granite boulders and were capable of wedging, growing in, and colonizing rocks and cliffs made of ancient lava flows. This is the first record of a tree species, apart from the previously recorded cacti, capable of primary colonization of rocks and rock rubble in hot deserts.

  20. Surface Deformation Associated with Geothermal Fluids Extraction at the Cerro Prieto Geothermal Field, Baja California, Mexico Revealed by DInSAR Technique

    NASA Astrophysics Data System (ADS)

    Sarychikhina, O.; Glowacka, E.; Mojarro, J.

    2016-08-01

    The Differential Synthetic Aperture Radar Interferometry (DInSAR) is widely used for surface deformation detection and monitoring.In this paper, ERS-1/2, ENVISAT and RADARSAT-2 synthetic aperture radar (SAR) images acquired between 1993 and 2014 were processed to investigate the evolution of surface deformation at the Cerro Prieto geothermal field, Baja California, Mexico. The conventional DInSAR together with the interferogram stacking method was applied. Average LOS (line of sight) displacement velocity maps were generated for different periods: 1993 - 1997, 1998 - 2000, 2004, 2005, 2007, 2009, and 2012 - 2014, revealing that the area corresponding to Cerro Prieto basin presented the important surface deformation (mainly subsidence) during the entire time of investigation. The changes in the surface deformation pattern and rate were identified. These changes have a good correlation in time with the changes of production in the Cerro Prieto geothermal field.

  1. The stratified microbial community at Laguna Figueroa, Baja California, Mexico: A possible model for prephanerozoic laminated microbial communities preserved in cherts

    NASA Astrophysics Data System (ADS)

    Stolz, John F.; Margulis, Lynn

    1984-12-01

    The microbial mat community of the evaporite flat at North Pond, Laguna Figueroa (Baja California, Mexico) was actively involved in the production of laminated sediments prior to 1978. Heavy rains in 1979 and 1980 flooded the mat with 1 and 3 meters of meteoric water respectively. The flooding deposited up to 10 cm of silicoclastic sediment over theMicrocoleus-dominated mat and resulted in the cessation of laminated sediment deposition. In 1982, the surface had been recolonized by species of cyanobacteria (Spirulina, Oscillatoria) and purple photosynthetic bacteria (Chromatium, Thiocapsa). The silicoclastic sediments and residual evaporites, which overlaid the laminated sediment, had been reworked into an anaerobic, sulfide-rich mud and contained well preserved sheaths of filamentous and coccoid bacteria.

  2. Relationship between metal enrichments and a biological adverse effects index in sediments from Todos Santos Bay, northwest coast of Baja California, México.

    PubMed

    Muñoz-Barbosa, A; Gutiérrez-Galindo, E A; Daesslé, L W; Orozco-Borbón, M V; Segovia-Zavala, J A

    2012-02-01

    In 1992 and 2004, heavy metals concentrations were measured in surficial sediments from Todos Santos Bay, located in Ensenada, Baja California, Mexico. The aim was to search for relationships between metal enrichment factors and a biological adverse effects index. Unlike Ni, the elements Cd, Cu and Zn showed significant correlations (p<0.05) between enrichment factors and the biological adverse effects index. Cu showed a 0.74:1 relationship, which means that any enrichment above 0.74 could represent biological adverse effects. On the other hand, Cd and Zn enrichments must be >5.5 and >1.5, respectively, in order for the sediments to be considered toxic. In general, data showed that most of the metal concentrations in Todos Santos Bay sediments could not cause adverse effects to biota. Only Ensenada's harbor and the zone next to a dredging dumping site showed metal enrichments that could be toxic. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Arsenic and mercury contamination of sediments of geothermal springs, mangrove lagoon and the Santispac bight, Bahía Concepción, Baja California peninsula.

    PubMed

    Leal-Acosta, María Luisa; Shumilin, Evgueni; Mirlean, Nicolai; Sapozhnikov, Dmitry; Gordeev, Vyacheslav

    2010-12-01

    In order to find out the environmental impact on the coastal zone, the composition of sediments of the intertidal geothermal hot spring zone and adjacent area of Playa Santispac in the pristine Bahía Concepción (Baja California peninsula) was studied. High concentrations of As (13-111 mg kg⁻¹) and Hg (0.55-25.2 mg kg⁻¹) were found in the sediments of the geothermal sources. Arsenic and Hg concentrations decrease rapidly in the adjacent small mangrove lagoon sediments and reach background levels (0.7-2.6 mg kg⁻¹ and 6-60 μg kg⁻¹ respectively) in the marine sediments collected in front of Playa Santispac.

  4. Lunar phase and catch success of the striped marlin (Tetrapturus audax) in sport fishing at Los Cabos, Baja California Sur, Mexico.

    PubMed

    Ponce-Díaz, G; Ortega-García, S; Hernández-Vázquez, S

    2003-06-01

    The influence of the lunar phases on the catch-per-unit effort (CPUE) of the striped marlin (Tetrapturus audax) captured by the Cabo San Lucas, Baja California Sur, Mexico sport-fishing fleet from October 1987 to June 1989 was analyzed. The information is from 3,377 fishing trips by 13 vessels that represent about 10% of the fleet. The analysis of the CPUE showed a maximum in January 1988 and a minimum in February 1989. Taking into account the knowledge of the factors that had influence on the fishing success is important in the resource management. No significant difference during the full moon compared with results during other lunar phases was found.

  5. Baseline study of morphometric traits of wild Capsicum annuum growing near two biosphere reserves in the Peninsula of Baja California for future conservation management.

    PubMed

    Murillo-Amador, Bernardo; Rueda-Puente, Edgar Omar; Troyo-Diéguez, Enrique; Córdoba-Matson, Miguel Víctor; Hernández-Montiel, Luis Guillermo; Nieto-Garibay, Alejandra

    2015-05-10

    Despite the ecological and socioeconomic importance of wild Capsicum annuum L., few investigations have been carried out to study basic characteristics. The peninsula of Baja California has a unique characteristic that it provides a high degree of isolation for the development of unique highly diverse endemic populations. The objective of this study was to evaluate for the first time the growth type, associated vegetation, morphometric traits in plants, in fruits and mineral content of roots, stems and leaves of three wild populations of Capsicum in Baja California, Mexico, near biosphere reserves. The results showed that the majority of plants of wild Capsicum annuum have a shrub growth type and were associated with communities consisting of 43 species of 20 families the most representative being Fabaceae, Cactaceae and Euphorbiaceae. Significant differences between populations were found in plant height, main stem diameter, beginning of canopy, leaf area, leaf average and maximum width, stems and roots dry weights. Coverage, leaf length and dry weight did not show differences. Potassium, sodium and zinc showed significant differences between populations in their roots, stems and leaves, while magnesium and manganese showed significant differences only in roots and stems, iron in stems and leaves, calcium in roots and leaves and phosphorus did not show differences. Average fruit weight, length, 100 fruits dry weight, 100 fruits pulp dry weight and pulp/seeds ratio showed significant differences between populations, while fruit number, average fruit fresh weight, peduncle length, fruit width, seeds per fruit and seed dry weight, did not show differences. We concluded that this study of traits of wild Capsicum, provides useful information of morphometric variation between wild populations that will be of value for future decision processes involved in the management and preservation of germplasm and genetic resources.

  6. Placental biomarkers of PAH exposure and glutathione-S-transferase biotransformation enzymes in an obstetric population from Tijuana, Baja California, Mexico.

    PubMed

    Dodd-Butera, Teresa; Quintana, Penelope J E; Ramirez-Zetina, Martha; Batista-Castro, Ana C; Sierra, Maria M; Shaputnic, Carolyn; Garcia-Castillo, Maura; Ingmanson, Sonja; Hull, Stacy

    2017-01-01

    Environmental exposures along the US-Mexico border have the potential to adversely affect the maternal-fetal environment. The purpose of this study was to assess placental biomarkers of environmental exposures in an obstetric population at the California-Baja California border in relation to detoxifying enzymes in the placenta and nutritional status. This study was conducted on consenting, full-term, obstetric patients (n=54), delivering in a hospital in Tijuana, Baja California (BC), Mexico. Placental polyaromatic hydrocarbon (PAH)-DNA adducts were measured in addition to placental glutathione-S-transferase (GST) activity and genotype, maternal serum folate, and maternal and umbilical cord blood lead and cadmium levels. A questionnaire was administered to the mothers to determine maternal occupation in a maquiladora, other exposures, and obstetric indicators. In univariate analysis, maternal serum folate levels were inversely correlated with total PAH-DNA adducts (rho=-0.375, p=0.007); adduct #1 (rho=-0.388, p=0.005); and adduct #3 (rho =-0.430, p=0.002). Maternal lead levels were significantly positively correlated with cord blood lead levels (rho=0.512, p<0.001). Cadmium levels were generally very low but significantly higher in mothers exposed to environmental tobacco smoke (ETS) (either at work or at home, n=10). In multivariate analysis, only maternal serum folate levels remained as a significant negative predictor of total DNA-PAH adducts levels in placenta. These findings affirm that placental tissue is a valuable and readily available source of human tissue for biomonitoring; and indicate that further study of the role of nutrition in detoxification and mitigation of environmental exposures in pregnant women is warranted.

  7. Temporal geochemical evolution of Neogene volcanism in northern Baja California (27° 30° N): Insights on the origin of post-subduction magnesian andesites

    NASA Astrophysics Data System (ADS)

    Pallares, Carlos; Bellon, Hervé; Benoit, Mathieu; Maury, René C.; Aguillón-Robles, Alfredo; Calmus, Thierry; Cotten, Joseph

    2008-09-01

    New field, major and trace element and whole rock K-Ar data on the Neogene volcanic fields of northern Baja California (Jaraguay and San Borja) show that the calc-alkaline activity of the Comondú arc vanished around 11 Ma, following the end of the subduction of the young oceanic Farallon plate. It was immediately replaced by magnesian andesite volcanism, showing paroxysmal activities between 8.5 and 3.8 Ma in Jaraguay, and 3.7 to 1.8 Ma in San Borja. Our modelling results show that the characteristic geochemical signature of the magnesian andesite suite (high MgO, Cr, Co and Ni contents; highly fractionated rare earth element (REE) patterns with strong depletion in heavy REE and Y; exceptional enrichments in Sr and Ba and relative depletion in Rb and Th) is consistent with an origin through dehydration melting of pargasite-rich lithospheric mantle at depths of ca. 80 km. The temporal geochemical evolution of the Baja California magnesian andesite suite is studied using a set of 98 K-Ar dated whole rock samples ranging in age from Upper Miocene to Pleistocene. It is marked by an increase of incompatible elements concentrated in pargasitic amphibole (Sr, Ba, K, light REE), which were released in large amounts during dehydration melting, and conversely by the progressive exhaustion in Rb and Th hosted in small quantities by this mineral. The progressive temporal depletion in Y and heavy REE of the suite is consistent with the increase of the amount of residual garnet in the lithospheric mantle as a product of the dehydration melting reaction. This melting occurred at minimal temperatures of 1050-1075 °C, consistent with a high thermal flux in the mantle wedge. This flux was linked to the opening of an asthenospheric window following ridge-trench collision, and later to the "no-slab" regime which followed the sinking of the Farallon plate into the deep mantle.

  8. Geological Evidence That Resolves the Baja-BC Controversy: Detrital Zircons Indicate That Vancouver Island Was Adjacent to Southern California in the Late Cretaceous

    NASA Astrophysics Data System (ADS)

    Guest, B.; Matthews, W.; Coutts, D. S.; Bain, H.; Hubbard, S. M.

    2015-12-01

    The Baja-BC hypothesis is at the center of a great earth sciences controversy. It stems from paleomagnetic observations that require large-scale displacements of continental crust from low latitudes (Baja, California) to moderate latitudes (British Columbia). Many geologists dispute the scale of the displacements due to a lack of corroborating geological evidence. We provide a robust, geological dataset that confirms the paleomagnetic observations. Detrital zircons from Cretaceous to Paleocene sandstone of the Nanaimo Group, which crops out in western Vancouver Island and the Gulf Islands of southwest British Columbia, are analyzed. The data show a clear transition from local <300 Ma western Coast Plutonic Complex sources in the Campanian, to sources that include a significant component of >300 Ma grains in the Maastrichtian-Paleogene. An identical pattern is observed in detrital zircon datasets from southern California forearc basin deposits, and schists interpreted as the subducted remnants of forearc deposits. With a high-n dataset (n=3041) we are able to rule out possible >300 Ma source regions in Canada and the northern United States, and uniquely tie Nanaimo Group rocks to the Mojave-Sonora region of SW United States. This implies that at the end of the Cretaceous, Vancouver Island and western mainland BC were adjacent to southern California and northwestern Mexico, requiring 1900 km of displacement during the latest Cretaceous and Paleocene, consistent with paleomagnetic results. An implication of this result is that the western Coast Batholith of southwest BC was positioned between the northern Peninsular Ranges and southern Sierra Nevada batholiths in the late Cretaceous, and likely represents a displaced segment of a once continuous Cordilleran arc batholith. These results have broad implications for our understanding of episodic arc magmatism in the Cordillera, the tectonic evolution of western North America, Laramide orogenesis, the development and

  9. [Community structure and association of waterbirds with spatial heterogeneity in the Bahia Magdalena-Almejas wetland complex, Baja California Sur, Mexico].

    PubMed

    Zárate-Ovando, Bulmara; Palacios, Eduardo; Reyes-Bonilla, Héctor

    2008-03-01

    Community structure and association of waterbirds with spatial heterogeneity in the Bahia Magdalena-Almejas wetland complex, Baja California Sur, Mexico. To test the hypothesis that spatial heterogeneity determines waterbird diversity in a coastal wetland, we compared waterbird density, diversity, and species composition among various habitats and landscapes units in Bahia Magdalena-Almejas, Baja California Sur, Mexico. Based on diversity patterns and bird distribution, we assessed the effect of coastal development on the waterbird community structure. To gather information on habitat features and waterbird populations we conducted waterbird censuses in 329 habitat segments along the internal coastline of the study area, from February 2002 to February 2003. We performed non-parametric analyses to test the null hypothesis of no diference on waterbird density, and diversity among landscape units and seasons. The species composition was evaluated using ordination techniques. Waterbird density was higher in winter and autumn in the three lagoons of the study area, particularly in the insular coast, sandy beach and dunes; it was higher in the few segments of antropic sustrate. Diversity was significantly higher in mangrove habitat along the peninsular coast, and in mangrove-dunes association on the insular coast. Although modification of coastal natural habitat and boat transit disturbance had no influence on waterbird density or diversity, the highest richness of waterbirds occurred in well preserved areas. Species composition analysis showed differences between Santo Domingo Channel and Magdalena Bay. Pelagic and mangrove habitat had a species composition difference higher than those associations in other habitats. Such differences in species assemblages by habitat and landscape units suggest that communities are structured according to the range of available natural resources in structurally complex habitats, and that dominant piscivorous waterbird species were

  10. Air-Sea CO2 fluxes and NEP changes in a Baja California Coastal Lagoon during the anomalous North Pacific warm condition in 2014

    NASA Astrophysics Data System (ADS)

    Ávila López, M. D. C.; Martin Hernandez-Ayon, J. M.; Camacho-Ibar, V.; Sandoval Gil, J.; Mejía-Trejo, A.; Félix-Bermudez, A.; Pacheco-Ruiz, I.

    2015-12-01

    The present study examines the temporal variability of seawater carbonate chemistry and air-sea CO2 fluxes (FCO2) in a Baja California Mediterranean-climate coastal lagoon. This study was carried out from Nov-2013 to Nov-2014, a period in which anomalous warm conditions were present in the North Pacific Ocean influenced the local oceanography in the adjacent coastal waters off Baja California. These ocean conditions resulted on a negative anomaly of upwelling index, which led to summer-like season (weak upwelling condition) that could be observed in the response of carbon dynamics and metabolic status in San Quintín Bay. Minor changes in dissolved inorganic carbon (DIC) concentration during spring months (~100 µmol kg-1) where observed and were associated to biological processes within the lagoon. High DIC (~2200 µmol kg-1), pCO2 (~800 μatm), and minimum pH (~7.8) values were observed in summer, reflecting the predominance of respiration processes apparently mostly linked to the remineralization of sedimentary organic matter supplied from macroalgal blooms. San Quintín Bay acted as a weak source of CO2 to the atmosphere during the study period, with maximum value observed in July (~10 mmol C m-2 d-1). Temporal biomass production of macroalgae contributed to about 50% of total FCO2 estimated in spring-summer seasons, that was a potencial internal source of organic matter to fuel respiration processes in San Quintín Bay. Eelgrass metabolism contributes in a lower degree in total FCO2. During the anomalous ocean conditions in 2014, the lagoon switched seasonally between net heterotrophy and net autotrophy during the study period, where photosynthesis and respiration processes in the lagoon were closer to a balance. Whole-system metabolism and FCO2 clearly indicated the strong dependence of San Quintín Bay on upwelling conditions and benthic metabolism activity, which was mainly controlled by dominant primary producer communities.

  11. Isopods of the genus Ligia as potential biomonitors of trace metals from the gulf of California and pacific coast of the Baja California peninsula.

    PubMed

    García-Hernández, Jaqueline; Hurtado, Luis A; Leyva-García, Germán; Güido-Moreno, Adrián; Aguilera-Márquez, Daniela; Mazzei, Veronica; Ferrante, Margherita

    2015-02-01

    Supralittoral and high intertidal coastal zones are exposed to pollution from both marine and terrestrial sources and undergo higher deposition rates than the subtidal zone. It is therefore important to identify organisms for this section of the coastal area that can be tolerant to contaminants. The aim of this study was to determine if supralittoral isopods of the genus Ligia can be used as biomonitors, since they are abundant and widely distributed. For this purpose, concentrations of trace elements were determined in Ligia isopods in toto from 26 locations across the Gulf of California and Pacific coast of the Baja California peninsula, which were collected during the summers of 2009 and 2010. The concentrations of trace elements followed the order of; Zn≥Cu>As>Cd>Pb>Hg. Elevated concentrations of copper (up to 1010 μg/g) were detected in Ligia from Santa Rosalía (SRo), a locality where industrial mining of copper has historically occurred. Industrial and municipal sewage discharges appear to have contributed to the high concentrations of zinc (326 μg/g) and lead (144 μg/g) found in organisms from Guaymas location. The high mercury concentration in organisms from Mazatlán (M) (2.01 μg/g) was associated with a thermoelectric plant. Natural sources of metals were also detected; coastal upwelling appears to be associated with high cadmium concentrations in Ligia from Punta Baja (PB) (256 μg/g) in the Pacific coast, whereas hydrothermal vents may have contributed to high concentrations of arsenic at Ensenada (E) (61 μg/g). Our results suggest that Ligia isopods reflect the natural and anthropogenic inputs of trace metals in the environment and could potentially be used as biomonitor organisms of the intertidal rocky shores of the Gulf of California and Pacific coast. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Volcanic Markers of the Post-Subduction Evolution of Baja California and Sonora, Mexico: Slab Tearing Versus Lithospheric Rupture of the Gulf of California

    NASA Astrophysics Data System (ADS)

    Calmus, Thierry; Pallares, Carlos; Maury, René C.; Aguillón-Robles, Alfredo; Bellon, Hervé; Benoit, Mathieu; Michaud, François

    2011-08-01

    The study of the geochemical compositions and K-Ar or Ar-Ar ages of ca. 350 Neogene and Quaternary lavas from Baja California, the Gulf of California and Sonora allows us to discuss the nature of their mantle or crustal sources, the conditions of their melting and the tectonic regime prevailing during their genesis and emplacement. Nine petrographic/geochemical groups are distinguished: "regular" calc-alkaline lavas; adakites; magnesian andesites and related basalts and basaltic andesites; niobium-enriched basalts; alkali basalts and trachybasalts; oceanic (MORB-type) basalts; tholeiitic/transitional basalts and basaltic andesites; peralkaline rhyolites (comendites); and icelandites. We show that the spatial and temporal distribution of these lava types provides constraints on their sources and the geodynamic setting controlling their partial melting. Three successive stages are distinguished. Between 23 and 13 Ma, calc-alkaline lavas linked to the subduction of the Pacific-Farallon plate formed the Comondú and central coast of the Sonora volcanic arc. In the extensional domain of western Sonora, lithospheric mantle-derived tholeiitic to transitional basalts and basaltic andesites were emplaced within the southern extension of the Basin and Range province. The end of the Farallon subduction was marked by the emplacement of much more complex Middle to Late Miocene volcanic associations, between 13 and 7 Ma. Calc-alkaline activity became sporadic and was replaced by unusual post-subduction magma types including adakites, niobium-enriched basalts, magnesian andesites, comendites and icelandites. The spatial and temporal distribution of these lavas is consistent with the development of a slab tear, evolving into a 200-km-wide slab window sub-parallel to the trench, and extending from the Pacific coast of Baja California to coastal Sonora. Tholeiitic, transitional and alkali basalts of subslab origin ascended through this window, and adakites derived from the partial

  13. The role of tropical cyclones on landscape dynamics in southern Baja California, Mexico based on Late Pleistocene-Holocene alluvial stratigraphy

    NASA Astrophysics Data System (ADS)

    McDonald, Eric; Antinao, Jose Luis; Rhodes, Edward J.; Brown, Nathan; Gosse, John

    2015-04-01

    Region-wide alluvial records provide evidence that time-transgressive changes in climate can be a major driver of landscape evolution. Historically, landfall of eastern Pacific tropical cyclones in southwestern North America during the late summer and early fall provide the strongest storms that have demonstrated geomorphic impact on the landscape. The alluvial fan record of the southern portion of Baja California (Mexico) was investigated to determine if linkages exist between region-wide fluvial deposits and tropical cyclones. The regional distribution and Pleistocene to Holocene morphostratigraphy of alluvial fans has been established for the southern portion of Baja California with primary focus on the La Paz and San José del Cabo basins. Six discrete morphopedosedimentary alluvial units (Qt1 through Qt6) were differentiated across the region using a combination of geomorphologic mapping, sedimentological analysis, and soil development further reinforced with geochronology using radiocarbon, optically stimulated luminescence and cosmogenic depth-profiles. A first phase of regional aggradation began before ~ 100 ka (Qt1) and culminated ~10 ka (Qt4). After deposition of Qt4, increasing regional incision of older units and the progressive development of a channelized alluvial landscape coincide with deposition of Qt5 and Qt6 units in a second, incisional phase. All units are conformed of multiple 1-3 m thick alluvial packages deposited in upper-flow regime and representing individual storms. Aggradational units (Qt1-Qt4) covered broad (>2 km) channels in the form of sheetflood deposition while incisional stage deposits are mostly confined to channels of ~0.5-2 km width. Continuous deposition of the thicker sequences is demonstrated by closely spaced luminescence dates in vertical profiles. In a few places disconformities between major units are evident and indicated by partly eroded buried soils. Analysis of historical terraces as part of the younger units

  14. Mantle Transition Zone Derivation of Ultramafic Xenoliths in San Quintin Volcanic Field, Baja California: Evidence from Micro-Laser Raman Spectroscopic Study.

    NASA Astrophysics Data System (ADS)

    Basu, A. R.; Chakrabarty, P.

    2016-12-01

    Spinel lherzolite xenoliths from the Holocene San Quintin Volcanic field in Baja California are well-studied for their mineralogical, petrological and geochemical characteristics, including their micro-structural and seismic properties that collectively suggest complex multiple histories of plastic deformation, re-crystallization and melt-rock interactions in the upper mantle. The ultramafic xenoliths are remarkable for their strong deformation displaying granular, porphryoclastic, tabular mosaic and equigranular microstructures. We used a Thermo ScientificTM DXRTMxi Raman Imaging microscope with an Ar ion 532 nm wavelength laser to image the various mineral phases in olivines and orthopyroxenes of several of the xenoliths. Many of the samples show hematite-decorated dislocations in the large ( 2mm) olivine grains showing sub-grain boundaries. We confirmed the hematite in the dislocation structures by their Raman spectra. Most interestingly, the olivine grains show Raman shift at 823.3 cm-1 and 855.8 cm-1: often these doublets show inversion and a slight shift to the higher side with respect to forsteritic olivine, indicating high pressure Mg2SiO4 phase. The presence of both high pressure and normal olivine within a 30 mµ range of the olivine in a number of samples studied indicate derivation of the xenoliths from the mantle transition zone in an upward flow and decompression while the hematite precipitated along the dislocations in the olivine. In some of the orthopyroxene grains adjacent to these olivines, showing high pressure Mg2SiO4 and normal forsteritic olivine, the presence of clinoenstatite lamellae are also confirmed by Raman studies. In summary, we present in this study three lines of evidence including exsolution of Fe3+ - bearing hematite along dislocations in olivine, presence of high pressure Mg2SiO4 containing this hematite-decorated dislocations and finally the clinoenstatite lamellae in orthopyroxene, indicating that the mineralogy of the spinel

  15. Tectonic and magmatic controls on the location of post-subduction monogenetic volcanoes in Baja California, Mexico, revealed through spatial analysis of eruptive vents

    NASA Astrophysics Data System (ADS)

    Germa, Aurélie; Connor, Laura J.; Cañon-Tapia, Edgardo; Le Corvec, Nicolas

    2013-12-01

    Post-subduction (12.5 Ma to less than 1 Ma) monogenetic volcanism on the Baja California peninsula, Mexico, formed one of the densest intra-continental areas of eruptive vents on Earth. It includes about 900 vents within an area ˜700 km long (N-S) and 70 to 150 km wide (W-E). This study shows that post-subduction volcanic activity was distributed along this arc and that modes exist in the volcano distribution, indicating that productivity of the magma source region was not uniform along the length of the arc. Vent clustering, vent alignments, and cone elongations were measured within eight monogenetic volcanic fields located along the peninsula. Results indicate that on a regional scale, vent clustering varies from north to south with denser spatial clustering in the north on the order of 1.9 × 10-1 vents/km2 to less dense clustering in the south on the order of 7.8 × 10-2 vents/km2. San Quintin, San Carlos, Jaraguay, and Santa Clara are spatially distinct volcanic fields with higher eruptive vent densities suggesting the existence of individual melt columns that may have persisted over time. In contrast, the San Borja, Vizcaino, San Ignacio, and La Purisima vent fields show lower degrees of vent clustering and no obvious spatial gaps between fields, thus indicating an area of more distributed volcanism. Insight into the lithospheric stress field can be gained from vent alignments and vent elongation measurements. Within the fields located along the extinct, subduction-related volcanic arc, elongation patterns of cinder cones and fissure-fed spatter cones, vent clusters, and vent alignments trend NW-SE and N-S. Within the Santa Clara field, located more to the west within the forearc, elongation patterns of the same volcanic features trend NE-SW. These patterns suggest that magmatism was more focused in the forearc and in the northern part of Baja California than in its southern region. Within the extinct arc, magma ascent created volcano alignments and elongate

  16. Numerical simulation of groundwater artificial recharge in a semiarid-climate basin of northwest Mexico, case study the Guadalupe Valley Aquifer, Baja California

    NASA Astrophysics Data System (ADS)

    Campos-Gaytan, J. R.; Herrera-Oliva, C. S.

    2013-05-01

    In this study was analyzed through a regional groundwater flow model the effects on groundwater levels caused by the application of different future groundwater management scenarios (2007-2025) at the Guadalupe Valley, in Baja California, Mexico. Among these studied alternatives are those scenarios designed in order to evaluate the possible effects generated for the groundwater artificial recharge in order to satisfy a future water demand with an extraction volume considered as sustainable. The State of Baja California has been subject to an increment of the agricultural, urban and industrials activities, implicating a growing water-demand. However, the State is characterized by its semiarid-climate with low surface water availability; therefore, has resulted in an extensive use of groundwater in local aquifer. Water level measurements indicate there has been a decline in water levels in the Guadalupe Valley for the past 30 years. The Guadalupe Valley aquifer represents one the major sources of water supply in Ensenada region. It supplies about 25% of the water distributed by the public water supplier at the city of Ensenada and in addition constitutes the main water resource for the local wine industries. Artificially recharging the groundwater system is one water resource option available to the study zone, in response to increasing water demand. The existing water supply system for the Guadalupe Valley and the city of Ensenada is limited since water use demand periods in 5 to 10 years or less will require the construction of additional facilities. To prepare for this short-term demand, one option available to water managers is to bring up to approximately 3.0 Mm3/year of treated water of the city of Ensenada into the valley during the low-demand winter months, artificially recharge the groundwater system, and withdraw the water to meet the summer demands. A 2- Dimensional groundwater flow was used to evaluate the effects of the groundwater artificial recharge

  17. Eruption and magma crystallization ages of Las Tres Vírgenes (Baja California) constrained by combined 230Th/ 238U and (U-Th)/He dating of zircon

    NASA Astrophysics Data System (ADS)

    Schmitt, Axel K.; Stockli, Daniel F.; Hausback, Brian P.

    2006-11-01

    Las Tres Vírgenes volcano is a calc-alkaline composite cone located near the main Gulf of California escarpment on the E coast of the Baja California peninsula. High-sensitivity ion microprobe U-series ( 230Th/ 238U) ages for zircon from La Vírgen tephra average 121 - 10 + 12 ka (1σ; MSWD = 2.7), with discrete age peaks at ˜ 100 and 160 ka. The noble gas mass spectrometric (U-Th)/He zircon age, corrected for disequilibrium and pre-eruptive storage, is 36 ± 3 ka. This result for the eruption age of La Vírgen tephra is significantly older than previously postulated historic or Holocene ages that were based on an 18th century map reference and 14C dating of accidental charcoal, respectively. The new (U-Th)/He zircon age is consistent with a > 26 ± 4 ka age derived from cosmogenic He exposure dating of an overlying basaltic lava flow [Hausback, B.P. and Abrams, M.J., 1996. Plinian eruption of La Virgen Tephra, Volcán Las Tres Virgenes, Baja California Sur, Mexico. Eos, Transactions, American Geophysical Union, 77(46, Suppl.): 813-814.]. U-Pb zircon analysis of ignimbrites erupted from the adjacent Early Pleistocene La Reforma and El Aguajito calderas yielded ages of 1.38 ± 0.03 Ma ( n = 12; MSWD = 1.0) and 1.17 ± 0.07 Ma ( n = 23; MSWD = 1.3), respectively. No evidence for these ages is found among La Vírgen zircons, whereas pre-Quaternary zircon xenocrysts are common. The La Vírgen magma, therefore, evolved unrelated to Early Pleistocene magmatism in adjacent calderas, but assimilated local basement rocks. A gap between average Th-U and (U-Th)/He zircon ages suggests that zircon crystallization was discontinuous in the La Vírgen magma chamber. In addition, partial resorption of zircon suggests episodic thermal rejuvenation, most likely by basaltic recharge. Based on the zircon record, the > 100 ka lifetime of the thermal anomaly that sustained repeated intrusive pulses significantly exceeds the age of the last eruption. This strengthens the view that Tres

  18. A New High-Precision Paleomagnetic Reference Vector From Mesa El Burro, Mesa Cartabón, and Mesa El Pinole, Baja California for the Tuff of San Felipe, a Miocene Ignimbrite Marker Bed Exposed in Baja California and Sonora, México

    NASA Astrophysics Data System (ADS)

    Bennett, S. E.; Oskin, M. E.

    2008-12-01

    High precision paleomagnetic vectors from regional ignimbrite markers are valuable for quantifying distributed shear deformation in plate boundary zones. In central Baja California, we measured a new high- precision paleomagnetic reference vector for the 12.50 Ma Tuff of San Felipe (Tsf), a regionally-extensive Miocene ignimbrite deposit which blanketed >4000km2 of present day northeastern Baja California and western Sonora (Oskin and Stock, 2003) prior to the opening of the northern Gulf of California. This new reference location is west of both the main Gulf topographic escarpment and the San Pedro Martír fault that marks the western edge of the Gulf Extensional Province. Because this reference location has remained tectonically stable since the eruption and deposition of Tsf, the paleomagnetic vector measured here is a good estimate of the magnetic field at the time Tsf cooled below the Curie temperature. We selected three mesas capped by Tsf for paleomagnetic sampling: Mesa El Burro 1 km south of El Metate, Mesa Cartabón 9 km southwest of El Metate, and Mesa El Pinole 20 km northwest of El Metate. These mesas are capped by 10-30 m of the Tuff of San Felipe and are amongst the most western exposures of this ignimbrite documented in Baja California. In the area of these mesas, Tsf was deposited on a generally flat landscape with minor paleo-topography incised into 15-110 m of coarse sedimentary rocks. These strata nonconformably overlie a variety of plutonic and metamorphic basement rocks. Locally, Tsf infills westward- draining paleo-drainages carved into the still-horizontal underlying conglomerates. 50 randomly-oriented cores were drilled in Tsf at these three mesas and 48 of these cores together yield a mean direction of 212.4° declination, -3.0° inclination with an α-95 confidence of 1.33°. This direction lies well off of the expected Miocene paleo-pole position and records an apparent geomagnetic excursion during reversed polarity subchron C5Ar.2r

  19. Neotectonic studies of northern Baja California, Mexico, with LANDSAT thematic mapper and SPOT panchromatic imagery: Partitioning of dextral and extensional strain at the Pacific-North America plate boundary

    NASA Technical Reports Server (NTRS)

    Miller, M. Meghan; Crippen, Robert E.; Dixon, Timothy H.

    1991-01-01

    Numerous studies of active faulting in southern California indicate that the San Jacinto, Elsinore, and adjacent faults west of the San Andreas fault accommodate a significant proportion of Pacific-North America relative plate motion. Because of the complex distribution of slip, little is known about the activities of these and similar structures in northern Baja California and the southward transition to the oceanic ridge transform-fault system in the Gulf of California. SPOT and LANDSAT Thematic Mapper imagery for northern Baja California was processed to optimize discrimination of lithologic and structural features. This data was used to suggest a preliminary kinematic framework for distribution of relative plate motion between 31 and 33 degrees north, in which continental borderland tectonics play an important role in partitioning of plate motion.

  20. Detección automática de NEOs en imágenes CCD utilizando la transformada de Hough

    NASA Astrophysics Data System (ADS)

    Ruétalo, M.; Tancredi, G.

    El interés y la dedicación por los objetos que se acercan a la órbita de la Tierra (NEOs) ha aumentado considerablemente en los últimos años, tanto que se han iniciado varias campañas de búsqueda sistemática para aumentar la población identificada de éstos. El uso de placas fotográficas e identificación visual está siendo sustituído, progresivamente, por el uso de cámaras CCD y paquetes de detección automática de los objetos en las imágenes digitales. Una parte muy importante para la implementación exitosa de un programa automatizado de detección de este tipo es el desarrollo de algoritmos capaces de identificar objetos de baja relación señal-ruido y con requerimientos computacionales no elevados. En el presente trabajo proponemos la utilización de la transformada de Hough (utilizada en algunas áreas de visión artificial) para detectar automáticamente trazas, aproximadamente rectilíneas y de baja relación señal-ruido, en imágenes CCD. Desarrollamos una primera implementación de un algoritmo basado en ésta y lo probamos con una serie de imágenes reales conteniendo trazas con picos de señales de entre ~1 σ y ~3 σ por encima del nivel del ruido de fondo. El algoritmo detecta, sin inconvenientes, la mayoría de los casos y en tiempos razonablemente adecuados.

  1. Long-term change in eelgrass distribution at Bahía San Quintín, Baja California, Mexico, using satellite imagery

    USGS Publications Warehouse

    Ward, David H.; Morton, Alexandra; Tibbitts, T. Lee; Douglas, David C.; Carrera-Gonzalez, Eduardo

    2003-01-01

    Seagrasses are critically important components of many marine coastal and estuarine ecosystems, but are declining worldwide. Spatial change in distribution of eelgrass, Zostera marina L., was assessed at Bahía San Quintín, Baja California, Mexico, using a map to map comparison of data interpreted from a 1987 Satellite Pour l'Observation de la Terre multispectral satellite image and a 2000 Landsat Enhanced Thematic Mapping image. Eelgrass comprised 49% and 43% of the areal extent of the bay in 1987 and 2000, respectively. Spatial extent of eelgrass was 13% less (-321 ha) in 2000 than in 1987 with most losses occurring in subtidal areas. Over the 13-yr study period, there was a 34% loss of submerged eelgrass (-457 ha) and a 13% (+136 ha) gain of intertidal eelgrass. Within the two types of intertidal eelgrass, the patchy cover class (<85% cover) expanded (+250 ha) and continuous cover class (≥85% cover) declined (-114 ha). Most eelgrass losses were likely the result of sediment loading and turbidity caused by a single flooding event in winter of 1992-1993. Recent large-scale agricultural development of adjacent uplands may have exacerbated the effects of the flood. Oyster farming was not associated with any detectable losses in eelgrass spatial extent, despite the increase in number of oyster racks from 57 to 484 over the study period.

  2. Anisotropy of Magnetic Susceptibility (AMS) of the Neogene Volcanic Succession at the Sierra Juarez - Las PintasVolcanic Province, Northeastern Baja California, Mexico: Preliminary Results

    NASA Astrophysics Data System (ADS)

    Mendoza-Borunda, R.; Cañón-Tapia, E.; Suárez-Vidal, F.; Gradilla-Martínez, L.

    2010-12-01

    The Sierra Juarez-Las Pintas Volcanic Province is among the largest in northern Baja California. For this work, we focused on a bimodal volcanic succession of late Miocene age, composed of an extensive ignimbrite unit and few dispersed basaltic flows that crop out in central Sierra Juarez and northern Sierra Las Tinajas. The ignimbrite is zoned, composed by three distinctive members: a basal unwelded white tuff, a mid-section unwelded orange tuff, and an upper red welded tuff. The basaltic flows are olivine-rich. Samples were collected in five sites that define a NE-SW section across the Sierra Juarez Escarpment, in the western boundary of the so-called Gulf Extensional Province. In each of these sites a stratigraphic column composed of more than one geologic unit was sampled. The total number of analyzed cores is ca. 160. The preliminary results show vertical and lateral variations of the AMS of the ignimbrite that can be interpreted in terms of the local flow direction and processes of emplacement of these volcanic deposits. Such variations, in turn, are likely to reflect variations in the dynamics of the eruptive process that produced them. Although the AMS of all the rocks in this province display a complex set of orientations, in this work is shown that when examined in detail important clues concerning the geological evolution of the province can be obtained from these data.

  3. Pycnogonids associated with the giant lion´s-paw scallop Nodipecten subnodosus (Sowerby) in Ojo de Liebre Bay, Guerrero Negro, Baja California Sur, Mexico

    PubMed Central

    de León-Espinosa, Angel; de León-González, Jesus A.

    2015-01-01

    Abstract Five species of epibenthic pycnogonids collected on the giant lion´s-paw scallop Nodipecten subnodosus are recorded. A new species of Eurycyde, Eurycyde bamberi, is described. Of the 19 species known in this genus; the new species is closest to Eurycyde hispida Kroyer, 1844 but differs from it in the absence of plumose spines and the shapes of the lateral process, first coxa, and ocular tubercle. The new species represents the third member of Eurycyde from the eastern Pacific in addition to Eurycyde spinosa Hilton, 1916 and Eurycyde clitellaria Stock, 1955. Besides Eurycyde bamberi, the following species were collected: Nymphopsis duodorsospinosa Hilton, 1942c; Callipallene californiensis (Hall, 1913); Nymphon lituus Child, 1979; and Pycnogonum rickettsi Schmitt, 1934. Pycnogonum rickettsi is recorded for first time from Mexican waters, as is Nymphon lituus from the western coast of Baja California Peninsula. Each of these four species are re-described and re-illustrated in order to fill in existing gaps in the literature of the region. PMID:26692802

  4. Pycnogonids associated with the giant lion´s-paw scallop Nodipecten subnodosus (Sowerby) in Ojo de Liebre Bay, Guerrero Negro, Baja California Sur, Mexico.

    PubMed

    de León-Espinosa, Angel; de León-González, Jesus A

    2015-01-01

    Five species of epibenthic pycnogonids collected on the giant lion´s-paw scallop Nodipecten subnodosus are recorded. A new species of Eurycyde, Eurycyde bamberi, is described. Of the 19 species known in this genus; the new species is closest to Eurycyde hispida Kroyer, 1844 but differs from it in the absence of plumose spines and the shapes of the lateral process, first coxa, and ocular tubercle. The new species represents the third member of Eurycyde from the eastern Pacific in addition to Eurycyde spinosa Hilton, 1916 and Eurycyde clitellaria Stock, 1955. Besides Eurycyde bamberi, the following species were collected: Nymphopsis duodorsospinosa Hilton, 1942c; Callipallene californiensis (Hall, 1913); Nymphon lituus Child, 1979; and Pycnogonum rickettsi Schmitt, 1934. Pycnogonum rickettsi is recorded for first time from Mexican waters, as is Nymphon lituus from the western coast of Baja California Peninsula. Each of these four species are re-described and re-illustrated in order to fill in existing gaps in the literature of the region.

  5. Biomonitoring with Micronuclei Test in Buccal Cells of Female Farmers and Children Exposed to Pesticides of Maneadero Agricultural Valley, Baja California, Mexico

    PubMed Central

    Castañeda-Yslas, Idalia Jazmin; Arellano-García, María Evarista; García-Zarate, Marco Antonio; Ruíz-Ruíz, Balam; Zavala-Cerna, María Guadalupe; Torres-Bugarín, Olivia

    2016-01-01

    Feminization of the agricultural labor is common in Mexico; these women and their families are vulnerable to several health risks including genotoxicity. Previous papers have presented contradictory information with respect to indirect exposure to pesticides and DNA damage. We aimed to evaluate the genotoxic effect in buccal mucosa from female farmers and children, working in the agricultural valley of Maneadero, Baja California. Frequencies of micronucleated cells (MNc) and nuclear abnormalities (NA) in 2000 cells were obtained from the buccal mucosa of the study population (n = 144), divided in four groups: (1) farmers (n = 37), (2) unexposed (n = 35), (3) farmers' children (n = 34), and (4) unexposed children (n = 38). We compared frequencies of MNc and NA and fitted generalized linear models to investigate the interaction between these variables and exposition to pesticides. Differences were found between farmers and unexposed women in MNc (p < 0.0001), CC (p = 0.3376), and PN (p < 0.0001). With respect to exposed children, we found higher significant frequencies in MNc (p < 0.0001), LN (p < 0.0001), CC (p < 0.0001), and PN (p < 0.004) when compared to unexposed children. Therefore working as a farmer is a risk for genotoxic damage; more importantly indirectly exposed children were found to have genotoxic damage, which is of concern, since it could aid in future disturbances of their health. PMID:26981119

  6. Lack of knowledge about mother-to-child HIV transmission prevention in pregnant women at Tijuana General Hospital, Baja California, Mexico.

    PubMed

    Becka, Chandra M; Chacón-Cruz, Enrique; Araneta, Maria Rosario; Viani, Rolando M

    2015-01-01

    The objective of this study was to identify determinants of human immunodeficiency virus (HIV) knowledge regarding mother-to-child transmission (MTCT) among pregnant women at Tijuana General Hospital, Baja California, Mexico. Between March and November 2003, patients from the prenatal care (n = 1294) and labor and delivery (L&D) units (n = 495) participated in a cross-sectional study to measure HIV knowledge. Less than one-third (30%) knew that HIV could be transmitted to a child during delivery, and 36% knew that HIV could be transmitted by breast-feeding. Only 27% knew that an MTCT could be prevented. Prenatal patients were more likely to know that MTCT was preventable (prenatal: 31% versus L&D 25%; P = .02). Logistic regression indicated that prenatal patients (odds ratio = 1.49, confidence interval 1.07-2.07) were more likely to know that HIV could be transmitted through breast-feeding. Overall, both groups had poor knowledge regarding MTCT of HIV.

  7. An economical non-destructive method for estimating eelgrass, Zostera marina (Potamogetonaceae) leaf growth rates: formal development and use in northwestern Baja California.

    PubMed

    Solana-Arellano, Elena; Echavarria-Heras, Héctor; Franco-Vizcaíno, Ernesto

    2008-09-01

    Seagrass beds provide much of the primary production in estuaries; host many fishes and fish larvae, and abate erosion. The present study presents original analytical methods for estimating mean leaf-growth rates of eelgrass (Zostera marina). The method was calibrated by using data collected in a Z. marina meadow at Punta Banda estuary in Baja California, Mexico. The analytical assessments were based on measurements of leaf length and standard regression procedures. We present a detailed explanation of the formal procedures involved in the derivation of these analytical methods. The measured daily leaf-growth rate was 10.9 mm d(-1) leaf(-1). The corresponding value projected by our method was 10.2 mm d(-1) leaf(-). The associated standard errors were of 0.53 and 0.56 mm d(-1) leaf(-1) respectively. The method was validated by projecting leaf-growth rates from an independent data set, which gave consistent results. The use of the method to obtain the mean leaf growth rate of a transplanted plot is also illustrated. Comparison of our leaf-growth data with previously reported assessments show the significant forcing of sea-surface temperature on eelgrass leaf dynamics. The formal constructs provided here are of general scope and can be applied to equivalent eelgrass data sets in a straightforward manner.

  8. Evolution of the 2014-2015 sea surface temperature warming in the central west coast of Baja California, Mexico, recorded by remote sensing

    NASA Astrophysics Data System (ADS)

    Robinson, Carlos J.

    2016-07-01

    Extraordinarily warm sea surface temperatures were present in the California Current System during 2014-2015. In several locations surface waters temperature registered new record high in the recent time series. This study focuses in the evolution of the warming in the southern part of the California Current System (CCS), off the west coast of Baja California, Mexico. Analysis of monthly sea surface temperature (SST), sea level pressure, and wind speed as measured by satellite from January 1988 to December 2015 show that recent warming occurred during two distinct periods. From May 2014 to April 2015, SST warming was related to weak coastal winds not associated to El Niño. During this period occurred the longest sustained record of 15 months of negative wind anomalies in the series. A reduction of wind stress suggests a weakened coastal upwelling, and consequently, cold water not transported into the surface. The second process of warming occurred from September to December 2015, during a strong El Niño condition.

  9. Biomagnification of mercury and its antagonistic interaction with selenium in yellowfin tuna Thunnus albacares in the trophic web of Baja California Sur, Mexico.

    PubMed

    Ordiano-Flores, Alfredo; Rosíles-Martínez, Rene; Galván-Magaña, Felipe

    2012-12-01

    Mercury and selenium concentrations were determined in muscle of 37 yellowfin tuna (Thunnus albacares) captured aboard of Mexican purse-seiners boats off western coast of Baja California Sur, between Punta Eugenia and Cabo Falso, from October to December 2006. Also, its prey (mainly, jumbo squid Dosidicus gigas and pelagic red crab Pleuroncodes planipes) were analyzed from the stomach contents. All the mercury values obtained were lower that mercury content recommended by standard legal limits for seafood adopted by Mexican norms (typically 0.5-1.0μg g(-1)). Mercury concentrations vary between 0.06 and 0.51μg g(-1) in yellowfin tuna, and from 0.01 to 0.20μg g(-1) in its prey, suggesting that mercury can accumulate in prey tissues and that of their predator. Biomagnification factors (BMF) between predator-prey associations were calculated. The BMFs were >1, indicating that mercury biomagnifies along the food web of yellowfin tuna. In all species studied there was a molar excess of selenium over mercury. The rank order of mean selenium/mercury molar ratios was for pufferfish (42.62)> diamond squid (15.09)>yellowfin tuna (10.29)>pelagic red crab (10.05)>panama lightfish (9.54)> jumbo squid (8.91). The selenium health benefit value (Se-HBV) was calculated to have an improved understanding of the health benefits and risk of fish consumption.

  10. Horizontal movements, vertical-habitat utilization and diet of the jumbo squid ( Dosidicus gigas) in the Pacific Ocean off Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Bazzino, Gastón; Gilly, William F.; Markaida, Unai; Salinas-Zavala, César A.; Ramos-Castillejos, Jorge

    2010-07-01

    We deployed four pop-up archival-transmitting (PAT) tags on jumbo squid ( Dosidicus gigas) collected in the Pacific Ocean off the main entrance to Magdalena Bay on the Baja California peninsula in June 2005. This is the first successful deployment of PAT tags on jumbo squid in an area outside the Gulf of California. Summary data were obtained through the ARGOS satellite system for three of the tags; the fourth tag was physically recovered. All of the tagged squid tended to remain on the shallow continental shelf for several days after tagging and then moved offshore into deeper water. Three of the four squid appeared to migrate in a general southerly direction while the fourth remained offshore of Magdalena Bay. All of the squid spent most daylight hours at depths that were associated with the hypoxic oxygen minimum layer, and at night they spent a majority of time in the upper 50 m of the water column. Stomach content analysis and tag temperature-depth data during the first days after tagging revealed that the squid were feeding on pelagic red crabs ( Pleuroncodes planipes) and several larger, neritic fishes over the continental shelf off Magdalena Bay during a seasonal nearshore upwelling. Comparison of our results with those previously collected in the Gulf of California reveal that Dosidicus gigas can vary its behavior and diet to suit local environmental conditions. This adaptability is likely to be an important factor in the ability of D. gigas to invade and colonize new areas.

  11. Biomonitoring with Micronuclei Test in Buccal Cells of Female Farmers and Children Exposed to Pesticides of Maneadero Agricultural Valley, Baja California, Mexico.

    PubMed

    Castañeda-Yslas, Idalia Jazmin; Arellano-García, María Evarista; García-Zarate, Marco Antonio; Ruíz-Ruíz, Balam; Zavala-Cerna, María Guadalupe; Torres-Bugarín, Olivia

    2016-01-01

    Feminization of the agricultural labor is common in Mexico; these women and their families are vulnerable to several health risks including genotoxicity. Previous papers have presented contradictory information with respect to indirect exposure to pesticides and DNA damage. We aimed to evaluate the genotoxic effect in buccal mucosa from female farmers and children, working in the agricultural valley of Maneadero, Baja California. Frequencies of micronucleated cells (MNc) and nuclear abnormalities (NA) in 2000 cells were obtained from the buccal mucosa of the study population (n = 144), divided in four groups: (1) farmers (n = 37), (2) unexposed (n = 35), (3) farmers' children (n = 34), and (4) unexposed children (n = 38). We compared frequencies of MNc and NA and fitted generalized linear models to investigate the interaction between these variables and exposition to pesticides. Differences were found between farmers and unexposed women in MNc (p < 0.0001), CC (p = 0.3376), and PN (p < 0.0001). With respect to exposed children, we found higher significant frequencies in MNc (p < 0.0001), LN (p < 0.0001), CC (p < 0.0001), and PN (p < 0.004) when compared to unexposed children. Therefore working as a farmer is a risk for genotoxic damage; more importantly indirectly exposed children were found to have genotoxic damage, which is of concern, since it could aid in future disturbances of their health.

  12. Fine scale daily movements and habitat use of East Pacific green turtles at a shallow coastal lagoon in Baja California Sur, Mexico

    USGS Publications Warehouse

    Senko, Jesse; Koch, Volker; Megill, William M.; Carthy, Raymond R.; Templeton, R.obert P.; Nichols, Wallace J.

    2010-01-01

    Green turtles spend most of their lives in coastal foraging areas where they face multiple anthropogenic impacts. Therefore, understanding their spatial use in this environment is a priority for conservation efforts. We studied the fine scale daily movements and habitat use of East Pacific green turtles (Chelonia mydas) at Laguna San Ignacio, a shallow coastal lagoon in Baja California Sur, Mexico where sea turtles are subject to high levels of gillnet bycatch and directed hunting. Six turtles ranging from 44.6 to 83.5 cm in straight carapace length were tracked for short deployments (1 to 6 d) with GPS-VHF telemetry. Turtles were active throughout diurnal, nocturnal, and crepuscular periods. Although they moved greater total distances during daytime, their speed of travel and net displacement remained consistent throughout 24-h periods. A positive selection for areas of seagrass and moderate water depth (5 to 10 m) was determined using Ivlev's electivity index, with neutral selection for shallow water (< 5 m) and avoidance of deep water (> 10 m). Turtles exhibited two distinct behavioral movement patterns: circular movements with high fidelity to the capture–release location and meandering movements with low fidelity to the capture–release location. Our results indicate that green turtles were active throughout the diel cycle while traveling large distances and traversing multiple habitats over short temporal scales.

  13. Trace metals in sediments and Zostera marina of San Ignacio and Ojo de Liebre lagoons in the central pacific coast of Baja California, Mexico.

    PubMed

    Macías-Zamora, J V; Sánchez-Osorio, J L; Ríos-Mendoza, L M; Ramírez-Alvarez, N; Huerta-Díaz, M A; López-Sánchez, D

    2008-08-01

    San Ignacio and Ojo de Liebre lagoons in central Baja California, Mexico are nursery and grazing grounds for whales and turtles. Ojo de Liebre Lagoon also supports a salt mine operation. By concentrating trace metals via evaporation, this activity might harm biota. Consequently, salt mining might be incompatible with the lagoon's ecological role. Eelgrass can incorporate these elements and reroute them to other organisms. Trace metals in sediments (Cd, Co, Cu, Mn, Ni, Pb, Zn, and Fe) were measured at both lagoons. Some (Cu, Mn, Pb, and Zn) were also measured in Zostera marina patches at both lagoons. The results did not show elevated metal concentration at any lagoon, either for sediments or eelgrass. No statistically significant differences between lagoons were found. However, eelgrass at both lagoons showed larger concentration ranges than in sediments. Also, a correlation exists between sediment metal concentration and its concentration in eelgrass. Surprisingly, several sediment metal concentrations are higher than those considered as elevated for the Southern California Bight.

  14. Deep-water bivalve mollusks collected during the TALUD XV cruise off the west coast of the southern Baja California Peninsula, Mexico.

    PubMed

    Hendrickx, Michel E; Valentich-Scott, Paul; Suárez-Mozo, Nancy Yolimar

    2016-01-01

    During the TALUD XV research cruise off the southern part of the Baja California Peninsula, Mexico, samples of macro-invertebrates obtained in the deep-sea (296-2136 m) revealed a rich fauna of bivalves (17 species belonging to 10 families). The number of species per station varied from one to five. The richest families were Nuculidae, Nuculanidae, Neilonellidae, Limidae, and Cuspidariidae. Solemyidae, Lucinidae, Poromyidae, Verticordiidae, and Pectinidae were each represented by a single species. Some species groups need a thorough revision and were tentatively identified (Nuculana cf. hamata, Limatula cf. saturna). Significant new distribution information is provided for two species, both recorded for the first time from off western Mexico: Ennucula panamina with an extension of its known distribution over 20° of latitude north and Jupiteria callimene with an extension of 16° 42' of latitude to the north. One species (Ennucula taeniolata) is reported in shallower depth and one in deeper water (Acesta sphoni). New records are provided for an additional nine species. Environmental and habitat conditions are given for the first time for many of the bivalve species.

  15. The stratified microbial community at Laguna Figueroa, Baja California, Mexico: a possible model for prephanerozoic laminated microbial communities preserved in cherts.

    PubMed

    Stolz, J F; Margulis, L

    1984-01-01

    The microbial mat community of the evaporite flat at North Pond, Laguna Figueroa (Baja California, Mexico) was actively involved in the production of laminated sediments prior to 1978. Heavy rains in 1979 and 1980 flooded the mat with 1 and 3 meters of meteoric water respectively. The flooding deposited up to 10 cm of silicoclastic sediment over the Microcoleus-dominated mat and resulted in the cessation of laminated sediment deposition. In 1982, the surface had been recolonized by species of cyanobacteria (Spirulina, Oscillatoria) and purple photosynthetic bacteria (Chromatium, Thiocapsa). The silicoclastic sediments and residual evaporites, which overlaid the laminated sediment, had been reworked into an anaerobic, sulfide-rich mud and contained well preserved sheaths of filamentous and coccoid bacteria. The Swaziland Sequence in the Barberton mountain land (which includes the Onverwacht and Fig Tree Group as well as the Swartkoppie zone between them) contains laminated sediments and carbon-rich chert. Structurally preserved microfossils have been found in the smooth black chert but not in the laminae. We concur with others who suggested that the laminated sediments from the Swaziland Sequence were deposited by an active stratified microbial community. However, we propose that these organisms which were preserved were originally buried in the associated sulfide-rich muds and were subsequently silicified.

  16. Structure, emplacement and lateral expansion of the San José tonalite pluton, Peninsular Ranges batholith, Baja California, México

    NASA Astrophysics Data System (ADS)

    Johnson, S. E.; Fletcher, J. M.; Fanning, C. M.; Vernon, R. H.; Paterson, S. R.; Tate, M. C.

    2003-11-01

    The 108 km 2 San José pluton forms part of the Jurassic to Cretaceous Peninsular Ranges batholith of northern Baja California, México. The pluton was formed by three nested, southward-migrating intrusive pulses, and the internal contacts between them indicate juxtaposition while the adjoining pulses were magmas. SHRIMP U-Pb zircon data indicate that the entire pluton was emplaced in less than 4.4 m.y.; ages of the individual pulses cannot be separated at the 95% confidence interval, owing primarily to low uranium content of zircon. Detailed structural data and geologic mapping are consistent with a component of asymmetrical, lateral expansion at the site of emplacement. The direction of maximum lateral expansion may have been controlled by thermal, compositional and resulting rheological gradients in the surrounding wall rocks. A carapace of predominantly solid-state deformation marks the northern two-thirds of the pluton, and the early stages of this fabric may have formed in the presence of a small amount of melt. Lack of evidence for syn- to post-emplacement regional ductile deformation around the pluton suggests that this carapace was deformed during the lateral expansion of the pluton.

  17. Results and evaluation of the first study of organochlorine contaminants (PCDDs, PCDFs, PCBs and DDTs), heavy metals and metalloids in birds from Baja California, México.

    PubMed

    Jiménez, Begoña; Rodríguez-Estrella, Ricardo; Merino, Rubén; Gómez, Gema; Rivera, Laura; José González, María; Abad, Esteban; Rivera, Josep

    2005-01-01

    Organochlorine compounds (OCs) including polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p-p'-DDE), heavy metals (Pb, Cd, Zn, Cu), and arsenic were measured in house sparrows (Passer domesticus) and common ground doves (Columbina passerina) from Baja California Sur, México. Concentrations of PCDD/Fs were low, with 21 pg/g for house sparrows, and 7.7 pg/g for common ground doves. Non-ortho-PCB concentrations in house sparrow and common ground doves were 58 and 254 pg/g, respectively, and are within the highest concentrations reported in species that are in the low levels of food webs. The major differences in organochlorine levels between species were found for ortho-PCBs and DDTs. ortho-PCB levels were higher in the seedeater species, whereas DDT levels were higher in the omnivorous species. Heavy metal levels were far below those associated with negative effects.

  18. [Size and age structure of the striped marlin Tetrapturus audax (Pisces: Xiphidae), at Cabo San Lucas, Baja California sur, México].

    PubMed

    Barrera, Felipe Neri Melo; Uraga, Roberto Felix

    2004-12-01

    The striped marlin (Tetrapturus audax) is found in temperate and tropical waters of the Pacific and Indian Ocean. It is particularly abundant in the southern tip of the Baja California peninsula. Specimens brought to Cabo San Lucas port (22 degrees 53' N y 109 degrees 54' W) by the sport fishery fleet that operates withing a radius of 54 km from 1988 to 1993 were sexes, measured and weighed. A total 1030 individuals were sampled. Dorsal fin spines (389) were collected for age estimation. The spines were sectioned and hyaline-opaque bands counted. The relation of length to spine radius was similar for males and females. The fourth dorsal spine reflected the growth of the fish. The rhythm of growth mark formation is yearly and related to the sea surface temperature. Ten age groups were found and the seventh group was the most abundant, followed by groups "6" and "8". The age structure of the striped marlin was stable in the study period. The observed sizes were 160-280 cm jaw length with 90% of the organisms measuring between 190 and 225 cm. The small individuals recruit to the fishery from June to December.

  19. Deep-water bivalve mollusks collected during the TALUD XV cruise off the west coast of the southern Baja California Peninsula, Mexico

    PubMed Central

    Valentich-Scott, Paul; Suárez-Mozo, Nancy Yolimar

    2016-01-01

    Abstract Background During the TALUD XV research cruise off the southern part of the Baja California Peninsula, Mexico, samples of macro-invertebrates obtained in the deep-sea (296–2136 m) revealed a rich fauna of bivalves (17 species belonging to 10 families). The number of species per station varied from one to five. The richest families were Nuculidae, Nuculanidae, Neilonellidae, Limidae, and Cuspidariidae. Solemyidae, Lucinidae, Poromyidae, Verticordiidae, and Pectinidae were each represented by a single species. Some species groups need a thorough revision and were tentatively identified (Nuculana cf. hamata, Limatula cf. saturna). New information Significant new distribution information is provided for two species, both recorded for the first time from off western Mexico: Ennucula panamina with an extension of its known distribution over 20° of latitude north and Jupiteria callimene with an extension of 16° 42' of latitude to the north. One species (Ennucula taeniolata) is reported in shallower depth and one in deeper water (Acesta sphoni). New records are provided for an additional nine species. Environmental and habitat conditions are given for the first time for many of the bivalve species. PMID:27346956

  20. Response of the pelagic system of the Pacific Ocean off Baja California Peninsula to the projected effects of climate change: insights from a numerical model.

    NASA Astrophysics Data System (ADS)

    Arellano, B.; Rivas, D.

    2015-12-01

    The response of the physical and biological dynamics of the Pacific Ocean off Baja California to the projected effects of climate change are studied using numerical simulations. This region is part of the California Current System, which is a highly productive ecosystem due to the seasonal upwelling, supporting all the trophic levels and important fisheries. The response of the ecosystem to the effects of climate change is uncertain and the information generated by models could be useful to predict future conditions. A three-dimensional hydrodinamical model is coupled to a Nitrate-Phytoplankton-Zooplankton-Detritus (NPZD) trophic model, and it is forced by the GFDL 3.0 model outputs. Monthly climatologies of variables such as temperature, nutrients, wind, and ocean circulation patterns during the historical period 1985-2005 are compared to the available observed data in order to assess the model's ability to reproduce the observed patterns. The system's response to a high-emission scenario proposed by the Intergovernmental Panel of Climate Change (IPCC) is also studied. The experiments are carried out using data correspondig to the RCP 6.0 scenario during the period 2006-2050.

  1. Diagnóstico y cinética de plasmas de NxOy y aire a baja presión. Aplicaciones atmosféricas

    NASA Astrophysics Data System (ADS)

    Tanarro Onrubia, Isabel

    Los procesos cinéticos que tienen lugar en plasmas de óxidos de nitrógeno y de aire presentan relevancia en diferentes campos de investigación como son los relativos al control de contaminantes atmosféricos emitidos en procesos de combustión, a su formación en las superficies de las naves supersónicas y los vehículos espaciales al entrar en la atmósfera, o a su presencia en la ionosfera terrestre. En general, los fenómenos que tienen lugar en sistemas tan alejados del equilibrio termodinámico como los plasmas luminiscentes, son capaces de originar determinadas especies intermedias y productos finales de reacción a temperaturas y presiones mucho menores que las de otros procedimientos físico-químicos; y hacen posible reproducir y caracterizar en laboratorio ciertas especies inestables y mecanismos primordiales de la alta atmósfera. Por otra parte, las técnicas de resolución temporal aplicadas a plasmas modulados en amplitud resultan notablemente más sensibles que las medidas estacionarias para estimar la relevancia de los distintos mecanismos elementales o incluso para determinar sus constantes de velocidad. En este trabajo se presenta un estudio espectroscópico y espectrométrico comparativo de plasmas de óxidos de nitrógeno y de aire a baja presión (0.001-1 mbar) generados en descargas de cátodo hueco continuas o moduladas, y se propone un modelo cinético único y relativamente sencillo, que explica satisfactoriamente los comportamientos observados en todos ellos. Dicho modelo se basa en la resolución de un sistema de ecuaciones diferenciales dependientes del tiempo, que incluye los mecanismos elementales de disociación e ionización de los precursores y los productos, reacciones homogéneas entre especies atómicas, iónicas y moleculares, y reacciones heterogéneas. Al abordar estos sistemas, se constata una gran carencia de datos experimentales o teóricos sobre secciones eficaces o constantes de velocidad para las reacciones de

  2. Paleopole for the 69 Ma Prospector Mountain Stock: A critique of the Carmacks/"Baja BC" transport estimate for Yukon, Canada

    NASA Astrophysics Data System (ADS)

    Symons, D. T. A.; Kawasaki, K.; McCausland, P. J. A.; Hart, C. J. R.

    2016-10-01

    The 69 Ma Prospector Mountain stock is located in southwestern Yukon in the northern Canadian Cordillera. This massive monzonite-syenogranite stock is thought to be the intrusive volcanic center for the surrounding coeval Carmacks Group volcanics. Anomalous paleomagnetic data from these volcanics have provided the only evidence for the commonly posited hypothesis that the Yukon-Tanana terrane (YTT) was part of the far-travelled (1950 ± 600 km northward) "Baja BC" terrane from 70 to 50 Ma. All other geologic evidence and averaged paleomagnetic data support a northward displacement of ˜415 ± 15 km. This study provides a direct test of the Carmacks volcanics' estimate and examines the possible causes of its anomalous results. Both the stock and volcanics are unmetamorphosed and rest unconformably on metamorphosed basement rocks of the YTT. Paleomagnetic and mineral magnetic results from 17 of 19 tested sites (218 specimens) in the Prospector stock and its peripheral skarn isolated a stable thermoremanent magnetization (TRM) in magnetite or low-Ti titanomagnetite that was mostly determined on demagnetization between temperatures of 500° and 580°C. The TRM has a direction of Decl. = 8.3°, Incl. = 82.4° (N = 17, k = 71.9, α95 = 4.2°), providing a nonsignificant northwards translation estimate of 70 ± 880 km for the YTT. The normal-polarity TRM direction at Prospector Mountain provides a highly significant paleomagnetic reversals test with the reversed-polarity TRM of the 70 Ma Swede Dome stock, another volcanic center of the Carmacks Group about 190 km to the north. The test affirms to a high probability that both stocks carry primary TRMs and have not been tectonically tilted significantly since emplacement. Combining the paleopoles for these two stocks with that for the 75 Ma Mount Lorne volcanic center stock about 210 km south of Prospector Mountain yields a combined northward translation estimate of 330 ± 400 km for the YTT since ˜71 Ma. This estimate

  3. Temporal constraints on landscape evolution in response to rifting along the western margin of the Gulf of California, central Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Mark, C.; Gupta, S.; Carter, A.; Mark, D. F.; Gautheron, C.; Martin Barajas, A.

    2011-12-01

    Rift escarpments and the high-elevation rift flanks associated with them are prominent topographic features at many developing and established passive margins. Numerical models and field investigations typically indicate that there are two principal mechanisms of rift escarpment evolution, commonly termed plateau downwearing and scarp retreat; however, many commonly studied passive margins are ancient, and have thus experienced significant post-rift modification, resulting in controversy as to which model is applicable at any particular margin. Rift flank uplift and the associated landscape changes have been less well studied; the erosional response to such uplift is often sufficient to bevel or erase the pre-rift landscape but insufficient to reset low-temperature thermochronometers, hindering field investigation. We present observations on rift landscape evolution from the Gulf of California: a ~1700 km long, highly oblique rift system. Although the precise timing of rifting remains controversial, it is known to have begun no earlier than the Mid-Miocene, and the incipient passive margins bounding the Gulf therefore retain many youthful features and provide an excellent natural laboratory for investigating landscape responses to rifting. This study examines the exhumation history of the escarpment and the development of the rift flank drainage network in the Loreto area of the Baja California Peninsula, which forms the western rift margin. Apatite (U-Th)/He (AHe) and apatite fission track (AFT) ages obtained from two escarpment-perpendicular transects from the footwall of the Loreto fault indicate that footwall denudation in response to rift flank uplift occurred at ~5.5 Ma. This age is younger than ages reported for other fundamental rift structures along the Baja California margin, and may indicate either a diachronous onset of rifting or a westward migration of extension after rifting began. A closely overlapping 40Ar/39Ar age from a lava situated near the

  4. Status of the peregrine falcon in the Rocky Mountains and the southwestern United States, Baja California, and Mexico (south of Texas)

    USGS Publications Warehouse

    Porter, Ron; Craig, G.R.; Ellis, D.H.; Enderson, J.H.; Hunt, W.G.; Schaeffer, Philip P.; Ehlers, Sharyn M.

    1978-01-01

    About 31 pairs of peregrines still nest north of Mexico, from Idaho and Montana south through West Texas, New Mexico and Arizona. At least thirty-six additional pairs nest in Mexico. Although the nesting sites are occupied, the tissues of the peregrine?s prey species still contain high concentrations of pesticides. The eggs in some Rocky Mountain eyries have shells which are precariously thin and have high residue levels of DDE in their contents. Increasing economic development is encroaching on the peregrine habitat throughout its range in western North America. In Baja California. and Mexico south of Texas this involves increased agricultural activity including use of organochlorine pesticides, increased tourism and increased use of the Gulf of California both for commercial and sport fishing, with their potential disturbance of eyrie sites and reduction of the peregrine?s aquatic feeding prey base. As the fish in the Gulf decrease in number, some of the avian species on which peregrines prey will likewise decrease. This ultimately may effect the peregrine. These factors may have been involved in the demise of the peregrine on Baja California?s Pacific coast. Furthermore, throughout its range, residential, industrial, mining, geothermal, recreational and other types of development and land use practices sometimes destroy habitat essential to the survival of the peregrine. A recent request for the protection of an historical site in California as Critical Habitat under Section 7 of the Endangered Species Act was rejected because peregrines, although observed there, were not known to have produced eggs or young at the site for several decades. With inadequate protection of abandoned, but still suitable, historical eyrie sites, the peregrine may have an insufficient number of eyries to reoccupy in recovery attempts. The lack of present occupancy of a site, without biological evidence that the site is no longer suitable for reoccupancy, is insufficient cause to give

  5. Palaeopole for the 69 Ma Prospector Mountain stock: a critique of the Carmacks/`Baja BC' transport estimate for Yukon, Canada

    NASA Astrophysics Data System (ADS)

    Symons, D. T. A.; Kawasaki, K.; McCausland, P. J. A.; Hart, C. J. R.

    2017-01-01

    The 69 Ma Prospector Mountain stock is located in southwestern Yukon in the northern Canadian Cordillera. This massive monzonite-syenogranite stock is thought to be the intrusive volcanic centre for the surrounding coeval Carmacks Group volcanics. Anomalous palaeomagnetic data from these volcanics have provided the only evidence for the commonly posited hypothesis that the Yukon-Tanana terrane (YTT) was part of the far-travelled (1950 ± 600 km northward) `Baja BC' terrane from 70 to 50 Ma. All other geologic evidence and averaged palaeomagnetic data support a northward displacement of ˜415 ± 15 km. This study provides a direct test of the Carmacks volcanics' estimate and examines the possible causes of its anomalous results. Both the stock and volcanics are unmetamorphosed and rest unconformably on metamorphosed basement rocks of the YTT. Palaeomagnetic and mineral magnetic results from 17 of 19 tested sites (218 specimens) in the Prospector stock and its peripheral skarn isolated a stable thermoremanent magnetization (TRM) in magnetite or low-Ti titanomagnetite that was mostly determined on demagnetization between temperatures of 500 and 580 °C. The TRM has a direction of Decl. = 8.3°, Incl. = 82.4° (N = 17, k = 71.9, α95 = 4.2°), providing a non-significant northwards translation estimate of 70 ± 880 km for the YTT. The normal-polarity TRM direction at Prospector Mountain provides a highly significant palaeomagnetic reversals test with the reversed-polarity TRM of the 70 Ma Swede Dome stock, another volcanic centre of the Carmacks Group about 190 km to the north. The test affirms to a high probability that both stocks carry primary TRMs and have not been tectonically tilted significantly since emplacement. Combining the palaeopoles for these two stocks with that for the 75 Ma Mount Lorne volcanic centre stock about 210 km south of Prospector Mountain yields a combined northward translation estimate of 330 ± 400 km for the YTT since ˜71 Ma. This

  6. Low-temperature thermochronology of northern Baja California, Mexico: Decoupled slip-exhumation gradients and delayed onset of oblique rifting across the Gulf of California

    NASA Astrophysics Data System (ADS)

    Seiler, Christian; Fletcher, John M.; Kohn, Barry P.; Gleadow, Andrew J. W.; Raza, Asaf

    2011-06-01

    The northern Gulf Extensional Province displays key structural relationships that characterize the magnitude, direction, and timing of Neogene rift-related transtension during the opening of the Gulf of California. Apatite fission track and (U-Th)/He thermochronology from the Sierra San Felipe document moderate cooling (4°C/Myr-7°C/Myr) during the early Paleogene associated with progressive unroofing caused by erosional downwearing of the ancestral Peninsular Ranges. Beginning at ˜45-35 Ma, a period of tectonic quiescence with low cooling rates (≤1°C/Myr) marks the development of a regional Oligocene-Miocene peneplain. Rift-related exhumation began at ˜9-7 Ma and attains ˜2.5 km in the hinges of two antiformal megamullions. Decoupling between exhumation and finite displacement in certain fault segments is explained by vertical deflections associated with extension-perpendicular folding of the fault surfaces. The main faults of the detachment system were active contemporaneously, thus forming a mechanically linked array of large-displacement normal faults in the hanging wall of the Main Gulf Escarpment. The Late Miocene onset of transtension in the Sierra San Felipe suggests that widespread deformation may only have localized in the Gulf Extensional Province between ˜9 and 7 Ma, some ˜3-5 Ma after a major plate reorganization associated with cessation of subduction in the trench to the west. Between ˜12 Ma and ˜9-7 Ma, plate boundary shearing was likely distributed between the continental borderland west of Baja California and the southern Basin and Range province in Mexico.

  7. PATHOGENIC LEPTOSPIRA SEROVARS IN FREE-LIVING SEA LIONS IN THE GULF OF CALIFORNIA AND ALONG THE BAJA CALIFORNIA COAST OF MEXICO.

    PubMed

    Avalos-Téllez, Rosalía; Carrillo-Casas, Erika M; Atilano-López, Daniel; Godínez-Reyes, Carlos R; Díaz-Aparicio, Efrén; Ramírez-Delgado, David; Ramírez-Echenique, María F; Leyva-Leyva, Margarita; Suzán, Gerardo; Suárez-Güemes, Francisco

    2016-04-28

    The California sea lion ( Zalophus californianus ), a permanent inhabitant of the Gulf of California in Mexico, is susceptible to pathogenic Leptospira spp. infection, which can result in hepatic and renal damage and may lead to renal failure and death. During summer 2013, we used the microscopic agglutination test (MAT) to investigate the prevalence of anti-Leptospira antibodies in blood of clinically healthy sea lion pups from seven rookery islands on the Pacific Coast of Baja California (Pacific Ocean) and in the Gulf of California. We also used PCR to examine blood for Leptospira DNA. Isolation of Leptospira in liquid media was unsuccessful. We found higher antibody prevalence in sea lions from the rookery islands in the gulf than in those from the Pacific Coast. Antibodies against 11 serovars were identified in the Gulf of California population; the most frequent reactions were against serovars Bataviae (90%), Pyrogenes (86%), Wolffi (86%), Celledoni (71%), and Pomona (65%). In the Pacific Ocean population, MAT was positive against eight serovars, where Wolffi (88%), Pomona (75%), and Bataviae (70%) were the most frequent. Serum samples agglutinated with more than one Leptospira serovar. The maximum titer was 3,200. Each island had a different serology profile, and islands combined showed a distinct profile for each region. We detected pathogenic Leptospira DNA in 63% of blood samples, but we found no saprophytic Leptospira. Positive PCR results were obtained in blood samples with high and low MAT titers. Together, these two methods enhance the diagnosis and interpretation of sea lion leptospirosis. Our results may be related to human activities or the presence of other reservoirs with which sea lions interact, and they may also be related to sea lion stranding.

  8. Arsenic content in groundwater from the southern part of the San Antonio-El Triunfo mining district, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Wurl, Jobst; Mendez-Rodriguez, Lía; Acosta-Vargas, Baudilio

    2014-10-01

    The San Antonio-El Triunfo mining district is located in a mountain region 60 km southeast of La Paz, the capital of the Mexican state of Baja California Sur. Mining activities, focused on gold and silver extraction, which began in the second half of the 18th century; the main activity took place between 1878 and 1911. The minerals were treated through the cyanide method, burned, and smelted. In effect between 800,000 and 1 million tons of mine waste materials were scattered in an area of approximately 350-400 km2. This area contains today several byproducts as a result from arsenopyrite oxidation, such as arsenolite (As2O3). The aim of this study was to analyze groundwater composition in order to define the actual concentrations of relevant parameters to detect ore mining contaminations, especially in respect to arsenic. In the autumn of 2010, 29 groundwater samples were obtained using flow-through bailer or down-hole pump methods, and a total of 37 variables were measured in each sample. Arsenic (dissolved) exceeded the values established by the World Health Organization (WHO, 2011) (0.01 mg/L) in 41% of the monitored sites. The maximum concentration of arsenic found in one observation well was 0.45 mg/L. Four water samples, which were characterized by elevated concentration of boron (max. conc. 9.5 mg/L), fluoride (max. conc. 3.25 mg/L) and alkaline pH values (>9), showed a composition typical for hydrothermal water. Because all four samples had arsenic concentration under 0.008 mg/L, we conclude that no significant impact of arsenic from hydrothermal fluids is found in the study area.

  9. Provenance of Conglomerates within a Late Cretaceous Turbidite Channel System on the North American Margin: the Rosario Formation, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Dos Santos, Thisiane; Kneller, Benjamin; Morton, Andrew; Armelenti, Garibaldi; Pantopoulos, George; De Ros, Luiz Fernando

    2017-04-01

    The Rosario Formation forms part of the Peninsular Ranges forearc basin complex, which crops out discontinuously along the Pacific coast of the Baja California Peninsula, Mexico. This study concerns the upper, deep marine part of the Rosario Formation , which includes several slope channel systems, one of these, the San Fernando channel systems consists of five channel complex sets (CCS1 to CCS5), each characterized by three filling stages. Stage I consists of predominantly clast­ and matrix-supported conglomerates, with subordinate medium to coarse grained sandstones. Stage II consists of units of clast-supported conglomerates with subordinate medium to coarse-grained sandstones, separated by mainly thinly-bedded turbidites (intercalation of thin beds of fine-grained sandstones and mudstones). Stage III consists mainly of hemipelagic mudstones. The main objective of this research is to determine source area and to compare the coarse fraction and finer fraction (fragments <2 cm) from conglomerates of each channel set, combining provenance methodology such as heavy minerals, clast counting, geochemistry, bulk petrography and U/Pb in detrital zircons by LA-ICPMS and SHRIMP. The heavy minerals assembly identified were Ca amphibole, epidote, clinozoisite, titanite, garnet, tourmaline, apatite, rutile and zircon, among them amphiboles are by far the most abundant detrital mineral. Clast counting and petrographic characterization showed that the pebble fraction of the conglomerates is constituted at least 18 different, and the majority being composed by pyroclastic, porphyritic volcanic and sandstone rocks. Bulk quantification indicates that the main provenance tectonic mode of the fine fraction of the conglomerates can be interpreted as dissected magmatic arc, with subordinate uplifted basement and recycled orogenic contributions. The preliminary conclusion is that the sedimentary supply to the Rosario Formation was mostly derived from volcanic and plutonic rocks of

  10. [Spatial and biogeographic characterization of macroalgal assemblages from Bahía del Rincón, Baja California Sur, Mexico].

    PubMed

    Riosmena-Rodríguez, R; Hinojosa-Arango, G; López-Vivas, J M; León-Cisneros, K; Holguin-Acosta, E

    2005-01-01

    Macroalgal studies in Baja California Sur have dealt mainly with occurrence and seasonality, but some areas are poorly known even for these basic data. Bahia del Rincón-La Rivera is an important high-productivity fisheries area where coastal infrastructure development is under way. A spatial characterization of the marine flora from Bahia del Rincón-La Rivera was done by intensive sampling at different depths and localities with skin and SCUBA diving. At least 500 m2 were surveyed in each site. Additionally. quantitative sampling was done in ten random 25 cm2 quadrates per site. In the intertidal section, density and cover estimates were used. We also investigated the historical records and geographical affinities. A total of 72 species were identified (most were red algae: 62%). We found no general trend in the biogeographical affinities, which varied with each taxonomic group. Most brown algae species were tropical-endemic; red algae temperate-cosmopolite and green algae tropical-cosmopolite. In the spatial assemblage structure we found a high similarity between the intertidal areas, but a low similarity in shallow or deeper areas (3-5 m). This pattern was the same when we compared the abundance of the main species. We suggest that there are significant spatial differences in recruitment and development of the assemblages in relation to vertical distribution (depth) and position along the shore. There is a clear-cut Gelidium-Jania belt in the intertidal zone and a Padina-Dictyota belt below the low tide. Sporadic and year-round species occur in the intertidal zone, annual and perennial species below the low tide line. Sites differ in recruitment and this affects the abundance of other species (such as coraline and Caulerpa species). Temperature and sedimentation affect seasonality, but community structure is relatively constant throughout the year.

  11. Cestodes of the blue shark, Prionace glauca (Linnaeus 1758), (Carcharhiniformes: Carcharhinidae), off the west coast of Baja California Sur, Mexico.

    PubMed

    Méndez, Oscar; Galván-Magaña, Felipe

    2016-03-03

    The cestode species recovered from the spiral intestines of 27 blue sharks (Prionace glauca) (Linnaeus, 1758) are reported from the western coast of Baja California Sur (BCS). The sampling was undertaken on a monthly basis from January 2003 to January 2004. The helminthological examination indicated the presence of four species of cestodes: Platybothrium auriculatum Yamaguti, 1952; Prosobothrium japonicum Yamaguti, 1934; Anthobothrium caseyi (Yamaguti, 1934) Ruhnke & Caira, 2009; and Paraorygmatobothrium prionacis (Yamaguti, 1934) Ruhnke, 1994. Of all the 27 sharks examined, 88.8% were infected with at least one cestode species. The most frequent species was P. auriculatum infecting 85% of the spiral intestines examined. In contrast the species with the highest mean intensity was P. prionacis (80.4 200). The species richness of cestodes in P. glauca is very similar in other regions of the world despite its wide distribution; however, this richness is low compared with other species of sharks within the same family. The feeding and host-specific are important factors that influence the parameters of infection of cestodes in this shark. On the west coast of BCS, Prionace glauca feeds mainly on red crab Pleuroncodes planipes Stimpson, 1860; squids Gonatus californiensis Young, 1972, Ancistrocheirus lesueurii (D'Orbigny, 1842), Haliphron atlanticus Steenstrup, 1861, and low proportion of fish teleosts as Merluccius productus (Ayres, 1855), Sardinops sp. Hubbs, 1929 and Scomber japonicus Houttuyn, 1872. We speculate that these prey could be involved as the second intermediate hosts of these cestodes, as in other members of these genera, although the life cycles of none are known.

  12. Latent classes of polydrug and polyroute use and associations with human immunodeficiency virus risk behaviours and overdose among people who inject drugs in Tijuana, Baja California, Mexico.

    PubMed

    Meacham, Meredith C; Roesch, Scott C; Strathdee, Steffanie A; Lindsay, Suzanne; Gonzalez-Zuniga, Patricia; Gaines, Tommi L

    2017-03-24

    Patterns of polydrug use among people who inject drugs (PWID) may be differentially associated with overdose and unique human immunodeficiency virus (HIV) risk factors. Subgroups of PWID in Tijuana, Mexico, were identified based on substances used, route of administration, frequency of use and co-injection indicators. Participants were PWID residing in Tijuana age ≥18 years sampled from 2011 to 2012 who reported injecting an illicit substance in the past month (n = 735). Latent class analysis identified discrete classes of polydrug use characterised by 11 indicators of past 6 months substance use. Multinomial logistic regression examined class membership association with HIV risk behaviours, overdose and other covariates using an automated three-step procedure in mplus to account for classification error. Participants were classified into five subgroups. Two polydrug and polyroute classes were defined by use of multiple substances through several routes of administration and were primarily distinguished from each other by cocaine use (class 1: 5%) or no cocaine use (class 2: 29%). The other classes consisted primarily of injectors: cocaine, methamphetamine and heroin injection (class 3: 4%); methamphetamine and heroin injection (class 4: 10%); and heroin injection (class 5: 52%). Compared with the heroin-only injection class, memberships in the two polydrug and polyroute use classes were independently associated with both HIV injection and sexual risk behaviours. Substance use patterns among PWID in Tijuana are highly heterogeneous, and polydrug and polyroute users are a high-risk subgroup who may require more tailored prevention and treatment interventions. [Meacham MC, Roesch SC, Strathdee SA, Lindsay S, Gonzalez-Zuniga P, Gaines TL. Latent classes of polydrug and polyroute use and associations with human immunodeficiency virus risk behaviours and overdose among people who inject drugs in Tijuana, Baja California, Mexico. Drug Alcohol Rev 2017

  13. Sierra San Pedro Mártir, Baja California, cool-season precipitation reconstructed from earlywood width of Abies concolor tree rings

    NASA Astrophysics Data System (ADS)

    Meko, D. M.; Touchan, R.; Díaz, J. Villanueva; Griffin, D.; Woodhouse, C. A.; Castro, C. L.; Carillo, C.; Leavitt, S. W.

    2013-12-01

    Tree ring data are analyzed for a multicentury record of drought history in the Sierra San Pedro Mártir (SSPM) of Baja California, Mexico. Climatic variation in the study area is of particular interest because the SSPM is a rich biotic environment at the southern limit of the California floristic province and the southern limit of the planetary jet stream. Future shifts in the jet stream would be expected to have amplified effect on this marginal environment. The study applies linear regression to tree ring indices of earlywood-width of Abies concolor to estimate a 353 year (1658-2010 C.E.) record of cool-season (October-April) precipitation, P, in SSPM. Time-nested regression models account for more than half the variance of grid point P in calibration periods of length 50-65 years. Cross-spectral analysis indicates strong tracking of observed P by the reconstruction over a broad range of frequencies. Robustness of the reconstruction is supported by synchrony of reconstructed P with tree ring variations in other tree species from SSPM. The reconstruction emphasizes the severity of the 1950s drought in a long-term context and the single-year intensity of droughts in the last decade: 2007 stands out as the driest reconstructed year, with a high percentage of missing rings in A. concolor. The reconstruction identifies the early twentieth century pluvial as the wettest epoch in the last 353 years in the SSPM. High-elevation tree species in SSPM may be especially well-suited to sensing snowpack-related moisture variations associated with a southerly branched jet stream and the types of weather systems active in the pluvial.

  14. Spectral Analysis of Pore Pressure Data Recorded from the 2010 Sierra EL Mayor (baja California) Earthquake at the NEES@UCSB Wildlife Field Site

    NASA Astrophysics Data System (ADS)

    Seale, S. H.; Lavallee, D.; Steidl, J. H.; Ratzesberger, H.; Hegarty, P.

    2010-12-01

    On 4 April 2010, the M7.2 Sierra el Mayor event occurred in Baja California, Mexico. The NEES@UCSB Wildlife field site in the Imperial Basin is located 110 km NNW of the hypocenter. The event was recorded on all channels: by three-component strong-motion accelerometers at the surface and in boreholes at various depths and by pore pressure transducers located in a saturated, liquefiable layer. We have computed the spectra of the pore pressure response in the frequency domain for signals recorded at different depths. At each depth, the spectrum is attenuated as a power law with a sharp discontinuity at a frequency close to 1 Hz. We report the value of the exponents that characterize the power-law behavior of these spectra. We also computed cross-spectral analysis of the pore pressure records from different depths. The functional behaviors of the curves of the cross-spectra are similar to that of the original spectra. For comparison, we present the spectrum of each component of the ground motion recorded at a nearby accelerometer. Partially due to the late arrival of the surface waves, the frequency content of the recorded pore pressure signal is a function of time. To gain a better understanding of the time-dependence of the frequency content, we performed spectral analysis of the signal in a moving window and wavelet transforms of the full signals. The spectral analysis suggests that, except for high frequencies, the curves exhibit a complex behavior as a function of the window position. We interpret and discuss the consequences of the estimated spectra, the cross-spectra, and the wavelet transforms.

  15. Molecular systematics of Batrachoseps (Caudata, Plethodontidae) in southern California and Baja California: mitochondrial-nuclear DNA discordance and the evolutionary history of B. major.

    PubMed

    Martínez-Solano, Iñigo; Peralta-García, Anny; Jockusch, Elizabeth L; Wake, David B; Vázquez-Domínguez, Ella; Parra-Olea, Gabriela

    2012-04-01

    Inferences about species boundaries and evolutionary history are often complicated by discordance between datasets. In recent times, considerable effort has been devoted to understanding the causes of discordance between the patterns of genetic variation and structure shown by different unlinked molecular markers. The genus Batrachoseps (Caudata, Plethodontidae), the most diverse group of salamanders in western North America, is characterized by limited morphological variation and discordance between molecular datasets, making it a challenging group for taxonomists but also a good model to test newly developed analytical methods to sort out possible sources of discordance. In this study, we present a comprehensive assessment of the evolutionary history of B. major, one of the most widespread species in the genus, based on extensive sampling and phylogenetic and coalescent analyses of data from mitochondrial and nuclear markers. We found non-monophyly of mtDNA in B. major, with two lineages (northern and southern) that are more closely related to other species in the genus than to each other, but this division was not apparent in nuclear DNA. Despite non-monophyly in gene trees, species tree analyses recovered a sister group relationship between the two lineages of B. major, and coalescent simulations suggested that there is no need to invoke gene flow to account for the discordance across gene trees. The possibility that these two lineages represent sister, cryptic taxa, is discussed in the context of Bayesian methods of species/lineage delineation. Contrary to prior expectations, B. major has experienced extensive diversification on the Baja California Peninsula, where four endemic lineages have persisted for at least 4 million years. Copyright © 2012 Elsevier Inc. All rights reserved.

  16. Resource use of an aquacultured shellfish in the reverse estuary Bahía San Quintín, Baja California, México

    NASA Astrophysics Data System (ADS)

    Wilkinson, G. M.; Emery, K.; Camacho-Ibar, V.; Pace, M.; McGlathery, K.; Sandoval Gil, J.; Hernandez-Lopez, J.

    2016-02-01

    Shellfish aquaculture is prominent in many coastal and estuarine environments. Filter feeding by cultured shellfish connects the benthic and pelagic environments in coastal ecosystems. Bahía San Quintín is a reverse estuary in Baja California, Mexico, where Pacific oysters (Crassostrea gigas) are cultivated. While oysters likely feed heavily on phytoplankton especially during upwelling periods, we hypothesized that other forms of organic matter available in high quantities such as seagrass (Zostera marina) and macroalgae (Ulva spp.) must also be used by the oysters, especially in the most inshore portions of the bay. We measured the carbon and hydrogen stable isotope composition of oysters and their potential food resources at upper, mid, and lower bay sites during upwelling and non-upwelling seasons and applied a Bayesian mixing model to evaluate resource use. Hydrogen isotopes provided a large separation between potential food resources. Although we did not find any strong seasonal effects due to upwelling, there was a strong spatial gradient in resource use. Phytoplankton were most important at the lower (oceanic) site (median resource use for two sampling times, 68 and 79 %) and decreased up the estuary as macroalgae became more important (43 and 56 % at the upper site). At all sites for both sampling times, seagrass was an unimportant resource for oysters. The contrast between high phytoplankton use at the lower site and increased macroalgal use at the upper site is likely due to available resource biomass. Our results illustrate the adaptability of oysters to varying resource availability and the possibility of a higher system carrying capacity than that based on phytoplankton alone given multiple potential food sources.

  17. Halocoryza Alluaud 1919, sea-side beetles of the Indian, Atlantic (sensu lato), and Pacific Oceans: a generic synopsis and description of a remarkable new species from Baja California Sur, México (Coleoptera, Carabidae, Scaritini, Clivinina).

    PubMed

    Erwin, Terry L

    2011-01-01

    Information on the three previously described species of Halocoryza Alluaud is updated and a new species for the genus from Isla Carmen, Sea of Cortés, Baja California Sur, México is described. Halocoryza whiteheadianasp. n. was found at UV light on a beach of that island. This species does not fit the profile of the other three species, i.e., living on coralline beach sands, or in the Mangrove intertidal zone. Two alternative possibilities as to why this is so are suggested and a study plan for testing these possibilities is proposed.

  18. Halocoryza Alluaud 1919, sea-side beetles of the Indian, Atlantic (sensu lato), and Pacific Oceans: a generic synopsis and description of a remarkable new species from Baja California Sur, México (Coleoptera, Carabidae, Scaritini, Clivinina)

    PubMed Central

    Erwin, Terry L.

    2011-01-01

    Abstract Information on the three previously described species of Halocoryza Alluaud is updated and a new species for the genus from Isla Carmen, Sea of Cortés, Baja California Sur, México is described. Halocoryza whiteheadiana sp. n. was found at UV light on a beach of that island. This species does not fit the profile of the other three species, i.e., living on coralline beach sands, or in the Mangrove intertidal zone. Two alternative possibilities as to why this is so are suggested and a study plan for testing these possibilities is proposed. PMID:21998544

  19. Neogene structural evolution of the Sierra San Felipe, Baja California: Evidence for proto-gulf transtension in the Gulf Extensional Province?

    NASA Astrophysics Data System (ADS)

    Seiler, Christian; Fletcher, John M.; Quigley, Mark C.; Gleadow, Andrew J. W.; Kohn, Barry P.

    2010-06-01

    The Sierra San Felipe, located in the Gulf Extensional Province of northeastern Baja California, experienced a complex deformation history of integrated normal and strike-slip faulting, block rotations and extension-parallel folding as a result of Neogene transtensional plate margin shear between the Pacific and North American plates. The eastern range-front of the Sierra San Felipe is defined by three left-stepping, en-echelon detachment faults that are linked by dextral and sinistral transfer faults and accommodation zones. The Las Cuevitas, Santa Rosa and Huatamote detachments comprise NE- to SE-dipping, moderate- to low-angle normal faults that accommodate between ~ 1.5 and 9 km of broadly E- to SE-directed extension and show strong along-strike displacement gradients. Hanging wall half-grabens are infilled with northwest tilted Miocene-Pliocene volcanic and sedimentary rocks that have been deposited nonconformably onto the batholithic basement. Stratigraphic relationships indicate that faulting on the Las Cuevitas and Santa Rosa detachment faults initiated synchronously as a kinematically linked fault system before ~ 7 Ma (~ 9-8 Ma based on the timing of footwall exhumation), during the so-called 'proto-gulf' phase of rifting. Paleostress calculations suggest a transtensional stress regime with NE- to SE-directed extension and permutating vertical to N-S trending, subhorizontal contraction. Fault kinematics and paleostress orientations of the fault array do not vary through time, but reflect the spatial distribution of fault planes with respect to a transtensional stress regime that lasted throughout the entire slip history of the detachments. Our data indicate that clockwise vertical-axis block rotations and constrictional folding were an integral part of the deformation history in the Sierra San Felipe since rifting began in the late Miocene, and may have played an important role in facilitating the transfer of deformation between the Main Gulf Escarpment

  20. Coupling of Pore Pressure and Ground Motion Data Recorded During the 2010 El Mayor-Cucapah (Baja California) Earthquake at the NEES@UCSB Wildlife Station

    NASA Astrophysics Data System (ADS)

    Lavallee, D.; Seale, S. H.; Steidl, J. H.

    2011-12-01

    Pore pressure built up during an earthquake and the hazard associated with soil liquefaction present a major challenge for our society, as was dramatically displayed during the 2011 Higashi Nihon Daishinsai (Tohoku-oki, Japan) earthquake. Currently, there is a consensus among scientists that a better assessment of the risk associated with liquefaction requires a better understanding of the coupling between pore pressure time histories and ground motion time histories. Specifically, there is a basic need to investigate the coupling as a function of the frequency content of the ground motion. The 2010 El Mayor-Cucapah (Baja California) earthquake (M 7.2) provides a remarkable opportunity to undertake such an investigation and lay the basis to model the coupling. The event was well recorded at the NEES@UCSB Wildlife station located 110 km from the hypocenter. The station is equipped with three-component strong-motion accelerometers at the surface and in boreholes at various depths and with pore pressure transducers located in a saturated, liquefiable layer. The recorded pore pressure and ground motion time histories are both characterized by a frequency content that is a function of time. A wavelet representation is a natural approach to investigate non-stationary time histories. To study the coupling between two signals we use the following procedure: We first compute the wavelet coefficients associated with the two signals. Then we compute the correlation between the wavelet coefficients of the two signals as a function of the frequency. Correlation coefficients provide information about the degree of linear dependence between the two signals. To account for the presence of multiplicative constants relating the wavelet coefficients of the first signal to the wavelet coefficients of the second signal, we compare the square norm of the wavelet coefficients of the two signals for the available frequency range. Additionally, investigating the distribution of the square

  1. Neogene Tectonic History of the Sierra San Pedro Mártir, Baja California Revealed by Careful Pairing of Cosmogenic Sampling with Topographic Analysis

    NASA Astrophysics Data System (ADS)

    Rossi, M. W.; Quigley, M.; Fletcher, J. M.; Whipple, K. X.; Díaz-Torres, J. J.; Seiler, C.; Fifield, L. K.; Heimsath, A. M.

    2015-12-01

    The Sierra San Pedro Mártir (SSPM), MX defines a prominent section of the Main Gulf Escarpment that marks the breakaway fault of the Gulf of California rift. The SSPM is an uplifted rift shoulder that has the highest topography and relief in Baja California, with local elevations exceeding 3,000 m and range relief (summit to baselevel) ranging from ~500 to 2,500 m. Prior studies report Eocene apatite fission track ages from the base of the escarpment and indicate low total exhumation, thus limiting the use of low-temperature thermochronology to constrain the timing and pattern of Neogene faulting of this important structure. However, topography is expected to record tectonic, climatic, and rock strength controls on long-term denudation rates in active margins, and morphometric analysis offers an alternative approach, particularly when combined with cosmogenic 10Be-derived, catchment-averaged denudation rates. Denudation rates and topographic metrics in the SSPM record along-strike gradients in rock uplift that increase asymmetrically from fault tips to a maximum within the northern half of the range. Surface uplift of an Eocene paleo-erosion surface and slope-break knickpoints found at increasingly higher elevations in northern segments of the SSPM fault system suggest that range asymmetry is due to a recent northward acceleration in rock uplift rate. By characterizing the relationship between channel steepness and 10Be-derived denudation rates, we extrapolate millennial-scale denudation rates to million-year time-scales to estimate ages for the transient increase in rock uplift rates as well as the initial onset of faulting. From this, we predict that the SSPM fault system initiated during the Middle Miocene (~16-14 Ma) in the center of the range and ~11-8 Ma ago near the fault tips. These age estimates are consistent with independent, regional geologic constraints and show that careful pairing of cosmogenic denudation rates with topographic analysis can be used

  2. Interannual correlations between sea surface temperature and concentration of chlorophyll pigment off Punta Eugenia, Baja California during different remote forcing conditions

    NASA Astrophysics Data System (ADS)

    Herrera-Cervantes, H.; Lluch-Cota, S. E.; Lluch-Cota, D. B.; Gutiérrez-de-Velasco, G.

    2013-05-01

    Interannual correlation between satellite-derived sea surface temperature (SST) and surface chlorophyll a (Chl a) are examined in the coastal upwelling zone off Punta Eugenia on the west coast of the Baja California Peninsula, area identified as intense biological productivity and oceanographic transition between mid-latitude and tropical ocean conditions. We used empirical orthogonal functions (EOF) analysis separately and jointly on the two fields from 1997 through 2007, a time period dominated by different remote forcing; ENSO conditions (weak, moderate and strong) and the largest intrusion of subarctic water reported in the last 50 yr. Coastal Upwelling Index anomalies (CUI) and the Multivariate ENSO Index (MEI) were used to identify the influence of local (wind stress) and remote (ENSO) forcing over the interannual variability of both variables. The individual EOF1 analysis showed the greater variability of SST and Chla offshore, their corresponding amplitude time series presented the highest peaks during the intrusion of subartic water (2002-2004) and were significantly correlated with the MEI (RSST ≈ 0.68, RChl a ≈ -0.30, P < 0.001) and moderately correlated with the CUI (RSST ≈ -0.4, RChl a ≈ 0.25, P < 0.001), showing similar trends. The joint EOF1 and the SST-Chl a correlations pattern show the area where both variables covary tightly; a band near to the coast with the largest correlations (R > |0.4|) mainly regulated by ENSO cycles. This was revealed when we calculate the homogeneous correlations for the periods El Niño-La Niña and the intrusion of subartic water. Both, SST and Chl a showed higher coupling and two distinct physical-biological responses; on average ENSO influence were clearly along the coast mostly in SST while the subarctic water influence, were observed offshore mostly in Chl a. We found a coastal chlorophyll bloom correlated strongly with high wind stress anomalies that reach the coast off Punta Eugenia during spring and

  3. Interannual correlations between sea surface temperature and concentration of chlorophyll pigment off Punta Eugenia, Baja California, during different remote forcing conditions

    NASA Astrophysics Data System (ADS)

    Herrera-Cervantes, H.; Lluch-Cota, S. E.; Lluch-Cota, D. B.; Gutiérrez-de-Velasco, G.

    2014-05-01

    Interannual correlation between satellite-derived sea surface temperature (SST) and surface chlorophyll a (Chl a) are examined in the coastal upwelling zone off Punta Eugenia on the west coast of the Baja California Peninsula, an area than has been identified as having intense biological productivity and oceanographic transition between midlatitude and tropical ocean conditions. We used empirical orthogonal functions (EOF) analysis separately and jointly on the two fields from 1997 through 2007, a time period dominated by different remote forcing: ENSO (El Niño-Southern Oscillation) conditions (weak, moderate and strong) and the largest intrusion of subarctic water reported in the last 50 years. Coastal upwelling index anomalies (CUI) and the multivariate ENSO index (MEI) were used to identify the influence of local (wind stress) and remote (ENSO) forcing over the interannual variability of both variables. The spatial pattern of the individual EOF1 analysis showed the greater variability of SST and Chl a offshore, their corresponding amplitude time series presented the highest peaks during the strong 1997-2000 El Niño-La Niña cycles and during the 2002-2004 period associated to the intrusion of subarctic water. The MEI is well correlated with the individual SST principal component (R ≈ 0.67, P < 0.05) and poorly with the individual Chl a principal component (R = -0.13). The joint EOF1 and the SST-Chl a correlation patterns show the area where both variables covary tightly; a band near the coast where the largest correlations occurred (| R | > 0.4) mainly regulated by ENSO cycles. This was spatially revealed when we calculated the homogeneous correlations for the 1997-1999 El Niño-La Niña period and during the 2002-2004 period, the intrusion of subarctic water period. Both, SST and Chl a showed higher coupling and two distinct physical-biological responses: on average ENSO influence was observed clearly along the coast mostly in SST, while the subarctic water

  4. Insight into the upper mantle beneath an active extensional zone: the spinel-peridotite xenoliths from San Quintin (Baja California, Mexico)

    NASA Astrophysics Data System (ADS)

    Cabanes, N.; Mercier, J.-C. C.

    1988-11-01

    Many of the peridotite xenoliths included in the San Quintin (Baja California Norte, Mexico) quaternary alkali-basalts have undergone a very intense shear deformation (deviatoric stresses up to 0.1 GPa), hence a first-order classification into coarse-grained lherzolites and deformed peridotites (porphyroclastic and mosaic textures) has been applied. All of these rocks show a very limited compositional variability in the Mg/(Mg+Fe2+) ratios (olivine: 0.894 0.905±0.005; orthopyroxene: 0.899 0.9105±0.005), and the observed trends in the Cr/(Cr+Al) spinel ratios (from 0.1 to 0.6) can be interpreted as resulting from gradual partial melting followed by homogenization of the bulk phases. A later and less accentuated melting event is also evidenced by internal core-rim variations in the spinels from a few samples and ascribed to the thermal effect of the host lava. Simultaneous application of exchange geothermometers which give the latest equilibrium temperatures (i.e. at the time of eruption: Fe-Mg exchange between olivine and spinel) and of pyroxene transfer thermobarometers yields two distinct behaviours: the porphyroclastic and mosaic peridotites record an event of deformation and recrystallization and were equilibrated at 800° 950° C and P≲-1 GPa at the time of eruption, but have also retained evidence of higher temperatures (1000° 1050° C) and pressures; the coarsegrained lherzolites, which yield conditions of 1000° 1050° C and P<-2 GPa at the time of eruption, were originally equilibrated at higher temperature and pressure conditions and were subsequently re-equilibrated to 1000° 1050° C by solid-state bulk diffusion, without exsolution. Clinopyroxenite veins provide evidence of magma injection into the host-peridotite, before deformation but after the major melting event. To explain the simultaneous sampling of both groups of peridotites by the San Quintin alkali basalts, we suggest that the ascending magma reached the critical limit for hydraulic

  5. Organic geochemistry of endoevaporitic environments: Microbial diversity and lipid biomarkers from gypsum deposits at the E.S.S.A Salt Works, Guerrero Negro, Baja, Mexico

    NASA Astrophysics Data System (ADS)

    Vogel, M. B.; Des Marais, D. J.; Jahnke, L. L.; Turk, K. A.; Kubo, M. D.

    2006-12-01

    We report lipid biomarker distributions and microbial diversity of endoevaporitic microbial communities from the gypsum crystallizer pond (Pond #9; ~170 % salinity) at the Exportadora de Sal, (ESSA) salt works in Guerrero Negro, Baja California Sur, Mexico. According to phylogenetic analysis using 16S rRNA sequences, gypsum crusts from this system host stratified communities of unicellular cyanobacteria (orange Euhalothece), filamentous cyanobacteria (green Oscillatoria), purple sulfur bacteria (Chromatium), and other halophilic microorganisms. Lipids collected from spatially discrete horizons of the crust indicate a shift in C16, C18 and C19 fatty acids from lower concentrations in the upper aerobic layers to higher concentrations in the deeper anaerobic zones of the crust. Compound specific isotopic analyses (CSIA) of fatty acids differentiate the more abundant C16, C18 and C19 homologues as isotopically lighter (~ -20% to -25% δ13C VPDB) from C15, C17 and C20 homologues which are isotopically heavier (~ -14% to -19% δ13C VPDB) and occur in lower abundance. CSIA of multiple compound classes reveals that gypsum domain lipids have significantly lighter δ13C values than those of lipids from the laminated benthic microbial mats living at lower salinities (i.e. ~100% to 115% salinity) in the ESSA system. This isotopic effect is consistent with intensive internal nutrient cycling within the crust. Squalane/squalene were detected in extracts from the gypsum crust indicating the presence of archaea. Diploptene is the most abundant triterpenoid of the C28 C32 hopanoids. Branched alkanes with quaternary substituted carbons (BAQCs) were also detected. These compounds have been linked with sulfur oxidizing microbial activity, which is known to be a major respiratory process in the crust's internal O2 budget (Sørensen et al., 2004). Abundant organosulfur compounds (OSC) and thiacycloalkanes in extracts indicate a vigorous internal sulfur cycle that influences both

  6. The Upper- to Middle-Crustal Section of the Alisitos Oceanic Arc, (Baja, Mexico): an Analog of the Izu-Bonin-Marianas (IBM) Arc

    NASA Astrophysics Data System (ADS)

    Medynski, S.; Busby, C.; DeBari, S. M.; Morris, R.; Andrews, G. D.; Brown, S. R.; Schmitt, A. K.

    2016-12-01

    The Rosario segment of the Cretaceous Alisitos arc in Baja California is an outstanding field analog for the Izu-Bonin-Mariana (IBM) arc, because it is structurally intact, unmetamorphosed, and has superior three-dimensional exposures of an upper- to middle-crustal section through an extensional oceanic arc. Previous work1, done in the pre-digital era, used geologic mapping to define two phases of arc evolution, with normal faulting in both phases: (1) extensional oceanic arc, with silicic calderas, and (2) oceanic arc rifting, with widespread diking and dominantly mafic effusions. Our new geochemical data match the extensional zone immediately behind the Izu arc front, and is different from the arc front and rear arc, consistent with geologic relations. Our study is developing a 3D oceanic arc crustal model, with geologic maps draped on Google Earth images, and GPS-located outcrop information linked to new geochemical, geochronological and petrographic data, with the goal of detailing the relationships between plutonic, hypabyssal, and volcanic rocks. This model will be used by scientists as a reference model for past (IBM-1, 2, 3) and proposed IBM (IBM-4) drilling activities. New single-crystal zircon analysis by TIMS supports the interpretation, based on batch SIMS analysis of chemically-abraded zircon1, that the entire upper-middle crustal section accumulated in about 1.5 Myr. Like the IBM, volcanic zircons are very sparse, but zircon chemistry on the plutonic rocks shows trace element compositions that overlap to those measured in IBM volcanic zircons by A. Schmitt (unpublished data). Zircons have U-Pb ages up to 20 Myr older than the eruptive age, suggesting remelting of older parts of the arc, similar to that proposed for IBM (using different evidence). Like IBM, some very old zircons are also present, indicating the presence of old crustal fragments, or sediments derived from them, in the basement. However, our geochemical data show that the magmas are

  7. CTB 80 en bajas frecuencias

    NASA Astrophysics Data System (ADS)

    Castelletti, G.; Dubner, G.; Golap, H.; Goss, W. M.

    CTB 80 is a supernova remnant (SNR) which shows, in radio wavelengths, a complex morphology composed by three arms or extended regions and a central nebula formed by winds from the pulsar PSR B1951+32 physically associated with the remnant. New observations of the SNR CTB 80 have been carried out using the Giant Metrewave Radio Telescope (GMRT, Pune-India) at 240 MHz (beam ˜ 20'') and 618 MHz (beam ˜ 8''), and at 324 MHz (beam ˜ 65'') and 1380 MHz (beam ˜ 80'') using the Very Large Array (VLA, USA). These radio-images show with unprecedented detail new structures in the nebula powered by the pulsar. Likewise, the high dynamic range attained in the images allows us identify faint structures in the extended regions which closely match the optical and infrared emission.

  8. Timing, Style, and Magnitude of Upper Crustal Extension, Sierra San Felipe, NE Baja California, Mexico: Constraints on Rift Processes in the NW Gulf of California Extensional Province

    NASA Astrophysics Data System (ADS)

    Givler, R.; Black, N.; Axen, G. J.; Lizarralde, D.; Kent, G. M.; Harding, A. J.; Holbrook, W. S.; Umhoeffer, P. J.; Fletcher, J. M.; Gonzalez-Fernandez, A.

    2003-12-01

    The Gulf Extensional province (GEP), NSF-MARGINS Rupturing Continental Lithosphere focus site, has extended primarily since Late Miocene time. Rift processes in NE Baja California include ENE-directed extension, distributed dextral shear, and detachment faulting, which were partly synchronous with formation of proto-oceanic pull-apart basins in the adjacent Gulf of California. New geologic mapping in the Sierra San Felipe constrains the age and magnitude of extension in the onshore part of the rift, allowing better understanding of strain partitioning in this strongly oblique rift. Strata in the Cañon El Parral (CEP) area, SSW of San Felipe, record early gulf-related extension. Early Miocene sedimentary strata intercalated with olivine basalt (Tb1) are overlain by the 12.6 Ma tuff of San Felipe (Tmr1). Unconformably above Tmr1 are tuffaceous sandstone (Tsst) and laterally equivalent fault-scarp facies, and higher ˜6.3 Ma ignimbrite deposits (Tmr3-4). These are overlain unconformably by Plio-Pleistocene conglomerate (TQcg1). Thickness changes, paleoflow indicators, and grain-size changes show that an ENE-striking, W-down fault controlled deposition of Tsst. Extension magnitude increased after Tmr3-4 time and began to wane during TQcg1deposition. Few faults cut TQcg1, implying very little Pleistocene strain; area-balanced cross sections indicate <40% extension there. The top-to-the-E Las Cuevitas detachment (LCD), W of San Felipe, was active in Miocene-Pleistocene time, controlling marine incursion. Pre-extensional hanging-wall conglomerate and eolian sandstone are overlain by basalt and ignimbrite, then by syn-LCD fluvial and marine beds, which were deposited in N and S sub-basins. Marine strata ( ˜6.0-1.8 Ma) in the N sub-basin grade W and upsection from silts to fault-scarp facies breccia at the LCD. A dextral E-striking fault separates the sub-basins, probably controlling the S edge of the deeper northern basin and offsetting a distinctive marine

  9. The supra-detachment tectono-sedimentary record of rifted margins: the example of the Los Barriles Basin, SE Baja California Sur.

    NASA Astrophysics Data System (ADS)

    Masini, Emmanuel; Robin, Cécile; Geoffroy, Laurent; Strzerzynski, Pierre

    2010-05-01

    The study of rifted margins have shown that the main controlling structures are changing from classical high-angle faults to low-angle detachment fault dominated extension when the crust thins to less than 10 km, which is the case in hyper-extended, magma-poor rifted margins. While the stratigraphic record related to classical high-angle faulting is well constrained, little is known about the tectono-sedimentary evolution of hyper-extended rift systems. A major question remains, how supra-detachment tectono-sedimentary systems are recorded in the stratigraphic record? This remains largely unexplored and must be better constrained by observations. In our poster, we present preliminary results from our study of a rift basin floored by a low-angle detachment system exposed at the southeastern edge of the Baja California Peninsula in the so-called Los Barriles area in the Gulf of California. This area represents one of the best examples of an active transtensional rift system from which the tectono-sedimentary evolution of the rift to drift transition can be studied in the field. The syn-tectonic sedimentary sequence is floored by a detachment fault and is limited oceanward by an extensional allochthon. The syn- to post-tectonic stratigraphy can be summarized into 4 main formations: (1) The Pescadero fluvial fm. (no available ages) evolves upsection from poorly organized polymictic in components and faulted breccias to more granitic and stratified conglomerates. It overlies the extensional allochthon and is tilted continentwards. The channel incisions show EW paleoflows and the upper Pescadero fm. is transitional to the following Refugio fm. (2) The overlying Refugio fm. (Lower Pliocene) occurs as thick marine sandy deposits within the basin axis, is granitic in composition and has average paleocurrents directions trending N-S. The upper part of the fm. is transitional to the following Barriles fm. (3) The Barriles fm. (Upper Miocene - Lower Pleistocene) occurs as very

  10. Structural and Seismic Stratigrapic study in the Center of the Magdalena Shelf in the Western Margin of Baja California Based on Seismic Reflection Data

    NASA Astrophysics Data System (ADS)

    González-Escobar, Mario; Salazar-Cárdenas, Rosa M.; Munguía, Luis; Martín, Arturo; Suárez-Vidal, Francisco

    2016-10-01

    The Magdalena Shelf is a shallow, low-relief surface located along the Baja California Pacific margin. As part of a forearc basin, the shelf was a convergent margin setting before the oblique divergent plate boundary formed in the Gulf of California at 12 Ma. It is thought that since 12-8 Ma, this basin has been a transtensional or strike-slip basin. To constrain the geometry, structural characteristics and some stratigraphic relationships, an active-source, seismic-reflection study was carried out in the central part of the shelf. As a result, the analyzed data show faults, basins and unconformities. Two out of four observed basins are clearly controlled by the Santa Margarita and San Lázaro faults that dip ~40° NE; a third basin is controlled by the Tosco-Abreojos fault. These three basins are part of the deformation zone that is associated with the Tosco-Abreojos fault system. The Iray-Margarita basin, on the other hand, is a fourth basin located at the northeast sector of the study area. An additional feature observed is a stepover lying between the overlapping ends of the Santa Margarita and San Lázaro faults. Small faults oriented sub-parallel to the above major faults are present, mainly throughout the western sector of the study area. Some of those minor faults cut through the seafloor indicating recent tectonic activity. Santa Margarita, San Lázaro and Tosco-Abreojos are also the names given to half-grabens controlled by the active faults that have the same names. The first two basins are affected by many more small faults in comparison with what we see in the third basin. Tectonically, this means that those two basins are the more active in the area of study. In all four basins, the upper seismic sequence consists of sediments controlled by faults of Neogene age. We found that the Iray-Santa Margarita basin is the deepest of all four basins (beyond the resolution of the data, >5 km), and lack of minor faults there indicates that the basin is not

  11. Late Pleistocene-Holocene Faulting History Along the Northern El Carrizal Fault, Baja California Sur, Mexico: Earthquake Recurrence at a Persistently Active Rifted Margin

    NASA Astrophysics Data System (ADS)

    Maloney, S. J.; Umhoefer, P. J.; Arrowsmith, J. R.; Gutiérrez, G. M.; Santillanez, A. U.; Rittenour, T. R.

    2007-12-01

    The El Carrizal fault is a NW striking, east dipping normal fault located 25 km west of the city of La Paz, Baja California Sur, Mexico and is the westernmost bounding fault of the gulf-margin system at this latitude. The fault is ~70 km long onshore and ~50 km long offshore to the north in La Paz Bay. As many as three Quaternary geomorphic surfaces formed on the footwall and were identified on the basis of mapping and topographic profiling. In the north, the El Carrizal fault splays into multiple strands and exhibits a pattern of alternating N-S and NW-trending segments. Results from geologic mapping, paleoseismic investigations, and preliminary optically stimulated luminescence (OSL) geochronology provide some of the first numerical constraints on late Pleistocene-Holocene faulting along the El Carrizal fault. A 20 m long, 2-3 m deep trench (Trench 28) was excavated across the fault 23 km south of La Paz Bay. The trench was photographed, hand logged, and sampled for OSL dating. The trench revealed a succession of fluvial and channel deposits of sands, gravels, and cobbles. The main fault zone is manifested by a 0.5 m thick wedge-shaped deposit that consists of silty-sand and also contains rotated blocks of caliche- cemented gravels. Preliminary OSL ages from a silty-sand unit offset 2 m by the fault average latest Pleistocene. A trench 4 km south of Trench 28 (Cuadradito Trench) was also documented and sampled for OSL analysis. Preliminary OSL ages from a fluvial sand unit deposited against faulted bedrock range from mid to late Holocene. Sedimentary comparisons and surficial mapping suggest that the Holocene unit at Cuadradito Trench may be correlative to sediment that overlies faulted units from Trench 28. Such a correlation would constrain the timing of the 2 m offset at Trench 28 to be between latest Pleistocene and mid Holocene. A quarry 10 km north of Trench 28 exposes Quaternary sand and gravels buttressed against a 5-10 m wide bedrock shear zone. Here

  12. The 2006 Bahía Asunción Earthquake Swarm: Seismic Evidence of Active Deformation Along the Western Margin of Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Munguía, Luis; Mayer, Sergio; Aguirre, Alfredo; Méndez, Ignacio; González-Escobar, Mario; Luna, Manuel

    2016-10-01

    The study of the Bahía Asunción earthquake swarm is important for two reasons. First, the earthquakes are clear evidence of present activity along the zone of deformation on the Pacific margin of Baja California. The swarm, with earthquakes of magnitude M w of up to 5.0, occurred on the coastline of the peninsula, showing that the Tosco-Abreojos zone of deformation is wider than previously thought. Second, the larger earthquakes in the swarm caused some damage and much concern in Bahía Asunción, a small town located in the zone of epicenters. We relocated the larger earthquakes with regional and/or local seismic data. Our results put the earthquake sources below the urban area of Bahía Asunción, at 40-50 km to the north of the teleseismically determined epicenters. In addition, these new locations are in the area of epicenters of many smaller events that were located with data from local temporary stations. This area trends in an E-W direction and has dimensions of approximately 15 km by 10 km. Most earthquakes had sources at depths that are between 4 and 9 km. A composite focal mechanism for the smaller earthquakes indicated right-lateral strike-slip motion and pure-normal faulting occurred during this swarm. Interestingly, the ANSS earthquake catalog of the United States Geological Survey (USGS) reported each one of these faulting styles for two large events of the swarm, with one of these earthquakes occurring 2 days before the other one. We associate the earthquake with strike-slip mechanism with the San Roque Fault, and the earthquake with the normal faulting style with the Asunción Fault. However, there is need of further study to verify this possible relation between the faults and the earthquakes. In addition, we recorded peak accelerations of up to 0.63 g with an accelerometer installed in Bahía Asunción. At this site, an earthquake of M w 4.9 produced those high values at a distance of 4.1 km. We also used the acceleration dataset from this site

  13. Present-day loading rate of faults in southern California and northern Baja California, Mexico, and post-seismic deformation following the M7.2 April 4, 2010, El Mayor-Cucapah earthquake from GPS Geodesy

    NASA Astrophysics Data System (ADS)

    Spinler, J. C.; Bennett, R. A.

    2012-12-01

    We use 142 GPS velocity estimates from the SCEC Crustal Motion Map 4 and 59 GPS velocity estimates from additional sites to model the crustal velocity field of southern California, USA, and northern Baja California, Mexico, prior to the 2010 April 4 Mw 7.2 El Mayor-Cucapah (EMC) earthquake. The EMC earthquake is the largest event to occur along the southern San Andreas fault system in nearly two decades. In the year following the EMC earthquake, the EarthScope Plate Boundary Observatory (PBO) constructed eight new continuous GPS sites in northern Baja California, Mexico. We used our velocity model, which represents the period before the EMC earthquake, to assess postseismic velocity changes at the new PBO sites. Time series from the new PBO sites, which were constructed 4-18 months following the earthquake do not exhibit obvious exponential or logarithmic decay, showing instead fairly secular trends through the period of our analysis (2010.8-2012.5). The weighted RMS misfit to secular rates, accounting for periodic site motions is typically around 1.7 mm/yr, indicating high positioning precision and fairly linear site motion. Results of our research include new fault slip rate estimates for the greater San Andreas fault system, including model faults representing the Cerro Prieto (39.0±0.1 mm/yr), Imperial (35.7±0.1 mm/yr), and southernmost San Andreas (24.7±0.1 mm/yr), generally consistent with previous geodetic studies within the region. Velocity changes at the new PBO sites associated with the EMC earthquake are in the range 1.7±0.3 to 9.2±2.6 mm/yr. The maximum rate difference is found in Mexicali Valley, close to the rupture. Rate changes decay systematically with distance from the EMC epicenter and velocity orientations exhibit a butterfly pattern as expected from a strike slip earthquake. Sites to the south and southwest of the Baja California shear zone are moving more rapidly to the northwest relative to their motions prior to the earthquake. Sites to

  14. Mapping variations in weight percent silica measured from multispectral thermal infrared imagery - Examples from the Hiller Mountains, Nevada, USA and Tres Virgenes-La Reforma, Baja California Sur, Mexico

    USGS Publications Warehouse

    Hook, S.J.; Dmochowski, J.E.; Howard, K.A.; Rowan, L.C.; Karlstrom, K.E.; Stock, J.M.

    2005-01-01

    Remotely sensed multispectral thermal infrared (8-13 ??m) images are increasingly being used to map variations in surface silicate mineralogy. These studies utilize the shift to longer wavelengths in the main spectral feature in minerals in this wavelength region (reststrahlen band) as the mineralogy changes from felsic to mafic. An approach is described for determining the amount of this shift and then using the shift with a reference curve, derived from laboratory data, to remotely determine the weight percent SiO2 of the surface. The approach has broad applicability to many study areas and can also be fine-tuned to give greater accuracy in a particular study area if field samples are available. The approach was assessed using airborne multispectral thermal infrared images from the Hiller Mountains, Nevada, USA and the Tres Virgenes-La Reforma, Baja California Sur, Mexico. Results indicate the general approach slightly overestimates the weight percent SiO2 of low silica rocks (e.g. basalt) and underestimates the weight percent SiO2 of high silica rocks (e.g. granite). Fine tuning the general approach with measurements from field samples provided good results for both areas with errors in the recovered weight percent SiO2 of a few percent. The map units identified by these techniques and traditional mapping at the Hiller Mountains demonstrate the continuity of the crystalline rocks from the Hiller Mountains southward to the White Hills supporting the idea that these ranges represent an essentially continuous footwall block below a regional detachment. Results from the Baja California data verify the most recent volcanism to be basaltic-andesite. ?? 2005 Elsevier Inc. All rights reserved.

  15. Incorporating Cutting Edge Scientific Results from the Margins-Geoprisms Program into the Undergraduate Curriculum, Rupturing Continental Lithosphere Part II: Introducing Euler Poles Using Baja-North America Relative Plate Motion Across the Gulf of California

    NASA Astrophysics Data System (ADS)

    Loveless, J. P.; Bennett, S. E. K.; Cashman, S. M.; Dorsey, R. J.; Goodliffe, A. M.; Lamb, M. A.

    2014-12-01

    The NSF-MARGINS Program funded a decade of research on continental margin processes. The NSF-GeoPRISMS Mini-lesson Project, funded by NSF-TUES, is designed to integrate the significant findings from the MARGINS program into open-source college-level curriculum. The Gulf of California (GOC) served as the focus site for the Rupturing Continental Lithosphere (RCL) initiative, which addressed several scientific questions: What forces drive rift initiation, localization, propagation and evolution? How does deformation vary in time and space, and why? How does crust evolve, physically and chemically, as rifting proceeds to sea-floor spreading? What is the role of sedimentation and magmatism in continental extension? We developed two weeks of curriculum, including lectures, labs, and in-class activities that can be used as a whole or individually. This component of the curriculum introduces students to the Euler pole description of relative plate motion (RPM) by examining the tectonic interactions of the Baja California microplate and North American plate. The plate boundary varies in rift obliquity along strike, from highly oblique and strike-slip dominated in the south to slightly less oblique and with a larger extensional component in the north. This Google Earth-based exercise provides students with a visualization of RPM using small circle contours of the local direction and magnitude of Baja-North America movement on a spherical Earth. Students use RPM to calculate the fault slip rates on transform, normal, and oblique-slip faults and examine how the varying faulting styles combine to accommodate RPM. MARGINS results are integrated via comparison of rift obliquity with the structural style of rift-related faults around the GOC. We find this exercise to fit naturally into courses about plate tectonics, geophysics, and especially structural geology, given the similarity between Euler pole rotations and stereonet-based rotations of structural data.

  16. Post subduction thermal regime of the western North America and effects on the Great Valley, Sierra Nevada and northern Baja California provinces

    NASA Astrophysics Data System (ADS)

    Erkan, Kamil

    the region shows that there is a significant lateral component of the heat flow in to the Sierra Nevada due to Basin and Range province and due to basal heating. The model further suggests that the lateral heating results in considerable thermal uplift at the eastern edge of the Sierra Nevada region. The model is also applicable in the Northern Baja California since this region was part of the same tectonic setting as the Sierra Nevada arc before the inland jump of the San Andreas Fault. The Coast Ranges are interesting with having spots of magmatic and volcanic arc activity likely associated with the cessation of subduction. The third paper is a study related to one of these spots 90 km north of San Francisco, characterized by elevated heat flow in an area of 2500 km2 (The Geysers anomaly). The geothermal system is associated with a very young (˜2 My) bimodal volcanism and magma intrusion at crustal levels. Taking advantage of a sealed, vapor dominated geothermal system due to rocks of very low permeability, forward and inverse models of the deeper magmatic source were constructed. We used extensive heat flow data that were collected over more than 20 years time period. The models revealed that the magmatic source in the Geysers must be as shallow as 7-8 km in order to satisfy the thermal data. Furthermore, the magma system must cover most of the thermally anomalous region. Another type of geothermal system is characterized by rising of hot waters by buoyancy forces without the necessity of a magmatic source at depth. We studied one of these systems in interior Alaska, called Chena Hot Springs, in the fourth paper. The explored system is 1 km long and temperatures are only 74°C. Although the system is moderate in temperature, the low-temperature surface conditions enable the system to be exploited for production of electricity. The geochemical analyses show that the source temperatures are around 121°C. We analyzed the temperature data from 17 exploration wells in

  17. Interdisciplinary approach on evaluation and sustainable usage of the water resources in the semi-arid Northwest Mexico to counter the imbalance of water: Case study Valle de Guadalupe, Baja California

    NASA Astrophysics Data System (ADS)

    Kretzschmar, T.; Hernandez, R.; Valenzuela, C.; Cabello, A.

    2012-12-01

    In the Baja California peninsula are several watersheds present, of which the hydrogeological conditions are of great importance to communities in the area. The Valle de Guadalupe watershed, for instance has a wine industry of national importance. Irrigation of crops is carried out exclusively with water from the aquifer, which consists of Quaternary sediments filling this depression of Post-Miocene age. Apart from the use of the aquifer by the wine industry, the water utility of Ensenada operates 10 drinking water wells with a total capacity of 320 L/s or 42% of supply in the valley. In the arid northern Mexico mountain front recharge is an important recharge source to the aquifers. Other important recharge sources are related to direct infiltration of the precipitation, recharge from runoff into streams (mountain block recharge) and the provision by active faults. The knowledge of the aquifer is crucial to maintain sustainable management of water resources in the Valle de Guadalupe. This intense use of water resources is reflected in a degradation of the aquifer water quality and reduced water table. The integrated approach for a sustainable evaluation and usage of the aquifer includes besides the hydrogeological evaluation, the determination of the water stress on the vineyards as well as the usage of treated waste water as alternative resource as well the evaluation of the effects of climatic variations and measurement and modeling of the vegetation, the main interface between atmosphere and soil, affecting the hydrology in the process of interception, infiltration, runoff and evapotranspiration. With these detailed ongoing studies we expect to identify and counter imbalance of water in the study area. This requires 1) modeling and hydrogeological studies for the determination of the present and future imbalance 2) estimation of the impacts of industrial activities on water resources 3) characterization of alternative water sources, 4) optimization of the water

  18. Resource inventory of marine and estuarine fishes of the West Coast and Alaska: A checklist of North Pacific and Arctic Ocean species from Baja California to the Alaska - Yukon border

    USGS Publications Warehouse

    Love, Milton S.; Mecklenburg, Catherine W.; Mecklenburg, T. Anthony; Thorsteinson, Lyman K.

    2005-01-01

    This is a comprehensive inventory of the fish species recorded in marine and estuarine waters between the Alaska–Yukon Territory border in the Beaufort Sea and Cabo San Lucas at the southern end of Baja California and out about 300 miles from shore. Our westernmost range includes the eastern Bering Sea and Aleutian Islands. In addition, we have also included our best impressions of the species that might reasonably be expected to be members of the West Coast ichthyofauna but have not yet been captured or reported within our study area. These species are marked with an asterisk (*) and have been reported (1) in the western Bering Sea; (2) off Canada’s Yukon Territory and adjacent portions of the Northwest Territories; (3) along the southern-eastern tip (non-Pacific side) of Baja California; and (4) in waters somewhat beyond 300 miles from shore. Although the term West Coast usually refers to the coast of the continuous western states, our usage herein means the entire study area. The West Coast inventory within this range encompasses fish fauna from 44 orders, 232 families, and a minimum of 1,450 species. Please note that introduced and invasive fish species are marked by double asterisks (**) and that their scientific names are highlighted in gray. We have compiled this document because the most geographically inclusive previous inventories (Jordan and Evermann 1896a, Jordan et al. 1930) are largely of historical interest and are out of date. More recent lists and compilations have either focused on relatively narrow taxonomic groups (e. g., Kramer et al. 1995, Love et al. 2002), are regional in scope (e. g., Hart 1973, Hubbs et al. 1979, Mecklenburg et al. 2002), or focus on commonly observed species (e. g., Miller and Lea 1972, Eschmeyer and Herald 1983). With the explosion of coastal research and environmental assessments, beginning in the 1970s, and more recently, renewed scientific interest in biodiversity (e.g., effects of global climate change), our own

  19. Regional orientation of tectonic stress and the stress expressed by post-subduction high-magnesium volcanism in northern Baja California, Mexico: Tectonics and volcanism of San Borja volcanic field

    NASA Astrophysics Data System (ADS)

    Negrete-Aranda, Raquel; Cañón-Tapia, Edgardo; Brandle, Jose Luis; Ortega-Rivera, M. Amabel; Lee, James K. W.; Spelz, Ronald M.; Hinojosa-Corona, Alejandro

    2010-04-01

    Because of its long-lived (Late Miocene to Pleistocene) post-subduction volcanic activity and location, the San Borja volcanic field (SBVF) is a key area for understanding the physical mechanisms controlling the spatial distribution of post-subduction volcanism on the Peninsula of Baja California. In this paper, we study the distribution and general characteristics of individual eruptive centers in the SBVF, aiming to provide insight into the changing physical nature of post-subduction magmatism and the control on vent location in a very unique tectonic setting. Volcanic activity has built more than 227 high-magnesium andesites (HMA) monogenetic scoria cones and thick lava flows capping large mesas during the last 12.5 Ma. The average (mean) eruptive center in the SBVF has a height of 85 m, a basal diameter of 452 m and a slope angle of 30°. Our volcanic alignment analysis of this field is based on field data, satellite images, and a quantitative method for detecting volcanic center alignments. The morphologic data, together with new 40Ar/ 39Ar geochronology data have been used to refine our alignment analysis and to better delineate the temporal evolution of post-subduction volcanic activity in this field. The available ages vary from 3.53 ± 0.18 to 10 ± 0.23 Ma suggesting that the long-lived HMA volcanism occurred almost continuously (with some concentration of pulses) throughout Late Miocene and extending to the Pleistocene and even into the Quaternary, replacing the arc-related activity of the Comondú arc which vanished in this area around 12.5 Ma. Alignment analysis confirms a NW-SE direction as the preferred orientation of volcanic alignments and shows that vent elongations do not display a strong parallelism in any particular direction, marking the absence of matches between lineaments defined by multiple vents and orientations of vent elongation. The results of the volcanic alignment analysis allowed us to infer the direction of the maximum

  20. Hyperparasitism by the bacteriophage (Caudovirales) infecting Candidatus Xenohaliotis californiensis (Rickettsiales-like prokaryote) parasite of wild abalone Haliotis fulgens and Haliotis corrugata from the Peninsula of Baja California, Mexico.

    PubMed

    Cruz-Flores, Roberto; Cáceres-Martínez, Jorge; Muñoz-Flores, Monserrat; Vásquez-Yeomans, Rebeca; Hernández Rodriguez, Mónica; Ángel Del Río-Portilla, Miguel; Rocha-Olivares, Axayácatl; Castro-Longoria, Ernestina

    2016-10-01

    Candidatus Xenohaliotis californiensis (CXc) is a Rickettsiales-like prokaryote that is considered the causal agent of Withering Syndrome (WS), a chronic disease of abalone, from the west coast of North America and it is listed by the International Organization for Animal Health (OIE) as a reportable agent due to its pathogenicity. This bacterium in red abalone Haliotis rufescens, black abalone Haliotis cracherodii, and yellow abalone Haliotis corrugata from California, US and Baja California, Mexico has been found to be infected by a bacteriophage. To date, there is no information on the epizootiology of CXc and its bacteriophage in natural populations of abalone; furthermore, it is unknown if the bacteriophage was also present in CXc infecting blue abalone Haliotis fulgens. The objective of this study was to determine the distribution, prevalence and intensity of CXc, as well as to determine the distribution and prevalence of the bacteriophage and to study interactions between host sex and hyperparasitism in blue abalone and yellow abalone. Tissue samples were obtained from seven localities where the commercial capture of wild abalone is carried out. Samplings were conducted throughout the 2012-2013 capture seasons and a total of 182 blue abalone and 170 yellow abalone were obtained. The prevalence and intensity of CXc and the prevalence of the bacteriophage were determined by histology. The identity of CXc was confirmed by PCR, product sequence analysis and in situ hybridization while the identity of the bacteriophage was corroborated by TEM. The prevalence of CXc infected and uninfected by the bacteriophage was 80% in blue abalone and 62% in yellow abalone. Low infection intensities were found in 86% of blue abalone and 82% of yellow abalone. Infection intensity was significantly higher in undifferentiated yellow abalone. The bacteriophage in CXc showed a prevalence of 22% and 31% in blue abalone and yellow abalone respectively. These results show that CXc and

  1. Cretaceous to Cenozoic sequential kinematics in the forearc-arc transition: effects of changing oblique plate convergence and the San Andreas system with implications for the La Paz fault (southern Baja California, Mexico)

    NASA Astrophysics Data System (ADS)

    Mattern, Frank; Pérez Venzor, José Antonio; Pérez Espinoza, Jesus Efraín; Rochin, Joel Hirales

    2010-01-01

    We studied metasediments and mylonitic arc granitoids from the forearc-arc transition of southern Baja California, Mexico. Thin section analyses and field evidence show that metamorphism of the forearc-arc transition is of the high T/P active margin type. The heat was provided by Cretaceous arc intrusions. Field observations and thin section analyses, including the time/temperature deformation path, demonstrate that the study area was first affected by dextral, ductile shearing followed by ductile, sinistral, possibly transpressive strike-slip parallel to the magmatic arc during the Cretaceous. Both intervals are related to changing oblique plate convergence and, thus, identified as trench-linked strike-slip effects. The geometric relationship between arc-dipping foliation, stretching lineation and shear sense indicates that the arc may have been pressed onto the rocks of the study area during sinistral shearing. The sinistral interval lasted up until regional cooling (Early Cenozoic?). Because the La Paz fault is closely associated with the forearc-arc transition, it must have the same Cretaceous to Early Cenozoic kinematic history. The northern segment of the La Paz fault is a modern, brittle, strike-slip fault interpreted as a dextral synthetic fault of the San Andreas system which opened the Gulf of California (Mar de Cortés/Golfo de California). We found no evidence for Miocene Basin and Range extension.

  2. Origins of late- Pleistocene coastal dune sheets, Magdalena and Guerrero Negro, from continental shelf low-stand supply (70-20 ka), under conditions of southeast littoral- and eolian-sand transport, in Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Peterson, Curt D.; Murillo-Jiménez, Janette M.; Stock, Errol; Price, David M.; Hostetler, Steve W.; Percy, David

    2017-10-01

    Shallow morpho-stratigraphic sections (n = 11) in each of two large coastal dune sheets including the Magdalena (7000 km2) and Guerrero Negro (8000 km2) dune sheets, from the Pacific Ocean side of Baja California Sur, Mexico, have been analyzed for dune deposit age. The shallow morpho-stratigraphic sections (∼2-10 m depth) include 11 new TL and 14C ages, and paleosol chronosequences, that differentiate cemented late Pleistocene dune deposits (20.7 ± 2.1 to 99.8 ± 9.4 ka) from uncemented Holocene dune deposits (0.7 ± 0.05 to at least 3.2 ± 0.3 ka). Large linear dune ridges (5-10 m in height) in the dune sheet interiors trend southeast and are generally of late Pleistocene age (∼70-20 ka). The late Pleistocene dune deposits reflect eolian transport of marine sand across the emerged continental shelf (30-50 km southeast distance) from low-stand paleo-shorelines (-100 ± 25 m elevation), which were locally oriented nearly orthogonal to modeled deep-water wave directions (∼300° TN). During the Holocene marine transgression, onshore and alongshore wave transport delivered remobilized shelf-sand deposits to the nearshore areas of the large dune sheets, building extensive barrier islands and sand spits. Submerged back-barrier lagoons generally precluded marine sand supply to dune sheet interiors in middle to late Holocene time, though exceptions occur along some ocean and lagoon shorelines. Reactivation of the late Pleistocene dune deposits in the dune sheet interiors lead to generally thin (1-3 m thickness), but widespread, covers of Holocene dune deposits (0.41 ± 0.05 to 10.5 ± 1.6 ka). Mechanical drilling will be required to penetrate indurated subsoil caliche layers to reach basal Pleistocene dune deposits.

  3. Estimation of Seismic and Aseismic Deformation in Mexicali Valley, Baja California, Mexico, in the 2006-2009 Period, Using Precise Leveling, DInSAR, Geotechnical Instruments Data, and Modeling

    NASA Astrophysics Data System (ADS)

    Sarychikhina, Olga; Glowacka, Ewa; Robles, Braulio; Nava, F. Alejandro; Guzmán, Miguel

    2015-11-01

    Ground deformation and seismicity in Mexicali Valley, Baja California, Mexico, the southern part of the Mexicali-Imperial valley, are influenced by active tectonics and human activity. In this study, data from two successive leveling surveys in 2006 and 2009/2010 are used to estimate the total deformation occurred in Mexicali Valley during 2006-2009. The leveling data span more than 3.5 years and include deformation from several natural and anthropogenic sources that acted at different temporal and spatial scales during the analyzed period. Because of its large magnitude, the aseismic anthropogenic deformation caused by fluid extraction in the Cerro Prieto geothermal field obscures the deformation caused by other mechanisms and sources. The method of differential interferograms stacking was used to estimate the aseismic (interseismic tectonic and anthropogenic) components of the observed displacement, using SAR images, taken in 2007 during a period when no significant seismicity occurred in the study area. After removing the estimated aseismic signal from the leveling data, residual vertical displacement remained, and to identify possible sources and mechanisms of this displacement, a detailed analysis of records from tiltmeters and creepmeters was performed. The results of this analysis suggest that the residual displacement is mainly caused by moderate-sized seismicity in the area of study. Modeling of the vertical ground deformation caused by the coseismic slip on source fault (primary mechanism) of the two most important earthquakes, May 24, 2006 (Mw = 5.4) and December 30, 2009 (Mw = 5.8), was performed. The modeling results, together with the analysis of geotechnical instruments data, suggests that this moderate-sized seismicity influences the deformation in the study area by coseismic slip on the source fault, triggered slip on secondary faults, and soft sediments deformation.

  4. Late Quaternary Range-Front Fault Scarps in the Western Sierra El Mayor, Baja California, Mexico: A Geomorphologic Expression of Slip Across an Active Low-Angle Normal Fault

    NASA Astrophysics Data System (ADS)

    Spelz, R. M.; Fletcher, J.; Owen, L.

    2006-12-01

    The western margin of the Sierra El Mayor (SEM), in northeastern Baja California, is controlled by an active, top-to-the-west, low-angle normal fault named the Canada David detachment (CDD) that accommodates part of the extensional component of shearing between the Pacific and North American plates. The CDD has a length of 60 km and shows a curvilinear trace with two major antiformal and synformal megamullion pairs. Late Quaternary slip has produced a broad array of Quaternary scarps cutting alluvial fans along nearly the entire length of the CDD. Detailed mapping reveals eight regional strath terraces distinguished by surface weathering characteristics, soil profile development and relative elevation. Relative height between terraces increases in domains where the CDD and basin deposits are being uplifted due to either the basinward migration of faulting (e.g., rolling hinge) or flexural uplift in antiformal megamullion domains. Linear diffusion analysis of 46 synthetic fault scarps, with a calculated angle of repose Θo = 28.75°, reveal fault scarp domains exhibiting both multi-modal and unimodal distribution of diffusion ages (kt). Uni-modal domains are typically younger, but there is no systematic variation in scarp age with distance along the CDD. Scarps yielding negative kt ages (i.e. scarps steeper than Θo) are common in the north, near inferred locations of important historic seismic events. Microseismicity drops off significantly adjacent to these very young scarp arrays, which likely reflects a recent post-seismic stress drop. Domains of high seismic risk are identified by high microseismicity and lack of young scarps. Minimum estimates of the diffusivity constant (k) are calculated by coupling scarp diffusion ages and 10Be surface exposure ages of the faulted deposits. In the southernmost SEM a Q6 terrace with a minimum surface exposure age t = 233±6.6 ky (weighted mean of six rock samples) is cut by scarps with an average kt = 11.25±9.31 m2, which

  5. Some characteristics of the complex El Mayor-Cucapah, MW7.2, April 4, 2010, Baja California, Mexico, earthquake, from well-located aftershock data from local and regional networks.

    NASA Astrophysics Data System (ADS)

    Frez, J.; Nava Pichardo, F. A.; Acosta, J.; Munguia, L.; Carlos, J.; García, R.

    2015-12-01

    Aftershocks from the El Mayor-Cucapah (EMC), MW7.2, April 4, 2010, Baja California, Mexico, earthquake, were recorded over two months by a 31 station local array (Reftek RT130 seismographs loaned from IRIS-PASSCAL), complemented by regional data from SCSN, and CICESE. The resulting data base includes 518 aftershocks with ML ≥ 3.0, plus 181 smaller events. Reliable hypocenters were determined using HYPODD and a velocity structure determined from refraction data for a mesa located to the west of the Mexicali-Imperial Valley. Aftershock hypocenters show that the El Mayor-Cucapah earthquake was a multiple event comprising two or three different ruptures of which the last one constituted the main event. The main event rupture, which extends in a roughly N45°W direction, is complex with well-defined segments having different characteristics. The main event central segment, located close to the first event epicenter is roughly vertical, the northwest segment dips ~68°NE, while the two southeast segments dip ~60°SW and ~52°SW, respectively, which agrees with results of previous studies based on teleseismic long periods and on GPS-INSAR. All main rupture aftershock hypocenters have depths above 10-11km and, except for the central segment, they delineate the edges of zones with largest coseismic displacement. The two southern segments show seismicity concentrated below 5km and 3.5km, respectively; the paucity of shallow seismicity may be caused by the thick layer of non-consolidated sediments in this region. The ruptures delineated by aftershocks in the southern regions correspond to the Indiviso fault, unidentified until the occurrence of the EMC earthquake. The first event was relocated together with the aftershocks; the epicenter lies slightly westwards of published locations, but it definitely does not lie on, or close to, the main rupture. The focal mechanism of the first event, based on first arrival polarities, is predominantly strike-slip; the focal plane

  6. Fluoride content by ion chromatography using a suppressed conductivity detector and osmolality of bitterns discharged into the Pacific Ocean from a saltworks: feasible causal agents in the mortality of green turtles (Chelonia mydas) in the Ojo de Liebre lagoon, Baja California Sur, Mexico.

    PubMed

    Tovar, Luis Raúl; Gutiérrez, Ma Eugenia; Cruz, Guillermo

    2002-09-01

    On December 1997, 94 corpses of green turtles, Chelonia mydas, were found at the Ojo de Liebre lagoon (OLL) adjacent to the industrial operation of Exportadora de Sal S. A (ESSA), the largest saltworks in the world, owned by the Mexican Government and Mitsubishi Corporation, located in Baja California Sur, Mexico. Every year about 551 x 10(6) m3 of seawater is solar evaporated, producing 7 x 10(6) tons of salt and 24.6 x 10(6) m3 of bitterns, the latter being discharged into the OLL, which is a costal lagoon of the Pacific Ocean. ESSA claimed that bitterns contain the same salts present in seawater, but 20-fold more concentrated than the former. Ion chromatography with a conductivity detector and ion suppression was used to determine the F-, Cl-, SO4(2-) and CO3(2-) contents of seawater, brines and bitterns collected at ESSA. Furthermore, the osmolality of brines and bitterns from ESSA was measured. F- content in bitterns was 60.5-fold more than that in seawater. The bitterns osmolality was 11,000 mosm/kg of water, whereas the turtle's plasma osmolality was about 400 mosm/kg of water. We concluded that the dumping of bitterns into the ocean should be avoided.

  7. Seismotectonics of the Cerro Prieto Geothermal Field, Baja California, Mexico.

    NASA Astrophysics Data System (ADS)

    Rebollar, C. J.; Reyes, L. M.; Quintanar, L.; Arellano, J. F.

    2002-12-01

    We studied the background seismic activity in the Cerro Prieto geothermal field (CPGF) using a network of 21 digital stations. Earthquakes are located below the exploitation area of the CPGF, between 3 and 12 km depth, within the basement. Earthquakes follow roughly a N30°E trend perpendicular to the Cerro Prieto fault. This activity is located on a horst-like structure below the geothermal field and coincides with the zone of maximum subsidence in the CPGF. Two earthquake swarms occurred along the SE-NW strike of the Cerro Prieto fault and in the neighborhood of the Cerro Prieto volcano. Magnitudes range from -0.3 to 2.5. A Vp/Vs=1.91 ratio of the activity below the volcano suggests a water-saturated medium and/or a partial-melt medium. We calculated 76 focal mechanisms of individual events. On June 1 and September 10, 1999, two earthquakes of Mw 5.2 and 5.3 occurred in the basement at depths of 7.4 and 3.8 km below the CPGF. Maximum peak accelerations above the hypocenter ranged from 128.0 to 432.0 cm/s2. Waveform modeling results in a fault geometries given by strike=236°, dip=60°, rake=-58° (normal) and strike=10°, dip=90°, rake=159° (right lateral strike-slip) for the June and September events. Observed triangular source time function of 0.7 seconds and a double source with a total duration of 1.9 seconds for the June and September events were used to calculate the synthetics seismograms. Static stress drops and seismic moments for the June and September events are: Δ\\sigma=82.5 MPa (825 bars), Mo= 7.65x1016 Nm (7.65x1023 dyne-cm) and Δ\\sigma=31.3 MPa (313 bars) and Mo=1.27x1017 Nm (1.27x1024 dyne-cm). These stress drops are typical of continental events rather than stress drops of events originated in spreading centers. We concluded from the focal mechanisms of the background seismicity and June and September 1999 events, that a complex stress environment exits in the CPGF due to the continual thinning of the crust in the Cerro Prieto basin.

  8. Un sistema protoestelar a bajas frecuencias en radio

    NASA Astrophysics Data System (ADS)

    Peri, C. S.; Benaglia, P.; Martí, J.; Sánchez-Sutil, J. R.; Ishwara-Chandra, C. H.

    2016-08-01

    Stars form in the coolest and densest places of the Galaxy. Protostellar systems are very complex, have several components, produce a rich phenomenology and experiment very interesting physical processes to be studied. There exist a lot of similarities and differences between protostellar systems related to all the mass ranges. A common characteristic related to high--mass protostars is the detection of non--thermal synchrotron radio emission coming from the jets. One system that presents this kind of evidence is 165474247, called that way because of the infrared source on its center. This source has been observed and studied in several radio frequencies and modeled as possible generator of high-energy photons. We present radio maps of the Giant Metrewave Radio Telescope, of 1 deg, at 610 MHz, never reported before, with a noise level of mJy. We detected the entire system of 165474247, center and lobes, and other sources in the region. We name some of them and their counterparts.

  9. Return to ranger submarine slide, Baja California, Mexico

    USGS Publications Warehouse

    Normark, W.R.

    1990-01-01

    Ranger Slide is a modest (12 km3) slide deposit of Pliocene and younger sediment on the continental slope in northern Sebastian Vizcaino Bay, Mexico. A limited survey using a deeply-towed instrument shows that hummocky terrain immediately downslope from the slide scar consists of large blocks of semiconsolidated sediment, some exceeding a kilometer in length and 107 m3 in volume. Most blocks have rotated, fallen apart, and/or deformed during movement. The form, structure, and processes related to emplacement of the blocks within the hummocky topographic zone of Ranger Slide may be common to many submarine slides on slopes involving semiconsolidated, terrigenous sediment. ?? 1990 Springer-Verlag New York Inc.

  10. A study of microseismicity in northern Baja California, Mexico

    NASA Technical Reports Server (NTRS)

    Johnson, T. L.; Koczynski, T.; Madrid, J.

    1976-01-01

    Five microearthquake instruments were operated for 2 months in 1974 in a small mobile array deployed at various sites near the Agua Blanca and San Miguel faults. An 80-km-long section of the San Miguel fault zone is presently active seismically, producing the vast majority of recorded earthquakes. Very low activity was recorded on the Agua Blanca fault. Events were also located near normal faults forming the eastern edge of the Sierra Juarez suggesting that these faults are active. Hypocenters on the San Miguel fault range in depth from 0 to 20 km although two-thirds are in the upper 10 km. A composite focal mechanism showing a mixture of right-lateral and dip slip, east side up, is similar to a solution obtained for the 1956 San Miguel earthquake which proved consistent with observed surface deformation.

  11. Large stratocumulus deck off the coast of Baja California

    NASA Technical Reports Server (NTRS)

    2002-01-01

    A bank of stratocumulus clouds is packed against the California coast so tightly it appears to have been painted in this MODIS image from March 31, 2002. California's San Joaquin Valley is greening up, while the Sierra Nevadas remain covered in snow. To the east, the salmon-colored rocks of the Colorado Plateau dominate southern Utah and northern Arizona. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  12. Comunidades de la Cuenca Baja del Río Merrimack

    EPA Pesticide Factsheets

    Lista de todas las comunidades que se incluyen en los límites 8, 10 y 12 del código de unidades hidrológicas (HUC) para la cuenca del río Merrimack y las ubicaciones de la ciudad de las estaciones de control de calidad del agua de la EPA.

  13. A study of microseismicity in northern Baja California, Mexico

    NASA Technical Reports Server (NTRS)

    Johnson, T. L.; Koczynski, T.; Madrid, J.

    1976-01-01

    Five microearthquake instruments were operated for 2 months in 1974 in a small mobile array deployed at various sites near the Agua Blanca and San Miguel faults. An 80-km-long section of the San Miguel fault zone is presently active seismically, producing the vast majority of recorded earthquakes. Very low activity was recorded on the Agua Blanca fault. Events were also located near normal faults forming the eastern edge of the Sierra Juarez suggesting that these faults are active. Hypocenters on the San Miguel fault range in depth from 0 to 20 km although two-thirds are in the upper 10 km. A composite focal mechanism showing a mixture of right-lateral and dip slip, east side up, is similar to a solution obtained for the 1956 San Miguel earthquake which proved consistent with observed surface deformation.

  14. Groundwater Exploration in Baja California, Mexico, Using Audiomagnetotellurics

    NASA Astrophysics Data System (ADS)

    Antonio, R.; Arroyo, A.; Romo, J.; Vazquez, R.

    2007-12-01

    Guadalupe Valley, in Ensenada B. C. Mexico, basis of the winery industry of the region, is known by their climatic attributes for vineyard cultivation. In this place, the crop growing depends totally on underground water extracted of an aquifer contained in two separate small basins. In order to estimate the depth to water level, as well as the thickness of one of these basins, we carry out a geophysical survey using audio-magnetotellurics (AMT). We carried out five profiles in a frequency range between 1 Hz and 750 kHz to estimate the electrical conductivity of the ground. We know that this physical property is enhanced by the permeability as well as by the salinity of fluids in the aquifer. In contrast, the crystalline rocks forming the basement of the basin are very bad conductors of electricity. Based on the AMT observations we construct 2-D models of the ground resistivity distribution. Our results show a clear resistivity contrast between sediments and bedrock. The sediments have resistivity values that oscillate from 40 to 100 Ohm-m, associated with lithology and/or permeability changes. Some conductive bodies (5 to 15 Ohms-m) are observed at depths shallower that 150 m, which might be caused by the presence of water with higher salinity, or alternatively, by clay lens. The bottom of the basin has resistivity values larger than 300 Ohm-m typical of the granitic rocks composing the bedrock. The spatial variation of the basement depth suggests the presence a normal fault, in agreement with a graben structure proposed in former studies.

  15. Diversidad de Sistemas Planetarios en Discos de Baja Masa

    NASA Astrophysics Data System (ADS)

    Ronco, M. P.; de Elía, G. C.

    The accretion process that allows the formation of terrestrial planets is strongly dependent on the mass distribution in the system and the presence of gas giant planets. Several studies suggest that planetary systems formed only by terrestrial planets are the most common in the Universe. In this work we study the diversity of planetary systems that could form around solar-type stars in low mass disks in absence of gas giants planets and search wich ones are targets of particular interest. FULL TEXT IN SPANISH

  16. Geothermal development in Cerro Prieto Baja California, Mexico (1983)

    SciTech Connect

    Manon M.A.

    1983-09-01

    The actual stage of the expansion program and some of the main characteristics of the Cerro Prieto Geothermal Field are presented. This is similar to the one presented in this same conference back in 1981, but it has been updated.

  17. 78 FR 62610 - North Baja Pipeline, LLC; Notice of Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-22

    ... Commission in the Public Reference Room or may be viewed on the Commission's Web site web at http://www.ferc... Washington, DC. There is an ``eSubscription'' link on the Web site that enables subscribers to receive...

  18. PBO Southwest Region: Baja Earthquake Response and Network Operations

    NASA Astrophysics Data System (ADS)

    Walls, C. P.; Basset, A.; Mann, D.; Lawrence, S.; Jarvis, C.; Feaux, K.; Jackson, M. E.

    2011-12-01

    The SW region of the Plate Boundary Observatory consists of 455 continuously operating GPS stations located principally along the transform system of the San Andreas fault and Eastern California Shear Zone. In the past year network uptime exceeded an average of 97% with greater than 99% data acquisition. Communications range from CDMA modem (307), radio (92), Vsat (30), DSL/T1/other (25) to manual downloads (1). Sixty-three stations stream 1 Hz data over the VRS3Net typically with <0.5 second latency. Over 620 maintenance activities were performed during 316 onsite visits out of approximately 368 engineer field days. Within the past year there have been 7 incidences of minor (attempted theft) to moderate vandalism (solar panel stolen) with one total loss of receiver and communications gear. Security was enhanced at these sites through fencing and more secure station configurations. In the past 12 months, 4 new stations were installed to replace removed stations or to augment the network at strategic locations. Following the M7.2 El Mayor-Cucapah earthquake CGPS station P796, a deep-drilled braced monument, was constructed in San Luis, AZ along the border within 5 weeks of the event. In addition, UNAVCO participated in a successful University of Arizona-led RAPID proposal for the installation of six continuous GPS stations for post-seismic observations. Six stations are installed and telemetered through a UNAM relay at the Sierra San Pedro Martir. Four of these stations have Vaisala WXT520 meteorological sensors. An additional site in the Sierra Cucapah (PTAX) that was built by CICESE, an Associate UNAVCO Member institution in Mexico, and Caltech has been integrated into PBO dataflow. The stations will be maintained as part of the PBO network in coordination with CICESE. UNAVCO is working with NOAA to upgrade PBO stations with WXT520 meteorological sensors and communications systems capable of streaming real-time GPS and met data. The real-time GPS and meteorological sensor data streaming support watershed and flood analyses for regional early-warning systems related to NOAA's work with California Department of Water Resources. Currently 19 stations are online and streaming with 7 more in preparation. In 2008 PBO became the steward of 209 existing network stations of which 140 are in the SW region that included SCIGN, BARD, BARGEN stations. Due to the mix of incompatible equipment used between PBO and existing network stations a project was undertaken to standardize existing network GPS stations to PBO specifications by upgrading power systems and enclosures. To date 96 stations have been upgraded. UNAVCO is currently funded through a USGS ARRA grant to construct 8 new GPS stations in the San Francisco Bay Area capable of streaming high rate data. At present 6 stations are built with 2 permits outstanding.

  19. 75 FR 8321 - North Baja Pipeline, LLC; Notice of Abbreviated Application of North Baja Pipeline LLC; To Amend...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-24

    ... necessity authorizing the construction and operation of the Yuma Lateral Pipeline Project (Yuma Lateral... to revise the initial recourse rates applicable to service on the Yuma Lateral to reflect a representative level of costs attributable to interruptible transportation service on the Yuma Lateral, in...

  20. Subsidence monitoring with geotechnical instruments in the Mexicali Valley, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Glowacka, E.; Sarychikhina, O.; Márquez Ramírez, V. H.; Robles, B.; Nava, F. A.; Farfán, F.; García Arthur, M. A.

    2015-11-01

    The Mexicali Valley (northwestern Mexico), situated in the southern part of the San Andreas fault system, is an area with high tectonic deformation, recent volcanism, and active seismicity. Since 1973, fluid extraction, from the 1500-3000 m depth range, at the Cerro Prieto Geothermal Field (CPGF), has influenced deformation in the Mexicali Valley area, accelerating the subsidence and causing slip along the traces of tectonic faults that limit the subsidence area. Detailed field mapping done since 1989 (González et al., 1998; Glowacka et al., 2005; Suárez-Vidal et al., 2008) in the vicinity of the CPGF shows that many subsidence induced fractures, fissures, collapse features, small grabens, and fresh scarps are related to the known tectonic faults. Subsidence and fault rupture are causing damage to infrastructure, such as roads, railroad tracks, irrigation channels, and agricultural fields. Since 1996, geotechnical instruments installed by CICESE (Centro de Investigación Ciéntifica y de Educación Superior de Ensenada, B.C.) have operated in the Mexicali Valley, for continuous recording of deformation phenomena. Instruments are installed over or very close to the affected faults. To date, the network includes four crackmeters and eight tiltmeters; all instruments have sampling intervals in the 1 to 20 min range. Instrumental records typically show continuous creep, episodic slip events related mainly to the subsidence process, and coseismic slip discontinuities (Glowacka et al., 1999, 2005, 2010; Sarychikhina et al., 2015). The area has also been monitored by levelling surveys every few years and, since the 1990's by studies based on DInSAR data (Carnec and Fabriol, 1999; Hansen, 2001; Sarychikhina et al., 2011). In this work we use data from levelling, DInSAR, and geotechnical instruments records to compare the subsidence caused by anthropogenic activity and/or seismicity with slip recorded by geotechnical instruments, in an attempt to obtain more information about the process of fault slip associated with subsidence.

  1. Aseismic Slip Observed on the Faults in Mexicali Valley, Baja California, Mexico.

    NASA Astrophysics Data System (ADS)

    Glowacka, E.; Sarychikhina, O.; Suarez, F.; Nava, F.; Farfan, F.; Cossio Battani, G. D.; Guzman, M.

    2007-05-01

    The Mexicali Valley, which is part of the Salton Trough, is located within an active tectonic region, in the boundary between the Pacific and North American plates; a region featuring a wide zone of transform faults associated with San Andreas fault system, and a zone of distributed deformation in the pull-apart center of Cerro Prieto. Since 1996, geotechnical instruments have operated in the Valley, for continuous recording of deformation phenomena. To date, the network includes three crackmeters, eight tiltmeters, and seven piezometers installed in the shallow aquifer; all instruments have sampling intervals in the 1 to 20 minutes range. The mainly vertical displacement at Saltillo fault (known before as southernmost part of Imperial fault) has been measured on a continuous basis since February 1996 by a crackmeter installed in Ejido Saltillo (Glowacka 1996; Nava and Glowacka, 1999). In 1998 a tiltmeter was installed on the fault and a second crackmeter , in a horizontal direction, about 60° from the fault strike, was installed about 1 km south of ES. Another crackmeter in the vertical plane crossing Morelia fault and a 3D Witness on the Cerro Prieto fault were installed in 2004. In 2003 seven digital water level meters were installed at depths up to 500 meters in the local piezometric wells, with the purpose of recording aquifer level changes. The observed deformation rates measured on the Saltillo fault are 6 cm/yr and 2 cm/yr for the vertical and horizontal components, respectively and occurs in steps (creep events), separated by months of quiescence, and large events account for 70 percent of the vertical displacement. Aseismic creep events have amplitudes of 1-3 cm and durations of 1-3 days. Much less precise measurements from the Cerro Prieto fault show vertical deformation on the fault with velocity around 3.1 cm/yr , and the rate does not depend on the local seismicity. Horizontal rates change slightly with the presence of seismicity when very small right lateral deformation (few mm/yr) can be observed. From the delay measured on different instruments installed on the Saltillo fault one can conclude that creep events have an apparent migration velocity of the order of 4 cm/s. Comparison between occurrence of creep events and the water level record done for the piezometer installed nearby, shows that in four cases a water level anomaly is associated with a creep event. We discuss some possible relation between creep phenomenon and water level changes, and tectonics, geology and anthropogenic activity in the Mexicali Valley. This research is sponsored partly by the CONACYT project 45997-F.

  2. The ambient acoustic environment in Laguna San Ignacio, Baja California Sur, Mexico.

    PubMed

    Seger, Kerri D; Thode, Aaron M; Swartz, Steven L; Urbán, Jorge R

    2015-11-01

    Each winter gray whales (Eschrichtius robustus) breed and calve in Laguna San Ignacio, Mexico, where a robust, yet regulated, whale-watching industry exists. Baseline acoustic environments in LSI's three zones were monitored between 2008 and 2013, in anticipation of a new road being paved that will potentially increase tourist activity to this relatively isolated location. These zones differ in levels of both gray whale usage and tourist activity. Ambient sound level distributions were computed in terms of percentiles of power spectral densities. While these distributions are consistent across years within each zone, inter-zone differences are substantial. The acoustic environment in the upper zone is dominated by snapping shrimp that display a crepuscular cycle. Snapping shrimp also affect the middle zone, but tourist boat transits contribute to noise distributions during daylight hours. The lower zone has three source contributors to its acoustic environment: snapping shrimp, boats, and croaker fish. As suggested from earlier studies, a 300 Hz noise minimum exists in both the middle and lower zones of the lagoon, but not in the upper zone.

  3. Distribution of phototrophic microbes in the flat laminated microbial mat at Laguna Figueroa, Baja California, Mexico.

    PubMed

    Stolz, J F

    1990-01-01

    The microbial mat community in the saltmarsh/evaporate flat interface at Laguna Figueroa involved in the deposition of laminated sediments was investigated. Pigment analysis, light microscopy and transmission electron microscopy were used to determine the relative abundance and distribution of phototrophic species. The community is vertically stratified into four distinct phototrophic populations. The layering could be distinguished by pigment and species composition. The two layers closest to the surface contained mostly oxygenic phototrophs and chlorophyll a as the primary photosynthetic pigment. Anoxic phototrophs predominated in the bottom two layers with bacteriochlorophylls a and c in the third layer and bacteriochlorophyll a and b in the bottom layer. The surface yellow layer was composed primarily of Navicula, Rhopalodia and other diatom species as well as the cyanobacteria Aphanothece sp. and Phormidium sp. Microcoleus chthonoplasces and Chroococcidiopsis sp. were the major cyanobacteria in the green colored second layer. In the third layer, pinkish-purple in color, purple photographs (Chromatium sp., Thiocapsa roseoparsicina) and filamentous green phototrophs (Chloroflexus sp., Oscillochloris sp.) were abundant. The fourth and deepest photosynthetic layer was salmon colored and composed primarily of Thiocapsa pfennigii, and other purple sulfur phototrophs. The pattern of alternating light (oxygenic community) and dark (anoxygenic community) layering preserved in older laminae is a consequence of this community structure. Study of the flat laminated mat over the 10-year period (1978-1988) including and after its destruction by catastrophic flooding events in 1978 and 1980, showed a succession of stratified communities culminating in the return of Microcoleus and the full compliment of layers by the fall of 1984.

  4. Observaciones interferométricas del RSN W44 en bajas frecuencias

    NASA Astrophysics Data System (ADS)

    Castelletti, G.; Dubner, G.; Brogan, C.; Kassim, N.

    Low frequencies observations in radio wavelengths are very useful to trace the energy distribution of relativistic electrons emitting synchrotron radiation and can be used to anchor the low frequency end of the intrinsic radio spectra. Furthermore, detailed low frequencies measurements can help to distinguish between thermal and nonthermal components in complex regions and thus delineate the distribution of ionized gas in the interstellar medium (ISM). In this work we discuss different aspects of the data reduction procedures at very low frequencies based on new radio observations of the supernova remnant (SNR) W44 carried out at 74 MHz and 330 MHz using the A, B, C, and D configurations of the radio interferometer Very Large Array (VLA, USA).

  5. Pleistocene - Holocene Rainfall and Productivity Records in Alfonso Basin Baja California Sur

    NASA Astrophysics Data System (ADS)

    Martinez-Perez, V. D. R.; Gonzalez-Yajimovich, O.; Mejia-Pina, K. G.

    2014-12-01

    Northwesterly winds dominate the southern Gulf of California during most of the year and are associated with high primary productivity due to upwelling. The North American Monsoon causes the wind direction to reverse during the summer months and this brings humid and warms conditions to the region. This climatic temporal-variation generates alternate sedimentation and as a consequence laminated deposits of biogenic and terrigenous composition, preserved by the presence of an oxygen minimum zone. A 5.4 m long piston core (36N) was recovered from Cuenca Alfonso during the DIPAL IV cruise on May 2011. The core was sampled at 1 cm intervals to produce high-resolution proxy records of primary productivity (biogenic opal, total organic carbon and carbonate content) and rainfall (terrigenous content). The core spans from late Pleistocene to the present and it's the longest analyzed record for the basin for the above-mentioned proxies. In general, the proxies show a negative trend towards the present, suggesting a more productive basin and wetter climate in the past. During climatic events like the Bølling-Allerød and the Holocene climatic optimum (HCO) CaCO3 content decreased and opal content increased; suggesting the presence of stronger NW winds and nutrient-richer waters. In contrast, during the Younger Dryas and 8.2 Kyr events the opal content decrease and the CaCO3 increase. At 5.5 KyBP the negative trends in all components intensify, especially during the Medieval Warm Period (MWP). An exception to this occurs during the little ice Age (LIA) where the opal and CaCO3 increase. The organic carbon content increases at the end of the HCO and during the MWP, and decreases during the BA, YD, 8.2 Kyr and LIA. The terrigenous content follows the 24°N summer insolation trend, but shows an increase during warm events (BA, HCO and MWP), and can be attributed to migration of the average position of the Intertropical Convergence Zone driven by variations in solar insolation.

  6. Environmental Service Learning: Outcomes of Innovative Pedagogy in Baja California Sur, Mexico

    ERIC Educational Resources Information Center

    Schneller, Andrew Jon

    2008-01-01

    This article reports on a longitudinal study of a two-semester middle school environmental learning course that departs from traditional Mexican expository pedagogies through the incorporation of experiential and service learning approaches. In the short term, course participants acquired a heightened awareness of environmental issues, augmented…

  7. Bimodal distribution of risk for childhood obesity in urban Baja California, Mexico.

    PubMed

    Wojcicki, Janet M; Jimenez-Cruz, Arturo; Bacardi-Gascon, Montserrat; Schwartz, Norah; Heyman, Melvin B

    2012-08-01

    In Mexico, higher socioeconomic status (SES) has been found to be associated with increased risk for obesity in children. Within developed urban areas, however, there may be increased risk among lower SES children. Students in grades 4-6 from five public schools in Tijuana and Tecate, Mexico, were interviewed and weight, height and waist circumference (WC) measurements were taken. Interviews consisted of questions on food frequency, food insecurity, acculturation, physical activity and lifestyle practices. Multivariate logistic models were used to assess risk factors for obesity (having a body mass index [BMI] ≥95th percentile) and abdominal obesity (a WC >90th percentile) using Stata 11.0. Five hundred and ninety students were enrolled; 43.7% were overweight or obese, and 24.3% were obese and 20.2% had abdominal obesity. Independent risk factors for obesity included watching TV in English (odds ratio [OR] 1.60, 95% confidence interval [CI] 1.06-2.41) and perceived child food insecurity (OR 1.57, 95% CI 1.05-2.36). Decreased risk for obesity was associated with female sex (OR 0.64, 95% CI 0.43-0.96), as was regular multivitamin use (OR 0.63, 95% CI 0.42-0.94). Risk obesity was also decreased with increased taco consumption (≥1×/week; OR 0.64, 95% CI 0.43-0.96). Independent risk factors for abdominal obesity included playing video games ≥1×/week (OR 1.18, 95% CI 1.11-2.96) and older age group (10-11 years, OR 2.47, 95% CI 1.29-4.73 and ≥12 years, OR 2.21, 95% CI 1.09-4.49). Increased consumption of tacos was also associated with decreased risk for abdominal obesity (≥1×/week; OR 0.56, 95% CI 0.40-1.00). We found a bimodal distribution for risk of obesity and abdominal obesity in school aged children on the Mexican border with the United States. Increased risk for obesity and abdominal obesity were associated with factors indicative of lower and higher SES including watching TV in English, increased video game playing and perceived food insecurity. Increased consumption of tacos (≥1×/week) was associated with decreased risk, possibly suggesting an association with children from middle income families. Regular multivitamin use was protective and future studies may focus on micronutrient supplementation as a means to prevent obesity in children or further investigate factors associated with vitamin use. Additionally, future studies need to examine the processes of acculturation on both sides of the US-Mexican border that contribute to increased risk for obesity in children in relation to SES.

  8. Geophysical Exploration of Faults, Fissures, and Fractures at Four Sites in Mexicali, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Lázaro-Mancilla, O.; Gonzalez-Fernandez, A.; Contreras-Corvera, A.; Stock, J. M.; Moreno-Ayala, D.; Ramirez-Hernandez, J.; Carreon-Diazconti, C.; Lopez, D. A. L.; Lopez, J. R.

    2014-12-01

    We conducted field geophysical measurements in areas in the City of Mexicali that are associated with geological faults, fissures, and fractures. The study sites are: 1) Instituto Tecnologico de Mexicali 2) The buried trace of the Michoacan de Ocampo fault in the urban zone 3) Rio Nuevo 4) A site reported by Frez (2013) with ground rupture SW of Cerro Prieto At Site 1, seismic reflection profiling used a cable with 24 geophones at 1 m spacing. The source was a 3.6 kg sledge hammer, with 3 impacts per shot point. 347 shot points at 2 m spacing provided 6 fold coverage along a straight line with minimal elevation changes. Sample rate was 2000/s, and record length 1 s; reflections were seen down to 0.3 s TWTT. Processing included: frequency filter, fk filter, predictive deconvolution, geometry, velocity analysis, NMO and stacking. Lateral changes in the seismic section are due to surface modification and/or the presence of faults.At site 2, we measured 222Radon in 36 locations along 17 profiles across the fault, using inherent alpha spectrometry with a Durridge RAD7 detector. Each site was measured at a depth of 60 cm, with 31 five-minute readings in a 3 hour period, interspersed with 10 minute of background purge and 3 five-minute background measurements. In a profile parallel to the fault, 78% of the readings were > 100 pCi/L, confirming the presence of the fault along the swath surveyed. At Site 3 we compiled observations of post-earthquake cracks, conducted reconnaissance, and measured some profiles using 100 MHz GPR. These observations showed that the cracks are associated with ground failure due to earthquake shaking. At Site 4 our new 222Radon gas measurements complemented a pre-existing profile that had high 222Radon values lacking a structural explanation. Related to this we found that this region has two NW-SE trending features: a magnetic anomaly low of 360 nT (Evans, Summer and Castillo, 1972) and a graben reported by the Mexican Geological Survey in 2003. Earthquake patterns and seismic studies in a wider area north of the border indicate a possible buried fault a few km west of the Imperial fault, as well as short NE-striking faults controlling basement structure. These results highlight some very useful methods for finding fault traces in a flat region covered with agricultural fields or disturbed by anthropogenic activity.

  9. Proceedings: third symposium on the Cerro Prieto geothermal field, Baja California, Mexico

    SciTech Connect

    Not Available

    1981-01-01

    These proceedings include both English and Spanish versions of each paper presented at the symposium. Illustrations and tables, which have been placed between the two versions, include captions in both languages. Forty-one papers are included. Five papers were indexed for EDB previously. Separate abstracts were prepared for thirty-three papers and three were listed by title.

  10. Superficial simplicity of the 2010 El Mayorg-Cucapah earthquake of Baja California in Mexico

    USGS Publications Warehouse

    Wei, S.; Fielding, E.; Leprince, S.; Sladen, A.; Avouac, J.-P.; Helmberger, D.; Hauksson, E.; Chu, R.; Simons, M.; Hudnut, K.; Herring, T.; Briggs, R.

    2011-01-01

    The geometry of faults is usually thought to be more complicated at the surface than at depth and to control the initiation, propagation and arrest of seismic ruptures1-6. The fault system that runs from southern California into Mexico is a simple strike-slip boundary: the west side of California and Mexico moves northwards with respect to the east. However, the Mw 7.2 2010 El Mayorg-Cucapah earthquake on this fault system produced a pattern of seismic waves that indicates a far more complex source than slip on a planar strike-slip fault. Here we use geodetic, remote-sensing and seismological data to reconstruct the fault geometry and history of slip during this earthquake. We find that the earthquake produced a straight 120-km-long fault trace that cut through the Cucapah mountain range and across the Colorado River delta. However, at depth, the fault is made up of two different segments connected by a small extensional fault. Both segments strike N130 ??E, but dip in opposite directions. The earthquake was initiated on the connecting extensional fault and 15s later ruptured the two main segments with dominantly strike-slip motion. We show that complexities in the fault geometry at depth explain well the complex pattern of radiated seismic waves. We conclude that the location and detailed characteristics of the earthquake could not have been anticipated on the basis of observations of surface geology alone. ?? 2011 Macmillan Publishers Limited. All rights reserved.

  11. Hydrography of Bahia Todos Santos, Baja California: Results of more than twenty five years of investigations.

    NASA Astrophysics Data System (ADS)

    Bustos-Serrano, H.; Canino-Herrera, S. R.; Morales-Chavez, R.; Martinez-Garcia, G. M.

    2007-05-01

    The first study of Bahia Todos Santos (BTS) was reported by Walton in 1955. We conducted oceanographic studies in BTS since 1979. The BTS has a connection with a coastal lagoon named Estero de Punta Banda (EPB), two islands at the western portion and the Port of Ensenada. The general hydrographic characteristics are: In winter the water became homogeneous, less saline (<33.4) and with low stability. During spring and summer a hydrographic structure of three layers is noticed. The deepest layer is composed of the southern California water mass with a relatively high salinity (>33.6) low temperature (13°C), low oxygen (~3mL L-1) and rich in nutrient concentration. The isothermal top layer has relatively high temperature (>17°C) and oxygen concentration (>6mL L-1). The intermediate transition layer (seasonal thermocline) has minimum salinity, maximum oxygen and high stability. During fall there is distribution of heat from the surface layer to the entire water column. The thermic waves propagate with decrease amplitude in ~3 months, from surface to bottom water. The California Current flow generally southward off the western United States and northern Mexico and is one of the major coastal upwelling of the word oceans. The upwelling events in BTS appear regularly at the SW portion and were typically characterized by an increase in pCO2, decrease of O2, increase of nutrients and a lower temperature. Upwelling activity increases surface nutrient availability causing rise in the primary productivity and hence increased zooplankton biomass. The annual upwelling event which had a maximum strength on May, the seasonal warming and cooling, and the water advection were the dominant modifying processes for the variability of seawater characteristics. Higher salinities are located close to the coastline and lower off the bay. The levels of oxygen, alkalinity, pH and chlorophyll indicate that the maximum concentration of phytoplankton is located at the center of the bay. The nitrification support the primary productivity and the NO3 levels were below detection limits; the N/P ratio in 2005 was from 10 to 25; and for 2006 was below 5. There is a net enrichment of anthropogenic nutrients at BTS. The heavy metals and pesticides studies started since the early 80's with problems still to solve for Tl, Cd. There is a net Pb enrichment and higher Cr concentrations at the NE of the bay. The EPB is a wetland ~7 Km. long located at the SE part of the BTS. The EPB is a net source of DIP (deltaDIP = +0.13 mmol m-2 day-1), that brings agricultural runoff to the BTS. It is typically a hypersaline system during summer and a net heterotrophic (p-r = -14 mmol m-2 day-1), and a net denitrifying (nfix-denit = -2.1 mmol m-2 day-1) system. Some anomalies were in 2005 the presence of a huge red tide observed inside BTS (about 50% of the bay) that last for more than six months, this HAB's has killed many fishes (anoxia) and marine mammals. The hydrographic conditions during the red tide were, temperature anomalies higher than 2°C above normal; high nutrient concentration above the normal. In 2006 the values were normal again. The Port of Ensenada, increased in size and activities (tourism, transportation, coastguards for national security, cement industry, research) these developments generate some management problems, like the beach and coastline modification. The aground of the APL Panama, activates the management agencies to prevent and control pollution.

  12. Genesis and evolution of the Cerro Prieto Volcanic Complex, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    García-Sánchez, L.; Macías, J. L.; Sosa-Ceballos, G.; Arce, J. L.; Garduño-Monroy, V. H.; Saucedo, R.; Avellán, D. R.; Rangel, E.; Layer, P. W.; López-Loera, H.; Rocha, V. S.; Cisneros, G.; Reyes-Agustín, G.; Jiménez, A.; Benowitz, J. A.

    2017-06-01

    The Cerro Prieto Volcanic Complex (CPVC), located in northwestern Mexico, is the only surface manifestation of the Cerro Prieto Geothermal Field, the third largest producer of geothermal energy in the world. This geothermal field and the Salton Sea in the USA sit in a pull-apart basin that belongs to the trans-tensional tectonic zone that includes the San Andreas Fault system and the Salton Trough basin to the NW and the East Pacific Rise to the SE. In spite of its strategic importance in the generation of geothermal energy, the origin of Cerro Prieto and its relationship with the geothermal reservoir were unknown. In this contribution, we discuss the origin, evolution, and mechanisms of formation of this small monogenetic volcano and the magmas that fed the system. The volcanic complex is located on top of the Cerro Prieto left lateral fault to the northwest of the Cerro Prieto Geothermal Field. The complex consists of a lava cone and a series of domes (˜0.15 km3) protruding from Tertiary sandstones and recent unconsolidated sediments of the alluvial plain of the Colorado River. The Cerro Prieto Volcanic Complex consists of seven stratigraphic units emplaced in a brief time span around 78-81 ka. Its activity began with the extrusion of a dacitic lava that came into contact with water-saturated sediments, causing brecciation of the lava. The activity continued with the emplacement of dacitic domes and a dyke that were destroyed by a phreatic explosion emplacing a lithic-rich breccia. This phreatic explosion formed a 300-m-wide and 40-m-deep circular crater. The activity then migrated ˜650 m to the SW where three dacitic lava domes were extruded and ended with the emplacement of a fissure-fed lava flow. Subsequent remobilization of the rocks in the complex has generated debris and hyperconcentrated flow deposits interbedded with fluviatile sediments in the surrounding terrain. All rocks of the CPVC are dacites with phenocrysts of plagioclase, orthopyroxene, and Fe-Ti oxides and minor quartz. Gabbro-dioritic dykes intruded in Tertiary sandstones and siltstones of the local basement contain phenocrysts of plagioclase, clinopyroxene, Fe-Ti oxides, and olivine. All CPVC rocks are chemically homogeneous suggesting discrete modifications by crustal assimilation, fractional crystallization, or magma mixing processes during upper crustal residence. Aeromagnetic results suggest that the depth of the magmatic source in the area is located below 3.5 km. CPVC rocks contain chemical anomalies typical of subduction zones, which suggests that all CPVC magmas could have been generated by partial melting of the remains of the subducted Farallon plate.

  13. Microbial Diversity and Bioremediation of a Hydrocarbon-Contaminated Aquifer (Vega Baja, Puerto Rico)

    PubMed Central

    Rodríguez-Martínez, Enid M.; Pérez, Ernie X.; Schadt, Christopher W.; Zhou, Jizhong; Massol-Deyá, Arturo A.

    2006-01-01

    Hydrocarbon contamination of groundwater resources has become a major environmental and human health concern in many parts of the world. Our objectives were to employ both culture and culture-independent techniques to characterize the dynamics of microbial community structure within a fluidized bed reactor used to bioremediate a diesel-contaminated groundwater in a tropical environment. Under normal operating conditions, 97 to 99% of total hydrocarbons were removed with only 14 min hydraulic retention time. Over 25 different cultures were isolated from the treatment unit (96% which utilized diesel constituents as sole carbon source). Approximately 20% of the isolates were also capable of complete denitrification to nitrogen gas. Sequence analysis of 16S rDNA demonstrated ample diversity with most belonging to the ∝, β and γ subdivision of the Proteobacteria, Bacilli, and Actinobacteria groups. Moreover, the genetic constitution of the microbial community was examined at multiple time points with a Functional Gene Array (FGA) containing over 12,000 probes for genes involved in organic degradation and major biogeochemical cycles. Total community DNA was extracted and amplified using an isothermal φ29 polymerase-based technique, labeled with Cy5 dye, and hybridized to the arrays in 50% formimide overnight at 50°C. Cluster analysis revealed comparable profiles over the course of treatment suggesting the early selection of a very stable microbial community. A total of 270 genes for organic contaminant degradation (including naphthalene, toluene [aerobic and anaerobic], octane, biphenyl, pyrene, xylene, phenanthrene, and benzene); and 333 genes involved in metabolic activities (nitrite and nitrous oxide reductases [nirS, nirK, and nosZ], dissimilatory sulfite reductases [dsrAB], potential metal reducing C-type cytochromes, and methane monooxygenase [pmoA]) were repeatedly detected. Genes for degradation of MTBE, nitroaromatics and chlorinated compounds were also present, indicating a broad catabolic potential of the treatment unit. FGA’s demonstrated the early establishment of a diverse community with concurrent aerobic and anaerobic processes contributing to the bioremediation process. PMID:16968977

  14. Sedimentary gravity flows from subaerial fan-deltas in Loreto Bay, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Navarro-Lozano, José O.; Nava-Sánchez, Enrique H.; Godínez-Orta, Lucio

    2010-05-01

    Fan-deltas from Loreto Bay show recent evidences of sedimentary gravity flows as a result from catastrophic events during hurricane rainfalls. The knowledge of hydrological characteristics of these flows is important for understanding the effects of storms on fan-deltas geomorphology in this region, as well as for the urban developing planning of the city of Loreto in order to avoid hazardous zones. The analysis of precipitation and hurricane tracks data for the period 1945 to 2009 indicates that hurricanes have caused catastrophic floods every 20 years. Stratigraphy from the channel incision shows a sequence of stream flow and debris flow controlled by changes in the competence and capacity of the stream, which are associated to the gentle slope (<2 °) of the fan-deltas. However fans from the north of the bay (Arce and Gúa) show deposits of debris flows associated to catastrophic floods, which have caused the incision channel to drift towards the southern part of the fans, while flows from Las Parras fan-delta, from the middle of the bay, are dominated by stream flows. These differences in the type of the flows are controlled by lithology, shape and size of the drainage basin, and slope of the transit zone in the feeder channel.

  15. Reconnaissance geologic map of part of the San Isidro Quadrangle, Baja California Sur, Mexico

    USGS Publications Warehouse

    McLean, Hugh; Hausback, B.P.; Knapp, J.H.

    1985-01-01

    Mapping was done on aerial photographs and transferred, where possible, to 1:50,000-scale topographic base maps. Areas with roads were field checked; however, in the northeast part of the map area, lack of roads prevented field checks. Previous geologic surveys of parts of the map area were made by horseback in the early 1920's; reports were published by Darton (1921), Heim (1922), and Beal (1948). Subsurface data from petroleum exploration and a geologic map were incorporated in a regional study by Mina (1957). The first radiometric ages of rocks from the map area were published by Gastil and others (1979). Recently determined radiometric ages and chemical analysis of volcanic rocks were reported by Hausback (1984) and by Sawlan and Smith (1984). Our study incorporates geologic mapping with age control based on new radiometric ages as well as paleontology, Flows and tuffs were dated by the K-Ar method. Fossil ages are based on diatom and mollusk assemblages.

  16. Coastal dynamics off Cabo Pulmo, Baja California Sur, México

    NASA Astrophysics Data System (ADS)

    Trasviña-Castro, A.; Gonzalez-Rodriguez, E.; Zaitsev, O. V.

    2013-05-01

    Cabo Pulmo is the one of the few coral reefs of the Mexican Pacific. It is located to the north of the Tropic of Cancer (at 23.5° N) and therefore formally in the subtropical region. It is part of the Gulf of California but its location near the tip of the Peninsula pose questions about the exchange of properties with the neighboring Pacific Ocean, some of which will be addressed here. It was declared National Park in 1995. Since then it became a no-take zone and a nature reserve for the preservation of the large variety of species found there. We report results based on meteorological and hydrographic observations as well as current measurements gathered between October 2010 and February 2012. These results include the presence of coastal currents forced by the tide, the wind and remote forcing. We believe the latter are associated, sometimes, to the mesoscale circulation of the entrance to the Gulf of California and, at other times, to coastal jets coming from the interior of the Gulf. We use displacement diagrams to discuss the trends of the residual circulation along the coast. During autumn, winter and even in spring the residual coastal flow is towards the Equator. This is attributed to the influence of the Northwesterly winds that blow over the Gulf of California in these months. It is in summer that the coastal residual circulation exhibits a poleward component being more intense during Southeasterly wind events. Finally, we present evidence of coastal exchange with the Pacific Ocean in the form of an intense jet. This coastal jet flows equatorward past Cabo Pulmo, continues towards the Pacific side of the Peninsula and generates offshore filaments when turning the cape.

  17. Vegetation response to hydrologic and geomorphic factors in an arid region of the Baja California Peninsula.

    PubMed

    Rodríguez-Moreno, Victor M; Bullock, Stephen H

    2014-02-01

    Remotely sensed imageries were used to analyze the response of desert vegetation to physiographic factors and accumulated precipitation in drier and wetter years within a region of >16,500 km(2) sampled with 5,000 random pixels of 30 m. Vegetation development was indexed by the annual maximum values for greenness (SAVI) and canopy water content (NDII). Precipitation was interpolated from the 0.25° grid of the Tropical Rainfall Measurement Mission satellite-based estimates, showing a regional average of ∼55 mm in the wetter year. The vegetation indices were only weakly related to total precipitation, often in a negative sense. Terrain factors that most often affected the vegetation indices, in multiple regression models, were Topographic Wetness Index, elevation, and slope gradient; these often had different signs for SAVI and for NDII. Models for NDII on intrusive igneous rocks gave better results than on extrusive igneous rocks. The strongest patterns in vegetation development were the contrast among Pacific coast, Cordillera, and Gulf coast subregions and the generally stronger results for NDII than SAVI.

  18. Gill erosion and herpesvirus in Crassostrea gigas cultured in Baja California, Mexico.

    PubMed

    Vásquez-Yeomans, Rebeca; García-Ortega, Mauricio; Cáceres-Martínez, Jorge

    2010-03-09

    Recurrent episodes of mortality of Crassostrea gigas cultured in northwestern Mexico have been occurring since 1997. Previous studies on bacteria, protozoans, and metazoans as presumptive causal agents have been inconclusive. However, erosions in the marginal indentation of gills have been frequently observed in oysters from areas affected by mortality events, and in 2000 those lesions were associated with the detection of a herpes-like virus. The present study aimed to describe the histological alterations of eroded gills and to determine whether ostreid herpesvirus 1 (OsHV-1) or a related virus was associated with them using in situ hybridization (ISH). Histology showed that gill filaments were fused. In severe cases, deformation of the interlamellar junctions, swelling, and the loss of water channels was observed. ISH analysis revealed the presence of OsHV-1 DNA or a related virus in cells of the gills. Some labeled cells were large with dark granules inside their cytoplasm. These cells were surrounded by infiltrating hemocytes. Some cells interpreted as hemocytes were labeled and observed in eroded and non-eroded areas of the gill. Large cells detected by ISH were also observed by conventional histology with hematoxylin-eosin staining. Whether the virus produces the erosions in the gills, or the erosions in the gills are produced by an unknown condition and favor the presence of the virus, remains unresolved. It is also not clear whether the lesions contribute to mortality.

  19. Environmental Service Learning: Outcomes of Innovative Pedagogy in Baja California Sur, Mexico

    ERIC Educational Resources Information Center

    Schneller, Andrew Jon

    2008-01-01

    This article reports on a longitudinal study of a two-semester middle school environmental learning course that departs from traditional Mexican expository pedagogies through the incorporation of experiential and service learning approaches. In the short term, course participants acquired a heightened awareness of environmental issues, augmented…

  20. Evaluation of the saturation state of Aragonite, at Baja California Coast, Mexico

    NASA Astrophysics Data System (ADS)

    Oliva, N. L.; Hernandez, J. M.; Camacho, V.; Deldagillo, F.; Torres, V.; Siqueiros-Valencia, A.; Castro, R.

    2012-12-01

    The carbonate ion is in excess in the surface waters of the world's ocean, and is necessary for the formation of carbonate structures such as oyster shells and echinoderm skeletons. Seasonal upwelling in the California Current system brings dense water with high partial pressure of carbon dioxide to the sea surface and into contact with the atmosphere in the near shore. In order to evaluate the saturation state of Aragonite (ΩA), from November 2009 to November 2011, biweekly monitoring of dissolved inorganic carbon (CID), total alkalinity (TA), temperature (T) and salinity (S), in the intertidal zone at "Arbolitos" was conducted. During the same period, a mooring buoy located 3 km from Arbolitos recorded data every 3 hours for T and carbon dioxide partial pressure (pCO2), at the sea and in the air 1 meter above the sea surface.The ΩA was calculated for both study sites where upwelling events occurred during the spring-summer months. The data at both Arbolitos and mooring buoy shows that during the upwelling season maximum DIC concentration (2150μmol kg -1) and maximum pCO2 (863 μatm) correspond to the lowest temperature (11°C) and ΩA values (1; equilibrium). During the ten upwelling events identified (T < 15 °C, pCO2 > 387 μatm), the ΩA values (3 to 1) were not lower than the saturation limit (value of 1).The results show that the calcifying organisms in this region are persisting in an environment with variable ΩA conditions. It was determined that the longer the duration of the upwelling event, the lower the ΩA value, and the higher the change in pCO2. The ΩA interval (approximately 3 to 1) is not the same from year to year. This suggests interannual variations in upwelling, possibly due to El Niño (present during the first six months of 2010), and La Niña conditions (from July 2010 to November 2011).; t; Characteristics of the ten events of upwelling, at arbolitos and at the moorign buoy. For both study sites it shows the duration, pCO2, ΩA y pH values.

  1. Use of digital multispectral videography to assess seagrass distribution in San Quintin Bay, Baja California, Mexico

    USGS Publications Warehouse

    Ward, D.H.; Tibbitts, T.L.; Morton, Alexandra; Carrera-Gonzalez, Eduardo; Kempka, R.

    2004-01-01

    Apparent threats to the spatial distribution of seagrass in San Quintín Bay prompted us to make a detailed assessment of habitats in the bay. Six coastal habitats and three seagrass subclasses were delineated using airborne digital multispectral videography (DMSV). Eelgrass, Zostera marina, was the predominant seagrass and covered 40% (1949 ha) of the areal extent of the bay in 1999. Eelgrass grew over a wide range of tidal depths from about –3.0 m mean lower low water (MLLW) to about 1.0 m MLLW, but greatest spatial extent occurred in intertidal areas –0.6 m to 1.0 m MLLW. Exposed-continuous (i.e., high density) eelgrass was the most abundant habitat in the bay. Widgeongrass, Ruppia maritima, was the only other seagrass present and covered 3% (136 ha) of the areal extent of the entire bay. Widgeongrass grew in single species stands in the upper intertidal (≥ 0.4 MLLW) and intermixed with eelgrass at lower tidal depths. Overall accuracy of the six habitat classes and three subclasses in the DMSV map was relatively high at 84%. Our detailed map of San Quintín Bay can be used in future change detection analyses to monitor the health of seagrasses in the bay.

  2. Lithofacies of deep marine basalts emplaced on a Jurassic backarc apron, Baja California (Mexico)

    SciTech Connect

    Busby-Spera, C.J.

    1987-09-01

    Basalts of the mid-Jurassic Gran Canon Formation, Cedros Island, Mexico, were emplaced on a volcaniclastic apron in a deep marine backarc basin. Elongate pillows and lava tubes, as well as paleocurrent data from the volcaniclastic apron, indicate a southward regional paleoslope away from the island arc source. Basalts emplaced on relatively proximal parts of the apron are nearly entirely pillowed and have thick flow units with mega-pillows. Basalts on distal parts of the apron (about 15 to 20 km down paleo-current) are dominated by pillow fragment breccias (flow foot rubble), and individual lava flows are generally thin, with small pillows, suggesting that the distal ends of lava flows, erupted upslope, are represented. These distal flow fronts, however, are interstratified with features that typically form close to a vent, including thick massive to mega-pillowed lavas and lava tubes up to 8 m in diameter. It is inferred that a fissure (or system of fissures) extended from the arc into the backarc basin, erupting basalt lavas onto both proximal and distal parts of the volcaniclastic apron. Such intraplate volcanism may be common on the hot frontal arc side of backarc basins. 26 references.

  3. Carbon isotope geochemistry of hydrocarbons in the Cerro Prieto geothermal field, Baja California Norte, Mexico

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.; Stallard, M. L.; Nehring, N. L.; Truesdell, A. H.

    1988-01-01

    Hydrocarbon abundances and stable-isotopic compositions were measured in wells M5, M26, M35 and M102, which represent a range of depths (1270-2000 m) and temperatures (275-330 degrees C) in the field. In order to simulate the production of the geothermal hydrocarbons, gases were collected from the pyrolysis of lignite in the laboratory. This lignite was obtained from a well which sampled rock strata which are identical to those occurring in the field, but which have experienced much lower subsurface temperatures. In both the well and the laboratory observations, high-temperature environments favored higher relative concentrations of methane, ethane and benzene and generally higher delta 13C-values in the individual hydrocarbons. The best correlation between the laboratory and well data is obtained when laboratory-produced gases from experiments conducted at lower (400 degrees C) and higher (600 degrees C) temperatures are mixed. This improved correlation suggests that the wells are sampling hydrocarbons produced from a spectrum of depths and temperatures in the sediments.

  4. Secuencias evolutivas e isocronas para estrellas de baja masa e intermedia

    NASA Astrophysics Data System (ADS)

    Panei, J.; Baume, G.

    2016-08-01

    We present theoretical evolutionary sequences for low- and intermediate-mass stars. The masses calculated range from 1.7 to 10 M. The initial chemical composition is . In addition, we have taken into account a nuclear network with 17 isotopes and 34 nuclear reactions. With respect to the mix, we considered overshooting with a parameter . The evolutionary calculations were initialized from the region of instability of Hayashi, in order to calculate isochrones of pre-sequence, too.

  5. Water-quality reconnaissance of Laguna Tortuguero, Vega Baja, Puerto Rico, March 1999-May 2000

    USGS Publications Warehouse

    Soler-Lopez, Luis; Guzman-Rios, Senen; Conde-Costas, Carlos

    2006-01-01

    The Laguna Tortuguero, a slightly saline to freshwater lagoon in north-central Puerto Rico, has a surface area of about 220 hectares and a mean depth of about 1.2 meters. As part of a water-quality reconnaissance, water samples were collected at about monthly and near bi-monthly intervals from March 1999 to May 2000 at four sites: three stations inside the lagoon and one station at the artificial outlet channel dredged in 1940, which connects the lagoon with the Atlantic Ocean. Physical characteristics that were determined from these water samples were pH, temperature, specific conductance, dissolved oxygen, dissolved oxygen saturation, and discharge at the outlet canal. Other water-quality constituents also were determined, including nitrogen and phosphorus species, organic carbon, chlorophyll a and b, plankton biomass, hardness, alkalinity as calcium carbonate, and major ions. Additionally, a diel study was conducted at three stations in the lagoon to obtain data on the diurnal variation of temperature, specific conductance, dissolved oxygen, and dissolved oxygen saturation. The data analysis indicates the water quality of Laguna Tortuguero complies with the Puerto Rico Environmental Quality Board standards and regulations.

  6. Shallow Miocene basaltic magma reservoirs in the Bahia de Los Angeles basin, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Delgado-Argote, Luis A.; García-Abdeslem, Juan

    1999-01-01

    The basement in the Bahı´a de Los Angeles basin consists of Paleozoic metamorphic rocks and Cretaceous granitoids. The Neogene stratigraphy overlying the basement is formed, from the base to the top, by andesitic lava flows and plugs, sandstone and conglomeratic horizons, and Miocene pyroclastic flow units and basaltic flows. Basaltic dikes also intrude the whole section. To further define its structure, a detailed gravimetric survey was conducted across the basin about 1 km north of the Sierra Las Flores. In spite of the rough and lineal topography along the foothills of the Sierra La Libertad, we found no evidence for large-scale faulting. Gravity data indicates that the basin has a maximum depth of 120 m in the Valle Las Tinajas and averages 75 m along the gravimetric profile. High density bodies below the northern part of the Sierra Las Flores and Valle Las Tinajas are interpreted to be part of basaltic dikes. The intrusive body located north of the Sierra Las Flores is 2.5 km wide and its top is about 500 m deep. The lava flows of the top of the Sierra Las Flores, together with the distribution of basaltic activity north of this sierra, suggests that this intrusive body continues for 20 km along a NNW-trending strike. Between the sierras Las Flores and Las Animas, a 0.5-km-wide, 300-m-thick intrusive body is interpreted at a depth of about 100 m. This dike could be part of the basaltic activity of the Cerro Las Tinajas and the small mounds along the foothills of western Sierra Las Animas. The observed local normal faulting in the basin is inferred to be mostly associated with the emplacement of the shallow magma reservoirs below Las Flores and Las Tinajas.

  7. Búsqueda de regiones de baja excitación en nebulosas planetarias

    NASA Astrophysics Data System (ADS)

    Vena Valdarenas, R. R.; Schmidt, E. O.; Volpe, M. G.; Weidmann, W.; Mudrik, A.

    2015-08-01

    We present early results from observations with narrow band filter ([NII], 6584 ) for a sample of austral planetary nebulae. The observations are being made from Bosque Alegre Astrophysical Station. The observation inherent aspects will be treated in detail.

  8. Carbon isotope geochemistry of hydrocarbons in the Cerro Prieto geothermal field, Baja California Norte, Mexico

    USGS Publications Warehouse

    Des Marais, D.J.; Stallard, M.L.; Nehring, N.L.; Truesdell, A.H.

    1988-01-01

    Hydrocarbon abundances and stable-isotopic compositions were measured in wells M5, M26, M35 and M102, which represent a range of depths (1270-2000 m) and temperatures (275-330??C) in the field. In order to simulate the production of the geothermal hydrocarbons, gases were collected from the pyrolysis of lignite in the laboratory. This lignite was obtained from a well which sampled rock strata which are identical to those occurring in the field, but which have experienced much lower subsurface temperatures. In both the well and the laboratory observations, high-temperature environments favored higher relative concentrations of methane, ethane and benzene and generally higher ??13C-values in the individual hydrocarbons. The best correlation between the laboratory and well data is obtained when laboratory-produced gases from experiments conducted at lower (400??C) and higher (600??C) temperatures are mixed. This improved correlation suggests that the wells are sampling hydrocarbons produced from a spectrum of depths and temperatures in the sediments. ?? 1988.

  9. Carbon isotope geochemistry of hydrocarbons in the Cerro Prieto geothermal field, Baja California Norte, Mexico

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.; Stallard, M. L.; Nehring, N. L.; Truesdell, A. H.

    1988-01-01

    Hydrocarbon abundances and stable-isotopic compositions were measured in wells M5, M26, M35 and M102, which represent a range of depths (1270-2000 m) and temperatures (275-330 degrees C) in the field. In order to simulate the production of the geothermal hydrocarbons, gases were collected from the pyrolysis of lignite in the laboratory. This lignite was obtained from a well which sampled rock strata which are identical to those occurring in the field, but which have experienced much lower subsurface temperatures. In both the well and the laboratory observations, high-temperature environments favored higher relative concentrations of methane, ethane and benzene and generally higher delta 13C-values in the individual hydrocarbons. The best correlation between the laboratory and well data is obtained when laboratory-produced gases from experiments conducted at lower (400 degrees C) and higher (600 degrees C) temperatures are mixed. This improved correlation suggests that the wells are sampling hydrocarbons produced from a spectrum of depths and temperatures in the sediments.

  10. Lipids of recently-deposited algal mats at Laguna Mormona, Baja California

    NASA Technical Reports Server (NTRS)

    Cardoso, J.; Brooks, P. W.; Eglinton, G.; Goodfellow, R.; Maxwell, J. R.; Philp, R. P.

    1976-01-01

    A preliminary survey of the lipid composition of the core of a recently deposited algal mat of a subtropical, hypersaline coastal pond is described. Two layers of the core were examined: the upper, 2-cm-thick layer, comprising the fresh algal mat of predominantly the blue-green species Microcoleus chthonoplastes, and the black anaerobic algal ooze at a depth of 10 cm. About 75% of the n-alkanes in the mat were accounted for by n-C17, with smaller amounts of higher homologues maximizing at n-C27. The ooze was characterized by a bimodal distribution with maxima at n-C17 and n-C27. The n-alkanoic acids distributions were similar to the corresponding n-alkane distributions. A marked decrease in the ratio of monounsaturated to saturated acids in the ooze relative to the mat was observed, which indicates a preferential removal of unsaturated components. Certain triterpenes of the hopane skeletal type were present in the mat and ooze. The presence of stanols and sterenes in the ooze with similar carbon number distributions suggests a relationship between them.

  11. Paleoseismology of the imbricate fault array in the Sierra Cucapah, northern Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Hernández, A. P.; Fletcher, J. M.; Spelz, R.; Rockwell, T. K.; Teran, O. J.

    2013-05-01

    The Mw 7.2 Mayor-Cucapah earthquake produced cascading slip along six distinct faults that extend 120 km and is regarded as the most complex surface rupture ever recorded on the Pacific North American plate margin. In general master faults do not control local topography and many are blind structures buried beneath several kilometers of sediments, suggesting the overall slip rates are very slow on this newly recognized system of faults. We have performed a detailed paleo-seismic study along the Borrego Graben, which forms a key segment of the 2010 rupture. We report the first determinations of the distribution, magnitude and recurrence intervals of the past three surface ruptures. The Borrego Valley is an asymmetric graben controlled by the east-dipping Borrego fault and here a telescopic sequence of six distinct alluvial fan surfaces that range in age to latest Pleistocene (20 ka) form important structural markers for determining cross cutting relationships and cumulative slip of the past three ruptures. In addition to systematic mapping of the fan deposits and surface ruptures, 49 topographic profiles were generated using LiDAR DEM's to document the absolute vertical displacement accumulated in multiple surface ruptures along the fault. Vertical offset ranges up to 8 m and older fan surface show systematically greater offset than adjacent younger fan surfaces. We document at least three major surface ruptures including the 2010 event and their distribution demonstrates the existence of two fault segments with contrasting rupture histories. Vertical displacement along the northern segment accumulated in the oldest and youngest 2010 surface ruptures, whereas, that on the southern segment is controlled by a rupture intermediate in age. All three events overlap for a distance of 1.5 km in the northern extreme of the southern segment and here the telescopic fan configuration observed along the length of the Borrego graben converts locally to a nested sequence with younger fans deposited on top of successively older fan surfaces. Vertical displacements associated with all three ruptures are very similar in magnitude, 2-4 m in the three events, which suggests the fault array ruptures in earthquakes of a characteristic magnitude. However, our data shows that the fault does not break in all its length in a single event and that each segment breaks alternate in consecutive seismic events, which is consistent with the elastic rebound theory. The kinematics of the 2010 rupture is complex and the Borrego fault system accommodates dextral-normal displacement, but the relative magnitude of these slip components is highly variable along strike. Stress inversion of the kinematic data indicate that all segments of the Borrego fault slipped in a manner consistent with a single three-dimensional stress field and the variation of the ratio of dip-strike slip is largely controlled by the strike of the fault. The inverted three-dimensional stress tensor has high Φ values and σ3 is oriented sub-horizontally with and EW trend. Such a stress configuration will produce prolate three dimensional strain that is consistent with the trans-tensional shearing of the plate margin.

  12. Nuevas estrellas preenanas blancas pulsantes de masa extremadamente baja descubiertas en el CASLEO

    NASA Astrophysics Data System (ADS)

    Corti, M.; Kanaan, A.; Córsico, A. H.; Kepler, S. O.; Althaus, L. G.; Koester, D.; Sánchez Arias, J.

    2016-08-01

    The Extremely Low Mass white dwarfs (ELM, M 0.18--0.20 M) could arise after the loss of large amount of mass suffered by a red giant star in a binary system. The low mass white dwarfs have become an important source of study because some of them are pulsating stars. The latter is an unprecedented opportunity to know their interior and the evolutionary channels leading to their origin, by employing asteroseismology. In this paper, we present photometric analysis of data obtained in the CASLEO (Complejo Astronómico El Leoncito) about four new pulsating stars, that according to their surface gravities and effective temperatures, would be pre-ELM white dwarf stars. With this discovery, the number of pulsating pre-ELM white dwarf stars known would increase to six members.

  13. Phytoplankton absorption, photosynthetic parameters, and primary production off Baja California: summer and autumn 1998

    NASA Astrophysics Data System (ADS)

    Aguirre-Hernández, Elsa; Gaxiola-Castro, Gilberto; Nájera-Martínez, Sila; Baumgartner, Timothy; Kahru, Mati; Greg Mitchell, B.

    2004-03-01

    To estimate ocean primary production at large space and time scales, it is necessary to use models combined with ocean-color satellite data. Detailed estimates of primary production are typically done at only a few representative stations. To get survey-scale estimates of primary production, one must introduce routinely measured Chlorophyll-a (Chl-a) into models. For best precision, models should be based on accurate parameterizations developed from optical and photosynthesis data collected in the region of interest. To develop regional model parameterizations 14C-bicarbonate was used to estimate in situ primary production and photosynthetic parameters (α* ,Pm* , and Ek) derived from photosynthesis-irradiance (P-E) experiments from IMECOCAL cruises to the southern California Current during July and October 1998. The P-E experiments were done for samples collected from the 50% surface light depth for which we also determined particle and phytoplankton absorption coefficients (ap, aφ, and aφ*). Physical data collected during both surveys indicated that the 1997-1998 El Niño was abating during the summer of 1998, with a subsequent transition to the typical California Current circulation and coastal upwelling conditions. Phytoplankton chl-a and in situ primary production were elevated at coastal stations for both surveys, with the highest values during summer. Phytoplankton specific absorption coefficients in the blue peak (aφ* (440)) ranged from 0.02 to 0.11 m2 (mg Chl-a)-1 with largest values in offshore surface waters. In general aφ* was lower at depth compared to the surface. P-E samples were collected at the 50% light level that was usually in the surface mixed layer. Using α* and spectral absorption, we estimated maximum photosynthetic quantum yields (φmax; mol C/mol quanta). φmax values were lowest in offshore surface waters, with a total range of 0.01-0.07. Mean values of φmax for July and October were 0.011 and 0.022, respectively. In July Pm* was approximately double and α* was about 1.4 times the values for October. Since the P-E samples were generally within the upper mixed layer, these tendencies in the photosynthetic parameters are attributed to deeper mixing of this layer during October when the mean mixed layer for the photosynthesis stations was 35 m compared to a mean of 10 m in July. Application of a semi-analytical model using mean values of P-E parameters determined at the 50% light depth provided good agreement with 14C in situ estimates at the discrete 50% light depth and for the water-column integrated primary production.

  14. A probabilistic view of chaparral and forest fire regimes in southern California and northern Baja California

    Treesearch

    Richard A. Minnich; Ernesto. Franco-Vizcaíno

    2009-01-01

    Fire suppression in industrialized countries encourages massive smoke emissions from high-intensity fires as a result of two inextricably related processes under current suppression policies: the nonrandom occurrence of vegetation fires in extreme weather states and the anomalous accumulation of spatially homogenous fuels. We propose as an organizing idea that the...

  15. La población de galaxias de baja luminosidad en el Grupo de NGC 5044

    NASA Astrophysics Data System (ADS)

    Cellone, S. A.; Buzzoni, A.

    We present preliminary results from a spectrophotometric study of the dwarf and low-luminosity galaxy population in the NGC 5044 Group. We selected galaxies with 19.5 <= BT <= 15.5 (-12.7 <= MB -5 log(h0) <= -16.7) from the catalog of Ferguson & Sandage (1990, AJ 100, 1), for observation with the ESO 3.6 m telescope + EFOSC2. We obtained direct images in the g, r, i, and z bands of the Gunn system for 33 galaxies in the catalog + 8 previously non-catalogued dwarf spheroidals. Spectroscopy (λ ; 4300 - 6400 Å) for a 13 galaxies subsample was also obtained. Our immediate goal is to obtain an accurate morphological and membership classification, allowing us to investigate the environmental effects on the structure and colors of the galaxies. The following stage is to do a morphological, dynamical, and evolutionary study of the low-luminosity galaxy population in this group.

  16. The Lambeosaurine Dinosaur Magnapaulia laticaudus from the Late Cretaceous of Baja California, Northwestern Mexico

    PubMed Central

    Prieto-Márquez, Albert; Chiappe, Luis M.; Joshi, Shantanu H.

    2012-01-01

    The taxonomy, osteology, phylogenetic position, and historical biogeography of the lambeosaurine hadrosaurid Magnapaulia laticaudus (new combination) are revised. The diagnosis of this species is amended on the basis on two autapomorphies (i.e., longest haemal arches of proximal caudal vertebrae being at least four times longer than the height of their respective centra; base of prezygapophyses in caudal vertebrae merging to form a bowl-shaped surface) and a unique combination of characters (i.e., downturned cranioventral process of the maxilla; tear-shaped external naris with length/width ratio between 1.85 and 2.85; neural spines of dorsal, sacral, and proximal caudal vertebrae being at least four times the height of their respective centra). A maximum parsimony analysis supports a sister taxon relationship between M. laticaudus and Velafrons coahuilensis. Both taxa constitute a clade of southern North American lambeosaurines, which forms a sister relationship with the diverse clade of helmet-crested lambeosaurines from northern North America that includes well-known genera like Corythosaurus, Lambeosaurus, and Hypacrosaurus. According to the results of a Dispersal-Vicariance analysis, southern North American lambeosaurines split from the northern forms via vicariance from a common ancestor that lived in both the northern and southern regions of the continent. PMID:22719869

  17. Model of the heat source of the Cerro Prieto magma-hydrothermal system, Baja California, Mexico

    SciTech Connect

    Elders, W.A.; Bird, D.K.; Williams, A.E.; Schiffman, P.; Cox, B.

    1982-08-10

    Earlier studies at Cerro Prieto by UCR have led to the development of a qualitative model for field flow in the geothermal system before it was drilled and perturbed by production. Current efforts are directed towards numerical modelling of heat and mass transfer in the system in this undisturbed state. A two-dimensional model assumes that the heat sources were a single basalt/gabbro intrusion which provided heat to the system as it cooled. After compiling various information on the physical properties of the reservoir, the enthalpy contained in two 1cm thick section across the reservoir orthogonal to each other was calculated. Next various shapes, sizes and depths for the intrusion as initial conditions and boundary conditions for the calculation of heat transfer were considered. A family of numerical models which so far gives the best matches to the conditions observed in the field today have in common a funnel-shaped intrusion with a top 4km wide emplaced at a depth of 5km some 30,000 to 50,000 years ago, providing heat to the geothermal system. Numerical modelling is still in progress. Although none of the models so far computed may be a perfect match for the thermal history of the reservoir, they all indicate that the intrusive heat source is young, close and large.

  18. Coastal submarine hydrothermal activity of Northern Baja California 2. Evolutionary history and isotope geochemistry

    SciTech Connect

    Vidal, V.M.V.; Vidal, F.V.; Isaacs, J.D.

    1981-10-10

    A geochemical model of the Punta Banda submarine hydrothermal system (PBSHS) and Ensenada quadrangle subaerial hot springs is developed using /sup 18/O//sup 16/O, D/H, /sup 34/S//sup 32/S, /sup 3/H, water and gas chemistry. The PBSHS water is a primary high temperature, acid, reducing fluid of old seawater origin which has been titrated by cold, alkaline groundwater of meteoric origin. The final exiting solutions represent a 1:1 mixture of the two primary mixing components. In contrast, the subaerial hot spring waters are of unmixed meteoric origin. The subaerial hot spring gas is predominantly atmospheric N/sub 2/, while the PBSHS contains large amounts of CH/sub 4/ and N/sub 2/ derived from trapped marine sediments of Cretaceous age, deltaS/sup 34/ values of sampled hydrothermal waters are similar to Cretaceous marine sulfate values and suggest that the waters contacted Cretaceous marine sedimentary strata. The presence of the Alisitos and Rosario marine sedimentary formations of Cretaceous age within the Ensenada-Punta Banda quadrangel renders support to the above hypothesis. The data also demonstrate the pyrite mineralization and deposition in submarine hydrothermal environments result from the complexing of ferrous iron with elemental sulfur and sulfide and that submarine hydrothermal activity acts as a major source of silica, Ca/sup 2 +/, and trace metals and as a major sink for seawater Mg/sup 2 +/ and SO/sub 4//sup 2 -/.

  19. Mercury in freshwater fish and clams from the Cerro Prieto geothermal field of Baja California, Mexico

    SciTech Connect

    Gutierrez-Galindo, E.A.; Munoz, G.F.; Flores, A.A.

    1988-08-01

    Several reports have expressed concern about the potential toxicity hazards and environmental contamination of mercury emissions from geothermal fields in Hawaii, New Zealand, Iceland, California and Mexico. Inorganic mercury discharged from the sources may accumulate in the sediments of rivers or lakes and, after microbiological methylation may become concentrated in the edible tissue of fish. This study involves assessment of geothermal mercury pollution arising from Cerro Prieto. For this purpose the fish Tilapia mossambica and the clam Corbicula fluminea were collected from the freshwater courses of the Mexicali Valley. Reports indicated that in 1982, 13 t of T. mossambica were destinated for human consumption. A further aim was to provide base line data and information relevant to the level of mercury contamination for the Mexicali Valley.

  20. Subsidence History of the Laguna Salada Basin in Northeastern Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Contreras, J.; Martin-Barajas, A.; Herguera, J.

    2008-12-01

    The Salton Trough region in southern California and the Mexicali valley in northwestern Mexico are areas of (i) rapid subsidence due to trans-tension along the San Andreas-Imperial fault system, and (ii) high flux of sediments transported by the Colorado River, all of which confer this region with a high potential to preserve a complete record of climatic and tectonic activity information. Here we present the subsidence history of the Laguna Salada basin, and the history of activity of the master bounding faults on its eastern side. The Laguna Salada is a lacustrine basin located west of the Mexicali valley and to the south of the Salton Trough. Sedimentological as well as time series analyses performed on two 42 m-long cores drilled in the center of the basin, estimated to span the past 50 and 70KaBP, indicate a modulation of the late Quaternary stratigraphy by cyclic variations in lake level driven by Milankovitch forcing. Based on these results we derive the long-term history of the basin from a gamma-ray log recovered from a 2.8 km-deep geothermal borehole drilled by the Mexican Power Company adjacent to the Laguna Salada fault. The stratigraphy of the deep borehole reveals a history of activity pulses related to the initial breakage of the Laguna Salada fault and its interaction with neighboring faults. A first pulse started at 1.5 Ma and records the initiation of the Laguna Salada fault and rapid uplift of the crystalline block of the Sierra Cucapa. A second pulse started around 1 Ma, and is very likely related to the hard linking of the Laguna Salada fault with the Cañada David detachment by the Cañon Rojo fault. The onset of the Laguna Salada fault at 1.5 Ma appears to be synchronous with an early Pleistocene regional fault reorganization among the San Jacinto, San Andreas and Elsinore fault systems in southern California, suggesting that this reorganization may have affected a large area from San Gorgonio pass to the northern Gulf of California.

  1. Gemini IV Mission Image - Baja California, Colorado river and Sonora Desert

    NASA Image and Video Library

    1965-06-05

    S65-34673 (3-7 June 1965) --- This photograph shows the north end of the Gulf of California at the mouth of the Colorado River as it was seen from the Gemini-4 spacecraft during orbital flight June 3-7, 1965. This picture was part of the Synoptic Terrain Photography experiments conducted during the flight to obtain high quality photographs of large land areas already mapped by aerial photography. In charge of these experiments was Dr. Paul D. Lowman Jr., NASA geologist from Goddard Space Flight Center, Greenbelt, Md. This picture was taken with a modified 70mm Hasselblad camera using Eastman color film, ASA 64 at a lens setting of 250th of a second at f/11.

  2. Hydrothermal flow regime and magmatic heat source of the Cerro Prieto geothermal system, Baja California, Mexico

    SciTech Connect

    Elders, W.A.; Bird, D.K.; Schiffman, P.; Williams, A.E.

    1984-01-01

    This detailed three-dimensional model of the natural flow regime of the Cerro Prieto geothermal field, before steam production began, is based on patterns of hydrothermal mineral zones and light stable isotopic ratios observed in rock samples from more than 50 deep wells, together with temperature gradients, wireline logs and other data. At the level so far penetrated by drilling, this hydrothermal system was heated by a thermal plume of water close to boiling, inclined at 45/sup 0/, rising from the northeast and discharging to the west. To the east a zone of cold water recharge overlies the inclined thermal plume. Fission track annealing studies show the reservoir reached 170/sup 0/C only 10/sup 4/ years ago. Oxygen isotope exchange data indicate that a 12 km/sup 3/ volume of rock subsequently reacted with three times its volume of water hotter than 200/sup 0/C. Averaged over the duration of the heating event this would require a flow velocity through a typical cross-section of the reservoir of about 6 m/year. The heat in storage in that part of the reservoir hotter than 200/sup 0/C and shallower than 3 km depth is equivalent to that which would be released by the cooling of about 1 or 2 km/sup 3/ of basalt or gabbro magma.

  3. Model for the heat source of the Cerro Prieto magma-hydrothermal system, Baja California, Mexico

    SciTech Connect

    Elders, W.A.; Bird, D.K.; Williams, A.E.; Schiffman, P.; Cox, B.

    1981-01-01

    Earlier studies at Cerro Prieto led to the development of a qualitative model for fluid flow in the geothermal system before it was drilled and perturbed by production. Current efforts are directed towards numerical modeling of heat and mass transfer in the system in this undisturbed state. This one-dimensional model assumes that the heat source was a single basalt/gabbro intrusion which provided heat to the system as it cooled. After compilation of various information of the physical properties of the reservoir, the enthalpy contained in two 1 cm thick sections across the reservoir orthogonal to each other was calculated. Various shapes, sizes and depths for the intrusion were considered as initial conditions and boundary conditions for the calculations of heat transfer. A family of numerical models which so far gives the best matches to the conditions observed in the field today have in common a funnel-shaped intrusion with a top 4 km wide emplaced at a depth of 5 km some 30,000 to 50,000 years ago, providing heat to the geothermal system.

  4. Lipids of recently-deposited algal mats at Laguna Mormona, Baja California

    NASA Technical Reports Server (NTRS)

    Cardoso, J.; Brooks, P. W.; Eglinton, G.; Goodfellow, R.; Maxwell, J. R.; Philp, R. P.

    1976-01-01

    A preliminary survey of the lipid composition of the core of a recently deposited algal mat of a subtropical, hypersaline coastal pond is described. Two layers of the core were examined: the upper, 2-cm-thick layer, comprising the fresh algal mat of predominantly the blue-green species Microcoleus chthonoplastes, and the black anaerobic algal ooze at a depth of 10 cm. About 75% of the n-alkanes in the mat were accounted for by n-C17, with smaller amounts of higher homologues maximizing at n-C27. The ooze was characterized by a bimodal distribution with maxima at n-C17 and n-C27. The n-alkanoic acids distributions were similar to the corresponding n-alkane distributions. A marked decrease in the ratio of monounsaturated to saturated acids in the ooze relative to the mat was observed, which indicates a preferential removal of unsaturated components. Certain triterpenes of the hopane skeletal type were present in the mat and ooze. The presence of stanols and sterenes in the ooze with similar carbon number distributions suggests a relationship between them.

  5. Summary of recent progress in understanding the Cerro Prieto Geothermal Field, Baja, California, Mexico

    SciTech Connect

    Lippmann, M.J.; Witherspoon, P.A.

    1980-07-01

    Geological and geophysical studies indicate that the Cerro Prieto reservoir is quite heterogeneous due to complex lithofacies fault structures, and hydrothermal alteration. Geochemical investigations have provided clues on the origin of the geothermal fluids, their recharge paths and on the reservoir processes accompanying the exploitation of the field. Well tests have yielded information on the permeability of the reservoir. (MHR)

  6. Clasificación de asterismos utilizando datos astrométricos

    NASA Astrophysics Data System (ADS)

    de Biasi, M. S.; Orellana, R. B.

    Based on accurate positions and proper motion data up to faint magnitudes, we have studied the regions of twenty three objects known in the literature as asterisms. A parametric method was applied to confirm the nature of these objects. The following objects have been classified: Alessi 11, Alessi 17, Brosch 1, Collinder 21, Dol-Dzim 1, Dolidze 31, Dolidze 43, Dolidze 50, Dolidze 51, NGC 272, NGC2063, NGC 2413, NGC 2664, NGC 5155, NGC 5284, NGC 6222, NGC 6360, NGC 6447, NGC 6476, NGC 6480, NGC 6605, NGC 6659, NGC 6728. FULL TEXT IN SPANISH

  7. Tratamiento de mostos utilizando el filtro anaerobio (treatment of must using an anaerobic filter). Master thesis

    SciTech Connect

    Negron, R.M.

    1982-12-01

    This study reports on the feasibility of treating the slops from rum distilleries with an anaerobic filter composed of an oxygen free reactor filled with a plastic filtering media, commercially known as 'Actifil' with a diameter of 5/8 inches (16mm). This filter is similar in appearance to an aerobic biofilter (trickling filter). The main difference between the two systems is that on the anaerobic filter the flow is upward so that the filter medium is always completely submerged.

  8. Are probiotics effective to prevent traveler’s diarrhea?

    PubMed

    Pinos, Yazmín; Castro-Gutiérrez, Victoria; Rada, Gabriel

    2016-12-23

    La diarrea aguda es la enfermedad más común que afecta a los viajeros, principalmente aquellos que se dirigen a regiones de alto riesgo. El uso de probióticos podría prevenir su aparición, sin embargo, los datos que apoyan su uso no son consistentes y no se recomiendan en las guías clínicas actuales. Utilizando la base de datos Epistemonikos, la cual es mantenida mediante búsquedas en múltiples bases de datos, identificamos cuatro revisiones sistemáticas que en conjunto incluyen siete estudios aleatorizados pertinentes a esta pregunta. Realizamos un metanálisis y tablas de resumen de los resultados utilizando el método GRADE. Concluimos que los probióticos podrían prevenir la diarrea del viajero, pero la certeza de la evidencia es baja.

  9. Summary of Synoptic Meteorological Observations (SSMO), Central American Coastal Marine Areas West Coast. Volume 1. Area 1 - Central Baja West, Area 2 - Southwest Baja, Area 3 - Gulf of California, Area 4 - Mazatlan, Area 5 - Puerto Vallarta

    DTIC Science & Technology

    1981-02-01

    2 *- lP 11-21 22« • 0 101 I 0-3 2 <i <t- lP .1 11-21 22- • 0 TOI > • 2 0-1 .j 5<IC «-10 .9 11-21 ,s 22« • 0 TOI > 1...INC oinrcTiOM HEIN « MD 01» r- 2 3-» 1*7 | I T0T1L CLOUO OI3C0 OftS COVC* «.T r.l 1.» s.c t 1,1 ,1 1.0...ipi 1 ^i •x ä /*-ro "i b &» b $ IO-H (A g O So I UJ i CO o i < o < i s s ui s UJ Ü I I q> s E « 3 e Ö

  10. Molecular identification of Fusarium species isolated from transgenic insect-resistant cotton plants in Mexicali valley, Baja California.

    PubMed

    Gonzalez-Soto, T; González-Mendoza, D; Troncoso-Rojas, R; Morales-Trejo, A; Ceceña-Duran, C; Garcia-Lopez, A; Grimaldo-Juarez, O

    2015-10-02

    Cotton production in the Mexicali valley is adversely affected by wilt and root rot disease associated with Fusarium species. In the present study, we sought to isolate and identify the Fusarium species in the rhizosphere of transgenic insect-resistant cotton plants grown in the Mexicali valley. Our analyses isolated four native fungi from the rhizosphere of cotton plants, namely, T-ICA01, T-ICA03, T-ICA04, and T-ICA08. These fungal isolates were categorized as belonging to Fusarium solani using their phenotypic characteristics and ITS region sequence data. Examination of the infection index showed that T-ICA03 and T-ICA04 caused systemic colonization (90%) of seeds followed by the occurrence of radicle and coleoptile decay. In contrast, T-ICA08 strain was less pathogenic against seed tissues (40%) in comparison to the other strains isolated. Our study showed that in transgenic insect-resistant cotton the disease "Fusarium wilt" is caused by the fungus, F. solani. Future studies are necessary to characterize the F. solani populations to determine whether phenological stages might influence the genetic diversity of the fungal populations present.

  11. Evolution of subsidence styles in forearc basin: example from Cretaceous of southern Vizcaino Peninsula, Baja California, Mexico

    SciTech Connect

    Busby-Spera, C.J.; Boles, J.R.

    1986-04-01

    Late Jurassic to Early Cretaceous arc magmatism is represented by volcaniclastic rocks of the Eugenia Formation in the northern Vizcaino Peninsula and by the metamorphosed Cedros-San Andres volcanoplutonic complex, with a dismembered ophiolitic basement, in the southern peninsula. The Vizcaino Peninsula became the site of forearc sedimentation by the Aptian-Albian (late Early Cretaceous), when arc magmatism moved abruptly eastward to the present-day Peninsular Range. On the southern Vizcaino Peninsula, a conformable stratigraphic section, complicated by later faulting, records a gradual transition from a ridged forearc, broken by basement uplifts and grabens (the Aptian-Albian Asunction Formation), to a broadly subsiding, deep marine forearc basin (the Cenomanian Valle Formation). The basal contact of the Asunction formation has irregular relief caused by brecciated basement rocks and talus accumulated along fault zones. An upward-fining sequence several hundred meters thick records abrupt uplift and gradual denudation of adjacent metamorphic basement. Contemporaneous andesite arc volcanism to the east supplied ash and fresh volcanic detritus to the grabens. Angular sand to boulder-size detritus of the Asunction Formation was derived locally, and includes basic to intermediate meta-igneous rock fragments, with epidote, actinolite, and chlorite, as well as serpentine. Abundant calcareous fossils are commonly unbroken, suggesting local sources for these as well. Angular to subrounded, sand to cobble-sized, intermediate to mafic volcanic rock fragments were derived from a more distant island arc to the east, which occasionally provided intermediate to felsic tuffs to the basin. This source is probably represented by the Aptian-Albian Alisitos Group, which forms much of the western wall of the Late Cretaceous Peninsular Range batholith.