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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 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.

  3. 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…

  4. 78 FR 62610 - North Baja Pipeline, LLC; Notice of Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-10-22

    ... Energy Regulatory Commission North Baja Pipeline, LLC; Notice of Application Take notice that on October 3, 2013, North Baja Pipeline, LLC (North Baja), 717 Texas Street, Suite 2400, Houston, Texas 77002... directed to Richard Parke, Manager, Certificates, North Baja Pipeline, LLC, 717 Texas Street, Suite...

  5. 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

  6. 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,…

  7. GOES Video of Odile Making Landfall in Baja

    NASA Video Gallery

    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...

  8. 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.

  9. 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.

  10. 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.

  11. A BIO-DIESEL BAJA VEHICLE AND STUDENT COMPETITION

    EPA Science Inventory

    The SAE Mini Baja® competition is an extremely popular design competition for students in engineering programs around the world. The competition focuses on the design of an off-road vehicle for performance and cost-of-production. The objective of the proposed effort is to ...

  12. 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.

  13. [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. PMID:12868282

  14. 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.

  15. 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.

  16. Subsurface eddies in the northern Baja California oxygen minimum zone

    NASA Astrophysics Data System (ADS)

    Gomez-Valdes, J.; Torres, H. S.; Zavala Sansón, L.

    2014-12-01

    Subthermocline (subsurface) eddies might be a common feature in eastern boundary currents. During October 2009 a high-resolution survey was carried out off northern Baja California to investigate subsurface eddies. Ocean currents velocities were obtained with a ship-mounted ADCP and with a Lowered-ADCP that was deployed with the Rosette-CTD system. We found a mesoscale anticyclone eddy at the San Quintin Basin oxygen minimum zone. The diameter of the core of the eddy was 64 km. The core of the eddy was warm (11 °C), salty and with low-oxygen concentration (1 ml/l): water properties, which were similar to those of the California Undercurrent off northern Baja California. The eddy showed a swirl velocity of 22 cm/s, a rotational period of 11 days and a Rossby number of 0.14. A discussion about the oceanographic settings and about the generation process of the eddy is presented. Numerical modeling studies of the mesoscale dynamics of the southern region of the California Current revealed that the California Undercurrent induce anticyclone eddies at the San Quintin Basin. As well as we discuss the ecological impact of subthermocline eddies from the San Quintin oxygen minimum zone on the adjacent environment.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Population in trans-border regions: the Southern California-Baja California urban system.

    PubMed

    Rubin-kurtzman, J R; Ham-chande, R; Van Arsdol, M D

    1996-01-01

    "This article is a case study of population growth and composition in the Southern California-Baja California trans-border urban system (TBS). The central question guiding the research is how the combination of geographic proximity and economic integration in two very different regions affects population characteristics in the Southern California-Baja California TBS. We begin by briefly defining trans-border urban systems. We then specify the attributes of the Southern California-Baja California TBS, contrasting them with attributes observed elsewhere in the United States and Mexico.... The data are drawn primarily from the U.S. and Mexican censuses. Secondary data from a variety of sources also are discussed." PMID:12347786

  4. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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...

  6. 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…

  7. 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

  8. 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

  9. 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).

  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. 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.

  12. 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.

  13. Milankovitch cycles in electrical resistivity logs from the Toa Baja scientific drillhole, Puerto Rico

    SciTech Connect

    Maltezou, F.; Anderson, R.N. )

    1991-03-01

    Milankovitch cycles in the upper part of the Toa Baja drillhole, detected by geophysical logs, are used to estimate sedimentation rates, and to localize the depths at which sedimentation rate changes occur. The log-derived age information is then combined with reference dates from palaeontological data and the Vail' global sea-level curve to build a detailed record of the chronology of the upper stratigraphic sequence in the well.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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. PMID:16502335

  19. 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.

  20. 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.

  1. Clay mineral and zeolite diagenesis in the Toa Baja well, Puerto Rico

    SciTech Connect

    Tribble, J.S. )

    1991-03-01

    Several diagenetic reactions typical of volcaniclastic sediments have been identified in the Toa Baja well. The zeolites heulandite and (less commonly) analcite, present in the upper half of the drilled section, give way to laumontite at depth. A decrease with depth in the expandability of mixed layer chlorite/smectite was observed. Corrensite was detected over the depth range 1,676-2,286 m. Temperatures implied by the depth ranges of diagenetic and indicator minerals are consistent with a paleothermal gradient of about 30-50C/km, assuming little or no erosion of section.

  2. Groundwater recharge by channel infiltration in El Barbon basin, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Ponce, V. M.; Pandey, R. P.; Kumar, S.

    1999-01-01

    The amount of groundwater recharge by channel infiltration is estimated for El Barbon basin, in Baja California, Mexico. The basin's lower portion includes the valleys of Ojos Negros and Real del Castillo Viejo, which are crossed by several ephemeral washes, including the mainstem El Barbon Wash. A distributed catchment model with the capability for nonlinear channel routing and channel abstraction is used to calculate groundwater recharge by channel infiltration for storm events of 2-, 5-, 10-, 25-, 50-, and 100-yr return period. The results confirm that event channel infiltration can be a substantial component of the vertical recharge.

  3. 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

  4. Geographic genetic architecture of pocket gopher (Thomomys bottae) populations in Baja California, Mexico.

    PubMed

    Alvarez-Castaneda, Sergio Ticul; Patton, James L

    2004-08-01

    Phylogenetic analyses of complete mitochondrial cytochrome b sequences support the monophyly of pocket gopher (Thomomys bottae) populations from the 1000 km length of the Baja California peninsula of Mexico, relative to other geographical segments of the species range in western North America. The Baja California peninsula is an area that encompasses considerable ecomorphological and infraspecific diversity within this pocket gopher species. However, detailed population analyses encompassing 35 localities distributed over the southern half of the peninsula reveal only trivial phylogeographical structure. Rather, most of the 72 unique 500-base pair haplotypes examined from 142 individuals is restricted to single populations, although a few haplotypes are shared broadly across geography. Individual populations are typically comprised of haplotype sets from different branches in a network of relationships. Analysis of molecular variance (amova) indicates that approximately half of the total pool of variation is contained among individuals within local populations, and that only about 25% can be explained by the regional subdivisions of current subspecies distributions or physiographic realms. A hypothesized historical vicariant event that has been causally linked to the phylogeographical structure of other, codistributed species has had little influence on these pocket gopher populations, explaining only 13% of the total variation. The temporal depth, estimated by coalescence parameters, of the haplotype lineage in Baja California is relatively recent, approximately 300,000 generations; both the mismatch distribution of pairwise comparisons and a significantly positive exponential growth estimate support a recent history of expanding populations; but current, or recent past, migration estimates have remained small, are largely unidirectional from north to south, and weak isolation by distance is present. All data suggest that pocket gophers have relatively recently

  5. 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.

  6. 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.

  7. 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.

  8. E/I corrected paleolatitudes for the sedimentary rocks of the Baja British Columbia hypothesis

    NASA Astrophysics Data System (ADS)

    Krijgsman, Wout; Tauxe, Lisa

    2006-02-01

    Paleomagnetic inclinations from sediments of the western terranes of Canada are consistently too shallow for their reconstructed paleogeographic positions. Two contradicting explanations for these discrepancies are: (1) terranes have been displaced northward with respect to the stable American craton by several thousands of kilometres between the Late Cretaceous (˜ 75 Ma) and the Eocene (˜50 Ma) and (2) sedimentary inclination error has caused a shallow bias in the paleomagnetic directions. Here, we apply the elongation/inclination (E/I) method to paleomagnetic data sets from sedimentary rocks of supposedly allochtonous terranes of western North America to correct for inclination flattening. Our results indicate that the paleomagnetic directions from the continental Silverquick sediments (95-92 Ma) of southern British Colombia are not seriously affected by inclination error, because the magnetic signal most likely concerns a chemical remanent magnetisation (CRM). In contrast, the marine sediments of the Nanaimo Group (84-72 Ma) of Vancouver Island region appear seriously affected by inclination flattening ( f = 0.7) and the E/I corrected mean inclinations are about 9° steeper than the original data. We arrive at corrected inclinations/paleolatitudes of I** = 57°/ λ = 38°N for the Silverquick and I** = 55°/ λ = 36°N for the Nanaimo sediments. Our corrected paleolatitudes indicate that the Canadian terranes were indeed located adjacent to the Baja Californian margin during the Late Cretaceous, thus supporting the Baja BC hypothesis.

  9. Cross section through the Toa Baja drillsite: Evidence for northward change in Late Eocene deformation intensity

    SciTech Connect

    Larue, D.K. ); Berrong, B. )

    1991-03-01

    A 55 km geologic cross section through the Toa Baja Drillsite, generated by integrating geologic mapping data from the foothills of the Central Mountains of Puerto Rico with onshore and offshore multichannel seismic reflection data, provides an opportunity to examine in profile from the arc interior northward to within 40 km of the current trench slope break. Three structural divisions are recognized. In the foothills of Puerto Rico, Cretaceous and Eocene rocks are separated by transpressional strike-slip faults. In the vicinity of the Toa Baja drillsite where both seismic reflection and borehole data are available, Eocene rocks, deformed by thrust faults, .ie above a lower unit, interpreted to be of Cretaceous age. Offshore, north of the drilling site, seismic reflections suggest Eocene rocks onlap structural basement, thought to be Cretaceous rocks, and both units appear only slightly deformed. All Eocene and Eocene ( ) rocks are overlain by little deformed Oligocene to Recent rocks. From south to north, or from the arc massif interior toward the present-day trench, there is an apparent decrease in amount of Late Eocene to Middle Oligocene strike-slip and shortening deformation. Deformation events occurred mostly in the arc-interior and were not directly associated with the plate boundary which was probably near the Puerto Rico Trench.

  10. 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.

  11. 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.

  12. 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.

  13. 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 Libraries…

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

    ... Foreign-Trade Zones Board Approval of Subzone Status; Pepsi Cola Puerto Rico Distributing, LLC, Toa Baja, Puerto Rico On December 7, 2012, the Executive Secretary of the Foreign-Trade Zones (FTZ) Board docketed an application submitted by the Puerto Rico Industrial Development Company, grantee of FTZ...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    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 ...

  20. Differential Energy Radiation from Two Earthquakes with Similar Mw: The Baja California 2010 and Haiti 2010 Earthquakes

    NASA Astrophysics Data System (ADS)

    Meng, L.; Shi, B.

    2010-12-01

    The Baja, Mexico, earthquake of the April 4, 2010, Mw 7.2 occurred in northern Baja California at shallow depth along the principal plate boundary between the North American and Pacific plates, 2 people killed in the Mexicali area. The January 12, 2010, Mw 7.0, Haiti, earthquake occurred in the vicinity of Port-au-Prince, the capital of Haiti, on the Enriquillo Plantain Garden Fault, and with estimates of almost 250,000 deaths. International media reports of such kind of disasters by Haiti earthquake is just resulted from poor building structure design comparing with Mexicali area. Although the moment magnitude of the Haiti earthquake is similar as the Baja earthquake, but the radiated energy of the Haiti earthquake almost as 15 times as the Baja earthquake, resulting stronger near-fault ground motions. For the Haiti earthquake and Baja earthquake with the similar moment magnitude, two special finite fault models are constructed to simulate the near-fault strong ground motion for comparison purpose. We propose a new technique based on the far-field energy integrand over a simple finite fault to estimate S-wave energy radiation with associated the composite source model. The fault slip distributions on both faults are generated based on the composite source model in which the subevent-source-function is described by Brune’s pulse. The near-field peak ground accelerations (PGAs) including the shallow velocity structures (V30, average shear-velocity down to 30 m ) from the Haiti earthquake is almost as 20 times as from Baja earthquake, while the peak ground velocities (PGVs) including the shallow velocity structures from Yushu earthquake is almost as 8 times as from the Baja earthquake. Therefore, the radiated seismic energy plays a significant role in determining the levels of strong grounds in which stronger ground accelerations usually could cause much more property damages on the ground. The source rupture dynamics related to the frictional overshoot and

  1. 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.

  2. 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.

  3. 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. PMID:27140393

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. Occurrence of Pyrodinium bahamense var. compressum along the southern coast of the Baja California Peninsula.

    PubMed

    Gárate-Lizárraga, Ismael; González-Armas, Rogelio

    2011-03-01

    As part of a continuing toxic microalgae monitoring program, 22 phytoplankton samples were collected from July to November 2010 at several sampling stations along the southern coast of the Baja California Peninsula. For the first time, the toxic dinoflagellate Pyrodinium bahamense var. compressum was found along the southeastern and southwestern coasts of the peninsula. P. bahamense var. bahamense was first observed off San José del Cabo, which is an extension of the range of this variety. Both varieties occur as solitary cells. P. bahamense var. compressum occurred at temperatures ranging between 24.5°C and 31°C, whereas var. P.bahamense occurred at 28.5°C to 29°C, indicating its tropical and subtropical nature. Occurrence of P. bahamense var. compressum along this coastline may be related to El Niño 2009-2010. PMID:21276986

  9. 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. PMID:26228068

  10. 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

  11. Zeolite to prehnite-pumpellyite facies metamorphism in the Toa Baja drill hole, Puerto Rico

    SciTech Connect

    Cho, M. )

    1991-03-01

    Secondary mineral assemblages in Eocene volcanic and volcaniclastic rocks of the Toa Baja drill hole progressively change as a function of depth. Four metamorphic zones are delineated with increasing depth: Ca-clinoptilolite{yields}heulandite{yields}laumontite{yields}prehnite-pumpellyite zone. The deepest belongs to the prehnite-pumpellyite facies, whereas the three zones at shallower depths (< 2,350 m) belong to the zeolite facies. Ca-clinoptilolite and heulandite exhibit continuous solid solution with varying Si/Al (2.9-5.2) and Ca/(Ca + Na + K) ratios (0.45-0.89). Pumpellyites are characterized by extensive variation in the Fe/(Fe + Al + Mg) ratio (0.29-0.74) and extreme Fe-enrichment in the laumontite zone. Temperatures estimated from mineral assemblages and facies transitions suggest that the North Coast Basin, Puerto Rico, has been subject to a metamorphic field gradient of {approximately}50 to 70C/km.

  12. 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

  13. 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.

  14. [Juvenile production of the red sea urchin Strongylocentrotus franciscanus (Echinodermata: Echinoidea) in Baja California, Mexico].

    PubMed

    Salas-Garza, A; Carpizo-Ituarte, E; Parés-Sierra, G; Martínez-López, R; Quintana-Rodríguez, R

    2005-12-01

    The red sea urchin Strongylocentrotusfranciscanus (Agassiz 1863) is harvested commercially in Baja California, Mexico, since 1970; however, in the last ten years the capture per unit effort (CPUE) has decreased from 310 kg/fishing unit/day to 120 kg/fishing unit/day. For this reason, actions were taken to develop a culture technology allowing massive production of juveniles for re-stocking natural populations or for growing them commercially. We summarize some of the basic studies and main achievements in this effort. In Baja California, considerably faster larval development (approximately 21 days) has been attained than in the US northwest coast (62 days). Spawning of red sea urchins was routinely induced with KCI while egg fertilization was performed using a 100,000-sperm/ml solution. Six microalgae species were tested and Rhodomonas sp. produced the best larval development. The mean survival rate at the end of the larval period was 25%, but results varied widely with bactch. From the feed ratios tested, best results were obtained using 7000 cel/ml during the first week of larval development, followed by 10,000 cel/ml during the second and 15,000 cel/ml during the third week. KCl proved the most consistent metamorphic inducer, regularly yielding metamorphosis percentages higher than 90%. Metamorphosis was considered complete when the functional jaw that juveniles use for first benthic feeding appeared (as soon as 20 days after induction). With this method several thousands of red sea urchin juveniles were produced. They reached up to 1.5 mm in size during the first 50 days of culture after metamorphosis, showing the great potential for mass production of this species in the laboratory. PMID:17469265

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. First record of a louse fly, Stilbometopa impressa (Bigot), and new host for Microlynchia pusilla (Speiser) (Hippoboscidae) from the Cape Region, Baja California Sur, México.

    PubMed

    Llinas, J; Jiménez, M L

    1996-04-01

    Nine of thirty California quail (Callipepla californica achrustera) captured in autumn of 1992, 17 km west of La Paz, Baja California Sur, México, were parasitized by louse flies. We identified eight Microlynchia pusilla and three Stilbometopa impressa from 30 quails in the ratio of 2.75:1. These are the first records of S. impressa for Cape Region and the first time either fly has been reported from the California quail in Baja California Sur. PMID:8722274

  1. Comparison of enterovirus and adenovirus concentration and enumeration methods in seawater from Southern California, USA and Baja Malibu, Mexico.

    PubMed

    Sassoubre, Lauren M; Love, David C; Silverman, Andrea I; Nelson, Kara L; Boehm, Alexandria B

    2012-09-01

    Despite being important etiological agents of waterborne illness, the sources, transport and decay of human viruses in recreational waters are not well understood. This study examines enterovirus and adenovirus concentrations in coastal water samples collected from four beaches impacted by microbial pollution: (1) Malibu Lagoon, Malibu; (2) Tijuana River, Imperial Beach; (3) Baja Malibu, Baja California; and (4) Punta Bandera, Baja California. Water samples were concentrated using a flocculation-based skim milk method and dead-end membrane filtration (MF). Viruses were enumerated using cell culture infectivity assays and reverse transcription quantitative polymerase chain reaction (RT-QPCR). Across concentration and quantification methods, enteroviruses were detected more often than adenoviruses. For both viruses, MF followed by (RT)QPCR yielded higher concentrations than skim milk flocculation followed by (RT)QPCR or cell culture assays. Samples concentrated by skim milk flocculation and enumerated by (RT)QPCR agreed more closely with concentrations enumerated by cell culture assays than MF followed by (RT)QPCR. The detection of viruses by MF and (RT)QPCR was positively correlated with the presence of infectious viruses. Further research is needed to determine if detection of viruses by rapid methods such as (RT)QPCR can be a useful water quality monitoring tool to assess health risks in recreational waters. PMID:22960486

  2. Vicariance and dispersal across Baja California in disjunct marine fish populations.

    PubMed

    Bernardi, Giacomo; Findley, Lloyd; Rocha-Olivares, Axayacatl

    2003-07-01

    Population disjunctions, as a first step toward complete allopatry, present an interesting situation to study incipient speciation. The geological formation of the Baja California Peninsula currently divides 19 species of fish into disjunct populations that are found on its Pacific Coast and in the northern part of the Gulf of California (also called the Sea of Cortez), but are absent from the Cape (Cabo San Lucas) region. We studied the genetic makeup of disjunct populations for 12 of these 19 fish species. Phylogeographic patterns for the 12 species can be separated into two major classes: a first group (eight species) showed reciprocal monophyly and high genetic divergence between disjunct populations. A second group (four species) displayed what appeared to be panmictic populations. Population structure between Pacific Coast populations, across the Punta Eugenia biogeographic boundary, was also evaluated. While dispersal potential (inferred by pelagic larval duration) was a poor predictor of population structure between Gulf of California and Pacific populations, we found that population genetic subdivision along the Pacific Coast at Punta Eugenia was always positively correlated with differentiation between Pacific and Gulf of California populations. Vicariant events, ongoing gene flow, and ecological characteristics played essential roles in shaping the population structures observed in this study. PMID:12940364

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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. PMID:17909708

  10. 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. PMID:17698443

  11. 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

  12. Paleocene Sepultura Formation: submarine canyon at La Mesa, Baja California, Mexico

    SciTech Connect

    Tellez-Duarte, M.A.; Navarro-Fuentes, J.C.; Valdez-Noriega, M.A.

    1988-03-01

    The Paleocene Sepultura Formation has been interpreted as the result of both deposition in a basin that varied in depth from strandline to at least 30-40 fathoms, and to widely distributed fluvial deposition. At La Mesa, east of Puerto Santa Catarina, Baja California, an excellent exposure exhibits canyon-fed sediments not reported in other places for this formation. The sediments at La Mesa consist of a sequence of alternating clastics and resedimented carbonate materials. The sequence begins with fine sandstone cut by channels, which indicates gravity-induced catastrophic sedimentation, such as debris flows. The channels are filled with massive nodular algal limestone with rip-up clasts of sandstone, some of them 1 m wide, with abundant Turritella pachecoensis and Venericardia sp. The massive limestone is overlain by clastic sediments that, in places, exhibit slumping and laminar bedding with limestone rip-ups. Apparently this unit is an upper-fan deposit. The nodular limestone grades laterally into thin-bedded calcarenites. These allodapic limestones exhibit A and B divisions of the Bouma sequence, similar to overbank levee deposits.

  13. 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.

  14. 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.

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

    PubMed

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

    1998-10-01

    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

  16. Seasonality of the transitional region of the California Current System off Baja California

    NASA Astrophysics Data System (ADS)

    Durazo, Reginaldo

    2015-02-01

    Hydrographic data collected over the period 1997-2013 are analyzed to investigate the seasonality of hydrographic features and associated geostrophic flows off the Baja California peninsula. The upper ocean in the region was found to be homogeneous in winter and spring but subdivided into two regions in the summer and autumn. In the first case, the system typically shows relatively low-temperature and salinity waters, which give it a subarctic character. In the second, only the region north of Punta Eugenia (28°N) maintains subarctic characteristics, while the southern region receives an inflow of tropical and subtropical waters that results from the weakening of northwesterly winds, which allows the poleward advection of surface waters. Also during this period, a positive wind stress curl promotes the zonal advection of North Pacific's eastern edge waters into the coast and to the north as a surface coastal flow. Average seasonal patterns of geostrophic flow at 200 dbar revealed that the differentiation into provinces is also evident at that depth, with two clearly defined cyclonic structures in summer and autumn, both separated at the latitude of Punta Eugenia. The analyses conducted also showed a clear continuity of the California undercurrent along the shelf break, with more diffuse currents in the winter. Poleward flows were observed throughout the water column, especially in summer and autumn, although the origin of the surface flow does not necessarily involve a surfacing of the California Undercurrent.

  17. 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.

  18. 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.

  19. 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.

  20. The endemic insular and peninsular species Chaetodipus spinatus (Mammalia, Heteromyidae) breaks patterns for Baja California.

    PubMed

    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

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. [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. PMID:23894976

  6. 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.

  7. 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.

  8. 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.

  9. Local Seismological Networks in Northern Baja California: Some Interpretation of Results.

    NASA Astrophysics Data System (ADS)

    Frez, J.; Acosta, J.; Nava, F.; Gonzalez, J.; Alvarez, M.

    2002-12-01

    Since 1997, we have installed local seismological networks in northern Baja California (Reftek stations, three digital components, one to four months operation, covering areas of about 50 km x 50 km) for detailed microseismicity surveys of several fault systems in the region: Cerro Prieto, San Miguel, Agua Blanca, Sierra Juarez, and areas in between. Immediate results are location of about 1500 hypocenters, determination of about 400 focal mechanisms, and some structural information on the crust. In this presentation, we focus on: a) a summary of the spatial distribution of the hypocenters, focal mechanisms, and P and T axes; b) the role of the Ojos Negros Valley in the regional seismotectonics, and c) the existence of orthogonal alignments of epicenters not necessarily associated with mapped fault traces. Most of the activity is not clearly associated with fault traces: the exception is the SE segment of the San Miguel fault, the same one where destructive earthquakes occurred in 1954 and 1956. Most of the activity appears to be correlated with valleys (Ojos Negros, Trinidad-San Matias), or to simply occur between fault traces, or to belong to epicenter alignments of ~15 km or more in length which are part of longer segments that are apparent in regional seismicity maps (SCSN and RESNOM catalogs). This regional and local alignments show an orthogonal pattern. In a simple interpretation, they could represent a very new fracture proccess in a still mostly homogeneous material, not yet expressed as fault ruptures. All P and T axes azimuthal distributions from the various areas of study show a well defined global maximum consistent with the direction of regional stresses (about NS and EW, for P and T axes, respectively). However, the P axes are distributed on the focal sphere as an almost NS strip, particularly for the Ojos Negros Valley, indicating an extensional regime.

  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. PMID:19928461

  11. Coarse-grained volcaniclastic sediments and associated penecontemporaneous volcanism, Alisitos Group, Baja California, Mexico

    SciTech Connect

    White, J.D.L.; Busby-Spera, C.J.

    1986-04-01

    Volcaniclastic rocks of Cretaceous age make up the Alisitos group, which is exposed over large areas of northern Baja California, Mexico, and is inferred to have been deposited within an island arc. Intimately intermixed penecontemporaneous intrusive, extrusive, and fragmental volcanic rocks characterize many of the intra-arc deposits within the Alisitos. Peperites, formed by mixing of magma and wet sediment, are useful for demonstrating contemporaneity of volcanism and sedimentation. Peperites were recently discovered at the type locality of the Alisitos group at Punta China, only 25 km south of Ensenada, Mexico. These intrude a 50-m thick section, dominated by mafic lithic lapilli tuff breccias and lava flows, that accumulated in a nearshore to beach environment. Near Punta Maria (about 100 km north of Guerrero Negro), coarse-grained volcaniclastics interpreted to have been deposited on a north to northwest-facing submarine slope are exposed in sea cliffs. Ammonite (Pervinquieria.) and belemnite fossils suggest a Cretaceous age and marine deposition for the Punta Maria sequence. Horizontal burrows and lack of wave reworking indicate subwave-base depth for most of the section. The most common rock types in the sequence are andesitic lithic lapilli tuff and tuff breccia, deposited from nonturbulent high-concentration sediment gravity flows (density-modified grain flow). Comparison of the Punta Maria and Punta China sections suggests that hydrostatic pressure and depositional slope play important roles in controlling the magma/sediment interaction. At Punta China, a shallow-water association was intruded by small sills, resulting in a highly dispersed peperite (explosive interaction). The Punta Maria section, comprising deeper water slope deposits, was intruded by a larger magma body that partly ingested a limestone and produced a thick carapace of hyaloclastite (nonexplosive interaction).

  12. 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. PMID:24391248

  13. Benthic production and processes off Baja California, northwest Africa and Peru: a classification of benthic subsystems in upwelling ecosystems

    SciTech Connect

    Rowe, G.T.

    1983-01-01

    Estimates of the standing stocks, secondary production and metabolism of the benthos have been compared in the coastal upwelling ecosystems off northwest Africa, Baja California, and southern Peru. Northwest Africa is characterized by shelf break upwelling and as a result standing stocks, macrobenthic production and sediment organic matter are highest out at the shelf-slope boundary. Sediment microbial activity and biomass on the other hand are highest nearshore in the dynamic zone where aeolian silt and sand are being blown into the sea from the Sahara Desert. Baja California is dominated by the red crab, Pleuroncodes planipes, having high rates of growth and metabolic utilization of organic matter, both on bottom and in the water. Peru benthos and metabolism are very different from the above areas because of the low oxygen concentrations in the bottom water. Organic matter is far higher in the sediment and heterotrophic metabolism is principally anaerobic rather than aerobic. A normal offshore benthic fauna is replaced by a mat of sulfur bacteria with unknown production and metabolic rates. Benthic subsystems in upwelling ecosystems can be placed in two categories: those overloaded with organic matter, depleted of oxygen and dominated by sulfate reduction and those that are not overloaded and remain aerobic. Peru and southwest Africa typify overloaded systems whereas NW Africa and Baja California are examples of aerobic systems. Although benthic metabolism and ionorganic nutrient regeneration are high in both types of subsystems, all upwelling ecosystems, with their dynamic open boundaries, export organic particulate matter and import inorganic nutrients at rates that are far in excess of that consumed or produced by benthic metabolism. 42 refs., 7 figs., 8 tabs.

  14. 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

  15. 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.

  16. Assessment of landscape change associated with tropical cyclone phenomena in Baja California Sur, Mexico, using satellite remote sensing

    NASA Astrophysics Data System (ADS)

    Martinez-Gutierrez, Genaro

    Baja California Sur (Mexico), as well as mainland Mexico, is affected by tropical cyclone storms, which originate in the eastern north Pacific. Historical records show that Baja has been damaged by intense summer storms. An arid to semiarid climate characterizes the study area, where precipitation mainly occurs during the summer and winter seasons. Natural and anthropogenic changes have impacted the landscape of southern Baja. The present research documents the effects of tropical storms over the southern region of Baja California for a period of approximately twenty-six years. The goal of the research is to demonstrate how remote sensing can be used to detect the important effects of tropical storms including: (a) evaluation of change detection algorithms, and (b) delineating changes to the landscape including coastal modification, fluvial erosion and deposition, vegetation change, river avulsion using change detection algorithms. Digital image processing methods with temporal Landsat satellite remotely sensed data from the North America Landscape Characterization archive (NALC), Thematic Mapper (TM), and Enhanced Thematic Mapper (ETM) images were used to document the landscape change. Two image processing methods were tested including Image differencing (ID), and Principal Component Analysis (PCA). Landscape changes identified with the NALC archive and TM images showed that the major changes included a rapid change of land use in the towns of San Jose del Cabo and Cabo San Lucas between 1973 and 1986. The features detected using the algorithms included flood deposits within the channels of active streams, erosion banks, and new channels caused by channel avulsion. Despite the 19 year period covered by the NALC data and approximately 10 year intervals between acquisition dates, there were changed features that could be identified in the images. The TM images showed that flooding from Hurricane Isis (1998) produced new large deposits within the stream channels

  17. 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. PMID:18494299

  18. 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

  19. 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

  20. 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

  1. 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

  2. Evolution of the east-central San Jose del Cabo basin, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    McTeague, M. S.; Umhoefer, P. J.; Schwennicke, T.; Ingle, J. C.; Cortes Martinez, M.

    2006-12-01

    The San Jose del Cabo basin at the southern tip of the Baja California peninsula records the early tectonic evolution of the west side of the Gulf of California. This study focused on the east central margin of the basin. The basal La Calera Formation unconformably overlies Cretaceous granite and consists of conglomerate, pebbly sandstone and conglomerate, and sandstone deposited in alluvial fans and fan-deltas. Deposition of the La Calera Formation was from ca. 9-14 Ma. The lower member of the Trinidad Formation was deposited beginning ca. 9-13 Ma and consists of sandstone, mudstone, and shelly mudstone deposited in nearshore and estuarine environments. These age estimates are based on sedimentation rates and foraminifera and coccoliths from the NN 11A nannozone (7.4 8.6 Ma, GTS 2004). The middle member of the Trinidad Formation consists of deeper water mudstones deposited by turbidity currents and suspension settling in a shelf to slope and conglomerates deposited by submarine debris flows on the shelf. The basin began earlier than previously thought. The oldest marine rocks are ca.9-13 Ma, while sedimentation on the east side began at ca. 9-14 Ma, synchronous with estimates of initiation of offset on the San Jose del Cabo fault. The Zapote fault is a down-to-the-east normal and sinistral-oblique fault that exposes a wedge of granite and older strata in the footwall to the west. The fault was active during sedimentation in the late Miocene and possibly later. The fault divides the study area into an eastern hanging wall subbasin and western footwall subbasin. The eastern subbasin formed an embayment in the eastern margin of the Cabo basin. A regional flooding surface (ca. 8 Ma) can be correlated across the fault that marks a major marine incursion. Depositional systems evolved rapidly from coarse-grained terrestrial systems to fine-grained marine and estuarine systems. The Cabo basin provides an excellent analogue for comparison with offshore basins, which are

  3. 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

  4. 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

  5. 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.

  6. 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.

  7. 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. PMID:26840744

  8. Rheological properties of the lower crust and upper mantle beneath Baja California: a microstructural study of xenoliths from San Quintin

    NASA Astrophysics Data System (ADS)

    Van der Werf, Thomas F.; Chatzaras, Vasileios; Tikoff, Basil; Drury, Martyn R.

    2016-04-01

    Baja California is an active transtensional rift zone, which links the San Andreas Fault with the East Pacific Rise. The erupted basalts of the Holocene San Quintin volcanic field contain xenoliths, which sample the lower crust and upper mantle beneath Baja California. The aim of this research is to gain insight in the rheology of the lower crust and the upper mantle by investigating the xenolith microstructure. Microstructural observations have been used to determine the dominant deformation mechanisms. Differential stresses were estimated from recrystallized grain size piezometry of plagioclase and clinopyroxene for the lower crust and olivine for the upper mantle. The degree of deformation can be inferred from macroscopic foliations and the deformation microstructures. Preliminary results show that both the lower crust and the upper mantle have been affected by multiple stages of deformation and recrystallization. In addition the dominant deformation mechanism in both the lower crust and the upper mantle is dislocation creep based on the existence of strong crystallographic preferred orientations. The differential stress estimates for the lower crust are 10-29 MPa using plagioclase piezometry and 12-35 MPa using clinopyroxene piezometry. For the upper mantle, differential stress estimates are 10-20 MPa. These results indicate that the strength of the lower crust and the upper mantle are very similar. Our data do not fit with the general models of lithospheric strength and may have important implications for the rheological structure of the lithosphere in transtensional plate margins and for geodynamic models of the region.

  9. 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.

  10. 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.

  11. Genetic structure of desert ground squirrels over a 20-degree-latitude transect from Oregon through the Baja California peninsula.

    PubMed

    Whorley, Joshua R; Alvarez-Castañeda, S Ticul; Kenagy, G J

    2004-09-01

    The genetic structure of populations over a wide geographical area should reflect the demographic and evolutionary processes that have shaped a species across its range. We examined the population genetic structure of antelope ground squirrels (Ammospermophilus leucurus) across the complex of North American deserts from the Great Basin of Oregon to the cape region of the Baja California peninsula. We sampled 73 individuals from 13 major localities over this 2500-km transect, from 43 to 22 degrees north. Our molecular phylogeographical analysis of 555 bp of the mitochondrial cytochrome b gene and 510 bp of the control region revealed great genetic uniformity in a single clade that extends from Oregon to central Baja California. A second distinct clade occupies the southern half of the peninsula. The minimal geographical structure of the northern clade, its low haplotype diversity and the distribution of pairwise differences between haplotypes suggest a rapid northward expansion of the population that must have followed a northward desert habitat shift associated with the most recent Quaternary climate warming and glacial retreat. The higher haplotype diversity within the southern clade and distribution of pairwise differences between haplotypes suggest that the southern clade has a longer, more stable history associated with a southern peninsular refugium. This system, as observed, reflects both historical and contemporary ecological and evolutionary responses to physical environmental gradients within genetically homogeneous populations. PMID:15315683

  12. 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

  13. 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

  14. 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

  15. Seismic Anisotropy of the Crust in the Regions of Northern Baja California and Sonora, Mexico, Using Receiver Functions

    NASA Astrophysics Data System (ADS)

    Obrebski, M.; Castro, R. R.

    2007-05-01

    We calculated receiver functions from teleseismic P waves recorded at the NARS-Baja broad band stations to investigate the seismic anisotropy of the crust in the regions of northern Baja California and Sonora. Seismic anisotropy is typically controlled by stress state in the fragile shallow crust and by the rock strain state in the ductile intermediate and deep crust. To emphasize phases produced by the anisotropic structure of the crust we partially remove the source effect performing a frequency domain deconvolution of the radial and transverse components by the vertical one. In order to enhance coherent information and decrease noise, we stack receiver functions obtained from P-wave arrivals with similar back azimuth, since they are expected to yield consistent receiver functions. We gave particular attention to the Ps converted phase arrival, which is the most prominent wave arrival after direct P phase and is generated by the P to S conversion at the Moho due to the sharp velocity drop. When a Ps arrival appears clearly on radial and transverse components, and does not overlap with other phases, we suppose that transverse energy rose from shear wave splitting and we retrieve apparent anisotropy parameters, namely the azimuth of the fast direction and the time delay using a method based on the calculation of the covariance matrix. Using this method we characterized the crustal anisotropy under the NARS-Baja station NE75, located in the Stable Central Peninsula Province. The results obtained at this station suggest that the anisotropy of the crust must be related to the metamorphism induced by the subduction of the Farallon plate. At other stations, the results show high dispersion and back azimuthal dependency, indicating the presence of a more complex structure under the stations analyzed. We also performed forward modeling of the crust structure by matching the receiver functions obtained from observed records with synthetic seismograms calculated using a

  16. 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…

  17. 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" is…

  18. 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). PMID:22187022

  19. Air-sea CO2 fluxes measured by eddy covariance in a coastal station in Baja California, México

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Loza, L.; Ocampo-Torres, F. J.

    2016-05-01

    The influence of wave-associated parameters controlling turbulent CO2 fluxes through the air-sea water interface is evaluated in a coastal region. The study area, located within the Todos Santos Bay, Baja California, México, was found to be a weak sink of CO2 with a mean flux of -1.32 µmol m-2s-1. The low correlation found between flux and wind speed (r = 0.09), suggests that the influence of other forcing mechanisms, besides wind, is important for gas transfer modulation through the sea surface, at least for the conditions found in this study. In addition, the results suggest that for short periods where an intensification of the wave conditions occurs, a CO2 flux response increases the transport of gas to the ocean.

  20. Acoustic televiewer log images of natural fractures and bedding planes in the Toa Baja Borehole, Puerto Rico

    NASA Astrophysics Data System (ADS)

    Paillet, Frederick L.; Goldberg, David

    Although borehole conditions made acoustic televiewer logging difficult in the Toa Baja borehole, more than 180 meters of continuous, acceptable quality televiewer logs were obtained in the intervals from 730 to 880 meters and from 2,515 to 2,675 meters in depth, indicating the presence of fractures that appear to be open in situ. Most of the largest, possibly open fractures in these intervals are either nearly parallel to directions given by the dipmeter log and may represent solution openings or minor washouts along bedding planes, or dip steeply to the south or southwest across bedding. The televiewer log confirms the presence of an apparently open set of fractures near 867 meters in depth, where circulation was lost during drilling, and in the interval from 2,600 to 2,650 meters in depth, where the temperature log indicates anomalous heat flow in the surrounding formation.

  1. Net primary productivity, upwelling and coastal currents in the Gulf of Ulloa, Baja California, México

    NASA Astrophysics Data System (ADS)

    González-Rodríguez, E.; Trasviña-Castro, A.; Gaxiola-Castro, G.; Zamudio, L.; Cervantes-Duarte, R.

    2012-08-01

    The Gulf of Ulloa, a highly productive area off the western coast of the Baja California Peninsula, is examined for five successive years (2003-2007) by using satellite data and seasonal net primary productivity (NPP) estimates obtained from a vertical generalised production model. The results identify that northwestern winds blow parallel to the coast throughout the year. However, highest NPP occurs from March to June. During this period, an equatorward coastal current transports water from neighbouring upwelling areas to the northern Gulf of Ulloa and in combination with local upwelling, which injects nutrients into the euphotic zone, produce the observed increase in NPP. The opposite situation occurs in late summer when a warm poleward current of tropical characteristics arrives and inhibits the productivity in the whole region and generates the yearly lowest NPP levels. Our findings reveal the importance of lateral advection in the modulation of the primary productivity in this subtropical upwelling region.

  2. 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.

  3. Teleconnections between upwelling along the Pacific coast of Baja California and marine and terrestrial gross primary production

    NASA Astrophysics Data System (ADS)

    Reimer, J. J.; Vargas, R.; Gaxiola-Castro, G.; Hernandez-Ayon, M.; Lara-Lara, R.

    2012-12-01

    Terrestrial processes are closely connected to the oceans through teleconnections in the atmosphere. The global terrestrial carbon cycle is known to be affected by a teleconnection to large scale atmospheric events such as El Niño/Southern Oscillation (ENSO; 2 to 7 year cycles), Pacific Decadal Oscillation (PDO), and North Atlantic Oscillation (NAO; decadal cycles). ENSO and PDO are the predominate atmospheric patterns which impact the Pacific coast of North America. Correlations between ENSO indices and gross primary production have shown that ENSO may partially explain the variability in the global terrestrial carbon cycle. We hypothesize that the remaining variability (for those ecosystems along eastern basin margins) may be explained by the teleconnection between terrestrial primary production and upwelling along continental margins. The study sites were selected along the Baja California peninsula due to the fact that each one is characterized by year round coastal upwelling (though stronger during the boreal spinr/summer months) and their respective terrestrial climate characteristics: 1. Punta Colonet/Sierra San Pedro Martir is located in a mediterranean climate with conifer forest; 2. Punta Abre Ojos (just south of Guerrero Negro) is located in the central desert region; 3. at approximate 29°00' N (west of Bahía de los Angeles) is in the central desert region but is also characterized by fog; and 4. Magdalena Bay is located in a subtropical desert region with sporadic rain events (here the marine portion of the transect will extend out from the mouth of the bay). Using ten years of MODIS Terra and Aqua (terrestrial gross primary production [TGPP]) and SeaWif's (chlorophyll a [chl. a] as a proxy for biomass) data for four transects along the Baja California peninsula (extending from approximately 300 km off the coast to up to 50 km inland depending on the transect) the gross primary production will be analyzed in relation to upwelling (represented by sea

  4. Bio-optical characteristics of a phytoplankton bloom event off Baja California Peninsula (30 31°N)

    NASA Astrophysics Data System (ADS)

    Barocio-León, Óscar A.; Millán-Núñez, Roberto; Santamaría-del-Ángel, Eduardo; Gonzalez-Silvera, Adriana; Trees, Charles C.; Orellana-Cepeda, Elizabeth

    2008-03-01

    A phytoplankton bloom was detected in the Southern California Current System, off the Baja California Peninsula (Mexico) on June 2003 with chlorophyll- a concentration (TChl a) of 10.13 mg m -3. Two stations (D1 and D2) were sampled on June 24, and D2 was resampled 6 days later; chlorophyll- a concentration had decreased by about one half. LAC MODIS-Chl a images were obtained and showed the spread of the bloom on the day after sampling. The phytoplankton community consisted primarily of dinoflagellate temporary cysts, mainly at the surface and at 5 m in station D1. Two Pseudo-nitzschia species ( P. australis, P. seriata) were also very abundant. Samples from the bloom had a specific phytoplankton absorption coefficient ( aph*(λ)) lower than the rest of the samples. Values varied from 0.0186 to 0.0455 m 2 mg -1 for aph*(440) and from 0.0092 to 0.0294 m 2 mg -1 for aph*(675), with ratios aph*(440): aph*(675) ranging from 0.99 to 2.20. These low ratios were associated with the combined effect of packaging, and with the relatively high ratios of fucoxanthin, peridinin, diadinoxanthin and chlorophyll- c2 to TChl a. Samples from the surface and 5 m depth at station D1 had higher ratios of Perid:TChl a (0.12-0.32) than the rest of the samples, suggesting that cysts have similar Perid:TChl a as free-living dinoflagellates. An unusual absorption spectrum with a broad maximum around 480-500 nm was associated with the high proportion of cysts and diatoms. The slope of the spectra between 443 and 488 nm was a good index to differentiate bloom samples containing high proportions of dinoflagellate temporary cysts. Further investigation of the absorption properties of dinoflagellate cysts is needed in order to detect these waters by remote sensing. Although much work is still necessary to understand and explain the bio-optical properties of a bloom, the present study is the first assessment off the Baja California coast to simultaneously consider aspects such as absorption

  5. Microstructural and seismic properties of the upper mantle underneath a rifted continental terrane (Baja California): An example of sub-crustal mechanical asthenosphere?

    NASA Astrophysics Data System (ADS)

    Palasse, L. N.; Vissers, R. L. M.; Paulssen, H.; Basu, A. R.; Drury, M. R.

    2012-09-01

    The Gulf of California rift is a young and active plate boundary that links the San Andreas strike-slip fault system in California to the oceanic spreading system of the East Pacific Rise. The xenolith bearing lavas of the San Quintin volcanic area provide lower crust and upper mantle samples from beneath Baja California peninsula. The microstructures, crystallographic preferred orientations (CPO) and petrology of the San Quintin xenoliths suggest that the continental lithosphere in this region has undergone several stages of deformation, recrystallisation and melt-rock interaction. Melt-rock interactions have led to enrichment in olivine while fine-grained microstructures suggest intense deformation in an active shear zone in the shallow upper mantle. In this study we highlight the effect of the fine-grained mylonitic shear zone development in the upper mantle as an important process of weakening of continental lithosphere. The results of the microstructural study show a reduction in CPO strength with increasing grain size reduction. Most CPOs are consistent with dominant slip on the {0kl}[100] system. As a consequence, corresponding seismic anisotropies decrease for both P- and S-waves with increasing grain size reduction. The shallow crystallographic fabric can be related to active shear zones, which accommodate the relative motion between the Northern Baja terrane and the Pacific plate. Estimates of the strain rate, stress and viscosity indicate that the shallow mantle beneath Northern Baja is thermally and chemically lithospheric but mechanically has similar viscosity as the asthenosphere. The Northern Baja terrane is an interesting case of continental crust lying directly on low viscosity upper mantle.

  6. 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.

  7. 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

  8. 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. PMID:23072623

  9. Chaetognatha in the Bahía Magdalena lagoon complex, Baja California Sur, México: species composition and assemblages.

    PubMed

    Cota Meza, M S

    2011-07-01

    The chaetognaths from 187 zooplankton samples collected from the Bahia Magdalena lagoon complex, Baja California Sur, Mexico during March, June, July, August, September, November, and December 1982 were studied. Twelve species belonging to two genera were identified. Sagitta euneritica and S. enflata were the most abundant and most frequent species with maximum abundance in July (40,000 org/100 m(3) and 6100 org/100 m(3) respectively). Sagitta pacifica, S. regularis and S. pseudoserratodentata were stenothermic (21 to 25 degrees C), whereas the rest of the species were eurythermic (15.5 to 29.5 degrees C). Sagitta euneritica contributed considerably to the zooplanktonic biomass, increasing the density in particular in BahíaAlmejas. The analysis of the species assemblages (Morisita index) showed that S. pacifica and S. regularis interact more frequently in August when there is a change of the water masses that converge in this zone during summer, when the California Countercurrent predominates. The composition of taxa during winter is characterized by the dominance of S. euneritica. Entering the warm period, an abrupt change occurs in taxa composition of the three zones studied: channels, Bahía Magdalena, and BahíaAlmejas. The amplitude and distribution of S. peruviana was influenced possibility by the oceanographic conditions of ENSO 1982. PMID:22315819

  10. 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.

  11. 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

  12. 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.

  13. 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. PMID:12597648

  14. Environmental Assessment and Finding of No Significant Impact: Presidential Permit Applications for Baja California Power, Inc. and Sempra Energy Resources

    SciTech Connect

    N /A

    2001-12-05

    In separate actions, Sempra Energy Resources (SER) and Baja California Power, Inc. (BCP) have applied to the US Department of Energy (DOE) for Presidential permits pursuant to Executive Order (EO) No. 10485, as amended by EO 12038, and 10 CFR Section 205.320 et seq. (2000), to construct, operate, maintain, and connect electric power transmission facilities crossing the international border between the Us and Mexico. SER and BCP each propose constructing separate new double-circuit, 230,000 volt (230 kV) transmission lines extending about six miles south from the Imperial Valley Substation (IV Substation), owned and operated by San Diego Gas and Electric Company (SDG and E), to the US/Mexico international border. In each case, the objective is to connect the proposed transmission lines to natural gas fueled electric generating plants being constructed in Mexico for the purpose of importing electrical power into the US onto the southern California electrical grid. The proposed transmission lines would traverse about six miles of federal land administered by the US Department of the Interior's Bureau of Land Management (BLM).

  15. 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.

  16. The Coastal upwellings of the Baja California Peninsula during the 1997-2003 ENSO conditions, through remote sensing

    NASA Astrophysics Data System (ADS)

    Castro, J.; Salas-de-Leon, D.; Aguirre-Gomez, R.

    2007-05-01

    Upwelling interannual variation study was conducted in Baja California peninsula based on several parameters. Wind stress (upwelling index), Sea Surface Temperature (SST), Area Sea Surface Temperature (15°C), Sea Surface High (SSH) and, Chlorophyll-a (Chl-a) data were analyzed in order to compare ENSO conditions between 1997 and 2003. Our result indicate that SST and SSH were expected to ENSO conditions. Upwellings index was high during weak El Nino 2003 and less evident during La Nina 1998-2001 events. On the other hand, Chl-a biomass was 50% lower during El Nino 1997-98 than records of La Nina 1998-2001 and showed its maximum value during transition conditions in 2002. Chl-a biomass was similar in El Nino 2003 and La Nina 1998-2001. Our data do not match with the current proposed hypothesis that El Nino depress primary productivity (PP), while La Niña promotes high PP. These conditions are according only with the strong El Nino 1997-1998 in the southern California Current System; however during weak-to moderate events the conditions area variable in the region and inter-events. This supports the idea that southern CCS is also modulated by different inter-annual oscillations, as the North Pacific Decadal Oscillation.

  17. Seismic-Wave Attenuation and Source Excitation in La Paz-Los Cabos, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Ortega, R.; Gonzalez, M.

    2007-05-01

    We present results from a regional study of seismic-wave attenuation and source excitation from small- magnitude earthquakes recorded at distances from 6 to 180 km in the La Paz-Los Cabos region, at the south end of the Baja California Peninsula. Data were recorded using 32 strong-motion seismic stations from the La Paz network (LAP). A least squares regression separating the excitation, site, and propagation effects was carried out. We performed the analyses in the time and frequency domains, and we compared these results with results from a coda-normalization method. The propagation term was parameterized to represent a geometrical spreading function and a frequency-dependent Q(f) at a reference distance of 40 km. We estimated the regional attenuation by measuring the maximum amplitude of the S- or Lg-waves as a function of frequency, defining a continuous piecewise propagation term, D(r,f), after separating the excitation and site terms. Our results show that the attenuation is lower compared to that of central or northern Mexico. Recorded data were of remarkably good quality in spite of the fact that the strong-motion network recorded only small-size earthquake.

  18. Anthropogenic contamination of metals in sediments of the Santa Rosalía harbor, Baja California peninsula.

    PubMed

    Shumilin, Evgueni; Jiménez-Illescas, Ángel Rafael; López-López, Silverio

    2013-03-01

    To know the environment impact on a harbor of the Santa Rosalía port on the Baja California peninsula, the concentrations of metals (Cd, Co, Cu, Mn, Pb, U and Zn) in harbor sediments were determined for 13 stations and compared with their average upper Earth´s crust abundance. The mean enrichment factors, calculated using Al as a normalizer, were higher than the unity for Ag, Ba, Bi, Cd, Co, Cu, Mn, Ni, Pb, Sb, U, V and Zn. Concentrations of slightly enriched Cd in the sediments are below the effect range low (ERL) sediment quality guidelines value only at three stations. The levels of Pb in the harbor sediments at four stations (1, 6, 9 and 11) are between the ERL (46.7 mg kg(-1)) and the effect range medium (ERM) (218 mg kg(-1)), and Pb content in the rest of the sediment samples is higher than the ERM, demonstrating the high extent of the anthropogenic impact of this metal on the sedimentary environment. The total concentrations of the potentially toxic elements Cu (3,390 ± 804 mg kg(-1)) and Zn (1,916 ± 749 mg kg(-1)) very strongly exceed their ERM, showing a high possibility of toxicological danger for marine biota, living inside or entering the harbor. PMID:23277367

  19. 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. PMID:21788056

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. 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

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

    PubMed

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

    2009-08-01

    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

  6. 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. PMID:27261252

  7. 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.

  8. 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. PMID:26856732

  9. 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.

  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. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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. PMID:17944851

  16. 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.

  17. 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).

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. The stratigraphic architecture of hyper-extended rift systems: A field perspective from Aps, Pyrenees and Baja-California

    NASA Astrophysics Data System (ADS)

    Masini, Emmanuel; Manatschal, Gianreto; Tugend, Julie; Mohn, Geoffroy; Robin, Cécile; Geoffroy, Laurent; Unternehr, Patrick

    2013-04-01

    The discovery of hyper-extended domains in deep water rifted margins challenged the classical view of the evolution of rift systems leading to continental breakup. In these hyper-extended domains, rift basins occur over less than 10km thick extended continental crust or exhumed subcontinental mantle. Neither their imaged stratigraphic architecture and drilled facies nor the subsidence history can be explained by classical McKenzie-type rift models. Studies performed on off- and on-shore examples demonstrate the importance of tectonic exhumation by detachment faulting. However, despite their apparent widespread occurrence in present-day rifted margins, the overall tectono-sedimentary evolution of these systems remains poorly understood. In this study we review and compare key multi-scale observations from 3 different hyper-extended rift systems. 1) The first example, in the Western Pyrenees, corresponds to a complete sediment-rich Cretaceous hyper-extended rift system that can be investigated. 2) The second example in the Swiss Alps, gives the access to supra-detachment sedimentary evolution in a sediment-starved context. 3) The last example exposed in Baja California Sur, shows supra-detachment sedimentary evolution in sediment-rich and shallow water environment. Based on these studies in three different settings, we conclude that the basins forming in the lower and upper plate position respective to detachment fault polarity develop as two different types of basins. Lower plate basins develop over top-basement detachment systems and discontinuous pieces of pre-rift strata (extensional allochthons). In this setting, the sequential development of low-angle detachment systems implies the creation of new real estate crust (new seafloor surfaces) and a complex syn-rift stratigraphic architecture. Through this domain, the deposition of syn- and post-tectonic sediments above exhumation surfaces are diachronous along stretching direction illustrating relative migration of

  3. Normal Fault Basin Geometries From Gravity Analyses in the La Paz - Los Cabos Region, Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Busch, M. M.; Coyan, J. A.; Arrowsmith, J. R.; Umhoefer, P. J.; Martinez-Gutierrez, G.

    2008-12-01

    The southern cape region of the Baja California peninsula is ruptured by an array of roughly north-striking, left-stepping active normal faults, which accommodate regional transtension. Dominant faults within this system include the Carrizal, San Juan de los Planes (SJP) (and offshore Espiritu Santo fault), La Gata, and San Jose del Cabo (SJC) faults. We conducted gravity surveys across the basins bounded by these faults to gain insight into fault slip rates and basin evolution to better understand the role of upper-crustal processes during development of an obliquely rifted plate margin. The geodetic location of each gravity observation station was measured to cm-scale accuracy with real-time kinematic GPS and the relative gravity was measured with a LaCoste and Romberg Model G gravity meter to an accuracy of 0.01 mgal. Gravity data were modeled as a 2D two-layer model with a bedrock density of 2.67 g/cm3 and a basin fill density of 2.1 or 2.2 g/cm3. The hanging wall of the east-dipping Carrizal fault hosts the La Paz basin. In the subsurface, this basin is a half-graben that is manifest as two smaller basins (few hundred meters deep) separated by a bedrock high, which likely reflects the two main east-dipping splays (Carrizal and Centenario faults). The SJP basin is a graben bound by the SJP fault on the west and the La Gata fault on the east and has a modeled maximum depth of approximately 1.5 km. This basin is marked by a series of relict normal faults dipping toward the basin center. The maximum depth to bedrock is just northwest of center, asymmetric toward the SJP fault, indicating that slip may be greater along the SJP than along the La Gata fault. It might also mark the possible location of basin inception, indicating that as the basin evolved, faulting moved outward to the presently active SJP and La Gata Faults. The SJC basin has a maximum depth of approximately 2.5 km. The favored gravity model depicts the SJC basin as resulting from slip along a series

  4. 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

    2015-12-01

    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

  5. From Subduction to Continental Breakup: Neogene and Quaternary Magmatic Evolution of Baja California Peninsula and the Adjacent Gulf of California, Mexico

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

    After the subduction stopped at ca. 12.5 Ma off Baja California Peninsula, calc-alkaline volcanic activity vanished progressively, and the Comondú volcanic arc was replaced by a post-subduction diversified volcanism which derived from at least five distinct magmatic sources located beneath the Baja California Peninsula and the Gulf of California. New field data, 40K-40Ar datings and geochemical and petrological studies of some volcanic fields and isolated volcanic centers, including San Esteban island, allow us to define the following volcanic suites from Late Miocene to Quaternary: 1) magnesian andesites, or "bajaites", 2) adakites, 3) tholeiitic basalts, 4) niobium- rich basalts (NEB), 5) calc-alkaline andesites, and 6) alkali basalts, in order of decreasing volumetric abundance. In the northern part of the Peninsula until the latitude of 29°N, where the oceanic ridge subduction has been documented, volcanism is mainly represented by magnesian andesites and alkali basalts. To the south, alkali basalts have not been reported, but, from Vizcaino peninsula to La Purísima volcanic field, we observe a close association of Late Miocene magnesian andesites, adakites, niobium-rich basalts and tholeiitic basalts. These rocks together indicate the presence of an asthenospheric window, related to the slab tear which developed within the downgoing oceanic plate. Tholeiites are considered as a product of partial melting of the lower plate asthenosphere, whereas adakites likely derive from partial melting of the edges of the slab window, and NEB and magnesian andesites from the melting of the supraslab mantle following its interaction with adakitic liquids. We propose that, after the oceanic accretion ceased off southern Baja California between 12 and 8 Ma, the slab tearing was due to the combination of the capture of the unsubducted remnant of the Magdalena plate by the Pacific plate and of the progressive sinking of the deep subducted oceanic plate. The slab tearing was

  6. 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. PMID:16583239

  7. Primary colonization and breakdown of igneous rocks by endemic, succulent elephant trees ( Pachycormus discolor) of the deserts in Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    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.

  8. 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.

  9. 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. PMID:25463869

  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. Local management of a “highly migratory species”: The effects of long-line closures and recreational catch-and-release for Baja California striped marlin fisheries

    NASA Astrophysics Data System (ADS)

    Jensen, Olaf P.; Ortega-Garcia, Sofia; Martell, Steven J. D.; Ahrens, Robert N. M.; Domeier, Michael L.; Walters, Carl J.; Kitchell, James F.

    2010-07-01

    Management of highly migratory fish species is generally assumed to require complicated international agreements. The effects of spatial closures for such species are thought to be diluted by their extensive movements. We tested these assumptions using a case study of striped marlin ( Kajikia audax) fisheries off of Baja California, Mexico. Beginning in 1977, Mexico instituted a series of long-line fishery closures and closed areas to reduce commercial fishing mortality rates on billfishes. Using data from the Japanese long-line fishery and the recreational billfish fishery in a stock reduction analysis (SRA) model, we show that temporary closures of Mexico’s EEZ to long-lining from 1977-1980 and 1984-1985 had a rapid effect on local abundance of striped marlin. Regional striped marlin abundance likely increased by 12-22% following the 4-year closure and 6-12% following the 2-year closure. Increases near Baja California may have been larger. Recreational catch-and-release appears to have a more modest effect because catches in the recreational fishery are substantially smaller than historic long-line catches. A 100% release rate over the 10-year period for which recreational catch data were available would likely have increased regional abundance by 2.8-7.5% relative to no recreational release. There is also evidence for a small effect of the El Niño Southern Oscillation (ENSO) on recruitment or net immigration, with stronger recruitment or net immigration during the cooler La Niña phase.

  12. 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

  13. [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

  14. Petrology and Sr-Nd-Pb-He isotope geochemistry of postspreading lavas on fossil spreading axes off Baja California Sur, Mexico

    NASA Astrophysics Data System (ADS)

    Tian, Liyan; Castillo, Paterno R.; Lonsdale, Peter F.; Hahm, Doshik; Hilton, David R.

    2011-02-01

    Postspreading volcanism has built large seamounts and volcanic ridges along the short axes of a highly segmented part of the East Pacific Rise crest that ceased spreading at the end of the middle Miocene, offshore Baja California Sur, Mexico. Lava samples from Rosa Seamount, the largest volcano, are predominantly alkalic basalts, mugearites, and benmoreites. This lavas series was generated through fractional crystallization and is compositionally similar to the moderately alkalic lava series in many oceanic islands. Samples from volcanic ridges at three adjacent failed spreading axes include mildly alkalic, transitional, and tholeiitic basalts and differentiated trachyandesites and andesite. The subtle but distinct petrologic and isotopic differences among the four sites may be due to differences in the degree of partial melting of a common, heterogeneous source. Postspreading lavas from these four abandoned axes off Baja California Sur together with those from other fossil spreading axes and from seamount volcanoes that grew on the East Pacific Rise flanks define a compositional continuum ranging from normal mid-ocean ridge basalt (NMORB)-like to ocean island basalt (OIB)-like. We propose that the compositional spectrum of these intraplate volcanic lavas is due to different degrees of partial melting of the compositionally heterogeneous suboceanic mantle in the eastern Pacific. A large degree of partial melting of this heterogeneous mantle during vigorous mantle upwelling at an active spreading center produces NMORB melts, whereas a lesser degree of partial melting during weak mantle upwelling following cessation of spreading produces OIB-like melts. The latter melts have a low (<8 RA) 3He/4He signature indicating their formation is different from that of OIBs from major "hot spot" volcanoes in the Pacific with high 3He/4He ratios, such as Hawaii and Galapagos.

  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. 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

  17. 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.

  18. 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.

  19. 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. PMID:19419023

  20. 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

  1. Cadmium concentration in liver and muscle of silky shark (Carcharhinus falciformis) in the tip of Baja California south, México.

    PubMed

    Terrazas-López, Rafael; Arreola-Mendoza, Laura; Galván-Magaña, Felipe; Anguiano-Zamora, Marlene; Sujitha, S B; Jonathan, M P

    2016-06-15

    Cadmium concentrations were determined in the tissues of muscle and liver of Carcharhinus falciformis (silky shark) sampled in Todos Santos, Baja California South, Mexico. This is one of the main shark species for human consumption in Mexico. Results indicate that accumulation of Cd varied in both sexes, based on its metabolism, sex, maturity and other biological characteristics. High Cd values were observed in the liver of adults of male (529.61μgg(-1)) and female (457.43μgg(-1)), whereas, in muscular tissues it was low (0.37μgg(-1)) than the prescribed permissible limits for seafood (0.5μgg(-1)). Substantial correlations were observed between body length and Cd values in adults except young male due to faster growth rate and its metabolism. The study indicated the impact of environmental conditions in the accumulation of Cd and its risk to the food web structure in the marine environment and health hazard for humans. PMID:27016957

  2. 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.

  3. Miocene tectono-stratigraphic history of La Mision basin, northwestern Baja California: implications for early tectonic development of southern California continental borderland

    SciTech Connect

    Ashby, J.R.; Minch, J.

    1988-03-01

    The middle Miocene La Mision basin in northwestern Baja California, Mexico, provides a rare opportunity to study an onshore portion of the southern California continental borderland. Stratigraphy, geometry of dispersal, and a variety of lithotypes within the volcanic and volcaniclastic sediments of the Rosarito Beach Formation provide clues to the nature of early tectonic evolution of this area during the Miocene. The elongated, trough-shaped La Mision basin formed in response to peninsular basement uplifts and the formation of volcanic highlands west of the present coastline. Lithologies and depositional environments represented within the basin sediments include: subaerial basalt flows and airfall tuffs, submarine muddy- and sandy-matrix mudflow breccias, lapilli tuffs, crystal tuffs, tuffaceous sandstones,d diatomites, and conglomerates. The environments of deposition range from fluvatile to intertidal to shallow marine. Early basin infilling is characterized by sediments and basalts, with a western source terrane, that were deposited against the faulted seacliffs. progressive infilling against the seacliff resulted in the formation of an extensive eastward-sloping basaltic platform extending eastward to the foothill coastal belt of the Peninsular Ranges. Marine transgression and subsequent regression are recorded by diverse marine volcaniclastic lithologies. Abundant fossils, K-Ar dates, and paleomagnetic data obtained from the La Mision basin allow precise correlation with other areas in the continental borderland and provide conclusive evidence that this block of the borderland was formed and in its present position by 16-14 Ma.

  4. 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 Bahi??a San Quinti??n, 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.

  5. 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.

  6. Spatio-temporal evolution of aseismic ground deformation in the Mexicali Valley (Baja California, Mexico) from 1993 to 2010, using differential SAR interferometry

    NASA Astrophysics Data System (ADS)

    Sarychikhina, O.; Glowacka, E.

    2015-11-01

    Ground deformation in Mexicali Valley, Baja California, Mexico, the southern part of the Mexicali-Imperial valley, is influenced by active tectonics and human activity, mainly that of geothermal fluid extraction in the Cerro Prieto Geothermal Field. Significant ground deformation, mainly subsidence (~ 18 cm yr-1), and related ground fissures cause severe damage to local infrastructure. The technique of Differential Synthetic Aperture Radar Interferometry (DInSAR) has been demonstrated to be a very effective remote sensing tool for accurately measuring the spatial and temporal evolution of ground displacements over broad areas. In present study ERS-1/2 SAR and ENVISAT ASAR images acquired between 1993 and 2010 were used to perform a historical analysis of aseismic ground deformation in Mexicali Valley, in an attempt to evaluate its spatio-temporal evolution and improve the understanding of its dynamic. For this purpose, the conventional 2-pass DInSAR was used to generate interferograms which were used in stacking procedure to produce maps of annual aseismic ground deformation rates for different periods. Differential interferograms that included strong co-seismic deformation signals were not included in the stacking and analysis. The changes in the ground deformation pattern and rate were identified. The main changes occur between 2000 and 2005 and include increasing deformation rate in the recharge zone and decreasing deformation rate in the western part of the CPGF production zone. We suggested that these changes are mainly caused by production development in the Cerro Prieto Geothermal Field.

  7. 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

  8. 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. PMID:23059106

  9. [Growth and mortality of the mother-of-pearl Pinctada mazatlanica in natural populations of the east coast of Baja California Sur, Mexico].

    PubMed

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

    2009-01-01

    The Mexican Pacific mother-of-pearl Pinctada mazatlanica was placed in forbidden fisheries status for the Mexican Federal Government and considered in extinction danger since 1939. This decree was modified in 1994 to allow the capture of spat for research or marine culture. We estimated the growth and mortality of mother-of-pearl from the eastern littoral of South Baja California wild stock in the periods 1992-93 and 1997-99. We used 38 sample stations at 2 bays and 6 insular complexes. The maximum length was 187.22 mm (179.83-195.81 mm, P > 0.95). Seasonal von Bertalanffy growth (ELEFAN I routine) values are: L(infinity) = 193.31 mm, k = 0.54 year(-1), t(0) = -0.1805 year, C = 0.49 and WP = 0.75. The growth performance index was Phi' = 4.305. The total mortality was calculated from a length-converted catch curve Z = 2.03 año(-1). Length-weight relationship W(i) = 0.0005418 * L(i)(2.7301). The growth parameters were similar to those for Pinctada margaritifera var. cumingi (open ocean wild stocks). The wild stock oysters differ from culture individuals at experimental repopulation conditions in Paz Bay. The total mortality is similar to that for Pinctada radiata in the Red Sea. PMID:19637688

  10. 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. PMID:11536585

  11. Intra-annual upwelling patterns and its linkage with primary production in the euphotic zone (24.5°N) of Southern Baja California coast

    NASA Astrophysics Data System (ADS)

    Cervantes-Duarte, Rafael; Prego, Ricardo; Gaxiola-Castro, Gilberto; López-López, Silverio; Aguirre-Bahena, Fernando; Murillo-Murillo, Iban

    2015-05-01

    The continental shelf of Southern Baja California has been scarcely researched south of 25°N despite it being oceanographically necessary to gain a better understanding of the north-eastern Pacific transitional zone between middle and tropical latitudes. Therefore, the intra-annual patterns of the upwelling cycle and primary production were studied in a monitoring station (24.5°N, 112.1°W; 85 m depth) from August 2008 to December 2011. Monthly, thermohaline vertical profiles were recorded and seawater sampled at 100, 33, 10, 3 and 1% irradiance depth levels. Dissolved oxygen, nutrients and chlorophyll-a concentrations and net primary production (NPP, remote sensed and in situ) were determined. Two half-yearly recurrent periods (P < 0.001) were observed: an intense (cold) period from February to July and a faint (warm) period from August to January. In the euphotic layer, nitrate concentrations were inversely related to temperature, showing their dependence on upwelling. NPP was directly related to the upwelling process, with an annual average of 1.21 ± 0.81 gC m-2 d-1 in the triennium 2009-2011. Although the influence of La-Niña event was observed during the warm period of 2010 and the cold period of 2011, this change did not significantly affect NPP (P < 0.05).

  12. 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. PMID:26692802

  13. [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. PMID:17354410

  14. 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

  15. 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.

  16. 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.

  17. 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

  18. 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.

    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

  19. 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

  20. Capillary electrophoresis finger print technique (CE-SSCP): an alternative tool for the monitoring activities of HAB species in Baja California Sur Costal.

    PubMed

    Herrera-Sepúlveda, Angélica; Hernandez-Saavedra, Norma Y; Medlin, Linda K; West, Nyree

    2013-10-01

    In Mexican waters, there is no a formal and well-established monitoring program of harmful algal blooms (HAB) events. Until now, most of the work has been focused on the characterization of organisms present in certain communities. Therefore, the development of new techniques for the rapid detection of HAB species is necessary. Capillary electrophoresis finger print technique (CE-SSCP) is a fingerprinting technique based on the identification of different conformers dependent of its base composition. This technique, coupled with capillary electrophoresis, has been used to compare and identify different conformers. The aim of this study was to determine if CE-SSCP analysis of ribosomal RNA (rRNA) gene fragments could be used for a rapid identification of toxic and harmful HAB species to improve monitoring activities along the coasts of Baja California Sur, Mexico.Three different highly variable regions of the 18S and 28S rRNA genes were chosen and their suitability for the discrimination of different dinoflagellate species was assessed by CE-SSCP.The CE-SSCP results obtained for the LSU D7 fragment has demonstrated that this technique with this gene region could be useful for the identification of the ten dinoflagellates species of different genera.We have shown that this method can be used to discriminate species and the next step will be to apply it to natural samples to achieve our goal of molecular monitoring for toxic algae in Mexican waters. This strategy will offer an option to improve an early warning system of HAB events for coastal BCS, allowing the possible implementation of mitigation strategies. A monitoring program of HAB species using molecular methods will permit the analysis of several samples in a short period of time, without the pressure of counting with a taxonomic expert in phytoplankton taxonomy. PMID:22744160

  1. [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. PMID:17354423

  2. Description of earthquake sequences using complex network theory: the cases of Italy (L'Aquila, 2009) and Southern California (Baja, 2010)

    NASA Astrophysics Data System (ADS)

    Daskalaki, E.; Papadopoulos, G. A.; Minadakis, G.; Spiliotis, K.; Siettos, C.

    2013-12-01

    Complex networks pertain to the structure of many real-world systems influencing their dynamics. Earthquakes are a highly complex natural process that develops in the space-time-size domains given that the state of the seismogenic layer of the Earth is characterized by self-organized criticality. Over the last years, complex network theory was tested as a tool to quantify the topological characteristics of seismic activity aiming to investigate possible correlation patterns between earthquakes. With the aid of complex network theory, we have analyzed foreshock and aftershock sequences associated with the mainshocks of L'Aquila (Italy), 6th April 2009, Mw=6.3, and of Baja (Southern California) 4th April 2010, Mw=7.2. After testing the catalogues for data completeness on the basis of the magnitude-frequency relationship, we selected magnitude cut-off of 1.3 and 1.0, respectively. We constructed the underlying network that describes the evolution of the two sequences in space and extracted the statistical properties of the underlying topology resulting in characteristic scale-free and small-world structures. We found that the corresponding earthquake networks form a scale-free degree distribution and we computed their basic statistical measures, such as the Average Clustering Coefficient, Mean Path Length and Entropy. Taking into account a spatio-temporal sensitivity analysis, we found that the statistical measures of the two networks change considerably before and after the two main shocks, thus underlying the space-time clustering of the sequences. Our findings are in agreement with the ones obtained by using well established classical methods of statistical seismology. Thus, we believe that the proposed approach has the potential to serve as a supplementary or stand-alone methodology towards the better assessment of seismicity clusters

  3. 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

    2016-01-01

    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. PMID:27394312

  4. 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.

  5. 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. PMID:26967136

  6. Annual patterns of nutrients and chlorophyll in a subtropical coastal lagoon under the upwelling influence (SW of Baja-California Peninsula)

    NASA Astrophysics Data System (ADS)

    Cervantes-Duarte, Rafael; Prego, Ricardo; López-López, Silverio; Aguirre-Bahena, Fernando; Ospina-Alvarez, Natalia

    2013-03-01

    The coastal lagoon of Bahía-Magdalena, located on the west coast of the Peninsula of Baja-California, is a subtropical ecosystem with an arid climate and very little freshwater input. During the 2005-2011 period the thermohaline properties varied between cold and warm half-yearly periods. They were influenced by the Transitional Water mass transported by the South California Current from February to July and by the Subtropical Surface Water from August to January. The nutrient concentrations increased (viz up to 16 μM of nitrate) from March to June, when the upwelling index was the highest. Similarly, the inter-annual variation of chlorophyll-a showed a six-monthly pattern with the highest average monthly concentrations being found in June (5 mg m-3in situ or 8 mg m-3 based on satellite information) and the lowest in December-January. A spatial zoning was also observed in the lagoon with a shallow inner zone that is warmer and richer in chlorophyll-a than the deeper closed mouth area. In the Bahía-Magdalena lagoon a spatial-temporal division into two zones and two seasons was repeated year after year with only minor differences. During the first semester in the outer zone, years 2006 and 2007 were colder and nutrient rich while 2010 was warmer, according to the upwelling conditions in the Southern California Region. Hence, among the coastal lagoons that present a prevailing marine influence, the coastal system of Bahía-Magdalena corresponds to an unusual type of subtropical coastal lagoon where the nutrient input is mainly due to upwelling phenomena.

  7. 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. PMID:21998544

  8. 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

  9. 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

  10. 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

    2015-10-01

    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 0.63g 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

  11. 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

  12. San José Island Accommodation Zone, Baja California Sur, Mexico: A Key to Onshore-Offshore Fault Relationships along the Western Margin of the Southern Gulf of California

    NASA Astrophysics Data System (ADS)

    Drake, W. R.; Umhoefer, P. J.

    2003-12-01

    The two-stage evolution of the southern Gulf of California included protogulf orthogonal rifting from ˜12 to ˜6 Ma, followed by overprinting from ˜6 to 0 Ma by the highly oblique-divergent, modern plate boundary. The San José Island accommodation zone, located ˜70 km north-northwest of La Paz, Baja California Sur, represents the transition between strike-slip partitioning to the south and the oblique-divergent structural overprinting to the north. The accommodation zone includes San José and San Francisquito islands, the San José Canal, and a 4 to 6 km wide belt along the coast of the Baja California peninsula. The accommodation zone separates the La Paz rift segment to the south from the Timbabichi rift segment to the north. The El Carrizal fault bounds the La Paz rift segment, and likely splays onshore in the southernmost accommodation zone. Kinematic data, fault mapping, and geomorphologic and bathymetric observations along the shoreline suggest the presence of en echelon, offshore faults in the San José Canal between the Baja peninsula and islands. The main faults in the southern San José Canal appear to be a series of right-stepping, east-dipping normal faults branching northward from the El Carrizal fault. Based on onshore fault trends in the northern accommodation zone, the northern Canal faults form a left-stepping link to the main bounding fault of the Timbabichi rift segment. The faults bounding the western edge of the islands are likely left-stepping, west-dipping normal faults. Steep, triangular facets and cliffs characterize the western edge of San José Island and suggest that the western island-bounding faults are active. The Pliocene basin, basin-bounding fault, and line of steep coastal cliffs on the eastern side of San José Island are likely associated with the northern end of the Espíritu Santo normal fault, which experienced a major earthquake in 1995. The basin and faults also may be the termination of a series of faults related to

  13. 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.

  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. 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

  16. 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

  17. 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

  18. Petrography of volcaniclastic rocks in intra-arc volcano-bounded to fault-bounded basins of the Rosario segment of the Lower Cretaceous Alisitos oceanic arc, Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Marsaglia, K. M.; Barone, M.; Critelli, S.; Busby, C.; Fackler-Adams, B.

    2016-05-01

    The Rosario segment of the Early Cretaceous Alisitos oceanic magmatic arc in Baja California displays a record of arc-axis sedimentation and volcanism that is well preserved in outcrops within a southern volcano-bounded and a northern fault-bounded basin that flanked an intervening subaerial edifice. This record includes volcanic and volcaniclastic rocks that range from felsic to mafic in composition. Volcaniclastic/tuffaceous sandstone samples from two previously published measured sections are mainly composed of volcanic clasts with moderate plagioclase content. Locally quartz and/or potassium feldspar are present in trace to moderate amounts. The proportions of volcanic lithic types exhibiting vitric, microlitic, lathwork, and felsitic textures are highly variable with no distinct stratigraphic trends, likely as a function of the mixed styles of eruption and magma compositions that produced pyroclasts, as well as erosion-produced epiclastic debris. The volcaniclastic fill of the basins is consistent with an oceanic arc setting, except for the relatively high felsitic volcanic lithic content, likely associated with subaerial, as opposed to the more common submarine felsic magmatism associated with arc extension in oceanic settings. There are no major differences in compositional modes of tuff and sandstone between the fault-bounded and volcano-bounded basin strata, even though they exhibit distinctly different volcaniclastic facies. This suggests that proximal arc-axis basins of varying types around a single major subaerial edifice provide a faithful record of volcanic trends in the arc segment, regardless of variation in transport and depositional processes.

  19. 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.

  20. Geochemical Relationships between Volcanic and Plutonic Upper to Mid Crustal Exposures of the Rosario Segment, Alisitos Arc (Baja California, Mexico): An Outstanding Field Analog to the Izu-Bonin-Mariana Arc

    NASA Astrophysics Data System (ADS)

    Morris, R.; DeBari, S. M.; Busby, C. J.; Medynski, S.

    2015-12-01

    Exposed paleo-arcs, such as the Rosario segment of the Cretaceous Alisitos Arc in Baja California, Mexico, provide an opportunity to explore the evolution of arc crust through time. Remarkable 3-D exposures of the Rosario segment record crustal generation processes in the volcanic rocks and underlying plutonic rocks. In this study, we explore the physical and geochemical connection between the plutonic and volcanic sections of the extensional Alisitos Arc, and elucidate differentiation processes responsible for generating them. These results provide an outstanding analog for extensional active arc systems, such as the Izu-Bonin-Mariana (IBM) Arc. Upper crustal volcanic rocks have a coherent stratigraphy that is 3-5 km thick and ranges in composition from basalt to dacite. The most felsic compositions (70.9% SiO2) are from a welded ignimbrite unit. The most mafic compositions (51.5% SiO2, 3.2% MgO) are found in basaltic sill-like units. Phenocrysts in the volcanic units include plagioclase +/- amphibole and clinopyroxene. The transition to deeper plutonic rocks is clearly an intrusive boundary, where plutonic units intrude the volcanic units. Plutonic rocks are dominantly a quartz diorite main phase with a more mafic, gabbroic margin. A transitional zone is observed along the contact between the plutonic and volcanic rocks, where volcanics have coarsely recrystallized textures. Mineral assemblages in the plutonic units include plagioclase +/- quartz, biotite, amphibole, clinopyroxene and orthopyroxene. Most, but not all, samples are low K. REE patterns are relatively flat with limited enrichment. Normalization diagrams show LILE enrichment and HFSE depletion, where trends are similar to average IBM values. We interpret plutonic and volcanic units to have similar geochemical relationships, where liquid lines of descent show the evolution of least to most evolved magma types. We provide a model for the formation and magmatic evolution of the Alisitos Arc.

  1. 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

  2. Migration of As, Hg, Pb, and Zn in arroyo sediments from a semiarid coastal system influenced by the abandoned gold mining district at El Triunfo, Baja California Sur, Mexico.

    PubMed

    Marmolejo-Rodríguez, Ana Judith; Sánchez-Martínez, Martha Alicia; Romero-Guadarrama, Juan Armando; Sánchez-González, Alberto; Magallanes-Ordóñez, Víctor René

    2011-08-01

    Extensive waste deposits (tailings) and ash from the ignition oven of the abandoned gold mine of mining district El Triunfo (MD-ET) in Baja California Sur, Mexico have released trace elements into the sediments of the Hondo-Las Gallinas-El Carrizal arroyo, which connects to the Pacific Ocean through an evaporitic basin. Migration of these elements through the arroyo is mainly caused by winds or tropical hurricanes that occur sporadically during the summer and cause the otherwise dry arroyo to overflow. To evaluate the concentration and distribution of the elements As, Hg, Pb, and Zn along the 48 km arroyo, surface sediments were collected from 26 sites, ranging from close to the MD-ET to the mouth of the arroyo at the Pacific Ocean. Concentrations in tailings and ash were for As 8890 and 505 000 mg kg(-1); for Hg 0.336 and 54.9 mg kg(-1); for Pb 92,700 and 19,300 mg kg(-1); and for Zn 49,600 and 1380 mg kg(-1). The average of the Normalized Enrichment Factor (Av-NEF) in surface sediments, calculated using background levels, indicates that the sediments are severely contaminated with As and Zn (Av-NEF = 22), Pb (Av-NEF = 24) and with a moderate contamination of Hg (Av-NEF = 7.5). The anthropogenic influence of those elements is reflected in the arroyo sediments as far as 18 km away from the MD-ET, whereas the samples closest to the discharge into the Pacific Ocean show a natural to moderate enrichment for As and Zn and low or no enrichment for Hg and Pb. A principal components analysis identified four principal components that explained 90% of the total variance. Factor 1 was characterized by a high positive contribution of the anthropogenic source elements, especially As, Pb, and Zn (37%), whereas Factor 2 was strongly correlated with the oxy-hydroxides of Fe and Mn (27%). Factor 3 was correlated with Li (16%) and Factor 4 with Al (10%), which indicates more than one source of lithogenic composition, though they played a minor role in the distribution of the

  3. 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

  4. 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. PMID:12243394

  5. Actividad de LOS Hoyos Coronales Solares de Baja Latitud

    NASA Astrophysics Data System (ADS)

    Bravo, S.; Mendoza, B.; Pirez-Enriquez, R.; Valdes-Galicia, J.

    1987-05-01

    Strong variations of the coronal holes of mid and low latitudes during the ascending and descending phase of the solar cycle have been observed by means of IPS records (the interplanetary scintillation of small diameter radio sources). This variations induce the propagation of disturbances in the interplanetary medium which produce the IPS and are also responsible of cosmic ray modulation. We suggest that the 11 years modulation is influenced by such a coronal hole behaviour.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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. PMID:22669641

  11. Subsurface geological and geophysical study of the Cerro Prieto geothermal field, Baja California, Mexico

    SciTech Connect

    Lyons, D.J.; van de Kamp, P.C.

    1980-01-01

    The subsurface investigation of the Cerro Prieto field and surrounding area is described including the stratigraphy, structure, hydrothermal alteration, and reservoir properties for use in designing reservoir simulation models and planning development of the field. Insights into the depositional, tectonic, and thermal history of the area are presented. The following types of data were used: well sample descriptions and analyses, well logs, geophysical surveys; physiography, and regional geology. (MHR)

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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. PMID:24078051

  17. 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.

  18. Structural and sedimentological study of the Cerro Prieto geothermal field, Baja California, Mexico

    SciTech Connect

    Vonder Haar, S.

    1981-06-01

    Geophysical and lithologic well logs from over fifty wells have been qualitatively and quantitatively analyzed using both manual and computer interpretation techniques. These logs were studied to make stratigraphic correlations throughout the Cerro Prieto field and to interpret the deltaic depositional environment of the field's lithologic units. Dipmeter and seismic data were of great value in making stratigraphic interpretations and extrapolations. Cross sections were constructed to illustrate lithofacies variations throughout the geothermal field. In turn, these sections were used to construct a three-dimensional model of the Cerro Prieto geothermal reservoir. Petrographic microscopy, scanning electron microscopy, and x-ray diffraction analyses of well-bore cuttings and cores were utilized to determine the degree and distribution of hydrothermal alteration by fluids at temperatures up to 350{sup 0}C, the origins of dissolution porosity, and the relative degree of fracture versus dissolution porosity. The results of these analyses were confirmed by log-derived determinations of formation fluid properties, porosity, and petrophysical properties and by studies of Cerro Prieto cores conducted under in-situ conditions. The results of this research were integrated into the Cerro Prieto reservoir model.

  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. 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.

  1. 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.

  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. 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.

  4. 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 Quinti??n 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 in 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 Quintin Bay can be used in future change detection analyses to monitor the health of seagrasses in the bay.

  5. 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.

  6. 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.

  7. Microbial Diversity and Bioremediation of aHydrocarbon-Contaminated Aquifer (Vega Baja, Puerto Rico)

    SciTech Connect

    Rodriguez-Martinez, E.M.; Perez, Ernie X.; Schadt, ChristopherW.; Zhou, Jizhong; Massol-Deya, Arturo A.

    2006-09-30

    Hydrocarbon contamination of groundwater resources hasbecome a major environmental and human health concern in many parts ofthe world. Our objectives were to employ both culture andculture-independent techniques to characterize the dynamics of microbialcommunity structure within a fluidized bed reactor used to bioremediate adiesel-contaminated groundwater in a tropical environment. Under normaloperating conditions, 97 to 99 percent of total hydrocarbons were removedwith only 14 min hydraulic retention time. Over 25 different cultureswere isolated from the treatment unit (96 percent which utilized dieselconstituents as sole carbon source). Approximately 20 percent of theisolates were also capable of complete denitrification to nitrogen gas.Sequence analysis of 16S rDNA demonstrated ample diversity with mostbelonging to the infinity, beta and gamma subdivision of theProteobacteria, Bacilli, and Actinobacteria groups. Moreover, the geneticconstitution of the microbial community was examined at multiple timepoints with a Functional Gene Array (FGA) containing over 12,000 probesfor genes involved in organic degradation and major biogeochemicalcycles. Total community DNA was extracted and amplified using anisothermal phi29 polymerase-based technique, labeled with Cy5 dye, andhybridized to the arrays in 50 percent formimide overnight at 50 degreesC. Cluster analysis revealed comparable profiles over the course oftreatment suggesting the early selection of a very stable microbialcommunity. A total of 270 genes for organic contaminant degradation(including naphthalene, toluene [aerobic and anaerobic], octane,biphenyl, pyrene, xylene, phenanthrene, and benzene); and 333 genesinvolved 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 werealso present, indicating abroad catabolic potential of the treatment unit. FGA's demonstrated theearly establishment of a diverse community with concurrent aerobic andanaerobic processes contributing to the bioremediationprocess.

  8. On the sources of PBDEs in coastal marine sediments off Baja California, Mexico.

    PubMed

    Macías-Zamora, J V; Ramírez-Álvarez, N; Hernández-Guzmán, F A; Mejía-Trejo, A

    2016-11-15

    Polybrominated diphenyl ethers (PBDEs) are widely distributed compounds in all types of matrices. In the northern portion of the Southern California Bight (SCB), there were reports of some of the largest PBDE concentrations in marine mammals and mussels. Because of this, we decided to analyze the status of PBDEs in the southern part of the SCB. An analysis of 91 samples of marine surface sediment was carried out. All of the 91 samples contained measurable amounts of PBDEs, which is a manifestation of the widespread distribution of these chemical substances. However, the levels detected are between one and two orders of magnitude smaller than those reported in southern California. Currents appear to control the distribution of PBDEs along the coast and the sedimentation sites with largest concentrations are favored by local bathymetry. Maximum concentrations were located in the middle and deeper platforms ranging from 0.02 to 5.90 (with a median 0.71) ng·g(-1) d.w. Deca-BDE mixture is largely predominant in the sediments followed by the penta-BDE mixture. The mass balance for the latitudinal strata shows the largest concentrations in the north where the largest population centers are present and with a very clear southward gradient. The mass balance calculation values showed about 36kg of PBDEs for the north, 22kg for the center, and 10kg for the south strata. In terms of depth, the PBDEs are mainly located on the middle and deep platforms rather than near point discharges, which is different than that reported by other authors. PMID:27459254

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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. PMID:26627811

  14. 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.

  15. Sedimentology of Upper Paleocene-Lower Eocene Sepultura Formation near Colonet, Baja California, Mexico

    SciTech Connect

    Miller, V.V.; Abbott, P.L.

    1988-03-01

    Upper Paleocene-lower Eocene braided-stream conglomerate of the Sepultura Formation crops out extensively within a paleovalley incised into the Cretaceous Peninsular Ranges batholith and the Alisitos Formation volcanics. The paleovalley trends just north of west as shown in 22-km long exposures within the modern San Telmo Canyon. Remnants of Sepultura fluvial-conglomerate infill reach a maximum thickness of 250 m and widths of 5-10 km. Conglomerate-clast assemblages are dominated by volcanic clasts (68-81%) along with the metamorphic (12-20%) and plutonic (2-8%) stones. The clast assemblage of andesitic and dacitic porphyries, volcaniclastics, granodiorites, aplites, and various metasediments appears to have been locally derived; all clasts are similar to the basement rocks exposed in the paleostream drainageway or just to the east of the metasedimentary belt. The Sepultura Formation contains none of the exotic, far-travelled, ultradurable rhyolitic gravels analogous to the Poway clasts that mark the time-equivalent deposits of the Mt. Soledad Formation in the San Diego area 220 km to the north. The Sepultura fluvial system supplied a gravel-rich braid delta that prograded westward over the inner shelf. Outcrops are up to 15 km wide and 23 km long, spanning braid-delta, transition-zone, and shallow-marine facies. Excellent exposures of reworked gravelly and biotite-rich sandy marine facies, some of which exhibit hummocky cross-stratification, occur in the vicinity of Punta Colonet. A late Paleocene age is indicated by the presence of turritella peninsularis. A late Paleocene age is indicated by the presence of Turritella peninsularis. A late Paleocene-early Eocene age is suggested by a sparse foraminiferal fauna (Ceratiopsos sp., Lanternosphaeridum lappaceum, Deflandrea speiosa, and Spindinium sp.).

  16. 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.

  17. 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

  18. 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.

  19. Population dynamics of Megapitaria squalida (Bivalvia: Veneridae) at Magdalena Bay, Baja California Sur, Mexico.

    PubMed

    Schweers, Tanja; Wolff, Matthias; Koch, Volker; Duarte, Francisco Sinsel

    2006-09-01

    The population dynamics of an intertidal population of Megapitaria squalida was studied from September 2002 to February 2003 in Bahia Magdalena, Mexico. To obtain information about the artisanal and recreational fishery of M. squalida, local fishermen at different parts of the bay were interviewed. Clam densities were determined at one unexploited and two exploited sites along perpendicular transects from the shore line. Average clam density was 2.01+/-1.41 ind/m2, densities did not differ significantly between the three sampling sites. The length-total mass relation was Mtot = 0.0001*SL3.1644 (r2 = 0.9804, n = 92) and the length-tissue mass relation was Mtis = 0.0002*SL2.7144 (r2 = 0.945, n = 92). Von Bertalanffy-growth parameters were determined using marked individuals. Strong interindividual and also seasonal differences in growth were observed. Average annual values were: K = 0.655, Linfinity = 83 mm. Since M. squalida can reach a shell length of more than 135 mm in deeper waters, it is necessary to consider intertidal and subtidal populations separately. Average total mortality (Z) was 1.61 y(-1). No fishing mortality was calculated because total mortality Z at the unexploited control site was higher than Z at the exploited sites. It appears that M. squalida migrates into deeper water with increasing shell length, as average shell length increased at lower tidal levels and marked specimens showed a clear migration towards deeper waters. As yet no overexploitation could be found in the study area. PMID:18491642

  20. Lung cell toxicity experimentally induced by a mixed dust from Mexicali, Baja California, Mexico

    SciTech Connect

    Osornio-Vargas, A.R.; Hernandez-Rodriguez, N.A.; Yanez-Buruel, A.G. ); Ussler, W. ); Overby, L.H.; Brody, A.R. )

    1991-10-01

    Lung disease caused by nonoccupational exposures to inorganic particles from the soil has been reported in several areas of the world. The authors tested the toxic potential of dust samples from a Mexican city (Mexicali) that is frequently affected by dust storms and is geographically related to the area of San Diego, CA, where constituents of the soil have been reported to be fibrogenic. They found that samples of Mexicali dust are a mixture of {approximately} 75% potassium aluminum silicates (illite) and {approximately} 20% silica. Respirable size particles were highly hemolytic and induced lactic dehydrogenase release from alveolar macrophages exposed in vitro. Animals instilled intratracheally with the dust developed a multifocal interstitial lung disease associated with deposits of the aluminum silicates, which were identified by x-ray microanalysis. Inhalation studies in rats demonstrated that the majority of particles were deposited preferentially at the first alveolar duct bifurcations. Twenty-four hours later, numerous particles had been ingested by alveolar macrophages that had migrated to those sites of deposition. It is proposed that alveolar macrophages are attracted to the deposited particles by complement fragments since Mexicali dust is capable of activating complement proteins from both serum and bronchoalveolar lavage. Activation resulted in alveolar macrophage chemotaxis.

  1. 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.

  2. 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

  3. New Technologies and Learning Environments: A Perspective from Formal and Non-Formal Education in Baja California, Mexico

    ERIC Educational Resources Information Center

    Zamora, Julieta Lopez; Reynaga, Francisco Javier Arriaga

    2010-01-01

    This paper presents results of two research works, the first approaches non-formal education and the second addresses formal education. In both studies in-depth interview techniques were used. There were some points of convergence between them on aspects such as the implementation of learning environments and the integration of ICT. The interview…

  4. Interaction of Extreme Halophilic Archaea With the Evaporites of the Solar Salterns Guerrero Negro Baja California, Mexico

    NASA Astrophysics Data System (ADS)

    Tamez, P.; Lopez-Cortés, A.

    2008-12-01

    Hypersaline environments have been significant reservoirs for the long-term evolution of specifically adapted microorganisms. Characterized to have higher salt concentrations (up to 35 g/L), they are worldwide distributed and have a commercial significance. Exportadora de Sal, Guerrero Negro, Mexico has a multipond salterns system designed to harvest common salt (NaCl) from sea water. To achieve this purpose, sea water is pumped through a set of shallow ponds where water evaporates and salts concentrate. Sequential precipitation of CaCO3, CaSO4 2H2O and NaCl occurs in a mineral formations call it evaporites. In the interior of those gypsum-encrusted and halite-encrusted minerals, communities of extremely salt-loving archaea prosper. Previous studies have showed the influence of Haloarchaeal cells in the formation of larger fluid inclusions than crystals formed in sterile salt solutions. S-layer envelopes and cells of Haloarcula strain SP8807 contributed to the nucleation of new crystals of NaCl. Given the significance of the scope in phylogenetic archaeal diversity research, this study had a polyphasic approach. SEM micrographs from a 21- 31% (w/v) gradient salt multipond system evaporites, gave an insight profile of the extreme halophilic archaeal communities thriving in the surface of the gypsum and halite evaporites. Halite crystals were form after 21 days of incubation in solid medium with archaeal cells. Both culture and non-culture dependent methods, Nested-PCR-DGGE analysis and sequencing of 16S rDNA amplified fragment genes from environmental samples and isolated strains were used for this purpose. We isolate three strains from Pond 9 (21.07% total salt concentration) and one strain from Cristallizer 20 (25.15% total salt concentration). 16S rDNA signaling gave 99% of similarity with Halogeometricum borinquense, sequence AF002984, two other strains were 99% of similarity with Halobacterium salinarum, sequence AJ496185 these strains shown different colony morphology. Other strain match, with 99% of similarity, with three sequences Haloarcula: Haloarcula japonica (EF645686), Haloarcula hispanica (DQ089681) and Haloarcula marismortui (X61689), differences among them were only 3 base pairs. We suggest that strain, C205030908, could correspond to Haloarcula californiae previously reported by Javor et al, (1982), from which there is not sequence known. Nested-PCR-DGGE analysis showed a pattern of 11 bands, meaning the archaeal community is more complex than we could detect by culture approach.

  5. Biosignatures in modern sulfates: texture, composition and depositional environments of gypsum deposits at Guerrero Negro, Baja, Mexico

    NASA Astrophysics Data System (ADS)

    Vogel, M. B.; Des Marais, D. J.; Jahnke, L. L.; Turk, K.; Kubo, M.

    2007-12-01

    Gypsum (CaSO4·H2O) is an important phase in biogeochemistry and sedimentology as a mineral sink for sulfur, a paleoclimatic indicator, and an endolithic niche for phototrophic and chemotrophic bacteria. Sulfate deposits are also important targets of exploration for evidence of habitable environments and life on Mars. Gypsum deposits from a range of sedimentary environments at the Guerrero Negro crystallizer ponds and sabkha settings were investigated for microscale structure and composition to differentiate fabrics formed under microbial influence from those formed under abiogenic conditions. Sub-sedimentary gypsum forms in sabkha environments as mm to cm scale selenite discs (termed bird beak gypsum; Warren, 2006) and selenite disc aggregates. Selenite discs and other sub-sedimentary gypsum are characterized by a sinuous axial microtexture and poikilitically enclosed detrital particles. Sub-aqueous gypsum forms as cements, granules (termed gypsooids), and massive botryoidal crusts that line the sediment water interface and margins of managed crystallizer ponds and natural anchialine pools. Sub-aqueous gypsum exhibits a wide range of textures and mineral/biofilm associations that include amorphous to euhedral, tabular, needle and lensoidal morphologies. Elemental sulfur forms rinds on prismatic, growth aligned gypsum twins and reticulate magnesian carbonate is interspersed with both twinned crystals and rosette aggregates in stratified sub-aqueous environments. Intracrystalline biofilms and cell material was observed in association with nearly all sub-aqueous morphologies but only scarce evidence has been found for intercrystalline microbial communities. Columnar microbial communities living in anchialine pools were found to host precipitation of mm scale gypsum granules in their EPS matrix. Fine scale gypsum textures are unlikely to persist through diagenetic alteration, but understanding their primary associations with sulfur and carbonates is necessary for interpreting sulfates or their replacement phases in the ancient record.

  6. Triggered Fault Slip in Southern California Associated with the 2010 Sierra El Mayor-Cucapah, Baja California, Mexico, Earthquake

    NASA Astrophysics Data System (ADS)

    Rymer, M. J.; Treiman, J. A.; Kendrick, K. J.; Lienkaemper, J. J.; Wei, M.; Weldon, R. J.; Bilham, R. G.; Fielding, E. J.

    2010-12-01

    Surface fracturing (triggered slip) occurred in the central Salton Trough and to the southwest, in the Yuha Desert area—all in association with the 4 April 2010 (M7.2) El Mayor-Cucapah earthquake and its aftershocks. Triggered slip in the central Salton Trough occurred on the ‘frequent movers’: the southern San Andreas, Coyote Creek, Superstition Hills, and Imperial Faults, all of which have slipped in previous moderate to large, local and regional earthquakes in the past five decades. Other faults in the central Salton Trough that also slipped in 2010 include the Wienert Fault (southeastern section of the Superstition Hills Fault), the Kalin Fault (in the Brawley Seismic Zone), and the Brawley Fault Zone; triggered slip had not been reported on these faults in the past. Geologic measures of slip on faults in the central Salton Trough ranged from 1 to 18 mm, and everywhere was located where previous primary (tectonic) or triggered slip has occurred. Triggered slip in the Yuha Desert area occurred along at least two dozen faults, only some of which were known before the 4 April 2010 El Mayor-Cucapah earthquake. From east to northwest, slip occurred in seven general areas; 1) in the Northern Centinela Fault Zone (newly named), 2) along unnamed faults south of Pinto Wash, 3) along the Yuha Fault (newly named), 4) along both east and west branches of the Laguna Salada Fault, 5) along the Yuha Well Fault Zone (newly revised name), 6) along the Ocotillo Fault (newly named), and 7) along the southeastern-most section of the Elsinore Fault. Faults that slipped in the Yuha Desert area include northwest-trending right-lateral faults, northeast-trending left-lateral faults, and north-south faults, some of which had dominantly vertical slip. Triggered slip along the Ocotillo and Elsinore Faults occurred only in association with the 14 June 2010 (M5.7) aftershock, which also initiated slip along other faults near the town of Ocotillo. Triggered slip on faults in the Yuha Desert area was most commonly less than 20 mm, but two significant exceptions are slip of about 50-60 mm on the Yuha Fault and of about 80 mm on the Ocotillo Fault. All triggered slips in the Yuha Desert area occurred along pre-existing faults, whether previously recognized or not.

  7. General characteristics of the diet of Trachinotus paitensis (Teleostei: Carangidae) from San Ignacio Lagoon, Baja California Sur, Mexico.

    PubMed

    Cruz Escalona, V H; Abitia Cárdenas, L A

    2004-03-01

    The food habits of Trachinotus paitensis, in San Ignacio Lagoon B.C.S., Mexico, were investigated. We observed that T. paitensis is carnivorous, feeding mainly on benthic invertebrates (the gastropods Anachis spp., Bittium spp., and the crustacean larvae). We concluded that T. paitensis is an opportunist predator that impacts mainly on epibenthic invertebrates. PMID:17357410

  8. Effects of upwelling, tides and biological processes on the inorganic carbon system of a coastal lagoon in Baja California

    NASA Astrophysics Data System (ADS)

    Ribas-Ribas, M.; Hernández-Ayón, J. M.; Camacho-Ibar, V. F.; Cabello-Pasini, A.; Mejia-Trejo, A.; Durazo, R.; Galindo-Bect, S.; Souza, A. J.; Forja, J. M.; Siqueiros-Valencia, A.

    2011-12-01

    The role of coastal lagoons and estuaries as sources or sinks of inorganic carbon in upwelling areas has not been fully understood. During the months of May-July, 2005, we studied the dissolved inorganic carbon system in a coastal lagoon of northwestern Mexico during the strongest period of upwelling events. Along the bay, different scenarios were observed for the distributions of pH, dissolved inorganic carbon (DIC) and apparent oxygen utilization (AOU) as a result of different combinations of upwelling intensity and tidal amplitude. DIC concentrations in the outer part of the bay were controlled by mixing processes. At the inner part of the bay DIC was as low as 1800 μmol kg -1, most likely due to high water residence times and seagrass CO 2 uptake. It is estimated that 85% of San Quintín Bay, at the oceanic end, acted as a source of CO 2 to the atmosphere due to the inflow of CO 2-rich upwelled waters from the neighboring ocean with high positive fluxes higher than 30 mmol C m -2 d -1. In contrast, there was a net uptake of CO 2 and HCO 3- by the seagrass bed Zostera marina in the inner part of the bay, so the pCO 2 in this zone was below the equilibrium value and slightly negative CO 2 fluxes of -6 mmol C m -2 d -1. Our positive NEP and ΔDIC values indicate that Bahía San Quintín was a net autotrophic system during the upwelling season during 2005.

  9. A legacy of change: The lower Colorado River, Arizona-California-Nevada, USA, and Sonora-Baja California Norte, Mexico

    USGS Publications Warehouse

    Mueller, G.A.; Marsh, P.C.; Minckley, W.L.

    2005-01-01

    The lower Colorado is among the most regulated rivers in the world. It ranks as the fifth largest river in volume in the coterminous United States, but its flow is fully allocated and no longer reaches the sea. Lower basin reservoirs flood nearly one third of the river channel and store 2 years of annual flow. Diverted water irrigates 1.5 million ha of cropland and provides water for industry and domestic use by 22 million people in the southwestern United States and northern Mexico. The native fish community of the lower Colorado River was among the most unique in the world, and the main stem was home to nine freshwater species, all of which were endemic to the basin. Today, five are extirpated, seven are federally endangered, and three are being reintroduced through stocking. Decline of the native fauna is attributed to predation by nonnative fishes and physical habitat degradation. Nearly 80 alien species have been introduced, and more than 20 now are common. These nonnative species thrived in modified habitats, where they largely eliminated the native kinds. As a result, the lower Colorado River has the dubious distinction of being among the few major rivers of the world with an entirely introduced fish fauna. ?? 2005 by the American Fisheries Society.

  10. Risk Factors for Intimate Partner Violence in a Migrant Farmworker Community in Baja California, México.

    PubMed

    Lopez, Marcella J; Mintle, Rachel A; Smith, Sylvia; Garcia, Alicia; Torres, Vanessa N; Keough, Allie; Salgado, Hugo

    2015-12-01

    Intimate partner violence (IPV) is one of the most common forms of violence against women worldwide. Among Mexican women, it is estimated that 15 to 71% have experienced physical or sexual abuse by an intimate male partner in their lifetime. This study examined the prevalence of four leading risk factors associated with IPV (alcohol consumption, education, socioeconomic status (SES), and gender roles) in adult women (n = 68) in a migrant farmworker community in México. Alcohol consumption among women was higher than the national average, and partner consumption was lower. Education level and SES were low, and women identified with a feminist ideology more than a traditional gender role. Results also revealed that 86.4% (n = 57) of participants identified violence against women as a common problem in the community, and the majority (94.0%, n = 62) of participants believe that IPV specifically is a problem within the community. PMID:24519259

  11. The hydrogeochemistry of a heavily used aquifer in the Mexican wine-producing Guadalupe Valley, Baja California

    NASA Astrophysics Data System (ADS)

    Daesslé, L. W.; Mendoza-Espinosa, L. G.; Camacho-Ibar, V. F.; Rozier, W.; Morton, O.; van Dorst, L.; Lugo-Ibarra, K. C.; Quintanilla-Montoya, A. L.; Rodríguez-Pinal, A.

    2006-10-01

    The Guadalupe Valley aquifer is the only water source for one of the most important wine industries in Mexico, and also the main public water supply for the nearby city of Ensenada. This groundwater is monitored for major ion, N-NO3, P-PO4, Fe, As, Se, Mo, Cd, Cu, Pb, Zn and Sb concentrations, as well as TDS, pH, dissolved oxygen and temperature. High concentrations of N-NO3 (26 mg l-1), Se (70 μg l-1), Mo (18 μg l-1) and Cu (4.3 μg l-1) suggest that groundwater is being polluted by the use of fertilizers only in the western section of the aquifer, known as El Porvenir graben. Unlike the sites located near the main recharge area to the East of the aquifer, the water in El Porvenir graben has low tritium concentrations (<1.9 TU), indicating a pre-modern age, and thus longer water residence time. No significant variations in water quality (generally <10%) were detected throughout 2001-2002 in the aquifer, suggesting that reduced rainfall and recharge during this dry period did not significantly affect water quality. However, the wells nearest to the main recharge area in the Eastern aquifer show a slight but constant increase in TDS with time, probably as a result of the high (˜200 L S-1) uninterrupted extraction of water at this specific recharge site. Relatively high As concentrations for the aquifer (10.5 μg l-1) are only found near the northern limit of the basin associated with a geological fault.

  12. Comparative functional ultrastructure of two hypersaline submerged cyanobacterial mats - Guerrero Negro, Baja California Sur, Mexico, and Solar Lake, Sinai, Egypt

    NASA Technical Reports Server (NTRS)

    D'Amelio, Elisa D'antoni; Des Marais, David J.; Cohen, Jehuda

    1989-01-01

    The ultrastructure of the submerged microbial mat from the Solar Lake (SL), Egypt, was compared to that of samples from the Guerrero Negro (GN), Mexico, salt pans. The locations and distributions of the main organisms were determined light microscopy, and the corresponding ultrathin sections were examined under TEM; chemical microprofile analyses were carried out on the day of sampling for microscopic studies. Both communities were found to be dominated by Microleus chthonoplastes, although several morphological species found in the GN mat were absent from the SL mat, including the Tropica nigra and the 'big' Microleus chthonoplastes component. The chemical microprofiles of oxygen, sulfide, pH, and the oxygenic photosynthesis in the two mats were virtually identical. In both mats, the photic zone was restricted to the upper 800 microns of the mat, and oxygenic photosynthesis was detected down to 600 microns.

  13. Triggered surface slips in southern California associated with the 2010 El Mayor-Cucapah, Baja California, Mexico, earthquake

    USGS Publications Warehouse

    Rymer, Michael J.; Treiman, Jerome A.; Kendrick, Katherine J.; Lienkaemper, James J.; Weldon, Ray J.; Bilham, Roger; Wei, Meng; Fielding, Eric J.; Hernandez, Janis L.; Olson, Brian P.E.; Irvine, Pamela J.; Knepprath, Nichole; Sickler, Robert R.; Tong, Xiaopeng; Siem, Martin E.

    2011-01-01

    Triggered slip in the Yuha Desert area occurred along more than two dozen faults, only some of which were recognized before the April 4, 2010, El Mayor-Cucapah earthquake. From east to northwest, slip occurred in seven general areas: (1) in the Northern Centinela Fault Zone (newly named), (2) along unnamed faults south of Pinto Wash, (3) along the Yuha Fault (newly named), (4) along both east and west branches of the Laguna Salada Fault, (5) along the Yuha Well Fault Zone (newly revised name) and related faults between it and the Yuha Fault, (6) along the Ocotillo Fault (newly named) and related faults to the north and south, and (7) along the southeasternmost section of the Elsinore Fault. Faults that slipped in the Yuha Desert area include northwest-trending right-lateral faults, northeast-trending left-lateral faults, and north-south faults, some of which had dominantly vertical offset. Triggered slip along the Ocotillo and Elsinore Faults appears to have occurred only in association with the June 14, 2010 (Mw5.7), aftershock. This aftershock also resulted in slip along other faults near the town of Ocotillo. Triggered offset on faults in the Yuha Desert area was mostly less than 20 mm, with three significant exceptions, including slip of about 50–60 mm on the Yuha Fault, 40 mm on a fault south of Pinto Wash, and about 85 mm on the Ocotillo Fault. All triggered slips in the Yuha Desert area occurred along preexisting faults, whether previously recognized or not.

  14. Structural Geometry of a Sector of the Colorado River Delta, Baja California, Mexico, Based on Seismic Reflections

    NASA Astrophysics Data System (ADS)

    Chanes-Martínez, J. Juan; González-Escobar, Mario; Suárez-Vidal, Francisco; Gallardo-Mata, Clemente G.

    2014-07-01

    A structural study in the SW section of the Colorado River delta using seismic reflection data is presented. The study area is located along the Cerro Prieto transform fault, which extends from the northern Gulf of California through the Mexicali Valley and is an active fault within the Pacific-North American plate boundary zone. The research was supported by a database of five seismic profiles with a total length of 215 km, collected in the early 80's by Petróleos Mexicanos. The results show a high density of faults, most of which are buried by sediments. Within the Cerro Prieto fault zone, several faults were identified, such as: Palmas, Mesa, and Pangas Viejas, until now unknown. In addition, even though the Indiviso fault was investigated and superficially identify prior to this work, herein mapped at depth. West of the Cerro Prieto fault zone lies the Las Tinajas basin, bound by the Dunas and Saldaña faults and by the Montague basin to the southeast. The deformation zone along the plate boundary is 18-km-wide, stretching from the Cerro Prieto fault in the east to the Pangas Viejas fault in the west. The orientations of the faults are NW-SE, and if projected from the southern side of the Sierra Cucapah southward, the faults tend to join the Cerro Prieto fault. In the Las Tinajas basin, the acoustic basement is deeper than 5,000 m. Some of the largest vertical displacements generated by the 2010 7.2-Mw El Mayor-Cucapah earthquake occurred southeast of the epicenter and coincided with the location of the Pangas Viejas Fault, which is buried by sediments. Before this event, seismic activity was very low, and no structures were known in the area. In this paper, we demonstrate that there are at least seven major faults that may now pose a high seismic hazard.

  15. Hydrothermal-flow regime and magmatic heat source of the Cerro Prieto geothermal system, Baja California, Mexico

    SciTech Connect

    Elders, W.A.; Bird, D.K.; Williams, A.E.; Schiffman, P.

    1982-01-01

    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 fifty 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 shows that 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 of about 6 m/year through the pores of a typical cross section of the reservoir having an average porosity of 10%. Although this is an extensional tectonic environment of leaky transform faulting in which repeated intrusions of basalt magma are likely, for simplicity of computation possible heat sources were modelled as simple two dimensional basalt intrusions of various sizes, shapes and locations. We have calculated a series of two-dimensional convective heat transfer models, with different heat sources and permeability distributions. The models which produce the best fit for the temperature distributions observed in the field today have in common a heat source which is a funnel-shaped basalt intrusion, 4 km wide at the top, emplaced at a depth of 5 km to 6 km about 40,000 to 50,000 years ago.

  16. Paleo-environmental interpretation of Paleocene Sepultura Formation in type locality, Mesa La sepultura, Baja California, Mexico

    SciTech Connect

    Arzate-Hernandez, L.; Tellezduarte, M.

    1988-03-01

    The Sepultura Formation in its type locality consists of two major lithostratigraphic units. The basal A unit overlies the Cretaceous Rosario Formation. It consists predominantly of fine-grained, poorly consolidated sandstones; some conglomerates; and thin beds of well-consolidated lenticular fossiliferous sandstones, which show some cyclic sedimentation. The poorly consolidated sandstones contain glauconitic layers; abundant shark teeth, benthic forams, and ostracods; and sparse mollusks, brachiopods, and Ophiomorpha-like trace fossils. These faunas indicate deposition in nearshore shallow waters. The interbedded consolidated lenticular sandstones probably indicate storm-induced deposition below wave base. This mechanism is assumed to be responsible for the high concentration of fossils consisting predominantly of unworn molluscan shells, scaphopods, echinoid spines, corals, and forams. In places, the elongated shells of Turritella pachecoensis show a preferential orientation to the southwest. At the top of the unit, a poorly fossiliferous red conglomerate indicates deltaic conditions. Overlying the conglomerate is unit B which shows a change in the sedimentary environment. It consists of a calcareous shallowing upward sequence of nodular to massive algal limestone with caliche at top. The microfossils of this unit show glauconitization in places, and consist, in addition to algal fragments, of forams, microscopic mollusks, and some ostracods and calcispherules from shallow waters (less than 30 m deep).

  17. Geogenic metal mobility in a coastal inlet impacted by cannery discharge, Magdalena Bay, Baja California Sur, Mexico.

    PubMed

    O'Shea, Beth; Capistrano, Christian; Lee, William

    2016-08-15

    Magdalena Bay is an important habitat for marine organisms, some of which have been the subject of metal bioaccumulation studies. Cannery waste is discharged into the bay providing a plausible source of contamination but this study finds that some metals occur geogenically. Bay sediments and rocks (n=59) were analyzed for total metals and clustered (HCA) into two distinct groups with PCA indicating concentrations of Cr, Cu, Mn, and Ni influenced samples near ophiolite outcrops, which reported some metal concentrations exceeding averages in the crust by an order of magnitude (up to 4450ppm Cr and 1269ppm Ni). Metals at the cannery are rarely elevated above crustal averages except Zn (max. 160ppm), however, acid-extracted Zn was below recommended sediment quality guidelines in contrast to 80% of ophiolitic samples reporting Ni extractability exceeding such guidelines. This study raises awareness of geogenic metals when considering sources of contamination in marine environments. PMID:27251444

  18. Efectos difusivos en la formación de enanas blancas de Helio de baja masa en sistemas binarios cerrados

    NASA Astrophysics Data System (ADS)

    De Vito, M. A.; Benvenuto, O. G.

    In the last years, and thanks to advances in observational techniques, many astronomers have discovered in a great number of binary radio-pulsars the presence of a helium white dwarf resulting from a previous evolutionary state in which the progenitor of this star experienced one or more episodes of mass transfer to the compact component in the pair. That is the case for PSR B1855+09 (van Kerkwijk, M. H., Bell, J. F, Kaspi, V. M., & Kulkarni, S. R. 2000, ApJ 530, L37), where the mass for the white dwarf is known accurately from measurements of the Shapiro delay of the pulsar signal, MWD = 0.258+0.028-0.016 M⊙; for PSR J02018 + 4232 (Bassa, C. G., van Kerkwijk, M. H., & Kulkarni, S. R. 2003, A&A, 403, 1067), the spectra confirm that the companion is a helium-core white dwarf of ≈ 0.2 M⊙. On the other hand, there are several authors (Ferraro, F., Possenti, A., Sabbi, E., & D'Amico, N. 2003, ApJ, 596, L211; Bassa et al. 2003) that have identified the optical binary companion to the BMSP PSR J1911 - 5958A, located in the halo of the Galactic globular cluster NGC 6752, like a blue star whose position in the color-magnitude diagram is consistent with the cooling sequence of a low-mass, ≈ 0.17 - 0.20 M⊙, low metallicity helium white dwarf at the cluster distance. Finally, the color and magnitude of the stellar companion for B 1620-26 indicate that is a white dwarf of 0.34 ± 0.04 M⊙ (Sigurdson, S., Richer, H. B., Hansen, B. M., Stairs, I. H. & Thorset, S. E. 2003, Science, 301, 193S). This has motivated us to study the formation of low mass helium white dwarfs in the context of binary evolution. For that purpose, using the code of binary evolution, entirely developed in the Facultad de Ciencias Astronómicas y Geofísicas of the Universidad Nacional de La Plata, Argentina, we have investigated the effects of diffusive processes on the evolution of a star member of a close binary system. A similar study was performed for Althaus, L. G., Serenelli, A. M., & Benvenuto, O. G. (2001, MNRAS, 323, 471) but in that paper the mass transfer was mimicked by subtracting mass to a progenitor of 1 M⊙ to obtain the mass for the desired object. Actually, our binary code has a full nuclear reactions network for hydrogen and helium burning that allowed us to follow the abundances of fifteen isotopes throughout the entire evolution of the star. We have also included a detailed equation of state. The mass loss treatment is non conservative. We have modified the conditions for the beginning and end of mass transfer episodes. In our previous version, we assumed it to occur when the stellar radius was greater or smaller, respectively, that the Roche Lobe radius for the star. This introduced numerical problems, especially at the end of mass transfer phases. We adopted H. Ritter (1988, A&A, 202, 93) formulation that considers a finite scale height in the stellar atmosphere. The numerical behaviour in much more satisfactory, besides that it constitutes a more appropriate description for the physical problem. We perform the calculations for the evolution of the primary star in a close binary system of initial mass 2 M⊙, initial period of 1 day, initial mass ratio of 1.4142 and solar metallicity. We have done the calculations in four cases: A) with diffusion and all Roche Lobe overflows, B) with diffusion and only the first Roche Lobe overflow, C) without diffusion and all Roche Lobe overflows, D) without diffusion and only the first Roche Lobe overflow. Cases B) and D) where performed to compare with results obtained for Althaus et al. (2001). The main conclusion of this work is that the age of these objects is mainly determined by diffusive effects, and the late stages of mass transfer, not considered in Althaus et al. (2001), constituted a minor effect on the scales of cooling times.

  19. [Relationship of food groups intake and C-reactive protein in healthy adults from Mexicali, Baja California, México].

    PubMed

    Ruiz-Esparza, Josefina; Robinson-Navarro, Octavio; Ortega-Vélez, María Isabel; Diaz-Molina, Raúl; Carrillo-Cedillo, Eugenia Gabriela; Soria-Rodriguez, Carmen G

    2013-09-01

    The high sensitivity C-reactive protein (hs-CRP) is an important biomarker in inflammatory processes. The objective was to analyze the relationship between the concentrations of hs-CRP in adults from a northern Mexico region with their typical food intake patterns. A sample of 72 university professors underwent clinical and anthropometric assessments and their hs-CRP levels were quantified with an immunoenzymometric assay. Additionally, they filled out a food intake frequency questionnaire, from which the servings of different food groups were obtained with the ESHA software. The average age of participants was 49.75 +/- 10.05 years and the average hs-CRP concentration was 1.66 (0.97, 3.52) mg/L. The value of the association between fruit consumption and hs-CRP level was protective, according to the logistic regression analysis, being the Odds Ratio (OR) 0.23 (95% CI: 0.05, 1.03); while for vegetables the OR was 0.66 (95% CI: 0.12, 3.68). Furthermore, high protein content foods, dairy products, oils and fats were associated with elevated levels of hs-CRP. In conclusion, in our study, the intake of some food groups like fruits and vegetables, and to a lesser extent cereals, were associated with low values of hs-PCR. PMID:24354239

  20. Hydrothermal alteration of sediments associated with surface emissions from the Cerro Prieto geothermal field, Baja, California, Mexico

    SciTech Connect

    Valette-Silver, J.N.; Esquer-Patino, I.; Elders, W.A.; Collier, P.C.; Hoagland, J.R.

    1981-01-01

    Surface emissions from the Cerro Prieto geothermal reservoir are restricted to a 100 km/sup 2/ area on the western side of the field, near the volcano Cerro Prieto and the lake Laguna Vulcano. Some 57 surface emissions, explored in 1979, were classified into hot springs, mud pots, pools, fumaroles and geysers (Valette and Esquer-Patino, 1979). A study of the mineralogical changes associated with these hydrothermal vents was initiated with the aim of developing possible exploration tools for geothermal resources. The Cerro Prieto reservoir has already been explored by extensive deep drilling so that relationships between surface manifestations and deeper hydrothermal processes could be established directly. Approximately 120 samples of surface sediments were collected both inside and outside of the vents. The mineralogy of the altered sediments studied appears to be controlled by the type of emission. A comparison between the changes in mineralogy due to low temperature hydrothermal activity in the reservoir, seen in samples from boreholes, and mineralogical changes in the surface emission samples shows similar general trends below 180/sup 0/C: increase of quartz, feldspar and illite, with subsequent disappearance of kaolinite, montmorillonite, calcite and dolomite. These mineral assemblages seem to be characteristics of the discharge from high intensity geothermal fields.

  1. 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.

  2. Polymorphic microsatellite loci for the sand pocket mouse Chaetodipus arenarius, an endemic from the Baja California Peninsula

    USGS Publications Warehouse

    Munguia-Vega, A.; Rodriguez-Estrella, R.; Nachman, M.; Culver, M.

    2009-01-01

    Fifteen polymorphic microsatellite loci were isolated from an enriched genomic library of the sand pocket mouse Chaetodipus arenarius. The mean number of alleles per locus was 11.53 (range five to 19) and the average observed heterozygosity was 0.764 (range 0.121 to 1.0). The markers will be used for detecting the impact of human-induced habitat fragmentation on patterns of gene flow, genetic structure, and extinction risk. In addition, these markers will be useful across the genus because most of the loci cross-amplified and were polymorphic in three other species of Chaetodipus. ?? 2008 The Authors.

  3. Water flowing north of the border: export agriculture and water politics in a rural community in Baja California.

    PubMed

    Zlolniski, Christian

    2011-01-01

    Favored by neoliberal agrarian policies, the production of fresh crops for international markets has become a common strategy for economic development in Mexico and other Latin American countries. But as some scholars have argued, the global fresh produce industry in developing countries in which fresh crops are produced for consumer markets in affluent nations implies “virtual water flows,” the transfer of high volumes of water embedded in these crops across international borders. This article examines the local effects of the production of fresh produce in the San Quintín Valley in northwestern Mexico for markets in the United States. Although export agriculture has fostered economic growth and employment opportunities for indigenous farm laborers, it has also led to the overexploitation of underground finite water resources, and an alarming decline of the quantity and quality of water available for residents’ domestic use. I discuss how neoliberal water policies have further contributed to water inequalities along class and ethnic lines, the hardships settlers endure to secure access to water for their basic needs, and the political protests and social tensions water scarcity has triggered in the region. Although the production of fresh crops for international markets is promoted by organizations such as the World Bank and Inter-American Development Bank as a model for economic development, I argue that it often produces water insecurity for the poorest, threatening the UN goal of ensuring access to clean water as a universal human right. PMID:22171411

  4. Trace Elements in the Marine Sediments of the La Paz Lagoon, Baja California Peninsula, Mexico: Pollution Status in 2013.

    PubMed

    Pérez-Tribouillier, Habacuc; Shumilin, Evgueni; Rodríguez-Figueroa, Griselda Margarita

    2015-07-01

    To determine the actual concentrations of trace elements in surface sediments from the La Paz Lagoon, as well as their associations and possible origins, 91 sediment samples were analyzed for more than 50 elements using a combination of ICP-MS and ICP-AES. The results of a principal component analysis are used to distinguish four associative groups within the elements. Natural enrichment of As, Cd and U occurs due to the supply of weathered phosphorites from the El Cien formation located to the north-west of the lagoon. Sediment quality indices for potentially toxic trace elements do not show any probable impact on the biota of the lagoon. Only the concentrations of As in 30 % of the stations and Cu in 20 % of them exceed related effect range low levels. The highest concentration of Pb (36.8 mg kg(-1)) was measured in the sediments near the City of La Paz. PMID:25773702

  5. Microfaunal evidence of age and depositional environments of the Cerro Prieto section (Plio-Pleistocene), Baja California, Mexico

    SciTech Connect

    Ingle, J.C. Jr.

    1982-01-01

    Microfossils including benthic and planktic foraminifera, ostracodes, calcareous algae, fish skeletal material, and fragments of pelecypods were found in 14 core samples from depths of 185 to 1952 m in the Cerro Prieto geothermal field, providing evidence of both the age and depositional history of sediments comprising the 3000-m-thick Pliocene and Pleistocene section in this area. Ostracodes of brackish water and marine origin constitute the most common microfossils present in this sequence occurring in 8 samples; in situ littoral and neritic species of benthic foraminifera occur in 5 samples with planktic species present in 2 samples. Distributional patterns of ostracodes and foraminifera together with previously analyzed lithofacies (Lyons and van de Kamp, 1980) indicate that the Cerro Prieto section represents an intertonguing complex of alluvial, deltaic, estuarine, and shallow marine environments deposited along the front of the Colorado River delta as it prograded across the Salton Trough during Pliocene and Pleistocene time. Foraminiferal evidence indicates that a sand and shale unit commonly present at depths between 700 and 1100 m represents a significant mid-Pleistocene marine incursion in the Cerro Prieto area. Tentative correlation of the Cerro Prieto section with the well dated Palm Springs Formation of the Imperial Valley, California area suggests that the Pliocene/Pleistocene boundary occurs at a depth of approximately 2000 m in the area of well M-93. Reworked specimens of Cretaceous foraminifera and fragments of the Cretaceous pelecypod Inoceramus were found in five samples further substantiating the Colorado Plateau provenance of a significant portion of the Colorado River deltaic sediments in the Cerro Prieto area.

  6. Actividad solar del ciclo 23. Predicción del máximo y fase decreciente utilizando redes neuronales

    NASA Astrophysics Data System (ADS)

    Parodi, M. A.; Ceccatto, H. A.; Piacentini, R. D.; García, P. J.

    Different methods have been proposed in order to predict the maximum amplitude of solar cycles, either as a consequence of the intrinsic importance of this event and because of its relation with solar storms and possible effects upon satellites, communication systems, etc. In this work, a neural network solar activity prediction is presented, measured through the sunspot number (SSN). The 16-units neural network, with a 12:3:1 architecture, was trained in a ``feed-forward" propagation way and learning by the so called ``back propagation rule". The annual mean SSN data in the 1700-1975 and 1987-1998 periods were used as the training set. The solar cycle 21 (1976-1986) was taken as the cross-validation data set. After performing the network training we obtained a prediction of the maximum annual mean for the current solar cycle 23, SSNmax= 135 ±17 at the year 2000, which is 13% smaller than the International Consensus Commitee's mean maximum prediction obtained through ``precursor techniques". On the other hand, our prediction is only about 4% smaller than the Consensus's neural network mean prediction. A ``multiple step" prediction technique was also performed and SSN annual mean predicted values for the near-maximum (from the present year 1999 to beyond the maximum) and the declining activity of solar cycle 23 are presented in this work. The sensibility of predictions is also tested. To do so, we changed the interval width and comparated our results with those of a previous neural network prediction and those of others authors using differents methods.

  7. Estudio numerico y experimental del proceso de soldeo MIG sobre la aleacion 6063--T5 utilizando el metodo de Taguchi

    NASA Astrophysics Data System (ADS)

    Meseguer Valdenebro, Jose Luis

    Electric arc welding processes represent one of the most used techniques on manufacturing processes of mechanical components in modern industry. The electric arc welding processes have been adapted to current needs, becoming a flexible and versatile way to manufacture. Numerical results in the welding process are validated experimentally. The main numerical methods most commonly used today are three: finite difference method, finite element method and finite volume method. The most widely used numerical method for the modeling of welded joints is the finite element method because it is well adapted to the geometric and boundary conditions in addition to the fact that there is a variety of commercial programs which use the finite element method as a calculation basis. The content of this thesis shows an experimental study of a welded joint conducted by means of the MIG welding process of aluminum alloy 6063-T5. The numerical process is validated experimentally by applying the method of finite element through the calculation program ANSYS. The experimental results in this paper are the cooling curves, the critical cooling time t4/3, the weld bead geometry, the microhardness obtained in the welded joint, and the metal heat affected zone base, process dilution, critical areas intersected between the cooling curves and the curve TTP. The numerical results obtained in this thesis are: the thermal cycle curves, which represent both the heating to maximum temperature and subsequent cooling. The critical cooling time t4/3 and thermal efficiency of the process are calculated and the bead geometry obtained experimentally is represented. The heat affected zone is obtained by differentiating the zones that are found at different temperatures, the critical areas intersected between the cooling curves and the TTP curve. In order to conclude this doctoral thesis, an optimization has been conducted by means of the Taguchi method for welding parameters in order to obtain an improvement on mechanical properties in aluminum metal joint. Los procesos de soldadura por arco electrico representan unas de las tecnicas mas utilizadas en los procesos de fabricacion de componentes mecanicos en la industria moderna. Los procesos de soldeo por arco se han adaptado a las necesidades actuales, haciendose un modo de fabricacion flexible y versatil. Los resultados obtenidos numericamente en el proceso de soldadura son validados experimentalmente. Los principales metodos numericos mas empleados en la actualidad son tres, metodo por diferencias finitas, metodos por elementos finitos y metodo por volumenes finitos. El metodo numerico mas empleado para el modelado de uniones soldadas, es el metodo por elementos finitos, debido a que presenta una buena adaptacion a las condiciones geometricas y de contorno ademas de que existe una diversidad de programas comerciales que utilizan el metodo por elementos finitos como base de calculo. Este trabajo de investigacion presenta un estudio experimental de una union soldada mediante el proceso MIG de la aleacion de aluminio 6063-T5. El metodo numerico se valida experimentalmente aplicando el metodo de los elementos finitos con el programa de calculo ANSYS. Los resultados experimentales obtenidos son: las curvas de enfriamiento, el tiempo critico de enfriamiento t4/3, geometria del cordon, microdurezas obtenidas en la union soldada, zona afectada termicamente y metal base, dilucion del proceso, areas criticas intersecadas entre las curvas de enfriamiento y la curva TTP. Los resultados numericos son: las curvas del ciclo termico, que representan tanto el calentamiento hasta alcanzar la temperatura maxima y un posterior enfriamiento. Se calculan el tiempo critico de enfriamiento t4/3, el rendimiento termico y se representa la geometria del cordon obtenida experimentalmente. La zona afectada termicamente se obtiene diferenciando las zonas que se encuentran a diferentes temperaturas, las areas criticas intersecadas entre las curvas de enfriamiento y la curva TTP. Para finalizar el trabajo de investigacion se ha realizado un

  8. Estudio numerico y experimental del proceso de soldeo MIG sobre la aleacion 6063--T5 utilizando el metodo de Taguchi

    NASA Astrophysics Data System (ADS)

    Meseguer Valdenebro, Jose Luis

    Electric arc welding processes represent one of the most used techniques on manufacturing processes of mechanical components in modern industry. The electric arc welding processes have been adapted to current needs, becoming a flexible and versatile way to manufacture. Numerical results in the welding process are validated experimentally. The main numerical methods most commonly used today are three: finite difference method, finite element method and finite volume method. The most widely used numerical method for the modeling of welded joints is the finite element method because it is well adapted to the geometric and boundary conditions in addition to the fact that there is a variety of commercial programs which use the finite element method as a calculation basis. The content of this thesis shows an experimental study of a welded joint conducted by means of the MIG welding process of aluminum alloy 6063-T5. The numerical process is validated experimentally by applying the method of finite element through the calculation program ANSYS. The experimental results in this paper are the cooling curves, the critical cooling time t4/3, the weld bead geometry, the microhardness obtained in the welded joint, and the metal heat affected zone base, process dilution, critical areas intersected between the cooling curves and the curve TTP. The numerical results obtained in this thesis are: the thermal cycle curves, which represent both the heating to maximum temperature and subsequent cooling. The critical cooling time t4/3 and thermal efficiency of the process are calculated and the bead geometry obtained experimentally is represented. The heat affected zone is obtained by differentiating the zones that are found at different temperatures, the critical areas intersected between the cooling curves and the TTP curve. In order to conclude this doctoral thesis, an optimization has been conducted by means of the Taguchi method for welding parameters in order to obtain an improvement on mechanical properties in aluminum metal joint. Los procesos de soldadura por arco electrico representan unas de las tecnicas mas utilizadas en los procesos de fabricacion de componentes mecanicos en la industria moderna. Los procesos de soldeo por arco se han adaptado a las necesidades actuales, haciendose un modo de fabricacion flexible y versatil. Los resultados obtenidos numericamente en el proceso de soldadura son validados experimentalmente. Los principales metodos numericos mas empleados en la actualidad son tres, metodo por diferencias finitas, metodos por elementos finitos y metodo por volumenes finitos. El metodo numerico mas empleado para el modelado de uniones soldadas, es el metodo por elementos finitos, debido a que presenta una buena adaptacion a las condiciones geometricas y de contorno ademas de que existe una diversidad de programas comerciales que utilizan el metodo por elementos finitos como base de calculo. Este trabajo de investigacion presenta un estudio experimental de una union soldada mediante el proceso MIG de la aleacion de aluminio 6063-T5. El metodo numerico se valida experimentalmente aplicando el metodo de los elementos finitos con el programa de calculo ANSYS. Los resultados experimentales obtenidos son: las curvas de enfriamiento, el tiempo critico de enfriamiento t4/3, geometria del cordon, microdurezas obtenidas en la union soldada, zona afectada termicamente y metal base, dilucion del proceso, areas criticas intersecadas entre las curvas de enfriamiento y la curva TTP. Los resultados numericos son: las curvas del ciclo termico, que representan tanto el calentamiento hasta alcanzar la temperatura maxima y un posterior enfriamiento. Se calculan el tiempo critico de enfriamiento t4/3, el rendimiento termico y se representa la geometria del cordon obtenida experimentalmente. La zona afectada termicamente se obtiene diferenciando las zonas que se encuentran a diferentes temperaturas, las areas criticas intersecadas entre las curvas de enfriamiento y la curva TTP. Para finalizar el trabajo de investigacion se ha realizado una optimizacion, con la aplicacion del metodo de Taguchi, de los parametros de soldeo con el objetivo de obtener una mejora sustancial en las propiedades mecanicas de las uniones metalicas de aluminio.

  9. [Habitat use patterns of the Black Brant Branta bernicla nigricans (Anseriformes: Anatidae) in natural and artificial areas of Guerrero Negro, Baja California Sur, Mexico].

    PubMed

    Cedillo, Israel Martínez; Carmona, Roberto; Ward, David H; Danemann, Gustavo D

    2013-06-01

    The Black Brant is a common inhabitant of the Western Artic American tundra, which migrates to Southern Pacific coasts during the winter season. Approximately, 31000 birds (31%) constitute the Mexican population of Brants at Guerrero Negro, Ojo de Liebre, and Exportadora de Sal lagoon complex; nevertheless, there is little information about the distribution patterns and zone usage. At Guerrero Negro Lagoon (GNL), Ojo de Liebre Lagoon (OLL, both natural sites), and at Exportadora de Sal (ESSA, artificial site) we determined by monthly censuses (from November 2006 to April 2007, 08:00-16:00h) and observed: (1) season and site effects on population structure (age groups), and (2) the tide level relationship with the abundance and proportion of feeding birds. Within a total of 150 observation hours and 98 birds, our results showed a general 0.68 proportion of adults, that was higher in winter than in spring. The statistics analysis showed no effects by site on the proportion of feeding birds, but we observed a temporal decrease at ESSA and at GNL. In contrast the proportion of feeding birds at OLL was constant. We observed an increase in the juveniles between winter and spring. This increase is related with the differential migration, which mentions that the juveniles are the last to leave the wintering area. In winter the relations of the tide level with the abundance of Brant were: direct at ESSA, inverse at OLL and no relation found at GNL. In spring, no relation was observed in the sites. The proportion of Brants feeding at OLL (the site with the higher abundance) was independent of the tide level. This is related with two possible behaviors of the geese: (1) they can move through the lagoon and take advantage of the tidal lag, which is up to four hours; and (2) they can modify their feeding strategies, more on floating eelgrass (Zostera marina). PMID:23885600

  10. Trace metal enrichments in nearshore sediments and accumulation in mussels (Modiolus capax) along the eastern coast of Baja California, Mexico: environmental status in 1995.

    PubMed

    Muñoz-Barbosa, Albino; Huerta-Diaz, Miguel Angel

    2013-12-15

    The biogeochemistry of trace metals in nearshore sediments and mussel was studied at 15 stations along a 1000 km long transect paralleling the west coast of the Gulf of California (GOC). Total trace metal (Me) and enrichment factor (EF(Me)) values in sediments were low due to negligible anthropogenic influence in the region. Past copper mining, however, near Santa Rosalia caused concentrations of Pb, Mn, Co, Zn and Cu which were 10-3.3×10(3) times greater than the average for the rest of the transect. Mussels also showed relatively high trace metal concentrations at the Santa Rosalia stations, but the variability in the spatial distribution was low and had undefined trends. Our results show that, with the exception of Co and Cu, the contamination caused by the copper mine affected sediments to a greater extent than mussels. PMID:24237993

  11. Organic S13C values vary slightly with salinity in microbial mats at Guerrero Negro, Baja California Sur, Mexico: Implications for stromatolite S13C values

    NASA Technical Reports Server (NTRS)

    Desmarais, D. J.; Peterson, E.; Kwong, E.; Bui, H.

    1986-01-01

    Stromatolites, layered sedimentary rock structures produced by communities of microorganisms, constitute the most abundant early evidence of life on Earth. Microbial mats, which are found most frequently in hypersaline marine or hot spring environments, serve as useful modern analogs of stromatolitic communities. Biochemical studies of mats were conducted to assist in the interpretations of stromatolites. The data suggest that salinity effects are insufficient by themselves to cause the C-13 differences observed betwwen Precambrain stromatolites and modern microbial mats.

  12. Development of a human-specific B. thetaiotaomicron IMS/ATP assay for measuring viable human contamination in surface waters in Baja California, Mexico

    EPA Science Inventory

    Immunomagnetic separation/adenosine triphosphate (IMS/ATP) assays utilize paramagnetic beads and target-specific antibodies to isolate target organisms. Following isolation, adenosine tri-phosphate (ATP) is extracted from the target population and quantified. An inversely-couple...

  13. Nuclear and mtDNA lineage diversity in wild and cultured Pacific lion-paw scallop, Nodipecten subnodosus (Baja California Peninsula, Mexico).

    PubMed

    Petersen, Jessica L; Ibarra, Ana Maria; May, Bernie

    2010-01-01

    Pacific lion-paw scallops were collected from natural aggregations in Laguna Ojo de Liebre (Pacific Ocean), the Gulf of California, and from aquaculture facilities for genetic diversity analyses. Mitochondrial DNA sequencing uncovered two highly supported clades separated by 2.5% divergence. Data from ten microsatellite markers suggest individuals from these mitogroups are introgressed, raising questions about the mitotype origin. Some evidence suggests gene flow between La Paz and Ojo de Liebre; otherwise the Gulf of California and Ojo de Liebre are acting as two distinct populations. It is unclear whether translocations between sites have influenced the observed genetic structure or whether gene flow has been facilitated by past geologic events. Finally, scallops spawned for aquaculture are unique from the wild and have significantly less diversity. These results warrant the attention of managers and producers who should work to monitor and conserve genetic diversity in both wild and aquaculture populations. PMID:24391254

  14. A Stepped Wedge, Cluster-Randomized Trial of a Household UV-Disinfection and Safe Storage Drinking Water Intervention in Rural Baja California Sur, Mexico

    PubMed Central

    Gruber, Joshua S.; Reygadas, Fermin; Arnold, Benjamin F.; Ray, Isha; Nelson, Kara; Colford, John M.

    2013-01-01

    In collaboration with a local non-profit organization, this study evaluated the expansion of a program that promoted and installed Mesita Azul, an ultraviolet-disinfection system designed to treat household drinking water in rural Mexico. We conducted a 15-month, cluster-randomized stepped wedge trial by randomizing the order in which 24 communities (444 households) received the intervention. We measured primary outcomes (water contamination and diarrhea) during seven household visits. The intervention increased the percentage of households with access to treated and safely stored drinking water (23–62%), and reduced the percentage of households with Escherichia coli contaminated drinking water (risk difference (RD): −19% [95% CI: −27%, −14%]). No significant reduction in diarrhea was observed (RD: −0.1% [95% CI: −1.1%, 0.9%]). We conclude that household water quality improvements measured in this study justify future promotion of the Mesita Azul, and that future studies to measure its health impact would be valuable if conducted in populations with higher diarrhea prevalence. PMID:23732255

  15. Land subsidence in the Cerro Prieto Geothermal Field, 1 Baja California, Mexico, from 1994 to 2005. An integrated analysis of DInSAR, levelingand geological data.

    SciTech Connect

    Sarychikhina, O; Glowacka, E; Mellors, R; Vidal, F S

    2011-03-03

    Cerro Prieto is the oldest and largest Mexican geothermal field in operation and has been producing electricity since 1973. The large amount of geothermal fluids extracted to supply steam to the power plants has resulted in considerable deformation in and around the field. The deformation includes land subsidence and related ground fissuring and faulting. These phenomena have produced severe damages to infrastructure such as roads, irrigation canals and other facilities. In this paper, the technique of Differential Synthetic Aperture Radar Interferometry (DInSAR) is applied using C-band ENVISAR ASAR data acquired between 2003 and 2006 to determine the extent and amount of land subsidence in the Mexicali Valley near Cerro Prieto Geothermal Field. The DInSAR results were compared with published data from precise leveling surveys (1994- 1997 and 1997-2006) and detailed geological information in order to improve the understanding of temporal and spatial distributions of anthropogenic subsidence in the Mexicali Valley. The leveling and DInSAR data were modeled to characterize the observed deformation in terms of fluid extraction. The results confirm that the tectonic faults control the spatial extent of the observed subsidence. These faults likely act as groundwater flow barriers for aquifers and reservoirs. The shape of the subsiding area coincides with the Cerro Prieto pull-apart basin. In addition, the spatial pattern of the subsidence as well as changes in rate are highly correlated with the development of the Cerro Prieto Geothermal Field.

  16. Fluctuations in Anoxia and the Depth of the Eastern Equatorial Pacific Thermocline Inferred from a 2000 Year Sediment Record of Water-Column Denitrification Off Baja California.

    NASA Astrophysics Data System (ADS)

    van Geen, A.; Mey, J. L., IV; Thunell, R.; Berelson, W.; Deutsch, C. A.

    2014-12-01

    High-resolution records of sediment 15N at three sites along the western margin of North America were recently shown to indicate a gradual weakening of water-column denitrification and therefore anoxia from 1860 to 1990 followed by two decades of intensifying denitrification and anoxia (Deutsch et al., Science August 8, 2014). An ocean general circulation model driven by wind and buoyancy fluxes reproduces these variations for the last 50 years and mechanistically links them to changes in the depth of the thermocline in the eastern Pacific. The data-model comparison shows that strong denitrification and anoxia are associated with a shallow thermocline in the eastern equatorial Pacific and vice-versa. We present here a longer record of sediment 15N from one of the previously studied sites, Soledad basin, indicating that the period of particularly weak denitrification and anoxia in the eastern Pacific reached in the early 1990s was unprecedented for the past 2000 years. This supports the notion that a concomitant deepening of the thermocline during the 20th century simulated by Intergovernmental Panel on Climate Change models may have been driven by the anthropogenic buildup of greenhouse gases. At the other end of the spectrum, the extended sediment 15N record indicates a period of particularly strong denitrification and anoxia extending from about 800 to 1200 AD. This coincides with the Medieval Warm Period of prolonged droughts indicated by tree-ring studies in the American West as well as reduced runoff recorded off coastal Peru. The particularly shallow thermocline inferred from the Soledad basin 15N record for this interval is consistent with the prolonged La Nina-like conditions in the equatorial Pacific that have been proposed to explain the Medieval droughts.

  17. Geochemistry of Lower Cretaceous limestones of the Alisitos Formation, Baja California, México: Implications for REE source and paleo-redox conditions

    NASA Astrophysics Data System (ADS)

    Madhavaraju, J.; Löser, Hannes; Lee, Yong Il; Santacruz, R. Lozano; Pi-Puig, T.

    2016-03-01

    Measurement of the major and trace elements were carried out on the Lower Cretaceous limestones interbedded in the volcano-sedimentary Alisitos Formation, northwestern México to understand the source of rare earth elements (REEs) and paleo-redox conditions. The five limestone beds (from the base up, Unit 5 to Unit 9) of the Alisitos Formation show large variations in SiO2 content (0.9-27.9%). A low concentration of CaO is observed in Unit 6 and Unit 8, and high content of CaO is observed in Unit 5, Unit 7 and Unit 9. The limestones are depleted in many trace elements with respect to Post-Archaean Australian Shale (PAAS), whereas Sr shows slight enrichment when compared to PAAS. The concentrations of ΣREE are higher in Unit 6 and Unit 8 (37.4 ± 7.5; 46.6 ± 19.4; respectively) than Unit5, Unit7, and Unit 9 (9.1 ± 3.2; 11.3 ± 9.4; 4.2 ± 2.5; respectively). The limestones of the Alisitos Formation show a non-seawater-like REE + Y pattern with positive Eu anomalies relative to PAAS (0.95-2.47). Variations in ΣREE, Al2O3, Zr, Sc, REE + Y patterns, and Y/Ho ratios are influenced mainly by the amount of terrigenous materials. The variations in the Eu/Eu*, La/Sc and La/Co suggest that the terrigenous materials included in the lower four limestone beds (from Unit 5, Unit 6, Unit 7 and Unit 8) were likely contributed by intermediate to felsic rocks whereas terrigenous materials from Unit 9 were derived from mafic to intermediate source rocks. The slightly negative to slightly positive Ce anomalies in the studied limestones resulted from variations in the bottom water oxygenation. This was also corroborated by V/Cr and Ni/Co ratios suggesting that the depositional environments experienced large fluctuations in oxygenation conditions ranging from oxic to anoxic conditions during the deposition of limestones of the Alisitos Formation.

  18. High resolution sup 40 Ar/ sup 39 Ar chronostratigraphy of the Late Cretaceous El Gallo Formation, Baja California del Norte, Mexico

    SciTech Connect

    Fulford, M.M.; Busby-Spera, C. ); Renne, P.R.

    1991-03-01

    Laser probe {sup 40}Ar/{sup 39}Ar analyses of individual sanidine grains from four tuffs in the alluvial Late Cretaceous (Campanian) El Gallo Formation yield statistically distinct mean dates ranging from 74.87 {plus minus} 0.05 Ma to 73.59 {plus minus} 0.09 Ma. The exceptional precision of these dates permits calculation of statistically significant sediment accumulation rates that are much higher than passive sediment loading would cause, implying rapid tectonically induced subsidence. The dates bracket tightly the age of important dinosaur and mammalian faunas previously reported from the El Gallo Formation. The dates support an age less than 73 Ma for the Campanian/Maastrichtian stage boundary, younger than indicated by several currently used time scales. Further application of the single grain {sup 40}Ar/{sup 39}Ar technique may be expected to greatly benefit stratigraphic studies of Mesozoic sedimentary basins and contribute to calibration of biostratigraphic and magnetostratigraphic time scales.

  19. Oxidative stress indicators and chemical contaminants in East Pacific green turtles (Chelonia mydas) inhabiting two foraging coastal lagoons in the Baja California peninsula.

    PubMed

    Labrada-Martagón, Vanessa; Rodríguez, Paola A Tenorio; Méndez-Rodríguez, Lia C; Zenteno-Savín, Tania

    2011-08-01

    In order to determine the potential effects of contaminants in juveniles of East Pacific green turtle, Chelonia mydas, captured alive, circulating trace metal and organochlorine pesticide concentrations were correlated with body condition, antioxidant enzyme activities and lipid peroxidation levels. Turtles were sampled in Punta Abreojos (PAO) and Bahía Magdalena (BMA). Turtles from PAO showed higher silicon and cadmium concentrations, but lower α-hexachlorocyclohexane, γ-hexachlorocyclohexane, hexachlorobenzene and aldrin concentrations than individuals from BMA. In BMA cadmium concentration decreased as the standard carapace length of the turtles increased. In PAO concentrations of α-hexachlorocyclohexane, heptachlor and hexachlorobenzene were positively correlated with the weight of the individuals. Lipid peroxidation levels were positively correlated with cadmium concentrations. In turtles captured in PAO, enzymatic antioxidant activities correlated mostly with pesticide concentrations, while in individuals from BMA enzyme activities were correlated with trace element concentrations. Correlations between antioxidant enzyme activities and concentration of xenobiotics suggest physiological sensitivity of East Pacific green turtles to chemicals. Regional differences found could be influenced by habitat conditions such as currents, upwellings (PAO) and agricultural activities (BMA). We suggest that, combined, circulating contaminant concentrations, lipid peroxidation levels and antioxidant enzyme activities in sea turtles could be used as biomarkers of the habitat conditions. PMID:21377544

  20. Future groundwater extraction scenarios for an aquifer in a semiarid environment: case study of Guadalupe Valley Aquifer, Baja California, Northwest Mexico.

    PubMed

    Campos-Gaytan, Jose Ruben; Kretzschmar, Thomas; Herrera-Oliva, Claudia Soledad

    2014-11-01

    Semiarid northwestern Mexico presents a growing water demand produced by agricultural and domestic requirements during the last two decades. The community of Guadalupe Valley and the city of Ensenada rely on groundwater pumping from the local aquifer as its sole source of water supply. This dependency has resulted in an imbalance between groundwater pumpage and natural recharge. A two-dimensional groundwater flow model was applied to the Guadalupe Valley Aquifer, which was calibrated and validated for the period 1984-2005. The model analysis verified that groundwater levels in the region are subject to steep declines due to decades of intensive groundwater exploitation for agricultural and domestic purposes. The calibrated model was used to assess the effects of different water management scenarios for the period 2007-2025. If the base case (status quo) scenario continues, groundwater levels are in a continuous drawdown trend. Some wells would run dry by August 2017, and water demand may not be met without incurring in an overdraft. The optimistic scenario implies the achievement of the mean groundwater recharge and discharge. Groundwater level depletion could be stopped and restored. The sustainable scenario implies the reduction of current extraction (up to about 50 %), when groundwater level depletion could be stopped. A reduction in current extraction mitigates water stress in the aquifer but cannot solely reverse declining water tables across the region. The combination of reduced current extraction and an implemented alternative solution (such as groundwater artificial recharge), provides the most effective measure to stabilize and reverse declining groundwater levels while meeting water demands in the region. PMID:25086715

  1. Geology, Geochemistry and Re-Os systematics of manganese deposits from the Santa Rosalía Basin and adjacent areas in Baja California Sur, México

    NASA Astrophysics Data System (ADS)

    Del Rio Salas, R.; Ruiz, J.; Ochoa-Landín, L.; Noriega, O.; Barra, F.; Meza-Figueroa, D.; Paz-Moreno, F.

    2008-06-01

    The manganese ores in the Santa Rosalía region, western Mexico, are mainly stratiform horizons or mantos, constrained to the initial stages of sedimentary cycles of the Miocene Boléo Formation. The manganese mineralization is generally restricted to isolated paleo-basins and related to NW-SE faults formed during the early stages of the opening of the Gulf of California. Jasper, Fe, and Mn oxides associated to the NW-SE structures may represent feeder zones for the mineralized system. The manganese oxide minerals include pyrolusite, cryptomelane, todorokite, hollandite, jacobsite, and pyrochroite. Trace elements in the manganese ores indicate a hydrothermal origin for the deposits of the Santa Rosalía area. Rare earth elements (REE) patterns obtained for manganese minerals from the Lucifer and El Gavilán deposits also support a hydrothermal origin, whereas the middle REE enrichment observed in samples from the Boléo district indicates mixing between hydrothermal and hydrogenous sources. Osmium and rhenium concentrations of the manganese minerals range between 33-173 ppt and 0.14-89 ppb, respectively. The initial 187Os/188Os ratios in the manganese oxides from Lucifer and the Boléo district range between 0.43 to 0.51 and 0.70 to 0.74, respectively. These ratios are different from seawater at 7 Ma (0.84-0.89), which suggests important contributions of osmium from underlying rocks such as the Miocene volcanic rocks and the Cretaceous quartz-monzonite basement. Field evidence, manganese oxide mineralogy coupled with major and trace element geochemistry and Re-Os systematics support a hydrothermal origin for the manganese deposits from the Santa Rosalía region. The ore deposition style indicates an exhalative-intraformational environment restricted to isolated basins in a diagenetic stage related to the initial evolution of the Gulf of California.

  2. 75 FR 30110 - Unblocking of Specially Designated National and Blocked Persons Pursuant to the Foreign Narcotics...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-28

    ..., Mexico; Calle Geiser 101, Colonia Colinas de Agua Caliente, Tijuana, Baja California, Mexico; Avenida... Agua Caliente, Tijuana, Baja California, Mexico; Calle Coronado 21760, Colonia Mesetas del...

  3. Gas geochemistry of a shallow submarine hydrothermal vent associated with the El Requesón fault zone, Bahía Concepción, Baja California Sur, México

    USGS Publications Warehouse

    Forrest, Matthew J.; Ledesma-Vazquez, Jorge; Ussler, William, III; Kulongoski, Justin T.; Hilton, David R.; Greene, H. Gary

    2005-01-01

    We investigated hydrothermal gas venting associated with a coastal fault zone along the western margin of Bahía Concepción, B.C.S., México. Copious discharge of geothermal liquid (≈ 90 °C) and gas is occurring in the intertidal and shallow subtidal zones (to a depth of 13 m) through soft sediments and fractures in rocks along a ∼750 m linear trend generally sub-parallel to an onshore fault near Punta Santa Barbara. Hydrothermal activity shows negative correlation with tidal height; temperatures in the area of hydrothermal activity were up to 11.3 °C higher at low tide than at high tide (measured tidal range ≈ 120 cm). Gas samples were collected using SCUBA and analyzed for chemical composition and stable isotope values. The main components of the gas are N2 (≈ 53%; 534 mmol/mol), CO2 (≈ 43%; 435 mmol/mol), and CH4 (≈ 2.2%; 22 mmol/mol). The δ13C values of the CH4 (mean = − 34.3‰), and the ratios of CH4 to C2H6(mean = 89), indicate that the gas is thermogenic in origin. The carbon stable isotopes and the δ15N of the N2 in the gas (mean = 1.7‰) suggest it may be partially derived from the thermal alteration of algal material in immature sedimentary organic matter. The He isotope ratios (3He / 4He = 1.32 RA) indicate a significant mantle component (16.3%) in the gas. Here, we suggest the name El Requesón fault zone for the faults that likely formed as a result of extension in the region during the late Miocene, and are currently serving as conduits for the observed hydrothermal activity.

  4. 77 FR 71480 - Additional Designations, Foreign Narcotics Kingpin Designation Act

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-30

    .... CARDONA MARTINEZ, Mayela (a.k.a. CARDONA DE IBARRA, Mayela), Calle Lago de La Doga 5312, Tijuana, Baja... (Mexico) (individual) . 2. CARDONA MARTINEZ, Pedro, Calle Lago La Doga 5301, Tijuana, Baja...

  5. 77 FR 14594 - Additions to the Identifying Information for an Individual Previously Designated Pursuant to the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-12

    ..., Planta Baja, Colonia Lomas Country Club, Huixquilucan, Estado de Mexico C.P. 52779, Mexico; Camino del..., No. 80 A, Planta Baja, Colonia Lomas Country Club, Huixquilucan, Estado de Mexico C.P. 52779,...

  6. 76 FR 59483 - Additional Designations, Foreign Narcotics Kingpin Designation Act

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-26

    ...; Camino del Remanso, No. 80 A, Planta Baja, Colonia Lomas Country Club, Huixquilucan, Estado de Mexico C.P..., Estado de Mexico C.P. 52779, Mexico; Camino del Remanso, No. 80 A, Planta Baja, Colonia Lomas...

  7. 2. Skewed view of E elevation of sugar mill looking ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Skewed view of E elevation of sugar mill looking NW. - Hacienda Azurarera Santa Elena, Sugar Mill Ruins, 1.44 miles North of PR Route 2 Bridge Over Rio De La Plata, Toa Baja, Toa Baja Municipio, PR

  8. Studies on California ants: a review of the genus Temnothorax (Hymenoptera, Formicidae)

    PubMed Central

    Snelling, Roy R.; Borowiec, Marek L.; Prebus, Matthew M.

    2014-01-01

    Abstract The following ten new species of the ant genus Temnothorax are described and illustrated: T. anaphalantus (California, Baja California), T. arboreus (California), T. caguatan (Oregon, California, Baja California), T. morongo (California, Baja California), T. myrmiciformis (California, Baja California), T. nuwuvi (Nevada), T. paiute (California, Nevada), T. pseudandrei (Arizona, California), T. quasimodo (California) and T. wardi (California). A key to workers of the twenty-two Temnothorax species known or expected to occur in California is provided. PMID:24493957

  9. 78 FR 8702 - Unblocking of Specially Designated Nationals and Blocked Persons Pursuant to the Foreign...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-06

    .... Na. 21741, Colonia Infonavit Presidentes, Tijuana, Baja California CP 22576, Mexico; c/o CASA DE... de Tijuana, Tijuana, Baja California CP 22300, Mexico; c/o CASA DE EMPENO RIO TIJUANA, S.A. DE C.V..., Baja California CP 22800, Mexico; c/o CASA DE EMPENO RIO TIJUANA, S.A. DE C.V., Tijuana,...

  10. Observação do abrilhantamento de limbo solar e de estruturas filamentares em 48 ghz utilizando a técnica de regularização adaptativa

    NASA Astrophysics Data System (ADS)

    Machado, W. R. S.; Mascarenhas, N.; Costa, J. E. R.; Silva, A. V. R.

    2003-08-01

    O radiotelescópio do Itapetinga tem sido utilizado em campanhas de observações de explosões solares gerando um grande número de mapas diários em 48 GHz como sub-produto destas observações. A resolução espacial do telescópio de 14m do Itapetinga nesta freqüência é de aproximadamente dois minutos de arco. Estruturas de interesse para análise da atmosfera solar quiescente tais como os filamentos e o anel de abrilhantamento do limbo são de dimensão angular moderada da ordem ou ligeiramente menores que a resolução do telescópio. É conhecido que a convolução da função de espalhamento do telescópio, PSF (padrão de ganho do feixe) borra as estruturas de dimensão angular abaixo do HPBW (largura a meia potência do feixe) e portanto é comum a busca por técnicas de restauração que eliminem pelo menos em parte este borramento. Estudamos a restauração destas radioimagens usando a técnica de regularização adaptativa e os resultados ressaltam estas estruturas espaciais de pequeno contraste. O algoritmo da regularização adaptativa faz uso de k imagens, chamadas protótipos, obtidas através da variação de parâmetros de um filtro de regularização. Para controle da qualidade da restauração utilizamos uma imagem de alta resolução espacial obtida na linha H-a e a PSF do Itapetinga para borrá-la. Pequenos desvios, entre a PSF utilizada para o borramento e a PSF utilizada na restauração, produziram alguns desvios notáveis na imagem restaurada porém a adição de ruído nas simulações de restauração foram mais influentes no cálculo da rugosidade da imagem e portanto mais limitante para a restauração. Apresentamos como nosso primeiro resultado uma imagem em 48 GHz com a presença clara do abrilhantamento de limbo que não estava evidente na imagem original e traços de estruturas filamentares, porém ainda sem grande evidência.

  11. 48. Detail of top of wall in S room showing ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    48. Detail of top of wall in S room showing strap-iron beam tie-back anchored in wall with severely deteriorated beam in place. - Hacienda Azurarera Santa Elena, Sugar Mill Ruins, 1.44 miles North of PR Route 2 Bridge Over Rio De La Plata, Toa Baja, Toa Baja Municipio, PR

  12. Espectroscopía de Microondas en Jets Supersónicos

    NASA Astrophysics Data System (ADS)

    Alonso, J. L.; López, J. C.; Lesarri, A.; Blanco, S.; Sanz, M. E.; Mata, S.; Cocinero, J. E.; Sánchez, R.

    Complejos con Enlace de Hidrógeno. El entorno de bajas temperaturas de una expansión supersónica es un excelente laboratorio para estudiar el comportamiento conformacional de los complejos con enlace de hidrógeno. Nuestro grupo ha observado por vez primera enlaces de hidrógeno axial y ecuatorial en los complejos de tetrahidropirano, sulfuro de pentametileno y sulfuro de trimetileno con HCl y HF [1-6] generados en las expansiones adiabáticas en He, Ne o Ar y caracterizados por espectroscopía de microondas con transformadas de Fouier. Existe controversia a la hora de considerar a las interacciones C-H\\cdotsO como enlaces de hidrógeno o como simples interacciones de van der Waals. Las interacciones C-H\\cdotsO han sido estudiadas en el dímero del dimetil eter generado en la expansión supersónica y caracterizado por espectroscopía de microondas [7]. Estas interacciones se han analizado en los complejos formados entre los alcanos sustituidos del trifluorometano y difluorometano con oxirano [8] caracterizándose la existencia de interacciones C-F\\cdotsH-C que contribuyen a la estabilización de estos complejos. Ablación Láser: Estructura de Aminoácidos. Los aminoácidos poseen puntos de fusión elevados (>200oC) y se presentan en fases condensadas como formas dipolares (+H3N-CH(R)-COO-) distintas de las neutras de las cadenas polipéptidas. Con el fin de obtener la estructura de estas formas neutras es necesario experimentar en fase gas, en un entorno libre de interacciones como el de una expansión supersónica. Para solventar el problema de su baja presión de vapor, se ha diseñado un nuevo instrumento que combina la espectroscopía de microondas en jet supersónicos con técnicas de ablación láser [9] que evita los métodos de vaporización por calentamiento que conducen a la descomposición de los aminoácidos. Diversos confórmeros de los aminoácidos naturales de la prolina [10], valina [11], cis- y trans- hidroxiprolina, serina, cisteina, ldots

  13. Astronomía Gamma desde El Leoncito

    NASA Astrophysics Data System (ADS)

    Rovero, A. C.; Colombo, E.; Sahade, J.; Weekes, T. C.

    La astronomía gamma, en el extremo de energías detectadas hasta el presente, se encuentra en desarrollo en muchas partes del mundo y proporciona resultados sorprendentes a medida que la tecnología avanza en el desarrollo de nuevos detectores. La técnica Cherenkov Atmosférica es la utilizada para la detección, mediante telescopios en tierra, del efecto secundario causado por la radiación gamma de muy altas energías (E ≈ TeV). Por medio de telescopios o arreglos de detectores y utilizando la técnica mencionada, se han podido detectar algunas fuentes puntuales de mucha importancia astrofísica como la Nebulosa del Cangrejo y la galaxia de núcleo activo Markarian 421. El sistema instalado en San Juan, en cooperación con el grupo de Radiación Gamma del Observatorio Whipple, está constituído por tres colectores de 1.5m que registran pulsos de luz generados por las cascadas de partículas producidas por rayos cósmicos de todo tipo al entrar en la atmósfera terrestre. El sistema opera por barrido en ascención recta de la fuente observada que, para esta etapa del experimento, es el Centro Galáctico. Esta fuente extensa es conocida como emisor gamma de energías inferiores al TeV y ha sido observada anteriormente en este rango de energía desde el hemisferio norte pero con elevaciones bajas, situación no óptima para este tipo de técnica. Se presentan los primeros resultados del análisis de los datos obtenidos observando la región del Centro Galáctico, luego de dos años de observaciones, así como una descripción de la técnica Cherenkov Atmosférica y del equipo utilizado en la experiencia.

  14. Un Marco Abierto: Un Manual de Matematicas y Ciencas Utilizando Inteligencias Multiples Disenado para Estudiantes Bilingues de Educacion General y Especial (An Open Framework: A Math and Science Manual Utilizing Multiple Intelligences Designed for Bilingual Students in General and Special Education).

    ERIC Educational Resources Information Center

    New York City Board of Education, Brooklyn, NY. Office of Bilingual Education.

    This manual incorporates a Multiple Intelligences perspective into its presentation of themes and lesson ideas for Spanish-English bilingual elementary school students in grades 4-8 and is designed for both gifted and special education uses. Each unit includes practice activities, semantic maps to illustrate and help organize ideas as well as…

  15. SpaceX Dragon, NASA Science Cargo Back On Dry Land

    NASA Video Gallery

    The SpaceX Dragon capsule has returned to California, after splashdown in the Pacific Ocean March 26 a few hundred miles west of Baja California following its International Space Station resupply m...

  16. Satellite Movie Shows Andres Weaken to a Tropical Storm

    NASA Video Gallery

    This animation of imagery from NOAA's GOES-West satellite from June 1 to 3 shows Hurricane Andres eye disappear and weaken to a tropical storm in the Eastern Pacific Ocean, south of Baja California...

  17. 77 FR 13606 - Ocean Transportation Intermediary License; Rescission of Order of Revocation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-07

    ... Number: 021014N. Name: Magic Transport, Inc. Address: Pepsi Industrial Park, PR-2, KM 19.5, Interior BO Candelaria, Toa Baja, PR 00949. Order Published: FR: 3/1/12 (Volume 77, No. 41, Pg. 12584). Vern W....

  18. GOES-14 Sees Hurricane Paul and Rafael - Duration: 34 seconds.

    NASA Video Gallery

    An animation of satellite observations from Oct. 13-16, 2012, shows Hurricane Paul affecting Baja California, Mexico, and Hurricane Rafael moving toward Bermuda. This visualization was created by t...

  19. PCEIS - THE PACIFIC COAST ECOSYSTEM INFORMATION SYSTEM, CHANGING THE WAY SCIENTISTS VIEW THE NATURAL HISTORY OF SPECIES

    EPA Science Inventory

    The Pacific Coast Ecosystem Information System (PCEIS) is a database that provides biological, ecological and geospatial information for over 8100 species from Alaska to Baja. PCEIS goes beyond capturing species’ taxonomic information by integrating monitoring information from Co...

  20. 78 FR 16465 - Foreign-Trade Zone 7-Mayaguez, Puerto Rico, Authorization of Production Activity, Pepsi Cola...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-15

    ... Activity, Pepsi Cola Puerto Rico Distributing, LLC (Soft Drink and Fruit Drink Beverages), Toa Baja, Puerto... inviting public comment (77 FR 70417, 11-26-2012). The FTZ Board has determined that no further review...

  1. IMPACT OF BURROWING SHRIMP POPULATIONS ON C, N CYCLING AND WATER QUALITY IN WESTERN NORTH AMERICAN TEMPERATE ESTUARIES

    EPA Science Inventory

    Thalassinid burrowing shrimp (predominantly, Neotrypaea californiensis and Upogebia pugettensis) inhabit large expanses of tide flats in North American Pacific estuaries, from British Columbia to Baja California. Feeding, burrowing, and burrow irrigation by burrowing shrimp can ...

  2. DISTRIBUTION AND ABUNDANCE OF BURROWING SHRIMP IN TWO OREGON ESTUARIES AND IMPLICATIONS FOR ESTUARINE-SCALE NITROGEN DYNAMICS

    EPA Science Inventory

    Thalassinid burrowing shrimp (Neotrypaea californiensis and Upogebia pugettensis) inhabit large expanses of Pacific estuarine tide flats, from British Columbia to Baja California. The spatial distribution of shrimp populations within estuaries has rarely been quantified because ...

  3. IMPACT OF BURROWING SHRIMP POPULATIONS ON NITROGEN CYCLING AND WATER QUALITY IN WESTERN NORTH AMERICAN TEMPERATE ESTUARIES

    EPA Science Inventory

    Thalassinid burrowing shrimp (predominantly, Neotrypaea californiensis and Upogebia pugettensis) inhabit large expanses of tide flats in North American Pacific estuaries, from British Columbia to Baja California. Feeding, burrowing, and burrow irrigation by burrowing shrimp can ...

  4. SPATIAL DISTRIBUTIONS OF BURROWING SHRIMP POPULATIONS IN TWO OREGON ESTUARIES

    EPA Science Inventory

    Thalassinid burrowing shrimp (Neotrypaea californiensis and Upogebia pugettensis) inhabit large expanses of Pacific estuarine tide flats, from British Columbia to Baja California. The spatial distribution of shrimp populations within estuaries has rarely been quantified because ...

  5. Color coded data obtained by JPL's Shuttle Multispectral Infrared radiometer

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Color coded data obtained from Baja California, Mexico to Texas by JPL's Shuttle Multispectral Infrared radiometer is pictured. The map shows where data was obtained on the 19th orbit of the mission. Yellow and green areas represent water. The first brown segment at left is Baja California, and the second begins at the coast of mainland Mexico and extends into Texas. The dark brown strips at the right are clouds.

  6. Prevalence of Taenia saginata Larvae (Cysticercus bovis) in Feedlot Cattle Slaughtered in a Federal Inspection Type Abattoir in Northwest México.

    PubMed

    Cueto González, Sergio Arturo; Rodríguez Castillo, José Luis; López Valencia, Gilberto; Bermúdez Hurtado, Rosa María; Hernández Robles, Erika Selene; Monge Navarro, Francisco Javier

    2015-05-01

    The prevalence of bovine cysticercosis was established using routine postmortem inspection of 52,322 feedlot cattle slaughtered at 1 Federal Inspection Type abattoir (TIF 301) located in the Mexicali Valley in Baja California, México. The study included 31,393 animals (60.0%) purchased and transported to Baja California from stocker operations located in 17 states of México and 20,929 animals (40.0%) native to Baja California. A total of 208 carcasses showed lesions suggestive of cysticercosis, and 109 were confirmed as positive for the parasite with a prevalence of 0.21%, equivalent to 2.1 cases/1000 carcasses inspected, 2.8 cases/1000 carcasses for cattle purchased in other states, and 1.0 cases/1000 carcasses for cattle native from Baja California. The sensitivity of the postmortem inspection, when compared to a gold standard of stereoscopic microscopy, was 52.4%. The prevalence of cysticercosis was 2.8 times higher in cattle from other states compared with those native to Baja California. Cysticerci were most frequently found in the heart, followed by liver and masseter muscles. In cattle from other states, 96.6% of cysticerci were classified as calcified and <4% as viable; in cattle native to Baja California, 29% of cysticerci were classified as calcified and 71% as viable. The prevalence of bovine cysticercosis established at TIF 301 was found to be 28% lower than a previous report for Baja California. However, given the sensitivity of the postmortem inspection calculated between 10% and 50%, it is possible that an undetermined number of carcasses pass as being free of cysticerci and that the meat reached both domestic and international wholesale markets, increasing the possibility of human infection and causing substantial economic loss through condemnation of infected meat and trade restrictions for endemic regions. PMID:25803448

  7. [In Process Citation].

    PubMed

    Molina Recio, Guillermo; Moreno Rojas, Rafael; García Rodríguez, María; Vaquero Abellán, Manuel

    2016-01-01

    Introducción: un gran número de encuestas nutricionales en Perú han identificado la magnitud y la ubicación de los diferentes tipos de desnutrición, siendo la forma crónica la más prevalente. Sin embargo, aunque las tasas pueden considerarse alarmantes (aún más en las zonas rurales), sólo un trabajo contiene información sobre las características de la ingesta, usando recordatorios de 24 horas (R24). Es decir, se carece de otros sistemas de estudio centrados en conocer las características gastronómicas de sus regiones y la biodisponibilidad de los alimentos, con el fin de localizar el origen de esta situación en cada área y proponer soluciones verdaderamente eficaces y eficientes.Objetivo: determinar el valor nutricional de los platos principales consumidos por los residentes de un barrio pobre de la Amazonía Peruana, para identificar las causas de la pérdida de un estado nutricional saludable.Métodos: noventa y ocho participantes completaron tres R24. Basándonos en estos datos, se seleccionaron los 25 platos más comúnmente consumidos y evaluamos su composición nutricional. Tomamos nota de las recetas, pesos y medidas caseras. Además, se observó la preparación y cocción. La composición nutricional media de cada plato se calculó por 100 g utilizando el software Nutriplato 4.6. También se calcularon lasganancias o pérdidas derivadas de los tratamientos culinarios.Resultados: dentro de los platos basados en la leche, el de más alta densidad de energía es el mingado de arroz. En el grupo de los pescados, la mayor cantidad de energía es aportada por el pescado frito, mientras que en las recetas a base de carne, las más energéticas son el tallarín con pollo, la res asada y el cerdo frito. Como platos preparados, el juane tiene la más alta densidad de energía de todas las recetas. Dentro de las guarniciones, aquellas que utilizan los plátanos como el ingrediente principal, el plátano frito y el madurito, son las más energ

  8. Hydrochemical tracers in the middle Rio Grande Basin, USA: 2. Calibration of a groundwater-flow model

    NASA Astrophysics Data System (ADS)

    Sanford, Ward E.; Plummer, L. Niel; McAda, Douglas P.; Bexfield, Laura M.; Anderholm, Scott K.

    té construit avec les logiciels MODFLOW, MODPATH et UCODE, et calibré en utilisant les concentrations en 14C et la position de certaines zones définies par les données hydrochimiques. L'estimation de certains paramètres a été réalisée en utilisant une combinaison de techniques de régression non linéaire et une méthode de recherche exhaustive (Brute Force Search) de l'erreur minimum entre les résultats des observations et les simulations. Les valeurs de la recharge calibrée sont substantiellement plus basses que celles estimées dans les modèles antérieurs. Les résultats d'une simulation en régime transitoire sur 30.000 ans suggèrent que la recharge au maximum de la dernière glaciation (last glacial maximum, LGM) était 10 fois supérieure au taux actuel, mais que la recharge qui a suivit la LGM était plus bas que la recharge actuelle. La calibración de un modelo de aguas subterráneas con el apoyo de datos hidroquímicos ha demostrado que la recarga relativamente baja en la cuenca media del Río Grande es probablemente responsable de una depresión de aguas subterráneas en el centro de la cuenca y de la presencia de una cantidad considerable de agua del Río Grande en el acuífero del Grupo Santa Fe. Los modelos propuestos con anterioridad para la cuenca tenían dificultades para reproducir estas características ya que no tenían datos hidroquímicos que permitieran delimitar los ritmos y distribución de recarga. El objetivo del presente estudio consistió en utilizar una gran cantidad de datos hidroquímicos disponibles para ayudar a calibrar los parámetros del modelo, incluyendo los ritmos de recarga. El modelo se construyó utilizando los modelos MODFLOW, MODPATH, y UCODE del USGS, mientras que la calibración se realizó en base a concentraciones de 14C y a la posición de ciertas zonas definidas con los datos hidroquímicos. La estimación de parámetros se realizó en base a una combinación de técnicas de regresiones no lineares y a una b

  9. Nutritional condition of Pacific Black Brant wintering at the extremes of their range

    USGS Publications Warehouse

    Mason, D.D.; Barboza, P.S.; Ward, D.H.

    2006-01-01

    Endogenous stores of energy allow birds to survive periods of severe weather and food shortage during winter. We documented changes in lipid, protein, moisture, and ash in body tissues of adult female Pacific Black Brant (Branta bernicla nigricans) and modeled the energetic costs of wintering. Birds were collected at the extremes of their winter range, in Alaska and Baja California, Mexico. Body lipids decreased over winter for birds in Alaska but increased for those in Baja California. Conversely, body protein increased over winter for Brant in Alaska and remained stable for birds in Baja California. Lipid stores likely fuel migration for Brant wintering in Baja California and ensure winter survival for those in Alaska. Increases in body protein may support earlier reproduction for Brant in Alaska. Predicted energy demands were similar between sites during late winter but avenues of expenditure were different. Birds in Baja California spent more energy on lipid synthesis while those in Alaska incurred higher thermoregulatory costs. Estimated daily intake rates of eelgrass were similar between sites in early winter; however, feeding time was more constrained in Alaska because of high tides and short photoperiods. Despite differences in energetic costs and foraging time, Brant wintering at both sites appeared to be in good condition. We suggest that wintering in Alaska may be more advantageous than long-distance migration if winter survival is similar between sites and constraints on foraging time do not impair body condition. ?? The Cooper Ornithological Society 2006.

  10. Genetic differentiation and demographic history in Drosophila pachea from the Sonoran Desert.

    PubMed

    Pfeiler, Edward; Erez, Tamar; Hurtado, Luis A; Markow, Therese A

    2007-05-01

    Genetic variation at six microsatellite DNA loci and a segment of the mitochondrial cytochrome oxidase subunit I (COI) locus was used to estimate gene flow, population structure, and demographic history in the cactophilic Drosophila pachea from the Sonoran Desert of North America, a species that shows a strict association with its senita host cactus (genus Lophocereus). For microsatellite analyses, thirteen populations of D. pachea were sampled, five in mainland Mexico and the southwestern USA, and eight on the Baja California (Baja) peninsula, covering essentially the entire range of the species. Analysis of molecular variance (AMOVA) of microsatellite data revealed that populations from both the mainland and the Baja peninsula generally showed little structure, although there were a few exceptions, suggesting some local differentiation and restriction of gene flow within both regions. Pairwise comparisons of F(ST) among each of the mainland and Baja populations showed evidence of both panmixia and population subdivision. AMOVA performed on grouped populations from both the mainland and Baja, however, revealed significant partitioning of genetic variation among the two regions, but no partitioning among localities within each region. Bayesian skyline analyses of the COI data set, consisting of four mainland and seven peninsular populations, revealed population expansions dating to the Pleistocene or late Pliocene in D. pachea from both regions, although regional differences were seen in the estimated timing of the expansions and in changes in effective population size over time. PMID:17567443

  11. Mass dynamics of wintering Pacific Black Brant: Body, adipose tissue, organ, and muscle masses vary with location

    USGS Publications Warehouse

    Mason, D.D.; Barboza, P.S.; Ward, D.H.

    2007-01-01

    We compared body size and mass of the whole body, organs, adipose tissue, and muscles of adult Pacific Black Brant (Branta bernicla nigricans (Lawrence, 1846)) collected concurrently in Alaska and Baja California during the fall, winter, and spring of 2002-2003. Head and tarsal lengths of males were similar between sites and slightly larger for females in Alaska than in Baja California. Brant appear to operate under similar physiological bounds, but patterns of nutrient allocation differ between sites. Birds wintering in Alaska lost similar amounts of adipose tissue during early winter as birds in Baja California gained during late winter before migration. Masses of the body, adipose tissue, and flight muscles during mid-winter were similar between sites. Seasonal adipose tissue deposition may, therefore, equally favor winter residency or long-distance migration. Gonad and liver masses increased in late winter for birds in Alaska but not for those in Baja California, suggesting birds wintering in Baja may delay reproductive development in favor of allocating reserves needed for migration. Phenotypic flexibility allows Brant to use widely divergent wintering sites. The wintering location of Brant likely depends more upon changes in environmental conditions and food availability, than upon physiological differences between the two wintering populations. ?? 2007 NRC.

  12. Alisitos Formation calcareous facies - Early Cretaceous episode of tectonic calm

    SciTech Connect

    Suarez-Vidal, F.

    1986-04-01

    The Alisitos Formation (Aptian-Albian), shaped as a marine volcanic arc, crops out along the western side of Baja California bounding the Peninsula Range batholith. Lithologically, this formation is formed by volcanic breccias, porphyritic flows, biohermal limestones, and tuffaceous and pyroclastic sediments. The distribution of the different facies depends on the nature of volcanism and the distance from a volcanic center, although the presence of massive biohermal limestone indicates that in the Early Cretaceous (during tectonic episodes), the volcanic activity decreased to the level that the environmental conditions were favorable for the development of an organic barrier reef behind an island arc. Such conditions pertained south of the Agua Blanca fault and extended to El Arco, Baja California. Based on field observation and petrologic analysis in the Alisitos limestone, an attempt has been made to re-create the environmental condition in the Punta China and San Fernando, Baja California, sites.

  13. Alisitos Formation, calcareous facies: Early Cretaceous episode of tectonic calm

    SciTech Connect

    Suarez-Vidal, F.

    1986-07-01

    The Alisitos Formation (Aptian-Albian), shaped as a marine volcanic arc, crops out along the western side of the peninsula of Baja California bounding the Peninsular Range batholith. Lithologically, this formation is formed by volcanic-breccias, porphyritic flows, biohermal limestones, and tuffaceous and pyroclastic sediments. The distribution of the different facies depends on the nature of volcanism and the distance from a volcanic center, although the presence of massive biohermal limestone indicates that in the Early Cretaceous (during the tectonic episodes), the volcanic activity decreased to the level that the environmental conditions were favorable for the development of an organic reef barrier, behind an island arc. Such conditions existed south of the Agua Blanca fault and extended to El Arco, Baja California. Based upon field observations and petrological analysis of the Alisitos limestone, an attempt is made to recreate the environmental condition in the Punta China and San Fernando, Baja California, sites.

  14. Seismic structure beneath the Gulf of California: a contribution from group velocity measurements

    NASA Astrophysics Data System (ADS)

    Di Luccio, F.; Persaud, P.; Clayton, R. W.

    2014-12-01

    Rayleigh wave group velocity dispersion measurements from local and regional earthquakes are used to interpret the lithospheric structure in the Gulf of California region. We compute group velocity maps for Rayleigh waves from 10 to 150 s using earthquakes recorded by broad-band stations of the Network of Autonomously Recording Seismographs in Baja California and Mexico mainland, UNM in Mexico, BOR, DPP and GOR in southern California and TUC in Arizona. The study area is gridded in 120 longitude cells by 180 latitude cells, with an equal spacing of 10 × 10 km. Assuming that each gridpoint is laterally homogeneous, for each period the tomographic maps are inverted to produce a 3-D lithospheric shear wave velocity model for the region. Near the Gulf of California rift axis, we found three prominent low shear wave velocity regions, which are associated with mantle upwelling near the Cerro Prieto volcanic field, the Ballenas Transform Fault and the East Pacific Rise. Upwelling of the mantle at lithospheric and asthenospheric depths characterizes most of the Gulf. This more detailed finding is new when compared to previous surface wave studies in the region. A low-velocity zone in northcentral Baja at ˜28ºN which extends east-south-eastwards is interpreted as an asthenospheric window. In addition, we also identify a well-defined high-velocity zone in the upper mantle beneath central-western Baja California, which correlates with the previously interpreted location of the stalled Guadalupe and Magdalena microplates. We interpret locations of the fossil slab and slab window in light of the distribution of unique post-subduction volcanic rocks in the Gulf of California and Baja California. We also observe a high-velocity anomaly at 50-km depth extending down to ˜130 km near the southwestern Baja coastline and beneath Baja, which may represent another remnant of the Farallon slab.

  15. Species profiles: Life histories and environmental requirements of coastal fishes and invertebrates (Pacific Northwest)--ghost and blue mud shrimp

    USGS Publications Warehouse

    Hornig, S.; Sterling, A.; Smith, S.

    1989-01-01

    Geographic range: The ghost shrimp is found in intertidal areas along the west coast of North America from Mutiny Bay, Alaska, to the mouth of the Tijuana River, San Diego County, California; MacGinitie (1934) and Ricketts and Calvin (1968) reported finding specimens as far south as El Estuario de Punto Banda, Baja California Norte, Mexico. The blue mud shrimp is found from southeastern Alaska to San Quentin Bay (Bahia de San Quentin) in Baja California Norte. The general distribution of the two species in the Pacific Northwest is identical (Figure 3).

  16. Satellite-Based Investigations of the Transition from an Oceanic to Continental Transform Margin

    NASA Technical Reports Server (NTRS)

    Miller, M. Meghan

    1998-01-01

    Detailed characterization of neotectonics evolution of the Valle de San Felipe and Arroyo Grande regions in northern Baja California. Reoccupied GEOMEX GPS sites, and occupied a regional GPS (Global Positioning System) network. The Baja California peninsula in Mexico offers a unique setting for studying the kinematic evolution of a complex, active strike-slip/rift plate boundary. We are currently conducting remote sensing, geologic, and geodetic studies of this boundary. The combined data sets will yield instantaneous and time integrated views of its evolution. This proposal solicits renewed funding from NASA to support remote sensing and geologic studies. During the late Cenozoic, Baja California has been the locus of changing fault geometry that has accommodated components of the relative motion between the North America and Pacific plates. Contemporary slip between the two plates occurs in a broad zone that encompasses much of southern California and the Baja California Peninsula. The transfer of slip across this zone in southern California is relatively well understood. South of the border, the geometry and role of specific faults and structural provinces in transferring plate margin deformation across the peninsula is enigmatic. Results We use Landsat Thematic Mapper imagery of the Baja California Peninsula to identify recent and active faults, and then conduct field studies that characterize the temporal and spatial structural evolution of the plate margin. These data address questions concerning the neotectonic development of the Gulf of California, the Baja California Peninsula, and their role in evolution of the post-Miocene Pacific - North American plate boundary. Moreover, these studies provide constraints on the geometry of active faults, allowing more exact understanding of the results of ongoing NASA-supported geodetic experiments. In addition, anticipated publication of the TM scenes will provide a widely available geological data base for relatively

  17. SELECTED AIR QUALITY TRENDS AND RECENT AIR POLLUTION INVESTIGATIONS IN THE U.S.-MEXICO BORDER REGION

    EPA Science Inventory

    The thirteen journal articles in this issue deal with air quality indicators due, in part, to population growth, cross-border traffic, and economic expansion since ratification of NAFTA; regions covered span from Tijuana, Baja California to Brownsville, Texas. This introductio...

  18. Experimental Analyses of Cooperation and Competition of Anglo-American and Mexican Children.

    ERIC Educational Resources Information Center

    Kagan, Spencer; Madsen, Millard C.

    Four experiments comparing behavior of children from Los Angeles, California, and Nuevo San Vicente, Baja California, Mexico, were conducted to analyze cooperative and competitive behavior of Anglo American city and Mexican rural children. Eighty children from each setting, 40 of age 7-9 and 40 of age 10-11, equally divided by sex, served as…

  19. Hurricane Juliette

    Atmospheric Science Data Center

    2013-04-19

    ... since 1973. According to the National Hurricane Center, deep convection surrounding Juliette's eye began to weaken on the morning of ... It travelled in a north-northwest direction over the Pacific Ocean until reaching the tip of Baja Peninsula, where the heaviest rainfall and ...

  20. 77 FR 74170 - Foreign-Trade Zone 7-Mayaguez, PR; Application for Subzone; Pepsi Cola Puerto Rico Distributing...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-13

    ... (the Board) by the Puerto Rico Industrial Development Company, grantee of FTZ 7, requesting special-purpose subzone status for the facility of Pepsi Cola Puerto Rico Distributing, LLC, located in Toa Baja, Puerto Rico. The application was submitted pursuant to the provisions of the Foreign-Trade Zones Act,...

  1. ORGANOCHLORINE CONTAMINANTS IN SEA TURTLES FROM THE EASTERN PACIFIC

    EPA Science Inventory

    We measured organochlorine residues in three species of sea turtles from the Baja California peninsula, Mexico. Seventeen of 21 organochlorine pesticides analyzed were detected, with heptachlor epoxide and y-hexachlorocyclohexane the most prevalent in 14 (40%) and 11 (31%) of th...

  2. Developmental and Cross-Cultural Differences in the Cooperative and Competitive Behavior of Young Children.

    ERIC Educational Resources Information Center

    Madsen, Millard C.

    An experimental task with accompanying apparatus was developed for use in the study of developmental and cultural differences in the cooperative-competitive behavior of children in a small Mexican town and in California. Two groups of 20 Mexican children (aged 7-8 and 10-11), from an elementary school in a town in Baja, California, Mexico, were…

  3. 75 FR 73156 - Bureau of Western Hemisphere Affairs; Executive Order 11423, as Amended; Notice of Receipt of...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-29

    ...The Department of State hereby gives notice that, on November 10, 2010, it received an application for a Presidential Permit to authorize the renovation and expansion of the San Ysidro border crossing facility on the U.S.-Mexico border at San Diego, California and Tijuana, Baja California, Mexico. The General Services Administration (GSA) filed this application and is acting as the project's......

  4. The Southern Yellowjacket, Vespula squamosa (Drury) (Hymenoptera: vespidae) in Guatemala, Central America

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Southern yellowjackets, Vespula squamosa (Drury) were collected at sites in Guatemala, in the Departments of Baja Verapaz, El Progresso, and Zacapa. Collection localities ranged in elevation from 500 to 1880 m. These locations were forested, or partially forested with some pasture land and coffee ...

  5. Photograph of Earth taken from Apollo 13 spacecraft during transearth journey

    NASA Technical Reports Server (NTRS)

    1970-01-01

    This photograph of the Earth was taken from the Apollo 13 spacecraft during its transearth journey home. The most visible land mass includes southwestern United States and northwestern Mexico. The penisula of Baja California is clearly seen. Most of the land area is under heavy cloud cover.

  6. STS-113 Flight Day 11 Highlights Replay

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The STS-113 eleventh flight day begins with Flight Engineer John Herrington and ISS Science Officer Peggy Whitson answering questions from the media. Earth Views from the Space Shuttle Endeavor payload bay, as the Space Shuttle Endeavor Expedition Five Crew travel over the Baja Peninsula are also presented.

  7. 13-Color Photometry of 16 Variable Be-Stars - Part One - Photometry

    NASA Astrophysics Data System (ADS)

    Alvarez, M.; Schuster, W. J.

    1982-07-01

    We present thirteen color photometry of 16 variable Be stars observed at the Observatorio Astronomico Nacional in San Pedro Martir in Baja California, Our data cover the years 1977 to 1979, and we include earlier measurements of Johnson and Mitchell from 1965 to 1968 that have been corrected in order to have a homogeneous set of data.

  8. Cyclone Dera

    Atmospheric Science Data Center

    2013-04-19

    ... was dissipating. Bud was situated in the eastern Pacific Ocean between Socorro Island and the southern tip of Baja California. South of ... March 12, 2001 (Terra orbit 6552). Dera was located in the Indian Ocean, south of Madagascar. The southern end of this large island is ...

  9. SUSTAINABLE COMMUNITY DEVELOPMENT &NDASH; WATER SLOW-SAND FILTRATION

    EPA Science Inventory

    Site Survey: When this project was developed, the village of Santa Cruz, Baja Verapaz, Guatemala was chosen as a target community for initial development and target implementation. The research team of six students and advisor traveled to the village in early August 2...

  10. Deep scattering layer migration and composition: observations from a diving saucer.

    PubMed

    Barham, E G

    1966-03-18

    The distribution of a myctophid fish and physonect siphonophores observed during dives in the Soucoupe off Baja California closely correlates with scattering layers recorded simultaneously with a 12-kcy/sec echo sounder. These organisms were observed while they were migrating vertically, and at their night and daytime levels. They are capable of rapid, extensive changes in depth. PMID:17817303

  11. Síntesis: Resultados iniciales del Estudio Nacional de Ex

    Cancer.gov

    El 4 de noviembre de 2010, el Estudio Nacional de Exámenes de Pulmóndio a conocer resultados iniciales que indican que hubo 20% menos muertes por cáncer de pulmón entre los participantes del estudio evaluados con tomografía computarizada espiral de baja d

  12. Trans-Pacific migrations of the loggerhead turtle (Caretta caretta) demonstrated with mitochondrial DNA markers.

    PubMed

    Bowen, B W; Abreu-Grobois, F A; Balazs, G H; Kamezaki, N; Limpus, C J; Ferl, R J

    1995-04-25

    Juvenile loggerhead turtles (Caretta caretta) have recently been documented in the vicinity of Baja California and thousands of these animals have been captured in oceanic fisheries of the North Pacific. The presence of loggerhead turtles in the central and eastern North Pacific is a prominent enigma in marine turtle distribution because the nearest documented nesting concentrations for this species are in Australia and Japan, over 10,000 km from Baja California. To determine the origin of the Baja California feeding aggregate and North Pacific fishery mortalities, samples from nesting areas and pelagic feeding aggregates were compared with genetic markers derived from mtDNA control region sequences. Overall, 57 of 60 pelagic samples (95%) match haplotypes seen only in Japanese nesting areas, implicating Japan as the primary source of turtles in the North Pacific Current and around Baja California. Australian nesting colonies may contribute the remaining 5% of these pelagic feeding aggregates. Juvenile loggerhead turtles apparently traverse the entire Pacific Ocean, approximately one-third of the planet, in the course of developmental migrations, but mortality in high-seas fisheries raises concern over the future of this migratory population. PMID:7731974

  13. Salton Sea and Imperial Valley, California as seen from the Apollo 7 spacecra

    NASA Technical Reports Server (NTRS)

    1968-01-01

    Salton Sea and Imperial Valley area of southern California, including a portion of northern Baja California, Mexico, as seen from the Apollo 7 spacecraft during its 17th revolution of the earth. Photographed from an altitude of 125 nautical miles, at ground elapsed time of 27 hours.

  14. Fragmented Economy, Stratified Society, and the Shattered Dream

    ERIC Educational Resources Information Center

    Mordechay, Kfir

    2011-01-01

    Across the massive megalopolis stretching from the northern suburbs of Los Angeles County through the metropolitan complex along the northern border of Baja California is a diverse area containing 24 million people, with a disproportionate percentage of Latinos and African Americans who are facing an educational and economic disaster. As it…

  15. 77 FR 61051 - Additional Designations, Foreign Narcotics Kingpin Designation Act

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-05

    ..., Sinaloa, Mexico; Sevilla 1526 302 A, Fraccionamiento el Cid, Mazatlan, Sinaloa CP 82110, Mexico; Privada de San Jeronimo, San Jeronimo, Algodones, Baja California CP 21298, Mexico; Privada Puerta de Roble... Sayavedra, Atizapan de Zaragoza, Estado de Mexico CP 52930, Mexico; DOB 24 Oct 1962; POB Culiacan,...

  16. Social Capital, Organic Agriculture, and Sustainable Livelihood Security: Rethinking Agrarian Change in Mexico

    ERIC Educational Resources Information Center

    Getz, Christy

    2008-01-01

    This paper explores the relevance of extra local market linkages and local-level social capital to sustainable livelihood outcomes in two agrarian communities on Mexico's Baja Peninsula. Contextualized by the specificity of Mexico's transition from state-directed rural development to neoliberally-guided rural development in the 1990s, findings…

  17. Mexico's New Braceros: How NAFTA Promotes Child Labor and Truancy in the Onion Fields of Mexicali.

    ERIC Educational Resources Information Center

    Bacon, David

    1997-01-01

    Although NAFTA has proven profitable for U.S. growers who have relocated agricultural production to Mexico, it has helped create an economic crisis that has forced thousands of Mexican children to leave school in order to work and supplement their parents' shrinking income. In Mexicali Valley (Baja California), approximately a fourth of the…

  18. Glaucoma

    MedlinePlus

    ... saber Preguntas comunes: Baja Visión Cómo ayudar a un ser querido Ojos sanos Ojos sanos Problemas de ... tener ojos sanos Para Profesionales Recursos ¿Qué es un examen completo de los ojos con dilatación de ...

  19. Islands of Time Before: The Miraculous Translation of Californian.

    ERIC Educational Resources Information Center

    Kottman, Karl

    1999-01-01

    Highlights the history of Californian (Luiseno), the native language of Baja California, including how the language was recorded by a young Mexican student at the Vatican's missionary school, the Collegium Urbanum in Rome. Discusses the political impact of the grammatical recording and subsequent translation of the language during the mid-19th…

  20. Measuring the contribution of benthic ecosystem engineering species to the ecosystem services of an estuary: A case study of burrowing shrimps in Yaquina Estuary, Oregon

    EPA Science Inventory

    Burrowing shrimps are regarded as ecosystem engineering species in many coastal ecosystems worldwide, including numerous estuaries of the west coast of North America (Baja California to British Columbia). In estuaries of the U.S. Pacific Northwest, two species of large burrowing...

  1. Measuring the contribution of benthic ecosystem engineering species to the ecosystem services of an estuary: A case study of burrowing shrimps in Yaquina Estuary, Oregon - April 2009

    EPA Science Inventory

    Burrowing shrimps are regarded as ecosystem engineering species in many coastal ecosystems worldwide, including numerous estuaries of the west coast of North America (Baja California to British Columbia). In estuaries of the U.S. Pacific Northwest, two species of large burrowing...

  2. Trans-Pacific migrations of the loggerhead turtle (Caretta caretta) demonstrated with mitochondrial DNA markers.

    PubMed Central

    Bowen, B W; Abreu-Grobois, F A; Balazs, G H; Kamezaki, N; Limpus, C J; Ferl, R J

    1995-01-01

    Juvenile loggerhead turtles (Caretta caretta) have recently been documented in the vicinity of Baja California and thousands of these animals have been captured in oceanic fisheries of the North Pacific. The presence of loggerhead turtles in the central and eastern North Pacific is a prominent enigma in marine turtle distribution because the nearest documented nesting concentrations for this species are in Australia and Japan, over 10,000 km from Baja California. To determine the origin of the Baja California feeding aggregate and North Pacific fishery mortalities, samples from nesting areas and pelagic feeding aggregates were compared with genetic markers derived from mtDNA control region sequences. Overall, 57 of 60 pelagic samples (95%) match haplotypes seen only in Japanese nesting areas, implicating Japan as the primary source of turtles in the North Pacific Current and around Baja California. Australian nesting colonies may contribute the remaining 5% of these pelagic feeding aggregates. Juvenile loggerhead turtles apparently traverse the entire Pacific Ocean, approximately one-third of the planet, in the course of developmental migrations, but mortality in high-seas fisheries raises concern over the future of this migratory population. PMID:7731974

  3. Explorers of the Local Region. Grade 3 Model Lesson for Unit 3, Standard 3. California History-Social Science Course Models.

    ERIC Educational Resources Information Center

    Smith, Denise

    Three Spanish explorers who visited the southern California region were Juan Cabrillo, Sebastian Vizcaino, and Gaspar de Portola. In the 1500s, the king of Spain sent explorers from Mexico to Baja and Alta, California, (most of today's California) looking for new wealth, gold, and a waterway to the Strait of Anian. Europeans thought that…

  4. Uranium-Series Ages of Marine Terrace Corals from the Pacific Coast of North America and Implications for Last-Interglacial Sea Level History

    USGS Publications Warehouse

    Muhs, D.R.; Kennedy, G.L.; Rockwell, T.K.

    1994-01-01

    Few of the marine terraces along the Pacific coast of North America have been dated using uranium-series techniques. Ten terrace sequences from southern Oregon to southern Baja California Sur have yielded fossil corals in quantities suitable for U-series dating by alpha spectrometry. U-series-dated terraces representing the ???80,000 yr sea-level high stand are identified in five areas (Bandon, Oregon; Point Arena, San Nicolas Island, and Point Loma, California; and Punta Banda, Baja California); terraces representing the ???125,000 yr sea-level high stand are identified in eight areas (Cayucos, San Luis Obispo Bay, San Nicolas Island, San Clemente Island, and Point Loma, California; Punta Bands and Isla Guadalupe, Baja California; and Cabo Pulmo, Baja California Sur). On San Nicolas Island, Point Loma, and Punta Bands, both the ???80,000 and the ???125,000 yr terraces are dated. Terraces that may represent the ???105,000 sea-level high stand are rarely preserved and none has yielded corals for U-series dating. Similarity of coral ages from midlatitude, erosional marine terraces with coral ages from emergent, constructional reefs on tropical coastlines suggests a common forcing mechanism, namely glacioeustatically controlled fluctuations in sea level superimposed on steady tectonic uplift. The low marine terrace dated at ???125,000 yr on Isla Guadalupe, Baja California, presumed to be tectonically stable, supports evidence from other localities for a +6-m sea level at that time. Data from the Pacific Coast and a compilation of data from other coasts indicate that sea levels at ???80,000 and ???105,000 yr may have been closer to present sea level (within a few meters) than previous studies have suggested.

  5. Hydrochemical tracers in the middle Rio Grande Basin, USA: 2. Calibration of a groundwater-flow model

    NASA Astrophysics Data System (ADS)

    Sanford, Ward E.; Plummer, L. Niel; McAda, Douglas P.; Bexfield, Laura M.; Anderholm, Scott K.

    té construit avec les logiciels MODFLOW, MODPATH et UCODE, et calibré en utilisant les concentrations en 14C et la position de certaines zones définies par les données hydrochimiques. L'estimation de certains paramètres a été réalisée en utilisant une combinaison de techniques de régression non linéaire et une méthode de recherche exhaustive (Brute Force Search) de l'erreur minimum entre les résultats des observations et les simulations. Les valeurs de la recharge calibrée sont substantiellement plus basses que celles estimées dans les modèles antérieurs. Les résultats d'une simulation en régime transitoire sur 30.000 ans suggèrent que la recharge au maximum de la dernière glaciation (last glacial maximum, LGM) était 10 fois supérieure au taux actuel, mais que la recharge qui a suivit la LGM était plus bas que la recharge actuelle. La calibración de un modelo de aguas subterráneas con el apoyo de datos hidroquímicos ha demostrado que la recarga relativamente baja en la cuenca media del Río Grande es probablemente responsable de una depresión de aguas subterráneas en el centro de la cuenca y de la presencia de una cantidad considerable de agua del Río Grande en el acuífero del Grupo Santa Fe. Los modelos propuestos con anterioridad para la cuenca tenían dificultades para reproducir estas características ya que no tenían datos hidroquímicos que permitieran delimitar los ritmos y distribución de recarga. El objetivo del presente estudio consistió en utilizar una gran cantidad de datos hidroquímicos disponibles para ayudar a calibrar los parámetros del modelo, incluyendo los ritmos de recarga. El modelo se construyó utilizando los modelos MODFLOW, MODPATH, y UCODE del USGS, mientras que la calibración se realizó en base a concentraciones de 14C y a la posición de ciertas zonas definidas con los datos hidroquímicos. La estimación de parámetros se realizó en base a una combinación de técnicas de regresiones no lineares y a una b

  6. Distribution of stable isotopes in arid storms . II. A double-component model of kinematic wave flow and transport

    NASA Astrophysics Data System (ADS)

    Yakirevich, Alexander; Dody, Avraham; Adar, Eilon M.; Borisov, Viacheslav; Geyh, Mebus

    édible par rapport aux observations a été obtenu après un ajustement des paramètres par une méthode d'essais et d'erreurs. L'analyse de sensibilité et l'application du modèle ont ensuite été réalisés. Le modèle est plutôt sensible aux changements des paramètres caractérisant les zones de stockage dans les dépressions. Le modèle rend compte de l'effet de mémoire isotopique dans l'eau dans le stockage des dépressions entre les événements séquentiels de pluie. L'utilisation d'un modèle à double composante d'écoulement et de transport par onde cinématique permet un ajustement qualitatif et quantitatif adapté entre les distributions des δ18O calculées et observées dans l'écoulement de surface. Resumen Un nuevo método matemático basado en un modelo de doble componente de onda cinemática de flujo y transporte permite caracterizar la distribución isotópica dinámica de las tormentas en zonas áridas y la escorrentía. Este modelo describe el transporte y la evolución del δ18O en la lluvia, flujo superficial y escorrentía en una cuenca rocosa de clima árido con detención superficial distribuida uniformemente. El modelo se calibró numéricamente utilizando un conjunto de datos de descarga temporal y de distribución de δ18O para lluvia y escorrentía recogida en una pequeña cuenca rocosa en el Centro de Experimentación de Sede Boker, Israel. Se obtuvo un buen ajuste a los datos tras un ajuste de parámetros mediante prueba y error. Se realizó un análisis de sensibilidad que indicó que el modelo resulta ser bastante sensible a cambios en los parámetros que caracterizan las zonas de baja detención superficial. El modelo también refleja el efecto de la memoria isotópica en el agua de estas zonas de detención entre los distintos periodos de lluvias. El uso de un modelo de doble componente de onda cinemática de flujo y transporte proporciona un buen ajuste cualitativo y cuantitativo entre los datos medidos y calculados de δ18O en la

  7. [In Process Citation].

    PubMed

    Santos, Carla Adriana; Fonseca, Jorge; Carolino, Elisabete; Lopes, Teresa; Sousa Guerreiro, António

    2016-01-01

    Introducción y objetivos: el cobre (Cu) es un oligoelemento muy estudiado, pero poco se sabe de su evolución en los pacientes alimentados por gastrostomía endoscópica (GEP). Pretendemos evaluar la evolución del Cu sérico desde la gastrostomía hasta 12 semanas después de la intervención en estos pacientes alimentados con preparaciones domésticas.  Métodos: realizamos un estudio observacional prospectivo para evaluar el Cu sérico, la albúmina, la transferrina y el índice de masa corporal (IMC) en el momento de la GEP, tras 4 semanas y 12 semanas después de la intervención. Los datos incluyen edad, género, NRS 2002 y enfermedad subyacente: cánceres de cabeza y cuello (CCC) y disfagia neurológica (DN). Después de la intervención, estos pacientes fueron alimentados conpreparaciones domésticas. Resultados: 146 enfermos (89 hombres), entre 21-95 años: CCC-56, DN-90. Valores de Cu entre 42-160 μg/dl (normal: 70-140 μg/dl); normales 89% (n = 130); bajos 11% (n = 16), albúmina baja: 53% (n = 77), transferrina baja: 65% (n = 94), IMC bajo: 53% (n = 78). Después de 4 semanas: valores normales de Cu en 93% y bajos en 7%, albúmina baja en 34%, transferrina baja en 52%. Tras 12 semanas: valores normales de Cu en 95% y bajos en 5%, albúmina baja en 25%, transferrina baja en 32%. No encontramos diferencias significativas en el Cusérico cuando se compara edad, género, enfermedad subyacente, IMC, albúmina y transferrina. Conclusiones: la mayoría de los enfermos presentan Cu sérico normal en el momento de la gastrostomía. Para los enfermos con Cu sérico bajo antes del procedimiento, la alimentación con preparaciones domésticas parece suficiente para su normalización progresiva. PMID:27238774

  8. Anarbylus switaki Murphy: an addition to the herpetofauna of the United States with comments on relationships with Coleonyx

    USGS Publications Warehouse

    Fritts, T.H.; Snell, H.L.; Martin, R.L.

    1982-01-01

    Anarbys switaki, a species previously known only from Baja California Sur, Mexico, occurs in eastern San Diego and southwestern Imperial Counties in California. In California, specimens tend to have continuous transverse bars on the body, are lighter in color, and more slender in body form than in southern Baja California. California populations appear to be confined to extremely rocky habitats in desert foothill situations between 200 and 600 m. The species appears to be secretive, and occurs in low densities within rock crevices and subterranean cavities. The morphological gap between Anarbylus and Coleonyx species may not warrant generic recognition. Anarbylus is part of a diverse lizard fauna in southern California and occurs in sympatry with 15 lizard species in a small area of southern California.

  9. Relationships of the avifauna of San Esteban Island, Sonora

    USGS Publications Warehouse

    Banks, R.C.

    1969-01-01

    Seven species of geographically variable birds have been reported as part of the resident avifauna of San Esteban Island in the Gulf of California, Sonora. Two of these, the Curvebilled Thrasher and the Blue-gray Gnatcatcher, may not actually have breeding populations there, at least at the present time. Of the seven, only two, the Verdin and the doubtfully resident thrasher, can be used in a determination of the relationships of the avifauna, and both show affinities to that of Sonora. The Ash-throated Flycatcher and the House Finch are represented by the same form on San Esteban and in both Sonora and Baja California at the latitude of the island. Neither the Ladder-backed Woodpecker nor the endemic Black-throated Sparrow shows greater similarity to the Baja California or Sonoran avifauna. The slight balance of evidence indicates that the avifauna of San Esteban Island is best considered with that of Sonora.

  10. Lithosphere thickness and rupture mode variation along the Gulf of California, Mexico

    NASA Astrophysics Data System (ADS)

    Perez-Campos, X.; Fernández, A.

    2014-12-01

    We study the lithosphere thickness along the Baja California peninsula and continental northwestern Mexico in order to identify the different rupture modes along the Gulf of California. We use receiver functions (RFs) of 29 seismological stations from three networks: NARS-Baja (Network of Autonomously Recording Seismographs), RESBAN (Broadband seismic network from the Gulf of California), and SSN (National Seismological Service, Mexico). Thickness of the lithosphere varies from 43 to 89 km. The largest values are found at stations located east of Sierra Madre Occidental, and are consistent with a continental lithosphere. The thinner lithosphere is found at station NE70 (Mexicali, Mexico), consistent with a pre-rift region that has experimented serveral extension episodes. From RFs retroprojected along various profiles, we can distinguish the different rupture modes along the Gulf and identify a region under the center of the peninsula where the listhosphere has been removed by the former subduction of the Guadalupe plate.

  11. STS-65 Pilot Halsell points camera out window on OV-102's aft flight deck

    NASA Technical Reports Server (NTRS)

    1994-01-01

    STS-65 Pilot James D. Halsell, Jr uses a handheld HASSELBLAD camera at aft flight deck overhead window W8 to take Earth photographs while aboard the orbiting Space Shuttle Columbia, Orbiter Vehicle (OV) 102. Part of Baja, California can be seen in the upper left quadrant of the photo. This photo was one of the first released by NASA following the International Microgravity Laboratory 2 (IML-2) mission.

  12. Can slabs melt beneath forearcs in hot subduction zones?

    NASA Astrophysics Data System (ADS)

    Ribeiro, J.; Maury, R.; Gregoire, M.

    2015-12-01

    At subduction zones, thermal modeling predict that the shallow part of the downgoing oceanic crust (< 80 - 100 km depth to the slab) is usually too cold to cross the water-rich solidus and melts beneath the forearc. Yet, the occasional occurrence of adakites, commonly considered as slab melts, in the forearc region challenges our understanding of the shallow subduction processes. Adakites are unusual felsic rocks commonly associated with asthenospheric slab window opening or fast subduction of young (< 25 Ma) oceanic plate that enable slab melting at shallow depths; but their genesis has remained controversial. Here, we present a new approach that provides new constraints on adakite petrogenesis in hot subduction zones (the Philippines) and above an asthenospheric window (Baja California, Mexico). We use amphibole compositions to estimate the magma storage depths and the composition of the parental melts to test the hypothesis that adakites are pristine slab melts. We find that adakites from Baja California and Philippines formed by two distinct petrogenetic scenarios. In Baja California, hydrous mantle melts mixed/mingled with high-pressure (HP) adakite-type, slab melts within a lower crustal (~30 km depth) magma storage region before stalling into the upper arc crust (~7-15 km depth). In contrast, in the Philippines, primitive mantle melts stalled and crystallized within lower and upper crustal magma storage regions to produce silica-rich melts with an adakitic signature. Thereby, slab melting is not required to produce an adakitic geochemical fingerprint in hot subduction zones. However, our results also suggest that the downgoing crust potentially melted beneath Baja California.

  13. Stratospheric dust-aerosol event of november 1974.

    PubMed

    Meinel, A B; Meinel, M P

    1975-05-01

    A strong incursion of dust and aerosol at an altitude of 20 kilometers was noted over Baja California and southern Arizona in mid-November 1974, as indicated by bluish-ashen daylight skies and colorful twilight glows of the type usually associated with volcanic eruptions. Infrared satellite observations and reports from other sources eliminated a possible oceanic origin in the eastern Pacific. The stratum is probably from the extensive eruption of Volcan de Fuego in Gautemala in October 1974. PMID:17734369

  14. Biology and conservation of Xantus's Murrelet: Discovery, taxonomy and distribution

    USGS Publications Warehouse

    Carter, H.R.; Sealy, S.G.; Burkett, E.E.; Piatt, J.F.

    2005-01-01

    The biology of Xantus's Murrelets Synthliboramphus hypoleucus is similar in many respects to better-studied Ancient Murrelets S. antiquus, especially regarding morphology and the species' precocial mode of post-hatching development. It nests mainly in rock crevices but also under shrubs on islands in southern California, United States, and northwestern Baja California, Mexico (27oN to 34oN). The species was discovered in 1859 by Janos Xantus. Two subspecies (S. h. hypoleucus and S. h. scrippsi) are recognized that show limited evidence of interbreeding. At sea, closely related Craveri's Murrelets S. craveri co-occur with Xantus's Murrelets off California and western Baja California during half the year, but the former species has a discrete breeding range in the Gulf of California, Mexico. Breeding was documented at 13 island groups between 1863 and 1976. Post-breeding dispersal as far north as central British Columbia, Canada (c. 52oN) was observed in the 1940s to 1960s. A few Xantus's Murrelets disperse south of breeding colonies to Magdalena Bay, Baja California (c. 24oN). The southernmost record is the type specimen collected by Xantus near Cabo San Lucas, Baja California (c. 23oN). Chief threats to this species include introduced mammalian predators on breeding islands, heightened predation by natural predators in human-modified island habitats, and oil pollution. In January 2005, a Pacific Seabird Group special symposium, "Biology and conservation of the Xantus's Murrelet," highlighted conservation concerns and promoted publication of recent studies of this little-known alcid, with nine symposium papers published in this issue of Marine Ornithology. Much of what we know about Xantus's Murrelets has been learned in recent years, and many aspects of biology remain to be described.

  15. Climatological data for the rice-growing areas along the North Coast of Puerto Rico

    USGS Publications Warehouse

    Roman-Mas, Angel; Green, Bruce

    1987-01-01

    Rainfall, temperature, wind velocity and pan evaporation data were collected from May 1983 to September 1985, in the rice growing areas of Vega Baja, Manati, and Arecibo in northern Puerto Rico. Daily values and statistics including mean, standard deviation, extremes, and totals for each month of record were compiled. Descriptions of equipment installation and operation, data processing, and significance of climatological data for rice cultivation are presented. (Author 's abstract)

  16. Apollo 10 view of the Earth

    NASA Technical Reports Server (NTRS)

    1969-01-01

    An Apollo 10 view of Earth from 26,000 nautical miles photographed from the spacecraft during its translunar journey toward the Moon. While the Yucatan Peninsula is obscured by clouds, nearly all of Mexico north of the Istmus of Tehuantepec can be clearly delineated. The Gulf of California and Baja California and the San Joaquin Valley can be easily identified. Also, the delta of the Rio Grande River and the Texas coast are visible.

  17. Influence of a multiyear event of low salinity on the zooplankton from Mexican eco-regions of the California Current

    NASA Astrophysics Data System (ADS)

    Lavaniegos, Bertha E.

    2009-12-01

    Data are presented from the southern part of the California Current System (CCS) for the period 1997-2007, derived from the IMECOCAL monitoring program. Apart from El Niño 1997 to 1998, and La Niña 1998-1999 the strongest perturbation occurred in 2002 due to an intrusion of subarctic water affecting all the CCS. The response of zooplankton biomass to the strong cooling and freshening of the upper layer was an immediate drop followed by a progressive recovery between 2003 and 2007. Though the low salinity influence ended in 2006, the increased zooplankton trend continued, reinforced by increased upwelling activity beginning 2005 off north Baja California region (30-32°N) and beginning 2006 off central Baja California (24-30°N). Multiple regression analysis was done between regional variables and Upwelling Index (UI) and two basin-scale proxies: the North Pacific Gyre Oscillation (NPGO), and Pacific Decadal Oscillation (PDO). The significant influence of the NPGO on surface salinity, salinity stratification, zooplankton volume and secondary consumers (zooplankton carnivores) suggests a basin scale control on these variables more than local mechanisms. The signature of the NPGO was also evident in the base of the trophic web, but more related to the group of crustacean herbivores in the north eco-region, and the tunicates in central Baja California. In this last region, the effect from NPGO on the zooplankton volume and tunicates was antagonist with UI indicative of similar importance of basin and local processes. However, when the time interval is limited to the post-subarctic intrusion (2003-2007) the significance of multiple regression models and physical variables was lost. Therefore, though data and bio-physical coupling analysis off Baja California suggest a better relation with NPGO compared to PDO, it is still not sufficient to explain the magnitude of the perturbation observed in 2002.

  18. The northern coast plutonic-metamorphic complex, southeastern Alaska and northwestern British Columbia

    NASA Astrophysics Data System (ADS)

    Brew, D. A.; Ford, A. B.

    The northern Coast plutonic-metamorphic complex is but one segment of an 8,000-km-long batholithic complex that extends the length of the North American Cordillera from Baja, California to the Aleutian Islands. Different segments of the Cordilleran batholithic complex have significantly different features. This report documents the main characteristics and inferred evolutionary history of the northern Coast plutonic-metamorphic complex that should facilitate comparisons between segments.

  19. Unusual records of deepwater teleosteans trawled off the western coast of Mexico.

    PubMed

    De La Cruz-Agüero, J; Moncayo-Estrada, R; Cota-Gómez, V M; Villalobos-Ortiz, H; Valdez-Pelayo, A

    2016-09-01

    The first records of three midwater species for the Mexican ichthyofauna (Holtbyrnia laticauda, Brama dussumieri and Cubiceps baxteri), caught off the coast of Baja California, Mexico, in mid 2014, are reported. As far as is known, they are the first verified specimens, geo-referenced and catalogued in a reference fish collection for the west coast of Mexico. The species' known distributions were extended northward in the eastern Pacific Ocean, ranging from 3495 to 8300 km. PMID:27458012

  20. El Informe a la Nación sobre el Estado del Cáncer, 1975-2012

    Cancer.gov

    El Informe a la Nación sobre el Estado del Cáncer (1975-2012) indica que continuó la baja de tasas de mortalidad de todos los cánceres juntos, así como de la mayoría de los cánceres en hombres y mujeres de todos los grupos raciales y étnicos principales.

  1. Cretaceous paleogeography of Peninsular California

    SciTech Connect

    Gastil, R.G.

    1986-04-01

    For the past 15 years, paleomagnetic studies on various rock types have consistently shown southern and Baja California to have been located at 10/sup 0/-17/sup 0/ lower latitude, relative to cratonal North America, than it is today. Similar studies on the Salinian block and in southwestern Oregon also indicate substantially lower latitudes for the deposition of Upper Cretaceous rocks. In seeming contradiction, apparent correlations across the Gulf of California plate boundary relate Cambrian(.) to Triassic stratal rocks of Sonora and the Great Basin to their contemporaries in Baja California, and Jurassic and Cretaceous arc rocks in the peninsula to those in mainland Mexico. Therefore, relative movement along the San Andreas system seems limited to approximately 300 km in a right-lateral direction since the Miocene. A possible accommodation to both sets of evidence places the Baja Peninsula near its present position relative to cratonal North America until about the Middle Jurassic, when it began moving relatively southeastward. This left-lateral motion placed it about 11/sup 0/ southeast by the Aptian-Albian and 17/sup 0/ southeast by the Campanian-Maestrichtian. The Late Jurassic to Late Cretaceous arcs trended southeast through Sonora, Sinaloa, and Jalisco, and then down the length of peninsular California. The right-lateral return of the peninsula began during the Late Cretaceous. The fault systems for the return motion cannot lie west of the Gulf of California, and thus, neither can the earlier left-lateral fault.

  2. Damage from the El Mayor-Cucapah earthquake, April 2010: Why society cannot afford to ignore seismic risks to agricultural regions

    NASA Astrophysics Data System (ADS)

    Stenner, H. D.; Mathieson, E. L.; Okubo, S.; Anderson, R.; Rodriguez C., M. A.

    2010-12-01

    The M7.2 El Mayor-Cucapah earthquake of April 4, 2010 in Mexico’s Baja California caused extensive damage to the agricultural area of Mexicali Valley. The damage included wide-spread liquefaction and lateral spreading which destroyed or damaged irrigation canals. Without water, wheat, alfalfa, and other crops were lost. Fields were cut by fissures and partially buried by massive sand blows. Regional tilting from the earthquake was a serious issue for the gravity-controlled irrigation system. Ruptured canals and groundwater from sand blows flooded fields, roads, and towns. Flooding further damaged crops and brought contamination with it. Fissures and scarps through farm communities cracked buildings; ruptured water, sewer, and other pipelines; and made roads temporarily difficult to pass. Economically, farmers, seasonal farm workers, and agricultural suppliers were affected; reducing their ability to consume the goods and services of businesses unrelated to agriculture. Similar damage was observed in earlier earthquakes over the past 100 years. Society quickly forgets how the earth responds to strong shaking. We hope to provide a vivid portrait of this agricultural disaster so that other farming communities prone to strong seismic shaking may visualize what can happen from their own inevitable future earthquake. Fissure and sand blows southeast of Cucapah, Baja California, April 16, 2010. Heavily damaged irrigation canal northwest of Zacamoto, Baja California, April 15, 2010.

  3. Variability of Extreme Precipitation Events in Tijuana, Mexico During ENSO Years

    NASA Astrophysics Data System (ADS)

    Cavazos, T.; Rivas, D.

    2007-05-01

    We present the variability of daily precipitation extremes (top 10 percecnt) in Tijuana, Mexico during 1950-2000. Interannual rainfall variability is significantly modulated by El Nino/Southern Oscillation. The interannual precipitation variability exhibits a large change with a relatively wet period and more variability during 1976- 2000. The wettest years and the largest frequency of daily extremes occurred after 1976-1977, with 6 out of 8 wet years characterized by El Nino episodes and 2 by neutral conditions. However, more than half of the daily extremes during 1950-2000 occurred in non-ENSO years, evidencing that neutral conditions also contribute significantly to extreme climatic variability in the region. Extreme events that occur in neutral (strong El Nino) conditions are associated with a pineapple express and a neutral PNA (negative TNH) teleconnection pattern that links an anomalous tropical convective forcing west (east) of the date line with a strong subtropical jet over the study area. At regional scale, both types of extremes are characterized by a trough in the subtropical jet over California/Baja California, which is further intensified by thermal interaction with an anomalous warm California Current off Baja California, low-level moisture advection from the subtropical warm sea-surface region, intense convective activity over the study area and extreme rainfall from southern California to Baja California.

  4. Mitochondrial Genetic Structure and Matrilineal Origin of White Sharks, Carcharodon carcharias, in the Northeastern Pacific: Implications for Their Conservation.

    PubMed

    Oñate-González, Erick C; Rocha-Olivares, Axayácatl; Saavedra-Sotelo, Nancy C; Sosa-Nishizaki, Oscar

    2015-01-01

    White sharks (Carcharodon carcharias, WS henceforth) are globally and regionally threatened. Understanding their patterns of abundance and connectivity, as they relate to habitat use, is central for delineating conservation units and identifying priority areas for conservation. We analyzed mitochondrial data to test the congruence between patterns of genetic connectivity and of individual movements in the Northeastern Pacific (NEP) and to trace the matrilineal origin of immature WS from coastal California and Baja California to adult aggregation areas. We analyzed 186 mitochondrial control region sequences from sharks sampled in Central California (CC; n = 61), Southern California Bight (SCB; n = 25), Baja California Pacific coast (BCPC; n = 9), Bahía Vizcaíno (BV; n = 39), Guadalupe Island (GI; n = 45), and the Gulf of California (GC; n = 7). Significant mitochondrial differentiation between adult aggregation areas (CC, GI) revealed two reproductive populations in the NEP. We found general concordance between movement patterns of young and adult WS with genetic results. Young sharks from coastal California and Baja California were more likely born from females from GI. Mitochondrial differentiation of young-of-the-year from SCB and BV suggests philopatry to nursery areas in females from GI. These results provide a genetic basis of female reproductive behavior at a regional scale and point to a preponderance of sharks from GI in the use of the sampled coastal region as pupping habitat. These findings should be considered in Mexican and US management and conservation strategies of the WS NEP population. PMID:26034138

  5. Further records of species of Gennadas (Crustacea, Decapoda, Dendrobranchiata, Benthesicymidae) in the Mexican Pacific.

    PubMed

    Hendrickx, Michel E

    2015-01-01

    Additional material of species of Gennadas was collected off western Mexico during the TALUD survey aboard the R/V "El Puma". Gennadas sordidus was by far the most common species collected and only a few specimens of the other three species, G. incertus, G. propinquus and G. scutatus, were obtained. New and previous records indicate that Gennadas sordidus is widely distributed along the west coast of Mexico, although there is only one record for it south of the Gulf of California. In this study it was collected in as many as 35 localities, both in the Gulf of California and off the west coast of Southern Baja California. Numbers of specimens also confirmed that it is the dominant species of Gennadas in the area. Gennadas incertus was found in six samples, all from off the west coast of northern Baja California. The other two species occurred each in two samples only, with sampling localities widely spread along the Baja California Peninsula. Compared with the rest of the eastern Pacific, the diversity of Gennadas in Mexican waters is intermediate (6 species) vs. 9 in Chile and 4 in the NW Pacific. PMID:26249961

  6. Net Slip across the Ballenas Transform Fault Measured from Offset Ignimbrite Deposits

    NASA Astrophysics Data System (ADS)

    Stock, J. M.; Martín, A.; Chapman, A.; López-Martínez, M.

    2008-12-01

    The Ballenas Transform Fault in the Gulf of California separates the Baja California Peninsula (to the W on the Pacific Plate) from Isla Angel de la Guarda (to the E on the North America plate). This active right-lateral fault originated in a Pliocene plate boundary reorganization when part of the rift margin jumped westward into the Baja California peninsula, transferring Isla Angel de la Guarda from the Pacific plate to the North America plate. The net slip along the Ballenas transform fault system is expected to be less than the 250-300 km of post-Miocene opening of the northern Gulf of California basins. Here we constrain the net slip using geological similarities between the west coast of the island and the east coast of Baja California. Reconnaissance geological mapping on Isla Angel de la Guarda reveals the presence of a middle Miocene high-silica rhyolite ignimbrite with an Ar/Ar age of 11.8±0.2 Ma on sanidine. This deposit is preserved in a paleo-low in Cretaceous (?) granitic rocks in the central part of the island. The major and trace element compositions are similar to those of the Tuff of San Felipe, identified in Sonora and Baja California, but not previously recognized on Isla Angel de la Guarda. The deposit from the island exhibits a paleomagnetic remanence vector toward the SW and nearly horizontal, similar to that of the Tuff of San Felipe, and far outside of the expected paleomagnetic remanence direction. The ignimbrite on Isla Angel de la Guarda has an age younger than that previously reported for the Tuff of San Felipe, but within the range of ages from other outcrops of the Tuff of San Felipe in Sonora (Vidal-Solano et al., 2008). We correlate this ignimbrite to a similar unit preserved in isolated locations northwest of Cataviña on the Baja California peninsula, for which paleomagnetic work shows a very similar remanence direction. Using the SE limit of these outcrops against the granitic rocks in both locations yields an estimate of ~130

  7. Effects of Ocean Climate on Transboundary Movement of Coastal Pelagic Resources Between the EEZs of Mexico and the United States

    NASA Astrophysics Data System (ADS)

    Baumgartner, T. R.; Garcia, J.; Sanchez, C.; Lo, N. C.; Charter, R.

    2007-05-01

    Interannual to multidecadal changes in ocean climate directly impact access to transboundary coastal pelagic resources between fisheries operating in U.S. and Mexican waters. This study provides a preliminary analysis of the scale of year-to-year shifts in the distribution of the Pacific sardine (Sardinops sagax caeruleus) with data from 2002 and 2003. One of the purposes of this initiative is to provide a template for collaborative research to guide regional policy development for responsible and sustainable utilization of the shared resource. This work is based on coordinated quarterly ocean surveys run by Mexican (the IMECOCAL program=Investigaciones Mexicanas de la Corriente de California) and U.S. scientists (the CalCOFI program=California Cooperative Oceanic Fisheries Investigations) allowing us to evaluate the annual state of the pelagic ecosystem from northern California to southern Baja California. The subject of this study is the "subarctic stock" of the Pacific sardine which is centered off California in the U.S. and extends southwards to the region off central Baja California. Estimates of sardine biomass in U.S. and Mexican waters, based on the rates of egg production measured during the IMECOCAL and CalCOFI surveys of April 2002 and April 2003, show order of magnitude differences in the relative proportions of biomass in the Mexican EEZ that is associated with the contrasts in ocean climate resulting from the regional effects of El Niño during April 2003. Results indicate a significant northward shift of the sardine stock off Mexico during 2003: we estimate that approximately 20 percent of the total biomass of the stock was located in the Mexican EEZ during spring of 2002 while the shift in ocean climate resulted in the presence of only 2 percent of the biomass of the stock in Mexican waters during April, 2003. A second, more southerly sardine stock extended from southern to central Baja California in April, 2003, but it was out of reach of the fleet

  8. Guiding the Search for Surface Rupture and Paleoseismic Sites using Low-Level Aerial Surveys, Geodetic Imaging, Remote Sensing and Field Mapping (Invited)

    NASA Astrophysics Data System (ADS)

    Hudnut, K. W.; Fletcher, J. M.; Teran, O.; Gonzalez-Garcia, J. J.; Hinojosa, A.; Rockwell, T. K.; Akciz, S. O.; Leprince, S.; Fielding, E. J.; Briggs, R. W.; Crone, A. J.; Gold, R. D.; Prentice, C. S.; Stock, J.; Avouac, J.; Simons, M.; Galetzka, J. E.; Lynch, D. K.; Cowgill, E.; Oskin, M. E.; Morelan, A.; Aslaksen, M.; Sellars, J.; Woolard, J.

    2010-12-01

    The significant earthquakes of 2010 produced surficial expressions ranging from blind faulting and coastal uplift in Leogane, Haiti and Maule, Chile to surface faulting in Baja California, Mexico and Yushu, China. In Haiti and Baja California geodetic imaging methods strongly guided field reconnaissance and surface rupture mapping efforts, yet in quite different ways. In these challenging examples, InSAR, UAVSAR and optical image differencing, as well as SAR pixel tracking methods, were used to locate and quantify ground deformation and ruptures. In Baja California prominent rupture occurred in parts of the Cucapah mountains, yet along an 11 km-long stepover section, the zone of faulting was discontinuous and obscured by rockfalls. Optical image differencing helped identify surface rupture, especially through this stepover. SAR pixel tracking confirmed that rupture occurred along the newly identified Indiviso fault in Baja California, though masked by ground failure in the Colorado River Delta. Also in Baja California (and extending north of the US-MX border), a complex set of NE-SW cross-faults and N-S breaks were imaged with UAVSAR, InSAR, and aerial photography allowing the intricate pattern of faulting to be scrutinized. In Haiti, surface rupture along the inferred source fault was not observed during initial reconnaissance. This led to extensive imagery- and field-based searches for surface deformation, aided by InSAR, which revealed that surface deformation was caused primarily by off-fault blind thrusting. In Baja California, high resolution (up to 3-5 cm GSD) aerial imaging by low-altitude aerial stereo photography was then used to identify promising locations for measuring slip vectors on the fault, and to aid in mapping the surface rupture in detail (at 1:500 scale). Digital aerial photography with 0.1 m GSD by NOAA using their DSS 439 camera was rapidly reduced to orthomosaics (at 0.25 m GSD) and then used as uniform base imagery for rupture mapping. In

  9. Functional genomic and phenotypic responses to desiccation in natural populations of a desert drosophilid

    PubMed Central

    Rajpurohit, Subhash; Oliveira, Cássia C.; Etges, William J.; Gibbs, Allen G.

    2014-01-01

    We used whole transcriptome microarrays to assess changes in gene expression and monitored mortality rates and epicuticular hydrocarbons (CHCs) in response to desiccation stress in four natural populations of Drosophila mojavensis from Baja California and mainland Mexico. Desiccation had the greatest effect on gene expression, followed by biogeographical variation at regional and population levels. Genes involved in environmental sensing and cuticular structure were up-regulated in dry conditions, while genes involved in transcription itself were down-regulated. Flies from Baja California had higher expression of reproductive and mitochondrial genes, suggesting that these populations have greater fecundity and higher metabolic rates. Host plant differences had a surprisingly minor effect on the transcriptome. In most cases, desiccation-caused mortality was greater in flies reared on fermenting cactus tissues than laboratory media. Water content of adult females and males was significantly different, and was lower in Baja California males. Different groups of CHCs simultaneously increased and decreased in amounts due to desiccation exposure of 9 and 18 hr and were population-specific and dependent on larval rearing substrates. Overall, we observed that changes in gene expression involved a coordinated response of behavioral, cuticular and metabolic genes. Together with differential expression of cuticular hydrocarbons, this study revealed some of the mechanisms that have allowed D. mojavensis to exploit its harsh desert conditions. Certainly, for D. mojavensis that uses different host plants, population-level understanding of responses to stressors associated with future climate change in desert regions must be evaluated across geographical and local ecological scales. PMID:23505972

  10. Southern Ocean influence on the eastern tropical North Pacific's intermediate-depth circulation during the Last Glacial Maximum

    NASA Astrophysics Data System (ADS)

    Carriquiry, José D.; Sanchez, Alberto; Leduc, Guillaume

    2015-08-01

    The oxygen and carbon isotopic compositions of benthic foraminiferal tests were measured on sedimentary sequences retrieved on the Magdalena Margin, off southern Baja California, Mexico. We reconstruct the hydrographic changes along the water column that occurred in the northeastern tropical Pacific since the Last Glacial Maximum (LGM) and compare those changes to the ones that occurred in the northwest Pacific (NWP, i.e., off Japan and Russia), in the northeast Pacific along the Californian Margin, as well as in the southeast Pacific (off Chile). The foraminiferal δ18O depth profiles across the North and southeast Pacific show similar trends between the LGM and the Holocene, indicating that changes in the oceanographic conditions between ~400 and 2000 m depth were very similar. Changes in the isotopic composition of dissolved inorganic carbon (δ13CDIC) in the Baja California Margin since the Last Glacial Maximum were reconstructed using the δ13C of shallow endobenthic foraminifers U. peregrina and the epibenthic Cibicides mckannai. The most striking result is a marked shift toward more positive δ13C values below 1200 m depth in the northeast Pacific (NEP) during the Holocene (relative to the LGM). This observation suggests that a nutrient-rich water mass ventilated the NEP during the LGM. At a basin scale, the δ13C values of NEP waters at intermediate depths were more negative relative to the NWP and southeast Pacific during the LGM, suggesting that the nutrient-rich water column along the NEP (i.e., Baja California Margin) was confined in that area as observed today.

  11. [Not Available].

    PubMed

    Flores Navarro-Pérez, Carmen; González-Jiménez, Emilio; Schmidt-RioVilla, Jacqueline; Meneses-Echávez, José Francisco; Correa-Bautista, Jorge Enrique; Correa-Rodríguez, María; Ramírez-Vélez, Robinson

    2016-01-01

    Objetivos: los objetivos de este estudio fueron analizar el nivel nutricional en una población de niños y adolescentes colombianos y determinar la posible relación entre el nivel nutricional y el estado nutricional según el índice de masa corporal (IMC) y la circunferencia de cintura (CC).Material y métodos: estudio transversal en 6.383 niños y adolescentes de entre 9 y 17,9 años de edad, de Bogotá, Colombia. Se aplicó de manera autodiligenciada el cuestionario Krece Plus validado en el estudio enKid como indicador del nivel nutricional con las categorías alto (test ≥ 9), medio (test 6-8) y bajo (test ≤ 5). Se tomaron medidas de peso, talla, CC, y se calculó el IMC como marcadores del estado nutricional.Resultados: de la población general, el 57,9% eran chicas (promedio de edad 12,7 ± 2,3 años). En todas las categorías del IMC, más del 50% de chicos y chicas siguen una dieta de muy baja calidad, que empeora progresivamente con el avance en edad. En ambos sexos, se observaron tendencias entre un nivel nutricional muy bajo con el desarrollo de sobrepeso. Asimismo, la obesidad abdominal por CC se relacionó con una puntuación baja en el Krece Plus en ambos sexos.Conclusiones: en escolares de Bogotá, una dieta de muy baja calidad se relacionó con alteraciones del estado nutricional (IMC y CC), especialmente entre chicas y adolescentes. Estos resultados deben alentar el desarrollo de intervenciones orientadas a mejorar los hábitos nutricionales entre los escolares colombianos. PMID:27571667

  12. Space geodetic observation of the deformation cycle across the Ballenas Transform, Gulf of California

    NASA Astrophysics Data System (ADS)

    Plattner, Christina; Malservisi, Rocco; Amelung, Falk; Dixon, Timothy H.; Hackl, Matthias; Verdecchia, Alessandro; Lonsdale, Peter; Suarez-Vidal, Francisco; Gonzalez-Garcia, Javier

    2015-08-01

    The Gulf of California, Mexico, accommodates ~90% of North America-Pacific plate relative motion. While most of this motion occurs on marine transform faults and spreading centers, several fault segments in the central Gulf come close to peninsular Baja California. Here we present Global Positioning System and interferometric synthetic aperture radar data near the Ballenas transform fault, separating the peninsula from Angel de la Guarda Island. We observe interseismic motion between June 2004 and May 2009 and displacements associated with the 3 August 2009 Mw 6.9 earthquake. From the interseismic data we estimate a locking depth of 9-12.5 km and a slip rate of 44.9-48.1 mm/yr, indicating that faults east of Angel de la Guarda deform at negligible rates and that the Ballenas Transform accommodates virtually all of the relative motion between the North American plate and the Baja California microplate. Our preferred model for coseismic slip on a finite rectangular fault plane suggests 1.3 m of strike-slip displacement along a vertical rupture plane that is 60 km long and extends from the surface to a depth of 13 km in the eastern Ballenas Channel, striking parallel to Baja California-North America relative plate motion. These estimates agree with the seismic moment tensor and the location of the major foreshock and aftershocks and are compatible with the fault location identified from high-resolution bathymetric mapping. The geodetic moment is 33% higher than the seismic moment in part because some afterslip and viscous flow in the first month after the earthquake are included in the geodetic estimate. Coulomb stress changes for adjacent faults in the Gulf are consistent with the location of smaller aftershocks following the 2009 main shock and suggest potential triggering of the 12 April 2012 Mw 6.9 Guaymas earthquake.

  13. Real-time GPS seismology with a stand-alone receiver: a preliminary feasibility demonstration

    NASA Astrophysics Data System (ADS)

    Colosimo, G.; Crespi, M.; Mazzoni, A.

    2010-12-01

    We show the feasibility of waveforms and coseismic displacements real-time estimation at few centimeters accuracy level by a stand-alone dual-frequency GPS receiver through a variometric approach. This approach is based on the time single-differences of the carrier phase observations collected at high-rate (1Hz or more) by a stand-alone receiver and on the standard GPS broadcast products (orbits, clocks). Time series of epoch-by-epoch displacements are estimated at first; then, they can be summed over the interval (limited to few minutes) when the earthquake occurs, provided the collected observations are continuous. The estimation biases due to mismodeling accumulate over time and display as a trend, which can be considered linear and easily removed thanks to the shortness of the interval. Since the proposed approach does not require any additional technological complexity nor centralized data analysis, in principle it can be embedded into the receiver firmware, providing also a significant contribution to tsunami warning systems. After a preliminary test regarding a simulated example, the effectiveness has been proven over real data. In details, we have analyzed the 1Hz GPS data recorded by the IGS station BREW during the Denali Fault, Alaska earthquake (Mw 7.9, November 3, 2002, 22:12:41 UTC) and the 5 Hz data collected by some stations included into the UNAVCO-Plate Boundary Observatory network and California Real Time Network (CRTN) during the Baja California, Mexico earthquake (Mw 7.2, April 04, 2010, 22:40:42 UTC). The comparisons with results obtained with different strategies show an agreement within few centimeters; examples for Baja California earthquake (waveforms for stations P496 e P744, to be compared with http://www.unavco.org/research_science/science_highlights/2010/M7.2-Baja.html) are shown in Figures 1 and 2. Fig. 1 - P496 Fig. 2 - P744

  14. Geophysical structures and late Neogene history of gulf and peninsular province of the Californias

    SciTech Connect

    Ness, G.; Francisco Suarez V.; Gustavo Calderon R.

    1986-07-01

    Researchers from the Continental Margins Study Group at Oregon State University, the Direccion General de Oceanografia, and CICESE have completed a 10-year reconnaissance-scale geophysical survey of the Pacific Exclusive Economic Zone of Mexico. Six cruises, aboard research vessels of the Armada de Mexico, have been completed, and approximately 50,000 nmi of survey track lines have been run. From these data and from other published sources, the authors have compiled a series of onshore-offshore maps of the region extending 1500 nmi from Point Conception in southern Alta California to Lazaro Cardenas in Michoacan. These maps include: Physiography, with 200-m contours of bathymetry and topography; Free-Air Gravity Anomalies, with 10-mgal contours of both onshore and offshore gravity: Marine Magnetic Anomalies and Oceanic Crustal Isochrons, with 50-nT contours over continental crust and 1-m.y. isochrons over oceanic crust; Seismo-Tectonics, with 1963-1982 WWSSN seismicity superimposed on interpreted onshore-offshore faults. Slow gulf rifting, at least in the south, began as early as about 12-14 Ma. Oceanic crust was first exposed there by about 9-10 Ma. Pacific-North American relative motion was distributed between faults in the gulf and faults on the Pacific side of Baja California until about 4-5 Ma. This rifting history is consistent with the history of changes in volcanic chemistry along the gulf side of Baja. Initial rifting in the southern gulf was diffuse, involving many small, independently active crustal blocks. Present-day faulting, onshore in northern Baja, in the northern and central gulf, and onshore in Jalisco and Colima, also involves many small, independently active fault blocks and slices that are similar to those occurring onshore in southern Alta California.

  15. Decadal variability in abundances of the dominant euphausiid species in southern sectors of the California Current

    NASA Astrophysics Data System (ADS)

    Brinton, Edward; Townsend, Annie

    2003-08-01

    Euphausiid abundance data from broadly based California Cooperative Oceanic Fisheries Investigation surveys in California and Baja California sectors of the California Current provided a time series distinguishing periodic, rhythmic and irregular species patterns. Comparisons with environmental indexes indicate significant correlations with warm-water species, most notably in coastal Nyctiphanes simplex. Oceanic warm-water species were similarly, but less extremely, allied with an index. Coastal warm-water N. simplex was uncommon off southern California before the atmospheric regime shift of the 1970s. It assumed a post-1978 pattern of rhythmic biannual abundance increases and decreases during 1981-2000. The near-tropical oceanic Euphausia eximia and Pacific Central subtropicals patterned similarly, but was more periodic than rhythmic. Euphausia pacifica, the most dominant and broadly ranging Euphausia species, peaked at irregular but distinct bi-decadal abundances during 6 strong La Niña episodes. The peaks uniformly collapsed by 90%, becoming El Niño-associated minima. The cold-water coastal northern species Thysanoessa spinifera frequently ranged far south off Baja California before 1960 but became limited to Central California in the 1980s. The importance of T. spinifera off the Californias is small compared with northern regions, but it extends to southern upwelling centers contributing to dominance, here, by cold-water euphausiids. Decadal periodicity of species abundances decreased in the 1990s, when trends became more common. Differences among sectors were minimal between the two Californias, but were often distinct between southern California and Central Baja California. Species abundances, comparing pre- and post-climate shift species averages, differed insignificantly for all species when logarithmic values were used. With arithmetic values, most 1977-1998 average values were the greater, but with large standard deviations.

  16. Model-based comparisons of phylogeographic scenarios resolve the intraspecific divergence of cactophilic Drosophila mojavensis.

    PubMed

    Smith, Gilbert; Lohse, Konrad; Etges, William J; Ritchie, Michael G

    2012-07-01

    The cactophilic fly Drosophila mojavensis exhibits considerable intraspecific genetic structure across allopatric geographic regions and shows associations with different host cactus species across its range. The divergence between these populations has been studied for more than 60years, yet their exact historical relationships have not been resolved. We analysed sequence data from 15 intronic X-linked loci across populations from Baja California, mainland Sonora-Arizona and Mojave Desert regions under an isolation-with-migration model to assess multiple scenarios of divergence. We also compared the results with a pre-existing sequence data set of eight autosomal loci. We derived a population tree with Baja California placed at its base and link their isolation to Pleistocene climatic oscillations. Our estimates suggest the Baja California population diverged from an ancestral Mojave Desert/mainland Sonora-Arizona group around 230,000-270,000years ago, while the split between the Mojave Desert and mainland Sonora-Arizona populations occurred one glacial cycle later, 117,000-135,000years ago. Although we found these three populations to be effectively allopatric, model ranking could not rule out the possibility of a low level of gene flow between two of them. Finally, the Mojave Desert population showed a small effective population size, consistent with a historical population bottleneck. We show that model-based inference from multiple loci can provide accurate information on the historical relationships of closely related groups allowing us to set into historical context a classic system of incipient ecological speciation. PMID:22571504

  17. A skin test survey of valley fever in Tijuana, Mexico.

    PubMed

    Fredrich, B E

    1989-01-01

    Results of a study of the prevalence of valley fever among 1128 residents of Tijuana, Baja California are presented. Children from primary and middle schools (n = 497) and adults from technical institutes and maquiladoras (assembly plants) were tested for reaction to both spherulin and coccidioidin during 1985-1986, and they completed a questionnaire containing 23 variables on their socio-environment. Place of residence was mapped. The population sampled is largely middle class. Discriminant analysis indicates the distribution of positive cases is not clustered, nor can it be correlated with geomorphic factors such as mesa tops, canyons, or valley bottoms. PMID:2588049

  18. Morphological variation in the hydromedusa genus Polyorchis on the west coast of North America

    SciTech Connect

    Rees, John T.; Larson, R. J.

    1980-11-01

    Morphological variation in the hydromedusan genus Polyorchis on the west coast of North American is analyzed in relation to gonad number, tentacle number, and radial canal diverticula number relative to the height of the bell. In specimens of Polyorchis examined, it is concluded that P. penicillatus (Eschscholtz, 1829) is highly variable morphologically over its known geographic range from Alaska to Baja California. P. montereyensis Skogsberg, 1948 is considered a synonym of P. penicillatus, while P. haplus Skogsberg. 1948, is retained as a valid species.

  19. Remote sensing of the biological dynamics of large-scale salt evaporation ponds

    NASA Technical Reports Server (NTRS)

    Richardson, Laurie L.; Bachoon, Dave; Ingram-Willey, Vebbra; Chow, Colin C.; Weinstock, Kenneth

    1992-01-01

    Optical properties of salt evaporation ponds associated with Exportadora de Sal, a salt production company in Baja California Sur, Mexico, were analyzed using a combination of spectroradiometer and extracted pigment data, and Landsat-5 Thematic Mapper imagery. The optical characteristics of each pond are determined by the biota, which consists of dense populations of algae and photosynthetic bacteria containing a wide variety of photosynthetic and photoprotective pigments. Analysis has shown that spectral and image data can differentiate between taxonomic groups of the microbiota, detect changes in population distributions, and reveal large-scale seasonal dynamics.

  20. California State Waters Map Series—Offshore of Pigeon Point, California

    USGS Publications Warehouse

    Cochrane, Guy R.; Watt, Janet T.; Dartnell, Peter; Greene, H. Gary; Erdey, Mercedes D.; Dieter, Bryan E.; Golden, Nadine E.; Johnson, Samuel Y.; Endris, Charles A.; Hartwell, Stephen R.; Kvitek, Rikk G.; Davenport, Clifton W.; Krigsman, Lisa M.; Ritchie, Andrew C.; Sliter, Ray W.; Finlayson, David P.; Maier, Katherine L.

    2015-01-01

    The Offshore of Pigeon Point map area lies within the cold-temperate biogeographic zone that is called either the “Oregonian province” or the “northern California ecoregion.” This biogeographic province is maintained by the long-term stability of the southward-flowing California Current, the eastern limb of the North Pacific subtropical gyre that flows from southern British Columbia to Baja California. At its midpoint off central California, the California Current transports subarctic surface (0–500 m deep) waters southward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current,

  1. A Study of the Planetary Nebula M57

    NASA Technical Reports Server (NTRS)

    Archie, Deithra; Moore, Brian

    2000-01-01

    We present an overview of the objects known as planetary nebulae. These emission nebulae are the end-product of the evolution of a dying star. our ground-based imagery is of the most famous of these objects, M57, also known as the Ring Nebula. Taken with the 2.12-meter telescope at San Pedro Matir in Baja, Mexico, these seeing-limited images show variations in ionization, density and temperature as a function of position in the nebula. Our ground-based imagery is compared to similar HST archival images.

  2. Analysis of organic matter in sediments and meteorites and paleochemical studies of extinct and contemporary life forms

    NASA Technical Reports Server (NTRS)

    Calvin, M.

    1975-01-01

    The insoluble organic materials present in the algal mats at Laguna Mormona, Baja California were studied. A series of six identical sediments collected from Mono lake which were stored under different conditions was investigated to see if any changes are observed in the lipid distribution patterns as a result of differences in sample storage conditions. Bacteria strains from Mono Lake sediments were cultured in bulk quantities and the sterol fractions from them were isolated and analyzed. Results add further support to the utility of the sterols as a chemotaxonomical tool in distinguishing and classifying these bacteria.

  3. A high-resolution Fourier-transform infrared spectrometer.

    NASA Technical Reports Server (NTRS)

    Johnson, H. L.; Forbes, F. F.; Thompson, R. I.; Steinmetz , D. L.; Harris, O.

    1973-01-01

    We have developed a Fourier-transform infrared spectrometer having a resolution of 0.5/cm over the range of wavelength from 1 to 5.5 microns. It has been used to observe the sun over this wavelength range from a Lear Jet flying at an altitude of 14 km, and to observe a number of stars from the ground, using the 229-cm telescope of the Steward Observatory and the 152-cm aluminum-mirror telescope at the Observatorio Astronomico Nacional in the Sierra de San Pedro Martir, Baja California, Mexico. The solar spectrum is given here, while the ground-based spectra are being published separately.

  4. Eggshell thinning and contaminant levels in bald eagle eggs from Arizona, 1977 to 1985

    USGS Publications Warehouse

    Grubb, T.G.; Wiemeyer, Stanley N.; Kiff, L.F.

    1990-01-01

    The mean eggshell thickness of 11 eggs of bald eagles (Haliaeetus leuccocephalus) and 21 samples of eggshell fragments (n = 32) collected from 14 nests in Arizona during 1977 to 1985 was 0.539 mm, 8.8% thinner than the pre-1947 (pre-DDT) mean for eggs from southern California and Baja California, Mexico. Eleven eggs analyzed for contaminants contained slightly elevated concentrations of DDE (3.3pmm wet weight) and mercury (0.14 ppm). Productivity of sampled pairs was low but improving. The predictive equations of Wiemeyer et al. (1984) were also verified.

  5. Taxonomic revision of the Trapdoor spider genus Eucteniza Ausserer (Araneae, Mygalomorphae, Euctenizidae)

    PubMed Central

    Bond, Jason E.; Godwin, Rebecca L.

    2013-01-01

    Abstract The mygalomorph spider genus Eucteniza Ausserer, 1875 comprises 15 nominal species known only from the southwestern United States (Texas) and Mexico (Northern, Central, and the Baja Peninsula). Eucteniza atoyacensis Bond & Opell, 2002 is considered a nomen dubium; E. rex (Chamberlin, 1940) and E. stolida (Gertsch & Mulaik, 1940) are both considered junior synonyms of E. relata (O.P.-Cambridge, 1895). Twelve new species are described: E. caprica, E. coylei, E. diablo, E. cabowabo, E. huasteca, E. zapatista, E. chichimeca, E. ronnewtoni, E. hidalgo, E. golondrina, E. panchovillai and E. rosalia. PMID:24363573

  6. San Pedro Mártir Observatory: a competitive astronomical site for the next generation of telescopes

    NASA Astrophysics Data System (ADS)

    Echevarria, J.; Michel, R.; Costero, R.

    2006-08-01

    We review some of the most important aspects of the astronomical Observatory at the Sierra de San Pedro Mártir, in Baja California, México. We put particular emphasis on our own results on seeing evaluation and compare the results with what we considered the best twenty sites in the world. We also compile the results on the San Pedro Mártir site in sensitive aspects like number of clear and photometric nights, scintillation, water vapour content and seismic activity among others.

  7. San Juanico Hybrid System Technical and Institutional Assessment: Preprint

    SciTech Connect

    Corbus, D.; Newcomb, C.; Yewdall, Z.

    2004-07-01

    San Juanico is a fishing village of approximately 120 homes in the Municipality of Comondu, Baja California. In April, 1999, a hybrid power system was installed in San Juanico to provide 24-hour power, which was not previously available. Before the installation of the hybrid power system, a field study was conducted to characterize the electrical usage and institutional and social framework of San Juanico. One year after the installation of the hybrid power system a''post-electrification'' study was performed to document the changes that had occurred after the installation. In December of 2003, NREL visited the site to conduct a technical assessment of the system.

  8. New genera of philopotine spider flies (Diptera, Acroceridae) with a key to living and fossil genera.

    PubMed

    Gillung, Jéssica P; Winterton, Shaun 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. PMID:21998545

  9. Assessing the geologic and climatic forcing of biodiversity and evolution surrounding the Gulf of California

    USGS Publications Warehouse

    Dolby, Greer; Bennett, Scott E K.; Lira-Noriega, Andres; Wilder, Benjamin T.; Munguia-Vega, Adrian

    2015-01-01

    For almost a century the Baja California peninsula (Peninsula), Gulf of California (Gulf), and broader Sonoran Desert region (figure 1) have drawn geologists and biologists alike to study its unique physical and evolutionary processes (e.g., Wittich 1920; Darton 1921; Nelson 1921; Johnston 1924; Beal 1948; Durham and Allison 1960). The challenge remains to untangle the long, intricate, and at times enigmatic geological and climatological histories that have shaped the high levels of endemism and biodiversity observed in the region today (Van Devender 1990; Grismer 2000; Riddle et al. 2000).

  10. Taxonomic revision of the Trapdoor spider genus Eucteniza Ausserer (Araneae, Mygalomorphae, Euctenizidae).

    PubMed

    Bond, Jason E; Godwin, Rebecca L

    2013-01-01

    The mygalomorph spider genus Eucteniza Ausserer, 1875 comprises 15 nominal species known only from the southwestern United States (Texas) and Mexico (Northern, Central, and the Baja Peninsula). Eucteniza atoyacensis Bond & Opell, 2002 is considered a nomen dubium; E. rex (Chamberlin, 1940) and E. stolida (Gertsch & Mulaik, 1940) are both considered junior synonyms of E. relata (O.P.-Cambridge, 1895). Twelve new species are described: E. caprica, E. coylei, E. diablo, E. cabowabo, E. huasteca, E. zapatista, E. chichimeca, E. ronnewtoni, E. hidalgo, E. golondrina, E. panchovillai and E. rosalia. PMID:24363573

  11. Scallopleaf sage (salvia vaseyi: Lamiaceae) discovered in Arizona

    USGS Publications Warehouse

    Cain, J.W., III; Felger, R.S.; Jansen, B.D.; Krausman, P.R.

    2010-01-01

    During the course of field work in Cabeza Prieta National Wildlife Refuge, southwestern Arizona, in 2003, James Cain and Brian Jansen collected Salvia vaseyi, previously known only from the western edge of the Sonoran Desert in California and Baja California. Our findings indicate this shrub might be more widespread in southwestern Arizona mountains. Salvia vaseyi in Arizona seems to represent a relict population. There are other shrubby Salvia in Arizona, but S. vaseyi is the most xeric-mhabiting species and has the narrowest ecological and geographical range.

  12. Boiling and condensation processes in the Cerro Prieto beta reservoir under exploitation

    SciTech Connect

    Truesdell, A. , Menlo Park, CA ); Manon, A.; Quijano, L. ); Coplen, T. ); Lippmann, M. )

    1992-01-01

    The deep Cerro Prieto (Baja California, Mexico) beta reservoir is offset vertically by the southwest-northeast trending, normal H fault. Under exploitation pressures in the upthrown block have decreased strongly resulting in boiling and high-enthalpy production fluids. Significant differences in fluid chemical and isotopic compositions are observed in the two parts of the reservoir and particularly in an anomalous zone associated with the H fault. These differences result from intense boiling and adiabatic steam condensation, as well as from leakage of overlying cooler water along the fault.

  13. California State Waters Map Series: offshore of San Francisco, California

    USGS Publications Warehouse

    Cochrane, Guy R.; Johnson, Samuel Y.; Dartnell, Peter; Greene, H. Gary; Erdey, Mercedes D.; Golden, Nadine E.; Hartwell, Stephen R.; Endris, Charles A.; Manson, Michael W.; Sliter, Ray W.; Kvitek, Rikk G.; Watt, Janet Tilden; Ross, Stephanie L.; Bruns, Terry R.

    2015-01-01

    Circulation over the continental shelf in the Offshore of San Francisco map area is dominated by the southward-flowing California Current, an eastern limb of the North Pacific Gyre that flows from Oregon to Baja California. At its midpoint offshore of central California, the California Current transports subarctic surface waters southeastward, about 150 to 1,300 km from shore. Seasonal northwesterly winds that are, in part, responsible for the California Current, generate coastal upwelling. Ocean temperatures offshore of central California have increased over the past 50 years, driving an ecosystem shift from the productive subarctic regime towards a depopulated subtropical environment.

  14. Niebla ceruchis from Laguna Figueroa: dimorphic spore morphology and secondary compounds localized in pycnidia and apothecia

    NASA Technical Reports Server (NTRS)

    Enzien, M.; Margulis, L.

    1988-01-01

    During and after the floods of 1979-80 Niebla ceruchis growing epiphytically on Lycium brevipes was one of the dominant aspects of the vegetation in the coastal dunal complex bordering the microbial mats at Laguna Figueroa, Baja California Norte, Mexico. The lichen on denuded branches of Lycium was far more extensively distributed than Lycium lacking lichen. Unusual traits of this Niebla ceruchis strain, namely localization of lichen compounds in the mycobiont reproductive structures (pycnidia and apothecia) and simultaneous presence of bilocular and quadrilocular ascospores, are reported. The abundance of this coastal lichen cover at the microbial mat site has persisted through April 1988.

  15. Further observations on scorpion genera Hadrurus and Hoffmannihadrurus (Scorpiones, Caraboctonidae)

    PubMed Central

    Soleglad, Michael E; Fet, Victor

    2010-01-01

    Abstract Multiple populations of Hadrurus pinteri from Baja California Sur, Mexico have been examined. It is demonstrated that the southern populations of this species have a larger number of accessory trichobothria (neobothriotaxy) than the northern populations, numbers exceeding the maximum currently recorded for the genus. Examination of carapace and chela coloration and its patterns show a close affinity between Hadrurus pinteri and the dark phase of Hadrurus concolorous. A new morphometric ratio of the carapace is defined that distinguishes Hadrurus from Hoffmannihadrurus, further supporting the monophyly of the latter genus. PMID:21594192

  16. Recent progress in Precambrian paleobiology

    NASA Technical Reports Server (NTRS)

    Schopf, J. W.

    1986-01-01

    Ongoing studies at UCLA include the following: (1) investigations in Archean and Proterozoic sequences of various locations; (2) laboratory and field studies of modern microbial biocoenoses (analogues of Precambrian microbial communities) especially those at Laguna Mormona, Baja California, Mexico; (3) development of new laboratory techniques for the separation and concentration of minute cellularly preserved fossils for isotopic and organic geochemical analyses; and (4) assembly of a computerized database for assessment of the timing and nature of major events occurring during Precambrian biotic evolution, and of the potential applicability of ancient microbiotas to problems of global biostratigraphy and biogeography.

  17. Ozone formation along the California-Mexican border region during Cal-Mex 2010 field campaign

    NASA Astrophysics Data System (ADS)

    Li, Guohui; Bei, Naifang; Zavala, Miguel; Molina, Luisa T.

    2014-05-01

    The purpose of this study is to evaluate the ozone (O3) formation along the California-Mexico border region using the WRF-CHEM model in association with the Cal-Mex 2010 field campaign. Four two-day episodes in 2010 are chosen based on plume transport patterns: 1) May 15-16 (plume north), 2) May 29-30 (plume southwest), 3) June 4-5 (plume east), and 4) June 13-14 (plume southeast). Generally, the predicted O3 spatial patterns and temporal variations agree well with the observations at the ambient monitoring sites in the San Diego-Tijuana region, but in the Calexico-Mexicali region, the model frequently underestimates the observation. In the San Diego-Tijuana region, the morning anthropogenic precursor emissions in the urbanized coastal plain are carried inland and mixed with the local biogenic emissions during transport, causing the high O3 level over the mountain region. Biogenic emissions enhance the O3 concentrations by up to 40 ppb over the mountain region in the afternoon. The factor separation approach is used to evaluate the contributions of trans-boundary transport of emissions from California and Baja California to the O3 level in the California-Mexico border region. The Baja California emissions play a minor role in the O3 formation in the San Diego region and do not seem to contribute to the O3 exceedances in the region, but have large potential to cause O3 exceedances in the Calexico region. The California emissions can considerably enhance the O3 level in the Tijuana region. Generally, the California emissions play a more important role than the Baja California emissions on O3 formation in the border region (within 40 km to the California-Mexico border). On average, the O3 concentrations in the border region are decreased by 2-4 ppb in the afternoon due to the interactions of emissions from California and Baja California. Further studies need to be conducted to improve the sea breeze simulations in the border region for evaluating O3 formation.

  18. Environmental sampling of lead near a battery reprocessing factory

    SciTech Connect

    Leung, H.W.

    1988-09-01

    Exposed workers in lead smelting plants and lead storage battery factories have reported illnesses related to inhalation of lead oxide fumes. The residential community of La Gloria, a town of about 15,000 people located approximately 13 km southwest of Tijuana, Baja California, Mexico was an area where residents were concerned about possible health effects and environmental contamination from lead due to the proximity of battery factory that used lead oxide in the battery grid separation procedure. This study was undertaken to investigate the lead levels in the soil, plant and water collected in various areas around this battery reprocessing plant.

  19. Body-wave Attenuation in the South-Central Region of the Gulf of California, México

    NASA Astrophysics Data System (ADS)

    Castro, R. R.; Vidales-Basurto, C. A.; Huerta, C. I.; Sumy, D. F.; Gaherty, J. B.; Collins, J. A.

    2014-12-01

    We present results from a recent study of seismic attenuation of body waves in the south-central region of the Gulf of California (GoC) obtained using records from the Network of Autonomously Recording Seismographs of Baja California (NARS-Baja), from the CICESE's Broadband Seismological Network of the GoC (RESBAN), and from the Ocean Bottom Seismographs (OBS) deployed as part of the Sea of Cortez Ocean Bottom Array experiment (SCOOBA). We examine 27 well-located earthquakes that occurred from October 2005 to October 2006 with magnitudes (Mw) between 3.5 and 4.8. We estimated S-wave site effects by calculating horizontal to vertical spectral ratios and determined attenuation functions with a nonparametric model by inverting the observed spectral amplitudes of 21 frequencies between 0.13 and 12.59 Hz for the SCOOBA (OBS) stations and 19 frequencies between 0.16 and 7.94 Hz for NARS-Baja and RESBAN stations. We calculated the geometrical spreading and the attenuation (1/Q) factors for two distance intervals (10-120 km and 120-220 km, respectively) for each frequency considered. The estimates of Q obtained with the SCOOBA (OBS) records for the interval 10-120 km indicate that the P waves attenuate more than S waves (QP=34 f 0.82, QS=59 f 0.90) for frequencies between 0.6 and 12.6 Hz; while for the 120-220 km interval, where ray-paths travel deeper, S waves attenuate more than P waves (QP=117 f 0.44, QS=51 f 1.12). The estimates of Q obtained using NARS-Baja and RESBAN records, within 10-120 km, indicate that P waves attenuate more than S waves (QP=69 f 0.87, QS=176 f 0.61) at frequencies between 0.3 and 6.3 Hz; while at the 120-220 km distance interval S waves attenuate slightly more than P waves (QP=39 f 0.64, QS=48 f 0.37) at high frequencies (f > 3 Hz). These results, based on a unique OBS dataset, provide an indirect mean to constrain future models of the thermal structure beneth the GoC.

  20. Low Frequency Waves Through the Gulf of California: Observations and Models

    NASA Astrophysics Data System (ADS)

    Flores-Morales, A. L.; Pares-Sierra, A.

    2007-05-01

    Long time series of sea surface temperature and surface height along the Mexican Pacific coast show that propagating coastal Kelvin waves, some cases propagate to the interior of the Gulf of California, while in some other cases they completely skip the gulf and the waves propagate through the gulf mouth to the western side of the peninsula de Baja California and to the north. Using satellite observations to identified events and a combination of numerical (ROMS) and analytical model, we investigate this phenomena focusing on discerning the set of conditions (mainly intensity and frequency of the waves) that determine which of these two main outcomes develops. Preliminary results are presented.

  1. Species profiles: life histories and environmental requirements of coastal fishes and invertebrates (Pacific Southwest): Common littleneck clam. [Protothaca staminea

    SciTech Connect

    Shaw, W.N.

    1986-04-01

    Common littleneck clam (Protothaca staminea) supports an important sport fishery in the Pacific Southwest Region, but has no commercial importance. The species is distributed from Alaska to Baja, California. The egg develops into the trochophore stage 12 h after fertilization, and the planktonic larval stage lasts about 3 weeks. Adults usually mature in the second or third year of life. Mortality is greatest early in life. Intraspecific competition among adults is more evident in mud than in sand. Most littleneck clams live in the lower intertidal zone. Littleneck clams concentrate heavy metals and are highly sensitive to copper.

  2. Comportamiento dinámico de asteroides en la resonancia 2:1

    NASA Astrophysics Data System (ADS)

    López García, F.; Brunini, A.

    El propósito de este trabajo es mostrar los resultados obtenidos del estudio del movimiento de asteroides cercanos a la conmensurabilidad 2:1 con el movimiento medio de Júpiter, analizando el comportamiento de órbitas de asteroides reales y ficticios. Se analizan los tiempos de Lyapunov obtenidos a partir de la integración de las ecuaciones del movimiento. Se han estudiado la órbitas utilizando el modelo de cinco cuerpos y se han considerado los casos planar y espacial. Las simulaciones numéricas se realizaron utilizando integradores simpléticos y el intervalo de tiempo de integración fue de T = 107 años.

  3. Determinación de la orientación global SAO-Hipparcos mediante una expansión en armónicos vectoriales

    NASA Astrophysics Data System (ADS)

    Cionco, R. G.; Vucetich, H.; Orellana, R.; Arias, E. F.

    En base a las diferencias de posición y movimientos propios de 101352 estrellas con posición SAO observadas por HIPPARCOS y utilizando la naturaleza vectorial de esas diferencias, determinamos 6 parámetros de orientación global (3 de rotación y 3 de desplazamiento axial), para los sistemas de referencia asociados a los marcos mencionados, mediante una descomposición en serie de armónicos vectoriales ortogonales.

  4. A taxonomic revision of the New World genus Oropodes Casey (Coleoptera, Staphylinidae, Pselaphinae)

    PubMed Central

    Chandler, Donald S.; Caterino, Michael S.

    2011-01-01

    Abstract The genus Oropodes is characterized and revised with 18 species being treated. Members of this genus are found in temperate forests to desert brush lands from Oregon to Baja California, but are associated primarily with dry forests and shrub lands of California. Keys to males and females, where known, are provided. Seven species are redescribed: Oropodes arcaps (California), Oropodes dybasi (Oregon), Oropodes ishii (California), Oropodes nuclere (California), Oropodes orbiceps (California), Oropodes rumseyensis (California), Oropodes yollabolly (California). The name Oropodes raffrayi (California) is raised from synonymy and the species is redescribed, NEW STATUS. Ten new species are described: Oropodes aalbui (California), Oropodes bellorum (California), Oropodes casson (California), Oropodes chumash (California), Oropodes esselen (California), Oropodes hardyi (California), Oropodes serrano (California), Oropodes tataviam (California), Oropodes tongva (California), and Oropodes tipai (Baja California, Mexico), NEW SPECIES. These species are placed into three species groups: the arcaps-group, the orbiceps-group, and the raffrayi-group. Data for a new record of Euplecterga fideli are given, and a list of the unassociated Oropodes females with distinctive genitalia is included with their label data. PMID:22371671

  5. Intraguild predation by shore crabs affects mortality, behavior, growth, and densities of California horn snails

    USGS Publications Warehouse

    Lorda, J.; Hechinger, R.F.; Cooper, S. D.; Kuris, A. M.; Lafferty, Kevin D.

    2016-01-01

    The California horn snail, Cerithideopsis californica, and the shore crabs, Pachygrapsus crassipesand Hemigrapsus oregonensis, compete for epibenthic microalgae, but the crabs also eat snails. Such intraguild predation is common in nature, despite models predicting instability. Using a series of manipulations and field surveys, we examined intraguild predation from several angles, including the effects of stage-dependent predation along with direct consumptive and nonconsumptive predator effects on intraguild prey. In the laboratory, we found that crabs fed on macroalgae, snail eggs, and snails, and the size of consumed snails increased with predator crab size. In field experiments, snails grew less in the presence of crabs partially because snails behaved differently and were buried in the sediment (nonconsumptive effects). Consistent with these results, crab and snail abundances were negatively correlated in three field surveys conducted at three different spatial scales in estuaries of California, Baja California, and Baja California Sur: (1) among 61 sites spanning multiple habitat types in three estuaries, (2) among the habitats of 13 estuaries, and (3) among 34 tidal creek sites in one estuary. These results indicate that shore crabs are intraguild predators on California horn snails that affect snail populations via predation and by influencing snail behavior and performance.

  6. Phylogeography of Ramalina menziesii, a widely distributed lichen-forming fungus in western North America.

    PubMed

    Sork, Victoria L; Werth, Silke

    2014-05-01

    The complex topography and climate history of western North America offer a setting where lineage formation, accumulation and migration have led to elevated inter- and intraspecific biodiversity in many taxa. Here, we study Ramalina menziesii, an epiphytic lichenized fungus with a range encompassing major ecosystems from Baja California to Alaska to explore the predictions of two hypotheses: (i) that the widespread distribution of R. menziesii is due to a single migration episode from a single lineage and (ii) that the widespread distribution is due to the formation and persistence of multiple lineages structured throughout the species' range. To obtain evidence for these predictions, we first construct a phylogenetic tree and identify multiple lineages structured throughout the species' range--some ancient ones that are localized and other more recent lineages that are widely distributed. Second, we use an isolation with migration model to show that sets of ecoregion populations diverged from each other at different times, demonstrating the importance of historical and current barriers to gene flow. Third, we estimated migration rates among ecoregions and find that Baja California populations are relatively isolated, that inland California ecoregion populations do not send out emigrants and that migration out of California coastal and Pacific Northwest populations into inland California ecoregions is high. Such intraspecific geographical patterns of population persistence and dispersal both contribute to the wide range of this genetically diverse lichen fungus and provide insight into the evolutionary processes that enhance species diversity of the California Floristic Province. PMID:24673777

  7. Correlating Volcanism in Coastal California with Slab Windows predicted from Pacific Plate Isochrons

    NASA Astrophysics Data System (ADS)

    Wilson, D. S.; McCrory, P. A.; Stanley, R. G.

    2006-12-01

    The geologic record of coastal California includes evidence of numerous volcanic centers younger than 30 Ma that do not appear to have erupted in an arc setting. By correlating these volcanic centers with specific slab windows predicted from analysis of magnetic anomalies on the Pacific plate, we add new constraints to tectonic reconstructions since 30 Ma. Our correlations -- such as erupting the Morro Rock-Islay Hill complex south of the Pioneer fracture zone and the Iversen Basalt south of the Mendocino fracture zone -- require larger displacements within western North America than advocated by most previous authors. Specifically, we infer at least 315 km of motion between the Sierra Nevada and rigid North America at an azimuth of about N60W, and at least 515 km between Baja California and rigid North America in a similar direction. Alternatively, smaller displacements would require revision of the Pacific-North America global plate circuit. A consequence of inferring a large displacement of Baja California is that the Pacific-North American plate boundary must have developed most of its current form prior to 10 Ma. We interpret a slab window developing between Cocos and Monterey plates after 19 Ma that reconstructs under nearly all of the southern California volcanic centers dated at 18-14 Ma. Reconstructing North American microplates using spherical plate tectonics allows us to animate kinematic models for interaction between oceanic and continental plates.

  8. Implications of volcanism in coastal California for the Neogene deformation history of western North America

    NASA Astrophysics Data System (ADS)

    Wilson, Douglas S.; McCrory, Patricia A.; Stanley, Richard G.

    2005-06-01

    The geologic record of coastal California includes evidence of numerous volcanic centers younger than 30 Ma that do not appear to have erupted in an arc setting. By correlating these volcanic centers with specific slab windows predicted from analysis of magnetic anomalies on the Pacific plate, we add new constraints to tectonic reconstructions since 30 Ma. Our correlations, such as erupting the Morro Rock-Islay Hill complex south of the Pioneer fracture zone and the Iversen Basalt south of the Mendocino fracture zone, require larger displacements within western North America than advocated by most previous authors. Specifically, we infer at least 315 km of motion between the Sierra Nevada and rigid North America at an azimuth of about N60°W and at least 515 km between Baja California and rigid North America in a similar direction. A consequence of inferring a large displacement of Baja California is that the Pacific-North American plate boundary must have developed most of its current form prior to 10 Ma. We interpret a slab window developing between Cocos and Monterey plates after 19 Ma that reconstructs under nearly all of the southern California volcanic centers dated at 18-14 Ma. Most of the sedimentary basins associated with volcanic rocks show brief periods of rapid subsidence synchronous with volcanism, followed by slow subsidence of variable but often extended duration, consistent with rapid extension of cold lithosphere over recently introduced hot asthenosphere.

  9. Carry-over effects of winter location contribute to variation in timing of nest initiation and clutch size in black brant (Branta bernicla nigricans)

    USGS Publications Warehouse

    Schamber, Jason L.; Sedinger, James S.; Ward, David H.

    2012-01-01

    We assessed carry-over effects from winter location on timing of nest initiation and clutch size of Black Brant (Branta bernicla nigricans) using observations of individually marked brant breeding at the Tutakoke River colony in Alaska, and wintering along a latitudinal gradient at three areas on the Pacific coast of Baja California: northernmost Bahia San Quintin (BSQ), Laguna Ojo de Liebre (LOL), and southernmost Laguna San Ignacio (LSI). Black Brant initiated nests according to a north—south trend in winter location, although year was a stronger predictor of initiation date than was wintering site. Female Black Brant that wintered at BSQ initiated nests 2.2 days earlier than females from LSI. Conversely, Black Brant showed only a weak south—north trend in clutch size; individuals from LSI laid slightly larger clutches than individuals from BSQ, probably because a smaller proportion of only high-quality females from the southernmost wintering area in Baja California were able to attain the nutritional condition necessary to breed. These results indicate that winter location can influence individual reproductive performance and, potentially, limit population growth of southern segments of the wintering Black Brant population.

  10. The human influence on seabird nesting success: Conservation implications

    USGS Publications Warehouse

    Anderson, D.W.; Keith, J.O.

    1980-01-01

    Based on studies of brown pelicans Pelecanus occidentalis californicus and Heermann's gulls Larus heermanni, disturbances by recreationists, educational groups, local fishermen and scientists alike can be seriously disruptive and damaging to breeding seabirds in the Gulf of California and off the west coast of Baja California. Similar instances have been identified throughout the world?the problem is not difficult to document, but it is difficult to eliminate. The increasing human-seabird contacts on islands in the Gulf of California and along the west coast of Baja California raise serious questions and immediate concern about the continued preservation of nesting colonies of marine birds in those areas. Conservation measures must consider the extreme sensitivity of many seabirds to the inter- and intraspecific behavioural imbalances created by human disturbances. In some cases, total exclusion of humans may be required; in others, limited access might be possible under closely managed conditions at certain times of the year. A symbiotic relationship between seabird conservation, legitimate research and tourism should be the desired goal.

  11. Plastid DNA Diversity Is Higher in the Island Endemic Guadalupe Cypress than in the Continental Tecate Cypress

    PubMed Central

    Rosas Escobar, Patricia; Gernandt, David S.; Piñero, Daniel; Garcillán, Pedro P.

    2011-01-01

    Background Callitropsis guadalupensis (Guadalupe cypress) is endemic to Guadalupe Island, Mexico, where it is the dominant species of the only forest. The species has suffered declining numbers following the introduction of goats to the island over 150 years ago. Callitropsis guadalupensis is closely related to Callitropsis forbesii (Tecate cypress), distributed in small isolated populations in mainland Baja California and southern California. The objective of the present study was to compare the genetic diversity of the island endemic to the continental species. Methodology/Principal Findings We measured genetic diversity in Callitropsis guadalupensis (n = 54) from Guadalupe Island and in Callitropsis forbesii (n = 100) from five populations in mainland Baja California. The plastid DNA trnS-trnG spacer and the trnL-trnF region were chosen for characterization. Thirty-four haplotypes were observed, of which six were shared between both species. One of these haplotypes was also shared with three other species, Callitropsis lusitanica, Callitropsis montana, and Callitropsis stephensonii. Haplotype diversity (h) and nucleotide diversity (π) were significantly higher for Callitropsis guadalupensis (h = 0.698, π = 0.00071) than for Callitropsis forbesii (h = 0.337, π = 0.00024). Conclusions/Significance Callitropsis guadalupensis shows no evidence of a founder effect or of a genetic bottleneck, and can be added to a growing list of insular species with higher genetic diversity than their mainland relatives. PMID:21283771

  12. Two species of the deep-water shrimp genus Nematocarcinus A. Milne-Edwards, 1881 (Crustacea, Decapoda, Caridea, Nematocarcinidae) from the Mexican Pacific.

    PubMed

    Hernandez-Payan, J C; Hendrickx, M E

    2016-01-01

    The distribution of two species of the deep-water shrimp genus Nematocarcinus A. Milne-Edwards, 1881, occurring off the west coast of Mexico is analyzed based on a large series of recently collected material. Nematocarcinus faxoni Burukovsky, 2000, is by far the most common and abundant species in the area and it is distributed throughout the central and southern Gulf of California and off the entire Baja California Peninsula south to 17º10'15"N. Based on characteristics observed in the new samples and in the type material, N. agassizii Faxon, 1893, is reinstalled as a valid species, and no longer considered a junior of N. gracilipes A. Milne-Edwards, 1881, as proposed by Cardoso & Burukovsky (2014). Along the Pacific coast of Mexico, N. agassizii exhibits a more restricted distribution and it was collected only off the Baja California Peninsula. Previous records of this species in the Gulf of California, where N. faxoni was the only representative of the genus captured during this survey, are considered doubtful. PMID:27395608

  13. A checklist of helminth parasites of Elasmobranchii in Mexico

    PubMed Central

    Merlo-Serna, Aldo Iván; García-Prieto, Luis

    2016-01-01

    Abstract A comprehensive and updated summary of the literature and unpublished records contained in scientific collections on the helminth parasites of the elasmobranchs from Mexico is herein presented for the first time. At present, the helminth fauna associated with Elasmobranchii recorded in Mexico is composed of 132 (110 named species and 22 not assigned to species), which belong to 70 genera included in 27 families (plus 4 incertae sedis families of cestodes). These data represent 7.2% of the worldwide species richness. Platyhelminthes is the most widely represented, with 128 taxa: 94 of cestodes, 22 of monogeneans and 12 of trematodes; Nematoda and Annelida: Hirudinea are represented by only 2 taxa each. These records come from 54 localities, pertaining to 15 states; Baja California Sur (17 sampled localities) and Baja California (10), are the states with the highest species richness: 72 and 54 species, respectively. Up to now, 48 elasmobranch species have been recorded as hosts of helminths in Mexico; so, approximately 82% of sharks and 67% of rays distributed in Mexican waters lack helminthological studies. The present list provides the host, distribution (with geographical coordinates), site of infection, accession number in scientific collections, and references for the parasites. A host-parasite list is also provided. PMID:27047240

  14. A checklist of helminth parasites of Elasmobranchii in Mexico.

    PubMed

    Merlo-Serna, Aldo Iván; García-Prieto, Luis

    2016-01-01

    A comprehensive and updated summary of the literature and unpublished records contained in scientific collections on the helminth parasites of the elasmobranchs from Mexico is herein presented for the first time. At present, the helminth fauna associated with Elasmobranchii recorded in Mexico is composed of 132 (110 named species and 22 not assigned to species), which belong to 70 genera included in 27 families (plus 4 incertae sedis families of cestodes). These data represent 7.2% of the worldwide species richness. Platyhelminthes is the most widely represented, with 128 taxa: 94 of cestodes, 22 of monogeneans and 12 of trematodes; Nematoda and Annelida: Hirudinea are represented by only 2 taxa each. These records come from 54 localities, pertaining to 15 states; Baja California Sur (17 sampled localities) and Baja California (10), are the states with the highest species richness: 72 and 54 species, respectively. Up to now, 48 elasmobranch species have been recorded as hosts of helminths in Mexico; so, approximately 82% of sharks and 67% of rays distributed in Mexican waters lack helminthological studies. The present list provides the host, distribution (with geographical coordinates), site of infection, accession number in scientific collections, and references for the parasites. A host-parasite list is also provided. PMID:27047240

  15. Rearing conditions and habitat use of white seabass (Atractoscion nobilis) in the northeastern Pacific based on otolith isotopic composition

    NASA Astrophysics Data System (ADS)

    Romo-Curiel, Alfonsina E.; Herzka, Sharon Z.; Sepulveda, Chugey A.; Pérez-Brunius, Paula; Aalbers, Scott A.

    2016-03-01

    White seabass, Atractoscion nobilis, is an important coastal resource throughout both California and Baja California, but whether this species comprises a single or multiple subpopulations in the northeastern Pacific is not known. The aim of this study was to infer larval rearing habitats and population structure of white seabass by sampling adults from three regions spanning a latitudinal temperature gradient and a distance of over 1000 km, and analyzing the isotopic composition (δ18O and δ13C) of otolith aragonite corresponding to the larval, juvenile and adult stages. Otolith cores revealed high isotopic variability and no significant differences among regions, suggesting overlapping rearing conditions during the larval stage, the potential for long distance dispersal or migration or selective mortality of larvae at higher temperatures. Back-calculated temperatures of aragonite precipitation derived using regional salinity-δw relationships and local salinity estimates also did not differ significantly. However, there were significant differences between the δ18O values of the first seasonal growth ring of age 0 fish as well as back-calculated aragonite precipitation temperatures, suggesting the presence of two potentially discrete subpopulations divided by Punta Eugenia (27°N) along the central Baja California peninsula. These findings are consistent with regional oceanographic patterns and are critical for understanding white seabass population structure, and provide information needed for the implementation of appropriate management strategies.

  16. Extracting the Global Sea Surface Temperature Evolutions of Different Timescales

    NASA Astrophysics Data System (ADS)

    Feng, J.; Wu, Z.

    2012-12-01

    A new data analysis procedure, involving empirical orthogonal functions (EOF) analysis and ensemble empirical mode decomposition (EEMD), is employed to extract the evolutions of global Sea Surface Temperature (SST) of different timescales spanning the period from 1880 to 2009 (130 yr). Specifically, EOF analysis serves as a means of lossy data compression to eliminate the spatial-temporally incoherent, noise-like part of the data; and EEMD decomposes SST time series into different time scales, which facilitates research on SST-related weather and climate phenomena that have various timescales. Through validation, it is shown that the difference between the results and the original SST time series are mostly white noises, both spatially and temporally incoherent. We apply the results to study El Niño-Southern Oscillation (ENSO) events. Each ENSO event is examined and we find an oceanic region off Baja California coast ( ) that is instrumental to some ENSO events, especially those recently called ENSO Modoki, whose initial warming may be traced back to earlier warming signals from Baja California.

  17. DNA fingerprinting differentiation between β-carotene hyperproducer strains of Dunaliella from around the world

    PubMed Central

    Olmos, Jorge; Ochoa, Leonel; Paniagua-Michel, Jesus; Contreras, Rosalía

    2009-01-01

    Background Dunaliella salina is the most important species of the genus for β-carotene production. Several investigations have demonstrated that D. salina produces more than 10% dry weight of pigment and that the species grows in salt saturated lagoons. High plasticity in the green stage and the almost indistinguishable differences in the red phase make identification and differentiation of species and ecotypes very difficult and time consuming. Results In this work, we applied our intron-sizing method to compare the 18S rDNA fingerprint between D. salina (CCAP 19/18), D. salina/bardawil (UTEX LB2538) and β-carotene hyperproducing strains of Dunaliella isolated from salt saturated lagoons in Baja, Mexico. All hyperproducer strains reached β-carotene levels of about 10 pg/cell. Optical microscopy did not allow to differentiate between these Dunaliella strains; however, 18S rDNA fingerprinting methodology allowed us to differentiate D. salina from D. salina/bardawil. Conclusion In Baja Mexico we found D. salina and D. salina/bardawil species by using intron-sizing-method. The National Center for Biotechnology Information (NCBI) Dunaliella 18S rDNA gene sequences were analyzed with our methodology and extraordinary correlation was found with experimental results. PMID:19563682

  18. Vicariance and dispersal form a ring distribution in nightsnakes around the Gulf of California.

    PubMed

    Mulcahy, Daniel G; Macey, J Robert

    2009-11-01

    Plate tectonics can have profound effects on organismal distribution and is often the driving force in speciation. Through geologic processes, the Baja California Peninsula depicts two faunal patterns: one through southern vicariance with Cape separation, and the other through dispersal onto the northern peninsula, referred to as a 'dual-peninsular effect.' Here we apply a hierarchical sampling strategy that combines population-level sequence data ( approximately 800bp, nad4 region) with complete mt-genome data (aligned 15,549bp) and 5 nuclear protein encoding loci (3315bp), to test whether both patterns have occurred in one group of nightsnakes (Hypsiglena). The geologic formation of the peninsula is thought to have occurred in three stages: (1) Cape separation from mainland Mexico; (2) the northern peninsula separated, forming the northern Gulf of California; and (3) the peninsula was united through volcanic activity, while moving northward causing collision with southern California. However, the timing of events is debated. We explore phylogenetic relationships and estimate dates of divergence for nightsnakes using our hierarchical sampling strategy. Our data support both 'southern-vicariance' and 'northern-dispersal' have occurred in nightsnakes, forming a ring distribution around the Gulf of California. Two divergent forms are sympatric on the southern half of the peninsula with no indication of hybridization. Nightsnakes represent the first group to depict the 'dual-peninsular effect' with extensive overlap on the Baja California Peninsula. PMID:19501659

  19. Sedimentary denitrification in the eastern tropical North Pacific in the last 2000 years

    NASA Astrophysics Data System (ADS)

    Juarez, M.; Sanchez, A.; Gonzalez-Yajimovich, O.

    2013-05-01

    The southwestern margin of the Baja California peninsula display intense coastal upwelling, which promotes high primary productivity and the settling of a great amount of organic matter. The oxidation of this organic matter consumes oxygen at a rate that exceeds supply. This condition and the presence of an oxygen minimum zone (OMZ) help to conserve the exported organic matter and can be used to infer changes in productivity. Here we present results of a study based on records of biogenic opal and δ15N to estimate changes in sedimentary denitrification in the eastern tropical North Pacific in the last 2000 years. A multicore (MAGD-MC02) was recovered during the LONO-09 cruise off the Magdalena margin, western Baja California Sur. This site was located within the eastern North Pacific OMZ at a depth of 680 m. The biogenic opal record showed little variability in the last 2000 years, but increased gradually towards the present. The records showed the same variability during the Medieval Warm Period, while denitrification decreased during the Little Ice Age, suggesting that denitrification in the Medieval Warm Period was synchronous with primary productivity, but during the Little Ice Age, the water column showed intensification in ventilation at intermediate depth without change in primary productivity. Keywords: Denitrification, Oxygen Minimum Zone, Ventilation, Primary Productivity, Medieval Warm Period, Little Ice Age.

  20. Latitudinal variation in population structure of wintering Pacific Black Brant

    USGS Publications Warehouse

    Schamber, J.L.; Sedinger, J.S.; Ward, D.H.; Hagmeier, K.R.

    2007-01-01

    Latitudinal variation in population structure during the winter has been reported in many migratory birds, but has been documented in few species of waterfowl. Variation in environmental and social conditions at wintering sites can potentially influence the population dynamics of differential migrants. We examined latitudinal variation in sex and age classes of wintering Pacific Black Brant (Branta bernicla nigricans). Brant are distributed along a wide latitudinal gradient from Alaska to Mexico during the winter. Accordingly, migration distances for brant using different wintering locations are highly variable and winter settlement patterns are likely associated with a spatially variable food resource. We used resightings of brant banded in southwestern Alaska to examine sex and age ratios of birds wintering at Boundary Bay in British Columbia, and at San Quintin Bay, Ojo de Liebre Lagoon, and San Ignacio Lagoon in Baja California from 1998 to 2000. Sex ratios were similar among wintering locations for adults and were consistent with the mating strategy of geese. The distribution of juveniles varied among wintering areas, with greater proportions of juveniles observed at northern (San Quintin Bay and Ojo de Liebre Lagoon) than at southern (San Ignacio Lagoon) locations in Baja California. We suggest that age-related variation in the winter distribution of Pacific Black Brant is mediated by variation in productivity among individuals at different wintering locations and by social interactions among wintering family groups.

  1. Coastal landforms and accumulation of mangrove peat increase carbon sequestration and storage

    PubMed Central

    Garcillán, Pedro P.

    2016-01-01

    Given their relatively small area, mangroves and their organic sediments are of disproportionate importance to global carbon sequestration and carbon storage. Peat deposition and preservation allows some mangroves to accrete vertically and keep pace with sea-level rise by growing on their own root remains. In this study we show that mangroves in desert inlets in the coasts of the Baja California have been accumulating root peat for nearly 2,000 y and harbor a belowground carbon content of 900–34,00 Mg C/ha, with an average value of 1,130 (± 128) Mg C/ha, and a belowground carbon accumulation similar to that found under some of the tallest tropical mangroves in the Mexican Pacific coast. The depth–age curve for the mangrove sediments of Baja California indicates that sea level in the peninsula has been rising at a mean rate of 0.70 mm/y (± 0.07) during the last 17 centuries, a value similar to the rates of sea-level rise estimated for the Caribbean during a comparable period. By accreting on their own accumulated peat, these desert mangroves store large amounts of carbon in their sediments. We estimate that mangroves and halophyte scrubs in Mexico’s arid northwest, with less than 1% of the terrestrial area, store in their belowground sediments around 28% of the total belowground carbon pool of the whole region. PMID:27035950

  2. Nutrients, Recycling, and Biological Populations in Upwelling Ecosystems

    SciTech Connect

    Whitledge, T. E.

    1980-01-01

    Nutrient recycling has been studied in the upwelling areas of Baja California, Northwest Africa, and Peru. Regeneration by biological populations in these areas contributes significant quantities of recycled nitrogen which is utilized in productivity processes. Each area has a different combination of organisms which leads to differences in the relative contributions of zooplankton, nekton, or benthos to the nutrient cycles. Comparisons of ammonium regeneration rates of zooplankton and nekton-micronekton populations in the three upwelling areas show that zooplankton recycle relatively less nitrogen in the Baja California and Peru systems than nekton. In the Northwest Africa upwelling region, however, zooplankton, fish, and benthic inputs are all substantial. In recent years the Peruvian upwelling system has been altered with the decline of the anchoveta population and an increase in the importance of zooplankton in nutrient recycling. The distribution of recycled nitrogen (ammonium and urea) in transects across the shelf at 10°S and 15°S indicates that regeneration is relatively more important at 10°S in the region of the wide shelf. In both areas the distribution of ammonium and urea are not entirely coincident thereby indicating differences in their production and/or utilization.

  3. Microsatellite variation among diverging populations of Drosophila mojavensis.

    PubMed

    Ross, C L; Markow, T A

    2006-09-01

    Divergence and speciation may occur by various means, depending on the particular history, selective environments, and genetic composition of populations. In Drosophila mojavensis, a good model of incipient speciation, understanding the population genetic structure within this group facilitates our ability to understand the context in which reproductive isolation among populations is developing. Here we report the genetic structure and relationships of D. mojavensis populations at nuclear loci. We surveyed 29 populations throughout the distribution of D. mojavensis for four microsatellite loci to differentiation among populations of this species. These loci reveal four distinct geographical regions of D. mojavensis populations in the south-western United States and north-western Mexico--(i) Baja California peninsula (Baja), (ii) Sonora, Mexico-southern Arizona, United States (Sonora), (iii) Mojave Desert and Grand Canyon (Mojave), and (iv) Santa Catalina Island (Catalina). While all regions show strong isolation, Mojave and Catalina are highly diverged from other regions. Within any region, populations are largely homogenous over broad geographical distances. Based on the population structure, we find clear geographical barriers to gene flow appear to have a strong effect in isolating populations across regions for this species. PMID:16910998

  4. Isolation by distance among California sea lion populations in Mexico: redefining management stocks.

    PubMed

    González-Suárez, M; Flatz, R; Aurioles-Gamboa, D; Hedrick, P W; Gerber, L R

    2009-03-01

    Understanding the spatial structure of a population is critical for effective assessment and management. However, direct observation of spatial dynamics is generally difficult, particularly for marine mammals. California sea lions (Zalophus californianus) are polygynous pinnipeds distributed along the Pacific coast of North America. The species' range has been subdivided into three management stocks based on differences in mitochondrial DNA, but to date no studies have considered nuclear genetic variation, and thus we lack a comprehensive understanding of gene flow patterns among sea lion colonies. In light of recent population declines in the Gulf of California, Mexico, it is important to understand spatial structure to determine if declining sea lion colonies are genetically isolated from others. To define population subdivision and identify sex biases in gene flow, we analysed a 355-bp sequence of the mitochondrial DNA control region and 10 polymorphic microsatellite loci from 355 tissue samples collected from six colonies distributed along Mexican waters. Using a novel approach to estimate sex biases in gene flow, we found that male sea lions disperse on average 6.75 times more frequently than females. Analyses of population subdivision strongly suggest a pattern of isolation by distance among colonies and challenge current stock definitions. Based on these results, we propose an alternative classification that identifies three Mexican management units: Upper Gulf of California, Southern Baja Peninsula, and Upper Pacific Coast of Baja. This revised classification should be considered in future assessment and management of California sea lion populations in Mexican waters. PMID:19226320

  5. Position of the Patella among Emirati Adult Knees. Is Insall-Salvati Ratio Applicable to Middle-Easterners?

    PubMed Central

    Althani, Saeed; Shahi, Alisina; Tan, Timothy L.; Al-Belooshi, Ali

    2016-01-01

    Background: Abnormal patellar height is associated with anterior knee pain and several conditions that affect the patellofemoral joint. The aim of this study was to 1) report the incidence of patella alta and patella baja and 2) investigate whether the normal limits of the Insall-Salvati ratio is applicable in adult Middle-Easterners. Methods: A radiographic review of the lateral radiographs of 736 Middle-Eastern knees were performed. Patellar tendon length (TL) and the patellar length (TP) was digitally measured and the ratios of these measures was used to calculate the Insall-Salvati ratio. Results: The overall mean TL/PL ratio was 1.20±0.17. The Insall-Salvati ratio was higher (p=0.0013) in males (1.22± 0.12) than in females (1.18±0.17). According to our measurement, the recommended levels for defining abnormal patellar position should be 0.86 for patella baja and 1.54 for patella alta. Conclusion: The use of TL/PL ratio demonstrated a higher incidence of patella alta and a higher mean TL/PL ratio compared to other techniques. The normal ranges for the TL/PL differs from western populations and may be attributed to lifestyle differences. PMID:27200391

  6. Active Deformation along the Southern End of the Tosco-Abreojos Fault System: New Insights from Multibeam Swath Bathymetry

    NASA Astrophysics Data System (ADS)

    Michaud, François; Calmus, Thierry; Ratzov, Gueorgui; Royer, Jean-Yves; Sosson, Marc; Bigot-Cormier, Florence; Bandy, William; Mortera Gutiérrez, Carlos

    2011-08-01

    The relative motion of the Pacific plate with respect to the North America plate is partitioned between transcurrent faults located along the western margin of Baja California and transform faults and spreading ridges in the Gulf of California. However, the amount of right lateral offset along the Baja California western margin is still debated. We revisited multibeam swath bathymetry data along the southern end of the Tosco-Abreojos fault system. In this area the depths are less than 1,000 m and allow a finer gridding at 60 m cell spacing. This improved resolution unveils several transcurrent right lateral faults offsetting the seafloor and canyons, which can be used as markers to quantify local offsets. The seafloor of the southern end of the Tosco-Abreojos fault system (south of 24°N) displays NW-SE elongated bathymetric highs and lows, suggesting a transtensional tectonic regime associated with the formation of pull-apart basins. In such an active tectonic context, submarine canyon networks are unstable. Using the deformation rate inferred from kinematic predictions and pull-apart geometry, we suggest a minimum age for the reorganization of the canyon network.

  7. Coastal landforms and accumulation of mangrove peat increase carbon sequestration and storage.

    PubMed

    Ezcurra, Paula; Ezcurra, Exequiel; Garcillán, Pedro P; Costa, Matthew T; Aburto-Oropeza, Octavio

    2016-04-19

    Given their relatively small area, mangroves and their organic sediments are of disproportionate importance to global carbon sequestration and carbon storage. Peat deposition and preservation allows some mangroves to accrete vertically and keep pace with sea-level rise by growing on their own root remains. In this study we show that mangroves in desert inlets in the coasts of the Baja California have been accumulating root peat for nearly 2,000 y and harbor a belowground carbon content of 900-34,00 Mg C/ha, with an average value of 1,130 (± 128) Mg C/ha, and a belowground carbon accumulation similar to that found under some of the tallest tropical mangroves in the Mexican Pacific coast. The depth-age curve for the mangrove sediments of Baja California indicates that sea level in the peninsula has been rising at a mean rate of 0.70 mm/y (± 0.07) during the last 17 centuries, a value similar to the rates of sea-level rise estimated for the Caribbean during a comparable period. By accreting on their own accumulated peat, these desert mangroves store large amounts of carbon in their sediments. We estimate that mangroves and halophyte scrubs in Mexico's arid northwest, with less than 1% of the terrestrial area, store in their belowground sediments around 28% of the total belowground carbon pool of the whole region. PMID:27035950

  8. Tomographic search for missing link between the ancient Farallon subduction and the present Cocos subduction

    NASA Astrophysics Data System (ADS)

    Gorbatov, Alexei; Fukao, Yoshio

    2005-03-01

    A striking feature of the tomographic images of the Earth's mid-mantle is the long, high-velocity belt extending in a north-south direction under the North and South American continents, which is believed to be the remnant subduction of the Farallon Plate. In the Oligocene epoch the North Farallon Plate subduction terminated off Baja California and the South Farallon Plate broke into the Cocos and Nazca plates. This important period of the Farallon subduction history is not clearly understood, due in part to the lack of high-resolution tomographic images. Our P-wave tomographic image of the mantle below Mexico indicates that the currently subducting slab of the Cocos Plate is torn apart from the already subducted slab of the ancient Farallon Plate in a region behind the slab window or slab gap off Baja California. We suggest that the southeastward advance of this slab tearing was synchronous with the counter-clockwise rotation of the Cocos Plate against the eastward to northeastward subduction of the ancient Farallon Plate. The Cocos slab torn apart from the deeper Farallon slab dips to the north to northeast with its strike oblique to the trench axis. This slab configuration delineates well with the intermediate-depth earthquake activity and the volcanic activity known as the Trans Mexican Volcanic Belt. Further to the south of the slab tearing of the subducted slab continues from the deeper Farallon part to the shallower Cocos part but with considerable distortion in the shallower part.

  9. Assessing long-term postseismic deformation following the M7.2 4 April 2010, El Mayor-Cucapah earthquake with implications for lithospheric rheology in the Salton Trough

    NASA Astrophysics Data System (ADS)

    Spinler, Joshua C.; Bennett, Richard A.; Walls, Chris; Lawrence, Shawn; González García, J. Javier

    2015-05-01

    The 4 April 2010 Mw 7.2 El Mayor-Cucapah (EMC) earthquake provides the best opportunity to date to study the lithospheric response to a large (>M6) magnitude earthquake in the Salton Trough region through analysis of Global Positioning System (GPS) data. In conjunction with the EarthScope Plate Boundary Observatory (PBO), we installed six new continuous GPS stations in the months following the EMC earthquake to increase station coverage in the epicentral region of northern Baja California, Mexico. We modeled the pre-EMC deformation field using available campaign and continuous GPS data for southern California and northern Baja California and inferred a pre-EMC secular rate at each new station location. Through direct comparison of the pre- and post-EMC secular rates, we calculate long-term changes associated with viscoelastic relaxation in the Salton Trough region. We fit these velocity changes using numerical models employing an elastic upper crustal layer underlain by a viscoelastic lower crustal layer and a mantle half-space. Forward models that produce the smallest weighted sum of squared residuals have an upper mantle viscosity in the range 4-6 × 1018 Pa s and a less well-resolved lower crustal viscosity in the range 2 × 1019 to 1 × 1022 Pa s. A high-viscosity lower crust, despite high heat flow in the Salton Trough region, is inconsistent with felsic composition and might suggest accretion of mafic lower crust associated with crustal spreading obscured by thick sedimentary cover.

  10. The EL Mayor-Cucapah Earthquake of April 4, 2010 (mw 7.2): Main Shock and Aftershocks Relocation and Relevant Aspects of the Strong Motion Data Recorded in the Epicenter Region. (Invited)

    NASA Astrophysics Data System (ADS)

    Munguia, L.

    2010-12-01

    The El Mayor-Cucapah earthquake (Mw = 7.2) was the largest earthquake to occur in northeastern Baja California since February 1892, when an earthquake of slightly lower magnitude occurred at the northwestern end of the Laguna Salada fault. This event, with epicenter located ~ 40 km south of the city of Mexicali, occurred on April 4, 2010 at 15:40 local time or 22:40 UTC. Thirteen strong motion stations of a network operated by CICESE in Baja California were triggered by the main shock. Those stations are located at distances of 12 to 140 km from the epicenter. Six of them are located on sediments of the Mexicali Valley, at less than 40 km from the epicenter; the other seven stations recorded at larger distances, on granitic rocks of the peninsular ranges of Baja California. In this study, we analyze the digital accelerograms produced by the main shock and by most of the larger aftershocks. At first, the P-wave arrival times measured on the accelerograms were combined with time readings from the closer-to-the-source weak-motion stations to relocate the hypocenters. With this, we attempted to improve the hypocenter locations obtained on the basis of more regional data sets. Due to lack of station coverage to the south of the main-shock’s epicenter, this task was particularly important for those aftershocks occurring along the SE extension of the ruptured area. Our located hypocenters had smaller location errors and provide a better insight about the extent of the main-shock rupture to southeast. Concerning the strong motion data, we noted that on sediments the recorded peak ground accelerations (PGA) varied from 0.148 to 0.815 g, while on the rock sites the PGA were in the range 0.013 to 0.074 g. The largest peak acceleration recorded was observed on the vertical component of the MDO station, sited on sediments. For ground velocity and displacement, the peak values from sedimentary sites are between 14 and 61 cm/sec and 9 and 52 cm, respectively. In such instances

  11. MRI Evaluation of Patella Alignment Before and After Anatomical Reconstruction of ACL Undergoing Unified Rehabilitation Programme Introduced by CMC Physical Therapy Team

    PubMed Central

    Straszewski, Dariusz; Plenzler, Marcin; Szczepaniak, Joanna; Śmigielski, Robert; Ciszkowska-Łysoń, Beata; Popieluch, Marcin; Kopko, Szymon

    2014-01-01

    Objectives: The aim of the study was to asses the impact of the functional rehabilitation on patella alignment with MRI imaging in patients who underwent the ACL reconstruction. The surgical approach with the use of patellar tendon graft is known to carry the risk of lowering patella height (patella baja), which, in turn, may lead to accelerated cartilage wear in patellofemoral joint. Methods: 30 patients after the anatomical reconstruction of ACL took part in this study (23 male, and 7 female, mean age = 28 ± 10,6 years). During the procedure a patellar tendon graft was used. The Insali-Salvati ratio measured with MRI (images taken pre-procedural, and 9 months after the surgery) was used for the assessment of patellar alignment. The measurements were taken by one radiology specialist on MRI scans in sagittal view in PD sequence. During the examination, patellar joint was in flexion (approx.10 degrees). As the point of reference for patella’s position ISR ratio was in the range of 0.8 - 1.2. All patients were operated on by the same team of surgeons and underwent an unified rehabilitation programme led by a team of selected physiotherapists. The main features of the programme were: an early muscle activation (second day after the procedure); mobilisation of the patella and tissues of the anterior compartment of the knee; weight bearing co-contraction exercises, and the sensomotoric training of the entire kinetic chain of the lower limb. The data recorded was statistically analysed using the Wilcoxon signed-rank test in order to establish parameters’ changes within the study group.. Results: The mean ISR value before the procedure was 0.84 (± 0,1), whereas 9 months after the surgery it was 0.85 (± 0,1). The results’ analysis did not show any statistically significant changes between ISR values. Nine months after the procedure patella baja has not been observed in any of the evaluated patients. Conclusion: The functional rehabilitation programme designed by

  12. A paleomagnetic investigation of vertical-axis rotations in coastal Sonora, Mexico: Evidence for distributed transtensional deformation during the Proto-Gulf shift from a subduction-dominated to transform-dominated plate boundary in the Gulf of California

    NASA Astrophysics Data System (ADS)

    Herman, Scott William

    The history of late Miocene (Proto-Gulf) deformation on the Sonoran margin of the Gulf of California is key to understanding how Baja California was captured by the Pacific plate and how strain was partitioned during the Proto-Gulf period (12.5-6 Ma). The Sierra el Aguaje and Sierra Tinajas del Carmen are located in southwestern coastal Sonora, Mexico, and represent the eastern rifted margin of the central Gulf of California. The ranges are composed of volcanic units and their corresponding volcaniclastic units which are the result of persistent magmatic activity between 20 and 8.8 Ma, including three packages of basalt and andesite that make excellent paleomagnetic recorders. Based on cross cutting relations and geochronologic data for pre-, syn-, and post-tectonic volcanic units, most of the faulting and tilting in the Sierra El Aguaje is bracketed between 11.9 and 9.0 Ma, thus falling entirely within Proto-Gulf time. A paleomagnetic investigation into possible vertical axis rotations in the Sierra el Aguaje has uncovered evidence of clockwise rotations between ~13º and ~105º with possible translations. These results are consistent with existing field relations, which suggest the presence of large (>45°) vertical axis rotations in this region. This evidence includes: a) abrupt changes in the strike of tilted strata in different parts of the range, including large domains characterized by E-W strikes b) ubiquitous NE-SW striking faults with left lateral-normal oblique slip, that terminate against major NW-trending right lateral faults, and c) obliquity between the general strike of tilted strata and the strike of faults. These rotations occurred after 12 Ma and largely prior to 9 Ma, thus falling into the Proto-Gulf period. Such large-scale rotations lend credence to the theory that the area inboard of Baja California was experiencing transtension during the Proto-Gulf period, rather than the pure extension that would be the result of strain partitioning

  13. Climatological Analysis of the Exclusive Economic Zone of Mexico Based on 10 Years of Satellite Imagery

    NASA Astrophysics Data System (ADS)

    Gonzalez Rodriguez, E.; Trasviña-Castro, A.; Aguirre Bahena, F.

    2013-05-01

    To visualize the variability of inorganic carbon in the waters of the Exclusive Economic Zone of Mexico we analysed over 10 years of monthly data 4-km resolution from the MODIS-AQUA satellite. This sensor provides various types of information and for this discussion we selected particulate organic carbon, sea surface temperature and euphotic zone depth. We constructed climatological maps for each month of the year to show the average, maximum, minimum and standard deviation of the three variables. The result of the average particulate organic carbon climatology indicates that the main areas of inorganic carbon production (> 200 mg m3) are the Gulf of California, the west coast of the peninsula of Baja California, the coast of Colima, the Gulf of Tehuantepec and in the Gulf of Mexico the coasts of Yucatan, Tabasco and Tamaulipas. The months presenting higher production occur between December and April. In comparison, lowest climatological mean sea surface temperature (below 14 oC) occurs on the west coast of the Baja California peninsula and it is observed associated with the highest mean particulate organic carbon (>250 mg m-3). Climatological mean sea surface temperature on the coast of Colima, Yucatan, Tabasco and Tamaulipas are about 25 °C and coincide with high values of particulate organic carbon (> 200 mg m-3). The climatological mean euphotic zone depth show lowest values (<50 m) coincide with the highest mean particulate organic carbon values indicating a clear relationship with a reduction of light penetration in the water column. Inspection of the standard deviation maps shows greatest variability of particulate organic carbon from December to February in the Gulf of California, the coast of Colima and the Gulf of Tehuantepec. In the west coast of the peninsula of Baja California greater variability of particulate organic carbon occurs from June to December. In the oceanic domain beyond the continental shelf, particulate organic carbon values are very

  14. Deep pockets for deep seas

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    Peter Auster, a fisheries ecologist with the National Undersea Research Center in Connecticut, plans to assess degradation of the deep-shelf seafloor from bottom trawling. Magnus Ngoile, an official with Tanzania's National Environmental Management Council, will work on building capacity of poor villagers to protect their coastline. And Alison Rieser, a lawyer with the University of Maine School of Law, will produce a textbook to educate scientists on how to apply the law for marine conservation.These individuals are among 11 recipients of the Pew Charitable Trust's 10th annual marine conservation fellowships, announced on July 12. With each recipient receiving an award of $150,000, the program is the world's largest award for marine conservationists. Other 1999 recipients will be involved with areas including investigating marine pollution in the Arctic region, examining economic incentives for conservation in Baja, Mexico, and establishing a marine conservation biology training program for minority students.

  15. Did stresses from the Cerro Prieto Geothermal Field influence the El Mayor-Cucapah rupture sequence?

    NASA Astrophysics Data System (ADS)

    Trugman, Daniel T.; Borsa, Adrian A.; Sandwell, David T.

    2014-12-01

    The Mw 7.2 El Mayor-Cucapah (EMC) earthquake ruptured a complex fault system in northern Baja California that was previously considered inactive. The Cerro Prieto Geothermal Field (CPGF), site of the world's second largest geothermal power plant, is located approximately 15 km to the northeast of the EMC hypocenter. We investigate whether anthropogenic fluid extraction at the CPGF caused a significant perturbation to the stress field in the EMC rupture zone. We use Advanced Land Observing Satellite interferometric synthetic aperture radar data to develop a laterally heterogeneous model of fluid extraction at the CPGF and estimate that this extraction generates positive Coulomb stressing rates of order 15 kPa/yr near the EMC hypocenter, a value which exceeds the local tectonic stressing rate. Although we cannot definitively conclude that production at the CPGF triggered the EMC earthquake, its influence on the local stress field is substantial and should not be neglected in local seismic hazard assessments.

  16. Marine turtles of the Gal?pagos Islands and adjacent areas of the eastern Pacific on the basis of observations made by J.R. Slevin 1905-1906

    USGS Publications Warehouse

    Fritts, T.H.

    1981-01-01

    The field notes of J. R. Slevin written during the expedition of the California Academy of Sciences to the Galapagos Islands in 1905-1096 contain previously unavailable data on the marine turtles of the eastern Pacific. 'Land basking' by green turtles in Galapagos was predominately, if not exclusively, a female behavior. These terrestrial emergences were not concentrated in the major reproductive season of Galapagos turtles. Female Chelonia were also collected on shore during daylight hours on Socorro Island southwest of Baja California, Mexico. Chelonia, green turtles, were observed to feed on seaweed, the leaves and shoots of mangrove trees, and the leaves of another unidentified shoreline shrub. Comparative data on the gonads of dark and yellow turtles indicated that the latter did not breed in Galapagos during Slevin's stay. Lepidochelys olivacea, the olive ridley, was recorded in Galapagos waters and fed on fish eggs

  17. Critically endangered western gray whales migrate to the eastern North Pacific

    PubMed Central

    Mate, Bruce R.; Ilyashenko, Valentin Yu.; Bradford, Amanda L.; Vertyankin, Vladimir V.; Tsidulko, Grigory A.; Rozhnov, Vyacheslav V.; Irvine, Ladd M.

    2015-01-01

    Western North Pacific gray whales (WGWs), once considered extinct, are critically endangered with unknown migratory routes and reproductive areas. We attached satellite-monitored tags to seven WGWs on their primary feeding ground off Sakhalin Island, Russia, three of which subsequently migrated to regions occupied by non-endangered eastern gray whales (EGWs). A female with the longest-lasting tag visited all three major EGW reproductive areas off Baja California, Mexico, before returning to Sakhalin Island the following spring. Her 22 511 km round-trip is the longest documented mammal migration and strongly suggests that some presumed WGWs are actually EGWs foraging in areas historically attributed to WGWs. The observed migration routes provide evidence of navigational skills across open water that break the near-shore north–south migratory paradigm of EGWs. Despite evidence of genetic differentiation, these tagging data indicate that the population identity of whales off Sakhalin Island needs further evaluation. PMID:25878049

  18. STS-114 Flight Day 5 Highlights

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Highlights of Day 5 of the STS-114 Return to Flight mission (Commander Eileen Collins, Pilot James Kelly, Mission Specialists Soichi Noguchi, Stephen Robinson, Andrew Thomas, Wendy Lawrence, and Charles Camarda) include video coverage of an extravehiclular activity (EVA) by Noguchi and Robinson. The other crew members of Discovery are seen on the flight deck and mid-deck helping the astronauts to suit-up. The objectives of the EVA are to test repair techniques on sample tiles in the shuttle's payload bay, to repair electrical equipment for a gyroscope on the International Space Station (ISS), and to install a replacement GPS antenna on the ISS. Noguchi and Robinson use a caulk gun and a putty knife to repair the sample tiles. The video contains several Earth views, including one of Baja California.

  19. Critically endangered western gray whales migrate to the eastern North Pacific.

    PubMed

    Mate, Bruce R; Ilyashenko, Valentin Yu; Bradford, Amanda L; Vertyankin, Vladimir V; Tsidulko, Grigory A; Rozhnov, Vyacheslav V; Irvine, Ladd M

    2015-04-01

    Western North Pacific gray whales (WGWs), once considered extinct, are critically endangered with unknown migratory routes and reproductive areas. We attached satellite-monitored tags to seven WGWs on their primary feeding ground off Sakhalin Island, Russia, three of which subsequently migrated to regions occupied by non-endangered eastern gray whales (EGWs). A female with the longest-lasting tag visited all three major EGW reproductive areas off Baja California, Mexico, before returning to Sakhalin Island the following spring. Her 22 511 km round-trip is the longest documented mammal migration and strongly suggests that some presumed WGWs are actually EGWs foraging in areas historically attributed to WGWs. The observed migration routes provide evidence of navigational skills across open water that break the near-shore north-south migratory paradigm of EGWs. Despite evidence of genetic differentiation, these tagging data indicate that the population identity of whales off Sakhalin Island needs further evaluation. PMID:25878049

  20. Succession in a microbial mat community: a gaian perspective.

    PubMed

    Stolz, J F

    1984-01-01

    The Gaia hypothesis originally proposed by James E. Lovelock states that the composition, oxidation-reduction state and temperature of the troposphere are actively regulated by the activities of the biota. The gaian concept has been extrapolated to include the composition of surface sediments through the process of biomineralization. The stratified microbial community dominated by the cyanobacterium Microcoleus chthonoplastes is actively involved in the deposition of laminated sediments at Laguna Figueroa, Baja California, Mexico. Unusually heavy rains in the winters of 1979 and 1980 flooded the evaporite flat with up to 3 meters of meteoric water and deposited 5-10 cm of allocthonous sediment. The composition of the microbial community changed as a succession of dominating microbial species ensued, ultimately leading to the recolonization of the surface sediment by the original Microcoleus-dominated community. The resiliency of bacterial communities is suggested to be an important mechanism of gaian control systems. PMID:11537776

  1. Black brant from Alaska staging and wintering in Japan

    USGS Publications Warehouse

    Derksen, Dirk V.; Bollinger, K.S.; Ward, David H.; Sedinger, J.S.; Miyabayashi, Y.

    1996-01-01

    Black brant (Branta bernicla nigricans) nest in colonies in arctic Canada, Alaska, and Russia (Derksen and Ward 1993, Sedinger et al. 1993). Virtually the entire population stages in fall at Izembek Lagoon near the tip of the Alaska Peninsula (Bellrose 1976) before southward migration (Dau 1992) to winter habitats in British Columbia, Washington, Oregon, California, and Baja California (Subcommittee on Black Brant 1992). A small number of black brant winter in Japan, Korea, and China (Owen 1980). In Japan 3,000–5,000 brant of unknown origin stop over in fall, and a declining population (<1,000) of birds winter here, primarily in the northern islands (Brazil 1991, Miyabayashi et al. 1994). Here, we report sightings of brant in Japan that were marked in Alaska and propose a migration route based on historical and recent observations and weather patterns.

  2. American Oystercatcher (Haematopus palliatus)

    USGS Publications Warehouse

    Simons, Theodore R.; Nol, E.; Boettcher, R.

    2012-01-01

    The American Oystercatcher is a large, conspicuous shorebird, common in coastal salt marshes and along sand beaches throughout the central part of its range. One of the few birds to specialize on bivalve mollusks living in saltwater, this species is completely restricted to marine habitats. Two races breed in North America—the eastern nominate race along the Atlantic coast from southern Maine south, and a second race along the Pacific coast from northwestern Baja California south. While the eastern race has been studied extensively across its range both during winter and the breeding season, the biology of the western race is poorly known and this population may also be at risk both from coastal development and hybridization with the American Black Oystercatcher (H. bachmani). Eastern oystercatchers regularly winter in large flocks, from Virginia south along the Atlantic and Gulf coasts.

  3. mtDNA and Y-chromosome polymorphisms in four Native American populations from southern Mexico

    SciTech Connect

    Torroni, A.; Chen, Yu.S.; Lott, M.T.; Wallace, D.C. ); Semino, O.; Santachiara-Beneceretti, A.S. ); Scott, C.R. ); Winter, M. )

    1994-02-01

    mtDNA sequence variation was examined in 60 Native Americans (Mixtecs from the Alta, Mixtecs from the Baja, Valley Zapotecs, and Highland Mixe) from southern Mexico by PCR amplification and high-resolution restriction endonuclease analysis. Four groups of mtDNA haplotypes (haplogroups A,B,C, and D) characterize Amerind populations. The comparison of their mtDNA variation with that observed in other populations from Mexico and Central America permits a clear distinction among the different Middle American tribes and raises questions about some of their linguistic affiliations. The males of these population samples were also analyzed for Y-chromosome RFLPs with the probes 49a, 49f, and 12f2. This analysis suggests that certain Y-chromosome haplotypes were brought from Asia during the colonization of the Americas, and a differential gene flow was introduced into Native American populations from European males and females. 31 refs., 4 figs., 5 tabs.

  4. West Nile Virus Infection of Birds, Mexico

    PubMed Central

    Guerrero-Sánchez, Sergio; Cuevas-Romero, Sandra; Nemeth, Nicole M.; Trujillo-Olivera, María Teresa Jesús; Worwa, Gabriella; Dupuis, Alan; Brault, Aaron C.; Kramer, Laura D.; Komar, Nicholas

    2011-01-01

    West Nile virus (WNV) has caused disease in humans, equids, and birds at lower frequency in Mexico than in the United States. We hypothesized that the seemingly reduced virulence in Mexico was caused by attenuation of the Tabasco strain from southeastern Mexico, resulting in lower viremia than that caused by the Tecate strain from the more northern location of Baja California. During 2006–2008, we tested this hypothesis in candidate avian amplifying hosts: domestic chickens, rock pigeons, house sparrows, great-tailed grackles, and clay-colored thrushes. Only great-tailed grackles and house sparrows were competent amplifying hosts for both strains, and deaths occurred in each species. Tecate strain viremia levels were higher for thrushes. Both strains produced low-level viremia in pigeons and chickens. Our results suggest that certain avian hosts within Mexico are competent for efficient amplification of both northern and southern WNV strains and that both strains likely contribute to bird deaths. PMID:22172633

  5. Benthic foraminifera of the Panamanian Province: distribution and origins.

    USGS Publications Warehouse

    Crouch, R.W.; Poag, C.W.

    1987-01-01

    Two hundred twenty-nine species of benthic foraminifera have been identified from 96 stations representing 33 localities on the eastern Pacific inner continental shelf, ranging from southern Peru to northern Baja California. Their distributions mark nearshore provincial boundaries that are nearly identical with those previously documented from the distribution of ostracodes and molluscs. Thirteen species are characteristic of the Panamanian Province, one is characteristic of the Chilean-Peruvian Province, and one is characteristic of the newly proposed Sonoran Subprovince. Seventeen species (7%) appear to be endemic to the eastern Pacific. Fifty-eight (25%) of the species recognized are disjunct from population centers in the western Pacific, 134 species (59%) are disjunct from modern assemblages of the Atlanto-Carribean region, and 40 species (17%) are disjunct from both the western Pacific and the Atlanto-Caribbean. The distribution of the remaining 57 species (25%) is poorly documented; we classify them as of unknown origin. -Authors

  6. In Brief: Commission for Environmental Cooperation priorities

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2009-11-01

    Members of the Joint Public Advisory Committee of the Commission for Environmental Cooperation (CEC) will host a 1 December live Webcast discussion on environmental priorities the commission should consider during the next 5 years. The priorities will relate to “healthy communities and ecosystems,” “climate change-low-carbon economy,” and “greening the economy in North America.” CEC is an international organization created by Canada, Mexico, and the United States under the North American Agreement on Environmental Cooperation. The meeting, in Los Cabos, Baja California Sur, Mexico, will include a virtual forum to allow online participation. More information will be available soon at http://www.cec.org.

  7. Migratory double breeding in Neotropical migrant birds

    PubMed Central

    Rohwer, Sievert; Hobson, Keith A.; Rohwer, Vanya G.

    2009-01-01

    Neotropical migratory songbirds typically breed in temperate regions and then travel long distances to spend the majority of the annual cycle in tropical wintering areas. Using stable-isotope methodology, we provide quantitative evidence of dual breeding ranges for 5 species of Neotropical migrants. Each is well known to have a Neotropical winter range and a breeding range in the United States and Canada. However, after their first bout of breeding in the north, many individuals migrate hundreds to thousands of kilometers south in midsummer to breed a second time during the same summer in coastal west Mexico or Baja California Sur. They then migrate further south to their final wintering areas in the Neotropics. Our discovery of dual breeding ranges in Neotropical migrants reveals a hitherto unrealized flexibility in life-history strategies for these species and underscores that demographic models and conservation plans must consider dual breeding for these migrants. PMID:19858484

  8. Dynamical response of the tropical Pacific Ocean to solar forcing during the early Holocene.

    PubMed

    Marchitto, Thomas M; Muscheler, Raimund; Ortiz, Joseph D; Carriquiry, Jose D; van Geen, Alexander

    2010-12-01

    We present a high-resolution magnesium/calcium proxy record of Holocene sea surface temperature (SST) from off the west coast of Baja California Sur, Mexico, a region where interannual SST variability is dominated today by the influence of the El Niño-Southern Oscillation (ENSO). Temperatures were lowest during the early to middle Holocene, consistent with documented eastern equatorial Pacific cooling and numerical model simulations of orbital forcing into a La Niña-like state at that time. The early Holocene SSTs were also characterized by millennial-scale fluctuations that correlate with cosmogenic nuclide proxies of solar variability, with inferred solar minima corresponding to El Niño-like (warm) conditions, in apparent agreement with the theoretical "ocean dynamical thermostat" response of ENSO to exogenous radiative forcing. PMID:21127251

  9. Dynamical Response of the Tropical Pacific Ocean to Solar Forcing During the Early Holocene

    NASA Astrophysics Data System (ADS)

    Marchitto, Thomas M.; Muscheler, Raimund; Ortiz, Joseph D.; Carriquiry, Jose D.; van Geen, Alexander

    2010-12-01

    We present a high-resolution magnesium/calcium proxy record of Holocene sea surface temperature (SST) from off the west coast of Baja California Sur, Mexico, a region where interannual SST variability is dominated today by the influence of the El Niño-Southern Oscillation (ENSO). Temperatures were lowest during the early to middle Holocene, consistent with documented eastern equatorial Pacific cooling and numerical model simulations of orbital forcing into a La Niña-like state at that time. The early Holocene SSTs were also characterized by millennial-scale fluctuations that correlate with cosmogenic nuclide proxies of solar variability, with inferred solar minima corresponding to El Niño-like (warm) conditions, in apparent agreement with the theoretical “ocean dynamical thermostat” response of ENSO to exogenous radiative forcing.

  10. Biodiversity and Archeological Conservation Connected: Aragonite Shell Middens Increase Plant Diversity

    PubMed Central

    Vanderplank, Sula E.; Mata, Sergio; Ezcurra, Exequiel

    2014-01-01

    Natural and cultural heritage sites frequently have nonoverlapping or even conflicting conservation priorities, because human impacts have often resulted in local extirpations and reduced levels of native biodiversity. Over thousands of years, the predictable winter rains of northwestern Baja California have weathered calcium from the clam shells deposited by indigenous peoples in middens along the coast. The release of this calcium has changed soil properties, remediated sodic and saline soils, and resulted in a unique microhabitat that harbors plant assemblages very different from those of the surrounding matrix. Native plant biodiversity and landscape heterogeneity are significantly increased on the anthropogenic soils of these shell middens. Protection of this cultural landscape in the Anthropocene will further both archeological and biodiversity conservation in these anthropogenic footprints from the Holocene. Along these coasts, natural and cultural heritage priorities are overlapping and mutually beneficial. PMID:26955068

  11. Evolución estelar en sistemas binarios

    NASA Astrophysics Data System (ADS)

    De Vito, M. A.; Benvenuto, O.

    Definición y clasificación de sistemas binarios; descripción del comportamiento del sistema frente a la variación de su masa; binarias de rayos X; transferencia de masa en sistemas binarios masivos aplicado al posible esclarecimiento del progenitor azul de la supernova SN 1987A; comentario acerca de la evolución de enanas blancas de helio de baja masa y su conexión con los sistemas binarios; reseña del trabajo de Kippenhahn y Weigert sobre el cual está basado el código evolutivo desarrollado en la FCAG por el Dr. Benvenuto y sobre el cual se trabajará para poder incluir la evolución de una estrella con pérdida de masa perteneciente a un sistema binario.

  12. The U.S.-Mexico Border Infectious Disease Surveillance Project: Establishing Binational Border Surveillance

    PubMed Central

    Waterman, Stephen; Lucas, Carlos Alvarez; Falcon, Veronica Carrion; Morales, Pablo Kuri; Lopez, Luis Anaya; Peter, Chris; Gutiérrez, Alejandro Escobar; Gonzalez, Ernesto Ramirez; Flisser, Ana; Bryan, Ralph; Valle, Enrique Navarro; Rodriguez, Alfonso; Hernandez, Gerardo Alvarez; Rosales, Cecilia; Ortiz, Javier Arias; Landen, Michael; Vilchis, Hugo; Rawlings, Julie; Leal, Francisco Lopez; Ortega, Luis; Flagg, Elaine; Conyer, Roberto Tapia; Cetron, Martin

    2003-01-01

    In 1997, the Centers for Disease Control and Prevention, the Mexican Secretariat of Health, and border health officials began the development of the Border Infectious Disease Surveillance (BIDS) project, a surveillance system for infectious diseases along the U.S.-Mexico border. During a 3-year period, a binational team implemented an active, sentinel surveillance system for hepatitis and febrile exanthems at 13 clinical sites. The network developed surveillance protocols, trained nine surveillance coordinators, established serologic testing at four Mexican border laboratories, and created agreements for data sharing and notification of selected diseases and outbreaks. BIDS facilitated investigations of dengue fever in Texas-Tamaulipas and measles in California–Baja California. BIDS demonstrates that a binational effort with local, state, and federal participation can create a regional surveillance system that crosses an international border. Reducing administrative, infrastructure, and political barriers to cross-border public health collaboration will enhance the effectiveness of disease prevention projects such as BIDS. PMID:12533288

  13. Marine Microbial Mats and the Search for Evidence of Life in Deep Time and Space

    NASA Technical Reports Server (NTRS)

    Des Marais, David J.

    2011-01-01

    Cyanobacterial mats in extensive seawater evaporation ponds at Guerrero Negro, Baja California, Mexico, have been excellent subjects for microbial ecology research. The studies reviewed here have documented the steep and rapidly changing environmental gradients experienced by mat microorganisms and the very high rates of biogeochemical processes that they maintained. Recent genetic studies have revealed an enormous diversity of bacteria as well as the spatial distribution of Bacteria, Archaea and Eukarya. These findings, together with emerging insights into the intimate interactions between these diverse populations, have contributed substantially to our understanding of the origins, environmental impacts, and biosignatures of photosynthetic microbial mats. The biosignatures (preservable cells, sedimentary fabrics, organic compounds, minerals, stable isotope patterns, etc.) potentially can serve as indicators of past life on early Earth. They also can inform our search for evidence of any life on Mars. Mars exploration has revealed evidence of evaporite deposits and thermal spring deposits; similar deposits on Earth once hosted ancient microbial mat ecosystems.

  14. Operationalizing the social-ecological systems framework to assess sustainability.

    PubMed

    Leslie, Heather M; Basurto, Xavier; Nenadovic, Mateja; Sievanen, Leila; Cavanaugh, Kyle C; Cota-Nieto, Juan José; Erisman, Brad E; Finkbeiner, Elena; Hinojosa-Arango, Gustavo; Moreno-Báez, Marcia; Nagavarapu, Sriniketh; Reddy, Sheila M W; Sánchez-Rodríguez, Alexandra; Siegel, Katherine; Ulibarria-Valenzuela, José Juan; Weaver, Amy Hudson; Aburto-Oropeza, Octavio

    2015-05-12

    Environmental governance is more effective when the scales of ecological processes are well matched with the human institutions charged with managing human-environment interactions. The social-ecological systems (SESs) framework provides guidance on how to assess the social and ecological dimensions that contribute to sustainable resource use and management, but rarely if ever has been operationalized for multiple localities in a spatially explicit, quantitative manner. Here, we use the case of small-scale fisheries in Baja California Sur, Mexico, to identify distinct SES regions and test key aspects of coupled SESs theory. Regions that exhibit greater potential for social-ecological sustainability in one dimension do not necessarily exhibit it in others, highlighting the importance of integrative, coupled system analyses when implementing spatial planning and other ecosystem-based strategies. PMID:25918372

  15. Repair of fresh patellar tendon rupture: tension regulation at the suture line

    PubMed Central

    2009-01-01

    The reported complications of the repaired patellar tendon have been attributed to the influence of the mechanical environment on the healing process. This study postulates that the healing complications can be minimised through tension regulation at the suture line using an absorbable reinforcement device. Twelve patients with fresh patellar tendon rupture were included in the study. They were prospectively followed up for an average period of 45 months. The patients resumed their pre-injury activities at an average of 6.1 months. The active knee movement averaged 0–154.6° compared to 0–156.7° in the contralateral knee. Radiologically no patella alta, patella baja or degenerative changes in the patellofemoral joints were noted. The results support use of the absorbable reinforcement device for tension regulation at the suture line. PMID:19809813

  16. Developing ultraviolet illumination of gillnets as a method to reduce sea turtle bycatch.

    PubMed

    Wang, John; Barkan, Joel; Fisler, Shara; Godinez-Reyes, Carlos; Swimmer, Yonat

    2013-10-23

    Fisheries bycatch of marine animals has been linked to population declines of multiple species, including many sea turtles. Altering the visual cues associated with fishing gear may reduce sea turtle bycatch. We examined the effectiveness of illuminating gillnets with ultraviolet (UV) light-emitting diodes for reducing green sea turtle (Chelonia mydas) interactions. We found that the mean sea turtle capture rate was reduced by 39.7% in UV-illuminated nets compared with nets without illumination. In collaboration with commercial fishermen, we tested UV net illumination in a bottom-set gillnet fishery in Baja California, Mexico. We did not find any difference in overall target fish catch rate or market value between net types. These findings suggest that UV net illumination may have applications in coastal and pelagic gillnet fisheries to reduce sea turtle bycatch. PMID:23883577

  17. Feasibility and use of school-based condom availability programs in Tijuana, Mexico.

    PubMed

    Zellner, Jennifer A; Martinez-Donate, Ana P; Hovell, Melbourne F; Sipan, Carol L; Blumberg, Elaine J; Carrizosa, Claudia M; Rovniak, Liza

    2006-11-01

    Condom availability programs (CAPs) may increase access to condoms and contribute to increased condom use among youth. This study describes the characteristics, degree of satisfaction, and gender differences among users of a CAP implemented in two high schools in Tijuana (Baja California, Mexico). A kiosk distributing free male condoms was set up in two high schools in Tijuana. Kiosk users (N=570) were more likely to be male, young, and/or enrolled in a lower SES school. Most kiosk users were either sexually active or planning to have sex. Females were less likely to request condoms and to continue using the kiosk, but more likely to request information on other contraceptive methods. Results demonstrate the feasibility of implementing CAPs in Mexican schools and suggest that these programs can improve adolescents' condom access. PMID:16715349

  18. The decline of cooperation, the rise of competition: developmental effects of long-term social change in Mexico.

    PubMed

    García, Camilo; Rivera, Natanael; Greenfield, Patricia M

    2015-02-01

    Using Greenfield's theory of sociocultural change and human development as a point of departure, we carried out two experimental studies exploring the implications of decades of globalised social change in Mexico for children's development of cooperation and competition. In rural San Vicente, Baja California, the baseline was 1970 and the historical comparison took place 40 years later. In Veracruz, the baseline was 1985 and the historical comparison took place 20 years later. In Veracruz, children were tested in both rural and urban settings. We hypothesized that cooperative behavior would decrease in all three settings as a result of the sociocultural transformations of the past decades in Mexico. The Madsen Marble Pull Game was used to assess cooperative and competitive behavior. As predicted by Greenfield's theory of social change and human development, the Marble Pull procedure revealed a striking decrease over time in levels of cooperative behavior, with a corresponding rise in competitive behavior, in all three settings. PMID:25611927

  19. Strain buildup and release, earthquake prediction and selection of VLB sites for the margins of the North Pacific

    NASA Technical Reports Server (NTRS)

    Scholz, C. H.; Johnson, T.

    1976-01-01

    Microearthquake studies of the southern section of the San Andreas fault system were conducted in order to elucidate the role of known but little studied complications in the fault system which could affect the SAFE measurement. Data reduction from microearthquake studies in Baja California, Mexico, was completed. In addition, styles of deformation on the Alpine fault in New Zealand and on the San Andreas fault were compared. Sections of these faults with comparable physical characteristics seem to deform in a similar manner, indicating that deformation style is controlled by certain fundamental relations and will continue in the future. The geology of eastern New Guinea is also discussed. Deformation in the area is proposed to be related to collision of a series of island arcs with central New Guinea, which is part of the Australian continent. Among other unusual properties, eastern New Guinea contains the highest anomaly of the gravimetrically determined geoid based on GEM 6 and surface gravity data.

  20. Thermal gradient analysis for the ESOPO spectrograph

    NASA Astrophysics Data System (ADS)

    Farah, A.; González, J. Jesús; Sierra, G.; Hernández, J. V.; Pedrayes, M.; Echevarría, J.; Costero, R.; Avila, G.; Arroyo, M.; Cobos, F.; Colorado, E.; Cordova, A.; Chapa, O.; Garcia, B.; Garfias, F.; Granados, F.; Guisa, G.; Luna, E.; Martínez, B.; Michel, R.; Murillo, F.; Pérez, F.; Quechol, S.; Quirós, F.; Tejada, C.

    2008-07-01

    ESOPO will be a spectrograph of medium resolution for the 2.1 m telescope of the National Observatory at San Pedro Martir, Baja California, Mexico. It has been developed by the Instituto de Astronomia of the Universidad Nacional Autonoma de Mexico (IA-UNAM). The main goal of this instrument is to modernize the capabilities of making science with that particular telescope. It is planned to achieve a spectral resolution between 500 and 5000. ESOPO is split into two arms; each one specialized in a specific wavelength range covering together all the visible light. A very important issue in spectrographs is to avoid inside thermal gradients. Different temperatures in the optical elements produce mechanical movements and image quality degradation during an exposition. The error budget analysis developed for ESOPO allows establishing the required limits for temperature gradients. In this paper is described the thermal analysis of the spectrograph, including specifications, finite element models, thermal equations and expected thermal gradients.