Recursos de colección

Aquatic Commons (36.279 recursos)

The Aquatic Commons is a thematic digital repository covering the natural marine, estuarine /brackish and fresh water environments . It includes all aspects of the science, technology, management and conservation of these environments, their organisms and resources, and the economic, sociological and legal aspects.

Subject = Earth Sciences

Mostrando recursos 1 - 20 de 391

  1. Mineralogical variations and physical properties of deep sea sediments, northwest Arabian Sea

    Khan, A.A.; Hamid, G.; Hasany, S.I.
    Charles Darwin the research ship undertook an Oceanographic Cruise in 1986, CD 86/17 of the North Arabian Sea. Sediment cores were collected between 15° and 25°N. In this study sediment cores collected from deep Indus and Oman basins (CD 1715, CD 1730, CD 1738) have been analyzed for mineralogy, water content and porosity. In general, the cores are mainly composed of clay to silt sized terrigenous and biogenic constituents. Quartz, Chlorite and Illite are the common minerals of Arabian Sea sediments. Porosity determined by water content of sediments has been correlated with quartz/chlorite and quartz/illite peak ratios to show a...

  2. Offshore geology of Pakistan and non-living resource prospects

    Khan, A.A.
    Offshore geology of Pakistan is characterized by active and passive continental margins. These continental margins show very unique features such as an active Makran subduction zone in the west and the Indus delta and a submarine fan in the east. The geology of these features of Pakistan EEZ is inadequately known. This is a major obstacle in exploring mineral resources. Detailed study of coastal and shelf geology is needed for better understanding of the geology of the area and comprehensive evolution of its non-living resource potential. An understanding of the geological events including tectonic movements, sedimentation processes and geochemical history...

  3. Concentration and distribution of heavy metals (lead, cadmium, chromium, copper, nickel, zinc) in Karachi shore and offshore sediments

    Saleem, Monawwar; Kazi, G.H.
    A study to measure the heavy metal pollution level in the sediment of coastal and offshore area indicates that high concentration of heavy metals were found around Manora channel and eastern coast of Karachi. In comparison with coastal areas, relatively low concentration of heavy metals was recorded in the offshore area. The result shows that sewage and industrial wastes are the main source of heavy metal pollution in the coastal area. The concentration of heavy metals in the sediments is as follows: Chromium 10.4-33.69, nickel 13.3-47.6, lead 10.0-39.04, cadmium 0.08-0.21, zinc 7.4-73.2 and copper 9.44-18.56 mg/kg. In the offshore areas...

  4. El ascenso del nivel del mar en la costa de la provincia de Buenos Aires

    Fiore, M.E.; D'Onofrio, E.E.; Grismeyer, W.H.; Mediavilla, D.G.
    Este trabajo de divulgación científica presenta la tendencia relativa del nivel medio del mar y su aceleración, para aquellas localidades de la provincia de Buenos Aires (Argentina) de las que se dispone de series de alturas de marea que cubren por lo menos los últimos ciencuenta años. Este es el caso del puerto de Buenos Aires y el de Mar del Plata. Éstas dos localidades poseen características geográficas e hidrodinámicas distintas, por lo que resulta de mayor interés comparar los resultados obtenidos. Se discuten los mismos, y la evolución del nivel medio durante esta centuria.

  5. Note on the geomorphology of a segment of Mekran coast

    Ishaq Mirza, M.
    The Lasbela coast formulates the southeastern part of Balochistan province. The plain area in the north of the coast is a triangular shaped valley bounded by mountains on both of its flanks called as the Lasbela plain.

  6. Textural and compositional variations in beach sands along Karachi coast

    Ibrahim, N.; Muhammad, M.J.; Zaidi, S.M.S.
    The texture of clastic sediments is a fairly reliable index of the erosional history and energy conditions of the depositional environment, while its mineralogy reflects the composition of the source rocks. The beach sands of Clifton, Sandspit, Hawkesbay and Paradise Point were studied to determine their erosional history, depositional environment and their source

  7. Proceedings of the Thirteenth Annual Pacific Climate (PACLIM) Workshop, Asilomar, California - April 14-17, 1996 [appendices]

    The appendices include the workshop agenda, a list of poster presentations, and a list of attendees.

  8. Proceedings of the Thirteenth Annual Pacific Climate (PACLIM) Workshop, Asilomar, California - April 14-17, 1996 [abstracts]

    Abstracts of 24 oral presentations and 25 poster presentations.

  9. Addendum I: Paleoclimate and the Solar-Insolation/Tidal-Resonance Climate Model

    Karlstrom, Thor
    Recent papers provide detailed analyses of more than 40 high-resolution time series culled from the extensive paleoclimate literature that appear to define cyclical elements of the Solar-Insolation/Tidal-Resonance Climate Model. This model was earlier referred to as the Milankovitch/Pettersson Climatic Theory. This paper provides comparable analyses of an additional 20 or so, evidently supportive, climate and volcanic time series. The tree-ring, historical, pollen, cultural, time-frequency, and hydrologic records range in length from 400 to 90,000 years and spatially from Alaska to Tierra del Fuego.

  10. Some perspectives on the late Quaternary paleoclimate of Beringia

    Mock, Cary J.; Anderson, Patricia M.
    EXTRACT (SEE PDF FOR FULL ABSTRACT): Analyses of the modern summer synoptic climatology of Beringia illustrate that the region cannot be treated as a homogenous climatic unit as a result of different circulation controls that operate over the region. GCM (general circulation model) simulations and information from the modern synoptic climatology were used to infer the summer paleosynoptic climatology of the region since the last glacial maximum. ... Variations in these climatic controls offer important implications in assessing the vegetation histories of western Beringia versus eastern Beringia.

  11. The near-AD 1600 multi-proxy puzzle

    Biondi, Franco; Lange, Carina B.; Hughes, Malcolm K.; Berger, Wolfgang H.
    EXTRACT (SEE PDF FOR FULL ABSTRACT): A varve chronology with annual resolution (AD 1117-1992) has been developed recently for Santa Barbara Basin. Varve thickness and water content show an exponential trend consistent with expected patterns in the presence of sediment compaction over time. Annual varve thickness was decomposed into orthogonal components using singular spectrum analysis (SSA) to identify and retrieve inter-decadal oscillations. ... This suggests a connection with global-scale decadal cycles identified in the subtropical Pacific gyre circulation and, possibly, with solar-driven phenomena. The near-1600 AD event coincides with (a) a similarly sudden change of state in nearby Santa Monica Basin...

  12. A late-Holocene pollen record from Lower Pahrangat Lake, southern Nevada, USA: high resolution paleoclimatic records and analysis of environmental responses to climate change

    Wigand, Peter E.
    EXTRACT (SEE PDF FOR FULL ABSTRACT): High resolution paleobotanical records provide sufficient detail to correlate events regionally. Once correlated events can be examined in tandem to determine the underlying inputs that fashioned them. Several localities in the Great Basin have paleobotanical records of sufficient detail to generate regional reconstructions of vegetation changes for the last 2 ka and provide conclusions as to the climates that caused them.

  13. Introduction

    Isaacs, Caroline M.
    The Thirteenth Annual PACLIM Workshop was held at the Asilomar Conference Center on April 14-17, 1996. Attended by about 100 registered participants, the workshop included 27 talks and 26 poster presentations. The talks consisted of a one-day theme session of seven 45-minute talks and two featured evening talks. Throughout the remainder of the meeting were nearly 20 shorter, 20-minute presentations. Poster presenters gave a short 1-2 minute introduction to their posters, which were displayed during the entire meeting. All presenters were invited to expand their abstracts into a manuscript for inclusion in the Proceedings volume, and nearly all presentations are included...

  14. Proceedings of the Thirteenth Annual Pacific Climate (PACLIM) Workshop, Asilomar, California - April 14-17, 1996 [front matter]

  15. Proceedings of the Twelfth Annual Pacific Climate (PACLIM) Workshop, Asilomar, California - May 2-5, 1995 [appendices]

    The appendices include the workshop agenda, a list of poster presentations, and a list of attendees.

  16. A rock-magnetic and geomagnetic secular variation record from late-Pleistocene Lake Estancia, New Mexico [abstract]

    Rowe, H.D.; Geissman, J.W.; Allen, Bruce D.; Anderson, Roger Y.
    EXTRACT (SEE PDF FOR FULL ABSTRACT): Exposed sediments of Late Pleistocene Lake Estancia contain a high resolution record of regional climate variability for the period about 12,000 to 32,000 years. A detailed rock-magnetic study is being performed on this well-dated, well-preserved sedimentary sequence to determine how the magnetic signature of sediments responded to regional climate change.

  17. Multiple-proxy lacustrine record of moisture transport over western North America from 24,000 to 12,000 YBP, Lake Estancia, New Mexico [abstract]

    Allen, Bruce D.; Anderson, Roger Y.; Yapp, Crayton J.
    EXTRACT (SEE PDF FOR FULL ABSTRACT): Pluvial Lake Estancia in central New Mexico experienced large and rapid fluctuations in surface area and elevation during the build-up to and termination of the last glacial maximum (LGM). Due to continuous groundwater discharge, a minimum pool covering about 400 square kilometers was maintained in the central basin until about 12,000 years ago, ensuring a continuous depositional sequence even during low stands of the lake. ... The sensitive response to fluctuations in climate by several independent proxies at Estancia show that transport of Pacific moisture over western North America changed dramatically during the last Ice...

  18. Response of Pacific Northwest vegetation to large-scale changes in climate during the last 100,000 years [abstract]

    Whitlock, Cathy; Bartlein, Patrick J.
    EXTRACT (SEE PDF FOR FULL ABSTRACT): Paleoclimatic variations in western North America depend on a hierarchy of temporal and spatial controls that can be examined using a combination of modeling studies and data synthesis. ... The regional vegetation response to large-scale changes in the climate system of the last 21,000 years is used as a conceptual model to help explain earlier vegetation and climate at two localities.

  19. A detailed 2,000-year late-Holocene pollen record from Lower Pahranagat Lake, southern Nevada, USA [abstract]

    Wigand, Peter E.; Hemphill, Martha L.
    EXTRACT (SEE PDF FOR FULL ABSTRACT): Preliminary analysis of 128 pollen samples and 7 radiocarbon dates from a 5-meter-long, 10-centimeter-diameter sediment core retrieved from Lower Pahranagat Lake (elevation 975 meters), Lincoln County, Nevada, gives us a rare, continuous record of vegetation change at 14-year intervals over the past 2,000 years.

  20. A late Pleistocene paleohydrologic record of Sierra Nevada runoff from Owens Lake, California [abstract]

    Bradbury, J. Platt
    EXTRACT (SEE PDF FOR FULL ABSTRACT): A 323-meter (about 800,000 year) core of lake deposits beneath Owens Lake playa, Inyo County, California, contains a nearly continuous paleolimnological record based on diatom assemblages. ... Throughout most of its history, Owens Lake was characterized by freshwater diatoms, indicating a positive hydrologic input from the Owens River and overflow to lake systems downstream.

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