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  • 1
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    Impacts of Hurricanes Katrina and Rita on the microbial landscape of the New Orleans area (2007)
    Details
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2007. This is the author's version of the work. It is posted here by permission of National Academy of Sciences of the USA for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences 104 (2007): 9029-9034, doi:10.1073/pnas.0610552104.
    Description: Floodwaters in New Orleans from Hurricanes Katrina and Rita were observed to contain high levels of fecal indicator bacteria and microbial pathogens, generating concern about long-term impacts of these floodwaters on the sediment and water quality of the New Orleans area and Lake Pontchartrain. We show here that fecal indicator microbe concentrations in offshore waters from Lake Pontchartrain returned to prehurricane concentrations within 2 months of the flooding induced by these hurricanes. Vibrio and Legionella species within the lake were more abundant in samples collected shortly after the floodwaters had receded compared with samples taken within the subsequent 3 months; no evidence of a long-term hurricane-induced algal bloom was observed. Giardia and Cryptosporidium were detected in canal waters. Elevated levels of fecal indicator bacteria observed in sediment could not be solely attributed to impacts from floodwaters, as both flooded and nonflooded areas exhibited elevated levels of fecal indicator bacteria. Evidence from measurements of Bifidobacterium and bacterial diversity analysis suggest that the fecal indicator bacteria observed in the sediment were from human fecal sources. Epidemiologic studies are highly recommended to evaluate the human health effects of the sediments deposited by the floodwaters.
    Description: This work was funded by NSF-NIEHS Oceans and Human Health Program (NSF OCE0432368, OCE0432479, OCE0430724 and NIEHS P50 ES12736, ES012740, ES012742), the NSF-SGER Program (OCE 0554402, OCE 0554674, OCE 0554850, OCE0600130), the NSF-REU Program, and by the Georgia Sea Grant College Program (NA04OAR170033).
    Keywords: Lake Pontchartrain ; Water quality
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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    PAPER (OA)
  • 2
    Electronic Resource
    Electronic Resource
    Gebel Dahanib, Egypt: A late Precambrian layered sill of komatiitic composition (1981)
    Springer
    Contributions to mineralogy and petrology 76 (1981), S. 42-52 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Gebel Dahanib is a well preserved, late Precambrian layered mafic-ultramafic sill about 1.5 km thick, forming a prominent peak in the Southeastern Desert of Egypt. Dunites, harzburgites and thin chromite layers at the base grade upward through pyroxenites to layered gabbros and rare anorthosite at the top. Peridotitic dykes from the main body, unsheared margins, and ubiquitous cumulate textures all suggest magmatic rather than tectonic emplacement. Olivine ranges from Fo94 to Fo76, orthopyroxene from En90 to En79, and abundant clinopyroxene is typically low Cr diopside or diopsidic augite. Plagioclase is exceptionally calcic (An94-An83) and typically is 10% more calcic at a given coexisting olivine composition than plagioclase in the Skaergaard and Stillwater intrusions. Assimilation of the country rock is common along the borders, and chilled margins are not developed. The bulk composition of the sill, estimated from whole rock analyses weighted according to outcrop areas, is SiO2=50.1%, A12O3= 8.9%, MgO=19.9%, CaO=12.1%, K2O=0.06%, TiO2=0.2%. REE contents in the original magma were less than four times chondritic abundances. The chemical and mineralogical characteristics of the Dahanib sill suggest comparisons with basaltic or pyroxenitic komatiites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373682
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Bathymetry estimates in the southern oceans from Seasat altimetry (1983)
    [s.l.] : Nature Publishing Group
    Nature 304 (1983), S. 406-411 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A mean sea surface height based on Seasat altimeter data has been high-pass filtered to reveal a pattern of geoid anomalies which are highly correlated with sea-floor topography. The technique is used to locate new bathymetric features in the poorly surveyed southern ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/304406a0
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Petrology and chemistry of recent lavas in the northern Marianas: Implications for the origin of island arc basalts (1979)
    Springer
    Contributions to mineralogy and petrology 70 (1979), S. 167-181 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Petrologic and chemical data are presented for samples from five volcanically active islands in the northern Marianas group, an intra-oceanic island arc. The data include microprobe analyses of phenocryst and xenolith assemblages, whole rock major and trace element chemistry including REE, and Sr isotope determinations (87Sr/86Sr=0.7034±0.0001). Quartz-normative basalt and basaltic andesite are the most abundant lava types. These are mineralogically and chemically similar to the mafic products of other intra-oceanic islands arcs. It is suggested, however, that they are not typical of the ‘island arc tholeiitic’ series, having Fe enrichment trends and K/Rb, for example, more typical of calc-alkaline suits. Major and trace element characteristics, and the presence of cumulate xenoliths, indicate that extensive near surface (〈 3 Kb) fractionation has occurred. Thus, even least fractionated basalts have low abundances of Mg, Ni and Cr, and high abundances of K and other large cation, imcompatible elements, relative to ocean ridge tholeiites. However, abundances of REE and small cation lithophile elements, such as Ti, Zr, Nb, and Hf are lower than typical ocean ridge tholeiites. The REE data and Sr isotope compositions suggest a purely mantle origin for the Marianas island arc basalts, with negligible input from subducted crustal material. Thus, subduction of oceanic lithosphere may not be a sufficient condition for initiation of island arc magmatism. Intersection of the Benioff zone with an asthenosphere under appropriate conditions may be requisite. Element ratios and abundances, combined with isotopic data, suggest that the source for the Marianas island arc basalts is more chondritic in some respects, and less depleted in large cations than the shallow (?) mantle source for ocean ridge tholeiites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374446
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    Paper (German National Licenses)
    Fulltext
  • 5
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    Seismic attenuation in the subduction zone of Costa Rica (2002)
    In:  [Talk] In: EGS XXVII General Assembly, 21.- 26.04.2002, Nice, France .
    Details
    Publication Date: 2019-08-01
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Talk
  • 6
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    Implications of subduction rehydration for earth's deep water cycle (2006)
    AGU (American Geophysical Union)
    In:  In: Earth's Deep Water Cycle. , ed. by Jacobsen, S. D. and Lee, S. F. M. v. d. Geophysical Monograph Series, 168 . AGU (American Geophysical Union), Washington, DC, pp. 163-276. ISBN 978-0-87590-433-7
    Details
    Publication Date: 2017-05-16
    Description: The "standard model" for the genesis of the oceans is that they are exhalations from Earth's deep interior continually rinsed through surface rocks by the global hydrologic cycle. No general consensus exists, however, on the water distribution within the deeper mantle of the Earth. Recently Dixon et a/. [2002] estimated water concentrations for some of the major mantle components and concluded that the most primitive (FOZO) are significantly wetter than the recycling associated EM or HIMU mantle components and the even drier depleted mantle source that melts to form MORB. These findings are in striking agreement with the results of numerical modeling of the global water cycle that are presented here. We find that the Dixon et a/. [2002] results are consistent with a global water cycle model in which the oceans have formed by efficient outgassing of the mantle. Present-day depleted mantle will contain a small volume fraction of more primitive wet mantle in addition to drier recycling related enriched components. This scenario is consistent with the observation that hotspots with a FOZO-component in their source will make wetter basalts than hotspots whose mantle sources contain a larger fraction of EM and HIMU components.
    Type: Book chapter , PeerReviewed
    Format: text
    Format: text
    Format: text
    Format: text
    Format: text
    DOI: 10.1029/168GM20
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    OceanRep: Book chapter
  • 7
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    Seismogenic zone structure beneath the Nicoya Peninsula, Costa Rica, from three-dimensional local earthquake P- and S-wave tomography (2006)
    Wiley
    In:  Geophysical Journal International, 164 (1). pp. 109-124.
    Details
    Publication Date: 2018-07-16
    Description: The subduction plate interface along the Nicoya Peninsula, Costa Rica, generates damaging large (Mw 〉 7.5) earthquakes. We present hypocenters and 3-D seismic velocity models (VP and VP/VS) calculated using simultaneous inversion of P- and S-wave arrival time data recorded from small magnitude, local earthquakes to elucidate seismogenic zone structure. In this region, interseismic cycle microseismicity does not uniquely define the potential rupture extent of large earthquakes. Plate interface microseismicity extends from 12 to 26 and from 17 to 28 km below sea level beneath the southern and northern Nicoya Peninsula, respectively. Microseismicity offset across the plate suture of East Pacific Rise-derived and Cocos-Nazca Spreading Center-derived oceanic lithosphere is ∼5 km, revising earlier estimates suggesting ∼10 km of offset. Interplate seismicity begins downdip of increased locking along the plate interface imaged using GPS and a region of low VP along the plate interface. The downdip edge of plate interface microseismicity occurs updip of the oceanic slab and continental Moho intersection, possibly due to the onset of ductile behaviour. Slow forearc mantle wedge P-wave velocities suggest 20–30 per cent serpentinization across the Nicoya Peninsula region while calculated VP/VS values suggest 0–10 per cent serpentinization. Interpretation of VP/VS resolution at depth is complicated however due to ray path distribution. We posit that the forearc mantle wedge is regionally serpentinized but may still be able to sustain rupture during the largest seismogenic zone earthquakes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1365-246X.2005.02809.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Seismogenic zone structure of the southern Middle America Trench, Costa Rica (2003)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 108 (B10). p. 2491.
    Details
    Publication Date: 2018-05-30
    Description: The shallow seismogenic portion of subduction zones generates damaging large and great earthquakes. This study provides structural constraints on the seismogenic zone of the Middle America Trench offshore central Costa Rica and insights into the physical and mechanical characteristics controlling seismogenesis. We have located ~300 events that occurred following the MW 6.9, 20 August 1999, Quepos, Costa Rica, underthrusting earthquake using a three-dimensional velocity model and arrival time data recorded by a temporary local network of land and ocean bottom seismometers. We use aftershock locations to define the geometry and characteristics of the seismogenic zone in this region. These events define a plane dipping at 19° that marks the interface between the Cocos Plate and the Panama Block. The majority of aftershocks occur below 10 km and above 30 km depth below sea level, corresponding to 30–35 km and 95 km from the trench axis, respectively. Relative event relocation produces a seismicity pattern similar to that obtained using absolute locations, increasing confidence in the geometry of the seismogenic zone. The aftershock locations spatially correlate with the downdip extension of the oceanic Quepos Plateau and reflect the structure of the main shock rupture asperity. This strengthens an earlier argument that the 1999 Quepos earthquake ruptured specific bathymetric highs on the downgoing plate. We believe that subduction of this highly disrupted seafloor has established a set of conditions which presently limit the seismogenic zone to be between 10 and 35 km below sea level.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2002JB002294
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Geodetic and Seismic Constraints on some Seismogenic Zone Processes in Costa Rica (2003)
    Details
    Publication Date: 2023-11-08
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Talk
  • 10
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    Seismic Attenuation in the Subduction Zone of Costa Rica (2002)
    Details
    Publication Date: 2023-11-08
    Type: Conference or Workshop Item , NonPeerReviewed
    Location Call Number Limitation Availability
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    OceanRep: Talk
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