Kastner Miriam

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  • Article
    Barite precipitation on suspended organic matter in the mesopelagic zone
    (Frontiers Media, 2020-10-28) Martinez-Ruiz, Francisca ; Paytan, Adina ; Gonzalez-Muñoz, Maria Teresa ; Jroundi, Fadwa ; Abad, María Del Mar ; Lam, Phoebe J. ; Horner, Tristan J. ; Kastner, Miriam
    Mechanisms underlying barite precipitation in seawater and the precise depths of barite precipitation in the water column have been debated for decades. Here we present a detailed study of water column barite distribution in the mesopelagic zone at diverse stations in the open ocean by analyzing samples collected using multiple unit large volume in-situ filtration systems in the Pacific, Atlantic and Indian oceans. Our results demonstrate that barite is an organo-mineral particularly abundant at intermediate depths throughout the world’s ocean regardless of saturation state with respect to barite. This is confirming the notion of precipitation at depths of intense organic matter mineralization. Our observations further support the link between barite formation and microbial activity, demonstrated by the association of barite particles with organic matter aggregates and with extracellular polymeric substances. Evidence for microbial mediation is consistent with previous experimental work showing that in bacterial biofilms Ba binds to phosphate groups on cell surfaces and within extracellular polymeric substances. This organo-accumulation promotes high concentrations of Ba leading to saturated microenvironments and nucleation sites favoring precipitation. The distribution of Ba isotopes in the water column and in particulate matter is also consistent with the proposed precipitation mechanism.
  • Article
    Anomalous porosity preservation and preferential accumulation of gas hydrate in the Andaman accretionary wedge, NGHP-01 site 17A
    (Elsevier, 2014-06-06) Rose, Kelly K. ; Johnson, Joel E. ; Torres, Marta E. ; Hong, Wei-Li ; Giosan, Liviu ; Solomon, Evan A. ; Kastner, Miriam ; Cawthern, Thomas ; Long, Philip E. ; Schaef, H. Todd
    In addition to well established properties that control the presence or absence of the hydrate stability zone, such as pressure, temperature, and salinity, additional parameters appear to influence the concentration of gas hydrate in host sediments. The stratigraphic record at Site 17A in the Andaman Sea, eastern Indian Ocean, illustrates the need to better understand the role pore-scale phenomena play in the distribution and presence of marine gas hydrates in a variety of subsurface settings. In this paper we integrate field-generated datasets with newly acquired sedimentology, physical property, imaging and geochemical data with mineral saturation and ion activity products of key mineral phases such as amorphous silica and calcite, to document the presence and nature of secondary precipitates that contributed to anomalous porosity preservation at Site 17A in the Andaman Sea. This study demonstrates the importance of grain-scale subsurface heterogeneities in controlling the occurrence and distribution of concentrated gas hydrate accumulations in marine sediments, and document the importance that increased permeability and enhanced porosity play in supporting gas concentrations sufficient to support gas hydrate formation. The grain scale relationships between porosity, permeability, and gas hydrate saturation documented at Site 17A likely offer insights into what may control the occurrence and distribution of gas hydrate in other sedimentary settings.
  • Preprint
    Active methane venting observed at giant pockmarks along the U.S. mid-Atlantic shelf break
    ( 2007-11) Newman, Kori R. ; Cormier, Marie-Helene ; Weissel, Jeffrey K. ; Driscoll, Neal W. ; Kastner, Miriam ; Solomon, Evan A. ; Robertson, Gretchen ; Hill, Jenna C. ; Singh, Hanumant ; Camilli, Richard ; Eustice, Ryan M.
    Detailed near-bottom investigation of a series of giant, kilometer scale, elongate pockmarks along the edge of the mid-Atlantic continental shelf confirms that methane is actively venting at the site. Dissolved methane concentrations, which were measured with a commercially available methane sensor (METS) designed by Franatech GmbH mounted on an autonomous underwater vehicle (AUV), are as high as 100 nM. These values are well above expected background levels (1-4 nM) for the open ocean. Sediment pore water geochemistry gives further evidence of methane advection through the seafloor. Isotopically light carbon in the dissolved methane samples indicates a primarily biogenic source. The spatial distribution of the near-bottom methane anomalies (concentrations above open ocean background), combined with water column salinity and temperature vertical profiles, indicate that methane-rich water is not present across the entire width of the pockmarks, but is laterally restricted to their edges. We suggest that venting is primarily along the top of the pockmark walls with some advection and dispersion due to local currents. The highest methane concentrations observed with the METS sensor occur at a small, circular pockmark at the southern end of the study area. This observation is compatible with a scenario where the larger, elongate pockmarks evolve through coalescing smaller pockmarks.
  • Article
    Fifty Years of Scientific Ocean Drilling
    (Oceanography Society, 2019-03-16) Becker, Keir ; Austin, James A. ; Exon, Neville ; Humphris, Susan E. ; Kastner, Miriam ; McKenzie, Judith A. ; Miller, Kenneth G. ; Suyehiro, Kiyoshi ; Taira, Masanori
    Nearly a century after the first systematic study of the global ocean and seafloor by HMS Challenger (1871–1876), US scientists began to drill beneath the seafloor to unlock the secrets of the ~70% of Earth’s surface covered by the seas. Fifty years of scientific ocean drilling by teams of international partners has provided unparalleled advancements in Earth sciences. Here, we briefly review the history, impacts, and scientific achievements of five decades of coordinated scientific ocean drilling.
  • Article
    Pulsed subduction accretion and tectonic erosion reconstructed since 2.5 Ma from the tephra record offshore Costa Rica
    (American Geophysical Union, 2005-09-27) Clift, Peter D. ; Chan, Lui-Heung ; Blusztajn, Jerzy S. ; Layne, Graham D. ; Kastner, Miriam ; Kelly, Robyn K.
    Tephra layers recovered by Ocean Drilling Program from the forearc and trench regions offshore the Nicoya Peninsula of Costa Rica allow the temporal evolution of the volcanic arc to be reconstructed since 2.5 Ma. Major and trace element analyses by microprobe methods reveal a dominant tholeiitic character and a provenance in the Costa Rican area. The tephra show long-term coherent variability in geochemistry. One tephra dated at 1.45 Ma shows minimum values in ɛ Nd and maximum Li/Y consistent with very high degrees of sediment recycling at this time. However, overall Li/Y and δ7Li increase with SiO2 content, suggesting addition of heavy Li through forearc tectonic erosion and crustal assimilation. Peak values in δ7Li starting at 1.45 Ma and lasting ∼0.5 m.y. indicate enhanced tectonic erosion of the forearc possibly caused by subduction of a seamount at 1.45 Ma. The tephra record indicates significant temporal variability in terms of sediment subduction, reconciling the geologic evidence for long-term tectonic erosion and geochemical evidence for recent sediment accretion in the modern Central American arc.