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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 41 (1994), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Dolomites from the upper calcareous-siliceous member of the Miocene Monterey Formation exposed west of Santa Barbara, California, were analysed for geochemical, isotopic and crystallographic variation. The data clearly document the progressive recrystallization of dolomite during burial diagenesis in marine pore fluids.Recrystallization is recognized by the following compositional and crystallographic variations. Dolomites have decreasing δ18O and δ13C compositions, decreasing Sr contents and increasing Mg contents with increasing burial depths and temperatures from east to west in the study area. δ18O values vary from 5·3‰ in the east to − 5·5‰ PDB in the west and are interpreted to reflect the greater extent and higher temperature of dolomite recrystallization in the west. δ13C values correlate with δ18O and decrease from 13·6‰ in the east to − 8·7‰ PDB in the west. Sr concentrations correlate positively with δ18O values and decrease from a mean of 750 ppm in the east to a mean of 250 ppm in the west. Mol% MgCO3 values inversely correlate with δ18O values and increase from a minimum of 41·0 in the east to a maximum of 51·4 in the west.Rietveld refinements of powder X-ray diffraction data indicate that the more recrystallized dolomites have more contracted unit cells and increased cation ordering. The fraction of the Ca sites in the dolomites that are occupied by Ca atoms increases slightly with the approach to stoichiometry. The fraction of the Mg sites occupied by Mg atoms strongly correlates with mol% MgCO3. Even in early diagenetic, non-stoichiometric dolomites, there is little substitution of Mg in Ca sites. During recrystallization, the amount of Mg substituting for Ca in Ca sites decreases even further. Most of the disorder in the least recrystallized, non-stoichiometric dolomites is related to substitution of excess Ca on Mg sites.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2017-12-11
    Description: ODP Leg 189 was designed to test the hypothesis that opening of the Tasmanian Seaway and initiation of circumpolar circulation contributed to the thermal isolation of Antarctica, leading to the development of initial ice-sheet and oceanic thermohaline circulation. The clay assemblages of the Tasmanian region contain the traces of two tectonic stages associated with ocean opening south of the south Tasman Rise near the Palaeocene–Eocene boundary and strike-slip activity between the western Tasmanian land-bridge and Antarctica during the Late Eocene. Earliest Oligocene clays indicate that cooling of Antarctic margins and activity of western boundary circulation progressed with the regional subsidence.
    Type: Article , PeerReviewed
    Format: text
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  • 3
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    Unknown
    PANGAEA
    In:  Supplement to: James, Noel P; Feary, David A; Surlyk, Finn; Toni Simo, J A; Betzler, Christian; Holbourn, Ann E; Li, Qianyu; Matsuda, Hiroki; Machiyama, Hideaki; Brooks, Gregg R; Andres, Miriam S; Hine, Albert C; Malone, Mitchell J; Shipboard Scientific Party (2000): Quaternary bryozoan reef mounds in cool-water, upper slope environments: Great Australian Bight. Geology, 28(7), 647-650, https://doi.org/10.1130/0091-7613(2000)28%3C647:QBRMIC%3E2.0.CO;2
    Publication Date: 2023-06-27
    Description: Bryozoan reef mounds are common features in the geological record, occurring within mid-ramp, slope paleoenvironments, especially in Paleozoic carbonate successions, but until now have not been recorded from the modern ocean. Recent scientific drilling in the Great Australian Bight (Ocean Drilling Program Leg 182) has confirmed the existence of shallow subsurface bryozoan reef mounds in modern water depths of 200-350 m. These structures have as much as 65 m of synoptic relief, and occur both as single mounds and as mound complexes. They are unlithified, have a floatstone texture, and are rich in delicate branching, encrusting and/or nodular-arborescent, flat-robust branching, fenestrate, and articulated zooidal bryozoan growth forms. The muddy matrix is composed of foraminifers, serpulids, fecal pellets, irregular bioclasts, sponge spicules, and calcareous nannofossils. The 14C accelerator mass spectrometry dates of 26.6-35.1 ka indicate that the most recent mounds, the tops of which are 7-10 m below the modern seafloor, flourished during the last glacial lowstand but perished during transgressive sea-level rise. This history reflects changing oceanographic current patterns; strong upwelling during lowstands, and reduced upwelling and lowered trophic resources during highstands. Large specimens of benthic foraminifers restricted to the mounds confirm overall mesotrophic growth conditions. The mounds are similar in geometry, scale, general composition, and paleoenvironments to older structures, but lack obvious microbial influence and extensive synsedimentary cementation. Such differences reflect either short-term local conditions or long-term temporal changes in ocean chemistry and biology.
    Keywords: 182-1131B; AGE; Age, standard deviation; Calculated; Deep Sea Drilling Project; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP; DSDP/ODP/IODP sample designation; Great Australian Bight; Joides Resolution; Leg182; Sample code/label
    Type: Dataset
    Format: text/tab-separated-values, 6 data points
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  • 4
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    Unknown
    PANGAEA
    In:  Supplement to: Malone, Mitchell J; Claypool, George E; Martin, Jonathan B; Dickens, Gerald Roy (2002): Variable methane fluxes in shallow marine systems over geologic time. The composition and origin of pore waters and authigenic carbonates on the New Jersey shelf. Marine Geology, 189(3-4), 175-196, https://doi.org/10.1016/S0025-3227(02)00474-7
    Publication Date: 2024-01-09
    Description: Carbon cycling is an important but poorly understood process on passive continental margins. In this study, we use the ionic and stable isotopic composition of interstitial waters and the petrology, mineralogy, and stable isotopic composition of authigenic carbonates collected from Ocean Drilling Program (ODP) Leg 174A (Sites 1071 and 1072) to constrain the origin of the carbonates and the evolution of methane on the outer New Jersey shelf. The pore fluids of the New Jersey continental shelf are characterized by (1) a fresh-brackish water plume, and (2) organic matter degradation reactions, which proceed through sulfate reduction. However, only minor methanogenesis occurs. The oxygen isotopic composition of the pore fluids supports a meteoric origin of the low salinity fluids. Authigenic carbonates are found in nodules, thin (~1-cm) layers, and carbonate cemented pavements. Siderite is the most common authigenic carbonate, followed by dolomite and calcite. The oxygen isotopic composition of the authigenic carbonates, i.e. 1.3-6.5 per mil PeeDee Belemnite (PDB), indicates an origin in marine pore fluids. The carbon isotopic composition of dolomite cements range from -16.4 to -8.8 per mil PDB, consistent with formation within the zone of sulfate reduction. Siderite d13C values show a greater range (-17.67-16.4 per mil), but are largely positive (mean=2.8 per mil) and are interpreted to have formed throughout the zone of methanogenesis. In contrast, calcite d13C values are highly negative (as low as -41.7 per mil)and must have formed from waters with a large component of dissolved inorganic carbon derived from methane oxidation. Pore water data show that despite complete sulfate reduction, methanogenesis appears not to be an important process presently occurring in the upper 400 m of the outer New Jersey shelf. In contrast, the carbon isotopic composition of the siderites and calcites document an active methanogenic zone during their formation. The methane may have been either oxidized or vented from shelf sediments, perhaps during sea-level fluctuations. If this unaccounted and variable methane flux is an areally important process during Neogene sea-level fluctuations, then it likely plays an important role in long-term carbon cycling on passive continental margins
    Keywords: 174-1071; 174-1072; 174-1072A; COMPCORE; Composite Core; DRILL; Drilling/drill rig; Joides Resolution; Leg174A; Ocean Drilling Program; ODP; South Atlantic Ocean
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 5
    Publication Date: 2024-01-09
    Keywords: 182-1134A; AGE; Age, maximum/old; Age, minimum/young; Ageprofile Datum Description; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; DRILL; Drilling/drill rig; Great Australian Bight; Joides Resolution; Leg182; Ocean Drilling Program; ODP
    Type: Dataset
    Format: text/tab-separated-values, 370 data points
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  • 6
    Publication Date: 2024-01-09
    Keywords: 182-1126D; Calcium carbonate; Carbon, inorganic, total; Carbon, organic, total; Carbon, total; Depth, composite; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Great Australian Bight; Hydrogen; Joides Resolution; Leg182; Nitrogen, total; Ocean Drilling Program; ODP; Sample code/label; Sulfur, total
    Type: Dataset
    Format: text/tab-separated-values, 189 data points
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  • 7
    Publication Date: 2024-01-09
    Keywords: 182-1130C; Calcium carbonate; Carbon, inorganic, total; Depth, composite; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Great Australian Bight; Joides Resolution; Leg182; Ocean Drilling Program; ODP; Sample code/label
    Type: Dataset
    Format: text/tab-separated-values, 28 data points
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  • 8
    Publication Date: 2024-01-09
    Keywords: 182-1129D; Calcium carbonate; Carbon, inorganic, total; Carbon, organic, total; Carbon, total; Depth, composite; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Great Australian Bight; Hydrogen; Joides Resolution; Leg182; Nitrogen, total; Ocean Drilling Program; ODP; Sample code/label; Sulfur, total
    Type: Dataset
    Format: text/tab-separated-values, 171 data points
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  • 9
    Publication Date: 2024-01-09
    Keywords: 207-1257B; Calcium carbonate; Carbon, inorganic, total; Carbon, total; Depth, composite; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Joides Resolution; Leg207; Nitrogen, total; Ocean Drilling Program; ODP; Sample code/label; South Atlantic Ocean
    Type: Dataset
    Format: text/tab-separated-values, 293 data points
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  • 10
    Publication Date: 2024-01-09
    Keywords: 207-1257C; Calcium carbonate; Carbon, inorganic, total; Carbon, total; Depth, composite; DEPTH, sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Joides Resolution; Leg207; Nitrogen, total; Ocean Drilling Program; ODP; Sample code/label; South Atlantic Ocean
    Type: Dataset
    Format: text/tab-separated-values, 52 data points
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