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  • 1
    Electronic Resource
    Electronic Resource
    Oxford UK : Blackwell Science Ltd
    Sedimentology 47 (2000), S. 0 
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The stable isotope geochemistry of Miocene sediments from the leeward margin of the Great Bahama Bank was examined to investigate burial diagenetic processes in periplatform carbonates. Data indicate that, in addition to differences in bulk proportions of neritic and pelagic carbonate along the slope, rhythmic variation in primary carbonate content has controlled patterns of burial diagenesis and associated geochemical signatures throughout much of the succession examined. The present study focuses on Ocean Drilling Program Sites 1006 and 1007, the most distal of five sites drilled from marginal to deep basin environments during Leg 166. These Miocene sections are characterized by their cyclic appearance, manifest as decimetre- to metre-scale alternations between light-coloured ooze/chalk/limestone and dark-coloured marl/marlstone. The section at Site 1006 contains a high proportion of pelagic carbonate and is unlithified to a subbottom depth of ∼675 m. Fluctuations in δ18O and δ13C values at this site are independent of lithological variation and reflect primary conditions. At Site 1007, located at the toe-of-slope and composed of a mixture of bank-derived and pelagic carbonate, limestones are densely cemented, show little evidence of compaction and have δ18O values up to 2‰ higher than coeval sediments at Site 1006. Marlstones at Site 1007 are poorly cemented, exhibit an increase in compaction-related features with depth and have lower and more variable δ18O values that are similar to those of coeval sediments at Site 1006. Isotopic and petrographic characteristics of limestone interbeds result from cement precipitation from cold sea water during the first ∼100 m of burial. Higher proportions of insoluble materials and pelagic carbonate seem to have inhibited diagenetic alteration in adjacent marlstones; in spite of significant compaction and pressure solution during burial, original isotopic compositions appear to be best preserved in these intervals at Site 1007. The documented contrasts in petrographic and isotopic patterns illustrate the role of primary sediment composition in controlling lithification processes in periplatform carbonates and stress the importance of considering such factors when interpreting geochemical data from ancient shelf and slope limestones.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Core, logging and high-resolution seismic data from ODP Leg 166 were used to analyse deposits of the Neogene (Miocene–Lower Pliocene) Bahamian outer carbonate ramp. Ramp sediments are cyclic alternations of light- and dark-grey wackestones/packstones with interbedded calciturbidite packages and minor slumps. Cyclicity was driven by high-frequency sea-level changes. Light-grey layers containing shallow-water bioclasts were formed when the ramp exported material, whereas the dark-grey layers are dominantly pelagic. Calciturbidites are arranged into mounded lobes with feeder channels. Internal bedding of the lobes shows a north-directed shingling as a result of the asymmetrical growth of these bodies. Calciturbidite packages occur below and above sequence boundaries, indicating that turbidite shedding occurred during third-order sea-level highstands and lowstands. Highstand turbidites contain shallow-water components, such as green algal debris and epiphytic foraminifera, whereas lowstand turbidites are dominated by abraded bioclastic detritus. Gravity flow depocentres shifted from an outer ramp position during the early Miocene to a basin floor setting during the late Miocene to early Pliocene. This change was triggered by an intensification of the strength of bottom currents during the Tortonian, which was also responsible for shaping the convex morphology of the outer ramp. The Miocene and Lower Pliocene of the leeward flank of Great Bahama Bank provides an example of the poorly known depositional setting of the outer part of distally steepened carbonate ramps. The contrast between its sedimentary patterns and the well-known Upper Pliocene–Quaternary slope facies associations of the flat-topped Great Bahama Bank shows the strong control that the morphology of a carbonate platform exerts on the depositional architecture of the adjacent slope and base-of-slope successions.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2024-02-03
    Keywords: 166-1003; Aragonite; COMPCORE; Composite Core; DEPTH, sediment/rock; Dolomite; High magnesium calcite; Joides Resolution; Leg166; Low magnesium calcite; Ocean Drilling Program; ODP; Quartz (peak area); South Atlantic Ocean
    Type: Dataset
    Format: text/tab-separated-values, 1260 data points
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  • 4
    Publication Date: 2024-02-03
    Keywords: 166-1007; Aragonite; COMPCORE; Composite Core; DEPTH, sediment/rock; Dolomite; High magnesium calcite; Joides Resolution; Leg166; Low magnesium calcite; Ocean Drilling Program; ODP; Quartz (peak area); South Atlantic Ocean
    Type: Dataset
    Format: text/tab-separated-values, 1570 data points
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  • 5
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    Unknown
    PANGAEA
    In:  Supplement to: Bernet, Karin H; Eberli, Gregor P; Gilli, Adrian (2000): Turbidite frequency and composition in the distal part of the Bahamas Transect. In: Swart, PK; Eberli, GP; Malone, MJ; Sarg, JF (eds.) Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 166, 1-16, https://doi.org/10.2973/odp.proc.sr.166.105.2000
    Publication Date: 2024-02-03
    Description: The lower slope and toe-of-slope sediments of the western flank of the Great Bahama Bank (Sites 1003 and 1007) are characterized by an intercalation of turbidites and periplatform ooze. In general, turbidites form up to 12% of the total mass of the sedimentary column. Based primarily on data from the Bahamas, it has been postulated that steep-sided carbonate platforms shed most of their sediments into the basin during sea-level highstands when the platforms are flooded. This highstand shedding is assumed to be less pronounced along platforms with a ramp-like depositional profile where sediment production is not restricted to sea-level highstand. Miocene to Pliocene sediments recovered in five drill holes during Leg 166 at the western margin of the Great Bahama Bank reveal that turbidite distribution follows a complex pattern that is dependent on several factors such as sedimentation rates, sea-level changes, and slope morphology. To identify the depositional sequences in the cores, the depths of seismic-sequence boundaries were used. The distribution of turbidites within sedimentary sequences varies strongly. Generally, turbidites are clustered at the upper and/or lower portions of the sequences indicating deposition of carbonate turbidites during both highstand and lowstand of sea level. Analyses of the Miocene turbidites show that (1) during high sea level, 60% of all turbidites were deposited at Site 1003 (309 out of 518 turbidites), while during low sea level, two thirds of all turbidites were deposited at Site 1007 (332 out of 486 turbidites); (2) the average thickness of highstand turbidites is 1.5 times higher than the average thickness of lowstand turbidites; and (3) the turbidites display slight differences in composition and sorting. In general, highstand turbidites are less sorted and contain an abundant amount of shallow-water constituents such as green algae, red algae, shallow-water benthic foraminifers (miliolids), and intraclasts. The lowstand turbidites are better sorted and contain abundant planktonic foraminifers and micrite. To complicate matters, highstand and lowstand turbidites seem to be deposited at different locations on the slope. At the lower slope (Site 1003), more turbidites were deposited during highstands, while at the toe of the slope, turbidites were dominantly deposited during sea-level lowstands. The result is a slope section with laterally discontinuous turbidite lenses within periplatform ooze, which is controlled by the interplay of sea-level changes, sediment production, and platform morphology.
    Keywords: Ocean Drilling Program; ODP
    Type: Dataset
    Format: application/zip, 4 datasets
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  • 6
    Publication Date: 2024-02-03
    Keywords: 166-1007; Bioclasts; Brachiopoda; Buliminida; COMPCORE; Composite Core; DEPTH, sediment/rock; Description; Echinodermata; Foraminifera, benthic; Foraminifera, planktic; Green algae; Indeterminata; Intraclasts; Joides Resolution; Leg166; Lithoclasts; Micrite; Miliolids; Mollusca; Nodosariidae; Ocean Drilling Program; ODP; Ooids; Point counting; Red algae; Rotaliida; Sediment type; South Atlantic Ocean
    Type: Dataset
    Format: text/tab-separated-values, 2128 data points
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  • 7
    Publication Date: 2024-02-03
    Keywords: 166-1003; Bioclasts; Brachiopoda; Buliminida; COMPCORE; Composite Core; DEPTH, sediment/rock; Description; Echinodermata; Foraminifera, benthic; Foraminifera, planktic; Green algae; Indeterminata; Intraclasts; Joides Resolution; Leg166; Lithoclasts; Micrite; Miliolids; Mollusca; Nodosariidae; Ocean Drilling Program; ODP; Ooids; Point counting; Red algae; Rotaliida; Sediment type; South Atlantic Ocean
    Type: Dataset
    Format: text/tab-separated-values, 2812 data points
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