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  • 1
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Of the several uncommon types of large-scale cross-stratification encountered in Late Holocene upper-pointbar sandy deposits of the Rhine, one is examined in detail. This type is structurally bipartite as it consists of a relatively coarse-grained, upper interval of large-scale foresets, which indentate with the oppositely dipping small-scale foresets in the underlying finer interval. The lower interval is usually of smaller, and incidentally of the same thickness as the upper one. Together they constitute the so called “interwoven set”.The interwoven set is regarded as formed by a mega ripple (dune) with in front of it, a simultaneously active system of small-scale, oppositely moving, ripples propelled by the backflow branch of the mega ripple's lee-side vortex.Comparison of dip, strike, and principal bedding-plane (= horizontal) sections brought to light dissimilarity in the crestline orientations of the mega-ripple and backflow-ripple systems. The latter's oblique, or incidentally perpendicular orientation with respect to the mega-ripple front indicates a conspicious component of lateral water movement, which in the present outcrop was consistent from the left to the right, for the observer looking down(main)stream.It is suggested that this lateral water movement is due to the radial (transverse) flow in the bend of a meandering river. From the sense of the radial flow the river's bend configuration (here: right hand turn) can be inferred. Relative wander velocities of mega- and backflow-ripple systems were deduced from the configuration in a horizontal section made through the interaction zone of the two structural intervals.
    Type of Medium: Electronic Resource
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  • 2
    In:  Supplement to: Tjalsma, R C (1983): Eocene to Miocene benthic foraminifers from DSDP Site 516, Rio Grande Rise, South Atlantic. In: Barker, PF; Carlson, RL; Johnson, DA; et al. (eds.), Initial Reports of the Deep Sea Drilling Project (U.S. Govt. Printing Office), 72, 731-755,
    Publication Date: 2018-12-20
    Description: DSDP Site 516 contains a complete middle Eocene to lower Miocene interval with a well-developed Oligocene sequence that is more than 300 m thick. In this paper, the most important and characteristic benthic foraminiferal species from this interval are described and illustrated, and their quantitative and biostratigraphic distribution is given. Middle Eocene benthic assemblages, derived from pelagic intercalations in a partly turbiditic sequence, are low in diversity. Benthic assemblages of fairly high diversity occur in limestones, chalks, and oozes of the upper Eocene to lower Miocene. The consistently high rate of new species appearances at Site 516 during late Eocene and Oligocene contrasted greatly with the very slow rate of change in abyssal faunas at that time; there were no significant faunal changes at the Eocene/Oligocene boundary. The assemblages are dominated by Cibicidoides (mostly C. ungerianus or C. kullenbergi) and Lenticulina. Buliminids were also important during the Eocene and early Oligocene. Faunal comparison with other Atlantic DSDP sites and drill holes in the Gulf of Mexico suggest an approximately mid-bathyal (500-1500 m) depth of deposition during late Eocene and Oligocene.
    Type: Dataset
    Format: text/tab-separated-values, 2414 data points
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  • 3
    Publication Date: 2018-09-28
    Type: Dataset
    Format: text/tab-separated-values, 177 data points
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