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  • 1
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The trigonometric relationship between slope inclination, the horizontally acting time-averaged traction force and the vertical depth of transport allows the estimation of one factor, when both others are known. Depth–transport functions can be deduced by comparing the depth distributions of living organisms and their skeletal remains, and this paper simplifies this comparison using foraminifera in which a single test represents an individual. Differences in distribution parameters between living individuals and empty tests allow depth–transport functions to be determined; these functions differ between species at a single transect according to the varying buoyancies of the tests. Within a single species, differences in depth–transport functions between locations are based on either slope inclination or traction intensities. After establishing a mean depth–transport function by averaging species-characteristic functions, the time-averaged traction force acting on the studied transect can be calculated. Transport intensities are also estimated using an erosion–deposition diagram that combines the relative frequency distributions of living individuals and empty tests. The proportion of ‘eroded’, ‘parautochthonous’ and ‘allochthonous’ tests mirrors the influence of both slope inclination and traction force for the deposition of empty tests. To test the model, six species of symbiont-bearing benthic foraminifers were investigated at two transects in front of a NW Pacific coral reef. One transect is distinguished by a strong slope flattening below the steep reef slope (30 m), whereas further steepening characterizes the equivalent part in the other transect. These differences are mirrored in the depth–transport functions as well as in the erosion–deposition diagrams of all species. The time-averaged traction forces differ in intensities between transects, because of the position of the reef front with respect to the predominant wind direction. However, the form of the functions is identical and distinguished by an increase from the surface to 35 m depth, followed by a decrease down to 105 m. This can be explained by successive onshore and offshore forces acting on the shallow slope, such as the tropical cyclones that cross the region every summer.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2011-09-01
    Description: Nineteen ichnotaxa occur in a 94-m-thick section of Gelasian-Calabrian siliciclastic deposits along the Stirone River. The most common trace fossils are grouped in 17 clusters based on a K-Means Cluster Analysis. This grouping is related to distal, archetypal and proximal Cruziana ichnofacies. Successions of ichnotaxa and clusters as represented in Detrended Correspondence Analyses determine environmental trends that helped establish a sequence stratigraphic scheme, which is not always obvious in the sedimentary record. The depositional sequences are separated by three sequence boundaries (A-C), which are well expressed in the ichnological record. Primary fabrics are less frequent in the archetypal and proximal Cruziana ichnofacies than in their idealized models. This is probably due to less intense storms in the small and protected paleo-Adriatic Sea and to intense bioturbation. Small-scale intervals with low ichnodiversity and ichnofabrics commonly dominated by one trace fossil are present. This suggests stressed conditions and opportunistic colonization related to small, but probably frequent, seafloor disturbances. The record of these disturbances-- possibly caused by storm and bottom currents, deposition, or possibly erosion--has been obliterated by subsequent bioturbation. The disappearance of Schaubcylindrichnus, the smaller size of Scolicia and Ophiomorpha, and a slight decrease in trace fossil diversity in the Calabrian part of the section is interpreted to record climate cooling. This is also supported by the general decrease in ichnodiversity in Pleistocene versus Pliocene shallow-marine to slope siliciclastic facies.
    Print ISSN: 0883-1351
    Electronic ISSN: 0883-1351
    Topics: Geosciences
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  • 3
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    In:  EPIC3Biogeosciences, 18(20), pp. 5719-5728, ISSN: 1726-4189
    Publication Date: 2021-12-22
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 4
    Publication Date: 2023-11-16
    Description: The Upper Cretaceous Postalm section in the Northern Calcareous Alps (Austria) exposes pelagic depositsof the northwestern Tethys whose cyclostratigraphy and palaeoenvironments were examined in thisstudy.The section displays rhythmic deposits of Santonian to late Campanian age (Gosau Group). The San-tonian/Campanian transition is characterised by condensed greyish carbonates, while the younger de-posits are composed of reddish foraminiferal packstones displaying distinct limestone-marl alternations.A biostratigraphic framework based on planktonic foraminifera and calcareous nannofossils is supportedby carbon and strontium isotope stratigraphy as well as magnetostratigraphy. The carbon isotope dataallow to correlate the Postalm section to other Tethyan reference sites and to identifyd13C events, such asthe Late Campanian Event. Spectral analyses of three independently assessed proxies (d13C, Fe contentand the thickness of limestone/marl couplets) in the upper, continuously exposed section part identified17 to 18 405 ka cycles spanning the mid to upper Campanian (Contusotruncana plummeraetoGansserinagansseriZones or CC21/UC15c to CC23a/UC16 nannofossil zones).
    Description: Published
    Description: 104704
    Description: 1A. Geomagnetismo e Paleomagnetismo
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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