178,813 research outputs found
Milankovitch Cyclicity and Stable Isotope Calibration in the Paleogene (invited)
No full textSignificant progress has been made over the last decade in the extension of astronomically calibrated geological time scales for the Neogene (Hilgen et al., 1999, Shackleton et al., 1999). The validity of these time scales has been supported by comparison of data from different parts of the world’s oceans, through the improvement of astronomical calculations, and independent dating methods and intercalibrations (Renne et al., 1994). While evidence of astronomical forcing has been found for intervals from most parts of the Cenozoic, extending astronomically calibrated time scales into the Paleogene faces some fundamental problems that require a different approach than the sophisticated “pattern matching” that worked so well for the Neogene. These challenges are related to uncertainties and limits of astronomical calculations, sparser data coverage, and a climate system that behaved quite differently to today’s “ice-house” setting. This contribution reviews some of the challenges that will have to tackled, presents a new set of astronomically calibrated benthic isotope data from the late Eocene, and suggests a new approach to synthesise astronomically calibrated durations for magnetic reversals that arise from floating time scales, which are so far more common in the Paleogene.Challenges and limits of astronomical calculations for time scale use:
One crucial challenge that is faced when tackling the astronomical calibration of the geological time scale is the fact that the Solar System is chaotic, limiting the age back to which one can compute astronomical solutions with confidence (Laskar, 1999). Thus, one has to constrain astronomical parameters from the rock record. Apart from tidal dissipation effects, which change the detailed interference of particularly obliquity and climatic precession cycles, a larger scale effect is more directly linked to the chaotic nature of the Solar System: amplitude variations of the obliquity and climatic precession cycles with periods of ~1.2 and ~2.4 million years can be affected by chaotic transitions in the planetary solutions. This contribution will review the effects these chaotic transitions can have on astronomical “target” curves, particularly during the Paleogene, and why astronomical time scale calibrations will have to take this into account.Astronomically calibrated stable benthic isotopes from the Eocene:
High-resolution lithological proxy measurements from ODP 1052 in the western Atlantic (Pälike et al., 2001) have provided duration estimates for magnetochrons from the late middle Eocene. This contribution presents high-resolution benthic stable isotope measurements from the same location. The astronomically calibrated isotope measurements co-vary with the lithological measurements and the astronomy in the obliquity frequency band, documenting the interaction of astronomy and climate during this transition from the Paleogene “green-house” world to the Oligocene “ice-house” world (Figure 1), and significant events that were not recognised in previous, lower resolution studies.Integration of floating time scales with magnetostratigraphy:
The geomagnetic polarity time scale (Cande & Kent, 1995) incorporates astronomically calibrated ages back to 5.23 Ma. Recent results have changed significantly the age of the Oligocene/ Miocene boundary (Shackleton et al. 1999, 2000). These changes, which we will show have now been corroborated by results from ODP 199, need to be incorporated into the astronomically calibrated polarity time scale. We present a new approach, using a combination of calibrated absolute ages, and constraints on sea-floor spreading rates obtained from astronomically calibrated magnetic reversals from floating time scales, to compute a consistent set of spline interpolated ages for sea-floor magnetic reversals. This approach allows us to incorporate durations of magnetic reversals that result from the floating time scales more common in the Paleogene so far. First results, constrained by results from ODP 1218 in the Oligocene, and ODP 1052 in the late middle Eocene, suggest that the Eocene/Oligocene boundary age could be slightly older than previously estimated. It is suggested that this approach might be a useful first step to integrate astronomically calibrated ages from the Cenozoic until a full coverage, with independent data from different ocean basins, becomes available
Shackleton, R, 135369
No full textThis record was harvested from a previous catalogue system and will be withdrawn in 2025. Information in this record may be superseded or incomplete. Visit this record in UMA's new catalogue at: https://archives.library.unimelb.edu.au/nodes/view/416186Surname: SHACKLETON. Given Name(s) or Initials: R. Military Service Number or Last Known Location: 135369. Missing, Wounded and Prisoner of War Enquiry Card Index Number: 6528.238339
Item: [2016.0049.48447] "Shackleton, R, 135369
D. R. Shackleton Bailey, Propertiana
No full textvan de Woestijne Paul. D. R. Shackleton Bailey, Propertiana. In: L'antiquité classique, Tome 26, fasc. 1, 1957. pp. 206-207
Shackleton Bailey (D. R.). Cicero
No full textVan Den Bruwaene Martin. Shackleton Bailey (D. R.). Cicero. In: Revue belge de philologie et d'histoire, tome 52, fasc. 1, 1974. Antiquité - Oudheid. pp. 157-158
Shackleton Bailey (D. R.). Cicero
No full textVan Den Bruwaene Martin. Shackleton Bailey (D. R.). Cicero. In: Revue belge de philologie et d'histoire, tome 52, fasc. 1, 1974. Antiquité - Oudheid. pp. 157-158
D. R. Shackleton Bailey, Ciero. Select Letters
No full textVan den Bruwaene Martin. D. R. Shackleton Bailey, Ciero. Select Letters. In: L'antiquité classique, Tome 51, 1982. p. 447
D. R. Shackleton Bailey, Ciero. Select Letters
No full textVan den Bruwaene Martin. D. R. Shackleton Bailey, Ciero. Select Letters. In: L'antiquité classique, Tome 51, 1982. p. 447
Emergence of the Shackleton Range from beneath the Antarctic Ice Sheet due to glacial erosion
No full textThis paper explores the long-term evolution of a subglacial fjord landscape in the Shackleton Range, Antarctica. We propose that prolonged ice-sheet erosion across a passive continental margin caused troughs to deepen and lower the surrounding ice-sheet surface, leaving adjacent mountains exposed. Geomorphological evidence suggests a change in the direction of regional ice flow accompanied emergence. Simple calculations suggest that isostatic compensation caused by the deepening of bounding ice-stream troughs lowered the ice-sheet surface relative to the mountains by ~ 800 m. Use of multiple cosmogenic isotopes on bedrock and erratics (26Al, 10Be, 21Ne) provides evidence that overriding of the massif and the deepening of the adjacent troughs occurred earlier than the Quaternary. Perhaps this occurred in the mid-Miocene, as elsewhere in East Antarctica in the McMurdo Dry Valleys and theLambert basin. The implication is that glacial erosion instigates feedback which can change ice-sheet thickness, extent and direction of flow. Indeed, as the sub-glacial troughs evolve over millions of years, they increase topographic relief and this changes the dynamics of the ice sheet
D. R. Shackleton Bailey, Cicero's Letters to Atticus. Vol. I. Books I-II ; D. R. Shackleton Bailey, Cicero's Letters to Atticus. Vol. II. Books III-IV
No full textVan den Bruwaene Martin. D. R. Shackleton Bailey, Cicero's Letters to Atticus. Vol. I. Books I-II ; D. R. Shackleton Bailey, Cicero's Letters to Atticus. Vol. II. Books III-IV. In: L'antiquité classique, Tome 35, fasc. 1, 1966. pp. 294-297
David R. Shackleton Bailey, Onomasticon to Cicero's Letters
No full textRaepsaet-Charlier Marie-Thérèse. David R. Shackleton Bailey, Onomasticon to Cicero's Letters. In: L'antiquité classique, Tome 66, 1997. p. 436
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