Global Change Abstracts The Swiss Contribution - SCNAT

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156 Global Change Abstracts – The Swiss Contribution | Past Global Changes 2 Past Global Changes 08.1-307 Pleistocene ice and paleo-strain rates at Taylor Glacier, Antarctica Aciego S M, Cuffey K M, Kavanaugh J L, Morse D L, Severinghaus J P USA, Switzerland, Canada Cryology / Glaciology , Paleontology Ice exposed in ablation zones of ice sheets can be a valuable source of samples for paleoclimate studies and information about long-term ice dynamics. We report a 28-km long stable isotope sampling transect along a flowline on lower Taylor Glacier, Antarctica, and show that ice from the last glacial period is exposed here over tens of kilometers. Gas isotope analyses on a small number of samples confirm our age hypothesis. These chronostratigraphic data contain information about past ice dynamics and in particular should be sensitive to the longitudinal strain rate on the north flank of Taylor Dome, averaged over millennia. The imprint of climatic changes on ice dynamics may be discernible in these data. Quaternary Research, 2007, V68, N3, NOV, pp 303-313. 08.1-308 Sequencing events across the Permian-Triassic boundary, Guryul Ravine (Kashmir, India) Algeo T J, Hannigan R, Rowe H, Brookfield M, Baud A, Krystyn L, Ellwood B B USA, Canada, Switzerland Geochemistry & Geophysics , Geology , Paleontology The Permian-Triassic boundary (PTB) section at Guryul Ravine (Kashmir, India) comprises a > 100-m-thick, apparently conformable succession of mixed siliciclastic-carbonate sediments deposited in a deep-shelf or ramp setting. This section, although long important in debates concerning placement of the PTB, has not previously been the focus of an integrated chemostratigraphic study. In the present study, samples from a 20-m-thick interval straddling the PTB were analyzed for major- and trace-element concentrations, TOC-TIC, REEs, and organic delta C-13-delta N-15 to investigate contemporaneous environmental changes. The Guryul Ravine section exhibits a sequence of discrete events that provide potentially important information about the character and cause(s) of the PTB. Two transient negative C-isotopic excursions within the upper changxingensis zone predate the Late Permian event horizon (LPEH, i.e., the global mass extinction event) by similar to 200-400 kyr and are associated with the onset of a major eustatic rise and with secondary extinction peaks. These excursions may record minor environmental disturbances prior to the main end-Permian crisis, supporting an intrinsic mechanism such as volcanism and climate change rather than an extrinsic mechanism such as a bolide impact. The onset of a large (similar to -4.0 to -4.5%), sustained negative C-isotope shift marks the LPEH, which is located at the Zewan-Khunamub formation contact similar to 260 cm below the biostratigraphically defined PTB, The Guryul Ravine section exhibits a stepwise extinction pattern, with the largest peak between the LPEH and PTB and a secondary peak just above the PTB, a pattern similar to that observed in the Meishan D GSSP. Palaeogeography Palaeoclimatology Palaeoecology, 2007, V252, N1-2, AUG 20, pp 328-346. 08.1-309 Sub-orbital sea-level change in early MIS 5e: New evidence from the Gulf of Corinth, Greece Andrews J E, Portman C, Rowe P J, Leeder M R, Kramers J D England, Switzerland Paleontology , Geochemistry & Geophysics , Geology New evidence from uplifted marine isotope stage (MIS) 5e carbonate deposits in the Gulf of Corinth demonstrate two rapid, sub-orbitally forced, sealevel oscillations in the early part of MIS 5e. Microbial bioherms with inter-grown marine coralline algae are interpreted as early highstand deposits. Presence of thin vadose flowstone (speleothem) coating inter-bioherm surfaces mark a short-lived regression of > 10 m, followed by sea-level recovery and re- establishment of the highstand, marked by coralline algae coating inter-bioherm cavity surfaces. These marine algae are then coated by a younger vadose flowstone, thick enough to provide an uncontaminated U/Th date of 134.8 +/- 12.0 ka. The dated flowstone is itself encrusted by marine fauna and the entire sequence overlain by highstand marine sediments and marine aragonite cements dated to 114-118 ka, part of the sustained MIS 5e highstand. The age of the younger flowstone demonstrates that the early highstand occurred before 134.8 +/- 2.0 ka, and uplift arguments suggest that the bioherms are unlikely to be older than similar to 136 ka. These data are consistent with the notion that most of termination II (TII) sea- level rise had occurred before 135 ka; indeed they suggest sea-level at this time reached about 2-4 (+/- 4) m below present sea-level, 6-18 (+/- 4) m higher than previous estimates. This early highstand was itself punctuated by a rapid sea-level oscillation of > 10 m (as yet undated), and this oscillation, supported by new TII sealevel data from the Red Sea (Siddall, M., Bard, E.,
Global Change Abstracts – The Swiss Contribution | Past Global Changes Rohling, E.J., Hemleben, C., 2006, Sea-level reversal during termination 11, Geology, 34, 817-820.), probably occurred in about 1000 yr. The flowstone dated at 134.8 2.0 ka is interpreted to record the early part of the ‘Aladdin’s Cave’ regressive event from Papua New Guinea, although in Greece only the first 16 m of the event is recorded. The new data presented here support a recently published Red Sea TII sea- level curve: they also highlight minor discrepancies in the absolute dating of these early MIS 5e sea-level events worldwide. Earth and Planetary Science Letters, 2007, V259, N3-4, JUL 30, pp 457-468. 08.1-310 Age and significance of former low-altitude corrie glaciers on Hoy, Orkney Islands Ballantyne C K, Hall A M, Phillips W, Binnie S, Kubik P W Scotland, USA, Switzerland Geomorphology , Paleontology , Cryology / Glaciology Geomorphological mapping provides evidence for two former low-level corrie glaciers on Hoy, both defined by end moraines. Five Be-10 exposure ages obtained from sandstone boulders on moraine crests fall within the range 12.4 +/- 1.5 ka to 10.4 +/- 1.7 ka (weighted mean 11.7 +/- 0.6 ka), confirming that these glaciers developed during the Loch Lomond (Younger Dryas) Stade (LLS) of 12.9-11.5 cal. ka BP, and demonstrate the feasibility of using this approach to establish the age of LLS glacier limits. The equilibrium line altitude (ELA) of one of the glaciers (99 m) is the lowest recorded for any LLS glacier, and the area-weighted mean ELA for both (141 m) is consistent with a general northward ELA decrease along the west coast of Britain. The size of moraines fronting these small (
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