Global Change Abstracts The Swiss Contribution - SCNAT

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 environmen-
tal 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.,