[Coral-List] Fossil reefs and sea-level rise during Last Interglacial

[Paul Blanchon]

Dear List,
Please find below the title and abstract of a paper recently published in
the April 16th edition of Nature that may be of interest. The authors would
be pleased to provide reprints for those without access to this journal.
(email: blanchons at gmail.com)

Blanchon P, Eisenhauer A, Fietzke J, Liebetrau V. (2009). Rapid sea-level
rise and reef back-stepping at the close of the last interglacial highstand..
Nature 458, 881-884. doi:10.1038/nature07933

Widespread evidence of a +4–6-m sea-level highstand during the
last interglacial period (Marine Isotope Stage 5e) has led to warnings
that modern ice sheets will deteriorate owing to global warming and
initiate a rise of similar magnitude by AD 2100. The rate of this
projected rise is based on ice-sheet melting simulations and downplays
discoveries of more rapid ice loss. Knowing the rate at which
sea level reached its highstand during the last interglacial period is
fundamental in assessing if such rapid ice-loss processes could lead
to future catastrophic sea-level rise. The best direct record of sea level
during this highstand comes from well-dated fossil reefs in stable
areas. However, this record lacks both reef-crest development up
to the full highstand elevation, as inferred from widespread intertidal
indicators at +6m, and a detailed chronology, owing to the
difficulty of replicating U-series ages on submillennial timescales.
Here we present a complete reef-crest sequence for the last interglacial
highstand and its U-series chronology from the stable northeast
Yucatan peninsula, Mexico. We find that reef development during
the highstand was punctuated by reef-crest demise at +3m and
back-stepping to +6m. The abrupt demise of the lower-reef crest,
but continuous accretion between the lower-lagoonal unit and the
upper-reef crest, allows us to infer that this back-stepping occurred
on an ecological timescale and was triggered by a 2–3-m jump in sea
level. Using strictly reliable 230Th ages of corals from the upper-reef
crest, and improved stratigraphic screening of coral ages from other
stable sites, we constrain this jump to have occurred 121 kyr ago
and conclude that it supports an episode of ice-sheet instability
during the terminal phase of the last interglacial period.



Saludos,
Paul.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Paul Blanchon
Reef Systems Unit (Pto. Morelos)
Inst. de Ciencias del Mar y Limnologia (ICML)
Universidad Nacional Autonoma de Mexico (UNAM)
Ap. Postal 1152, CP 77500 Cancun,
Q. Roo, MEXICO

Tel. +52 (998) 87-10219 ext 126
Fax: +52 (998) 87-10138
E-mail: blanchons at gmail.com <blanchons at yahoo.com>
Web: www.icmyl.unam.mx/arrecifes
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~