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| Titel |
The Mediterranean coral Cladocora caespitosa as a Pleistocene palaeoclimate archive |
| VerfasserIn |
Sam Royle, Julian Andrews, Jennifer Turner, Alina Marca |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250087817
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| Publikation (Nr.) |
 EGU/EGU2014-1876.pdf |
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| Zusammenfassung |
| The Mediterranean coral Cladocora caespitosa has much potential as a palaeoclimate
indicator. The work of Montagna et al. (2007), Montagna et al. (2006) and Silenzi et al.
(2005) have shown that, at various resolutions, modern samples of this coral faithfully record
sea surface temperatures in their trace elemental compositions. As this species is abundant in
Mediterranean deposits dating back to the late Pleistocene this opens up the possibility of
using well preserved fossil samples to analyse the palaeoclimate of previous interglacials at a
sub-seasonal scale.
This study is based on modern samples from Mljet, Croatia and fossil samples from the
actively uplifting southern coast of the Gulf of Corinth, Greece, dating from the interglacial
marine isotope stages (MIS) 1, 5c, 5e and 7c.
High resolution (N = 200 μm, approximately bi-monthly) mass-spectrometric analysis of
stable oxygen isotopes, trace element content and bulk sample analysis of multiply
substituted oxygen isotopologues were all carried out on fossil and modern samples using the
modern data to aid in calibrating the fossil data.
There are seasonal signals found in the geochemical profiles for the high resolution
techniques in all well preserved samples. However, it is clear from the modern data that C.
caespitosa precipitates its aragonitic skeleton out of equilibrium with ambient seawater for all
of the geochemical parameters studied.
Intra-site trace element composition is too variable to provide reliable palaeoenvironmental
data. Average sample Δ47calculated temperatures of approximately -2 to +8°C, from the
same locality, in comparison to the -20.5°C recorded at the site, confirm that this species
does not precipitate its skeletal aragonite in isotopic equilibrium.
Using modern samples, measured δ18Owater and recorded temperature values; C.
caespitosa is, however, shown to precipitate at a relatively constant negative offset from
oxygen isotopic equilibrium. This allows the calculation of a species specific δ18O
aragonite-water temperature relationship of T = 4.406 – 4.34(δ18Oaragonite - δ18Owater+
0.2).
Using this palaeotemperature equation, and assuming a δ18Owater value for the Gulf of
Corinth equal to modern at +1.15V SMOW, seemingly realistic average annual growth
temperatures were found for the fossil samples. These calculated values suggest that,
compared to today, during the early part of MIS 1 and in MIS 5c the Gulf of Corinth
had slightly cooler average temperatures (by 1-2°C), 5e was very similar, and
7c was on average warmer by around 2.5°C. These results suggest that fossil C.
caespitosa δ18O values can preserve a reliable sub-seasonal palaeotemperature
signal.
Montagna, P., McCulloch, M., Mazzoli, C., Silenzi, S., & Odorico, R. (2007). The
non-tropical coral Cladocora caespitosa as the new climate archive for the Mediterranean:
high-resolution (similar to weekly) trace element systematics. Quaternary Science Reviews,
26(3-4), 441–462. doi:10.1016/j.quascirev.2006.09.008
Montagna, P., McCulloch, M. T., Mazzoli, C., Silenzi, S., & Schiaparelli, S. (2006). Li/Ca
ratios in the Mediterranean non-tropical coral Cladocora caespitosa as a potential
paleothermometer. Geophysical Research Abstracts, 8.
Silenzi, S., Bard, E., Montagna, P., & Antonioli, F. (2005). Isotopic and elemental records
in a non-tropical coral (Cladocora caespitosa): Discovery of a new high-resolution climate
archive for the Mediterranean Sea. Global and Planetary Change, 49(1-2), 94–120.
doi:10.1016/j.gloplacha.2005.05.005 |
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