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| Titel |
Ooids - a shallow marine proxy for coastal aridity |
| VerfasserIn |
Barbara Mauz, Noureddine Elmejdoub |
| 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 |
250091661
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| Publikation (Nr.) |
 EGU/EGU2014-5964.pdf |
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| Zusammenfassung |
| This paper aims at outlining shallow marine carbonates that can be used to infer coastal and
hinterland climate for the time period of deposition.
The carbonates used are ooids resulting from abiotic precipitation of aragonite around a
nucleus. It is thought that ooid formation requires high CO32- concentration, microbial
activity and less than 3-5 m of warm, agitated sea water. In the modern analogues (Bahamas,
Arabian Gulf, Gulf of Suez) the environmental factors controlling the formation of tangential
ooids are (i) seabed morphology and tidal currents allowing for water agitation, (ii) absence
of fluvial discharge and (iii) minimum annual sea-surface temperature of around 20°C.
Albeit significant environmental differences in terms of annual rainfall, sea surface
temperature and salinity, Bahamian ooids are indistinguishable from those formed on shores
of the Arabian Peninsula. These modern analogues have however in common that no
terrestrial sediment is delivered to the shore. Thus, ooids are a proxy for the absence of
riverine sediment supply to the coast.
Our test sites, situated on the southern coast of the Mediterranean, show sharp switches
between siliciclastic and oolitic nearshore environments during the last interglacial sea-level
highstand. These switches confirm the absence of fluvial sediment discharge when the
carbonate factory was active.
Applying this concept to a number of chronologically constrained coastal sites in
the Mediterranean, we are able to infer spatially differential response to external
climatic forcing: some coastal areas respond instantaneously and exclusively to
external forcing while others respond delayed and prolonged. The spatial difference
underlines the importance of shelf geometry for coastal response to climate change. |
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