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| Titel |
The Aptian evaporites of the South Atlantic: a climatic paradox? |
| VerfasserIn |
A.-C. Chaboureau, Y. Donnadieu, P. Sepulchre, C. Robin, F. Guillocheau, S. Rohais |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 3 ; Nr. 8, no. 3 (2012-06-11), S.1047-1058 |
| Datensatznummer |
250005594
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| Publikation (Nr.) |
 copernicus.org/cp-8-1047-2012.pdf |
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| Zusammenfassung |
| For a long time, evaporitic sequences have been interpreted as indicative of
an arid climate. Such systematic interpretations led to the suggestion that
the Central segment of the South Atlantic (20–0°) was characterized
by an arid climate during the upper Aptian. Indeed, synchronous to this
period that corresponds to the rifting and to the opening of this part of
the South Atlantic, a large evaporitic sequence spreads out from the equator
to 20° S. Using the fully ocean atmosphere coupled model FOAM, we test
the potential for the Aptian geography to produce an arid area over the
Central segment. Sensitivity to the altitude of the rift shoulders
separating the Africa and the South America cratons, to the water depth of
the Central segment and to the drainage pattern have been performed. Using
seawater salinity as a diagnostic, our simulations show that the southern
part of the Central segment is characterized by very high salinity in the
case of catchment areas draining the water out of the Central segment.
Conversely, whatever the boundary conditions used, the northern part of the
Central segment remains humid and salinities are very low. Hence, we
conclude that the evaporites deposited in the southern part of the Central
segment may have been controlled by the climate favouring aridity and high
saline waters. In contrast, the evaporites of the northern part can hardly
be reconciled with the climatic conditions occurring there and may be due to
hydrothermal sources. Our interpretations are in agreement with the gradient
found in the mineralogical compositions of the evaporites from the North to
the South, i.e. the northern evaporites are at least 4 times more
concentrated than the southern one. |
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