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| Titel |
Fossil marl prairie as indicator for aridification and coastal uplift in equatorial East Africa during the last glaciation |
| VerfasserIn |
Markus Reuter, W. E. Piller  , M. Harzhauser , A. Kroh , B. Berning |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250029786
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| Schlagwörter |
Fazies, Faziesanalyse, Sedimentologie, Sedimente, Sedimentgeologie, Pleistozän, Quartär, Ostafrikanisches Grabenbruchsystem |
| Geograf. Schlagwort |
Tansania |
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| Zusammenfassung |
| Facies analyses of Pleistocene deposits from southern coastal Tanzania (Lindi District)
document that sediments have formed in a wetland that developed on a coastal terrace in
front of the Lindi Fracture Zone. The exposed sedimentary succession reveals one
transgression/regression cycle. A rising relative sea level is indicated by back-stepping tidal
flats. The overlying palustrine limestones were precipitated in a marl prairie that developed
due to falling relative sea level. In marl prairies, carbonate precipitates seasonally in barely
flooded grasslands within periphyton mats. Despite the special mode of carbonate production
descriptions of the sedimentary facies are cursory because marl prairies are so far
reported only from the Recent Everglades (Florida/USA) where they produce an
unspectacular calcite mud. The Pleistocene marl prairie from Africa is the first fossil
example and, in contrast to the Everglades marl prairies, the periphyton is excellently
preserved because of a better calcification of the associated cyanobacteria. The
unique preservation allows us to characterize a marl prairie facies in great detail
for the first time. Located at the interface between land and sea marl prairies are
sensitive to changes in water balance and a useful recorder for climate and sea level
changes. Radiocarbon dating of Assiminea gastropods from the studied sediments
reveal the emergence of the coastal terrace started at ~44 ka BP. This coincides
with a eustatic sea level fall prior to the last glaciation maximum and a phase of
tectonic uplift at the Lindi Fracture Zone. Along the entire coast of Tanzania terraces
were periodically elevated due to extensional episodes in the eastern branch of
the East African Rift System during the Quaternary. However, the exact timing of
these tectonic pulses was so far impossible. Our results show that the emergence of
the Lindi coast was linked to a period of tectonic activity in the East African Rift
System after ~50 ka. The decline of the marl prairie was initiated at ~33 ka BP
due to the onset of the Last Glacial Aridity Maximum in equatorial East Africa. |
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