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| Titel |
Cyclone trends constrain monsoon variability during late Oligocene sea level highstands (Kachchh Basin, NW India) |
| VerfasserIn |
Markus Reuter, W. E. Piller  , M. Harzhauser , A. Kroh |
| 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 ; 9, no. 5 ; Nr. 9, no. 5 (2013-09-04), S.2101-2115 |
| Datensatznummer |
250085220
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| Publikation (Nr.) |
 copernicus.org/cp-9-2101-2013.pdf |
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| Schlagwörter |
Klimawandel, Paläoklima, Zyklon, Sturm, Monsun, Atmosphärische Zirkulation, Klimarekonstruktion, Oligozän, Paläogen |
| Geograf. Schlagwort |
Indien |
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| Zusammenfassung |
| Climate change has an unknown impact on tropical cyclones and the Asian monsoon.
Herein we present a sequence of fossil shell beds from the shallow-marine
Maniyara Fort Formation (Kachcch Basin) as a recorder of tropical cyclone
activity along the NW Indian coast during the late Oligocene warming period
(~ 27–24 Ma). Proxy data providing information about the atmospheric
circulation dynamics over the Indian subcontinent at this time are important
since it corresponds to a major climate reorganization in Asia that ends up
with the establishment of the modern Asian monsoon system at the
Oligocene–Miocene boundary. The vast shell concentrations are comprised of a mixture
of parautochthonous and allochthonous assemblages indicating storm-generated
sediment transport from deeper to shallow water during third-order sea level
highstands. Three distinct skeletal assemblages were distinguished, each
recording a relative storm wave base. (1) A shallow storm wave base is shown
by nearshore molluscs, reef corals and Clypeaster echinoids; (2) an
intermediate storm wave base depth is indicated by lepidocyclinid
foraminifers, Eupatagus echinoids and corallinacean algae; and (3) a deep
storm wave base is represented by an
Amussiopecten bivalve-Schizaster echinoid assemblage. These wave
base depth estimates were used for the reconstruction of long-term tropical
storm intensity during the late Oligocene. The development and
intensification of cyclones over the recent Arabian Sea is primarily limited
by the atmospheric monsoon circulation and strength of the associated
vertical wind shear. Therefore, since the topographic boundary conditions
for the Indian monsoon already existed in the late Oligocene, the
reconstructed long-term cyclone trends were interpreted to reflect monsoon
variability during the initiation of the Asian monsoon system. Our results
imply an active monsoon over the Eastern Tethys at ~ 26 Ma followed by
a period of monsoon weakening during the peak of the late Oligocene global
warming (~ 24 Ma). |
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