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| Titel |
Neogene vegetation development in the Amazon Basin: evidence from marine well-2, Foz do Amazonas (Brazil) |
| VerfasserIn |
Raul Bogota-Angel, Farid Chemale Junior, Roberto Davila, Emilson Soares, Ricardo Pinto, Dermeval Do Carmo, Carina Hoorn |
| 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 |
250090471
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| Publikation (Nr.) |
 EGU/EGU2014-4710.pdf |
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| Zusammenfassung |
| Origen and development of the highly diverse Amazon tropical forest has mostly been
inferred from continental sites. However, sediment records in the marine Foz do Amazonas
Basin can provide important information to better understand the influence of the Andes
uplift and climate change on its plant biomes evolution since the Neogene. Sediment analyses
of samples from BP-Petrobras well 1 and 2, drilled in the Amazon Fan, allowed to infer the
onset of the transcontinental Amazon river and the fan phase during the middle to late
Miocene (c. 10.5 Ma). As part of the CLIMAMAZON research programme we performed
pollen analysis on the 10.5 to 0.4 Ma time interval. 76 ditch cutting samples of the upper
4165 m sediments of well 2 permitted us to infer changes in floral composition
in the Amazon Basin. The palynological spectra across this interval (nannofossil
based age model) include pollen, fern spores, dinocysts and foram lignings. When
possible pollen and fern spores were grouped in four vegetation types: estuarine,
tropical, mountain forest and high mountain open treeless vegetation. Pollen is
generally corroded and reflects the effects of sediment transportation while reworked
material is also common. Good pollen producers such as Poaceae, Asteraceae and
Cyperaceae are common and reflect indistinctive vegetation types particularly those
associated to riverine systems. Rhizophora/Zonocostites spp. indicate "close-distance"
mangrove development. Tropical forest biomes are represented by pollen that resemble
Moraceae-Urticaceae, Melastomataceae-Combretaceae, Sapotaceae, Alchornea,
Euphorbiaceae, Rubiaceae, Bignoniaceae, Mauritia and Arecaceae. Myrica, and particularly
sporadic occurrences of fossil fern spores like Lophosoria, and Cyathea suggest
the development of a moist Andean forest in areas above 1000 m. First indicators
of high altitudes appear in the last part of late Miocene with taxa associated to
current Valeriana and particularly Polylepis, a neotropical taxon currently growing
along the Andean fluvial system on altitudes between c. 2000 up to c. 4800 m.
Alnus is an important Andean forest taxa since Pliocene. In summary, the Neogene
palynological record of the Amazon Fan strongly reflects and confirms the influence of the
uplift of the Andes and its transcontinental character from late Miocene onwards. |
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