van Soelen E. E., Kim J. H., Ventura SantosR., Dantas E. L., Vasconcelos de Almeida F., Pinheiro Pires J., Roddaz Martin, Sinninghe Damsté J. S. (2017). A 30 Ma history of the Amazon River inferred from terrigenous sediments and organic matter on the Ceara Rise. Earth and Planetary Science Letters, 474, p. 40-48. ISSN 0012-821X.
Titre du document
A 30 Ma history of the Amazon River inferred from terrigenous sediments and organic matter on the Ceara Rise
Année de publication
2017
Auteurs
van Soelen E. E., Kim J. H., Ventura SantosR., Dantas E. L., Vasconcelos de Almeida F., Pinheiro Pires J., Roddaz Martin, Sinninghe Damsté J. S.
Source
Earth and Planetary Science Letters, 2017,
474, p. 40-48 ISSN 0012-821X
The history of the Amazon River is a much-discussed subject, and the timing of the development of a transcontinental system in particular is a matter of some controversy, with estimations varying between the Early Miocene and the Pliocene or even the Pleistocene. To shed further light on this, we studied the sediment provenance of an Oligocene to Late Pleistocene marine sedimentary section from the Ceara Rise (ODP Site 925), a topographic high in the central Atlantic Ocean, using major element concentrations and Nd isotopic composition in 85 samples. In addition, the carbon isotopic composition of bulk organic matter and changes in the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) were used to identify periods of increased river outflow. On the basis of these results, we suggest that the history of the development of the Amazon River is characterized by specific steps. During the late Oligocene/Early Miocene (30-18.3 Ma), the terrigenous mass accumulation rates (TARs) were high, and sediment and GDGT compositions suggest that a large river system existed, which at times received weathering products from a younger and probably Andean sediment source. A shift to a younger Andean sediment provenance after 8.7 Ma indicates that the Amazon River became permanently connected with the Andes. Between 18.3 and 4.5 Ma, TARs were generally low, and GDGTs were derived for the most part from in situ production in marine waters. Around 4.5 Ma, the river expanded, probably due to ongoing tectonic activity, and uplift in the Andes increased Andean rock erosion. This led to a strong increase in terrigenous sediment deposition and enhanced organic matter preservation on the Ceara Rise, and the delivery of terrestrial (both soil and riverine) branched GDGTs to the Ceara Rise.
Plan de classement
Hydrologie [062]
;
Géologie et formations superficielles [064]
Description Géographique
AMAZONE BASSIN ; ATLANTIQUE OUEST ; BRESIL ; PEROU ; COLOMBIE ; ZONE EQUATORIALE
Localisation
Fonds IRD [F B010070986]
Identifiant IRD
fdi:010070986
