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Late Miocene onset of the Amazon River and the Amazon deep-sea fan; evidence from the Foz do Amazonas Basin

J. Figueiredo, C. Hoorn, P. van der Ven and E. Soares
Late Miocene onset of the Amazon River and the Amazon deep-sea fan; evidence from the Foz do Amazonas Basin
Geology (Boulder) (July 2009) 37 (7): 619-622

Abstract

New biostratigraphic, isotopic, and well log data from exploration wells on the outer continental shelf and uppermost Amazon deep-sea fan, Brazil, reveal that the Amazon River was initiated as a transcontinental river between 11.8 and 11.3 Ma ago (middle to late Miocene), and reached its present shape and size during the late Pliocene. Prior to the late Miocene the continental shelf was a carbonate platform that received moderate siliciclastic sediment supply from the Proterozoic basement in eastern Amazonia. Average sedimentation rates on the Amazon Fan show three stages of development: (1) 11.8-6.8 Ma ago, low sedimentation rates (0.05 m/ka) prevailed on the fan, because the Amazon River was not yet entrenched and some sediments were partially trapped in continental basins; (2) 6.8-2.4 Ma ago, sedimentation rates (0.3 m/ka) increased, the river entrenched, and deposition fully migrated onto the Amazon Fan; (3) 2.4 Ma ago to the present, very high sedimentation rates (1.22 m/ka, with peaks of 11 m/ka) prevailed on the fan and the modern Amazon River developed. All these paleogeographic and depositional events are closely related to Andean tectonism (late Miocene-Pliocene) and were exacerbated by global cooling and sea-level fall during the late Miocene.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 37
Serial Issue: 7
Title: Late Miocene onset of the Amazon River and the Amazon deep-sea fan; evidence from the Foz do Amazonas Basin
Affiliation: University of Liverpool, Department of Earth and Ocean Science, Liverpool, United Kingdom
Pages: 619-622
Published: 200907
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 27
Accession Number: 2009-072264
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Annotation: With GSA Data Repository Item 2009145
Illustration Description: illus. incl. sketch map
N03°00'00" - N09°00'00", W50°00'00" - W44°00'00"
S04°30'00" - N01°00'00", W73°30'00" - W49°30'00"
N02°00'00" - N10°00'00", W50°00'00" - W44°00'00"
Secondary Affiliation: University of Amsterdam, NLD, NetherlandsPETROBRAS, BRA, Brazil
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200939
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