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Detrital zircons reveal sea-level and hydroclimate controls on Amazon River to deep-sea fan sediment transfer

Cody C. Mason, Brian W. Romans, Daniel F. Stockli, Russel W. Mapes and Andrea Fildani
Detrital zircons reveal sea-level and hydroclimate controls on Amazon River to deep-sea fan sediment transfer
Geology (Boulder) (April 2019) 47 (6): 563-567

Abstract

We use new U-Pb detrital zircon (DZ) geochronology from the Pleistocene Amazon submarine fan (n = 1352 grains), integrated with onshore DZ age data, to propose a sedimentary model for sea level-modulated and hydroclimate-modulated sediment transfer in Earth's largest source-to-sink system. DZ ages from the modern Amazon River sediment display a progressive downstream dilution by older cratonic zircons, leading to the expectation of a submarine fan with high proportions of craton-derived sediment. Our new DZ age data from the submarine fan and mixture modeling suggest that higher proportions of sediment were supplied from the distant central Andes to the Amazon fan during the last two glacioeustatic lowstands, and thus the observed DZ age spectra of the modern lower Amazon River indicate a relative increase in craton-derived sediment during the Holocene. We interpret that during interglacials, when sea level was high and the submarine fan inactive, the lower Amazon River did not efficiently transfer sand-sized sediment to the margin and thus became enriched in craton-derived sediment. During sea-level lowstands, increased gradients and incision in the lower Amazon River due to base-level lowering resulted in enhanced connectivity and transfer of Andes-sourced zircons to the deep sea. These results are also consistent with interpreted patterns of Andean-Amazon hydroclimate anti-phasing (enhanced precipitation in the central Andes and increased aridity in the northern Amazon Basin) during the Last Glacial Maximum. Our results suggest that sand-sized sediment in the Amazon submarine fan records multi-millennial patterns of sea level and South American hydroclimate.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 47
Serial Issue: 6
Title: Detrital zircons reveal sea-level and hydroclimate controls on Amazon River to deep-sea fan sediment transfer
Affiliation: University of West Georgia, Department of Geosciences, Carrollton, GA, United States
Pages: 563-567
Published: 20190416
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 41
Accession Number: 2019-038016
Categories: Quaternary geologyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: GSA Data Repository item 2019206
Illustration Description: illus. incl. geol. sketch map
N06°57'01" - N06°57'01", W47°45'44" - W47°45'44"
N06°56'58" - N06°56'58", W47°55'10" - W47°55'10"
N05°37'56" - N05°37'56", W47°44'08" - W47°44'08"
Secondary Affiliation: Virginia Polytechnic Institute and State University, USA, United StatesUniversity of Texas at Austin, USA, United StatesExxonMobil, USA, United StatesEquinor Research Center, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, 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: 201920
Program Name: ODPOcean Drilling Program
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