Geological Society of America

69 D32. Geochemistry (Posters)

Sunday, 22 October 2017
9:00 AM - 5:30 PM
Halls 4EF

CONSTRAINING THE OUTFLOW OF THE AMAZON RIVER FOR THE PAST ~40 KA USING BA/CA

Paper number: 69-27
Program: Technical Sessions
Time: 9:00 AM – 5:30 PM

Authors

Jamie Dix Presenting Author
University of California, Los Angeles, los angeles, CA
Yama Dixit
University of California, Los Angeles, los angeles, CA
Whitney C. Doss
Univ of Colorado-Boulder, Boulder, CO
Ryan Dill
Univ of Colorado-Boulder, Boulder, CO
Fengming Chang
Chinese Academy of Sciences, Qingdao
Aradhna K. Tripati
University of California, Los Angeles, Los Angeles, CA

Abstract

The Amazon River is a critical part of the global water cycle and is associated with a region of high biodiversity. It is the world’s largest river by discharge amount, has the largest drainage basin, and holds approximately 20% of the world’s fresh water. Although dramatic changes in Amazon River outflow could have devastating effects regionally and worldwide, it is unclear how the outflow of the Amazon will respond to short and long-term climate change. However, the geochemical record of foraminifera from the Amazon Fan can be used to determine past behavior of this system caused by climate change. Understanding conditions associated with large reductions in Amazon River outflow can help us evaluate the likelihood of such a devastating scenario occurring in the future in response to anthropogenic carbon emissions.

Previous work used oxygen isotope ratios in foraminifera to infer a >60% reduction in Amazon River outflow around 12 kya in response to abrupt climate changes in the high latitudes of the Northern Hemisphere. This dramatic reduction in outflow is believed to have occurred on timescales of only decades to centuries. Using oxygen isotope ratios to reconstruct river outflow can be ambiguous due to its dependence on the hydrologic cycle and glacial meltwater. Here, barium/calcium ratios were used to determine freshwater outflow, and magnesium calcium ratios were used to determine temperature. Ba/Ca results are consistent with a significant decrease in river outflow around 12 ka during the Younger Dryas, and we will present a quantitative reconstruction of changes in outflow to evaluate the potential for this river system to undergo abrupt changes.

Geological Society of America Abstracts with Programs. Vol. 49, No. 6

doi: 10.1130/abs/2017AM-308175

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