Geological Society of America

T268 Cenozoic Paleoclimates and Ecosystems (Posters)

Tuesday, 24 October 2017
9:00 AM - 6:30 PM
Halls 4EF

PALEOCLIMATIC RECONSTRUCTION OF LATE EOCENE MYANMAR VIA STABLE ISOTOPE PROXIES

Paper number: T268-21
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Virginia Littell Presenting Author
University of Washington, Seattle, WA
Fernando Poblete
Universidad de O'Higgins, Rancagua
Huasheng Huang
University of Amsterdam, Amsterdam
Carina Hoorn
University of Amsterdam, Amsterdam
Kyaing Sein
Myanmar Geosciences Society, Yangon
Alexis Licht
University of Washington, Seattle, WA
Guillaume Dupont-Nivet
Université de Rennes, Rennes
Zaw Win
University of Shwebo, Shwebo
Andrew J. Schauer
University of Washington, Seattle, WA
Hnin Hnin Swe
University of Yangon, Yangon
Myat Kay Thi
University of Yangon, Yangon
Day Wa Aung
University of Yangon, Yangon
Pierrick Roperch
Université de Rennes, Rennes

Abstract

The Asian monsoons affect the lives of one third of the human population, yet the controls on monsoon intensity and longevity are not fully understood. Recent studies have highlighted that the South Asian monsoon is as old as the Eocene; early monsoonal intensity has been proposed to be driven by variations in atmospheric pCO₂.

This study proposes to trace the response of the South Asian monsoon to decreasing pCO₂ during the Eocene Oligocene Transition (EOT) in the sedimentary archives of central Myanmar. To do so, we present new stable isotope data from the upper Eocene – lower Oligocene Yaw Formation in a preliminary approach to reconstruct late Eocene monsoonal intensity.

The two sources of isotope data are fossil freshwater shells and lignite layers. Pristine, unaltered bivalve and gastropod shells – confirmed with cathodoluminescence and scanning electron microscopy – were subsampled and analyzed for δ¹⁸O values. Lignite samples were analyzed for bulk organic matter δ¹³C content. The oxygen isotope data provides insight into annual rainfall seasonality and overall monsoon rainfall intensity, while the carbon isotopes record vegetation types and temporal shifts in ecosystems. These preliminary data are the first step in reconstructing the evolution of South Asian monsoonal intensity during the EOT, and will be followed by further investigation of younger sedimentary units in central Myanmar.

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

doi: 10.1130/abs/2017AM-301586

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