T15 Landscape Responses to Neogene Climate Change

Sunday, 22 September 2019
8:00 AM - 12:00 PM
Room 228AB, North Building

AN ASSESSMENT OF EAST ASIAN SUMMER MONSOON PRECIPITATION NEAR THE PALEOGENE-NEOGENE BOUNDARY USING FOSSIL WOOD SUBSTRATES

Paper number: T15-14
Program: Technical Sessions
Time: 11:30 AM – 11:45 AM

Authors

Abstract

The East Asian Summer Monsoon (EASM) system is the source of >75% of total precipitation that falls over southeastern Asia every year. Models suggest that monsoon strength and variability may increase simultaneously with rising CO2 levels over time; however, quantitative data for this relationship in the geologic record is lacking. Here we present new high-resolution carbon isotope (δ13C) data from mummified fossil wood samples recovered from Nanning Basin, Guangxi, China from the late Oligocene (28.1 – 23.0 Ma), in order to quantify monsoon precipitation during the last time CO2 levels were comparable to modern (>400 ppmv). These data show, on average, ~2.5 times more precipitation falling during the summer than winter with rainfall rates ranging from 4-7 mm/day during the summer rainy seasons. These values suggest that the overall strength of the monsoon near Paleogene-Neogene boundary was similar in strength to the monsoon seen in southeastern Asian today. Further, these data reveal low year-to-year variability, signifying a stable monsoon system under elevated CO2 conditions. Analysis of seasonal and daily rainfall rates near Paleogene-Neogene boundary provides the first quantitative measure of EASM precipitation seasonality at annual resolution. Understanding of past EASM dynamics can provide valuable insight on potential impacts of elevated CO2 levels on seasonal precipitation variability across southeastern Asia.

Geological Society of America Abstracts with Programs. Vol. 51, No. 5

doi: 10.1130/abs/2019AM-338642

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