Super-fine temporal resolution past climate reconstruction from micro analysis of giant clam shell

2014 Fiscal Year Final Research Report

• Project/Area Number: 25870147
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Stratigraphy/Paleontology; Geochemistry/Cosmochemistry
• Research Institution: The University of Tokyo
• Principal Investigator: SHIRAI Kotaro 東京大学, 大気海洋研究所, 助教 (70463908)
• Project Period (FY): 2013-04-01 – 2015-03-31
• Keywords: シャコガイ / 極端現象 / 古環境復元 / Sr/Ca比 / 古環境指標 / 成長線解析

Outline of Final Research Achievements

For the understanding and future prediction of extreme events, establishing a new method to reconstruct past-environment at diurnal scale is required. Giant clam holds great advantages for this purpose, namely the shell forms daily growth line which enable to identify a time axis at hourly scale, and holds continuous and long term environmental records up to few hundreds years. The aim of this study is to examine the giant clam shell as very high resolution past environmental proxy. Incremental width of daily growth line in fossil shell from Holocene climatic optimum showed clear seasonal fluctuation, wide in summer while narrow in winter. The low-resolution profile of the shell Sr/Ca and Mg/Ca ratio showed seasonal fluctuation along a growth direction. The 2-micrometer resolution profile of Sr/Ca ratio in the fossil shell showed clear diurnal fluctuation, indicating daily insolation cycles.

Free Research Field

地球化学