Geological Society of America

T251 Phanerozoic Evolution in the Oceans: Effects of Warming and Chemical Changes

Tuesday, 3 November 2015
1:30 PM - 5:30 PM
Room 316

OXYGEN ISOTOPIC VARIATIONS IN MODERN CETACEAN TEETH AND BONES: IMPLICATIONS FOR PALEOECOLOGICAL, PALEOCLIMATIC AND PALEOCEANOGRAPHIC STUDIES

Paper number: T251-14
Program: Technical Sessions
Time: 4:50 PM – 5:05 PM

Authors

Burcu Ciner
Florida State University, Tallahassee, FL
Burcu Ciner
Balikesir University, Balikesir
Yang Wang Presenting Author
Florida State University, Tallahassee, FL
Yang Wang Presenting Author
National High Magnetic Field Laboratory, Tallahassee, FL
William Parker
Florida State University, Tallahassee, FL

Abstract

The oxygen isotope ratios (δ¹⁸O) preserved in marine sediments have been widely used to reconstruct past ocean temperatures. However, there remain significant uncertainties associated with this method, owing to assumptions about the δ¹⁸O of ancient seawater which affects the temperature inferred from sediment δ¹⁸O records. In this study, oxygen isotope compositions of phosphate in teeth and bones from a diverse group of modern cetaceans, including sperm whale, pygmy sperm whale, short-finned pilot whale, killer whale and Cuvier’s beaked whale, and three fossil whales were determined. The data were used to assess if the oxygen isotope ratios of biogenic phosphate (δ¹⁸O_p) from cetaceans are a reliable proxy for the oxygen isotopic composition of ocean water (δ¹⁸O_w). The δ¹⁸O_p values of modern cetaceans range from 15.5‰ to 21.3‰, averaging 19.6±0.8‰ (n=136). Using a greatly expanded global cetacean δ¹⁸O_pdataset, the following regression equation is derived for cetaceans:

δ¹⁸O_w= 0.95317(+0.03293) δ¹⁸O_p – 17.971(+0.605), r= 0.97253.

The new equation, when applied to fossil cetacean teeth and bones, yielded reasonable estimates of ancient seawater δ¹⁸O_w values. Intra-tooth oxygen isotopic variations within a whale tooth record changes in the isotopic composition of environmental water during the time of tooth growth, providing insights into the life history or migratory behavior of the whale. The results from this study demonstrated the potential of using oxygen isotopes in the phosphate component of cetacean teeth and bones to examine the migratory behaviors and environmental preferences of both modern and ancient whales and to track past changes in ocean water oxygen isotopic composition.