Oxygen Isotopes in Foraminifera: Overview and Historical Review

Feb 6, 2013 // by Athena // Blog // Comments Off

Prof Paul Pearson has published a paper of oxygen isotopes in foraminifera, one of the main techniques in the Descent into the Icehouse project.

The paper shows how

the oxygen isotope ratio (δ¹⁸0) of calcite depends mainly on the isotope ratio of the water it is precipitated from, the temperature of calcification, and, to a lesser extent, the pH. Foraminifera and other organisms can potentially preserve their original isotope ratio for many millions of years, although diagenetic processes can alter the ratios. Guidelines to assess the preservation of foraminifera are reviewed. A variety of empirical paleo-temperature equations have been proposed and some of the most important are discussed. Work on oxygen isotope ratios of foraminifera was instrumental in the discovery of the orbital theory of the ice ages and continues to be widely used in the study of rapid climate change. Compilations of deep sea benthic foraminifer oxygen isotopes have revealed the long history of global climate change over the past 100 million years. Planktonic foraminifer oxygen isotopes are used to investigate the history of past sea surface temperatures, revealing the extent of past ‘greenhouse’ warming and global sea surface temperatures.

Read and download the paper here

Foram art: calcite tests of selected benthic (left) and planktonic (right) foraminifera. These are from exceptionally well-preserved Paleogene sediments of Tanzania (33–45 Ma). Scale is approximate; diameters are from about 0.20–0.75 mm. Images: P. N. Pearson and I. K. McMillan. Note the literature is split between those who use the adjective ‘planktonic’ versus ‘planktic’ and between those who use ‘benthonic’ versus ‘benthic’. It so happens that planktonic and benthic are clearly in the ascendancy as of 2012, by roughly 10:1 and 30:1 respectively, as shown by a word search on abstracts. It has been argued that planktic is the correct Greek form of the adjective (Rodhe, 1974; Emiliani, 1991) but it has been pointed out that planktonic, like electronic, is perfectly good English, however ugly it may be in Greek (Hutchinson, 1974). The majority usage is followed here. Courtesy: Paul Peason Source: OXYGEN ISOTOPES IN FORAMINIFERA: OVERVIEW AND HISTORICAL REVIEW