Marine carbon cycle revealed by geochemistry of biogenic calcium carbonate

Abstract

Biogenically precipitated calcium carbonate such as coral skeleton, foraminifera shell, fish otolith, and bivalve shell are useful archives to reflect past ocean environment. I will present results of past environmental reconstruction using geochemistry of such biogenic calcium carbonate, focusing on boron isotope (δ¹¹B) measurement in particular. δ¹¹B measurement is one of the most difficult measurements in geochemistry because of 1) low concentration of boron in calcium carbonate; 2) susceptible to experimental contamination; and 3) strong isotope fractionation due to a large mass difference in isotopes (¹¹B and ¹⁰B). I will overview my recent marine carbon cycle studies using δ¹¹B measurements of coral skeleton by thermal ionization mass spectrometry (TIMS) and foraminifera shell by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS).