Clumped isotopes

Clumped isotopes are heavy isotopes that are bonded to other heavy isotopes. The relative abundance of clumped isotopes (and multiply-substituted isotopologues) in molecules such as methane, nitrous oxide, and carbonate is an area of active investigation.[1] The carbonate clumped-isotope thermometer, or "13C–18O order/disorder carbonate thermometer", is a new approach for paleoclimate reconstruction,[1] based on the temperature dependence of the clumping of 13C and 18O into bonds within the carbonate mineral lattice.[2] This approach has the advantage that the 18O ratio in water is not necessary (different from the δ18O approach), but for precise paleotemperature estimation, it also needs very large and uncontaminated samples, long analytical runs, and extensive replication.[3] Commonly used sample sources for paleoclimatological work include corals, otoliths, gastropods, tufa, bivalves, and foraminifera.[4][5] Results are usually expressed as Δ47 (said as "cap 47"), which is the deviation of the ratio of isotopologues of CO2 with a molecular weight of 47 to those with a weight of 44 from the ratio expected if they were randomly distributed.[6]

  1. ^ a b Eiler, J.M. (2007). ""Clumped-isotope" geochemistry—The study of naturally-occurring, multiply-substituted isotopologues". Earth and Planetary Science Letters. 262 (3–4): 309–327. doi:10.1016/j.epsl.2007.08.020.
  2. ^ Lea, D.W. (2014). "8.14 - Elemental and Isotopic Proxies of Past Ocean Temperatures". In Holland, H.D.; Turekian, K.K. (eds.). Treatise on Geochemistry, Second Edition. Vol. 8. Oxford: Elsevier. pp. 373–397. doi:10.1016/B978-0-08-095975-7.00614-8. ISBN 9780080983004.
  3. ^ Ghosh, P.; Adkins, J.; Affek, H.; et al. (2006). "13C-18O bonds in carbonate minerals: A new kind of paleothermometer". Geochimica et Cosmochimica Acta. 70 (6): 1439–1456. doi:10.1016/j.gca.2005.11.014.
  4. ^ Ghosh, P.; Eiler, J.; Campana, S.E.; Feeney, R.F. (2007). "Calibration of the carbonate 'clumped isotope' paleothermometer for otoliths". Geochimica et Cosmochimica Acta. 71 (11): 2736–2744. doi:10.1016/j.gca.2007.03.015.
  5. ^ Tripati, A.K.; Eagle, R.A.; Thiagarajan, N.; et al. (2010). "13C-18O isotope signatures and 'clumped isotope' thermometry in foraminifera and coccoliths". Geochimica et Cosmochimica Acta. 74 (20): 5697–5717. doi:10.1016/j.gca.2010.07.006.
  6. ^ Affek, Hagit (2012). "Clumped isotope paleothermometry: Principles, applications, and challenges". Reconstructing Earth's Deep-Time Climate—The State of the Art in 2012, Paleontological Society Short Course, November 3, 2012. 8: 101–114.