Coupled 230Th/234U-ESR analyses for corals: A new method to assess sealevel change
Although coupled 230Th/234U-ESR analyses have become routine for dating teeth, they have never been used for corals. While the ESR age depends on, and requires assumptions about, the time-averaged cosmic dose rate, over(D, -)cos (t), 230Th/234U dates do not. Since over(D, -)cos (t) received by corals depends on the attenuation by any intervening material, over(D, -)cos (t) response reflects changing water depths and sediment cover. By coupling the two methods, one can determine the age and a unique over(D, -)cos, coupled (t) simultaneously. From a coral's water depth and sedimentary history as predicted by a given sealevel curve, one can predict over(D, -)cos, sealevel (t) . If over(D, -)cos, coupled (t) agrees well with over(D, -)cos, sealevel (t), this provides independent validation for the curve used to build over(D, -)cos, sealevel (t). For six corals dated at 7-128 ka from Florida Platform reef crests, the sealevel curve by Waelbroeck et al. [2002. Sea-level and deep water temperature changes derived from benthonic foraminifera isotopic records. Quat. Sci. Rev. 21, 295-305] predicted their over(D, -)cos, coupled (t) values as well as, or better than, the SPECMAP sealevel curve. Where a whole reef can be sampled over a transect, a precise test for sealevel curves could be developed.
|Keywords||Coral reefs, Coupled 230Th/234U-ESR dating, Paleo-cosmic dose rate determination, Quaternary sealevel fluctuations|
Blackwell, B.A.B. (Bonnie A.B.), Teng, S.J.T. (Steve J.T.), Lundberg, J, Blickstein, J.I.B. (Joel I.B.), & Skinner, A.R. (Anne R.). (2007). Coupled 230Th/234U-ESR analyses for corals: A new method to assess sealevel change. Radiation Measurements, 42(6-7), 1250–1255. doi:10.1016/j.radmeas.2007.05.006