Proxy geochemistry

Bismuth forms both 3+ and 5+ cations, although the former are by far the more common in nature. The ionic radius of Bi is even closer to that of La, than Ac, so again La is taken as the proxy. As noted above, Bi has the same electronic configuration as Pb, with a lone pair. It is unlikely therefore that the Shannon (1976) radius for Bi is universally applicable. Unfortunately, there is too little known about the magmatic geochemistry of Bi, to use its partitioning behavior to validate the proxy relationship, or propose a revised effective radius for Bi. The values of DWD u derived here should be viewed in the light of this uncertainty. 

Barnes CE, Cochran JK (1993) Uranium geochemistry in estuarine sediments Controls on removal and release processes. Geochim Cosmochim Acta 57 555-569 Berkman PA, Foreman DW, Mitchell JC, Liptak RJ (1992) Scallop shell mineralogy and crystalline characteristics Proxy records for interpreting Antarctic nearshore marine hydrochemical variability. Contrib Antartic Research 57 27-38... 

Druffel, E. R.M. 1995. Geochemistry of corals Proxies of past ocean chemistry, ocean circulation and climate. National Academy of Sciences Colloquium on Carbon Dioxide and Climate Change. 

Bassinot, F., Melieres, F., Gehlen, M., Levi, C. Labeyrie, L. 2004. Crystallinity of foraminifer shells a proxy to reconstruct past bottom water changes Geochemistry, Geophysics, Geosystems, 5, doi 10.1029/2003GC000668. 

Erez, J. 2003. The source of ions for biomineralization in Eoraminifera and their implications for paleoceano-graphic proxies. In DOVE, P. M., De YOREO, J. J. Weiner, S. (eds) Biominerahzation. Reviews in Mineralogy and Geochemistry, 54, 115-149. 

Rosell-Mele, a., Bard, E., Emeis, K.-C. etal. 2001. Precision of the current methods to measure the alkenone proxy Uk and absolute alkenone abundance in sediments Results of an interlaboratory comparison study. Geochemistry, Geophysics, Geosystems, 2, 2000GC000141. 

Bijma, J., Spero, H. J. Lea, D. W. 1999. Reassessing foraminiferal stable isotope geochemistry impact of the oceanic carbonate system (experimental results). In-. Fischer, G. Wefer, G. (eds) Use of Proxies in Paleoceanography Examples from the South Atlantic, Springer-Verlag, BerUn, 489-512. 

Druffel ERM (1997) Geochemistry of corals proxies of past ocean chemistry, ocean circulation, and climate. Proceedings of the National Academy of Sciences of the USA 94 8354-8361. 

If this is correct, these studies give the value of the B(OH)4 species for the particular pR at which the calcium carbonate formed, and thus can be used to calculate Oempirioai- Bccause of this consistency, the Kaldhana et al. value (16) has been used for all of the boron isotope studies to date. 7 important point to make here is that, in geochemistry, where we are applying chemical principles to complex natural systems, deviations from the expected relationship are common. We use empirical relationships determined from laboratory and natural ground-truthing studies to establish the relationships, and to be confident that the proxy measurement is traly approximating the condition of interest. 

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