Trace-element chemistry of non-marine ostracod shells: a preliminary evaluation of cleaning methods

Abstract. Trace-element analysis of ostracod shells has been shown to be a powerful tool in Quaternary palaeoenvironmental reseach (e.g. Chivas et al., 1986). Particular use has been made of Sr/Ca and Mg/Ca ratios in ostracod shells as palaeosalinity and palaeotemperature indictors. However, work on trace elements such as Cd, Zn, Cu and Ba in benthic foraminifera (e.g, Boyle, 1981) has shown that chemical cleaning of the shell is necessary to remove surface-bound contaminants, so that only the lattice-bound elements are analyzed. This note describes the application of selected cleaning methods to non-marine ostracod shells and evaluates their effect on shell chemistry with particular reference to Sr, Mg, Mn and Fe.

Samples of ostracod shells were taken from late Quaternary lacustrine marls from Wallywash Great Pond, Jamaica. Adult valves of the genus Cypretta Vàrva 1895 were selected at random and subjected to one of three cleaning methods as follows.

Method A: shells cleaned thoroughly with a clean nylon paint brush (0000) and deionised water, until all visible particles (under x40 magnification) had been removed. Shells cleaned by methods B and C were also initially treated in this way.

Method B: shells cleaned in a basic hydroxylamine hydrochloride solution at 80°C for 30 minutes and then rinsed in deionised water (Boyle, 1981).

Method C: shells cleaned in a basic sodium dithionite complexing reagent at 80°C for 30 minutes and then rinsed with deionised water (Boyle, 1981).

Nine individual valves were cleaned using each method. Once cleaned, the valves were individually dissolved in 3ml. . .