ISOTOPIC COMPOSITION OF STRONTIUM IN PERMIAN LIMESTONES, EASTERN KANSAS

The strontium ( 87 86) ratios in ten samples of Permian limestones from eastern Kansas vary from 0.7070 to 0.7091. This range is beyond the possible analytical error of ± 0.0003 per single analysis determined from sixteen analyses of an interlaboratory standard. The possible reasons for this range may be: (1) actual fluctuations in local environments in Permian seas; (2) preferential leaching of radiogenic 87Sr from argillaceous constituents during the analytical procedures; (3) secondary enrichment of 87Sr in the limestones due to recrystallization; (4) some other process or a combination of any of the above. Comparison of total strontium and silica contents with the isotopic Sr ( 87 86) data indicate no direct correlation between these parameters; hence the range is most probably due to reason 1. In addition, attempts to pinpoint the isotopic composition of Sr on the marine geochron proposed by Hurley et al. (1965) have failed, and the data suggest that present methods of determining this geochron are inadequate at present. © 1969.