ABSTRACT

Spectrographic analysis has shown that large regional variations in Sr, Ba, St, Al, Ti, Co, Mn, Fe and Ni, occur in Corallian reef and subreef rocks between exposures in Oxford, Yorkshire, and northern Switzerland. Vertical variations between reef and subreef are also marked. Strontium values for the majority of samples studied are markedly higher than previously reported for Jurassic rocks, and lower than in similar rock types of recent age. A correlation of diagenetic and geochemical data throws some light on the timing and nature of the mechanisms which produce a net loss of strontium within rocks. Diffractometer analysis has shown the presence of a low ordered silicate gel in rocks collected from Oxford localities. Mossbauer spectroscopy indicates that large quantities of iron (&g ; 10,000 ppm) proxying for calcium, were introduced into these same rocks. This iron probably originated from an external source, and was introduced at the same time as the low ordered silica gel.