A QUANTITATIVE APPROACH TO SOIL OCCURRENCE IN ALLUVIAL DEPOSITS AND ITS APPLICATION TO THE OLD RED SANDSTONE OF BRITAIN

Palaeosols (fossil soils) are a major component of alluvial deposits i n the geological record. Not only do these typically show considerable variations in their degrees of development within single formations, but they also exhibit highly complex stratigraphic relationships with one another. A simple quantitative approach to these variations is pre sented which provides a graphical means of assessing differences in so il (palaeosol) development within a sequence with calcic or petrocalci c horizons. To illustrate the approach, a range of palaeosols from the Siluro-Devonian (Old Red Sandstone) of Britain are characterized in t erms of the likely frequency and magnitude of depositional events whic h occurred during their formation. In particular, two alluvial suites from the Manorbier area of South Wales are analysed using this approac h. The technique should be widely applicable to other alluvial success ions and provides a means of graphically presenting relationships betw een multiple palaeosols, although the wide range of rates of formation of calcic and petrocalcic horizons precludes their use to provide nar row estimates of deposition rates.