An evaluation of flysch provenance - example from the Gramscatho Group of south Cornwall
Proceedings of the Ussher Society
The Ussher Society
Recent work has suggested that plate tectonic environments can be reconstructed utilizing clast mode petrography and bulk geochemistry of flysch sandstones. An assessment of the relative effects of processes that may modify sedimentary composition is made by examining the clast modes, bulk geochemistry and general petrography within a graded turbidite unit of the Gramscatho Group. Within the medium-fine sand lower half of the turbidite unit, clast mode variation is limited. The geochemistry of the sample suite is dominated by the non-framework matrix mineralogy with progressive element enhancement in the more muddy fractions of the unit. Although variations in element absolute abundances occur as a function of grainsize-related matrix content, the ratios of many element pairs (e.g. Ti-K, Cr-Y) remain constant, implying no major change in matrix composition through the unit. Diagenetic, metamorphic and microstructural effects are the dominant controls on the modification of original sediment composition. These processes are qualitatively evaluated in terms of the relative effects they will have on the endmember compositions of the various provenance diagrams.
Vol. 7 (1), pp. 62 - 66