Possible sources of clastic sediment in the Late Proterozoic Torridon Group, from geochemical mass balance

Abstract

AbstractEquations are derived which link the content of relatively insoluble components Si, Al, Fe and K in source rock and derived alluvial sediment. The equations also involve the ratio of specific suspended load to dissolved loadand specific bed load to suspended load (Tb/Ts) for the rivers which deposited the sediments. These ratios are generally unknown, but by analogy with modern rivers are taken to occupy the rangesand 0 ≦Tb/Ts≦1. This is sufficient to put close limits on the possible composition of the source rock. The equations suggest that clastic sediment forming the Late Proterozoic Torridon Group of Scotland was derived from sediments or metasediments, rather than fromaverageupper continental crust, granitoids or gneisses like those presently exposed nearby.