Abstract

Sediments are weathered pieces of rocks that are mixed in rivers (mostly) and transported to basins, becoming sorted along the way. This conceptual understanding of sediment formation has been generally understood for many years, although recent updates to this understanding are still made (e.g. the importance of cation exchange). Here I will show how this conceptual understanding can be represented using quantitative schemes to make predictions about sedimentary geochemistry and improve our understanding of Earth’s surface. First, I demonstrate a statistical method to describe the major-element composition of sediments in terms of the composition of their protolith and how intensely they have been weathered. Applying this method to large compilations of sediment compositions allows us to reconstruct the composition of the Archean continents, and produce a Phanerozoic history of weathering intensity. Second, I show how modern-day river sediments can be reliably predicted using a simple mixture model of their source regions. Finally, I show how this mixing model can be ‘inverted’, allowing higher order river sediments to be ‘unmixed’ to produce geochemical maps of their source regions.