The geochemistry of river water, river sediments, and suspended matter in three mountainous watersheds in New Zealand and Taiwan is used to determine chemical erosion yields in regions of rapid tectonic uplift. Suspended matter from all three rivers is depleted in soluble alkali metals and alkaline earths compared to upper continental crust material and marine clays, reflecting the bedrocks' origin as marine sediments that had undergone previous weathering cycles prior to uplift and subjection to the current chemical weathering regime. The New Zealand rivers are depleted in Mg²⁺ and enriched in Ca²⁺ and Na⁺+ K^+...