Chemical weathering plays an important role in sequestering atmospheric CO2, but its potential influence onglobal climate over geological timescales remains debated. To some extent, this uncertainty arises from thedifficulty in separating the respective contribution of sedimentary and crystalline silicate rocks to past weath-ering rates in the geological record; two types of rocks having presumably different impact on the long-termcarbon cycle. In this study, we investigate the use of rare earth element (REE) and neodymium isotopes (εNd)inleached iron oxide fractions of river sediments for tracing the origin of weathered rocks on continents. A newindex, called‘concavity index’(CI), is defined for measuring the degree of mid-REE enrichment in geologicalsamples, which enables the determination of the source of iron oxides in sediments, such as seawater-derived Fe-oxyhydroxide phases, ancient marine Fe oxides derived from the erosion of sedimentary rocks, and recentsecondary oxides formed in soils via alteration of crystalline silicate rocks or pyrite oxidation. Using this index,we demonstrate that theεNddifference between paired Fe-oxide and detrital fractions in river sediments (definedhere asΔεNd Feox-Det) directly reflects the relative contribution of sedimentary versus crystalline silicate rocksduring weathering. While rivers draining old cratons and volcanic provinces display near-zeroΔεNd Feox-Detvalues indicative of dominant silicate weathering (0.5 ± 1.1;n= 30), multi-lithological catchments hostingsedimentary formations yield systematically higher values (2.7 ± 1.2;n= 44), showing that sedimentary rockweathering can be traced by the occurrence of riverine Fe oxides having more radiogenic Nd isotope signaturescompared to detrital fractions. This assumption is reinforced by the evidence that calculatedΔεNd Feox-Detvaluesagree well with previous estimates for carbonate and silicate weathering rates in large river basins.Examining the influence of climate and tectonics on measured Nd isotopic compositions, wefind thatΔεNdFeox-Detis strongly dependent on temperature in lowlands, following an Arrhenius-like relationship that reflectsenhanced alteration of silicate rocks and formation of secondary Fe oxides in warmer climates. In contrast, inhigh-elevation catchments,ΔεNd Feox-Detdefines striking correlation with maximum basin elevation, which wealso interpret as reflecting the intensification of silicate weathering and associated Fe oxide formation as ele-vation decreases, due to the combined effects of thicker soils and warmer temperature.Overall, our newfindings are consistent with previous assertions that the alteration of sedimentary rocksprevails in high-elevation environments, while silicate weathering dominates infloodplains. This novel approachcombining REE and Nd isotopes opens new perspectives for disentangling the weathering signals of sedimentaryand crystalline silicate rocks in the geologic record, which could be used in future studies to reassess the causalrelationships between mountain uplift, erosion and climate throughout Earth's history.