What does a mean mean? The temporal evolution of detrital cosmogenic denudation rates in a transient landscape

摘要: In equilibrium landscapes, 10 Be concentrations within detrital quartz grains are expected to quantitatively refl ect basin-wide denudation rates. transient though is derived from both the incising, adjusting lowland and unadjusted, relict upland, integrated still provide a rate averaged across two domains. Because fi eld samples can only snapshot of current upstream-averaged erosion rate, we employ numerical landscape evolution model explore how Be-derived rates vary over time space during adjustment. Model results suggest that longitudinal pattern mean generated by river’s progressive dilution low-volume, high-concentration detritus uplands integration high-volume, low-concentration lowlands. The proportion these materials in any sample depends on what fraction upstream area remains unadjusted. boundary part changes time, trend cosmogenic nuclide‐derived time. These insights then used guide our interpretation geomorphic nuclide data South Fork Eel River (SFER) California Coast Range (United States). northward-propagating crustal thickening rock uplift associated with passage Mendocino triple junction generates mobile wave progressively sweeps longitudinally down SFER. consequences this forcing be replicated environment observed eld. SFER contains landforms including knickpoints river terraces along mainstem tributary channels defi ne clear between an incised, upland. We report nine nested, using terrestrial river-borne sediment. nd increase downstream direction ~0.2 mm/yr upper catchment ~0.5 at outlet. Using comparisons modeled landscape, show rates, paired distribution topography throughout watershed, immaturity landscape’s Later transient, predicted decrease before they become uniform. This has potentially far-reaching implications for quantifying history response landscapes nuclides.