Constraining the evolution of river terraces with integrated OSL and cosmogenic nuclide data

We present a framework for consistent incorporation of optically-stimulated luminescence dates with cosmogenic radionuclide concentrations measured in a single alluvial section, and apply it on two late Quaternary terraces in the Negev Desert, Israel, to derive constraints on their evolution. We solve an integrated, self-consistent and co-dependant set of equations to reproduce either dataset based on three model parameters of (i) uniform cosmogenic inheritance, (ii) constant terrace aggradation rate and (iii) subsequent exposure time. A subset of all possible parameter combinations, which approximates the measurements within the uncertainties of their best-fits, yields a better constraint of the alluvial history than that obtained by any of these dating proxies alone. The derived set of common solutions indicates similar paleo-inheritances of ∼1 × 10^{5 10}Be atoms g^-1 in both terraces; progressive deposition of the higher terrace (T2) began at ∼250 ka, lasted for a period of ∼80 ka, was abandoned at ∼170 ka and since that time has remained intact; the lower terrace (T1) was most likely deposited at ∼3 ka and rapidly abandoned by ∼2 ka. In an alternative interpretation for T2, which treats the two geochronometers separately, this terrace might have experienced discrete events of aggradation at (216 ± 13) ka and deep truncation at 118-29+42 ka, significantly separated in time. In the currently active channel of the Neqarot canyon, contemporary stripping of the lowest terrace located along the stream is suggested by decreasing values of ¹⁰Be downstream along the river channel.