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 × 105 10Be 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.
Bibliographical noteFunding Information:
We thank Michael Davis for significant contribution both in fieldwork and OSL measurements, Nadia Teutsch for the ICP-MS analyses, and Yaakov Refael for technical assistance. BG thanks Ezra Zilberman for inspiring discussions, Dad for participation in fieldwork and statistical advice, and Frédéric Herman for an opportunity to present an early draft of this work at a seminar in ETH. We thank Ed Nissen and an anonymous reviewer for thoughtful comments that significantly improved this manuscript. This research was funded by ISF grant 188/06 and the Lady Davis Foundation.
- Aggradation rate
- Cosmogenic inheritance
- Cosmogenic isotopes (Be)
- Intercomparison of dating proxies