Browsing by Author "Guralnik, B"

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    10Be exposure ages of ancient desert pavements reveal Quaternary evolution of the Dead Sea drainage basin and rift margin tilting
    (Elsevier, 2010-02-15) Guralnik, B; Matmon, A; Avni, Y; Fink, D
    Early to late Pleistocene 10Be exposure ages of abandoned surfaces in the Negev desert reveal the regional drainage evolution history and its relationship with the subsidence of the western margin of the Dead Sea Rift. The dated desert paved surfaces have developed over originally westward-flowing rivers, which were abandoned by early Pleistocene and whose relicts are now progressively tilted towards the rift axis. The slow and non-destructive subsidence coupled with extreme hyperaridity enabled the preservation of these ancient surfaces along some of the main water divides in the Negev, nearly irrespective of their distance from the rift axis. Constraints on the tilting history are obtained from analyzing the spatial pattern of the exposure ages, suggesting subsidence rates as low as 120–300 m Ma–1 in the southern Arava Valley since the late Pliocene. It is shown that the transition from the Pliocene to current drainage pattern occurred over a short period during the early Pleistocene, and that the governing fluvial response that followed the delineation of current basins is represented by a continuous spectrum of ages of inset terraces.
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    Constraining the evolution of river terraces with integrated OSL and cosmogenic nuclide data
    (Elsevier, 2011-02) Guralnik, B; Matmon, A; Avni, Y; Porat, N; Fink, D
    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 +42 -29 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. © 2010, Elsevier Ltd.