Early Holocene and Late Pleistocene slip rates of the southern Dead Sea Fault determined from ¹⁰Be cosmogenic dating of offset alluvial deposits

Abstract

[1] Two sites located along the Wadi Araba Fault (WAF) segment of the Dead Sea Fault are targeted for tectonic-morphological analysis. 10 Be cosmogenic radionuclide (CRN) dating of embedded cobbles is used to constrain the age of offset alluvial surfaces. At the first site a 48 ± 7 m offset alluvial fan, for which 10 Be CRN model ages average 11.1 ± 4.3 ka, yield a slip rate of 5.4 ± 2.7 mm/a, with conservative bounds of 1.3-16.4 mm/a. At the second site the scattered distributions of the 10 Be CRN ages from an offset bajada attest to the complex processes involved in sediment transport and emplacement. There, two offsets were identified. The 160 ± 8 m offset of an incised alluvial fan dated at 37 ± 5 ka shows a slip rate of 4.5 ± 0.9 mm/a, with a conservative minimum value of 3.2 mm/a. A larger offset, 626 ± 37 m, is derived from a prominent channel incised into the bajada. Cobbles from the bajada surface have ages from 33 to 141 ka, with a mean of 87 ± 26 ka. A slip rate of 8.1 ± 2.9 mm/a is derived from the mean age, with conservative bounds of 3.8-22.1 mm/a. These results and other published slip rates along the linear WAF segment, from GPS to geological time scales, lack the resolution to fully resolve the question of temporal variations versus consistency of the fault slip rate of the WAF. Yet, given the uncertainties, they are not inconsistent with each other.

Variable behavior of the Dead Sea Fault along the southern Arava segment from GPS measurements

“…2). The slip rate of about 5 mm/yr proposed by geodetic studies along the southern part of the DSF is consistent with paleoseimological and geomorphological studies (Klinger et al, 2000;Le Bé on et al, 2010Niemi et al, 2001). Historical records document the strong earthquake potential of the southern DSF, despite a general seismic quiescence over the past few centuries (Ambraseys et al, 1994).…”

Quaternary morphotectonic mapping of the Wadi Araba and implications for the tectonic activity of the southern Dead Sea fault

“…Relative ages of alluvial surfaces can be distinguished as a function of surface height above active streams, degree of incision by surficial rills and regressive gullies, surface darkness and geometric relationship between the deposits [e.g., Klinger et al , 2003; Le Béon et al , 2010]. For example, darker surfaces, related to desert varnish and desert pavement, typical in arid areas, indicate older surfaces [ Bull , 1991; Quade , 2001].…”

“…These different studies converge to a mean value of 4–6 mm/yr between present and 20 Ma ago. Some, however, suggest that the slip rate could have been as high as ∼10 mm/yr during the late Pleistocene [ Klinger et al , 2000a; Le Béon et al , 2010].…”

Quaternary tectonic evolution of the Northern Gulf of Elat/Aqaba along the Dead Sea Transform

“…North of the GEA, the DST passes along the Arava (Wadi 'Arabah) Valley. Mapping of offset surface features, aided by field observations, aerial photo analysis, and paleoseismic trenches [e.g., Zak and Freund , ; Garfunkel et al ., ; Ginat et al ., ; Klinger et al ., , ; Niemi et al ., ; Le Béon et al ., , ] and recent gravimetric and magnetic studies [ Haberland et al ., ; ten Brink et al ., ] revealed that the DST traverses the central Arava Valley predominantly as a single, almost continuous, sinistral strike‐slip fault. Modeling of gravity and magnetic data [ ten Brink et al ., , ], and seismic profiles [ Frieslander , ] revealed separate longitudinal basins along the Arava Valley.…”

“…Generalized tectonic settings of the Dead Sea fault or transform (DST) [modified after Le Béon et al ., , and references therein]. The DST separates the Arabian Plate from the Levantine Subplate.…”