Reply to Discussion on ‘Geological offsets and age constraints along the northern Dead Sea fault, Syria'

Abstract

We welcome discussion on the geology of the Dead Sea Fault in Syria but we have to disagree with Westaway's (2004, and discussion) mapping assumptions, his estimates of timing of fault slip, and his proposed offsets and slip rates. As he notes, our new 40Ar–39Ar ages on the basalts adjacent to the Dead Sea Fault significantly clarify and refine the chronology of the lavas. Westaway (2004) used the old whole-rock K–Ar ages of Mouty et al. (1992) in NW Syria to constrain timing of fault motion and slip rates. The dispute appears to relate to the interpretation of the relationship between the basalts and the strike-slip fault. Westaway suggests that the northern Dead Sea Fault was active before eruption of the lavas; our mapping clearly shows that the fault post-dates and cuts both the Coastal Ranges folding and the basaltic flows that unconformably overlie the folded Mesozoic sedimentary rocks. Westaway claims that the northern Dead Sea Fault in western Syria is transpressive not transtensional. This is difficult to understand when the northern Dead Sea Fault is split along the Al-Ghab depression, a classic rhomb-shaped transtensional basin where inward dipping normal faults (Searle et al. 2010, fig. 3a, e …