Temporal and spatial relations between large-scale fault systems: Evidence from the Sinai-Negev shear zone and the Dead Sea Fault

Abstract

In the major zones of crustal deformation within the Arabia-Sinai-Nubia plates, the interactions between the Sinai-Negev Shear Zone (SNSZ) and the Dead Sea Fault system (DSF) shed light on the interplay between neighboring, large-scale fault systems.The SNSZ is composed of several ~E-W to ENE–WSW trending, mainly normal and dextral, strike-slip faults that are tens to hundreds of kilometers long. These faults form a ~ 120 km wide shear zone in the Sinai sub-plate. On reaching the plate-bounding Dead Sea Fault system (DSF), individual lineaments of the SNSZ are observed in the Arabian plate offset left-laterally by 105 km, which is the total estimated offset of the DSF. In this contribution, we review the geologic setting of the SNSZ and its complex relations with the DSF in light of newly obtained age-strain analyses. For this we use in-situ U-Pb geochronology in conjunction with twin analysis of syn-faulting calcite from both systems. The results indicate that the deformation along the SNSZ initiated in the Campanian-Maastrichtian or earlier, as the oldest dates are 73–71 Ma. The main phase of fault activity began in the late Oligocene – early Miocene (27–22 Ma) as documented by numerous dates that were obtained along several lineaments of the SNSZ. The activity continued until ~10 Ma, after which no direct ages have been obtained. The dominant phase of activity along the SNSZ at 27–22 Ma preceded the timing of initiation of lateral faulting along the DSF at ~20–18 Ma by a few Myr. For the overlapping period of activity between 20 and 10 Ma, episodes of fault activity along the SNSZ followed by episodes of fault activity along the DSF. Moreover, dominant episodes of activity along one fault system were associated with a decrease in activity along the other system. The temporal relations between the SNSZ and DSF highlight the possibility that these fault systems are mechanically interrelated, but the exact mechanism for this fault interaction needs further study.We consider the paleo-strain (or paleo-stress) that control the evolution and style of the SNSZ and assess them at the central Sinai-Negev region during the Cenozoic. We show that the formation of new plate boundaries at the region, i.e., the Red Sea - Suez rift and the DSF, affected the strain field within the SNSZ. The proximity of the two systems indicates that the DSF-related stress originated within the SNSZ and possibly caused structural and style changes in the latter system. Syn-faulting calcite-twins analyses within the SNSZ show pronounced spatial and temporal variations of the principal strain directions between and along individual faults. This observation demonstrates that the imposed stress within the central Sinai-Negev were not uniform over time. The high angle (>70o) between the traces of the SNSZ and the direction of the DSF-related maximum shortening likely suppressed the dextral motion along the SNSZ post-20 Ma. Field evidence, U-Pb dates, and recent seismicity shows that the current SNSZ is a long-lived structure that has been active during the Miocene alongside the dominantly DSF and may still be sporadically active today.