Geosciences Dept. PhD Seminar: Strain field along the Dead Sea Fault, revealed by magnetic fabrics of carbonate rocks

Abstract:

In order to reconstruct the strain field along the southern segment of the Dead Sea Fault (DSF), we measured and analyzed the magnetic fabrics of carbonate rocks, outcropping along the DSF. We measured the magnetic fabrics of (1) pure calcite-bearing limestones that consist diamagnetic fabrics, and (2) chalks that consist composite fabric of calcite (diamagnetic sub-fabric) and clays (paramagnetic sub-fabric). Using low-temperature Anisotropy of Magnetic Susceptibility (AMS) measurements, we separated the diamagnetic sub-fabrics from the composite fabric. The results of 61 sampling localities, corresponding to ~1000 core samples, indicate that 87% of the diamagnetic fabrics (limestone) and diamagnetic sub-fabrics (chalk) along the DSF are of tectonic origin, and therefore are extremely sensitive strain indicators. The magnetic fabrics suggest that maximum horizontal shortening directions along the southern segment of the DSF differ from the remote direction and are commonly parallel to the DSF. This parallelism characterizes the entire southern segment of the DSF and is not related to the geometry of the faults. We suggest that the deflection of the maximum horizontal shortening parallel to the transform plate boundary is a kinematic consequence of Sinai-Arabia plates and expressing a component of divergent motion along the southern section of the DSF. We show that magnetic fabrics of carbonate rocks are sensitive and reliable micro-structural indicators for determination of strain field along major fault systems.

Seminar Organizer: Prof. Eyal Haifetz