Evolution of the Red Sea Continental Margin from Integrated Analyses of Gravity, Magnetic, and Receiver Function Observations

Abstract:

The development of evolutionary models and constraints for the extensional mechanisms which govern continental rifting is of fundamental significance toward understanding the breakup of continents and the role of volcanism in achieving successful rifting. To analyze the transitional nature of the Red Sea rift (RSR) passive margins and to quantify the mechanism through which extension has been accommodated, we examined a total of 3531 high-quality radial receiver functions from multiple temporary deployments in Saudi Arabia and the Levant as well as data recently acquired by the Egyptian National Seismic Network. Egypt is characterized by a relatively constant crustal thickness of approximately 37 km, while the southern Arabian Shield is roughly 35 km on average. The crust beneath the Eastern Desert of Egypt is significantly thinned with an average thickness of about 26 km. Observations of V_p/V_s across the Arabian-Nubian Shield indicate highly similar intermediate to mafic compositions, supporting well-accepted theories for juvenile arc accretion of relatively uniform makeup. Thinned crust as far as 130 km inland on the Egyptian margin indicates a highly asymmetric crustal structure across the Red Sea, supporting a model invoking simple shear extensional mechanisms. Joint modeling using satellite gravity and magnetic data with RF Moho depth constraints reveals the presence of high-density high-magnetic susceptibility mafic complexes which we interpret as volcanic margins in the northern RSR at ~25.5°N and the southern RSR at ~19.5°N. We believe the development of the northern RSR margin is accompanied by isolated volcanism associated with slow spreading rates since the Oligocene.