Seismic refraction profiles now number 9 in the Gulf of Aden and 15 in the Red Sea with a further intensive study by the Cambridge University group between latitudes 22 and 23°N. The results of these surveys indicate that the main trough of the Gulf of Aden is underlain by oceanic crust while only the deep axial zone and a questionable amount of the main trough of the Red Sea are underlain by oceanic crust. Seismic reflexion profiles reveal the nature of Layer 1 and the upper surface of Layer 2. A strong subbottom reflector is found beneath the main trough of the Red Sea at 0.5 km but is found to be absent in the axial zone. This survey together with the refraction work and geological evidence suggests a complex history for the main trough of the Red Sea. Reflexion profiles and dredging in the Gulf of Aden indicate that the thickness of sediments increases away from the central rough zone and that the sediment is underlain by volcanic material. |