10. Long-period cycles: A case study from the Arabian-Nubian Craton

Abstract

Publisher Summary This chapter discusses the long-period cyclicity and its causes within the Arabian–Nubian Craton since 640 Ma up till the recent. The Arabian–Nubian Shield occupies an area of 3 million km2, with outcrops in the following countries: Saudi Arabia, Yemen, Jordan, Palestine, Egypt, Sudan, Eritrea, Ethiopia, and Somalia. In the first three countries, it is called the “Arabian Shield” with extensive outcrops in Saudi Arabia, while in the latter five countries, it is known as the “Nubian Shield.” The Arabian–Nubian Shield is a late Upper Proterozoic feature. It was not present as a shield prior to about 650Ma BP. Consequently, it is rather a young feature as compared with the African cratons and other Archean cratons. Most workers agree that there are no rocks older than 1000–1200 Ma within the Arabian–Nubian Shield. The period between 1000–650 Ma was spent in the cratonization of the area occupied now by the Arabian–Nubian Shield, which involved three stages: First stage—the separation of the Mozambique Craton and the formation of an ocean in eastern Africa; Second stage–the formation of island arcs, subduction, accretion, erosion, sedimentation, magmatism, and metamorphism; and Third stage—the formation of the newly born Arabian–Nubian Shield by lateral accretion, suturing its segments, and continental collision as well. The period from 640 Ma onwards to the onset of the Phanerozoic witnessed extensive faulting, graben and horst formation, intermontane basins, etc., associated with the Najd Fault system.