History and paleogeography during the Pan-African orogen to stable platform transition: Reappraisal of the evidence from the Elat area and the northern Arabian-Nubian Shield

The ca. 70 Ma-long orogen to platform transition period in the northern Arabian-Nubian Shield saw marked changes in topography, tectonic regime, igneous activity, and sedimentation processes. Following a batholithic phase at the end of the orogenic period, fast erosion began ca. 610 m.y. ago and removed the upper 8-12 km of the orogenic edifice in <20 Ma, lowering the average relief by ∼2 km. Later the area was differentiated into basins and highs, and thick volcanic piles and thick immature molasse-like sediments formed, modifying the relief. Extension during this period is likely and it probably further reduced the relief, but this was not documented, while oblique compression is evident in places. Continuing igneous activity produced various magmas, mostly high-level alkali-rich (potassium-rich) plutons that seem to have been emplaced in a plutonic phase 580 ± 10 m.y. ago. This was followed by intrusion of extensive swarms of basaltic to rhyolitic dikes, indicating regional dilation (∼20 km). The following part of the transition period saw the decline of igneous (now having an intraplate character) and tectonic activity, which express progressive stabilization and cooling of the lithosphere. Locally, sediments and volcanics still formed but, generally, erosion dominated, though it was slower than before. This produced a uniform low-relief landscape on which extensive drainage systems formed, which (together with warming) promoted significant chemical weathering and transport of sediments over long distances (up to 1000 km). At the onset of the platformal stage, regional subsidence towards the (present) north eventually led to deposition of a widespread cover of mature sediments since the Early Cambrian (530-525 m.y. ago). South of the area of aggradation a vast peneplain developed, but it was buried as sedimentation gradually spread southward in the late Cambrian and still later.