Tectonic geomorphology and rates of crustal processes along the Red Sea margin, north-west Yemen

Abstract

The geomorphology of an extended continental margin of the Red Sea is examined in north-west Yemen where there are tight constraints on the temporal evolution of the margin from the start of plume volcanism at 30.5 Ma through to the present day. Red Sea rifting was preceded by impingement of the Afar plume which produced a large range of mountains reaching up to 3.7 km above MSL. A new drainage system has evolved from an elevated flat plateau since plume-related volcanism and uplift began. The main wadis have deep incised valleys which run almost perpendicular to the Red Sea coastline and major extensional faults, indicating that gravity is the main control on their orientation. The rate of surface uplift in the region since 30.5 Ma has averaged at least 0.08 mm/year as pre-volcanic Late Cretaceous/Tertiary marine sandstones are now situated at an elevation of up to 2.65 km above MSL. The resultant denudation was sufficient to produce enough sedimentation to continu- ally fill the accommodation space created by subsidence and extension along the margins of the Red Sea. Up to 8 km of clastic sediments and evaporites have been deposited since early Miocene times (approximately 24 Ma) in the Red Sea. This material indicates that an average of 3 km of denudation has taken place across the Yemen Highlands, implying that the original volcanic rock volume may have been up to three times larger than that preserved at the present day.