Crustal geometry of the northeastern Gulf of Aden passive margin: localization of the deformation inferred from receiver function analysis

Abstract

S U M M A R YHere we use receiver function analysis to retrieve crustal thickness and crustal composition along the 35-My-old passive margin of the eastern Gulf of Aden. Our aims are to use results from the 3-D seismic array to map crustal stretching across and along the Aden margin in southern Oman. The array recorded local and teleseismic events between 2003 March and 2004 March. Seventy-eight events were used in our joint inversions for Vp/Vs ratio and depth. The major results are: (1) Crustal thickness decreases from the uplifted rift flank of the margin towards the Sheba mid-ocean ridge. We found a crustal thickness of about 35 km beneath the northern rift flank. This value decreases sharply to 26 km beneath the post-rift subsidence zone on the Salalah coastal plain. This 10 km of crustal thinning occurs across a horizontal distance of less than 30 km showing a localization of the crustal thinning below the first known rifted block of the margin. (2) A second rift margin transect located about 50 km to the east shows no thinning from the coast to 50 km onshore. The lack of crustal thickness variation indicates that the maximum crustal stretching could be restricted to offshore regions. (3) The along-strike variations in crustal structure demonstrate the scale and longevity of the regular along-axis rift segmentation. (4) Extension is still observed north of the rifted domain, 70 km onshore from the coast, making the width of margin larger than first expected from geology. (5) The crust has a felsic to normal composition with a probably strong effect of the sedimentary layer on the Vp/Vs ratio (comprised between 1.67 and 1.91).

Architecture of rifted continental margins and break-up evolution: insights from the South Atlantic, North Atlantic and Red Sea–Gulf of Aden conjugate margins

“…The OCT is also marked by rapid thinning of the crust (Leroy et al 2004;Tiberi et al 2007;Leroy et al 2012) and high values of heat-flow (Lucazeau et al 2008;Lucazeau et al 2010;Watremez et al 2011).…”

Lithospheric low-velocity zones associated with a magmatic segment of the Tanzanian Rift, East Africa

“…This error computation allows to quantify the widening of the objective function due to an azimuthal dependency, a complex geometry interface or noisy data. Following Tiberi et al (2007), two errors were computed: one to account for the scattering of the data set (Eb) and the second to consider the crustal P-wave velocity uncertainty (Evp). For Eb error, we computed a standard deviation and the 95 per cent ellipse error from 200 subsets of data processed with the H-k stacking method (Fig.…”

Do ridge–ridge–fault triple junctions exist on Earth? Evidence from the Aden–Owen–Carlsberg junction in the NW Indian Ocean

“…After rifting and break-up of the African continental lithosphere in the Aden rift (Lepvrier et al, 2002;Fournier et al, 2004Bellahsen et al, 2006;Petit et al, 2007;Tiberi et al, 2007;Gunnell et al, 2007), the nascent Sheba Ridge, first recognized by Matthews et al (1967) and Laughton et al (1970), rapidly propagated westward (~200 km/Ma), as indicated by the age of the oldest magnetic anomaly identified in the Gulf of Aden at the longitude of 54°E (An 5D, 17-18 Ma; Leroy et al, 2004;d'Acremont et al, 2006) and 51°E (An 5C, 16 Ma;Sahota, 1990;Huchon and Khanbari, 2003). Accretion at the Sheba Ridge is presently oblique at a poorly constrained full rate of about 2.5 cm yr -1 in its easternmost end.…”