Fault reactivation and rift localization: Northeastern Gulf of Aden margin

Abstract

The Gulf of Aden and the Sheba spreading ridge (Gulf of Aden) forms the southern boundary of the Arabian Plate. Its orientation (075°E) and its kinematics (about 030°E divergence) are interpreted as the result of an oblique rifting. In this contribution, a field study in the northeastern Gulf of Aden allows us to confirm the Oligo‐Miocene synrift directions of extension and to precise the normal fault network geometry. The synrift extensions are 020°E and 160°E (possibly in this chronological order); the normal faults strike 070°E, 090°E, and 110°E. The results show that some characteristics are consistent with oblique rifting analogue models, while some others are not. Especially, fault reactivation of Mesozoic structures is shown to have occurred significantly at the beginning and during rifting. These data are therefore compared to analogue models of oblique reactivation, and this comparison demonstrates that fault reactivation played a key role during the early stage of the Gulf of Aden rifting. Finally, scenarios of the lithospheric evolution during the eastern Gulf of Aden opening (preexisting weaknesses in the lithosphere or not) are discussed to better constrain the deformation history of the northern margin. Especially, we show that rift localization processes may imply stress rotations through time.

Complex rift geometries resulting from inheritance of pre-existing structures: Insights and regional implications from the Barmer Basin rift

“…Complex fault-networks and zig-zag geometries occur where pre-existing structures interact with the evolving, rift-generated faults (e.g. Morley, 1995;Morley, 1999;Morley et al, 2004;Bellahsen and Daniel, 2005;Henza et al, 2010Henza et al, , 2011. The average 15 component of sinistral oblique-slip of west-striking faults, compared with the normal-sense dip-slip of southwest-striking faults, indicates that the former were non-ideal for extension, and are interpreted as being influenced by pre-existing rift-basement structures.…”

“…Morley, 1999) breach-faults, and facilitated displacement transfer between southwest-striking faults that accommodated greater displacement (e.g. Bellahsen and Daniel, 2005). The northwest orientated slip direction on both fault-sets suggests that mutualslipping occurred (e.g.…”

The rift to break-up evolution of the Gulf of Aden: Insights from 3D numerical lithospheric-scale modelling

“…Previously, the structural pattern of the Gulf of Aden has been elucidated thanks to field and seismic studies that were conducted onshore and offshore Oman (Fournier et al, 2004;d'Acremont et al, 2005;Bellahsen et al, 2006) and in Yemen (Huchon and Khanbari, 2003). They allow to recognise three general fault populations (i) displacement-normal with a fault azimuth of N115°E, (ii) rift-parallel with N075°E and (iii) an orientation that is intermediate in between the two former directions (N095°E).…”

“…They allow to recognise three general fault populations (i) displacement-normal with a fault azimuth of N115°E, (ii) rift-parallel with N075°E and (iii) an orientation that is intermediate in between the two former directions (N095°E). The inversion of fault slip data sets allowed to compute stress tensors corresponding to several local directions of extension (N025°E, N160°E and N-S) in Oman (Lepvrier et al, 2002;Fournier et al, 2004;Bellahsen et al, 2006), in Yeme n (Huchon et al, 1991;Huchon and Khanbari, 2003) and on Socotra Island (Fournier et al, 2007). Offshore, near the OCT, both the faults and basins mainly strike perpendicular to the Gulf of Aden opening direction (d 'Acremont et al, 2005).…”

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.…”