CARLMAG and VARUNA cruises are part of a continuing program of geological and geophysical studies of the eastern terminus of the Gulf of Aden and its junction with the Owen Basin, which began around ten years ago with our partners at ISTeP (SU). The objective is to characterize the fault system that accompanied the convergence of the Indian plate towards Eurasia and its sliding along Africa and Arabia, particularly after the Himalayan collision. The studied area includes the fossil Owen Fracture Zone, and the intersection of the active Owen transform fault with the Carlsberg Ridge. This Owen/Carlsberg system was discussed in Tuzo Wilson's seminal paper on transform faults, 'A new class of faults and their bearing on continental drift' published in Nature in 1965. Due to increased piracy since 2005, few modern oceanographic vessels have worked in the region.  Neither the Owen transform fault, one of the 10 largest oceanic transform faults, nor its intersection with the end of the Carlsberg Ridge had been the subject of dedicated studies before CARLMAG and VARUNA cruises.

The aim was therefore to fill this gap using conventional geophysical surveys aboard the BHO Beautemps-Beaupré operated by the SHOM (Naval Hydrographic and Oceanographic Service), the only French oceanographic vessel available in these waters. The hypothesis put forward is that the Owen Fault / Carlsberg Ridge system has recorded major tectonic events since the beginning of the formation of the Himalayan chain: Eocene India/Eurasia collision, abandonment of the Wharton Ridge, Miocene opening of the Gulf of Aden, detachment of Somalia from Nubia, initiation of the intraplate oceanic deformation zone between India and Australia and uplift of the Owen Ridge around 8 Ma, reorganization of the India/Arabia boundary around 2-3 Ma.

CARLMAG and VARUNA missions have been very data productive, including multibeam bathymetric mapping, bottom reflectivity, high-resolution acoustic sounder of sediments, seismic reflection, magnetism, and gravimetry. The tectonic deformations mapped, imaged, and dated have enabled us to propose a coherent regional geodynamic scheme, characterizing the kinematic fluctuations and discussing their origin.