Paleogene magnetic isochrons and palaeo-propagators in the Arabian and Eastern Somali basins, NW Indian Ocean

Abstract

We present a revised magnetic isochron map of the conjugate Arabian and Eastern Somali basins based on an up-to-date compilation of Indian, French, and other available seasurface magnetic data. We have used the magnetic anomaly and the modulus of the analytical signal computed from the magnetic anomaly to identify and precisely locate the young and old edges of magnetic chrons in both basins. In addition to the major, well-defined anomalies, we have also used correlatable second-order features of the magnetic anomalies, the 'tiny wiggles', to strengthen the interpretation. The resulting isochrons and tectonic elements have been validated using the stochastic method of palaeogeographical reconstruction. The magnetic anomaly pattern in both basins depicts clear oblique offsets, characteristics of pseudofaults associated with propagating ridge segments. Our tectonic interpretation of the area revealed: (1) a complex pattern of ridge propagation between Chrons 28n (c. 63 Ma) and 25n (c. 56 Ma), with dominant eastward propagation between Chrons 26n (c. 58 Ma) and 25n; (2) numerous, systematic westward propagations between Chrons 24n (c. 53 Ma) and 20n (c. 43 Ma); (3) asymmetric crustal accretion (caused by ridge propagation and asymmetric sea-floor spreading) in the conjugate basins during the whole period; (4) a slowing of India-Somalia motion after c. 52 Ma.

Early oceanic opening off Western India–Pakistan margin: The Gop Basin revisited

“…Widely observed highly reliable imprints of large scale ridge propagation in the area (Miles and Roest, 1993;Chaubey et al, 1998Chaubey et al, , 2002Dyment, 1998;Miles et al, 1998;Royer et al, 2002) indeed strengthen this inference.…”

“…Additional time constraints come from the adjacent Arabian Basin, where the seafloor spreading history is well established (e.g., Chaubey et al, 1998Chaubey et al, , 2002Dyment, 1998;Royer et al, 2002). Fig.…”

“…The conjugate Arabian and Eastern Somali basins (Northwestern Indian Ocean) have been formed by seafloor spreading along the Carlsberg Ridge since early Tertiary time; the Laxmi and Laccadive ridges mark the landward boundary of this oceanic crust in the Arabian Basin (McKenzie and Sclater, 1971;Norton and Sclater, 1979;Naini and Talwani, 1982;Schlich, 1982;Bhattacharya et al, 1992;Chaubey et al, 1993Chaubey et al, , 1998Chaubey et al, , 2002Miles and Roest, 1993;Miles et al, 1998;Dyment, 1998;Royer et al, 2002). However, between the Laxmi Ridge and the India-Pakistan continental shelf is a wide region of deep offshore, whose genesis and evolution still remains to be confidently established.…”

Seaward dipping reflectors along the SW continental margin of India: Evidence for volcanic passive margin

“…The latter was interpreted as due to densely spaced igneous intrusives and flows (Chaubey et al 2002b). Even though, the nature of crust of the ridge is equivocal (Bhattacharya and Chaubey 2001 and references therein;Verzhbitsky 2003), the recent studies suggest that the ridge is comprised of thinned continental crust, which was intruded-extruded by magmatic events during Madagascar-India continental rifting and passage of the Indian Plate over the Réunion hotspot (Murty et al 1999;Kothari et al 2001;Chaubey et al 2002aChaubey et al , 2008. The Arabian Basin, conjugate to the eastern Somali Basin, is located west of the Laccadive Ridge.…”

Geoelectric structure of northern Cambay rift basin from magnetotelluric data

“…The eruption of the DVP by the Reunion hotspot has been inferred as late syn-rift-tobreakup volcanism contemporaneous with the separation of the Seychelles and India ~ 65 Ma ago. As the Indian plate started moving northward, the adjacent offshore areas were influenced by the Reunion hotspot, resulting in various magmatic intrusions within the stretched continental crust of the WCMI (Bhattacharya and Chaubey 2001;Chaubey et al 2002;Royer et al 2002). The region was uplifted around the impingement location of the hot mantle plume and developed a four-way radially deviating mega-fracture pattern.…”