Early spreading and continental to oceanic basement transition beneath the Indus deep-sea fan: northeastern Arabian Sea

• Published in: Marine geology 1997-09, Vol.141 (1), p.221-235
• Main Authors: Malod, J.A., Droz, L., Kemal, B. Mustafa, Patriat, P.
• Format: Article
• Language: English
• Subjects: Arabian basin; continental margin; Indian Ocean; magnetic anomaly; Marine; oceanic spreading; rifting; seismic reflection
• ISSN: 0025-3227; 1872-6151
• DOI: 10.1016/S0025-3227(97)00074-1

A seismic survey to study the Indus deep-sea fan penetrated into basement. This enabled the mapping of basement structures and a description of the geodynamical evolution of a part of the northeastern Arabian Sea. The main tectonic structure of the basement is an E-W graben (Gop rift) with a prominent central E-W horst, the Palitana horst. This rift is cut obliquely by several NE-SW faults. Large E-W magnetic anomalies are not the continuation of the magnetic anomaly sequence of the oceanic Arabian basin. However, these anomalies are linked to inverse magnetisation in the crust, suggesting that the rift is either underlain by stretched continental crust intruded by linear volcanic bodies, related to the Deccan Traps, or by oceanic crust older than chron 28 (64 Ma) as proposed in the Laxmi basin southeastwards. Accompanying these structures, NE-SW faults with a strike slip pattern may have played the role of transform direction during the separation of the Laxmi ridge from the Indian continent. We propose that rifting and oceanic spreading have occurred around a triple junction connecting the oceanic Laxmi basin, the Narmada Son lineament and the Gop rift. This phase preceded oceanic spreading in the Arabian basin. This interpretation is in agreement with the previously proposed initial separation of India and the Seychelles before chron 28. The Laxmi ridge could be a part of the Seychelles microplate subsequently left attached to India.