Possible Basement Transverse Faults in the Western Alborz, Northern Iran

Transverse basement (TB) faults are important structures in the mountain belts or sedimentary basins influencing various aspects of them. The origin of these faults is diverse, but their effect on the shape and configuration of continental margins is characteristics. The Western Alborz range that borders the South Caspian basin to southwest is a complex range with principal faults and known earthquakes such as 1990 Rudbar (Mw 7.3). However, TB faults are less known in this range. This paper attempts to compile available data from aeromagnetic survey, local geology maps, tectonic maps, remote sensing and earthquake data to introduce several important TB faults or lineament in the Western Alborz. Qezel Owzan-West Talesh, Lahijan-Sepidrud, Takestan-Polrud and Valian-Hezar are large TB faults or lineaments across the Western Alborz. Some of introduced TB faults and lineaments are possibly continuing within the South Caspian basin. The TB faults introduced or assessed in this paper are more or less correlating with irregularities of the northern margin of the Alborz Range. This correlation is clearer for the Lahijan-Sepidrud TB fault, F-1lineament and to a lesser degree for Amlash, Polrud-Takestan and Valian-Hezar lineaments. Detail geometry, origin, effect on sedimentation along the continental margin and their relationship with huge regional magmatism in the Cretaceous and Eocene in the Western Alborz suggested subjects for further investigations on these faults and lineament.