The past of a future syntaxis across the Zagros

Abstract Longitudinal components of the Zagros mountain chain change in character and width across N-S trending zones of strike-slip transfer faults lying between 51° and 54°E. To the northwest, a fold-thrust belt with consistent SW vergence has a width of c. 220 km in front of an imbricate belt c. 160 km wide. To the southeast, an imbricate zone c. 80 km wide is fronted by a gently tapering festoon of upright periclines that is c. 350 km wide and punctured by over a hundred emergent salt diapirs. Pre-Zagros stages of the transfer zones in the Zagros are preserved on the Arabian platform and the two most obvious bound what we call the incipient Qatar syntaxis. This is at an early stage of one of the many syntaxes that compartmentalize the Alpine-Himalayan mountain chain. We use structures in the Hormuz salt to map and gauge the tectonic pulse of basement blocks that jostled as ocean basins opened and closed diachronously like zip fasteners along the Tethyan margin of Gondwana. This incipient syntaxis was a lithospheric key that went up while others went down during the rifting and riffling, but not drifting, of the still-born Hormuz basin we call Proto-Tethys.