Structure and evolution of the passive margin of the eastern tethys

Abstract

An extensive passive margin was formed in the Triassic along the periphery of Arabia, including the Tauric carbonate platform. This event is related to the opening of the Mesozoic Tethys when a number of microcontinents split off from Gondwana. Triassic extension and continental rifting resulted in the formation of a structural pattern which is uniform from the Dinarides to Oman. It includes the following elements: 1. (1) shelf, 2. (2) continental slope, 3. (3) deep basin probably with a floor of attenuated sialic crust, 4. (4) inner carbonate platform. In the Jurassic-Cretaceous stable conditions prevailed, influenced only by eustatic oscillations of the sea level. Turbidites accumulated on the continental rise while cherts and radiolarites were deposited in the deep basins (Hawasina, Pichakun, Antalya, Pindus) below the CCD level. Sedimentation on the shelf was controlled by north-northeast transverse tectonic elements which also continued across the passive margin, dividing it into a number of segments. Collision with an island arc led to obduction of the oceanic crust, deformation of the passive margin and overthrusting of its sedimentary cover onto the Arabian shelf. Obduction and deformation lasted for about 10 m.y. and created a new tectonic pattern with concentric structural zones surrounding the Arabian promontory. These zones include: 1. (1) the flysch basin—a remnant of the closing Tethys; 2. (2) an uplift—a site of periodical emergence and erosion, corresponding to the frontal part of the ophiolitic nappes; 3. (3) the Border furrow—a depocenter of low-energy calcareous marls, 4. (4) the Arabian shield constantly emerged during the Tertiary. Tectonic deformation of these zones caused by the collision of Arabia with Eurasia began prior to the Early Miocene and it is still going on. Data on Afghanistan demonstrate that its central part (the Gelmend-Argandab and Kabul blocks) belonged during the Paleozoic and Early Mesozoic to the continental shelf of India.