Writers : Eftekharnegad,Jamshid;Behrouzi,Argang
Refference : Geosciences Scientific Quarterly Journal,No.1
Publishing Year : 1370

Abstract :

New findings were obtained during a mapping campaign carried out recently (1985-1988) by a team of the Geological Survey of Iran in the northern part of the Torbat_e_Jam Quadrangle Map. These findings are reported and discussed here as far as they are relevant to the Aghdarband area.
_ The rocks exposed to the north of the Triassic of Aghdarband ("Northern Frame") comprise a sequence from the Upper Devonian (Upper Frasnian) to the Lower Carboniferous (Tournaisian). This sequence corresponds to the Geirud Formation and Mobarak Limestone (Central Alborz Mountains), and to upper parts of the Khoshyeilagh Formation (Eastern Alborz Mountains), respectively.
_ Oceanic sedimentary and volcanic rocks outcrop below their Jurassic coverbeds 50 kilometers southwest of Aghdarband along the north_eastern side of the Mashhad_Fariman_Torbatjam depression. Metamorphosed shales and siltstones_ the latter showing turbidity features_, radiolarites and radiolarian red shales are exposed at the whole length between Mashhad and the Afghan border, together with spilitic diabase_partly showing pillow structures-and andesite as well as with ultrabasic rocks. The grade of metamorphism decreases from Mashhad towards southeast. Two structural units can be distinguished. Bodies consisting of sparry limestone interposed in the lower unit yielded an Early Permain microfauna. Ophiolitic rocks of melange character are exposed in the southwestern cor ier of the erosional Window of Aghdarband, 15 km WSW of the village Aghdarband (Darreh Anjir). There, a limestone block yielded a microfauna of late permian age.
_ A thick sequence consisting of red (and green) shales, sandstones and conglomerates, informally named Qara Gheitan Formation, is exposed in the area to the south of the Aghdarband area. Its Early Scythian age is indicated by limestone pebbles containing microfaunas of Carboniferous and Late Permian age, and by its position below the Late Scythian Sefid Kuh Limestone Formation. Basal parts of the Qara Gheitan Formation rest transgressively on ultrabasic rocks at Darreh Anjir.
- Both the deformation and the metamorphism in the zone situated to the north of the Fariman_Torbatjam lineament is attributed to the Kimmerian orogeny.
_We consider kopet Dagh to be the extreme NW_margin of the epi_Baikaliar Afro-Arabian Paleozoic Platform, and we can not find any evidence of a Hercyniar Orogeny as it is defined with reaard to the Turan Plate.