Analysis of Middle Jurassic course grain deposits, in the East of Kopet-Dagh Basin, Iran

رخساره‌های رسوبی

Article 3, Volume 4, Issue 2, June 2011, Pages 135-150   

Document Type: مقالات پژوهشی

DOI: 10.22067/sed.facies.v4i2.9888

Authors

Mehdi Reza Poursoltani^* ; Mostafa Kargar

Abstract

Kashafrud Formation, siliciclastic strata, Middle Jurassic in age, commences with basal fluvio conglomerates. The strata are described in terms of 3 facies association (conglomerate, sandstone and mudstone), which were deposited in a fluvio-deltaic and turbities environments. The basal Kashafrud strata at 2 areas (8 sections), in the eastern Kopet-Dagh basin, consist predominantly of boulder to pebble conglomerate, locally interbedded with sandstone and shale, has been studied. The thickness of facies association ranges from 2.8 m at Agh-Darband section to 27 m at Pol-Gazi section. The basal association comprises 2 gravely lithofacies (Gcm, Gmm), and 3 sandy lithofacies (Sm, St, Sr), and 2 architectural elements (SB, GB). Imbrication of gravels indicates a generally northerly paleoflow for the studied sections. Clast-supported conglomerate is mostly orthoconglomerate, composed mainly of rounded to angular and poorly to very poorly sorted clasts of volcanic and sedimentary rocks, up to 40 cm in diameter. The facies is present in bed sets up to 9 m thick, which mainly rest on erosional surfaces that are locally concave-up, implying that the conglomerates are channel fills. The beds are crudely stratified, with bedding defined by layers of sand and shale. Matrix-supported conglomerate (paraconglomerate) forms units up to 1m thick, which only at Agh-Darband section has been identified, with clasts up to 50 cm in diameter composed entirely of the locally adjacent volcanic basement rocks.

Keywords

Conglomerate; Middle Jurassic; Kashfrud; Iran