S. Mahmoud Hoseini-Nezhad

The Upper Devonian deposits are relatively thick and developed in eastern Alborz. These deposits are located in Shirband area which is attributed to Geirud Formation. Shirband Upper Devonian deposits are situated by a discontinuity with the same gradient on Mila Formation and also under Mobarak Formation. The thin limestone, shaly limestone, and shale layers of the Geirud Formation are gradually followed by thin limestone and shale layers of the Mobarak Formation. Study of conodont fossils in this section probably indicates continuity deposits between the Geirud and Mobarak Formations. On the basis of studying conodonts, seven standard biozones were determined with the Famennian age (arranged from oldest to youngest): 1—triangularis to linguiformis zone, 2—crepida zone, 3—rhomboidea zone, 4—trachytera to marginifera zone, 5—postera zone, 6—postera to expansa zone, and 7—praesulcata to sulcata zone. © 2014, Saudi Society for Geosciences.

The Tremadocian of the East Alborz Region is dominated by condensed fine clastic sediments. These beds have yielded low to medium diversity trilobite associations, which belong to the olenid, nileid and raphiophorid biofacies, characteristic of an outer shelf environment. Five successive trilobite biozones can be recognised in the Tremadocian succession of Alborz. The lower Tremadocian Asaphellus inflatus-Dactylocephalus and Psilocephalina lubrica zones are characterised by medium diversity trilobite associations with strong links to contemporaneous faunas of South China. Three upper zones are documented in the section at Gerd-Kuh, the successive Vachikaspis insueta and Kayseraspis zones represent a low diversity interval during a time of rapid changes in the sea level changes; the medium diversity fauna of the Asaphellus fecundus-Taihungshania miqueli zone shows strong links to the faunas of Mediterranean segment of Gondwana. Brachiopods in Gerd-Kuh are represented by the monotaxic Tarfaya Association and the low diversity Paralenorthis-Xinanorthis Association. The recurrent oligotaxic Protambonites Association invaded the area in the late Tremadocian during short term regressive episodes. © 2015, Micropaleontology Press. All rights reserved.

The latest Carboniferous-Early Permian Dorud Group in the Chaman-Saver area of eastern Alborz, Iran is more than 222m thick and includes thick sequences of oncolitic limestone, sandy limestone, sandstones and shales. The Emarat and Ghosnavi formations of this Group are dated here as latest Gzhelian to early Sakmarian Stages. During the Asselian Stage, the sea level fell abruptly and epeirogenic episodes occurred. These events generated a broad, shallow carbonate platform suitable for the growth and diversity of smaller foraminifers in the Chaman-Saver area which, consequently, displays faunal differences with the rest of the Alborz Mountains. Three foraminiferal biozones are proposed: Nodosinelloides potievskayae-Vervilleina bradyi Zone (latest Gzhelian), Calcitornella heathi-Nodosinelloides sp. Zone (latest Gzhelian-Asselian), and Rectogordius iranicus n. gen. n. sp.-Hemigordius schlumbergeri Zone (early Sakmarian). The new taxa described herein include: Pseudovidalina iranica n. sp., P. damghanica n. sp., Rectogordius iranicus n. gen. n. sp. and Tezaquina sp. 1. © 2012 John Wiley & Sons, Ltd.

A low diversity Lower Ordovician trilobite assemblage is described from the middle part of the Lashkarak Formation at Simeh-Kuh, northwest of Damghan, northern Iran. Co-occurrence with conodonts of the lowermost Paroistodus proteus Biozone suggests an uppermost Tremadocian age. This assemblage includes four taxa, including one new genus and two new species, Damghanampyx ginteri nov. gen. nov. sp. and Asaphellus fecundus nov. sp. The third diagnosable species from the formation is Taihungshania miqueli (Bergeron, 1894) which has previously been reported from southern France and the Turkish Taurides, suggesting north Gondwanan faunal affinities. © 2007 Elsevier Masson SAS. All rights reserved.