Italiana Paleontologia Stratigrafia November 2OOJ CARBONIFEROUS - PERMIAN STRATIGRAPHY AND FUSULINIDS OF EAST IRAN. GZHELTAN AND ASSELIAN DEPOSITS OF THE OZBAK-KUH REGION ERNST JA. LEVEN' &. AZIZOLAH TAHERI' Receit,ed March 25, 2002; accepted May 23, 20A3 Key-ttords: Carboniferous, Permian, Gzhelian, Asselian, fusuli- Introduction nids, stratigraphy, paleontology, East Iran. The most complete Carboniferous-Permian se- Abstract. Deposits of the Gzhelian-Asselian Stages were rec- quences of East Iran are exposed in the Ozbak-Kuh ognised by fusulinid occurrences in the upper part of the Sardar For- and Shirgesht areas (north of Tabas) and in the Kuh-e- mation (Zaladu Member) of the Ozbak Kuh region, East Iran. These Shotori (east and southeast of Tabas) (Stòcklin 1971). deposits cannot be referred to the Bage-Vang Formarion, which con- tains Bolorian fusulinids of the early Permian and lies at the base The geological development and the Carboniferous- of a transgressive carbonate sequence. The results obtained in the Permian stratigraphy of the region were outlined during Carboniferous-Permian section of East Iran are similar to those of the geological mapping in the 1960s and described in a western and southern Tethys. Everywhere the Asselian and, locally, number of pubiications (Stócklin et aI. 1965; Ruttner et the Sakmarian deposits are closely related to the Upper Carbonifer- al. 1.968, 1.97A). Later, the data on rhe Upper Paleozoic ous ones. After the late Sakmarian-Yakhtashian regression, carbon- ate platforms were formed from the Bolorian time through the Late stratigràphy were summartzed by Stepanov (1971) Permian. The Zaladu Member contains 10 genera - Rauserites, Kush- and in the Stratigraphic Lexicon of Iran (Stòcklin anella (? ), Schelltuienìa, Anderssonites (?), Praep se ud.ofusulina, Quasi 1.971). Partoazar (1995) published a synthesis on the triticites, Ruzbenzevites, Paraschu-agerina, .Dseudoschu^agerina, Sphaer- Permian deposits of Iran including the Carboniferous- oschuagerina (?) and 3Z species and subspecies of fusulinids. New Permian sequences the' Tabas area. According to species and subspecies are described: Rauserites infrequentis, R. ta- of these section basensis, R. fusoideus, R. inobsercabilú, À (?) persicus, Quasitriticites publications, the Carboniferous-Permian iranícus, Ruzbenzetites zaladuensis zaladuensis, R. zaladuensis bretis, comprises three formations: Shishtu, Sardar and Jamal. and R. ferganensis curtus. The Shishtu Formation is composed mostly of Devonian deposits but its uppermost beds belong to the Tournaisian Riassunto. Rocce dei piani Gzheliano e Asseliano sono state Stage of the Lower Carboniferous (Mississippian). The riconosciute in base ai fusulinidi nella parte superiore della Formazio- ne Sardar (Membro Zaladr), nella regione dell'Ozbak Kuh nell'Iran Sardar Formation corresponds to the remaining part orientale. Questi depositi non possono essere attribuiti alla Forma- of the Carboniferous and, probably, basal Permian. zione Bage-Vang, che contiene fusulinidi Boloriani del Permiano infe- The Jamal Formation is entirely Permian in age. Some riore e si tror.a alla base di una successione carbonatica trasgressiva. I attempts were made to subdivide the Sardar and Jamal risultati ottenuti nella sezione Carbonifero-Permiana dell'Iran orien- formations. was suggested to distinguish two members tale rìproducono i dati della Tetide occidentale e meridionale. Ovun- It que l'Asseliano e localmente anche i sedimenti del Sakmanano sono - Sardar 1 and Sardar 2 (Ruttner & Stocklin 1966). Their strettamente connessi con quelli del Carbonifero superiore. Dopo il mutual boundary is not distinct, but Stepanov (1971) tardo Sakmariano-Yakhtashiano, si formarono piattaforme carbona- thinks that it coincides approximately with the .Lower- tiche dal Boloriano sino al Permiano superiore. Il membro Zaladu Middle Carboniferous (Dinantian-Silesian) boundary'. contiene 10 generi di fusulinidi: Rauserites, Kushanella (?), Scbelkt,ie- the nia, Anderssonites (?), Praepseudofusulina, Quasitriticites, Ruzbenze Parroazar (1995) distinguished the lowermost part of v- it e s, Par a s c hu' age r i n a, P s e u d o s c b u a ge r in a, S p h a er o s c h ro a ger i na (? ) e Jamal Formation as an independent unit, named Bage- 37 specie o sottospecie di fusulinidi. Sono descritte le seguenti specie Vang, which he referred to the Asselian-Sakmarian. e sottospecie nuove di fusulinidi: Rauserites infrequentis, R. tabasen- In the year 2000, Taheri studied two sections, which sis, R. fusoideus, R. inobseruabilri, R. (?) persicus, Quasitriticites inni- cus, Ruzhenzevites zaladuensis zaladuensis, R. zaladuensis bret;is, and were thoroughly sampled for microfauna. The Zaladu sec- R. ferganensis curtws. tion is located in the Ozbak-Kuh Mountains (Fig. 1) and the 1 Geological Institute, Russian Academy of Scìences, Pyzhevsky 7, Moscow, Russia. 2 Department of Geology, Faculty of Sciences, Shahrood Universit,v, Shahrood, Iran. 400 E. Ja. Le'uen 8t A. Taberi -\'- General characteristics of the Zaladu ,''f' \( 7'u:0" section The section is located on the rehran ffil I Tigh-Madanu mountain, near the vil- lage of Gushkamaq in the Ozbak- Kuh region (Fig. t). It is a key sec- tion for establishing the upper limit t'5 of the Sardar Fm. The type section of Kashan Ghah-Reisch the formation, located in the Kuh-e- a Li Shotori Range (Stócklin et al. 1965), )ì is composed mainly of shallow-water 'ìÈ shales and sandstones with rare thin t limestone interbeds. The latter no- ( ticeably increase in frequency in the Zaladu section. According to Partoa- zar (1995), the Sardar Formation is divisible into three parts correspond- ing to three sedimentary cycles. The first cycle begins with reddish brown sandstones and quartzites, which are abruptly replaced by organogenic lime- stones (beds 1-4 of Partoazar; not con- sidered in this paper); the second cy- cle is marked by thin conglomerates replaced upward by green shales with thin interbeds of sandstones and lime- stoóès (bed S ofPartoazar); the third cycle starts again with red conglom- erates passing upwards to sandstones, shales and fusulinid limestones (beds 6 and 7 of Partoazar). According to cP!'iao*er 1o km Parroazar, the first and second cycles embrace the interval from the Visean to the Moscovian. The deposits of the Fig. 1 - lndex map of studied area with the localities of the Zaladu scction r Li.J "'""1" . "r" 'ol.r "d to the As.e- lian-Sakmarian interval of the Early Permian. As shown below, this dating of the uppermost part of the Sardar Bage-Vang section is situated to the sourh, in the Shirgesht Formation was correct, although Partoazar's inference area. The samples from both sections were processed in the was based on the wrong prerequisites: he correlated this Geological Institute of the Russian Academy of Sciences part of the section to the Bage-Vang Formation on rhe (Moscow), where about 600 oriented thin sections were basis of incorrect dating of fusulinids from this formation prepared. The thin sections contain abundant fusulinids and as Asselian-Sakmarian. However, Kahler (1924) found small foraminifera. Their analysis allows unambiguous dat- previor-rsly in the same location the fusulinids Misellina, ing of the Jamal Fm. and the upper part of the Sardar Fm. Cbalaroschzt,agerina and others forms, which indicated the The fusulinid collection from the Zaladtt section is stored Bolorian age of the Bage-Vang Fm. in its type section. in the Geological Institute (GIN) of the Russian Academy So, neither the data of Partoazar (1995) nor the of Sciences, collection number GIN 4223. earlier data of Stòcklin et al. (1965), Ruttner et al. (1968, This article presents the results of investigations 1920), Stepanov (1971), and Kahler (1974) can define of the upper part of the Sardar Formation of the Zaladu the age of the upper limit of the Sardar Fm. Except for section, which yielded abundant fusulinid assemblages, the beds correlated with the Bage-Vang Fm., Partoazar characteristic of the Llppermost Carboniferous and the determined the Sardar Fm. to be not younger than the Asselian Stage of the Lower Permian. Ve called Zaladu Moscovian Stage. On the contrary, according to Kahler Member this part of the Sardar Formation and we de- (1974), the Sardar Fm. spans not only the entire Carboni- scribe its tvDe-section. ferous, but also the Lower Permian, up to the Artinskian Carboniferous- Permian stratigraphlt of East Iran 401 ded towards the top, where they are bioconstructed and biociastic, locally PARTOA.L{R. Lithnlrr;4r Samples IIliTHIS P.{PM ferruginous, and reddish colored. At 1995 the top there are thin shale interbeds. of bra- JLIR.q.SSIC 1 -:+ -.:+:r:..: JUF-{55it The limestones yielded remains -1"1-l* chiopods, corals, bryozoans, crinoids, and aigae. Abundant fusulinids are 1o- ttl cally rock-forming. t_tl Fermhn tÈt I The relatioships of the Zaladt E AMAL F lÉlrl 4: Member with the underlying deposits tEt+l r-ll lfÈlll lr'llE I T ururamed is unclear. Partoazar (1995) supposed a s E funÍrÈti'rn significant unconformity and a hiatus lillÉ Fi; l* of lFlú l- h.l corresponding to the entire Kasimov- *-lHI ld t:t 5ÉÌ,lnariax HlHl la ian and Gzhelian. He did not present acB 4l I lF any paleontological evidence, but his El I l- hypothesis looks very probable due dt | | v---É? ..''+--ú -l-?t I-ZIISEIII -t to the presence of basal conglomer- Hl ,itt*1i*-. T-- | | ates and generally transgressive litho- lEse-zlr8 I lÉlh t,.1 logical changes along the section. An l=lEl ÉzhFlìÉn lnlS I indirect evidence is provided by a fu- rl iltrllla lEl#! 'flnF- sulinid-proved hiatus corresponding to ElEl the Kasimovian and most part of Gzhe- t! Ht I lllal* El'ÉliÉtl=l lian stages in a section in the Anorak IHITIH rrrl-!llb o area, 3OO km of the lo ldl lts z Kastnornan? Hl,qlE to the south-west l"l lp |f, Èl section under consideration (unpub- '! utlHt I lished data). I t_lt: 4 ".----.É? -.''..''++ f.?-* The Zaladu Member is covered =lnlÉll" L} by.