Correlation

[28]  Eastern Iran. In eastern Iran the sediments synchronous to that discussed above were reliably recorded only in the Ozbak-Kuh Mountains of the Tabas region, where the Zaladou Formation was first recognized [Leven and Taheri, 2003]. The formation is subdivided there into two parts. The 50-m-thick lower unit is mainly composed of terrigenous sediments bearing few faunal remains. Its age is conventionally estimated as Kasimovian-early Gzhelian. The overlying 35-m-thick part of the formation is carbonate in composition. Fusulinids were encountered in the upper 15 m of the section. This faunal bed yields in its lower part Ruzhenzevites ferganensis and numerous Rauserites including the characteristic Gzhelian forms. The upper 5 m of the section contain Pseudoschwagerina, the genus typical for the middle zone of the Asselian. Limestones of the Zaladou Formation are overlain by the dolomite sequence over 100 m thick.

[29]  In the Anarak section the terrigenous portion of the Zaladou Formation is missing, probably cut by the fault. The Gzhelian-Asselian Anarak limestone is as a whole correlated with the carbonate portion of the Zaladou Formation in the Ozbak-Kuh section. In both sections the beds bearing the upper Gzhelian Ruzhenzevites ferganensis, and the overlying layers with the Asselian Pseudoschwagerina are recorded in the upper part of the limestone sequence (Table 2). Also in both sections these beds are extremely thin (15-20 m) and embrace two or three Gzhelian and two Asselian fusulinid zones. It is hardly the result of a low sedimentation rate, which is evidenced by the occurrence of coarsely detritic facies of fusulinid limestone, from a wackestone to rudstone. The most likely reason is the short-term, non-identified hiatuses that are quite probable considering the shallow character of the limestones. This inference is indirectly confirmed by frequently occurring sharp differences between fusulinid assemblages in adjacent beds without any succession.

[30]  In both the Anarak region and Ozbak-Kuh Mountains the Zaladou limestones are overlain by dolomites that we distinguish as the Tighe-Maadanou Formation. These units make up the Anarak Group. The latter unconformably overlies the Moscovian Absheni Formation and is also unconformably overlain by the Bolorian-Upper Permian Shirgesht Group [Leven and Gorgij, 2006; Leven et al., 2006]. All these facts underline the similarity of the discussed sections and indicate that at least in the second half of the Carboniferous and in the Permian the sedimentary sequences in the studied areas were accumulated in a single basin with like conditions of sedimentation. In the current structure these regions are referred to the different, namely, Yazd (Anarak region) and Tabas (Ozbak-Kuh region), fault blocks (Figure 1).

[31]  The Carboniferous-Permian sections in the Shotori Mountains are also referred to the Tabas block. The sediments in part or completely synchronous to the Zaladou and Tighe-Maadanou formations, i.e. to the Anarak Group, are likely represented there by a white quartz sandstone sequence, 60 m thick, that occurs between the shaly Sardar Group and the Jamal Formation's limestone and is separated by stratigraphic unconformities. The unconformity at the base of the quartz sandstone is underlined by the presence of coal beds.

[32]  The sediments that can be referred to the Anarak Group are recorded in the Pashte-Badam block (Kalmard region) west of the Tabas block. According to Arefifard and Davydov [2004] and to our observations, they are represented by the 300-m-thick Khan Formation composed of interbedded conglomerates, quartz sandstones, shales, and limestones. Fusulinids derived from the middle and upper portions of the section indicate the Asselian and Sakmarian age. The lower part of the formation is probably Gzhelian or Kasimovian, which is evidenced by the findings of Ferganites and Daixina, not related to the section [Kahler, 1977].

[33]  Alborz. The analogue of the Anarak Group in the central and eastern Alborz is the Dorud Formation distinguished by Assereto [1963]. In the type section north of Teheran he subdivided it into four parts. Subsequently Bozorgnia [1973] separated its lowest part as the Dozdeband Formation based on findings of the Visean-Serpukhovian conodonts and Bashkirian foraminifers [Ahmadzadeh, 1971; Bozorgnia, 1973]. According to our preliminary data, the Dozdeband Formation includes the Moscovian sediments as well. If this will be confirmed, the formation can be correlated with the Sardar Group of the central and eastern Iran, whereas the Anarak Group will correspond to Beds 2-4 of the Dorud Formation in its initial interpretation. The age of the Dorud Formation is commonly estimated as the Asselian-Sakmarian or even Asselian-Artinskian. In so doing the records by Kahler [1976] are cited. In the middle of the formation (Bed 3 after Assereto) he encountered the Asselian Pseudoschwagerina and numerous fusulinids that he referred to different species of the Lower Permian, including the Artinskian, Triticites and Pseudofusulina. These species are closely similar and certain of them actually resemble the Sakmarian and Yakhtashian Darvazites. However, they are no less related to Praepseudofusulina reported from a great deal of Asselian sections, including the Anarak section discussed in this paper.

[34]  Unlike the central Iran sections, where the Dorud Formation includes sandstone beds, in the eastern Alborz, namely, in the Gheselghaleh section nearby Gorgan, it is mainly composed of limestone. Its age without the proper substantiation, mostly based on the geologic position and by analogy with the western sections, was determined as the middle Asselian-Sakmarian [Lys et al., 1978]. The limestone is overlain by dolomites of the Kuh-e-Sariambar Formation presumably dated as the Artinskian and Kubergandian. In our opinion, considering the records on the Anarak and Ozbak-Kuh sections, both units correspond to the Zaladou and Tighe-Maadanou formations, i.e. to the Anarak Group. The additional collections of fossils in the Gheselghaleh section will permit the more valid conclusion.

[35]  Zagros. The stripe of mainly Upper Permian sediments stretching along the Shahreza-Abadeh-Hambast Range is commonly referred to central Iran. However, they strongly differ from the deposits of the Anarak section primarily in a greater abundance and diversity of fusulinids, among which the Eopolydiexodina members dominate. In this regard they are similar to the sections described from certain Zagros regions. Undoubtedly the Late Permian basin located in the modern Zagros area differed in environmental conditions from the basin that occupied central and eastern Iran and Alborz. These basins were likely separated from each other, which explains the above- mentioned difference in benthic fauna. It is not, however, improbable that the basin was single though relatively deeper in the northern part, where the Late Permian benthic biota was oppressed and did not evolve.

[36]  The sediments that can be correlated with the Anarak Group were studied by Baghbani [1993] in the vicinity of Shahreza town, in the Tang-e-Darchaleh section. They were distinguished as the Vazhnan Formation represented by the 142-m-thick variegated interbedded sandstone and limestone sequence. Bearing the basal conglomerates at its base the formation overlies the Moscovian sediments yielding Ozawainella mosquensis and with no visible unconformity but with a probable hiatus is overlain by limestones of the Surmaq Formation that bears the Kubergandian fusulinids slightly above its base. The lower portion of the Vazhnan Formation contains the Asselian Pseudoschwagerina and Sakmarian Robustoschwagerina. Based on this fact Baghbani estimated the age of the formation as the Asselian-Sakmarian. However, on the photos in his paper the forms identified as "Robustoschwagerina" possess distinct septal flutings, which are not characteristic of this genus as its septa are completely straight. Thus we assign these forms to Pseudoschwagerina; if so, the Sakmarian age of the sediments is not proved. However, considering that Pseudoschwagerina and "Robustoschwagerina" were found at the base of the formation, the assignment of its upper part to the Sakmarian cannot be excluded. In that case the Vazhnan Formation can be correlated with the Asselian-Sakmarian portion of the Anarak Group and we can state that despite the relation of the discussed sections to different biogeographic provinces, they are characterized by the same transgressive-regressive cycle of sedimentation in the time span between the Moscovian and Kubergandian (Bolorian-Kubergandian) ages.

[37]  In a vast territory of southern Iran from Luristan on the west to Iranian Baluchistan on the east the Sigillaria persica-bearing sandstone that overlies various horizons of the Lower Paleozoic and is transgressively overlain by the Upper Permian limestones, most likely corresponds to the Vazhnan Formation.


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