Three major biogeographic realms are usually recognized in the distribution of the Late Paleozoic foraminifers: North American or Midcontinent-Andean, Boreal or Uralian-Franklinian, and Tethyan (Reitlinger 1975; Ross and Ross 1985). Two antitropical transitional realms (or provinces) periodically appear in the north and south from the Tethyan realm. The northern transitional zone that has been tentatively called the Arctic province (Rui et al. 1991) appears in response to cooler-water environments and possesses somewhat endemic biotas and has a low-diversity taxonomic composition. It extends along the northern margin of Pangaea, from the Northern Urals in the east up to the Canadian Arctic and Alaska in the west (Figure 11). This province exists only in the Late Moscovian-Kasimovian through Gzhelian and the late Asselian-early Sakmarian. Beginning from the late Sakmarian through Artinskian and the early Kungurian, the entire Boreal realm became completely isolated from other realms. At the time it had relatively cooler water, but was in general very similar to the entire area from the Pre-Caspian, along the Urals to the Canadian Artic. The southern transitional zone or, the Peri-Gondwanan province (Australian by Miklukho-Maclay 1963), does exhibit cooler climate faunas. This leads to observations of biogeographic differences with other realms that have been proposed and recently accepted (Leven 1993; Kalvoda 2002; Ueno 2006). It exists from the latest Sakmarian and Artinskian through Guadalupian (Figure 11). One more transitional zone, sometimes called the "McClaude realm," includes several accreted terranes of western North America (Ross 1997). In the late Carboniferous and early Cisuralian, the fauna there closely resembled fusulinids of the North American realm. During the late Cisuralian it possessed significant Tethyan elements but many of these elements of the North American fauna can still be found today (Skinner and Wilde 1965).

Fusulinaceans were distributed in different carbonate to mixed carbonate-siliciclastic shallow water conditions in tropical-subtropical belts (up to 40-45E south/north latitude; Belasky 1996) and often formed foraminiferal limestone with numerous specimens that are collected and studied in many sections throughout the globe. As a result, foraminifers are a great indicator of paleoclimate/paleoenvironments within a high-resolution spatial and temporal framework. It is assumed that the majority of the fusulinaceans host the photosynthetic symbionts that are found in many of the larger living foraminifera (Ross 1982). Because large, extant tropical foraminifera with symbionts live in conditions with temperature ranges between 35-15EC, which never fall below 14EC for several weeks (Hohenegger 2004) it seems reasonable that fusulinaceans may have lived under similar conditions (Ross 1972; Murray 1991). Temperature appears to control the diversity of extant larger foraminifera assemblages. Shallow water assemblages with optimal water temperature (30-20EC) for foraminifera are generally much more diverse than those with temperatures greater than approximately 31EC and/or less than approximately 20EC (Murray 1991; Beavington-Penney and Racey 2004).

Perigondwania-Neodutkevitchia fauna that are found in the Khan Formation in the Posht-e-Badam block, Central Iran, also occur in South Tibet, East Hindu Kush, Karakorum, South and Central Afghanistan, central Pamir and Oman (Nie and Song 1983b; Gaetani et al. 1995; Angiolini et al. 2006; Premoli Silva 1965; Leven 1993; 1997) and strictly indicate the southern antitropical temperate zone. The fusulinid assemblages in these regions appear to be restricted taxonomically and include either Eoparafusulina with thin septa or Perigondwania-Neodutkevitchia faunas. Furthermore, these assemblages contain an unusually large number of specimens with double proloculi that might indicate a stressful environment, which is marginal for these surviving fusulinids. Based on these observations, it is suggested that this temperate zone was geographically and climactically quite narrow. It probably represents a narrow climatic belt (30-40E southern hemisphere) where environmental conditions were marginal for fusulinids with an annual temperature range around 14-20EC. Thus, it is hard to overestimate the biogeographic significance of the Perigondwania-Neodutkevitchia fauna.

This fauna might also have an important paleotectonic significance. The petrographic and sedimentologic studies of the Gachal and Khan Formations, and especially the transition between these formations, which are critical for understanding details of paleotectonics of the area, were beyond the scope of the current project. Nevertheless, some general paleotectonic observations can be suggested. On most of the paleotectonic models, the Iran microcontinent has the northernmost position within the Cimmerian Continent. The Posht-e-Badam block was a part of the Cimmerian Plates (terranes) that were proposed to have separated from Gondwana in the Late Carboniferous (Golonka and Ford 2000; Stampfli and Borel 2002). Detailed petrographic, biostratigraphic and taphoniomic studies of the Pennsylvanina-Cisuralian glacial-postgacial transition in Oman were interpreted as recording continental breakup and the onset of Neotethyan spreading between northern Gondwana and the Cimmerian terranes at mid-Sakmarian times, as constrained by brachiopod assemblages (Angiolini et al. 2003). Similar brachiopod assemblages associated with Perigondwania-Neodutkevitchia fusulinid fauna were recovered in Central Oman (Angiolini et al. 2006) and so this continental breakup and onset of Neotethyan spreading is probably latest Sakmarian-early Artinskian in age as suggested by the fusulinids and conodonts.

The biostratigraphic and paleontologic data from the Khan Formation can also be applied in an effort to gain better understanding of the local and regional tectonic framework and post-Permian tectonic development of the area. Figure 13 shows the distribution of fusulinid assemblages of different affinities in Iran and the surrounding areas. Fusulinids in localities 1-8 are typical Tethyan, whereas fusulinids from the Posht-e-Badam block belong to temperate transitional cool to cold water fauna of higher latitude. There are no common forms in Tethyan and Peri-Gondwanan assemblages, and taxonomically they are sharply different. This might suggest that in the early Permian, the Posht-e-Badam block was far south in comparison to the rest of the locations that formed recent Iran.