ABSTRACT Sixty-four surface samples from the Lower Paleozoic rock units (mainly the Lalun, Abastu, and Abarsaj Formations) near the village of Kholin-Darreh in the Fazel Abad area, southeastern Caspian Sea, northern Iran, were analyzed to determine their age relationships. The samples from the Lalun Formation are barren, but those from the Abastu and Abarsaj Formations contain well-preserved and abundant palynomorph entities, which are dominated by acritarchs (23 species belonging to 15 genera) and chitinozoans (29 species distributed among 15 genera). Scolecodonts and graptolite remains as well as a few cryptospores were also observed, although these were not determined in detail. Based on the restricted stratigraphic range of acritarch species, an Early Ordovician (Tremadocian) age is assigned to the Abastu Formation, while based upon index chitinozoan and acritarch taxa, a Late Ordovician (Katian to Hirnantian) age is assigned to the Abarsaj Formation. Likewise, based on the presence of diagnostic chitinozoan taxa, the Abarsaj Formation can be assigned to the Armoricochitina nigerica, Ancyrochitina merga, Tanuchitina elongate , and Spinachitina oulebsiri chitinozoan biozones. These chitinozoan assemblages reflect a clear paleobiogeographic affinity with the so-called “North Gondwana Domain.” The composition of acritarch assemblages also appears to be consistent with newly proposed hypotheses of a Late Ordovician phytoplanktonic biogeographical differentiation between a Laurentian/Baltica realm and a Gondwanan realm, with the present assemblages belonging to the latter. The presence of some chitinozoan and acritarch taxa from the Baltic and Laurentia in Gondwanan chitinozoan biozones of the Fazel Abad area suggests the existence of counterclockwise marine currents, which brought planktonic organisms (acritarchs, chitinozoans, and graptolites) from lower latitudes (Baltica) to higher latitudes (North Gondwanan Domain) settings. The presence of a low-diversity acritarch assemblage in the Abastu Formation and taxonomically diverse chitinozoan, acritarch, and scolecodont assemblages in the Abarsaj Formation suggests a marine depositional environment for these two formations. Two major hiatuses are present within the studied Lower Paleozoic succession in the Fazel Abad area. The first hiatus appears between the Lalun Formation (Early Cambrian) and the Abastu Formation (Tremadocian) and includes the Middle-Upper Cambrian Mila Formation. The second hiatus occurs between the Abastu Formation (Tremadocian) and the Abarsaj Formation (Katian–Hirnantian) and spans the interval of the Floian-Sandbian, which corresponds to uplift related to the initial stage of rifting of the Paleo-Tethys Ocean.

Abstract Iran is a resource-rich country, with large deposits of iron, copper, zinc, and gold, as well as industrial minerals and oil and gas. Most of these resources were formed in response to complex and protracted contractional deformation events related to the subduction and eventual closure of the Neotethys ocean in the late Mesozoic and Cenozoic. Here we focus on porphyry Cu ± Mo ± Au and related epithermal Au deposits, which were once thought to be synonymous with subduction, but are now recognized to also form during collisional and other postsubduction tectonic processes. Recent advances in tectonic and paleogeographic reconstructions, and new geochronological and geochemical data reveal that in fact most of Iran’s major porphyry and epithermal deposits fall into this postsubduction category (e.g., Sungun, Sari Gunay, Meiduk, Sar Cheshmeh). The same applies to several major deposits in neighboring Turkey (e.g., Kişladağ, Çöpler), whereas continued subduction beneath the Makran in western Pakistan accounts for some of the only “normal” subduction-related porphyry deposits in the region (e.g., Saindak, Reko Diq). Few igneous rocks or mineral deposits associated with the Paleotethys ocean occur in Iran, although several Paleozoic ophiolite belts are preserved, and Early Cambrian Kiruna-type iron oxide-apatite deposits are found in the Bafq district of eastern Central Iran. Arc magmatism associated with Mesozoic subduction of the Neotethys ocean is widespread in the Sanandaj-Sirjan zone, but no porphyry or epithermal deposits of this age have been discovered to date, likely due to erosion down to batholithic levels. Arc magmatism shifted to the Urumieh-Dokhtar magmatic arc and the Lut block in the late Paleogene-early Neogene, and the first significant porphyry deposits formed in the Eocene and Oligocene. However, the main period of porphyry formation occurred later in the early to mid-Miocene, synchronous with terminal collision between the Afro-Arabian and Eurasian plates. Several large porphyry Cu (Sungun, Meiduk, and Sar Cheshmeh), as well as the porphyry-related Sari Gunay epithermal Au deposit, were formed at this time (~20–11 Ma) along the length of the orogen. Active subduction continues only beneath the Makran of southeastern Iran and western Pakistan, where the large Saindak (~22 Ma) and Reko Diq (13–10 Ma) porphyry deposits occur. Mineral exploration in Iran to date has been largely restricted to areas of outcrop, but the potential for extensions of known deposits, or “blind” discoveries below widespread Quaternary cover is considered to be high.

Abstract Microvertebrate samples from the Upper Devonian Hojedk section, southeastern Iran, and the Napier Formation, northwestern Australia, have yielded scales of agnathan thelodonts, dated as early/mid-Famennian ( crepida–marginifera/trachytera conodont zones). These scales are referred to Arianalepis megacostata , a new genus and species, and Arianalepis sp. indet., a second indeterminate species of this new turiniid genus. Further recorded scales of Australolepis seddoni from the Napier Formation confirm the age range for this taxon as extending into the late Frasnian. The new remains post-date the previously youngest thelodonts from Iran and Western Australia and provide the first evidence of thelodonts surviving the Frasnian–Famennian extinction events.

Abstract The Maikop Series forms an important source rock in the former Paratethys. Deposition is often interpreted as anoxic, linked to restriction of the Paratethys. The Pirembel formation in the Talysh Mountains (Azerbaijan) is attributed to the Maikop Series and was deposited above the Eocene volcanic Peshtasar formation. Dating the onset of anoxia could help to distinguish glacio-eustatic from tectonic causes of restriction. We integrated magnetostratigraphy and biostratigraphy to date the onset of Pirembel sedimentation and used geochemistry to characterize the tectonic setting of the Peshtasar volcanic rocks. The onset of Maikop sedimentation in the Talysh was determined to be 37.7 Ma, ruling out a link with the major sea-level drop at the Eocene–Oligocene Transition (33.9 Ma) and favouring a tectonic cause. Extrapolating the average sedimentation rate (34 cm kyr) suggests that the entire Pirembel formation belongs to the Late Eocene. We hypothesize that the end of volcanism is important in the transition to Pirembel sedimentation. The palaeomagnetic and geochemistry results for the volcanic rocks cluster in three groups, suggesting three distinct episodes of volcanism. Volcanic sills within the Eocene Arkevan formation plot exactly on these groups, confirming the relationship between the Arkevan and Peshtasar formations. Volcanic rocks of the Talysh show continental-arc signatures and may be related to an Eocene volcanic belt extending towards southeastern Iran. Supplementary material: The full analytical data of the Ar–Ar dating are available at http://www.geolsoc.org.uk/SUP18851