New Permian Aliyak and Kariz Now Formations, Alborz Basin, NE Iran: Correlation with the Zagros Mountains and Oman
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GEOLOGICAL JOURNAL Geol. J. (2014) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/gj.2599 New Permian Aliyak and Kariz Now formations, Alborz Basin, NE Iran: correlation with the Zagros Mountains and Oman SAKINEH AREFI FARD1* and VLADIMIR I. DAVYDOV2,3 1Geology and Geophysics Department, TAMU, College Station, Texas, USA 2Permian Research Institute, Department of Geosciences, BSU, Boise, Idaho, USA 3Kazan (Volgan region) Federal University, Kazan, Russia Two new Permian-aged formations ‘Kariz Now Formation’ and ‘Aliyak Formation’ are proposed for a 65–150 m-thick succession in the Kariz Now area, with the type section for both (79.5 m thick) located 9 km northeast of Aliyak village ca. 100 km southeast of Mashhad city, north- eastern Iran. The lower Kariz Now Formation is composed of siliciclastics. The age of this Formation is poorly constrained but its correlation with the Shah Zeid Formation in the Central Alborz suggests a possible Asselian-Hermagorian age for the Kariz Now Formation, which implies a hiatus of Yakhtashian–mid Midian (Artinskian–mid Capitanian) age between the siliciclastics of the Kariz Now Formation and carbonates of the disconformably overlying Aliyak Formation. There is also the possibility of a potential correlation of this Formation with the Kungurian Faraghan Formation in the Zagros area. The succeeding Aliyak Formation is mostly composed of carbonate rocks capped by a thin basaltic lava flow. The Aliyak Formation is unconformably overlain by dolostones that are correlated with the Middle Triassic Shotori Formation. Samples were collected from the Kariz Now and Aliyak formations, but fossils were only recovered from the Aliyak Formation. These include calcareous algae, small foraminiferans, fusulinids, crinoid stems and brachiopods. The recovered fusulinid assemblage from the Aliyak Formation is consistent with that of the upper Capitanian Monodiexodina kattaensis–Codonofusiella erki and Afghanella schencki–Sumatrina brevis zones of the Zagros Mountains and with the upper part of the Ruteh Fm in the Alborz Mountains. Although not radiometrically dated, the basaltic lava flow most probably corresponds to similar basaltic lava flows occurring in the uppermost part of the Ruteh Formation in Central Alborz. Thus, the Permian in the studied region developed in a basin that extended westward as far as the Central Alborz. A late Capitanian age for the Aliyak Formation implies it correlates with the Capitanian KS5 in Al Jabal Al-Akhdar in Oman, with Aliyak Unit 5 potentially representing the Permian maximum flooding surface MFS P25. Copyright © 2014 John Wiley & Sons, Ltd. Received 17 May 2014; accepted 11 July 2014 KEY WORDS lithostratigraphy; fusulinids; taxonomy; biostratigraphy; palaeogeography; microfacies; depositional environment; northeastern Alborz; Iran 1. INTRODUCTION We have studied the succession in the Kariz Now area, located near the easternmost tectonic boundary of the Alborz The E–W-trending Alborz Mountains extends laterally for Terrane, with the Sabzevar, Farah and Turan terranes about 2000 km in northern Iran, from the lesser Caucasus (Fig. 1). It has been considered a part of the Alborz or of Armenia and Azerbaijan in the northwest, to the Sabsevar terranes (Alavi, 1991; Aghanabati, 1993, 2004) Paropamisus Mountains of northern Afghanistan to the located south of the Palaeotethys Suture. In this study, we east (Fig. 1). These mountains contain the tectono- describe the stratigraphy of the Permian deposits and pro- stratigraphic record of the Alborz Terrane, also known as pose a palaeogeographic model of this poorly known region the ‘Alborz Block’ or ‘NW Iran Terrane’ (Fig. 1; Sengör, within the context of the surrounding regions. 1990; Alavi, 1991, 1996; see review in Ruban et al., This paper focuses on the Permian deposits in the Kariz Now 2007). The Alborz Terrane lies at the intersection of several area, which we propose to divide into two lithostratigraphic regional tectonic sutures and its boundaries and palaeo- units: a lower siliciclastic unit named the Kariz Now Formation tectonic history are complicated (Afshar-Harb, 1970, and the upper carbonate unit named the Aliyak Formation. We 1994; Alavi Naeini, 1972; Berberian et al., 1996; Zanchi document for the first time the details of the sedimentary and et al., 2009). volcanic rocks and precise taxonomy of calcareous algae and foraminiferans recovered in the limestones of the Aliyak *Correspondence to: S. Arefifard, Geology and Geophysics Department, Formation, and compare them to those in the Central Alborz fi TAMU, College Station, TX, USA. E-mail: sare [email protected] Mountains, Zagros, Oman and other regions. Copyright © 2014 John Wiley & Sons, Ltd. S. AREFI FARD AND V. I. DAVYDOV Figure 1. (a) Main tectono-stratigraphic units of Iran, Caucasus and Afghanistan (adapted from Alavi, 1991; Aghanabati, 1993; Bagheri and Stampfli, 2008). Ag = Aghdarband tectonic window; Bb = Band-e-Bayan; BFTB = Baluchestan Fold Thrust Belt; Bj = Birjand ophiolitic mélange; BM = Binalud Mountains; DF = Doruneh Fault; EO = Erevan-Ordoband; Fa = Fariman; GS = Gorgan Schist; Jm = Jazmouriam; Kr = Kermanshah ophiolite; Ma = Masouleh; MZT = Main Zagros thrust belt; Na = Nain Ophiolitic mélange; Nz = Neyriz ophiolite; Pb = Posht-e-Badam Terrane; PBB = Posht-e-Badam Block; Sz = Sabzevar zone; UD = Uromieh-Dokhtar volcanic belt; YB = Yazd Block. (b) Enlarged map showing location of the Aliyak section, Kariz Now area. This figure is available in colour online at wileyonlinelibrary.com/journal/gj Copyright © 2014 John Wiley & Sons, Ltd. Geol. J. (2014) DOI: 10.1002/gj NEW LOWER AND MIDDLE PERMIAN FORMATIONS, NE IRAN 2. LITHOSTRATIGRAPHY OF THE ALIYAK AND Locality and type section: The type section of this Formation KARIZ NOW FORMATIONS is sandstone beds in the Aliak Section located at latitude 35° 19′45″N and longitude 60°03′37″E(Figs.1and2). The Permian deposits at the Aliyak section in the Kariz Now area begin with quartz sandstones and are followed by Lithology and thickness: ThethicknessoftheKarizNow carbonate deposits including limestone and dolostone, and Formation varies from northwest to southeast in the study area terminate with a thin basaltic lava flow. Based on the lithologic from 30 to 60 m. In the type section, it is 39 m thick and con- characteristics of these deposits and their stratigraphic sists of the following two units, from the base upwards (Fig. 3): relations, two lithostatigraphic units were recognized: the • Unit 1 (29 m thick) Red, medium-bedded (12–14), lower siliciclastic unit defined as the Kariz Now Formation medium- to coarse-grained quartz sandstone with and the upper carbonate unit defined as the Aliyak Formation. small-scale cross-bedding and laminations. • Unit 2 (10 m thick) Red to orange, medium-bedded (12–15), medium- to fine-grained quartz sandstone with carbonate 2.1. ‘Kariz Now Formation’ cement, small-scale cross-bedding and laminations. Name: The proposed ‘Kariz Now Formation’ is named after Lower boundary and underlying formation: In the the Kariz Now Village, located 151 km southeast of studied area, the Kariz Now Formation overlies an undiffer- Mashhad City (Figs. 1 and 2). entiated Proterozoic–Lower Cambrian unit with an angular Figure 2. Geological map of the Kariz Now area exhibiting the main structural features. This figure is available in colour online at wileyonlinelibrary.com/journal/gj Copyright © 2014 John Wiley & Sons, Ltd. Geol. J. (2014) DOI: 10.1002/gj S. AREFI FARD AND V. I. DAVYDOV Figure 3. Stratigraphic log of the Aliyak Formation in Aliyak Section, Kariz Now area, NE Iran with some key foraminiferal taxa, A = undifferentiated Soltanieh–Barut formations, B = Proterozoic–Lower Cambrian, Sh. = Shotori Formation, Tr. = Triassic. This figure is available in colour online at wileyonlinelibrary.com/journal/gj unconformity boundary (Figs. 4a, 4b and 4c). In the Alborz micaceous shales of the Soltanieh Formation and the Lower area, this undifferentiated unit is divided into the Proterozoic– Cambrian cherty, stromatolite-bearing recrystallized dolostone Lower Cambrian thick-bedded to massive, cherty interbedded with micaceous shales of the Barut Formation stromatolite-bearing dolostone with a few intercalations of (Figs. 3 and 4). Copyright © 2014 John Wiley & Sons, Ltd. Geol. J. (2014) DOI: 10.1002/gj NEW LOWER AND MIDDLE PERMIAN FORMATIONS, NE IRAN Lithology and thickness: The thickness of the Aliyak For- mation varies from northwest to southeast across the study area, from 35 to 90 m, based on the geological map report of the Kariz Now area (Boubee de Gramont et al., 1979). The maximum thickness (90 m) is an estimate in an area affected by structural complication. In the type section, it is 40.5 m thick and consists of the following seven units, from the base upwards (Fig. 3): • Unit 1 (1 m thick) Grey, medium-bedded sandy dolostone. • Unit 2 (11 m thick) Dark grey, medium-bedded partly crystallized limestone with small foraminiferans, algae, brachiopods, crinoid ossicles and ostracods. • Unit 3 (11 m thick) Grey, medium- to thick-bedded, medium to coarse crystalline dolostone. • Unit 4 (2 m thick) Grey, medium-bedded limestone (wackestone–packstone) with fusulinids, small foraminiferans, algae, crinoid stems and/or ossicles, and brachiopods (Fig. 3, sample K30). • Unit 5 (1 m thick) Grey, medium-bedded algal lime- stone (wackestone). • Unit 6 (14 m thick) Dark grey, medium- to thick- bedded medium crystalline dolostone. • Unit 7 (0.5 m thick, Fig. 4d) Dark green basaltic lava