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Early Barremian orbitolinid record from the Moghan area, NW Iran: Northern margin of the Neotethys
Accepted Manuscript Early Barremian orbitolinid record from the Moghan area, NW Iran: Northern margin of the Neotethys Mohsen Yazdi-Moghadam, Mehdi Sarfi, Mohammad Sharifi, Behrooz Ariafar, Fereshteh Sajjadi, Parisa Abbasi PII:
S0195-6671(17)30002-2
DOI:
10.1016/j.cretres.2017.05.014
Reference:
YCRES 3611
To appear in:
Cretaceous Research
Received Date: 1 January 2017 Revised Date:
4 May 2017
Accepted Date: 9 May 2017
Please cite this article as: Yazdi-Moghadam, M., Sarfi, M., Sharifi, M., Ariafar, B., Sajjadi, F., Abbasi, P., Early Barremian orbitolinid record from the Moghan area, NW Iran: Northern margin of the Neotethys, Cretaceous Research (2017), doi: 10.1016/j.cretres.2017.05.014. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Early Barremian orbitolinid record from the Moghan area, NW Iran: Northern Margin
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of the Neotethys
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Mohsen Yazdi-Moghadama*, Mehdi Sarfib, Mohammad Sharific, Behrooz Ariafara, Fereshteh Sajjadic, Parisa Abbasic
National Iranian Oil Company Exploration Directorate, Sheikh Bahayi Square, 1994814695 Tehran, Iran,
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Email:[email protected]
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School of Earth Sciences, Damghan University, 36716-41167 Damghan, Iran
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Department of Geology, Faculty of Sciences, University of Tehran, Tehran, Iran
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Abstract
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carbonate deposits of the Moghan area, NW Iran. According to geologic map of the Razi,
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these rocks were previously assigned to general age of the Early Cretaceous. The early
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Barremian age is documented based on stratigraphic range of the marker Valserina turbinata
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(Foury) .Other orbitolinids such as Eopalorbitolina charollaisi Schroeder, Eopalorbitolina
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Orbitolinid foraminifers are reported for the first time from lower Barremian shallow marine
pertenuis (Foury), Paleodictyoconus cf. cuvillieri (Foury), Montseciella cf. alguerensis
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Cherchi and Schroeder, Paracoskinolina cf. maynci (Chevalier), Orbitolinopsis cf. buccifer
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Arnaud-Vanneau and Thieuloy, and Dictyoconus? pachymarginalis Schroeder also coexist.
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Obtained biostratigraphic data suggest that the range of Dictyoconus? pachymarginalis,
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hitherto known from the Aptian, has to be extended into the early Barremian. Most of the
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orbitolinid taxa are well known in Europe as northern Tethyan margin endemic forms.
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Therefore, the study area can be considered as part of the northern Tethys margin during the
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ACCEPTED MANUSCRIPT Barremian. This study also extends the palaeobiogeographic distribution of northern Tethyan
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orbitolinids eastwards as far as northwest Iran.
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Keywords: Orbitolinids, Barremian, Tethys, Iran, Moghan, Micropalaeontology
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1. Introduction
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Early to middle Cretaceous shallow marine rocks crop out widely in different parts of Iran
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somewhat, composed of carbonate deposits rich in larger benthic foraminifera (mainly
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(James and Wynd, 1965; Stöcklin and Setudehnia, 1971; Setudehnia, 1972). These rocks are
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et al., 2013; Schlagintweit and Wilmsen, 2014).
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Orbitolinids have been reported from different structural units in Iran including Zagros
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Mountains in the south, Kopet Dagh and Alborz in the north and Central Iran in the middle
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orbitolinids) and calcareous green algae (e.g., Schroeder et al., 2010; Taherpour Khalil Abad
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2010; Yazdi-Moghadam and Amiri, 2010; Shirazi and Abedi, 2012; Carević et al., 2013;
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Schlagintweit et al., 2013a; 2013b; Taherpour Khalil Abad et al., 2013; Afghah and
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(Henson, 1948; James and Wynd, 1965; Schroeder, 1965; Sampò, 1969; Schroeder et al.,
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Haghighi, 2014; Schlagintweit and Wilmsen, 2014; Hosseini et al., 2016).
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In many localities of Central Iran, the orbitolinid foraminifer bearing carbonates are mapped
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as “Orbitolina limestone” which were assigned to a general Early Cretaceous age.
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During the field geology dealing with stratigraphy and hydrocarbon evaluation of Mesozoic
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and Cenozoic rocks of NW Iran (Moghan area), several sections were sampled and studied.
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One of the measured sections located in eastern most part of the investigated area, includes a
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succession of “Orbitolina limestone” (Fig. 1).
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these orbitolinid bearing deposits can potentially be considered as reservoir rocks in the
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investigated area (e.g., FOL, 2000), the accurate dating of these strata is of great importance
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for hydrocarbon exploration studies.
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It is the only locality in the Moghan area that Lower Cretaceous carbonate rocks crop out. As
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faunal elements. In the absence of other index macro- and microfossil groups (e.g.,
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planktonic foraminifera, nannoplanktons, rudists), orbitolinids are of immense practical use
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for dating of these shallow marine strata as their ranges have recently been calibrated with
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ammonite biostratigraphic data (e.g., Clavel et al., 2010; 2013).Therefore, this study focuses
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Within the study section (Sarv Abad) (Fig. 1), orbitolinid foraminifers are the dominant
on this group of agglutinating foraminifera for biostratigraphy and age dating of their hosting
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rocks in the Moghan area.
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2. Material and methods
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named Sarv Abad section (Fig. 2). Some 38 rock samples have been collected with maximum
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spacing interval of 3 m. In order to study oriented sections of orbitolinids, several thin
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sections in different orientations were prepared from each sample using conventional
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methods. The generic classification of Loeblich and Tappan (1987) was used and updated in
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The material of this study comes from one section located in south eastern Moghan area,
some instances with additional sources such as Cherchi and Schroeder (1999) and Granier et
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al. (2013). All samples and thin sections presented in this paper are deposited in the
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collection of National Iranian Oil Company Exploration Directorate (NIOCEXP), Tehran,
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Iran and are labelled as EHGH 3108 to EHGH 3145.
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3. Geological setting
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Moghan area, etc.) each of them is characterized by a long and different depositional history
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(e.g., Stöcklin and Setudehnia, 1971; Setudehnia, 1972; Berberian and King, 1981; Alavi,
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2004). The northwest Iran is marked by a structural unit named as Moghan area. The area as
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a part of Alp-Himalayan orogenic belt has an extension around 6500 km2. From geological
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point of view, the Moghan area is considered as a terminal northwestern part of the Alborz-
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Azerbaijan zone having a general NW-SW trend (Nabavi, 1976).
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Iran is composed of several structural units (Zagros, Kopet Dagh, Central Iran, Alborz,
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39.42״N, and 48ᵒ, 20׳, 46״E (Fig.1). In other words, the area is located in eastern Paratethys
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The area covers northern parts of the Ardabil and East Azerbaijan provinces at 39ᵒ, 30׳,
domain extending from Carpathian in Romania to Aral Lake in Kazakhstan including the
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present day Black Sea and Caspian Sea basins (e.g., Rögl, 1998). These two basins are further
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subdivided into several side basins.
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As a part of the south Caspian basin, the Moghan area is located in northwestern corner of
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south by the northern flank of the Talysh-Lesser Caucasus orogenic belt. From tectonic point
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of view, the Moghan area together with the Kura through are considered to have a back-arc
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Iran and bounded towards the north by southeastern part of the Kura through and towards the
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early Paleogene time due to a high sediment supply from neighbouring rising mountains
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(FOL, 2000; Amini, 2006). The marine sedimentary successions of the Moghan area cropped
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out in some restricted exposures in southern parts of the basin (Willm et al., 1961) in
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localities such as Salavat, Kurd-Kandi, Zargar and Kaleybar. The mountainous area, north of
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Namin (Sarv Abad) is the only locality throughout the basin in which shallow marine Lower
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Cretaceous rocks are exposed. Based on geological map of Razi, Cretaceous shallow marine
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limestones crop out at north of Namin and are generally assigned to the Lower Cretaceous
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(Khalatbari-Jafari, 2005).
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setting. These areas were subjected to rapid siliciclastic sedimentation during late Mesozoic-
ACCEPTED MANUSCRIPT 4. Sarv Abad section
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north of the city Namin, in an area consisting of some NW-SW trending minor folds and
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thrust sheets.
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The section is measured and sampled in vicinity of Sarv Abad village, several kilometers
The sedimentary succession in this area is composed of three units including pre-Jurassic,
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Jurassic and Cretaceous deposits (Fig. 1).
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alluvium and consists of alternation of red micaceous shales and sandstones interbedded with
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grey cherty dolostones at the upper part. These strata were barren of micro-or macrofossils
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and they are assigned to the Infra-Cambrian or lower Paleozoic based on geological map of
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Razi, scale: 1:100,000.
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The base of pre-Jurassic unit (PJ), the oldest rocks exposed in the study area, is covered by
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Jurassic shales and sandstones (J1) which in turn are topped by Upper Jurassic thin to
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medium bedded dolomitic limestones and limestones (J2). The shales and sandstones are also
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devoid of any micro- or macrofauna that based on their stratigraphic position, these strata
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The pre- Jurassic rocks are unconformably overlain by a relatively thick succession of Lower
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(J2) contain Late Jurassic benthic foraminifera including Alveosepta jaccardi (Schrodt) (Sarfi
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have been ascribed to the Early Jurassic age on the geological map. The top limestone beds
and Yazdi-Moghadam, 2016).
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The Cretaceous succession is characterized by lithological diversity allowing further
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subdivision into three units (K1, K2, and K3).The K1 unit is composed of bioclastic
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orbitolinid bearing limestones resting disconformably on the Upper Jurassic limestone beds
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(J2). The K2 unit comprises clastic rocks including polygenetic conglomerates, sandstones
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and shales. This unit disconformably overlies the K1 unit. The K3 unit consists mainly of thin
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ACCEPTED MANUSCRIPT to medium bedded limestones containing pelecypod shells. The boundary between the K2
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and K3 units is also disconformable. These two units (K2 and K3) are considered to be of
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Late Cretaceous age based on their stratigraphic position.
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5. The K1 unit (“Orbitolina limestone”)
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bedded limestones(wackestones to packstones and grainstones) lain disconformably on Upper
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Jurassic carbonate unit (J2). Apart from the orbitolinids, smaller benthic foraminifera,
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This 55-m-thick orbitolinid bearing unit consisting mainly of bioclastic medium to thick
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2).Green algae appear in few levels in the middle and upper parts of the section.
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echinoids, and brachiopods are also widely distributed throughout the succession (Fig.
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5A-G, I, and Fig. 8A-D), Eopalorbitolina charollaisi Schroeder (Fig. 3C-G), Eopalorbitolina
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pertenuis (Foury) (Fig. 4E-H), Eopalorbitolina sp. (Fig. 3H), Paleodictyoconus cf. cuvillieri
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(Foury) (Fig. 6J,K), Montseciella cf. alguerensis Cherchi and Schroeder (Fig. 6A-I),
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Orbitolinopsis cf. buccifer Arnaud-Vanneau and Thieuloy (Fig. 5H), Orbitolinopsis sp. (Fig.
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3A, B), Paracoskinolina cf. maynci (Chevalier) (Fig. 5K), Falsurgonina sp. (Fig. 5J), and
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Dictyoconus? pachymarginalis Schroeder (Fig. 4A-D).
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Orbitolinids are present with high abundance in the lower part of the section (0-30 m) and
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The orbitolinid association shown in Figures 3-6 includes Valserina turbinata (Foury) (Fig.
with low abundance in the upper part (40-50 m).The middle part of the succession (30-40 m)
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is marked by only a few occurrences of Paleodictyoconus cf. cuvillieri. By comparison, this
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part is characterized by several occurrences of green algae. The assemblages of non-
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orbitolinid foraminifera and algae which are not of direct biostratigraphic significance, have
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not been considered and will be the subject of further studies.
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6. Stratigraphy and discussion
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and nannofossils are absent in the Sarv Abad section. We also did not find rudists in the
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examined succession. Therefore, among the benthic foraminifera and calcareous algae
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present, orbitolinids are the main and stratigraphically important taxa for biostratigraphy. The
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55-m-thick unit (K1) in the Sarv Abad section consists mainly of shallow marine limestones
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with a relatively diverse assemblage of orbitolinids including Valserina turbinata,
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Eopalorbitolina charollaisi, Eopalorbitolina pertenuis, Falsurgonina sp., Paleodictyoconus
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cf. cuvillieri, Montseciella cf. alguerensis, Orbitolinopsis cf. buccifer, Orbitolinopsis sp.,
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Owing to shallow marine nature of the studied rocks, ammonites, planktonic foraminifera,
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the Lower Cretaceous rocks cropping out at Sarv Abad, the important stratigraphic index
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microfossil is Valserina turbinata. Under the generic name Palorbitolina Schroeder, Becker
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(1999) introduced Palorbitolina turbinata zone within the lower Barremian platform
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carbonates of the Organya basin (Spanish Pyrenees). This last author considered the
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Palorbitolina turbinata zone to correspond to Compressissima ammonite zone. An
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Paracoskinolina cf. maynci, and Dictyoconus? pachymarginalis. For detailed age dating of
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established by Schroeder et al. (2002) based on orbitolinid data from SE France. According to
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these authors, Eygalierina (=Valserina) turbinata occurs from upper Nicklesi into the
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Caillaudianus ammonite zone (Fig.7). Recently (Clavel et al., 2009; 2010; 2013) and Granier
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orbitolinid phylogenic scheme for the late Hauterivian-early Aptian time span was
et al. (2013) carried out biostratigraphic studies in SE France and French Swiss Jura. They
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reported the occurrence of Valserina turbinata within the lower Barremian from upper Hugii
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to Pulchella ammonite zone. Our biostratigraphic analysis is based on the work of these latter
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authors for northern margin of the Neotethys. It is worth noting that none of the orbitolinids
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from the Moghan area have already been reported from the Arabian plate (Schroeder et al.,
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2010, fig. 3).In the Sarv Abad section Valserina turbinata is found nearly throughout the
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succession but it is much common in lower 25 m of the section. Eopalorbitolina pertenuis,
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Vanneau, 1980; Becker, 1999; Schroeder et al., 2002; Clavel et al., 2007; Clavel et al., 2009;
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Clavel et al., 2010; Clavel et al., 2013; Granier et al., 2013; Schlagintweit et al., 2013b).
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Montseciella cf. alguerensis occurs from the late Hauterivian to early late Barremian
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(Cherchi and Schroeder, 1999; Clavel et al., 2009; 2010; 2013). The other orbitolinids
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including Paleodictyoconus cf. cuvillieri, Orbitolinopsis cf. buccifer, and Paracoskinolina cf.
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maynci have wider stratigraphic ranges from the late Hauterivian to early Aptian (Ullastre et
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al., 2002; Clavel et al., 2009; 2013; Granier et al., 2013). The basal part of the examined
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and Eopalorbitolina charollaisi range from the late Hauterivian to early Barremian (Arnaud-
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the top by the last occurrence of the species which is located a few meters below the upper
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boundary of the section. This suggests an early Barremian age for the entire carbonate
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succession of the K1 unit at Sarv Abad. The accompanying association of orbitolinids also
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supports the early Barremian dating. Of particular note, is the presence of Dictyoconus?
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pachymarginalis. This species was first described from upper Bedoulian and Gargasian
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succession at Sarv Abad is characterized by the first occurrence of Valserina turbinata and
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marker in Europe, Dictyoconus? pachymarginalis has only been reported from the Gargasian
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strata (Schlagintweit, 1990; Masse et al., 1992). Its occurrence from Bedoulian and Gargasian
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aged rocks is documented from Central Iran (Yazdi-Moghadam and Amiri, 2010;
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limestone beds of the Alborz Mountains, northern Iran (Schroeder, 1965). As a biozonal
Roozbahani, 2011; Schlagintweit et al., 2013b; Schlagintweit and Wilmsen, 2014) and
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northeastern Iran (Taherpour Khalil Abad et al., 2013). Based on our new biostratigraphic
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data, the lower limit of this taxon has to be extended into the lower part of the Barremian. It
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is worth mentioning that, according to Schlagintweit and Wilmsen (2014) the upper limit of
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Dictyoconus? pachymarginalis is unknown. Further biostratigraphic data are required to
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reveal the exact range of Dictyoconus? pachymarginalis in Iran. It is important to mention
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that the recorded Dictyoconus? pachymarginalis of this study does not display the embryonic
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Further investigations are required to reveal whether or not the early Barremian
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representatives bear the same structure in their embryonic apparatus.
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7. Conclusions
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found in the lower Barremian shallow marine deposits of the eastern part of the Moghan area,
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NW Iran.
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A relatively diversified and mostly well-preserved assemblage of orbitolinid foraminifers was
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Paracoskinolina cf. maynci, Montseciella cf. alguerensis, and Eopalorbitolina pertenuis are
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reported for the first time from Iran. Apart from Dictyoconus? pachymarginalis, the
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remainder of orbitolinid inventory shows a close similarity to the assemblages already known
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from other regions of Europe (Swiss Jura, SW France) that are situated at northern margin of
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the Tethys. This strong northern Tethyan affinity allowed us to apply the updated orbitolinid
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ranges of SW France and Swiss Jura for northwest Iran. Dictyoconus? pachymarginalis is
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known for the first time from the early Barremian, suggesting that the range of this orbitolinid
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foraminifer should be considered as whole Barremian to early late Aptian. Although this
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orbitolinid foraminifer has already been reported from the southern margin of the Neotethys
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The recognized assemblage includes 10 species belonging to 8 genera from which
(e.g., Mancinelli and Chiocchini, 2006), the species together with the other recognized
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orbitolinids in this study, are not so far known from the Arabian plate (including the Zagros
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Mountains).
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Acknowledgment
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We thank National Iranian Oil Company and Damghan University to support this study.
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Bernard Clavel (Messery) and Felix Schlagintweit (Munich) are appreciated for their
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and Lorenzo Consorti (Barcelona) are kindly acknowledged. The authors would also like to
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appreciate Eduardo Koutsoukos (Heidelberg) for his careful editing.
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(Oligocene to Miocene). Annalen des Naturhistorischen Museums in Wien. Serie A für
Roozbahani, P.R., 2011. Lithostratigraphy and biostratigraphy of the Lower Cretaceous of the
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Jalmajird area (northeast of Khomeyn, Central Iran Basin), Iran. GeoAlp, 9: 48-58. Sampò, M., 1969. Microfacies and microfossils of the Zagros Area southwestern Iran (from prePermian to Miocene), 12. HJ Brill, 108 pp.
283 284 285 286
Sarfi, M., Yazdi-Moghadam, M., 2016. Stratigraphy of the Upper Jurassic shallow marine carbonates
287
of the Moghan area (NW Iran), with paleobiogeography implication on Alveosepta jaccardi
288
(Schrodt, 1894). Geopersia, 6 (2): 187-196.
289
Schlagintweit, F., 1990. Allochthonous Urgonian limestones of the Northern Calcareous Alps: facies
290
and palaeogeographic framework within the Alpine Orogeny. Cretaceous Research, 11 (3):
291
261-272.
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ACCEPTED MANUSCRIPT Schlagintweit, F., Bucur, I.I., Rashidi, K., Hanifzadeh, R., Wilmsen, M., 2013a. Torremiroella
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hispanica Brun and Canérot, 1979 (benthic foraminifera) from the Lower Cretaceous of
294
Central Iran and its palaeo-biogeographic significance. Cretaceous Research, 46: 272-279.
295 296
Foraminifera) from the Lower Aptian sensu lato (Bedoulian) of Central Iran. Carnets de
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Geologie-Notebooks on Geology, CG2013_L04: 255-272.
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Schlagintweit, F., Bucur, I.I., Rashidi, K., Saberzadeh, B., 2013b. Praeorbitolina claveli n. sp.(benthic
Schlagintweit, F., Wilmsen, M., 2014. Orbitolinid biostratigraphy of the top Taft Formation (Lower Cretaceous of the Yazd Block, Central Iran). Cretaceous Research, 49: 125-133.
298 299 300 301
Iran)(Studien über primitive Orbitolinidae III). Eclogae Geologiace Helvetiae, 58 (2): 976-
302
979.
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Schroeder, R., 1965. Dictyoconus pachymarginalis n. sp. aus dem Apt des Elburz-Gebirges (Nord-
Schroeder, R., Clavel, B., Cherchi, A., Busnardo, R., Charollais, J., Decrouez, D., 2002. Lignées
304
phylétiques d'Orbitolinidés de l'intervalle Hauterivien supérieur-Aptien inférieur; leur
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importance stratigraphique. Revue de Paléobiologie, 21 (2): 853-863.
306
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Schroeder, R., van Buchem, F.S., Cherchi, A., Baghbani, D., Vincent, B., Immenhauser, A., Granier,
307 308
eastern Arabian Plate and implications for regional stratigraphic correlations. GeoArabia
309
Special Publication, 4 (1): 49-96.
310
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B., 2010. Revised orbitolinid biostratigraphic zonation for the Barremian–Aptian of the
Setudehnia, A., 1972. Stratigraphic lexicon of Iran. Union International des Sciences Geologiques, 3:
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320-321.
311 312
Shirazi, M.P.N., Abedi, F., 2012. Microbiostratigraphy Of The Early Cretaceous Sequence In
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Northeast Of Shiraz, Zagros Basin, Southwest Iran. Journal of American Science, 8 (3).
314
Stöcklin, J., Setudehnia, A., 1971. Stratigraphic lexicon of Iran, Part I: central, north and east Iran,
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Report No. 18. Geological Survey of Iran, 338 pp.
316
Taherpour Khalil Abad, M., Schlagintweit, F., Vaziri, S.H., Aryaei, A.A., Ashouri, A.R., 2013.
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Balkhania balkhanica Mamontova, 1966 (benthic foraminifera) and Kopetdagaria sphaerica
318
Maslov, 1960 (dasycladalean alga) from the Lower Cretaceous Tirgan Formation of the Kopet
319
ACCEPTED MANUSCRIPT Dagh mountain range (NE Iran) and their paleobiogeographic significance. Facies, 59 (1):
320
267-285.
321 322
Narieda (parte S de la serie del Cretácico inferior de Organyà). Pirineo catalán, España.
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Treballs del Museu de Geologia de Barcelona, 11: 67-95.
324
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Ullastre, J., Schroeder, R., Masriera, A., 2002. Sobre la estratigrafía del singular corte de la Roca de
Willm, C.H., Brasseur, R., Revoo, G., Marchand, J., Rochet, J., Hindermeyer, J., 1961. Geological Report No. 235 on Moghan Area, IFP mission in Azerbaijan, National Iranian Oil Company.
325 326 327
from the Sarvestan Section, south of Esfahan, Iran, The 1st International Applied Geological
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Congress, Department of Geology, Islamic Azad University-Mashad Branch, Iran, pp. 976-
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980.
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Yazdi-Moghadam, M., Amiri, F., 2010. Lower Cretaceous Agglutinating Larger Benthic Foraminifera
Fig. 1. Location and geological map of the studied section in the Moghan area (modified after
331
Khalatbari-Jafari, 2005)
332 333
distribution of index orbitolinids.
334
Figure 3. Index orbitolinids of the Sarv Abad section; A, B: Orbitolinopsis sp., C-G: Eopalorbitolina
335
charollaisi Schroeder, H: Eopalorbitolina sp. A, B: sample EHGH 3142; E: sample EHGH 3127; F,
336
H: sample EHGH 3123; G: sample EHGH 3121; I: sample EHGH 3111; J: sample EHGH 3116.
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Fig. 4. Index orbitolinids of the Sarv Abad section; A-D: Dictyoconus? pachymarginalis Schroeder,
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Fig. 2. Stratigraphic column of the Lower Cretaceous carbonate strata in the Sarv Abad section and
E-H: Eopalorbitolina pertenuis (Foury). A: sample EHGH 3125; B, C, D: sample EHGH 3142; E:
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sample EHGH 3127; F: sample EHGH 3123, G: sample EHGH 3121; H: sample EHGH 3123.
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Fig. 5. Index orbitolinids of the Sarv Abad section; A-G, I: Valserina turbinata (Foury), H:
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Orbitolinopsis cf. buccifer Arnaud-Vanneau and Thieuloy, J: Falsurgonina sp., K: Paracoskinolina
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cf. maynci (Chevalier). A, C, D: sample EHGH 3111; B, E: sample EHGH 3118; F, H, J: sample
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EHGH 3116; I: sample EHGH 3109; G: sample EHGH 3115; K: sample EHGH 3119.
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Schroeder, J, K: Paleodictyoconus cf. cuvillieri (Foury). A, E: sample EHGH 3123; B, C: sample
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EHGH 3127; D, F: sample EHGH 3127; G, I: sample EHGH 3116; H: sample EHGH 3115; J, K:
347
sample EHGH 3111.
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Fig. 7. Stratigraphic ranges of the selected late Hauterivian – early Bedoulian orbitolinids (after
349
Clavel et al, 2013) supplemented with Dictyoconus? pachymarginalis Schroeder. Tethyan ammonite
350
zonation is adopted from Reboulet et al. (2006). The grey rectangle points to the biostratigraphic
351
interval of the Sarv Abad section.
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Fig. 6. Index orbitolinids of the Sarv Abad section; A-I: Montseciella cf. alguerensis Cherchi and
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dimensional reconstruction of the embryo axially cut to show the internal structure. B and C: embryo
354
based on Fig. 5B, D. D: basal section based on Fig. 5I.
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List of taxa mentioned in the text with author attributions and dates
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Alveosepta jaccardi (Schrodt, 1894)
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Fig. 8. Drawing of embryonic apparatus and basal section of Valserina turbinata (Foury). A: three
358
Eopalorbitolina charollaisi Schroeder in Schroeder and Conrad, 1968
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Dictyoconus? pachymarginalis Schroeder, 1965
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Eopalorbitolina sp.
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Eopalorbitolina pertenuis (Foury, 1968)
Falsurgonina sp.
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Montseciella cf. alguerensis Cherchi and Schroeder, 1999
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Orbitolinopsis cf. buccifer Arnaud-Vanneau and Thieuloy, 1972
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Orbitolinopsis sp.
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Paleodictyoconus cf. cuvillieri (Foury, 1963)
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Valserina turbinata (Foury, 1968)
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Paracoskinolina cf. maynci (Chevalier, 1961)
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Some orbitolinids are reported for the first time from Iran and the Middle East. Dictyoconus? pachymarginalis is known for the first time from the early Barremian.
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Range of early Barremian orbitolinids of the northern Tethys margin eastwards is extended to NW Iran.
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S0195-6671(17)30002-2
DOI:
10.1016/j.cretres.2017.05.014
Reference:
YCRES 3611
To appear in:
Cretaceous Research
Received Date: 1 January 2017 Revised Date:
4 May 2017
Accepted Date: 9 May 2017
Please cite this article as: Yazdi-Moghadam, M., Sarfi, M., Sharifi, M., Ariafar, B., Sajjadi, F., Abbasi, P., Early Barremian orbitolinid record from the Moghan area, NW Iran: Northern margin of the Neotethys, Cretaceous Research (2017), doi: 10.1016/j.cretres.2017.05.014. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Early Barremian orbitolinid record from the Moghan area, NW Iran: Northern Margin
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of the Neotethys
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Mohsen Yazdi-Moghadama*, Mehdi Sarfib, Mohammad Sharific, Behrooz Ariafara, Fereshteh Sajjadic, Parisa Abbasic
National Iranian Oil Company Exploration Directorate, Sheikh Bahayi Square, 1994814695 Tehran, Iran,
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Email:[email protected]
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b
School of Earth Sciences, Damghan University, 36716-41167 Damghan, Iran
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c
Department of Geology, Faculty of Sciences, University of Tehran, Tehran, Iran
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Abstract
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carbonate deposits of the Moghan area, NW Iran. According to geologic map of the Razi,
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these rocks were previously assigned to general age of the Early Cretaceous. The early
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Barremian age is documented based on stratigraphic range of the marker Valserina turbinata
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(Foury) .Other orbitolinids such as Eopalorbitolina charollaisi Schroeder, Eopalorbitolina
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Orbitolinid foraminifers are reported for the first time from lower Barremian shallow marine
pertenuis (Foury), Paleodictyoconus cf. cuvillieri (Foury), Montseciella cf. alguerensis
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Cherchi and Schroeder, Paracoskinolina cf. maynci (Chevalier), Orbitolinopsis cf. buccifer
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Arnaud-Vanneau and Thieuloy, and Dictyoconus? pachymarginalis Schroeder also coexist.
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Obtained biostratigraphic data suggest that the range of Dictyoconus? pachymarginalis,
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hitherto known from the Aptian, has to be extended into the early Barremian. Most of the
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orbitolinid taxa are well known in Europe as northern Tethyan margin endemic forms.
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Therefore, the study area can be considered as part of the northern Tethys margin during the
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orbitolinids eastwards as far as northwest Iran.
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Keywords: Orbitolinids, Barremian, Tethys, Iran, Moghan, Micropalaeontology
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1. Introduction
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Early to middle Cretaceous shallow marine rocks crop out widely in different parts of Iran
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somewhat, composed of carbonate deposits rich in larger benthic foraminifera (mainly
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(James and Wynd, 1965; Stöcklin and Setudehnia, 1971; Setudehnia, 1972). These rocks are
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et al., 2013; Schlagintweit and Wilmsen, 2014).
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Orbitolinids have been reported from different structural units in Iran including Zagros
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Mountains in the south, Kopet Dagh and Alborz in the north and Central Iran in the middle
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orbitolinids) and calcareous green algae (e.g., Schroeder et al., 2010; Taherpour Khalil Abad
36
2010; Yazdi-Moghadam and Amiri, 2010; Shirazi and Abedi, 2012; Carević et al., 2013;
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Schlagintweit et al., 2013a; 2013b; Taherpour Khalil Abad et al., 2013; Afghah and
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(Henson, 1948; James and Wynd, 1965; Schroeder, 1965; Sampò, 1969; Schroeder et al.,
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Haghighi, 2014; Schlagintweit and Wilmsen, 2014; Hosseini et al., 2016).
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In many localities of Central Iran, the orbitolinid foraminifer bearing carbonates are mapped
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as “Orbitolina limestone” which were assigned to a general Early Cretaceous age.
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During the field geology dealing with stratigraphy and hydrocarbon evaluation of Mesozoic
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and Cenozoic rocks of NW Iran (Moghan area), several sections were sampled and studied.
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One of the measured sections located in eastern most part of the investigated area, includes a
44
succession of “Orbitolina limestone” (Fig. 1).
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these orbitolinid bearing deposits can potentially be considered as reservoir rocks in the
47
investigated area (e.g., FOL, 2000), the accurate dating of these strata is of great importance
48
for hydrocarbon exploration studies.
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It is the only locality in the Moghan area that Lower Cretaceous carbonate rocks crop out. As
50
faunal elements. In the absence of other index macro- and microfossil groups (e.g.,
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planktonic foraminifera, nannoplanktons, rudists), orbitolinids are of immense practical use
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for dating of these shallow marine strata as their ranges have recently been calibrated with
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ammonite biostratigraphic data (e.g., Clavel et al., 2010; 2013).Therefore, this study focuses
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Within the study section (Sarv Abad) (Fig. 1), orbitolinid foraminifers are the dominant
on this group of agglutinating foraminifera for biostratigraphy and age dating of their hosting
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rocks in the Moghan area.
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2. Material and methods
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named Sarv Abad section (Fig. 2). Some 38 rock samples have been collected with maximum
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spacing interval of 3 m. In order to study oriented sections of orbitolinids, several thin
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sections in different orientations were prepared from each sample using conventional
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methods. The generic classification of Loeblich and Tappan (1987) was used and updated in
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The material of this study comes from one section located in south eastern Moghan area,
some instances with additional sources such as Cherchi and Schroeder (1999) and Granier et
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al. (2013). All samples and thin sections presented in this paper are deposited in the
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collection of National Iranian Oil Company Exploration Directorate (NIOCEXP), Tehran,
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Iran and are labelled as EHGH 3108 to EHGH 3145.
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3. Geological setting
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Moghan area, etc.) each of them is characterized by a long and different depositional history
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(e.g., Stöcklin and Setudehnia, 1971; Setudehnia, 1972; Berberian and King, 1981; Alavi,
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2004). The northwest Iran is marked by a structural unit named as Moghan area. The area as
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a part of Alp-Himalayan orogenic belt has an extension around 6500 km2. From geological
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point of view, the Moghan area is considered as a terminal northwestern part of the Alborz-
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Azerbaijan zone having a general NW-SW trend (Nabavi, 1976).
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Iran is composed of several structural units (Zagros, Kopet Dagh, Central Iran, Alborz,
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39.42״N, and 48ᵒ, 20׳, 46״E (Fig.1). In other words, the area is located in eastern Paratethys
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The area covers northern parts of the Ardabil and East Azerbaijan provinces at 39ᵒ, 30׳,
domain extending from Carpathian in Romania to Aral Lake in Kazakhstan including the
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present day Black Sea and Caspian Sea basins (e.g., Rögl, 1998). These two basins are further
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subdivided into several side basins.
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As a part of the south Caspian basin, the Moghan area is located in northwestern corner of
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south by the northern flank of the Talysh-Lesser Caucasus orogenic belt. From tectonic point
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of view, the Moghan area together with the Kura through are considered to have a back-arc
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Iran and bounded towards the north by southeastern part of the Kura through and towards the
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early Paleogene time due to a high sediment supply from neighbouring rising mountains
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(FOL, 2000; Amini, 2006). The marine sedimentary successions of the Moghan area cropped
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out in some restricted exposures in southern parts of the basin (Willm et al., 1961) in
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localities such as Salavat, Kurd-Kandi, Zargar and Kaleybar. The mountainous area, north of
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Namin (Sarv Abad) is the only locality throughout the basin in which shallow marine Lower
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Cretaceous rocks are exposed. Based on geological map of Razi, Cretaceous shallow marine
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limestones crop out at north of Namin and are generally assigned to the Lower Cretaceous
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(Khalatbari-Jafari, 2005).
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setting. These areas were subjected to rapid siliciclastic sedimentation during late Mesozoic-
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north of the city Namin, in an area consisting of some NW-SW trending minor folds and
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thrust sheets.
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The section is measured and sampled in vicinity of Sarv Abad village, several kilometers
The sedimentary succession in this area is composed of three units including pre-Jurassic,
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Jurassic and Cretaceous deposits (Fig. 1).
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alluvium and consists of alternation of red micaceous shales and sandstones interbedded with
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grey cherty dolostones at the upper part. These strata were barren of micro-or macrofossils
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and they are assigned to the Infra-Cambrian or lower Paleozoic based on geological map of
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Razi, scale: 1:100,000.
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The base of pre-Jurassic unit (PJ), the oldest rocks exposed in the study area, is covered by
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Jurassic shales and sandstones (J1) which in turn are topped by Upper Jurassic thin to
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medium bedded dolomitic limestones and limestones (J2). The shales and sandstones are also
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devoid of any micro- or macrofauna that based on their stratigraphic position, these strata
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The pre- Jurassic rocks are unconformably overlain by a relatively thick succession of Lower
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(J2) contain Late Jurassic benthic foraminifera including Alveosepta jaccardi (Schrodt) (Sarfi
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have been ascribed to the Early Jurassic age on the geological map. The top limestone beds
and Yazdi-Moghadam, 2016).
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The Cretaceous succession is characterized by lithological diversity allowing further
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subdivision into three units (K1, K2, and K3).The K1 unit is composed of bioclastic
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orbitolinid bearing limestones resting disconformably on the Upper Jurassic limestone beds
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(J2). The K2 unit comprises clastic rocks including polygenetic conglomerates, sandstones
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and shales. This unit disconformably overlies the K1 unit. The K3 unit consists mainly of thin
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and K3 units is also disconformable. These two units (K2 and K3) are considered to be of
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Late Cretaceous age based on their stratigraphic position.
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5. The K1 unit (“Orbitolina limestone”)
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bedded limestones(wackestones to packstones and grainstones) lain disconformably on Upper
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Jurassic carbonate unit (J2). Apart from the orbitolinids, smaller benthic foraminifera,
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This 55-m-thick orbitolinid bearing unit consisting mainly of bioclastic medium to thick
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2).Green algae appear in few levels in the middle and upper parts of the section.
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echinoids, and brachiopods are also widely distributed throughout the succession (Fig.
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5A-G, I, and Fig. 8A-D), Eopalorbitolina charollaisi Schroeder (Fig. 3C-G), Eopalorbitolina
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pertenuis (Foury) (Fig. 4E-H), Eopalorbitolina sp. (Fig. 3H), Paleodictyoconus cf. cuvillieri
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(Foury) (Fig. 6J,K), Montseciella cf. alguerensis Cherchi and Schroeder (Fig. 6A-I),
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Orbitolinopsis cf. buccifer Arnaud-Vanneau and Thieuloy (Fig. 5H), Orbitolinopsis sp. (Fig.
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3A, B), Paracoskinolina cf. maynci (Chevalier) (Fig. 5K), Falsurgonina sp. (Fig. 5J), and
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Dictyoconus? pachymarginalis Schroeder (Fig. 4A-D).
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Orbitolinids are present with high abundance in the lower part of the section (0-30 m) and
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The orbitolinid association shown in Figures 3-6 includes Valserina turbinata (Foury) (Fig.
with low abundance in the upper part (40-50 m).The middle part of the succession (30-40 m)
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is marked by only a few occurrences of Paleodictyoconus cf. cuvillieri. By comparison, this
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part is characterized by several occurrences of green algae. The assemblages of non-
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orbitolinid foraminifera and algae which are not of direct biostratigraphic significance, have
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not been considered and will be the subject of further studies.
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6. Stratigraphy and discussion
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and nannofossils are absent in the Sarv Abad section. We also did not find rudists in the
140
examined succession. Therefore, among the benthic foraminifera and calcareous algae
141
present, orbitolinids are the main and stratigraphically important taxa for biostratigraphy. The
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55-m-thick unit (K1) in the Sarv Abad section consists mainly of shallow marine limestones
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with a relatively diverse assemblage of orbitolinids including Valserina turbinata,
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Eopalorbitolina charollaisi, Eopalorbitolina pertenuis, Falsurgonina sp., Paleodictyoconus
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cf. cuvillieri, Montseciella cf. alguerensis, Orbitolinopsis cf. buccifer, Orbitolinopsis sp.,
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Owing to shallow marine nature of the studied rocks, ammonites, planktonic foraminifera,
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the Lower Cretaceous rocks cropping out at Sarv Abad, the important stratigraphic index
148
microfossil is Valserina turbinata. Under the generic name Palorbitolina Schroeder, Becker
149
(1999) introduced Palorbitolina turbinata zone within the lower Barremian platform
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carbonates of the Organya basin (Spanish Pyrenees). This last author considered the
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Palorbitolina turbinata zone to correspond to Compressissima ammonite zone. An
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Paracoskinolina cf. maynci, and Dictyoconus? pachymarginalis. For detailed age dating of
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established by Schroeder et al. (2002) based on orbitolinid data from SE France. According to
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these authors, Eygalierina (=Valserina) turbinata occurs from upper Nicklesi into the
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Caillaudianus ammonite zone (Fig.7). Recently (Clavel et al., 2009; 2010; 2013) and Granier
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orbitolinid phylogenic scheme for the late Hauterivian-early Aptian time span was
et al. (2013) carried out biostratigraphic studies in SE France and French Swiss Jura. They
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reported the occurrence of Valserina turbinata within the lower Barremian from upper Hugii
158
to Pulchella ammonite zone. Our biostratigraphic analysis is based on the work of these latter
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authors for northern margin of the Neotethys. It is worth noting that none of the orbitolinids
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from the Moghan area have already been reported from the Arabian plate (Schroeder et al.,
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2010, fig. 3).In the Sarv Abad section Valserina turbinata is found nearly throughout the
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succession but it is much common in lower 25 m of the section. Eopalorbitolina pertenuis,
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Vanneau, 1980; Becker, 1999; Schroeder et al., 2002; Clavel et al., 2007; Clavel et al., 2009;
165
Clavel et al., 2010; Clavel et al., 2013; Granier et al., 2013; Schlagintweit et al., 2013b).
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Montseciella cf. alguerensis occurs from the late Hauterivian to early late Barremian
167
(Cherchi and Schroeder, 1999; Clavel et al., 2009; 2010; 2013). The other orbitolinids
168
including Paleodictyoconus cf. cuvillieri, Orbitolinopsis cf. buccifer, and Paracoskinolina cf.
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maynci have wider stratigraphic ranges from the late Hauterivian to early Aptian (Ullastre et
170
al., 2002; Clavel et al., 2009; 2013; Granier et al., 2013). The basal part of the examined
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and Eopalorbitolina charollaisi range from the late Hauterivian to early Barremian (Arnaud-
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the top by the last occurrence of the species which is located a few meters below the upper
173
boundary of the section. This suggests an early Barremian age for the entire carbonate
174
succession of the K1 unit at Sarv Abad. The accompanying association of orbitolinids also
175
supports the early Barremian dating. Of particular note, is the presence of Dictyoconus?
176
pachymarginalis. This species was first described from upper Bedoulian and Gargasian
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succession at Sarv Abad is characterized by the first occurrence of Valserina turbinata and
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marker in Europe, Dictyoconus? pachymarginalis has only been reported from the Gargasian
179
strata (Schlagintweit, 1990; Masse et al., 1992). Its occurrence from Bedoulian and Gargasian
180
aged rocks is documented from Central Iran (Yazdi-Moghadam and Amiri, 2010;
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limestone beds of the Alborz Mountains, northern Iran (Schroeder, 1965). As a biozonal
Roozbahani, 2011; Schlagintweit et al., 2013b; Schlagintweit and Wilmsen, 2014) and
182
northeastern Iran (Taherpour Khalil Abad et al., 2013). Based on our new biostratigraphic
183
data, the lower limit of this taxon has to be extended into the lower part of the Barremian. It
184
is worth mentioning that, according to Schlagintweit and Wilmsen (2014) the upper limit of
185
Dictyoconus? pachymarginalis is unknown. Further biostratigraphic data are required to
186
reveal the exact range of Dictyoconus? pachymarginalis in Iran. It is important to mention
187
that the recorded Dictyoconus? pachymarginalis of this study does not display the embryonic
188
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189
Further investigations are required to reveal whether or not the early Barremian
190
representatives bear the same structure in their embryonic apparatus.
191
7. Conclusions
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found in the lower Barremian shallow marine deposits of the eastern part of the Moghan area,
194
NW Iran.
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A relatively diversified and mostly well-preserved assemblage of orbitolinid foraminifers was
196
Paracoskinolina cf. maynci, Montseciella cf. alguerensis, and Eopalorbitolina pertenuis are
197
reported for the first time from Iran. Apart from Dictyoconus? pachymarginalis, the
198
remainder of orbitolinid inventory shows a close similarity to the assemblages already known
199
from other regions of Europe (Swiss Jura, SW France) that are situated at northern margin of
200
the Tethys. This strong northern Tethyan affinity allowed us to apply the updated orbitolinid
201
ranges of SW France and Swiss Jura for northwest Iran. Dictyoconus? pachymarginalis is
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known for the first time from the early Barremian, suggesting that the range of this orbitolinid
203
foraminifer should be considered as whole Barremian to early late Aptian. Although this
204
orbitolinid foraminifer has already been reported from the southern margin of the Neotethys
205
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The recognized assemblage includes 10 species belonging to 8 genera from which
(e.g., Mancinelli and Chiocchini, 2006), the species together with the other recognized
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orbitolinids in this study, are not so far known from the Arabian plate (including the Zagros
207
Mountains).
208
Acknowledgment
209
We thank National Iranian Oil Company and Damghan University to support this study.
210
Bernard Clavel (Messery) and Felix Schlagintweit (Munich) are appreciated for their
211
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and Lorenzo Consorti (Barcelona) are kindly acknowledged. The authors would also like to
213
appreciate Eduardo Koutsoukos (Heidelberg) for his careful editing.
214
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Fig. 1. Location and geological map of the studied section in the Moghan area (modified after
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Khalatbari-Jafari, 2005)
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distribution of index orbitolinids.
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Figure 3. Index orbitolinids of the Sarv Abad section; A, B: Orbitolinopsis sp., C-G: Eopalorbitolina
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charollaisi Schroeder, H: Eopalorbitolina sp. A, B: sample EHGH 3142; E: sample EHGH 3127; F,
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H: sample EHGH 3123; G: sample EHGH 3121; I: sample EHGH 3111; J: sample EHGH 3116.
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Fig. 4. Index orbitolinids of the Sarv Abad section; A-D: Dictyoconus? pachymarginalis Schroeder,
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Fig. 2. Stratigraphic column of the Lower Cretaceous carbonate strata in the Sarv Abad section and
E-H: Eopalorbitolina pertenuis (Foury). A: sample EHGH 3125; B, C, D: sample EHGH 3142; E:
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sample EHGH 3127; F: sample EHGH 3123, G: sample EHGH 3121; H: sample EHGH 3123.
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Fig. 5. Index orbitolinids of the Sarv Abad section; A-G, I: Valserina turbinata (Foury), H:
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Orbitolinopsis cf. buccifer Arnaud-Vanneau and Thieuloy, J: Falsurgonina sp., K: Paracoskinolina
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cf. maynci (Chevalier). A, C, D: sample EHGH 3111; B, E: sample EHGH 3118; F, H, J: sample
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EHGH 3116; I: sample EHGH 3109; G: sample EHGH 3115; K: sample EHGH 3119.
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Schroeder, J, K: Paleodictyoconus cf. cuvillieri (Foury). A, E: sample EHGH 3123; B, C: sample
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EHGH 3127; D, F: sample EHGH 3127; G, I: sample EHGH 3116; H: sample EHGH 3115; J, K:
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sample EHGH 3111.
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Fig. 7. Stratigraphic ranges of the selected late Hauterivian – early Bedoulian orbitolinids (after
349
Clavel et al, 2013) supplemented with Dictyoconus? pachymarginalis Schroeder. Tethyan ammonite
350
zonation is adopted from Reboulet et al. (2006). The grey rectangle points to the biostratigraphic
351
interval of the Sarv Abad section.
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Fig. 6. Index orbitolinids of the Sarv Abad section; A-I: Montseciella cf. alguerensis Cherchi and
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dimensional reconstruction of the embryo axially cut to show the internal structure. B and C: embryo
354
based on Fig. 5B, D. D: basal section based on Fig. 5I.
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List of taxa mentioned in the text with author attributions and dates
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Alveosepta jaccardi (Schrodt, 1894)
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Fig. 8. Drawing of embryonic apparatus and basal section of Valserina turbinata (Foury). A: three
358
Eopalorbitolina charollaisi Schroeder in Schroeder and Conrad, 1968
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Eopalorbitolina sp.
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Eopalorbitolina pertenuis (Foury, 1968)
Falsurgonina sp.
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Montseciella cf. alguerensis Cherchi and Schroeder, 1999
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Orbitolinopsis cf. buccifer Arnaud-Vanneau and Thieuloy, 1972
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Orbitolinopsis sp.
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Paleodictyoconus cf. cuvillieri (Foury, 1963)
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Valserina turbinata (Foury, 1968)
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Some orbitolinids are reported for the first time from Iran and the Middle East. Dictyoconus? pachymarginalis is known for the first time from the early Barremian.
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Range of early Barremian orbitolinids of the northern Tethys margin eastwards is extended to NW Iran.
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