Aretz et al_2011.pdf - ORBi - Université de Liège

_________________________________________________________________________________________________________
Kölner Forum Geol. Paläont., 19 (2011)
M. ARETZ, S. DELCULÉE, J. DENAYER & E. POTY (Eds.)
Abstracts, 11th Symposium on Fossil Cnidaria and Sponges, Liège, August 19-29, 2011
_________________________________________________________________________________________________________
Visean corals of the Kiyasar area (North of Iran)
Victor OGAR 1 , Mostafa FALAHATGAR 2 & Hossein MOSADDEGH 3
1 Kyiv Taras Shevchenko National University, 90, Vasilkivska str., Kyiv, Ukraine, 03022;
ogar_victor@ukr.net;
2 Department of Geology, Payame Noor University; Shiraz, Iran; mostafa.mo2@gmail.com
3 School of Earth Sciences, Damghan University, PO Box 36715-364, Damghan, Iran; hosadegh@gmail.com
Lower Carboniferous corals in the North of Iran have been studied in detail by FLÜGEL (1963) and
KHAKSAR (1996). FLÜGEL studied mainly the Upper Visean corals from the Talartal and Semnan sections.
From the Lower Visean he indicated only three species: Siphonophyllia cylindrica cylindrica MCCOY, 1844, S.
cylindrica latitabulata (GORSKY, 1932) and Caninophyllum archaici archaici (MILNE-EDWARDS & HAIME, 1852).
Later KHAKSAR studied corals of the Mobarak formation in 8 outcrops, but they were mainly
Tournaisian in age. For the Visean part of the sections he indicated only three species, also known in the
Tournaisian sediments of the central Alborz Mountains. These are: Amplexizaphrentis iranensis KHAKSAR,
Kueichouphyllum alborence major KHAKSAR and Zaphriphyllum mobarakense KHAKSAR. Thus, there were only
fragmentary data on Lower Visean corals in the north of Iran.
The authors studied corals in the Kiyasar section, which is located in Northern Iran and the eastern limit
of Alborz Mountains (latitude N: 36 14'18", longitude E: 53 32'57"). During the Early Carboniferous time the
Alborz Mountains were part of the Gondwana margin (BRENCKLE et al. 2009). The Mobarak Formation
includes alternations of thin to thick-bedded limestone, dolomitic limestone with interbedded shale and
dark marl. Facies analyses show that this formation is composed of shallowing upward cycles, which are
deposited on carbonate ramp.
The Mobarak Formations is conformably overlain by sandy limestone of the Geirud Formation (Upper
Devonain) and covered with sandstones of the Dorud Formation (Lower Permian) (Fig. 1). The thickness of
the Mobarak Formation in the Kiyasar section is 250 m. This formation can be divided into 4 units. Studied
corals were collected from Unit 3 and partly from lower part of Unit 4. Unit 3 is 106 m thick, and starts with
thick-bedded limestone and continues with alternations of mediumbedded
limestone to a layer with ichnofossils and black shales and
marl. Unit 4 has a thickness of 50 m which starts with dark marls
and medium-bedded dolomitic limestone then continues with
medium-bedded limestone and interbedded shale.
Most of the studied specimens are rugose corals (Fig. 2).
Dominant genera are Siphonophyllia, Bifossularia, Kueichouphyllum and
Amygdalophyllum; subordinate occur Adamanophyllum, Clisiophyllum,
Arachnolasma and Amplexizaphrentis. Among the corals there is also
the tabulate corals ?Turnacipora and the heterocoral Hexaphyllia
mirabilis (DUNCAN, 1867). For many taxa it is the first record in this
region.
Bifossularia from the Mobarak Formation is very similar to B.
ussowi (GABUNIA 1919) from the lowermost part of the Visean of the
Kuznetsk Basin (DOBROLYUBOVA et al. 1966). Many specimens
belong to Kueichouphyllum. We have determined one as K. gracile YÜ,
1933. It was described for the first time in China as subspecies and
then diagnosed as independent species in Armenian (PAPOJAN 1969
). In Armenia this species occurres in uppermost lower Visean and
the lowermost middle (?) Visean.
Turnacipora was separated from Michelinia by investigation of the
fine microstructure of the walls (LAFUSTE & PLUSQUELLEC 1985). The
specimens described by LAFUSTE & PLUSQUELLEC as T. megastoma
Fig. 1. Stratigraphy of the Kiyasar
section
123