Aretz et al_2011.pdf - ORBi - Université de Liège

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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
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Late Ordovician-early Silurian Tabulate Corals and Stromatoporoids of
the Zeravshan Range, Central Asia
Firuza A. SALIMOVA & Firdaus S. KARIMOVA
ОАО ‘Regional Geology’, State Committee of Geology and Mineral Resources, Akhunbabaev, 21, 111800,
Tashkent, Uzbekistan; firuza_salimova@yahoo.com, Firdaus52@mail.ru
The Late Ordovician to Llandovery faunas of the Zeravshan Range are relatively well documented (KIM
1966; KIM et al. 1978, 2007). In general, the Late Ordovician faunas of the Zeravshan Range show distinct
Gondwanan signatures, in such groups like trilobites and brachiopods, which have strong similarity to the
contemporaneous faunas of temperate latitude peri-Gondwana and especially to those of Central Iran,
Byrma, South China and Kazakhstan. The Upper Ordovician sequence in the Zeravshan Range comprises
mainly siliciclastic rocks with a brief episode of carbonate sedimentation in the late Katian (Archalyk Beds),
suggesting warming prior to the terminal Ordovician glaciation during the Hirnantian. This warming
episode coincided with the invasion of a moderately diverse fauna of tabulate corals and stromatoporoids
dominated by Ecclimadiction, Lyopora, Nyctopora, Catenipora, Reuchia, Agetolites, Agetolitella, Palaeofavosites,
Plasmoporella, Granulina, Acdalopora, Acdalina, Paolites, Propora, Visbilites, Stelliporella, Taeniolites, Sumsarolites
and Pycnolithus. The associated faunal assemblage includes also rugose corals and early pentameridines
Holorhynchus and Proconchidium. The coelenterate fauna shows distinct affinity to the late Ordovician
faunas of South China, Kazakhstanian terranes and Baltoscandia (partly). The Rhuddanian coelenterate
assemblage is also documented in the Zeravshan Range from the overlying Minkuchar Beds (KIM et al
1978, 2007). It differs from the Archalyk Assemblage to a considerable extent and includes representatives
of Labechia, Clathrodictyon, Ecclimadictyon, Actinodictyon, Halysites, Acidolites, Syringopora and also
transitional genera Раlаеоfavosites, Саtenipora and Propora. In taxonomic composition the Minkuchar
Assemblage shows similarity to the coral and stromatoporoid faunas of the Baltoscandia and
Kazakhstanian terranes.
Early Palaeozoic palaeogeography of Central Asia is still very poorly understood. According to BISKE
(1995) and BURTMAN (2006) the Zeravshan Range is situated within the boundaries of the peri-Gondwanan
Karakum-Tajik microplate but the time of its separation from mainland Gondwana is not defined.
Acknowledgements:
The research is supported by the Paleontological Society International Research Program - Sepkoski
Grants (RUG1-33014-XX-09
BISKE, Yu.S. (1996): Palaeozoic structure and geological history of South Tien Shan. - St Petersburg State University, St
Petersburg, 192 pp. [In Russian]
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Geologicheskogo Instituta, 570: 1-214. [In Russian].
KIM, A.I. (1966): Tabulatomorphic Corals of the Paleozoic of the Zeravshan-Hissar mountain area. - Tashkent: FAN, 71
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