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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Carboniferous buildups in the Donets Basin (Ukraine)
Victor OGAR
Kyiv Taras Shevchenko National University, 90, Vasilkivska str., Kyiv, 03022, Ukraine; ogar_victor@ukr.net
The Carboniferous deposits of the Donets Basin contain organic buildups at different stratigraphic
intervals and built by various organisms (Fig. 1). Some of these buildings were known previously, but
many of them are described for the first time. Among organogenic constructions studied in this region
biostromes and bioherms are identified.
The Tournaisian and most of the Visean deposits are represented by a half kilometer thick layer of
laminated bioclastic limestones formed in carbonate platform conditions (the Mokrovolnovakha series).
From the top of the Visean Stage up to the top of the Upper Carboniferous the section is represented by
cyclic coal-bearing series. This multikilometer series was formed as a result of frequent alternation of
marine and continental conditions.
The Upper Visean coral buildups are studied in the Southern Donets Basin for the first time. In the
middle part of the Donetsk suite C1 v f near the village Styla a coral biostrome build by fasciculate colonies of
Siphonodendron junceum (FLEMING) with a visible length of about 3 m and height of about 1 m is
distinguished among the layered limestones with gigantoproductid brachiopods. The Upper Serpukhovian
coral bioherms were described in detail by POLJAKOVA (1986). These rather complex bioconstructions are
built up by colonial rugose corals (Siphonodendron, Lonsdaleia, Aulina, and Lithostrotion), chaetetids
(Chaetetiporella) and stromatoporoid-like fossils (Kyklopora). Colonies form a carcass enclosing solitary
rugose corals, as well as algae, bryozoans, foraminifera, brachiopods, gastropods and other organisms.
Bioherms and biostromes compose a group of continuous limestone D1 and D5. Their thickness ranges from
several to 11 meters. Drilling results show that the thickness of these structures can grow to several tens of
meters.
Lower Carboniferous coral biostromes similar to those described in the Donets Basin are known in
Western Europe – in Belgium, North-western Ireland, Spain and other countries where bioconstructors are
also consist of Siphonodendron colonies and other colonial rugose corals and chaetetids (ARETZ & WEBB 2007;
KUZNEZOV & ANTOSHKINA 2006; SOMERVILLE et al. 2003).
Middle Carboniferous organic constructions of the Donets Basin were not previously documented.
Considerable in size colonies of the rugose corals Lytvophyllum, tabulate corals Multithecopora and
chaetetids Chaetetes (Boswellia) occur in the lower part of the Bashkirian stage near the village Starobeshevo
(limestone D5 9 , E1, E2).
Coral limestone K8, L5, and partly L6 are studied in the Moscovian stage. They are regarded to be coral
biostromes. The central parts (cores) of these constructions are composed of coral baundstone (colonies of
Donophyllum, Petalaxis, and chaetetids). Along strike it is replaced by packstones and wackstone. The
thickness of the limestone surrounding coral biostromes reaches 10 m.
For the first time probable microbial bioherms of Moscovian age were described in the Northern Donets
Basin (OGAR 2007). They are located in the limestone L6 and L7. Unlike coral biostromes these buildings
have a lenticular shape. Their cores are composed of massive biomicritic limestones. Macrofauna is rarely
found. The characteristic feature of limestone texture is the presence of cylindrical channels, which are
probably the traces of life of unknown biodestructors for which the author proposed the name Tubulus
(from Lat. tubulus - tube). Nucleuses of bioherms are overlapped by loose crinoidal limestone with
frequent fragments of other groups of fauna, among them massive rugose corals Ivanovia and Petalaxis and
chaetetids. There is no doubt that these layers are part of the bioherms and can be regarded as reef trail.
The apparent length of them ranges from a few tens to a few hundred meters with maximum thickness of
6-8 m.
Chaetetid-sponge biostromes are associated with the upper part of Moscovian deposits in the northern
Donets Basin (limestone N2 and N3 near the village Kalynove). The height of chaetetid colonies forming
these bioconstructions reaches 30-40 cm with strike length of 1.2 m. The biostrome consists of Chaetetes
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