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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In the Pădurea Craiului Massif Upper Aptian (Gargasian)–?Lower Albian corals occur within the
Vârciorog Formation. The succession in the Subpiatră quarry consists of limestones containing rudist
biostromes (lower part of succession), coral biostromes (upper part), while the middle part is dominated by
Bacinella irregularis facies (mostly oncoids) (BUCUR et al. 2010). Coral biostromes contains among others
Cyatophora sp., Latusastraea sp., Calamophylliopsis sp. and Amphiaulastraea sp. (Fig. 1C). Bacinella facies
contains rare, and small corals (Fig. 1E). Corals occur also within intercalations of black limestone and
sandy limestones within siliciclastic parts of the Vârciorog Formation. Sandy limestones contain poor
diversified corals, mostly Calamophylliopsis fotisaltensis (BENDUKIDZE) (Fig. 1F) and Cyatophora steinmanni
FRITZSCHE. Low taxonomic diversity indicate a stressful environment (high input of siliciclastic sediments).
Digitate colonies of Cyatophora steinmanni and large skeletons of Calamophylliopsis preserved in situ, lack of
encrustations and borings indicate that they were adapted to enhanced sedimentation, continuously baffled
by sediment during their growth, and formed a constratal growth fabric. Corals from black limestones are
more diversified. Some of them are encrusted by microbial crusts or by photrophic Lithocodium/Bacinella
consortium.
It is worth to underline that coral assemblages from two analysed areas have developed during the Late
Aptian (Gargasian). It is well recognized worldwide that during the late Early Aptian (Oceanic Anoxic
Event 1a) and mid-Late Aptian warming interval many carbonate platforms were drowned on the northern
Tethyan and Atlantic realms. Some sub-tropical carbonate platforms which did not drown during that time
were affected by increased terrigenous input (HELDT 2010). The dominance of Bacinella facies in Pădurea
Craiului (Subpiatră limestones) may be a similar response of neritic platform system to factors that caused
OAE1a reported in basinal facies. Bacinella facies, with rare corals, were reported from Lower Aptian
(Oman: IMMENHAUSER et al. 2005; Croatia: HUCK et al. 2010) and Middle Aptian (Slovenia: KOCH et al. 2002)
of the southern and central Tethyan domain. Thus, if the hypothesis of a northwards decreasing
Lithocodium–Bacinella facies during Aptian is justified (HUCK et al. 2010) that suggests the central Tethyan
platform domain of Padurea Craiului during that time.
These studies were supported by Romanian research grants CNCSIS 3/1330 and ID 95.
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palaeoenvironmental evolution of the Tunisian carbonate platform margin during the Late Aptian. -
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