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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A lower Givetian Patch-reef (Hanonet Formation) from the Mont d’Haurs
fortifications (Givet, Ardenne, France): environment, stromatoporoids and
tabulate corals
Emilie PINTE 1 , Benoit L.M. HUBERT 1 , Bruno MISTIAEN 1 & Catherine CRÔNIER 2
1 Laboratoire de Paléontologie stratigraphique, FLST – ISA, Géosystèmes FRE 3298, 41 rue du Port, 59046
Lille cedex, France; emilie.pinte@icl-lille.fr, benoit.hubert@icl-lille.fr, bruno.mistiaen@isa-lille.fr
2 Laboratoire Géosystèmes, FRE 3298 CNRS, USTL, UFR des Sciences de la Terre - bâtiment SN5, F- 59655
Villeneuve d'Ascq cedex, France; Catherine.Cronier@univ-lille1.fr
The Mont d’Haurs section (50°07’43” N; 04°49’20”E) is located on the eastern part of the Meuse river,
and belongs to southeastern border of the Dinant synclinorium. The fortification outcrop (269 metres thick)
includes a lithologic interval from the upper part of the Hanonet through the Mont d’Haurs formations
(lower to middle Givetian). The work focuses on a succession of three ovoidal and reefal lenses belonging
to the last 15 metres of the Hanonet Formation (HUBERT 2009). Each patch-reef is 0.5 to 1.5 metres thick. A
detailed sedimentological analysis and biological determination were performed bed by bed to constrain
facies and faunal occurrences.
The Hanonet Formation corresponds to an alternation of dark argillaceous limestone, with local nodules
and nodular limestone, and regularly centimetre-thick yellow-brownish shaly interbeds. The patch-reef
body is surmounted by a distinct argillaceous interbed containing the solitary rugose corals Calceola
sandalina. Two main microfacies were recognized and correspond to 1/Argillaceous Wackestone-Packstone
with abundant and diverses bioclasts and bioturbation (MF1b, PRÉAT & MAMET 1989), 2/ Argillaceous
Boundstone-Floatstone with laminar stromatoporoids and tabulate and rugose corals (MF4b, PRÉAT &
MAMET 1989).
The biodiversity and morphology of stromatoporoids and tabulate corals were performed on 250
collected samples. Six species of stromatoporoids assigned to Clathrocoilona, Stromatoporella and
Stromatopora and 15 species of tabulate corals assigned to Favosites, Cladopora, Alveolites, Crassialveolites,
Platyaxum, Roseoporella, Remesia and Syringopora were recognized. Stromatoporoids and tabulate corals are
growing on soft substrate. Morphological trends are dominated by lamellar (or laminar) and low tabular
and can be interpreted as an adaptation to open marine environment and low to moderate agitation.
Clustering analyses using Hierarchical Cluster Analysis were performed in order to identify groups of
similar taxa and recognized possible assemblages according to the macro and micro-facies. Moreover, a
Detrended Correspondence Analysis (DCA - HILL & GAUCH 1980) was performed to identify indirectly
environmental gradients that may have influenced the distribution of faunas. Such an environmental
gradient has been identified from four successsive biological assemblages: 1/ Trilobite-Algae-Bivalves,
2/Crinoid-Brachiopod-Bryozoan-Ostracod, 3/ Stromatoporoid-Tabulate coral-Worm-Bioturbation, and
4/Rugose corals. This faunal distribution indicates an environmental gradient from classical open-marine
to reefal faunas.
HILL, M.O. & GAUCH, H.G. (1980): Detrended correspondence analysis: an improved ordination technique. - Vegetatio,
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HUBERT, B.L.M. (2009): Detailed lithology and faunal occurrence of the historical givetian section: the fortifications of
the Mont d’Haurs (Givet, France). - Annales de la Société Géologique du Nord, 15: 53-65
PREAT, A. & MAMET, B. (1989): Sédimentation de la plateforme carbonatée givétienne franco-belge. - Bulletin Centres
Recherches Exploration-Production d’Elf-Aquitaine, 13/1: 47-86.
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