Ostracods and lithofacies of the Devonian-Carboniferous boundary beds in the Avesnois, North of France
Casier, J.-G.; Préat, A. (2003). Ostracods and lithofacies of the Devonian-Carboniferous boundary beds in the Avesnois, North of France. Bull. Kon. Belg. Inst. Natuurwet. Aardwet. = Bull. - Inst. r. sci. nat. Belg., Sci. Terre 73: 83-107
In: Bulletin van het Koninklijk Belgisch Instituut voor Natuurwetenschappen. Aardwetenschappen = Bulletin de l'Institut Royal des Sciences Naturelles de Belgique. Sciences de la Terre. KBIN: Brussel. ISSN 0374-6291, meer
Seven major carbonate microfacies are defined in the Devonian-Carboniferous (D-C) transitional strata (90 m) of the Bocahut quarry (Avesnes "basin"), and ten levels ranging through the Epinette, Etroeungt, Avesnelles and Hastiere formations are recognized. The "bathymetric" sequences range from open marine spiculite, below the storm wave base to semi-restricted lagoon. A standard sequence records a shallowing-upward trend, from environments below the storm wave base to strongly eroded supratidal pre-evaporitic environments. Faunal components (echinoderms, brachiopods...) point to an open marine domain for the first six microfacies. Except for the "black" mudstones of microfacies containing rare algae, the environment is located within the dysphotic-euphotic zone.Ostracods are abundant and diversified throughout the studied section. Sixty-six species are identified and belong to an assemblage of the Eifelian ecotype indicating oxygenated shallow marine environments generally between storm and fair-weather wave bases. The absence of some platycopid ostracods at the base of the Hastiere Formation could be related to the hiatus observed between the Avesnelles and Hastiere formations. That hiatus probably corresponds to the Hangenberg Event; however, its effect on the distribution of ostracods was very reduced.Ostracods and sedimentology show that the Bocahut quarry displays the most complete succession presently known through the D-C transition in Northern France (Avesnes "basin") and Southern Belgium (Dinant basin) although it is far from being continuous.Two new species are described: Saccelatia? advena nov. sp. and Healdianella dorsosulcata nov. sp.
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