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Nouvelles études micropaléontologiques sur le stratotype de la limite Campanien-Maastrichtien à Tercis (SO France) : les gilianelles (microproblematica) extraites par acétolyse [New micropalaeontological studies on the stratotype of the Campanian-Maastrichtian boundary at Tercis (SW France): the gilianelles (microproblematica) extracted through acetolysis]

Description et illustration de quarante-quatre gilianelles (microproblematica) et de dix autres microproblematica du Crétacé de la coupe stratotypique de Tercis (limite Campanien-Maastrichtien), Sud-Ouest France [Description and illustration of forty-four gilianelles (microproblematica) and ten other microproblematica of the Cretaceous of the stratotype section at Tercis (Campanian-Maastrichtian boundary), South-West France]

The Abiod at Ellès (Tunisia): stratigraphies, Campanian-Maastrichtian boundary, correlation [L'Abiod d'Ellès (Tunisie) : stratigraphies, limite Campanien-Maastrichtien et corrélation]

New micropalaeontological studies on the type section of the Campanian-Maastrichtian at Tercis (SW France): new ostracodes obtained using acetolysis

Nouvelles études micropaléontologiques sur le stratotype de la limite Campanien-Maastrichtien à Tercis (SO France) : compléments sur les ostracodes extraits par acétolyse

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Traces de volcanisme explosif dans le Campanien pyrénéen aux alentours du stratotype de limite Campanien-Maastrichtien à Tercis (SO France, N Espagne). Repérage biostratigraphique avec une étude particulière du foraminifère Radotruncana calcarata [Traces of explosive volcanism in the Pyrenean Campanian around the Campanian-Maastrichtian boundary type section at Tercis (SW France, N Spain). Biostratigraphy with emphasis on the foraminifer Radotruncana calcarata]

Keywords: Micropalaeontology , volcanism , Campanian-Maastrichtian , stratotype , foraminifers , Tercis , Pyrenees

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Abstract:

Pyroclastic material including idiomorphic crystals of sanidine, biotite, and apatite, first identified in the type section at Tercis are contemporaneous with the Radotruncana calcarata (planktonic foraminifer) total range zone. A search was undertaken to define the palaeogeographical extent and to determine the importance of these remains of a previously unknown Campanian regional alkaline volcanic episode. A preliminary biostratigraphical search was carried out in the Tercis area and in the western Pyrenees followed by detailed micropalaeontological studies in southwestern France and northern Spain. The findings from five upper Campanian platform and flysch facies are reported in detail and deductions from three others are summarized. First, The microfaunal count of the boundary stratotype at Tercis has been increased by the use of acetolytic techniques to disaggregate indurated carbonates. So isolated tests of some key biostratigraphic markers are documented for the first time. The paucity in specimens of Radotruncana calcarata previously seen in thin sections from the type outcrop is not due to a scarcity of this particular taxon but to a general dearth of globotruncanids in the platform facies deposits of the Aturian Basin. The study shows that acetolysis multiplies the power of investigation of indurated limestones. Thus, the abundance and diversity of microproblematica discovered and studied in the stratotype section since 2006 has been confirmed and two new forms of incertae sedis are reported, one of which is called here Velafer ovatus. Today, 70 species of microproblematica are recognized at Tercis. These microproblematica allow a chronologic calibration of the deposits like or even more precise than those obtainable using ammonites or planktonic foraminifers. Sections sampled in the western Pyrenean flysch facies include the stratigraphic interval comprising the total range zone of Rd. calcarata for which we suggest here a duration of 0.80 ±0.05 Ma. No microproblematica were found in these deep detrital facies. All sections reaching the Campanian-Maastrichtian boundary contain a Contusotruncana (foraminifer) of which the morphology, illustrated anew from 3 discrete sections, is consistent with that of the specimens identified at this level in the Tercis type-section; they were called C. contusa or C. contusa?/C. patelliformis? These micropalaeontological studies substantiate the choice of Tercis as the best section in the world for location of the stratotype of the Campanian-Maastrichtian stage boundary; they show again its striking regional a

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