Ressaut de marée et Mascaret – exemples de la Garonne et de la Seine

In this article, we present a study on the tidal bore dynamics based on the analysis of the database acquired in 2011 during two simultaneous field campaigns in the Seine and Garonne Rivers. We have shown that in the Garonne River, contrary to the common view, undular tidal bore can form for a large majority of tides, even sometimes at neap tide when the river discharge is low. We have identified, from surface elevation measurements, low-steepness, low-frequency undular tidal bores which are not visually observable. Such low-frequency tidal bores have been also identified and characterised for the first time in the Seine River. In this river, the first undulation wave height can be higher than 1 m. We have shown that the secondary wave steepness strongly increases when the Froude number exceeds the critical value F_c. The large-steepness tidal bore regime corresponds to what is commonly termed in French mascaret.     

Erratum to “The Albian-Cenomanian boundary at Eggardon Hill, Dorset (England): An anomaly resolved?” [Proc. Geol. Assoc. 120 (2009) 108-120]

Re-examination of the classic exposures of the Eggardon Grit (topmost Upper Greensand Formation) at Eggardon Hill, Dorset shows that the upper part of this unit has a more complex stratigraphy than has been previously recognised. The Eggardon Grit Member, as described herein, is capped by a hardground and associated conglomerate, and is entirely of Late Albian age. The hardground is probably the lateral equivalent of the Small Cove Hardground, which marks the top of the Upper Greensand succession in southeast Devon. The conglomerate is overlain by a thin sandy limestone containing Early Cenomanian ammonites. This limestone is almost certainly the horizon of the Early Cenomanian ammonite fauna that has previously been attributed to the top of the Eggardon Grit. The limestone is regarded as a thin lateral equivalent of the Beer Head Limestone Formation (formerly Cenomanian Limestone) exposed on the southeast Devon coast. The fauna of the limestone at Eggardon suggests that it is probably the age equivalent to the two lowest subdivisions of the Beer Head Limestone in southeast Devon, with a remanié fauna of the Pounds Pool Sandy Limestone Member combined with indigenous macrofossils of the Hooken Nodular Limestone Member. The next highest subdivision of the Beer Head Limestone in southeast Devon (Little Beach Bioclastic Limestone Member), equates with the ammonite-rich phosphatic conglomerate of the ‘Chalk Basement Bed’, which caps the Beer Head Limestone at Eggardon, and which was previously regarded as the base of the Chalk Group on Eggardon Hill.Petrographic analysis of the Eggardon Grit shows that lithologically it should more correctly be described as a sandy limestone rather than sandstone. The original stratigraphical definition of the unit should probably be modified to exclude the softer, nodular calcareous sandstones that have traditionally been included in the lower part of the member.Without the apparently clear evidence of unbroken sedimentation across the Albian-Cenomanian boundary, suggested by the previous interpretation of the Eggardon succession, it is harder to argue for this being a prevalent feature of Upper Greensand stratigraphy in southwest England. Correlation of the Eggardon succession with successions in Dorset and southeast Devon reveals a widespread regional break in sedimentation at the Albian-Cenomanian boundary. The sand-rich facies above this unconformity represent the true base of the Chalk Group, rather than the ‘Chalk Basement Bed’ of previous interpretations.Selected elements of regionally important Upper Greensand ammonite faunas previously reported from Shapwick Quarry, near Lyme Regis, and Babcombe Copse, near Newton Abbot, are newly figured herein.     

Vol.34 No.1( Sum136 )

Review on the development of studies on the tectonic and orogen process of　orogenic belt,and discussing on some new key problems 　　………………………　　　 ZH ANG Guo- wei,DONG Yun- peng,YAO An- ping(9)　…………………………A primary research on some major issues of desertification 　　………………………　　　 WANG Min,YUE L e- ping,LI Zhi- pei,NIE H ao- gang(1 7)　………………………On the put out fire in coal field burning regions of Xinjiang　　………………………　　　 ZH AN…     

Tectonique superposée de la zone de faille d’Arakapas (Massif de Troodos,Chypre)

Résumén

Une analyse tectonique du couloir faillé d’Arakapas est menée à partir de la mesure de plus de 3 000 plans striés relevés dans les formations ophiolitiques du Troodos et du Kellaki. Des mesures ont également été effectuées dans les formations du Crétacé terminal — Paléogène et du Néogène, afin de préciser l’âge des différents stades de la déformation. Elles ont été traitées par les méthodes des dièdres droits et du calcul du tenseur des contraintes. Il est montré que le couloir d’Arakapas a été le siège de plusieurs déformations successives. Au Néogène règne un régime en extension qui succède à un jeu décrochant dextre contemporain des compressions d’âge Crétacé terminal à Miocène. Un jeu décrochant antérieur peut-être mis en évidence. Il serait compatible avec le fonctionnement en faille transformante océanique proposé par divers auteurs.     

AbstractsofActaGeologicaSinica(ChineseEdition) Vol.78,No.4,2004

A New Study on the Stratotype and Biostratigraphy of the Yixian Stage in the Yixian-Beipiao Region, Liaoning --Establishment and Study of the Yixian StratotypeWANG Wuli, ZHANG Lijun, ZHENG Shaolin, ZHENG Yuejuan, ZHANG Hong, LI Zhitong and YANG Fanglin (Shenyang Institute of Geology and Mineral Resources, Shenyang, Liaoning 110032)     

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