In SE-France and nearby Switzerland, biostratigraphic studies on the Urgonian limestone are conducted since decades, mainly using ammonites, echinoids, orbitolinids, and dasycladalean algae. The fundamental outcome, though called into question by other authors, is fully confirmed by the results of recent tests, using dinocysts and calcareous nannofossils: the Urgonian limestone is early Barremian in Ardeche; in the Subalpine Chains, it ranges from the latest Hauterivian to the early Aptian p.p.; in the French and adjacent Swiss Jura, the "Urgonien jaune" is late Hauterivian p.p., while the overlying "Urgonien blanc" is late Hauterivian p.p. and early Barremian p.p. Resulting from these dating elements and carbonate facies distribution, internal deposits including rudists evidently follow a prograding path, from the Jura in the direction of the SW, towards the Vocontian Basin. This progradation is on the contrary of a depositional model proposed by other authors, calling for the Urgonian limestone to be more or less isochronously transgressive in the opposite direction, on top of an emergent unconformity of regional extent, allegedly corresponding to the absence of early Barremian deposits.
Dating and progradation of the Urgonian limestone from the Swiss Jura to South-East France / B. Clavel, J. Charollais, M. Conrad, R.J. du Chene, R. Busnardo, S. Gardin, E. Erba, R. Schroeder, A. Cherchi, D. Decrouez, B. Granier, J. Sauvagnat, M. Weidmann. - In: ZEITSCHRIFT DER DEUTSCHEN GESELLSCHAFT FÜR GEOWISSENSCHAFTEN. - ISSN 1860-1804. - 158:4(2007), pp. 1025-1062. [10.1127/1860-1804/2007/0158-1025]
Dating and progradation of the Urgonian limestone from the Swiss Jura to South-East France
E. Erba;
2007
Abstract
In SE-France and nearby Switzerland, biostratigraphic studies on the Urgonian limestone are conducted since decades, mainly using ammonites, echinoids, orbitolinids, and dasycladalean algae. The fundamental outcome, though called into question by other authors, is fully confirmed by the results of recent tests, using dinocysts and calcareous nannofossils: the Urgonian limestone is early Barremian in Ardeche; in the Subalpine Chains, it ranges from the latest Hauterivian to the early Aptian p.p.; in the French and adjacent Swiss Jura, the "Urgonien jaune" is late Hauterivian p.p., while the overlying "Urgonien blanc" is late Hauterivian p.p. and early Barremian p.p. Resulting from these dating elements and carbonate facies distribution, internal deposits including rudists evidently follow a prograding path, from the Jura in the direction of the SW, towards the Vocontian Basin. This progradation is on the contrary of a depositional model proposed by other authors, calling for the Urgonian limestone to be more or less isochronously transgressive in the opposite direction, on top of an emergent unconformity of regional extent, allegedly corresponding to the absence of early Barremian deposits.File | Dimensione | Formato | |
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