RT Conference Proceedings
T1 Formal proposal for the Global Boundary Stratotype Section and Point (GSSP) of the Bathonian Stage, at the base of the Zigzag Zone in the Ravin du Bès Section (Bas-Auran, Subalpine Basin, SE France).
A1 Fernández López, Sixto Rafael
A1 Pavia, Giulio
A1 Erba, Elisabetta
A1 Guiomar, Myette
A1 Henriques, María Helena Paiva
A1 Lanza, Roberto
A1 Mangold, Charles
A1 Olivero, Davide
A1 Tiraboschi, Daniele
AB The Global Boundary Stratotype Section and Point (GSSP) for the base of the Bathonian Stage isproposed at the base of limestone bed RB071 (bed 23 in Sturani 1967) in the Ravin du Bès Section (43º57’38’’N, 6º18’55’’E), Bas-Auran area, in the Chaudon-Norante commune, around 25 km at theSouth-Southeast of Digne-les-Bains, in the “Alpes de Haute Provence” French department. The Ravindu Bès Section, as formal candidate GSSP for the base of the Bathonian Stage, satisfies most of therequirements recommended by the International Commission on Stratigraphy (ICS): 1) The exposure extends over 13 m in thickness, comprising more than five metres of fossiliferous levels below andabove the boundary. The Bathonian basal bed corresponds to the “Marno-calcaires à Cancellophycus”,is located 7.8 m below the “Terres Noires” Formation and forms part of a transgressive-facies cycle.At the Bajocian-Bathonian transition, no vertical (bio-, ichno- or tapho-) facies changes, stratigraphicgaps or hiatuses have been recorded. There is no evidence of taphonomic condensation (i.e. mixture of fossils of different age or different chronostratigraphic units). Structural complexity, synsedimentary and tectonic disturbances, or important alterations by metamorphism are not relevant constraints in theBas-Auran area. 2) There is a well-preserved, abundant and diverse fossil record across the boundary interval, with key markers (ammonites and nannofossils) for worldwide correlation of the uppermostBajocian and Lower Bathonian. The boundary can be characterized by both primary and secondary(auxiliary) biostratigraphic markers. The section appears to be suitable for biostratigraphic study of microfossils, such as foraminifera, but as yet there are no published studies. The base of Bathonian Stage and Zigzag Zone in Bas-Auran corresponds to the renewal of parkinsonids and the first occurrence level of Gonolkites convergens Buckman. This level coincides with the first occurrence ofMorphoceras parvum Wetzel. Calcareous nannofossils, as secondary global marker, are present in all beds and allow characterizing the Bajocian-Bathonian transition. 3) Regional analyses of sequencestratigraphy and manganese chemostratigraphy are available. Spectral gamma-ray data corroborate anEarly Bathonian deepening half-cycle of second order. No data are currently available for strontium isotope (87Sr/86Sr ratio), oxygen isotope (δ18O) or carbon isotope (δ13C) chemostratigraphy. Bajocian and Bathonian deposits have been remagnetized with a steady normal polarity. Volcanogenic depositssuitable for direct radio-isotope dating are not known in the section. 4) The criteria of accessibility, conservation and protection are assured by the “Réserve Naturelle Géologique de Haute Provence”,protected under national law as recognised by UNESCO. The Cabo Mondego Section (Portugal), which provides complementary data of the ammonite succession at the Sub-Mediterranean ParvumSubzone and its chronocorrelation with the Northwest European Convergens Subzone, is suggested asthe Bathonian auxiliary section and point (ASP) within this GSSP proposal.
YR 2007
FD 2007
LK https://hdl.handle.net/20.500.14352/53983
UL https://hdl.handle.net/20.500.14352/53983
LA eng
DS Docta Complutense
RD 29 abr 2024