The first 40Ar-39Ar date from Oxfordian ammonite-calibrated volcanic layers (bentonites) as a tie-point for the Late Jurassic. - Archive ouverte HAL Access content directly
Journal Articles Geological Magazine Year : 2013

The first 40Ar-39Ar date from Oxfordian ammonite-calibrated volcanic layers (bentonites) as a tie-point for the Late Jurassic.

Abstract

Eight volcanic ash layers, linked to large explosive events caused by subduction-related volcanism from the Vardar Ocean back-arc, interbedded with marine limestones and cherts, have been identified in the Rosso Ammonitico Veronese Formation (northeastern Italy). The thickest ash layer, attributed to the Gregoryceras transversarium ammonite Biozone (Oxfordian Stage), yields a precise and reliable 40Ar-39Ar date of 156.1 ± 0.89 Ma, which is in better agreement with GTS2004 boundaries than with the current GTS2012. This first biostratigraphically well-constrained Oxfordian date is proposed as a new radiometric tie-point to improve the Geologic Time Scale for the Late Jurassic, where ammonite-calibrated radiometric dates are particularly scarce.

Dates and versions

hal-00872116 , version 1 (11-10-2013)

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Cite

Pierre Pellenard, Sébastien Nomade, L. Martire, F. de Oliveira Ramalho, Fabrice Monna, et al.. The first 40Ar-39Ar date from Oxfordian ammonite-calibrated volcanic layers (bentonites) as a tie-point for the Late Jurassic.. Geological Magazine, 2013, 150 (6), pp.1136-1142. ⟨10.1017/S0016756813000605⟩. ⟨hal-00872116⟩
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