Discussion of the paper by Godet et al. 2011, entitled “Reconciling strontium-isotope and K–Ar ages with biostratigraphy: the case of the Urgonian platform, Early Cretaceous of the Jura Mountains, Western Switzerland” (Swiss Journal of Geosciences, 104, 147–160)

The Cretaceous of the Swiss Jura Mountains: an improved lithostratigraphic scheme

“…This is confirmed by biostratigraphic data in the neighbouring regions (Charollais et al 2013a;Mojon et al 2013). The Hauterive Marls start in the late Valanginian Peregrinus Zone and reach up into the early Hauterivian Loryi Zone (the upper part of the Peregrinus Zone and the Furcillata Zone are condensed).…”

“…dated outcrops of the Grand Essert, Gorges de l'Orbe, and Vallorbe formations with Sr-isotope ratios (measured on brachiopods) and calibrated them on ammonite zones, and they also furnished some K-Ar numerical ages (measured on glauconite). Their interpretations, however, are partly in contradiction with the biostratigraphy presented here, and the opposing views have not yet been reconciled (Charollais et al 2013a;Godet et al 2013;Clavel et al 2013Clavel et al , 2014.…”

“…In the area of the type locality, the base of the formation contains a 2-3 m thick marly, oolitic, and fossiliferous interval (Charollais et al 2013), which, in a quarry close to St.-Cergue (Swiss Jura), measures 5.7 m and has been described as the ''Marnes d'Arzier'' (De Loriol 1868; Jaccard 1869; Arn et al 2005). In the southern Jura, the top of the The main part of the Vuache Formation is dated as early Valanginian by ammonites (Baumberger 1901(Baumberger , 1903(Baumberger -1910, ostracodes, echinids, and calpionellids (Busnardo and Thieuloy 1989;Deville 1990;Blondel 1990;Charollais et al 1983Charollais et al , 1989Charollais et al , 2008Charollais et al , 2013a. Specifically, the ''Marnes d'Arzier'' at the base of the formation have furnished dinocysts (Muderongia macwahaei forma B), which correspond to the Pertransiens ammonite zone (Monteil 1992(Monteil , 1993Leereveld 1997).…”

Some key Lower Cretaceous sites in Drôme (SE France)

“…Thus, L'Estellon section can be regarded as a "Rosetta Stone" for the Urgonian biostratigraphy. A comparison of these updated microfossil appearances with their ranges shown on current orbitolinid charts CLAVEL et al, 2007CLAVEL et al, , 2010a provide contrasting results: for instance, our results call for the definitive withdrawal of one mented chart (ARNAUD-VANNEAU's that denies lower Barremian occurrences as documented herein) and lead to question the conclusions of the several publications relying on such biostratigraphic framework (see similar discussions in CONRAD et al, 2012, andCHAROLLAIS et al, 2013). …”

Reply to the discussion by Charollais et al. on “Reconciling strontium-isotope and K–Ar ages with biostratigraphy: the case of the Urgonian platform, Early Cretaceous of the Jura mountains, Western Switzerland” by Godet et al. (2011), Swiss Journal of Geosciences, 104, 147–160

“…In their discussion, Charollais et al (2013) challenge our recently published ages for the Urgonian formation of the western Swiss Jura (Godet et al 2011), which were derived by a chemostratigraphic approach. In our paper, we integrated strontium-isotope analyses on well-preserved rhynchonellids and K-Ar analyses on well-preserved glauconite grains with existing biostratigraphic data (Godet et al 2011).…”