The Cretaceous of the Swiss Jura Mountains: an Improved Lithostratigraphic Scheme
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View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by RERO DOC Digital Library Published in "Swiss Journal of Geosciences 109(2): 201–220, 2016" which should be cited to refer to this work. The Cretaceous of the Swiss Jura Mountains: an improved lithostratigraphic scheme Andre´ Strasser1 • Jean Charollais2 • Marc Andre´ Conrad3 • Bernard Clavel4 • Antoine Pictet5 • Bruno Mastrangelo6 Abstract In the course of the HARMOS project of the finally the drowning of this platform followed by the pre- Swiss Geological Survey, the lithostratigraphic subdivi- dominance of pelagic conditions. The common lateral and sions of the Cretaceous sedimentary rocks outcropping in vertical changes in facies and sedimentation rates as well as the Swiss Jura Mountains were revisited. New formation numerous hiatuses within the formations testify to a com- names are proposed where only inadequate facies terms plex interplay of tectonics, climate, and sea level that existed so far. As in some cases outcrop conditions in the controlled the Swiss Jura realm during the Cretaceous. Swiss Jura do not allow for logging complete sections to characterise the formations, type localities in neighbouring Keywords Swiss Jura Á Cretaceous Á Lithostratigraphy Á France have been chosen. The following formations (Fm.) Geological maps are defined to describe the Cretaceous lithological units (from bottom to top): Goldberg Fm., Pierre-Chaˆtel Fm., Re´sume´ Dans le cadre du projet HARMOS du Service Vions Fm., Chambotte Fm., Vuache Fm., Grand Essert ge´ologique suisse, les subdivisions lithostratigraphiques Fm., Gorges de l’Orbe Fm., Vallorbe Fm., Perte du Rhoˆne des roches se´dimentaires cre´tace´es du Jura suisse ont e´te´ Fm., Narlay Fm. Dating of the formations is based on nouvellement de´finies. De nouveaux noms de formation biostratigraphy (ammonites, echinids, dasycladalean algae, sont propose´s pour remplacer quelques termes de facie`s foraminifera, calpionellids, dinocysts, nannofossils). The inade´quats. Dans certains cas, les conditions d’affleurement fossils indicate Berriasian through to Coniacian ages. The dans le Jura suisse ne permettent pas de lever des coupes lithostratigraphic units describe the general evolution from comple`tes qui caracte´risent les formations : des coupes en a shallow, peritidal platform to deeper-water shelf envi- France voisine ont donc e´te´ choisies. Les formations (Fm.) ronments, then the installation of a carbonate platform, and suivantes sont de´finies pour de´crire les unite´s lithologiques http://doc.rero.ch du Cre´tace´, de la base au sommet : Fm. du Goldberg, Fm. de Pierre-Chaˆtel, Fm. de Vions, Fm. de la Chambotte, Fm. Editorial handling: W. Winkler and A. Morard. du Vuache, Fm. du Grand Essert, Fm. des Gorges de & Andre´ Strasser l’Orbe, Fm. de Vallorbe, Fm. de la Perte du Rhoˆne, Fm. de [email protected] Narlay. La datation des formations est base´e sur la bios- 1 tratigraphie (ammonites, e´chinides, algues dasycladales, Department of Geosciences, University of Fribourg, Chemin ` du Muse´e 6, 1700 Fribourg, Switzerland foraminiferes, calpionelles, dinocystes, nannofossiles). Ces ˆ 2 fossiles indiquent des ages Berriasien a` Coniacien. L’en- Sciences de la Terre et de l’Environnement, University of chaıˆnement des unite´s lithostratigraphiques re´sulte de Geneva, Rue des Maraıˆchers 13, 1211 Geneva, Switzerland ´ ´ ´ 3 l’evolution generale d’une plate-forme peu profonde, voire Chemin de Planta 71, 1223 Cologny, Switzerland pe´ritidale, vers des milieux d’eau plus profonde, suivie par 4 Chemin des Champs d’Amot 24, 74140 Messery, France l’installation d’une plate-forme carbonate´e, et finalement 5 Institut des Sciences de la Terre, University of Lausanne, l’ennoiement de cette plate-forme et la pre´dominance de Ge´opolis, 1015 Lausanne, Switzerland conditions pe´lagiques. Des changements de facie`setde 6 Chemin du Creˆt-de-la-Tour 4, 1248 Hermance, Switzerland taux de se´dimentation late´raux et verticaux ainsi que de 1 nombreuses lacunes sont courants au sein des formations, historical type localities are not accessible any more ce qui indique une interaction complexe de changements (abandoned quarries, vegetation cover) and it will be nec- tectoniques, climatiques et eustatiques qui controˆlaient essary to choose reference sections suitable for future l’e´volution de la re´gion du Jura suisse durant le Cre´tace´. detailed studies. Figure 2 summarises the proposed scheme for the lithostratigraphic subdivisions of the Cretaceous in the Swiss Jura. The most common historical terms corre- 1 Introduction sponding to these formations are listed in Table 1.Itis important to note that the limits between the formations are The Swiss Geological Survey has initiated the HARMOS not necessarily isochronous, that hiatuses are common, and project in order to update and homogenise the lithostrati- that the age attribution of some units presented here is graphic nomenclature and the legends of the Swiss Geo- disapproved by some authors (see below). Figure 3 is a logical Atlas 1:25,000 (see Strasky et al. 2016, this compilation of the formation thicknesses given in the volume). At the same time, this was an occasion to revise descriptions to the maps of the Swiss Geological Atlas the lithostratigraphic subdivisions forming the geological 1:25,000. In Fig. 4, the formations are plotted along the record in Switzerland. time axis and the ammonite zones (according to Hardenbol Here, we present a revision and improvement of the et al. 1998 and Reboulet et al. 2014). In the following, each lithostratigraphic scheme for the Cretaceous sedimentary formation is briefly characterised. Detailed information is deposits in the Swiss Jura Mountains. So far, several units also available in the on-line stratigraphic lexicon developed have not been defined as formations complying with the by the Swiss Committee on Stratigraphy and the Swiss recommendations of the International Commission on Geological Survey (www.strati.ch). The coordinates of the Stratigraphy (Salvador 1994) or of the Swiss Committee on type sections are given in Table 2. Stratigraphy (Remane et al. 2005). For example, facies terms such as ‘‘Purbeckian’’ or ‘‘Urgonian’’ are still found 2.1 Goldberg Formation in the legends and descriptions of many previously pub- lished geological maps. It is our goal to propose a coherent This formation was first defined in the area of Biel by scheme that subdivides the Cretaceous sedimentary record Ha¨feli (1964, 1966), the type locality being in an aban- into formations that can easily be identified in the field and doned quarry (Fig. 1; Table 2). It corresponds to the that can be mapped at the 1:25,000 scale. Where appro- ‘‘Purbeck facies’’ of the western and southern Jura Moun- priate, we also propose members that further subdivide the tains (Lory 1857). The formation overlies the Twannbach sediment stack and may be used as guide horizons in field Formation (Ha¨feli 1966; Bla¨si 1980), mostly of Tithonian mapping and in lateral correlation of logs (however, it is age. The lower boundary of the Goldberg Formation has beyond the scope of this contribution to describe and for- been originally placed above the ‘‘calcaire aˆpre’’ (Jaccard mally define these members). Although the scheme basi- 1869;Ha¨feli 1966), a horizon with cornieule texture cally focuses on lithostratigraphy, short chapters dealing interpreted as the result of subaerial exposure (Rameil with the dating of the units and the palaeogeographic 2005). However, this boundary is often difficult to locate evolution of the Jura realm are included. due to the poor outcrop conditions of the Goldberg for- http://doc.rero.ch mation. The Goldberg Formation is overlain by the Pierre- Chaˆtel Formation, the base of which is commonly 2 Cretaceous formations expressed as a sharp transgressive surface (Fig. 5a, b). The deposits are characterised by alternations of lime- Cretaceous outcrops in the Swiss Jura Mountains are found stone beds and marly layers, with locally a predominance only in the area southwest of Biel but extend into France of marls (usually leading to a morphological depression: towards the west and south (Fig. 1). While the Berriasian ‘‘combe purbeckienne’’). The thickness of the formation to Barremian sedimentary rocks are well represented over varies between 5 and 30 m, depending on the geographical the entire area, the Aptian, Albian, and Late Cretaceous in location (Fig. 3). At Mount Sale`ve (map 48, Gene`ve), the Swiss part of the Jura are visible only as isolated pat- Lombard (1965) indicated 42–46 m, whereas Strasser and ches. For several formations, outcrop conditions in the Hillga¨rtner (1998) measured only 23 m. This discrepancy Swiss Jura do not allow a full description; therefore, their is due to the difficulty of placing the boundary with the type localities have been chosen in France. This is feasible underlying Twannbach Formation that displays, at Sale`ve, because the overall lithologies of the formations involved very similar lithologies. are similar in nearby France, although the formation Facies of the Goldberg Formation are extremely variable, thicknesses and ages may change significantly. Some of the representing lacustrine, tidal-flat, beach, hypersaline, 2 15 Gb Biel N 51 60 20 km 162 67 Lake Neuchâtel France 95 GO Champagnole Va 42 Na 17 5 Switzerland Vaud 25 117 Lake Geneva GE Cretaceous outcrops Geneva 48 Swiss-French border 48 Geological map 1:25’000 Vu PR Salève Type localities Na Narlay Fm. PR Perte du Rhône Fm. Va Vallorbe Fm. GO Gorges de l’Orbe Fm. Vi GE Grand Essert Fm. Vu Vuache Fm. Rhône River Ch Ch Chambotte Fm. Vi Vions Fm. http://doc.rero.ch PC PC Pierre-Châtel Fm. Gb Goldberg Fm. Chambéry Fig. 1 Cretaceous outcrops in the Swiss and French Jura Mountains, type localities of the formations and the positions of the maps listed in compiled from the on-line geological maps supplied by the Swiss and Fig.