Swiss J Geosci (2016) 109:241–255 DOI 10.1007/s00015-016-0209-4 Reorganisation of the Triassic stratigraphic nomenclature of northern Switzerland: overview and the new Dinkelberg, Kaiseraugst and Zeglingen formations Peter Jordan1,2 Received: 12 November 2015 / Accepted: 9 February 2016 / Published online: 3 March 2016 Ó Swiss Geological Society 2016 Abstract In the context of the harmonisation of the Swiss massive halite deposits. It continues with sulfate and marl stratigraphic scheme (HARMOS project), the stratigraphic sequences and ends with littoral stromatolitic dolomite. In nomenclature of the Triassic sedimentary succession of the WSW–ENE trending depot centre total formation northern Switzerland has been reorganised to six forma- thickness is 150 m and more, and thickness of salt layers tions (from base to top): Dinkelberg, Kaiseraugst, Zeglin- reaches up to 100 m. In the High Rhine area, the thickness gen, Schinznach, Ba¨nkerjoch, and Klettgau Formation. is reduced due to subrecent subrosion. At some places The first three are formally introduced in this paper. evidence points to syn- to early-post-diagenetic erosion. The Dinkelberg Formation (formerly «Buntsandstein») For practical reasons, the six formations are organised in encompasses the siliciclastic, mainly fluvial to coastal three lithostratigraphic groups: Buntsandstein Group (with marine sediments of Olenekian to early Anisian age. The the Dinkelberg Formation), Muschelkalk Group (combin- formation is some 100 m thick in the Basel area and ing the Kaiseraugst, Zeglingen and Schinznach Forma- wedges out towards southeast. The Kaiseraugst Formation tions) and Keuper Group (combining the Ba¨nkerjoch and (formerly «Wellengebirge») comprises fossiliferous silici- Klettgau Formations). clastic and carbonate sediments documenting a marine transgressive—regressive episode in early Anisian time. It Keywords Triassic stratigraphy Á Northern Switzerland Á starts with sandstone, dolomite, continues with subtidal Lithostratigraphy Á Dinkelberg Formation Á Kaiseraugst limestone and marl and ends with bituminous shale and Formation Á Zeglingen Formation supratidal dolomite. Thickness decreases from approxi- mately 50 m in the High Rhine area to 10 m in the south and east. In the Lake Constance area, a transition to the 1 Introduction siliciclastic marginal facies of the Vindelician High (Eschenbach Formation in Germany) is documented by 1.1 Motivation and concept borehole evidence. The Zeglingen Formation (formerly «Anhydritgruppe») documents a regressive marine evap- The Triassic succession of northern Switzerland (Fig. 1) oritic megacycle during the Illyrian (late Anisian). At most encompasses around 225–550 m of marine to terrestrial places, except in far eastern Switzerland, it starts with sediments (Fig. 2). Classically, they have been subdivided in «Buntsandstein», «Muschelkalk» and «Keuper». In the published sheets of the Geological Atlas of Switzerland Communicated by W. Winkler and A. Morard. 1:25,000, the «Muschelkalk» is subdivided, from base to top, in «Wellengebirge», «Anhydritgruppe», «Haupt- & Peter Jordan muschelkalk», and «Trigonodusdolomit». «Buntsandstein» [email protected] and «Keuper» are usually taken as complete, undivided 1 Geologisch-Pala¨ontologisches Institut, University of Basel, mapping units. Only in areas of flat-lying strata and good Bernoullistrasse 32, 4056 Basel, Switzerland outcrop conditions, for instance in the Klettgau area, a 2 Gruner Bo¨hringer AG, 4104 Oberwil, Switzerland further subdivision was introduced for «Keuper» with 242 P. Jordan 2600000 2650000 2700000 2750000 F D Germany France Austria Bern map section SI Switzerland 300 Schaffhausen SL1 Konstanz RL2 BK BR1 261 Stein a. Rh. 1280000 291 BS1 290 ZT3 243 HE1 KZ1 542 ZZ1 314 500 251 227 Basel 325 OT2 ZT1 WE2 WE RU 632 323 298 288 BX RK 289 481 327 LI1 224 St. Gallen Aarau Zürich SO SH 259 500 384 PF1 Triassic strata 300 Solothurn 415 Wells (total thickness of 1230000 1280000 1230000 the Triassic strata in m) 400 200 Isopach (in m) outcropping area Luzern Keuper Group N EN1 200 179 Muschelkalk Group 01020kmBern Buntsandstein Group 2600000 2650000 2700000 2750000 Fig. 1 Outcrop area and thickness of the Triassic strata in northern OT2 Otterbach OT2, PF1 Pfaffnau 1, RK Riniken, RL2 Rietheim L2, Switzerland and localization of complete Triassic sections. Abbrevi- RU Ruckfeld, SH Schafisheim, SI Siblingen, SL1 Schlattingen SLA-1, ations (wells): BK Benken, BR1 Berlingen 1, BS1 Basel 1, BX Buix, SO Sonnengarten GTB1, WE Weiach, WE2 Weiach 2, ZT1 Zurzach EN1 Entlebuch 1, HE1 Herdern 1, KZ1 Kreuzlingen 1, LI1 Lindau 1, T1, ZT3 Zurzach T3, ZZ1 Zurzach Z1 additional map signatures. The classification used in the Another approach was to formally consolidate the cur- explanatory notes of the Atlas sheets and the description of rent Swiss scheme, because many outcrop studies and deep the respective core sequences of the deep boreholes are boreholes were recorded according to the traditional compiled in Fig. 3. stratigraphic nomenclature. This was supported by the None of the units in use have ever been formally argument, that existing map units should be maintained, defined. In the context of the harmonisation of the Swiss especially from the perspective of a Swiss-wide harmoni- stratigraphic scheme [HARMOS project, Morard et al. sation. Finally, a pragmatic approach has been preferred, 2012; Strasky et al. 2015 (submitted/this volume)] it was which is mainly based on the traditional Swiss scheme, decided to revise the stratigraphic nomenclature of the though with some important divergences which will be Triassic strata of northern Switzerland following the discussed later in this paper. guidelines of the Swiss Committee on Stratigraphy (Re- mane et al. 2005). Several approaches have been evaluated. 1.2 Outcrop conditions and additional data source One rejected approach was the adoption of the recently revised stratigraphic scheme of southwestern Germany, The concept of Remane et al. (2005) asks for accessible recapitulated in Geyer et al. (2011). In German areas outcrops as type sections. Since the outcrop conditions of adjacent to northern Switzerland, more than 20 formations Triassic units are today often bad, a mixed concept of are in use to describe the Triassic succession. However, superficial type sections and—mostly borehole based— many of the formations, having considerable thicknesses in reference sections had to be established for the present the centre of the Central European Basin, are only repre- task. The requirement for a borehole based reference sec- sented by a few metres of sediment along the River Rhine. tion is that the core material is properly stored and acces- Following the concept of Remane et al. (2005), a formation sible for future research. Finally, type and reference represents a mappable unit. Consequently, according to the sections should be published in papers or reports that are Swiss Geological Survey a formation should be at least accessible to the public. Initially, no additional field or some 30–50 m thick, to be represented on the 1:25,000 laboratory work was planned to revise the Triassic strati- sheets of the Geological Atlas of Switzerland. graphic nomenclature. Reorganisation of the Triassic stratigraphic nomenclature of northern Switzerland… 243 Nomenclature Nomenclature in northern Switzerland in southern Germany Age Epoch Period Weissenstein Arietenkalk Fm. Beggingen Mb. Angulatenton Fm. Sinem. Fm. Schambelen Mb. Early Jurassic Jurassic Staffelegg Staffelegg Psilonoten Fm. Het. Exter Fm. Belchen Mb. Rh. Gruhalden Mb. Trossingen Fm. Norian Seebi Mb. Löwenstein Fm. ? Steigerwald Fm. Gansingen / Berlingen Mb. Beaumont Horizont Klettgau Fm. Ergolz Mb. Stuttgart Fm. Late Triassic Carnian markerbed 1 ? no formal Grabfeld Fm. subdivision yet markerbed 2 Bänkerjoch Fm. Ladinian Asp Mb. Erfurt Fm. Stamberg Mb. Triassic Rottweil Fm. ? Liedertswil Mb. Meißner Fm. Kienberg Mb. Schinznach Fm. Trochitenkalk Fm. Leutschenberg Mb. Diemel Fm. discontinuity, hiatus no formal Middle Triassic subdivision yet crinoids Heilbronn Fm. Zeglingen Fm. oolites chert nodules Anisian bed rich in fossils Karlstadt Fm. halite limestone no formal Jena Fm. subdivision yet dolomite fine sand, silt Kaiseraugst Fm. Freudenstadt Fm. coarse sand Rötton Fm.. Ca-sulfate Plattensandstein Fm. variegated, dolomitic, partly silty clay, no formal marl and mudstone subdivision yet ? dark marl and clay, partly bituminous Dinkelberg Fm. Vogesensandstein Fm. dark dolomitic clay, marl Early Trias. Olenekian Rotliegendes or Zechstein (informal) Perminan Fig. 2 Simplified section of Triassic strata in northern Switzerland Markerbed 1 and 2 of Ba¨nkerjoch Formation according to Nagra [this paper, Pietsch et al. 2015 (submitted/this volume), Jordan et al. (2001) and Jordan et al. (2015) (submitted) Fm. Formation, Mb. 2015 (submitted/this volume)] and correlation with the current Member stratigraphic scheme of adjacent Germany (Geyer et al. 2011). 244 P. Jordan Bitterli-Brunner & Équipe du projet Mühlberg (1908) Disler (1914) Herzog (1956) Hofman (1981) Müller et al. (1984) Dronkert (1987) Gürler (1987) Widmer et al. (1991)Hofman et al. (2000) Bitterli et al. (2000) Hauber et al. (2000) Jordan et al. (2011) Geyer et al. (2011) This paper Fischer (1988) GeORG (2013) Schinznach Leutschen- Hauptmuschelkalk Trochitenkalk Trochitenkalk Hauptmuschelkalk Trochitenkalk Hauptmuschelkalk Trochitenkalk Trochitenschichten Trochitenkalk Hauptmuschelkalk Trochitenkalk Trochitenkalk-Fm. HM HM HM HM HM HM HM