The Staffelegg Formation: a new stratigraphic scheme for the Early Jurassic of northern Switzerland

Abstract

The deposits of the Early Jurassic in northern Switzerland accumulated in the relatively slowly subsiding transition zone between the southwestern part of the Swabian basin and the eastern part of the Paris basin under fully marine conditions. Terrigenous fine-grained deposits dominate, but calcarenitic and phosphorit-rich strata are intercalated. The total thickness varies between 25 and 50 m. In the eastern and central parts of N Switzerland, sediments Sinemurian in age constitute about 90% of the total thickness. To the West, however, in the Mont Terri area, Pliensbachian and Toarcian deposits form 70% of the total thickness. Stratigraphic gaps occur on a local to regional scale throughout N Switzerland. Such hiatus comprise a subzone to a stage in time. With respect to lithology and fossil content, the Early Jurassic deposits in northern Switzerland are similar to those in SW Germany. Nonetheless, an exact stratigraphic correlation is hardly possible, particulary in the southern and southwestern Folded Jura where distinct facies changes occur over short distances. Revised existing and new litho- and biostratigraphic data form the base to refine the stratigraphic subdivision of the deposits that have been informally called “Lias”. The name Staffelegg Formation is suggested and defined as the mapping unit for the Early Jurassic. The Staffelegg Formation is introduced for Early Jurassic sediments in northern Switzerland between the Doubs River and Mt. Weissenstein in the west and the Randen Hills located north of the city of Schaffhausen in the east. The Staffelegg Formation starts within the Planorbis zone of the Hettangian. The upper boundary to the overlying Aalenian Opalinus-Ton is diachronous. The lithostratigraphic names previously in use have been replaced by new ones, in accordance within the rules of lithostratigraphic nomenclature. The Staffelegg Formation comprises 11 members and 9 beds. Several of these beds are important correlation horizons in terms of allostratigraphy. Some of them correspond to strata or erosional unconformities encountered in the Swabian realm, some of them can be correlated with strata in the Paris basin. The facies transition to the Paris basin is expressed by introduction of a corresponding lithostratigraphic unit.

Zusammenfassung

Die Sedimente des Früh-Juras der N-Schweiz wurden in dem insgesamt etwas langsamer subsidierenden Übergangsbereich zwischen dem südwestlichen Teil des Schwäbischen Beckens und dem Pariser Becken unter vollmarinen Bedingungen abgelagert. Terrigen-klastische Pelite herrschen vor, die von kalkarenitischen und phosphoritreichen Einschaltungen untergliedert werden. Die Mächtigkeit des Früh-Juras variiert zwischen 25 und 50 m. Sedimente des Sinemuriums machen im östlichen und zentralen Bereich der N-Schweiz bis zu 90% der Mächtigkeit aus, nach Westen hingegen, im Mont-Terri-Gebiet, repräsentieren Sedimente des Pliensbachiums und Toarciums 70% der Mächtigkeit. Gebietsweise sind für bestimmte Zeitabschnitte des Früh-Juras keine Sedimente überliefert. Solche Hiatus können zeitlich eine Subzone bis Stufe umfassen. Die Abfolgen in der N-Schweiz ähneln hinsichtlich Lithologie und Fossilinhalt denen SW-Deutschlands, sind aber nur bedingt mit der südwestdeutschen stratigraphischen Nomenklatur in Einklang zu bringen, vor allem im Bereich des südlichen und westlichen Faltenjuras. Hier treten engräumig abrupte Fazieswechsel auf. Basierend auf reviderten, bestehenden und neuen litho- und biostratigraphischen Daten wird für die Schichtfolge, die bisher informell als “Lias” bezeichnet wurde, der Name “Staffelegg-Formation” vorgeschlagen und für die N-Schweiz als Kartiereinheit definiert. Die Staffelegg-Formation beginnt mit der Planorbis-Zone des Hettangiums. Die Grenze zur nächst jüngeren Formation, dem Opalinus-Ton, ist heterochron. Die bisher für die frühjurassischen Schichten verwendeten Bezeichnungen wurden durch neue, den heutigen Nomenklatur-Regeln konforme Namen ersetzt. Insgesamt werden für die Staffelegg-Formation 11 Member und 9 Bänke definiert. Etliche dieser Bänke sind im Sinne der Leitflächen-Stratigraphie wichtig: Ein Teil von ihnen lässt sich mit Schichten oder Erosionshorizonten im Schwäbischen Becken korrelieren, ein anderer Teil mit Horizonten im Pariser Becken. Der Faziesübergang zum Pariser Becken führt im westlichen Untersuchungsgebiet zu einer entsprechend angepassten lithostratigraphischen Untergliederung.

Résumé

Les dépôts du Jurassique inférieur du nord de la Suisse se sont accumulés dans la zone de transition, en lente subsidence, entre la partie sud-ouest du bassin de Souabe et la partie orientale du bassin de Paris, dans des conditions entièrement marines. Les dépôts terrigènes pélitiques dominent; des couches calcarénitiques et riches en phosphates y sont intercalées. L’épaisseur de ces dépôts varie entre 25 et 50 mètres. Dans les parties orientale et centrale du nord de la Suisse, les sédiments d’âge Sinémurien constituent 90% de cette épaisseur, alors qu’à l’ouest, dans la région du Mont Terri, ceux du Pliensbachien et du Toarcien en constituent 70%. Des lacunes stratigraphiques apparaissent à l’échelle locale et régionale dans tout le nord de la Suisse. Ces hiatus vont de la sous-zone à la étage. Les sédiments du Jurassique inférieur du nord de la Suisse sont similaires à ceux du sud-ouest de l’Allemagne du point de vue lithologique et de leurs fossiles. Une corrélation stratigraphique exacte est cependant difficilement possible, en particulier dans les parties sud et sud-ouest du Jura plissé où de nets changements de faciès apparaissent sur de courtes distances. Sur la base de données litho- et biostratigraphiques existantes et révisées ou nouvelles, nous proposons, pour désigner ces séries appelées jusqu’à présent de manière informelle “Lias”, le nom de “Formation de la Staffelegg”, qui servira dorénavant d’unité cartographique. Cette formation commence dans la Zone à Planorbes de l’Hettangien. La limite avec les Argiles à Opalinus aaléniennes sus-jacentes est hétérochrone. Les appellations utilisées jusqu’à présent pour ces séries du Jurassique inférieur ont été remplacées par de nouveaux noms en conformité avec les règles de nomenclature qui prévalent de nos jours. Au total, 11 membres et 9 bancs ont été définis pour la Formation de la Staffelegg. Plusieurs de ces bancs représentent d’importants horizons de corrélation en terme de stratigraphie séquentielle: certains correspondent à des couches ou surfaces d’érosion qui se retrouvent dans le bassin de Souabe, d’autres avec des horizons du bassin de Paris. La transition de faciès en direction du bassin de Paris requiert une subdivision lithostratigraphique adaptée en conséquence.

1 Introduction

1.1 History of Jurassic stratigraphy of northern Switzerland

The term Jurassic is directly linked to the Swiss Jura Mountains (Fig. 1). Alexander von Humboldt recognised the mainly limestone-dominated mountain range of the Swiss Jura Mountains as a separate formation that was not, at the time, included in the established stratigraphic system defined by Abraham Gottlob Werner and named it “Jurakalk” in 1795 (Hölder 1950, 1964). The separation of the term Jurassic into three sections goes back to von Buch (1839). Keferstein (1825), Thurmann (1832), Roemer (1836), and von Buch (1839) were the first who assigned the term “Lias”, previously used in England, to the lowest part of the three Jurassic sections (for more details of the term Lias see Arkell 1956; Donovan and Hemingway 1963; Hains and Horton 1969).

Fig. 1

Geological overview of the study area, situated in northern Switzerland, and legend of symbols used in Figs. 2, 3, 4

The Jurassic stratigraphy of northern Switzerland is closely linked to that of central and western Europe. Although related to the stratigraphic studies in central and western Europe, the Jurassic stratigraphy of northern Switzerland developed differently in many aspects. This is not only due to the more or less pronounced lithologic variations, compared to Mid- and Western Europe, but also to the fact that Switzerland is a multilingual country (Rominger 1846; Studer 1853, 1872; Moesch 1857; Disler 1941; Schweizerische Geologische Kommission, Arbeitsgruppe für Stratigraphische Terminologie 1973). The following institutions have had a considerable influence on Swiss stratigraphic nomenclature:

• a) Büro der Schweizerischen Geologischen Kommission (later Geologische Landesaufnahme): Einheitslegende für den Geologischen Atlas der Schweiz 1:25,000 (cf. Lang 1892; Aeppli 1915; Buxtorf and Schwarz 1960),

• b) Schweizerische Geologische Kommission, Arbeitsgruppe für Stratigraphische Terminologie (1973) and

• c) Schweizerisches Komitee für Stratigraphie (SKS; Remane et al. 2005).

Since Hedberg (1976), the International Commission on Stratigraphy has decided on an internationally valid standard for the stratigraphic classification of rocks that is based on a clear lithostratigraphic concept. The Swiss Committee of Stratigraphy (SKS) has a mandate to enforce this concept in Switzerland (Remane et al. 2005). The Swiss Committee of Stratigraphy receives support in this from the Swiss Geological Survey, which, in turn, is responsible for the publishing of geological maps. Both institutions have a shared responsibility for establishing a database (under development) that is linked to the internet, which names from the Swiss stratigraphy and their validity can be queried (www.stratigrahie.ch).

Unlike in Germany and France, the Early Jurassic stratigraphy in northern Switzerland is mainly based on geological mapping and less on palaeontological studies and, therefore, on lithostratigraphy. The first stratigraphic subdivision of the northern Swiss Mesozoic was established by Peter Merian (1821, 1831). Reflecting his education by Johann Friedrich Ludwig Hausmann at the University of Göttingen, his stratigraphic concept was strongly influenced by the stratigraphic subdivision in northern Germany (Buxtorf 1940). In contrast, Thurmann (1832, 1836) and Gressly (1841, 1853) followed the stratigraphy used in France and England.

Reflecting the pioneering litho- and biostratigraphic studies of Quenstedt (1843, 1858) and Oppel (1856–1858), stratigraphy established in southwestern Germany increasingly influenced that in northern Switzerland (e.g., Rominger 1846; Heer 1852; Marcou 1857a, b; Waagen 1864; Greppin 1870; Mathey et al. 1872). Nonetheless, some elements of the French stratigraphic subdivision were kept (e.g., Gressly 1853; Desor 1856; Rollier 1898; Tobler 1905; Leuthardt 1933). Because of the lack of a uniform nomenclature, French and German terms were mixed along the borders between western and northern Switzerland (e.g., Gressly 1853; Studer 1853, 1872; Mayer-Eymar 1864).

Another attempt to establish a uniform and generally applicable stratigraphical subdivision was the legend for the “Geologischer Atlas der Schweiz 1:25’000”, since 1930 (Buxtorf and Schwarz 1960). At this time, the deposits of the Opalinum zone were included in the Liassic (i.e. “Lias”), in accordance with the French nomenclature (e.g., Frank 1930; Bureau der Geologischen Kommission 1936). Later, the mapping unit “Lias” was extended to include the sediments of the Rhaethian as well (e.g., Buxtorf and Christ 1936; Tschopp 1960). However, this use was not made mandatory for all of Switzerland (e.g., Disler 1941; Buser 1952).

During the International Congress on the Jurassic in Luxemburg (1962, Colloque du Jurassique à Luxembourg), a standard stratigraphic subdivision of the Jurassic was recommended. Biostratigraphically, the Liassic spans the period from the Hettangian to the Toarcian (i.e. Planorbis to the Levesquei zone after Dean et al. 1961; see Hölder 1963). According to this definition, the Liassic was biostratigraphically shorter than the Early Jurassic, which also includes the Planorbis to Concavum zones (Hettangian to Aalenian; e.g., Hölder 1962, 1963). Later, in 1967 at the “Colloque du Jurassique à Luxembourg”, it was decided to establish a biostratigraphic range for the Early Jurassic congruent to that of the Liassic (i.e. Planorbis to Levesquei zone; Hallam 1975). This stratigraphic nomenclature reached consensus in Switzerland with the foundation of the Arbeitsgruppe für Stratigraphische Terminologie in 1971 (now: Schweizerisches Komitee für Stratigraphie).

The majority of lithostratigraphic terms of the N Swiss Early Jurassic that are in use today were adapted from the stratigraphy of SW Germany (cf. Studer 1872; Buser 1952; Waibel and Burri 1961; Fischer 1969; Müller et al. 1984). Literature from the nineteenth and twentieth centuries contains a large number of names and definitions that differ more or less significantly from the French or SW German nomenclature (Fig. 2). The few of these that became widely known, or were established in the last few years, are shown in Figs. 2 and 4.

Fig. 2

Names of the Early Jurassic rocks (“Lias”) and its subunits previously in use (for legend see Fig. 3). Fe-Oolith. L. = Fe-Oolithische Lagen; FJ = Folded Jura; G. = Gächlingen Bed; G.Bd. = Gipf Bed?; Ins. Merg., Insektenm. =  Insektenmergel; O. biod. L. = Obere Biodetritische Lage; O. spätig-biod. L. = Obere spätig-biodetritische Lagen; Pleyd.-B. = Pleydellien-Bank; Pleydellienb. =  Pleydellienbank; Schamb. =  Schambelen Member; Sch., -sch. = Schichten; TJ = Tabular Jura; U. biod. L. =  Untere Biodetritische Lage; U. sp. biod. L. =  Untere spätig-biodetritische Lagen; VH =  Variabilis-Horizont; VS =  Variabilis-Schichten; # =  zones sensu Dean et al. (1961), sensu Bloos (1979) and sensu Schlegelmilch (1992); I = Psilonotenbank (e.g., LGRB 2004; Bloos et al. 2005; Etzold et al. 2010); II = Oolithenbank (e.g., Schloz 1972; Bloos et al. 2005; Schmid et al. 2008); III = Kupferfelsbank (e.g., LGRB 2004; Schmid et al. 2008); IV = Davoei-Bank (e.g., Schlatter 1991; LGRB 2004); V = Unterer Stein (e.g., Urlichs 1977; Röhl and Schmid-Röhl 2005); * = likely

Fig. 3

Early Jurassic biostratigraphy and lithostratigraphy of northern Switzerland. Nor. = Norian; ? Protosaccul. = ? Protosacculina; Rhaet. = Rhaetian; Rhaetogon. = Rhaetogonyaulax; # = zones sensu Dean et al. (1961), sensu Bloos (1979), sensu Brenner (1986) and sensu Schlegelmilch (1992); see also Beutler et al. (2005), von Hillebrandt and Krystyn (2009), Etzold et al. (2010). 1 Klettgau area; 2 Lindau well; 3 Weiach well; 4 eastern Tabular Jura; 5 eastern Aargau Tabular Jura (Fig. 7); 6 western Aargau Tabular Jura (Fig. 8); 7 Basel Tabular Jura (Fig. 9); 8–9 easternmost Folded Jura (Figs. 10, 11, 12); 9 Hauenstein area (see Figs. 13, 14, 15, 16); 10 Bölchen area (see Figs. 17, 18); 11 Passwang area (see Figs. 18, 19, 20, 21); 12 eastern Weissenstein area (see Figs. 22, 23); 13 Weissenstein area (see Fig. 24); 14 Grenchenberg area; 15 Moutier area (see Fig. 25); 16 Mont Terri area (16a eastern area: see Fig. 26; 16b western area: see Fig. 27)

Fig. 4

Former unit names and their revised stratgraphic range (see also Fig. 3). Fe-Oolith. Lagen = Fe-Oolithische Lagen; Insektenm. =  Insektenmergel; Nor. = Norian; O. biod. L. = Obere Biodetritische Lage; O. sp.-biodetr. Lagen = Obere spätig-biodetritische Lagen; Posidon./Posidoniensch. =  Posidonienschiefer; ? Protosaccul. = ? Protosacculina; Psilon.-/Psiloc.-Sch. = Psilonoten-/Psiloceras-Schichten; Rhaet. = Rhaetian; Rhaetogon. = Rhaetogonyaulax; # = zones sensu Dean et al. (1961), sensu Bloos (1979), sensu Brenner (1986) and sensu Schlegelmilch (1992)

To fulfill the rules of stratigraphic nomenclature, it is suggested to introduce the Staffelegg Formation for the strata previously subsumised as “Lias” (Fig. 3). In the stratigraphic scheme suggested here, the individual lithostratigraphic units are all dated chronostratigraphically. With the exclusive use of a chronostratigraphic hierarchy for the terms of geochronology, we are following the nomenclature of the Swiss Committee of Stratigraphy (Remane et al. 2005).

1.2 Palaeogeography and Early Jurassic stratigraphy

The continuous improvement of palaeogeographic reconstructions influenced the stratigraphic classification in northern Switzerland until now. Heer (1865) undoubtedly introduced the most lasting scheme for the Early Jurassic in northern Switzerland but also for the neighbouring areas in southern Germany (e.g., Altmann 1965; Jordan 1983; Schlatter 1990).

Investigation of the Late Triassic and the boundary to the Early Jurassic in northern Switzerland also had a significant influence on the palaeogeographic concepts for the Early Jurassic (e.g., Erni 1926; Hölder 1964; and references therein). It was discussed whether the sandy sediments of the Rhaetian in N Switzerland are Rhaetian or Early Jurassic in age (e.g., Rollier 1898, 1917; Buxtorf 1907 vs. Erni 1910, 1926). Furthermore, the absence of marine Rhaetian sediments in large areas of N Switzerland (Fig. 5) has been interpreted as a stratigraphic gap or caused by later erosion (e.g., Erni 1910 vs. Buxtorf 1907, 1910; Schalch and Peyer 1919; Etzold and Schweizer 2005; Etzold et al. 2010).

Fig. 5

Isopach map for the Rhaetian rocks in N Switzerland, SE France and SW Germany (data sources as given in Table 1)

Fig. 6

Isopach map for the Early Jurassic rocks in N Switzerland, SE France and SW Germany (data sources as given in Table 1). Note that especially large uncertainties are attached to the thickness information from wells in the Molasse Basin and the Upper Rhinegraben (in particular for the determination of the Early to Middle Jurassic boundary, but also for the determination of the Early to Late Toarcian boundary; e.g., Pratje 1924; Théobald 1967; Lutz and Cleintuar 1999)

Fig. 7

Detailed section of the Early Jurassic strata at Frick (Gruhalde clay pit). α = position of the boundary between Late Hettangian and Early Sinemurian sensu Hoffmann (1934), Walliser (1956a,b) and Schlatter in Maisch et al. (2008); β = position of the boundary between Late Pliensbachian and Early Toarcian sensu Schlatter (1982), Riegraf et al. (1984) and Kuhn and Etter (1994: Basisschicht); γ = Promicroceras cf. planicosta (Sow. 1814) at 7.63 m and 9.22 m (W. Etter, pers. comm. 2005); δ = Promicroceras cf. planicosta (Sow. 1814) at 16.98 m (W. Etter, pers. comm. 2005); ε = Asteroceras sp. at 15.72 m (W. Etter, pers. comm. 2005); ζ = “Schlotheimia cf. extranodosa” (see Maisch et al. 2008: fig. 3); η = revision of “Psiloceras (Caloceras) cf. johnstoni (Sow. 1824)” (see Maisch et al. 2008: fig. 3); π = compare Etzold et al. (1975); ψ = biostratigraphic range according to Jordan (1960) and Schlatter (1991)

Fig. 8

Detailed section of the Early Jurassic strata at Hof Schönau (Olsberg/AG), temporary exposure. Ammonites have been collected by T. Bolinger (Olsberg/AG; CTB). α = see Pratje (1922); β = see Schlatter (1976); γ = phosphoritic, Gryphaea-bearing, macrofossil-rich encrinite, highly conglomeratic in parts (packstone after Dunham 1962); δ = reworked?; ε = loosely collected Schlotheimia sp. (NMB J 29358; det. Wiedenmayer 1980), compare the biostratigraphic range of the genus Schlotheimia in Fig. 7

Fig. 9

Detailed section of the Early Jurassic strata at Füllinsdorf (Im Ischlag/BL), temporary exposure. α = loosely collected Lytoceras cf. jurense (Zieten); β = for the biostratigraphic range of Prodactylioceras davoei (Sow.) see Schlatter (1991)

The stratigraphic and palaeogeographic considerations were the base to reconstruct the land-sea distribution in Germany and Switzerland in Rhaetian to Sinemurian times (Ehrat 1920; Pratje 1924; Rüger 1924). Particularly the direction of the transgression of the Early Jurassic sea was discussed for a many years (e.g., Wepfer 1925; Hölder 1964). This dispute, known in the literature as the “Stratigrapher War” (Wetzel 1932), chiefly concerned Vollrath’s (1924) hypothesis, which, based on the use of the index fossil method, posited that Early Jurassic sediments could not be subdivided into individual biostratigraphic units but could, instead, be grouped into contemporaneous faunal provinces. During and after the 2nd World War, stratigraphic studies on the Triassic-Jurassic boundary in northern Switzerland were restricted to a local geological scale (e.g., Vonderschmitt 1941; Peyer 1943a, b, 1956). The methodological argument was finally provided by Walliser (1956a, b), based on results found in SW Germany, and he proved the opponents of Vollrath’s hypothesis right.

2 Materials and methods

While revising the stratigraphy of the Early Jurassic strata in northern Switzerland, the joint subdivision of stratigraphic succesions into lithofacies units and quasi time units was used (see Lutz et al. 2005). Because of the large number of coexisting homonyms (e.g., Insektenmergel, Obliqua-Schichten; see Fig. 4) and synonyms (e.g., Davoei-Schichten, Numismalis-Schichten, Belemnitenkalke; see Figs. 2, 3), new, unencumbered names for the individual lithostratigraphic units were introduced.

The new stratigraphic subdivision of the northern Swiss Early Jurassic strata is based on data from many different sources (see Table 1). The most significant and high quality data comes from the Klettgau area, Tabular Jura and the eastern Folded Jura. By contrast, because of the rare outcrops, there are only patchy data from the Bernese Jura and Mont Terri area. Based on new and hitherto unpublished sections, and new and revised biostratigraphic data (ammonites, ostracodes), the chrono- and lithostratigraphic classification of the stratigraphic inventory of the whole study area was specified more precisely.

Table 1 Compilation of data sources used for isopach maps and stratigraphic classification

In the past 60 years, knowledge about the facies and thickness of the northern Swiss Early Jurassic has been expanded by exploration wells drilled by the oil- and salt industry, geothermal projects, deep boreholes drilled by Nagra, ground water wells, large construction projects and also by outcrops that were made while economically exploiting Early and Middle Jurassic mudstones (e.g., Büchi et al. 1965; Hauber 1971; 2000; Meyer and Furrer 1995; Mumenthaler et al. 1997; Reisdorf 2001; Nagra 2001; Wetzel and Allia 2003; Häring et al. 2008). In addition, cores, cuttings and unpublished well data were used (see Table 1).

For biostratigraphic purposes, fossils stored in various collections were examined. Fossil finds related to the present stratigraphic scheme are mentioned in text and figures, respectively. In addition, several unpublished diploma and master theses from the Universities of Basel, Bern, Neuchâtel and Zürich, from 1957 to 2008, have been considered; most of them are listed in the publications by Andrey (1974), Jordan (1983), Kuhn and Etter (1994) and Meyer and Furrer (1995).

3 Staffelegg Formation

Names previously in use are given in Fig. 2.

Type locality

Buessge (S Thalheim/canton Aargau; coord.: 646.925/253.050 and 649.750/253.000; Jordan 1983; Fig. 10; = section Kaltenbrunnen of Erni 1910: 43).

Fig. 10

Detailed section of the Early Jurassic strata at Buessge (AG), Type locality of the Staffelegg Formation. Ammonoid zones in parentheses were not verified in the Staffelegg area. α = “Schlotheimia sp.” (Jordan 1983) = ? Saxoceras sp. (see Etzold et al. 1975: 124p. and Urlichs 1977: 16p.); β = data from Jordan (1983); γ = data from Müri in Jordan (1983)

Fig. 11

Detailed section of the Early Jurassic strata at the Staffelegg clay pit (AG). α = data from Jordan (1983); β = loosely collected Pleuroceras sp. at the “Staffelberg” (collection of the Geologisches Institut der ETH Zürich; see Jordan 1983); γ = loosely collected (Reisdorf et al. subm.); δ = data from Ziegler in Jordan (1983)

Fig. 12

Detailed section of the Early Jurassic strata at Dottenberg (SO). α = data from Jordan (1983); β = own data; γ = data from Imhof in Jordan (1983); δ = compare Figs. 13, 15, 16, 17 and Etzold et al. (1975), Schlatter (1983b, 1991), Brandt (1985)

Fig. 13

Detailed section of the Early Jurassic strata at the Erlimoos clay pit (SO). α = compare Jordan (1983: section Dottenberg) and Fig. 12; β = data from Goldschmid (1965); γ = “Coroniceras aff. sauzeanum (d’Orb.)”, “Coroniceras aff. bisculatum (Brug.)”, “Arnioceras cf. Bodleyi (Hyatt)”; data from Goldschmid (1965); δ = loosely collected Acanthopleuroceras cf. maugenesti (d’Orb.), Acanthopleuroceras sp., Liparoceras sp., Beaniceras cf. senile (Buckm.), Beaniceras sp. (own data); ε = Lytoceras fimbriatum (Sow.), Androgynoceras maculatum (Y. & B.), Androgynoceras intracapricornus (Qu.), Liparoceras bronni Spath, Prodactylioceras davoei (Sow.), Amaltheus cf. stokesi (Sow.), Pleuroceras sp. indet., Catacoeloceras raquinianum (d’Orb.), Osperlioceras bicarinatum (Zieten) = Pseudopolyplectus bicarinatus (Zieten), Hildoceras semipolitum (Buckm.); data from Imhof in Jordan (1983); ζ = data from Imhof in Jordan (1983)

Fig. 14

Detailed section of the Early Jurassic strata at Hof Horn (NW Olten). α = whitish and bluish chert nodules (see also Moesch 1874; Buxtorf 1907; Fischer and Luterbacher 1963: 28); β = Arnioceras sp., Arnioceras cf. cuneiforme Hyatt, Arnioceras cf. robustum (Quenst.); γ = Coroniceras multicostatum (Sow.), loosely collected

Fig. 15

Detailed section of the Early Jurassic strata at Wirbligen (BL), temporary exposure; modified after Reisdorf (2001). α = compare Jordan (1983: section Dottenberg) and Fig. 12; Etzold et al. (1975), Schlatter (1983b, 1991), Brandt (1985); β = revision of “Paltechioceras s.l.”; γ = Xiphoceras sp. (revision of “Apoderoceras sp.”; loosely collected)

Fig. 16

Detailed section of the Early Jurassic strata at Weisle (BL); see also Erni (1926) and Goldschmid (1965). α = compare Jordan (1983: section Dottenberg) and Fig. 12; Etzold et al. (1975); Schlatter (1983b, 1991); Brandt (1985); β = data from Goldschmid (1965); γ = reworked?; δ = data from Imhof in Jordan (1983); ε = own data; ζ = “Arnioceras hartmanni (Oppel)”, data from Goldschmid (1965); η = loosely collected Microderoceras sp. (own data)

Fig. 17

Detailed section of the Early Jurassic strata at the Fasiswald clay pit (W Olten). α = compare Jordan (1983: section Dottenberg) and Fig. 12; see also Etzold et al. (1975); Schlatter (1983b, 1991); Brandt (1985); β = “0.15 m Grauer Kalk, Gryphaea cymbium” of Celliers (1907: 17); see also Delhaes and Gerth (1912); γ = Microderoceras sp. (own data); δ = ostracods (own data, det. E. Beher 2004): Anchistrocheles? tuningensis Beher, Bairdia molesta; ε = Asteroceras sp. (reworked?, own data, compare Schlatter 1983b; finder: C.A. Meyer, Basel 2009); ζ = Aegasteroceras gr. simile Spath (own data, biostratigraphic range according to Schlatter 1983b, 1991); η = Echioceras s.l. (own data); θ = ostracods (own data, det. E. Beher 2004): Acrocythere oeresundensis, Acrocythere michelseni, Bairdia molesta, Bairdia? extracta, Cytherelloidea modesta, Gramannicythere acclivisulcata, Gammacythere ubiquita, Isobythocypris tatei, Ledahia sp., Ogmoconcha amalthei; λ = ?Echioceras s.l. (own data); μ = ostracods (own data, det. E. Beher 2004): Acrocythere oeresundensis, Bairdia molesta, Bairdia praehilda, Cardobairdia liassica, Cuneoceratina amlingstadtensis, Cytherella sp., Cytherelloidea lacertosa, Gammacythere ubiquita, Isobythocypris tatei, Ledahia bispinosa, Nanacythere sp., Ogmoconcha amalthei, Ogmoconchella sp. 1 (Beher 2004), Polycope sp.; π = ostracods (own data, det. E. Beher 2004): Cytherelloidea modesta, Ledahia bispinosa, Progonoidea auleata; ρ = Lytoceras sp., Liparoceras (Parinodiceras) gr. zieteni (Trueman), Aegoceras sp., Derolytoceras sp. (own data); σ = Lytoceras sp.; χ = Lytoceras sp., Liparoceras sp., Haugia sp.? (own data; see also Erni in Mühlberg 1915); ψ = faunal list in Etter (1990); ω = Lytoceras sp., Grammoceras (gr. fallaciosum) sp. (own data); * = in the Fasiswald section, the Müsenegg Bed can even be completely eroded (see Erni in Mühlberg 1915); ** = see also Erni in Mühlberg (1915)

Fig. 18

Detailed section of the Late Triassic and Early Jurassic strata at Chuenisrüti and Wuest (BL). α = Obtusussandsteine after Buxtorf (1907); β = see also Delhaes and Gerth (1912); compare Figs. 13, 15, 16; γ = “Arietites” (Erni 1910, 1926); δ = data from Imhof in Jordan (1983); compare Etzold et al. (1975), Schlatter (1983b, 1991) and Brandt (1985); ε = “Amaltheus costatus” (approximate stratigraphic position after Delhaes and Gerth 1912)

Fig. 19

Detailed section of the Early Jurassic strata at Titterten TRG 3 (BL), temporary exposure; modified after Reisdorf (2001)

Fig. 20

Detailed section of the Early Jurassic strata at Limmeren (N Mümliswil/SO; see section “Limmernbach SW Ramisgraben”, Delhaes and Gerth 1912). α = ostracods (own data, det. E. Beher 2004; for the stratigraphic range of the ostracods see Beher 2004 and Franz et al. 2009): Acrocythere michelseni, A. oeresundensis, Gramannicythere acclivisulcata, Gramannicythere sp. 1; β = ostracods (own data, det. E. Beher 2004): Ektyphocythere vitiosa, Gramannicythere acclivisulcata; γ = ostracods (own data, det. E. Beher 2004): Bythocypris postera, Cytherelloidea lacertosa, C. modesta, Gammacythere ubiquita, Liasina vestibulifera, Ogmoconcha amalthei; δ = ostracods (own data, det. E. Beher 2004): Bairdia molesta, Cardobairdia sp. 1 Beher, Ogmoconcha amalthei; ε = ostracods (own data, det. E. Beher 2004): Kinkelinella sermoisensis, Ledahia bispinosa, L. mouherense, Ogmoconcha sp., Paracypris sp. (semidisca?); * = note the erosional unconformity between beds 30 and 31

Fig. 21

Detailed section of the Early Jurassic strata at Säge (S Seewen/SO), drawn after Hess (1962, pers. comm. 2010). α = (A, B, C) faunal list of the ostracod and foraminiferal assemblages in Hess (1962), compare Riegraf (1985); see also Bitterli (1960), Richter (1987) and Tröster (1987)

Underlying strata

Knollenmergel/Obere Bunte Mergel or “Rhät” (Middle or Late Keuper).

Overlying strata

Opalinus-Ton (Early to Middle Jurassic, Late Toarcian to Early Aalenian, Levesquei to Opalinum zone).

Subdivision in the Klettgau area and Tabular Jura (from base to top)

Schambelen Member, Beggingen Member, Frick Member, Grünschholz Member, Breitenmatt Member, Rickenbach Member, Rietheim Member, Gross Wolf Member.

Subdivision in the eastern Folded Jura (from base to top)

Schambelen Member, Beggingen Member, Frick Member, Fasiswald Member, Weissenstein Member, Breitenmatt Member, Rietheim Member, Gross Wolf Member.

Subdivision in the western Folded Jura (Mont Terri area; from base to top)

Beggingen Member, Mont Terri Member, Breitenmatt Member, ?Rickenbach Member, Rietheim Member, Gross Wolf Member.

Occurrence

Northern Switzerland.

Thickness

Usually 25–50 m (Fig. 6).

Chronostratigraphic age

Early to Middle Jurassic (Planorbis to Opalinum zone; Schlatter 1983a; Nagra 1989, 1990).

Description

The Staffelegg Formation is a siltstone-marl-dominated heterogeneous, sedimentary succession. Additionally, limestones and subordinately also sandstones may occur especially in the Sinemurian part. In the Folded Jura, these sediments may make up the major portion of the Staffelegg Formation. Facies changes may occur within short distances in the Folded Jura. The Staffelegg Formation displays a small thickness compared to the occurrences of the Early Jurassic of southeastern France and southwestern Germany. A gradual decrease in thickness can be detected which continues from southwestern Germany into northern Switzerland (Fig. 6; Büchi et al. 1965; Müller et al. 1984).

4 Lithostratigraphic subunits of the Staffelegg Formation

4.1 Schambelen Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Schambelen (SW Brugg/canton Aargau; coord.: 659.310/257.000; e.g., Heer 1852; Jordan 1983; temporary exposure; excavation campaign at Schambelen by the Natural History Museum Basel and the Geologisch-Paläontologischer Arbeitskreis Frick in 2004).

Underlying strata

Knollenmergel (Zanclodonmergel)/Obere Bunte Mergel or “Rhät” (Middle and Late Keuper, respectively; e.g., Frey 1969; Jordan 1983; Achilles and Schlatter 1986).

Overlying strata

Beggingen Member or Weissenstein Member.

Subdivision

Hallau Bed (only in the Klettgau area and in the Zürcher Weinland area at the base of the Schambelen Member).

Occurrence

Klettgau area, Zürcher Weinland, Tabular Jura, eastern Folded Jura.

Thickness

0 to ca. 9 m (see Jordan 1983; Bitterli-Brunner and Fischer 1988; Nagra 1990, 1992).

Chronostratigraphic age

Early to Late Hettangian (Planorbis to Liasicus zone; Fig. 10; Trümpy 1959; Schlatter 1983a, 1990; Achilles and Schlatter 1986; Maisch et al. 2008).

Description

The Schambelen Member is mainly composed of marly terrigenous mudstone. Subordinate amounts of thin, sometimes bituminous, limestone and silt- and sandstone occur (Figs. 7, 10; see Schalch and Peyer 1919; Bader 1925; Jordan 1983; Nagra 2001). The boundary to the underlying strata is marked by an erosional unconformity (see Schalch and Peyer 1919; Altmann 1965; Achilles and Schlatter 1986). With exception of the Basel Tabular Jura, the basal portion of the Schambelen Member is bituminous, thin-bedded and has a carbonate content of 5–8% (see Tanner 1978; Jordan 1983; Schlatter 1983a). In the Klettgau area, this dark grey to black terrigenous mudstone is restricted to the Hallau Bed (= schwarze, geradschiefrige, posidonienschieferähnliche Mergelschiefer of Schalch and Peyer 1919; see Achilles and Schlatter 1986). Mudstone with these characteristics belongs to the Liasicus zone in the whole distribution area of the Schambelen Member, and, according to fossils found in Frick and the northern Klettgau area, possibly also to the Planorbis zone (= Untere, bituminöse Insektenmergel of Jordan 1983; Figs. 7, 10; Schlatter 1983a; Maisch et al. 2008). This mudstone becomes continuously greenish grey and slightly sandy upwards. The distinctive fine bedding and the bituminous content are then lost (= Obere, schwaichelähnliche Insektenmergel of Jordan 1983; Fig. 10). In the Klettgau area, a change to dark, greenish to brownish grey, silty to fine sandy mudstone without distinct fine bedding occurs above the Hallau Bed (= Schwaichel; Schalch and Peyer 1919). These sediments belong entirely to the Liasicus zone (Schlatter 1983a). To the Southwest, the Schambelen Member wedges out completely but is also present in the Basel Tabular Jura, although with a different facies (see Tanner 1978; Jordan 1983; Wetzel et al. 1993). There, this sediment is developed as dark grey to blackish, occasionally, fine sandy terrigenous mudstone containing pyrite; its biostratigraphic age was not yet determined unequivocally. Strübin (1901) listed a poorly preserved fragment of a questionable Psiloceras sp. from these unbedded sediments from the section Niederschönthal (= Schöntal, coord.: 621.650/261.700).

In addition, the lithostratigraphic affiliation of the limestone from the Gelterkinden—Sissach area, that contains ammonites of the Early Hettangian, is uncertain (Psiloceras plicatulum (Qu.), det. F. Wiedenmayer 1980 [NMB J 29354]; Psiloceras cf. distinctum (Pompecki), det. R. Zingg 1965 [NMB J 9787); Psiloceras (Caloceras) ex gr. johnstoni hercynum W. Lange, det. R. Schlatter 2006 [NMB J 33220; NMB J 33221; NMB J 33230; NMB J 33231]; cf. Berg 1961; Hölder 1964: 12; Bloos 1981).

4.1.1 Hallau Bed

Names previously in use are given in Fig. 4.

Type locality

Hallau (Bratelen, Hallauerberg; canton Schaffhausen; coord.: 676.400/284.500; temporary exposure, see Achilles and Schlatter 1986).

Underlying strata

Knollenmergel in the Klettgau area, “Rhät” in the Zürcher Weinland area (Middle and Late Keuper, respectively).

Overlying strata

The Hallau Bed forms the base of the Schambelen Member.

Occurrence

Klettgau area, Zürcher Weinland.

Thickness

0 to some 2 m (see Schlatter 1983a; Nagra 1993, 2001).

Chronostratigraphic age

Early Hettangian (Planorbis to Liasicus zone, Planorbis to Portlocki subzone; Schlatter 1983a; Achilles and Schlatter 1986).

Description

The definition of the Hallau Bed follows the southern German subdivision scheme of Altmann (1965; there called Psilonotenbank, see Bloos et al. 2005 and Etzold et al. 2010). The Hallau Bed is basically understood as a condensation and reworking horizon (Altmann 1965; Bloos et al. 2005). Sediments of the same age from SW Germany contain several levels with ammonite associations (e.g., Altmann 1965; Bloos 1999).

At the type locality Hallau, this condensation horizon begins with a 5–15 cm thick black marl which is rich in echinoderm remains (Schalch and Peyer 1919; Achilles and Schlatter 1986). Two distinct limestone layers follow, being separated by a 70 cm thick, thinly bedded dark brown to black, bituminous terrigenous mudstone (Schalch and Peyer 1919; Altmann 1965; Achilles and Schlatter 1986). The two limestone beds are 10–40 cm thick coquinas which regularly contain middle- to coarse-grained sand and glauconite. The upper limestone layer may contain iron ooids in addition (Schalch and Peyer 1919; Nagra 2001). In the Klettgau area, the limestone of the Hallau Bed can be completely replaced by easily weathering black clayey marl (see Altmann 1965). About 3 km SW of Hallau, the lower limestone layer of the Hallau Bed wedges out; therefore, the oldest sediments of the Early Jurassic are represented by roughly 25 cm of dark brown terrigenous mudstone (Altmann 1965). The wells Benken (coord.: 690.989/277.843) and Lindau 1 (coord.: 692.815/255.098) represent the southernmost localities where the Hallau Bed was encountered so far (see Altmann 1965; Frey 1969, 1978; Nagra 2001). The southernmost find of an ammonite from the Hallau Bed to date was reported 3 km SW of Hallau (Wilchingerberg; Altmann 1965: 63).

4.2 Beggingen Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Beggingen (Hölderli, canton Schaffhausen; coord.: 682.120/290.980; temporary exposure, Schlatter 1976).

Underlying strata

Obere Bunte Mergel or “Rhät” or Schambelen Member.

Overlying strata

Fasiswald Member or Weissenstein Member or Frick Member or Mont Terri Member.

Subdivision

Schleitheim Bed, Gächlingen Bed.

Occurrence

Northern Switzerland.

Thickness

From ?0 m in the Folded Jura (Jordan 1983: section Salhöchi, coord.: 641.100/253.650; see Gsell 1968: section Schürmatt, coord.: 640.160/253.160), some 1 m in the Tabular Jura (Buser 1952; Nagra 1984) to ca. 5 m in the Klettgau area (Schalch 1895), to 7 m in the Weissenstein area (Ledermann 1981).

Chronostratigraphic age

Early Hettangian (Liasicus zone; Figs. 22, 23) to Late Sinemurian (Obtusum zone; Figs. 7, 8, 10; Schlatter 1976; Jordan 1983 vs. Fig. 12).

Fig. 22

Detailed section of the Late Triassic and Early Jurassic strata at Schoren (BE). α = “Insektenmergel” (compare Fig. 24); β = beds rich in Plagiostoma (Rollier 1910); γ = reworked? (see Schloz 1972; Schlatter 1988 and Fig. 7)

Fig. 23

Detailed section of the Early Jurassic strata at Lucheren (BE). α = beds rich in Plagiostoma (Rollier 1910); β = bluish chert nodules (see also Buxtorf 1907; Fischer and Luterbacher 1963 = 28); γ = whitish chert nodules; δ = bluish and grey chert nodules; ε = greyish black chert nodules; ζ = bluish and grey to dark grey chert nodules; π = compare Figs. 12, 13, 15, 16, 17, 18; ψ = for the biostratigraphic range of Lytoceras cf. fimbriatum (Sow.) see Schlatter (1991)

Fig. 24

Detailed section of the Late Triassic and Early Jurassic strata at Käspisbergli (Günsberg; SO). α = beds rich in Plagiostoma (Rollier 1910); β = “Grès à Cardinia, Gressly 1862” in Waagen (1864); γ = “Calcaire à Gryphées Gressly 1862” in Waagen (1864); δ = “Schlotheimia angulata” (Buxtorf 1907); ε = see also Bitterli and Strub (1975); ζ = loosely collected: Euagassiceras sp. (own data); “A. bisulcatus” (see Waagen 1864); * = data from Buxtorf (1907)

Description

The Beggingen Member always lies on top of an erosive surface (Figs. 7, 8, 10, 12, 13, 14, 15, 16, 17, 18, 25, 27). It mainly consists of condensed arenitic limestone, that may be dolomitised in some cases (Fig. 18; Müller 1862; Delhaes and Gerth 1912; Jordan 1983). Individual limestone banks may end in a hardground (Fig. 10; see Jordan 1983; Wetzel et al. 1993). The following facies variations can appear at the base of the Beggingen Member:

Fig. 25

Detailed section of the Late Triassic and Early Jurassic strata at Hautes Roches (BE). ? = uncertain biostratigraphic affiliation (compare with Fig. 22); α = “Insektenmergel”? (compare with Fig. 22); β = see also Erni (1910, 1926) vs. Vollrath (1924: 22) and Frank (1930: 385); γ = see also Erni (1910, 1926) and Elber (1921); δ = loosely collected Waehneroceras sp. (= Curviceras), reworked? (own data); ε = Arietites (Arietites) cf. bisulcatus (Brugiére), data from B. Hostettler (FPJ, 2005); ζ = Coroniceras sp. (loosely collected, own data); π = Arnioceras cf. oppeli (Guérin-Franiatte), Arnioceras cf. ceratitoides (Qu.) (own data); Arnioceras cf. oppeli (Guérin-Franiatte), Arnioceras cf. falcaries (Qu.), Arnioceras cf. robustum (Qu.), data from B. Hostettler (FPJ, 2005); ψ = Microderoceras sp., Asteroceras cf. alamanicum (Guérin-Franiatte), data from B. Hostettler (FPJ, 2005); ω = ostracods (own data, det. E. Beher 2004): Acrocythere oeresundensis, Bairdia? extracta, Bairdia molesta, Bythocypris postera, Isobythocypris tatei, Ledahia bispinosa, Ogmoconcha aff. amalthei, Paracypris sp., Paracypris alemannica

Fig. 26

Detailed section of the Early Jurassic strata at Les Salins (SE Courtemautruy/JU). α = compare Fig. 27; β = compare Richter (1987: 141), Pharisat et al. (1993) and Kuhn and Etter (1994); γ = Aegoceras cf. maculatum (Y. & B.); note the large minimal thickness solely for the sediments of the Davoei zone (at least 7.8 m); δ = Becheiceras sp., Prodactylioceras davoei (Sow.); ε = Lytoceras fimbriatum (Sow.), Becheiceras sp., Androgynoceras capricornus (Schl.), Oistoceras angulatum (Qu.), Prodactylioceras davoei (Sow.), P. davoei enode (Qu.); ζ = Lytoceras fimbriatum (Sow.), Amaltheus cf. stokesi (Sow.), Amaltheus bifurcus (Howarth), see also Schmidt et al. (1924), Glauser (1936) and Vonderschmitt (1942); π = Dactylioceras sp., Discina sp.; ψ = Dactylioceras sp.

Fig. 27

Detailed section of the Early Jurassic strata at Courtemautruy (JU). α = no indications for disturbances caused by postjurassic tectonic processes or landslides could be detected in this sedimentary succession (section established by Reisdorf 2005); β = compare Buxtorf (1910); γ = loosely collected Angulaticeras angulatoides (Qu.); δ = ostracods (own data, det. E. Beher 2004): Bairdia fortis, Isobythocypris tatei, Ledahia sp., Ogmoconcha sp.; ε = loosely collected Arietites sp., Arietites s.l.; ζ = loosely collected Paracoroniceras s.l.; η ostracods (own data, det. E. Beher 2004): Bairdia molesta, Cardobairdia liasica, Ledahia sp., Pseudohealdia? sp.; λ = Beaniceras sp.; π = ostracods (own data, det. E. Beher 2004): Bairdia fortis; χ = Coroniceras sp.; ψ = ostracods (own data, det. E. Beher 2004): Bairdia molesta, Cardobairdia liasica, Isobythocypris tatei; ω = ostracods (own data, det. E. Beher 2004): Bairdia fortis, Bairdia molesta, Bairdia michelseni?, Bairdiacypris anisica brevis, Bythocypris postera, Cardobairdia sp. 3, Cardobairdia liasica, Isobythocypris tatei, Ledahia sp., Ogmoconcha sp., Ostracode E, Paracypris? redcarensis (Beher 2004)

• a) calcareous sandstones (Figs. 17, 22; Lehner 1920; Erni 1910, 1926; Buser 1952: 33p.; Büchi et al. 1965; Nagra 2001), which, in contrast to the Weissenstein Member, are characterised by their abundancy of Cardinia sp. or Gryphaea arcuata Lam. In general, the calcareous-shelled fossils in these arenites are corroded to a lesser or stronger degree because of diagenetic lime dissolution, bivalves (e.g., Cardinia sp., Gryphaea sp.) are often only preserved as external molds (see Lehner 1920; Keller 1922; Waibel 1925).

• b) Quartz-conglomerates (Erni 1926);

• c) dolomite-conglomerates (Lehner 1920; Erni 1926; Fig. 8);

• d) flat pebble conglomerates (Suter 1927); more unfrequently,

• e) limestone-breccias (Keller 1922);

• f) bonebeds (Lehner 1920; Erni 1926; Suter 1927).

If the erosive contact of the Staffelegg Formation incises down to sediments of the Middle Keuper, then the Beggingen Member often set in with unlayered, light grey to black marls of up to 20 cm thickness (see Erni 1910; Buser 1952; Jordan 1983; Figs. 13, 14, 15, 16). In the oldest layers of the Beggingen Member (Liasicus to Bucklandi zone), bivalves commonly occur, most of which belong to the genera Cardinia and Plagiostoma (Figs. 7, 10, 24, 25, 27; see Schalch and Peyer 1919; Elber 1921; Maisch et al. 2008). These facies-dependent faunal associations were the reason to give it initially the chronostratigraphically misleading name Cardinienschichten (see Schleitheim Bed and Gächlingen Bed). In the Klettgau area and from there in a south-western direction to the Frick area (canton Aargau), the basal layers of the Beggingen Member contain iron-ooids (Figs. 7, 10; see Jordan 1983; Schlatter 1989). In contrast, the upper layers (Bucklandi to Obtusum zone) occur over a larger area in northern Switzerland and consist mainly of locally strongly phosphoritic arenitic limestone which are rich in fossils; the bivalve Gryphaea arcuata Lam. occurs in great abundance, locally rock-forming (Figs. 7, 8, 10, 12, 16, 18, 24, 25, 27; see von Buch 1839; Jordan 1983). Marl or marly terrigenous mudstone of small thicknesses is interbedded (Figs. 7, 10, see Buser 1952). In the Folded Jura, the facies of the Beggingen Member interfingers with that of the Weissenstein Member (the Beggingen Member may in such a case even disappear completely, leaving only the Weissenstein Member; see Jordan 1983; Figs. 3, 10, 14, 15, 17, 24).

4.2.1 Schleitheim Bed

Names previously in use are given in Fig. 4.

Type locality

2 km SE of Schleitheim (Buckforen; canton Schaffhausen; coord.: 679.700/287.470; Schlatter 1976).

Underlying strata

Obere Bunte Mergel or “Rhät” or Schambelen Member.

Overlying strata

The Schleitheim Bed forms the base of the Beggingen Member.

Occurrence

Klettgau area, Zürcher Weinland, Tabular Jura, ?Weissenstein area (because of poor outcrop conditions, in contrast to Jordan et al. 2008, the Schleitheim Bed has not been differentiated in the Weissenstein area.).

Thickness

0–65 cm (Brändlin 1911; possibly even up to 130 cm: Buxtorf 1907; Fischer and Luterbacher 1963; Fig. 24).

Chronostratigraphic age

Late Hettangian (Angulata zone, Complanata subzone; Schlatter 2001).

Description

At the base, the Schleitheim Bed contains a large number of bivalves, especially the genera Cardinia and Plagiostoma. The Schleitheim Bed always has an erosive base; in the Klettgau area and from there in southwestern direction to the Frick area, these layers are iron ooliths (Fig. 7; Schalch and Peyer 1919; Schlatter 1989; Maisch et al. 2008). In the Tabular Jura of the canton Aargau (Rietheim – Frick area), the iron oolithic facies changes into a bioclastic packstone facies (see Schalch 1880; Schalch and Peyer 1919). In the Basel Tabular Jura, the Schleitheim Bed is bioclastic packstone (see Erni 1910; Tanner 1978). The ±30 cm thick, black to yellowish marls, in which iron-containing, iron oolith to bioclastic packstone concretions are embedded are an additional facies variation (see Brändlin 1911; Buser 1952).

In the eastern Basel Tabular Jura as well as in the eastern Folded Jura, the Schleitheim Bed is absent because of erosion (Figs. 14 and 17; see Buser 1952). In the Weissenstein area, similar sediments occur again, but here within the basal part of the Beggingen Member (= Schleitheim Bed?; Figs. 23, 24; see Buxtorf 1907). Here, it may display an iron-oolithic facies (Fig. 22).

4.2.2 Gächlingen Bed

Names previously in use are given in Fig. 4.

Type locality

1 km WNW of Gächlingen (Lugmer, canton Schaffhausen; coord.: 678.650/284.700; temporary exposure, Schlatter 1976).

Occurrence

Klettgau area, Zürcher Weinland, Tabular and Folded Jura (with an interruption possibly extending to the Weissenstein area and the Mont Terri area: In contrast to Jordan et al. 2008, because of poor outcrop conditions, the Gächlingen Bed has not been differentiated there.).

Thickness

0 to ±50 cm (Nagra 2001; Fig. 10).

Chronostratigraphic age

Early Sinemurian (Bucklandi zone, Conybeari subzone; Bloos 1976).

Description

The Gächlingen Bed is included in the basal beds of the Beggingen Member (e.g., Klettgau area, Tabular Jura; Fig. 7) or at its base (e.g., Folded Jura; Fig. 10). Wacke- to packstone of small thickness, containing iron ooids (see Jordan 1983; Hofmann et al. 2000). Bivalves, especially of the genus Cardinia, occur occasionally in rock-forming abundance. Besides the index ammonites of the Bucklandi zone, the Gächlingen Bed can also contain ammonites of the genus Schlotheimia (e.g., “Riesenangulaten”; see Walliser 1956a; Hahn 1971; Bloos 1976; Maisch et al. 2008).

Laterally, the Gächlingen Bed may change into a duff horizon with concretionary limestone and ultimately wedges out entirely (Fig. 7; see Buser 1952; Hofmann 1981; Nagra 1989; Maisch et al. 2008).

The stratigraphic position of the coquinas (with Cardinia and/or Plagiostoma) that occur in the western part of the study area (Weissenstein area; section Hautes Roches and Mont Terri area; Buxtorf 1907 vs. Rollier 1910; Elber 1921; Erni 1926; Figs. 22, 23, 24, 25, 27) is not yet resolved beyond doubt. In these sediments, the Bucklandi zone has so far only been proven in the Mont Terri area, using a loosely collected Angulaticeras angulatoides (Qu.) (= section Courtemautruy, Fig. 27; note that the Courtemautruy Bed of Jordan et al. 2008 is no longer kept because of the lack of suitable outcrops). In addition, it should be mentioned that iron ooids have so far only been found in such limestones in the eastern Weissenstein area (Fig. 22, Erni 1910: 38 vs. Vollrath 1924: 22; Bitterli and Strub 1975; own data).

4.3 Weissenstein Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Käspisbergli 1 km N of Günsberg (canton Solothurn, see Rollier 1904; coord.: 610.560/235.140; Fig. 24; Buxtorf 1907).

Underlying strata

Schambelen Member or Beggingen Member or Fasiswald Member.

Overlying strata

Beggingen Member or Fasiswald Member.

Occurrence

Eastern Folded Jura to Weissenstein area (see Pratje 1924; Bitterli and Strub 1975; Jordan 1983), well Altishofen 1 (coord.: 639.500/228.000; see Fischer and Luterbacher 1963).

Thickness

Up to some 22 m (Fischer and Luterbacher 1963); facies interfingering with the Beggingen Member.

Chronostratigraphic age

Early to Late Sinemurian (Semicostatum to Obtusum zone; Figs. 10, 15; Jordan 1983; loosely collected Promicroceras sp., E Ulmethöchi/BL, coord.: ca. 616.700/247.800 [NMB J 33219, det. R. Schlatter 2005]).

Description

Beige, calcareous sandstones or sandy limestones, respectively, usually 6–22 m thick or sometimes much less (Figs. 10, 12, 13, 14, 15, 24; Delhaes and Gerth 1912; Heim 1919; Fischer and Luterbacher 1963; Wetzel et al. 1993; = Feinsandkalklage sensu Jordan 1983). These partially silicified and sometimes dolomitised sediments occasionally contain bluish chert concretions, but very rarely macrofossils which are of biostratigraphic use (Figs. 14, 15, 18, 23; see Delhaes and Gerth 1912; Bitterli and Strub 1975; Jordan 1983). The Weissenstein Member is characterised by spatially close facies-changes and alternations with the Beggingen Member (see Erni 1926; Buser 1952; Jordan 1983; Wetzel et al. 1993) and the Fasiswald Member, respectively (Figs. 10, 14, 15, 17, 24).

The more or less fossil-rich, sandy limestone or calcareous sandstone that are found at the base of the Staffelegg Formation in the Grindel—Erschwil area are, however, not attributed to the Weissenstein Member (see facies variations of the Beggingen Member; see Erni 1910; Lehner 1920; Keller 1922; Waibel 1925).

4.4 Frick Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Gruhalde clay pit in Frick (canton Aargau; coord.: 643.000/261.900; see Beher 2004).

Underlying strata

Beggingen Member.

Overlying strata

Grünschholz Member or Fasiswald Member.

Occurrence

Klettgau area, Tabular Jura, Zürcher Weinland, eastern Folded Jura (here facies interfingering with the Fasiswald Member).

Thickness

The maximum thicknesses lie around some 20 m in the Tabular Jura (Fig. 7; Gsell 1968); in the Folded Jura, however, the thicknesses are significantly below 10 m (Fig. 10; Jordan 1983).

Chronostratigraphic age

Late Sinemurian (Obtusum to Raricostatum zone, Stellare subzone to Densinodum and Raricostatum subzone; Schlatter 1976, 1983b, 1999; Beher 2004; cf. Fig. 12 vs. Jordan 1983).

Description

Generally macrofossil-poor, bioturbated, monotonous succession of dark grey, terrigenous claystones or siltstones, containing mica. (Fig. 7, 10; see Hofmann 1959; Frey 1978; Schlatter 1999; Nagra 2001). Interlayering with thin, fine-grained sandstones or layers with marcasite, pyrite or clay iron-stone concretions can occur. Lime- and/or phosphorite concretions are often seen at the top of the Frick Member (see Peters 1964; Nagra 1984, 1990; Schlatter 1991). The youngest sediments of the Frick Member can show different degrees of reworking such as flat pebble conglomerates, reworked ammonites etc. (see Schlatter 1983b, 1991; Beher 2004).

In the occurences of the Frick Member in the eastern Folded Jura, interfingering of facies with the Fasiswald Member is observed.

Towards the southwest, the mudstone succession is significantly thinner than in the Tabular Jura and the Klettgau area, and, increasingly, limestone concretions and limestone beds are intercalated (Fig, 10; see Jordan 1983; Wetzel et al. 1993; Reisdorf 2001).

4.5 Grünschholz Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Grünschholz (NW Galten; canton Aargau; coord.: 651.000/265.700; see Buser 1952, outcrop no longer accessible).

Underlying strata

Frick Member.

Overlying strata

Breitenmatt Member.

Occurrence

Klettgau area, Zürcher Weinland, Tabular Jura.

Thickness

In the Klettgau area, rarely more than 1 m thick; thickness in the Tabular Jura is rarely more than 1.5 m and never above 2 m (Brändlin 1911; Schalch 1916; Gsell 1968).

Chronostratigraphic age

Late Sinemurian to Early Pliensbachian (Raricostatum to Jamesoni zone, Densinodum and Raricostatum to Nodogigas and Taylori subzone; Fig. 7, Schlatter 1983b, 2000).

Description

Strata consisting of calcareous marl and predominantly concretionary limestone beds containing glauconite and calcareous phosphoritic concretions (Figs. 7, 9; see Schlatter 1991, 1999). The phosphorite is mainly associated to bioturbated domains. The Grünschholz Member rest on top of an erosive surface that is more or less distinctive (Schlatter 1999; Beher 2004).

4.6 Fasiswald Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Fasiswald clay pit (NNW Hägendorf; canton Solothurn; coord.: 629.100/245.100; Fig. 17; cf. Erni in Mühlberg 1915).

Underlying strata

Beggingen Member or Weissenstein Member or Frick Member.

Overlying strata

Breitenmatt Member.

Occurrence

In the entire northern Swiss Folded Jura (except for the Mont Terri area) and areas south of the Folded Jura (i.e. Schafisheim borehole; Nagra 1992); in the eastern Folded Jura there is facies interfingering with the Frick Member; in the southern Jura chains this facies interfingers with the Weissenstein Member; facies interfingering with the Mont Terri Member has not been observed so far.

Thickness

Up to ca. 27 m (Fig. 23).

Chronostratigraphic age

Early Sinemurian to Early Pliensbachian (Semicostatum to Jamesoni zone; Jordan 1983; Schlatter 1991, 2000; Maisch and Reisdorf 2006a, b; own data).

Description

The Fasiswald Member consists of alternating brown, light- to dark grey, quartz containing limestone, encrinite, silty-sandy terrigenous mudstone and marl, respectively (Figs. 10, 12, 13, 15 16, 17, 18, 19, 20, 25; see Mühlberg 1908; Delhaes and Gerth 1912; Heim 1919). In the Hauenstein area and from there further to the west, and in the well Schafisheim (coord.: 653.620/246.760), limestone beds are silicified to a varying degree and may contain black chert-concretions which may reach a size of several tens of centimeters (Spiculaefazies of Jordan 1983; Figs. 15, 17, 18; see Delhaes and Gerth 1912; Nagra 1992; Maisch and Reisdorf 2006a). Gryphaea obliqua (Sow.) occurs in great abundance in the area of the Fasiswald Member (Figs. 15, 17; see Jordan 1983; Wetzel et al. 1993; Reisdorf 2001). Biostratigraphically useful macrofossils are, however, quite rare (Jordan 1983; Beher 2004; Reisdorf own data). As a rule, one to two packages of limestone beds several meters in thickness occur; they may appear as distinct ridges in the landscape (Jordan 1983). Especially in the Weissenstein area, the facies of the Fasiswald Member interfingers with the Weissenstein Member (Fig. 3; see also Fischer and Luterbacher 1963) while in the eastern Folded Jura, the Fasiswald Member overlies the Beggingen Member, Frick Member or the Weissenstein Member (Figs. 10, 12, 13, 15, 16; see Buxtorf 1907; Jordan 1983; Reisdorf 2001).

4.7 Mont Terri Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Les Salins (SE Courtemautruy; canton Jura; coord.: 578.800/248.080; Fig. 26).

Underlying strata

Beggingen Member.

Overlying strata

Breitenmatt Member.

Occurrence

Mont Terri area.

Thickness

Up to ca. 25 m thick (Buxtorf 1910; Laubscher 1963).

Chronostratigraphic age

Late Sinemurian to Early Pliensbachian (?Obtusum to Davoei zone; own data).

Description

Middle to dark grey mica bearing terrigenous mudstone and marl with occasional nodular to compact limestone layers are characteristic (Fig. 26; Buxtorf 1910; Glauser 1936; Rickenbach 1947). This member is only rare exposed entirely. According to Buxtorf (1910) and Laubscher (1963) it starts with terrigenous mudstone, which successively changes into a limestone-marl-alternation. The general appearance of the Mont Terri Member resembles therefore the gradual dovetailing of facies of the Frick Member with the Fasiswald Member in the eastern Folded Jura (compare Figs. 10, 15, 16, 19; Pratje 1924; Jordan 1983; Wetzel et al. 1993; Bath and Gautschi 2003).

In spite of their macroscopic similarity, the stratigraphic architecture and the lithological inventory of the Mont Terri Member markedly differ from those of both the Frick Member and the Fasiswald Member. Lithologically, these differences in facies in the Mont Terri area are so pronounced that they should not be seen as mere facial variations. As explained in greater detail below, the character of the Mont Terri Member can be boiled down to the following: The Mont Terri Member stands out, not by dint of its having a unique stratigraphic architecture or a unique lithological inventory, but in fact due to the very lack of such unique qualities.

Buxtorf (1910) measured a 10–12 m thick terrigenous mudstone interval (= Obtusustone sensu Buxtorf 1910, Fig. 2) in a temporary exposure SE of Cornol (coord.: ca. 580.550/249.100). This succession is assigned to the here newly introduced basis of the Mont Terri Member (Fig. 3). This mudstone most closely resembles the easternmost occurrences of the Frick Member in the Folded Jura with respect to facies, although it is significantly thicker than the latter (compare section Buessge, Fig. 10; see Jordan 1983; Bath and Gautschi 2003). The more western occurrences of the Frick Member differ more clearly from the basal interval of the Mont Terri Member. More frequent interfingering of the Frick Member with the Fasiswald Member in this area leads to the characteristic broadening of the lithological inventory of the Frick Member, in particular the occurrence of crinoidal mudstone and wackestones as well as one to two prominent Gryphaea-rich intervals (Gryphäenkonglomerathorizonte after Jordan 1983; Wetzel et al. 1993). Judging by the information in Buxtorf (1910), the latter seems to be absent in the basal part of the Mont Terri Member (see also Vonderschmitt 1942).

The upper part of the Mont Terri Member (= knollige Kalkbänke after Buxtorf 1910; Laubscher 1963; Fig. 4) resembles the Fasiswald Member: In the type section Les Salins (Fig. 26), this limestone-marl-alternation is about 13 m thick and does not exhibit the characteristic lithological inventory of the Fasiswald Member, namely calcarenites in spiculae-facies or without spiculae, encrinites linked to Gryphaea-rich intervals, as well as one to two packages of limestone beds several meters in thickness.

The biostratigraphic range of the Mont Terri Member is not completely clear yet and is based on the current knowledge of unexpectedly heterogeneous stratigraphic features (Fig. 3). Hitherto, ammonites are only known from the limestone-marl-alternation of the Mont Terri Member (own data; cf. Mathey 1883). In the type section Les Salins (Fig. 26) as well as in the tectonically overprinted partial section S of Cornol (coord.: 579.950/249.500; Aegoceras sp., ?Oistoceras sp., own data) and SSW of Courtemautruy (coord.: 578.100/248.050; Echioceras sp.; Aegoceras sp., own data), ammonite finds document the Raricostatum and Davoei zones for this stratigraphic level and therefore indicate that deposition continued to the late Early Pliensbachian (Fig. 3).

The stratigraphic position of the Sinemurian/Pliensbachian boundary could not be identified precisely in the type section of the Mont Terri Member (Fig. 26). The above mentioned partial section SSW Courtemautruy, however, yielded a precise localisation of the biostratigraphic boundary. In that partial section, the oldest sediments of the Pliensbachian (Jamesoni and Ibex zones) in the Mont Terri area are rather thin: here, Echioceras sp. (Raricostatum zone) and Aegoceras sp. (Davoei zone) occur in close proximity in a monotonous interval consisting of marls and a few nodular limestones or limestone beds. These limestones can be classified as mudstones to wackestones.

The stratigraphic constellation exposed in the partial section of SSW of Courtemautruy (Fig. 26) suggests that neither the Sinemurian-/Pliensbachian-boundary nor the Ibex/Davoei zone-boundary can be found in a belemnite- and gryphaeid-rich wackestone to packstone or phosphoritic limestone/marl-alternation in the area where the Mont Terri Member is present (compare Breitenmatt Member; see Jordan 1983; Maisch and Reisdorf 2006a, b). This definition of the boundary, however, conflicts with the situation in the Courtemautruy section (Fig. 27), which lies about 500 m southwest of the type section Les Salins and which, for the most part, represents the Beggingen Member.

In this section, a Coroniceras sp. (Bucklandi zone) was found in situ in a bioclastic packstone, which is rich in gryphaeid oysters at the base and lies below an ammonite breccia (own data). In the marl layer, which contains gryphaeid oysters, limestone- and phosphorite-concretions, immediately below this packstone, however, the ammonite Beaniceras sp. of the middle Early Pliensbachian Ibex zone was found (own data). All additional ammonites found in this outcrop (all collected loosely, not in situ) are from the Early Sinemurian. Determination of the ostracod-fauna collected at this locality did not yield a proper solution for this unexpected biostratigraphic contradiction (Fig. 27). A closer examination of the section of Courtemautruy yielded no distinct evidence for a tectonic overprint by folding or thrusting.

Based on the available bio- and lithostratigraphical data from the study area, two differing possible positions of the boundary between the Beggingen Member and the Mont Terri Member are shown in the stratigraphic scheme of the Staffelegg Formation (Fig. 3). In the eastern Mont Terri region, the position of this boundary is purely based on lithostratigraphic correlation with areas to the eastern Folded Jura (= boundary within the Obtusum zone; Fig. 3).

Based on the section Courtemautruy, the proposed boundary differs significantly from that of the traditional stratigraphic nomenclature: for the western Mont Terri area, the boundary is set at a diachronous erosional base that reaches from the Ibex zone to the Bucklandi zone (cf. Frank 1926: 404; Söll 1965: 157; Kant 1972: 29).

4.8 Breitenmatt Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Breitenmatt (ESE Gansingen; canton Aargau; coord.: 654.040/265.280; Buser 1952; outcrop no longer accessible).

Underlying strata

Grünschholz Member or Fasiswald Member or Mont Terri Member.

Overlying strata

Rickenbach Member or Rietheim Member or Gross Wolf Member (Erlimoos Bed).

Subdivision

Trasadingen Bed and Müsenegg Bed.

Occurrence

Northern Switzerland.

Thickness

Smallest thickness of ±50 cm in the Tabular Jura and the Klettgau area (Fig. 9; Schalch 1880: 225; Buxtorf 1901: 21; Buser 1952: 61p.); thickest occurrences together with the Müsenegg Bed (±4 m in the Weissenstein area; Buxtorf 1907); without the Müsenegg Bed the thickness can still be well above 2 m (maximum of 2.8 m in the Klettgau area; Hofmann 1981). In the Mont Terri area, the Breitenmatt Member is ca. 1.7 m thick.

Chronostratigraphic age

Early to Late Pliensbachian (Jamesoni to Spinatum zone; Jordan 1983; Schlatter 1991, 2000; Maisch and Reisdorf 2006a, b).

Description

Interval rich in fossils, consisting of marls and phosphoritic, predominantly concretionary limestones; belemnites and gryphaeid oysters dominate the macrofauna; presence of ichnofossils results in a spotted appearance (Figs. 7, 9, 10, 12, 13, 15 16, 17, 18, 19, 20, 26; see Braun 1920; Glauser 1936; Rickenbach 1947; Gsell 1968; Schlatter 1991). Belemnite-rich (so-called belemnite battlefields) horizons of Early Pliensbachian age containing glauconite can provide a strong gamma-log signal (Nagra 1984, 1990, 2001). Partial silicification of calcareous fossils is also often seen (especially in gryphaeid oysters; e.g., Mandy 1907; Jordan 1983).

Distinct hardgrounds are sometimes developed in the Breitenmatt Member (Jordan 1983; Müller et al. 1984; Nagra 1992; Wetzel et al. 1993). In general, the Breitenmatt Member is significantly thinner than age-equivalent sediments in southern Germany and eastern France (see Vonderschmitt 1942; Gwinner et al. 1967: Table 1; Wirth 1968; Etzold et al. 1975; Debrand-Passard 1984). In the Mont Terri area, the facies of the Breitenmatt Member is limited to the Davoei zone, including a thin phosphoritic interval that has been attributed to the Mont Terri Member by Jordan et al. (2008: fig. 14.31). However, in the remaining study area, the Breitenmatt Member represents a highly condensed interval that, together with the Müsenegg Bed, can span all the ammonite-zones of the Pliensbachian (Fig. 3; see Pratje 1924; Schlatter 1991; Wetzel and Reisdorf 2007). In addition, the Breitenmatt Member has been exposed to pronounced synsedimentary and postsedimentary erosion and reworking processes (see Müller et al. 1984; Brandt 1985; Schlatter 1991). It’s biostratigraphical extent is therefore only incompletely preserved, especially in the Folded Jura (Figs. 3, 19 and 20; Schlatter 1991; Wetzel et al. 1993).

4.8.1 Trasadingen Bed

Names previously in use are given in Fig. 4.

Type locality

A now filled up pit 200 m SW of Trasadingen (Kilchstieg, canton Schaffhausen; coord.: 674.100/280.050; Schalch 1880).

Underlying strata

The Trasadingen Bed represents the uppermost bed of the Breitenmatt Member in the Tabular Jura and the Klettgau area.

Overlying strata

Rickenbach Member.

Occurrence

Klettgau area, Zürcher Weinland, Tabular Jura, ?Mont Terri area.

Thickness

Up to 30 cm (Fig. 7).

Chronostratigraphic age

Early Pliensbachian (Davoei zone, Davoei and Oistoceras subzones; Schlatter 1991).

Description

Middle grey, splintery marly limestone which has a spotted appearance because of their burrows (Figs. 7 and 9; Schalch 1880, 1916; Schlatter 1991). This most conspicuous lithostratigraphic horizon of the Breitenmatt Member wedges out laterally and passes into a calcareous marl (see Brändlin 1911; Schlatter 1991). In the study area, the biostratigraphy of this bed correlates with the first and last occurrence of the ammonite Prodactylioceras davoei (Sow.) within a limestone layer (see Brändlin 1911; Schlatter 1991; see also Fig. 26).

4.8.2 Müsenegg Bed

Names previously in use are given in Figs. 2 and 4.

Type locality

Müsenegg (S Schinznach; canton Aargau; coord.: 652.570/253.350; Jordan 1983).

Underlying strata

The Müsenegg Bed represents the uppermost bed of the Breitenmatt Member in the Folded Jura, except in the Mont Terri area.

Overlying strata

Rietheim Member or Gross Wolf Member.

Occurrence

Folded Jura (except for the Mont Terri area).

Thickness

From 0 to 70 cm thick (Figs. 17, 19, 23).

Chronostratigraphic age

Late Pliensbachian (Margaritatus to Spinatum zone; Fig. 18; see Buxtorf 1907; Hess 1962; Jordan 1983; Maisch and Reisdorf 2006a, b).

Description

Condensed phosphoritic marl and/or one marly limestone bed (Figs. 10, 11, 13, 15 16, 17, 21, 23). The Müsenegg Bed can be capped by a hardground (Figs. 13, 23; Wetzel et al. 1993). The distinct, irregular light to dark grey spotted appearance of the Müsenegg Bed is characteristic; it is caused by the diverse ichnofauna occurring in these strata (Jordan 1983; Wetzel and Reisdorf 2007). Bivalves of the genus Gryphaea are the most conspicuous component of the macrofauna (see Erlimoos Bed).

Therefore, the petrography of the Müsenegg Bed is sometimes difficult to differentiate from that of older layers of the Breitenmatt Member. In such case, a certain stratigraphic classification can only be achieved with index fossils of the Late Pliensbachian. The biostratigraphically orderless appearance of index fossils like ammonites, foraminifers and ostracods indicates substantial reworking and bioturbation during the deposition of the Müsenegg Bed (Hess 1962; Jordan 1983; Wetzel and Reisdorf 2007).

4.9 Rickenbach Member

Names previously in use are given in Figs. 2 and 4.

Type locality

700 m NNE of Rickenbach (“Hintern Egg” = Waldegg, canton Baselland; coord.: 631.180/260.320; Buxtorf 1901; the section is not accessible at the present time).

Underlying strata

Breitenmatt Member.

Overlying strata

Rietheim Member (Schlatter 1982; cf. Joachim 1970: 16; Etzold et al. 1975).

Occurrence

Klettgau area, Zürcher Weinland, Tabular Jura, ?Bernese Jura (Elber 1921), ?Mont Terri area (Fig. 26).

Thickness

In the Tabular Jura, minimal thicknesses are probably around 25 cm (Nagra 1990); the questionable Rickenbach Member in the Mont Terri area is also only a few decimeters thick (Fig. 26; see Glauser 1936; Bitterli 1960); maximum thickness is significantly above 5 m in the Klettgau area (Schalch 1880; possibly up to ca. 10 m?, Hofmann 1981); in the Tabular Jura, thickness of around 2 m is observed (see Buxtorf 1901).

Chronostratigraphic age

Late Pliensbachian to Early Toarcian (Margaritatus to Tenuicostatum zone, Stokesi to Paltum subzone; Figs. 7, 9; Schlatter 1982, 1985: 13, 1991).

Description

Condensed interval of reduced thickness (except in the northern Klettgau area; see Schalch 1916; Gsell 1968; Nagra 2001 and references therein), consisting of glauconitic, phosphoritic, fossil-rich (especially rich in belemnites; so-called belemnite battlefields) marls and concretionary limestones (Figs. 7, 9, 26; see Brändlin 1911; Pratje 1924; Buser 1952). At the top of the Rickenbach Member, bluish grey marls (= Blaugraue Mergel sensu Schlatter 1982) can be found in the Klettgau area and in the Tabular Jura, greenish grey to blackish grey clayey marls occur (= Basisschicht of Kuhn and Etter 1994; Fig. 7), both in small thicknesses.

4.10 Rietheim Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Rietheim (canton Aargau; coord.: 662.910/271.865; outcrop in the bed of a stream; see Kuhn and Etter 1994).

Underlying strata

Rickenbach Member or Breitenmatt Member.

Overlying strata

Gross Wolf Member.

Subdivision

Unterer Stein.

Occurrence

Klettgau area, Zürcher Weinland, Tabular Jura, eastern Folded Jura to Hauenstein area, Weissenstein area, Bernese Jura, Mont Terri area.

Thickness

The thickness of about 10 m in the Klettgau area decreases towards the south and southwest (Tabular Jura and Folded Jura) markedly to a few centimetres (see Elber 1921; Riegraf 1985: 62; Kuhn and Etter 1994; Nagra 2001; Reisdorf 2001). By contrast, the Rietheim Member attains a thickness of some 20 m in the Mont Terri area (Fig. 26; Rickenbach 1947; Bitterli 1960; Contini and Lamaud 1978). Additionally, the Rietheim Member does not occur areawide in the Folded Jura due to erosion (Figs. 13, 15 16, 17, 18, 19, 20, 21, 23; see Erlimoos Bed; see Kuhn and Etter 1994; Reisdorf 2001).

Chronostratigraphic age

Early Toarcian (Tenuicostatum to Bifrons zone, Paltum to Crassum subzone; Schlatter 1982; Richter 1987; Kuhn and Etter 1994; Maisch and Reisdorf 2006a, b).

Description

Bituminous, predominantly thinly bedded shale and marl layers which can be clearly separated from the under- and overlying members by their brownish, dark grey to black colour (Figs. 7, 9 10, 11, 26; see Bitterli 1960; Richter 1987; Kuhn and Etter 1994; Nagra 2001). Thin limestone beds and calcareous concretions occur in addition in the Rietheim Member (Figs. 7, 10, 11, 26; see Senftleben 1923; Pratje 1924; Kuhn and Etter 1994; Nagra 2001). These are prominent in thin Early Toarcian sections. Where the Rietheim Member reaches large thickness (Klettgau area, Mont Terri area), the limestone beds are outweighed by siliciclastic sediments.

Some of the limestone beds are important lithostratigraphic markers that can be correlated as far as France and southwestern Germany (cf. Riegraf et al. 1984: 14p.; Kuhn and Etter 1994; Röhl et al. 2001). The most important marker bed for the Early Toarcian in northern Switzerland, the Unterer Stein, is usually developed even the Rietheim Member is very thin (Fig. 9; see Buxtorf 1907; Elber 1921; Vogel 1934; Jordan 1983).

4.10.1 Unterer Stein (in the rank of a bed)

Names previously in use are given in Fig. 4.

Type locality

Bad Boll (SSW Göppingen, southern Germany; Oppel 1856–1858).

Occurrence

Klettgau area, Zürcher Weinland, Tabular Jura (may wedge out laterally in the Basel Tabular Jura), eastern Folded Jura to the Hauenstein area, Bernese Jura, Weissenstein area, Mont Terri area.

Thickness

0 up to 25 cm (e.g., Kuhn and Etter 1994; Maisch and Reisdorf 2006a, b), in the Mont Terri area roughly twice as thick (e.g., Rickenbach 1947).

Chronostratigraphic age

Early Toarcian (Falcifer zone, Exaratum subzone; Kuhn and Etter 1994; Röhl et al. 2001).

Description

As a rule, the Untere Stein (= erster Stinkstein; von Wurstemberger 1876) is included in the basal layer interval of the Rietheim Member (Figs. 7, 9 10, 11, 26; e.g., Elber 1921; Pratje 1924; Kuhn and Etter 1994). It may also represent the basal layer of the Rietheim Member (e.g., in the Weissenstein area; Buxtorf 1907; Vogel 1934) and/or its topmost bed, for instance in the eastern Folded Jura (Jordan 1983). It is a distinct, bituminous limestone bed exhibiting clear lamination and having conchoidal-splintery fractures (Kuhn and Etter 1994; Etter and Kuhn 2000).

4.11 Gross Wolf Member

Names previously in use are given in Figs. 2 and 4.

Type locality

Gross Wolf clay pit (canton Aargau; coord.: 645.725/253.350; Jordan 1983).

Underlying strata

Rietheim Member or Breitenmatt Member.

Overlying strata

Opalinus-Ton.

Subdivision

(1) The Gross Wolf Member has the Gipf Bed or the Erlimoos Bed, respectively, at the base. Which of these two basal layers that is developed is strongly dependent on the next lower member. (2) In the eastern Folded Jura, but also in the occurrences in the Molasse basin to the south, the Eriwis Bed forms the uppermost bed of the Gross Wolf Member (see Jordan 1983; Nagra 1992).

Occurrence

Northern Switzerland.

Thickness

The minimum thickness is ±60 cm (eastern Folded Jura; Figs. 13, 16, 19); maximum thickness is around 5.3 m in the eastern Folded Jura and 6.1 m in the Molasse basin (Fig. 11; Jordan 1983; Nagra 2001; some 19 m in the Buix well?, Schmidt et al. 1924: 13).

Chronostratigraphic age

Late Toarcian to Early Aalenian (Variabilis to Opalinum zone; Tröster 1987; Nagra 1989, 1990, 1992; Etter 1990; Maisch and Reisdorf 2006a, b).

Description

Condensed interval consisting of grey phosphoritic marls and concretionary marly limestones with pyrite and abundant macrofossils (especially belemnites and ammonites; Figs. 9 10, 11, 12, 13, 15 16, 17, 18, 19, 20, 21; see Elber 1921; Vogel 1934; Tröster 1987; Reisdorf 2001). However, unlike the sediments of the Sinemurian and Pliensbachian, the Gross Wolf Member seems to be almost completely barren of gryphaeid oysters (Senftleben 1923: 22 mentions a possible exception). The fossil-rich basal and topmost beds of the Gross Wolf Member deserve special attention (= Gipf Bed or Erlimoos Bed respectively; Eriwis Bed). They are stratigraphic index beds in the study area (see Jordan 1983; Nagra 1992; Kuhn and Etter 1994). Also, sediments of the Thouarsense zone have been observed, amalgamated in an ammonite- and belemnite-rich limestone bed in the thin occurrences in the Hauenstein—Passwang area (Figs. 13, 17, 18, 20; cf. Fischer 1964: 86p.; Etzold 1980; Riegraf et al. 1984: 61).

The boundary between the Gross Wolf Member and the Opalinus-Ton is not identical to the biostratigraphic boundary between the Early and Middle Jurassic. The latter can lie either within the Gross Wolf Member or within the Opalinus-Ton in northern Switzerland (see Nagra 1984, 1989, 1990; Etter 1990; Reisdorf et al. subm.; cf. Franz and Nitsch 2009). The sedimentological expression of the boundary between these two stratigraphic units is mainly characterised by a sharp change in colour from predominantly grey marl in the Gross Wolf Member to dark grey to black mica-bearing, silty terrigenous mudstone in the Opalinus-Ton (see Etter 1990; Nagra 2001; Wetzel and Allia 2003).

4.11.1 Gipf Bed

Names previously in use are given in Figs. 2 and 4.

Type locality

Gipf clay pit (SW Frick; canton Aargau; coord.: 642.125/261.775; Rieber 1973).

Underlying strata

Rietheim Member.

Overlying strata

The Gipf Bed forms the basal layer of the Gross Wolf Member.

Occurrence

The Gipf Bed is only developed within the area where the Rietheim Member is present (Fig. 3): Klettgau area, Zürcher Weinland, Tabular Jura, eastern Folded Jura and possibly also in the Mont Terri area. In the Hauenstein area, there is a significant reduction in thickness and facies interfingering with the Erlimoos Member is observed (see Jordan 1983; Wetzel and Reisdorf 2007).

Thickness

0 to some 175 cm (see Jordan 1983; Richter 1987; Tröster 1987).

Chronostratigraphic age

early Late Toarcian (Variabilis zone; Rieber 1973; Jordan 1983; cf. Knitter and Ohmert 1983; Knitter and Riegraf 1984; Richter 1987; Etzold et al. 1989; Kuhn and Etter 1994).

Description

The facies of the Gipf Bed varies widely in the study area. This facies variation is mainly related to the thickness of the Gipf Bed. Essentially, the observed facies are condensed, yellowish to grey, glauconite-bearing, sometimes pyritic and sometimes bituminous marls, rich in fossils (especially belemnites; Jordan 1983; Nagra 1990; Kuhn and Etter 1994; cf. Fischer 1964). Concretionary limestone layers of up to about 20 cm thickness can be intercalated in the thickest intervals of these marls (Richter 1987; Tröster 1987; Kuhn and Etter 1994; cf. Fischer 1964). In addition, the Gipf Bed can contain limestone clasts that originate from the Rietheim Member or, in the case of oolithic clasts, may even be derived from the Gipf Bed itself (Richter 1987 vs. Rieber 1973; Kuhn and Etter 1994). The bituminous facies is characterised by one bioturbated layer, where it is thinly developed, and even by several, if thicker (Riegraf et al. 1984: 61pp.; Richter 1987), which then resemble the youngest layers of the Rietheim Member (e.g., Fucoidengrenzbank of Kuhn and Etter 1994; see Richter 1987). In the thinnest occurrences (40 cm and less) that are occur in the western Tabular Jura and the eastern Folded Jura, the marly facies of the Gipf Bed can merge laterally with a ferruginous or iron oolithic limestone which is occasionally overgrown by stromatolites (Fig. 10, Rieber 1973; Jordan 1983; Kuhn and Etter 1994; cf. Knitter and Riegraf 1984; Riegraf 1986).

4.11.2 Erlimoos Bed

Names previously in use are given in Figs. 2 and 4.

Type locality

Erlimoos clay pit (NE Olten; canton Solothurn; coord.: 633.400/247.050; Fig. 13).

Underlying strata

Rietheim Member (including Unterer Stein) or Breitenmatt Member (including Müsenegg Bed).

Overlying strata

The Erlimoos Bed forms the base of the Gross Wolf Member.

Occurrence

Hauenstein area to Bernese Jura and adjacent areas to the south in the Molasse Basin (see Jordan 1983; Nagra 1992; Figs. 17, 20). In the Hauenstein area facies interfingering occurs between the Erlimoos Bed and the Gipf Bed (see Kuhn and Etter 1994; Maisch and Reisdorf 2006a, b).

Thickness

0–40 cm (e.g., Figs. 19, 20).

Chronostratigraphic age

Early Late Toarcian (Variabilis zone; Imhof in Jordan 1983; Kuhn and Etter 1994; Reisdorf 2001).

Description

Strongly condensed, phosphoritic, glauconitic marls rich in fossils or marly limestone of small thickness (Figs. 12, 13, 17 18, 19, 20, 21; see Erni in Mühlberg 1915; Jordan 1983; Kuhn and Etter 1994). In addition, clasts and even boulders occur, as well as macrofossils that display evidence of reworking, such as phosphatised ammonites (Fig. 19; see Erni in Mühlberg 1915; Imhof in Jordan 1983; cf. Groschopf et al. 1977: 115p.). In the Hauenstein area, the Erlimoos Bed also contains disarticulated and often fragmented reptilian skeletal elements (= exhumed and reworked vertebrate fragments of the Rietheim Member?; Figs. 13, 17; see Meyer and Furrer 1995; Reisdorf et al. subm.).

The biostratigraphically orderless appearance of index fossils (ammonites, ostracods, foraminifers) indicates substantial reworking and bioturbation during the formation of the Erlimoos Bed (see Hess 1962; Jordan 1983; Richter 1987; Wetzel and Reisdorf 2007). In some areas, the erosive base cuts down to the Ibex zone, possibly even down to the Jamesoni zone of the Breitenmatt Member (Figs. 3, 17; see Erni in Mühlberg 1915; Jordan 1983; Wetzel et al. 1993).

The Erlimoos Bed and certain phosphoritic layers of the Pliensbachian (see Breitenmatt Member and Müsenegg Bed) may have a quite similar appearance. In contrast to the Breitenmatt Member (including the Müsenegg Bed), the Erlimoos Bed is, however, often overgrown by sponges in phosphoritic preservation and pyritised stromatolites: Even larger surfaces may be encrusted here without significant gaps (Figs. 13, 17, 18, 20; see Jordan 1983; cf. Ohmert 1976; Etzold 1980). This stratigraphic level is detectable even in drill cores because of its peculiar facies. An additional feature of the Erlimoos Bed is the absence of gryphaeid oysters, unlike the Breitenmatt Member.

4.11.3 Eriwis Bed

Names previously in use are given in Figs. 2 and 4.

Synonym Erimis Bed (Jordan et al. 2008).

Type locality

Eriwis (canton Aargau; coord.: 652.000/256.250; Etter 1990; Kuhn and Etter 1994).

Underlying strata

The Eriwis Bed forms the topmost layer of the Gross Wolf Member.

Overlying strata

Opalinus-Ton (e.g., Etter 1990; Wetzel and Allia 2003; Franz and Nitsch 2009).

Occurrence

Eastern Folded Jura and adjacent areas to the south in the Molasse basin of the Swiss Midland (Fig. 23; see Buxtorf 1907; Jordan 1983; Nagra 1992; Pfirter 1997).

Thickness

?0 to ca. 30 cm (Figs. 19, 23; see Fischer and Luterbacher 1963; Jordan 1983).

Chronostratigraphic age

Late Toarcian (Levesquei zone; Aalensis subzone; Etter 1990; Reisdorf et al. subm.).

Description

Only a few centimetre thick, condensed horizon of the Aalensis subzone (see Etter 1990; Wetzel and Reisdorf 2007; Reisdorf et al. subm.; cf. Etzold 1980). Occasionally brownish, sometimes reddish, dark grey marl layer which may pass laterally into a marly limestone (Figs. 11 11, 12, 13, 15 16, 17, 18, 23). This phosphoritic condensed horizon is characterised by its abundance of ammonites (especially the genera Cotteswoldia and Pleydellia, among others also C. aalensis Zieten 1832) and belemnites (Jordan 1983; Etter 1990; Nagra 1992; cf. Etzold et al. 1989). Based on these characteristics, the Eriwis Bed is clearly and visibly separated from the overlying Opalinus-Ton (see Jordan 1983; Etter 1990; Reisdorf 2001). The latter is characterised by dark grey to black, partially silty to sandy terrigenous mudstone and marl with mica (Etter 1990; Reisdorf 2001; Wetzel and Allia 2003). In the Schafisheim well the lithostratigraphic boundary between the Gross Wolf Member and the Opalinus-Ton is set below a 15 cm thick, reworked horizon that contains iron ooids and Mid-Jurassic foraminifera. This mudstone horizon is noteworthy because it also contains corroded ammonites of the Late Toarcian (Cotteswoldia aalensis Zieten 1832; Tröster 1987; Nagra 1992).

5 Concluding remarks

The total thickness of the Early Jurassic deposits in northern Switzerland is around 25–50 m and thus is significantly thinner than in the adjacent areas of Germany and France (Fig. 6). Lithostratigraphic units of the Early Jurassic that are conformable with the southwest German or eastern French nomenclature therefore only occur in reasonable thickness in the northernmost Tabular Jura (Hofmann 1981; Debrand-Passard 1984; Hofmann et al. 2000, 2002; Bloos et al. 2005). The often small thickness of the majority of the northern Swiss Early Jurassic strata, however, only qualify the complete stratigraphic interval as a mappable unit (= Staffelegg Formation).

In the Klettgau area, the Tabular Jura and the eastern Folded Jura, up to 90% of the total thickness is represented by Sinemurian deposits. By contrast, Pliensbachian and Toarcian deposits account for up to 70% of the total thickness of the Early Jurassic in the western Folded Jura (Mont Terri area). The Early Jurassic strata of the Klettgau area and the Tabular Jura show strong analogies to the facies in southwestern Germany. Significant changes in facies occur towards the south, accompanied by a gradual decrease in thickness (Figs. 3, 6). In addition, stratigraphic gaps occur on a local to regional scale throughout northern Switzerland (Fig. 3). Such hiatus may span a subzone to a stage in time. Consequently it is not always possible to fully reconcile the Early Jurassic sediments, especially of the Folded Jura, with the stratigraphic nomenclature of southwestern Germany (cf. Bloos et al. 2005; Schmid et al. 2008). Especially, in the southernmost and westernmost Folded Jura and in the Molasse Basin abrupt facies changes occur. The impression of strongly differentiated facies patterns is intensified by the folding of the Jura Mountains that led to a shortening of original distances (cf. Laubscher 1965, 2008).

In the westernmost part of the study area (Mont Terri area) the facies and thickness of the Early Jurassic strata show stronger affinities to those found in eastern France than in southwestern Germany (cf. Vonderschmitt 1942; Théobald 1967; Debrand-Passard 1984; Pharisat et al. 1993). The most striking is that thickness of Sinemurian to Toarcian strata is remarkably thicker than to the East, in particular the Early Toarcian bituminous deposits (Fig. 26; Rickenbach 1947; Bitterli 1960; Contini and Lamaud 1978). The strata of the Late Sinemurian to Early Pliensbachian in the Mont Terri area distinctly differ from the sediments of the same age to the east (Fig. 3). The lithology in the Mont Terri area requires a new member (= Mont Terri Member) that differs from the previous stratigraphic nomenclature of northern Switzerland. Because of lacking outcrops in a area east of the Mont Terri it is impossible to precisely define the lateral extent of the Mont Terri Member. The maximum age of this member in the eastern Mont Terri area is Obtusum zone, based solely on lithostratigraphic correlation. The dating in the western Mont Terri area is, however, based on an ammonite of the Ibex zone that was found just above strata of the Semicostatum zone (Fig. 27). Consequently, the base of the Mont Terri Member is heterochronous. Following this interpretation, the erosion during the Early Pliensbachian that cut down into the strata of Early Sinemurian age is likely to have occurred in some parts of the Mont Terri area (Fig. 3).

The Early Jurassic strata in northern Switzerland can be subdivided into three facies domains: (1) Klettgau area, Tabular Jura and immediately adjacent areas of the Molasse basin (mainly corresponding to the facies in southwestern Germany, i.e. Swabian Basin), (2) eastern Folded Jura and immediately adjacent area of the Molasse basin (with a discrete “northwestern Swiss facies” of the Swabian Basin) and, (3) Mont Terri area (Folded Jura; facies that shows a strong affinity to the eastern Paris Basin in its stratigraphic architecture).

The main characteristics of the stratigraphic architecture of these three facies domains are represented by 11 members and 9 beds in the Staffelegg Formation. The members that have been defined for the Folded Jura differ significantly from the classification schemes previously in use for the Early Jurassic of northern Switzerland. The beds defined within the Staffelegg Formation serve as connecting elements between the traditional and new stratigraphic nomenclature. They represent supraregional marker beds with the exception of the Müsenegg Bed and the Eriwis Bed. Some of the beds are developed as thin strata in the sense of allostratigraphy (Hallau Bed, Müsenegg Bed, Gipf Bed; cf. Lutz et al. 2005). Namely the Hallau Bed (Planorbis to Liasicus zone), Schleitheim Bed (Angulata zone), Gächlingen Bed (Bucklandi zone), Trasadingen Bed (Davoei zone) and the Unterer Stein (Falcifer zone) have lithostratigraphic equivalents in southwestern Germany (Fig. 2).

Only one of these beds, Unterer Stein, can be traced with some confidence to the Mont Terri area and from there to France (cf. Riegraf et al. 1984: 14p.; Pharisat et al. 1993; Kuhn and Etter 1994). The questionable Trasadingen Bed in the Mont Terri area (Fig. 26) could be correlatable to the so-called Banc à Davoei in France (cf. Debrand-Passard 1984: 136). The Gipf Bed and Erlimoos Bed, in contrast, correlate with erosion horizons of the Variabilis zone in southwestern Germany and eastern France (cf. Rieber 1973; Debrand-Passard 1984; Knitter and Ohmert 1983). The Gipf Bed and Erlimoos Bed occur in characteristic development south of the Rhine River, in particular when they are thin. The same is true for the Müsenegg Bed (Margaritatus to Spinatum zone) and the Eriwis Bed (Aalensis subzone) that only occur in the Folded Jura and in the Molasse Basin to the south.

The Staffelegg Formation is introduced for Early Jurassic sediments in northern Switzerland between the Doubs River and the Mount Weissenstein in the West and the Randen Hills north of the city of Schaffhausen in the East. To the South and East, in boreholes in the Molasse Basin, a transition to a facies more proximal to the Vindelician land mass was observed (cf. Büchi et al. 1965; Trümpy 1980; Stoll-Steffan 1987). Early Jurassic strata underneath the frontal part of Imbricated Molasse (e.g., well Entlebuch 1; Vollmayr and Wendt 1987) and those of the Lake Constance area cannot be consistently subdivided into the members and beds of the Staffelegg Formation (cf. Stoll-Steffan 1987). For these occurrences additional lithostratigraphic units are required to account for the coastal facies of the Swabian Basin. An extension of the Staffelegg Formation to the area of Lake Bienne (well Hermrigen, coord.: 584.600/214.880) and to areas further to the west is not advisable, however, since the Early Jurassic occurrences in these areas are developed in the facies of the Rhodanian Basin (cf. Fischer and Luterbacher 1963; Büchi et al. 1965; Jordan et al. 2008 and references therein).