The Middle to Late Triassic Bänkerjoch and Klettgau Formations of Northern Switzerland

Home , Ergolz, Exter Formation, Fricktal, Gansingen, Gervillia, Hemmental

Swiss J Geosci (2016) 109:257–284 DOI 10.1007/s00015-016-0218-3

The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland

1,2 1,2 3 4 Peter Jordan • Johannes S. Pietsch • Hansruedi Bla¨si • Heinz Furrer • 2 4 1 5 Nicole Ku¨ndig • Nathan Looser • Andreas Wetzel • Gaudenz Deplazes

Received: 13 November 2015 / Accepted: 24 May 2016 / Published online: 16 July 2016 Ó Swiss Geological Society 2016

Abstract In the context of the harmonisation of the Swiss Member includes coarse alluvial and fluvial sandstones of lithostratigraphic scheme, the Late Ladinian to Early Vindelician origin. It is restricted to the Lake Constance Norian Ba¨nkerjoch Formation and the Norian to Rhaetian area. For practical reasons, the Gruhalde Member (for- Klettgau Formation of northern Switzerland are formally merly «Obere Bunte Mergel» and «Knollenmergel») defined. The Ba¨nkerjoch Formation replaces the «Gipske- encompasses all playa sediments above the Gansingen uper». Delimitation generally follows the traditional Swiss Member and Berlingen Member. Evidence in good out- scheme with the onset and offset of sulphate facies as basal crops suggests that it consists of several sedimentary cycles and upper boundary. The Klettgau Formation includes six separated by long time spans of omission and erosion. The members (from base to top): The Ergolz Member Seebi Member (formerly «Stubensandstein») includes (formerly «Schilfsandstein» and «Untere Bunte Mergel») layers of coarse-grained sandstones of Vindelician origin consists of variegated silty dolomitic marl with dolocretes with calcitic, siliceous or clayey matrix. Locally, matrix and channels filled by fine-grained sand of Scandinavian fraction increases and becomes mostly dolomitic in the origin. The Gansingen Member (formerly «Gansinger upper part. The Belchen Member (formerly «Rha¨t») con- Dolomit s.l.») starts with partly porous dolomite with sists of partly fossiliferous sandstone and greenish dark Carnian bivalves and continues with an alternation of marl of estuarine to marine origin. Due to late Triassic and dolomite beds with thin dolomitic marl interlayers. At early Jurassic erosion, the Belchen Member is restricted to several places, the member has been eroded to great parts northwestern Switzerland and the Lake Constance area. during the Late Triassic. Towards east and southeast, dolomitic sulphates, locally altered to dolomite or lime- Keywords Northern Switzerland Á Ba¨nkerjoch formation Á stone, replace the marine carbonates. The Berlingen Klettgau formation Á Middle to late Triassic Á Lithostratigraphy

Editorial handling: W. Winkler and A. Morard. 1 Introduction & Peter Jordan [email protected] In the context of the harmonisation of the Swiss strati- 1 Institut fu¨r Geologie und Palaöntologie, Universita¨t Basel, graphic scheme (HARMOS project, Morard 2012, Strasky Bernoullistrasse 32, 4056 Basel, Switzerland et al. 2016, this issue), the subdivision of the Triassic strata 2 Gruner Bo¨hringer AG, Mu¨hlegasse 10, 4104 Oberwil, of northern Switzerland into six formations has been Switzerland accepted by the Swiss Committee on Stratigraphy on 22nd 3 H.R. Bla¨si Geo-Consulting, Steinackerstrasse 2, November 2014 with the proviso to hand in the formal 3184 Wu¨nnewil, Switzerland definition later (Jordan 2016). In the present study, the 4 Palaöntologisches Institut und Museum, Universita¨tZu¨rich, Ba¨nkerjoch and Klettgau Formations of Middle to Late Karl-Schmid-Strasse 4, 8006 Zurich, Switzerland Triassic age are introduced and the subdivision of the latter 5 Nagra, Hardstrasse 73, Postfach 5430 Wettingen, Switzerland into six members is defined. 258 P. Jordan et al.

Due to the poor outcrop conditions of the Triassic strata anhydrite, massive or in alternation with shale and dolo- in northern Switzerland, the concept of Remane et al. mite, starting with the first occurrence of sulphate sedi- (2005) asking for stratotypes has to be softened. With the ments and ending with the offset of sulphate facies (Fig. 2). agreement of the Swiss Committee on Stratigraphy the It differs slightly from the Grabfeld Formation (e.g., Etzold definition of formations and members is completed with and Schweizer 2005; Geyer et al. 2011), which replaced the borehole reference sections. The requirement for a bore- former «Gipskeuper» in Germany (see Sect. 2.3). hole-based reference locality is that the core material is properly stored and accessible for future research (Jordan 2.2 Type locality and reference sections 2016). Type localities have been chosen based on suit- ability and disposability of local names, present-day Today, the only accessible outcrops are abandoned gypsum accessibility, and existence of published records. All type quarries: Riepel south of the Ba¨nkerjoch Pass and Sta¨gli- localities of the formations and members have recently matt south of the Staffelegg Pass (both located in the been recorded, some of them after specific excavations. municipality of Ku¨ttigen AG), as well as a quarry in However, some of the proposed type localities are rather Oberehrendingen AG at the northern flank of the La¨gern nominal than formal, as the base and the top have never range. All three quarries are localised in the Folded Jura, been accessible or the development of the strata is where the sulphate rocks acted as viscous horizons during incomplete or untypical. Further explanations are given in thrusting and folding. Thus, all three outcrops show tec- the respective type locality descriptions. tonic overprint. The least tectonic overprint occurs in the To define the two formations and the members of the Riepel quarry, where also the present-day outcrop condi- Klettgau Formation several concepts have been considered. tions and accessibility are quite good. The stratigraphic The recently reviewed stratigraphic scheme of southern succession of the Riepel quarry (coord. 2645.300/ Germany (Etzold and Schweizer 2005; Geyer et al. 2011) 1253.850) has been repeatedly recorded (Schindler 1962; could not be directly adopted for several reasons: Most of Rick 1990; Kleiner 2009; Meier 2011) under differing the German formations are defined in the centre of the outcrop conditions and from various scientific points of Germanic Basin and wedge out towards the South. Con- view. It is the only outcrop where the top and base of the sequently, the formations reach only a few metres of formation have been exposed. Further, it can easily be thickness in the High Rhine region and in the adjacent correlated to the chosen borehole reference section at Swiss area. Remane et al. (2005) define formations as Weiach (Matter et al. 1988) (see below). The Riepel sec- mappable units. Referring to the current concept of the tion includes the upper four stratigraphic units I to IV of the Geological Atlas at 1:25,000 scale of the Swiss Geological current informal stratigraphic scheme developed for Nagra Survey, a mappable unit has to have a thickness of at least wells (Matter et al. 1988), including the markerbed 2 (see 30 m. A second approach to combine German formations below). The lowermost unit V is apparently missing, as and to adopt them as members failed by significant dif- well as the markerbed 1 expected in the uppermost unit I. ferences in delimitating the stratigraphic succession in For those reasons, the Riepel quarry was chosen as the type present-day German and traditional Swiss schemes. Addi- locality (Fig. 3), whereas the name of the formation derives tionally many recent outcrop and borehole records and from the nearby Ba¨nkerjoch road pass. studies refer to the traditional stratigraphic nomenclature. The corresponding sequence (drilling depth In this context, the shifting of formation or member 739.35–814.08 m) of the Weiach well (coord. 2676.745/ delimitations can create confusions or misinterpretations. 1268.618, Matter et al. 1988), was chosen as the reference However, the opportunity has been used to review and section. It shows a complete succession, including all five formally define the formations and members for the informal subdivisions of Matter et al. (1988) and Dronkert stratigraphic interval in question and to discuss their lateral et al. (1990) and both marker horizons of Nagra (1992b) variations and relation to the stratigraphic units of the (see below). Furthermore it represents the typical facies of adjacent German territory. northeastern Switzerland and relates well to the outcrops in southern Germany.

2Ba¨nkerjoch formation 2.3 Delimitation

2.1 Main characteristics The delimitation of the Ba¨nkerjoch Formation follows the traditional Swiss deﬁnition of the former «Gipskeuper». It The Ba¨nkerjoch Formation corresponds to what was used differs from the current German scheme where the Grabfeld to be the «Gipskeuper» in traditional (informal) Swiss Formation starts with the Grundgips Member. According to stratigraphy (Fig. 1). It is a succession of gypsum and that scheme, the underlying Grenzschichten Submember, Gr n cwie ( Schweizer and Etzold of work the column summarizing the in indicated partly also is nomenclature German the with equivalence Lateral omtos( Formations Ba the of scheme subdivision new the with northern Switzerland of Triassic Late and Middle the for nomenclature stratigraphic historical 1 Fig. Ba Triassic late to middle The ¨ ucekl Group Muschelkalk . krohadKlettgau and nkerjoch orlto fthe of Correlation ih column right 2005 ). MK ). ¨ krohadKeta omtoso otenSizrad259 Switzerland northern of formations Klettgau and nkerjoch

Mühlberg (1908) Schmassmann Bitterli-Brunner & Hofmann et Diebold et Bitterli-Dreher Etzold & Équipe du projet Disler (1914) Schalch (1916) Büchi et al. (1965) Gsell (1968) Fischer (1969) Müller et al. (1984) Nagra (2001) This paper Mühlberg (1915) (1953) Fischer (1988) al. (2000) al. (2006) et al. (2007) Schweizer (2005) GeORG (2013)

Arietenkalk Arietenkalk Arietenkalk Arietenkalk Arietenkalk Arietenkalk Arietenkalk Arietenkalk Arieten- oder Arietenkalk Weissenstein Mb. und und und und und und und Gryphitenkalk (inf.) Angulatenschichten Angulatenschichten Angulatenschichten Angulatenschichten Angulatenschichten Angulatenschichten Angulatenschichten Calcaires et Beggingen Mb. Sinemurian Lias Marnes de Hochfelden

Jurassic Insektenmergel Scham- Cardinienschichten Psiloceras- Psiloceras- Insektenmergel

Early Jurassic Insektenmergel Psilonotenschichten Insektenmergel Insektenmergel und Insektenmergel Insektenmergel Psilonotenton Fm belen Schichten Schichten (Psilonotenschichten) Psiloceras-Schichten Staffelegg Fm.

Lias Group Mb. Hettangian Rhétien Rhätkeuper- Rhät Rhät Rhät Rhät Rhät Rhät Rhät “Rhät”? Belchen Mb. (Exter) Fm. Rhaetian ?

Knollenmergel Knollen- Knollen- Knollen- Knollen- Knollenmergel- Knollenmergel Knollenmergel mergel mergel mergel mergel (Trossingen) Fm. Marnes irisées

d Obere Bunte Mergel supérieures

n Norian Dolomit Obere a

s i (Knollenmergel und Stubensandstein-

Stubensand- Stubensandstein- e

Mergelgruppe Stubensandstein Stubensandstein t Stubensandstein Seebi Mb.

s (Löwenstein) Fm. Obere bunte Obere bunte stein Formation Obere Bunte b Stubensand- Stubensandstein)

Obere bunte t stein s.s. (Obere bunte Mergel Mergelschichten Mergel Mergel S

Mergel) r e Gruhalde Mb.

p Obere Bunte Bunte Mergel l Rote

Bunte Mergel Obere Bunte Mergel e Bunte Mergel .

e Keuper Mergel (Obere) g Wand

(des Mittelkeupers) m r

i Bunte )

t e Marnes irisées

a s Mergel

r u moyennes Late Triassic

e Beaumont- B

a ... mit g

e Klettgau Formation

S Gansinger Gansinger Gansinger Gansinger Gansinger e Horizont

Gansingerdolomit e Gansingen Mb.

Sand- t

(

n Hauptsteinmergel Dolomit Dolomit Dolomit Dolomit Dolomit Keuper Group Hauptsteinmergel Hauptsteinmergel lagen Hauptsteinmergel Gansinger Dolomit Gansinger U Beaumont- Triassic Dolomit* (Gansinger Dolomit) (Hauptsteinmgl.) Dolomit Berlingen Mb.

Untere bunte Untere bunte Untere bunte Untere Bunte Untere Bunte Untere Bunte . Dunkle

Carnian Bunte Mergel

t Mergel

Mergel Mergelschichten Mergel Mergel Mergel Mergel F

Schilfsandstein

)

Schilfsandstein- d

(-Bereich) Untere Bunte Mergel a

a Grés à rosaux gruppe Schilfsandstein- g

s Schilfsand- t Ergolz Mb.

(Normal- und und l

Formation t stein h

c Rinnenfazies) Schilfsandstein S Schilfsandstein- Schilfsandstein- Schilfsandstein- ( Schilfsandstein (Schilfsandstein) S Schilfsandstein gruppe schichten Gruppe Schilfsandstein Schilfsandstein Schilfsandstein

. Estherien-

schichten

)

d l Mittlerer Marnes irisées

k f Gipskeuper

s ? b inférieures

p Keupergips Gipskeuper Gipskeuper Gipskeuper Gipskeuper Gipskeuper Gipskeuper Gipskeuper Gipskeuper Gipskeuper Gipskeuper a Gypskeuper Gipskeuper i Bänkerjoch Fm. r Unterer

( Gipskeuper

Grenzdolomit Grenzdolomit Grenzdolomit Grenzdolomit Grenzdolomit Lettenkohle Letten- (Estherienschiefer Lettenkeuper- Asp Member Lettenkohle Lettenkohle Estherienschiefer Estherienschiefer Estherienschiefer Lettenkohle Lettenkohle Lettenkohle Lettenkohle kohle Ladinian Estherienschiefer Unterer Keuper und Grenzdolomit) (Erfurt-) Fm. Unterer Dolomit Muschelkalk supér. Schinznach Fm. Middle Triassic MK Gr. * Beaumont-Dolomit ~ not described or Hauptsteinmergel ~ no outcrops hiatus Beaumont-Sulfat 260 P. Jordan et al.

Nomenclature Nomenclature in northern Switzerland in southern Germany Age Epoch Period

oolitic Weissenstein Arietenkalk Fm. Beggingen Mb. Angulatenton Fm. Sinem.

chert nodules Fm.

Schambelen Mb. Psilonoten Fm. Early Jurassic Jurassic Het. Staffelegg Staffelegg bed rich in fossils Belchen Mb. Exter Fm. Rh. limestone ? Gruhalden Mb. Trossingen Fm. dolomite

Seebi Mb. Löwenstein Fm. Norian fine sand, silt

Steigerwald Fm. middle or coarse sand Gansingen Mb./Berlingen Mb. Beaumont Horizont Klettgau Formation Ca-sulphate Stuttgart Fm.

variegated, dolomitic, partly silty clay Ergolz Mb. Late Triassic marl and mudstone

dark marl and clay, partly bituminous

dark dolomitic marl Carnian

markerbed 1 Triassic

? no formal subdivision yet Grabfeld Fm. Bänkerjoch Formation

markerbed 2 Ladinian Middle Triassic missing in some areas Asp Mb. Erfurt Fm. stratigraphic discontinuity Stamberg Mb. Rottweil Fm. Schinznach Fm.

Fig. 2 Schematic synoptic sections of the Ba¨nkerjoch and Klettgau Formations (the latter with its subunits), compared on the right side with the current stratigraphic units in Germany (Etzold and Schweizer 2005; Geyer et al. 2011) including the «Fra¨nkische Grenzdolomit» and the «Bo¨hrin- boundary of the former «Gipskeuper». In southern Ger- gen Sulfat» or «Gru¨ne Mergel», are part of the Erfurt For- many, the whole «Estherienschichten» are part of the mation (corresponding to the former «Lettenkeuper») (Etzold Grabfeld Formation though their upper part is mostly and Schweizer 2005). In the old south-western Germany devoid of massive sulphate layers (Etzold and Schweizer (Grand Duchy of Baden) scheme, the «Bo¨hringen Sulfate» is 2005). The overlying Stuttgart Formation starts with the taken as the base of the «Gipskeuper» (with the «Badische transgression of the siliciclastic fluvial «Schilfsandstein Grenzdolomit» or «Oberer Linguladolomit» as top of facies» (see below). In the traditional Swiss stratigraphic the «Lettenkeuper») (Deecke 1916, Etzold and Schweizer scheme the term «Estherienschichten» was unknown in 2005). Most Swiss stratigraphers had traditionally followed this context. The upper boundary of the «Gipskeuper» was the latter delimitation concept, which is now formally adopted defined with the offset of diagenetic sulphates. Relative to by the definition of the Ba¨nkerjoch Formation. The overall the ‘‘Leitbank’’ concept of southern Germany (e.g., Etzold thickness of the disputed layers never exceeds more than and Schweizer 2005), this limit varies regionally. In most 2–4 m in northern Switzerland. cases, it is located somewhere within the equivalents of the The discrepancy between the German and Swiss middle («Graue») «Estherienschichten» (A. Etzold, pers. schemes is more relevant for the definition of the upper Comm. 2016). At very few places, i.e. only at places where The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 261

Type locality of the Bänkerjoch Formation: Section Riepel quarry, Küttigen AG Coord.: 2 645 300 / 1 253 850 Kleiner (2009) (Meier 2011) Subdivision after Subdivision after Stage Formation Rick (1990) Lithology Sediment structures Subdivision after Member Weathering profile Lithology Sediment structures Weathering profile Kleiner (2009) Subdivision after (Meier 2011) Subdivision after Stage Formation Member Rick (1990) Subdivision after

2 m II Zyklische Serie Ergolz-Member Tectonic Klettgau-Formation overprint to Rick (1990) completed according Schilfsandstein Top of actual outcrop IIIA mation r

IIIB markerbed 2 Gipskeuper Gipskeuper Bänkerjoch Fo

I Ladinian

IIIC

Carnian Strong tectonic overprint

IV Base of Bänkerjoch Formation actual outcrop Gipskeuper Gipskeuper Gipskeuper Member enkohle t sp Let A chinznach Fm. S completed according to Rick (1990)

II Zyklische Serie

Fig. 3 Type section of the Ba¨nkerjoch Formation, at Riepel gypsum quarry in Ku¨ttigen AG. Key see Fig. 4 262 P. Jordan et al.

Key to sections Lithology Fossils / components Sedimentary structures

limestone fossils in general stratigraphic discontinuity dolomite foraminifera channel marlstone / marly limestone brachiopods cross-bedding clayey marlstone gastropods desiccation cracks claystone bivalvia trace fossils, Asteriacites sandy claystone gryphaeid oysters burrows, bioturbation sandy dolomite coquina cavernous, cellular / porose/ druses dolomitic marlstone belemnites/ammonites resp. ceratites chert nodules sandy marlstone crinoids, echinoderm remains nodular, with the corresponding lithology sandy limestone estheria lenticular, with the corresponding lithology calcareous sandstone vertebrate remains breccia sandstone neoselachii (sharks) charact. vein network (in evaporites) clayey sandstone K plant remains / coal laminated Fe-oolite, pisolitic iron ore stromatolites sulphate-rich rock (anhydrite) finely layered fish remains gypsum thin-bedded gypsum crystals anhydrite thick-bedded mica halite P pyrite / phosphoritic uneven or undulating bedding root horizons chicken-wire (evaporites) ooids

Fig. 4 Key to all stratigraphic sections

fluvial channels had deeply eroded in the underlying strata, A more sophisticate way to distinguish the Ba¨nkerjoch the offset of sulphates corresponds more or less to the onset Formation from the overlying Klettgau Formation (and the of fine grained sandstone («Schilfsandstein facies»). As the underlying Schinznach Formation, Pietsch et al. 2016) is the offset of sulfate facies is not easy to define in destructive presence of corrensite, a chlorite/montmorillonite mixed drilling and, due to sulphate leaching, in surface outcrops, layer (e.g., Frey 1969) which is mostly restricted to high the upper boundary of the Ba¨nkerjoch Formation is newly saline evaporite environments (e.g., Ru¨gner 2000). The defined at the top of a dolomite horizon which can be found observation that corrensite is restricted to the «Gispkeu- in nearly all known bore holes and surface outcrops of per» (now Ba¨nkerjoch Formation) and to the older evapor- northern Switzerland. In southern Germany, this dolomite ite «Anhydritgruppe» (now Zeglingen Formation, Jordan horizon marks the top of the «Graue Estherien- 2016) by Peters (1964) was later confirmed e.g. by Peters schichten» (Etzold and Schweizer 2005). This results in a et al. (1986) and Matter et al. (1988). However, not every discrepancy of decimeter to a few meters to the previous clay horizon of the Ba¨nkerjoch Formation reveals corrensite, definition of the top of the «Gispkeuper» in some well and corrensite may also be found in some layers directly documented core descriptions of northern Switzerland. For above the dolomite horizon now defining the upper limit of instance, the some 20 cm thick «Dolomitbank, hart (=Basis Ba¨nkerjoch Formation (M. Mazurek, pers. Comm. 2016). des Schilfsandsteins)» of the reference section of Weiach (Matter et al. 1988) is now the top layer of the Ba¨nkerjoch 2.4 Subdivision Formation. In the reference section of Siblingen of the overlying Klettgau Formation (see below), the 1.42 m In agreement with the Swiss Committee on Stratigraphy thick «Dolomit […] und Tonmergel […], mit Gipsknol- and the involved stakeholders, it was decided to postpone a len», originally taken as the base of the «Schilfsandstein formal subdivision of the 30–130 m thick Ba¨nkerjoch s.l.» (Nagra 1992b) is now the top bed of the Ba¨nkerjoch Formation (Fig. 2). Formation. At places, where the dolomite horizon should The traditional subdivision in northeastern Switzerland be missing, the offset of sulphate facies will stay the cri- includes the German allostratigraphic markerbeds (Leit- terion to draw the upper limit of Ba¨nkerjoch Formation. ba¨nke) concept introduced, for instance by Schalch (1916), The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 263 a petrographic concept by Schindler (1962) and a genetic • II: Heavily veined sulphcretes (‘‘cyclic sequence’’). concept by Dronkert et al. (1990). The latter was used with • I: Anhydrite nodules and clay/siltstone. minor modifications to record most of the recent boreholes. The concept of Dronkert et al. (1990) derives from an The markerbeds (Leitba¨nke) in northeastern Switzerland initially purely lithological scheme introduced by Matter include after Schalch (1916) and Hofmann et al. (2000) et al. (1988) and later applied to all Nagra deep borehole (base to top): records. For recording the Benken well (Nagra 2001), the • «Myoconcha-Bank» (Schalch 1916, see Etzold and scheme was expanded with the adjunction of the marker- Schweizer 2005), one or a few thin dolomite beds rich beds of Schalch (1916) and Hofmann et al. (2000). The in vertebrate remains and marine bivalves. Schalch markerbeds have later also been identified in existing deep (1916) mentioned the following genera: Myophoria, boreholes of central northern Switzerland (Jordan et al. Pseudocorbula, Gervillia, Anoplophora and Myocon- 2016). The extended scheme includes from base to top: cha. Schalch (1916) correlated the «Myoconcha- • V: Dolomite and sulphate with clay interlayers, partly Bank» with the «Fra¨nkische Grenzdolomit» , i.e. the dolomite and sulphate breccia in clay matrix. base of the «Grundgipsschichten» and thus, the Grab- • IV: Banded massive sulphate with silt to claystone feld Formation in southern Germany (see above). interlayers. • «Pseudocorbula-Bank» (Hofmann et al. 2000) • III: Thin-layered sulphate/claystone sequences, includ- or «Muschelbank mit Mytilus» (Schalch 1916), a dolo- ing in its middle part the markerbed 2, which mite, often a coquina, containing quartz grains. Schalch corresponds to the «Muschelbank mit Mytilus» Schalch (1916) reported the finding of species of the marine (1916) which is identified by Hofmann et al. (2000) bivalve genera Mytilus, Pseudocorbula and Myoconcha. as «Pseudocorbula-Bank» or «Bleiglanzbank». Hofmann et al. (2000) correlate the «Pseudocorbula • II: Cyclic sequence consisting of clay, clay with Bank» with the «Bleiglanz Bank» of southern Ger- sulphate noduls and (often chicken wire type) sulphate many. This bed is taken as the base of the «Mittlerer beds. Gipskeuper» (e.g. Geyer and Gwinner 1986). • I: Silt to Claystone with sulphate nodules, including in • «Quarzitische Bank» , a (nearly) carbonate-free sand- its lower part (but not at the bottom) the markerbed 1, stone or sandy dolomite containing the marine bivalve which corresponds to the Quarzitische Bank of Schalch Gervillia. The «Quarzitische Bank» or «Engelhofen- (1916). Platte» is taken as the base of the «Estherien- schichten» by the German stratigraphers (e.g. Geyer and Gwinner 1986). 2.5 Genetic and palaeogeographic interpretation In the context of a prospection campaign, Schindler The Ba¨nkerjoch Formation was deposited under (semi) arid (1962) proposed a petrographic stratigraphy, which is more conditions in the southern extension of the Germanic suitable for potential gypsum quarry sites assessment. It Basin. The basin was influenced by periodic marine includes from base to top: ingressions from southwest and rare signals of erosional • Lower gypsum group. events in the Bohemian (Vindelician) Massive (Beutler and • Lower variegated group. Nitsch 2005). Fully marine conditions are documented by • Intermediate strata poor in sulphates. the bivalve fauna of dolomite and sandy interlayers • Upper gypsum group. including the marker horizons «Pseudocorbula- • Upper variegated group. Bank» and «Quarzitische Bank» (see above). The latter simultaneously documents a short-term progradation of the The scheme of Dronkert et al. (1990) is based on a Vindelician costal facies summarised as Benk Formation in genetic and sedimentological approach. It includes from southern Germany (e.g. Beutler 2005). The dominant sed- base to top: imentary environments, however, were peri-marine (salina) • V: Banded sulpharenites with dolomite and clay (partly to terrestrial evaporites (sabkha), organized in regressive breccias). cycles. According to Dronkert et al. (1990), the «Gipske- • IV: banded, massive sulpharenites. uper», i.e. the present-day Ba¨nkerjoch Formation can be • IIIC: Banded sulpharenites with stringers of red subdivided in two mesocycles, with the upper one con- nodules. sisting of 27 microcycles. In adjacent southern Germany • IIIB: Clay, anhydrite nodules and banded sulpharenites. even eight regressive mesocyles have been documented • IIIA: Banded nodular sulphates with clay and dolomite (Etzold and Schweizer (2005) and references therein). beds. 264 P. Jordan et al.

2.6 Formal deﬁnition of the Ba¨nkerjoch formation Overlying strata Ergolz Member of the Klettgau Formation (this Names previously in use «Gipskeuper», further paper). synonyms are given in Upper boundary Top of a horizon consisting Fig. 1. of one or more dolomite Origin of name Ba¨nkerjoch, a road pass layers above the offset of close to the type locality. sulphate facies. This Type locality Abandoned gypsum quarry dolomite horizon Riepel in Ku¨ttigen AG corresponds to the uppermost (coord. 2636.250/1251.300), bed of the «Graue (Schindler 1962; Rick 1990; Estherienschichten» of Kleiner 2009; Meier 2011) southern Germany. At places (Fig. 3). where the dolomite horizon Type region Eastern Folded Jura. is missing, the offset of Reference locality Weiach well (coord. sulphate facies is taken as the 2676.745/1268.618), drilling upper boundary (for 739.35–814.08 m (Matter discussion, see Sect. 2.3). In et al. 1988), fully cored and few cases, the siliciclastic conserved in the Nagra core sandy channel shack (Kernlager). («Schilfsandstein») facies of Underlying strata Asp Member of the the Ergolz Member erodes Schinznach Formation down to the dolomite (Pietsch et al. 2016). horizon or the sulphate Lower boundary Onset of the evaporitic facies. However, in many facies. In most cases, the cases, the dolomite horizon Ba¨nkerjoch Formation starts is overlain by (sulphate-free) with massive anhydrite beds variegate claystone, marl and of various thicknesses or a dolomite. conglomerate of anhydrite Subdivision No formal subdivision yet. and dolomite in a clay For the traditional matrix. The top of the Asp subdivision see Sect. 2.4 Member is represented in Subdivision. most cases by a (cavernous) Occurrence Northern Switzerland. dolomite. With respect to Thickness 30–130 m (Fig. 5) clay mineralogy, the Chronostratigr. Age Late Ladinian to Early boundary corresponds to the Carnian (DSK 2002, 2005; onset of corrensite (see Sect. Kozur and Bachmann 2008). 2.3). A further criterion is the Description Evaporitic sequence offset of bituminous shale deposited in a marine to and dolomite that are terrestrial salina or sabkha. abundant in the Asp Member The sequence can be of the Schinznach subdivided in regressive Formation. meso- and microcycles and The delimitation follows The equivalents of the consists of sulphates, sulphate the traditional Swiss southern shale alternations, shale with scheme German «Fra¨nkischer nodular sulphate and shale. Grenzdolomit» (or «Gru¨ner Fossiliferous dolomite and Mergel») and the underlying sandstone beds document evaporites («Bo¨hringen marine ingressions and Sulfat») are part of the siliciclastic pulses from the Ba¨nkerjoch Formation. Vindelician High. (Fig. 2). The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 265

Isopach of the Bänkerjoch Formation Bänkerjoch Formation Isopach of the Klettgau Formation Klettgau Formation Reference section (W: Well Weiach) Erosive occurence boundary of the Belchen Member Type locality (R: gypsum pit Riepel) Western border of the Seebi Member Western border of the Berlingen Member Reference section (Si: Well Siblingen, B: Well Berlingen-1, G: Gruhalde / Frick, C: Chilchzimmersattel / Belchen) Type locality (Se: Seebi quarry) 0 2.55 10 15 20 0 2.55 10 15 20 km km

Bänkerjoch Formation is missing Klettgau Formation missing (recent erosion) (recent erosion)

pre-Berlingen Mb. strata missing due to erosion

Wells and outcrops - overview Well (thickness of the formation in m) Wells and outcrops Outcrop (thickness of the formation in m) Local maximum, not delimited by isolines Local minimum, not delimited by isolines

1 Well Basel-1 31 Well Klingnau K36 2 Well Otterbach OT2 32 Well Zurzach S2 Germany 3 Neue Welt, outcrop 33 Well Ruckfeld-1 4 Weissenstein area, outcrops*) 34 Well Zurzach L3 5 Pratteln Erlimatt, outcrop 35 Well EWS Münzlishausen Rhine 6 Ergolz/ Riedacker, outcrop 36 Well Tegerfelden T1 Bänkerjoch and Klettgau Formations River 7 Niederschönthal, outcrop 37 Ennetbaden, outcrop are missing (recent erosion) 8 Chilchzimmersattel, outcrop 38 Well Degernau-1 9 Belchen Süd, tunnel 39 Erzingen-Klettgau, outcrop Schaffhausen 10 Well Pfaffnau 1 40 Well Weiach 11 Hemmiken Steingraben, outcrop 41 Well EWS Osterfingen Lake Constance 12 Zeglingen-Rohr, outcrop 42 Well Sonnengarten GTB1 13 Well Gösgen SB4 43 Well Siblingen 14 Well Altishofen-1 44 ancient path Schleitheim - Fützen, outcrop 15 Gruhalde clay pit Frick, outcrop 45 Seebi quarry Schleitheim, outcrop Basel 16 Frick and surrounding area 46 ancient quarry Beggingen, outcrop 17 Well EWS Frick 47 Steinbruch Worberg, outcrop 18 Well Frick 5 48 Well Benken 19 Riepel gypsum pit, outcrop 49 Well Lindau-1 20 Well Densbüren-Asp 50 Well Schlattingen SLA-1 21 Well EWS Gansingen Galten 4 51 Well Herdern-1 22 Röt quarry Gansingen, outcrop 52 Well Berlingen-1 Zurich 23 Gansingen-Sulz, outcrop 53 Well Kreuzlingen-1 24 Well EWS Gansingen 25 Well Schafisheim *): Bänkerjoch and Klettgau Formation together: > 62 m (probably 112 m) 26 Well Schinznach Bad S3 27 Well Riniken 28 Well Böttstein 29 Well Beznau 7904 30 Well AKW Beznau SB8v Switzerland

Fig. 5 Isopach maps for the Ba¨nkerjoch Formation and for the Klettgau Formation in northern Switzerland. Wells and outcrops used as database are shown in the overview map and description at the bottom

Lateral equivalents The Ba¨nkerjoch Formation 3 Klettgau formation mostly corresponds to the Grabfeld Formation of 3.1 Main characteristics southern Germany (excluding the sulphate-free upper part of The Klettgau Formation encompasses around 30–75 m of the «Estherienschichten») playa sediments with ﬂuvial and marine intercalations of and the uppermost part of Late Triassic age (Fig. 1). It includes what was formerly Erfurt Formation (e.g. Etzold known as «Sandsteinkeuper» (e.g. Hofmann et al. and Schweizer 2005, Geyer 2000), «Mergelkeuper», (e.g. Jordan et al. 2008), or, more et al. 2011) neutrally, «Oberer Mittelkeuper». Additionally, it also Towards the East, it correlates comprises the «Oberer Keuper» or «Rha¨t». In other words, to the massive siliciclastic the Klettgau Formation encompasses the whole interval Benk Formation which may between the Ba¨nkerjoch Formation (this paper) and the reach as far as the Lake Staffelegg Formation of Early Jurassic age (Reisdorf et al. Constance area according to 2011) (Fig. 2). the palaeogeographic reconstruction by Beutler and 3.2 Type locality and reference sections Nitsch (2005). Towards the South, the Ba¨nkerjoch In northern Switzerland, there is no outcrop displaying the Formation wedges out. whole Klettgau Formation with all its members. 266 P. Jordan et al.

Fig. 6 Type section of the Type locality of the Klettgau Formation and the Seebi Member: Klettgau Formation and of the Seebi Member at Seebi quarry Section Seebi quarry, Schleitheim SH in Schleitheim SH. Key see Coord.: 2 680 575 / 1 291 800 Fig. 4 . (2000) rmation Stage Hofmann et al Fo Sediment structures Colors Lithology Fossils/ components Fossils/ Subdivision after Member Weathering profile Remarks

1 beige

beige Marl with some coarse sand layers (badly outcropping) 2

greenish-beige 3

greenish-beige Member 4 Norian Marly layers (badly outcropping)

Seebi 5

6A greenish-beige greenish-beige 6B beige 6C beige Coarse sandstones 7 beige 8 beige 10 from top: green / purple-red / black grey 12 black, red-purple, green yellow 14 brick-red =15 tion 16 light green - red banded

17 brick-red - light red banded gau Forma

18 light beige, light grey Gruhalde Member

Klett 19 light grey 21 dark grey greenish - yellow weathered dark grey 22 greenish - yellow weathered dark grey (matrix), greenish (sand layers) 23 24 greenish a lot of reworked components

grey rnian 30A’ grey - beige

Ca 30A black and green, streaked black (matrix), light grey (nodules) 30B blood-red, beige, partly green (streaks) 30C tea-green (bleached)

Gansingen Mb. 30D 30A: reddish-white, streaks, up to 70 cm dark grey 30B: light grey to greenish-grey red 30C: dark grey 33 darl grey 30D: reddish-white, streaks, dark grey light beige matrix: light green (clay layers) 35 dark grey with nodules: reddish-white, streaks lighter layers

gap ca. 1 m

12.6 m massive, red flag-stone (Schilfsandstein) Ergolz Member Ergolz 1 m Schilfsandstein Mergel Bunte Obere Stubensandstein The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 267

The best outcrop today is the Gruhalde clay pit in Frick overlain by sandy limestone of the Weissenstein Member (coord. 2642.925/1261.890–2643.075/1261.950), although (Staffelegg Formation, Reisdorf et al. 2011) delimitation the youngest part of the formation, now defined as Belchen becomes more sophisticated (see Sect. 4.6 Belchen Member, is missing here due to erosion during the Early Member). Jurassic. Furthermore, the section includes only very thin interlayers of coarse Vindelician sand inputs, which are 3.4 Subdivision more dominant in northeastern Switzerland (now Berlingen and Seebi Members). The Klettgau Formation is subdivided, from bottom to top, Regrettably, as the municipality name ‘‘Frick’’ was in: already occupied by another stratigraphic unit (Reisdorf • Ergolz Member. et al. 2011) and local name ‘‘Gruhalde’’ was preferred to • Gansingen Member. be given to member excellently outrcroping here, another • Berlingen Member. type locality had to be found for the formation. After • Gruhalde Member. consideration of other still accessible outcrops, the Seebi • Seebi Member. quarry outcrop (coord. 2680.575/1291.800) near Schlei- • Belchen Member. theim SH was chosen (Fig. 6) for four reasons: The quarry is a formally protected national geotope; it is sit- The members will be described and formally defined in uated in the Klettgau area, where the famous vineyards the following. grow on Late Triassic marl and sandstone; the latter was renowned in masonry as «sandstone from Klettgau»; and 3.5 Genetic and palaeogeographic interpretation the local name Klettgau was not used for a stratigraphic unit yet. From a stratigraphic point of view, it shows quite The Klettgau Formation incorporates sediments deposited a good, though incomplete section including the coarse during a very long time span, around 26–30 million years Vindelician sand inputs, the «Stubensandstein» (now according to DSK (2002). This time span is characterised Seebi Member). by several changes in the environment including long Consequently, the Klettgau Formation relies, besides the periods of omission and erosion. The common pattern type locality, mainly on the following reference sections: during this time is a broad depression connecting the Central European Basin with the Tethys Ocean, which • Gruhalde clay pit in Frick AG (this paper, cf. Peters reaches from Hessia to northern Switzerland and, via the 1964; Gsell 1968). so-called Burgundy gateway, further to southern France • Belchen/Chilchzimmersattel outcrop in Eptingen BL (Beutler and Nitsch 2005). Within this depression several (this paper, cf. Erni 1910). marine ingressions, generally from southwest, are docu- • Siblingen well (Nagra 1992b). mented. Riverine input originates initially from Scandi- • Berlingen-1 well (Bu¨chi et al. 1965; Bla¨si 1995). navia. Later the direction of sediment transport changed to ENE-WSW. Northern Switzerland was then episodically 3.3 Delimitation covered by clastic delivery from the Vindelician High, which limited the depression in the southeast (Beutler and The Klettgau Formation always overlays the Ba¨nkerjoch Nitsch 2005; Etzold and Schweizer 2005). For more details Formation. The boundary is located at the top of a horizon see discussion below where the different members are consisting of one or more dolomite layers above the offset introduced. of Ba¨nkerjoch Formation sulphate facies. For further discussion see Sect. 2.3. 3.6 Formal definition of the Klettgau formation The upper boundary of the Klettgau Formation is defined by a heterochronous (Late Early Hettangian to Names previously in use are given in Fig. 1. Early Sinemurian) transgression of the Staffelegg Forma- Origin of name Klettgau area, where the type locality tion over an erosional surface of variable reach in depth. In is located. most areas in northern Switzerland, the upper boundary of Type locality Abandoned quarry Seebi (Hofmann the Klettgau Formation is clearly defined by the overlying et al. 2000; Schalch 1916)in of dark, often fossiliferous, marine marl and limestone over Schleitheim SH (coord. 2680.575/ continental playa-type greyish to variegated dolomite 1291.800), formally protected as a marlstone. However, in northwestern Switzerland, where geotope by cantonal law (Fig. 6). the sandy to marly estuarine to marine Belchen Member is 268 P. Jordan et al.

Type region Klettgau. Lateral To the North, the Klettgau Formation Reference Gruhalde clay pit in Frick AG (coord. Equivalents corresponds (from bottom) to the localities 2642.925/1261.890–2643.075/ uppermost parts of the Grabfeld 1261.950). Formation, the Stuttgart Formation, Siblingen well (coord. 2680.091/ the Steigerwald Formation, the 1286.694), drilling meter 48.78–84.49 Hassberge Formation (disputed, see (Nagra 1992b), fully cored and below), the Lo¨wenstein Formation, the conserved in the Nagra core shack Trossingen Formation, and the Exter (Kernlager). Formation (e.g. Etzold and Schweizer Berlingen well (coord. 2719.686/ 2005; DSK 2005; Geyer et al. 2011). 1280.194), drilling meter Towards the South, the Klettgau 2064.5–2140.0), partly cored Formation corresponds to the Quarten (Berlingen Member type section fully Formation of the Helvetic domain cored and conserved in the SEAG core («Quartenschiefer», Frey 1968). shack at Wermatswil). Belchen/Chilchzimmersattel road cut close to Eptingen BL (coord. 4 Members of the Klettgau formation 2627.690/1246.165). Underlying strata Ba¨nkerjoch Formation (this paper). 4.1 Ergolz member Lower boundary Top of a horizon consisting of one or more dolomite layers above the offset 4.1.1 Main characteristics of sulphate facies of Ba¨nkerjoch Formation (see Sect. 2.3). The Ergolz Member replaces the former «Schilfsand- Overlying strata Staffelegg Formation (Reisdorf et al. stein» and «Untere Bunte Mergel» of Swiss stratigraphers 2011). (Fig. 1). As such, it mostly corresponds to the Stuttgart Upper boundary Transgression of Early Jurassic marine Formation and the (locally eroded) «Obere Bunte Esthe- sediments (for details see discussion of rienschichten» of the Grabfeld Formation of southern Ger- Belchen Member and Gruhalde many. The latter comprise often silty (but not sandy) and in Member below). most cases sulphate-free variegate claystone to dolomitic Subdivision Ergolz Member, Gansingen Member, marl and thin layers of dolomite and fine-grained sandstone. (from bottom) Berlingen Member, Seebi Member, They are followed, cut or fully eroded by channels filled by Gruhalde Member, Belchen Member fine to middle grained sandstone («Rinnenfazies», Etzold (see Sects. 4.1–4.6). and Schweizer 2005) or silty to sandy variegate marl with Occurrence Northern Switzerland. dolocretes etc. («U¨ berflutungsfazies» or, in the older litera- Thickness 30–60 m, locally up to 75 m (Fig. 5). ture, «Normalfazies», Etzold and Schweizer 2005). At some Chronostratigr. Carnian to Rhaetian (DSK 2002, 2005; localities, «Rinnenfazies» dominates and only the upper- Age Kozur and Bachmann 2008). most part of the section is build up by «U¨ berflutungsfazies». Description A quite heterogeneous succession At other places, different levels of «Rinnenfazies» sepa- dominated by variegated playa rated by «U¨ berflutungsfazies» can be distinguished. And, sediments, mostly silty shales and finally, at some other places, «Rinnenfazies» can be fully dolocretes, fine-grained to coarse- absent or only be represented by thin horizons of fine grained carbonatic or quarzitic fluvial sandstone. sandstones in channels and overspill layers, estuarine to shallow-marine fossiliferous sandstone, marine shale 4.1.2 Type locality and locally fossiliferous carbonates, now mostly dolomite, sulphate The natural outcrop along the Ergolz creek near Riedacher/ partially replaced by calcite, bonebeds Fu¨llinsdorf BL was studied by Stru¨bin (1901), Disler at several levels (Fig. 2). (1914) and, in 2000, by A. Etzold (pers. comm 2015). The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 269

b Type locality of the Ergolz Member: Fig. 7 Type section of the Ergolz Member at Ergolz/Riedacher in Section Ergolz / Riedacker Coord.: 2 621 225 / 1 263 525 Fu¨llinsdorf BL. Key see Fig. 4

These records have been reviewed on-site in spring 2015 and spring 2016 (Jordan et al. 2016). The actual outcrop covers most of the overlying Gansingen Member and all of Stage Fossils / components Fossils Formation Lithology Sedimentary structures Colors Etzold (p. comm. 2015) Subdivision accord. to Member Remarks Weathering profile the Ergolz Member (Fig. 7). grey / beige red banded

1 m The Ergolz section represents the common appearance beige of the Ergolz Member dominated by «U¨ berﬂutungs-

1 to Disler (1914) Gruhalde Mb. completed according fazies» (overbank deposits, see above) with distal echoes of «Rinnenfazies». The reddish ﬁne sand of the «Rinnen- light beige - light grey, 2 red banded fazies» (channels) proper are suitable for masonry and can Dolomit

Gebänderter be found in many abandoned or active quarries like Seebi 1) 3 1) Avicula gansingensis (Schalch 1916)orRo¨t near Gansingen (Wildi 1976),

beige - light beige respectively. 4 left bank of Ergolz creek grey - greenish grey Gansingen Member beige - light beige light beige 5 beige 4.1.3 Delimitation olivegrey - grey-brown banded Hauptsteinmergel light brown - beige 6 yellow - olivegrey (Gansingendolomit s. str.) light olivegrey with red-purple streaks 7 light brown- beige The lower boundary of the Ergolz Member is always olivegrey - red-purple spotted K? 9 light beige - beige grey - greenish grey identical with the lower boundary of the Klettgau Forma-

Mergel variegated to dark grey

Dunkle 10 11 brown-grey tion (see Sects. 2.3 and 3.3 for deﬁnition and discussion). 12 yellow - dark grey grey - reddish grey 13 brown - brown-beig red-brown In most cases, the Ergolz Member is overlain by massive, 14 grey - red-grey red - yellow banded at some places porous, marine limestone, which is nowadays 15 brown 16 red dolomitised. It can easily be distinguished from dolocretes in 17 red-brown

2. Schilfsandstein grey the underlying Ergolz Member. Only where the overlying 2) 18 2) Estheria laxitesta 19 grey - light red Gansingen Member has been almost fully eroded, its basal 20 beige grey layer may be nodular (see discussion below). Klettgau Formation 21 yellow-grey, gree and red spotted grey-purple, red spotted Towards northeast, the upper boundary is successively

reddish brown deﬁned by the onset of sulphate rocks, today partly altered

Carnian 23

Gaildorf-Horizont breccia in cracks green into dolomite or limestone, i.e. the eastern facies of the 24 grey red- greyish brown

right bank of Ergolz creek Gansingen Member, or the onset of the coarse-grained 25 grey - grey-green sandstone of the Berlingen Member (see respective dis- 26 beige Ergolz Member 27 dark red cussions below). red / grey-green banded 28 grey - greyish green grey - greyish green

1. Schilfsandstein 29 K single brecciated, calcitic grey - greyish green nodules yellow - grey-green 4.1.4 Genetic and palaeogeographic interpretation 30 dark grey dark grey - reddish dolcrete humous streaks and layers 31 green-grey - darl grey In the lowest part, the equivalent to the «Obere Bunte

green-grey - darl grey Qz-sand in cracks, dolcrete Estherienschichten» of the German scheme corresponds to

light beige the end of a regressive cycle, where the evaporitic envi- 33 ronment was replaced by a playa to ﬂuvial environment. K 34 grey-green The overlaying «Schilfsandstein» facies documents a K 35 dark grey - black grey large belt of meandering or even anastomosed rivers 36 Obere Bunte Estherienschichten red to grey draining from Scandinavia into the Tethys near Lyon red and green 37 light beige light green to yellow (Beutler and Nitsch 2005). An analysis of borehole and 38 black beige to grey 40 red light beige to light red outcrop data conﬁrms the concept of Wurster (1968) that 41 red and green the channel facies is concentrated along NNE–SSE trend- 42 light beige to light green 43 red and green light beige to light green ing lineaments (Fig. 8, key Fig. 9). 44 light beige grey to light green In southern Germany, two sedimentary cycles each 45 light beige left bank of Ergolz creek beginning with abundant sandy channels and ending with light green Bänkerjoch Formation 46 dark red Graue Estherienschichten nearly pure overbank facies are well documented (Etzold green 270 P. Jordan et al.

Wells including the Belchen Member Belchen Member Wells including the Seebi Mb. Direction of sand input Gruhalde and Seebi Member Outcrops including the Belchen Member Outcrops including the Seebi Mb. Erosive occurence boundary (in the W broadly according to Reisdorf et al. 2011) Western border of the Seebi Mb. Belchen Member is missing or the boarder Klettgau / Staffelegg Fm. is not outcropping Thickness of the coarse sandstone in total < 1m or no information about the member Type locality (C: Chilchzimmersattel/ Belchen) Type locality (Gr: Gruhalde/ Frick, S: Seebi) 0 5 10 15 20 Reference section of the Seebi Member: Bk: Well Benken 0 5 10 15 20 km km

pre-jurassic eroded

Klettgau Formation is missing Klettgau Formation is missing S (recent erosion) (recent erosion) Dolomite facies

pre-jurassic eroded Gr

thin coarse sand horizons in the Gruhalde Member

Wells including the Gansingen and Berlingen Mb. Gansingen and Berlingen Member Wells including the Ergolz Member Direction of sand input Ergolz Member Outcrops including the Gansingen and Berlingen Mb. Outcrops including the Ergolz Member Type locality (E: Ergolz/ Riedacker) Western border of the Berlingen Member Thickness of the channel facies > 20m Reference section (W: Well Weiach) No information about the Member or the Member is missing No information about the Member Type locality (Ga: Gansingen / Röt, Be: Well Berlingen 1) Channel facies, mostly overlaid with normal facies 0 5 10 15 20 Reference section of the Gansingen Member: Gr: Gruhalde/ Frick Western border coarse sand debris (DSK 2005) 0 5 10 15 20 km km

Scandinavian facies Klettgau Formation is missing Klettgau Formation is missing (recent erosion) (recent erosion)

Vindelician facies Be

Ga W E Gr

intra-formationally (pre-Berlingen Member) eroded

Fig. 8 Lithology and facies of the members of the Klettgau Formation. Vindelician facies adjacent to Ergolz Member according to Beutler and Nitsch (2005). Key see Fig. 9

Fig. 9 Key to Fig. 8 Depositional environment Lithology

Playa / fluvial channels Middle to coarse sand

Fluvial fan intercalated with playa Fine sand

Brakish estuarine to shallow marin Fine sand, marl

Brakish lagoonal to shallow marin Limestone, Dolomite

Sabkha, salina, evaporitic in general Sulfate

and Schweizer 2005). There is evidence that these two Origin of name Name of the creek along type section. cycles can also be distinguished in northern Switzerland. Type locality Section along the Ergolz creek (coord. 2621.225/1263.525) near 4.1.5 Formal deﬁnition of the Ergolz member Riedacher/Fu¨llinsdorf BL (Stru¨bin 1901,Disler1914; Jordan et al. 2016) Names «Schilfsandstein» and «Untere Bunte (Fig. 7). previously in Mergel», further synonyms are given in Type region Basel area. use Fig. 1. The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 271

Reference Weiach well (coord. 2676.745/ 4.2 Gansingen member localities 1268.618), drilling meter 727.62–739.35 («Schilfsandstein sensu 4.2.1 Main characteristics lato» of Matter et al. 1988 without basal «Dolomitmergelbank»; see Sect. The Gansingen Member corresponds to the Beaumont 2.3), fully cored and conserved in the Horizon of the Steigerwald Formation in southern Ger- Nagra core shack (Kernlager). many. Originally, the fossiliferous «Dolomit von Gansin- Underlying Ba¨nkerjoch Formation. gen» was described as a local curiosity by von Alberti strata (1864). In the mid-twentieth century, the term «Gansingen Lower boundary Top of a horizon consisting of one or Dolomit» became more and more popular among Swiss more dolomite layers above the offset geologists, first as an equivalent to the basal «Hauptstein- of sulphate facies of Ba¨nkerjoch mergel» then to the whole Beaumont Horizon. For Swiss Formation (see Sect. 2.3). In rare cases, stratigraphers the «Gansingen Dolomit» was a succession the «Rinnenfazies» channels have rich in dolomite forming small cliffs and ridges within the eroded at a level below the dolomite surrounding marlstones (e.g. Mu¨ller et al. 1984). This horizon. In this case, the lower concept was consequently applied to the core recordings of boundary is defined by the onset of the Nagra deep drilling program (e.g. Matter et al. 1988; fluvial sand facies. Nagra 1992a, b, 2001) and is now adopted for the definition Overlying strata Gansingen Member or Berlingen of the Gansingen Member. Member. Towards northeast the marine late diagenetic dolomite Upper boundary In western and central northern facies (initially limestone) is successively replaced by an Switzerland: Sharp contact from evaporitic facies. The primary calcium sulphate is partly variegated dolomitic marl with replaced by dolomite or even calcite as, for instance, in the dolocrete to initially marine limestone Seebi section (Jordan et al. 2016). According to the Nagra now being fully dolomitised borehole records (e.g. Matter et al. 1988;Nagra1992a, b, 2001) (dolomite facies of Gansingen this facies is also integrated in the Gansingen Member. This Member). In Schaffhausen area: agrees with Schalch (1916) who correlated the heterogeneous Sharp contact to sulphates, locally dolomite and limestone outcropping in the Klettgau and being replaced by dolomite or calcite adjacent Wutach area as equivalents of the «Hauptstein- (evaporitic facies of Gansingen mergel». He also included the local «Duro¨hrlestein» variety, Member,seebelow).InLake characterised by thin dark bituminous calcite (anthraconite or Constance area: sharp onset of stinkstone) interlayers. Berlingen Member sand facies. Subdivision No formal subdivision yet. 4.2.2 Type locality and reference sections Occurrence Northeastern Switzerland. Thickness 6–23 m. In order to maintain the name Gansingen, the Ro¨t quarry Chronostratigr. Carnian (DSK 2002, 2005; Kozur and near the village of Gansingen was chosen as type locality Age Bachmann 2008). (Fig. 10). At that place, the Gansingen Member is very Description Variegated playa type and fluvial silty fossiliferous, in some layers even forming a coquina, as to sandy overbank sediments with already mentioned by von Alberti (1864) and later descri- dolocretes, fluvial channels filled with bed by Wildi (1976). However, only 0.4–1.0 m of the very reddish fine-grained sandstone (Fig. 2). basal layers of the Gansingen Member resisted here Late Lateral To the North: Stuttgart Formation and Triassic erosion (Jordan et al. 2016). Equivalents uppermost parts of the Grabfeld Thus, the 6 m thick undisturbed succession of the Formation (Etzold and Schweizer Gruhalde clay pit in Frick AG was determined as reference 2005; Geyer et al. 2011). To the East: section of the Gansingen Member (Peters 1964; Gsell marginal facies adjacent to the 1968; Jordan et al. 2016). Vindelician High (Beutler and Nitsch 2005). To the 4.2.3 Delimitation South: «Equisetenschiefer» of the Helvetic Quarten Formation (Frey In most cases, the lower boundary of the Gansingen 1968). Member is sharp, independent if it is dolomitised limestone asne ebra Ro at Member Gansingen 10 Fig. 272 e Fig. Key see AG. Gansingen in quarry 4 yescino the of section Type ¨ t

Carnian Norian Stage Section Röt quarry,GansingenAG Type localityoftheGansingenMember: Klettgau Formation Formation Ergolz Member Gansingen Member Gruhalde Member Member Stuttgart-Formation Untere Steinmergelkeuper-Fm. Obere Steinmergelkeuper-Fm. Dunkle Mergel (Steigerwald-Fm., Subdivision after Etzold Schilfsandstein i. e. S. Gansinger-Dolomit) (Arnstadt-Fm.) (2015), pers. comm.

6A -6C Fossils/ components - 7M 7A 8D 8A 8C 8B 31 30 29 28 25 24 22 20 18 17 16 15 14 13 12 10 19 11 9 4 3 2 1 5 1 m

Lithology

Sediment structures

Weathering profile Coord.: 2651600/1266775 purple-grey -beige red-purple /yellow-brown red-purple /yellow-brown red-purple /yellow-brown purple-brown yellow-grey dark red,green light grey-beige-purple grey-purple -red-purple greenish grey red-brown light red-purple beige red-purple red-purple changingtored-beige light red light green red-purple - bloodred red-purple beige red-purple -bloodred grey-green -grey-purple grey red-purple beige, partlypurple grey-pruple -red-purple beige grey-purple beige grey-purple grey-beige light grey,beige grey beige below:yellow-beige green, crust red - grey-pruple beige beige light beige-grey Colors .Jra tal. et Jordan P. The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 273 or calcitised/dolomitised sulphate rock resting on top of Origin of name Name of the municipality where the variegated dolomite marl. Only where Late Triassic erosion type locality is situated. cut down to the basal layers, the latter may be disintegrated Type locality Ro¨t quarry in Gansingen AG (coord. to nodules by subrosion processes. Generally, due to the 2651.600/1266.775) (Wildi 1976; compact texture (even when porous) and the local presence Jordan et al. 2016) (Fig. 10). of ooids or bivalves, the basal bed of the Gansingen Type region Fricktal. Member can easily be distinguished from dolocrete nod- Reference Gruhalde clay pit in Frick AG (coord. ules or layers of the underlying Ergolz Member. locality 2642.000/1261.925). The upper boundary is in most cases more gradual. At Underlying Ergolz Member. the reference section in the Gruhalde clay pit in Frick, strata where the outcrop conditions are excellent and a bed by Lower boundary Sharp onset of marine, today bed analysis of carbonate and clay mineral contents is completely dolomitised, limestone with available (Peters 1964), the upper boundary was deﬁned ooids and molluscs; forming molds where dolomite contents drop from 85 % to less than 50 % when dissolved, or evaporitic sulphate, and desiccation features document the change from marine now altered to dolomite or limestone in to playa environment. This quite sophisticated concept many cases, over variegated marl with applies to boreholes and good outcrops. At other places the dolocretes of terrestrial playa origin. change in resistance to present-day erosion may help. Overlying strata Gruhalde Member, locally Seebi At some places, the upper boundary is erosive. At the Member (see Sect. 4.2.3). type locality, the Gansingen Member is overlain by prob- Upper boundary Gradual drop in dolomite or calcite ably younger parts of the Gruhalde Member (see above). In content, desiccation features, at some the Klettgau area, the Gansingen Member is locally places erosive (see Sect. 4.2.3). directly overlain by coarse sandstone of Seebi Member Subdivision No formal subdivision yet. (Nagel 1990). Occurrence Northeastern Switzerland. Thickness 0–6 m. 4.2.4 Genetic and palaeogeographic interpretation Chronostratigr. Carnian (DSK 2002, 2005; Kozur and Age Bachmann 2008). The corresponding «Beaumont Horizon» in adjacent Description In northwestern and central northern Upper Rhine Graben area is interpreted by Beutler and Switzerland, locally fossiliferous or Nitsch (2005) to document a marine transgression con- oolitic, partly cavernous massive necting the Tethys and the Central European Basin. In the dolomite continuing upward to area discussed here, the low diverse and dwarfed fauna laminated (stromatolitic) dolomite with found in Frick and Gansingen outcrops (Wildi 1976) with marly intercalations. Towards several species of gastropods and bivalves is dominated by northeastern Switzerland lateral euryhaline genera as Bakevellia, Costatoria and Pseu- transition into sulphate rocks in most docorbula, also characteristic for brachyhaline or hypos- cases altered to dolomite or limestone. aline environments of the German Lettenkeuper (Erfurt Lateral To the North: Beaumont Horizon of the Formation) (Hagdorn 2015). The occurence of Unionites in Equivalents Steigerwald Formation (Etzold and Gansingen suggest brackish environment. Stenohaline Schweizer 2005; Geyer et al. 2011). To organisms as cephalopods or echinoderms are missing. The the East: Berlingen Member (this restricted marine facies was bordered, to the east, by salina paper). To the South: To¨di or littoral sabkha-type evaporitic environments (also part of Grenzdolomit of the Helvetic Quarten Seebi Member). The sabkha is again replaced eastwards by Formation (Frey 1968). siliciclastic marginal facies adjacent to the Vindelician High (Berlingen Member). In a regressive cycle, the mar- 4.3 Berlingen member ine to lagoonal environment was successively replaced by a playa environment (Fig. 8). 4.3.1 Main characteristics 4.2.5 Formal deﬁnition of the Gansingen member In the wells Berlingen and Herdern (both in Canton Thur- gau), a coarse-grained sandstone with calcitic matrix is found Names «Gansinger Dolomit» (sensu lato), at the level where the Gansingen Member is expected (sandy previously in further synonyms are given in Fig. 1. layers of «Bunte Mergel (mit Sandlagen)» by Bu¨chi et al. use 274 P. Jordan et al.

Fig. 11 Type section of the Berlingen Member in well Type locality of the Berlingen Member: Berlingen-1 at Berlingen TG. Section well Berlingen-1 Key see Fig. 4. Depth values Coord.: 719 685 / 280 195, Elevation: 593 m without brackets according to indications on core storage box (Bla¨si 1995); depth values with brackets according to original (unpublished) soil proﬁle («depth according to Schlumberger diagram») Stage Depth (m) Lithology Sediment structures Colors Formation Büchi et al. (1965) Member Subdivision after Weathering profile Remarks 2 m Mb. Gruhalde Mergel 2119.5 Obere Bunte

dark brown-red, dark green dark green, dark brown-red (2123.5) middle to coarse Kiesel- black-grey grained sandstone sandstein 2123.4 Berlingen Mb. white-grey, partly greenish (2125.0) brown-red, green, dark blue-grey, wine red, grey, dark green-grey,

Carnian light grey and white-grey banded

(2127.5) brown-red-grey banded Klettgau Formation Untere

Bunte Mergel dark green - light grey-green banded Ergolz Mb. (2130.3) stein Schilfsand-

1965). The sandstone can clearly be distinguished from the thick interval consists of two sandstone successions sepa- fine-grained Ergolz Member sandstone. These layers are rated by a marl interlayer with dolomite nodules. significantly older than the Seebi Member, to which they show some similarities. Bla¨si (1995) correlated these layers 4.3.3 Genetic and palaeogeographic interpretation with the «Kieselsandstein» of southern Germany (now Hassberge Formation, e.g. Etzold and Schweizer 2005). The Berlingen Member is interpreted as a sandy marginal facies of the Vindelician High. From the genetic point of 4.3.2 Type locality and reference sections view it shows affinities to the Hassberge Formation of southern Germany (e.g. Etzold and Schweizer 2005), even The Berlingen Member is entirely restricted to subcrops in though it is probably significantly older (Fig. 8). boreholes in far northeastern Switzerland. Consequently, the well Berlingen-1 (Bu¨chi et al. 1965), where the suc- 4.3.4 Formal definition of the Berlingen member cession is well developed and fully cored, was chosen as the type locality for this member (Fig. 11). The core sec- Names «Sandlagen», «Kieselsandstein» (see tion, now defined as Berlingen Member, goes from drilling previously in Fig. 1). meter 2120.8–2125.0. This is more than the interval out- use lined as «Kieselsandstein» by Bla¨si (1995). The 4.2 m Origin of name Name of the type locality. The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 275

Type locality Berlingen-1 well (coord. 2719.686/ important palaeogeographic revolutions, such as the Old- 1280.194), drilling metre Kimmerian discontinuity. In fact, it is a 3–20 m thick 2120.8–2125.0 (Bu¨chi et al. 1965). The succession of predominantly variegated playa-type dolo- member comprises the interval denoted mitic marl. In traditional Swiss stratigraphy it was sum- as «Kieselsandstein» by Bla¨si (1995) marised as «Obere Bunte Mergel». and, additionally, the overlaying sandstone interval (Fig. 11). The cores 4.4.2 Type locality are conserved in the SEAG core shack at Wermatswil. In whole northern Switzerland, the Gruhalde clay pit in Type region Lake Constance area. Frick AG gives actually the best insight in the succession Underlying Ergolz Member. of the Gruhalde Member. The section was originally strata described by Peters (1964), Gsell (1968), Frey (1969), Gygi Lower boundary Onset of sandstone over variegated and Rieber (1989), Meyer and Furrer (1995) and, in 2000, marl. by A. Etzold (pers. comm. 2015). Reisdorf et al. (2011) Overlying strata Gruhalde Member. revised the Jurassic part of the section. From April to Upper boundary Reset of variegated marl over October 2015, the Triassic part was recorded anew by sandstone. Jordan et al., (2016) using the results by the authors cited Subdivision No formal subdivision yet. above (Fig. 12). Occurrence Northeastern Switzerland. The lower boundary of the Gruhalde Member has been Thickness Up to 5 m. defined at the base of the first desiccation horizon, which is Chronostratigr. Carnian (DSK 2002, 2005; Kozur and marked by persistent, regularly spaced teepee-type struc- Age Bachmann 2008). tures in a thin bedded alternation of light dolomite and Description Middle-grained to coarse-grained, green dolomitic marl. The boundary is accompanied by a poorly sorted sandstone with quartz, dramatic decrease in dolomite content (Peters 1964). feldspar and rocky fragments of the The first part of the type section is a 2.8 m thick suc- surrounding members. The matrix cession of variegated, predominantly greenish-grey, dolo- contains quartz cement, sulphate or mitic marl and dolomite, which show some affinities to the clay in alternation with layers of clayey underlying Gansingen Member including the persistence of sandstone and claystone with dolomite the strata in outcrop scale. nodules (Fig. 2). The second part (1.8 m thick) is dominated by bright to Lateral To the West and North: presumably dark (brownish) red dolomitic marl. At various levels, Equivalents Gansingen Member, a correlation with paraconformities can be suspected: A. Etzold (pers. comm. the significantly younger Hassberge 2015) correlates the clearly visible, 1.2 m thick layer of Formation of southern Germany has bright red marl with the «Rote Wand» marker horizon in been postulated by Bla¨si (1995), but the German Steigerwald Formation. Consequently, he not yet proven. To the East and South: places the Old-Kimmerian discontinuity above this layer. marginal facies of Vindelician High, But without further dating, it is not possible to localise the possibly sandy layers within the discontinuity definitely. Equivalents of the Old-Kimmerian Helvetic Quarten Formation. Discontinuity probably lie somewhere within the second part. For instance, another striking horizon witnessing probably an important time gap can be recognised below 4.4 Gruhalde member the bright red marl. Finally a dolomite horizon above this second part can be interpreted as a soil horizon docu- 4.4.1 Main characteristics menting a third significant time gap. The horizontal strat- ification and persistence of most layers in outcrop The Gruhalde Member encompasses all sediments between dimension are again characteristic for this part of the the Gansingen or Berlingen Members (below) and the Gruhalde Member. Belchen Member or Staffelegg Formation (above). In The third part is about 5 m thick and is first variegated, northeastern Switzerland it is interrupted by the massive then changing to light grey color with purple striation sandy interval of the Seebi Member. further up. It is characterised by non-persisting layers and The Gruhalde Member represents a very long time span, abundant channel structures. The channel fills consist of some 20 Myr according to the stratigraphic scheme for silty marl to coarse-grained sandstone, with mainly quartz southern Germany (DSK 2002). This time includes several and subordinately dolomite intraclasts and extraclasts, 276 P. Jordan et al.

Type locality of the Gruhalde Member: Coord.: from 2 642 925 / 1 261 890 Section Gruhalde clay pit (Tonwerke Keller AG) / Frick AG to 2 643 075 / 1 261 950 ation Stage (1964) / Gsell (1968) Lithology Formation / components Fossils Colors Sedimentary structures Subdivision after Peters Member Weathering profile Remarks Fossils / components Fossils structures Stage Colors Lithology Sedimentary Form Member (1964) / Gsell (1968) Weathering profile Remarks Subdivision after Peters

1) dark grey 25 green, grey desiccation cracks 1 1) according to Reisdorf et al. (2011) yellow-beige (channel) level of predators grey-beige, mergel 26 rust / goethite

nsekten- reddish banded

I dolomitic marl layers Staffelegg Hettangian

Schambelen red layers

grey-beige, marly layers inbetween 27 reddish banded

grey ember

channels, E-W

28 grey-beige, light grey reddish banded Gansingen M

purple (red) “banded dolomite” macroscopic bedded, in the polished and thin section 2a thin bedding recognizable 29a grey-beige,

Part 4 reddish banded

light grey

Gansinger Dolomit 29b grey-beige “Schaumkalk” (porous limestone)

ten 30 green h

31 light beige rust horizon 2b grey with light grey horizons green jointed

32 re Mergelruppe re tion

e red, partly greed dotted e Mergelschic r e Unt rma t 2c grey, with yellow streaks o F

33 red Carnian Norian tgau tgau 2d resp. Un green 34 yellow reddish green 2e Klet 35 red 2f grey 36 red, white weathered 37 green with yellow lenses markerbed: sandstone with clay 3 38 clasts and ooids, above oolithe red with yellow lenses 39 Klettgau Formation gelschichten 4 40 green

5 Gruhalde Member

light grey ein red

6 level of Plateosaurus Member 41 fsandst golz 7 light grey Er 42 green 8 purple 43 red 44 brick-red calcitic joints

resp. Schil red white - light grey 45 9 green gelgruppe resp. Obere Mer Obere gelgruppe resp. r 46 yellow

10 red with grey dots wedging out gruppe 47 red weathered

Obere Me Obere 11 grey, white weathered

12 beige partly with cristallized cavities sandstein f greenish, basal red with yellow and blue spots 13a yellow weathered 13b reddish with white

bleaching continuous markerbed Schil nodulous dolomite: yellow darkt red to red-brown (”Rote Wand”) marl: green ? 13c Base actual outcrop 13d red (channel facies) Part 2 13f brick-red green-white 48 red with yellow and blue spots 14 red whit local green bleaching (1 cm) 15 green-grey change in scale yellow 16 green-grey 17 layer not continuous nodular dolomite: yellow 18 49 marl: green 21 red-grey red-beige to grey (dolomite beds) 23 Carnian Part 1 Part 3 50 green

51 grey section outside and below channel completed according to Peters (1964) green, grey, beige dark 25 52

green, grey desiccation cracks Bänkerjoch-Formation The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 277 b Fig. 12 Type section of the Gruhalde Member, at Gruhalde clay pit 4.2.3). In both cases, it is manifested in the morphologic in Frick AG. Key see Fig. 4 change from the crest-forming Gansingen Member to the receding terrace or depression-forming Gruhalde Member. In the area, where the Berlingen Member occurs, the feldspar and mica. The matrix is dolomitic. Quartz grains lower boundary of the Gruhalde Member is defined by the show pressure solution and syntaxial growth. The channels offset of the coarse-grained sandstone. This delimitation is are cut into dolomitic marl, which represents overbank still somewhat vague in the Herdern well (Bu¨chi et al. deposits affected by pedogenesis. The finding of many 1965), at the western limit of the Berlingen Member. It bones including articulated skeletons of the prosauropod becomes more obvious towards east (e.g. in the Berlingen dinosaur Plateosaurus engelhardti (e.g., Sanders 1992; well, Bu¨chi et al. 1965). Foelix et al. 2011; Hofmann and Sander 2014) points to a The recurrence of the Gruhalde Member in the area terrestrial playa environment traversed by some channels. where the Seebi Member occurs is marked by the offset of This is supported by sedimentological evidence (e.g., the coarse-grained sand facies or sandy dolomite facies. Meyer and Wetzel 2015). The latter is present above the pure sand facies (see Sect. The upper, fourth part of the Gruhalde Member at the 4.5 for further discussion). type locality starts with a 20 cm thick persistent marker The upper boundary of the Gruhalde Member is defined horizon consisting of well sorted, fine-grained sandstone by the transgression of the estuarine to marine Belchen (predominantly quartz, feldspar, intraclasts, ooids and Member or fully marine Staffelegg Formation, generally mica). It alternates laterally and vertically with oolitic separated by a sharp erosional contact. lenses. The presence of miliolid foraminifers in the sandstone and oolite documents marine to brackish conditions. 4.4.4 Subdivision The remaining 10 m of the upper part consist mainly of greyish to light purple marl where some channels, filled Based on scarce outcrop and borehole data, no satisfactory with dolomite and dolomitic marl, occur. In the basal levels subdivision for the Gruhalde Member could be defined. In of this upper part Plateosaurus remains were also found, some good outcrops like at the type locality a detailed while in the uppermost part fragmentary but articulated stratigraphy and correlation with the German scheme is defi- skeletons of prosauropod and a fully articulated theropod nitely possible (see Sect. 4.4.3). Other outcrop and borehole dinosaur have been excavated (e.g. Meyer and Thu¨ring evidence show that at many places variable small and in some 2003; Foelix et al. 2011). cases significant parts of the succession are missing mainly A. Etzold (pers. comm. 2015) suggests to correlate the due to erosion during the Late Triassic. This makes the lower two parts of the Gruhalde Member in Frick with identification of strata very sophisticated particularly in bad the «Rote Wand» of the Steigerwald Formation. The and incomplete outcrops. The Gruhalde Member therefore middle (third) part can be correlated, due to the presence of encompasses all strata formerly called «Bunte Mergel», «O- coarse-grained sand, with the German Lo¨wenstein Forma- bere Bunte Mergel», and «Knollenmergel». tion (previously «Stubensandstein»). The presence of Pla- teosaurus remains points to a Late Norian age (C.A. 4.4.5 Genetic and palaeogeographic interpretation Meyer, pers. comm. 2015) and, thus, to the upper part of Lo¨wenstein Formation (Etzold and Schweizer 2005; Geyer With a glimpse to the more complete succession in the et al. 2011). The uppermost part of the section may cor- adjacent southern Germany the history of the Gruhalde relate with the German Trossingen Formation (although a Member can be synoptically summarised as follows: marine ingression is not reported from there, Geyer et al. The marine episode documented in the Gansingen 2011). It is overlain by a thin layer of coarse sandstone Member is followed by a coastal playa. Coarse-grained containing a marine fauna with Waehneroceras sp. of Late detrital input is restricted to northeastern Switzerland. Early Hettangian age (Meyer and Furrer 1995, Reisdorf Evidences at the Seebi quarry suggest that it is linked with et al. 2011). It marks the base of the Early Jurassic erosion affecting parts of the Gansingen Member. Possibly, Staffelegg Formation (Reisdorf et al. 2011). sedimentation continued in what is called Hassberge and Mainhart Formations in southern Germany (e.g. Etzold and 4.4.3 Delimitation Schweizer 2005) (Fig. 8). Following the Old-Kimmerian orogenic movements, At many places, the lower boundary of the Gruhalde erosion cut at least down to the «Rote Wand», but at some Member is defined by an erosional surface (see Sect. 4.2.2 places even the basal layers of the Gansingen Member and 4.2.3). In complete sections, the lower boundary is were affected. The fluvial coarse-grained siliciclastics of gradual given by the decrease in dolomite content (Sect. the Seebi Member are well documented in northeastern 278 P. Jordan et al.

Switzerland and extended probably into central northern Intercalated strata Seebi Member. Switzerland, but were later mostly eroded. In northeastern Boundaries Lower boundary: onset of coarse Switzerland the sandy facies developed to a possibly grain sandstone or, at some coastal sabkha type environment, where sandstone and places, sandy dolomite, over marls were dolomitised. At the same time, a playa devel- variegated marl. oped in northwestern Switzerland, slowly prograding Upper boundary Onset of variegated marl over towards east, where rivers carved channels into the muddy sandy dolomite or, at some plains. The playa was drowned later, resulting in a short places, coarse sandstone. episode of marine or brackish sediments, but at least in the Subdivision No formal subdivision yet. Frick area, playa sedimentation continued, accentuated by Occurrence Northern Switzerland. ephemeral channel incisions. Thickness 3–20 m. At some places erosion eliminated most of the previously Chronostratigr. Age Carnian to Rhaetian (?) (DSK deposited sediments before the deposition of the Belchen 2002, 2005; Kozur and Member. Only few metres of the oldest well-layered varie- Bachmann 2008). gated strata were left over, like, for instance, at the type Description Heterogeneous succession of locality of the Belchen Member (see Sect. 4.6.2). variegated to greyish dolomitic marl with dolomite interlayers, 4.4.6 Formal deﬁnition of the Gruhalde member mostly dolocrete, but also oolitic shallow marine dolomites, and Names previously in «Obere Bunte intercalations of coarse sand, in use Mergel», «Knollenmergel», most cases sandy dolomite to further synonyms are given in dolomitic sandstone. Widespread, Fig. 1. often channel-type erosion Origin of name Name of the type locality. affected the succession (Fig. 2). Type locality Gruhalde clay pit (coord. Lateral Equivalents To the North: Steigerwald 2642.925/1261.890–2643.075/ Formation, Lo¨wenstein 1261.950) in Frick AG (Peters Formation, Trossingen Formation 1964; Gsell 1968; Gygi and (e.g. Etzold and Schweizer 2005; Rieber 1989; Meyer and Furrer Geyer et al. 2011). To the east: 1995; Reisdorf et al. 2011; Jordan Partly Seebi Member (this paper). et al. 2016) (Fig. 12). To the south: Upper part of the Type region Fricktal. Helvetic Quarten Formation Reference localities None. above «To¨di Underlying strata Gansingen Member or Berlingen Grenzdolomit»: «Untere Member. Schiefer», «Grobdetritische Lower boundary Mostly erosional, in rare Lagen», «Obere Schiefer complete sections the transition is (Quartenschiefer s.str.)» (Frey gradual and the lower boundary is 1968). deﬁned where the underlying compact dolomite succession ends and the clay content 4.5 Seebi member increases. Overlying strata Belchen Member (this paper) or 4.5.1 Main characteristics Staffelegg Formation (Reisdorf et al. 2011). The Seebi Member corresponds to former «Stubensand- Upper boundary Where the Belchen Member is stein». It consists of middle-grained to coarse-grained absent: transition of marine sandstones or conglomerates and the overlying sandy Jurassic sediments (claystone, dolomite as found in the Schaffhausen area. marl, limestone, sandy limestone, sandstone) over greyish or 4.5.2 Type locality and reference sections variegated dolomitic marl. Where the Belchen Onset of sandstone, sometime The abandoned Seebi quarry (coord. 2680.575/1291.800) Member is present with bonebeds or thin claystone. near Schleitheim SH (also type locality for the Klettgau The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 279

Formation) shows in its higher level a representative, but Reference Benken well (coord. 2690.990/ incomplete section of the Seebi Member. This section was localities 1277.843), drilling metre already described by Schalch (1916) and Hofmann et al. 709.12–720.60 («Stubensandstein» in (2000) and was newly recorded in May 2016 by Jordan Nagra 2001), fully cored and conserved et al., (2016) (Fig. 6). in the Nagra core shack (Kernlager). The 5.2 m thick section comprises all three character- Underlying Gruhalde Member, at rare places istic lithotypes of the Seebi Member: coarse grained strata Gansingen Member (Nagel 1990). sandstone to conglomerate, sometimes cross-bedded, Lower boundary Onset of coarse-grained sandstone or forming 5–15 cm thick partly channelised beds; silty to conglomerate, in some cases sandy sandy dolomitic mudstone; and dolomite marl. The section dolomite over variegated marl, in most ends with a conglomerate bed with no overlaying strata cases above an erosional discontinuity. visible. Overlying strata Gruhalde Member. The reference section (drilling meter 709.12–720.60) of Upper boundary Reset of variegated marl over the Benken well (coord. 2690.990/1277.843) shows the sandstone or sandy dolomite. Seebi Member in a more distal marly facies («Stuben- Subdivision No formal subdivision yet. sandstein» in Nagra 2001): It starts with a 4 m thick Occurrence Northeastern Switzerland. alternation of coarse-grained sandstones and conglomer- Thickness 1–10 m (correlated coarse sandstone or ates, sandy marl and sandy dolomites. The matrix of the sandy dolomite occurrences with a sandstones is calcitic in the lower part and dolomitic in the thickness less than 1 m are taken as upper part. It is followed by an approximately 1.9 m thick part of the Gruhalde Member). sandy dolomite succession and a succession of 5.4 m Chronostratigr. Norian (DSK 2002, 2005; Kozur and crumbly and cavernous brownish caliche-type dolomite Age Bachmann 2008). nodules in a dolomitic to clayey matrix. At some levels Description Poorly sorted sandstones and oncoids and chert in form of nodules and joint fills are conglomerates with predominantly found. polycrystalline quartz grains of Sandy dolomites in the upper part of the Seebi Member volcanic, metamorphic or mylonitic are also reported in the Schlattingen well (Albert et al. origin, dolomite and clay pebbles, 2012) and in outcrops in the Klettgau area (Hofmann et al. feldspar and, in most cases, calcitic 2000). In the Siblingen well (Nagra 1992b) the Seebi matrix; dolomitic sandstones; and Member is represented by sandy dolomites only. In the crumbly sandy dolomitised sulphcretes Herdern and Berlingen wells (Bu¨chi et al. 1965) the Seebi (Fig. 2). Member is developed in a purely sandy facies. Lateral To the North and Northeast: middle Equivalents part of the Lo¨wenstein Formation of 4.5.3 Genetic and palaeogeographic interpretation southern Germany (e.g. Etzold and Schweizer 2005; Geyer et al. 2011). To Following the Old-Kimmerian orogenic movements, the the South: coarse grained detritc layers Seebi Member represents a widespread progradation of («Grobdetritische Schichten», Frey fluvial facies from the East, i.e. from the Vindelician High. 1968) of the Helvetic Quarten It was successively replaced by a playa to sabkha envi- Formation. ronment. Sulphcretes formed or original gypsum deposits were altered to dolomite (Fig. 8). 4.6 Belchen member 4.5.4 Formal definition of the Seebi member 4.6.1 Main characteristics Names «Stubensandstein», further synonyms previously in are given in Fig. 1. There was much confusion with the term «Rha¨t» or «Oberer use Keuper» when it was used as a lithostratigraphic unit. Tradi- Origin of name Name of the type locality. tionally it included «Rha¨tsandstein» and «Rha¨tmergel». For Type locality Abandoned Seebi quarry (coord. most authors, the term «Rha¨tsandstein» is restricted to a light 2680.575/1291.800) in Schleitheim SH grey to light green middle- to coarse-grained (mostly) car- (Schalch 1916; Hofmann et al. 2000; bonate-free sandstone that becomes white and disintegrates to Jordan et al. 2016) (Fig. 6). glistening sand when weathered. There is more confusion Type region Klettgau area. about the term «Rha¨tmergel». The most widespread 280 P. Jordan et al. description is dark marl overlaying or replacing «Rha¨tsand- The sandy succession is followed by 1.5–1.8 m of dark stein» laterally. Some authors like Achilles and Schlatter silty dolomitic marl with lenses and dwelling structures (1986) denied to address some specific occurrences as «Rha¨t», filled by reddish sandstone to siltstone. because their fossil record proved that they were not of The sequence is overlain by an 8–15 cm thick sandy Rhaetian but Norian age. However the German stratigraphic limestone bed full of disintegrated shells (deposited convex table (DSK 2002) dates the «Postera Sandstein» of the lower up) of various marine bivalves (Protocardia rhaetica Exter Formation as Late Norian, while overlying «Contorta- Merian, 1953, Palaeocardita sp. Modiolus sp.). Further Schichten» and «Triletes-Schichten» are of Rhaetian age. findings include inarticulate brachiopods (Discina sp.), The purely lithostratigraphic definition of the Belchen reptile bones, scales and teeth of bony fish (e.g. Sargodon Member aims to bring such discussions to an end. The tomicus Plieninger, 1847) and shark teeth (Hybodus compilation of Erni (1910) and a detailed examination of cloacinus Quenstedt, 1858, Lissodus minimus Agassiz, the recent borehole findings show that the Belchen Member 1839; det. R. Kindlimann). This layer, here interpreted as a starts in almost all cases with a sandstone deposited above tempestite, is probably identical with the bonebed already a more or less prominent erosion surface. Only in a few mentioned by Merian (1857) «auf der Weide oberhalb des cases thin dark shale layers are reported at the base. In Kilchzimmers» (cited following Erni (1910), i.e. on the almost all cases the sandstone contains little to no car- southwestern side of Chilchzimmersattel). Mu¨hlberg bonate and shows the typical pressure solution and syn- (1893) (cited in Erni 1910) reported a specimen of taxial growth of quartz grains. The sandstone is followed Rhaetavicula contorta (Portlock, 1843) from this bed, a by dark marl, which may include sand or silt layers similar finding that is neither confirmed by Erni (1910) nor by the to the basal sandy facies. Erosion during the latest Triassic recent record. or earliest Jurassic eliminated the Belchen Member in The supposed tempestite is overlain by some 20 cm of central northern Switzerland. black shale to grey marl, very similar to the marl found below. 4.6.2 Type locality The onset of the overlying Staffelegg Formation is marked by a sharp contact followed by a 10–15 cm thick Close to Erni’s key section («Rha¨tprofil bei P. 1015 no¨r- slightly nodular limestone, rich in fossils including Gry- dlich Bo¨lchen (=Belchen)»; Erni 1910), a new complete phaea arcuata Lamarck, 1801, and Cardinia sp. In an section has been excavated along a forest road near overlying more massive limestone, separated by a marly Chilchzimmersattel BL (Jordan et al. 2016) (Fig. 13). The interlayer of 15–20 cm thickness, Arnioceras sp. and section is overturned due to tectonic folding. There is some Paracoroniceras sp. were found, documenting the Arnio- jointing with small offset, but correlation across these ceras semicostatum Zone of Sinemurian age. Thus, the discontinuities is easy. Belchen Member of the Klettgau Formation is followed The section starts within the Ergolz Member and directly by the Beggingen Member of the Staffelegg For- includes also about 2–3 m of the Gansingen Member fol- mation, and the Schambelen Member is missing here. lowed by 3 m of variegated marlstone representing the The type locality of the Belchen Member includes both Gruhalde Member. The local facies corresponds best to the lithologies, the gritty weathering sandstone and the dark lower part of the Gruhalde type section. It is suggested that marl, typical for what Erni (1910) called «Rha¨t». Looser the moderate thickness of the member results from erosion (2015) correlates a borehole sequence «A» from the Adler prior to the deposition of the Belchen Member. area, south of Pratteln BL, where the Belchen Member is The Belchen Member begins with a 2.5 m thick alter- 6 m thick, with the type section. Based on carbon isotope nation of 5–20 cm thick greenish sandstone layers alter- stratigraphy, he concludes that the Belchen Member at the nating with thin dark shale interlayers. At the bottom Chilchzimmersattel section only covers the earlier part of carbonised horizons with plant and bone remains as well as the time span documented in the Adler «A» section. Based some marine bivalve are found. Bioturbation is common. on stable carbon isotope geochemistry, the Belchen The sandstone layers consist mostly of well-sorted mid- Member at the type section and in the Adler area was sized quartz grains with pressure solution and syntaxial deposited in the Late Rhaetian (Looser 2015). A prelimi- overgrowth rims. There is little feldspar and no mica (at nary palynostratigraphic analysis proves a middle Rhaetian other sites, for instance in the Adler area, mica is abundant age (GTr 18 and GTr 19, sensu Heunisch, 1999); the in corresponding layers, Looser 2015). Asteriacites lum- uppermost zone of the Rhaetian, GTr 20, is missing (pers. bricalis (von Schlotheim, 1820) resting traces (Cubichnia) communication E. Schneebeli-Hermann, 19.02.2016). of Ophiuroidea (brittle stars) and bivalves indicate a shal- This also applies to the Herdern-1 and Berlingen-1 low marine environment. When weathered, the sandstone wells, where 1.5 and 15.0 m, respectively, fine- to middle- becomes white and disintegrates to glistening sand. grained, well-sorted greyish sandstone is reported, which is The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 281

Fig. 13 Type section of the Belchen Member at Belchen/ Type locality of the Belchen Member: Chilchzimmersattel in Eptingen Section Belchen/ Chilchzimmersattel BL. Key see Fig. 4 Coord.: 2 627 690 / 1 246 165 Stage Lithology Sediment structures Colors Fossils/ components Fossils/ Formation Member Erni (1910) Subdivision after Remarks Weathering profile

not analyzed

1 m Fossils in the basal part of the Beggingen Mb:

: Arnicoceras sp., Paracoroniceras sp. (in 1) : Grypaea arcuata (often in 1, 2 and 3) 1 : Cardinia sp. (often in 1, 2 and 3) Chlamys sp. (rarley in 1, 2 and 3) Sinemurian

Staffelegg Fm. Staffelegg 2 : Pleurotomaria (one time in 2) Beggingen Mb. : Zeileria vicinalis (rarley in 1, 2 and 3) 3 grey 4a grey 4b dark, conquina limestone (umbrella-texture, 5 tempestit), slightly sandy, reddish weathering dark grey, 6 : Modiolus sp., Palaeocardita sp., reddish ?Protocardia sp. weathering : Discina sp. : Hybodus sp., Lissodus sp.

reddish sand layers and burrows in dark, rusty, wheatering, silty clay

8 white 9

10 in a loose hand piece from this part: 11 Rhaetian : Asteriacites, bivalves 12

Belchen Member 13 14 light grey, mostly red, 15 rarley greenish weathered 16 17 partly white 18

Klettgau Formation 19 20 21 K 22 ? K 23 24

light green Norian Keuper Rhät Unterer Lias Gruhalde Mb.

very similar to the sandstone of the basal Belchen Member is developed as bonebed, very rarely as thin dark claystone at the Chilchzimmersattel section. layer. The upper boundary is defined by the transgression of 4.6.3 Delimitation the marine Staffelegg Formation (Reisdorf et al. 2011). The delimitation of the Belchen Member is clear where sand- The lower boundary of the Belchen Member is erosive and stone is overlain by marl or limestone of the Schambelen starts in almost all cases with the typical light grey to light Member or the Beggingen Member (Reisdorf et al. 2011), green quarzitic sandstone. At some places, the basal layer respectively. Otherwise the boundary can be drawn by 282 P. Jordan et al. fossil records. Ammonites, bivalves (Gryphaea, Cardinia) Lower boundary Onset of sandstone succession, at some and crinoids prove Early Jurassic, while bonebeds and localities with bonebed, or more rarely, a other bivalves (Protocardia, Palaeocardita, Rhaetavicula) thin dark shale layer at the base, above are typical for the Late Triassic. variegated or greenish-grey marl. Delimitation becomes more difficult where the sandy Overlying strata Staffelegg Formation (Reisdorf et al. limestone of the Weissenstein Member overlays directly 2011). the sandstone of the Belchen Member and index fossils are Upper boundary Transgression of marine sediments missing. In this case, quartz grain or carbonate analysis can with characteristic fossils of Early be applied: the typical angular grains are restricted to the Jurassic age (e.g., ammonites, crinoids, Belchen Member, which is generally poor in calcite. In the bivalves such as Gryphaea sp.) over far northeastern Switzerland (Lake Constance area) quartzitic sandstone and dark marl and delimitation becomes even more complicated as the Early claystone (see discussion above). Hettangian calcitic sandstone, not yet formally defined as a Subdivision No formal subdivision yet. member of the Staffelegg Formation (Kiefer et al. 2015), Occurrence Northern Switzerland. overlays slightly calcitic sandstone of the Belchen Mem- Thickness 0–6 m in northwestern Switzerland ber. Kiefer et al. (2015) suggested as criteria for delimi- (Erni 1910), up to 15 m in the Lake tation a significant increase in calcite matrix and the Constance area (Bu¨chi et al. 1965; presence of crinoids, which are not known from the Bel- Kiefer et al. 2015). chen Member. A direct superposition of the shales of the Chronostratigr. (?) Norian to (at least middle) Rhaetian Schambelen Member over the shales of the Belchen Age (Achilles and Schlatter 1986; DSK Member has not yet been reported. 2002, 2005; Kozur and Bachmann 2008; Looser 2015). 4.6.4 Genetic and palaeogeographic interpretation Description Predominantly middle-grained, well- sorted, mostly carbonate-free quartzitic The lower part of the Belchen Member documents a sandstone with thin shale interlayers brackish estuarine to marine environment, where open sea overlain by dark marl and claystone was located to the West, and is interpreted as a seaway with sandy interlayers and burrows, connecting the Tethys with the marine Germanic Basin bonebeds (Fig. 2). (Beutler and Nitsch 2005). With time the estuarine facies Lateral To the North and Northwest, the became progressively restricted towards east. It was Equivalents Belchen Member corresponds to the replaced increasingly by shallow marine sandstones and Exter Formation (e.g. Etzold and finally by silstone and marl. This succession was later cut Schweizer (2005); Geyer et al. 2011). by regional erosion of Late Triassic or Early Jurassic age, Towards the South it is missing or it is which cut deepest in central northern Switzerland (Aare a not distinguishable part of the Massif–Black Forest High, e.g. Tru¨mpy 1980) (Fig. 8). Vindelician marginal facies documented in the Helvetic Quarten 4.6.5 Formal definition of the Belchen member Formation.

Names «Rha¨t», further synonyms are given in Acknowledgments This paper has beneﬁted from valuable discus- previously in Fig. 1. sions, constructive reviews and useful suggestions from Peter Bitterli- use Dreher, Reto Burkhalter, Andreas Etzold, Hans Hagdorn, Albert Origin of the Belchen area where the type locality is Matter, Martin Mazurek, Christian A. Meyer, Alain Morard, Edgar Nitsch, and Walter Wildi. Special thanks are also due to the members name situated. of the Swiss Committee for Stratigraphy, and, especially of the Type locality Road cut section (coord. 2627.690/ Eastern Jura Mountains sub group and its late president, Werner 1246.165) below Chilchzimmersattel Heckendorn. The National Cooperative for the Disposal of Radioac- road pass 2.5 km SW Eptingen BL tive Waste/Nagra is thanked for ﬁnancial support. (Jordan et al. 2016) close to the original section of Erni (1910) (Fig. 13). References Type region Belchen–Hauenstein area. Reference None. Achilles, H., & Schlatter, R. (1986). Palynostratigraphische Unter- localities suchungen im ‘Rha¨t-Bonebed’ von Hallau (Kt. Schaffhausen) Underlying Gruhalde Member. mit einem Beitrag zur Ammonitenfauna im basalen Lias. strata Eclogae Geologicae Helvetiae, 9, 149–179. The middle to late Triassic Ba¨nkerjoch and Klettgau formations of northern Switzerland 283

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