ANDRA BGR CHEVRON CRIEPI DOE ENRESA ENSI GRS IRSN JAEA NAGRA NWMO OBAYASHI SCK •••CEN SWISSTOPO

Mont Terri Project

TECHNICAL REPORT 2014-07

August 2014

SO ( Sedimentology of the Opalinus-Ton)

Biostratigraphy of the Basal Part of the Opalinus-Ton at the Mont Terri rock laboratory, Switzerland

A.G. Reisdorf (1,2), B. Hostettler (1), A. Waltschew (3) , D. Jaeggi (4) and U. Menkveld-Gfeller (1)

(1) Naturhistorisches Museum der Burgergemeinde Bern, Switzerland, (2)Geologisch-Paläontologisches Institut, University of Basel, (3)Nürnberg, Germany, (4)swisstopo, Switzerland

Mont Terri Project, TR 2014-07

Distribution:

Standard distribution:

ANDRA (S. Dewonck)

BGR (K. Schuster)

CHEVRON (P. Connolly)

CRIEPI (T. Oyama)

DOE ( P. Nair, J. Birkholzer)

ENRESA (J.C. Mayor)

ENSI (E. Frank)

DOE (P.Nair, J. Birkholzer)

GRS (K. Wieczorek)

IRSN (J.-M. Matray)

JAEA (N. Shigita)

NAGRA (T. Vietor)

NWMO (M. Jensen)

OBAYASHI (Masaaki Fukaya)

SCKCEN (F. Druyts)

SWISSTOPO (P. Bossart, A. Möri and Ch. Nussbaum)

Additional distribution:

Every organisation & contractor takes care of their own distribution.

Mont Terri Project, TR 2014-07

Table of Contents

List of Figures ...... - 3 - List of Plates ...... - 3 - List of Tables...... - 3 - 1 Introduction ...... - 5 - 2 Geological setting ...... - 6 - 3 Materials and methods ...... - 9 - 4 Results ...... - 11 - 4.1 Groups of organisms - 11 - 4.2 Classification of ammonites recovered from the Mont Terri rock laboratory - 12 - 5 Discussion and conclusions ...... - 15 - References: ...... - 21 -

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List of Figures

Figure 1-1. Location map: the Mont Terri rock laboratory is located in Canton Jura adjacent to the Mont Terri highway tunnel along the A16 Transjurane connecting Biel to Porrentury.

Figure 2-1. Cross section of the Mont Terri ramp fold with the location of the Mont Terri rock laboratory indicated in red. Note that the folded Jura is overthrusted onto the tabular Jura in the NW.

Figure 2-2. Section of the basal strata of the Opalinus-Ton at the ”Galerie de Reconnaissance” of the Mont Terri Rock Laboratory (modified after Bläsi et al. 1996). Colour coding of the facies types is the same as of Figures 3-1 and 3-2.

Figure 2-3. Simplified geological map of the Mont Terri rock laboratory with the most important tectonic faults indicated.

Figure 3-1. Simplified geological map of the Mont Terri rock laboratory with sampling sites for macrofossils.

Figure 3-2. Simplified geological map of the Mont Terri rock laboratory with sampling sites for microfossils.

Figure 5-1. Chrono- and lithostratigraphical correlation of the late Toarcian and early Aalenian sediments in northern Switzerland and SW Germany (not to scale).

Figure 5-2. Current and traditional stratigraphic nomenclature: lithostratigraphic units of the latest Early Jurassic and early Middle Jurassic of northern Switzerland and SW Germany and their biostratigraphic/chronostratigraphic range (strongly modified after Feist-Burkhardt & Pross 2010).

Figure 5-3. Sample of the pyrite horizon at tunnel metre GM 901, unprepared on the left, prepared on the right (NMBE D4583).

List of Plates

Plate 1. Typical ammonites from the basal strata of the Opalinus-Ton at the Mont Terri rock laboratory (also noted are the sampling site and register number of the Naturhistorisches Museum der Burgergemeinde Bern). Specimens coated with ammonium chloride.

List of Tables

Table 5-1. List of biostratigraphically relevant ammonites that were found in the outcrops, the drill core material, and in the material excavated from the Opalinus-Ton at the Mont Terri rock laboratory.

Appendix

Micropalaeontological investigation (by A. Waltschew).

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Abstract

For the first time since the existence of the Mont Terri Project, the Opalinus-Ton (“Opalinus Clay“) has been the subject of a macropalaeontological study. Extractions of ammonites were made from a number of small exposures as well as a drill core at the Mont Terri rock laboratory. Additionally, ammonites were obtained from excavated material from a particular stretch of drifting.

It was possible to make a biostratigraphical subdivision of the Opalinus-Ton’s basal strata from the faunal spectrum. In the >10-meter-thick basal strata of the Opalinus-Ton, Pleydellia aalensis s.l., P. fluitans , P. subcompta ?, P. leura and P. costula were found. As proven by the stratigraphical occurrence of these ammonites, a significant part of the Opalinus-Ton of the Mont Terri rock laboratory is most definitely part of the latest Toarcian (aalensis Subzone, Aalensis Zone).

In addition, the exposed section provides evidence that the Late Toarcian ammonite fauna was succeeded without significant lithofacies change by an Early Aalenian faunal assemblage that included Leioceras opalinum . Our micropalaeontological data set is corroborated by these macropalaeontological and lithological facts. However, it should be noted that the ostracod stratigraphy for northern Switzerland as compiled by Tröster (1987) does not coincide with the Late Toarcian/Early Aalenian ammonite zones: the decisive index ostracod species Aphelocythere kuhni crosses the Toarcian/Aalenian boundary and thus is not suitable for determining an exact biostratigraphic boundary of the Early/Middle Jurassic in the Mont Terri rock laboratory.

The basal strata of the Opalinus-Ton of the Mont Terri Rock Laboratory are lithofacially significantly different from the deposits of the same age of the Tabular Jura and the eastern Folded Jura, which appear in a mostly phosphoritic marly facies (= Gross Wolf Member after Reisdorf et al. 2011, “Jurensis-Schichten” sensu Jordan 1983, “Jurensismergel” sensu Müller et al. 1984). However, close examination of the facies and thickness relationships of the latest Toarcian in the Mont Terri area reveals a strong affinity with the strata found south of Freiburg i. Br., Germany (cf. for example Etter 1990; Geologisches Landesamt Baden-Württemberg 1996; Wetzel & Allia 2003).

Consistent with this, the base of the Opalinus-Ton in the Mont Terri rock laboratory cannot be correlated chronostratigraphically with the occurrences of this formation further to the east of Switzerland, e.g., those encountered by the Nagra drilling campaigns.

It is necessary to consider these facts when developing sequence stratigraphic models (including the average net sedimentation rate). Finally, it has to be noted that the strata assigned to a large number of the experiments that have been conducted and are currently being conducted in the Mont Terri rock laboratory are of Toarcian age (Early Jurassic). In other words, the traditional chronological assignment of the Opalinus-Ton only to the Aalenian age does not apply for the basal strata of this formation.

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1 Introduction

The Opalinus-Ton ( Moesch 1857, = “Opalinus Clay”) has been selected as the preferred host rock for disposal of nuclear waste in Switzerland since its properties, such as sorption of radionuclides, self- healing of excavation-induced fractures and cracks, and especially its very low permeability, has been assessed as safe long-term storage. Furthermore, the Opalinus-Ton is available in sufficient thickness and in ideal depth ranges in regions of no or low tectonic deformation.

The Mont Terri project is an international research project, which is dedicated to the research of the Opalinus-Ton, an argillaceous rock of very low permeability. A total of 15 partners from various countries all over the world are involved in this project, which started in 1996 at the Mont Terri. The Mont Terri rock laboratory is operated by the Federal Office of Topography (swisstopo) which furthermore directs the Mont Terri Project. Currently, 44 experiments are being conducted which focus on three main topics: i) characterization of the rock, ii) development of devices and techniques and iii) demonstration experiments. Most of these experiments are dedicated to investigating the Opalinus- Ton as a host rock for nuclear waste disposal; however, the number of experiments dealing with CO 2 sequestration, well bore-sealing and geothermal issues in rocks of very low permeability is continuously increasing.

In 1989, the security gallery of the Mont Terri tunnel of the A16 highway was excavated (Figure 1-1), which revealed the Opalinus-Ton to a length of almost 250 m, yielding a true thickness of about 150 m (e.g., Bläsi et al. 1991, 1996; but see Nussbaum & Bossart 2008). This unique access to the Opalinus- Ton is situated 300 m below the surface and led to the initiation of the underground research activities north of the town of St. Ursanne in Canton Jura, Switzerland, in 1996. Within the last 18 years, the Mont Terri rock laboratory evolved to a system of galleries and niches more than 600 m long, with numerous experiments and more than 1000 drilled boreholes. Currently, 44 experiments are ongoing, some of which will allow data collection for the next 15-20 years.

Until now, numerous geological data have been collected, mainly focusing on lithostratigraphy and tectonic features; however, a thorough biostratigraphic analysis was lacking. Recently found ammonites that were collected from pre-existing niches within the Opalinus-Ton revealed that a biostratigraphic analysis is essential in order to verify the location of the (biostratigraphic) Toarcian/Aalenian boundary. The knowledge of the exact location of this boundary, but also the biostratigraphic subdivision of the Opalinus-Ton itself, is important mainly for three reasons. Firstly, until now the Early/Middle Jurassic (Aalensis zone/Opalinum zone) boundary is thought to be nearly, or even exactly, in concordance with the lithostratigraphic boundary between the Staffelegg Formation (“Lias”) and the Opalinus-Ton (Figure 5-2) . However, this hypothesis is not based on biostratigraphic data but solely on a lithostratigraphic correlation with other Opalinus-Ton deposits of northern Switzerland (i.e., in the Klettgau area, Tabular Jura, eastern Folded Jura and Molasse Basin; see e.g. Wetzel & Allia 2003 and Reisdorf et al. 2011 for stratigraphic data of these areas). Secondly, the Opalinus-Ton in the Mont Terri area is structurally superimposed. Theoretically, biostratigraphic data could help to understand the tectonic architecture of these more or less monotonous argillaceous deposits. And finally, a biostratigraphically controlled facies model of the Opalinus-Ton may help to prevent an inaccurate correlation of observations made in the Mont Terri rock laboratory with regard to potential sites for future repository of nuclear waste to the east.

This paper represents our preliminary report of the biostratigraphic situation of the Opalinus-Ton encountered at numerous outcrops, windows within the shotcrete lining as well as in boreholes in the Mont Terri rock laboratory. The locations where the samples for analysis of macro- and microfossils were extracted are given (Figures 3-1 and 3-2) . Index fossils are displayed on plates in the appendix. The biostratigraphy of the Opalinus-Ton at the Mont Terri rock laboratory is studied systematically, yielding a well-defined model of ammonite biozones and biosubzones, which enables us to distinguish strata of the Early Jurassic (Toarcian) and Middle Jurassic (Aalenian) in age. A comparison of the observations at Mont Terri to known sections in Germany is made. Furthermore, possible implications for the correlation between the Opalinus-Ton at Mont Terri and the potential sites for future underground disposal of nuclear waste in Switzerland are discussed.

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Figure 1-1. Location map: the Mont Terri rock laboratory is located in Canton Jura adjacent to the Mont Terri highway tunnel along the A16 Transjurane connecting Biel to Porrentruy.

2 Geological setting

The Mont Terri rock laboratory is located entirely in argillaceous deposits of the Opalinus-Ton, which are part of the back limb of the ramp-like Mont Terri anticline (Figure 2-1). The bedding dips towards the SSE with a continuous change of inclination from 50° in the southern part of the rock lab to 30° i n the northern part ( Figure 2-2). On a larger tectonic scale, the area lies in the Rhine-Bresse Graben transfer zone. The geometry of this ramp structure is strongly affected by inherited faults of various orientations. A review of the structural and tectonic features is given by Nussbaum et al. (2011).

The Opalinus-Ton at Mont Terri – in contrast to observations in Switzerland more to the east – consists of three main facies types: an argillaceous facies, rich in clay minerals of illite, mixed-layered illite-smectites, chlorite and kaolinite (Bossart et al. 2008), which represents about 65% of the strata between the bounding Passwang Formation on top, respectively the Staffelegg Formation at the base (Figure 2-2 and Figure 2-3); about 30% is represented by an sandy facies, with quartz contents of up to 30% and more; and 5% is represented by an exotic carbonate-rich facies, consisting of bioclastic layers of crinoids and debris of bivalves, occurring in elongated lenses of cm- to dm-thickness.

Wetzel & Allia (2003) provided a depositional model for the Opalinus-Ton of northern Switzerland: the formation was accumulated under fully marine conditions in a shallow basin, which was affected by differential synsedimentary subsidence. The depositional water depth was 20-50 m, thus in the range of, and somewhat below, the storm-wave base. This hypothesis is supported by the abundance of sedimentary structures and storm-induced accumulations of well-sorted beds of crinoids and bivalves in the Mont Terri area (Müller & Jaeggi 2012). Furthermore, at Mont Terri, all deposits are bioturbated to a certain degree; however, at many stratigraphic levels the original lamination is preserved, which

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At Mont Terri and adjacent areas, the Opalinus-Ton is barely exposed at the surface. Until now, there is no resilient detailed biostratigraphic data for the Opalinus-Ton at Mont Terri. A brief lithological description of the Opalinus-Ton was given from an old borehole near Buix by Schmidt et al. (1924). These authors encountered a thickness of 157.5 m for the Opalinus-Ton. More recent data from the security gallery of the Mont Terri highway tunnel (Schaeren & Norbert 1989; Bläsi et al. 1991; Bläsi 1996) revealed a “true thickness” of 150 m (in contrast to Nussbaum & Bossart 2008). Especially Bläsi et al. (1991) provided a detailed lithostratigraphic description of the Opalinus-Ton at Mont Terri, which was accessible through the reconnaissance gallery. Schaeren & Norbert (1989) and Bläsi et al. (1991) determined the base of the Opalinus-Ton in a lithological transition of argillaceaous beds to more marly beds. The latter have been identified as “Jurensis-Mergel” (=?Gross Wolf Member of the Staffelegg Formation after Reisdorf et al. 2011). The thickness of the Opalinus-Ton is given as 150 m (Bläsi et al. 1991). It is still an open question if this calculated thickness value is affected by tectonics (as already discussed by Bläsi et al. 1991): In any case, an important tectonic overprint is confirmed by numerous studies on structural data conducted during the evolution of the rock laboratory (see also Nussbaum et al. 2011). Accordingly, tectonic overprint could play a key role in the tectonic as well as stratigraphic architecture, and therefore influence thicknesses of the encountered deposits.

However, the top beds of the Opalinus-Ton are condensed. The overlying lithostratigraphic unit is the Sissach Member of the Passwang Formation ( Figure 5-2; e.g., Wetzel & Allia 2003; Jordan et al. 2008). Biostratigraphically, this boundary is situated within the Comptum subzone (late Opalinum zone; Burkhalter 1996). In southwestern Germany, the Comptum bed (Comptum subzone in age) marks the upper boundary of the Opalinus-Ton Formation (Franz & Villinger 2001; Geyer et al. 2011).

Figure 2-1. Cross section of the Mont Terri ramp fold with the location of the Mont Terri rock laboratory indicated in red. Note that the folded Jura is overthrusted onto the tabular Jura in the NW.

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Figure 2-2. Section of the basal strata of the Opalinus-Ton at the ”Galerie de Reconnaissance” of the Mont Terri Rock Laboratory (modified after Bläsi et al. 1996). Colour coding of the facies types is the same as of Figures 3-1 and 3-2.

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Figure 2-3. Simplified geological map of the Mont Terri rock laboratory with the most important tectonic faults indicated.

3 Materials and methods

All examined fossils and rock samples within the context of this study originate from the basal strata of the Opalinus-Ton (“Opalinus Clay”; Figure 2-2). The material was removed from the Mont Terri rock laboratory in November 2012 and July 2013, or rather, from its excavated material. Only one rock sample of a certain horizon rich in pyrite (Figure 5-3) was taken from the rock laboratory previously in May 2012.

The greatest quantity of material with more than 150 samples of macro- and microfossils originates from the excavated material of the FE gallery. Since the FE gallery has been placed parallel to the bedding of the rock in the rock laboratory, samples originating from it can be classified as belonging to a closely limited lithostratigraphic section of a thickness of about 3 m (Figure 3-1). In contrast, sample material was taken in situ from an 11.5 m-long drill core of the BCS5 drilling (Figure 3-1) . This borehole with a diameter of 350 mm (drill core 290 mm) telescoped to 198 mm (drill core 168 mm) was placed at an angle of approximately 50° to the bedding dip.

Moreover, for an extraction of samples in situ in the Opalinus-Ton, several niches and small-scale outcrops (“windows”) were available in the rock laboratory, which otherwise is completely covered with shotcrete. In particular, the places where samples were taken were the following: HE niche, MI niche, MF gallery 98 West and East, FM-C niche South and East, gallery 98, window 1 West, gallery 98, window 3 East, gallery 98, window 7 East and niche C North (see Figures 3-1 and 3-2).

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The extracted macrofossils were prepared with techniques appropriate to their mode of preservation at the Naturhistorisches Museum der Burgergemeinde Bern. Pyrite steinkerns and preservations of shells altered into calcite were sand-blasted with sodium hydrogen carbonate; fossils with periostracum preservation were prepared in a purely mechanical way with an air tool. An air tool was also used for the removal of the cone-in-cone structures (“Nagelkalk”) adhering to many bivalve and gastropods shells; however, with this method, it was impossible to completely remove the cone-in- cone structures adhering to belemnites (without damaging the fossils). Therefore, we abstained from a complete preparation of this belemnites. All of this work was done by Bernhard Hostettler and Gino Bernasconi. Microfossils were extracted by standard procedures from the sample material. The processing and evaluation of the samples were done by Anton Waltschew. Finally, ammonites and microorganisms (ostracods) were used for the biostratigraphic dating of the strata exposed area by area in the Mont Terri rock laboratory. All macrofossils displayed in this preliminary report are kept in the collection of the Naturhistorisches Museum der Burgergemeinde Bern.

Figure 3-1. Simplified geological map of the Mont Terri rock laboratory with sampling sites for macrofossils (in red). The dashed line indicates the Toarcian/Aalenian boundary.

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Figure 3-2. Simplified geological map of the Mont Terri rock laboratory with sampling sites for microfossils (in red). The dashed line indicates the Toarcian/Aalenian boundary.

4 Results

4.1 Groups of organisms

The spectrum of the extracted macrofossils can be classified as belonging to the following groups of organisms:

Gastropods: Costatrochus subduplicatus var . palinurus (D`Orbigny 1850) nach Gründel & Hostetler (subm.) Two more species not yet classified.

Bivalves: Palaeonucula hammeri Nuculana claviformis Pseudomytiloides dubius Entolium sp. Bositra buchi Nicaniella sp.

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Ammonites: see chapter 4.2

Belemnites Belemnites indet.

Brachiopods: Discinisca papyracea

Crustaceans: Mecochirus sp. remains of bony fishes (scales, bones)

4.2 Classification of ammonites recovered from the Mont Terri rock laboratory

Preliminary Note

Schulbert (2001) separates the Pleydellia genus with the morphological characteristics of a narrowly umbilicate shell with a fastigate to lanceolate cross section from the Cotteswoldia genus. However, based on Lehmann (1976: 155), the Pleydellia specimens pictured by Schulbert (2001) can more accurately be described as platicone or even widely umbilicate. Also, according to Schlegelmilch (1992: 17), members of both the Pleydellia and Cotteswoldia genera have a fastigate to lanceolate cross section. In addition, transitions in the shape of the shell can be noted between both genera. Therefore, the genera Pleydellia BUCKMAN 1899 and Cotteswoldia BUCKMAN 1902 cannot be separated from one another with absolute certainty by objective morphological criteria. For these reasons, we are abstaining from separating the two genera in accordance with Arkell (1957) and Schlegelmilch (1992); taxonomically, the genus Pleydellia BUCKMAN 1899 receives priority.

Superfamily Hildoceratoidea HYATT 1867 Family Hildoceratidae HYATT 1867 Genus Pleydellia BUCKMAN 1899

Individual morphospecies of the Pleydellia genus are all interconnected by transitions. The forms listed as species here rather correspond to morphotypes of one and the same species. For biostratigraphic reasons, it can sometimes be sensible to describe certain morphotypes as chrono-subspecies. The following chrono-subspecies were identified in the collected material:

Pleydellia aalensis (ZIETEN , 1832) Plate 1, Fig. 6 Pleydellia cf. aalensis (ZIETEN , 1832) Plate 1, Fig. 7 According to Schlegelmilch (1992), this ammonite species is characterized by unevenly bifurcated sinus ribs that bifurcate and trifurcate at the umbilical margin. With increasing diameter, the location of the split shifts in the direction of the midflank area in some specimens. Intercalated ribs are more or less visible.

Pleydellia cf. fluitans (DUMORTIER , 1874) Plate 1, Fig. 9 This ammonite species is characterized by relatively strong ribs, either single or bifurcating in the midflank area. Ribs on the ventrolateral shoulder strongly prorsiradiate. The umbilicus is relatively wide developed.

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Pleydellia cf. subcompta (BRANCO , 1879) Plate 1, Fig. 8 This ammonite species is similar to P. aalensis , but has uneven rib spacing.

Pleydellia lotharingica (BRANCO , 1879) Plate 1, Fig. 11 This ammonite species is characterized by falcate, strong, slightly prorsiradiate fastigate ribs. Intercalated ribs may also be found. The shell is moderately widely umbilicate and has a clearly offset keel.

Pleydellia leura (BUCKMAN , 1890) Plate 1, Figs. 1 & 2 Characteristics of this ammonite species are moderately widely umbilicate shells as well as slightly prorsiradiate, distant simple ribs.

Pleydellia costulata (ZIETEN , 1830) Plate 1, Fig. 4 According to Schlegelmilch (1992), strong, lamellar simple ribs that strongly prorsiradiate on the ventrolateral shoulder are the characteristics of this ammonite species. Also, the shell is slightly more umbilicate than that of the otherwise similar P. leura .

Pleydellia sp. Plate 1, Figs. 13 & 16 Two specimens that could not classified more closely.

Family Graphoceratidae BUCKMAN 1905 Genus Leioceras HYATT 1867

Leioceras opalinum (REINECKE , 1818) Plate 1, Fig. 12 Name giver to the Opalinus-Ton, this ammonite species is moderately widely to widely umbilicate. It is characterized by dense, partly hair-thin, strongly prorsiradiate simple ribs on the ventrolateral shoulder, which become less distinct crossing the stepped keel.

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Plate 1. Typical ammonites from the basal strata of the Opalinus-Ton at the Mont Terri rock laboratory (also noted are the sampling site and register number of the Naturhistorisches Museum der Burgergemeinde Bern). Specimens coated with ammonium chloride. The indicated size of the specimen (d in mm) corresponds with the largest diameter of the ammonite.

Fig. 1: Pleydellia leura (BUCKMAN , 1890); Opalinus-Ton; Mont Terri rock laboratory, HE niche, 250 cm (NMBE D4048-2), d=38 mm

Fig. 2: Pleydellia leura (BUCKMAN , 1890); Opalinus-Ton; Mont Terri rock laboratory, HE niche, 250 cm (NMBE D4048-1), d=26.5 mm

Fig. 3: Pleydellia leura (BUCKMAN , 1890); Opalinus-Ton; Mont Terri rock laboratory, excavated material of the FE gallery (NMBE D4051), d=17 mm

Fig. 4: Pleydellia costulata (ZIETEN , 1830); Opalinus-Ton; Mont Terri rock laboratory, BCS5 drilling, -583 cm (NMBE D4053), d=27 mm

Fig. 5: Pleydellia leura (BUCKMAN , 1890); Opalinus-Ton; Mont Terri rock laboratory, HE niche, 255 cm (NMBE D4049), d=31 mm

Fig. 6: Pleydellia aalensis (ZIETEN , 1832); Opalinus-Ton Fm.; Mont Terri rock laboratory, excavated material of the FE gallery (NMBE D4047), d=31 mm

Fig. 7: Pleydellia cf. aalensis (ZIETEN , 1832); Opalinus-Ton; Mont Terri rock laboratory, BCS5 drilling, -535 cm (NMBE D4052), d=33 mm

Fig. 8. Pleydellia cf. subcompta (BRANCO , 1879); Opalinus-Ton; Mont Terri rock laboratory, HE niche, 250 cm (NMBE D4050), d=34 mm

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Fig. 9: Pleydellia cf. fluitans (DUMORTIER , 1874); Opalinus-Ton; Mont Terri rock laboratory, excavated material of the FE gallery (NMBE D4054), d=36 mm

Fig. 10: indet.; Opalinus-Ton; Mont Terri rock laboratory, MFG98 West, 40 cm above main fault (NMBE D4049), d=22 mm

Fig. 11: Pleydellia lotharingica (BRANCO , 1879); Opalinus-Ton; Mont Terri rock laboratory, MFG98 West, 35 cm (NMBE D4055-2), d=31 mm

Fig. 12: Leioceras opalinum (REINECKE , 1818); Opalinus-Ton; Mont Terri rock laboratory, MFG98 West, 35 cm (NMBE D4055-1), d=53 mm

Fig. 13: Pleydellia sp.; Opalinus-Ton; Mont Terri rock laboratory, MFG98 West, 40 cm above main fault (NMBE D4056), d=42.5 mm

Fig. 14: indet.; Opalinus-Ton; Mont Terri rock laboratory, MFG98 West, 40 cm above main fault (NMBE D4058), d=9 mm

Fig. 15: indet.; Opalinus-Ton; Mont Terri rock laboratory, MFG98 West, 40 cm above main fault (NMBE D4060), d=17.5 mm

Fig. 16: Pleydellia sp.; Opalinus-Ton; Mont Terri rock laboratory, MI niche, 1.0 m (NMBE D4073), d=46.5 mm

5 Discussion and conclusions

Bläsi et al. (1991) subdivide the Opalinus-Ton in the Mont Terri rock laboratory into four subunits. The lowest of these subunits, from a lithostratigraphic point of view, the «”argillaceous” Opalinus-Ton rich in fossils», occurs between the tunnel meters 902.50 to 1024.50. This subunit is followed by the «Opalinus-Ton with calcareous intercalations of sandstone and biodetritus» (tunnel meters 869.0 to 902.50), «”argillaceous” Opalinus-Ton» (tunnel meters 835.0 to 869.0) and again «Opalinus-Ton with calcareous intercalations of sandstone and biodetritus» (tunnel meters 781.0 to 835.0). This lithofacies of the Opalinus-Ton in the Mont Terri rock laboratory differs from the deposits of Opalinus-Ton of the Folded Jura and Tabular Jura of northern Switzerland as well as neighbouring areas in southern Germany (cf. Wetzel & Allia 2003; Franz & Nitsch 2009).

Within the context of our biostratigraphic study, we examined the two subunits which were lowest from a lithostratigraphic point of view. We only came across ammonites in the «”argillaceous” Opalinus-Ton rich in fossils». The discovery of ammonites in this subunit permit far-reaching conclusions concerning biostratigraphic distinction between the Early and Middle Jurassic in the Mont Terri area. These ammonites are discussed concerning their stratigraphic occurrence and the essential results of our micro-biostratigraphic study: for the latter, ostracods are decisive. Details concerning the totality of the discovered microfauna can be found in the appendix.

From a detailed lithostratigraphic point of view, the subunit of the «”argillaceous” Opalinus-Ton rich in fossils» has three essential variations of facies, which are in part not strictly divided from one another but may merge. Starting with the deepest variety of facies from a lithostratigraphic point of view, these are: • a shell coquina facies • a argillaceous facies with low share of biodetritus • a cephalopod facies with shell coquina and burrows.

The first variety of facies is a grey claystone rich in coquina with numerous fragments and juvenile shells of Bositra buchi about 1-2 mm in size. Other genera of bivalves, gastropods and ammonites occur regularly in it. All those invertebrates with a primarily non-calcite exoskeleton mineralogy are recrystallized. The ammonites are, for the most part, strongly compressed. Their recrystallized shells can only be found in the phragmocone zone. The body chambers are frequently covered with brownish remains of the periostracum. In certain regions of the shell coquina facies, however, only slightly compressed pyrite steinkerns also occur. According to up-to-date biostratigraphic nomenclature (see Feist-Burkhardt & Pross 2010), the discovered ammonite fauna belongs to the Late Toarcian/Early Jurassic (cf. below). Facies variety 1 occurs in the excavated material of the FE-gallery as well as in the material of drill core BSC5. It should be noted that in the material of the drill core BSC5, between the drill metres 4 and 6, transitions from the facies variety 1 to facies variety 2 occur.

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In this context, the facies rich in coquina in the facies variety 2 (=argillaceous facies with low share of biodetritus) is mainly linked to the ichnofauna.

A gray micaceous claystone represents the second facies variety . This facies variety was found in the drill core BSC5 (cf. above) as well as in the FE-gallery. In the claystone, single, closely horizontally as well as laterally limited accumulations of shells and detritus of Bositra buchi occur, with diameters of up to 10 mm. Other genera of bivalves, gastropods, belemnites and ammonites, however, rarely occur. It is of biostratigraphic relevance that among the ammonites, only specimens to be found were those that must be placed in the Late Toarcian (Early Jurassic) (cf. below).

Grey claystone rich in cephalopods and coquina with numerous pyritized burrows of different diameter (from 1 to 3 mm) are characteristic of the third facies variety . The burrows run parallel as well as vertical to the bedding of the rock. Notably that fragments of thick-shelled shells such as Palaeonucula and Nuculoma occur frequently. The fragments of the shells are preserved as recrystallized calcite. The ammonites phragmocone is almost always pressed flat, whereas the body chamber is often completely filled with sediments and, as a consequence, bodily preserved. Juvenile ammonite shells (up to 2 mm) have evenly turned into pyrite and thus are preserved as steinkerns. From a biostratigraphic point of view, it is significant that only in this facies variety we found ammonites which must be placed in the Aalenian (Middle Jurassic) (cf. below). Possible transitions between the second and third facies variety could not be studied in the Mont Terri rock laboratory because of the lining of the tunnel (shotcrete). Therefore, the question must remain open whether index ammonites of the Early Aalenian may also be found in the second facies variety (= argillaceous facies with low share of biodetritus).

In principle, we also encounter the characteristic facies varieties of the «”argillaceous” Opalinus-Ton rich in fossils» in the basal layers of the Opalinus-Ton in northern Switzerland as well as in the adjacent occurrences in SW Germany. For example, the Nagra drilling campaigns described the lithological subunits of the basal layers of the Opalinus-Ton as “low in sand, fossil-rich Opalinus-Ton” (Nagra 1989, 1990, 1992) and “mudstones” (the latter also containing biodetritus; Nagra 2001) respectively. In contrast to the Mont Terri area, the boundary between the Staffelegg Formation and Opalinus-Ton in these areas is marked by a sharp lithologic change (Jurensismergel Formation and Opalinuston Formation in the stratigraphic nomenclature of Southern Germany; see Bloos et al. 2005): the top-most marls of the Gross Wolf Member (previously “Jurensis-Mergel”)/the Jurensismergel Formation are followed by “homogenic pelites” rich in mica and “laminated pelites” of the Opalinus- Ton/Opalinuston Formation respectively (Etter 1990; Wetzel & Allia 2003; Franz & Nitsch 2009; Reisdorf et al. 2011). Interestingly, there is a correspondent between the lithological indistinctly developed transition of the Early and Mid-Jurassic strata in the Mont Terri rock laboratory and those found in the Wittnau drilling (near Freiburg i.Br., Germany; cf. Geologisches Landesamt Baden-Württemberg 1996). Not only that, but also the lithofacies and ammonite-fauna discovered in the Wittnau drilling seem to show great conformity with the findings from the Mont Terri rock laboratory in the respective layers. This particular stratigraphic constellation has thus far not been considered in previous examinations. It is especially noteworthy in this context that in the Wittnau drilling, the strata between 87 and 59.56 m show great affinity to the shell coquina facies of the «”argillaceous” Opalinus-Ton rich in fossils» sub-unit of the Mont Terri rock laboratory: in both cases, shell accumulations of Bositra dominate these facies. There is a considerable difference, however, between the two occurrences with regard to the lithostratigraphic affiliation ( Figure 5-1): at the Mount Terri rock laboratory, the facies is solely assigned to the Opalinus-Ton, whereas the Wittnau drilling results classify them as belonging to the Jurensismergel (today: Jurensismergel Formation; e.g., Geologisches Landesamt Baden-Württemberg 1996; Bossart & Thury 2008). Because the entire stratigraphic section at the Mont Terri rock laboratory declared as Opalinus-Ton has been assigned to the Aalenian period by previous examiners, there are significant deviations from the Wittnau drilling not only with regard to lithostratigraphy but also with regard to biostratigraphy. The consequences of the different stratigraphic affiliation, i.e. distinction, become clear in Figure 5-2.

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Figure 5-1. Chrono-, bio- and lithostratigraphical correlation of the late Toarcian and early Aalenian sediments in northern Switzerland and SW Germany (not to scale).

Reflecting on the new stratigraphic studies, further complications become evident; however, these can for the most part be biostratigraphically resolved with the results of our study. First, it needs to be noted that already Contini (1970) realised that in the region of the Jura Fran-comtois (E France), the biostratigraphic boundary between the Toarcian and Aalenian (= boundary between Early and Middle Jurassic) runs within the «marnes à Opalinum». This biostratigraphic affiliation concurs with the views of Jordan et al. (2008) and Reisdorf et al. (2011), who also assign the basis of the Opalinus-Ton in the Mont Terri region to the Late Toarcian (Early Jurassic; Figure 5-2). The latter authors base this opinion on biostratigraphic data from northern Switzerland and southwestern Germany. Feist- Burkhardt & Pross (2010) also place the biostratigraphic boundary between the Early and Middle Jurassic at Mont Russelin (canton Jura) in the lithology of the Opalinus-Ton ( Figure 5-2). Specifically, they draw the distinguishing boundary between the Torulosum subzone (Aalensis zone, Late Toarcian) and the Opalinum subzone (Opalinum zone, Aalenian; Figure 5-2). This means that there is a distinct difference with regard to fine-scale biostratigraphy between the classification of Feist- Burkhardt & Pross (2010) and Reisdorf et al. (2011): based on Etter (1990: 65), Reisdorf et al. (2011) do not distinguish a Torulosum subzone in their biostratigraphic classification. In other words, according to Reisdorf et al. (2011), the facies of the Opalinus-Ton does not begin with a Torulosum subzone but is already within the Aalensis subzone ( Figure 5-2).

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Figure 5-2. Current and traditional stratigraphic nomenclature: lithostratigraphic units of the latest Early Jurassic and early Middle Jurassic of northern Switzerland and SW Germany and their biostratigraphic/chronostratigraphic range (much modified after Feist-Burkhardt & Pross 2010).

This fine-scale stratigraphic detail is important for two reasons: i) because it is in consistent compliance with the European Standard ammonite biostratigraphy (Cresta et al. 2001; Schmid et al. 2008: 867; Feist-Burkhardt & Pross 2010: 12; that, however, is not put into uniform practice: cf., for example, Franz & Nitsch 2009; Geyer et al. 2011: fig. 89), a Torulosum subzone was only recently added to the Toarcian ( Figure 5-2); ii) because in Southwest Germany, the Torulosum subzone itself is represented by sediments of several meters' thickness (at Wittnau near Freiburg im Breisgau, they are even 23 m thick; Geologisches Landesamt Baden-Württemberg 1996; Franz & Nitsch 2009; Geyer et al. 2011).

By means of the ammonite faunal assemblages characterized by Schulbert (2001: 108 p.), the tunnel sections studied in the Mont Terri rock laboratory can be dated down to the level of an ammonite subzone ( Table 5-1). The samples of fossils and rocks from the BCS5 drilling and the HE niche must, as a result, be classified as belonging exclusively to the Aalensis subzone (Aalensis zone), and therefore to the late Early Jurassic (Late Toarcian). The same applies to the material from the excavated material of the FE gallery (cf. Table 5-1); as already explained above, the ammonites recovered there come from two variations of facies of the «”argillaceous” Opalinus-Ton rich in fossils»: the “shell coquina facies” and the “argillaceous” facies with low share of biodetritus”. The ammonites recovered from the tunnel outcrops MI niche, MF GA West and East, FM-C-21 South and East, gallery 98 and window 1 West have however, to be classified as belonging to the Opalinum subzone (Opalinum zone) and, therefore, the Early Aalenian (Middle Jurassic; Figure 2-2). All these ammonites were taken from the facies variety of the “cephalopod facies with shell coquina and burrows”.

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s.l. species ammonite ammonite P.fluitans? P.costulata P. aalensisP. P.lotharingica Pleydellia leura Pleydellia P.subcompta ?

sampling site opalinum Leioceras BCS5 drilling HE niche FE gallery MFG West MFG East MI niche FM-C21East FM-C21South gallery 98, window 1 West Table 5-1. List of biostratigraphically relevant ammonites that were found in the outcrops, the drill core material, and in the material excavated from the Opalinus-Ton at the Mont Terri rock laboratory.

Nevertheless, an exact biostratigraphic delimitation was not yet possible under the circumstances regarding the outcrops in the Mont Terri rock laboratory ( Figures 2-2, 3-1 and 3-2): between the HE niche and the MFG98 west and (respectively) east windows, there is a stretch of about four to five meters where it is not possible to access the Opalinus-Ton because it is covered by shotcrete. It is in these tunnel sections that we can expect to find the biostratigraphic boundary between the Early and Middle Jurassic. In case it is even possible to distinguish a Torulosum subzone in the strata of the Mont Terri rock laboratory (cf. Etter 1990: 65), it is presumed to be in this outcrop gap as well. This problem is at least relevant for the correlation with deposits of the same age in Southwest Germany (e.g., the Wittnau drilling; cf. Geologisches Landesamt Baden-Württemberg 1996).

Micropaleontological data: The overall results from evaluation of 16 samples will not be able to solve these fine-scale stratigraphic problems. Contrary to the results of Tröster (1987) from deposits of northern Switzerland, the only index ostracod species from the Toarcian/Aalenian range, namely Aphelocythere kuhni TRIEBEL & KLINGLER 1969, does not appear for the first time in the Opalinus zone. In accordance with the Wittnau drilling and other sections in Southwest Germany, Aphelocythere kuhni already occurs here in the Aalensis subzone, i.e. in the Toarcian ( Figure 2-2; Knitter 1987; Geologisches Landesamt Baden-Württemberg 1996; Franz et al. 2009).

Be that as it may, another lithostratigraphic problem can be solved by means of the biostratigraphic studies in the Mont Terri rock laboratory: in the rock laboratory, two conspicuous pyrite horizons were found, both of which we debated with regard to their suitability as supraregional marker beds. The most strikingly marked pyrite horizon (thickness varies between 5 mm and 3 cm) occurs at tunnel metre GM 908, about 5.8 m below the base of the «Opalinus-Ton with calcareous intercalations of sandstone and biodetritus» according to Bläsi et al. (1991) ( Figures 2-2 and 5-3). The other pyrite horizon, less strikingly marked, occurs at GM 901, about 0.8 m above the base of the carbonate rich facies. According to the results of our biostratigraphic study, these two horizons must be placed in the Opalinus subzone (Opalinus zone, Aalenian; Figure 2-2). In the Wittnau drilling, a prominent pyrite horizon also occurs; it is, however, at a biostratigraphic level which must be classified as belonging to the Torulosum subzone (Geologisches Landesamt Baden-Württemberg 1996: figs. 9, 11). Therefore, there is no correlation of these pyrite horizons in terms of allostratigraphy (cf. Lutz et al. 2005).

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Figure 5-3. Sample of the pyrite horizon at tunnel metre GM 908, unprepared on the left, prepared by sand-blasting on the right (NMBE D4583).

Final conclusions

The true thickness of the strata of the Opalinus-Ton, which biostratigraphically belong to the Late Toarcian (Early Jurassic), is hard to calculate in the Mont Terri rock laboratory because of the tectonic situation of this occurrence. A thickness of more than 10 meters is assumed. Given the fact that the facies of the Opalinus-Ton biostratigraphically reaches into the Toarcian ( Figure 2-2), the abnormally high total thickness of the Opalinus-Ton estimated at 150 m in the rock laboratory can at least partially be explained.

Consistently with this, the base of the Opalinus-Ton in the Mont Terri rock laboratory cannot be correlated chronostratigraphically with the occurrences of this formation further to the east of Switzerland, e.g. those encountered by the Nagra’s drilling campaigns ( Figure 5-1). When developing sequence stratigraphic models (including the average net sedimentation rate), it is necessary to consider these facts.

The Opalinus-Ton facies or sedimentation started earlier in the Mont Terri region than further to the east ( Figure 5-1).

Undoubtedly the multitude of the experiments that have been conducted and are currently being conducted in the Mont Terri rock laboratory are located in strata that should not be assigned to the Aalenian but to the Toarcian ( Figures 3-1 and 3-2).

Acknowledgments

Rudolf Schlatter (Naturkundemuseum Leipzig) kindly verified our identifications of the ammonites. At the Naturhistorisches Museum der Burgergemeinde Bern all facilities were at our disposal. The teams of the Mont Terri Consortium and swisstopo made this study possible due to their interest and financial support. We thank the mentioned persons and institutions for their support.

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Appendix

Waltschew, A. (Nürnberg D)

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Biostratigraphic interpretation with ammonites Toarcian Aalenian

Facies types according to Bläsi et al. (1991) facies shalyfacies shalyfacies sandy facies sandy sandyfacies carbonat richcarbonat

Sample Number (see Figure 3-2) 1 9 2 10 11 12 13 3 4 5 6 14 15 7 16 8 Foraminifera Saccorhiza ramosa (B RADY 1879) Lagenammina jurassica (B ARNARD 1959) Reophax metensis F RANKE 1936 Reophax agglutinans (T ERQUEM 1866) Thurammina jurensis (F RANKE 1936) Lituotuba irregularis T APPAN 1955 Subbdelloidina scorpionis ( D'O RBIGNY 1850) Ammobaculites fontinensis (T ERQUEM 1870) Ammobaculites vetusta T ERQ . & B ERTH . 1875 Haplophragmoides sp. Vinelloidea infraoolithica (T ERQUEM 1870) Ophthalmidium sp. Lingulina costata (K ÜBLER & Z WINGLI 1866) Lingulina opalina (B ARTENSTEIN 1937) Lingulina sp. Frondicularia sp. Pseudonodosaria vulgata (B ORNEMANN 1854) Nodosaria regularis T ERQUEM 1862 Nodosaria striatojurensis K LÄHN 1923 Nodosaria simoniana D'O RBIGNY 1850 Nodosaria spp. Dentalina communis D'O RBIGNY 1826 Dentalina integra (K ÜBLER & Z WINGLI 1866) Dentalina jurensis T ERQUEM 1870 Dentalina vetusta D'O RBIGNY 1850 Dentalina spp. Lenticulina acutiangulata (T ERQUEM 1863) Lenticulina dorbignyi (R OEMER 1839) Lenticulina helios (T ERQUEM 1870) Lenticulina muensteri (R OEMER 1839) h Lenticulina polygonata (F RANKE 1936) Lenticulina varians Lenticulina spp. Planularia cordiformis (T ERQUEM 1863) Palmula deslongchampsi (T ERQUEM 1863) Citharina hechti (B ARTENSTEIN 1937) Citharina sp. Reinholdella dreheri (B ARTENSTEIN 1937) h Reinholdella traubensis O HM 1967 h Spirillina oolithica (S CHWAGER 1867) h Eoguttulina bilocularis (T ERQUEM 1864)

Table A-1. Stratigraphical occurrence and frequency of the Foraminifera in the Opalinus-Ton at the Mont Terri rock laboratory. seldom not seldom abundant

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Biostratigraphic interpretation with ammonites Toarcian Aalenian

Facies types according to Bläsi et al. (1991) shaly facies shaly facies shaly sandy facies sandy sandy facies sandy

Sample Number (see Figure 3-2) 1 9 2 10 11 12 13 35 14 15 7 16 8 Ostracoda Bythocypris sp. Cytherella reticuloornata K NITTER 1983 Cytherella sp. (smooth) Cytherelloidea cadomensis B IZON 1960 Cytheropteron groissi K NITTER 1984 Cytheropterina alafastigata (F ISCHER 1962) Cytheropterina cribra (F ISCHER 1962) Metacytheropteron opalinum P LUMHOFF 1963 Monoceratina scrobiculata T RIEBEL & B ART . 1938 Monoceratina stimulea (S CHWAGER 1866) Monoceratina striata T RIEBEL & B ART . 1938 Monoceratina ungulina T RIEBEL & B ART . 1938 Otocythere callosa T RIEBEL & K LINGLER 1959 Eucytherura liasssica B ATE & C OLEMAN 1975 Rutlandella transversiplicata B ATE & C OLEMAN 1975 Aaleniella reticulata K NITTER 1983 Liasina? cylindrica A INSWORTH 1986 Kinkelinella fischeri M ALZ 1966 Kinkelinella sermoisensis (A POSTOLESCU 1959) Praeschuleridea gallemannica M ALZ 1966 Praeschuleridea punctulata (P LUMHOFF 1963) Praeschuleridea ventriosa (P LUMHOFF 1963) Praeschuleridea sp. Aphelocythere kuhni T RIEBEL & K LINGLER 1959 Aphelocythere hamata P LUMHOFF 1963 Aphelocythere pygmaea P LUMHOFF 1963 Acrocythere pumila P LUMHOFF 1963 Paracypris sp. 1 (short) Paracypris sp. 2 (long) Paracypris spp. Pseudomacrocypris aequabilis (O ERTLI 1959) Trachycythere sp. Gen. et sp. incert. 5 P LUMHOFF 1963 Ogmoconchella sp. Polycope discus F ISCHER 1961 Polycope pelta F ISCHER 1961

Table A-2. Stratigraphical occurrence and frequency of the Ostracoda in the Opalinus-Ton at the Mont Terri rock laboratory. seldom not seldom abundant

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section Mont Terri Rock Laboratory (”Galerie de Reconnaissance”) coord.: 2’579’345 / 1’247’740 - 2’579’455/1’247’500

Toarcian Aalenian stage Late ? Early sub-stage Opalinus-Ton formation sensu BLÄSI et al. (1996) Aalensis ? Opalinum ammonite zone marls argillaceous and silty partly shales, marls argillaceous silty, and shales silty marls sandy argillac., & sandst. marly limest., sandy layers and lenses sandstone shales, sandy and sandstones marly shales silty lenses sandstone marls, and shales sandy beds limestone and sandstone marls, and shales sandy B to according Opalinus-Ton the of types facies LÄSI ta.(1991) al. et 10 12 13 14 15 16 11 1 9 2 3 4 5 6 7 8 micro-fauna apesites sample FE-Gallery HE-Niche Fault 98-Main Gallery MI-Niche/FM-C C- Drillcore BCS-5 yiehorizon pyrite horizon pyrite

macro-fauna eked(04 oiidatrBäie l (1991) al. et Bläsi after modified & (2014) Jaeggi Menkveld Waltschew, Hostettler, Reisdorf,

profile + + lithology 1024.5 meters tunnel 1000 980 960 940 920 900 890 880 869 850 835 820 800 781 (m)

fossils

Pleydellia leura Pleydellia costulata Pleydellia aalensis s.l. Pleydellia subcompta ? ammonites Pleydellia fluitans ? Pleydellia lotharingica Leioceras opalinum Foraminifera Saccorhiza ramosa (BRADY 1879) Lagenammina jurassica (BARNARD 1959) Reophax metensis FRANKE 1936 Reophax agglutinans (TERQUEM 1866) Thurammina jurensis (FRANKE 1936) Lituotuba irregularis TAPPAN 1955 Subbdelloidina scorpionis (D'ORBIGNY 1850) Ammobaculites fontinensis (TERQUEM 1870) Ammobaculites vetusta TERQ. & BERTH. 1875 Haplophragmoides sp. Vinelloidea infraoolithica (TERQUEM 1870) Ophthalmidium sp. Lingulina costata (KÜBLER & ZWINGLI 1866) Lingulina opalina (BARTENSTEIN 1937) Lingulina sp. Frondicularia sp. Pseudonodosaria vulgata (BORNEMANN 1854) Nodosaria regularis TERQUEM 1862 Nodosaria striatojurensis KLÄHN 1923 Nodosaria simoniana D'ORBIGNY 1850 Nodosaria spp. Dentalina communis D'ORBIGNY 1826 Dentalina integra (KÜBLER & ZWINGLI 1866) Dentalina jurensis TERQUEM 1870 Dentalina vetusta D'ORBIGNY 1850 Dentalina spp. Lenticulina acutiangulata (TERQUEM 1863) Lenticulina dorbignyi (ROEMER 1839) Lenticulina helios (TERQUEM 1870) Lenticulina muensteri (ROEMER 1839) Lenticulina polygonata (FRANKE 1936) Lenticulina varians Lenticulina spp. Planularia cordiformis (TERQUEM 1863) Palmula deslongchampsi (TERQUEM 1863) Citharina hechti (BARTENSTEIN 1937) Citharina sp. Reinholdella dreheri (BARTENSTEIN 1937) Reinholdella traubensis OHM 1967 Spirillina oolithica (SCHWAGER 1867) Eoguttulina bilocularis (TERQUEM 1864) 10 12 13 14 15 16 11 1 9 2 3 4 5 6 7 8 micro-fauna samples

Figure A-1. Occurrence of the Foraminifera in the section of the basal strata of the Opalinus-Ton at the ”Galerie de Reconnaissance” of the Mont Terri Rock Laboratory (modified after Bläsi et al. 1996). Colour coding of the facies types is the same as of Figures 3-1 and 3-2.

- 27 - Mont Terri Project, TR 2014-07

section Mont Terri Rock Laboratory (”Galerie de Reconnaissance”) coord.: 2’579’345 / 1’247’740 - 2’579’455/1’247’500

Toarcian Aalenian stage Late ? Early sub-stage Opalinus-Ton formation sensu BLÄSI et al. (1996) Aalensis ? Opalinum ammonite zone marls argillaceous and silty partly shales, marls argillaceous silty, and shales silty marls sandy argillac., & sandst. marly limest., sandy layers and lenses sandstone shales, sandy and sandstones marly shales silty lenses sandstone marls, and shales sandy beds limestone and sandstone marls, and shales sandy B to according Opalinus-Ton the of types facies LÄSI ta.(1991) al. et 14 15 16 10 12 13 11 1 4 5 6 7 8 9 2 3 micro-fauna apesites sample FE-Gallery HE-Niche Fault 98-Main Gallery MI-Niche/FM-C C- Drillcore BCS-5 yiehorizon pyrite horizon pyrite

macro-fauna eked(04 oiidatrBäie l (1991) al. et Bläsi after modified & (2014) Jaeggi Menkveld Waltschew, Hostettler, Reisdorf,

profile + + lithology 1024.5 meters tunnel 1000 940 920 980 960 900 890 880 869 850 835 820 800 781 (m)

fossils

Pleydellia leura Pleydellia costulata Pleydellia aalensis s.l. Pleydellia subcompta ? ammonites Pleydellia fluitans ? Pleydellia lotharingica Leioceras opalinum Bythocypris sp. Ostracoda Cytherella reticuloornata KNITTER 1983 Cytherella sp. (smooth) Cytherelloidea cadomensis BIZON 1960 Cytheropteron groissi KNITTER 1984 Cytheropterina alafastigata (FISCHER 1962) Cytheropterina cribra (FISCHER 1962) Metacytheropteron opalinum PLUMHOFF 1963 Monoceratina scrobiculata TRIEBEL & BART. 1938 Monoceratina stimulea (SCHWAGER 1866) Monoceratina striata TRIEBEL & BART. 1938 Monoceratina ungulina TRIEBEL & BART. 1938 Otocythere callosa TRIEBEL & KLINGLER 1959 Eucytherura liasssica BATE & COLEMAN 1975 Rutlandella transversiplicata BATE & COLEMAN 1975 Aaleniella reticulata KNITTER 1983 Liasina? cylindrica AINSWORTH 1986 Kinkelinella fischeri MALZ 1966 Kinkelinella sermoisensis (APOSTOLESCU 1959) Praeschuleridea gallemannica MALZ 1966 Praeschuleridea punctulata (PLUMHOFF 1963) Praeschuleridea ventriosa (PLUMHOFF 1963) Praeschuleridea sp. Aphelocythere kuhni TRIEBEL & KLINGLER 1959 Aphelocythere hamata PLUMHOFF 1963 Aphelocythere pygmaea PLUMHOFF 1963 Acrocythere pumila PLUMHOFF 1963 Paracypris sp. 1 (short) Paracypris sp. 2 (long) Paracypris spp. Pseudomacrocypris aequabilis (OERTLI 1959) Trachycythere sp. Gen. et sp. incert. 5 PLUMHOFF 1963 Ogmoconchella sp. Polycope discus FISCHER 1961 Polycope pelta FISCHER 1961 10 12 13 14 15 16 11 1 9 2 3 4 5 6 7 8 micro-fauna samples

Figure A-2. Occurrence of the Ostracoda in the section of the basal strata of the Opalinus-Ton at the ”Galerie de Reconnaissance” of the Mont Terri Rock Laboratory (modified after Bläsi et al. 1996). Colour coding of the facies types is the same as of Figures 3-1 and 3-2.

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