DÉPARTEMENT DE GÉOSCIENCES – SCIENCES DE LA TERRE
UNIVERSITÉ DE FRIBOURG (SUISSE)

High-frequency palaeoenvironmental changes
in mixed carbonate-siliciclastic sedimentary
systems (Late Oxfordian, Switzerland, France, and
southern Germany)

THÈSE

présentée à la Faculté des Sciences de l'Université de Fribourg (Suisse)
pour l'obtention du grade de *Doctor rerum naturalium*

Stéphanie VÉDRINE

de Paris, France

Thèse N° 1579

Multiprint SA, Fribourg, 2007
Acceptée par la Faculté des Sciences de l'Université de Fribourg (Suisse)
sur la proposition de :

<table><tr><td>Prof. André STRASSER</td><td>Université de Fribourg (Suisse)</td><td>Directeur</td></tr><tr><td>Dr. Bernard PITTET</td><td>Université de Lyon 1 (France)</td><td>Expert</td></tr><tr><td>Prof. John REIJMER</td><td>Université Libre d'Amsterdam (Pays-Bas)</td><td>Expert</td></tr><tr><td>Prof. Bernard GROBETY</td><td>Université de Fribourg (Suisse)</td><td>Président du jury</td></tr></table>

Fribourg, le 5 octobre 2007

<figure><img src="image_1.png" /></figure>

Le Doyen: Prof. Titus Jenny

<figure><img src="image_2.png" /></figure>

Directeur de thèse: Prof. André Strasser
"En science, la phrase la plus excitante à entendre, celle qui annonce de nouvelles découvertes, n'est pas «Eureka» mais «c'est drôle...»."

Isaac Asimov
<figure><img src="image_3.png" /></figure>
# TABLE OF CONTENTS

<table><tr><td>ABSTRACT</td><td>3</td></tr><tr><td>RÉSUMÉ</td><td>5</td></tr><tr><td>ZUSAMMENFASSUNG</td><td>7</td></tr><tr><td>ACKNOLEDGEMENTS</td><td>9</td></tr></table>

## 1 - INTRODUCTION

<table><tr><td>1.1 OBJECTIVES AND APPROACH</td><td>11</td></tr><tr><td>1.2 GENERAL CONTEXT</td><td>12</td></tr><tr><td>1.2.1 Geography and palaeogeography</td><td>12</td></tr><tr><td>1.2.2 Stratigraphy</td><td>14</td></tr><tr><td>1.2.3 Eustatic sea-level changes</td><td>17</td></tr><tr><td>1.2.4 Palaeoclimate</td><td>17</td></tr><tr><td>1.2.5 Global and regional tectonics</td><td>18</td></tr><tr><td>1.3 METHODS</td><td>18</td></tr></table>

## 2 - FACIES AND MICROFACIES ANALYSIS

<table><tr><td>2.1 INTRODUCTION</td><td>19</td></tr><tr><td>2.2 METHODOLOGY</td><td>19</td></tr><tr><td>2.3 SHALLOW PLATFORM FACIES</td><td>19</td></tr><tr><td>2.3.1 Non-skeletal carbonate elements</td><td>19</td></tr><tr><td>2.3.2 Skeletal carbonate elements</td><td>22</td></tr><tr><td>2.3.3 Carbonate mud</td><td>25</td></tr><tr><td>2.3.4 Other constituents</td><td>25</td></tr><tr><td>2.3.5 Sedimentary structures</td><td>26</td></tr><tr><td>2.3.6 Early diagenesis</td><td>27</td></tr><tr><td>2.4 DEEP PLATFORM AND BASIN FACIES</td><td>27</td></tr><tr><td>2.4.1 Non-skeletal elements</td><td>28</td></tr><tr><td>2.4.2 Skeletal elements</td><td>28</td></tr><tr><td>2.4.3 Others constituents</td><td>29</td></tr><tr><td>2.4.4 Carbonate mud</td><td>29</td></tr><tr><td>2.4.5 Reworked sediments</td><td>31</td></tr><tr><td>2.4.6 Sedimentary structures</td><td>31</td></tr><tr><td>2.5 MICROFACIES CLASSIFICATION</td><td>31</td></tr><tr><td>2.6 DEPOSITIONAL ENVIRONMENTS</td><td>32</td></tr><tr><td>2.6.1 Shallow platform</td><td>34</td></tr><tr><td>2.6.2 Deep platform and basin</td><td>34</td></tr></table>

## 3 - SEQUENCE ANALYSIS

<table><tr><td>3.1 INTRODUCTION</td><td>35</td></tr><tr><td>3.2 DEPOSITIONAL SEQUENCES</td><td>35</td></tr><tr><td>3.2.1 Definition</td><td>35</td></tr><tr><td>3.2.2 Formation of depositional sequences</td><td>36</td></tr><tr><td>3.2.3 Criteria for sequence identification and interpretation</td><td>36</td></tr><tr><td>3.3 SEQUENCE MODEL AND TERMINOLOGY APPLIED</td><td>39</td></tr><tr><td>3.3.1 Discontinuity surfaces and deposits</td><td>39</td></tr><tr><td>3.4 TYPES OF DEPOSITIONAL SEQUENCES IN THE STUDIED SECTIONS</td><td>40</td></tr><tr><td>3.5 HIERARCHY AND STACKING OF DEPOSITIONAL SEQUENCES</td><td>43</td></tr><tr><td>3.5.1 Superposition of relative sea-level changes</td><td>44</td></tr><tr><td>3.6 ALLOCYCLIC AND AUTOCYCLIC PROCESSES</td><td>45</td></tr></table>

## 4 - STUDIED SECTIONS

<table><tr><td>4.1 PLATFORM SECTIONS</td><td>47</td></tr><tr><td>4.1.1 Swiss Jura</td><td>47</td></tr><tr><td>4.1.2 Lorraine</td><td>72</td></tr><tr><td>4.2 DEEP PLATFORM SECTIONS</td><td>76</td></tr><tr><td>4.2.1 Haute-Marne</td><td>76</td></tr><tr><td>4.2.2 Swabian Jura</td><td>77</td></tr><tr><td>4.3 BASIN SECTIONS</td><td>82</td></tr><tr><td>4.3.1 South-East France</td><td>82</td></tr></table>

## 5 - STRATIGRAPHIC CORRELATIONS

<table><tr><td>5.1 METHODS OF CORRELATION</td><td>87</td></tr><tr><td>5.1.1 Biostratigraphy</td><td>87</td></tr><tr><td>5.1.2 Lithofacies</td><td>87</td></tr><tr><td>5.1.3 Discontinuity surfaces and depositional sequences</td><td>88</td></tr><tr><td>5.2 CORRELATION ON SHALLOW PLATFORM</td><td>88</td></tr><tr><td>5.3 CORRELATION FROM DEEP PLATFORM TO BASIN</td><td>89</td></tr><tr><td>5.4 PLATFORM-TO-BASIN CORRELATION</td><td>95</td></tr><tr><td>5.5 DISCUSSION</td><td>95</td></tr></table>
<table><tr><td>5.5.1</td><td>On the shallow platform</td><td>98</td></tr><tr><td>5.5.2</td><td>On the deep platform and in the basin</td><td>98</td></tr><tr><td>5.5.3</td><td>Platform-basin relationships: a conceptual model</td><td>98</td></tr><tr><td>5.5.4</td><td>Elementary sequences: a challenge</td><td>100</td></tr></table>

## 6 - CYCLOSTRATIGRAPHY

<table><tr><td>6.1</td><td>CONCEPTS AND METHODOLOGY</td><td>101</td></tr><tr><td>6.2</td><td>ADVANTAGES AND LIMITS</td><td>102</td></tr><tr><td>6.3</td><td>CYCLOSTRATIGRAPHIC TIME FRAME</td><td>102</td></tr><tr><td>6.4</td><td>COMPARISON WITH OTHER STUDIES</td><td>104</td></tr></table>

## 7 - HIGH-FREQUENCY PALAEOENVIRONMENTAL CHANGES ON THE SWISS JURA PLATFORM

<table><tr><td>7.1</td><td>PLATFORM EVOLUTION THROUGH TIME</td><td>105</td></tr><tr><td>7.2</td><td>ONCOIDS</td><td>111</td></tr><tr><td>7.2.1</td><td>Stratigraphic and spatial distribution</td><td>111</td></tr><tr><td>7.2.2</td><td>Controlling factors</td><td>111</td></tr><tr><td>7.3</td><td>BENTHIC FORAMINIFERA</td><td>118</td></tr><tr><td>7.3.1</td><td>Stratigraphic and spatial distribution</td><td>118</td></tr><tr><td>7.3.2</td><td>Controlling factors</td><td>122</td></tr></table>

## 8 - PALAEOCLIMATE

<table><tr><td>8.1</td><td>PALAEOCLIMATE DURING THE OXFORDIAN</td><td>125</td></tr><tr><td>8.1.1</td><td>Sedimentological indicators</td><td>127</td></tr><tr><td>8.1.2</td><td>Floral and faunal indicators</td><td>128</td></tr><tr><td>8.1.3</td><td>Geochemical indicators</td><td>128</td></tr><tr><td>8.2</td><td>CLAY MINERALS</td><td>128</td></tr><tr><td>8.2.1</td><td>Introduction</td><td>128</td></tr><tr><td>8.2.2</td><td>Material and analytical methods</td><td>130</td></tr><tr><td>8.2.3</td><td>Results and interpretations</td><td>131</td></tr></table>

<table><tr><td>8.3</td><td>CARBON AND OXYGEN ISOTOPES</td><td>139</td></tr><tr><td>8.3.1</td><td>Introduction</td><td>139</td></tr><tr><td>8.3.2</td><td>Material and analytical methods</td><td>140</td></tr><tr><td>8.3.3</td><td>Results and interpretations</td><td>140</td></tr><tr><td>8.4</td><td>CONCLUSIONS</td><td>143</td></tr></table>

## 9 - CONTROLLING FACTORS OF MIXED CARBONATE-SILICICLASTIC PLATFORMS

<table><tr><td>9.1</td><td>THE INTERPLAY OF TECTONICS, EUSTASY, AND CLIMATE</td><td>145</td></tr><tr><td>9.1.1</td><td>Tectonics</td><td>145</td></tr><tr><td>9.1.2</td><td>Eustasy</td><td>145</td></tr><tr><td>9.1.3</td><td>Climate</td><td>146</td></tr><tr><td>9.2</td><td>FACTORS CONTROLLING THE SEDIMENTATION OF THE SWISS JURA PLATFORM</td><td>147</td></tr></table>

## 10 - CONCLUSIONS AND OUTLOOK

<table><tr><td>REFERENCES</td><td>153</td></tr><tr><td>PLATES</td><td>169</td></tr><tr><td>ANNEX</td><td>205</td></tr><tr><td>CURRICULUM VITAE</td><td>215</td></tr></table>
ABSTRACT

The main goal of this study is to monitor the high-frequency palaeoenvironmental changes occurring during a marine transgression in mixed carbonate-siliciclastic sedimentary systems. Based on a well-established bio- and sequence-stratigraphic framework, a narrow time window in the Bimammatum Zone of the Late Oxfordian is investigated. Seven shallow platform sections (Swiss Jura, Lorraine), two deep platform sections (Haute-Marne, Swabian Jura), and one basin section (SE France) have been logged and analysed in detail. Then, the deposits have been interpreted in terms of palaeoenvironments and sequence- and cyclostratigraphy with a high time resolution. Facies and microfacies analysis allows to propose depositional models for the Swiss Jura platform and the other studied areas. The high-resolution sequence- and cyclostratigraphic analysis permits defining hierarchically stacked depositional sequences: medium-scale, small-scale, and elementary sequences, formed through orbitally controlled sea-level changes with periodicities of 400, 100, and 20 kyr, respectively.

This study investigates deposits comprised in the first half of a medium-scale sequence, corresponding to two small-scale sequences, each composed of five elementary sequences. In the shallow platform sections, an elementary sequence generally consists of one to four beds including more or less developed marl intervals. In the deep platform sections, an elementary sequence generally consists of one or two limestone beds with a more or less developed marl interval. In the basin section, an elementary sequence is defined by one marl-limestone couplet.

The good correlation of depositional sequences over long distances between the seven shallow platform sections and the similar number of elementary

sequences in all sections are valuable arguments that allocyclic processes must have been involved in the formation of these depositional sequences. Additional factors such as the position on the platform and the pre-existing morphology have to be considered in the formation of depositional sequences on a shallow platform. The presence of thickness variations at the scale of small-scale and elementary sequences reveals variable sediment accumulation rates, interpreted as resulting mainly from differential subsidence due to the activity of tectonic blocks. The relief created by tectonics therefore contributed significantly to the general facies distribution. Furthermore, the irregular distribution of siliciclastics can be explained by localized depressions, which were created by differential subsidence and served as depocenters.

The vertical and lateral distribution of facies, oncoids, and benthic foraminifera is investigated within the narrow high-resolution time framework established (20-kyr time resolution). Significant lateral facies changes are evidenced by comparison of time-equivalent small-scale and elementary sequences between the Swiss Jura sections. They reflect the dynamics and complexity of sedimentary systems where juxtaposed sub-environments evolved and shifted through space and time.

Four types of oncoids are defined based on surface morphology, configuration and composition of the cortex, and the encasing sediment. Micrite-dominated oncoids (types 1 and 2) have a smooth surface and *Bacinella-Lithocodium* oncoids (types 3 and 4) display a lobate surface. The stratigraphic and spatial distribution of these oncoid types shows a correlation with the sequence-stratigraphic evolution, and thus with relative sea-level fluctuations. At the scale of 100-kyr and 20-kyr sequences, type 1 and 2 oncoids are
preferentially found around sequence boundaries and
in transgressive deposits, while type 3 and 4 oncoids
are preferentially found around maximum floodings
and in highstand deposits. This implies that changes of
water energy and water depth were direct controlling
factors. Discrepancies in oncoid distribution point to
additional controlling factors. Platform morphology
defines the distribution and type of the lagoon where
the oncoids flourished. A low accumulation rate is
required for oncoid growth. Additionally, humidity
changes in the hinterland act on the terrigenous influx,
which modifies water transparency and trophic level
and thus plays a role in the biotic composition and
diversity in the oncoid cortex. This study demonstrates
that oncoids are valuable proxies for high-resolution
palaeoenvironmental and palaeoecological studies.

The benthic foraminifer assemblages of the Swiss
Jura sections include agglutinated forms (Textularids),
in a lower amount porcelaneous forms (Miliolids), and
locally hyaline foraminifera (only *Lenticulina*). The
distribution of porcelaneous and hyaline foraminifera
shows a correlation with the sequence-stratigraphic
evolution. Miliolids are preferentially found in the
highstand deposits of the elementary and/or small-scale
sequences. The hyaline foraminifera, rare in the studied
sections, are preferentially found in the transgressive
deposits of elementary sequences. Consequently, the
benthic foraminifera are indirectly linked to relative
sea-level (accommodation changes) and indirectly to
climate changes (sediment and nutrient input).

The distribution of the benthic foraminifer
*Mohlerina basiliensis* and *Bacinella-Lithocodium*
oncoids shows a strong correlation. The co-occurrence
of these two components suggests that they require
similar ecological conditions. In addition, the
successively later occurrence of *M. basiliensis* from
“distal” to “proximal” sections illustrates the stepwise
flooding of the platform and thus implies a dependence
on normal-marine conditions.

Clay-mineral assemblages and stable isotopes give
palaeoenvironmental information on the scale of 400
kyr and 100 kyr but a higher time resolution is difficult
to obtain probably due to time averaging by sedimen-
tological and/or diagenetic processes. The medium-
scale trends of the kaolinite content and K/I ratio
between all sections from shallow platform to basin
show a correlation, particularly around the medium-
scale SB Ox6+ and MF Ox6+. Clay mineral distribu-
tion was not only controlled by climate changes but
also by relative sea-level changes and platform mor-
phology. Carbon and oxygen isotope analysis shows
minor fluctuations (±1‰) that probably reflect varia-
tions of local environmental conditions (e.g., salinity,
temperature, trophic level).

***
# RÉSUMÉ

Le but principal de cette étude est d'examiner les changements paléoenvironnementaux de haute fréquence survenant durant une transgression marine dans des systèmes sédimentaires mixtes silico-carbonatés. Basée sur un cadre biostratigraphique et séquentiel bien établi, une fenêtre de temps précise dans la zone à Bimammatum de l'Oxfordien supérieur est étudiée. Sept coupes de plate-forme peu profonde (Jura suisse, Lorraine), deux coupes de plate-forme profonde (Haute-Marne, Jura souabe) et une coupe de bassin (SE France) ont été levées et analysées en détail. Les dépôts ont ensuite été interprétés en terme de paléoenvironnments et de stratigraphie séquentielle et cyclostratigraphie avec une haute résolution dans le temps. L'analyse des faciès et microfaciès permet de proposer des modèles de dépôt pour la plate-forme du Jura Suisse et les autres zones d'étude. L'analyse séquentielle et cyclostratigraphique de haute résolution permet de définir l'empilement hiérarchique des séquences de dépôt (séquences à moyen terme, à court terme et élémentaires) formées par les fluctuations du niveau marin avec des périodicités de 400, 100, et 20 ka respectivement, contrôlées par les cycles orbitaux.

Cette étude examine les dépôts situés dans la première moitié d'une séquence à moyen terme, correspondant à deux séquences à court terme, chacune composée de cinq séquences élémentaires. Dans les coupes de plate-forme peu profonde, une séquence élémentaire consiste généralement en un à quatre bancs incluant des intervalles marneux plus ou moins développés. Dans les coupes de plate-forme profonde, une séquence élémentaire consiste généralement en un à deux bancs calcaires avec un intervalle marneux plus ou moins développé. Dans la coupe de bassin, une séquence élémentaire est définie par un banc calcaire et un intervalle marneux.

La bonne corrélation des séquences de dépôt sur de longues distances entre les sept coupes de plate-forme peu profonde ainsi que le nombre similaire de séquences élémentaires dans toutes les coupes sont des arguments valables pour montrer que des processus allocycliques doivent avoir joué un rôle dans la formation de ces séquences de dépôt. Des facteurs additionnels tels que la position sur la plate-forme et la morphologie pré-existante doivent être considérées dans la formation des séquences sur une plate-forme peu profonde. La présence de variations d'épaisseurs à l'échelle des séquences élémentaires et à court terme révèle des taux d'accumulation sédimentaire variables, interprétés comme résultant principalement de la subsidence différentielle due à l'activité tectonique de blocs. Le relief créé par la tectonique contribue aussi significativement à la distribution générale des faciès. De plus, la distribution irrégulière des siliciclastiques peut être expliquée par des dépressions locales, créées par la subsidence différentielle, et servant de dépôt-centres.

La distribution verticale et horizontale des faciès, des oncoïdes et des foraminifères benthiques est étudiée dans le cadre de temps haute résolution établi dans ce travail (résolution temporelle de 20 ka). Des changements de faciès latéraux sont mis en évidence par comparaison des séquences élémentaires et à court terme entre les coupes du Jura suisse. Ils reflètent la dynamique et complexité des systèmes sédimentaires où des environnements juxtaposés évoluent et se modifient dans le temps et dans l'espace.

Quatre types d'oncoïdes sont définis à partir de la morphologie de surface, la configuration et composition du cortex et le sédiment encaissant. Les oncoïdes dont le cortex est dominé par la micrite (types 1 et 2) ont une surface lisse tandis que les oncoïdes
riches en *Bacinella-Lithocodium* (types 3 et 4) ont une surface lobée. La distribution stratigraphique et spatiale de ces types d'oncoïdes montre une corrélation avec l'évolution séquentielle et donc les fluctuations du niveau marin relatif. A l'échelle des séquences élémentaires et à court terme, les oncoïdes de type 1 et 2 sont préférentiellement trouvées autour des limites de séquence et dans les cortèges de dépôt transgressifs tandis que les oncoïdes de type 3 et 4 sont préférentiellement trouvés autour des maxima d'inondation et dans les cortèges de haut niveau marin. Cela implique que des changements d'énergie et de profondeur d'eau ont été des facteurs contrôlant directs. Des disparités dans la distribution des oncoïdes suggèrent des facteurs contrôlant additionnels. La morphologie de la plate-forme définit la distribution et le type de lagon où les oncoïdes se développent. Un faible taux d'accumulation sédimentaire est requis pour la croissance des oncoïdes. Des changements d'humidité dans l'arrière-pays agissent sur l'influx terrigène ce qui modifie la transparence et le niveau trophique de l'eau et joue donc un rôle dans la composition et la diversité biotique dans le cortex des oncoïdes. Cette étude démontre que les oncoïdes sont des indicateurs valables pour des études paléoenvironnementales et paléoécologiques de haute résolution.

Les assemblages de foraminifères benthiques des coupes du Jura suisse comprennent des formes agglutinées (Textularidés), dans une plus faible proportion des formes porcelanées (Miliolidés) et localement des foraminifères hyalins (seulement *Lenticulina*). La distribution des foraminifères porcelanés et hyalins montre une corrélation avec l'évolution séquentielle. Les Miliolidés sont préférentiellement trouvés dans les cortèges de dépôt de haut niveau marin de certaines séquences élémentaires et/ou à court terme. Les foraminifères hyalins, rare dans les coupes étudiées, sont préférentiellement trouvés dans les dépôts transgressifs de certaines séquences élémentaires. Par conséquence, les foraminifères benthiques sont indirectement liés aux changements du niveau marin relatif (changements d'accommodation) ainsi qu'aux changements climatiques (apports sédimentaires et de nutriments).

La distribution du foraminifère benthique *Mohlerina basiliensis* et des oncoïdes riches en *Bacinella-Lithocodium* montre une forte corrélation. La co-existence de ces deux composants suggère qu'ils requièrent des conditions écologiques similaires. De plus, l'apparition de plus en plus tardive des *M. basiliensis* des coupes distales aux coupes proximales illustre l'inondation par étape de la plate-forme et implique alors une dépendance aux conditions marines.

Les assemblages des minéraux argileux et les isotopes stables donnent des informations paléoenvironnementales à l'échelle des séquences de 400 ka et 100 ka; une plus haute résolution est difficile à obtenir probablement à cause de l'homogénéisation du temps par des processus sédimentologiques et/ou diagénétiques. Les tendances à moyen terme du contenu en kaolinite et du rapport kaolinite/illite entre toutes les coupes, de la plate-forme peu profonde au bassin, montre une corrélation particulièrement autour de la limite de séquence SB Ox6+ et du maximum d'inondation à moyen terme MF Ox6+. La distribution des minéraux argileux n'était pas seulement contrôlée par des changements climatiques mais aussi par des changements du niveau marin relatif et de la morphologie de la plate-forme. L'analyse des isotopes de l'oxygène et du carbone montre des fluctuations mineures (± 1 ‰) qui reflètent probablement des variations de conditions environnementales locales (par exemple, la salinité, la température et/ou le niveau trophique).

***
# ZUSAMMENFASSUNG

Das Ziel dieser Studie ist es, hochfrequente Umweltveränderungen nachzuzeichnen, welche ein gemischt siliziklastisch-karbonatisches Sedimentsystem während einer marinen Transgression beeinflussten. Basierend auf einem gut etablierten bio- und sequenzstratigraphischen Rahmen wird ein enges Zeitfenster in der Bimammatum Zone des Späten Oxfordians untersucht. Sieben Profile der flachen Plattform (Schweizer Jura, Lorraine), zwei Profile der tiefen Plattform (Haute-Marne, Schwäbischer Jura) und ein Beckenprofil (Südost-Frankreich) wurden im Detail aufgenommen und analysiert. Dann wurden die Sedimente hinsichtlich Ablagerungsräume sowie Sequenz- und Zyklostratigraphie mit einer hohen Zeitauflösung interpretiert. Die Fazies- und Mikrofaziesanalysen erlauben es, Ablagerungsmodelle für die Schweizer Jura Plattform und die anderen untersuchten Gebiete vorzuschlagen. Die hochauflösende sequenz- und zyklostratigraphische Analyse führt zur Definition hierarchisch gestapelter Ablagerungssequenzen (medium-scale, small-scale und Elementarsequenzen), welche orbital kontrollierten Meeresspiegelschwankungen mit Periodizitäten von jeweils 400, 100 und 20 ka entsprechen.

Diese Studie untersucht Ablagerungen, welche die ersten Hälfte einer medium-scale Sequenz aufbauen und zwei small-scale Sequenzen entsprechen, die jeweils aus fünf Elementarsequenzen bestehen. In den Profilen der flachen Plattform bestehen die Elementarsequenzen generell aus ein bis vier Bänken einschliesslich mehr oder weniger entwickelter Mergelintervalle. In den Profilen der tiefen Plattform bestehen Elementarsequenzen aus ein oder zwei Kalkbänken mit einem mehr oder weniger ausgebildeten Mergelhorizont. Im Beckenprofil ist die Elementarsequenz durch ein Kalk-Mergel-Paar definiert.

Die gute Korrelation der Ablagerungssequenzen über grosse Distanzen zwischen den sieben Profilen der flachen Plattform und der ähnlichen Anzahl elementarer Sequenzen in allen Profilen sind gute Argumente dafür, dass allozyklische Prozesse bei der Bildung dieser Sequenzen beteiligt gewesen sein müssen. Andere Faktoren wie die Position auf der Plattform und die vorgegebene Plattform-Morphologie müssen jedoch ebenfalls in Betracht gezogen werden. Mächtigkeitsschwankungen innerhalb der small-scale und Elementarsequenzen deuten auf variable Sedimentationsraten hin. Diese werden hauptsächlich als das Resultat der differenziellen Subsidenz tektonisch aktiver Blöcke interpretiert. Das durch die Tektonik entstandene Relief hat demnach signifikant zur generellen Faziesverteilung beigetragen. Ebenso kann die unregelmässige Verteilung der Siliziklastika durch lokale Depressionen erklärt werden, die durch differentielle Subsidenz entstanden sind und als Sedimentationszentren dienten.

Die vertikale und laterale Verteilung von Fazies, Onkoiden und benthischen Foraminiferen wird innerhalb des etablierten hochauflösenden Zeitrahmens untersucht (20 ka Zeitauflösung). Signifikante laterale Fazieswechsel können im Vergleich mit zeitäquivalenten small-scale und Elementarsequenzen zwischen den Profilen im Schweizer Jura nachgewiesen werden. Sie reflektieren die Dynamik und Komplexität von sedimentären Systemen, wo sich verschiedene Ablagerungsräume nebeneinander entwickelten und sich in Zeit und Raum verlagerten.

Vier Typen von Onkoiden werden definiert, basierend auf Oberflächenmorphologie, Konfiguration und Zusammensetzung des Kortex und dem umgebenden Sediment. Mikrit-dominierte Onkoide (Typen 1 und 2) haben eine glatte Oberfläche, Bacinella-
Lithocodium Onkoide (Typen 3 und 4) zeigen eine lappige Oberfläche. Die stratigraphische und räumliche Verteilung dieser Onkoidtypen zeigt eine Korrelation mit der sequenzstratigraphischen Entwicklung und somit mit relativen Meeresspiegelschwankungen. Bei den 100 ka und 20 ka Sequenzen werden Onkoide der Typen 1 und 2 vorzugsweise an Sequenzgrenzen und in transgressiven Ablagerungen gefunden, während Onkoide der Typen 3 und 4 den schnellsten Meeresspiegelanstieg und Hochstandsablagerungen charakterisieren. Dies impliziert dass Änderungen der Wasserenergie und Wassertiefe direkt kontrollierende Faktoren waren. Diskrepanzen in der Onkoidverteilung weisen auf zusätzliche kontrollierende Faktoren hin. Die Plattformmorphologie definiert die Verteilung und die Art der Lagunen, wo Onkoide gedeihen. Eine langsame Sedimentationsrate ist für die Onkoidbildung erforderlich. Zusätzlich beeinflussen Änderungen der Niederschlags im Hinterland den Terrigeneintrag, der die Wassertransparenz und das trophische Niveau modifiziert und so für die biotische Zusammensetzung und Diversität im Onkoidkortex eine Rolle spielt. Diese Arbeit zeigt, dass Onkoide wertvolle Indikatoren für hochauflösende Paläoumwelt- und Paläoökologiestudien sind.

Die Foraminiferen-Vergesellschaftungen in den Profilen des Schweizer Jura umfassen agglutinierte Formen (Textulariden), weniger häufig porzellanschalige Formen (Milioliden) und lokal hyaline Foraminiferen (ausschliesslich *Lenticulina*). Die Verteilung der porzellanschaligen und hyalinen Foraminiferen zeigt eine Korrelation mit der sequenzstratigraphischen Entwicklung. Milioliden werden vorzugsweise in Hochstandsablagerungen der elementaren und small-scale Sequenzen gefunden. Die hyalinen Foraminiferen, die in den untersuchten Profilen selten sind, werden bevorzugt in den transgressiven Ablagerungen von Elementarsequenzen gefunden. Folglich besteht ein indirekter Zusammenhang zwischen den benthischen Foraminiferen und den relativen Meeresspiegelschwankungen sowie den Klimawechseln (Sediment- und Nährstoffeintrag).

Die Verteilungen der benthischen Foraminifere *Mohlerina basiliensis* und der *Bacinella-Lithocodium* Onkoide zeigen eine starke Korrelation. Das gemeinsame Auftreten dieser zwei Komponenten deutet darauf hin, dass sie ähnliche ökologische Bedingungen brauchten. Zusätzlich illustriert das sukzessiv spätere Auftreten von *M. basiliensis* von „distal“ nach „proximal“ die schrittweise Überflutung der Plattform und impliziert so eine Abhängigkeit von normal-marinen Bedingungen.

Tonmineral-Vergesellschaftungen und stabile Isotope informieren über die Umweltbedingungen für die 400 ka und 100 ka Sequenzen; eine höhere Auflösung ist auf Grund von Zeitmittlung durch sedimentologische und/oder diagenetische Prozesse schwierig zu erreichen. Die medium-scale Trends des Gehalts an Kaolinit und des K/I Verhältnisses zwischen allen Profilen von der seichten Plattform bis ins Becken zeigen eine Korrelation, vor allem an der medium-scale Sequenzgrenze SB Ox6+ und beim schnellsten Meeresspiegelanstieg MF Ox6+. Die Tonmineralverteilung wurde demnach nicht nur durch Klimaänderungen sondern auch durch relative Meeresspiegelschwankungen und Plattformmorphologie kontrolliert. Kohlenstoff- und Sauerstoffisotopenanalysen zeigen geringfügige Schwankungen (±1%), welche wahrscheinlich Variationen in den lokalen Umweltbedingungen reflektieren (Salinität, Temperatur, Nährstoffeintrag).

* * *
ACKNOWLEDGEMENTS

This work would not have been possible without
the support of many colleagues, friends, and family to
whom I am truly thankful.

First of all, I would like to thank my thesis director (my “Doktorvater”), Prof. André STRASSER, for his exceptional human and professional qualities. As he warned me the first day, a thesis is an adventure. However, his kindness, his unbelievable availability, his eternal good mood, and his (Swiss German) rigor without a bit of stress made of this Swiss “adventure” the best experience of my life. He offered me the unique opportunity to participate in scientific congresses all around the world and to discover some modern carbonate platforms by plane, boat, kayak, swim, and/or dive. I thank him very much for his confidence from the start until now. Thank you very very much André!

I further thank the experts, Bernard PITTET (University of Lyon 1) and John REJMER (Free University Amsterdam) for taking time to read the manuscript and having accepted to participate in the jury. Thank you, Bernard PITTET, who gave me the location of the Balingen-Tieringen section in southern Germany.

I would like to thank Prof. Christian CARON, the institute's director, and his wife, Prof. Michèle CARON, micropalaeontologist, who continuously have taken care of me, as one of their grand-daughters, since my first day in Fribourg. I will never forget their extraordinary kindness and hospitality as well as their confidence when they lent me their private car for my fieldwork in the Swiss Jura Mountains, only one month after I passed my driving licence. Thanks to their enthusiasm and generosity, I also could take advantage of the winter pleasures (skiing) in the Préalpes ski stations. Christian and Michèle also took

care of my working conditions: first class office (high-
tech computer, optical and binocular microscopes...),
equality with the other PhD students and with some
flowers from Michele's garden. I will never forget all
the things that you did and still do for me. Thank you
very very much Michèle and Christian!

Many thanks go to Jonas TRESCH, my office
neighbour. He supported me during the different steps
of the thesis. I thank him very much for his kindness,
his peaceful attitude, his sense of humour, his help in
the field, and his availability for answering my various
questions and for having helped to put a name on
strange things. I could never have dreamed of a better
colleague! Thank you very much Jonas!

I would also like to thank Elias SAMANKASSOU for his kindness, his listening, and his patience during all these years. His confidence during the practical and block courses allowed me to better appreciate the teaching but still not enough for... Thanks to Silvia SPEZZAFERRI for all the lunch discussions on life and science as well as for having given me the opportunity to participate in the EGU 2007. I hope that in few months we can reveal to the entire world the phylogeny of *Mohlerina basiliensis*. Thanks to Jon MOSAR, for his dynamic attitude that always impressed me. Thanks to Jean-Pierre BERGER for his continuous good humour.

Thanks to Wolfgang HUG, who highlighted
the opening questions and found a new section to
investigate, and Neils RAMEIL, who advised me a lot at
the beginning on how to manage and finish a thesis.

Without the technical staff, Patrick DIETSCHE,
Daniel CUENNET, and Jean-Paul BOURQUI, no scientific
results would have been possible. I really thank
them for their patience and precision. Thanks also
to Christophe NEURURER for the sample preparation for SEM analyses on the Swiss Jura oncoids, some benthic foraminifera, and green grains as well as his thirst of “why doing this”, which clarified my ideas. Thank you also to Nicole BRUEGGER, for her help with the administrative tasks.

I would like to thank Thierry ADATTE and his collaborators (University of Neuchâtel) for the measurements, determinations and interpretations of the clay minerals, and Laszlo KOCISI and Torsten VENNEMANN (University of Lausanne) for the measurements of the stable isotopes.

Thanks to M. VAN TROOST, director of the Révoi quarry (Pagny-sur-Meuse), exploited by the NOVACARB society, who gave me permission to work in the quarry and who took care of our security.

I also thank Bernard GROBÉTY for having accepted to be the president of the jury and for his good humour.

Thanks to all the scientific staff as well as the PhD and master students: Vincent SERNEELS, Luc, Pierre, Noémie, Daniel (Marty), Richard, Claudius, Katja, Martin, Thibault, Giordana, Stephan, Laureline, Pia, Maëlle, Sophie, Elie, Paola, Reto... and good luck for the future!

Special thanks to Noémie STIENNE, for her dynamic style, her good humour, and her help for the re-rent of my flat and other services. I wish you all the best for the future. Thanks to Richard WAITE for the translation of the abstract into the German Zusammenfassung. The Belize trip with André, Daniel, Noémie, and Richard was an unforgettable scientific and human experience...Keep the planet clean! Lands and oceans!

The financial support by the Swiss National Science Foundation (grants 20-67736.02 and 20-109214.05) is gratefully acknowledged.

I would like to thank my good friends: Annabel, Millena, Marie, Joseph, Caroline, François, who over the distance and with the help of the msn messenger are still here!

I deeply thank my family: my parents, Yves and Eliane, my brother, Eric, and his wife, Valérie, for having accepted my choices and having endlessly supported me during all my studies.

And last but not least, thank you, Hugo, for your help and advises that were very precious for me. You always supported and encouraged me in spite of the distance. Thank you with all my heart.

***
# 1 - INTRODUCTION

Modern shallow-water carbonate systems commonly display a highly complex pattern of juxtaposed depositional environments with a patchy facies distribution (facies mosaics: GISCHLER & LOMANDO 1999; RIEGL & PILLER 1999; RANKEY 2002). Considering the complexity of today's shallow-water carbonate systems it must be expected that also the sedimentary record of such systems is complex. There is no reason to believe that Phanerozoic carbonate systems were less complex than modern ones, although plate-tectonic configuration, climatic conditions, amplitude of sea-level changes, sea-water geochemistry, and the evolution of the participating organisms certainly preclude a direct comparison. Complexity is added by the fact that only a part of the history is recorded. Information is missing due to non-deposition and/or erosion, only a part of the organisms participating in the ecosystems is fossilized, and diagenesis may create a preservational bias. On ancient carbonate platforms, the reconstruction of lateral facies distribution is often hampered not only by discontinuous outcrop but also by lack of sufficiently high time resolution. This case study proposes a way to improve the temporal and spatial resolution for the interpretation of carbonate rocks. To obtain a sedimentary record as complete as possible, a period of transgression was studied where the sediment preservation potential is best because of a high accommodation gain.

A marine transgression is the flooding of land by the sea and is caused by subsidence and/or sea-level rise. Today many coasts experience transgression due to sea-level rise resulting from thermal expansion of the ocean water and from melting of continental ice (ICCP 2001). It is therefore appropriate to study transgressions in the geological past and to evaluate the effects they can have on depositional environments

and ecosystems. Shallow carbonate platform deposits were chosen for investigation due to their high sensitivity to sea-level and climate changes.

In the last 10 years, the Fribourg research group investigated the Jura platform and other regions with high-resolution sequence- and cyclostratigraphy (e.g., STRASSER et al. 1999). A time interval of about 20 myr from the Oxfordian to the Valanginian has been investigated by several PhD studies (PASQUIER 1995; PITTET 1996; HILLGÄRTNER 1999; DUPRAZ 1999; COLOMBIÉ 2002; HUG 2003; RAMEIL 2005; TRESCH 2007). This study uses the well-defined biostratigraphic and sequence-stratigraphic framework established by PITTET (1996), GYGI et al. (1998), DUPRAZ (1999), and HUG (2003) for the Oxfordian interval and focuses on a narrow time window (Fig. 1.1).

## 1.1 OBJECTIVES AND APPROACH

This study aims to identify, within a narrow and high-resolution time framework (20-kyr time resolution), high-frequency palaeoenvironmental changes occurring on the shallow carbonate platform of the northern margin of the Tethys Ocean during the early Late Oxfordian. The methodology is based on (1) a facies and microfacies analysis that allows for the interpretation of depositional environments and (2) a high-resolution sequence-stratigraphic and cyclostratigraphic analysis that allows defining depositional sequences, which formed through sea-level changes that were induced by the 400-, 100-, and 20-kyr orbital cycles. Comparisons of sections from the shallow platform with deeper-marine sections will help to evaluate the expression and importance of controlling factors (e.g., sea level, climate, tectonics).
<figure><img src="image_4.png" /><figcaption>**Fig. 1.1** - Stratigraphic ranges of studies carried out by the Fribourg sequence- and cyclostratigraphic working group in the Jura Mountains. Numerical ages from GRADSTEIN et al. (1995).</figcaption></figure>

The main objective is to investigate the evolution of the Late Oxfordian transgression from shallow platform to basin environments with high time resolution. To reach this goal, the following steps are realized:

* Logging the field outcrops at a cm-scale and performing facies and microfacies analysis in order to interpret them in terms of depositional environments and to develop a facies model for the different palaeogeographic settings (Chapter 2).

* Interpretation of the hierarchical stacking pattern and facies evolution in terms of sequence stratigraphy (Chaps 3 and 4).

* High-resolution correlations of all sections based on biostratigraphy and sequence stratigraphy (Chap. 5).

* Identifying the controlling factors of sea-level changes and establishing a cyclostratigraphic framework (Chap. 6).

* Interpreting high-frequency palaeoenvironmental and palaeoecological changes with a 20-kyr time resolution (Chap. 7). Improving the understanding of the platform dynamics and the marine transgression by evaluating the importance of the controlling factors (Chaps 7, 8 and 9).

## 1.2 GENERAL CONTEXT

### 1.2.1 Geography and palaeogeography

The studied outcrops are located in northern Switzerland, in the east and southeast of France, and in southern Germany (Fig. 1.2a). Six carbonate platform sections were analysed in the Swiss Jura Mountains (Fig. 1.2b). Two supplementary platform sections were investigated in France; in Lorraine west of Nancy, and in Haute-Marne north of Dijon (Fig. 1.2c). One deep-shelf section was analysed in the Swabian Jura south of Balingen (Germany), and one basin section was studied in SE France near Castellane (France; Fig. 1.2d).

During the Late Oxfordian, the study area consisted of a patchwork of low-relief islands in a shallow epicontinental sea at the northern (passive) margin of the Alpine Tethys (THIERRY et al. 2000). Erosion of crystalline massifs to the north (i.e. Bohemian Massif, Rhenish Massif, Massif Central, London-Brabant Massif; Fig. 1.3) furnished siliciclastics to the Paris Basin and to the northern Tethyan platform. The study area ranged from 24°N to 35°N palaeolatitude (DERCOURT et al. 1993; THIERRY et al. 2000).

The **Swiss Jura platform** corresponded to a shallow-water carbonate platform with tidal flats, oncoid-rich lagoons, oolitic bars, and coral patch-reefs. Synsedimentary tectonics structured the platform into highs and depressions that shifted their position through time (ALLENBACH 2001).

The **Lorraine carbonate platform** was probably connected to the SE to the Jura platform, to the NW to the Paris Basin, and sloped from the London-Brabant landmass located about 100 km to the north (ZIEGLER 1990; CECCA et al. 1993). It was bounded by the Vittel fault to the south (HUMBERT 1971; MARCHAND & MENOT 1980; GEISTER & LATHUILIÈRE 1991; COLLIN & COURVILLE 2000). A tectonic tilt of the platform to the north is observed in the Late Oxfordian (CARPENTIER 2004). The platform evolved from a shallow marine carbonate-dominated platform in the Middle Oxfordian to a mixed siliciclastic-carbonate platform in the Late Oxfordian (OLIVIER et al. 2004a; CARPENTIER 2004).

The **Haute-Marne** was located between the Burgundy platform and the Lorraine platform. This area corresponded to a deeper-water platform (“distal platform”; LORIN et al. 2004) sloping to the Paris Basin. In the Late Oxfordian, sedimentation
was characterized by thick marl deposits (Marnes de Latrecey) and limestones (Calcaires de Latrecey; COURVILLE & VILLIER 2003).

**The Swabian Jura deep shelf** was located about 50 km to the east of the Jura platform (MEYER & SCHMIDT-KALER 1989, 1990; GYGI 1990). Located in

the deeper part (estimated palaeobathymetry of 100-200 m; PITTET & MATTIOLI 2002; OLIVIER et al. 2004b) of a gently inclined carbonate ramp marginal to the Tethys Ocean, this deep platform was characterized by hemipelagic sedimentation with siliceous-sponge and microbialite bioherms (Swabian facies; e.g., WAGENPLAST 1972; GWINNER 1976; KEUPP et al. 1990;

<figure><img src="image_5.png" /><figcaption>**Fig. 1.2** - Geographical location of the studied sections (a) in central Europe; (b) in the Swiss Jura Mountains; (c) in eastern France and southern Germany; (d) in the southeast of France.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**Fig. 1.3** - Palaeogeography of the northern margin of the Alpine Tethys during the Late Oxfordian (modified from MEYER & SCHMIDT-KALER 1989; ZIEGLER 1988; THIERRY et al. 2000). The studied areas are in bold.</figcaption></figure>

LEINFELDER et al. 1994; OLIVIER et al. 2004b). Also considered as an intraplatform basin, the Swabian Jura is confined by the Swiss Jura platform to the SW and by the Franconian (Bohemian) platform to the NE. It opened southwards towards the “deep” Helvetic basin.

The **SE France basin** (or Dauphinois Basin) and the Helvetic rim basins represent a branch of the Alpine Tethys, which was bordered to the north by the Jura platform and to the south and southwest by the Corbières-Provence platform. During the Late Jurassic, the SE France Basin was a passive margin basin characterized by synsedimentary tectonics and horst and graben structures (DEBRAND-PASSARD et al. 1984). Throughout the Late Jurassic and Early Cretaceous, this area was characterized by hemipelagic to pelagic sedimentation with instability phases generating gravity deposits with biodetrital influx from the surrounding platforms.

### 1.2.2 Stratigraphy

The studied interval comprises platform and basin deposits of the beginning of the Bimammatum zone (Semimammatum and Berrense ammonite subzones) in the Late Oxfordian (Figs 1.4 and 1.5).

## Lithostratigraphy and biostratigraphy

Facies and lithostratigraphy of the Middle and Late Oxfordian deposits from **northern Switzerland** have been investigated extensively by, e.g., ZIEGLER (1962), BOLLIGER & BURRI (1967, 1970), GYGI (1969, 1992, 1995), and GYGI & PERSOZ (1986). GYGI (2000a, b) gives an excellent summary of the history of lithostratigraphic classification of northern Switzerland. In the Swiss Jura Mountains, the studied interval concerns the very top of the Röschenz Member and most of the Hauptmumienbank Member and its lateral equivalent, the Steinebach Member, which all belong to the middle part of the Vellerat Formation (Fig. 1.4). The Röschenz Member is composed of marls and thin limestone beds whereas the Hauptmumienbank and Steinebach members consist of relatively massive limestone beds. The Hauptmumienbank (“main mummy bed”, STEINMANN 1880) Member has a typical oncolitic facies while the Steinebach Member features oolites and coral boundstones.

The biostratigraphic framework for the Oxfordian and Kimmeridgian in the Jura Mountains was established using ammonites from platform and basin deposits (ENAY et al. 1988; GYGI 1995). Dating of the platform deposits was improved by mineralostratigraphic correlations (PERSOZ & REMANE 1976; GYGI & PERSOZ 1986). These authors used the vertical distribution of kaolinite and detrital quartz to correlate ammonite-rich basin sections with biostratigraphically less well constrained sections on the platform. The Hauptmumienbank and Steinebach members are dated of the Hypselum subzone, equivalent to the Semimammatum and Berrense subzones placed at the beginning of the Bimammatum zone (GYGI & PERSOZ 1986, GYGI 2000b; Fig. 1.4).

In **Lorraine**, the lithostratigraphy of Middle to Late Oxfordian deposits has been studied by HUMBERT (1971), MARCHAND & MENOT (1980), and CARPENTIER (2004). In this study, the *Calcaires à polypiers de Pagny* (CPP), the *Oolithe de Saucourt inférieure* (OSI), and the *Marnes à huîtres de Pagny* (MHP) members are examined (Fig. 1.4). The *Calcaires à polypiers de Pagny* are characterized by grey limestones (mudstones-wackestones to oyster lumachella packstones-grainstones) intercalated with dark marls. Laterally and locally, these limestones pass into coral and/or bivalve patch-reefs. The total thickness of this member varies between 3 and 10 metres. The *Oolithe de Saucourt* comprises all the
<figure><img src="image_7.png" /><figcaption>**Fig. 1.4** - Bio- and lithostratigraphy for the studied interval of all the sections from shallow platform to basin. Ammonite biostratigraphy and sequence stratigraphy from HARDENBOL et al. (1998). Lithostratigraphy of the Swiss Jura after GYGI (1995), Lorraine after CARPENTIER (2004) and CARPENTIER et al. (2006), Haute-Marne after COURVILLE & VILLIER (2003), Swabian Jura after SCHWEIGERT (1995a), and SE France according to ENAY et al. (1984).</figcaption></figure>

oolitic facies intercalated between the different marly facies at the base of the Late Oxfordian present in the Marne Valley area. This formation can be subdivided into three members, which are laterally continuous over most of the Lorraine platform. The *Oolithe de Saucourt inférieure* designates the first oolitic and oncolitic facies, which cover the *Calcaires à polypiers de Pagny*. The *Marnes à huîtres de Pagny* correspond to dark marly facies (slightly silty), which overlie the *Oolithe de Saucourt inférieure*. They pass laterally into more or less argillaceous carbonate facies (more or less rich in oysters or lumachella). The third member is the *Oolithe de Saucourt supérieure*, which is rich in ooids and oncoids.

The biostratigraphy of the studied deposits is based on the recent discovery of two ammonites, one at the base and the other at the top of the *Calcaires à polypiers de Pagny* (CARPENTIER 2004). They correspond, respectively, to the species *Perisphinctes (Dichotomoceras) bifurcatoïdes* and *Perisphinctes*

(*Perisphinctes hallatus* (determination of R. Enay) and indicate the Bifurcatus and the Bimammatum zones. Consequently, the Bifurcatus-Bimammatum limit is positioned within the *Calcaires à polypiers de Pagny*.

In **Haute-Marne**, the studied interval concerns the member of the *Calcaires de Latrecey*. This member is characterized by homogeneous carbonate facies with quite poor and poorly diversified benthic macrofauna and corresponds to outer, deep-water platform environments (Fig. 1.4; COURVILLE & VILLIER 2003). Ammonites indicate that the *Calcaires de Latrecey* belong to the Semimammatum subzone and probably reach into the Berrense subzone (COURVILLE & VILLIER 2003).

The **western Swabian Jura** (Swabian Alb, southern Germany) exposes deeper-water carbonate facies (i.e., marl-limestone alternations and siliceous
sponges) of the upper part of the Impressa-Mergel Formation (Fig. 1.4; SCHWEIGERT 1995a), also described as the Malm-alpha Formation (QUENSTEDT 1843). Ammonite biostratigraphy indicates the Bifurcatus and Bimammatum ammonite zones (SCHWEIGERT 1995a, b; SCHWEIGERT & CALLOMON 1997).

In the **SE France basin**, the studied interval displays marl-limestone alternations belonging to the *Marnes et calcaires grumeleux* and the *Calcaires lités ou massifs* (ENAY et al. 1984), which are dated by ammonites and dinocysts of the Bifurcatus and Bimammatum zones (ATROPS 1982, 1984; Fig. 1.4).

## Sequence- and cyclostratigraphy

This study examines platform and basin deposits that lie between the third-order sequence boundaries (SB) Ox6 and Ox7 defined by HARDENBOL et al. (1998) in European basins. Between Ox6 and Ox7, an additional major sequence boundary (SB Ox6+ of HUG 2003) was identified in the Hypselum subzone (Fig. 1.4; HUG 2003; STRASSER et al. 2005). This sequence boundary coincides with the 2nd-order maximum regression according to HARDENBOL et al. (1998).

Based on the absolute ages given by GRADSTEIN et al. (1995), HARDENBOL et al. (1998) date SB Ox6 at 155.81 Ma and SB Ox7 at 155.15 Ma (Fig. 1.5). This implies a time span of 600 to 700 kyr between these two large-scale (3rd-order) sequence boundaries. In the corresponding interval, PITTET (1996), HUG (2003), and STRASSER et al. (2000) counted 8 small-scale sequences, each composed of five elementary sequences. This suggests that a small-scale sequence formed within 75 to 87.5 kyr, and an elementary sequence within 15 to 17.5 kyr. These values approach those of the first orbital eccentricity cycle (100 kyr) and of the precession cycle (between 18 and 22 kyr in the Oxfordian; BERGER et al. 1989). Furthermore, the systematic stacking of 5 elementary sequences into one small-scale sequence over the entire Middle Oxfordian to Early Tithonian interval investigated in the Swiss Jura points to an orbital control on the formation of the depositional sequences (STRASSER 2008). It is implied that these orbital cycles induced climate changes that translated into sea-level fluctuations, which in turn controlled the formation of the observed depositional sequences.

<figure><img src="image_8.png" /><figcaption>**Fig. 1.5** - Bio-, chrono-, and sequence-stratigraphic framework of the Oxfordian, according to HARDENBOL et al. (1998) and compared with the HAQ et al. (1987, 1988) eustatic charts. The studied time interval is shaded. For this study, the sequence-boundary positions of the Tethyan realm are used.</figcaption></figure>
<figure><img src="image_9.png" /><figcaption>**Fig. 1.6** - Comparisons of several eustatic and regional sea-level curves for the Oxfordian/Kimmeridgian. The studied time interval is shaded.</figcaption></figure>

### 1.2.3 Eustatic sea-level changes

The Oxfordian and Kimmeridgian stages are characterized by a long-term transgressive trend. During the Oxfordian, a T-R facies cycle is recognized (e.g., HAQ et al. 1987; HARDENBOL et al. 1998; JACQUIN et al. 1998; HALLAM 2001; Fig. 1.6). A long-term eustatic sea-level curve for the Jurassic has been published by HAQ et al. (1987) and HALLAM (1988). Regional long-term sea-level curves have been published for the Oxfordian by, e.g., GYGI (1986), SURLYK (1991), and O'DOGHERTY et al. (2000); they all indicate a transgression at the Late Oxfordian (Fig. 1.6).

High-frequency eustatic sea-level fluctuations with low amplitudes, related to insolation changes in the Milankovitch-frequency band, were superimposed

on this long-term sea-level trend. A reconstruction of high-frequency eustatic sea-level fluctuations has been attempted for the studied interval (VÉDRINE 2005; VÉDRINE & STRASSER 2005).

### 1.2.4 Palaeoclimate

Late Jurassic climate was characterized by a greenhouse period with high atmospheric CO₂ levels (e.g., MOORE et al. 1992), a monsoonal rainfall pattern (PARRISH 1993), warm and humid conditions and markedly reduced latitudinal temperature gradients with respect to the present day (HALLAM 1984, 1985; WIGNALL & RUFFELL 1990). However, superimposed on this record of warmth is mounting evidence for cooler climate periods with high-latitude seasonal ice ("cool mode", FRAKES et al. 1992).

<figure><img src="image_10.png" /><figcaption>**Fig. 1.7** - Evolution of humidity-aridity and temperature for the Oxfordian/Kimmeridgian. The studied time interval is shaded.</figcaption></figure>
In the Middle and Late Oxfordian, abundant rainfall in the hinterland allowed vegetation growth and continental run-off of siliciclastics into the study area (GYGI 1986; PITTET 1996). Associated nutrient input periodically led to eutrophication and to crises of coral reefs (DUPRAZ & STRASSER 1999). Towards the Late Oxfordian and Kimmeridgian, climate became more arid, as indicated by generally less siliciclastics and by evaporite pseudomorphs (HUG 2003; RAMEIL 2005; cf. Fig. 1.7 and Chap. 8)). FRAKES et al. (1992) indicate up to 27°C for the Late Oxfordian ocean surface temperatures according to oxygen isotopes measured on planktonic foraminifera and belemnites. Based on δ¹⁸O analyses of Middle Oxfordian samples (modified bulk) from the Swiss Jura platform, PLUNKETT (1997) calculated palaeotemperatures of 26-27°C.

This general climatic evolution was controlled by high-frequency climate changes related to orbital (Milankovitch) cycles (PITTET 1996). These not only controlled siliciclastic input through periodically increased rainfall but also periodic evaporite formation (HUG 2003). Furthermore, they were responsible for low-amplitude sea-level fluctuations that led to the formation of hierarchically stacked depositional sequences (STRASSER et al. 1999, 2000).

**1.2.5 Global and regional tectonics**

At a global scale, increased tectonic subsidence rates during Oxfordian-Kimmeridgian times correlate with intensified rifting and wrench activity within the Arctic-North Atlantic rift system and along the northern Tethyan margin ("Oxfordian crisis"; ARNAUD 1988). In Late Jurassic times, the Swiss Jura was part of the passive northern margin of the Tethys Ocean (e.g., WETZEL et al. 2003). The tectonic regime was extensional and pre-existing tectonic structures in the basement were reactivated (BURKHALTER 1996; WETZEL & ALLIA 2000; ALLENBACH 2001; WETZEL et al. 2003). This caused differential subsidence and/or rotation of fault-bounded blocks, which morphologically differentiated the depositional area into swells and depressions. The relief created by tectonics contributed significantly to the general facies distribution on the shallow platform.

**1.3 METHODS**

Based on facies and microfacies analyses, this study concentrates on the transgressive part of sequence Ox6+. Three domains of sedimentation are investigated: shallow platform, deep platform, and basin. Seven shallow platform sections, two deep platform sections, and one basin section have been logged at a cm scale and densely sampled for a detailed sedimentological analysis. Samples were taken at the base, in the middle, and at the top of beds. In total, 505 polished slabs and thin sections, plus 60 washing residues of marls were examined. Field observation, texture analysis, and semi-quantification of skeletal and non-skeletal elements were performed in order to interpret the depositional environments (cf. Chap. 2).

Based on the hierarchical stacking pattern, bed surfaces, facies, and microfacies, a high-resolution sequence- and cyclostratigraphic analysis was carried out for this transgressive interval. Sequence analysis is based on the comprehensive sedimentological analysis of sections and is first made separately for each section. In a second step, the sections are correlated and a best-fit solution is sought for. This methodology is summarized in STRASSER et al. (1999). The terminology follows that of the sequence-stratigraphic model of VAIL et al. (1977, 1991). A depositional sequence is defined as a succession of genetically related sediments. Different orders of depositional sequence are identified in the studied sections: medium-scale, small-scale, and elementary sequences (cf. Chap. 3). These depositional sequences were caused by sea-level fluctuations, which were related to climate changes, themselves controlled by the astronomical parameters of the Earth's orbit. Consequently, the observed depositional sequences are the sedimentological expression of orbital cycles and are attributed to the precession cycle (20 kyr) for the elementary sequences, and to the short- and long-eccentricity cycles (100 kyr and 400 kyr) for the small- and medium-scale sequences, respectively.

This methodology provides a precise sequential and chronological framework, in which palaeoenvironmental and palaeoecological changes on the shallow platform can be monitored through time and space. In addition, platform-basin relationships (i.e., carbonate mud and clay exportation) can be discussed based on a best-fit sequence-stratigraphic platform-to-basin correlation of all sections.

***
# 2 - FACIES AND MICROFACIES ANALYSIS

## 2.1 INTRODUCTION

Facies is the sum of all organic and inorganic characteristics of sedimentary rocks including color, texture, grain size, mineralogical composition, fossil content, and sedimentary structures (FLÜGEL 2004; TUCKER & WRIGHT 1990). Microfacies describes an association of all sedimentological and palaeontological criteria observable in thin section or on polished slab (FLÜGEL 2004). Facies and microfacies assist in interpreting environmental parameters that control deposition and the distribution of organisms and grains. Facies and microfacies analyses also allow for the interpretation of depositional sequences, i.e. the recognition of shallowing/deepening trends.

The depositional environment is the area in which organisms live and sediments are deposited. Fossils are the most important indicators of ancient environments because strong interactions exist between organisms and their environment. From the facies and microfacies analyses, and from the study of floral and faunal associations, the physical, chemical, and ecological parameters influencing the depositional environment can be deduced.

## 2.2 METHODOLOGY

The facies and microfacies analyses are based on very detailed field, macroscopic, and microscopic observations. First, sections were logged at a cm-scale and densely sampled. The hierarchical stacking pattern of beds and bed surfaces was examined. Thin sections and the respective polished slabs, and the marl washings were examined under the binocular and optical microscope. The Dunham classification is used for the description of texture. The abundance of skeletal and non-skeletal grains was evaluated semi-

quantitatively (cf. Chaps 4 and 7). Matrix and cements were also examined. These informations are then integrated to interpret the depositional environment.

In the following paragraphs, the elements of platform and basinal facies and microfacies are described. The interpretation is based on comparison with the literature (e.g., FLÜGEL 2004) and on the sedimentological context within which the elements occur.

## 2.3 SHALLOW PLATFORM FACIES

### 2.3.1 Non-skeletal carbonate elements

#### Peloids

The peloids occurring in the studied samples are spherical to elliptical micritic grains without any internal structures (Pl. 5/6). They are commonly smaller than 1 mm of diameter. Several modes of formation are possible: fecal, microbial, reworked cohesive mud, internal molds of fossils, complete micritization of bioclasts or other carbonate grains (TUCKER & WRIGHT 1990; FLÜGEL 2004; SAMANKASSOU et al. 2006). Peloids are abundant in lagoons and are preserved in low-energy subtidal and intertidal zones.

#### Oncoids

Oncoids (from the Greek ονκοσ, “lump”; HEIM 1916) are irregularly formed calcareous components with non-concentric micritic laminae, round or lobate shapes, dense texture with or without inclusions, and in some cases with indistinct boundaries. They are mainly due to biogenic accretion around a nucleus.
<table><caption>**Fig. 2.1** - Classification of the oncoids found in the Hauptmumienbank Member. Morphological criteria, cortex configuration and composition, surrounding sediment, and depositional environmental conditions are indicated.</caption><thead><tr><th rowspan="2"></th><th rowspan="2"></th><th colspan="2">Micrite-dominated oncoids</th><th colspan="2">Bacinella-Lithocodium oncoids</th></tr><tr><th>type 1</th><th>type 2</th><th>type 3</th><th>type 4</th></tr></thead><tbody><tr><td rowspan="3">Morphological criteria</td><td>Prevailing size</td><td>few millimeters</td><td>few mm to 1 cm</td><td>few cm to 5 cm</td><td>few mm to 10 cm</td></tr><tr><td>Shape and surface</td><td>elliptical to spherical smooth</td><td>elliptical smooth</td><td>elliptical lobate</td><td>elliptical lobate</td></tr><tr><td>Nucleus</td><td colspan="2">bioclastic or lithoclastic nucleus</td><td>bioclasts or without nucleus</td><td>no nucleus recognizable</td></tr><tr><td rowspan="3">Cortex configuration and composition</td><td>Lamination type</td><td>concentric and continuous but barely visible</td><td>irregular and truncated</td><td>rarely continuous</td><td>no lamination</td></tr><tr><td>Microfabric</td><td>micritic laminations or homogeneous</td><td>micritic laminations and organism-bearing laminations</td><td>organism-bearing laminations and few micritic laminations</td><td>microbial meshwork</td></tr><tr><td>Bioclasts</td><td>rare</td><td>common bioclasts</td><td></td><td>rare</td></tr><tr><td rowspan="3">Surrounding sediment</td><td>Microencrusters</td><td>no fauna associated</td><td>serpulid worms, Bullopora</td><td colspan="2">abundant microencrusters: Bacinella, Lithocodium</td></tr><tr><td>Classification</td><td>mudstone - wackestone</td><td>packstone and locally wackestone</td><td colspan="2">mudstone - wackestone and locally packstone</td></tr><tr><td>Associated fauna and grains</td><td colspan="2">mainly benthic foraminifera, peloids, and ooids</td><td>brachiopods, commonly Mohlerina basiliensis, bivalves</td><td>echinoderms, commonly Mohlerina basiliensis</td></tr><tr><td rowspan="3">Depositional environment</td><td>Relative energy</td><td>moderate and intermittent</td><td>high and intermittent</td><td>low and intermittent</td><td>very low</td></tr><tr><td>Bathymetry</td><td colspan="2">subtidal</td><td colspan="2"></td></tr><tr><td>Sedimentation rate</td><td colspan="2">low</td><td colspan="2"></td></tr><tr><td></td><td>Environment</td><td>protected lagoon</td><td></td><td colspan="2">fully marine lagoon</td></tr></tbody></table>

PERYT (1983) defined them as “a group ofalgally (red algae excepted), cyanobacterially and bacterially coated grains, which are initiated in marine and freshwater phreatic environments”.

The oncoids found in the Hauptmumienbank Member display a wide variability in size, shape, and composition (VÉDRINE et al. 2007). Observed oncoid sizes vary between a few millimetres to a few centimetres. The oncoids have a well-defined rounded or irregular shape and smooth, wavy, or lobate contours. The final shape follows in many cases that of the nucleus, although a higher sphericity is obtained. If a nucleus is present, it is of bio- or lithoclastic nature and the envelope has a variable thickness. The cortex is characterized by micritic and/or organism-bearing laminations, which are continuous or discontinuous when the oncoid surface was eroded (Pl. 4).

Types of oncoids are mainly defined and differentiated by the surface morphology, the cortex structure and by the presence, the nature, and the abundance of microencrusters in their cortex. Microfacies analysis of the encasing sediment furnishes the environmental context within which the oncoids

were formed. In the Hauptmumienbank Member, oncoids are mainly found in wackestones, locally floatstones or rudstones, with bioclasts, ooids, and peloids. Transported micrite-dominated oncoids are also observed in ooid-rich grainstones. Texture, faunal composition, and sedimentary structures suggest a deposition in shallow-water lagoons. Based on more than 300 thin sections and macroscopic samples from the Hauptmumienbank Member, four types of oncoids can be distinguished (Fig. 2.1). Transitions between types also exist, suggesting a continuum.

**Type 1 oncoids** have diameters of a few millimetres and correspond to elliptical or spherical particles with relatively smooth contours. The cortex is micritic, homogeneous, and without microencruster inclusions (Pl. 4/1). This pattern probably results from the trapping of fine-grained sediment on the oncoid surface by microorganisms. Laminations are difficult to distinguish. Type 1 oncoids are preferentially found in peloidal and bioclastic (foraminifera, bivalves, echinoderms) mudstones-wackestones of protected and moderate-energy lagoonal environments. This type of oncoid is relatively rare in the studied interval (cf. Chap. 7 and Fig. 7.5).
**Type 2 oncoids** have diameters of a few millimetres (up to 1 cm) and present elliptical shapes with smooth contours. The cortex has irregular and locally truncated micritic laminae, and different growth phases can be distinguished in many cases (Pl. 4/2-5). This suggests relatively high-energy conditions with intermittent periods of wave agitation leading to a partial erosion of the cortex. The cortex of the micrite-dominated oncoids presents a relatively low-diversity fauna such as serpulid worms and *Bullopora*. Occasionally, ooids are incorporated in the cortex (Pl. 4/3). These oncoids are found in packstones with normal-marine or semi-restricted fauna (brachiopods, oysters, foraminifera, echinoderms, bivalves, serpulids, ostracodes) and also in marls. Type 2 oncoids are common in all studied sections (Fig. 7.5).

**Type 3 oncoids** have diameters of a few millimetres to a few centimetres (up to 5 cm) and sub-elliptical shapes with wavy contours. The cortex is made of alternating organism-bearing and thin micritic laminations (Pl. 4/6-7). The organism-bearing laminations are formed by two microencrustres: *Bacinella irregularis* (RADOICIC 1959; Pl. 10/1) and *Lithocodium aggregatum* (ELLIOTT 1956; Pl. 10/2). *Bacinella irregularis* is an enigmatic microencruster with an irregular micritic meshwork and interspaces filled with calcite spar. This is assumed to represent a cyanobacterial structure (e.g., SCHMID 1996; DUPRAZ 1999; SHIRAISHI & KANO 2004). *Lithocodium*, originally interpreted as a codiacean alga by ELLIOTT (1956), is characterized by inner cavities and an aggregated outer wall with numerous alveoli (complex wall structure) probably containing symbiotic and photosynthetic algae (SCHMID & LEINFELDER 1996). These authors thus attributed it to a loftusiacean foraminifer with an encrusting life habit. Recently, CHERCHI & SCHROEDER (2006) interpreted *Lithocodium* as colonies of calcified cyanobacteria because of the absence of apertures connecting neighbouring cavities, and because of the very irregular form and arrangement of these hollows. These *Bacinella-Lithocodium* oncoids can be compared to the porostromate oncoids of PERYT (1981) because of the presence of cyanobacteria in their cortex. The alternation of micrite laminae and organism-bearing laminae suggests calm periods, during which *Bacinella-Lithocodium* could grow, and more agitated periods, when micrite laminae were formed by the rolling on the lagoon floor. Type 3 oncoids are preferentially found in wackestones with normal-marine fauna (brachiopods, oysters, foraminifera, echinoderms, bivalves) indicating relatively low-energy conditions. The *Bacinella-Lithocodium*

association characterizes lagoonal environments with oligotrophic conditions, low accumulation rate, clear, oxygenated, shallow, and normal-marine waters (e.g., LEINFELDER et al. 1993; DUPRAZ & STRASSER 1999; IMMENHAUSER et al. 2005). DUPRAZ & STRASSER (1999), who examined the encrustations of Oxfordian coral reefs in the Swiss Jura, correlated the *Bacinella-Lithocodium* association with episodes of relatively high coral diversity. *Bacinella* and *Lithocodium* have also been identified in the microbial crusts associated with other coral and sponge reefs of the Late Jurassic (e.g., HELM & SCHÜLKE 1998; SCHMID & LEINFELDER 1996; SHIRAISHI & KANO 2004). This may suggest that palaeoecological conditions for *Bacinella-Lithocodium* bearing oncoids were analogous. The presence of the benthic foraminifer *Mohlerina basiliensis* (MOHLER 1938; SCHLAGINTWEIT & EBLI 1999; SCHLAGINTWEIT et al. 2005), preferentially in wackestones with type 3 and/or 4 oncoids, suggests that oncoids and benthic foraminifera were, at least partly, controlled by similar environmental parameters.

**Type 4 oncoids** have diameters of a few millimetres to several centimetres (up to 10 cm) and display irregular shapes with lobate contours. Exclusively composed of *Bacinella* and/or *Lithocodium* meshwork, they have no nucleus nor laminations (Pl. 4/8). Type 4 oncoids are found in bioclastic wackestones, commonly associated with type 3 oncoids. Low-energy conditions with no or only rare agitation are suggested. Locally, type 4 oncoids develop into carpet-like structures and build-ups of *Bacinella* (e.g., HUG 2003; IMMENHAUSER et al. 2005).

Oncoids are considered as good proxies for palaeoenvironmental studies (DAHANAYAKE 1977, 1978, 1983; KUSS 1990; HUG 2003). Based on this study, water energy, water depth, trophic level, and sediment accumulation rate appear as the main direct environmental controlling parameters (VÉDRINE et al. 2007; cf. Chap. 7 for more discussion on the controlling factors).

## Ooids

In the shallow platform deposits examined, three types of ooids have been observed. Ooids with thinly laminated fine-radial cortices (type 3 of STRASSER 1986; Pl. 5/1) are very common and imply high-energy marine environments (DAVIES et al. 1978). The ooids can also be transported into quiet-water environments and be incorporated into packstones and wackestones.
These radial ooids commonly display a partial or
complete micritization (micritized type 3 ooids; Pl.
5/2-3).

Some oo-oncoids (type 2 of STRASSER 1986) are
occasionally found in the studied deposits. They
consist of a radial ooid, which is enveloped by an
oncoid cortex, characterized by irregular micritic thin
laminae (Pl. 5/4-5). This points to a change from higher
energy, where the radial ooids (type 3 of STRASSER
1986) formed to quiet waters in a protected lagoonal
environment, where microbial activity was favoured.

Lithoclasts

Lithoclasts are common in the studied Oxfordian
shallow marine sediments. They consist of slightly
rounded mudclasts or consolidated sediment fragments
with bioclasts and/or ooids (Pl. 5/7-8). These clasts
indicate erosion and redeposition of material derived
from pre-existing carbonate sediments.

2.3.2 Skeletal carbonate elements

Skeletal grains comprise complete and fragmented
fossils. None of the observed organisms has
biostratigraphic significance.

Calcareous algae

Calcareous algae are relatively rare in the studied
deposits. Charophytes are macrophytic green algae
that grow predominantly in oligotrophic freshwater
environments. Oogons and stems have been found
only at the base of the Hautes-Roches section. The
microencrusting green alga *Thaumatoporella* is
locally present in the microbial encrustations of
corals. Dasycladacean algae are rarely observed in
thin sections (Pl. 6/6). Their absence may be caused
by bad preservation conditions due to an original
aragonite skeleton mineralogy. No red alga fragments
were identified in the studied thin sections.

Ostracodes

In this study, ostracodes are mostly seen in thin
section and have therefore not been determined. They
have been found in the shallow platform as well as in
the basin sections (Pl. 6/3). Ostracodes can be useful in

the biostratigraphic analysis of marine and non-marine
sediments, particularly in freshwater environments
where other fossils are lacking.

Serpulids

Small reworked tube-clusters of serpulids (suspension-feeding polychaete worms) are observed in the Savagnières section (Pl. 1/2, Pl. 6/7). Furthermore, they commonly occur as encrusters on shell debris (Pl. 11/5) or in oncoids (Pl. 4/4).

Serpulids are relatively tolerant of changes in
salinity, water temperature, substrate, and water depth
(MILLIMAN 1974).

Bivalves

In the studied shallow-water deposits, bivalves
are common. In addition to undetermined bivalves,
three groups of bivalves could be identified: oysters,
inocerams, and lithophages. Oysters are common on
firm- and hardgrounds (Pl. 6/1, Pl. 3). The accumulation
of (monospecific) oyster shells may indicate
environments with brackish conditions. Inocerams
have a very coarse ostracum composed of vertically
oriented calcite prisms (honeycomb pattern; Pl. 6/2).
They tolerate fluctuations in bathymetry, types of
sediment, and oxygenation (MACLEOD & HOPPE 1992).
Lithophages chemically and mechanically perforate
hard substrates. They are commonly observed in corals
(Pl. 6/8).

Gastropods

In the studied sections, gastropods are locally
present (Pl. 5/3). Some large gastropods of the species
*Bourgetia striata* (grazers, herbivores and detritus
feeders) abound with in-situ echinoids, brachiopods,
and crinoids in the marly interval at the base of the
Hautes-Roches section (DUPRAZ 1999). This association
indicates open-marine conditions.

Benthic foraminifera

In the studied shallow-water carbonates, a variety
of benthic foraminifera is observed. Most of them
belong to the suborders Textulariina, Lagenina and
Miliolina.

Textulariids are common in the studied deposits.
<table><caption>Tab. 2.1 - Main microfacies occurring in the Swiss Jura and Lorraine sections classified according to the depositional environments that they represent.</caption><thead><tr><th>Code</th><th>Folk</th><th>Texture<br>Dumham</th><th>Major components</th><th>Other components</th><th>Sedimentary<br>features</th><th>Interpretation</th></tr></thead><tbody><tr><td colspan="7" style="background-color: #333333; color: white; font-weight: bold; text-align: left; padding: 5px;">SHALLOW PLATFORM</td></tr><tr><td colspan="7" style="background-color: #666666; color: white; font-weight: bold; text-align: left; padding: 5px;">Clays and marls</td></tr><tr><td>si1</td><td>Clays</td><td></td><td>coal debris</td><td></td><td></td><td>argillaceous lagoon</td></tr><tr><td>si2</td><td>Argillaceous marls</td><td></td><td>unifossiliferous or with restricted fauna (charophytes, gastropods, ostracodes)</td><td>foraminifera, serpulids, coal debris</td><td></td><td>protected lagoon</td></tr><tr><td>si3</td><td>Bioclastic marls</td><td></td><td>normal-marine fauna (echinoderms, bivalves, foraminifera)</td><td>oncoids, serpulids, ostracodes</td><td></td><td>protected to semi-open lagoon</td></tr><tr><td>si4</td><td></td><td></td><td>normal-marine fauna (brachiopods, echinoderms)</td><td>corals, ooids</td><td>nodular aspect</td><td>open lagoon</td></tr><tr><td>si5</td><td>Sandy marls</td><td></td><td>normal-marine fauna (oysters, echinoderms, foraminifera, ostracodes, gastropods)</td><td>quartz</td><td></td><td>argillaceous lagoon with siliciclastic input</td></tr><tr><td colspan="7" style="background-color: #666666; color: white; font-weight: bold; text-align: left; padding: 5px;">Tidal mudflat</td></tr><tr><td>tf1</td><td>Marls - biomicrite</td><td>m - P</td><td>oysters, peloids, quartz, glauconite</td><td>type 3 ooids, mudclasts</td><td>lenticular<br>bedding, ripples</td><td>bidirectional current in tidal mudflat</td></tr><tr><td>tf2</td><td>Micrite</td><td>M</td><td>undifferentiated bioclasts</td><td></td><td>birdseyes</td><td>emersion on tidal flat</td></tr><tr><td colspan="7" style="background-color: #666666; color: white; font-weight: bold; text-align: left; padding: 5px;">Inner lagoon - Protected</td></tr><tr><td>pr1</td><td>Biomicrite</td><td>M</td><td></td><td>echinoderms, foraminifera (Lenticulina, Spirillina), bivalves</td><td>bioturbation</td><td>muddy lagoon</td></tr><tr><td>pr2</td><td>Biomicrite</td><td>M-W-P</td><td>dominated by semi-restricted to normal-marine fauna (ostracodes, inocerams), foraminifera (Textularids, Miliolids, Lenticulina), quartz</td><td>echinoderms, organic matter debris, chamosite</td><td></td><td>protected lagoon with low-diversity fauna (probably tidal channels or bioclastic bars)</td></tr><tr><td>pr3</td><td>Pelmicrite</td><td>W-P</td><td>peloids</td><td>semi-restricted to normal-marine fauna (ostracodes, inocerams, echinoderms, oysters, brachiopods), foraminifera (Textularids, Lenticulina, Miliolids), quartz, organic matter</td><td></td><td>tidal channels in protected to semi-open lagoon</td></tr><tr><td colspan="7" style="background-color: #666666; color: white; font-weight: bold; text-align: left; padding: 5px;">Outer lagoon - Semi-Open</td></tr><tr><td>sol1</td><td>Biomicrite</td><td>W - M</td><td>foraminifera (Textularids, Lenticulina), brachiopods, bivalves, serpulids, fine quartz</td><td>peloids, organic matter debris</td><td>black facies</td><td>bioclastic lagoon with siliciclastic input</td></tr><tr><td>sol2</td><td>Biomicrite</td><td>W</td><td>normal-marine fauna (brachiopods, serpulids, echinoderms, coral rubble), quartz</td><td>organic matter</td><td></td><td>bioclastic lagoon with siliciclastic input</td></tr><tr><td>sol3</td><td>Onco-biomicrite</td><td>W - P</td><td>type 2 oncoids, foraminifera (Textularids, Lenticulina, Miliolids), quartz</td><td>normal-marine fauna (bivalves, echinoderms, ostracodes, serpulids), peloids, grapestones, organic matter, chamosite</td><td></td><td>oncolitic and bioclastic lagoon with siliciclastic input</td></tr><tr><td>sol4</td><td>Onco-oomicrite</td><td>W - P</td><td>type 2 oncoids, type 3 ooids</td><td>type 2 ooids, peloids, foraminifera (Textularids), little quartz</td><td></td><td>oncolitic lagoon</td></tr><tr><td>sol5</td><td>Oncomicrite</td><td>W-P-Rud</td><td>type 2 oncoids</td><td>normal-marine fauna (ostracodes, inocerams, oysters, serpulids, echinoderms), foraminifera (Textularids, Lenticulina, Miliolids), type 3 oncoids, peloids, quartz</td><td></td><td>oncolitic lagoon</td></tr><tr><td>sol6</td><td>Pel-oomicrite</td><td>P</td><td>peloids, micritized type 3 ooids, type 2 oncoids, little quartz</td><td>foraminifera (Textularids, Lenticulina, Miliolids), corals, brachiopods, echinoderms, bivalves, sometimes type 2 ooids</td><td></td><td>tidal bar or channel? in oncolitic lagoon</td></tr><tr><td>sol7</td><td>Pel-biomicrite</td><td>M-W-P</td><td>peloids, foraminifera (Textularids, Lenticulina), normal-marine fauna (dasycladaceans, ostracodes, bryozoans, bivalves, serpulids, echinoderms, corals, brachiopods, oysters), quartz</td><td>type 2 and 1 oncoids</td><td></td><td>tidal bar or channel? in bioclastic lagoon</td></tr><tr><td colspan="7" style="background-color: #666666; color: white; font-weight: bold; text-align: left; padding: 5px;">Outer lagoon - Open</td></tr><tr><td>ol1</td><td>Biomicrite</td><td>W - P</td><td>dominated by normal-marine fauna (echinoderms, oysters, brachiopods), foraminifera (Lenticulina, Textularids, Miliolids), peloids</td><td>type 2 and 3 oncoids, serpulids, gastropods, ostracodes, lithoclasts, peloids (old type 3 ooids)</td><td></td><td>bioclastic lagoon</td></tr><tr><td>ol2</td><td>Biomicrite</td><td>W-P-G</td><td>dominated by normal-marine fauna (brachiopods, oysters, echinoderms, calcareous sponges, serpulids, corals)</td><td>foraminifera (Textularids, Miliolids), peloids, type 2 oncoids</td><td></td><td>bioclastic lagoon - locally bars</td></tr><tr><td>ol3</td><td>Onco-oomicrite</td><td>W-P-Rud</td><td>type 3 and 2 oncoids, type 3 ooids</td><td>foraminifera (Textularids, Mohlerina, Miliolids), peloids, type 2 ooids, normal-marine fauna (brachiopods, echinoderms)</td><td></td><td>oncolitic lagoon</td></tr><tr><td>ol4</td><td>Oncomicrite</td><td>W-F (Rud)</td><td>type 3 oncoids</td><td>open-marine fauna (serpulids, oysters, brachiopods, echinoderms, inocerams), foraminifera (Textularids, Lenticulina, Mohlerina, Miliolids), type 2 oncoids, peloids, micritized type 3 ooids</td><td></td><td>oncolitic lagoon</td></tr><tr><td>ol5</td><td>Oncomicrite</td><td>M-W-F</td><td>type 3 and 4 oncoids</td><td>foraminifera (Textularids, Lenticulina, Mohlerina, Miliolids), normal-marine fauna (echinoderms, oysters, brachiopods, gastropods), type 2 oncoids, micritized type 3 ooids, peloids</td><td></td><td>oncolitic lagoon</td></tr><tr><td>ol6</td><td>Pel-biomicrite</td><td>W</td><td>peloids, foraminifera (Miliolids, Textularids, Mohlerina, Lenticulina), normal-marine fauna (echinoderms, brachiopods)</td><td>type 3 oncoids</td><td></td><td>tidal channel in oncolitic lagoon</td></tr></tbody></table>

These agglutinating foraminifera have a labyrinthic or alveolar (complex) internal microstructure (Pseudocyclammina sp., Pl. 8/2 and 8/4; Alveosepta sp.; Everticyclammina sp.) or a simple internal microstructure (Nautiloculina sp., Pl. 8/5; Ammobaculites sp.; Tolypammina sp., Pl. 13/3). Textulariids are ubiquitous ranging from transitional

environments with brackish and marsh conditions to bathyal and abyssal depths (FLÜGEL 2004).

Among the Lagenid foraminifera, *Lenticulina* sp. is the most common hyaline foraminifer (Pl. 8/8-9). It occurs from platform to basin and may be found reworked in lagoons.
<table><thead><tr><th>Code</th><th>Folk</th><th>Texture<br>Dumham</th><th>Major components</th><th>Other components</th><th>Sedimentary<br>features</th><th>Interpretation</th></tr></thead><tbody><tr><td colspan="7"><strong>High-energy deposits</strong></td></tr><tr><td>bar1</td><td>Oosparite</td><td>G</td><td>micritized type 3 ooids</td><td>type 3 ooids, type 2 oncoids, lithoclasts, grapestones</td><td></td><td>(active) ooid bar</td></tr><tr><td>bar2</td><td>Oomicrite</td><td>W-P</td><td>micritized type 3 ooids, foraminifera (Textularids, Miliolids, Lenticulina)</td><td>type 2 ooids, type 2 oncoids, normal-marine fauna (brachiopods, serpulids), peloids, litho-oncoids</td><td></td><td>(inactive) ooid bar</td></tr><tr><td>bar3</td><td>Oomicrite</td><td>W - P</td><td>micritized type 3 and 2 ooids, quartz</td><td>few type 2 oncoids</td><td>iron color</td><td>abandoned ooid bar - channel?</td></tr><tr><td>bar4</td><td>Oo-pelmicrite</td><td>W</td><td>type 2 ooids, peloids, quartz</td><td>foraminifera (Lenticulina), micritized type 3 ooids, type 2 oncoids</td><td></td><td>abandoned ooid bar - channel?</td></tr><tr><td>bar5</td><td>Oosparite/micrite</td><td>G - P</td><td>type 3 ooids</td><td>echinoderms, oysters, lithoclasts, grapestones</td><td>isopque<br>cement</td><td>(active) ooid bar in subtidal lagoon</td></tr><tr><td>bar6</td><td>Oomicrite</td><td>W-P-G</td><td>type 3 ooids</td><td>type 2 oncoids, foraminifera (Textularids, Lenticulina), normal-marine fauna (bryozoans, ostracodes, bivalves, serpulids, brachiopods, echinoderms, corals), peloids, quartz, grapestones</td><td></td><td>(active to inactive) oo-bioclastic bar in subtidal lagoon, washover deposit?</td></tr><tr><td>bar7</td><td>Oo-Onco-biomicrite /sparite</td><td>W-P-G</td><td>type 3 ooids (sometimes micritized), type 2 oncoids, normal-marine fauna (brachiopods, echinoderms, corals)</td><td>peloids, foraminifera (Textularids, Lenticulina, Miliolids, Mohlerina), type 2 ooids</td><td>cross<br>stratification</td><td>(active to inactive) oo-bioclastic bar in subtidal lagoon</td></tr><tr><td>bar8</td><td>Oo-biomicrite</td><td>P - G</td><td>oysters, type 3 ooids</td><td>echinoderms, peloids, agglutinated foraminifera, gastropods, lithoclasts, grapestones, quartz</td><td>locally<br>herringbone<br>cross<br>stratifications</td><td>oo-bioclastic bar with siliciclastics in sandtidal flat</td></tr><tr><td>bar9</td><td>Biomicrite</td><td>G</td><td>oysters, ostracodes, echinoderms</td><td>quartz, lithoclasts</td><td>vertical and<br>horizontal<br>burrows</td><td>bioclastic bar in tidal sandflat</td></tr><tr><td>bar10</td><td>Biomicrite</td><td>P</td><td>oysters, quartz</td><td>type 3 ooids, gastropods, quartz</td><td>ferrug. color</td><td>bioclastic bar with siliciclastic input</td></tr><tr><td>bar11</td><td>Biomicrite</td><td>P</td><td>oysters</td><td>type 3 ooids, echinoderms</td><td>large shells</td><td>bioclastic bar - lumachella</td></tr><tr><td colspan="7"><strong>Coral reefs</strong></td></tr><tr><td>c1</td><td>Biolithite</td><td>B (P)</td><td>microencrusted corals (in situ)</td><td>sponges, serpulids, type 3 ooids, bivalves</td><td></td><td>coral patch-reef</td></tr><tr><td>c2</td><td>Biolithite</td><td>B (M-W-P)</td><td>microencrusted corals (in situ and in rubble)</td><td>peloids, type 3 and 1 ooids, type 2 and 1 oncoids, brachiopods, serpulids, sponges, foraminifera (Placopsilina, Bulopora), lithoclasts, quartz</td><td></td><td>coral patch-reef</td></tr><tr><td>c3</td><td>Biolithite</td><td>B (P)</td><td>microencrusted corals rubble</td><td>type 3 ooids, peloids, bioclasts (bivalves, echinoderms, brachiopods, serpulids), type 2 oncoids</td><td></td><td>close to coral patch-reef</td></tr><tr><td>c4</td><td>Biolithite</td><td>B (P)</td><td>microencrusted corals rubble</td><td>brachiopods, sponges, peloids, serpulids, gastropods, echinoderms</td><td></td><td>close to coral patch-reef</td></tr></tbody></table>

**Tab. 2.1 (continued)** - Main microfacies occurring in the Swiss Jura and Lorraine sections classified according to the depositional environments that they represent.

Miliolids are commonly found in the studied deposits (Pl. 8/7). They are made of a porcelaneous wall without pores, characterized by a shiny and smooth appearance. They usually characterize protected environments when they are abundant.

*Mohlerina basiliensis* (MOHLER 1938) has been found in the Swiss Jura deposits. This foraminifer occurs from the Middle-Late Bathonian to the Valanginian and displays a double-layered wall microstructure with a thick outer hyaline radial-fibrous calcite layer and a thin inner micritic layer (Pl. 9). Its taxonomy is still in debate (cf. Annex 1; VÉDRINE in press). It was previously attributed to the suborder Spirillina (e.g., DARGA & SCHLAGINTWEIT 1991), then to the suborder Involutinina, family Ventrolaminidae, and genus *Archaeosepta* (TASLI 1993), and more recently to the suborder Rotaliina and the family Discorbidae (e.g., BERNIER 1984; BUCUR et al. 1996). However, the double-layered structure of *Mohlerina basiliensis* does not match with the perforated hyaline test, which characterizes the suborders Spirillina, Involutinina, and Rotaliina. The most probable attribution is given by SEPTFONTAINE

(1981) who placed *Mohlerina basiliensis* with the suborder Fusulinina, which has a similar double-layered microstructure. As the suborder Fusulinina occurs only in the Late Palaeozoic. SEPTFONTAINE (1981) called them “Mesozoic Fusulinina”. *Mohlerina basiliensis* preferentially occurs in low-energy facies and is always associated with *Bacinella-Lithocodium* oncoids. As the *Bacinella-Lithocodium* association indicates oligotrophic, clear, oxygenated, and normal-marine waters (e.g., DUPRAZ & STRASSER 1999), it is suggested that *Mohlerina basiliensis* requires similar ecological conditions (cf. Chap. 7; VÉDRINE 2008).

In the studied deposits, Textulariids, *Lenticulina*, and Miliolids are commonly associated (Tab. 2.1). Low-diversity fauna suggests more restricted conditions whereas maximum diversity indicates open-marine environments. The spatial and stratigraphic distribution of agglutinated, hyaline, and porcelaneous foraminifera of the Swiss Jura sections is analysed in Chap. 7 and their main controlling factors are discussed.
## Encrusting foraminifera

Bullopora (QUENSTEDT 1856) is abundant in the studied deposits. Different species exist but Bullopora tuberculata (SOLLAS), characterized by spines on the test, is easily recognizable (Pl. 10/3; SCHMID 1996). Bullopora is composed of small chambers linked by tubes and presents a perforated calcareous test. This foraminifer is attached to the substratum or can colonize dead corals.

Placopsilina (D'ORBIGNY 1850) is an encrusting foraminifer, which particularly agglutinates quartz grains (Pl. 10/5 and 10/8). Placopsilina is abundant in the studied bioherms and in oncoid levels. Placopsilina is found together with microbial crusts, suggesting a simultaneous growth in a same environment, especially in columnar forms (Pl. 10/8).

Troglotella incrustans (WERNLI & FOOKES 1992; Pl. 10/2 and 10/4) is a cryptic encrusting foraminifer, which can perforate calcareous substrate (SCHMID & LEINFELDER 1996; CHERCHI & SCHROEDER 2006). Troglotella is commonly associated with the cyanobacterium Lithocodium aggregatum (Pl. 10/2). This suggests that Troglotella probably fed on the photoautotrophic symbionts of Lithocodium (SCHMID & LEINFELDER 1996).

## Echinoderms

Echinoderms are mainly represented by spines and plates of sea urchins (Pl. 6/5). These strictly stenohaline organisms, i.e. very intolerant to salinity changes, indicate open-marine environments with normal salinity. However, echinoderm fragments are easily transported by currents, which explains their occasionally great abundance in internal lagoons, associated with euryhaline organisms.

## Brachiopods

In the studied deposits, two groups of articulate brachiopods are observed: Terebratulids and Rhynchonellids. Terebratulids (Pl. 6/4 and Pl. 11/6) are bulbous in shape, commonly circular or ovoid in outline. They are distinguished by a very short hinge line, a punctuated shell, and smooth or ribbed shells. Rhynchonellids are easily recognized by their strongly ribbed wedge-shaped or nut-like shells and their zigzagged frontal commisure. Rhynchonellids appear

to be more sensitive to bad environmental conditions (high turbidity) and to the lack of hard substrate than Terebratulids (GAILLARD 1983). Brachiopods are stenohaline organisms and imply normal-marine conditions.

## Corals

Corals appear commonly in the Oxfordian deposits (Pl. 6/8-10). They mainly form patch-reefs (e.g., Court section) and carpets (e.g., Hautes-Roches section) in lagoons and indicate open-marine environments. Coral rubble frequently occurs, indicating wave or storm current transport on the platform.

Input of siliciclastics and associated nutrients as well as water chemistry were the major controlling factors for reef development (DUPRAZ 1999; DUPRAZ & STRASSER 1999). Bathymetry played a subordinate role on the shallow Jura platform, but opening and closing of lagoons linked to low-amplitude sea-level fluctuations as well as fluctuating terrigenous run-off created periodic changes in trophic conditions (DUPRAZ & STRASSER 1999). Demise of corals generally coincides with low sea level and humid climate (DUPRAZ & STRASSER 1999).

### 2.3.3 Carbonate mud

In the studied sections, the majority of rocks is formed by mud-supported sediments that reflect low-energy settings. Detailed geochemical investigations of the micrite matrix have not been undertaken in this study. The origin of lime mud is still discussed in the scientific community (a compilation is given in FLÜGEL 2004). For the Vellerat Formation in the Swiss Jura Mountains, DUPRAZ (1999) proposes two sources of micrite: bacterial activity (automicrite) and bioerosion (allomicrite). Carbonate mud produced on shallow-marine platforms is also a major source for periplatform sediments deposited on slopes and in basins (PITTET et al. 2000).

### 2.3.4 Other constituents

#### Siliciclastics

Siliciclastics commonly derive from continental areas and are transported onto the platform by rivers, currents and/or wind. The main components are clay
minerals, quartz, feldspars, and heavy minerals. Based on clay mineral analyses of Oxfordian deposits in the Swiss Jura, GYGI & PERSOZ (1986) and PITTET (1996) have observed that: (1) kaolinite and illite have a negative correlation, (2) the mineralogy is independent of facies, (3) there is a low smectite content. In this study, clay mineral analyses have been performed with a high time resolution (cf. Chap. 8).

Subangular quartz grains, ranging from 0.02 to 0.1 mm in diameter (average size 0.08 mm) are locally abundant. Quantities of up to 40% can be reached locally, but 10% are rarely exceeded.

It is admitted that most siliciclastics were brought onto the platform by rivers (GYGI & PERSOZ 1986) probably from northern crystalline massifs (Fig. 1.3). The study of nature and distribution of siliciclastics is thus important for the palaeoclimatic and palaeohydrological conditions in the source area (cf. Chap. 7).

### Organic matter

In siliciclastic intervals, small fragments of plant matter are locally present in the Court and Pagny-sur-Meuse sections. However, most of the organic matter is finely dispersed in the matrix (cf. Chap. 2.3.6).

### Pyrite

Pyrite is commonly present in most sections as framboids and cubic crystals. In sedimentary systems, pyrite formation results from bacterial degradation of organic matter in reducing conditions.

### Chamosite/glauconite

In the studied shallow platform deposits, a low amount of dispersed small green grains is observed in oyster-rich packstones of the Pagny-sur-Meuse section. Geochemical analysis (EDX analysis) indicates a glauconite composition: hydrous silicate of iron and potassium (cf. Annex 2). According to VAN HOUTEN & PURUCKER (1984), glauconite typically occurs in deeper, open-marine settings, whereas chamosite forms preferentially in lagoons. Recently, EL ALBANI et al. (2005) identified glauconite in the Purbeckian facies, characteristic of shallow lagoonal environments, and showed that the glauconite composition changes with the chemical conditions imposed by the local environment.

### 2.3.5 Sedimentary structures

#### Birdseyes

Only the Court section presents a level of birdseyes (Pl. 11/1). Birdseyes are mm-scale cavities in carbonate mud that are created by active algal/microbial growth and decomposition, and/or by trapping of gas released during the decomposition of organic matter (FLÜGEL 2004; SHINN & ROBBIN 1983). They occur in the upper intertidal and supratidal zones and are typical sedimentary structures of tidal flat facies.

#### Bioturbation and perforations

Bioturbation is frequent in the studied interval and indicated by differences of color and texture or differential dolomitization (Pl. 1/1, probably *Thalassinoides*). Nodular limestones are common and result from intense bioturbation. Bioturbation is characteristic of soft sediments while perforations are representative of indurated sediments. Levels of intense bioturbation and/or bioperforation indicate low sedimentation rates or omission phases (HILLGÄRTNER 1999).

In the Vorbourg section, at the top of an oolite bar, a perforated and oyster-encrusted hardground is exposed (Pl. 3/1-3). In the Pagny-sur-Meuse section, a similar hardground is observed (Pl. 3/4-6). These surfaces are interpreted as subtidal hardgrounds.

#### Herringbone cross beddings

Herringbone cross bedding is observed at the base of the “Oolithe de Saucourt inférieure” (Pagny-sur-Meuse section, Fig. 4.17a). These structures form when current periodically flows in opposing directions (bi-directional currents) such as on a sandflat or in a tidal channel. Such structures are thus interpreted as resulting from tidal currents.

#### Lenticular bedding

In the examined sediments, lenticular bedding is observed in the marly deposits at the base of the Pagny-sur-Meuse (Pl. 15/2, Fig. 4.17a). Lenticular bedding is a diagnostic feature for bi-directional currents. Such structures point to low-energy environments such as tidal mudflats (REINECK & SINGH 1975).
<table><thead><tr><th>Code</th><th>Texture<br>Folk</th><th>Texture<br>Dumham</th><th>Major components</th><th>Other components</th><th>Sedimentary<br>features</th><th>Interpretation</th></tr></thead></table>

DEEP PLATFORM

Marl-limestone alternations (para- to autochthonous)

<table><tr><td>dp1</td><td>Marls</td><td>m</td><td>Miliolids, ostracodes, Spirillina, echinoderms</td><td>sponges, Tolypammina, belemnites</td><td>pyrite, glauconite</td><td>hemi-pelagic sedimentation</td></tr><tr><td>dp2</td><td>Marls</td><td>m</td><td>sponges, tuberoids, echinoderms, foraminifera (Lenticulina, Spirillina), belemnites</td><td>ammonites</td><td>glauconite</td><td>hemi-pelagic sedimentation</td></tr><tr><td>dp3</td><td>Micrite</td><td>M</td><td>undifferentiated bioclasts</td><td></td><td>birdseyes</td><td>distal platform sedimentation</td></tr><tr><td>dp4</td><td>Bioticrite</td><td>M</td><td>echinoderms, Spirillina, calcispheres, encrusting foraminifera, Lenticulina</td><td>quartz</td><td>intense bioturbation</td><td>hemi-pelagic sedimentation</td></tr><tr><td>dp5</td><td>Bioticrite</td><td>W</td><td>undifferentiated bioclasts</td><td>ostracodes, tuberoids, lithoclasts, encrusting foraminifera, Protoglobigerinids</td><td>bioturbation</td><td>hemi-pelagic sedimentation</td></tr></table>

Siliceous sponge reefs

<table><caption>Tab. 2.2 - Main microfacies occurring in the Haute-Marne and Swabian Jura sections representing deep platform environments.</caption><tr><td>dp6</td><td>Bioticrite</td><td>B - M</td><td>siliceous sponges/microbialites</td><td>brachiopods, bivalves, tuberoids, peloids</td><td></td><td>siliceous sponge-microbialites bioerms</td></tr><tr><td>dp7</td><td>Bioticrite</td><td>W</td><td>reworked siliceous sponges</td><td>tuberoids</td><td>nodular aspect</td><td>reworked sponges - close to sponge reefs</td></tr><tr><td>dp8</td><td>Bioticrite</td><td>B (P)</td><td>siliceous sponges/microbialites</td><td>serpulids, echinoderms, peloids, glauconite</td><td>nodular aspect</td><td>in marly intervals - sponge reefs</td></tr><tr><td>dp9</td><td>Bioticrite</td><td>W - P</td><td>tuberoids, echinoderms, encrusting foraminifera</td><td>peloids, bivalves, brachiopods, serpulids, gastropods, Lenticulina, sponges fragments, glauconite</td><td></td><td>around sponge reefs</td></tr><tr><td>dp10</td><td>Pel-bioticrite</td><td>P</td><td>peloids, tuberoids</td><td>encrusting foraminifera, echinoderms, brachiopods, undifferentiated bioclasts</td><td></td><td>around sponge reefs</td></tr></table>

<table><thead><tr><th>Code</th><th>Texture<br>Folk</th><th>Texture<br>Dumham</th><th>Major components</th><th>Other components</th><th>Sedimentary<br>features</th><th>Interpretation</th></tr></thead></table>

BASIN

Marl-limestone alternations (para- to autochthonous)

<table><tr><td>b1</td><td>Marls</td><td>m</td><td>-</td><td>foraminifera, bivalve fragments</td><td></td><td>hemi-pelagic sedimentation</td></tr><tr><td>b2</td><td>Marls</td><td>m</td><td>-</td><td>ooids</td><td>pyrite</td><td>hemi-pelagic sedimentation</td></tr><tr><td>b3</td><td>Bioticrite</td><td>M</td><td>Globochaete, echinoderms, Spirillina, Lenticulina, ostracodes, encrusting foraminifera, calcispheres</td><td>pyrite, quartz</td><td>bioturbation</td><td>hemi-pelagic sedimentation</td></tr><tr><td>b4</td><td>Bioticrite</td><td>W</td><td>ostracodes, bivalves, echinoderms, Lenticulina</td><td>radiolarians, Protoglobigerinids, encrusting foraminifera</td><td></td><td>hemi-pelagic sedimentation</td></tr><tr><td>b5</td><td>Bioticrite</td><td>W</td><td>radiolarians, Protoglobigerinids</td><td>ammonites, Globochaete, ostracodes, echinoderms, Lenticulina, calcispheres, Spirillina, encrusting foraminifera</td><td>bioturbation</td><td>hemi-pelagic sedimentation</td></tr></table>

Resediments sediments (allochthonous to para-autochthonous)

<table><caption>Tab. 2.3 - Main microfacies occurring in the SE France section representing basin environment.</caption><tr><td>b6</td><td>Intramicrite</td><td>P - Rud</td><td>lithoclasts, calcareous sponges fragments, radiolarians, Protoglobigerinids</td><td>echinoderms, bivalves, encrusting foraminifera, type 3 ooids,</td><td></td><td>breccia - probably debris flows</td></tr><tr><td>b7</td><td>Intramicrite</td><td>P - G</td><td>lithoclasts</td><td>type 3 ooids, Lenticulina, echinoderms, undifferentiated bioclasts, tuberoids?</td><td>slump, grading</td><td>calcareanites - probably turbidites reworked by contour currents or tempestites?</td></tr></table>

2.4.1 Non-skeletal elements

In Balingen-Tieringen, lithoclasts and peloids are commonly observed (Tab. 2.2). Lithoclasts are sub-rounded particles, mainly composed of sponge fragments, foraminifera, and peloids embedded in a micritic matrix. In the resediments of the Vergons section, lithoclasts and ooids occur locally.

2.4.2 Skeletal elements

Sponges and tuberoids

Sponges and tuberoids commonly occur in the Balingen-Tieringen section (Tab. 2.2; Pl. 7/5 and Pl. 13/3). Siliceous sponges are typical dwellers of deep

platform and basinal environments, forming sponge reefs. These sponge boundstones pass laterally to marl-limestone alternations more or less rich in tuberoids. This term was suggested for irregularly shaped, dark calcareous lumps of varied size (0.1 mm to several millimetres), which show various internal microstructures (dense or peloidal micrite, locally still visible sponge microstructure) corresponding to transported sponge fragments that are in decomposition (FRITZ 1958; FLÜGEL & STEIGER 1981; Pl. 7/7-9 and Pl. 13/3-4). Some tuberoids are encrusted by nubeculariids and other microencrusting foraminifera (Pl. 7/10), and/or perforated by lithophages. This indicates that these particles stayed a certain time on the sediment surface in a semi-lithified state before being buried in carbonate mud.
The distribution of siliceous sponges in deep-
marine environments is mainly controlled by trophic
level, substrate, and sedimentation rate (OLIVIER et al.
2004b). The abundance of tuberoids and lithoclasts
in some beds implies the proximity of sponge reefs
(FLÜGEL & STEIGER 1981) and strong bottom currents
(BRACHERT 1992; PAWELLEK & AIGNER 2003).

Radiolarians

In the studied limestones, radiolarians are locally
abundant, particularly in the carbonate-dominated
part of the Vergons section (Pl. 7/4, 6; Tab. 2.3). The
preservation of radiolarian tests is relatively poor; they
are generally calcitized.

Planktonic foraminifera

Protoglobigerinids are observed in the Balingen-
Tieringen and Vergons sections, where they are
commonly associated with ammonites and radiolarians
(Pl. 8/10-12). These planktonic foraminifera are known
from the Liassic to the Early Cretaceous and their
abundance is essentially linked to increased nutrient
supply (HEMLEBEN et al. 1988).

Cephalopods

Cephalopods are common in the Vergons section and occur locally in the Balingen-Tieringen deep-platform section. They are represented by ammonites, aptychi, and belemnites. Ammonites usually are seen at the surfaces of limestone beds or in marly intervals whereas belemnites have a more widespread distribution.

Filaments

Filaments, interpreted as juvenile shells of pelagic
bivalves, locally occur in the Vergons section (Pl.
7/3).

Glochochaete

*Glochochaete* (LOMBARD 1945) are common con-
stituents of the Vergons section. They are fibro-radial
calcite spheres with a diameter of 10 to 100 µm and
show a characteristic cross under polarized light. They
occur in clusters, isolated, or serially arranged (Pl.

7/3). They are interpreted as calcified cysts of unicel-
lular planktonic green algae. *Glochochaete* are abun-
dant in open-marine pelagic carbonates but also occur
in shallow-marine environments (TOMASOVYCH 2004).

Calcispheres

Calcispheres are commonly present in the Vergons
section and locally in the Latrecey section. They con-
sist of small globules with diameters of 20 to 100 µm.
Their test is made of calcite, commonly displaying
several layers with different texture (hyaline, micro-
granular, and/or fibro-radial). In pelagic sediments,
calcispheres are generally interpreted as cysts of dino-
flagellates (KEUP 1991).

Benthic foraminifera

In the Balingen-Tieringen section, the most
common benthic foraminifera are *Lenticulina* and
Miliolids (Tab. 2.2). Encrusting foraminifera such
as *Bullopora tuberculata*, *Tolypammina* sp., and
Nubeculariids are common (Pl. 10). In the Latrecey
and Vergons sections, *Spirillina* and *Lenticulina* occur
(Tabs 2.2 and 2.3). Compared to shallow platform
environments, benthic foraminifera are relatively
rare. Most of the specimens have probably been
exported from the platform and thus cannot be used
for palaeoecological interpretations.

2.4.3 Others constituents

Millimetric green grains are observed at the base
of the Balingen-Tieringen section (cf. Annex 2).
EDX analyses have shown that they are glauconite,
corroborating the deeper, open-marine setting (VAN
HOUTEN & PURUCKER (1984).

2.4.4 Carbonate mud

A source of micrite in basinal settings is nan-
nofossils; degradation of foraminiferal tests is
considered to be only a minor contribution (FLÜGEL
2004). However, for the Late Oxfordian deep-shelf
deposits, the relative scarcity of nannofossils and
insignificant bioerosion in autochtonous sponge reefs
that could have produced fine-grained carbonate
suggest that carbonate mud exportation from the
shallow platform was important (PITTET & STRASSER
<figure><img src="image_11.png" /><figcaption>**Fig. 2.2** - Distribution of main components in the studied sedimentary systems from shallow platform (Swiss Jura and Lorraine) to basin (SE France).</figcaption></figure>
1998a, b; c.f. Chap. 5). PITTET et al. (2000) observed that the marly intervals are richer in nannofossils than the limestone beds. The higher the sediment accumulation rate, the lower is the nannofossil record. This suggests that the main factor responsible for the generally low nannofossil content is dilution by allochthonous carbonate mud.

### 2.4.5 Reworked sediments

Episodically, resediments interrupt the “normal” sedimentation in the Vergons section. Calcarenites occur at several levels (beds 48, 50, and 71; Fig. 4.23; Pl. 13/7-8) and have a packstone-grainstone texture with allochthonous particles (microfacies b7, Tab. 2.3). They are interpreted as turbidites reworked by contour currents (PELLATON & ULLRICH 1997). A level of breccia is also identified (bed 53; Pl. 2/3). The matrix of this bed has a packstone texture with autochthonous and allochthonous particles (microfacies b6, Tab. 2.3) and is interpreted as a debris flow (PELLATON & ULLRICH 1997).

### 2.4.6 Sedimentary structures

#### Bioturbation

Bioturbation is very common in deep-water marine environments. In the Vergons section, bioturbation is common within limestones and locally marked by nodular bed surfaces (Pl. 17/6). In the Latrecey section, trace fossils such as *Zoophycos* locally occur. *Chondrites* are locally present in the Balingen-Tieringen section.

## 2.5 MICROFACIES CLASSIFICATION

Based on 505 polished slabs and thin sections as well as on 60 washing residues of marls, a microfacies classification has been established for the three studied sedimentary domains (Tabs 2.1, 2.2 and 2.3; Annex 3). According to the microfacies and the associated sedimentary features, the depositional environments are interpreted.

For the platform, discriminating criteria are components, fauna association and diversity, Dunham classification, and terrigenous particles. Environmental conditions such as energy, salinity, oxygenation, and trophic level are also evaluated (Fig. 2.3). For example, the co-occurrence of stenohaline organisms such as corals, brachiopods, and echinoderms indicates normal salinity in open-marine environments, whereas charophytes, ostracodes, and gastropods imply restricted environments. High-diversity fauna indicates normal salinity and open-marine conditions whereas low-diversity fauna indicates protected environments with variable salinity. Siliciclastics are generally more abundant in proximal environments (protected lagoon to semi-open lagoon) but can be transported by currents onto the platform and deposited in depressions (PITTET 1996).

Contrary to platform facies, deeper marine facies are less diversified and classified according to their lithology and the abundance of para-autochthonous and/or allochthonous particles. Marl-limestone alternations are common in deep platform and basin environments. Sponge reefs occur only in the Swabian Jura, resediments only in SE France.

<table><caption>**Fig. 2.3** - Characterization of depositional environments and environmental conditions of lagoonal deposits investigated in the Swiss Jura Mountains. Water energy, salinity, oxygenation, and trophic level are used as discriminating factors.</caption><thead><tr><th>Environments</th><th>Protected</th><th>Semi-open</th><th>Open</th></tr></thead><tbody><tr><th>Environmental conditions</th><td>Semi-restricted</td><td colspan="2">Normal-marine</td></tr><tr><th>Fauna association</th><td>euryhaline fauna (charophytes, ostracodes, gastropods)</td><td colspan="2">stenohaline fauna (echinoderms, brachiopods, corals)</td></tr><tr><th>Fauna diversity</th><td>low</td><td>moderate</td><td>high</td></tr><tr><th>Energy</th><td>low</td><td colspan="2">low to high</td></tr><tr><th>Salinity</th><td>low, variable</td><td colspan="2">normal, constant</td></tr><tr><th>Trophic level</th><td>eutrophic</td><td>mesotrophic</td><td>oligotrophic</td></tr></tbody></table>
<figure><img src="image_12.png" /><figcaption>Fig. 2.4 - Block diagram showing the spatial relations (not to scale) between the studied environments. Modified from PITTET (1996).</figcaption></figure>

The major organic and inorganic components of these domains are schematically positioned along a platform-basin transect (Fig. 2.2), and the major microfacies types are presented in Pl. 11 to Pl. 13.

## 2.6 DEPOSITIONAL ENVIRONMENTS

Based on facies and microfacies analyses, depositional environments can be interpreted. A three-dimensional block-diagram is used to better illustrate the lateral coexistence of the interpreted depositional environments, particularly on the shallow platform (Fig. 2.4).

### 2.6.1 Shallow platform

In the Late Oxfordian, the Swiss Jura region corresponded to a shallow carbonate platform (Fig. 1.3). The presence of tidal structures implies tidal (sand or mud) flat environments (Tab. 2.1). Tidal flats consist of areas regularly to rarely cover by water, dominated by weak current and wave action due to their position behind beach-barriers and around lagoons. Three types of shallow lagoon are considered in this study. The protected lagoon consists of marls and limestones with semi-restricted fauna (e.g., bivalves, gastropods,

ostracodes, inocerams, serpulids, Miliolids), a relatively low-diversity fauna, and intense bioturbation (Tab. 2.1). Due to its proximity to the hinterland, the terrigenous input is important in protected lagoons. The semi-open and open lagoons are mainly characterized by carbonate-dominated facies, from mudstone to grainstone, with a higher diversity fauna, normal salinity conditions and a relatively low turbidity (Tab. 2.1). Coral patch-reefs and/or coral carpets commonly occur in open lagoons (Tab. 2.1). Coral reefs and ooid bars exist on the platform edge or within the platform, probably depending on the tectonically induced morphology (Fig. 2.4). Siliciclastics are common but heterogeneously distributed. They concentrate in depressions, formed by differential subsidence, or in-between ooid shoals and coral reefs.

### 2.6.2 Deep platform and basin

Deep platform and basin environments are mainly dominated by hemipelagic to pelagic sedimentation. In the deep platform facies of the Swabian Jura, marl-limestone alternations pass laterally into sponge reefs (Tabs 2.2 and 2.3). The limestone facies are commonly sponge boundstones and wackestones-packstones with bioclasts and tuberoids. Marls contain sponges, tuberoids, echinoderms, benthic foraminifera (Lenticulina, Spirillina, Miliolids),
ostracodes, *Tolypammina*, ammonites, and belemnites. The abundance of tuberoids and lithoclasts in some beds implies variations in water-energy conditions (bottom currents) probably related to relative sea-level changes (BRACHERT 1992; PAWELLEK & AIGNER

2003). In basin environments, sedimentation is much more monotonous than on shallow-water platform environments (Tabs 2.2 and 2.3). Marl-limestone alternations are episodically interrupted by reworked sediments mainly generated by slope instabilities.

* * *
# 3 - SEQUENCE ANALYSIS

## 3.1 INTRODUCTION

Sequence stratigraphy is a conceptual model that explains stratigraphic patterns and the evolution of sedimentary basins mainly as the effects of large-scale eustatic sea-level changes and tectonics (e.g., VAIL et al. 1977; POSAMENTIER et al. 1988, 1992; POSAMENTIER & JAMES 1993; HUNT & TUCKER 1992, 1995; KOLLA et al. 1995; MIALL 1986, 1991, 1997; NYSTUEN 1998). Sequence stratigraphy is a relatively new methodology, introduced by the research group of EXXON (VAIL et al. 1977) for documenting and interpreting the sedimentary record.

Originally, the sequence-stratigraphic model was developed on the basis of seismic studies on passive continental margins and mostly in siliciclastic systems, which had a low vertical resolution, and which only allowed to identify major lithological changes and stratigraphic geometries. Even with the technical advance in seismics, coring, and downhole logging, outcrop-based studies offer a higher level of detail and the advantage of working with real rocks and surfaces. Yet, a disadvantage is the common lack of information on geometries of large-scale sediment bodies in outcrop. The methods based on identification of remarkable surfaces interpreted as time lines (e.g., subaerial unconformities, transgressive and maximum-flooding surfaces calibrated by other stratigraphical methods) and therefore places sequence stratigraphy in a chronostratigraphic framework.

Over the years, the initial concepts of sequence stratigraphy were refined by integrating the results of numerous case studies. This led to a continuous questioning and redefining of the principles and terminology and ever finer stratigraphic subdivisions for different sedimentary environments. Different

schools of thought and different models developed, depending on how sequences are identified and subdivided and on the interpretation of which kinds of processes have controlled the genesis of depositional sequences. In addition, the evolution of concepts and theories has been studied by MIALL & MIALL (2001) from a sociological point of view. The main models are the original EXXON model of VAIL et al. (1977), the genetic sequences of GALLOWAY (1989), the T-R sequences of EMBRY (1993, 1995), the base-level cycles of CROSS (1991) and CROSS & LESSENGER (1998), and the regime theory of THORNE & SWIFT (1991a, b) that led to the accommodation-supply model of SCHLAGER (1993) (for a detailed review see NYSTUEN 1998).

Eventually, it has been realized that eustatic variations are not necessarily the dominant factor controlling the formation of depositional sequences in tectonically unstable settings or in carbonate systems (e.g., CLOETINGH 1988; HUBBARD 1988; SCHLAGER 1989, 1991, 1993). Also the validity of global correlations of apparently eustatic events as presented in global cycle charts (HAQ et al. 1988) was questioned (MIALL 1991, 1992).

## 3.2 DEPOSITIONAL SEQUENCES

### 3.2.1 Definition

A depositional sequence is a succession of genetically related sediments whose facies evolution and/or stacking pattern is repetitive within a section. Depositional sequences are commonly delimited by discontinuity surfaces or intervals of well-marked (facies) change, indicating an inversion in the trend of environmental change. They are the stratigraphic expression of recurring environmental changes, independent of scale and time. This is the original
<figure><img src="image_13.png" /><figcaption>**Fig. 3.1** - Theoretical model of depositional sequences controlled by relative sea-level fluctuations (accommodation). Sequences are subdivided into deposits, which correspond to the system tracts of VAIL et al. (1977). For discussion refer to text.</figcaption></figure>

definition of VAIL et al. (1977) and will be used in our case study. For simplicity, the terms “cycle” and “cyclic” will be used for such changes, although recurrences in natural systems are at the most quasi-periodic (SCHWARZACHER 2000). In this study, the term “sequence” is used synonymously with “depositional sequence”.

### 3.2.2 Formation of depositional sequences

The term “eustasy” describes a global sea level with reference to a fixed datum (e.g., centre of the Earth; POSAMENTIER et al. 1988). Because it is generally not clear whether investigated sedimentary records have primarily been controlled by eustatic sea-level changes, by tectonic movements and/or by sedimentary processes, the term “relative sea level” has been introduced. Relative sea level includes eustasy (i.e., net sea-level change) and local subsidence and/or uplift by referring to the position of a datum (e.g., basement) or the sea floor (POSAMENTIER et al. 1988). A depositional sequence results from one cycle of relative sea level.

The combination of changing eustatic sea level and vertical crustal movements (subsidence) creates

accommodation space, which can be filled with sediment over time (Fig. 3.1). On shallow carbonate platforms, accommodation variations through time are generally represented by thickness variations of depositional sequences (or beds) and facies evolution. However, the stacking pattern depends not only on variations of accommodation space but also on variations of sediment accumulation (POSAMENTIER et al. 1992; SCHLAGER 1993). Accommodation loss or gain does not always result from a decrease or increase of relative sea level but can also come from more or less sediment supply or *in situ* production. KENDALL & SCHLAGER (1981) stated that “stratigraphic sequences of shallow-water deposits and their facies patterns are primarily controlled by the rates and types of sedimentation, local crustal movements, and eustatic sea level”.

### 3.2.3 Criteria for sequence identification and interpretation

Criteria to identify and interpret depositional sequences are multiple. Sedimentological analysis provides various parameters such as deepening-up and shallowing-up trends in general facies evolution,
variations of fauna and flora composition, interpretation of beds and discontinuities, and vertical variations in bed thickness and stacking patterns. Specific analyses of diagenetic features or geochemical signatures (e.g., stable isotopes), the study of clay-mineral abundance and composition, and palynofacies can give supporting evidence (e.g., BLONDEL et al. 1993; JOACHIMSKI 1994; BUDD et al. 1995; PASQUIER 1995; PITTET & GORIN 1997; PLUNKETT 1997; HILLGÄRTNER 1999; RAMEIL et al. 2000; COLOMBIÉ 2002; D'ARGENIO et al. 2004).

## Facies evolution

Facies evolution is the sedimentary expression of environmental changes, which can be the result of intrinsic cycles within the depositional system (autocycles), or which follow cyclic or quasi-linear external forcing mechanisms (allocycles; STRASSER 1991). Lateral and vertical facies evolution is the main tool for sequence-stratigraphic analysis. In this study, the examination of lateral facies variations is limited by the outcrop extension. Vertical facies variations marked as deepening-up and shallowing-up trends are commonly linked to bathymetric changes on the shallow platform. However, migrating sediment bodies can produce a shallowing-up sequence also at constant relative sea level (e.g., PRATT & JAMES 1986).

## Discontinuity surfaces, bedding and stacking pattern

Discontinuity surfaces on shallow-marine carbonate platforms are characterized by a wide variety of diagnostic features (HILLGÄRTNER 1999). All surfaces reflect reactions of the sedimentary system to rapid and drastic environmental changes. Changes in energy regime, relative sea level, accumulation rate, and sediment type are expressed, in the sedimentary record, by subaqueous erosion, subaerial exposure (including erosion), or subaqueous omission. Discontinuity surfaces may correspond to sequence boundaries, transgressive surfaces, maximum-flooding surfaces, or else they may result from an autocyclic process. Single beds are always delimited by discontinuity surfaces of various types (HILLGÄRTNER 1999). One bed may represent an entire depositional sequence, but in many cases a depositional sequence includes several beds. If facies contrast is low, several sequences may be amalgamated in one bed. Stacking pattern and thickness variations of all depositional

sequences reflect environmental changes through time that caused variations in accommodation and/or accumulation rate (STRASSER et al. 1999). For example, on carbonate platforms, a thickening-up trend of beds commonly points to increasing accommodation space while a thinning-up trend may reflect a loss of accommodation. However, thinning-up can also be created by rapid deepening that reduces the carbonate production.

## Bioturbation

The degree of bioturbation is closely related to specific environmental conditions. Hence, it can be an excellent tool to interpret depositional sequences (PEMBERTON et al. 1992). The intensity of bioturbation is a function of sediment accumulation rate, oxygenation, and nutrient availability (e.g., WETZEL 1991; WIGNALL 1993). In platform environments, terrigeneous input can significantly increase nutrient levels, which may result in major overturns of benthic communities and consequently in a drop of carbonate production and accumulation rate (e.g., HALLOCK & SCHLAGER 1986; DUPRAZ & STRASSER 1999). The intensity of bioturbation seems to be independent of substrate type (e.g., muddy vs. grainy) but is particularly high below firm- and hardgrounds (HILLGÄRTNER 1999). This implies that sediment accumulation rate is the most important controlling factor on bioturbation intensity in these environments.

## Clay content

Variation of clay content in platform carbonates is commonly expressed by differential weathering of the outcrop strata. This accentuates the stacking pattern of beds and depositional sequences. However, even marly intervals may, once excavated, reveal additional limestone beds (cf. Chap. 4). Most clay minerals in marly sediments are of detritic origin and result from erosion of crystalline bedrock and/or palaeosols. Clays are generally transported by rivers to the coastal plain and to marine depositional settings. Marl deposits (clay minerals and carbonate mud) commonly accumulate in low-energy conditions in supratidal to subtidal environments and thus can be reworked by currents and waves (cf. Chap. 7). In marginal-marine settings, they are deposited in shallow protected lagoons and in deeper, open-marine environments below the action of waves.
<figure><img src="image_14.png" /><figcaption>**Fig. 3.2** - Different models for clay occurrence in marginal-marine environments caused by relative sea-level changes and climate (modified from STRASSER & HILLGÄRTNER 1998). Examples of depositional sequences are taken from the studied sections. For legend of symbols, refer to Fig. 4.1.</figcaption></figure>

The relative abundance of clay minerals in carbonates is the result of two phenomena (EINSELE & RICKEN 1991): (1) variations of terrigeneous input with a constant rate of carbonate production (dilution cycle) or (2) variations in carbonate production with constant terrigeneous influx (productivity cycle). Both phenomena are closely connected on shallow carbonate platforms (HILLGÄRTNER 1999) as well as in hemipelagic settings (EINSELE & RICKEN 1991). The occurrence and distribution of clay minerals on shallow carbonate platforms can be related to three main types of environmental changes caused by relative sea-level fluctuations and climate changes (STRASSER & HILLGÄRTNER 1998; Fig. 3.2):

(a) A relative sea-level fall enlarges the emersion area in coastal settings. Consequently, an increase of continental erosion, pedogenesis and subsequent clay input to shallow-marine environments can be postulated. Accordingly, the clays are associated with the shallowest facies. The occurrence of charophytes (cf. Chap. 2) points to the formation of freshwater ponds on the partly emergent platform.

(b) A relative sea-level fall and low sea level can lead to isolation of pools and shallow lagoons decreasing and/or cutting off open-marine influence. Such environmental isolation reduces water energy, enabling the settling out of clay minerals. In this
case, marly intervals are characterized by relatively
restricted fauna, increased bioturbation (lowered
accumulation rates) or dysoxic facies due to reduced
water circulation.

(c) A relative sea-level rise and high sea level can also provoke low-energy conditions by rising wave base. Marls deposited under such conditions are characterized by open-marine constituents, indicating a relatively deep facies. Bioturbation intensity may be high, due to lower carbonate production. A sea-level rise can also lead to an additional input of clay minerals by the erosion and reworking of previously exposed palaeosols during transgression.

Furthermore, an elevation of rainfall in the hinter-
land increases the surface run-off and may increase the
clay input into the marine depositional system. Clay
minerals in marginal-marine environments, there-
fore, can be interpreted as a climate signal depending
mainly on palaeolatitude and on atmospheric circu-
lation patterns (e.g., PERLMUTTER & MATTHEWS 1989,
1992; KINDLER et al. 1997; PITTET & STRASSER 1998a).
In certain palaeogeographic positions and palaeocli-
matic regimes, climate may be more humid at high
sea-level stands, in other contexts more rain occurs at
low sea levels (PITTET 1996). The kaolinite/illite ratio
can furnish information on the climatic conditions (cf.
Chap. 8).

Other criteria

Stable isotope analyses (δ¹³C, δ¹⁸O) are commonly
used to interpret depositional and diagenetic histories
of shallow carbonate limestones (e.g., ALLAN &
MATTHEWS 1982; JOACHIMSKI 1991, 1994; cf. Chap.
8). For example, subaerial exposure may be identified
by isotopic signatures even if sedimentary evidence
is lacking (PLUNKETT 1997). However, particularly in
shallow-marine carbonates, diagenetic overprinting
of the original isotopic signals must be considered
when using stable isotopes for the interpretation
of depositional sequences. Palynofacies analyses
investigate particulate and amorphous organic matter
in order to determine the ratio of terrestrial and marine
influences. Such ratios then have been used to interpret
depositional sequences in different environments (e.g.,
PITTET & GORIN 1997). Geochemical analyses of trace
elements have been used to investigate environmental
conditions and to relate trace element evolution to
depositional sequences (COLOMBIÉ 2002; VINCENT et
al. 2006).

3.3 SEQUENCE MODEL AND
TERMINOLOGY APPLIED

The Fribourg approach is a combination of sequence- and cyclostratigraphic aspects developed for studying depositional sequences on shallow-water carbonate platforms, but its principles are generally applicable (cf. Chap. 6). Methodology and reasoning for interpretation are summarized in STRASSER et al. (1999) and STRASSER et al. (2000). Over more than a decade, the approach for interpreting successions of carbonate rock in outcrops have been improved and refined by high-resolution outcrop studies in Mesozoic carbonate platform environments in the French and Swiss Jura Mountains (STRASSER 1994; PASQUIER 1995; PITTET 1996; PASQUIER & STRASSER 1997; PITTET & STRASSER 1998a, b; STRASSER & HILLGÄRTNER 1998; HILLGÄRTNER 1999; COLOMBIÉ 2002; COLOMBIÉ & STRASSER 2003, 2005; HUG 2003). The nomenclature and terminology are partly based on the sequence-stratigraphic model of VAIL et al. (1991). However, the stacked depositional sequences of different sizes are not attributed to different orders that have a predefined connotation of time (STRASSER et al. 1999). Consequently, the applied nomenclature has the advantage of being purely descriptive at the beginning. The time attribution is only given after a thorough sequence- and cyclostratigraphic analysis. The Fribourg approach avoids the term “systems tract” because large-scale geometries are mostly not visible in outcrop. Accordingly, this study speaks of lowstand, transgressive, and highstand “deposits” instead of “system tracts” (Fig. 3.1).

3.3.1 Discontinuity surfaces and deposits

Discontinuity surfaces and deposits of a sequence
are independent of the temporal scale of relative
sea-level change. A sequence boundary (SB) forms
during the fastest relative sea-level fall (Fig. 3.1). It
causes decrease of accommodation space creating
the highest possibility for subaerial exposure (i.e.,
birdseyes, desiccation cracks, karst dissolution).
It can be a surface or interval marked by exposure
structures, restricted facies, subaerial erosion or
pedogenesis. In platform settings, lowstand deposits
are very thin, missing, or reworked in the transgressive
sediments. They are commonly represented by low-
energy facies with low-sedimentation rate. It is very
difficult to distinguish, in terms of facies, deposits
that correspond to a lowstand of relative sea level
("lowstand deposits", LD) from deposits that
formed during the initial phase of the subsequent
transgression (“early transgressive deposits”, eTD).
In the traditional sequence stratigraphic model, the
sediments of the lowstand systems tract are located
below the platform edge on the slope (VAIL et al.
1991). Thus, in order to avoid confusion, all deposits
that are located between well-developed SB and TS,
corresponding to a low sea level and/or the beginning
of the subsequent transgression, are labelled early
transgressive deposits (eTD). These deposits have the
lowest preservation potential and tend to be eroded
and reworked during the subsequent transgression
(WALKER 1995). Consequently, transgressive surfaces
in many cases directly overlie the sequence-bounding
exposure surfaces (SB/TS).

The transgressive surface (TS) corresponds
to the first flooding, permitting the restoration of
sedimentation (Fig. 3.1). It is marked by rapid facies
changes from the relatively shallowest facies to
deeper sedimentary environments. Just after the initial
flooding, carbonate production is still in “start up”
mode (KENDALL & SCHLAGER 1981) and thus the TS
is commonly characterized by reworked clasts (“lag
deposit”) and an abrupt increase in mean grain diameter.
Because of rapid cementation of carbonates during
subaerial exposure, erosion during transgression is less
important than in siliciclastic systems (“transgressive
surface of erosion (TSE)”, NUMMEDAL & SWIFT 1987;
“ravinement surface”, SWIFT 1968). The “start up”
phase is equivalent to the “lag time” of STRASSER
(1991). Deposits that indicate relative deepening and/
or opening of the system are called “transgressive
deposits” (TD) (Fig. 3.1). They correspond to the
phase when accommodation increases during relative
sea-level rise, after an initial flooding. At the beginning
of a sea-level rise, accommodation is created on the
shallow platform, but carbonate production is still low
(“start-up” phase). Carbonate export from the platform
is still limited, and the deep shelf records only little
carbonate (PITTET & STRASSER 1998a).

With increasing water depth and the recovery of the
carbonate factory, conditions become ideal for maxi-
mum carbonate production and thus the previously
created accommodation space begins to fill up (“catch
up” phase, KENDALL & SCHLAGER 1981). A maximum-
flooding surface or interval indicates the fastest rela-
tive sea-level rise and matches with the most important
bathymetry (Fig. 3.1). Intensively bioturbated and/or
marly intervals or distinct omission surfaces testify to
reduced sedimentation rate. If a distinct single surface
is developed, this is denoted as “maximum flooding

surface" (MFS) generally displaying hardgrounds,
intensely bioturbated surfaces, or ferruginous crusts. In
the case of repeated maximum-flooding surfaces or an
interval that lacks distinct surfaces but clearly shows
the most open-marine conditions, the term "maximum
flooding" (MF) is used. If the sea floor drops below
the photic zone during maximum flooding, carbonate
production and accumulation will be reduced ("give-
up" phase). However, in shallow-water, maximum
flooding may also be indicated by the thickest beds
because accommodation gain is highest. In basinal
setting, the maximum flooding corresponds to a con-
densed section (CS) characterized by low accumula-
tion rates (LOUTIT et al. 1988; BASSANT 1999).

After the maximum flooding, facies indicate a
shallowing trend that correspond to a slow-down in
relative sea-level rise and an initial fall: these are the
"highstand deposits" (HD) (Fig. 3.1). In some cases,
facies permit to distinguish early highstand deposits
(eHD) that still correspond to relatively open or
deep environments, and late highstand deposit (IHD)
that show shallowing up. During the highstand, the
carbonate platform is usually in "keep-up" mode
(KENDALL & SCHLAGER 1981). If the carbonate
production matches the creation of accommodation
space, the platform will grow predominantly vertically
(aggradation). However, when carbonate production
is higher than the creation of accommodation space
(especially in the late highstand phase), sediment fills
up to sea level and the platform progrades towards
the basin. Therefore, during highstand conditions,
the carbonate export from the platform to the basin
increases.

3.4 TYPES OF DEPOSITIONAL SEQUENCES
IN THE STUDIED SECTIONS

On the shallow platform, three types of depositional
sequence are distinguished. They are defined by their
characteristic facies evolution and the enhancement
or attenuation of characteristic surfaces, which
indicate bathymetric changes (Fig. 3.3). Rather than
shallowing or deepening trends, facies evolution may
also indicate changes from more open-marine to more
restricted conditions and vice versa. In deeper marine
environments, one type of depositional sequence
exists: the marl-limestone alternation (or couplet)
(Fig. 3.4). These types of sequences are observed at
the scale of elementary and small-scale sequences (cf.
Chap. 3.5).
**Example for a SB-sequence**

(Savagnières section; from 5.4 to 7.0 m)

<figure><img src="image_15.png" /></figure>

**Example for a TS-sequence**

(Savagnières section; 8.1 to 9.7 meters)

<figure><img src="image_16.png" /></figure>

**Example for a MF-sequence**

(Voyeboeuf section; 8.35 to 9.55 meters)

<figure><img src="image_17.png" /><figcaption>**Fig. 3.3** - Examples of SB-, TS-, MF-sequences from the studied sections (see text for discussion). For symbols, refer to Fig.4.1.</figcaption></figure>
## Deepening-shallowing sequences defined by sequence boundaries (SB-sequences)

In SB-sequences, facies evolution through time indicates that water depth first increased, then decreased. In shallow-water carbonate-dominated environments, their evolution is commonly asymmetric, i.e., many depositional sequences are composed of a thin deepening-up and a thick shallowing-up part (e.g., STRASSER 1988; JONES & DESROCHERS 1992; PRATT et al. 1992). The shallowing-up trend is due to the high production and accumulation rates of carbonate platform systems, which — as long as environmental conditions are favourable — easily outpace relative sea-level rise ("catch-up phase", KENDALL & SCHLAGER 1981). The shallowing-up trend may additionally be enhanced by the deceleration of sea-level rise and a subsequent fall. Prolonged emersion can lead to vadose cementation. If the climate is humid enough, a prolonged emersion may also produce chemical dissolution of carbonate grains (leaching), (incipient) pedogenesis, and karstification.

This type of depositional sequence corresponds to the definition of classical sequence stratigraphy where the sequence boundaries form during relative sea-level fall. However, the boundaries of such sequences may also be generated in subtidal or intertidal environments that reflect the relatively shallowest conditions within the sequence. Deepening-shallowing sequences that never reach intertidal or supratidal facies have been termed "subtidal cycles" by OSLEGER (1991). Shallowing-up sequences can also be created by progradation or migration of sedimentary systems (e.g., GINSBURG 1971; PRATT & JAMES 1986) without being related to sea-level fall. However, if supratidal facies and/or vadose diagenesis are directly superimposed on subtidal sediments, or if regressive surfaces of erosion can be correlated over large distances, relative sea-level fall must have been involved (STRASSER 1991).

## Deepening-shallowing sequences defined by flooding surfaces (TS-sequences)

These sequences display a facies evolution comparable to the sequences described above. The main difference is that the bounding discontinuities mark a rapid facies change from the relatively shallowest (or most restricted) to deeper (or more marine) sedimentary environments, which is attributed to transgressive

surfaces. As these surfaces are the most visible in the field and as evidence of subaerial exposure may lack or may not be well expressed, they define the depositional sequence (Fig. 3.3). Facies changes related to sea-level fall or maximum flooding may be identifiable but are commonly too subtle to be developed as well-expressed diagnostic surfaces or intervals. Such sequences are usually strongly asymmetric and can be compared to the "parasequences" of VAN WAGONER et al. (1990), which are defined as being bounded by marine flooding surfaces.

## Shallowing-deepening sequences defined by maximum flooding and/or condensation (MF-sequences)

In such sequences, facies evolution shows an inverse trend (shallowing to deepening). Depositional sequences are bounded by maximum-flooding surfaces, which are the best marked diagnostic surfaces seen in the field (Fig. 3.3). Some maximum-flooding surfaces are intensely bioturbated, suggesting low sedimentation rates; others are developed as firm- or hardgrounds, partly with fossil or mineral encrustations, suggesting strongly reduced sedimentation rates. This type of sequences can be compared to the "genetic sequences" defined by GALLOWAY (1989).

These three types of platform sequences have to be regarded as models or end members in a continuous spectrum of sequence architectures. In reality, any given sequence can combine features of the above-mentioned type-sequences to a different extent. For example, in transitional zones where the long-term trend of relative sea-level changes from rise to fall, all types of discontinuities can be well expressed. It may occur that a MF-sequence overlaps with a subsequent SB-sequence. SB-sequences generally form when the general, long-term sea-level trend is falling. TS- and MF-sequences tend to form when long-term sea level is rising.

## Basinal sequences

This type of depositional sequence consists of one marl-limestone alternation (Fig. 3.4). In some, but specifically in larger-scale depositional sequences, lowstand deposits consist of relatively thick packages of resedimented carbonates (STROHMENGER & STRASSER 1993). Major maximum floodings can be expressed
**Example for a basinal sequence**

(Vergons section; from 9.9 to 11.95 m)

<figure><img src="image_18.png" /><figcaption>**Fig. 3.4** - Examples of basinal sequence (see text for discussion). For symbols, refer to Fig.4.1.</figcaption></figure>

through sediment starvation, i.e. condensed sections and/or discontinuity surfaces that display evidence for condensation (e.g., iron/manganese crusts, glauconite, fossil concentrations, and bioturbation). In terms of sea-level variations, quantitative analysis of ammonite faunas in marl and limestone facies may define bathymetric increase and decrease (REBOULET & ATROPS 1997). In the present study, however, such analyses have not been performed.

The formation of marl-limestone alternations is subject of debate (e.g., EINSELE & RICKEN 1991; BÖHM 2003; WESTPHAL et al. 2004b). Their origin may be explained in part by periodic changes in: (1) **pelagic carbonate productivity** (EINSELE & RICKEN 1991; CLAPS et al. 1995; MATTIOLI 1997); (2) **import of carbonate mud from shallow platforms** (e.g., DAVAUD & LOMBARD 1973; GAILLARD 1983; BOARDMAN & NEUMANN 1984; BRACHERT 1992; MILLIMAN et al. 1993; PASQUIER & STRASSER 1997; PITTET & STRASSER 1998a; BETZLER et al. 1999; PITTET et al. 2000; COLOMBIÉ & STRASSER 2003); (3) **clay input from the hinterland**, and/or (4) **post-depositional processes** like differential diagenesis affecting carbonates during burial (e.g., EDER 1982; HALLAM 1986; MUNNECKE & STAMTLEBEN

1996; MUNNECKE et al. 1997; BÖHM 2003; WESTPHAL et al. 2004a, b). However, it has been demonstrated in many cases that marl-limestone alternations were deposited with Milankovitch periodicities (e.g., COTILLON 1991): orbitally forced insolation variations caused climatic and sea-level changes that acted on carbonate production and deposition, and/or on clay input. Differential diagenesis may subsequently have accentuated the contrast between limestones and marls.

## 3.5 HIERARCHY AND STACKING OF DEPOSITIONAL SEQUENCES

In all the studied sections, the depositional sequences are commonly stacked in a hierarchical pattern. In this high-resolution study, three hierarchies of sequences are recognized and described: elementary, small-scale, and medium-scale sequences. A part of this study is dedicated to the identification and correlation of the smallest depositional sequences (elementary sequences) and to their interpretation.
## Elementary sequences

These sequences are the smallest units recognizable in the sedimentary record and are defined as having formed through one cycle of environmental change (STRASSER et al. 1999). In the studied sections, they commonly consist of two to three beds, bounded by discontinuity surfaces. The thickness of elementary sequences usually ranges from a few centimeters to a few tens of centimeters. Deepening-shallowing trends or shallowing-up trends of facies evolution can be identified in many cases (SB- or TS-sequences). When accommodation is low, elementary sequences may not be deposited or eroded ("missed beats" of GOLDHAMMER et al. 1990). Consequently, the best chance of recording elementary sequences on the platform is during long-term transgression when accommodation space is created while carbonate production keeps up. Beds that can be clearly attributed to event deposits (e.g., tempestites, turbidites) are not considered as elementary sequences.

In basinal settings, elementary sequences consist of one marl-limestone couplet, interpreted as being related to change in planktonic carbonate productivity and/or input of clays, and/or carbonate mud export from the platform. In some cases, however, one cycle of sea-level change can produce two couplets because carbonate mud may be exported during transgression as well as during regression (PITTET & STRASSER 1998a).

## Small-scale sequences

Small-scale sequences in the studied sections are composed of five elementary sequences and measure from a few tens of centimeters to a few meters. They commonly show a well-defined deepening-shallowing facies evolution (SB- or TS-sequences), but shallowing- deepening trends also occur (MF-sequences). Asymmetry in the facies evolution (shallowing vs. deepening) is present (STRASSER 1991).

In basinal settings, small-scale sequences are commonly defined by thickening-upwards or thinning- upwards trends of a set of five limestone beds (cf. Fig. 3.4). These trends are often subtle and observable only in parts of the studied sections.

## Medium-scale sequences

Medium-scale sequences generally are composed of four small-scale sequences. If a smaller number

of small-scale sequences builds up the medium-scale sequence, this is always accompanied by evident features of erosion or non-deposition. Facies evolution is comparable to that of the small-scale sequences but usually shows a higher degree of complexity. Additionally, medium-scale sequences are delimited by well-developed discontinuity surfaces, testifying to exposure or condensation. Commonly, they display a rather symmetric deepening-shallowing facies evolution and a well-developed MF. Thickening-up of beds and small-scale sequences may appear in the lower part, thinning-up in the upper part, indicating overall increasing then decreasing accommodation. In addition, dolomitization is a common phenomenon at the base and top of medium-scale sequences; to a lesser degree in the early transgressive deposits at the base and well developed in the highstand deposits (RAMEIL 2005).

In the basin, medium-scale sequences can only be detected on the basis of abrupt changes in the stacking pattern of the small-scale sequences. This is expressed by changes in thickness of limestone and/or marl layers, which mirror general changes in sedimentation rate and changes in the ratio of lime *versus* clay sedimentation. More abundant gravity deposits (e.g., slumps, turbidites) indicate slope instability during sea- level lowstand. A gradual increase of marls towards the center of the sequence can be present implying maximum flooding. In many cases, however, changes in colour and weathering aspect due to changing contents of iron or clay are the only elements that permit to delimit the medium-scale sequences. The thickness of medium-scale sequences on the platform and in the basin varies from a few meters to a few tens of meters.

### 3.5.1 Superposition of relative sea-level changes

The observed hierarchical stacking of elementary, small-scale and medium-scale sequences cannot be explained by a simple sinusoidal curve of sea- level change. For the studied interval, the three orders of sequences described above are attributed to superimposed relative sea-level fluctuations with three different amplitudes and frequencies (e.g., GOLDHAMMER et al. 1990; MITCHUM & VAN WAGONER 1991; OSLEGER & READ 1991; STRASSER 1994; LEHRMANN & GOLDHAMMER 1999; Fig. 3.5). This superimposition of relative sea-level changes not only creates depositional sequences at different scales, but also leads to multiplication of their characteristic
<figure><img src="image_19.png" /><figcaption>**Fig. 3.5** - Superposition of medium-term, short-term, and high-frequency sea-level fluctuations can explain the stacking of sequences observed in the studied interval.</figcaption></figure>

discontinuity surfaces. Thus, a sequence boundary of a large-scale sequence will in many cases not consist of one well-marked surface but of a group of regressive discontinuity surfaces, each of them bounding small-scale or elementary sequences (MONTAÑEZ & OSLEGER 1993; PASQUIER & STRASSER 1997).

## 3.6 ALLOCYCLIC AND AUTOCYCLIC PROCESSES

Commonly, it is not straightforward to distinguish whether extrinsic (eustatic sea level, tectonics, climate change) and/or intrinsic processes have been involved in the deposition of the observed sedimentary succession (e.g., migration of sediment bodies; STRASSER 1991). At the scale of elementary

sequences, auto- and allocyclic processes have to be considered when interpreting the sedimentary record. However, autocyclic processes are less important in the formation of larger-scale sequences.

Different autocyclic models have been developed to explain the stacking pattern and/or the facies evolution of shallow-marine sedimentary successions. Shallowing-up sequences in peritidal carbonate systems have been explained by the combination of vertical aggradation and lateral progradation of tidal flats during a stable relative sea level ("tidal-flat model" according to GINSBURG 1971; in LEHRMANN & GOLDHAMMER 1999). Other models relate the deposition of shallowing-up sequences to the migration of islands and coeval subtidal areas and channels ("tidal flat - island model"; PRATT & JAMES 1986; SATTERLEY 1996).
These models, however, convince only for laterally discontinuous shallowing-up sequences (SCHLAGER 2005). Also shoal and tidal channel deposits are strongly controlled by autocyclic processes. However, they are of limited lateral extension, displaying rather a local depositional geometry.

Allocyclic forcing of sedimentary systems can be imposed by large-scale tectonics or climate changes. However, sea-level fluctuations have the most direct influence in shallow-marine depositional settings (e.g., ANDERSON & GOODWIN 1990). Allocyclic processes affect the sedimentation over a much larger area than autocyclic processes (HILLGÄRTNER 1999). Depositional sequences, which can be correlated between widely-spaced sections, therefore have mainly been controlled

by allocyclic processes. Different studies made by the Fribourg working group showed that small- and medium-scale sequences can be traced between measured sections for distances of up to 100 km (e.g., PASQUIER 1995; PASQUIER & STRASSER 1997; PITTET & STRASSER 1998b; HILLGÄRTNER 1999; COLOMBIÉ 2002; COLOMBIÉ & STRASSER 2003; RAMEIL 2005; TRESCH 2007). Therefore, it is possible to establish a sequence-stratigraphical framework at least on the level of small- and medium-scale sequences. The interpretation and correlation of elementary sequences remains a challenge. An attempt to push the limits of high-resolution sequence-stratigraphical interpretations by correlating elementary sequences over short and long distances is presented in Chapter 5.

* * *
**4 - STUDIED SECTIONS**

Sections have been investigated and sampled in great detail. For each section, a sedimentological description and facies interpretation and then a sequence- and cyclostratigraphic interpretation are given. Where sedimentological data are not sufficient to propose an unequivocal sequence-stratigraphical interpretation, a best-fit solution is used based on comparison and correlation of the section with other sections. For methods and procedure of correlation refer to Chap. 5. The sections are presented in the following way (Fig. 4.1):

**Column 1** indicates biostratigraphy.

**Column 2** indicates lithostratigraphy.

**Column 3** displays the sequence-stratigraphic interpretation. Small-scale and elementary sequences are numbered for the studied interval and are counted from SB/TS to SB/TS, even when they are not well delimited.

**Column 4** shows the logged section with the weathering profile and sedimentary structures (on the left side), and texture, relative abundance of constituents and quartz content (on the right side). The relative abundance of each constituent in a thin section is indicated by the number of symbols (cf. Fig. 4.1; Chap. 2): one symbol: present; two symbols: common; three symbols: abundant.

**Column 5** indicates the relative abundance of nonskeletal grains such as peloids, oncoids (four types), and ooids (three types). The width of the bars indicates the degree of relative abundance.

**Column 6** gives the interpretation of the depositional environments. On the left side, facies type is indicated for each thin setion (cf. Tabs 2.1, 2.2, 2.3). Additionally, the relative bathymetric trend between supratidal and shallow subtidal is illustrated on the right side for the platform sections.

The location of each section is indicated on a geographical map (legend in Fig. 4.2). The first section (Voyeboeuf) is described in more detail to clearly demonstrate the methodological approach.

**4.1 PLATFORM SECTIONS**

**4.1.1 Swiss Jura**

Six sections were investigated in the Swiss Jura Mountains (Fig. 4.3). The sections correspond to shallow-water carbonate platform environments from tidal flat to open-marine lagoon. This study investigates the deposits of the top part of the marly Röschenz Member and of the oncoid-rich Hauptmumienbank and/or ooid-rich Steinebach members belonging to the Vellerat Formation. Biostratigraphic data are based on ammonites from platform and basin sections (GYGI 1995; cf. Chap. 1). The Röschenz Member is attributed to the lower part of the Hypselum subzone and the Hauptmumienbank and Steinebach members to the upper part of the Hypselum subzone (Fig. 1.4).

Most of the studied sections were first described by R. GYGI through the 1980's (sedimentological logs in GYGI 2000b). PITTET (1996) and HUG (2003) presented a sedimentological and sequence-stratigraphic interpretation of several sections. PITTET (1996) labeled long-term sequence boundaries and transgressive surfaces. HUG (2003) placed sequence boundary Ox6+ between Ox6 and Ox7 of HARDENBOL et al. (1998) and identified medium-scale, small-scale, and elementary sequences. Differences in location of sequence boundaries and transgressive surfaces between these authors and my own study are mainly explained by additional sedimentological evidences. PITTET (1996)
<figure><img src="image_20.png" /><figcaption>Fig. 4.1 - Legend for all the studied sections.</figcaption></figure>
<figure><img src="image_21.png" /><figcaption>**Fig. 4.2** - Legend for all maps describing geographical positions of the measured sections.</figcaption></figure>

also presented clay-mineral and palynofacies analyses
and DUPRAZ (1999) improved the palaeoenvironmen-
tal and palaeoecological interpretations of coral-reef
ecosystems from the Hautes-Roches, Savagnières, and
Pertuis sections.

Voyeboeuf (Figs 4.4 and 4.5a-b; Pl. 14/1)

**Geography and stratigraphy**

The Voyeboeuf section is located on the south side
of the Banné anticline south of Porrentruy, on the east
side of the road linking Porrentruy to Courgenay. The

<figure><img src="image_22.png" /><figcaption>**Fig. 4.4** - Location of the Voyeboeuf section. Based on topographic map of St-Ursanne (1085), Carte nationale de la Suisse, 1:25 000.</figcaption></figure>

<figure><img src="image_23.png" /><figcaption>**Fig. 4.3** - Location of the six sections studied in the Swiss Jura Mountains.</figcaption></figure>

Voyeboeuf section covers about 11.5 m of lagoonal
deposits from sandy bioclastic limestones attributed to
the top part of the Röschenz Member, dated of the lower
Hypselum subzone (GYGI 1995; cf. Chap. 1) to massive
oncoid-rich beds belonging to the Hauptmumienbank
Member, dated of the upper Hypselum subzone.

**Sedimentological interpretation**

The base of the section is characterized by nodular
bioclastic mudstones-wackestones rich in ostracodes
and quartz (from base to 0.85 m) interpreted as
protected lagoon deposits. More massive oncoid-
rich wackestones-packstones with a relatively high-
diversity fauna (from 0.85 to 1.1 m) are interpreted as
semi-open lagoon deposits and mark a slight opening
of the depositional environment. The following nodular
ostracode-rich mudstones (from 1.1 to 1.4 m) suggest
a slight protection of the depositional environment.

The first massive limestone beds (from 1.4 to 2.2
m) consist of inoceram-rich mudstones-wackestones.
The increase of inoceram abundance and the gradual
decrease of quartz content point to an opening of the
depositional environment. The following beds consist
of oncoid-rich wackestones (from 2.35 to 2.8 m)
interpreted as semi-open lagoon deposits and peloid-
rich wackestones-mudstones (from 2.8 to 2.95 m)
<figure><img src="image_24.png" /><figcaption>Fig. 4.5a - Voyage section (1).</figcaption></figure>
<figure><img src="image_25.png" /><figcaption>Fig. 4.5b - Voyagebeuf section (2).</figcaption></figure>
interpreted as protected lagoon deposits. This suggests a slight shallowing of the depositional environment. An important increase of accommodation space is indicated by the deposition of a thick peloid-oncoid-ooid wackestone-packstone bed (from 2.95 to 4.15 m). The following beds (from 4.15 to 6.8 m) become thinner (i.e., thinning-up trend) suggesting a general decrease of the accommodation space. Clay-rich intervals are more common, suggesting a more humid climate or local remobilization of siliciclastics. The marls and the thin undulated mudstone beds (from 6.45 to 6.85 m) consist of shallow facies with coal debris in the marls and a low diversity fauna (i.e., ostracodes, benthic foraminifera, echinoderms) in the limestones. This interval corresponds to an important shallowing of the depositional environment.

Then, an increase of accommodation space and a deepening phase is marked by the deposition of a massive and thick wackestone bed (from 6.85 to 7.85 m). This bed rich in *Bacinella-Lithocodium* oncoids suggests low-energy conditions in an open lagoon. The following beds (from 7.85 to 8.45 m) are peloid and foraminifer (miliolid) packstones-wackestones with a small amount of quartz and are interpreted as a more protected lagoonal environment. The deposition of marls rich in oncoids, foraminifera and ostracodes (at 8.7 m) probably reflects a shallowing of the depositional environment. The following beds are ostracode and serpulid mudstones, also interpreted as protected lagoon deposits. Then follow peloid and foraminifer (textulariid) wackestones, interpreted as semi-open to open lagoon deposits. This facies evolution points to a slight opening of the depositional environment. The wavy bed surface (9.35 m) probably results from an intense bioturbation, suggesting a lower sedimentation rate. This bed surface is overlain by a clay-rich interval (from 9.35 to 9.45 m) that may reflect a climate change in the hinterland or a remobilization of siliciclastics formerly stored on the proximal platform. The evolution from peloid-foraminifer wackestone to inoceram-echinoderm mudstone (from 9.45 to 10.25 m) associated with an increase in quartz content points to lower-energy conditions probably due to protection of the depositional environment behind a shoal field. The surface of this bed is also wavy, characterizing bioturbation, and covered by a thin marl-limestone interval. The interval from 10 to 10.25 m consists of thin clay levels intercalated with three bioturbated mudstones rich in inocerams and echinoderms. These deposits are interpreted as more protected lagoonal environments. More massive and thicker wackestone beds (from 10.45 m) with a

normal-marine and relatively diversified fauna but no quartz content suggest a slight opening of the system until a relative sea-level drop is implied by the increase of quartz content (11.4 m).

## Sequence-stratigraphic interpretation

The relatively sandy facies, the thin beds implying low accommodation, and the protected-lagoonal fauna at the transition between the Röschenz and Hauptmumienbank members all point to an important sequence boundary. The nodular sandy limestones (1.3-1.4 m) are interpreted as the corresponding medium-scale SB Ox6+. The following massive limestone beds (from 1.4 m) represent an important relative sea-level rise. The base of these limestones (at 1.4 m) is interpreted as the medium-scale TS Ox6+. The depositional sequences of this section present commonly sequence boundaries amalgamated with transgressive surfaces (SB/TS) due to very thin or absent lowstand or early transgressive deposits.

The small-scale sequence 1 consists of five elementary sequences. The transgressive deposit of the first elementary sequence (1.1) consists of inoceram-ostracode mudstones with a small amount of quartz while the highstand deposit contains more diversified bioclast wackestones without quartz. The second elementary sequence is relatively thin and composed of three beds. The first bed is characterized by type 2 oncoids and serpulids and is interpreted as the transgressive deposit. The following beds, interpreted as the highstand deposit, begin with *Bacinella-Lithocodium* oncoids and end with peloids and type 2 oncoids. This evolution probably reflects an energy change and a relative sea-level drop. The third elementary sequence is the thickest sequence of the section. It suggests maximum accommodation gain. The maximum flooding of this elementary sequence is assumed to be located at the top of the first bed where type 2 oncoids abund. This MF is interpreted as being also the MF of small-scale sequence 1 (MF 1). The fourth elementary sequence is composed of three beds. The transgressive deposit corresponds to the first relatively thick bed, which is bioclastic and peloidal while the highstand deposit is richer in micritized ooids. The fifth elementary sequence is thin, pointing to a decrease of accommodation space. The first two beds are interpreted as the transgressive deposit. The maximum flooding is positioned at the wavy surface (6.45 m) at the top of the second bed. The clay level and two thin wavy beds are interpreted as the highstand deposit.
The clay level at 6.62 m with the coal debris found just below reflects a relative sea-level drop and is thus interpreted as the small-scale sequence boundary SB 2. The first elementary sequence (2.1) is relatively thick. Bioclastic mudstones with a small amount of quartz are interpreted as protected lagoon deposits that formed during transgression. The thick oncoid-rich bed showing an evolution from *Bacinella-Lithocodium* oncoids (type 3 and 4) to micrite-dominated oncoids (type 2) is interpreted as the highstand deposit. The facies at the base of this massive bed are interpreted as the deepest and most open marine and are thus attributed to a maximum flooding. The second, third and fourth elementary sequences have the same pattern and consist of a more or less thin clay level, one or two massive, thick limestone beds, another clay level, and one limestone bed. For each sequence, the sequence-stratigraphic interpretation is the following: the sequence boundary is placed in the clay interval below the massive limestone bed, which is interpreted as the transgressive deposit; the wavy surface at the top of this massive bed is considered as the maximum flooding, and the highstand deposit corresponds to the second clay level and to the limestone bed. The highly bioturbated surface (9.35 m) of the third elementary sequence is considered to represent the maximum flooding of the medium-scale sequence (MF Ox6+). In the fifth elementary sequence, clay levels and quartz gradually disappear, indicating a slight opening of the depositional environment. In the following bed, the quartz content significantly increases, suggesting a terrigenous input probably caused by a relative sea-level drop. This limit at 11.38 m is interpreted as the small-scale SB 3.

Vorbourg (Figs 4.6 and 4.7a-c; Pl. 14/4-5)

Geography and stratigraphy

The Vorbourg section is located in northwestern
Switzerland north of Delémont (canton Jura) (Fig. 4.6).
The studied section crops out in a parking lot along
the small road that cuts through the Béridier anticline,
close to the Vorbourg chapel. This section represents
a good reference section for the Hauptmumienbank
Member (cf. section RG 366 in GYGI 2000b). Along the
parking area, marly deposits, which are partly covered
by vegetation, constitute the Röschenz Member dated
of the lower Hypselum subzone (GYGI 1995; cf. Chap.
1). The massive limestones of the Hauptmumienbank
and Steinebach members, dated of the upper Hypselum
subzone, are exposed in the southern extremity of

<figure><img src="image_26.png" /><figcaption>**Fig. 4.6** - Location of the Vorbourg section. Based on topographic map of Delémont (1086), Carte nationale de la Suisse, 1:25 000.</figcaption></figure>

the parking. The Vorbourg section consists of 12.5
m lagoonal deposits, covering the top part of the
marly Röschenz Member and most of the oncoid-rich
Hauptmumienbank Member.

**Sedimentological interpretation**

The base of the section (from 0 to 4.6 m) consists of fossiliferous yellowish marls, pointing to relatively low-energy environments, and higher energy deposits (ooid-peloid-foraminifer packstones) interpreted as washover deposits. This succession was probably deposited in a marly, semi-open lagoon. The marly level (from 4.1 to 4.6 m) presents a relatively semi-restricted faunal association with ostracodes, gastropods, and type 2 oncoids suggesting a more protected lagoonal environment.

Then the sedimentation style changes: marly
deposits disappear and are replaced by massive and
thick limestones rich in oncoids. This well-marked
facies change (at 4.6 m) also marks the beginning of
an increase of accommodation space. The following
beds (from 4.6 to 5.55 m) consist of (a few tens of
centimetres) thick packstone beds rich in type 2
oncoids, in foraminifera, and radial ooids. These
oncoid beds are interpreted as semi-open lagoonal
deposits. The following bed (from 5.55 to 5.75 m),
dominated by brachiopods, echinoderms and coral
rubble, marks an important opening and deepening of
the depositional environment. Radial ooid grainstone
bars, formed by autocyclic processus, migrated over
this bioclastic deposit and momentarily interrupted
<figure><img src="image_27.png" /><figcaption>Fig. 4.7a - Vorbourg section (1).</figcaption></figure>
<figure><img src="image_28.png" /><figcaption>Fig. 4.7b - Vorbourg section (2).</figcaption></figure>
<figure><img src="image_29.png" /><figcaption>Fig. 4.7c - Vorbourg section (3).</figcaption></figure>

the oncolitic sedimentation (from 5.75 to 6.55 m). Ooid bars become thinner and show a facies change (at 6.85 m) to a thick bioturbated wackestone bed with micritized ooids, *Bacinella-Lithocodium* (type 3) oncoids, foraminifera, and brachiopods. This evolution suggests lower energy conditions in an open lagoonal environment and probably reflects the migration and/or desactivation of ooid bars. This massive and thick bed is followed by a thinner bed (from 7.5 to 7.7 m) interpreted as a channel deposit and probably indicating a decrease of accommodation. The following massive and thick bed (from 7.7 to 8.55 m) consisting of *Bacinella-Lithocodium* (type 3) oncoid wackestones-

floatstones is interpreted as open lagoonal deposit. At its top, a small channel occurs, pointing to a decrease of accommodation. The following massive and thick bed (from 8.55 to 9.85 m) is a packstone (locally rudstone) with *Bacinella-Lithocodium* (type 3) oncoids, foraminifera, and micritized ooids.

This bed is followed by thin nodular rudstone beds (from 9.85 to 10.2 m) rich in *Bacinella-Lithocodium* (type 3) oncoids and benthic foraminifera. These rudstone beds point to higher energy conditions probably due to a decrease of water depth. This interval is overlain (from 10.2 to 13.65 m) by packstone bars containing micritized ooids. The thickness of these
deposits points to an increase of accommodation space. From 13.65 to 14.4 m, a nodular wackestone bed rich in micritized ooids and then a second wackestone bed rich in oo-oncoids, peloids, and foraminifera suggest lower energy conditions. At 14.4 m, a perforated and oyster-encrusted hardground caps these beds and probably reflects a sediment starvation (lower accumulation rate) during a rapid deepening of the depositional environment. This hardground is covered by an important marl interval. This abrupt lithological change marks the turnover of the system towards a siliciclastic-dominated sedimentary system probably caused by a climatic change to more humid conditions. The marly level (from 14.4 to 15.6 m) consists of yellowish marls rich in terebratulid brachiopods, benthic foraminifera, and type 2 oncoids. This interval includes three thin nodular limestone beds: one type 2 oncoid rudstone at 14.65 m, one boundstone of serpulids with sponge spicules at 15.1 m, and one wackestone rich in brachiopods and broken oncoids at 15.3 m. In the final part of the section, limestone beds with brachiopods (from 15.6 to 16.3 m) dominate and represent open-marine conditions.

## Sequence-stratigraphic interpretation

The marly interval at the top of the Röschenz Member represents the shallowest facies and is interpreted as the medium-scale sequence boundary SB Ox6+. The following rapid lithological change (from marl to limestone), recognized all over the Swiss Jura, is interpreted as the major transgressive surface TS Ox6+ corresponding to the beginning of the early Bimammatum transgression. This transgressive surface is the equivalent of the long-term TS 2 of PITTET (1996).

Sequence boundaries, transgressive surfaces, and maximum floodings of elementary sequences are precisely defined from facies and microfacies analyses and stacking pattern. The sequence boundaries are commonly amalgamated with the well-marked transgressive surfaces because of very thin or not developed lowstand and early transgressive deposits. In small-scale sequence 1, five elementary sequences have been identified. The first and second elementary sequences are rich in type 2 oncoids and interpreted as semi-open lagoonal deposits. In the first elementary sequence (1.1), the first nodular oncoid packstone bed is considered as the transgressive deposit and the two following beds as the highstand deposit. The maximum flooding is placed at the slight texture change from packstone to wackstone/packstone (at 4.75 m). The

second elementary sequence is the smallest sequence and shows a gradual decrease of quartz content. The peloid-foraminifer packstone (at 5.1 m) is interpreted as an early transgressive deposit and the two following beds as the transgressive and highstand deposits, respectively. The maximum flooding of this sequence is assumed to be located between the two massive and thick beds (at 5.3 m), where type 2 oncoids are abundant and brachiopods and corals are present. The third elementary (1.3) is the thickest sequence of this section, suggesting maximum gain of accommodation. The bioclastic (i.e., brachiopods, echinoderms, corals) wackestone/packstone bed (from 5.55 to 5.75 m) and the radial ooid grainstone beds (from 5.75 to 6.85 m) are interpreted as transgressive deposits. High sediment accumulation rate kept water depth low and allowed for the formation of channel just below the maximum flooding. The facies evolution to micritized ooid and type 3 oncoid bioturbated wackestone then points to more open-marine conditions in a deeper depositional environment. This facies change (at 6.9 m) is interpreted as the maximum flooding of the third elementary sequence. This well-expressed maximum flooding is also the maximum flooding of small-scale 1, which is confirmed by lateral correlation. The wackestone-floatstone bed (from 6.85 to 7.7 m) rich in micritized ooids *Bacinella-Lithocodium* oncoids, and foraminifera is interpreted as the highstand deposit in an open lagoon. Channels at the end of this highstand deposit probably indicate a slight decrease of accommodation space and thus a relative sea-level fall. The fourth elementary sequence mainly consists of one massive and thick wackestone-floatstone bed rich in *Bacinella-Lithocodium* oncoids and foraminifera. A small channel occurs in the highstand deposit and suggests a slight sea-level fall. In the fifth elementary sequence, mainly composed of one massive and thick bed, a texture evolution from wackestone to packstone-rudstone suggests higher energy conditions in the second part of this bed, thus interpreted as the highstand deposit.

The rudstone interval (from 9.85 to 10.2 m) suggests higher energy conditions and probably reflects a relative sea-level drop. This interval is thus interpreted as small-scale SB 2. The small-scale sequence 2 consists of five elementary sequences. The first elementary sequence (2.1) begins with thin nodular oncoid rudstones, interpreted as early transgressive deposits. The following oolitic packstones were controlled by autocyclic processus, which makes the identification of elementary sequences difficult. However, fine laminations and thinner beds at 11.95 m
<figure><img src="image_30.png" /><figcaption>**Fig. 4.8** - Location of the Hautes-Roches section. Based on topographic map of Moutier (1106), Carte nationale de la Suisse, 1:25 000.</figcaption></figure>

suggest a hydrodynamic change, which is interpreted as corresponding to the sequence boundary of the second elementary sequence. The following sequence boundary is placed at the transition from nodular to more massive oolitic beds rich in coarse quartz (at 13.95 m). The oyster-encrusted hardground (at 14.4 m), which caps the top of the carbonate-dominated part, is interpreted as the maximum-flooding surface of the third elementary sequence. This maximum-flooding surface is interpreted as belonging to the medium-scale MF Ox6+. The fourth and fifth elementary sequences are defined within the marly interval and are composed of a thin nodular limestone bed, interpreted as the transgressive deposit, and marls rich in brachiopods, interpreted as the highstand deposit.

**Hautes-Roches** (Figs 4.8 and 4.9a-b)

**Geography and stratigraphy**

The Hautes-Roches section is situated on the southern flank of the Mont Raimeux. This section is along a forest path to the south of the hamlet of Hautes-Roches (Fig. 4.8). The Hautes-Roches section is dominated by ooid bars belonging to the Steinebach Member. Locally there are some coral patch-reefs and clays are abundant at the base and top of the section. This section is only about 7 m thick.

**Sedimentological interpretation**

At the base of the section, the marly interval presents charophyte oogones and stems, gastropods

(i.e., large *Bourgetia striata*), in situ urchins and benthic foraminifera. This restricted fauna indicates protected marly lagoonal environment.

The deposition of limestone beds points to an opening of the system and a stop of the siliciclastic input. The first two beds (from 0.6 to 0.95 m) are coral boundstones with a bioclastic matrix. The development of coral patch-reefs marks an important opening of the depositional environment associated to an increase of accommodation space. The third bed is a packstone rich in coral rubble and ooids interpreted as a peri-reefal bar. The presence of ooids since the first bed announces the ooid grainstones from 1.1 m onwards. The beds from 1.1 to 4.3 m consist of high-energy ooid bars. A subtidal sandwave occurs at 1.4 m. These ooid bars are topped at 4.3 m by a bioperforated hardground. This surface is assumed to have formed in a subtidal high-energy environment and represents an omission period due to a rapid decrease of accommodation.

This hardground is overlain by a thin marly interval containing a level of coral carpet indicating an increase of the accommodation space. The following limestone beds (from 4.4 to 5.4 m) consist of ooid-rich packstones to grainstones with local coral rubble, type 2 oncoids, echinoderms, and grapestones. These beds are interpreted as ooid bars. They are covered by a thin marl level, which is followed by a thick nodular wackestone bed rich in normal-marine fauna (i.e., corals, sponges, brachiopods). This facies evolution probably reflects a slight deepening and opening of the depositional environment. The top part of the section consists of marly deposits (from 5.8 m) with two relatively thick nodular limestone beds (at 5.9 m and 6.4 m). The marls contain a normal-marine fauna (i.e., brachiopods, echinoderms, foraminifera) and the nodular limestones are mainly composed of corals, sponges, and serpulids. This marly interval displays low energy conditions probably due to the deepening of the system and/or protection of the depositional area by a shoal field.

**Sequence-stratigraphic interpretation**

The marly interval rich in charophytes and gastropods at the base of the section represents the shallowest facies and is thus interpreted as the medium-scale SB Ox6+. The base of the first limestone bed (at 0.65 m) represents the medium-scale TS Ox6+, previously identified by PITTET (1996) as a long-term transgressive surface. Indeed, this rapid facies change from clay-dominated to limestone-dominated and the
<figure><img src="image_31.png" /><figcaption>Fig. 4.9a - Hautes-Roches section (1).</figcaption></figure>
<figure><img src="image_32.png" /><figcaption>Fig. 4.9b - Hautes-Roches section (2).</figcaption></figure>

evolution from charophytes to sponges and brachiopods reflect an important relative sea-level rise.

Small-scale sequence 1 is almost entirely composed of high-energy deposits, which makes the sequence-stratigraphic interpretation difficult because the bars are subject to autocyclic processes. However, with the help of sedimentary structures and bedding changes, sequence boundaries may be proposed. Five elementary sequences have been identified in this small-scale sequence. The first elementary sequence mainly consists of a marly interval and three limestone beds. The first two beds, composed of bioconstruction levels, are interpreted as the transgressive deposits and the third bed, composed of ooids, is interpreted as the highstand deposit. The facies change from an open-marine environment with a small reef installation to higher-energy deposits dominated by ooids and coral rubble is interpreted as the maximum-flooding surface. The next four elementary sequences consist of high-energy deposits. In the top part of these ooid bars, beds are thinner and point to a decrease of the accommodation space. The hardground, followed by a marl level, probably reflects a rapid sea-level drop and is interpreted as small-scale SB 2.

In small-scale sequence 2, only the first three elementary sequences have been investigated. The first elementary sequence consists of a thin marl level with limestone nodules and two thicker limestone beds. The maximum flooding of this sequence is placed at a texture change (at 4.5 m) between the two limestone beds. The second elementary sequence consists entirely of ooid grainstones making the identification of the maximum flooding difficult.

The third elementary sequence consists of a nodular bioclastic (brachiopods, corals, sponges) wackestone bed followed by a thin marly interval. The maximum-flooding surface is assumed to be located at the top of the nodular limestone bed (5.8 m). Based on lateral correlation, this maximum flooding is interpreted as the medium-scale MF O6+.

## Court (Figs 4.10 and 4.11a-c)

### Geography and stratigraphy

The Court section is located on the northern flank of the Graitory anticlinal near “La Bâme” along the road leading from Court to Moutier (Fig. 4.10). The

<figure><img src="image_33.png" /><figcaption>Fig. 4.10 - Location of the Court section. Based on topographic map of Moutier (1106), Carte nationale de la Suisse, 1:25 000.</figcaption></figure>
<figure><img src="image_34.png" /><figcaption>Fig. 4.11a - Court section (1).</figcaption></figure>
<figure><img src="image_35.png" /><figcaption>Fig. 4.11b - Court section (2).</figcaption></figure>
<figure><img src="image_36.png" /><figcaption>Fig. 4.11c - Court section (3).</figcaption></figure>

studied section is about 17 m thick and exposes the top part of the marly Röschenz Member and the ooid-rich Steinebach Member.

## Sedimentological interpretation

The base of the section is characterized by marls with local wash-over deposits (packstones-

wackestones) rich in quartz, peloids, ostracodes, and benthic foraminifera (Fig. 4.11). This suggests protected conditions with storm influence (PITTET 1996). Then, massive packstone beds appear (at 4.6 m) associated with a gradual decrease in quartz content and organic matter debris. These beds are interpreted as semi-open to protected lagoon deposits influenced by siliciclastic input. From 5.5 to 8.5 m, thick high-
energy (radial) ooid bars appear, which are interpreted as subtidal deposits. Then coral reefs develop in an open lagoon. The top part of these bioconstructions is very irregular and covered by tidal facies with birdseyes and undifferentiated bioclasts. The presence of birdseyes indicates a decrease of accommodation space and a shallowing of the depositional environment up to the intertidal zone.

Some coral patch-reefs again develop from 10.9 to 12.4 m in association with normal-marine fauna (e.g., brachiopods). High-energy deposits (from 12.4 m to 15.9 m), still deposited in the subtidal zone, then follow. From 13.7 to 14.35 m, detrital quartz, more type 2 oncoids and even some type 1 oncoids are noticed and suggest a hydrodynamic change to lower energy associated with a minor siliciclastic input. These thick deposits are overlain (from 15.6 to 15.85 m) by an ooid-peloid packstone bed with horizontal laminations and a small amount of quartz. This bed indicates lower energy conditions. Its wavy surface (at 15.9 m), probably bioturbated, and the red coloration point to a period of sediment starvation. The following succession (from 16 to 17.15 m) consists of bioclastic wackestone rich in normal-marine fauna (corals, calcareous sponges, and brachiopods) and quartz. It is interpreted as semi-open to open lagoonal deposits.

## Sequence-stratigraphic interpretation

The marly interval reveals protected lagoonal facies and is a candidate for medium-scale SB Ox6+. The rapid facies change (at 4.6 m) toward limestone-

<figure><img src="image_37.png" /><figcaption>**Fig. 4.12** - Location of the Savagnières section. Based on topographic map of Les Bois (1124), Carte nationale de la Suisse, 1:25 000.</figcaption></figure>

dominated facies suggests an increase of carbonate productivity due to the flooding of the platform during sea-level rise. This limit is considered to represent the transgressive surface TS Ox6+, previously identified by PITTET (1996) as the long-term TS 1.

Small-scale sequence 1 consists of five elementary sequences. The first elementary sequence displays massive packstone beds. The transgressive deposit is relatively rich in oncoids and the highstand deposit is placed in the more marly limestone with bioturbations. The second elementary sequence is entirely made of high-energy deposits, which makes the identification of sequence-stratigraphic elements difficult. The transgressive deposit of the third elementary sequence is also composed of high-energy deposits and the highstand deposit consists of coral bioconstructions. The fourth elementary sequence is entirely made of coral bioconstructions. The fifth elementary is the thinnest sequence but has large lateral thickness variations due to the platform morphology created in particular by coral patch-reefs.

The small-scale SB 2 is assumed to be located in the tidal-flat facies with birdeyes representing the shallowest facies. Small-scale sequence 2 also consists of five elementary sequences. The first elementary sequence consists of a relatively massive bed mainly dominated by corals. The overlying marly interval is considered to represent the sequence boundary of the second elementary sequence. The second and third elementary sequences are entirely composed of ooid-rich bars making their sequence-stratigraphic interpretation uncertain. However, the well-marked surface at 15.9 m, at the top of an ooid bar, is interpreted as the maximum-flooding surface of the third elementary sequence. By lateral correlation, this maximum-flooding surface is interpreted as belonging to the medium-scale MF Ox6+.

## Savagnières (Figs 4.12 and 4.13a-b; Pl. 14/2)

### Geography and stratigraphy

The Savagnières section, on the top of the Chasseral anticline, is approximately situated at half way between Les Bugnenets and Les Pontins, along the road relating Val-de-Ruz to St-Imier (Fig. 4.12). The Savagnières section is about 12.5 m thick and dominated by limestones. No important marl/clay deposits exist, contrary to all the other sections.
<figure><img src="image_38.png" /><figcaption>Fig. 4.13a - Savagnières section (1).</figcaption></figure>
<figure><img src="image_39.png" /><figcaption>Fig. 4.13b - Savagnières section (2).</figcaption></figure>
## Sedimentological interpretation

The base of the section (from the base to 2.2 m) is characterized by thin nodular limestone beds mainly interpreted as protected lagoonal deposits. From the base to 1.35 m, the beds are bioturbated wackestones to mudstones rich in quartz and with a low-diversity fauna (i.e., ostracodes and inocerams). The following beds (from 1.35 to 1.8 m) show a higher-diversity fauna and a decrease of quartz content, indicating a slight opening of the depositional environment. Then, the inverse trend is observed (from 1.8 to 2.2 m) to less-diversified fauna and a smaller amount of quartz.

The deposition of relatively thick massive limestones and the disappearance of siliciclastics imply an important increase of accommodation space. Massive and thick beds from 2.3 to 2.85 m are packstones-wackestones composed of type 2 oncoids, interpreted as semi-open lagoonal deposits. The following beds from 2.85 to 3.8 m are wackestones composed of *Bacinella-Lithocodium* (type 3) oncoids and are interpreted as open lagoonal deposits. The peloid wackestones from 3.8 to 4.25 m are interpreted as relatively protected lagoonal deposits, whereas the bioclastic wackestones from 4.25 to 5.4 m are attributed to relatively open lagoonal deposits. Thinner beds (from 5.35 to 5.5 m) are considered as small channels. This succession (from 2.2 to 5.5 m) shows a thickening- and then thinning-up trend, suggesting accommodation space variations. At the base of the following bed (5.5 m), which is a peloid-bioclast wackestone, quartz reappears and rapidly disappears. From 6.1 to 6.85 m, some radial ooids are mixed with peloids and bioclasts pointing to the proximity of ooid bars. The following bed is characterized by echinoderm- and oyster-rich wackestone at its base, and by *Bacinella-Lithocodium* oncoid floatstone. This bed represents an open lagoonal environment. In the following thin bed (from 7.95 to 8.2 m), changes of texture and grain content point to relatively higher energy conditions in a shallower environment.

At 8.2 m the texture and facies change from (undifferentiated) bioclast wackestone to serpulid- and oyster-rich grainstone indicates a water energy change, probably related to a decrease of the accommodation space. This high-energy level contains a serpulid-oyster buildup. The following facies consist of peloid-bioclast wackestone-packstone (from 8.3 to 8.4 m), interpreted as relatively protected lagoon deposits, ooid-bioclast wackestones (from 8.4 to 9.1 m), interpreted as bar deposits, and type 2 oncoid wackestones-packstones

(from 9.1 to 9.55 m), interpreted as semi-open lagoonal deposits. Then radial ooid- and peloid-rich packstone beds are deposited from 9.55 to 10.5 m and suggest the migration of oo-bioclastic bars abandoned in a shallow subtidal environment. A thinning-up trend from massive, thick beds to thin highly bioturbated beds is noticed from 9.55 to 11.75 m and is associated to a texture change from packstone-wackestone to mudstone and to a decrease of fauna diversity. This evolution points to decreasing energy probably due to protection behind a shoal field. In addition, the intense bioturbation in the thinnest beds probably resulted from a lower accumulation rate during a deepening phase. At the end of the section, thicker wackestone beds (at 11.75 m) dominate, suggesting a higher accommodation.

## Sequence-stratigraphic interpretation

The medium-scale SB Ox6+ is placed in the nodular sandy limestones (2.1-2.2 m), interpreted as protected lagoon deposits. The base of the first massive limestones (at 2.2 m), showing the opening of the depositional environment, is interpreted as the medium-scale TS Ox6+, previously interpreted by PITTET (1996) as a long-term transgressive surface. This evolution points to a relative sea-level rise.

Small-scale sequence 1 consists of five elementary sequences. The first elementary sequence is composed of four wackestone-packstone beds. The first two beds, mainly composed of bioclasts, are interpreted as the early transgressive deposit and the transgressive deposit, respectively. The two following beds, dominated by oncoids, are interpreted as the highstand deposit. The maximum flooding is assumed to be located at 2.3 m between the second and third bed where laminations exist. The second elementary sequence consists of two thick and massive beds. The first bed is interpreted as the transgressive deposit and the second as the highstand deposit. The maximum-flooding surface is assumed to be located between these two beds (at 3.45 m) where *Bacinella-Lithocodium* oncoids, brachiopods, and benthic foraminifera are abundant. In the third elementary sequence, the maximum-flooding surface is placed at the top of the first bed where brachiopods are present. The top of the highstand deposit presents tidal channel structures, suggesting a decrease of accommodation space. The fourth elementary sequence consists of three beds. The maximum flooding is assumed to be located between the first and second bed. The fifth elementary sequence consists of two beds: one thick bed and one thinner
bed. The maximum flooding is placed at the *Bacinella-Lithocodium* oncoid-rich mudstone level (7.9 m).

The thin wackestone bed at the top of the fifth elementary sequence announces an important relative sea-level fall. The serpulid-oyster build-up is considered to represent the small-scale SB 2. In small-scale sequence 2 only the first three elementary sequences have been investigated. The transgressive deposit of the first elementary sequence consists of two beds. The second bed presents a slightly wavy surface, probably due to intense bioturbation. It is interpreted as the maximum-flooding surface. The following nodular bed is considered to represent the highstand deposit. The second elementary sequence consists of an ooid-rich transgressive deposit and a bioclastic highstand deposit. The third elementary sequence is composed of a massive bed, interpreted as the transgressive deposit and a level of thin bioturbated beds, interpreted as the highstand deposit. The top of this massive bed (at 11.6 m) is interpreted as the maximum-flooding surface. This MFS is attributed to the medium-scale MF 0x6+ by lateral correlation.

*Pertuis* (Figs 4.14 and 4.15a-c; Pl. 14/3)

**Geography and stratigraphy**

The Pertuis section is located on the southern flank of the Mont d'Amin anticline halfway between Les Bugnenets and Vue des Alpes. The outcrop is along the road leading to Val de Ruz in direction of Dombresson (Fig. 4.14). The section begins after a forest clearing with a parking lot and old wood constructions. The section is about 15.5 m thick and exposes the top part of the clay-rich Röschenz Member, almost totally covered by vegetation, and the oncoid-rich Hauptmumienbank Member.

**Sedimentological interpretation**

This section presents three different intervals: (1) a marl-dominated interval with high quartz content in the limestones (from base to 3.85 m), (2) a limestone interval (from 3.85 to 12.7 m) and, (3) limestone-dominated interval with high quartz content (from 12.7 to 14.5 m). The base of the section (from base to 1.5 m) is characterized by marls with a low diversity fauna and plant debris, interpreted as protected lagoonal deposits. The following succession (from 1.2 to 3.85 m) consists of marls and peloid/bioclastic wackestones with a more diversified and normal-marine fauna (e.g.,

<figure><img src="image_40.png" /><figcaption>**Fig. 4.14** - Location of the Pertuis section. Based on topographic map of Val de Ruz (1144), Carte nationale de la Suisse, 1:25 000.</figcaption></figure>

brachiopods) and high quartz content. These deposits are interpreted as semi-open lagoonal deposits.

The deposition of massive and thick oncoid-rich limestones (from 3.85 m) associated with the disappearance of detrital quartz marks an increase of accommodation space and deepening of the depositional environment. The first limestone beds are wackestones-packstones rich in radial ooids and/or type 3 and 2 oncoids (from 3.85 to 5.5 m), pointing to more open-marine environments. After these ooid-rich facies, *Bacinella-Lithocodium* (type 3) oncoid wackestones to floatstones predominate (from 5.5 to 9.3 m). This facies indicates lower-energy conditions in an open lagoon and thus reflects an important deepening of the depositional environment. It coincides with a thickening-up trend (from 5.5 to 10.7 m) that points to an increase of the accommodation space. The following beds are peloid-foraminifer wackestones (from 9.3 to 11.4 m), interpreted as open lagoonal deposits, and bioclastic mudstones with a small amount of quartz (from 11.4 to 12.05 m) interpreted as protected lagoonal deposits. This facies evolution and bedding pattern from 9.3 m upward point to a shallowing of the depositional environment and decrease of accommodation space. In addition, a change of oncoid types (from 11.8 to 12.0 m) in a mudstone bed from *Bacinella-Lithocodium* (type 3) oncoids to micrite-dominated (type 2) oncoids suggests an environmental change probably due to more eutrophic conditions (cf. Chap. 7).
<figure><img src="image_41.png" /><figcaption>Fig. 4.15a - Pertuis section (1).</figcaption></figure>
<figure><img src="image_42.png" /><figcaption>Fig. 4.15b - Pertuis section (2).</figcaption></figure>
<figure><img src="image_43.png" /><figcaption>Fig. 4.15c - Pertuis section (3).</figcaption></figure>

The following deposits consist of two slightly undulating beds interbedded with very thin marly layers. These beds consist of foraminifer wackestones with quartz and correspond to a protected lagoonal environment. Then, three relatively thick and massive bioclastic (e.g., benthic foraminifera, coral rubble) wackestones (from 12.3 to 12.95 m) are deposited and point to a new increase of accommodation space. The two following beds are nodular peloid-bioclast wackestones-packstones with quartz that are separated by a thin marly interval (at 12.95 m). The second bed is thicker than the first one and finely laminated in its top part. This bed is followed by a marly interval rich in quartz and benthic foraminifera (from 13.5 to 13.7 m). All deposits from 12.95 to 14.55 m are interpreted as relatively protected lagoonal deposits. The return to more massive limestone beds (at 13.7 m) points to an opening of the environment.

## Sequence-stratigraphic interpretation

The facies change from marl-dominated to limestone-dominated facies suggests an opening of the environment with a significant decrease of siliciclastics. This facies change at 3.85 m is interpreted as a transgressive surface and as belonging to the medium-scale TS Ox6+. PITTET (1996) also interpreted this surface as a long-term transgressive surface. Consequently, the marly interval (3.75-3.85 m), below the base of the massive limestones, is interpreted as the sequence boundary and as belonging to the medium-scale SB Ox6+. This facies evolution indicates an important relative sea-level rise associated with an increase of accommodation space.

Small-scale sequence 1 consists of five elementary sequences. The first elementary sequence is dominated