Palaeoenvironmental control on sponge-microbialite reefs and contemporaneous deep-shelf marl-limestone deposition (Late Oxfordian, southern Germany)

Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233 – 263 www.elsevier.com/locate/palaeo

Palaeoenvironmental control on sponge-microbialite reefs and contemporaneous deep-shelf marl-limestone deposition (Late Oxfordian, southern Germany) Nicolas Olivier*, Bernard Pittet, Emanuela Mattioli Universite´ Claude Bernard Lyon 1, UFR des Sciences de la Terre, UMR CNRS 5125 Pale´oenvironnements et Pale´obiosphe`re, Ge´ode, 2 rue Raphae¨l Dubois, 69622 Villeurbanne cedex, France Received 18 December 2003; received in revised form 1 June 2004; accepted 1 June 2004

Abstract The Late Oxfordian (Bimammatum Zone) deep-shelf deposits of southern Germany are characterised by abundant reefs that laterally pass into marl-limestone alternations. The bioconstructions are made from three main components, sponges, microbialites and allochthonous sediment. A detailed morphological analysis of sponge-microbialite reefs in the Plettenberg section (Swabian Alb, southern Germany) is combined with investigation of calcareous nannofossil assemblages in laterally correspondent marllimestone alternations in order to trace the evolution of palaeoenvironmental conditions during reef development. Fluctuations of CaCO3 content in deep-shelf deposits provides evidence of a succession of small-scale lithological units, generally formed by five to six marl-limestone couplets. Within a small-scale lithological unit, a close link is observed between growth patterns of sponge-microbialite reefs and the changes in the nannofossil assemblage composition. Phases of expansion of the build-ups correspond to carbonate deposits, characterised by a relative dominance of large, oligotrophic nannoplankton species (large Watznaueria britannica, Watznaueria manivitiae and Schizosphaerella spp.). Marly intervals reveal a high relative abundance of small-sized taxa (mainly Lotharingius hauffii, small W. britannica and subordinated Biscutum dorsetensis), and bioconstructions show a net reduction in size, or a total demise. This suggests that the same palaeoenvironmental parameters controlled, at the same time, marl versus limestone deposition, reef growth-phases, and calcareous nannofossil assemblage composition. Successive reef growth-phases recognized within a bioherm are correlated to the limestone hemi-couplets. Each reef growth-phase is composed of several stacked elementary sequences, comprising the following succession: (i) sponge, (ii) microbialites and (iii) carbonate mud. In turn, the microbialitic crust is formed of three successive microbial layers: (1) a fine crust of dense to clotted micrite; (2) a centimetre-scale to multicentimetric columnar layer of clotted to peloidal micrite; (3) a centimetre-scale stromatolitic crust. The passage from an initial dense microbial layer, with numerous microencrusters, to a final stromatolitic crust is interpreted as resulting from an increase of the microbial growth-rate, mainly driven by changes in the accumulation rate.

* Corresponding author. E-mail addresses: [email protected] (N. Olivier)8 [email protected] (B. Pittet)8 [email protected] (E. Mattioli). 0031-0182/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2004.06.003

234

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Deep-shelf deposits resulted from changes in platform carbonate production and export basinwards controlled both by sealevel and climate changes. Climate controlled the intensity of carbonate production in shallow-platform environments and export towards the deep-shelf, as well as the trophic conditions of the deep-shelf marine-waters. Low trophic conditions favoured platform carbonate production and export basinwards, and a large development of the sponge-microbialite reefs in the deep-shelf. However, a high carbonate accumulation rate in the deep-shelf was also commonly responsible for the demise of sponge-microbialite reefs. During unfavourable and higher trophic conditions (during marl deposition), reduced development and frequent demise of the sponge-microbialite reefs is observed. D 2004 Elsevier B.V. All rights reserved. Keywords: Sponge reef; Microbialites; Calcareous nannofossils; Accumulation rate; Trophic level; Oxfordian

1. Introduction Sponge-microbialite build-ups are common sedimentary features in the Late Jurassic of the northern Tethyan shelves (Gwinner, 1976; Lang, 1989; Meyer and Schmidt-Kaler, 1990; Leinfelder et al., 1996, 2002). They are typically observed in outer-ramp, outer-shelf and/or epicontinental basin environments (Gaillard, 1983; Keupp et al., 1990; Leinfelder, 1993, 2001; Leinfelder et al., 1994; Dromart et al., 1994). Their development has been related to various palaeoenvironmental parameters, such as bathymetry, light penetration, sedimentation rate, oxygenation, salinity, substrate stability and water-energy (Brachert, 1992; Leinfelder et al., 1993a,b, 1996; Leinfelder, 2001; Dromart et al., 1994, Keupp et al., 1993, 1996). However, only few studies on sponge reefs have dealt with the close relationship between the architecture of the sponge build-ups and surrounding sediments (Lang, 1989; Brachert, 1992). Oxfordian deep-shelf sediments of epicontinental basins in the northern Tethyan Realm are commonly composed of marllimestone couplets, and are stacked into smalland large-scale depositional lithological units (Gaillard et al., 1996; Pittet and Strasser, 1998a). Formation of marl-limestone alternations in deep shelves and epicontinental basins is a subject of debate (e.g. Bo¨hm et al., 2003). Their origin could be explained in part by: (i) pelagic carbonate production (No¨el et al., 1994; Claps et al., 1995; Mattioli, 1997); (ii) import of carbonate mud from shallower areas (e.g. Davaud and Lombard, 1973; Gaillard, 1983; Boardman and Neumann, 1984; Brachert, 1992; Milliman et al., 1993; Pittet et al., 2000); and/or (iii) diagenetic

redistribution of carbonates (e.g. Eder, 1982; Hallam, 1986; Munnecke and Samtleben, 1996; Munnecke et al., 1997; Bo¨hm et al., 2003). In Upper Oxfordian deep-shelf deposits of southern Germany, calcareous nannoplankton abundance negatively correlates with carbonate content and cannot be responsible for the formation of carbonate-rich layers (Pittet and Mattioli, 2002). However, nannofossils may be responsible for the carbonate production in the marliest intervals. Variations in the accumulation rate, evidenced by recurrent condensation levels and the over-regional correlation of the depositional lithological units, point to a control by climate and/or sea-level changes (Pittet and Strasser, 1998a). These factors directly controlled the export of carbonate mud from the Jura shallow-platform to the Swabian Alb deep-shelf, and thus the formation of marllimestone couplets (Fig. 1; Pittet et al., 2000). In these deep-shelf settings, calcareous nannoplankton can provide useful information on the trophic conditions that occurred in the water-column, and thus can be used as palaeoenvironmental proxies (e.g. Okada and Honjo, 1973; Roth, 1983; Erba, 1992; Pittet and Mattioli, 2002; Bornemann et al., 2003). In southern Germany, the Oxfordian deep-shelf deposits provide abundant and excellent examples of sponge- and microbialite-rich stratigraphic reefs (Leinfelder et al., 1996; Schmid et al., 2001). The Plettenberg section in particular allowed us to analyse the mode of development of the two main reef components (i.e. sponges and microbialites) and the close relationship between sponge-microbialite reefs and associated lateral deposits, the marl-limestone couplets.

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

235

Fig. 1. (A, B) Location of the Plettenberg section in southern Germany, near Balingen. (C) Palaeogeographic map of the Oxfordian– Kimmeridgian interval (modified after Meyer and Schmidt-Kaler, 1989; Pittet and Mattioli, 2002).

The present work aims to: (1) understand the geometric relationships between sponge-microbialite reefs and marl-limestone bundles in the Upper Oxfordian of southern Germany; and (2) constrain the main palaeoenvironmental factors that controlled both sponge-microbialite reef development and architecture, and the formation and organisation of marllimestone couplets in deep-shelf environments. Sponge-microbialite reef morphology and composition are analysed together with their lateral equivalents (i.e. marl-limestone bundles) and are compared to calcareous nannofossil assemblage that represents a proxy for reconstructing palaeoenvironmental conditions in deep-shelf waters.

2. Geological framework The study area is located in southern Germany, in the western part of the Swabian Alb (Fig. 1). In the Late Jurassic, it belonged to the northwestern margin of the Tethys Ocean (Ziegler, 1988). Palaeogeographical reconstruction points to deep-shelf (b100 m) environments, about 50 km from the shallow Jura platform, opening to the south onto the deeper Helvetic Basin (Meyer and Schmidt-Kaler, 1989). In these deep-shelf environments, siliceous spongemicrobialite reefs are common in the Upper Jurassic of the Swabian and Franconian Alb (e.g. Wagenplast, 1972; Gwinner, 1976; Keupp et al., 1990; Leinfelder

236

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Fig. 2. Legend for Fig. 3.

et al., 1994). This depositional setting shows variable non-bioconstructed facies represented by a mixed carbonate-siliciclastic material. This shelf-basin was strongly influenced by siliciclastic inputs from emerged lands situated to the north of the study area (i.e. the Rhenish Massif; Fig. 1). A section located in the Plettenberg quarry near Balingen is analysed here. In this section, sponges are abundant, and bioconstructions are common and develop laterally into marl-limestone deposits. The studied stratigraphic interval (Figs. 2 and 3) extends from the Bimammatum Zone to the beginning of the Planula Zone (Schweigert, 1995a,b; Schweigert and Callomon, 1997), thus corresponding to the Late Oxfordian and Early Kimmeridgian (Matyja and Wierzbowski, 1988, 1994; Atrops et al., 1993; Schweigert, 1995a,b). Lithostratigraphically, the base of the studied section comprises the upper part of the Impressa-Mergel Formation (Schweigert, 1995a), also described as Malm-alpha2 (Quenstedt, 1843) of the Bifurcatus and Bimammatum Zones, and the Wohlgeschichtete Kalke Formation (Geyer and Gwinner, 1984) of the Planula Zone, base of the Malm-beta of Quenstedt (1843).

3. Methods The relationship between the reef architecture and the lateral deposits has been analysed in the field and redrawn from photographs in order to study the sponge-microbialite-reef development in its sedimen-

tary context. This study focuses on the lower, marldominated interval of the Plettenberg quarry section, where lateral transitions from the sponge-microbialite reefs to marl-limestone bundles are well visible, allowing a detailed bed-by-bed sedimentological analysis. The surface proportions of the different reef components were calculated by putting a 1-cm grid across random reef-surfaces and point-counting at the intersections. Seventy thin sections and 50 polished slabs were used for the facies, microfacies and microbialite microfabric analyses, in order to identify the geometric relationship between the different reef components (i.e. sponge, microbialites and carbonate mud). Each limestone and marl hemi-couplet occurring laterally to the bioconstructions was sampled and analysed for its carbonate and nannofossil contents (Fig. 4). Forty-five samples were collected and slides were prepared according to the settling method described in Geisen et al. (1999), slightly modified as follows. Powdered rock-samples were dried, weighed and diluted in water to which a small amount of bSavon de MarseilleQ was added. Soap prevents flocculation and formation of aggregates, and raises the pH of the suspension. The suspension was ultrasonically cleaned (10 min) and homogenised by magnetic stirring (10 min), then poured into a settling device to let the particles settle on the cover-slide over 24 h. The coverslides obtained, on which the sediment was thus homogeneously distributed, were mounted on a slide with Rhodopass. This method allowed an

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263 237

Fig. 3. Detail of the Plettenberg section (legend in Fig. 2). The section is divided into a marl-dominated lower part and a limestone-dominated upper part. Based on facies, CaCO3 content (and erosional profile) and sedimentary structures, the lower part of the section displays a well-marked stacking pattern. Small-scale lithological units (marl-limestone bundles) and elementary units (marl-limestone couplets) can be distinguished. Tizianiformis, bauhini and tonnerrense ammonite horizons based on Schweigert and Callomon (1997). Position of the berrense and bimammatum horizons are approximately shown based on their occurrences in the Gosheim section (Schmid et al., 2001; Fig. 1) where they were found just above the transition between the marl- and the limestone-dominated intervals (Strasser et al., 2000).

238

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Fig. 4. (A) Schematic reconstruction of the Swabian deep-shelf setting during the Oxfordian. This deep-shelf environment is characterised by an abundant sponge-microbialite-reef development. The mixed carbonate-siliciclastic deposits characteristic of Upper Oxfordian deep-shelf settings record both calcareous nannoplankton accumulations and the export of carbonate mud from the adjacent, shallow, carbonate-dominated Jura platform (Pittet and Mattioli, 2002). (B) Sketch showing the close relationships between the successive reef-growth phases and the lateral marl-limestone bundles that record a variable amount of calcareous nannofossils. Laterally to the sponge-microbialite reef, each limestone bed and marly level were sampled for calcareous nannofossil analysis.

absolute quantification of nannofossils per gram of rock by a simple calculation (Geisen et al., 1999). A standard number of 300 specimens, both coccoliths and the nannolith Schizosphaerella spp., were counted under a polarizing-light microscope (1250) over a variable surface area (810 3 to 25610 3 cm2), according to the richness of nannofossils on the slide. In nine samples, only a total of 100–150 specimens could be counted, due to the paucity of nannofossils in the slide. Fifty-five taxa were recognized in the entire studied interval, 10 of them being differentsized morphotypes of two coccolithophorid species (Watznaueria manivitiae and Watznaueria britannica; Fig. 5). The preservation state of the nannofossils was evaluated under the light-microscope. Different preservational classes were recognized on the basis of etching and overgrowth of the specimens, as established by Roth (1984). In the present work, only the taxa recorded continuously (i.e. in all the studied samples) and/or with a mean relative abundance higher than 2% will be

discussed (Figs. 6 and 7). These taxa have been determined to be of palaeoenvironmental significance in deep-shelf settings of the Toarcian of Central Italy (Mattioli and Pittet, 2004) and the Oxfordian of southern Germany (Pittet and Mattioli, 2002). Some small-sized taxa have been grouped because of their very similar distribution in the Plettenberg section (Biscutum dorsetensis, Zeugrhabdotus erectus (Fig. 5), Biscutum dubium, Discorhabdus rotatorius, Zeugrhabdotus fissus, Diazomatolithus lehmani and Ethmorhabdus gallicus). One other species has been split into different morphotypes according to size (i.e. Watznaueria britannica). Watznaueria manivitiae also displays different-sized morphotypes (b8, 8–13 and N13 Am), but these have been grouped because of their similar stratigraphic distribution. In Figs. 5 and 6, the absolute and relative abundances of the nine most abundant species and groups of species are shown. Relative abundances are calculated with respect to the total nannofossil abundance (coccoliths and nannoliths).

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

4. The Plettenberg section 4.1. General composition and organization The 29 m analysed in the Plettenberg quarry are Upper Oxfordian deposits, which show a marldominated lower half and a carbonate-dominated

239

upper half (Figs. 2 and 3). Bioherms are omitted in the representation of the Plettenberg section in order to prevent a more complex bedding-pattern due to potential disruption by local sponge abundance. Based on carbonate content, marls (CaCO3V65%), calcareous marls (65–75% CaCO3), marly limestones (75–85% CaCO3) and limestones

Fig. 5. Microphotographs illustrating nannofacies typical of carbonate-poor (A) and carbonate-rich (B) samples. (A) In a sample with 66% CaCO3, nannofossils are relatively more abundant and the assemblage is dominated by small specimens: the white arrows show three W. britannica (b5.5 Am) and one B. dorsetensis in the middle. Microphotographs (E), (H), (K) and (I) also display species typical of carbonate-poor samples. (B) In a sample with 78% CaCO3, nannofossils are less abundant and large specimens (here a W. britannica N8 Am) are common. In (C), (F) and (J), specimens typical of carbonate-rich samples are shown. Microphotographs (C) to (E) show differently sized W. britannica specimens. Scale bars=5 Am.

240 N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Fig. 6. Absolute abundance of calcareous nannofossils (quantified per gram of rock) compared to lithology (CaCO3 content) in the Plettenberg section. The absolute abundance of taxa significant for palaeoenvironmental reconstructions (with average percentage z2%) is also shown. The small-sized species comprises Biscutum dorsetensis, B. dubium, Discorhabdus rotatorius, Zeugrhabdotus erectus, Z. fissus, Diazomatolithus lehmani and Ethmorhabdus gallicus. Watznaueria britannica is subdivided into three differently sized morphotypes that have different distributions in the analysed succession. The differently sized morphotypes of W. manivitiae have been grouped together, because of their similar distribution. Shaded and non-shaded areas indicate the three analysed small-scale lithological units.

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263 Fig. 7. Relative abundance (percentage in the total nannofossil assemblages) of the most abundant calcareous nannofossil taxa. See also legend for Fig. 6. Shaded areas highlight the relative abundance peaks.

241

242

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

(CaCO3N85%) were distinguished. Limestones are most commonly wackestones, but rare mudstones and packstones are also present (Fig. 3). These deep-shelf deposits contain 10 to 30% autochthonous and parautochthonous particles (common brachiopods, echinoderms, foraminifera, ammonites, belemnites, sponges and associated encrusters; scarce bivalves, ostracods and gastropods). Sponges are always present, and abundant both in marls and limestones. Fragments of reworked microbialites or encrusting sponges (tuberoids) are frequent and glauconite locally occurs in low quantities. Associated with microbialite crusts, sponges locally form small (metre-scale) bioconstructions in the lower, marl-dominated part of the section, and metre-scale to decametric bioconstructions in the upper, limestone-dominated part of the section. These reefs are dominantly composed of siliceous sponges, associated with microbialites and benthic organisms (mainly brachiopods). Dish- and tube-shaped siliceous sponges, as well as microbialite crusts, display larger dimensions in the large bioherms of the limestone-dominated interval than in the small bioherms of the marl-dominated interval. Based on the detailed analysis of facies, sedimentary structures and CaCO3 content, a wellexpressed, hierarchical stacking-pattern of deposits is observed in the marl-dominated part of the section. Some intervals of the section, corresponding to 0.2–2-m-thick marly levels are characterised by a low CaCO3 content, a high number of sponges, brachiopods, ammonites and belemnites, and form the main depressions on the erosional profile. Intercalated between these marliest levels, 1.5–3m-thick bundles of marl-limestone couplets are observed (Fig. 3). In detail, these limestone-dominated bundles show first a progressive increase in CaCO3 content, corresponding to calcareous marlmarly limestone to marly limestone–limestone couplets, and secondly, a decrease in CaCO3 content marked by calcareous marl-marly limestone couplets, which progressively grade into a new, lowCaCO3 content, marly level. Thus, two orders of lithological units are distinguished in the Plettenberg section (Fig. 3): (1) a small-scale lithological unit formed of five to six marl-limestone alternations, which are bounded by the lowest CaCO3 content (i.e. the marliest levels); and (2) an elementary unit

that corresponds to one CaCO3 fluctuation (or marllimestone couplet). 4.2. Geometrical relationship between sponge-microbialite reefs and marl-limestone bundles Sponges are always present, and abundant both in the marls and limestones. They locally form lenticular bodies of metre-scale to decametric dimensions (Figs. 8 and 9). All the sponge-microbialite bioconstructions outcropping in the Plettenberg quarry are stratigraphic reefs (sensu Dunham, 1970). The base of the section is dominantly marly, and sponge-microbialite-reef development is laterally limited to some few metres, rarely 10 m. Upwards through the section, the deposits are dominated by limestones and the sponge-microbialite reefs are less abundant, but their lateral expansion is generally more important. At the base of the Kimmeridgian (Planula Zone; Fig. 3), only localised reefs are observed. Their lateral expansion most commonly reaches a few tens of metres. The relationship between sponge-microbialite-reef architecture and lateral deposits is particularly well marked in the marl-dominated lower part of the section, where a detailed analysis was performed. The marl-dominated lower part of the section is made of a succession of marl-limestone couplets forming well-visible bundles that indicate cyclical changes in CaCO3 content (Fig. 3). Where spongemicrobialite bioherms occur, each centimetric to decimetric limestone bed laterally passes into a reefgrowth phase of the stratigraphic build-up (Fig. 9). These reef-growth phases form layers that have a comparable, or slightly greater, thickness than the corresponding limestone bed. The sponge build-ups had then probably little relief above the surrounding sea-floor. Moreover, a differential compaction between muddy sediments and solid reefs has probably enhanced the differences in thickness observed between reefs and the laterally deposited marls and limestones. Only when successive sponge build-ups are stacked is a positive relief (up to 3 m) above the sea-floor observed (Fig. 8). Transition from the reefbody to lateral deposits is progressive, with a reduction in the number of sponges (Fig. 10A and B). Each marly level tends to onlap this previous bioconstructed relief, either being reduced in thickness or totally disappearing in the reef-body. The

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

243

Fig. 8. (A, B) Marl-dominated part of the section at the base of the Plettenberg quarry showing several sponge-microbialite reefs and their relationships with marl-limestone alternations. The different marl-limestone bundles that compose small-scale lithological units (S1–S5) can be correlated to the successive reef-growth phases. The maximum lateral development of the reefs occurs in the carbonate-rich deposits, whereas clay-rich sediments correspond to a reduction in size, or to the total demise of the sponge-microbialite reefs. Note that the sponge build-ups tend to develop on pre-existing reefs and form low to moderate reliefs (about 1–2 m) with respect to the lateral marl-limestone deposits.

marly intervals that continue within the reef-structure contain numerous sponges and an abundant fauna (belemnites, ammonites and brachiopods), but generally do not form a real framework (Fig. 10C and D). At a metric to decametric scale, the stratigraphic sponge-microbialite reefs display a lenticular shape that corresponds to a phase of initiation, lateral expansion, then reduction in size of the build-up. Reef size-expansion was initiated when an increase in carbonate deposition occurred (i.e. laterally to small pluricentimetric limestone beds). The maximum lateral development of the reef size, and of the corresponding sponge-microbialite reef units, generally occurred during limestone-dominated intervals (bSchwammb7nkeQ; Roll, 1934; i.e. occurrence of thick limestone beds with respect to marly levels), whereas the marlier levels (bSchwammb7nkemergelQ) correspond to a reduction in size, or to the total demise, of the sponge-microbialite reefs (Figs. 8 and 9; Brachert, 1992). In some cases, limestone beds cap the sponge build-ups (Fig. 9A–D), and carbonate deposition seems to have been responsible for the demise of these reefs (Leinfelder et al., 1996).

4.3. Sponge-microbialite reef composition The sponge fauna mainly consists of siliceous sponges, which formed the skeletal framework of the build-ups. In the marl-dominated part of the section, the bioherms are formed by three main components, sponges, microbialites and allochthonous mud. Each of them constitutes about 30% of the reef volume. The remaining 10% corresponds to brachiopods, bivalves, oysters and calcareous sponges. Siliceous sponges are composed of more than two-thirds hexactinellids and less than one-third lithistids, as commonly observed in other Swabian Alb sponge-reefs (e.g. Schmid et al., 2001). The dominant growth forms of the sponges are decimetric plate- or dish-shapes, and more rarely vases and cylinders. In larger bioconstructions of the limestone-dominated upper part of the section, sponges show larger dimensions, and are essentially represented by tube- and dish-shaped forms (up to 1 m in diameter). Microbialites are always well developed, and locally can be the dominant component of the bioherms. In the field, and at a macroscopic scale, microbialites are recognisable by their darker colour

244

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Fig. 9. (A, B) Relationship between small-scale depositional units and stratigraphic sponge-microbialite reefs in the marl-dominated part of the section. Build-ups form lenticular bodies of reduced size (decimetres to metres) and display low-relief shapes. During carbonate-dominated episodes, sponge-microbialite reefs are occasionally capped by a thick limestone bed (black arrows). Rapid carbonate deposition is probably responsible for the demise of these reefs. (C, D) Details of a metre-sized, lenticular bioherm showing numerous growth interruptions. Each growth-phase (labelled 1–9) of the build-up can be correlated to the successive carbonate beds of the marl-limestone alternations that compose a small-scale lithological unit. Note that maximum lateral extension of the sponge build-up corresponds to the thicker carbonate bed (number 5) of the small-scale unit. The reduction in size of the sponge-microbialite reefs corresponds to the marliest deposits. At its top, the reef is capped by the first carbonate bed of the next small-scale lithological unit. (E, F) Detail of another small, lenticular bioherm. Here, the stacking pattern of the marl-limestone alternations that compose the small-scale lithological unit S4 is more chaotic than in (C, D) because of the proximity to the sponge build-up. In this case, the demise of the build-up was contemporaneous with the marl deposits. For further explanation, see text.

compared to the non-microbial deposits, and form an irregular, non-gravitational outer surface (Camoin and Montaggioni, 1994). A succession of three main

layers of microbialites can be distinguished, on the basis of their macro- and mesoscopic forms and internal structures (Fig. 11). This succession is

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

245

Fig. 10. (A) Lateral transition between the bioherm shown in Fig. 9E and marl-limestone alternations. (B) Detail of a transition zone between a reef-body (not visible on the photo, but situated to the left) and marl-limestone alternations. From left to right, note the reduction in the thickness of this transition zone mainly composed of siliceous sponges. (C) Lenticular bioherm showing reef-growth phase interruptions marked by marly levels. (D) Detail of a marly level (between the dotted lines). Note the local high density of sponges within this marly level (white arrows) when compared to the carbonate-richer, bioconstructed interval where sponges are sparsely distributed (black arrow) and are associated with abundant allochthonous mud and microbialites.

observed both in the marl-dominated and carbonatedominated parts of the section. These microbial layers have previously been illustrated in the Oxfordian outer-shelf bioherms of southeastern France (Gaillard, 1983; Dromart et al., 1994), and their succession on the upper surface of sponges corresponds to the bfundamental structureQ of a sponge-microbialite growth reef sensu Gaillard (1983). Microscopically, these microbial carbonates are made of three types of micritic fabrics: dense, clotted and peloidal (Leinfelder et al., 1993a; Riding, 2000). The first mesoscopic layer of microbialites (microbial layer 1) appears as a relatively fine, non-continuous microbialitic layer that does not exceed 1.5 cm in height. It is directly observed on upper surfaces of the vase-, tube- or dish-shaped sponges (m1; Fig. 11). This crust was never observed on the lower surfaces of the sponges, except in cases where they were turned over.

Its outer surface is generally flat or slightly wavy. Internally, microbial layer 1 may display a laminated structure, usually enhanced by numerous nubeculariids. Its mesofabric is mainly mesoclotted, and thus corresponds to thrombolites (Aitken, 1967; Shapiro, 2000), but can also locally be massive or leiolitic (Gaillard, 1983; Braga et al., 1995). Microscopically, microbial layer 1 is essentially made of a clotted micrite with few zones of dense micrite (Fig. 12A). In the continuation of microbialitic layer 1, and/or directly on the top sponge-surface, a microbial layer 2 can develop, with a columnar shape (m2; Fig. 11). In the limestone-dominated part of the section, these columns can reach a height up to 15 cm and a width of 2 cm, whereas they are less developed, and show significantly smaller dimensions (1–3 cm high), in the marl-dominated part of the section. Microbial layer 2 locally displays a well-developed, convex-upward

246

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Fig. 11. (A, B) Dish-shaped siliceous sponges (s) encrusted by microbial layers 1, 2 and 3. Layer 1 (m1) has a massive to clotted appearance showing a relatively flat upper-surface, and rests directly on the upper-surface of the sponge. Note the numerous nubeculariids associated with this crust (white dots). The second microbialitic crust (m2) with a clotted fabric tends to develop a columnar morphology. The third microbial layer (m3) has a laminated (stromatolitic) fabric and is generally covered by allochthonous mud (a) with numerous tuberoids.

lamination, which is generally largely spaced, with sparse associated microencrusters (e.g. nubeculariids). Microscopically, microbial layer 2 dominantly consists of clotted to peloidal micrite (Fig. 12B). In the upper part of columns of microbial layer 2, or covering them, a last microbial layer 3 is observed (m3; Fig. 11). In the marl-dominated part of the section, where microbial layer 2 is reduced or absent, microbial layer 3 can also directly encrust the sponge-surface. This layer usually is of lighter colour compared to microbial layers 1 and 2, making its distinction difficult with non-microbial carbonate mud (Fig. 11A). Depending on the density of the lamination, microbial layer 3 is either a stromatolite or a laminated thrombolite (cf. Leinfelder et al., 1993a; Schmid, 1996; Dupraz, 1999). Where lamination is relatively sparse, microbial layer 3 tends to be structureless (leiolitic). At a microscopic scale, lamination is marked by thin, micritic horizons (58–220 Am thick), which can be traced laterally for several centimetres. These micritic horizons may cover both a lighter layer of micrite and a layer of peloidal micrite (Fig. 12C and D). Microbial layer 3 is generally covered by

allomicrite, but may also be directly overlain by a new generation of sponges. In the marl-dominated part of the section, the complete succession of the mesoscopic microbial layers 1, 2 and 3 does not occur everywhere in the bioherms. However, the succession from sponges to microbialites is observed whatever the location within the bioherm, and occurs throughout its development. In some cases, thrombolitic columns (microbial layer 2) form the last stage of microbialite growth before being directly covered by sediments. This scenario is more frequently observed in the limestone-dominated than in the marl-dominated intervals. In some other cases, microbial layer 1 is lacking, and the microbial crust directly begins with thrombolitic columns of microbial layer 2. Associated with microbialites, microfauna is abundantly represented in Upper Jurassic reefs (Leinfelder et al., 1993a,b, 1994). In the studied sponge-microbialite reefs, microencrusters are poorly diversified. On the upper sponge-surfaces, and associated with microbialites, nubeculariids are the most common microencrusters (Fig. 12A and B). They are more abundant in microbial layer 1 than in thrombolitic

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

247

Fig. 12. (A) Microbial layer 1 (m1), composed of dense to clotted micrite on a hexactinellid sponge (s). Note the abundant microencrusters (mainly Tolypammina; dashed white arrow) directly on the upper surface of the sponge, and the nubeculariids (white arrow) associated with the first microbialitic crust. The top of the photograph displays microbial layer 3 (m3) directly on m1. (B) Another example of microbial layer 1. Note the bivalve boring extending from the upper surface of the sponge (s), suggesting a gap between the death of the sponge and microbialite formation. Nubeculariids (white arrow) are always associated with m1, which progressively transformed into microbial layer 2 (m2). (C) Columns of microbial layer 2 (m2) made of clotted to peloidal micrite. These columns are overlain by the laminated microbial layer 3 (m3). Note the numerous Terebella (white arrows), both on the top of the columns of m2 and on the laminae of m3. (D) Microbial layer 1 (m1) on the lower part of a vertical lithistid sponge (s). This first microbial crust progressively passes into a columnar microbial layer 2 (m2) in the lower half of the photograph, whereas microbial layer 3 (m3) encrusts both m2 and m1, and the upper part of the lithistid sponge.

domes or columns of microbial layer 2. They are only rarely observed associated with microbial layer 3. The agglutinated worm-tubes of Terebella are observed on, and only rarely in, the thrombolitic columns, but are abundant on the laminations of microbial layer 3 (Fig. 12C and D). Sessile foraminifera are also common, mainly represented by Bullopora and Tolypammina. Bullopora is present both within the

skeletal meshwork of siliceous sponges and in the interstices within the microbial crusts. Tolypammina is mainly observed encrusting the upper surface of siliceous sponges (Fig. 12A). Few calcareous sponges are observed on microbial layers 1 and 2. Serpulids, bryozoans and calcareous sponges constitute a common fauna observed on the lower surfaces of the sponges.

248

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

4.4. Calcareous nannofossil assemblages and distributions Absolute abundance of the nine most common, or ecologically significant, taxa was compared to total nannofossil abundance and wt.% CaCO3 content. Total nannofossil abundances, the values of which vary from 4 to 370 million nannofossils per gram of rock, very clearly negatively covary with wt.% CaCO3 (Fig. 6). Calcareous nannofossils are systematically more abundant in marly hemi-couplets and marly intervals, as opposed to carbonate-rich layers or intervals. 4.4.1. Calcareous nannofossils in the elementary units Calcareous nannofossils are more abundant in marls and calcareous marls (V75% CaCO3) and they become rarer in marly limestones and limestones (N75% CaCO3) in the elementary unit of the Plettenberg section. When considering the average absolute abundance of nannofossils per gram of rock, the marliest levels (V75% CaCO3) contain 3.75 times more nannofossils than the more calcareous levels. The absolute quantity of the nine analysed taxa strongly covaries with total nannofossil abundance. This means that the majority of the taxa are more abundant in carbonate-poor than in carbonate-rich hemi-couplets (Fig. 6). However, an important difference is observed in relative abundances (percentages) of the analysed taxa. The small-sized taxa (Lotharingius hauffii and small Watznaueria britannica; Figs. 5 and 7) clearly dominate the marl assemblages, their relative abundances being, on average, being twice as high in the marls, as opposed to the carbonate-rich hemi-couplets. Conversely, the taxa characterised by large size (large W. britannica, Watznaueria manivitiae and Schizosphaerella spp.) have an opposite pattern, being more abundant in the limestones, with for example, the relative abundance of W. manivitiae being, on average, more than twice as high in the limestones than in the marls (Fig. 7). 4.4.2. Calcareous nannofossils in the small-scale lithological units Calcareous nannofossil abundance and distribution fit well with the small-scale lithological unit characterised by the initiation, development and

eventual demise of the sponge-microbialite reefs (Figs. 6 and 7). Relative to the lithology (i.e. marldominated or carbonate-dominated intervals), some species are more or less represented in the smallscale lithological units. The thin carbonate levels present in the marliest intervals, between two smallscale lithological units, are also relatively enriched in the small taxa (Lotharingius hauffii and small Watznaueria britannica; Fig. 5) when compared to levels with similar CaCO3 content in the carbonaterich intervals (Fig. 7). A similar trend is observed in the large-sized taxa, which are systematically more abundant in the marliest levels of the carbonate-rich bundles than in the marly intervals sandwiched between two small-scale lithological units (Fig. 7). Some other taxa (such as Watznaueria barnesiae and Cyclagelosphaera margerelii) display an intermediate distribution related to CaCO3 content, being relatively more abundant in the transitional intervals of the small-scale lithological unit, from the marl- to carbonate-dominated interval. The three small-scale lithological units analysed in the present study display the same pattern of nannofossil distribution. The highest absolute abundance of nannofossils is observed within the clay-dominated intervals, where the small-sized taxa (Lotharingius hauffii and small Watznaueria britannica) dominate the assemblage. When the first observed sponge-microbial reefs are initiated, and the lithologies become progressively more calcareous, absolute abundance drastically decreases and taxa like Watznaueria barnesiae and Cyclagelosphaera margerelii are relatively more abundant. Finally, in the carbonate-richer portion of the units, absolute abundances are the lowest, and the assemblage is dominated by large-sized coccoliths (large W. britannica, Watznaueria manivitiae) and nannoliths (Schizosphaerella spp.; Figs. 6 and 7). Some differences exist between the three analysed small-scale lithological units. The mean absolute abundance of the second unit is the highest (110106 nannofossils/g rock) and more fluctuating than in the first and third units, where mean abundances are, respectively, 37.5106 and 77.5106 nannofossils/g rock. Also, the transition between the first and the second units displays the best average preservation of nannofossils.

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

5. Interpretation 5.1. Sponge-microbialite reefs or sponge-microbialite mounds? Schmid et al. (2001) described the deep-shelf sponge microbialite-rich deposits of Gosheim (about 15 km south of Plettenberg) as siliceous spongemicrobial mud-mounds. Following the classification of James and Bourque (1992), mounds are a bstructure containing more than 25% of detrital or microbially generated structureless micriteQ (Schmid et al., 2001, p. 345). The bioconstructions observed in the Plettenberg quarry cannot be considered as mounds for several reasons. Although allochthonous mud constitutes about 30% of the reef volume, the different bioconstructions display a clear skeletal framework made by siliceous sponges, which undoubtedly served as substrates for microbialite development. Furthermore, structureless microbialites (leiolites) form only a minor part of the microbial crusts, which mainly display thrombolitic and, to a lesser degree, stromatolitic fabrics. These internal structures clearly emphasize the constructor role played by microbialites on a previous framework (i.e. sponges). However, Plettenberg sponge-microbialite reefs show a clear lateral variability from a bcentralQ part having a true framework and a positive relief to lateral deposits. Around this central part, sponges are still abundant but microbial crusts are lacking. In this transitional zone, between the sponge-microbialite framework and the lateral limestone bed, sponges trapped abundant mud and can have a mud-mound appearance. Consequently, based on the studied section, the observed bioconstructions can be a matter of debate in terms of internal structure, but Plettenberg sponge-microbialite bioherms can be considered as real, organic-framed reefs (sensu Riding, 2002). 5.2. Nannofossil assemblages and the carbonate signal 5.2.1. Nannofossil preservation In the Plettenberg section, the absolute abundances of nannofossils are generally very low when CaCO3 content is high; conversely, their highest abundances are generally recorded in marly hemi-couplets. This pattern could be explained by diagenesis. However, the

249

richest, marly samples display in turn good, moderate and poor preservation of nannofossils (Fig. 13A), and no significant difference in abundance is observed among samples with this differing preservational states (Figs. 6 and 7). This may be due, in part, to the fact that the species that represent from 73 to 99% of the total assemblage are taxa resistant to dissolution and with a comparable preservation potential (mainly species of the family Watznaueriaceae and Schizosphaerella spp.; Pittet and Mattioli, 2002; Lees et al., in press). Preservation thus could however have controlled species richness, through dissolution of the most delicate and rare taxa (Fig. 13B). A high diagenetic resistance to dissolution has been inferred for Watznaueria barnesiae (e.g. Thierstein, 1980; Roth and Krumbach, 1986; Erba, 1992; Henriksson and Malmgren, 1999), for Cyclagelosphaera margerelii (Thierstein and Roth, 1991), for Schizosphaerella spp. (Ka¨lin, 1980; Mattioli, 1997; Noe¨l et al., 1994) and for Lotharingius hauffii (Mattioli, 1997). Seven of the analysed coccolith taxa belong to the same family (Watznaueriaceae), and display the same rim-structure and crystallite organisation (Bown, 1987; Young and Bown, 1991). Namely, they are characterised by elliptical (L. hauffii, Watznaueria britannica, W. barnesiae and Watznaueria manivitiae) or circular (C. margerelii) coccoliths with two shields, the distal shield being composed of imbricate elements joined along inclined sutures. Such organisation and the crystallographic orientation of the rim-elements are possibly responsible for the high resistance to dissolution of these coccoliths (Young and Bown, 1991). Some of the small taxa (i.e. Biscutum spp. and Zeugrhabdotus spp.) are considered to be delicate, because of their small size and coccolith structure (Thierstein, 1980). However, these taxa have abundance peaks in samples with 60–70% CaCO3. This carbonate content is above the generally accepted limit of 55% carbonate content, in which wellpreserved assemblages can be found (Thierstein and Roth, 1991). Moreover, rare specimens of these delicate taxa are also recorded in some carbonatericher samples (N75% of CaCO3; Figs. 6 and 7). 5.2.2. Role of nannofossils in the formation of marllimestone couplets A high calcareous nannofossil production and accumulation in the sediments cannot be invoked to

250

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Fig. 13. Plots showing mean absolute abundance of nannofossils in the Plettenberg section split into elementary units (A), small-scale lithological units (B) and preservation of the analysed samples (C). Species richness (number of species) is split by preservation (D). Error bars: 95% confidence interval. N: number of samples. In bold: significant differences (S).

explain the formation of the limestone hemicouplets of the Plettenberg section. Accumulation rate may significantly influence nannofossil abundance in the sediments (Pittet et al., 2000; Mattioli and Pittet, 2002; Pittet and Mattioli, 2002; Giraud et al., 2003). At times of high accumulation rate, microfossils may undergo significant dilution by sedimentary input. In the Oxfordian of southwestern Germany, the pattern of nannofossil abundance and the observation that, very often, carbonate-rich phases on the shallow-platforms correspond to carbonate-dominated sediments within the adjacent basins, seem to suggest that production and export potential of shallow-platforms controlled, in turn, the formation of marl-limestone alternations in the

basins, and thus the abundance of nannofossils in the sediments (Pittet et al., 2000; Pittet and Mattioli, 2002). Calcareous nannofossils have probably produced an important portion of the carbonates only in the marliest layers of the Plettenberg section. A similar pattern has been described in another Upper Oxfordian section of the Swabian Alb area (Balingen-Tieringen; Pittet and Mattioli, 2002). Both in the Balingen-Tieringen and Plettenberg sections, total nannofossil abundance negatively correlates with the carbonate content, and the highest nannofossil abundance is recorded in marls and condensed intervals, suggesting a control by the accumulation rate on the recorded nannofossil abundance in carbonate mud.

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

5.2.3. Nannoplankton composition in the marl-limestone couplets Nannoplankton distribution in the Plettenberg section shows high relative-abundances of small taxa (mainly Lotharingius hauffii and the small-sized Watznaueria britannica; Figs. 7 and 13A) in marly hemi-couplets, and a relative dominance of large specimens and/or taxa (large W. britannica, Watznaueria manivitiae and Schizosphaerella spp.) in the limestones. Relatively few papers deal with the ecological preferences of Jurassic nannoplankton. Schizosphaerella spp. have been reported by different authors as having higher relative abundances in Jurassic carbonate-rich sediments, whereas coccoliths are in general more abundant in marls (Noe¨l et al., 1994; Claps et al., 1995; Mattioli, 1997; Mattioli and Pittet, 2002). Schizosphaerella spp. have been interpreted as an index of low trophic conditions (Noe¨l et al., 1994; Claps et al., 1995; Pittet and Mattioli, 2002), or of steady nutrient recycling in ocean surface-waters (Mattioli, 1997). The large Watznaueria manivitiae (=Cyclagelosphaera deflandrei Cooper, 1989; Fig. 13B) is considered as being a typical component of Late Jurassic–Early Cretaceous low-latitude assemblages (Cooper, 1989), and its distribution is thus possibly controlled by temperature. Alternatively, it has been proposed that this species proliferates under oligotrophic conditions at times of carbonate-dominated sedimentation (Pittet and Mattioli, 2002). Watznaueria britannica (=Ellipsagelosphaera communis Busson et al., 1992) has been suggested as a mesotrophic (Lees and Bown, 2002; Lees et al., in press), or eutrophic taxon (Busson et al., 1992, 1993). However, recent studies (Giraud et al., 2003) have demonstrated variations in abundances relative to carbonate content, and possibly therefore indicate different ecological requirements, for differently sized W. britannica. In the studied section, the large specimens (N8 Am) have a similar distribution to Schizosphaerella spp. and Watznaueria manivitiae. They are more abundant in limestones, possibly indicating an affinity with relatively more oligotrophic conditions. Conversely, the small specimens (b5.5 Am) are more abundant in marls and have distributions comparable to Lotharingius hauffii and other small-sized taxa.

251

The small-sized taxa, except Lotharingius hauffii and small Watznaueria britannica, have been grouped because they show a similar distribution in the Plettenberg section. This group of small-sized coccoliths is dominated by Biscutum dorsetensis, Zeugrhabdotus erectus, and is also characterised by Biscutum dubium, Discorhabdus rotatorius, Zeugrhabdotus fissus, Diazomatolithus lehmani and Ethmorhabdus gallicus. In the Cretaceous, Z. erectus, D. rotatorius and D. lehmani are interpreted as being indices of eutrophic conditions in surface-waters (e.g. Roth and Bowdler, 1981; Roth and Krumbach, 1986; Premoli Silva et al., 1989; Watkins, 1989; Erba, 1992; Erba et al., 1992). However, a change in the ecological preferences of these taxa passing from the Jurassic to the Cretaceous cannot be excluded. Lotharingius hauffii has been interpreted to indicate high trophic conditions in the Lower Jurassic (Bucefalo Palliani et al., 1998, 2002; Mattioli and Pittet, 2004). Watznaueria barnesiae has been commonly associated with low-fertility conditions in the Cretaceous (Roth, 1989; Roth and Krumbach, 1986; Premoli Silva et al., 1989; Watkins, 1989; Erba, 1992; Erba et al., 1992). However, it has also been interpreted as being an eurytopic species (Mutterlose and Kessels, 2000). Pittet and Mattioli (2002) have shown that W. barnesiae is common in intermediate and low trophic conditions in the Upper Jurassic of southwestern Germany. Cyclagelosphaera margerelii has been reported as the dominant species in lagoonal environments characterised by high trophic conditions (Busson et al., 1992; 1993) and important salinity variations (Tribovillard et al., 1992). In a locality very close to Plettenberg (Balingen-Tieringen), the highest abundance of C. margerelii has been related to periods of moderate to high trophic conditions (Pittet and Mattioli, 2002). In the Plettenberg section, the differences observed in the nannofossil assemblage compositions between marls and limestones may be interpreted in terms of environmental change, probably related to changes in trophic resources. It is reasonable to infer higher trophic conditions in times of marl deposition, with respect to carbonate-rich levels, because numerous authors have already inferred a clear difference in nannoplankton productivity between marls and lime-

252

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

stones (e.g. Watkins, 1989; Erba et al., 1992; Claps et al., 1995; Mattioli, 1997; Mutterlose and Ruffell, 1999; Pittet and Mattioli, 2002).

nate-dominated) of the lithological units might correspond to low trophic conditions. 5.3. Factors controlling sponge-microbialite growth

5.2.4. Nannoplankton composition in the small-scale lithological units A pattern similar, but more accentuated, to the one observed for the marl-limestone alternations is recorded for the small-scale lithological units (Fig. 14). The unit boundaries are characterised by the highest nannofossil abundances and the highest occurrences of taxa interpreted as indicative of mesoto eutrophic conditions, namely Lotharingius hauffii, the small Watznaueria britannica, Biscutum dorsetensis, Zeugrhabdotus erectus and the other smallsized taxa. At the base of the three studied small-scale lithological units, where the marl-limestone alternations become increasingly rich in carbonates, relative abundances of taxa putatively indicative of intermediate trophic conditions (Cyclagelosphaera margerelii and Watznaueria barnesiae) are the highest. Large coccoliths and nannoliths (large W. britannica, Watznaueria manivitiae and Schizosphaerella spp.) dominate the nannofossil assemblages in the middle part of the small-scale lithological units (i.e. the marllimestone bundles), where carbonate content is at its highest (Fig. 14). A very similar succession, although on a longer time scale, of the relative abundances of different nannofossil taxa has already been noticed in the Upper Oxfordian Balingen-Tieringen section (Pittet and Mattioli, 2002; Bartolini et al., 2003), where sedimentological and geochemical evidence points to a transition from a more humid climate, and meso- to eutrophic surface-water conditions, to a more arid climate, and oligotrophic oceanic waters. Pittet and Mattioli (2002) have thus described the successive maxima in relative abundances of different nannofossil taxa in terms of a trophic continuum, from high-mesotrophic (L. hauffii and small W. britannica) to oligotrophic conditions (W. manivitiae and Schizophaerella spp.). Similarly, the change in nannofossil assemblage composition in the three studied small-scale lithological units of the Plettenberg section may be interpreted as a trophic continuum. The small-scale lithological-unit boundaries (marl-dominated) may thus represent the highest trophic conditions in the surface-waters of the Plettenberg area, whilst the intermediate parts (carbo-

Long distance (kilometre-scale) lateral continuity of marl-limestone bundles in the Swabian deepshelf suggests that small-scale lithological units can be considered as isochronous units (Freyberg, 1966; Brachert, 1992; Pittet and Strasser, 1998a). Streim (1961a,b) has shown that comparable Upper Jurassic sedimentary units of the Franconian Alb also correspond to cyclical changes in spongebiostrome associations. Similarly, Brachert (1992) has shown that the roofs of the different units that make up the sponge bioherms could also be considered as isochronous surfaces. Even if slight diachronous deposition occurred between the reefgrowth and the lateral deposits, because of the relief above the sea-floor formed by sponges, the surfaces delimiting both marl-limestone couplets and corresponding sponge-microbialite growthphases represent the same episode in the sedimentary record. Thus, the sponge-microbialite-reef development and demise can be compared to the sedimentary evolution recorded in the lateral deposits. The analysis of the sponge-microbialite reefs in the Plettenberg quarry evidences a close link between their architecture and the dynamics of sedimentary deposition, CaCO3 content and calcareous nannofossil composition of the laterally correlated sediments. The relationship between carbonate phases and the size of the sponge-microbialite reefs has been illustrated by many authors in the Upper Jurassic of the Swabian Alb (Gwinner, 1976; Meyer and Schmidt-Kaler, 1989) and of other outer-shelf areas (e.g. France; Gaillard, 1983). Based on sedimentological, micropalaeontological and geochemical evidence (Pittet and Strasser, 1998a; Pittet et al., 2000; Pittet and Mattioli, 2002; Bartolini et al., 2003), a model of sponge-microbialite-reef development during the deposition of marl-limestone couplets and small-scale lithological units can be proposed (Fig. 14). In this model, the interplay of two dominant factors (carbonate accumulation rate and nutrient level) can likely explain the changes in sponge-microbialite-reef architecture observed in

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Fig. 14. Model for the development of individual sponge build-ups in marl-dominated deposits driven by trophic level and carbonate accumulation in the Swabian deep-shelf. For discussion, see text.

253

254

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

the Upper Oxfordian–Lower Kimmeridgian of southern Germany. 5.3.1. Origin of the cyclic organisation of deep-shelf deposits Pittet and Strasser (1998a) have illustrated long and short-term sedimentary cycles in the Upper Jurassic of the Swabian deep-shelf, which correspond to the large- and small-scale depositional lithological units (or sequences) recorded in the Plettenberg section. Long-term (million-year-scale) and shorter-term relative sea-level changes were responsible for the formation of these large- and small-scale lithological units. Pittet and Strasser (1998a) suggested that smallscale lithological units formed in tune with the orbital 100-kyr eccentricity cycle, whereas large-scale lithological units were essentially eustatic in origin (thirdorder sequences; Vail et al., 1991). The mean duration of the small-scale lithological units, and the hierarchical stacking pattern between these sequences and the five to six marl-limestone couplets per small-scale lithological unit, also suggest an orbital control on their formation in the Plettenberg section. Thus, the 100-kyr eccentricity and the 20-kyr precession cycles (Berger et al., 1989) are probably indirectly responsible for the formation of the small-scale lithological units and of the marl-limestone couplets, respectively. Orbital control of these small-scale lithological units, and of the marl-limestone couplets, has already been proposed for the Upper Jurassic of the Franconian Alb (Schwarzacher, 1991; Brachert, 1992). Orbital parameters could induce low amplitude sea-level variations, coupled with climatic changes. Humid periods with relatively low sea-level led to increased terrigenous run-off, lowering both carbonate production on the shallow-platform (Hallock and Schlager, 1986; Schlager, 1989) and export basinwards (Schlager et al., 1994). On the Jura platform, more-humid climates occurred during relatively low sea-level stands (Pittet and Strasser, 1998b). In these meso- to eutrophic conditions, marls were deposited in the basin and the sponge-microbialite reefs had a growth-phase reduction or interruption. The nannofossil abundances recorded in the marly sediments are the high because of weak dilution by allochthonous (platform-derived) carbonate mud. In the water-column, calcareous nannoplankton assemblages were dominated by putative meso- to eutrophic taxa. Conversely, during dry

periods, where presumed oligotrophic conditions prevailed, carbonate production was favoured on the shallow-platform, resulting in basinward export of carbonate mud (Heath and Mullins, 1984). During times of carbonate deposition, the maximum lateral extension of the sponge-microbialite reefs occurred. Nannofossil abundances were the lowest in these intervals, due to significant sedimentary dilution by allochthonous carbonates. The assemblage is dominated by ostensibly oligotrophic taxa. Only a too-high background supply of allochthonous platform-derived carbonate mud could lead to the reef’s demise. Growth-form of the reefs is geometrically linked to the enclosing sediment composition (i.e. marl or limestone). Such relationships have been previously recognized in deep-shelf settings of the Upper Jurassic (Brachert, 1992) and in basinal Neoproterozoic calcimicrobial reefs of northwestern Canada (Turner et al., 1997). Such geometrical relationships between reef-growth form and the lateral deposits also suggest a marl-limestone couplet formation dominantly triggered by external factors (i.e. sea-level and climate) rather than a purely diagenetic self-organization. The environmentally driven cycles of calcareous nannoplankton assemblages in marl-limestone alternations, and the proposed trophic preference continuum from meso- to eutrophic taxa in the marls and oligotrophic taxa in the limestone of the small-scale lithological units, add weight to this hypothesis. 5.3.2. Accumulation rate The stratigraphic sponge-microbialite reefs observed in the Plettenberg section have a thickness that is comparable to, or slightly greater, than the thickness of the correlative small-scale lithological units. Thus, the sponge-microbialite bioherms had a low relief above the surrounding sea-floor. This indicates that the reef growth-rate was comparable to, or only slightly higher, than the mean accumulation rate of the small-scale lithological units deposited on the deep-shelf. Furthermore, the observed topographic highs formed by the spongemicrobialite reefs were probably enhanced by differential compaction (Koch and Schorr, 1986; Lang, 1989). Because of the absence of a high relief (constratal growth sensu Insalaco, 1998), accumulation rate is likely an important factor that controlled the sponge-microbialite-reef development in the Swa-

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

bian Alb deep-shelf (Leinfelder et al., 1994, 1996; Krautter, 1995). The first limestone bed at the base of some of the small-scale lithological units covers some sponge-microbialite reefs, indicating that, in the marldominated half of the section, more-important carbonate input may have produced the final demise of some bioconstructions (Fig. 9A–D). During carbonate-dominated episodes, relatively thick limestone beds are also observed capping many sponge-microbialite reefs, and only bioherms that developed on topographic highs, created by pre-existing build-ups, were protected from carbonate accumulation, whereas those situated on topographic lows declined. Although the lateral continuity of the elementary sponge-microbialite sequences could not be demon-

255

strated at the scale of the different bioherms analysed in Plettenberg, they are generally considered to be the foundation of sponge-microbialite bioherms (Gaillard, 1983; Pawallek and Aigner, 2003). Such sequences correspond to the growth of an individual sponge, which is encrusted by successive generations of microbial crusts (Fig. 15): (1) the colonisation and growth of a sponge (stage A) created a limited, but existent, relief above the sea-floor. The encrusting probably initiated during the life of the sponges, but was restricted on local dead-parts (stage B; Fig. 15). It mainly consisted of serpulids, calcareous sponges, and thecideidinid brachiopods on the lower surface of the sponge (Gaillard, 1983), and by microbial layer 1 on its upper surface. This first microbialite layer is

Fig. 15. Idealized succession of the three observed microbial layers (m1, m2 and m3) on the upper-surface of a dish-shaped sponge related to the lamination of the different microbialitic microfabrics, the nubeculariid abundance and the microbial growth rate. (A) Living sponge; (B) first phase of encrustation produced microbial layer 1 (dense micrite) with associated microencrusters (mainly nubeculariids and Tolypammina) on local dead-parts of the upper surface of the sponge. Other microencrusters (mainly serpulids, calcareous sponges and bryozoans) are present on their lower surface; (C) growth of microbial layer 2 made by columns of clotted to peloidal micrite; (D) growth of microbial layer 3 displaying a laminated (stromatolitic) fabric. The succession of these three microbial layers is interpreted as having been mainly controlled by accumulation rate and light. See text for further explanations.

256

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

associated with numerous nubeculariids and can be laminated, indicating a rhythmic and relative low microbial growth-rate (Dromart et al., 1994). Both the relatively homogeneous, or leiolitic, aspect (massive crust of Gaillard, 1983) and the generally flat upper surface of this crust imply that there was probably no, or little, disruptive influence by sediment particles, and that the accumulation rate was close to zero. Within dead parts of the sponge framework, low light conditions permitted growth of sciaphilic encrusters, such as Bullopora and Tolypammina (Gaillard, 1983; Fqrsich and Werner, 1991); (2) the total demise of the sponge allowed larger microbial colonisation with microbial layer 2 (stage C; Fig. 15). A progressively higher accumulation rate, and a probable disruptive influence of allochthonous particles on microbial films, led to formation of a thrombolitic columnar shape (Reitner, 1993). Both lower frequency of nubeculariids and sparser lamination, as well as the more peloidal micrite, suggest a faster microbial growth-rate compared to microbial layer 1. Such change in the microbialite texture, coupled with the fact that peloidal columns generally show their maximum dimensions in the upper parts of sponges, could be interpreted as a reaction to compete against sediment burial, the biofilms located on the highest parts having a longer time to develop. On the other hand, a possible light-dependence (i.e. phototropism) of biofilms cannot be excluded (Gaillard, 1983; Olivier et al., 2003); (3) a laminated thrombolitic or stromatolitic crust (i.e. microbial layer 3) developed (stage D; Fig. 15). This latter covered the previous thrombolitic columns and frequently onlapped on them, confirming that those thrombolitic columns were some few centimetres above the sea-floor. A new increase in the accumulation rate could explain the evolution of such microbialitic texture. Stromatolites can reflect higher sedimentation rates better than thrombolites (Soudry and Weissbrod, 1995; Macintyre et al., 1996). Relief between thrombolitic columns was progressively infilled, allowing microbial films to extend over larger surfaces during periods of reduced accumulation rate, thus forming a laminated microbialite crust. The presence of lamination, underlined by dense micritic horizons, is probably due to episodic lithification of the sediment agglutinated by microbial films (Macintyre et al., 1996). The formation of firm substrates allowed colonisation by numerous aggluti-

nated worms (Terebella). These organisms are interpreted to be sciaphilic microorganisms (Dupraz and Strasser, 2002), but may also reflect low oxygenation at the sea-floor (Leinfelder et al., 1996; Schmid, 1996). Microbial layer 3 is largely found directly below large dish-shaped sponges. The initiation and development of a new sponge generation on earlylithified microbialites, or on previously dead sponges, led to a progressive decrease in light-intensity below the sponges, allowing the settlement of Terebella and of other encrusters, such as Bullopora; (4) finally, microbialitic structures were covered by allomicrite. The latest microbial communities probably could not outcompete too-high accumulation rates, whereas sponges, which could tolerate a higher sedimentation rate (Leinfelder, 2001) initiated a new framework above the sea-floor. The progressive upward and outward succession from a thrombolitic (microbial layer 2) to a stromatolitic (microbial layer 3) fabric is common in the fossil record (Aitken, 1967; Kennard and James, 1986; Feldmann and McKenzie, 1997; Middleton, 2001) and in modern settings (Feldmann and McKenzie, 1998). In Upper Jurassic deep-shelf deposits, such successions were interpreted as reflecting either an increase in accumulation rate (Gaillard, 1983; Dromart et al., 1994) or a shallowing trend, with a concomitant increase in water-energy (Pawallek, 2001; Pawallek and Aigner, 2003). In the studied sponge-microbialite bioherms, tuberoids are present both laterally to the thrombolitic columns, and included in the stromatolitic layers. Thus, waterenergy does not seem to have varied, passing from one type of microbial layer to the other. The succession of the three microbial layers was not observed in all parts of the sponge reefs, and it is difficult to laterally correlate the different thrombolitic levels from adjacent sponge substrates. This apparent lack of lateral continuity can be explained by the position of the sponges serving as substrates for microbialites within the framework (e.g. their elevation above the sediment) and by differences in microbialite development. Reef-parts that were slightly raised above the sediment grew a higher and more complete microbialitic succession. Locally, sediment supply could definitively cover the thrombolitic columns, and thus the third stromatolitic layer is lacking in low topographic areas. Thus, the

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

succession of microbialitic crusts on a sponge substrate is interpreted as being directly controlled by variations of the accumulation rate (Fig. 15). This emphasizes the point that accumulation rate did not only differ between marl and limestone levels, but also displays substantial high-frequency cyclic changes within a limestone bed. 5.3.3. Trophic level Phases of sponge-microbialite build-up appear to correlate to changes in trophic conditions (Keupp et al., 1996; Fig. 14). A reduction in size of the spongemicrobialite reefs is observed during phases of marl deposition. This reduction is observed both at the scale of the marl-limestone couplet and of the smallscale lithological unit. This observation suggests that sponge-growth and microbialite formation were more effective when low to moderate nutrient conditions prevailed, explaining the larger extension of the reefs during phases of carbonate deposition. Generally, sponges are considered as being tolerant to fluctuating nutrient conditions (Keupp et al., 1996; Leinfelder et al., 1996). However, sponges in the studied sections are dominantly hexactinellids that are well adapted to low trophic conditions (Leinfelder et al., 1996; Leinfelder, 2001), possibly indicating why they were present in more distal palaeoenvironments than lithistids (Gaillard, 1983). The absence of welldeveloped microbialites in marly intervals indicates that microbial films were probably not well adapted to clay-rich levels (Dupraz, 1999; Dupraz and Strasser, 1999, 2002). Hence, less-abundant sponges, and reduced microbialite development in marly intervals, led to the loss of a real reef-framework. The result is the reef’s demise in the marliest part of the small-scale lithological units when higher nutrient conditions might have occurred. This scenario is further supported by the calcareous nannofossil distributions (Fig. 14). Taxa potentially indicative of high trophic conditions in the water-column are more abundant in marl-dominated layers (and intervals) in the Plettenberg section. At the scale of the elementary sponge-microbialite succession, the microbial crusts probably represent higher trophic conditions than sponges, which are generally interpreted as reflecting more oligotrophic conditions (Leinfelder, 2001). Temporal pulses of nutrient-release could have favoured benthic micro-

257

bial blooms, such as it mentioned for some Quaternary coral-thrombolite reefs (Camoin et al., 1999; Sprachta et al., 2001). 5.3.4. Other factors Other factors, such as fluctuations in bottom-water oxygenation or sea-level changes (influencing in turn depth and energy) have variously been inferred as controls on sponge-microbialite-reef development and demise (Lang, 1989; Oschmann, 1990; Brachert, 1991, 1992; Leinfelder, 1993, 2001; Leinfelder et al., 1993a,b; Leinfelder and Keupp, 1995; Schmid et al., 2001). Although sponges did not systematically form build-ups, they were always present in the studied sections, both in marls and limestones. Also, benthic foraminifera were present in both the marls and limestones (Schmalzriedt, 1991; Pittet and Strasser, 1998a). These observations suggest that significant fluctuations in bottom-water oxygenation did not occur at the studied locality. Furthermore, Jurassic sponges seem to have been well adapted to fluctuating oxygen levels (Leinfelder et al., 1993b). The abundant agglutinated worm-tubes of Terebella, associated with microbial layers 2 and 3, could also emphasize periods of low oxygenation (Leinfelder et al., 1996). However, their presence in the last stage of microbialite development could be explained either by a reduction in light-intensity in response to colonisation by a new generation of sponges on early lithified parts of microbialites, or by nutrient-richer waters. The direct impact of short-term bathymetric changes (of a few metres) on the Jura shallowplatform (Pittet, 1994, 1996) is unlikely to explain the rapid fluctuations in sponge-microbialite-reef development at the scale of the marl-limestone couplet in a relatively deep epicontinental basin (50–100 m; Meyer and Schmidt-Kaler, 1989). Furthermore, sedimentary structures pointing to the direct impact of storms are absent in the studied sections. Only, in proximal settings close to the Jura platform, storm deposits have been observed (Pittet and Strasser, 1998a). However, abundant sponge and microbialite fragments (tuberoids) testify the impact of bottomwater currents. Tuberoids are more abundant in the limestones than the marls, and they commonly contributed 10 to 30% to the limestone beds (Pittet and Strasser, 1998a). Thus, fluctuations in waterenergy conditions, related to changes in sea-level

258

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

(Brachert, 1992; Pawallek, 2001; Pawallek and Aigner, 2003), probably only weakly influenced sponge-microbialite-reef development, and higherenergy conditions cannot explain the larger development of reefs during carbonate phases. Possibly, tuberoids were more abundant in limestones than marls because sponges and microbial films were more productive and formed larger build-ups. Increases in nutrients linked to higher terrigenous input probably caused higher turbidity in the watercolumn, which could directly reduce the light-intensity at the sea-floor and affect the benthos (i.e. reef components). Assuming microbial development within the photic zone of a sponge-microbialite bioconstruction (Gaillard, 1983; Dromart et al., 1994), periods of reduced light-penetration may have been responsible for the absence of microbialites, which may have played a role in the loss of a rigid framework. However, sponge reefs devoid of microbial crusts are known (Werner et al., 1994), and pure microbialite structures probably occurred in deep and aphotic basins (Bo¨hm and Brachert, 1993; Dromart et al., 1994; Leinfelder et al., 1996). Thus, reduced light cannot be the only factor responsible for the disappearance of sponge-microbialite bioconstructions in the marliest levels, which is more likely related to trophic conditions.

6. Conclusions (1)

(2)

Analysis of the sponge-microbialite-reef architecture in the Upper Oxfordian deep-shelf facies of southern Germany (Plettenberg section, Swabian Alb) shows close relationships between stratigraphic reefs and contemporaneous marllimestone bundles. This may be explained by: (i) slow, vertical growth of the sponge-microbialitereefs; (ii) preferential lateral expansion of the build-ups and (iii) a change in the palaeoenvironmental conditions during successive deposition of marls and limestones. Sponge-microbialite-reef geometry, stacking pattern of the lateral deposits (i.e. marl-limestone bundles) and calcareous nannofossil abundance and assemblage composition display cyclical variations that correspond to small-scale lithological units. This emphasizes that the palae-

oenvironmental conditions occurring both in the surface-waters (deduced by calcareous nannoplankton analysis) and in the benthos (spongemicrobialite reefs) were closely linked, indeed even similar. (3) Trophic conditions in deep-shelf surface-waters may be indicated by the maximum relative abundances of different nannofossil taxa. In a small-scale lithological unit, the successive maximum relative abundances of (i) smallsized taxa, mainly Lotharingius hauffii and small Watznaueria britannica, in the marly levels; (ii) intermediate-sized taxa, like Watznaueria barnasae and Cyclagelosphaera margerelii, in calcareous marls and marly limestones; and (iii) large-sized taxa, such as large Watznaueria britannica, Watznaueria manivitiae and Schizosphaerella spp., in carbonate-rich intervals, is interpreted as representing a trophic preference continuum, from high mesotrophic to oligotrophic conditions, respectively. (4) Low trophic conditions (limestone deposits), both on the platform and the deep-shelf, favoured large developments of sponge-microbialite reefs, but also enhanced the import of platform carbonate mud in deep-shelf environments. Carbonate mud could cover, and sometimes caused the demise of, the low-relief sponge-microbialite reefs. In contrast, while unfavourable high trophic conditions prevailed (marl deposits), sponge and microbialite growth was reduced and reefs commonly died. However, such conditions also prevented high influx of platform carbonate mud, and thus favoured colonisation by sponges. (5) Variations in the accumulation rate during deposition of the limestones seem to have mainly controlled the internal architecture of spongemicrobialite reefs. Each reef-growth phase consist of the succession of several generations of sponges, encrusted by three successive microbial layers. Variation in the accumulation rate, coupled with autogenic factors, such as the positions within the framework (i.e. degree of elevation above the sea-floor) directly influenced the microbial crust succession on sponges. Other factors, such as sea-level changes and water-

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

(6)

energy probably played a minor role, and their impact cannot be demonstrated in the deep-shelf deposits of the Plettenberg section. The formation of small-scale lithological units and of marl-limestone couplets, as well as the development of the sponge-microbialite reefs, are likely controlled by palaeoclimatic changes from more humid to drier conditions, induced by the 100-kyr eccentricity and the 20-kyr precession cycles. Climatically driven variations (i) of the accumulation rate of carbonate mud imported from shallow-platform environments, and (ii) of the trophic conditions in the entire water-column, dominantly controlled both calcareous nannofossil assemblages and spongemicrobialite-reef development.

Acknowledgments We would like to thank M. J7ger for facilities in the Plettenberg quarry. We are grateful to C. Gaillard for his comments on an early version of this manuscript. The very constructive and thoughtful reviews of J.A. Lees and F.T. Fqrsich greatly improved the quality of this paper. N. Olivier acknowledges benefiting from a doctoral fellowship from the French Ministry of Education and Research. This study was supported by the National Science Research Council of France (UMR CNRS 5125 bPale´oenvironnements et pale´obiosphe`reQ, Lyon).

References Aitken, J.D., 1967. Classification and environmental significance of cryptalgal limestones and dolomites, with illustratrions from the Cambrian and Ordovician of southwestern Alberta. J. Sediment. Petrol. 37, 1163 – 1178. Atrops, F., Gygi, R., Matyja, B.A., Wierzbowski, A., 1993. The Amoeboceras faunas of the Middle Oxfordian–lowermost Kimmeridgian, Submediterranean succession, and their correlation value. Acta Geol. Pol. 43, 213 – 227. Bartolini, A., Pittet, B., Mattioli, E., Hunziker, J.C., 2003. Regional control on stable isotope signature in deep-shelf sediments: an example of the Late Jurassic of southern Germany (Oxfordian– Kimmeridgian). Sediment. Geol. 160, 107 – 130. Berger, A., Loutre, M.F., Dehant, V., 1989. Astronomical frequencies for pre-Quaternary palaeoclimate studies. Terra Nova 1, 474 – 479.

259

Boardman, M.R., Neumann, A.C., 1984. Sources of periplatform carbonates: northwest Providence Channel, Bahamas. J. Sediment. Petrol. 54, 1110 – 1123. Bfhm, F., Brachert, C., 1993. Deep-water stromatolites and Frutexites Maslov from the Early and Middle Jurassic of SGermany and Austria. Facies 28, 145 – 168. Bfhm, F., Westphal, H., Bornholdt, S., 2003. Required but disguised: environmental signals in limestone–marl alternations. Palaeogeogr. Palaeoclimatol. Palaeoecol. 189, 161 – 178. Bornemann, A., Aschwer, U., Mutterlose, J., 2003. The impact of calcareous nannofossils on the pelagic carbonate accumulation across the Jurassic–Cretaceous boundary. Palaeogeogr. Palaeoclimatol. Palaeoecol. 199, 187 – 228. Bown, P.R., 1987. Taxonomy, evolution, and biostratigraphy of Late Triassic–Early Jurassic calcareous nannofossils. Spec. Pap.Palaeontol. Assoc. 38, 118. Brachert, T.C., 1991. Environmental control on the fossilization of siliceous sponges: a proposal. In: Keupp, H., Reitner, J. (Eds.), Fossil and Living Sponges. Springer, Berlin, pp. 543 – 553. Brachert, T.C., 1992. Sequence stratigraphy and paleo-oceanography of an open-marine mixed carbonate/siliciclastic succession (Late Jurassic, southern Germany). Facies 27, 191 – 216. Braga, J.C., Martin, J.M., Riding, R., 1995. Controls on microbial dome fabric development along a carbonate-siliciclastic shelfbasin transect, Miocene, SE Spain. Palaios 10, 347 – 361. Bucefalo Palliani, R., Cirilli, S., Mattioli, E., 1998. Influences of the relative sea level fluctuations on the primary production, an example from the Early Toarcian Umbria-Marche basin (Central Italy). Palaeogeogr. Palaeoclimatol. Palaeoecol. 142, 33 – 50. Bucefalo Palliani, R., Mattioli, E., Riding, J., 2002. The response of marine phytoplankton and sedimentary organic matter to the Early Toarcian (Lower Jurassic) oceanic anoxic event in northern England. Mar. Micropaleontol. 46, 223 – 245. Busson, G., NoJl, D., Corne´e, A., 1992. Les coccolithes en bboutons de manchetteQ et la gene`se des calcaires lithographiques du Jurassique supe´rieur. Rev. Pale´obiol. 11, 255 – 271. Busson, G., NoJl, D., Contini, D., Mangin, A.-M., Corne´e, A., Hantzpergue, P., 1993. Omnipre´sence de coccolithes dans des calcaires lagunaires du Jurassique moyen et supe´rieur de France. Bull. Cent. Rech. Explor. Prod. Elf-Aquitaine 17, 291 – 301. Camoin, G.F., Montaggioni, L.F., 1994. High energy coralgalstromatolite frameworks from Holocene reefs (Tahiti, French Polynesia). Sedimentology 41, 655 – 676. Camoin, G.F., Gautret, P., Montaggioni, L.F., Gabioch, G., 1999. Nature and environmental significance of microbialites in Quaternary reefs: the Tahiti paradox. Sediment. Geol. 126, 271 – 304. Claps, M., Erba, E., Masetti, D., Melchiorri, F., 1995. Milankovitchtype cycles recorded in Toarcian black shales from the Belluno Trough (Southern Alps Italy). Mem. Sci. Geol. Padova 47, 179 – 188. Cooper, M.K.E., 1989. Nannofossil provincialism in the Late Jurassic–Early Cretaceous (Kimmeridgian to Valanginian) period. In: Crux, J.A., van Heck, S.E. (Eds.), Nannofossils and their Applications, British Micropalaeontol. Soc. Series. Ellis Horwood, Chichester, pp. 223 – 246.

260

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Davaud, E., Lombard, A., 1973. Statistical approach to the problem of alternating beds of limestone and marls (Upper Oxfordian of the French Jura). Eclogae Geol. Helv. 68, 491 – 509. Dromart, G., Gaillard, C., Jansa, L.F., 1994. Deep-marine microbial structures in the Upper Jurassic of Western Tethys. In: Bertrand-Sarfati, J., Monty, C. (Eds.), Phanerozoic Stromatolites, vol. II, Kluwer Academic Publishers, Dordrecht, pp. 295 – 318. Dunham, R.J., 1970. Stratigraphic reefs versus ecologic reefs. Am. Assoc. Pet. Geol. Bull. 54, 1931 – 1932. Dupraz, C., 1999. Pale´ontologie, pale´oe´cologie et e´volution des facie`s re´cifaux de l’Oxfordien moyen-supe´rieur (Jura suisse et franc¸ais). Geofocus 2, 1 – 200. Dupraz, C., Strasser, A., 1999. Microbialites and microencrusters in shallow coral bioherms (Middle to Late Oxfordian, Swiss Jura Mountains). Facies 40, 101 – 130. Dupraz, C., Strasser, A., 2002. Nutritional modes in coral microbialite reefs (Jurassic, Oxfordian, Switzerland). Evolution of trophic structure as a response to environmental change. Palaios 17, 449 – 471. Eder, W., 1982. Diagenetic redistribution of carbonate, a process in forming limestone–marl alternations (Devonian and Carboniferous, Rheinisches Schiefergebirge, W. Germany). In: Einsele, G., Seilacher, A. (Eds.), Cyclic and Event Stratification. Springer, Berlin, pp. 98 – 112. Erba, E., 1992. Calcareous Nannofossil distribution in pelagic rhythmic sediments (Aptian-Albian Piobbico Core, Central Italy). Riv. Ital. Paleontol. Stratigr. 97, 455 – 484. Erba, E., Castradori, D., Guasti, G., Ripepe, M., 1992. Calcareous nannofossils and Milankovitch cycles: the example of the Albian Gault Clay Formation (southern England). Palaeogeogr. Palaeoclimatol. Palaeoecol. 93, 47 – 69. Feldmann, M., McKenzie, J.A., 1997. Messinian stromatolite– thrombolite associations, Santa Pola, SE Spain: an analogue for the Palaeozoic? Sedimentology 44, 893 – 914. Feldmann, M., McKenzie, J.A., 1998. Stromatolite–thrombolite associations in a modern environment, Lee Stocking Island, Bahamas. Palaios 13, 201 – 212. Freyberg, B.V., 1966. Der Faziesverband im unteren Malm Frankens: Ergebnisse der Stromatometrie. Erlanger Geol. Abh. 62 (112 pp.). Fqrsich, F.T., Werner, W., 1991. Palaeoecology of coralline spongecoral meadows from the Upper Jurassic of Portugal. Pal7ontol. Z. 65, 35 – 69. Gaillard, C., 1983. Les biohermes a` spongiaires et leur environnement dans l’Oxfordien du Jura me´ridional. Doc. Lab. Ge´ol. Fac. Sci. Lyon 90, 1 – 515. Gaillard, C., Atrops, F., Marchand, D., Hanzo, M., Lathuilie`re, B., Bodeur, Y., Ruget, C., Nicollin, J.P., Werner, W., 1996. Description stratigraphique pre´liminaire des faisceaux alternants de l’Oxfordien moyen dans le bassin dauphinois (Sud-Est de la France). Geol. Fr. 1, 17 – 24. Geisen, M., Bollmann, J., Herrle, J.O., Mutterlose, J., Young, J.R., 1999. Calibration of the random settling technique for calculation of absolute abundances of calcareous nannoplankton. Micropaleontology 45, 437 – 442.

Geyer, O.F., Gwinner, M.P., 1984. Die Schw7bische Alb und ihr Vorland, 3rd edn. Samml. Geol. Fqhrer, vol. 67. Borntraeger, Berlin-Stuttgart. 275 pp. Giraud, F., Renaud, S., Pittet, B., Mattioli, E., Audouin, V., 2003. Variations de la morphologie et de l’abondance chez Watznaueria britannica (coccolithophoride´s) en relation avec les parame`tres pale´oenvironnementaux au Jurassique. 3e`me Symposium de Morphome´trie et e´volution des formes, 13 et 14 Mars 2003, Paris, pp. 267 – 284. Gwinner, M.P., 1976. Origin of the Upper Jurassic limestones of the Swabian Alb (Southwest Germany). Contrib. Sedimentol. 5, 1 – 75. Hallam, A., 1986. Origin of minor limestone-shale cycles: climatically induced or diagenetic? Geology 14, 609 – 612. Hallock, P., Schlager, W., 1986. Nutrient excess and the demise of coral reefs and carbonate platforms. Palaios 1, 389 – 398. Heath, K.T., Mullins, H.T., 1984. Open-ocean, off bank transport of fine-grained carbonate sediment in the Northern Bahamas. In: Stow, D.A.V., Piper, D.J.W. (Eds.), Fine-Grained Sediments: Deep-Water Processes and Facies. Blackwell Science, Oxford, pp. 199 – 208. Henriksson, A.S., Malmgren, B.A., 1999. Ranking of differential dissolution of terminal Cretaceous calcareous nannofossils using a statistical approach. Rev. Esp. Micropaleontol. 31, 289 – 296. Insalaco, E., 1998. The descriptive nomenclature and classification of growth fabrics in fossil scleractinian reefs. Sediment. Geol. 118, 159 – 186. James, N.P., Bourque, P.A., 1992. Reefs and mounds. In: Walker, R.G., James, N.P. (Eds.), Facies Models: Response to Sea Level Change, Geol. Assoc. Can., pp. 323 – 347. K7lin, O., 1980. Schizosphaerella punctulata Deflandre and Dangeard: wall ultrastructure and preservation in deep-water carbonate sediments of the Tethyan Jurassic. Eclogae Geol. Helv. 73, 983 – 1008. Kennard, J.M., James, N.P., 1986. Thrombolites and stromatolites; two distinct types of microbial structures. Palaios 1, 492 – 503. Keupp, H., Koch, R., Leinfelder, R.R., 1990. Controlling processes in the development of the Upper Jurassic spongiolites in Southern Germany: state of the art, problems and perspectives. Facies 23, 141 – 174. Keupp, H., Jenish, A., Hermann, R., Neuweiler, F., Reitner, F., 1993. Microbial carbonate crusts—a key to the environmental analysis of fossil spongiolites. Facies 29, 41 – 54. Keupp, H., Brugger, H., Galling, U., Hefter, J., Herrmann, R., Jenisch, A., Kempe, S., Michaelis, W., Seifert, R., Thiel, V., 1996. Paleobiological controls of jurassic spongiolites. In: Reitner, J., Neuweiler, F., Gunkel, F. (Eds.), Global and Regional Controls on Biogenic Sedimentation: I. Reef evolution. Research Reports, Gfttinger Arb. Geol. Pal7ont. Sb., vol. 2, pp. 209 – 2414. Koch, R., Schorr, M., 1986. Diagenesis of Upper Jurassic SpongeAlgal Reefs in SW Germany. In: Schroeder, J.H., Purser, B.H. (Eds.), Reef Diagenesis. Springer-Verlag, Berlin, pp. 224 – 244. Krautter, M., 1995. Kieselschw7mme als potentielle Indikatoren fqr Sedimentationsrate und N7hrstoffangebot am Beispiel der Oxford-Schwammkalke von Spanien. Profil 8, 281 – 304.

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263 Lang, B., 1989. Upper Jurassic Sponge bioherm facies of the Northern Frankenalb (Urspring; Oxfordian): microfacies, paleoecology, paleontology. Facies 20, 199 – 274. Lees, J.A., Bown, P.R., 2002. Aspects of coccolithophore palaeoecology and palaeobiology from the Kimmeridge Clay Formation (Kimmeridgian-Bolonian), Dorset, UK. Abstracts of the 9th INA Conference, Parma 2002. Journal of Nannoplankton Research, vol. 24(2), p. 131. Lees, J.A., Bown, P.R., Young, J.R., Riding, J.B., in press. Evidence for annual records of phytoplankton productivity in the Kimmeridge Clay Formation Stone Bands (Upper Jurassic, Dorset, UK). Mar. Micropaleontol. Leinfelder, R.R., 1993. Upper Jurassic reef types and controlling factors—a preliminary report. Profil 5, 1 – 45. Leinfelder, R.R., 2001. Jurassic reef ecosystems. In: Stanley Jr., G.D. (Ed.), The History and Sedimentology of Ancient Reef Systems. Kluwer/Plenum Press, New York, pp. 251 – 309. Leinfelder, R.R., Keupp, H., 1995. Upper Jurassic mud mounds: allochthonous sedimentation versus autochthonous carbonate production. In: Reitner, J., Neuweiler, F. (Eds.), Mud Mounds: A Polygenic Spectrum of Fine-Grained Carbonate Buildups. Facies, vol. 32, pp. 17 – 26. Leinfelder, R.R., Nose, M., Schmid, D.U., Werner, W., 1993a. Microbial crust of the Late Jurassic: composition, palaeoecological significance and importance in reef construction. Facies 29, 195 – 230. Leinfelder, R.R., Krautter, M., Nose, M., Ramalho, M.M., Werner, W., 1993b. Siliceous sponge facies from the Upper Jurassic of Portugal. Neues Jahrb. Geol. Pal7ontol. Abh. 189, 199 – 254. Leinfelder, R.R., Krautter, M., Laternser, R., Nose, M., Schmid, D.U., Schweigert, G., Werner, W., Keupp, H., Brugger, H., Herrmann, R., Rehfeld-Kiefer, U., Schroeder, J.H., Reinhold, C., Koch, R., Zeiss, A., Schweizer, V., Christmann, H., Menges, G., Luterbacher, H., 1994. The origin of Jurassic reefs. Current research developments and results. Facies 31, 1 – 56. Leinfelder, R.R., Werner, W., Nose, M., Schmid, D.U., Krautter, M., Laternser, R., Takacs, M., Hartmann, D., 1996. Paleoecology, growth parameters and dynamics of coral, sponge and microbolite reefs from the Late Jurassic. In: Reitner, J., Neuweiler, F., Gunkel, F. (Eds.), Global and Regional Controls on Biogenic Sedimentation: I. Reef evolution. Research Reports. Gfttinger Arb. Geol. Pal7ont. Sb., vol. 2, pp. 227 – 248. Leinfelder, R.R., Schmid, D.U., Nose, M., Werner, W., 2002. Jurassic reef patterns—the expression of a changing globe. In: Kiessling, W., Fluegel, E., Golonka, J. (Eds.), Phanerozoic Reef Patterns. SEPM Spec. Publ., vol. 72, pp. 465 – 520. Macintyre, I.G., Reid, P., Steneck, R.S., 1996. Growth history of stromatolites in a Holocene fringing reef, Stocking Island, Bahamas. J. Sediment. Res. 66, 231 – 242. Mattioli, E., 1997. Nannoplankton productivity and diagenesis in the rhythmically bedded Toarcian-Aalenian Fiuminata sequence (Umbria-Marche Apennine, Central Italy). Palaeogeogr. Palaeoclimatol. Palaeoecol. 130, 113 – 134. Mattioli, E., Pittet, B., 2002. The contribution of calcareous nannoplankton to the carbonate production in the Early Jurassic. Mar. Micropaleontol. 45, 175 – 190.

261

Mattioli, E., Pittet, B., 2004. Spatial and temporal distribution of calcareous nannofossils along a proximal-distal transect in the Lower Jurassic of the Umbria-Marche Basin (central Italy). Palaeogeogr. Palaeoclimatol. Palaeoecol. 205, 295 – 316. Matyja, B.A., Wierzbowski, A., 1988. The two Amoeboceras invasions in submediterranean Late Oxfordian of Central Poland. In: Rocha, R.B., Soares, A.F. (Eds.), 2nd International Symposium on Jurassic Stratigraphy, Lisboa I, pp. 421 – 432. Matyja, B.A., Wierzbowski, A., 1994. On correlation of submediterranean and boreal ammonite zonations of the Middle and Upper Oxfordian: new data from Central Poland. Ge´obios, Me´m. Spe´c. 17, 351 – 358. Meyer, R.K.F., Schmidt-Kaler, H., 1989. Pal7ogeographischer Atlas des sqddeutschen Oberjura (Malm). Geol. Jahrb., Reihe A Allg. Reg. Geol. BR Dtschl. Nachbargeb. Tekton. Stratigr. Palafntol. 115, 3 – 77. Meyer, R.K.F., Schmidt-Kaler, H., 1990. Paleogeography and development of sponge reefs in the Upper Jurassic of Southern Germany—an overview. Facies 23, 175 – 184. Middleton, L.D., 2001. Middle Cambrian offshore microbialites and shoaling successions, western Wyoming: implications for regional paleogeography. Rocky Mt. Geol. 36, 81 – 98. Milliman, J.D., Freile, D., Steinen, R.P., Wilber, R.J., 1993. Great Bahama Bank aragonitic muds: mostly inorganically precipitated, mostly exported. J. Sediment. Petrol. 63, 589 – 595. Munnecke, A., Samtleben, C., 1996. The formation of micritic limestones and the development of limestone–marl alternations in the Silurian of Gotland, Sweden. Facies 34, 42 – 44. Munnecke, A., Westphal, H., Reijmer, J.J.G., Samtleben, C., 1997. Microspar development during early marine burial diagenesis: a comparison of Pliocene carbonates from the Bahamas with Silurian limestones from Gotland (Sweden). Sedimentology 44, 977 – 990. Mutterlose, J., Kessels, K., 2000. Early Cretaceous calcareous nannofossils from high latitudes: implications for palaeobiogeography and palaeoclimate. Palaeogeogr. Palaeoclimatol. Palaeoecol. 160, 347 – 372. Mutterlose, J., Ruffell, A., 1999. Milankovitch-scale palaeoclimate changes in pale-dark bedding rhythms from the Early Cretaceous (Hauterivian and Barremian) of eastern England and northern Germany. Palaeogeogr. Palaeoclimatol. Palaeoecol. 154, 133 – 160. NoJl, D., Busson, G., Corne´e, A., Mangin, A.M., 1994. Le nannoplancton calcaire et la formation des alternances calcaires-marnes dans le Lias des bassins de Marches-Ombrie (Italie). Riv. Ital. Paleontol. Stratigr. 99, 515 – 550. Okada, H., Honjo, S., 1973. The distribution of oceanic coccolithophorids in the Pacific. Deep-Sea Res. 20, 1 – 13. Olivier, N., Hantzpergue, P., Gaillard, C., Pittet, B., Leinfelder, R., Schmid, D.U., Werner, W., 2003. Microbialite morphology, structure and growth: a model of the Upper Jurassic reefs of the Chay Peninsula (western France). Palaeogeogr. Palaeoclimatol. Palaeoecol. 193, 383 – 404. Oschmann, W., 1990. Environmental cycles in the Late Jurassic northwest European epeiric basin: interaction with atmospheric and hydrospheric circulation. Sediment. Geol. 69, 313 – 332.

262

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263

Pawallek, T., 2001. Fazies-, Sequenz-, und Gamma-Ray-Analyse im hfheren Malm der Schw7bischen Alb (SW-Deutschland) mit Bemerkungen zur Rohstoffgeologie (hochreine Kalke). Tqbinger Geowiss. Arb., A Geol. Palafntol. Stratigr. 61, 1 – 246. Pawallek, T., Aigner, T., 2003. Apparently homogenous breefsQlimestones built by high-frequency cycles: Upper Jurassic, SWGermany. Sediment. Geol. 160, 259 – 284. Pittet, B., 1994. Mode`le d’estimation de la subsidence et des variations du niveau marin: Un exemple de l’Oxfordien du Jura suisse. Eclogae Geol. Helv. 87, 513 – 543. Pittet, B., 1996. Controˆles climatiques, eustatiques et tectoniques sur des syste`mes mixtes carbonates-siliciclastiques de plate-forme: exemples de l’Oxfordien (Jura suisse, Normandie, Espagne). PhD thesis, Fribourg University, Switzerland. 258 pp. Pittet, B., Mattioli, E., 2002. The carbonate signal and calcareous nannofossil distribution in an Upper Jurassic section (BalingenTieringen, Late Oxfordian, southern Germany). Palaeogeogr. Palaeoclimatol. Palaeoecol. 179, 73 – 98. Pittet, B., Strasser, A., 1998a. Depositional sequences in deep-shelf environments formed through carbonate mud import from the shallow platform (Late Oxfordian, German Swabian Alb and eastern Swiss Jura). Eclogae Geol. Helv. 91, 149 – 169. Pittet, B., Strasser, A., 1998b. Long-distance correlations by sequence stratigraphy and cyclostratigraphy: examples and implications (Oxfordian from the Swiss Jura, Spain, and Normandy). Geol. Rundsch. 86, 852 – 874. Pittet, B., Strasser, A., Mattioli, E., 2000. Depositional sequences in deep-shelf environments: a response to sea-level changes and shallow-platform carbonate productivity (Oxfordian, Germany and Spain). J. Sediment. Res. 70, 392 – 407. Premoli Silva, I., Erba, E., Tornaghi, I., 1989. Paleoenvironmental signals and changes in surface fertility in Mid-Cretaceous Corgrich facies of the Fucoid Marls (Central Italy). Geobios 11, 225 – 236. Quenstedt, F.A., 1843. Das Flfzgebirge Wqrttembergs. Mit besonderer Rqcksicht auf den Jura. Laupp, Tqbingen. 558 pp. Reitner, J., 1993. Modern cryptic microbialite/metazoan facies from Lizard Island (Great Barrier Reef, Australia): formation and concepts. Facies 29, 3 – 40. Riding, R., 2000. Microbial carbonates: the geological record of calcified bacterial–algal mats and biofilms. Sedimentology 47, 179 – 214. Riding, R., 2002. Structure and composition of organic reefs and carbonate mud mounds: concepts and categories. Earth-Sci. Rev. 58, 163 – 231. Roll, A., 1934. Form, Bau und Entstehung der Schwammstotzen im sqddeutschen Malm. Pal7ontol. Z. 16, 197 – 246. Roth, P.H., 1983. Jurassic and Lower Cretaceous calcareous nannofossils in the Western North Atlantic (Site 534): biostratigraphy, preservation and some observations on biogeography and paleoceanography. In: Sheridan, R.E., et al. (Eds.), Init. Rep. DSDP, vol. 76. U.S. Govt. Printing Office, Washington, pp. 587 – 621. Roth, P.H., 1984. Preservation of calcareous nannofossils and finegrained carbonate particles in mid-Cretaceous sediments from the southern Angola Basin. In: Hay, W.W., et al. (Eds.), Init.

Rep. DSDP, vol. 75. U.S. Govt. Printing Office, Washington, pp. 651 – 655. Roth, P.H., 1989. Ocean circulation and calcareous nannofossil evolution during the Jurassic and Cretaceous. Palaeogeogr. Palaeoclimatol. Palaeoecol. 74, 111 – 126. Roth, P.H., Bowdler, J.L., 1981. Middle Cretaceous calcareous nannoplankton biogeography and oceanography of the Atlantic Ocean. Spec. Publ.-Soc. Econ. Paleontol. Mineral. 32, 517 – 546. Roth, P.H., Krumbach, K.R., 1986. Middle Cretaceous calcareous nannofossils biogeography and preservation in the Atlantic and Indian oceans: implications for paleoceanography. Mar. Micropaleontol. 10, 235 – 266. Schlager, W., 1989. Drowning unconformities on carbonate platforms. In: Crevello, P.D., Wilson, J.L., Sarg, J.F., Read, J.F. (Eds.), Controls on Carbonate Platform and Basin Development. Spec. Publ.-Soc. Econ. Paleontol. Mineral., vol. 44, pp. 15 – 26. Schlager, W., Reijmer, J.J.G., Droxler, A., 1994. Highstand shedding of carbonate platforms. J. Sediment. Res., Sect. B Stratigr. Glob. Stud. 64, 270 – 281. Schmalzriedt, A., 1991. Die Mikrofauna in Schw7mmen, Schwammriff-und bNormalQ-Fazies des unteren und mittleren Malm (Oxfordium und Kimmeridgium, Ober-Jura) der westlichen und mittleren Schw7bischen Alb (Wqrttemberg). Tqb. Mikropal7ontol. Mitt. 10, 1 – 120. Schmid, D.U., 1996. Marine Mikrobolithe und Mikroinkrustierer aus dem Oberjura. Profil 9, 101 – 251. Schmid, D.U., Leinfelder, R.R., Nose, M., 2001. Growth dynamics and ecology of Upper Jurassic mounds, with comparisons to Mid-Palaeozoic mounds. Sediment. Geol. 145, 343 – 376. Schwarzacher, W., 1991. Milankovitch cycles and the measurement of time. In: Einsele, G., Ricken, W., Seilacher, A. (Eds.), Cycles and Events in Stratigraphy. Springer-Verlag, Berlin, pp. 855 – 863. Schweigert, G., 1995a. Amoebopeltoceras n.g., eine neue Ammonitengattung aus dem Oberjura (Ober-Oxfordium bis UnterKimmeridgium) von Sqdwestdeutschland und Spanien. Stuttg. Beitr. Naturkd., B 227, 1 – 12. Schweigert, G., 1995b. Zum Auftreten der Ammonitenarten Amoeboceras bauhini (Oppel) und Amoeboceras schulginae Mesetzhnikov im Oberjura der Schw7bischen Alb. Jahresh. Ges. Naturkd. Wqrttemb. 151, 171 – 184. Schweigert, G., Callomon, J.H., 1997. Der bauhini-Faunenhorizont und seine Bedeutung fqr die Korrelation zwischen tethyalem und subborealem Oberjura. Stuttg. Beitr. Naturkd., B 247, 1 – 69. Shapiro, R.S., 2000. A comment on the systematic confusion of thrombolites. Palaios 15, 166 – 169. Soudry, D., Weissbrod, T., 1995. Morphogenesis and facies relationships of thrombolites and siliclastic stromatolites in a Cambrian tidal sequence (Elat area, southern Israel). Palaeogeogr. Palaeoclimatol. Palaeoecol. 114, 339 – 355. Sprachta, S., Camoin, G., Golubic, S., Le Campion, Th., 2001. Microbialites in a modern lagoonal environment: nature and distribution, Tikehau Atoll (French Polynesia). Palaeogeogr. Palaeoclimatol. Palaeoecol. 175, 103 – 124.

N. Olivier et al. / Palaeogeography, Palaeoclimatology, Palaeoecology 212 (2004) 233–263 Strasser, A., Hillg7rtner, H., Hug, W., Pittet, B., 2000. Third-order depositional sequences reflecting Milankovitch cyclicity. Terra Nova 12, 303 – 311. Streim, W., 1961a. Stratigraphie, Fazies und Lagerungsverh7ltnisse des Malm bei Dietfurt und Hemau (Sqdliche Frankenalb). Erlanger Geol. Abh. 38, 1 – 49. Streim, W., 1961b. Malm und Oberkreide auf Blatt Laaber. Die Umbiegung der Frankenalb nordwestlich von Regensburg. Erlanger Geol. Abh. 39, 1 – 26. Thierstein, H.R., 1980. Selective dissolution of Late Cretaceous and earliest Tertiary calcareous nannofossils: experimental evidence. Cretac. Res. 2, 165 – 176. Thierstein, H.R., Roth, P.H., 1991. Stable isotopic and carbonate cyclicity in Lower Cretaceous deep-sea sediments: dominance of diagenetic effects. Mar. Geol. 97, 1 – 34. Tribovillard, N.P., Gorin, G., Belin, S., Hopfgartner, G., Pichon, R., 1992. Organic-rich biolaminated facies from a Kimmeridgian lagoonal environment in the French Southern Jura mountainsa˜ A way of estimating accumulation rate variations. Palaeoegeogr. Palaeoclimatol. Palaeoecol. 99, 163 – 177. Turner, E.C., James, N.P., Narbonne, G.M., 1997. Growth dynamics of Neoproterozoic calcimicrobial reefs, Mackenzie Mountains, Northwest Canada. J. Sediment. Res. 67, 437 – 450.

263

Vail, P.R., Audemard, F., Bowman, S.A., Eisner, P.N., Perez-Cruz, C., 1991. The stratigraphic signatures of tectonics, eustasy and sedimentology—an overview. In: Einsele, G., Ricken, W., Seilacher, A. (Eds.), Cycles and Events in Stratigraphy. Springer-Verlag, Berlin, pp. 617 – 659. ¨ kologische untersuchung der fauna aus Wagenplast, P., 1972. O bank-und schwammfazies des weiBen Jura der Schw7bischen alb. Arb. Inst. Geol. Pal7ontol. 67, 1 – 99. Watkins, D., 1989. Nannoplankton productivity fluctuations and rhythmically-bedded pelagic carbonates of the Greenhorn Limestone (Upper Cretaceous). Palaeogeogr. Palaeoclimatol. Palaeoecol. 74, 75 – 86. Werner, W., Leinfelder, R.R., Fqrsich, F.T., Krautter, M., 1994. Comparative palaeoecology of marly coralline sponge-bearing reefal associations from the Kimmeridgian (Upper Jurassic) of Portugal and southwestern Germany. Cour. Forschungsinst. Senckenberg 172, 381 – 397. Young, J.R., Bown, P.R., 1991. An ontogenetic sequence of coccoliths from the Late Jurassic Kimmeridge Clay of England. Palaeontology 34, 843 – 850. Ziegler, P.A., 1988. Evolution of the Artic-North Atlantic and the Western Tethys. Mem.-Am. Assoc. Pet. Geol. 43, 1 – 198.