Mapping the rise and demise of Urgonian platforms
Transcription
Mapping the rise and demise of Urgonian platforms
Cretaceous Research 39 (2013) 29e46 Contents lists available at SciVerse ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes Mapping the rise and demise of Urgonian platforms (Late Hauterivian - Early Aptian) in southeastern France and the Swiss Jura Bernard Clavel a, Marc André Conrad b, Robert Busnardo c, Jean Charollais d, Bruno Granier e, f, * a 24 Chemin des Champs d’Amot, F-74140 Messery, France 71 Chemin de Planta, CH-12223 Cologny, Switzerland c Chemin Meruzin, F-69370 St Didier au Mont d’Or, France d Département de Géologie et de Paléontologie, Sciences de la Terre et de l’Environnement, 13 Rue des Maraîchers, CH-1211 Genève 4, Switzerland e Université de Brest, UMR 6538 Domaines Océaniques, 29238 Brest, France f CNRS, UMR 6538 Domaines Océaniques, 29238 Brest, France b a r t i c l e i n f o a b s t r a c t Article history: Received 26 July 2011 Accepted in revised form 9 February 2012 Available online 12 April 2012 Lower Cretaceous carbonate deposits historically called “Urgonian limestones” are widely exposed around the margins of the Vocontian basin in southeastern France and in the adjacent Swiss Jura. This paper presents the history of their rise, growth and sudden demise. Eleven maps were constructed for deposits ranging in age from the Late Hauterivian pro parte to the Early Aptian (Bedoulian) pro parte. Based on sequential interpretations, they illustrate the present geographical distribution of the inner platform facies (Urgonian limestones stricto sensu, with rudists), the outer platform facies (essentially bioclastic deposits) and the basinal facies (slope, hemipelagic, pelagic deposits). These maps depict only the final terms of each successive sequence (the late highstand intervals). Chronostratigraphy is constrained by ammonites found mainly in basinal deposits, by echinoids, by rudists and to a lesser extent by dinoflagellates and calcareous nannoplancton. Inner platform, outer platform and slope (talus) deposits are dated by rich assemblages of orbitolinids and dasycladalean algae. Currently 39 species of orbitolinids have been recognized and their ranges collated with those of the ammonites in the area. In the Jura and in Provence the oldest Urgonian deposits are dated early Late Hauterivian, thus showing the synchroneity of the onset of platform carbonates development on both the southern and northern margins of the basin. Thereafter, growth of the platforms led a clearly regressive shallowingupward trend, resulting from a stepwise progradation toward the center of the Vocontian area, coordinated with cyclical exposures in the inner platform areas. The maximum reduction of the platform deposits occurred early in Late Barremian times, coeval with a noticeable turnover in the orbitolinids assemblages. Thereafter, carbonate platform deposition shifted toward the margins of the Vocontian basin. In Early Aptian time, a well-dated discontinuity of regional extent marks the sudden, almost synchronous disappearance of the Urgonian deposits. Ó 2012 Elsevier Ltd. All rights reserved. Keywords: Urgonian Late Hauterivian Barremian Bedoulian Aptian SE France Swiss Jura Orbitolinids Vocontian basin Paleogeography Sequence stratigraphy 1. Introduction Sequence stratigraphic interpretation (according to EXXON model, Van Wagoner et al., 1988; Catuneanu et al. 2011) of a number of sections and a new biostratigraphic calibration (based among other considerations on a refined orbitolinid scale) made * Corresponding author. Département des Sciences de la Terre et de l’Univers, UFR des Sciences et Techniques, Université de Bretagne Occidentale (UBO), 6 avenue Le Gorgeu - CS 93837, F-29238 Brest Cedex 3, France. Tel.: þ33 (0) 2 98 01 62 89. E-mail addresses: b.clavel1@orange.fr (B. Clavel), bruno.granier@univ-brest.fr (B. Granier). 0195-6671/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.cretres.2012.02.009 feasible the recognition of successive sequences in the development of the Urgonian platforms of southeastern France and the adjacent Swiss Jura. Their build-up and rapid disappearance took place in an interval of time ranging from Late Hauterivian to Early Aptian. Here we present transects that illustrate the results obtained to date supplemented thereafter by eleven paleogeographic maps that portray the successive periods of highstand deposits. They include the Ha5 sequence of the Lower Hauterivian through the Bd 3e4 of upper Lower Aptian. A special emphasis is made on the termination of Urgonian facies deposition, with a number of correlated sections in the Jura, Subalpine, Vivarais, Provence and Vocontian provinces supporting the idea of a rapid, nearly 30 B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 contemporaneous demise of shallow-water carbonates everywhere in the studied area. So it is now possible to reconstruct the development of the Urgonian platforms, dating it to an interval involving the Late Hauterivian, the Barremian and the Early Aptian. Available paleontological criteria are briefly discussed, followed by an examination of the rise and sudden demise of the platform carbonates, and differences in their development on either side of the Vocontian basin. 2. Dating the Urgonian limestones Paleontological studies involving primarily orbitolinids and dasycladalean algae are progressing. However recent advances of this work in southeastern France and the adjacent Swiss Jura (Fig. 1) have made feasible the development of a reasonably precise stratigraphic framework, making it possible to date depositional sequences and their discontinuities as observed in the field. Biostratigraphic analysis of the Urgonian limestones relies primarily on the presence in the interior of the platforms, on their margins, and in adjacent talus deposits, of numerous orbitolinids and dasycladalean algae (Clavel et al., 1987, 2007). A recent work, published by Clavel et al. (2009), deals with the distribution of orbitolinids in southeastern France and adjacent portions of the Swiss Jura, in strata dated Late Hauterivian (sequences Ha3 to Ha7 pars), Barremian (sequences Ha7 pars to Ba5 pars) and Early Aptian (sequences Ba5 pars to Bd4 pars). Here (Fig. 2), this distribution is supplemented by frequencies, based on data from a number of sections. Among them 23 include levels containing orbitolinids associated with, framed, or capped by beds containing Fig. 1. General location map. A: Jura and Subalpine chains; B: Vivarais; C: Provence. See Fig. 3 for details. B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 31 Fig. 2. Stratigraphic distribution of the orbitolinids and their calibration with the ammonites in southeastern France and the Swiss Jura. Strata are dated Late Hauterivian, Barremian and Early Aptian. A pronounced turnover in species occurs in lower Upper Barremian strata, coeval with a maximum reduction of the Urgonian platform deposits. Data in Clavel et al. (2009) are revised as follows: distributions of Eopalorbitolina charollaisi and Valserina turbinata are corrected. In accordance with observations by J.-P. Masse (Marseille, oral comm.) and new studies on the Barremian stratotype (Vermeulen, 2005), the TST of the sequence Ba4 begins at the base of the ammonite Sartousiana Zone. stratigraphically significant ammonites (Clavel et al., 1986; Charollais et al., 2003, 2009). Currently, 27 species of orbitolinids are listed in the Upper Hauterivian pro parte (sequences Ha3 to Ha7 pars) of the Jura of the Swiss Canton Vaud and of the Vercors massif in France, Urgonian deposits containing orbitolinids are directly dated Late Hauterivian by assemblages of dinoflagellates and calcareous nannofossils (Clavel et al., 2007). Currently, 36 species of orbitolinids are listed in an interval of time involving the whole of the Early Barremian and the base of the Late Barremian (sequences Ha7 pars to Ba4 pars). A pivotal turnover of orbitolinids occurred during the lowstand of Ba4 sequence, which included the maximum regression of the sea on the Urgonian platforms. Nearly half of the species of orbitolinids present at that moment disappeared. A similar loss took place among the dasycladalean algae. Present higher in the same interval are other fossils that serve to define the Barremian-Aptian boundary: echinoids (Heteraster couloni, H. oblongus), rudists, dasycladalean algae and charophytes (Martin-Closas et al., 2009). However, their presence provides sufficiently precise biostratigraphic criteria only for a half-stage. 3. Distribution of the facies around the Vocontian basin Three transects, dated and interpreted in a sequence stratigraphy point of view, have been used to illustrate the rise, the stepwise growth and sudden demise of the Urgonian platforms on either margin of the Vocontian basin (Figs. 3e6). The transects are located respectively on the northern, western and southern margins of the basin. Those shown in Figs. 4 and 5, i.e. on the northern and western margins illustrate the development of the platforms in a relatively stable tectonic setting. On the other hand, the transect shown in Fig. 6, i.e. on the southern margin, is located in a structurally complex area. 3.1. Northern margin of the Vocontian area: Jura and northern Subalpine chains A first transect perpendicular to the structural trends of the Jura in a tract between the French Jura and the Subalpine Chains (Bornes massif) has already been published by Charollais et al. (2001, 2003). The new transect (Fig. 4) trending NNE-SSW runs for about 300 km beginning in the Neuchâtel Jura and continues across the northern subalpine chains, the Chartreuse and Vercors massifs. It improves an earlier version by Clavel et al. (1995, fig. 7), for it benefits from substantial data acquired later (Clavel et al., 2007, 2010; MartinClosas et al., 2009). This transect illustrates the regional, pulsed, rapid progradation of the outer and inner platform deposits toward the southsouthwest. Progradation was also directed toward the southeast (Charollais et al., 2003). This pattern changes to aggradation after Ba1 sequence: surface areas of the successive platforms may then be relatively small during sequences Ba2 to Bd1. Sequence Bd2 marks a new change in trend to retrogradation. The demise of the platform took place during the next sequence, i.e. Bd3, that is 32 B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 Fig. 3. Location maps of the transect areas. 3A: Jura - Subalpine chains; 3B: Vivarais (1: Montagne de la Serre; 2: Les Darboussières; 3: Gorges de l’Ardèche; 4: Forêt de Bois Sauvage; 5: Mas de Gras/Chirolong; 6: Saint Montan; 7: Viviers). 3C: Provence (1: Marseille area; 2: La Fare; 3: Alpilles; 4: SW Monts de Vaucluse; 5: Gorges de la Nesque; 6: Ventoux; 7: Rissas). Red arrows ¼ the illustrated transects. B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 33 Fig. 4. Schematic lithostratigraphical transect across the Urgonian limestones in the Jura and Subalpine chains sited on the northern, relatively stable margin of the Vocontian basin. 1: charophytes from La Lance (Blanc-Alétru, 1995; Clavel unpublished); 2.: charophytes from Bellegarde e Montanges (Martin-Closas et al., 2009); 3: charophytes from Chartreuse, Pas du Frou and Berland sections (Mojon and Médus, 1990; Arnaud et al., 1998; Mojon, 2002; Clavel et al., 2002, 2007; Martin-Closas et al., 2009) and from Vercors, Font Renard and Gorges du Nant sections (Clavel et al., 2007; Martin-Closas et al., 2009); 4: charophytes from the Chartreuse, Pas du Frou and Berland sections (Mojon and Médus, 1990; Arnaud et al., 1998; Mojon, 2002; Clavel et al., 2002, 2007; Martin-Closas et al., 2009); 5: charophytes from the Chartreuse, Pas du Frou sections (Clavel et al., 2002; Martin-Closas et al., 2009); 6: ammonites (Ancyloceras matheroni, Pseudohaploceras matheroni) from the Vercors, le Faz and Rochefort-Samson sections (Paquier, 1900; Jacob, 1907; Girod and Weiss, 1965; Arnaud et al., 1998); 7: ammonite (Ancyloceras gr. matheroni) from the Chartreuse, Cirque de Roche Blanche section (Gidon, 1952; Arnaud et al., 1998); 8: ammonite (Deshayesites gr. saxbyi) from the Geneva Jura, Bellegarde e Montanges section (“Valserine valley”, Clavel et al., 2007). 34 B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 Fig. 5. Schematic lithostratigraphical transect across the Urgonian limestones in the Vivarais. 1: ammonites (Holcodiscus diversecostatus, Astieridiscus menglonensis) from the Gorges de l’Ardèche - Serre de Tourre (coll. Busnardo, Clavel et al., nearing completion); 2: ammonites (Toxoceras moutonianum, Holcodiscus perezi) from Mas de Gras (Schroeder et al., 2000; Clavel et al., 2007); 3: ammonite (Toxoceras gr. moutonianum) from the Forêt de Bois Sauvage e Chastelas de Baravon section (Renaud, 1978); 4: ammonites (Puezalpella cf. uhligi, Silesites cf. cirtense) from the Gorges de l’Ardèche - Serre de Tourre section. (Clavel et al., nearing completion); 5: ammonite (Pseudocrioceras sp.) from the Gorges de l’Ardèche - Pont d’Arc section (coll. Busnardo, Clavel et al., nearing completion). B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 Fig. 6. Schematic lithostratigraphical transect across the Urgonian limestones of Provence. 35 36 B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 Fig. 7. Latest Barremian and earliest Aptian evolution of the northern Urgonian platform in a proximal setting (innermost platform). The section illustrates the succession of the Urgonian strata near Bellegarde-Montanges, west of Geneva in the French Jura (Ain Department). Five sequences (Ba2 to Bd1) are missing below a conspicuous disconformity, while farther south the deposits that represent these sequences are present. Log: Martin-Closas et al., 2009; biostratigraphy: Clavel et al., 2007; sequence stratigraphy: this work. For symbols, see Fig. 13. B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 during the Early Aptian Weissi ammonite Zone. In Chartreuse, there is no record of sequences younger than Bd2 due to postdepositional (Late Cretaceous) erosion. In southern Vercors too, erosion may even cut deeply into Barremian strata. We found relicts of Upper Barremian and Lower Aptian platform carbonates deposits farther south in the Vocontian basin where they are found within huge debris flows and megaslumps involving mostly slope facies (see sub-section 3.4). The paleogeographic setting at Bellegarde-Montanges (southern Jura, southwest of Geneva) is illustrated in Fig. 7. The rudistid limestone forming the lower third of the section is dated by orbitolinids and dasycladalean algae as lowermost Barremian (Ba1 sequence). A large, conformable discontinuity terminates this unit. The hiatus involved covers the stratigraphic range of five sequences (Ba2 to Bd1, i.e. Barremian pro parte and Lower Aptian pro parte). These missing sequences are present south, because there the hiatus is progressively shorter. At Bellegarde, the sequences Bd2 and Bd3 are dated Early Aptian by ammonites and orbitolinids. Fresh or brackish water deposits containing charophytes occur at the base of the series (Martin-Closas et al., 2009). As shown by the small maps in Fig. 8, highstand deposits of the sequences Ba4 and Ba5 follow a southward progradational trend. In contrast, above the discontinuity the trend is clearly retrogradational, starting with Bd1 sequence. 37 Fig. 9 depicts the depositional environments underneath the final discontinuity of the Lower Aptian (Bedoulian) Urgonian strata in the northern Vocontian domain. The succession has been correlated with the Bedoulian stratotype at Cassis-La Bédoule, east of Marseille (Moullade et al., 1998a, 1998b). The Selli Oceanic anoxic Event (OAE1a) matches the HST of the Bd3 sequence. 3.2. Western margin of the Vocontian basin: Vivarais - Ardèche transect Located on the western margin of the Vocontian basin this transect (Fig. 5) trending WSW-ENE with a length of about 35 km, subtends the area between the Montagne de la Serre and the Rhône valley and cuts across the Cevennes fault. It occupies only the central part of the platform. In this region a general, eastwardly progradation in the direction of the Vocontian basin occurred. Eastward progradation takes place in strata dated Early Barremian and Late Barremian pro parte. Higher up, aggradation occurs where the transect crosses the center of the platform. Platform conditions ceased to exist in strata referred to the middle Lower Aptian (Weissi Zone). Six sections (Fig. 8) present the depositional environments and final discontinuity of the Lower Aptian (Bedoulian) Urgonian strata in Vivarais (western margin of the Vocontian domain). Correlations Fig. 8. Depositional environments and the final discontinuity between Urgonian facies and upper Lower Aptian (upper Bedoulian) strata in Vivarais (Ardèche): dating the overall demise of the Urgonian platform in the western Vocontian area. Correlated with the Bedoulian stratotype at Cassis-La Bédoule, east of Marseille. Location of the Selli Oceanic Anoxic Event (OAE1a) noted. 1) Cassis-La Bédoule: log and biostratigraphy: Moullade et al., 1998a, 1998b; sequence stratigraphy: this work; 2) Bourg-Saint-Andéol (Font de Beaume), Vallon-Pont-d’Arc (Mézelet), and others sections: logs and biostratigraphy: Busnardo in Elmi et al. (1996); Busnardo, unpublished; sequence stratigraphy: this work. 38 B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 Fig. 9. Depositional environments and the final discontinuity between Urgonian facies and upper Lower Aptian (upper Bedoulian) strata in the Jura and Vercors dating the overall demise of the Urgonian platform in the northern Vocontian area, and correlated with the Bedoulian stratotype at Cassis-La Bédoule, east of Marseille. The location of the Selli Oceanic anoxic Event (OAE1a), above the flooding event, is highlighted. 1) Cassis-La Bédoule: log and biostratigraphy: Moullade et al., 1998a, 1998b; sequence stratigraphy: this work; 2) L’Achard: log and depositional environments: Arnaud-Vanneau, 1980, modified; biostratigraphy: Arnaud-Vanneau, 1980; Busnardo, unpublished; sequence stratigraphy: this work; 3) Les Rimets: log: Clavel, unpublished; biostratigraphy: Arnaud-Vanneau, 1980; Busnardo, unpublished; sequence stratigraphy: this work; 4) Bellegarde e Montanges: log: Clavel et al., 2007; Delamette in Clavel et al. (2007); biostratigraphy: Delamette in Clavel et al. (2007); sequence stratigraphy: this work; 5) La Presta: log : Clavel et al., 2007; biostratigraphy: Renz and Jung, 1978; sequence stratigraphy: this work. Fig. 10. Latest Barremian and earliest Aptian evolution of the southern Urgonian platform in a distal setting (outermost platform). The section illustrates the succession of the Urgonian strata at Gorges de la Nesque, northeast of Avignon (Provence). Log: Masse, 1976, modified; ammonites: Masse,1976; Busnardo, unpublished; bio- and sequence stratigraphy: this work. For symbols, see Fig. 13. 40 B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 are made with the Bedoulian stratotype at Cassis-La Bédoule, east of Marseille. 3.3. Southern margin of the Vocontian basin: Provence transect As shown by the transect in the Marseille area (Fig. 5), the oldest inner platform deposits are dated early Late Hauterivian. So the onset of Urgonian limestone deposition was synchronous in the southern and northern margins of the basin. However, in southern Provence these Upper Hauterivian platform deposits are unconformably overlain by Upper Barremian hemipelagic sediments of the South-Provence furrow (Masse, 1976). Higher in the succession of this area, platform progradation began in the basal Barremian, moving northward in the direction of the Vocontian basin. However, here too the demise of shallow-water carbonates occurred during Early Aptian times (Masse, 1976; Masse and Fenerci-Masse, 2011), above Bd2 sequence. The transect is located on the southern margin of the Vocontian basin. Note the conspicuous progradational trend, ending in the middle Early Aptian. Post-depositional erosion may have caused ablation and downslope transportation of Lower Aptian deposits. The Gorges de la Nesque section northeast of Avignon was first surveyed by Masse (1976). Here, the Upper Barremian sequences appear to be complete and inner platform deposits with rudists are found high enough to include the Lower Aptian Bd1 sequence. As shown in the small maps of Fig. 10, the rise of the platforms clearly follows a northward progradational trend. Like that of the northern margin of the basin, a change in trend to retrogradation occurs at the base of Bd2 sequence. The transgression is marked by a change in facies to outer platform deposits. Fig. 11 shows the depositional environments and the terminating discontinuity of the Lower Aptian (Bedoulian) Urgonian strata in the Monts de Vaucluse (Provence) and the Gard (southern margin of the Vocontian domain). Again, correlations are made with the Bedoulian stratotype at Cassis-La Bédoule, east of Marseille. Fig. 11. Depositional environments and the final discontinuity between Urgonian facies and upper Lower Aptian (upper Bedoulian) strata in the Monts de Vaucluse (Provence) and the Gard (southern margin of the Vocontian domain): dating the overall demise of the Urgonian platform in the southern Vocontian area. Correlated with the Bedoulian stratotype at Cassis-La Bédoule, east of Marseille. Location of the Selli Oceanic Anoxic Event (OAE1a) noted. 1) Cassis-La Bédoule: log and biostratigraphy: Moullade et al., 1998a, 1998b; sequence stratigraphy: this work; 2) Plateau d’Albion: logs and depositional environments: Masse, 1976; biostratigraphy: Kilian, 1888; sequence stratigraphy: this work; 3) Le Rissas: logs, depositional environments and biostratigraphy: Monier, 1986; sequence stratigraphy: this work; 4) Gorges de la Nesque: logs and depositional environments : Masse, 1976 modified; biostratigraphy: Leenhardt, 1883; Masse, 1976; sequence stratigraphy: this work. Rustrel-Lagarde: logs and depositional environments: Masse, 1976 modified; biostratigraphy and sequence stratigraphy: this work; 5) Gargas - Le Chêne: logs and depositional environments: Moullade, 1963; biostratigraphy: Leenhardt, 1883; Moullade, 1963; Moullade et al., 2009; sequence stratigraphy: this work; 6) Serviers: logs and depositional environments: Clavel, unpublished; biostratigraphy: Dumas, 1876; Pellat, 1903; Thieuloy, 1990; Conte, 1999, 2001; Masse and Fenerci-Masse, 2011; sequence stratigraphy: this work. B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 41 Fig. 12. Schematic lithostratigraphical transect across the northwestern margin of the Vocontian basin illustrating the geographical distribution of Urgonian, slope and basinal deposits dated Early Barremian pro parte to Early Aptian pro parte, according to Ferry (1988). A: paleogeographic map; B: location map; C: lithostratigraphical transect according to Ferry (1988), revised; D: lithology and significant fauna according to Ferry (1976); bio- and sequence stratigraphy according to the present authors. 3.4. Fourth transect: the northwestern margin of the Vocontian basin The relationship of the edge of the Urgonian platform to the northwestern margin of the Vocontian basin has been discussed in several publications (Ferry, 1976, 1979, 1988; Ferry and Flandrin, 1979). We refigure their principal conclusions (Fig. 12). During Late Barremian and Early Aptian times the northwestern margin of the Vocontian basin sank to form a saddle (the Rhodanian corridor) separating the Vercors and Vivarais Urgonian platforms. The related fan is represented, farther in the deep Vocontian Trough, by bioclastic debris flows, megabreccias, along with large lenses of slump ranging up to 10 sq km in area from the ablated margins of the platforms. The largest lenses have been mapped by the aforementioned authors. Here (Fig. 12) these phenomena are illustrated by a revision of Ferry’s original profile (1988) and his La Chaudière section (1976) whereby the debris flows correspond to lowstand deposits. Correlations are also made with the stratotypic sections. 4. Paleogeographical maps The 11 maps of Figs. 13 and 14 illustrate the progradation and retrogradation of the platforms in the several domains (Jura, Subalpine, Vivarais, Provence, and Vocontian), surrounding the Vocontian basin. They are built to show highstand deposits, so represent only the upper part of the sequences named. In the Late Hauterivian pro parte, inner platform deposits, commonly with rudists (historically the Urgonian limestones sensu stricto), are first developed only in the Jura and southern Provence, Marseille area. They then expand, progressively and concentrically, toward the depositional center of the basin. In lowermost Barremian strata (Ba1 sequence), highstand deposits appear in the Vivarais and the northern subalpine chains. Progradation continued southward in Vercors (south of Grenoble), eastward in the Vivarais and northward in Provence. By Early Aptian times (sequences Bd1 and Bd2), Urgonian deposits are present in all of the northern Subalpine chains, the Vivarais and southern Provence. The main steps of this evolution are as follows, noting that because the succession of outcrop sections is diachronous, none of them can span the whole of the time represented by these Urgonian deposits: 1. onset of the carbonate platforms, with bioclastic marginal and rudistid inner platform deposits. These appear as early as the base of the Late Hauterivian in the central Jura and Provence (references for 1, 2, 3, 4: Clavel et al., 1986, 1987, 1995, 2002, 2007, 2010; Charollais et al., 2003, 2008, 2009; Conrad et al., 2011; Schroeder et al., 2000; Martin-Closas et al., 2009); 2. stepwise progradation expands in all directions toward the Vocontian basin; 3. cyclical exposures occur in the innermost platform areas, paired with long hiatuses in the more distal areas (Jura); 4. a maximum reduction of the platform deposits occurs early in Late Barremian time; 5. Upper Barremian and Lower Aptian platform debris are transported into the basin (Ferry, 1976, 1979, 1988; this work). 42 B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 Fig. 13. Geographical distribution of the Urgonian, slope and basinal deposits from Upper Hauterivian pro parte (Ha5 sequence) to Lower Barremian pro parte (Ba2 sequence). Only highstand deposits are shown. 6. platform demise dated Early Aptian is sudden and almost synchronous in all localities (this work), a conclusion that does not concern the whole of the Provence platform because earlier, near the transition from the Barremian to the Aptian, two segments, a Northern and a Southern domains, get individualized by the collapse of the median segment of this platform, that is by the genesis of the South Provence basin (Masse and Fenerci-Masse, 2011). 5. Dating the end of the Urgonian platforms as illustrated by sections of the upper portion of the Urgonian limestones in the southern Jura and in southeastern France From a stratigraphic standpoint these sections are properly dated, directly by ammonites or indirectly by coeval assemblages of orbitolinids, dasycladalean algae and charophytes. Because the ranges of the microfossils have been calibrated in basinal or transitional (talus) settings on the ammonite zones they allow us to identify the sequences in the platform environments too. Fig. 15 depicts the known distribution of the most significant Bedoulian ammonites in the stratotypic section of Cassis-la Bédoule, along with the corresponding biozonation and a tentative scheme of their sequential distribution. The paleontological data and correlations shown in Figs. 8, 9 and 11 are based mainly on literature. They are constructed to delineate the demise of the Urgonian platforms on the northern (Fig. 9), western (Fig. 8) and southwestern (Fig. 11) margins of the Vocontian basin. Each of the 15 outcrop sections shown in Figs. 8, 9 and 11 is correlated with the Lower Aptian basinal deposits at Cassis-La Bédoule, east of Marseille. At this location a conspicuous discontinuity caused by emergence occurs just above Bd2 sequence. Based on paleontological evidence (ammonites and orbitolinids below and above the discontinuity), the Urgonian platforms lost their identities almost synchronously everywhere in the area surrounding the Vocontian basin, during the lowstand of our Bd3 sequence, in the upper part of the Weissi ammonite Zone. Below the discontinuity, the distribution of three types of sedimentation (lagoon, shoal -eventually preserved in channels- and outer ramp) shows that the facies of the inner platform are progressively younger toward the margins of the basin, thus B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 43 Fig. 14. Geographical distribution of the Urgonian, slope and basinal deposits dated Early Barremian pro parte (Ba3 sequence) and Early Aptian pro parte (sequence Bd3/4). Only highstand deposits are shown. Note the inception of a northward transgressive, onlapping trend in sequence Ba4. Arrows shown in sequences Ba4 and Bd3/4 indicate downslope transportations of platform deposits. For symbols, see Fig. 13. illustrating the retrogressive-transgressive character of Urgonian deposits during Early Aptian times. 6. Discussion The phenomenon responsible for the termination of the Urgonian platforms is often referred to as a typical example of “drowning” events. However this name does not offer a key to an understanding of how and why Urgonian sedimentation came to an end. The “drowning” concept was first introduced to explain stratigraphic events during which production of carbonate sediments stopped abruptly: it was assumed to be caused by a rapid rise of the relative sea-level “submerging” the platform to a level below the euphotic zone (Schlager, 1981). In our opinion, the same concept is better expressed by the term “give-up” (Neumann and MacIntyre, 1985). Schlager (1989) suggested that drowning events could also be effected by a decrease in the clarity of the water (due to an increase of its turbidity) or even by a sea-water cooling. His concept originally applied to isolated platforms (like the Bahamas). When platform growth take place on the margin of a continent (Florida for example), a rapid transgression leads to a landward shift of the shoreline and to the back stepping of the carbonate facies, but not to their demise. For example, for the Wilmington platform illustrated by Schlager (1989), it is correct to say that there is no record of Lower Valanginian carbonate sediments in the distal part of the continental shelf, however shallow-water carbonates are present in the proximal area: there facies belts are merely backstepped at the distances prescribed by the amplitude of the related transgression. In the Urgonian platforms, the flooding events of the sequences Bd3 and Bd4 led to deposition of hemipelagic facies immediately above the fossilized Urgonian platforms. Carbonate sedimentation probably backstepped on previously emergent tracts. Hypothetically, we suggest that the rise in relative sea-level made possible connections with cooler northern seaways which caused a change in sedimentation from tropical carbonates to cooler-water carbonates. 44 B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 Fig. 15. Stratotypic Bedoulian section at Cassis e La Bédoule. Log and biostratigraphy: Moullade et al., 1998a, 1998b; Ropolo et al., 1998, 2008a, 2008b; additional biostratigraphic data from Bogdanova and Tovbina (1994); sequence stratigraphy: this work. Location of the Selli Oceanic Anoxic Event (OAE1a) noted. B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 7. Conclusions Advances in paleontological studies, particularly those concerning the taxonomy and distribution of the orbitolinids, permit a calibrated interregional correlation of the strata in an Urgonian facies that then delimited the Vocontian basin and its adjuncts. The bulk of Urgonian limestones range in age from the time represented by the youngest beds of the Upper Hauterivian substage, the whole of the Lower Barremian and the lower Upper Barremian. Within this interval the depositional setting is clearly progradational on both margins of the Vocontian basin, confirming a model explicitly described and named more than a decade ago (Clavel et al., 1995, 2007). This interpretation is clearly the opposite of that put forward by H. Arnaud (in Adatte et al., 2005) and Godet et al. (2010) as discussed in detail in Conrad et al. (2011). In the long term the “maximum regression” (that is, the maximum reduction of the platform deposits) observed in the early Late Barremian (during the lowstand of the Ba4 sequence) is coeval with a pivotal turnover in the distribution of the orbitolinids, and as yet not properly documented with that of the dasycladalean algae. From that point in time, the carbonate factory moved toward the margins of the basin and succeeding platforms are generally narrow fringes with an aggradational rather than a progradational pattern. In Early Aptian time, that is in the Weissi ammonite Zone, a pronounced discontinuity marks the final, almost synchronous disappearance of the carbonate platforms. Acknowledgments The core of this paper was presented during STRATI2010 (4ème Congrès Français de Stratigraphie, UPMC, Paris, August 30eSeptember 2, 2010) in the form of a set of conferences and posters: http://www.univ-brest.fr/geosciences/conference/ ocs/index.php/CFS/STRATI2010/schedConf/presentations We thank the guest editors, Michel Moullade and Peter Skelton, as well as Serge Ferry and an anonymous reviewer, whose comments and suggestions have helped improving the original manuscript. References Adatte, T., Arnaud-Vanneau, A., Arnaud, H., Blanc-Alétru, M.-C., Bodin, S., Carrio Schaffhauser, E., Föllmi, K.B., Godet, A., Raddadi, M.C., Vermeulen, J., 2005. The Hauterivian e Lower Aptian sequence stratigraphy from Jura platform to vocontian basin: a multidisciplinary approach. Géologie Alpine, Colloques et Excursions 7, 181 p. Arnaud, H., Arnaud-Vanneau, A., Blanc-Alétru, M.-C., Adatte, T., Argot, M., Delanoy, G., Thieuloy, J.-P., Vermeulen, J., Virgone, A., Virlouvet, B., Wermeille, S., 1998. Répartition stratigraphique des orbitolinidés de la plate-forme urgonienne Subalpine et jurassienne (SE de la France). Géologie alpine 74, 3e89. Arnaud-Vanneau, A., 1980. Micropaléontologie, paléoécologie et sédimentologie d’une plate-forme carbonatée de la marge passive de la Téthys: l’Urgonien du Vercors septentrional et de la Chartreuse (Alpes occidentales). Géologie alpine, Mémoire hors-série 10, 874. Blanc-Alétru, M.-C., 1995. Importance des discontinuités dans l’enregistrement sédimentaire de l’Urgonien jurassien. Micropaléontologie, sédimentologie, minéralogie et stratigraphie séquentielle. Géologie alpine, Mémoire hors-série 24, 299. Bogdanova, T.N., Tovbina, S.Z., 1994. On development on the Aptian ammonite zonal standard for the Mediterranean region. Géologie alpine, Mémoire hors-série 20, 51e59. Catuneanu, O., Galloway, W.E., Kendall, C.G., Miall, A.D., Posamentier, H.W., Strasser, A., Tucker, M.E., 2011. Sequence stratigraphy: methodology and nomenclature. Newsletters on Stratigraphy 44/3, 173e245. Charollais, J., Clavel, B., Schroeder, R., Busnardo, R., Cherchi, A., Massera, M., Müller, A., Orsat, V., Zaninetti, L., 2001. Installation et évolution de la plateforme urgonienne du Jura aux chaînes subalpines septentrionales (Bornes, Bauges, Chartreuse), Suisse, France. Archives des Sciences 54/3, 139e169. Charollais, J., Clavel, B., Schroeder, R., Busnardo, R., Decrouez, D., Cherchi, A., 2003. La migration de la plate-forme urgonienne entre le Jura plissé et les Chaînes Subalpines septentrionales (France, Suisse). Geobios 36/6, 665e674. 45 Charollais, J., Clavel, B., Busnardo, R., 2008. Biostratigraphie et découpage sequentiel des formations du Crétacé inférieur de la plate-forme jurassienne (France, Suisse). In: A terra. O conflitos e ordem. Homenagem ao Professor Ferreira Soares. Museu Mineralógico e Geológico da Universidade de Coimbra, pp. 197e207. Charollais, J., Clavel, B., Busnardo, R., Conrad, M., Müller, A., Decrouez, D., 2009. Olistolithes et coulées bioclastiques: prémices de l’installation de la plate-forme urgonienne aux confins des Bornes et des Aravis (Haute-Savoie, France). Archives des Sciences 62/1, 35e70. Clavel, B., Busnardo, R., Charollais, J., 1986. Chronologie de la mise en place de la plate-forme urgonienne du Jura au Vercors (France). Comptes rendus de l’Académie des Sciences (Série 2) 302/8, 583e586. Clavel, B., Charollais, J., Busnardo, R., 1987. Données biostratigraphiques nouvelles sur l’apparition des faciès urgoniens du Jura au Vercors. Eclogae geologicae Helvetiae 80/1, 59e68. Clavel, B., Charollais, J., Schroeder, R., Busnardo, R., 1995. Réflexions sur la biostratigraphie du Crétacé inférieur et sur sa complémentarité avec l’analyse séquentielle: exemple de l’Urgonien jurassien et subalpin. Bulletin de la Société géologique de France 166/6, 663e680. Clavel, B., Schroeder, R., Charollais, J., Busnardo, R., Martin Closas, C., Decrouez, D., Sauvagnat, J., Cherchi, A., 2002. Les “Couches inférieures à orbitolines” (Chaînes subalpines septentrionales): mythe ou réalité ? Revue de Paléobiologie 21/2, 865e871. Clavel, B., Charollais, J., Conrad, M., Jan du Chêne, R., Busnardo, R., Gardin, S., Erba, E., Schroeder, R., Cherchi, A., Decrouez, D., Granier, B., Sauvagnat, J., Weidmann, M., 2007. Dating and progradation of the Urgonian limestone from the Swiss Jura to South-East France. Zeitschrift der Deutschen Gesellschaft für Geowissenschaften 158/4, 1025e1062. Clavel, B., Busnardo, R., Charollais, J., Conrad, M., Granier, B., 2009. Nouvelles données sur la répartition biostratigraphique des orbitolinidés à l’Hauterivien supérieur, au Barrémien et à l’Aptien inférieur dans le Sud-Est de la France et le Jura franco-suisse. Archives des Sciences 62/2, 125e146. Clavel, B., Busnardo, R., Charollais, J., Conrad, M., Granier, B., 2010. Répartition biostratigraphique des orbitolinidés dans la biozonation à ammonites (plateforme urgonienne du Sud-Est de la France). Partie 1: Hauterivien supérieur Barrémien basal. Carnets de Géologie, Article 2010/06, 53. doi:10.4267/2042/ 33369. Conrad, M.A., Clavel, B., Granier, B., Charollais, J., Busnardo, R., Erba, E., Gardin, S., Jan du Chêne, R., Decrouez, D., Cherchi, A., Schroeder, R., Sauvagnat, J., Weidmann, M., 2011. (online). Discussion of: stratigraphic, sedimentological and palaeoenvironmental constraints on the rise of the Urgonian platform in the western Swiss Jura, by A. Godet et al. Sedimentology 2010 (57), 1088e1125, Sedimentology, 5 p. doi: 10.1111/j.1365-3091.2011.01277.x. Conte, G., 1999. Eléments de la faune de l’Aptien inférieur (Bédoulien) de Serviersla- Baume (Gard). Bulletin de la Société d’Étude des Sciences Naturelles de Nîmes et du Gard 62, 11e15. Conte, G., 2001. Présence de Paradeshayesites similis Bogdanova 1991 dans l’Aptien inférieur de Serviers-la-Baume (Gard). Bulletin de la Société d’Étude des Sciences Naturelles de Nîmes et du Gard 63, 49. Dumas, E., 1876. Statistique géologique, minéralogique, métallurgique et paléontologique du département du Gard. Deuxième partie. Arthus Bertrand, Paris, 735 p. Elmi, S., Busnardo, R., Clavel, B., Camus, G., Kieffer, G., Bérard, P., Michaëly, B., 1996. Carte géologique de la France au 1/50.000, feuille Aubenas (865). Bureau de Recherches Géologiques et Minières, Notice explicative, 170 p. Ferry, S., 1976. Cônes d’épandage bioclastiques en eau profonde et glissements sousmarins dans le Barrémien et l’Aptien inférieur vocontiens de la Drôme. Implications paléostructurales. Thèse, Université Claude Bernard, Lyon. Ferry, S., 1979. Les turbidites bioclastiques: mode de transport du sable calcaire des plates-formes urgoniennes au bassin vocontien. Geobios hors-série 3, 149e158. Ferry, S., 1988. Contrôle eustatique de la resédimentation calcaire en fosse vocontienne (Mésozoïque, SE de la France). Livret guide de l’excursion du Groupe Français du Crétacé en Fosse vocontienne (25e27 mai 1988). In: Ferry, S., Rubino, J.-L. (Eds.), Eustatisme et séquences de dépôt dans le Crétacé du Sud-Est de la France. GéoTrope 1, pp. 40e55. Ferry, S., Flandrin, J., 1979. Mégabrèches de resédimentation, lacunes mécaniques et pseudo- “hard-grounds” sur la marge vocontienne. Géologie alpine 55, 76e92 (Grenoble). Gidon, P., 1952. Une ammonite de l’Urgonien en Grande Chartreuse. Compte Rendu sommaire des Séances de la Société Géologique de France 11, 237e238. Girod, J.-P., Weiss, J., 1965. Sur une ammonite de l’Urgonien des Monts du Matin (Vercors). Travaux du Laboratoire de Géologie de la Faculté des Sciences de Grenoble 41, 271e273. Godet, A., Föllmi, K.B., Bodin, S., De Kaenel, E., Matera, V., Adatte, T., 2010. Stratigraphic, sedimentological and palaeoenvironmental constraints on the rise of the Urgonian platform in the western Swiss Jura. Sedimentology 57/4, 1088e1125. Jacob, C., 1907. Étude paléontologique et stratigraphique sur la partie moyenne des terrains crétacés dans les Alpes françaises et les régions voisines. Thèse, Grenoble, 374 p. Kilian, W., 1888. Description géologique de la Montagne de Lure. Annales des Sciences géologiques 20, 215. Kuhnt, W., Holbourn, A., Moullade, M., 2011. Transient global cooling at the onset of Early Aptian oceanic anoxic event (OAE) 1a. Geology 39/4, 323e326. 46 B. Clavel et al. / Cretaceous Research 39 (2013) 29e46 Leenhardt, F., 1883. Étude géologique de la région du Mont Ventoux. Thèse, Montpellier, 273 p. Martin-Closas, C., Clavel, B., Schroeder, R., Charollais, J., Conrad, M., 2009. Charophytes from the Barremian-Lower Aptian of the Northern Subalpine Chains and Jura Mountains, France: correlation with associated marine assemblages. Cretaceous Research 30/1, 49e62. Masse, J.-P., 1976. Les calcaires urgoniens de Provence. Valanginien - Aptien inférieur. Thèse, Université d’Aix-Marseille II, Marseille, 3 vol., 516 p. Masse, J.-P., Fenerci-Masse, M., 2011. Drowning discontinuities and stratigraphic correlation in platform carbonates. The Late Barremian - Early Aptian record of southeast France. Cretaceous Research 32/6, 659e684. Mojon, P.-O., 2002. Les formations mésozoiques à Charophytes (Jurassique moyen e Crétacé inférieur) de la marge téthysienne nord-occidentale (Sud-est de la France, Suisse occidentale, nord-est de l’Espagne). Sédimentologie, micropaléontologie, biostratigraphie. Géologie alpine, Mémoire HS 41, 1e386. Mojon, P.-O., Médus, J., 1990. Précisions biostratigraphiques sur l’ “Urgonien” des chaînes subalpines septentrionales du Sud-Est de la France et mise en évidence de Cypridea gigantissima, un nouvel ostracode lacustre de l’Aptien inférieur. Archives des Sciences 43/3, 429e452. Monier, P., 1986. De la plate-forme urgonienne provençale au bassin vocontien: étude stratigraphique, cartographique et paléogéographique de la série crétacée du Mont Ventoux e Chaînes Subalpines méridionales e Sud-Est de la France. Thèse, Université Claude Bernard, Lyon 1, 186 p. Moullade, M., 1963. Révision des stratotypes de l’Aptien. II- Gargas (Vaucluse). In: Colloque sur le Crétacé inférieur, Lyon. Mémoires du BRGM 34, pp. 201e214. Moullade, M., Masse, J.-P., Tronchetti, G., Kuhnt, W., Ropolo, P., Bergen, J.A., Masure, E., Renard, M., 1998a. Le stratotype historique de l’Aptien inférieur (région de Cassis-La Bédoule, SE France): synthèse stratigraphique. Géologie méditerranéenne XXV/3e4, 289e298. Moullade, M., Tronchetti, G., Busnardo, R., Masse, J.-P., 1998b. Description lithologique des coupes types du stratotype historique de l’Aptien inférieur dans la région de Cassis-La Bédoule (SE France). Géologie méditerranéenne méditerranéenne XXV/3e4, 15e29. Moullade, M., Tronchetti, G., Babinot, J.-F., 2009. Le Gargasien de Gargas (Vaucluse, SE de la France): synthèse des données de terrain et révision de la microfaune de foraminifères et d’ostracodes. Carnets de Géologie, Article 2009/10, 15. doi:10.4267/2042/30051. Neumann, A.C., MacIntyre, I.G., 1985. Reef response to sea level rise: keep-up, catchup or give-up. In: Gabrie, C., Toffart, J.L., Salvat, B. (Eds.), Proceedings of the Fifth International Coral Reef Congress (Tahiti, 27 Maye1 June 1985). Symposia and Seminars (A) 3, pp. 105e110. Paquier, V., 1900. Rercherches géologiques dans le Diois et les Baronnies orientales. Thèse Grenoble, 402 p. Pellat, E., 1903. Le Néocomien (Valanginien et Hauterivien) et le Barrémien entre Mons et Brouzet (Gard) ; quelques mots sur les faciès urgoniens de Martigues et d’Apt ; sur l’Aptien des environs d’Uzès, et le Barrémien de Lussan (Gard). Bulletin de la Société géologique de France (4ème série) 3, 119e127. Renaud, B., 1978. Le Crétacé inférieur de la vallée de l’Ibie et de la région de Lagorce e Rochecolombe, Ardèche. Stratigraphie-sédimentologie-analyse structurale. Thèse 3ème cycle, Université Claude Bernard, Lyon, 149 p. Renz, O., Jung, P., 1978. Aptian to Maastrichtian in the Swiss Jura Mountains. Eclogae geologicae Helvetiae 71/1, 1e18. Ropolo, P., Conte, G., Gonnet, R., Masse, J.-P., Moullade, M., 1998. Les faunes d’Ammonites du Barrémien supérieur/Aptien inférieur (Bédoulien) dans la région stratotypique de Cassis- La Bédoule (SE France): état des connaissances et propositions pour une zonation par Ammonites du Bédoulien-type. Géologie méditerranéenne XXV/3e4, 167e175. Ropolo, P., Moullade, M., Gonnet, R., Conte, G., Tronchetti, G., 2006. The Deshayesitidae Stoyanov, 1949 (Ammonoidea) of the Aptian historical stratotype region at Cassis-La Bédoule (SE France). Carnets de Géologie, Memoir 2006/01, 46. doi:10.4267/2042/4744. Ropolo, P., Conte, G., Moullade, M., Tronchetti, G., Gonnet, R., 2008a. The Douvilleiceratidae (Ammonoidea) of the Lower Aptian historical stratotype area at Cassis-La Bédoule (SE France). Carnets de Géologie, Memoir 2008/03, 60. doi:10.4267/2042/18125. Ropolo, P., Moullade, M., Conte, G., Tronchetti, G., 2008b. About the stratigraphic position of the Lower Aptian Roloboceras hambrovi (Ammonoidea) level. Carnets de Géologie, Letter 2008/03, 7. doi:10.4267/2042/18124. Schlager, W., 1981. The paradox of drowned reefs and carbonate platforms. Geological Society of America, Bulletin 92/4, 197e211. Schlager, W., 1989. Drowning unconformities on carbonate platforms. In: Crevello, P.D., Wilson, J.L., Sarg, J.L., Read, J.F. (Eds.), Controls on Carbonate Platform and Basin Development. SEPM Special Publication 44, pp. 15e25. Schroeder, R., Clavel, B., Conrad, M.A., Zaninetti, L., Busnardo, R., Charollais, J., Cherchi, A., 2000. Corrélations biostratigraphiques entre la coupe d’Organyà (Pyrénées catalanes, NE de l’Espagne) et le Sud-Est de la France pour l’intervalle Valanginien e Aptien. Treballs del Museu de Geologia de Barcelona 9, 5e41. Thieuloy, J.-P., 1990. Un Ancyloceratide géant de l’Aptien du Gard (France): Toxoceratoides? sp. inc. “gigantomorphe godeti” nov. Géologie alpine 66, 101e106. Van Wagoner, J.C., Posamentier, H.W., Mitchum, R.M., Vail, P.R., Sarg, J.F., Loutits, T.S., Hardenbol, J., 1988. An overview of the fundamentals of sequence stratigraphy and key definitions. In: Wilgus, C.K., Hastings, B.S., Posamentier, H., Van Wagoner, J., Ross, C.A., Kendall, C.G.St.C. (Eds.), Sea-level Changes: An Integrated Approach. SEPM Special Publication 42, pp. 39e45. Vermeulen, J., 2005. Boundaries, ammonite fauna and main subdivisions of the stratotype of the Barremian. Géologie alpine, Colloques et Excursions 7, 147e173.