Microporous and tight limestones in the Urgonian Formation (late Hauterivian to early Aptian) of the...

Sedimentary Geology 230 (2010) 21–34

Contents lists available at ScienceDirect

Sedimentary Geology

j ourna l homepage: www.e lsev ie r.com/ locate /sedgeo

Microporous and tight limestones in the Urgonian Formation (late Hauterivian toearly Aptian) of the French Jura Mountains: Focus on the factors controlling theformation of microporous facies

Chadia Volery a,⁎, Eric Davaud a, Christophe Durlet b, Bernard Clavel c, Jean Charollais a, Bruno Caline d

a University of Geneva, Earth and Environmental Sciences, Department of Geology and Paleontology, Rue des Maraîchers 13, 1205 Genève, Switzerlandb University of Bourgogne, UMR CNRS 5561 Biogeosciences, Blvd Gabriel 6, 21000 Dijon, Francec Ch. des Champs d'Amot 24, 74140 Messery, Franced Total Exploration and Production, CSTJF, Avenue Larribau, 64000 Pau, France

⁎ Corresponding author. University of Geneva, EarthDept. of Geology and Palaeontology, Rue des MaraîchersTel.: +41 22 0 79 750 30 58 (mobile); fax: +41 0 22 3

E-mail addresses: Chadia.Volery@unige.ch, chadia@iEric.Davaud@unige.ch (E. Davaud), b.clavel1@orange.frjdcharollais@bluewin.ch (J. Charollais), bruno.caline@to

0037-0738/$ – see front matter © 2010 Elsevier B.V. Aldoi:10.1016/j.sedgeo.2010.06.017

a b s t r a c t

Article history:Received 2 March 2010Received in revised form 22 June 2010Accepted 24 June 2010Available online 1 July 2010

Editor: B. Jones

Keywords:MicroporosityMicriteCarbonateReservoirUrgonian

Microporous and tight limestones, with contrasting porosity and permeability values directly related to themicrofabric of the micritic matrix, outcrop in the Urgonian Formation of the French Jura Mountains. Thisstudy investigates the factors controlling the differentiation between the microporous and tight facies, andproposes a diagenetic model for the development and preservation of the microporosity in these limestones.The petrophysical properties are not related to the depositional texture, the petrographical content or themineralogical composition. However, the tight layers contain indications of emersion (e.g.: bird eyes,keystone vugs, and desiccation cracks). The sedimentation in very shallow conditions up to emersion isconfirmed by the covariant more positive values of oxygen and carbon isotopes. The microporous intervalssystematically occur a few meters below the tight layers affected by emersion. This position stronglysuggests the importance of meteoric water input rapidly after sedimentation in the differentiation betweentight and microporous limestones.The diagenetic model proposed for the development and preservation of the microporous facies involvespartial early cementation of the interstitial mud, mainly composed of low-Mg calcite crystals (sedimentationduring a calcite sea period), inside a meteoric phreatic lens by in situ dissolution–reprecipitation processes(“hybrid Ostwald ripening”). This early cementation partly preserves the original microfabric andintercrystalline microporosity and allows the carbonate sediment to resist compaction during burial.The identification of the conditions favorable to the development of microporosity in these Urgonianlimestones may improve the knowledge and modeling of some microporous carbonate reservoir rocks.

and Environmental Sciences,13, 1205 Genève, Switzerland.79 32 10.nfomaniak.ch (C. Volery),(B. Clavel),tal.com (B. Caline).

l rights reserved.

© 2010 Elsevier B.V. All rights reserved.

1. Introduction

Limestones characterized by a microporous intercrystalline frame-work made up of sub-rhombic low-Mg calcite crystals with sizesgenerally smaller than 8 μm (micrites, lato sensu) account for manycarbonate reservoirs, especially in the Middle East (Alsharhan andNairn, 2003; Volery et al., 2009). The mean porosity and permeabilityof these reservoirs rate about 20% and 100 mD, respectively. However,despite a considerable economic interest, the genesis of microporouslimestones remains poorly understood. Some studies have investi-

gated these rocks (e.g.: Budd, 1989; Kaldi, 1989; Moshier, 1989;Perkins, 1989; Lambert et al., 2006; Richard et al., 2007), but little isknown about the main factors involved in the development of theintercrystalline microporosity.

Recently, an inventory of shallow-marine microporous carbonateformations in the Middle East revealed that microporous limestonesdeveloped during periods of calcite seas (Volery et al., 2009). Aprecursor mud mainly composed of low-Mg calcite crystals wasnecessary to formmicroporous limestones. This essential prerequisitewas confirmed with the study of Late Miocene lacustrine microporousmicrites from the Madrid Basin presenting identical matrix micro-fabric to the Cretaceousmarinemicroporous limestones of theMishrifFormation in the Middle East (Volery et al., 2010).

In the JuraMountains, the Urgonian Formation (late Hauterivian toearly Aptian) constitutes thick limestones deposited during a periodof calcite seas (Sandberg, 1983; Hardie, 1996; Lowenstein et al., 2001;Dickson, 2002) and characterized by several microporous horizons(Richard et al., 2007). One of them, recently exposed in the region of

22 C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

Bellegarde-sur-Valserine (Ain, France) shows a remarkable alterna-tion of tight and microporous limestones.

The aims of this article are to describe and compare tight andmicroporous layers of this section, and to identify the factorscontrolling the differentiation of these two facies with contrastingpetrophysical properties.

2. Geological setting

The Urgonian Formation crops out in the French–Swiss JuraMountains and the northern Subalpine Chains in South-East France. Itcorresponds to a carbonate platform settled in the domain of theAlpine Tethys and deformed during the Alpine orogeny.

During the late Jurassic, the opening of the Alpine Tethys (Cavazzaet al., 2004) induced the development of several carbonate platforms.The Urgonian limestones settled on the northern passive margin ofthe Ligurian basin and form the youngest carbonate platform of theregion with an age of late Hauterivian to early Aptian (Clavel et al.,1987; Charollais et al., 2003; Clavel et al., 2007). Due to the southwardprogradation of the sediments, the base of the Urgonian Formation islate Hauterivian in the Jura Mountains and early Barremian in theSubalpine Chains (Clavel et al., 2007). The platform attains about50 km in width and extends over more than 400 km around theVocontian basin (Clavel et al., 1986).

Several subaerial exposures in the inner platform under arid tosemi-arid climate (Ruffell and Batten, 1990) punctuated the sedi-mentation of the Urgonian limestones (Hunt and Tucker, 1993).During the lower Aptian, a sizeable sea-level fall exposed the platform(Hunt and Tucker, 1993; Moss and Tucker, 1995; Clavel et al., 2007),marking the end of shallow-marine sedimentation in the region. Later,in the lower Aptian, a transgression brought basin deposits over theshallow-water Urgonian limestones (Hunt and Tucker, 1993; Char-ollais et al., 2007; Clavel et al., 2007). The Alpine Tethys Ocean closedin the latest stages of the Cretaceous (Cavazza et al., 2004).

The study area is located in the southern part of the JuraMountains, about two kilometers north of the town of Bellegarde-sur-Valserine in the locality of Pierre-Blanche (Fig. 1). This geologicaldomain remained globally preserved from Alpine deformations untilthe Late Miocene. Main folding and thrusting of the Jura Mountainsbegan during the Serravallian (~12 Ma) (Laubscher, 1992; Burkhardand Sommaruga, 1998).

Fig. 1. The Pierre-Blanche section (lower outcrop: 46°07′45″ N and 5°48′40″ E; upperoutcrop: 46°07′36″ N and 5°48′37″ E) is situated in the southern part of the French JuraMountains near the town of Bellegarde-sur-Valserine.

The ensuing Mesozoic sedimentation was limited and the lateCretaceous to Paleocene emersion removed much of these deposits(Moss and Tucker, 1995; Donzeau et al., 1997). During the Tertiaryperiod, the development of the foreland basin associated with theAlpine orogeny received hundreds of meters of marine and continen-tal molassic sediments from the Oligocene until the middle-Miocene(Homewood et al., 1986). However, no precise data exists on theburial depth of the Urgonian limestones in the Bellegarde-sur-Valserine region (Richard et al., 2007).

3. Methods

The sampling of fragments was done about every 50 cm. Sixty thinsections were prepared (impregnated with epoxy and polished) on 39different samples and 32 plugs were made in laboratory to measurepetrophysical properties.

Thin sections were studied with classical petrographical techni-ques, using light microscopy and cathodoluminescence. Cathodolu-minescence was performed with a luminoscope ELM-3R coupled witha pelletier cooling MRc5 digital camera. After cathodoluminescenceobservations, thin sections were immersed in alizarin and potassiumferricyanide solution (AF) to respectively highlight calcite and iron-rich mineral phases. For each thin section, an inventory of diageneticphases including cements, dissolutions, replacements, fractures andstylolitization was established and chronologically ordered usingclassical principles of cement stratigraphy.

Scanning electron microscopy (SEM) was performed on 33fragments coated with gold using a Jeol JSM 6400 with a workingcurrent set at 15 kV. Porosity and permeability were measured inTotal E&P laboratories (Pau, France) for 32 samples. Porosity wasmeasured with helium. Permeability was calculated with nitrogenand corrected for the Klinkenberg effect. The mineralogical andchemical compositions of 32 samples were identified by X-raydiffraction (XRD) and X-ray fluorescence (XRF) analyses in TotalE&P laboratories. Diffraction peaks were measured for angles from4.5° to 70°. The XRD device was an XPert Pro manufactured byPanalytical and the XRF device a Pioneer S4 of Bruker. The stableisotopic composition of O and C was measured on 33 whole rocksamples with the AP2003 mass spectrometer manufactured byAnalytical Precision in Total E&P laboratories. Values were normalizedwith the reference material NBS 19 (TS-Limestone).

The biostratigraphic study of the section is based on orbitolinidsand is correlated with the ammonite zones (Clavel et al., 2007;Charollais et al., 2009).

4. Observations and interpretations

4.1. Facies and deposit environments

The section studied constitutes two outcrops vertically separatedby about 15m (Fig. 2). The lower outcrop was only recently exposed,while the upper one existed from about ten years ago.

Three types of limestones characterized by different cohesionswere observed: microporous, semi-microporous and tight (Fig. 2).Microporous limestones are chalky and pulverulent. Semi-micropo-rous limestones possess a chalky texture but have a stronger cohesionthan the microporous ones. Tight limestones are typical hard rocksonly breakable with a hammer. These different types of limestonesalternate stratigraphically.

Depositional textures present in the section run from wackestoneto grainstone and from floatstone to floatstone with grainstonematrix. Relatively high energy facies are dominant (Fig. 3ABC).Oncoids and peloids constitute a significant proportion of allochems.The principal bioclasts are small foraminifera, bivalves (with frequentrudists), echinoderms, green algae (dasyclads), gastropods and somelarge foraminifera (especially orbitolinids). The limestone matrix is

Fig. 2. Synthetical log with petrographical descriptions (depositional textures, petrographical contents and SEM matrix microfabrics), biostratigraphy, stable isotopes values,mineralogical composition, petrophysical properties, macro-cements proportions (C1 to C6), and interpretations of the depositional environments and the sequence stratigraphy.The porosity and permeability values directly reflect the microfabric of the matrix. Tight layers develop just below sequence boundaries characterized by emersion. For clarity in thetext, the section is divided into 10 units. (Meaning of the abbreviations in the sedimentary profile: WA: wackestone, PA: packstone, GR: grainstone, FL: floatstone, FP: floatstone withpackstone matrix, FG: floatstone with grainstone matrix.)

23C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

made of micrite crystals. The following interpretations of depositionalenvironments are made according to Godet (2006).

The section was divided into ten units alternating between tightand (semi-) microporous facies (Fig. 2). The first unit is characterizedby 1.5m of microporous limestones composed of open lagoonal facies.Unit 2 is formed by a thin bed (~20 cm) of tight limestones topped byan indurate and bored surface (bs1). Some bird eyes and circum-granular cracks (Fig. 3E) affect the muddy facies of this bed, indicatinga very calm intertidal to supratidal depositional environment. Unit 3comprises approximately five meters of microporous limestones withrare variations towards semi-microporous facies. The sedimentationof these layers occurred in an open lagoon. Unit 4 is composed ofabout two meters of tight limestones. These layers, rich in largebioclasts (especially bivalves), show bird eyes, circumgranular anddesiccation cracks (Fig. 3FG), indicating deposition in an intertidal tosupratidal environment. Unit 5 is characterized by about two metersof semi-microporous limestones formed by relatively high energyopen lagoonal deposits. Unit 6 is made up of more than 4.5m of tightlimestones presenting open lagoonal facies. The succession isinterrupted by three erosion surfaces draped with clays. Unit 7,

composed of one meter of tight limestones, constitutes the base of theupper outcrop. The muddy facies of this layer contains bird eyes,circumgranular and desiccation cracks, suggesting that the sedimen-tation occurred within the intertidal to supratidal zone. Unit 8 isformed by a few more than two meters of semi-microporouslimestones settled in an open lagoon. This unit ends with a sizeablesubaerial erosion surface (ses). The morphology of the surface showssubstantial channel erosion (Fig. 4). Unit 9 is composed of one bed(~20 cm) of tight limestones showing wave ripples. This verybioclast-rich bed contains some keystone vugs suggesting a beachdeposit and finishes with an indurate bored surface (bs2) (Fig. 3H).Unit 10 constitutes almost two meters of tight limestones. Algal mats(fine horizontal laminations) (Fig. 3D) directly overlie relatively highenergy facies (wave ripples).

4.2. Biostratigraphy

Orbitolinids indicate that the section is Late Hauterivian in age. Itbegins in the Ha5 sequence (Ligatus zone) and ends in the Ha6

Fig. 3. Thin-section photomicrographs. A) Packstone to grainstone composed of oncoids, peloids, foraminifera, bivalves, echinoderms and green algae (sample 143, tight facies).B) Packstone to grainstone with oncoids, peloids, foraminifera, bivalves, echinoderms and gastropods (sample 135, semi-microporous facies). C) Packstone to grainstone rich inoncoids, peloids, foraminifera, bivalves, echinoderms, green algae and gastropods (sample 113, microporous facies). D) Algal mats (sample 123, tight facies). E)Wackestone showingcircumgranular cracks (white arrow) and bird eyes (black arrows) (sample 111, tight facies). F) Floatstone to floatstone with packstone matrix affected by circumgranular cracks(white arrows) and bird-eyes (black arrow) (sample 130, tight facies). G) Circumgranular cracks (white arrows) andwrinkled cracks (black arrows) in a floatstone to floatstone withpackstone matrix (sample 133, tight facies). H) Borings of the bs2 bored surface (sample 161, tight facies). Note some bivalves still present inside the burrow (white arrows).

24 C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

Fig. 4. Sketch with photographs showing the spectacular subaerial erosion surface (ses) in the upper outcrop. In the north part, a bored surface (bs2) occurs about 20cm above thesubaerial erosion surface. Whitish microporous limestones exist at the base of the upper outcrop.

25C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

sequence (Balearis zone) (Clavel et al., 2007; Charollais et al., 2009;Clavel et al., 2009).

4.3. Sequence stratigraphy

Two third-order sequences (Ha5 and Ha6) constitute the Pierre-Blanche section (Clavel et al., 2007; Charollais et al., 2009; Clavel et al.,2009). A comparison with nearby sections (Charollais et al., 2003)suggests that the sequence boundary SBHa6 is located somewherebetween the inferior and superior outcrops (Fig. 2).

Inside the Ha5, three high-frequency sequences are identifiedaccording to variations of the depositional environments anddiscontinuities. The first high-frequency sequence boundary (hfSB)is placed at the top of unit 2 and is underlined by a bored surface(bs1). Unit 2 represents the shallowest deposits of the lower part ofthe outcrop. The second hfSB is situated at the end of the intertidal tosupratidal deposits of unit 4. Deeper facies settled during units 5 and

Fig. 5. Diagram presenting the relative chronology of the 18 diagenetic phases recorded insyntaxial or blocky calcite cements: C1 to C6), dissolutions, fractures and stylolites (vertical adiagenesis, 2) shallow burial diagenesis, 3) burial diagenesis, and 4) telogenesis.

6. The following sequence boundary is not exposed. It corresponds tothe third-order sequence boundary SBHa6 occurring after unit 6.

In the upper outcrop, three high-frequency sequences are partiallyexposed. The first hfSB is located at the top of unit 7 characterized byintertidal to supratidal limestones. Subtidal lagoonal conditions comeback after unit 7, during the sedimentation of unit 8. The second hfSBcorresponds to the discontinuity with channels that incise the top ofunit 8. A few centimeters above, at the top of unit 9, the bs2 boredsurface probably corresponds to a transgressive surface. Intertidal tosupratidal facies of unit 9 may represent the LST only preserved at thebase of the channels. The following unit 10 with proliferation of algalmats may correspond to the TST of the last high-frequency sequence.

4.4. Cement stratigraphy

Cathodoluminescence and AF staining permit to determine 18diagenetic phases corresponding to macro-cements precipitation(notably six different syntaxial or blocky calcite cements: C1 to C6),

the Pierre-Blanche section. These phases include macro-cements (notably six differentnd horizontal). They are grouped into four diagenetic environments: 1) synsedimentary

26 C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

dissolution, fracturing and stylolitization (Table 3, Fig. 5, Fig. 6).Diagenetic phases affect the entire section, except for the first fourones. The C1 to C6 calcite cements were visually quantified for eachsample. However, no constant behavior in the content of thesecements exists inside the same unit (Fig. 2). The 18 diagenetic phasesare divided into four stages corresponding to different diageneticenvironments (Fig. 5).

4.4.1. Stage 1: synsedimentary diagenesisThe diagenetic phases of this stage are chronologically and

spatially associated with unconformities of the section. In units 2and 9, situated just below bored surfaces (bs1 and bs2), micriticcements form thin equant isopachous fringes and meniscus betweengrains (Fig. 6A). Equant isopachous inclusions-rich calcite cements arealso observed in intraclasts and bored pebbles in units 2 and 9(Fig. 6D). These early cements, sometimes associated with bird-eyesand desiccation cracks or keystones vugs, were probably precipitatedin vadose to phreatic marine to mixed waters. Indices of sulphates,dolomite and aragonite cements are lacking. A first blocky calcitecement (C1), Mg-poor, Fe-poor and non-luminescent is foundthroughout units 1 to 8 (Fig. 6CEG). Small embayments of dissolutionsometimes affect the top of this cement. The characteristics of the C1cement (blocky, non-luminescent, Mg and Fe-poor) suggest that itwas precipitated from meteoric waters. Such waters might beintroduced in the sediment during the exposure event associatedwith the subaerial erosion surface (ses) at the end of unit 8.

4.4.2. Stage 2: shallow burial diagenesis

This stage occurs before pressure–dissolution processes and isdominated by the precipitation of three different blocky calcitecements (C2, C3, and C4) each divided into two subzones (a and b)(see Table 3 for details). C2 and C3 are characterized by Mg-poor,variable Fe content and inclusion-poor calcite with a yellow to orangeand brown luminescence (Fig. 6CEGJ). The marine versus meteoricorigin of the parent waters is unknown. C4 occurred after a fracturingphase (F1). This cement is Mg-poor, Fe-poor and contains thick non-luminescent zones that alternate with thin yellow to orange bands(Fig. 6BFHIK). Small dissolution embayments are sometimes observedbetween cements C4a and C4b. The characteristics of the cement C4and the dissolution embayments suggest the introduction of meteoricwaters into the sediment. The percolation of these meteoric watersmay be linked to the exposure surface at the top of the UrgonianFormation.

4.4.3. Stage 3: burial diagenesisThis stage is affected by several fracturing phases (F2, F3, and F4)

and stylolitization (Fig. 6F). It is also characterized by an Fe-richblocky calcite cement (C5) with dark brown luminescence(Fig. 6BFHIK). The features of the C5 cement (luminescent, Fe-rich)suggest that it was precipitated from burial reduced waters associatedwith pressure–dissolution processes. At the end of this third stage, thedevelopment of sub-vertical stylolites indicates a compressive regime,probably related to the post-Miocene folding of the Jura.

Fig. 6. Non-polarized light microscopy (LM) and cathodoluminescence (CT) photomicrA) Luminescent micritic cement (m) forms menisci between peloids and intraclasts. It develo162, CT). B) Bird eye filled with micritic and bioclastic internal sediment (is). Blocky calciovergrowths (C1) around an echinoderm fragment (ec) followed by the precipitation of thdeveloped in a cavity created by dissolution, probably during telogenesis (sample 162, CT).LM). E) Blocky calcite cements C1, C2a, and C2b precipitated below an echinoderm fragmencalcite cement C3 postdates the microfracturing (sample 119, CT). F) A double stylolite (whcalcite cement C5 occurred during or after the stylolitization phase (sample 130, CT). G) Thefragment (ec). Dissolution gulfs affect C1 and are sealed by C2 (sample 137, CT). H) The bdissolution of an aragonite gastropod (sample 163, CT). I) Secondary pore partly filled with tdue to aragonite to low-Mg calcite replacement. Dissolution gulfs (dg) intersect C3 and C4 (sC1, C2, C3 and C4 (sample 109, CT). K) Detailed view of the blocky calcite cements C4, C5 a

4.4.4. Stage 4: telogenesisThe relatively recent exhumation of the Urgonian limestones

brings the section to meteoric waters. This results in a dissolutionphase (dissolution embayments affect C3 to C5 cements) and in theprecipitation of an Fe-poor non-luminescent cement (C6, Fig. 6CIK)that locally constitutes speleothems.

4.5. SEM observations

The microfabrics of the micritic matrix observed with the SEM aredescribed according to Loreau's classification (Loreau, 1972) (Fig. 7).Units 1 and 3 generally present punctic microfabrics with veryabundant microporosity (Fig. 8A). Unit 5 shows serrate microfabricswith abundant microporosity (Fig. 8B). Serrate and meshed micro-fabrics characterize unit 8. Microporosity is especially present in theserrate facies. Unit 7 possesses a meshed microfabric, with very littlemicroporosity. Units 2, 4, 6, 9 and 10 almost always presentcompletely tight coalescent microfabrics (Fig. 8CD).

The micritic crystals are rhombic in shape and reach about 5 μm insize in the punctic and serrate microfabrics (Fig. 8AB, Fig. 9A), whilethey generally only attain 3 μm and present subhedral rhombic toanhedral shapes in the meshed and coalescent facies (Fig. 8CD,Fig. 9B). Inside the same samples, the microfabric is identical in themicritic allochems (peloids, oncoids, ooids, mud clasts, agglutinatedforaminifera…) as in the matrix.

4.6. Petrophysical properties

Units 1, 3, 5 and 8 characterized by microporous to semi-microporous limestones possess mean porosities and permeabilitiesrating 15.6% and 4.1 mD respectively (varying from 3.6 to 24.6% andfrom less than 0.01 to 12.7 mD). The mean porosity and permeabilityof units 2, 4, 6, 7, 9 and 10 made up of tight limestones rate 2.9% and0.1 mD respectively (varying from 1.3 to 4.9% and from less than 0.01to 1.8 mD) (Table 1, Fig. 2).

4.7. Mineralogical and chemical compositions

The mineralogical composition is very constant throughout thesection studied: almost only low-Mg calcite (more than 99.7% low-Mgcalcite) (Table 2, Fig. 2). Two samples show slight differenceswith lesscontent of low-Mg calcite (unit 6, sample 141: 98.7%; unit 10, sample123: 96.2%) and the presence of low clay percentages (unit 6, sample141: 0.6%; unit 10, sample 123: 1.2%). The total composition iscompleted with quartz and goethite.

The magnesium content always rates less than 0.22% (Table 2). Anexception is recorded in the algal mat facies of unit 10, with a value of0.57% (sample 123). This relatively highmagnesium content is relatedto the presence of clay minerals. The strontium content also remainsvery low, always rating less than 158 ppm throughout the section(Table 2). Again, the algal mat facies diverges from the average with arelatively high value of 372 ppm (unit 10, sample 123). Magnesiumand strontium show a covariant evolution throughout the section.

ographs illustrating the diagenetic phases registered in the Pierre-Blanche section.ped before the micritic internal sediment (is) and the blocky calcite cement C3 (samplete cements C4 and C5 close the bird eye cavity (sample 117, CT). C) Syntaxial calcitee blocky calcite cements C2a, C2b, C3a, C3b and C6. The non-luminescent cement C6D) Intraclast early cemented by isopachous inclusions-rich calcite cement (sample 111,t (ec). They developed before microfracturing of the brachiopod shell (br). The blockyite lines) affects the blocky calcite cements C3 and C4. The precipitation of the blocky

blocky calcite cements C1, C2, C3a, C3b and C4 form overgrowths around an echinodermlocky calcite cements C4, C5 and C6 partly close a secondary pore (po) linked to thehe blocky calcite cements C3a, C3b, C4, C5 and C6. C3a exhibits anhedral limits probablyample 114, CT). J) Original intergranular porosity filled with the blocky calcite cementsnd C6 stained with AF in a partly filled pore (po) (sample 163, LM).

27C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

Fig. 7. Sketch illustrating the Loreau's classification. This classification is based on theprevailing nature of the contacts between micrite crystals. The punctic microfabric ischaracterized by euhedral to subhedral crystals having punctual contacts. The serratemicrofabric describes micrites with euhedral to subhedral crystals connected by theirfaces. In the meshed microfabric, the micritic framework possesses euhedral tosubhedral crystals meshed inside each other. Finally, the coalescent microfabric ischaracterized by coalesced crystals with subhedral to anhedral shapes.

28 C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

4.8. Stable isotopes

The stable isotopes values vary between −5.9 and −2.7‰ PDB inδ18O and −1.0 and +0.9‰ PDB in δ13C (Table 2, Fig. 2). Oxygen andcarbon isotopes present a covariant trend. Units 1, 3, 5, 6 and 8 haverelatively constant values ranging from −5.9 to −4.1‰ PDB in δ18Oand from−1.0 to +0.1‰ PDB in δ13C (mean: δ18O=−5.0‰; δ13C=−0.4‰). Units 2, 7, 9 and 10 possess higher values varying between−4.2 and −2.7‰ PDB in δ18O and +0.1 and +0.9‰ PDB in δ13C(mean: δ18O=−3.7‰; δ13C=+0.4‰). Unit 4 presents two highvalues (mean: δ18O=−3.9‰; δ13C=+0.4‰) and two low values(mean: δ18O=−5.3‰, δ13C=−0.2‰).

Fig. 8. SEM photomicrographs of the micritic matrix. A) Punctic microfabric with rhombic cryWell connected and abundant microporosity. B) Serrate microfabric with rhombic crystmicroporosity. C) Meshed microfabric with rhombic to subhedral rhombic crystals usually srhombic to anhedral crystals generally less than 3 μm in size (sample 141, tight facies).

5. Discussion

5.1. Tight versus microporous limestones

The distribution of the porosity and permeability values through-out the Pierre-Blanche section highlights the strong relationshipbetween the type of limestones (tight to microporous) and thepetrophysical properties (Fig. 2). Limestones of the tight facies (units2, 4, 6, 7, 9 and 10) are characterized by very low porosity andpermeability values (phimean=2.9%; Kmean=0.1 mD). On the con-trary, layers made of microporous and semi-microporous limestones(units 1, 3, 5 and 8) have relatively high porosities and permeabilities(phimean=15.6%; Kmean=4.1 mD).

Moreover, the comparison between porosity and permeabilityvalues and SEM-observations indicates that the petrophysical prop-erties are directly related to the microfabrics of the micritic matrix(Fig. 10). Limestones of the tight facies almost only present coalescentmicrofabrics made of subhedral rhombic to anhedral small crystals(b3 μm). Only twice, meshed microfabrics are observed in such tightlimestones. On the contrary, layers characterized by microporousfacies always possess punctic microfabrics with large rhombic crystals(~5 μm). In an intermediate state, semi-microporous limestones showserrate to meshed microfabrics.

The alternation between tight and microporous layers cannot beexplained in terms of different depositional textures (Fig. 11) andpetrographical content. The most frequent limestones in the sectionare packstones to grainstones and floatstones with packstone matrixto floatstones with grainstone matrix. These limestones containingbivalves, echinoderms, green algae, large and small foraminifera,

stals. The largest crystals generally reach 5 μm in size (sample 113, microporous facies).als characterized by size up to 5 μm (sample 134, semi-microporous facies). Somemaller than 3 μm (sample 144, tight facies). D) Coalescent microfabric with subhedral

Table 1Porosity and permeability values for the three types of limestones. Microporouslimestones have high porosities and permeabilities (phimean=20.3%; Kmean=5.9 mD).Semi-microporous limestones possess intermediate values of porosity and permeability(phimean=11.0%; Kmean=2.4 mD). Tight limestones present very low porosities andpermeabilities (phimean=2.9%; Kmean=0.1 mD).

phi K

[%] [mD]

Microporous limestones 109 24.6 12.7110 19.6 2.1113 20.5 6.4115 14.4 3.7125 19.3 5.7126 19.1 7.4127 19.7 3.5128 22.7 3.7129 23.1 8.1Mean 20.3 5.9

Semi-microporous limestones 112 3.6 0.3114 15.8 12.5118 14.5 3.3121 12.4 1.5124 10.7 0.2134 11.9 0.8135 4.0 b0.01136 15.2 2.7137 10.4 b0.01Mean 11.0 2.4

Tight limestones 111 2.6 1.78117 4.1 b0.01130 1.3 b0.01131 3.8 b0.01132 3.3 b0.01133 1.4 b0.01138 1.8 b0.01139 4.9 b0.01140 2.9 b0.01141 1.6 b0.01142 4.8 b0.01143 2.4 b0.01144 3.0 b0.01162 2.3 b0.01Mean 2.9 0.1

Fig. 9. Backscattered-SEM photomicrographs of the micritic matrix. The samples wereimpregnated by epoxy, polished and slightly etched (1min in a solution of 2.5 g EDTA/250 ml H2O). A) Punctic microfabric made of rhombic crystals with size sometimesreaching about 5 μm. The black zones represent the microporous network (sample 125,microporous facies). B) Coalescent microfabric with subhedral rhombic to anhedralcrystals with size generally about 3 μm (sample 111, tight facies). There is almost nomicroporosity.

29C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

oncoids and peloids, characterize both the tight and the microporousfacies (Fig. 2).

The mineralogical composition is very constant throughout theentire section. Samples are almost always composed of more than 99%low-Mg calcite. Only two samples possess more than 0.5% clays andless than 99% low-Mg calcite. Tight limestones are not enriched withclays in comparison tomicroporous layers (Fig. 2). Consequently clayswhich are often considered to be a factor favoring compaction(Ehrenberg and Boassen, 1993; Ehrenberg, 2004; Lambert et al., 2006)cannot be involved in the formation of these tight limestones.

The Sr content varies slightly, but shows no systematic highervalues in tight layers (Table 2). A differential diagenesis as inlimestone–marl alternations (Munnecke and Samtleben, 1996;Westphal, 2006) linked to a differential aragonite enrichment of theprecursor mud (Lasemi and Sandberg, 1993) is thus not conceivablefor the formation of the tight andmicroporous limestones observed inthe Pierre-Blanche section.

Cathodoluminescence combined with AF staining shows the greatcomplexity of the diagenetic history of these limestones (Table 3,Fig. 5, Fig. 6). However, except for the first and second cement phasesrestricted to the tight units 2 and 9, all the other diagenetic phasesaffect the tight and the microporous units without distinction.Moreover, the proportion of the six main calcite cements (C1 to C6)does not indicate differential macro-cementation between tight andmicroporous layers (Fig. 2). Such an absence of relationship suggeststhat the differentiation between tight and microporous limestones isonly related to early micro-transformations of the micritic matrix.Optical microscope technologies logically remain powerless todirectly observe these features.

Nevertheless, conventional petrography study brings importantclues to understand the context of formation of Pierre-Blanche'smicroporous limestones. Tight intervals of units 2, 4, 7, 9 and 10contain indications of sedimentation in very shallow conditionssubject to emersions (Fig. 2). Limestones of units 2, 4 and 7 possessbird eyes and desiccation cracks indicating intertidal to supratidalenvironments. Unit 9 presents keystone vugs suggesting beachsedimentation. Finally, unit 10 with algal mats constitutes evidentsupratidal deposits.

The oxygen isotopic composition is consistent with relativelyshallow burial diagenesis in contact with meteoric waters (Moss andTucker, 1995; Richard et al., 2007). This interpretation is confirmed bythe carbon isotope values that reflect interactions of the sedimentwith isotopically light CO2 meteoric waters from the vadose zone(James and Choquette, 1984; Morse and Mackenzie, 1990; Richardet al., 2007). The stable isotopic composition of the very shallow-water deposits affected by subaerial exposure (tight units) is higherthan the mean values. Covariant positive peaks of δ13C and δ18Ocharacterized units 2, 4, 7, 9 and 10 (Fig. 2). Such peaks never occur inlagoonal limestones. Covariant trends of δ13C and δ18O are known tocharacterize sedimentation in enclosed lakes (Talbot, 1990; Bellancaet al., 1992; Leng et al., 2006). In this marine environment, they mayexpress deposition in a restricted lagoon mainly influenced byevaporation (Ufnar et al., 2008), with positive peaks indicatingsedimentation in very shallow conditions up to emersion, and

Table 2Calcite, clays, magnesium, strontium contents and stable isotopes values. The samplesare almost only composed of low-Mg calcite. The magnesium and strontium contentsshow a covariant trend. The δ18O and δ13C also present a covariant evolution. The algalmats (sample 123) of the uppermost tight layers are characterized by the highestvalues.

Calcite Clays MgO Sr δ13C δ18O

[mass%] [mass%] [mass%] [ppm] [‰PDB] [‰PDB]

109 99.9 0.0 0.10 97 −0.8 −5.9110 99.9 0.0 0.11 104 −0.5 −5.2111 99.8 0.1 0.21 157 +0.3 −3.8112 99.9 0.0 0.12 135 −0.3 −5.0113 99.9 0.0 0.11 87 −0.7 −5.3114 99.9 0.0 0.09 114 −1.0 −5.9115 99.9 0.0 0.11 84 −0.5 −5.1117 99.8 0.0 0.19 103 +0.1 −4.2118 99.9 0.0 0.13 85 −0.5 −5.0121 99.9 0.0 0.12 80 −0.4 −5.1123 96.2 1.2 0.57 372 +0.9 −2.7124 99.9 0.0 0.14 89 +0.1 −4.8125 99.9 0.0 0.10 79 −0.6 −5.2126 99.9 0.0 0.09 68 −0.5 −5.3127 99.8 0.0 0.11 84 −0.4 −5.1128 99.9 0.0 0.12 74 −0.1 −4.4129 99.9 0.0 0.08 109 −0.5 −5.2130 99.9 0.0 0.20 144 +0.4 −3.7131 99.7 0.2 0.14 92 −0.3 −5.1132 −0.1 −5.5133 99.8 0.1 0.20 127 +0.3 −4.1134 99.9 0.0 0.11 87 −0.4 −5.3135 99.8 0.0 0.11 84 −0.5 −5.7136 99.9 0.0 0.12 94 −0.2 −4.7137 99.9 0.0 0.12 88 −0.3 −5.1138 99.9 0.0 0.15 119 +0.0 −4.7139 99.9 0.0 0.12 88 −0.3 −4.9140 99.9 0.0 0.12 82 −0.6 −4.7141 98.7 0.6 0.13 89 −0.1 −4.1142 99.9 0.0 0.12 110 −0.4 −5.1143 99.9 0.0 0.14 106 −0.5 −5.2144 99.8 0.0 0.14 109 −0.2 −4.7162 99.9 0.0 0.18 129 +0.1 −4.2

30 C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

negative peaks speaking for deposition in deeper waters. Suchisotopic composition reinforces the interpretation based on birdeyes, desiccation cracks, keystone vugs and algal mats, emplacingunits 2, 4, 7, 9 and 10 in intertidal to supratidal environments.

Unit 6 is also made up of tight limestones, but intertidal tosupratidal features are not present and stable isotope compositionsremain around the mean values. However, these lagoonal depositsprobably experienced subaerial exposure linked to the third-orderregional regression (SBHa6) (Fig. 2).

On the contrary, semi-microporous limestones of unit 8 aresituated just below a major sequence boundary (ses). This unusualsituation for semi-microporous facies is due to the erosion of theupper tight interval. Indeed, far from the channel centre, tightlimestones occur laterally below the subaerial erosion surface (ses)(Fig. 4).

5.2. Diagenetic model

The systematic position of tight layers just below sequenceboundaries characterized by emersion suggests the important roleplayed by meteoric waters in the differentiation of tight andmicroporous limestones. Moreover, as the petrophysical propertiesare directly linked to the microfabric of the micritic matrix, theproposed diagenetic model involves early transformations of thecarbonate mud, inside a meteoric phreatic lens (Fig. 12).

In a purely calcitic mud impregnated with slightly unsaturatedwater with respect to calcite, the smallest crystals are the most

unstable. They are preferentially dissolved and nourish overgrowthsaround the largest crystals that represent themost stable crystals. Thisprocess is called “Ostwald ripening” (Ostwald, 1887; Baronnet, 1982;Morse and Casey, 1988). However, in the marine context of Pierre-Blanche, the carbonate mud is mineralogically heterogeneous. Low-Mg calcite crystals mainly compose the muddy sediment, as theCretaceous was characterized by calcite seas (Sandberg, 1983; Hardie,1996; Lowenstein et al., 2001; Dickson, 2002), but aragonite and high-Mg calcite crystals resulting from disintegration of organisms alsoconstitute part of the mud (Fig. 12). In this context, the dissolution ofaragonite and high-Mg calcite crystals and the smallest low-Mg calcitecrystals leads to the ion enrichment in the fluids that nourishovergrowths around the most stable low-Mg calcite crystals (Voleryet al., 2009). This process, affecting a mud of relatively constantchemical composition (CaCO3 with variable Mg content) butcharacterized by different mineralogies, could be named “hybridOstwald ripening”.

During an emersive episode, a meteoric lens may developthroughout the carbonate sediment. In the vadose zone, dissolutionmostly occurs. However, in the uppermost meters of the phreatic zone(ionic active zone), selective dissolution of small and unstable crystalspermits the precipitation of calcite overgrowths around the moststable micrite crystals (according to the “hybrid Ostwald ripening”process) (Fig. 12). These overgrowths are visible in the size andmorphology of crystals composing the matrix and the micriticallochems. Indeed, the microporous facies possesses larger crystals(~5 μm) than the tight facies (b3 μm). Moreover, micrite crystals ofmicroporous limestones have a euhedral rhombic shape, consistentwith overgrowths precipitation, contrary to tight limestones.

These calcite overgrowthsmay consolidate themicritic frameworkof the carbonate mud. Because of this partial early cementation, thecarbonate sediment resists compaction and partly conserves itsoriginal microfabric with intercrystalline microporosity during burial.On the contrary, carbonate sediments from the vadose zone, the lowerpart of the phreatic meteoric lens and the phreatic marine zone thathave not experienced calcite overgrowths will undergo compactionand become tight limestones (Fig. 12). The semi-microporous faciesprobably results of an intermediate state of early cementation. Theprecursor sediments also experienced calcite overgrowths andconsolidation of their micritic framework, but in a less efficient way(shorter immersion or immersion in a less ionically active zone of themeteoric lens) than for the microporous facies. During burial, they aremore affected by compaction and change into limestones withstronger cohesion, but have lower petrophysical properties than themicroporous limestones (Table 1).

To summarize, alternations between tight and microporous lime-stones in the Pierre-Blanche section are principally due to thedevelopment and shifting of the vadose and phreatic meteoric zoneslinked to synsedimentary emersion episodes. Later, circulation oftelogenetic meteoric fluids within the microporous units (dissolutionembayments affect the blocky calcite cements C3 to C5) probablyimproves the intercrystalline microporosity of the matrix, thusamplifying the petrophysical differences between tight and micropo-rous layers. However, fluids involved in late dissolution phases wereable to circulate in microporous limestones, because their precursorcarbonate sediments were rapidly cemented after sedimentation andhave resisted compaction. The original differentiation between tightand microporous limestones occurs very early in the diagenetichistory.

6. Conclusions

The Urgonian limestones of the Pierre-Blanche section comprisealternations of hard tight limestones and chalky microporous lime-stones. Contrasting porosity and permeability values differentiate the

Fig. 10. Graph of porosity versus permeability for the four different types of matrix microfabric. Punctic microfabrics possess the highest porosity and permeability values. Serratemicrofabrics present also relatively high petrophysical properties. Coalescent and meshed microfabrics generally have very low porosities and permeabilities.

Fig. 11. Graph of porosity versus permeability in relation to the different depositional textures. No clear relationship can be detected. (Meaning of the abbreviations: WA:wackestone, PA: packstone, GR: grainstone, FL: floatstone, FP: floatstone with packstone matrix, FG: floatstone with grainstone matrix.)

31C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

Table 3Main characteristics of the 18 diagenetic phases found in the Pierre-Blanche section. The 18 phases are divided into four main diagenetic stages.

Diageneticphase

Morphology Calcite cement: Fe contentand luminescence

Remarks Affectedunits

Parent waters,probable origin

Step 1:Synsedimentary diagenesis(associated with uncomformities)

Micritic cement Meniscus+equantisopachous

Fe-poor, cloudyluminescence

Locally associatedwith bird-eyes+desiccation cracks;cut by burrows

2+9 Marine to mixed waters,linked to unconform. atthe top of units 2+9

Inclusions-richcalcite cement

Equant isopachous Fe-poor, cloudybrown luminescence

In intraclasts+bored pebbles

2+9 Marine to mixed waters,linked to unconform. atthe top of units 2+9

Calcite cement(C1)

Syntaxial Fe-poor, non-luminescentwith sometimesyellow bands

Aroundenchinodermfragments, poorlydeveloped

1 to 8 Meteoric waters, linked tothe subaerial erosionsurface at the top of unit 8

Minordissolution

Embayments affectingC1+aragonite biocl.

Sealed by C2 1 to 8 Meteoric waters, linked tothe subaerial erosionsurface at the top of unit 8

Step 2:Shallow burial diagenesis

Calcite cement(C2)

Blocky 2 subzones: a) Fe-rich,brown to dark orange;b) Fe-rich to Fe-poor,bright yellow

All units Shallow burial slightlyreduced waters

Microfractures All units Lithostatic pressureCalcite cement(C3)

Blocky 2 subzones: a) Fe-rich,orange with brownbands; b) Fe-rich, finelybanded brown

Anhedral growthfaces indicatereplacement ofaragonite by low-Mgcalcite

All units Shallow burialslightly reduced waters

Fractures (F1) All units Lithostatic pressureCalcite cement(C4)

Blocky Fe-poor, 2 non-luminescentsubzones (C4a+C4b)separated by yellow tobrown bands

All units Meteoric waters, prob.linked to the unconform.at the top of the Urgonianlimestones

Rare minordissolution

Embayments affectingC4a

All units Meteoric waters, prob.linked to the unconform.at the top of the Urgonianlimestones

Step 3:Burial diagenesis

Fractures (F2) All units UnknownCalcite cement(C5)

Blocky Fe-rich, dark brownluminescence

All units Burial reduced waters

Stylonites Horizontal All units Lithostatic pressureFractures (F3) Partly sealed by C5 All units Compression prob. linked

to the Jura foldingStylonites Sub-vetical Partly sealed by C5 All units Compression prob. linked

to the Jura foldingFracture (F4) Partly sealed by C5 All units Compression prob. linked

to the Jura foldingStep 4:Telogenesis(Urgonian limestone exhumation)

Majordissolution

Embaymenetsaffecting C3 to C5

Partly sealed by C6 All units Percolation of relativelyrecent meteoric waters

Calcite cement(C6)

Blocky+speleothems Fe-poor, poorlyluminescent

Overgrowthsaround C5 or crustsin open fractures

All units Percolation of relativelyrecent meteoric waters

32 C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

two facies. These petrophysical properties directly correspond to themicrofabrics of the micritic matrix.

Thedifferentiationbetween the tight and themicroporous facies is notrelated to the depositional texture or the petrographical content.Moreover, the mineralogical and geochemical compositions remain veryconstant throughout all the section and cannot explain the differentiation.

Tight limestones are systematically situated just below a sequenceboundary characterized by emersion. This position suggests the impor-tance of meteoric water input rapidly after sedimentation, in thedifferentiation between tight andmicroporous limestones. The diageneticmodelproposed for the formationofmicroporous limestones is basedona“hybrid Ostwald ripening” process. Inside the upper meteoric phreaticzone, the most unstable crystals (the smallest low-Mg calcite crystals,aragonite and high-Mg calcite crystals coming from the disintegration oforganisms) are preferentially dissolved. Ions in solution reprecipitatearound themost stablemicrite crystals representedby the largest low-Mgcalcites. These overgrowths consolidate the micritic framework. Becauseof this partial early cementation, the carbonate sediment resists

compaction and partly preserves its original microfabric with intercrys-tallinemicroporosity during burial. On the contrary, carbonate sedimentsthat did not undergo early cementation strongly suffer compaction andchange into tight limestones.

Most of the carbonate sediments evolve into tight limestonesduring burial. However, when a sediment composed of a micriticmatrix mainly made of low-Mg calcite crystals (calcite sea period)experienced partial early cementation (linked to the development of ameteoric phreatic lens) rapidly after sedimentation, microporouslimestones can develop. The understanding of these two main factorsmay greatly improve the knowledge and modeling of some micropo-rous carbonate reservoirs.

Acknowledgements

This research was funded by the University of Geneva and by TotalExploration and Production. The authors would like to thank the twoanonymous reviewers for their constructive remarks.

Fig. 12. Sketch illustrating the differentiation between the microporous and tight facies. Pictures 1 to 4 represent a shallow-marine carbonate platformwith sedimentation occurringin a calcite sea and during a long-term transgression or highstand period (Volery et al., 2009). Pictures A to D (microporous facies) andW to Z (tight facies) show the evolution of themicritic sediment (width of the pictures: ~15 μm). Stage 1: Carbonate muds constitute the matrix of a sediment rich in oncoids, peloids, foraminifera, bivalves, echinoderms, greenalgae and gastropods. These muds are mainly composed of low-Mg calcite crystals, with some aragonite needles and high-Mg calcite crystals coming from the disintegration oforganisms (pictures A and W). Stage 2: During a short-term regression, a meteoric phreatic lens develops in the sediment. Inside the lens (mostly at its top), the dissolution of themost unstable crystals (aragonites, high-Mg calcites and smallest low-Mg calcites) nourishes overgrowths around the most stables micrite crystals (largest low-Mg calcites) (pictureB). The precipitation of these calcite overgrowths consolidates the original microfabric of the matrix, while partly preserving the primary intercrystalline microporosity. Carbonatesediments situated outside of the meteoric lens are unaffected by these dissolution–reprecipitation processes. They remain mostly unchanged (picture X). Stage 3: A transgressionsubmerges again the sediments. The return to marine conditions stops the dissolution–reprecipitation processes affecting the micritic matrix and no more modifications occur(picture C). Carbonate sediments that have transited inside the meteoric lens constitute an early cemented layer. Sediments situated outside of the meteoric lens remain mostlyunchanged (picture Y). Stage 4: The deposition of sediments (light gray) in the accommodation space causes the compaction of the previous deposits (dark gray). The earlycemented layer resists to compaction and results in microporous limestones (picture D, punctic to serrate microfabric). On the contrary, sediments that did not undergo earlycementation strongly suffer compaction and change into tight limestones (picture Z, coalescent microfabric).

33C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

References

Alsharhan, A.S., Nairn, A.E.M., 2003. Sedimentary Basins and Petroleum Geology of theMiddle East. Elsevier, Amsterdam.

Baronnet, A., 1982. Ostwald ripening in solution — the case of calcite and mica. Estud.Geol. 38, 185–198.

Bellanca, A., Calvo, J.P., Censi, P., Neri, R., Pozo, M., 1992. Recognition of lake-levelchanges in Miocene lacustrine units, Madrid Basin, Spain. Evidence from faciesanalysis, isotope geochemistry and clay mineralogy. Sed. Geol. 76 (3–4), 135–153.

Budd, D.A., 1989. Micro-rhombic calcite and microporosity in limestones: a geochem-ical study of the lower cretaceous Thamama group, U.A.E. Sed. Geol. 63 (3–4),293–311.

Burkhard, M., Sommaruga, A., 1998. Evolution of the western Swiss Molasse basin:structural relations with the Alps and the Jura belt. In: Mascle, A., Puigdefabregas,C., Luterbacher, H.P., Fernandez, M. (Eds.), Cenozoic Foreland Basins of WesternEurope. Geological Society, London, pp. 279–298.

Cavazza, W., Roure, F.M., Spakman, W., Stampfli, G.M., Ziegler, P.A., 2004. The TransmedAtlas: The Mediterranean Region from Crust to Mantle. Springer, Berlin.

Charollais, J., Clavel, B., Schroeder, R., Busnardo, R., Decrouez, D., Cherchi, A., 2003. Lamigration de la plate-forme urgonienne entre le Jura plissé et les Chaînessubalpines septentrionales (France, Suisse) — Evolution of the Urgonian platformbetween the Jura and the Septentrional Subalpine Chains (France, Switzerland).Geobios 36 (6), 665–674.

Charollais, J., Weidmann, M., Berger, J.-P., Engesser, B., Hotellier, J.-F., Gorin, G.,Reichenbacher, B., Schäfer, P., 2007. La molasse du bassin franco-genevois et sonsubstratum. Arch. Sci. 60 (2–3), 59–174.

Charollais, J., Clavel, B., Busnardo, R., Conrad, M., Müller, A., Decrouez, D., 2009. Olistolithes etcoulées bioclastiques, prémices de l’installation de la plate-forme urgonienne auxconfins des Bornes et des Aravis (Haute-Savoie, France). Arch. Sci. 62, 35–70.

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 desSciences 302 (8), 583–586.

Clavel, B., Charollais, J., Busnardo, R., 1987. Données biostratigraphiques nouvelles surl'apparition des faciès urgoniens du Jura au Vercors. Eclogae Geol. Helv. 80 (1), 59–68.

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 toSouth-East France. Zeitschrift der Deutschen Gesellschaft für Geowissenschaften158 (4), 1025–1062.

Clavel, B., Decrouez, D., Charollais, J., Busnardo, R., 2009. "Paracoskinolina" praereichelin. sp., un orbitolinidé (foraminifère) nouveau de l'Hauterivien supérieur et duBarrémien inférieur (Crétacé) à faciès urgonien (SE France, Jura franco-suisse,Préalpes suisses). Arch. Sci. 62, 1–10.

Dickson, J.A.D., 2002. Fossil echinoderms as monitor of the Mg/Ca ratio of thePhanerozoic oceans. Science 298, 1222–1224.

Donzeau, M., Wernli, R., Charollais, J., Monjuvent, G., 1997. Notice explicative, Cartegéologique France (1/50'000), feuille Saint-Julien-en-Genevois (653). BRGM, Orléans.

Ehrenberg, S.N., 2004. Factors controlling porosity in Upper Carboniferous–LowerPermian carbonate strata of the Barents Sea. AAPG Bull. 88 (12), 1653–1676.

Ehrenberg, S.N., Boassen, T., 1993. Factors controlling permeability variation insandstones of the Garn Formation in Trestakk Field, Norwegian continental shelf.J. Sed. Res. 63 (5), 929–944.

34 C. Volery et al. / Sedimentary Geology 230 (2010) 21–34

Godet, A., 2006. The Evolution of the Urgonian Platform in the Western Swiss JuraRealm and Its Interactions with Palaeoclimatic and Palaeoceanographic Changealong the Northern Tethyan Margin (Hauterivian–Earliest Aptian). University ofNeuchâtel, Neuchâtel.

Hardie, L.A., 1996. Secular variation in seawater chemistry: an explanation for thecoupled secular variation in the mineralogies of marine limestones and potashevaporites over the past 600 m.y. Geology 24 (3), 279–283.

Homewood, P., Allen, P.A., Williams, G.D., 1986. Dynamics of the Molasse Basin ofwestern Switzerland. In: Allen, P.A., Homewood, P. (Eds.), Foreland Basins.Blackwell, Oxford, pp. 199–217.

Hunt, D., Tucker, M.E., 1993. The Middle Cretaceous Urgonian platform of southeasternFrance. In: Simo, J.A.T., Scott, R.W., Masse, J.-P. (Eds.), Cretaceous CarbonatePlatforms. AAPG, Tulsa, pp. 409–453.

James, N.P., Choquette, P.W., 1984. Diagenesis 9: limestones — the meteoric diageneticenvironment. Geosci. Can. 11 (4), 161–194.

Kaldi, J., 1989. Diageneticmicroporosity (chalky porosity),MiddleDevonianKee Scarp reefcomplex, NormanWells, Northwest Territories, Canada. Sed. Geol. 63 (3–4), 241–252.

Lambert, L., Durlet, C., Loreau, J.-P., Marnier, G., 2006. Burial dissolution of micrite inMiddle East carbonate reservoirs (Jurassic–Cretaceous): keys for recognition andtiming. Mar. Petrol. Geol. 23 (1), 79–92.

Lasemi, Z., Sandberg, P.A., 1993. Microfabric and compositional clues to dominant mudmineralogy of micrite precursors. In: Rezak, R., Lavoie, D.L. (Eds.), CarbonateMicrofabrics. Springer, New-York, pp. 173–185.

Laubscher, H., 1992. Jura kinematics and the Molasse Bassin. Eclogae GeolegicaeHelvetiae 85 (3), 653–675.

Leng, M.J., Lamb, A.L., Heaton, T.H.E., Marshall, J.D., Wolfe, B.B., Jones, M.D., Holmes, J.A.,Arrowsmith, C., 2006. Isotopes in lake sediments. In: Leng, M.J. (Ed.), Isotopes inPalaeoenvironmental Research. Springer, Dordrecht, pp. 147–184.

Loreau, J.-P., 1972. Pétrographie de calcaires fins au microscope électronique àbalayage: introduction à une classification des “micrites”. Comptes Rendus del'Académie des Sciences 274 (6), 810–813.

Lowenstein, T.K., Timofeeff, M.N., Brennan, S.T., Hardie, L.A., Demicco, R.V., 2001.Oscillations in Phanerozoic seawater chemistry: evidence from fluid inclusions.Science 294, 1086–1088.

Morse, J.W., Casey, W.H., 1988. Ostwald processes and mineral paragenesis insediments. Am. J. Sci. 288 (6), 537–560.

Morse, J.W., Mackenzie, F.T., 1990. Geochemistry of Sedimentary Carbonates. Elsevier,Amsterdam.

Moshier, S.O., 1989. Development of microporosity in a micritic limestone reservoir,Lower Cretaceous, Middle East. Sed. Geol. 63 (3–4), 217–240.

Moss, S., Tucker, M.E., 1995. Diagenesis of Barremian–Aptian platform carbonates (theUrgonian Limestone Formation of SE France): near-surface and shallow-burialdiagenesis. Sedimentology 42 (6), 853–874.

Munnecke, A., Samtleben, C., 1996. The formation of micritic limestones and thedevelopment of limestone–marl alternations in the Silurian of Gotland, Sweden.Facies 34 (1), 159–176.

Ostwald, W., 1887. Lehrbuch der Allgemeinen Chemie, 2. Verlag von WilhelmEngelmann, Leipzig.

Perkins, R.D., 1989. Origin of micro-rhombic calcite matrix within Cretaceous reservoirrock, West Stuart City Trend, Texas. Sed. Geol. 63 (3–4), 313–321.

Richard, J., Sizun, J.P., Machhour, L., 2007. Development and compartmentalization ofchalky carbonate reservoirs: the Urgonian Jura-Bas Dauphine platform model(Genissiat, southeastern France). Sed. Geol. 198 (3–4), 195–207.

Ruffell, A.H., Batten, D.J., 1990. The Barremian–Aptian arid phase in western Europe.Palaeogeogr. Palaeoclimatol. Palaeoecol. 80, 197–212.

Sandberg, P.A., 1983. An oscillating trend in Phanerozoic non-skeletal carbonatemineralogy. Nature 305, 19–22.

Talbot, M.R., 1990. A review of the palaeohydrological interpretation of carbon andoxygen isotopic ratios in primary lacustrine carbonates. Chemical Geology: IsotopeGeoscience section 80 (4), 261–279.

Ufnar, D.F., Gröcke, D.R., Beddows, P.A., 2008. Assessing pedogenic calcite stable-isotope values: can positive linear covariant trends be used to quantify palaeo-evaporation rates? Chem. Geol. 256 (1–2), 46–51.

Volery, C., Davaud, E., Foubert, A., Caline, B., 2009. Shallow-marine microporouscarbonate reservoir rocks in the Middle East: relationship with seawater Mg/Caratio and eustatic sea level. J. Pet. Geol 32 (4), 313–325.

Volery, C., Davaud, E., Foubert, A., Caline, B., 2010. Lacustrine microporous micrites ofthe Madrid Basin (Late Miocene, Spain) as analogues for shallow-marinecarbonates of the Mishrif reservoir Formation (Cenomanian–early Turonian,Middle East). Facies 56 (3), 385–397.

Westphal, H., 2006. Limestone–marl alternations as environmental archives and therole of early diagenesis: a critical review. Int. J. Earth Sci. 95 (6), 947–961.