Diagenetic evolution of Tortonian temperate carbonates close to evaporites in the Granada Basin (SE Spain)

    Diagenetic evolution of Tortonian temperate carbonates close to evaporites in the Granada Basin (SE Spain) ´ Puga-Bernab´eu, X. Guichet A. L´opez-Quir´os, M. Barbier, J.M. Mart´ın, A. PII: DOI: Reference:

S0037-0738(16)00064-6 doi: 10.1016/j.sedgeo.2016.02.011 SEDGEO 4998

To appear in:

Sedimentary Geology

Received date: Revised date: Accepted date:

26 October 2015 10 February 2016 12 February 2016

Please cite this article as: L´ opez-Quir´ os, A., Barbier, M., Mart´ın, J.M., Puga´ Guichet, X., Diagenetic evolution of Tortonian temperate carbonates Bernab´eu, A., close to evaporites in the Granada Basin (SE Spain), Sedimentary Geology (2016), doi: 10.1016/j.sedgeo.2016.02.011

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ACCEPTED MANUSCRIPT Diagenetic evolution of Tortonian temperate carbonates close to evaporites in the Granada Basin (SE Spain) López-Quirós, A.1, 2*, Barbier, M.2, Martín, J.M.3, Puga-Bernabéu, Á.3,

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Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Avda. de las

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Guichet, X.2

Palmeras 4, 18100 Armilla, Granada, Spain. 2

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IFP Énergies Nouvelles, 1-4 Avenue de Bois-Préau, 92852 Rueil-Malmaison, France.

Departamento de Estratigrafía y Paleontología, Universidad de Granada. Campus de

*Corresponding author: [email protected]

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:

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Fuentenueva s.n., 18002 Granada, Spain.

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Abstract

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The Granada Basin (SE Spain) is a small basin located in the central part of the Betic

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Cordillera, structured as such in the late Tortonian and initially connected to the Atlantic Ocean and to the Mediterranean Sea. During the late Tortonian, normal marine conditions prevailed, leading to the deposition of skeletal carbonate sediments on

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platforms around structural highs. The marine connections were later interrupted, first to the Atlantic Ocean and then to the Mediterranean Sea, and a thick evaporite sequence, marking the transition from marine to continental conditions, was deposited during the latest Tortonian. In this work, the diagenetic evolution of the Tortonian Temperate Carbonates (TTC), underlying and close to the evaporite bodies, is revealed and discussed. The diagenetic study includes petrographic analyses (conventional petrography, cathodoluminescence, and fluorescence), geochemical analyses (major, minor and trace elements, and δ13C and δ18O stable isotopes), and microthermometry of fluid inclusions. In the TTC, marine diagenetic processes such as micritization and fibrous calcite-cement precipitation and mechanical compaction took place during or 1

ACCEPTED MANUSCRIPT just after deposition (Eogenesis). An initial burial event (Mesogenesis 1) is characterized by: 1) stabilization of the temperate-water carbonates by freshwater, and

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2) porosity occlusion via precipitation of low-Mg bladed and syntaxial/mosaic calcite

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cements. The TTC were then subaerially exposed (or got close to the surface) during

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evaporite deposition and underwent pedogenesis, Mg-smectite infiltration, and pyrite formation (Telogenesis 1). Subsequent brine-related diagenetic alterations, such as dolomitization and silica, halite, and sylvite replacements of carbonate grains occurred

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during a second burial episode (Mesogenesis 2) concomitant with the Messinian

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lacustrine deposition, this being followed by chemical compaction (stylolite formation). Finally, the area was uplifted and the TTC exhumed. Microstalactitic (dripstone) and fiber/whisker calcite cement precipitation and extensive dissolution relate to this

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Pliocene-Quaternary late event (Telogenesis 2). In the study case diagenetic history is closely linked to basin evolution, as diagenetic pathways of carbonate rocks were

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related to major geodynamic events, including basin restriction leading to evaporite deposition, and several episodes of subsidence and uplift. Up to now, only very few

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diagenetic studies have attempted to demonstrate this correlation between diagenetic history and basin evolution. Keywords: Granada Basin, Temperate-water carbonates, Diagenesis, Migrating brines, Evaporites, Tortonian.

1. Introduction

The study of diagenesis bears significant economic interest, given that diagenesis accounts for porosity and permeability evolution (Ehrenberg, 2007).

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ACCEPTED MANUSCRIPT Diagenetic transformations can strongly influence the ability of the sedimentary rocks to host economic quantities of water, gas, oil, and minerals (Ehrenberg and Nadeau, 2005;

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Rossi, 2010). In this respect, it is essential to ascertain the chemical conditions, nature,

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and timing of the diagenetic processes altering sediment and sedimentary-rock

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properties.

Focusing on the diagenetic evolution of carbonate rocks underlying evaporites, the present work examines the impact of brine circulation and associated diagenetic

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transformations on potential, carbonate-rock reservoirs close to evaporites, calibrating

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their relative importance with respect to other, non-evaporite-linked diagenetic transformations that these same rocks could have undergone. The relevance of this study relates to the considerable interest for the exploration and production of pre-salt

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reservoirs, which represent some of the main oil and gas sources discovered over the last decade. For example, the “Pre-Salt Carbonates of the South Atlantic” have emerged

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as among the most prolific petroleum systems in the world, providing many billions of barrels of oil reserves (Beasley et al., 2010; Verwer and Lukasik, 2014).

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The Granada Basin (SE Spain), selected for this study, is located in the central part of the Betic Cordillera. This basin was initially marine and was isolated from the sea during the latest Tortonian. As a result, a thick (up to 500 m thick) salt (halite) sequence accumulated at its centre (García Veigas et al., 2013). In the Granada Basin, post-salt sediment burial is not deep enough to reach the critical values needed to induce halokinesis salt movements (Hudec and Jackson, 2007). This young sedimentary basin thus provides the suitable context to check the effects of early diagenetic processes in carbonates underlying evaporites before a strong burial event occurs, such as the one undergone by the South Atlantic carbonate reservoirs. The structural and

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ACCEPTED MANUSCRIPT sedimentological framework of the Granada Basin is well constrained (see below), but no diagenetic studies have been conducted until now in any of its deposits.

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The Tortonian temperate-carbonate (TTC) sediments, deposited prior to the

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evaporites in the Granada Basin, constitute the target for this work. Temperate-water

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carbonates (Lees and Buller, 1972), also known as cool-water (Brookfield, 1988) or non-tropical carbonates (Nelson, 1988), are common shallow-water marine deposits in the Neogene basins of southern Spain. In the Mediterranean-linked basins of the Betic

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Cordillera (sensu Braga et al., 2003), such as the Granada Basin, they developed at

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different times during the Neogene and alternate with tropical carbonates (Martín et al., 2010). In the Atlantic-linked basins (Guadalquivir and Ronda basins) their presence was overwhelming in siliciclastic-free, shallow-water platform areas all along the Neogene

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(Baceta and Pendón, 1999; Gläser and Betzler, 2002; Martín et al., 2009; Braga et al.,

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2010; Aguirre et al., 2015).

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2. Geological Setting

The Granada Basin is a small (50 x 50 km) Neogene intramontane basin located in the central sector of the Betic Cordillera (Fig. 1), at the contact between the two major domains, i.e. the Internal Zones (cropping out at Sierra Tejeda, Sierra de la Pera and Sierra Nevada), and the External Zones (cropping out at Sierra Gorda and Sierra Arana; Fig. 2). Its Neogene-Quaternary infilling (Fig. 3) unconformably overlies an irregular, fault-controlled, basement palaeorelief surface (Morales et al., 1990). The main fault systems have an EW orientation (Sanz de Galdeano, 2008). Secondary faults, trending NW-SE, cut and displace the major EW faults and define the principal

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ACCEPTED MANUSCRIPT subsiding areas of the central and eastern part of the basin (Rodríguez-Fernández and Sanz de Galdeano, 2006).

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The current Granada Basin depression formed in the late Tortonian (at around

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8.3 Ma: Braga et al., 2003; Rodríguez-Fernández and Sanz de Galdeano, 2006; Corbí et

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al., 2012). The sedimentary infilling extends from the upper Tortonian to the Quaternary. Older continental and marine, lower-middle Miocene sediments (Braga et al., 1996), cropping out at the eastern and southern margins of the depression (Figs 2

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and 3), were deposited in a former basin with a completely different structure (Braga et

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al., 2003).

During the late Tortonian (8.3 to 7.3 Ma) major tectonic activity took place in the north-eastern and eastern highland edges of the basin (Sierra Arana and Sierra

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Nevada, Figs. 2 and 3), leading to the deposition of significant quantities of terrigenous sediments at the base of the uplifted areas (Braga et al., 1990, 2003; Martín and Braga,

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1997). Marine conditions prevailed and skeletal carbonate sediments accumulated in siliciclastic-free areas on platforms all around the margins of the basin. Temperate-

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water carbonates (Puga-Bernabéu et al., 2008) formed first, between 8.3 and 7.8 Ma (Corbí et al., 2012), followed by tropical, coral-reef carbonates (Braga et al., 1990), between 7.8 and 7.3 Ma (Corbí et al., 2012). The Tortonian Temperate Carbonates (TTC) have been studied in detail at one locality (Alhama de Granada) by PugaBernabéu et al. (2008). They consist of carbonates (calcarenites and calcirudites), and mixed siliciclastic-carbonate sediments, containing abundant fragments of bryozoans, bivalves, and coralline algae, and smaller amounts of echinoids, benthic foraminifers and brachiopods. During the late Tortonian the Granada Basin was a marine embayment initially connected to the Atlantic Ocean to the northwest (Martín et al., 2014) and to the

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ACCEPTED MANUSCRIPT Mediterranean Sea to the south and west (Braga et al., 1990). In the course of the late Tortonian, these marine connections were interrupted first to the Atlantic Ocean and

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then to the Mediterranean Sea (Martín et al., 1984, 2014; Braga et al., 1990; 2003). As a

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result the basin desiccated (Martín et al., 1984) in the latest Tortonian (7.3 to 7.2 Ma,

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Corbí et al., 2012). An evaporitic basin developed with stromatolites at the margin (Martín et al., 1984; García-Veigas et al., 2015), selenite gypsum accumulating in its shallow-water areas (Dabrio et al., 1982) and halite in its centre (García-Veigas et al.,

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2013). The resulting evaporitic unit, the “Lower Evaporite Unit” sensu Dabrio et al.

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(1982), marks the marine-to-continental transition in basin evolution (Martín et al., 1984).

During the Messinian, the uplift of the Granada Basin continued and it was filled

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by continental alluvial-fan, and fluviatile and lacustrine deposits including carbonates and evaporites (the “Upper Evaporite Unit” sensu Dabrio et al., 1982) (Dabrio et al.,

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1982; Martín et al., 1984; Fernández et al., 1996; García-Alix et al., 2008; Figs. 2 and 3). Finally, during the Pliocene and the Quaternary, deposition was limited to small,

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fault-controlled, high-subsidence depocentres (Morales et al., 1990; RodríguezFernández and Sanz de Galdeano, 2006; García-Alix et al., 2008), filled by detrital sediments (Fig. 3).

3. Database and analytical methods

3.1. Facies analysis This study is based on the detailed examination of two outcrop sections near the village of Cacín, located between Ventas de Huelma and Alhama de Granada (Fig. 4A). 6

ACCEPTED MANUSCRIPT The two sections are named Cacín-1 (3630 m south of Cacín) and Cacín-2 (1400 m southward from Cacín-1) (Fig. 4B). Both outcrops lie within the depositional area of the

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evaporites (Fig. 4A). According to the dipping of the TTC in the Cacín River Canyon

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(general dip of the strata is about 5° to north-northwest), both sections represent the

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same stratigraphic interval. At Cacín, TTC are up to 40 m thick. They unconformably overlie and onlap an irregular basement palaeorelief made up of Triassic dolostones and are covered by upper Tortonian marls, about 50 m thick (Fig. 5A). These marls are the

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basinal, lateral equivalents of coastal fan-delta detrital deposits and coral-reef

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limestones (Fig. 3). The whole succession is capped by uppermost Tortonian evaporites (Fig. 5A), consisting here of a 40 m-thick selenite-gypsum succession (Dabrio et al., 1982; García-Veigas et al., 2015).

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Outcrop sections were logged in detail (Fig. 5) and 32 carbonate rock samples were collected (17 from Cacín-1 and 15 from Cacín-2). Facies analysis was made, based

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on macroscopic and microscopic observations on thin sections. Facies types were differentiated and interpreted in terms of lithology, components, textures, grain sizes,

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sedimentary-structures and bioturbation, following Purser (1980) and Tucker and Wright (1990). Facies classification is after Dunham (1962), Embry and Klovan (1971), and James and Bourque (1992).

3.2. Petrographic analysis Thirty-two thin sections (from each rock sample), about 30 μm thick, were prepared and impregnated by a blue epoxy (EpoBlue®) to distinguish pores from textural components. The thin sections were stained with Alizarin red-S and potassium ferricyanide in order to distinguish calcite from dolomite, as well as ferroan phases in both minerals (Dickson, 1966). Thin sections were scanned before and after the staining

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ACCEPTED MANUSCRIPT using a high-resolution scanner (EPSON PERFECTION V750 PRO). All thin sections were examined under polarized and cross-polarized light with a Nikon Eclipse LV 100

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POL optical microscope. During the petrographic study, several sets of images were

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taken with a camera (ProgRes C10) connected to the microscope and captured with the

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ProgRes 2.1 image-management program. The thin-section study using the petrographic microscope allowed the reconstruction of the paragenetic sequences by careful examination of the relationships among grains, cements, and porosity. Four thick

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sections (100 μm) were prepared to calibrate the microthermometry of fluid inclusions.

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Cathodoluminescence (CL) microscopy with an optical polarization microscope (Nikon Eclipse ME 600) equipped with a Technosym Cold CL connected to an OPEA system (Cathodyne OPEA, France) was used to identify different cement types, growth

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features, and relationships among the crystals (see Meyers, 1974; Scholle and UlmerScholle, 2003). The gun potential was 16-20 kV, with a 420-66 μA beam current, 0.05

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Torr vacuum and 5 mm beam width. For further investigation on the origin of depositional and diagenetic carbonate

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phases, the thin sections were also examined with a Nikon Eclipse LV 100 POL microscope equipped with a Mercury vapour lamp (100 W). Applied to carbonates UVlight enables the identification of organic substances, to distinguish grains and textures, and to highlight diagenetic fabrics, specifically different stages of cement-growth generations, and porosity evolution (Dravis and Yurewicz, 1985). SEM examinations were performed on two carbon-coated samples (from the Cacín-2 outcrop) analysed with a Zeiss Evo Ma 10 (10-15 Kv beam current). Highresolution images, surface topographies, and spectrographic analyses of the composition of the samples were made using Secondary Electron Image (SEI), Backscattered Electron Image (BEI) and Energy Dispersive X-ray Spectroscopy (EDS), respectively.

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3.3. Mineralogical and geochemical analysis

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X-ray diffraction (XRD) was used to identify minerals as well as to determine

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the average bulk composition. For XRD determinations, 19 powders from carbonates

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were prepared with an agate mortar, and then analysed with an X’pert PRO PW 3040/60 diffractometer operated at 50 kV, 30 mA. Samples were scanned in the 2θ range from 2

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to 79°, with a step size of 0,033° (2θ)/sec. The counting time was 120 min per sample. Major, minor and trace elements were analysed by Inductively Coupled Plasma

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Mass Spectrometry (ICP-MS). Thirty-one powders from carbonate rocks were sampled with a dental drill (Dremel 225). Contamination between two subsequently drilled

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samples was avoided by using diluted HCl to dissolve the carbonates from the drill

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before each sampling. Sample splits of the powders between 0.25 and 0.5 g were analysed in the ACME Analytical Labs Ltd. (Vancouver, Canada). Prepared powders

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were digested for one hour, in a heating block of a hot water bath, with a modified Aqua Regia solution of equal parts concentrated HCl, HNO3 and DI H2O. Samples were made

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up to volume with diluted HCl. Analyses were performed for 37 elements, of which Ca, Mg, Mn, Fe, Sr, Na, K, Ba, S, Zn, and Al were considered the most important in this study because of their significance in carbonate sedimentology and diagenesis (Brand and Veizer, 1980; Banner, 1995). Thirty-two carbonate powders were sampled with a micro-drill (OLYMPUS SZ61 – MicroMill Sampling System) from six thin sections, in order to measure carbon and oxygen stable-isotope composition (δ13CPDB and δ18OPDB) of bioclastic components and cement phases (<200µm). A micro-drill was used in order to avoid mixing all the cement phases. The same procedure as for the sampling of major, minor, and trace elements was followed to avoid contamination between subsequently drilled samples. 9

ACCEPTED MANUSCRIPT The isotope analyses were performed at the GeoZentrum Nordbayern (FriedrichAlexander-Universität, Erlangen-Nürnberg, Germany). The carbonate powders

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resulting from micro-drilling were reacted with 100% phosphoric acid at 70°C using a

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Gasbench II connected to a Thermo Finnigan Five Plus mass spectrometer. The values

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were presented in per mil relative to the V-PDB standard. All measurements were calibrated by assigning a δ13C value of +1.95‰ and a δ18O of -2.20‰ to NBS19. Reproducibility, checked by replicate analysis of laboratory standards, proved better

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than ± 0.04‰ for δ13C and ± 0.08‰ for δ18O (1 std. dev.).

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4.1. Sedimentology

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4. Results

In the two study sections (Cacín-1 and Cacín-2), three major sedimentary facies were distinguished. They are most clearly exposed at Cacín-2 section (Fig. 5A, B and

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C). The main textural components of these facies are shown in Figure 6D to I. The first facies consists of metre- to decimetre-thick beds of a moderately sorted, cross-bedded (Fig. 5B-1 and C), sandy, bioclastic grainstone to rudstone (Fig. 6A). Bioclasts come mainly from bryozoans, echinoderms, coralline algae, bivalves and brachiopods. Siliciclastic and dolomitic detrital grains, removed from the basement, are common. This facies is interpreted as a shoal deposit originally close to the shore line. Comparable shoal deposits are a common feature in temperate-water carbonates from the Mediterranean-linked Neogene basins of the Betic Cordillera (Martín et al., 1996; Betzler et al., 1997a; Martín et al., 2004; Braga et al., 2006; Puga et al., 2007, 2008).

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ACCEPTED MANUSCRIPT The second facies consists of decimetre-thick beds of poorly sorted, sandy packstone to grainstone (Fig. 6B). The field appearance is chaotic (Fig. 5B-2), showing

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no sedimentary structures with the exception of some burrows at the top of the beds.

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Brachiopod, bivalve, coralline-algal and bryozoan fragments are common. Sub-angular,

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up to 750 µm in size, quartz and feldspar grains also appear, mixed with the skeletal grains and the micritic matrix. This facies occurs as an intershoal deposit, interbedded with the bioclastic bars of the shoals (Fig. 5 B and C).

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The third facies, occurring on top of the section (Fig. 5B and C), consists of

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planar-parallel, finely bedded bioclastic conglomerates (Fig. 5B-3 and 6C). Clasts in the conglomerate are mainly cm-sized, angular to well-rounded siliciclastic and dolomitic basement pebbles. Bioclastic grains are the same as those found in the previous facies.

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This facies was the result of the mixing on the platform of bioclastic carbonate with terrigenous sediment, the latter supplied by continental (fluvial) flows entering the sea.

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Temperate-carbonate facies similar to the ones described here are well exemplified in most of the Neogene basins in the western Mediterranean. They

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characterize inner-ramp deposits within the temperate-carbonate realm (Martín et al., 1996; Betzler et al., 1997a; Martín et al., 2004; Braga et al., 2006; Puga et al., 2007, 2008).

4.2. Diagenesis The petrographic study of TTC samples from Cacín sections shows that the carbonate sediments underwent the effects of seven major diagenetic processes (micritization, cementation, compaction, neomorphism, clay infiltration, dolomitization

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ACCEPTED MANUSCRIPT and dissolution), and four, less intense, minor ones (pyrite formation, silica

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precipitation, and halite and sylvite replacement). These processes are described below.

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1) Micritization

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This process was found at the border of bioclasts (Fig. 7A and B), such as bryozoan, foraminifer, and brachiopod shells, as well as of some carbonate lithoclasts (Fig. 7A). It appears as a thin, µm-sized micrite envelope, and when affecting crinoid fragments, it

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prevents the development of syntaxial overgrowths. In general, micritization helps to

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preserve grains from subsequent leaching/dissolution processes.

2) Cementation

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In the study samples, cements, although sharing the same mineralogy, exhibit a great variety of types and fabrics (Fig. 8). Observed fabrics are:

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Fibrous calcite cement: This is a non-ferroan, up to ~10 μm in width and ~50 μm in length, isopachous (radiaxial) fibrous calcite cement (Fig. 8A and B). It consists of

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inclusion-rich dirty crystals, which display a dull-green colour under UV light and a dull-orange luminescence under CL. Bladed calcite cement: This cement consists of a non-ferroan, up to 50 μm in width and 100 μm in length, bladed (to dogtooth) calcite cement (Fig. 8C to F). It occurs as a circumgranular, pore-lining cement rim around skeletal and non-skeletal grains. This cement displays a dull- to bright-orange luminescence under CL and it is black under UV light. Syntaxial and mosaic calcite cements: Both cements consist of non-ferroan, inclusionrich sparite crystals. Syntaxial cements occur as overgrowths around echinoid fragments (Fig. 8G). Mosaic cements, exhibiting the typical polycrystalline, xenomorphic pattern

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ACCEPTED MANUSCRIPT (Fig. 8H), fill in inter- and intra-granular voids, and also crystallize within grain microfractures created by mechanical compaction. Both cements display a concentric zoning

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under CL, with alternating non-luminescent and dull-orange zones (Fig. 8I) and

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contribute to significantly reduce the inter-particle, primary-pore network.

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Dripstone (pendant or microstalactitic) calcite cement: This occurs as thin (up to 70 μm) crusts beneath grains or under the roofs of intergranular and solution voids, and is often observed together with “whisker crystals” (Supko, 1971; also termed “needle-

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fibre cement”, Ward, 1970, James, 1972) precipitated after the microstalactitic calcite

50 μm in length (Figs. 8J to L).

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3) Compaction

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cement .The latter consists of elongated, fine-fibre crystals, up to 2 μm in diameter and

The study samples show the effect of both mechanical and chemical compaction.

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Mechanical compaction: This process implies the reorganization, deformation, and fracturing of bioclastic grains such as coralline-algal fragments and brachiopod/bivalve

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shells (Figs. 9A and B). Bladed and mosaic calcite-cements fill in micro-fractures created by mechanical compaction (Fig. 9A). Chemical compaction: In TTC samples, this is exemplified by microstylolites (grain-tograin sutured contacts; Fig. 9C), and, locally, by more persistent stylolites, cross-cutting grains and all the above-described cements, except for the dripstone/whisker cements. Insoluble material (e.g. clay; Fig. 9D) usually concentrates at the stylolite.

4) Neomorphism Bivalve and gastropod shells, originally in aragonite are now replaced by low-Mg calcite. This transformation took place in most cases by inversion and the initial

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ACCEPTED MANUSCRIPT structure/fabric of the previous mineral is normally preserved. The mineralogical change of echinoid plates and spines from high-Mg calcite into low-Mg calcite was via

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incongruent dissolution (Land, 1967), and no dolomite was formed. Recrystallization

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took also place in TTC samples, as attested to by the transformation of micrite (<4μm)

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into microsparite (4-10μm), and sparite (>10μm; Figs. 10A and B).

5) Clay minerals

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Clay minerals such as Mg-smectite and illite were identified by X-Ray Diffraction and

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EDS (Energy Dispersive X-ray Spectroscopy) as a later, pore-filling material in intraand inter-particle voids, introduced after precipitation of the fibrous, bladed and syntaxial/mosaic calcite cements (Fig. 11A). They are also found in stylolites (Fig. 9D).

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SEM observations show silt-size terrigenous grains and pyrite crystals within the clay

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(Fig. 11B).

6) Dolomitization

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In the study samples, dolomitization is characterized either by the crystallization of ~50 μm in size, planar-e (sensu Sibley and Gregg, 1987), euhedral dolomite rhombohedrons, or by the development of up to ~40 μm thick overgrowth around terrigeneous dolomitic grains (Fig. 12). The euhedral dolomite crystals exhibit dark cores with limpid rims (Fig. 12A and B). They replace the initial micrite or the Mg smectite-rich matrix (Fig. 11C). Detrital dolomite and overgrowths (Fig. 12C) display different green intensities in the EDS mapping (Fig. 12D).

7) Dissolution This process took place at two different times, named dissolution stages 1 and 2.

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ACCEPTED MANUSCRIPT 1. Dissolution stage 1 equally affected the micrite matrix and some bioclasts (such as bryozoan skeletons and brachiopod/bivalve shells). This dissolution phase was

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responsible for the creation/enhancement of moldic and vuggy porosity (Fig. 13A),

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which, in some cases, was later partially to totally occluded by bladed and

dissolved shells are preferentially compacted.

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syntaxial/mosaic calcite cements. It clearly preceded mechanical compaction as

2. Dissolution stage 2. A second phase of dissolution affected grains and fibrous,

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bladed and syntaxial/mosaic calcite cements (Fig. 13B to D). In addition, this late

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dissolution also affected dolomite and it was also active along stylolites. A more significant, intra-particle porosity was generated during this latter dissolution process

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(Fig. 13D).

8) Silicification, and halite and sylvite crystallizations

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These processes were not very significant in extent. Silica cement followed by halite and sylvite crystallizations (Fig. 14A and B) are observed either within the pore

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network, or as replacements. Both, halite and sylvite replaced Mg-smectite, former calcite cements and carbonate grains. Sylvite also replaced halite crystals.

4.3. Geochemistry analysis 4.3.1. Major, Minor, and Trace elements The results of the element geochemistry analyses are given in Table 1 and are represented in cross-plots in Figure 15. Mg/Ca: The Mg/Ca molar ratio ranged from 0.01 to 0.07, with bulk composition from 23.32 to 37.93 wt% for Ca and from 0.25 to 1.04 wt% for Mg. The concentration

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ACCEPTED MANUSCRIPT of these elements was negatively correlated, as the Mg content decreased with increasing amounts of Ca (Fig. 15A). The calcite samples analysed were low-Mg calcite

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(<4%).

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Sr/Ca: The Sr/Ca molar ratio ranged from 0.00063 to 0.00093, with Sr ranging

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from 692.2 to 447.1 ppm. The concentration of Ca and Sr was positively correlated (Sr increased parallel to Ca; Fig. 15B).

Fe/Al and Fe/K: These ratios were positively correlated as the Fe increased with

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the Al and K contents (Figs. 15 C and D). The amounts of Fe and Al ranged from 0.09

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to 0.82 wt% and from 0.06 to 0.36 wt%, respectively. The amount of K was from 0.02 wt% to 0.13 wt%.

K/Al: The K/Al molar ratios were positively correlated as the K increased

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parallel to Al (Fig. 15E).

Fe/Mn: The Fe and Mn contents reflected good covariance between these two

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elements. The amount of Mn ranged from 94 to 810 ppm. The concentration of Fe and Mn was positively correlated as the Fe increased parallel to Mn (Fig. 15F).

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Sr/Mn: Sr and Mn concentrations were negatively correlated, since the Mn decreased as Sr increased (Fig. 15G) Fe/Zn: The concentration of Fe and Zn was positively correlated, as Fe increased parallel to Zn (Fig. 15H). Zn amount ranged from 3 to 17.5 wt%. Fe/Ca: Fe and Ca were negatively correlated, as Fe concentration decreased with increasing Ca amount (Fig. 15I).

4.3.2. Stable Isotopes: Carbon and oxygen isotopes (δ13CV-PDB vs. δ18OV-PDB) The stable-isotope study was made on selected samples from calcitic bioclasts (7 from brachiopod/bivalve shells and 3 from echinoderm skeletons) and diagenetic calcite

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ACCEPTED MANUSCRIPT cements (3 from fibrous calcite, 4 from bladed calcite, 7 from luminescence, mosaic sparry-calcite and 5 from non-luminescence, mosaic sparry-calcite). Isotopic analyses

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were also performed on euhedral dolomite (3 samples) but no values were reliable due

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to the presence of micrite inclusions inside the tiny dolomite crystals. The results of O

PDB

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and C isotope analysis are listed in Table 2 and are represented as δ18OV-PDB vs. δ13CVcross-plots in Fig. 16. In addition, the ranges of δ18O and δ13C isotope values for

calcitic skeletal components and for the main diagenetic cement generations are also

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displayed in Table 2. Isotope data of the studied samples fall into two groups. Group 1 is represented by a significant part of the calcitic brachiopod/bivalve

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shells, which exhibits positive values of δ13CV-PDB (+1.18 to +3.03‰) and negative to slightly positive δ18OV-PDB (-1.77 to 0.32‰). These values fall in the marine-seawater,

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O/C calcite field (Veizer et al., 1999).

Group 2 shows a wide range of isotopic values, with δ13CV-PDB varying between

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+0.9‰ and -0.88‰ and δ18OV-PDB between -9.03‰ and -3.32‰. This second group

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includes echinoderm skeletons and fibrous, bladed, and mosaic calcite cements.

5. Interpretations and discussion The sequence of diagenetic events in a carbonate system depends on factors such as the sediment itself, grain size, texture, mineralogy, nature of pore fluid and climate (Tucker and Wright, 1990; Tucker, 1993; Flügel, 2004). The classification scheme proposed by Choquette and Pray (1970) for carbonate diagenetic regimes was followed in this study. These authors distinguish between Eogenesis, in which rocks are affected by surficial syn- to post-depositional diagenetic processes; Mesogenesis, in which buried rocks are no longer are affected by surficial diagenetic processes; and

17

ACCEPTED MANUSCRIPT Telogenesis, in which diagenetic processes are associated with uplift and related

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subaerial exposure.

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5.1 Sequence of diagenetic events

Syn-depositional diagenesis is shown by micritization of skeletal grains, fibrous calcite-cement precipitation and mechanical compaction. Micritization of skeletal grains

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is a diagenetic process that occurs at the sediment-water interface in the marine realm

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under low-energy conditions (Tucker and Wright, 1990; Adams and Mackenzie, 1998; Flügel, 2004). This process is due to microorganism (bacteria, alga and fungi) activity on carbonate-grain surfaces (Carols, 2002). Alternative explanations for micritization

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have been given by Neugebauer, 1978 and Martín-García et al. (2009). Fibrous calcite was the first cement to be formed. This cement commonly

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crystallizes in well-oxygenated and moderate- to high-hydrodynamic marine phreatic conditions (Moore, 2001). According to Ehrenberg et al. (2002), isopachous, syn-

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depositional marine cements reflect a high saturation state of CaCO3 and a low sedimentation rate during their crystallization. Some of the grain fragments in the sediment include broken fibrous calcite coats, which indicate that they underwent remobilization after fibrous calcite-cement precipitation. However, the oxygen and carbon isotope compositions of the fibrous calcite cement (Fig. 16) do not match the values reported by Veizer et al. (1999) for Miocene seawater calcite cements. Consequently, if the fibrous calcite cement crystallized from a marine phreatic realm, then the initial chemical composition of the cement may have been changed later during the diagenesis, most likely by recrystallization.

18

ACCEPTED MANUSCRIPT Mechanical compaction postdates the precipitation of the fibrous calcite cement (Fig. 9A). In between the two events, some dissolution occurred, clearly preceding

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mechanical compaction, since dissolved shells are preferentially compacted.

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The next diagenetic episode encompasses the two major cementation phases

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observed, which resulted in the precipitation of the bladed and the syntaxial/mosaic sparry calcite cements. As pointed out above, both syntaxial and mosaic calcite cements consist of non-ferroan, inclusion-rich sparite crystals and display the same concentric

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zoning under CL (Fig. 8I), and so it is inferred that they grew at the same time. Thin

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sections indicate that the bladed calcite cement clearly predates the syntaxial/mosaic sparry calcite cements. All these cements also crystallized within microfractures created by mechanical compaction (Fig. 9A). Crystal fabrics and cathodoluminescence patterns

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(from concentric to sector zoning in the syntaxial/mosaic sparry cements; Fig. 8I) point to a reducing, shallow-burial realm dominated by fresh waters or by mixed, marine-

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fresh waters (Moore, 2001; Flügel, 2004). The fact that a dissolution phase occurred before the formation of the bladed and the syntaxial/mosaic sparry calcite cements is in

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line with fresh-waters. Calcite cements crystallizing from fresh-waters are commonly depleted in Sr2+, Mg2+, and enriched in Fe2+, Mn2+, Zn2+ compared to their marine precursors (Brand and Veizier, 1980; Scholle and Ulmer-Scholle, 2003). The Mg/Ca molar ratio ranges from 0.01 to 0.07 (Fig. 15A) indicating a low-Mg Calcite, which is the stable form of CaCO3 in fresh water. The Sr and Mn contents are negatively correlated (Fig. 15G), pointing to diagenetic stabilization of the carbonates by fresh water (Brand and Veizer, 1980). Furthermore, the positive correlation of the Fe/Zn ratio and low Fe/Ca ratio (Figs. 15H and I) are consistent with the stabilization of the TTC rocks by fresh water during shallow burial diagenesis (Brand and Veizer, 1980).

19

ACCEPTED MANUSCRIPT The δ18OV-PDB and δ13CV-PDB values determined from the bladed and the syntaxial/mosaic sparry calcite cements are lighter than the isotopic composition of the

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Miocene seawater calcites (Veizer et al., 1999). They exhibit a wide range of negative,

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oxygen isotopic composition (-9.03‰ to -3.32‰ in δ18OV-PDB), and a small, positive to

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negative range of carbon isotopic composition (+0.9‰ to -0.88‰; Fig. 16; Table 2). Such fractionation in oxygen composition may be related to higher temperatures from the burial of the carbonates. Based on the presence of monophasic, aqueous fluid

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inclusions, it can be inferred that these calcite cements crystallized at temperatures

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below 55 to 60°C (Goldstein and Reynolds, 1994; Goldstein, 2001). With this information, and the oxygen-isotope compositions taken into account, these calcite cements can be assumed to have crystallized from fluids evolving from marine to

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meteoric (0‰ to -8‰ in δ18OSMOW). The fact that the echinoderm plates display the same fluorescence and luminescence colour as these cements points to a stabilization

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process (Brand and Veizer, 1980), from high-Mg calcite to low-Mg calcite. In the case of bivalve and gastropod shells originally in aragonite and now replaced by low-Mg

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calcite the mineralogical stabilization took place by inversion. Furthermore, the echinoderm plates display the same oxygen/carbon isotopic composition as these calcite cements, reflecting the geochemical resetting of the bioclasts during stabilization. Mg-smectite and illite occur as a pore-filling, internal sediment in the TTC sediments post-dating all the above-mentioned (fibrous, bladed, and syntaxial/mosaic) cements. The type of smectite (Mg-rich) is commonly found in evaporitic, continental playa environments (Hillier et al., 1995). Such clay presumably formed within a surficial, mud-flat, marginal evaporitic environment and percolated inside the TTC sediments. The presence of coarser terrigenous grains (silt) within the clay points to a near-surface process as well. All this suggests that the TTC sediments were subaerially

20

ACCEPTED MANUSCRIPT exposed, or got close to the surface, during the incorporation of the clay minerals. Positive correlation of Fe/K and K/Al ratios in the carbonates (Fig. 15D and E) testifies

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to this terrigenous (aluminosilicate and clay) influence.

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Pyrite is also found associated with the Mg-smectite (Fig. 11B). Pyrite (FeS2) is

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a common early-diagenetic mineral formed within organic-rich sediments in reducing surficial/shallow-depth environments (Raiswell, 1982; Passier et al., 1997). According to Berner (1970), pyrite results from the reaction of sulfide (produced via bacterial

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sulfate reduction) with either Fe3+ (in sediments) or Fe2+ produced by bacterial Fe3+ reduction (Lovley, 1991).

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Dolomitization occurred afterwards as “partial dolomitization” in TTC sediments. Dolomite rhombs replaced Mg-smectite in the carbonates and, to a lesser

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extent, micritic (microsparite) carbonate matrix (Figs. 11C, 12 A and B). Cloudy cores in dolomite crystals resulted from the incorporation of inclusions and impurities within

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the crystalline network. Such a dirty dolomite is generally the result of a quick crystallization near or at surface conditions (Tucker and Wright, 1990). The fact that the

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dolomite replaces Mg-rich smectite associated with pyrite points to a reducing environment. Such conditions are thought to have occurred during the deposition of the Tortonian Evaporites (García-Veigas et al., 2013). The shallow burial conditions and the high Mg-content in the smectite could have been additional factors that prompted dolomitization. The role of Mg-clays acting as templates for the precipitation of dolomite has been pointed out by Martín-Pérez et al. (2015) in some present-day caves in western Spain. Dolomite formation could be linked to reflux brines formed during deposition of the overlying evaporites. Silicification, halite, and sylvite crystallization occurred after dolomitization (some dolomite crystal are now replaced by these minerals; Fig. 14). They resulted

21

ACCEPTED MANUSCRIPT probably from the percolation of highly-saline, silica-rich brines migrating through the TTC sediments. The diagenetic transformations introduced were not, however,

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significant in extent.

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The occurrence of stylolithes affecting all the previous, above-mentioned

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diagenetic features points to the role play by chemical compaction as a major, late-stage diagenetic process. Chemical compaction resulted from pressure-dissolution and reprecipitation of carbonates at burial depths of several hundred metres.

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The latest diagenetic stage to be recognized is exemplified by the crystallization

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of non-luminescent, microstalactitic calcite cement and calcite fibres/whisker crystals. Such fabric and CL pattern suggest that this dripstone (pendant or microstalactitic) calcite cement probably formed within the meteoric vadose-zone (Moore, 2001, Flügel,

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2004). Calcite fibres/whisker crystals are also found in vadose environments (Jones and Kahle, 1993). The structural inversion and final uplift of the study area involved the

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interaction with meteoric waters as the carbonate rocks were being exposed, implying

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extensive dissolution as well.

5.2 Diagenetic evolution in relation to the regional geodynamic In the late Miocene, the Granada Basin was subjected to two main burial episodes, separated by a minor subaerial exposure event (Martín et al., 1984). The first burial episode occurred during the late Tortonian, followed by the subsequent exposure during the latest Tortonian, at the time of evaporite deposition (Fig. 17). The second burial episode coincided with the accumulation of the Messinian lacustrine strata (up to 300 m thick). The study area within the Granada Basin (Cacín) was uplifted in the early Pliocene (García-Alix et al., 2008) and subaerially exposed since then (Fig. 17).

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ACCEPTED MANUSCRIPT The diagenetic processes observed agree with the regional history: syndepositional

processes

(Eogenesis),

comprising

micritization,

fibrous-calcite

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cementation, dissolution (dissolution stage 1) and mechanical compaction, occurred

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during the late Tortonian.

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The first diagenetic burial episode (Mesogenesis 1), concomitant to Tortonian marl deposition, is characterized by the precipitation of the bladed and syntaxial/mosaic cements and the stabilization of the temperate-water carbonates by fluids evolving from

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marine to fresh waters.

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Clay (Mg-rich smectite) was incorporated into TTC sediments when they were subaerially exposed or got close to the surface (Telogenesis 1) in the latest Tortonian, at the time of the lower-evaporite deposition. Pyrite formed as well within the Mg-

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smectite contemporaneously or shortly afterwards (Fig. 17). The diagenetic evolution continued with a second burial phase (Mesogenesis 2)

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in Messinian times. Dolomite formation occurred sometime in the early Messinian as well as silica precipitation and halite and sylvite replacements. The Tortonian evaporites

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may have provided the reducing brines which percolated through the TTC sediments and promoted such diagenetic transformations at shallow burial depths. Maximum burial diagenesis at Mesogenesis 2 is characterized by chemical compaction with stylolite formation (Fig. 17). Finally, the uplift of the study area from the early Pliocene to the present day favoured microstalactitic and fibre/whisker calcite-cement precipitation and extensive dissolution (dissolution stage 2) (Fig. 17).

5.3. Comparable examples

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ACCEPTED MANUSCRIPT In temperate and tropical-carbonates diagenetic features are controlled mainly by a) the depositional setting and the relative sea-level fluctuations, b) the pore-fluid

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chemistry and their residence time, and c) the basin tectonic evolution (James and Bone,

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1989; Nelson et al., 1994; Hood and Nelson, 1996; Caron et al., 2005; Caron and

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Nelson, 2009). The main differences between the two types of carbonates are highlighted by the facts that in the temperate-water carbonates early diagenesis is strongly conditioned by the original composition and preservation potential of the

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bioclasts, as extensive leaching of aragonite skeletons usually takes place directly on the

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sea floor (Alexandersson, 1978; Betzler et al., 1997b; James et al., 2005, 2011), while in tropical carbonates widespread synsedimentary cement-precipitation is normally ubiquitous (Bathurst, 1975; James and Choquette, 1990). In temperate-water carbonates

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diagenetic studies have been carried out mainly on Cenozoic examples from New Zealand and southern Australia (Nelson et al., 1988; Reeckmann, 1988; James and

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Bone, 1989; Dix and Nelson, 2006; Caron and Nelson, 2009). All these studies, however, have failed in connect diagenesis to basin evolution, as shown for TTC of the

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Granada Basin where the diagenetic history is consistently integrated within the geodynamic framework. Most diagenetic studies on carbonates are overall carried out as individual study cases given the diversity of depositional and diagenetic processes that affect the shallow-water carbonates, and the variety of regional tectonic settings. Therefore, comparisons between different basins are not always straightforward. In this respect, Jurassic carbonates in the Paris Basin are one of the few wellstudied examples (Vincent et al., 2007; Brigaud et al., 2009; Carpentier et al., 2014) that can be directly compared with the TTC in the Granada Basin. In both cases, the diagenetic pathways of carbonate rocks were linked to major geodynamic events, which 24

ACCEPTED MANUSCRIPT include several episodes of subsidence and uplift, and the development of telogenetic features during the final exhumation of the basins. A significant difference during the

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telogenetic evolution of both basins lies in the fact that the final exhumation of the TTC

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(Telogenesis 2) was not accompanied by extensive fracturing as in the Paris Basin,

underwent

dissolution

by

meteoric

fluids

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which generated a more complex diagenetic evolution of the limestones. TCC and

subsequent

precipitation

of

microstalactitic and fibre/whisker calcite-cements during the progressive basin inversion

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(uplifting). In the case of the Paris Basin, open fractures, which likely formed in a

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transitional, compressional- to-extensional tectonic regime (Carpentier et al., 2014), were used as pathways for fluorine and sulphur fluids contemporaneously to the dissolution of the limestones by meteoric waters, yielding to the subsequent fluorite and

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pyrite precipitation in the resulting cavities. The comparison of the diagenetic evolution of the TTC with other shelf

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carbonates from different ages and tectonic settings such as the Persian Gulf, Indonesia, Louisiana, Mediterranean-Sea and Paris Basin, yields the following results:

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(1) Micritization and formation of bioclast rims was a common process during the earliest diagenesis in most shallow-water limestones (Wilson and Evans, 2002, Wilson et al., 2013; Daraei et al., 2014), as well as in the TCC. (2) Dissolution during the early burial and extensive leaching of aragonite (Crevello et al., 1985; Wilson et al., 2013) was not a widespread phenomenon as might be expected in the TTC, probably due to the existence of a prior neomorphic, aragonite-to-calcite inversion (mineralogical stabilization) that prevented dissolution.

25

ACCEPTED MANUSCRIPT 3) The development of the syntaxial overgrowths was very minor in the TTC and was presumably conditioned by the facies type (Wilson and Evans, 2002; Wilson et al.,

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2013) and subsequent abundance of suitable skeletal (crinoid and echinoid) particles.

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4) Dolomitization formed mainly by replacement of Mg-rich smectite in the TTC.

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Direct replacement of the limestones was a very minor process. Mg-rich fluids were not released during chemical-compaction as exemplified by Vincent et al. (2007).

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5) Pyrite in the TCC is scarce and its precipitation is linked to the degradation of organic matter, favouring sulphate reduction, during the first telogenetic stage

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contemporaneously to evaporite formation. Sulphate-rich waters may have reached the carbonates through the existing fracture network, as shown in the example described by

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Carpentier et al. (2014).

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Carbonates and evaporites are intimately associated in a variety of sedimentary

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environments (e.g. semi-restricted carbonate platforms, evaporitic basins, lacustrine basins) and thus diagenetic studies dealing with these two types of rocks together have

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focused on carbonate to evaporite transitions (Rouchy, 2001; Schoenherr et al., 2009; Daraei et al., 2014; Amel et al., 2015). In these environments, the diagenesis is influenced by the different solubility of the carbonates and evaporites under the influence of meteoric waters. However, in sedimentary sequences where carbonates and evaporites are not genetically linked, as in the case of the TTC, the influence of the evaporites on the diagenetic evolution is conditioned by the ability of the highly saline fluids to percolate into the limestone units. In the Granada Basin, the influence that evaporites close to the TTC exerted on the carbonates was only slight and restricted to the replacement by dolomite, halite and sylvite. This weak influence suggests the absence of a well-developed fracture network throughout the Upper Tortonian marls

26

ACCEPTED MANUSCRIPT between the evaporites and the TTC, which is consistent with the more ductile nature of

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those soft sediments.

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6. Conclusions

The paragenetic sequence in the TTC sediments from the Granada Basin shows a diagenetic evolution that encompasses five episodes: Eogenesis (syn-depositional),

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late Tortonian in age; Mesogenesis 1 (first burial event), late Tortonian in age;

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Telogenesis 1 (first uplift event, contemporaneous to evaporite deposition), latest Tortonian in age; Mesogenesis 2 (shallow- to deep-burial event), Messinian in age, and Telogenesis 2 (second uplift event), Pliocene to Recent in age.

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During the syn-depositional stage (Eogenesis) marine diagenetic processes such as micritization, fibrous calcite-cement precipitation and mechanical compaction

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occurred. The first burial diagenetic event (Mesogenesis 1) is characterized by the stabilization of the temperate-water carbonates by fluids evolving from marine to fresh

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water, and by porosity occlusion by bladed and syntaxial/mosaic calcite cements. The first uplifting episode (Telogenesis 1) involved clay (Mg-smectite) incorporation in TTC sediments, during evaporite deposition, and pyrite formation. During the second burial episode (Mesogenesis 2) dolomite, silica, and halite/sylvite formed first, at shallow-burial conditions, in connection with reducing brines percolating from the evaporite deposits. Later on, in deeper burial conditions, pressure-dissolution features (stylolites) developed in a closed diagenetic system. The last diagenetic episode (Telogenesis

2)

comprises

microstalactitic

precipitation and extensive dissolution.

27

and

fibre/whisker

calcite-cement

ACCEPTED MANUSCRIPT The study case clearly exemplifies the close link between diagenetic history and basin evolution. Diagenetic processes were related to major geodynamic events, including

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basin restriction leading to evaporite deposition, and several episodes of subsidence and

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correlation between diagenetic history and basin evolution.

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uplift. Up to now, only very few diagenetic studies have succeeded in showing a tight

Acknowledgements

This work is part of the “Study MFT08.003” (IFP Énergies Nouvelles, France). A

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significant part of this work was carried out at IFP Énergies Nouvelles laboratories in

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Rueil-Malmaison (France), during an internship stay of the senior author (ALQ) sponsored by IFP. JMM and APB work was funded by the project "Productores de carbonato en plataformas carbonatadas neógenas de la Cordillera Bética. Factores que

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controlan la composición y la resedimentación” (CGL2013-47236-P) (2014-18) (Ministerio de Economía y Competitividad, Spain and Fondo Europeo de Desarrollo

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Regional FEDER). Thanks are given to Prof. Michael Joachimsky (University of Erlangen) for the isotopic analysis, ACME Lab for the measurement of the element

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concentrations, and Dr Julio Aguirre and Dr Isabel Sánchez-Almazo (University of Granada), and Dr. Javier García-Veigas (University of Barcelona) for their helpful comments. We would also like to thank Editor Dr. Brian Jones and two anonymous referees for their suggestions to improve the paper. We thanks David Nesbit for the correction of the English text.

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O.G., Strauss, H., 1999. 87Sr/86Sr, δ13C and δ18O evolution of Phanerozoic seawater. Chemical Geol. 30, 59–88.

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Verwer, K., Lukasik. J., 2014. Pre-Salt Carbonates of the South Atlantic. AAPG 2014 Annual Conference and Exhibition, Houston, Texas, USA, Abstract 90189. Vincent, B., Emmanuel, L., Houel, P., Loreau, J-P., 2007. Geodynamic control on carbonate diagenesis: Petrographic and isotopic investigation of the Upper Jurassic formations of the Paris Basin (France). Sediment. Geol. 197, 267–289. Ward, W. C., 1970. Diagenesis of Quaternary eolianites of N.E. Quintana Roo, Mexico. Rice Univ. Ph.D. dissert., Houston, p.206. Wilson, M.E.J., Evans, M.J., 2002. Sedimentology and diagenesis of Tertiary carbonates on the Mangkalihat Peninsula, Borneo: implications for subsurface reservoir quality. Marine and Petroleum Geology 19, 873–900.

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Figure captions

Figure 1. Neogene sedimentary basins of the Betic Cordillera, Spain (modified from

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Braga et al., 2003). 1): Fortuna Basin, 2): Lorca Basin, 3): Sorbas Basin, 4): Tabernas

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Basin, 5): Guadix-Baza Basin, 6): Granada Basin, 7): Ronda Basin, and 8): Guadalquivir Basin.

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Figure 2. Simplified geological map of the Granada Basin and location of the studied outcrops (modified from Dabrio et al., 1982 and Martín et al., 1984). (P-M: Palaeozoic–

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Mesozoic; Aq-lT: Aquitanian–lower Tortonian; uT: upper Tortonian; Me: Messinian; Pl-Q: Pliocene–Quaternary). 1-a: Nevado-Filábride and Alpujárride basement rocks

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from the Betic Internal Zones; 1-b: Subbetic basement rocks from the Betic External Zones; 2-a: Older Miocene continental and marine deposits; 2-b: Bioclastic calcareous sandstones (conglomerates) and limestones (coastal and shallow-marine, platform deposits; TTC unit); 2-c: Conglomerates, sands and silts (fan-delta deposits); 2d: marls (open-marine deposits); 3: Evaporite unit (marine to continental transitional deposits); 4-a: Silts and clays (distal-lake deposits); 4-b: Sandstone turbidites and silts (proximallake deposits); 4-c: Conglomerates, sands and silts (marginal, fluviatile deposits); 4-d: Lacustrine gypsum (gypsarenites); 4e: sands, silts and coal (lignites); 4-f: Limestones; 5: Alluvial and fluviatile detrital deposits. Blue dots mark the position of the sampled TTC sections.

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Figure 3. Miocene to Quaternary stratigraphy of the Granada Basin (after Braga et al.,

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1990).

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Figure 4. Study area. A) Satellite view of the southern part of the Granada Basin. B) Location of Cacín-1 and Cacín-2 sections (yellow dots).

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Figure 5. TTC outcrops at Cacín. A) Panoramic view of the Cacín River Canyon. B)

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Cacín-2 section. Close-up pictures are from the three major facies identified: 1) crossbedded grainstone to rudstone (blue in C); 2) chaotic packstone to grainstone (yellow in C); 3) bioclastic conglomerates (green in C). C) Sedimentary log of the Cacín-2

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outcrop. D) Cacín-1 section (red line marks the position of the sampled log). Old

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Roman Bridge can be seen at the background of the picture.

Figure 6. Major facies and textural components in the TTC sediments at Cacín. A)

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Plain-Polarized Light (PPL) photomicrograph showing cross-bedded grainstone-torudstone microfacies. B) PPL photomicrograph showing chaotic packstone-tograinstone microfacies. C) PPL photomicrograph showing bioclastic conglomerate microfacies. D) PPL photomicrograph showing broken longitudinal/tangential sections of bryozoans.E) PPL and Cross-Polarized Light (CPL) photomicrographs showing large bivalve shell with homogeneous, calcite wall structure.F) PPL photomicrograph of an echinoid spine, in cross section. Porosity in blue.G) PPL photomicrograph showing a crustose coralline red algal fragment.H) PPL photomicrograph showing planktonic foraminifers and detrital, irregularly shaped grains.I) CPL photomicrograph showing metamorphic-rock lithoclasts. Staining in red is for calcite.

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ACCEPTED MANUSCRIPT Figure 7. Micritization at Cacín samples. A) PPL photomicrograph showing micritization of a brachiopod shell (yellow arrow) and of a carbonate lithoclast ( white

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arrow). B) PPL photomicrograph showing micritization on a benthic foraminifer shell

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(yellow arrow).

Figure 8. A) and B) PPL photomicrographs showing fibrous calcite cement (yellow arrows) formed around skeletal grains (isopachous calcite cement crusts). C) PPL

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photomicrograph showing bladed (to dogtooth) calcite cement (yellow arrow) (stained

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sample). D) and E) PPL and corresponding fluorescence photomicrographs showing bladed (to dogtooth) calcite cement (yellow arrows). F) Cathodoluminescence (CL) photomicrograph showing bladed (to dogtooth) calcite cement (yellow arrow) inside a

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bivalve shell. This cement displays a dull to bright orange luminescence. G) PPL photomicrograph showing syntaxial-overgrowth calcite cement (yellow arrow)

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developed around an echinoderm grain. H) and I) PPL and corresponding CL photomicrograph showing syntaxial (yellow arrow) and mosaic (blue arrow) calcite

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cements displaying the same concentric zoning under cathodoluminescence. The typical pattern consists of alternating non-luminescent and dull orange zones. J) PPL photomicrograph showing dripstone (pendant or microstalactitic) calcite cement (yellow arrow). Calcite fibres/whisker crystals (red arrow) are also present together with the microstalactitic calcite cement. Stained sample. K) SEM photomicrograph (BSD) showing the same cements as in J. L) PPL (right) and corresponding fluorescence (left) photomicrographs showing in detail calcite fibres/whisker crystals (red arrow). Stained sample. Porosity in blue.

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(red arrow: fibrous calcite cement; yellow arrow: bladed calcite cement; blue arrow:

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mosaic calcite cement). The precipitation of the fibrous calcite cement was prior to the

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formation of the fracture. Bladed and mosaic calcite cements fill in the space created by mechanical fracturing as well as the inter-granular voids between bioclasts. B) CL photomicrograph showing mechanical compaction (yellow arrow) affecting a bivalve

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fragment. C) PPL photomicrographs showing micro-stylolites (grain-to-grain sutured

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contacts) (yellow arrows). The stylolites clearly cut and thus postdate prior mechanical compaction features (microfracture) (red arrow) D) Fluorescence photomicrograph showing residual silty clay concentrated along an irregular stylolite surface (yellow

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Figure 10. Recrystallization at Cacín TTC samples. A) and B) PPL photomicrographs showing recrystallization in bryozoan skeletons from micrite into sparite (sample A;

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yellow arrow), and from micrite into microsparite (sample B; yellow arrow). Sample A is stained with Alizarin. Porosity in blue.

Figure 11. Clay minerals in TTC samples at Cacín. A) PPL photomicrograph showing pore-filling, silty clay (ochre colour and turbid "muddy" appearance) (yellow arrow). Porosity in blue. B) SEM (EDS mapping) showing silty clay (red colour) with small pyrite crystals (blue arrow) and dolomite (white arrow). Porosity shown in black. C) SEM (EDS mapping) showing pore-filling Mg-smectite (Mg-s; grey colour), after crystallization of calcite cement (brownish-grey colour). Dolomite (red arrow) in turn is replacing Mg-smectite.

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Figure 12. Dolomitization in TTC samples at Cacín. A) and B) SEM (BSD) and CL

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photomicrographs of rhombohedral dolomite replacing the carbonate matrix. The

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euhedral dolomite crystals exhibit dark cores and limpid rims. C) and D) PPL

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photomicrograph and corresponding SEM (EDS mapping) of a detrital dolomite grain (red arrow) and its diagenetic dolomite overgrowth (blue arrow). In the EDS mapping, the detrital dolomite nucleus exhibits a greener colour intensity, reflecting a higher

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Mg2+ content.

Figure 13. Dissolution processes observed at Cacín TTC samples. A) PPL photomicrograph showing dissolution 1 stage affecting micrite matrix (red arrow), and

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bioclasts (bryozoans, brachiopods and bivalves) (white arrows). Vuggy porosity resulted (yellow arrow). B) and C) PPL and fluorescence photomicrographs showing

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dissolution 2 stage affecting bladed (to dogtooth) calcite cement (yellow and white arrows). D). PPL photomicrograph (stained sample) showing late intra-particle porosity

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created by dissolution in stage 2 (white arrow). Porosity shown in blue in A, B and D pictures.

Figure 14. Silicification, halite, and sylvite crystallizations. A) SEM (EDS mapping) showing silica cement (blue in colour) and Mg-smectite (Mg-s), dolomite (D), halite (H) and sylvite (S) (white arrows). B) SEM (EDS mapping) showing the replacement of Mg-smectite (green) (white arrow) by dolomite (purple) (yellow arrow), halite (dark orange) (red arrow) and sylvite (orange) (blue arrow).

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ACCEPTED MANUSCRIPT Figure 15. Cross-plots of major, minor, and trace elements from Cacín TTC samples (revealed by ICP-MS analysis). A) Mg/Ca; B) Sr/Ca; C) Fe/Al; D) Fe/K; E) K/Al; F)

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Fe/Mn; G) Sr/Mn; H) Fe/Zn; I) Fe/Ca.

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Figure 16. A scatter plot of δ13C and δ18O values of Cacín TTC samples. Isotope data fall into two groups. Group 1, represented by a significant part of the calcitic brachiopod/bivalve shells, yields positive values of δ13CV-PDB and negative to slightly

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positive δ18OV-PDB. These values fall in the marine-seawater, O/C calcite field (Veizer et al., 1999). Group 2 exhibits a wide range of δ18OV-PDB and relatively small range of

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δ13CV-PDB isotopic values. This second group includes echinoderm skeletons and fibrous, bladed, and mosaic calcite cements. These latter isotope values reflect the

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effects of fluids evolving from marine to meteoric.

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Figure 17. TTC diagenetic evolution. The paragenetic sequence in the TTC show a diagenetic evolution that encompasses five diagenetic episodes: Eogenesis (syn-

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depositional to shallow burial) and Mesogenesis 1 (shallow burial to burial), both late Tortonian in age; Telogenesis 1 (subsequential uplift) during the latest Tortonian at the time of evaporite deposition; Mesogenesis 2, Messinian in age; and Telogenesis 2, Pliocene to Recent in age.

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Table 1. Geochemistry-analysis results of Cacín TTC samples. Major, and minor and trace element contents are given in wt% and ppm, respectively. Fe (%)

Sr (ppm)

Ca (%)

Mg (%)

K (%)

CA01 CA02 CA03 CA04b CA05 CA06 CA07 CA08 CA09 CA10 CA11 CA12 CA13 CA14 CA15 CA16 C01 C02 C03a C04 C05 C06a C07 C08 C09b C10a C11 C12a C13a C15 C16

349 305 273 257 314 313 810 559 272 238 432 201 295 173 371 307 218 249 150 586 297 181 406 258 94 154 113 98 374 347 298

0,54 0,21 0,30 0,21 0,25 0,25 0,68 0,35 0,28 0,27 0,40 0,35 0,30 0,21 0,35 0,19 0,14 0,27 0,23 0,82 0,54 0,40 0,49 0,30 0,13 0,22 0,10 0,09 0,32 0,29 0,29

483,0 692,2 460,9 582,8 566,3 619,5 453,9 447,1 531,5 511,1 529,4 565,1 575,3 542,1 618,7 527,8 616,5 640,7 644,3 467,8 644,5 575,3 450,7 548,2 519,6 562,3 593,0 514,6 643,8 546,2 502,5

29,60 34,98 33,36 37,93 35,98 33,84 31,30 32,71 32,29 33,02 31,86 31,27 32,21 33,35 33,00 34,75 35,59 32,85 32,33 23,32 31,9 29,84 26,46 30,57 32,61 31,73 35,03 34,25 31,58 33,66 33,05

0,76 0,33 0,32 0,26 0,27 0,29 0,26 0,28 0,37 0,30 0,31 0,30 0,25 0,29 0,29 0,26 0,35 0,45 0,49 1,04 0,67 0,48 0,75 0,46 0,32 0,52 0,33 0,34 0,38 0,38 0,27

0,09 0,02 0,04 0,02 0,03 0,02 0,03 0,04 0,04 0,03 0,03 0,04 0,02 0,03 0,04 0,03 0,03 0,03 0,04 0,13 0,09 0,07 0,08 0,06 0,03 0,06 0,03 0,03 0,05 0,07 0,05

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Zn (ppm)

Al (%)

15,9 3,0 5,4 3,2 4,6 4,2 9,1 7,5 7,7 7,7 5,4 6,1 3,4 9,9 7,1 3,1 8,2 7,5 10,7 13,6 13,4 17,5 13,7 10,6 5,2 8,7 4,7 4,2 5,5 7,4 9,3

0,36 0,08 0,15 0,06 0,10 0,08 0,13 0,14 0,18 0,12 0,10 0,15 0,07 0,12 0,13 0,09 0,09 0,10 0,12 0,36 0,27 0,19 0,23 0,17 0,07 0,16 0,07 0,08 0,13 0,16 0,15

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ACCEPTED MANUSCRIPT

Table 2. Oxygen and carbon stable-isotope values for calcitic skeletal components and diagenetic cements at Cacín TTC samples. Outcrops codes: Cacín-1 (CA); Cacín-2 (C). 18

0,74 2,58 1,93 3,03 1,48 1,18 0,74 0,90 0,89 -0,13 0,24 0,32 0,55 0,66 -0,19 -0,88 0,59 -0,28 -0,25 0,24 -0,44 0,33 0,67 0,23 -1,58 -0,74 0,20 0,08 0,02

-3,37 -0,05 -0,85 0,32 -1,77 -1,54 -4,30 -7,09 -7,44 -5,28 -5,84 -6,90 -6,31 -6,41 -8,82 -8,26 -8,85 -4,46 -4,74 -3,32 -6,41 -6,30 -9,03 -8,65 -4,57 -3,61 -7,59 -4,18 -5,60

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Brachiopod/bivalve shells … … … … … … Echinoderms skeletons … … Radiaxial fibrous calcite cement … … Dull orange bladed cement … … … Orange mosaic cement … … … … … … Non-luminescence mosaic cement … … … …

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CA 02c CA 02d CA 03b CA 03d CA 14c CA 14d C 02c CA 02a CA 03f C 08b C 15d CA 02g CA 14a CA 02e CA 03a CA 03c CA 03e C 12a C 12b C 13c C 15b C 15c CA 02b CA 02f C 13a C 13b C 15a C 02a C 08c

13

δ CV-PDB ‰ δ OV-PDB ‰

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ACCEPTED MANUSCRIPT

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Graphical abstract

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ACCEPTED MANUSCRIPT Highlights

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The diagenetic history of temperate-water carbonates underlying evaporites is shown Diagenetic processes fit well within sedimentary and tectonic evolution of the basin Two main burial episodes separated by a minor subaerial exposure event distinguished Brines percolating from the evaporites promote dolomite, silica and halite formation

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