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NeptuniandykesandassociatedfeaturesinsouthernSpain:mechanicsofformationandtectonicimplications–Discussion

ARTICLEinSEDIMENTOLOGY·DECEMBER1995

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J.M.Molina

UniversidaddeJaén

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P.A.Ruiz-Ortiz

UniversidaddeJaén

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Sedimentology (1995) 42, 957-969

DISCUSSIONS

Neptunian dykes and associated features in southern Spain: mechanics of formation and tectonic implications J. M. MOLINA,* P. A. RUIZ-ORTIZ* and J. A. VERAt *Departamento de Geologia, Facultad de Ciencias Experimentales, Universidad de JaBn, 23071 JaBn, Spain +Departamento de Estratigrafia y Palaeontologia, Facultad de Ciencias, Universidad, 18071 Granada, Spain

In the last 11 years we have published vari- ous papers describing neptunian dykes and palaeokarst in the External Zones of the Betic Cordillera. These new data have allowed us to improve the original genetic models. Winterer & Sarti (1994) present a revised interpretation of the neptunian dykes in southern Spain from an analy- sis of a limited number of localities and give some alternative interpretations for the origin of the dykes. Regarding their interpretation, we wish to raise the following main points: (1) to stress the importance of the karstic dissolution in the genesis of the neptunian dykes at some localities, (21 to present the main arguments in favour of emergence (bauxites, calcretes, geochemistry of speleothems, karstic morphologies and related facies) and (3) to raise some other points of disagreement, mainly regarding the palaeogeogra- phy and the analogous modern example proposed by Winterer & Sarti (1994).

FRACTURING VERSUS KARSTIFICATION

We cannot accept fracturing and karstic dissolu- tion as alternative models, because, in our earlier publications, we have stressed the key impor- tance of synsedimentary fracturing in the genesis of the cavities, some of which were filled later by pelagic sediments forming neptunian dykes. Systematic analysis of the fractures led us to establish a genetic model which was integrated into the general geodynamic framework of the western Tethys during the Middle Jurassic (Vera et al., 1984). In our publications in which the general genetic model is presented (Vera et al., 1984, 1988; Molina, 1987; Garcia-Herndndez et al., 1988a) the fracturing is introduced as the first step leading to the genesis of the neptunian

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dykes; later, and in some locations, these fractures were enlarged by submarine or subaerial dissolu- tion. The emergence and karstification occurred in the highest parts of the fractured blocks. Specifically, the subaerial exposure is related to the tilting of blocks by listric faults and the local emergence of some pelagic swells (Garcia- Hernandez ef al., 1988a, 1989; Vera et al., 1988). The tilting of blocks and, in general, the tectonic evolution of each block determined the variable appearance of the same stratigraphic discontinu- ity from place to place. Lateral changes from subaerial palaeokarst to surfaces with littoral and/or submarine erosion, and from these to paraconformity surfaces (omission surfaces and hardgrounds) occur. In this context of diversity we consider two types of neptunian dykes: those that were submerged all the time and others in which there was emergence and karstification. In fact, synsedimentary fracturing is considered so important in our models that it appears in the title of several recent papers (Molina et al., 1989; Molina & Ruiz-Ortiz, 1990; Ruiz-Ortiz et a]., 1990). Wright & Smart (1994) consider the palae- okarst model of Molina et al. (1985) as a typical example of palaeokarst in extensional tectonic regimes. This fracturing process presented in our papers (Vera et al., 1984, fig. 5 ; 1988, fig. 12; Molina, 1987, fig. 48; Molina et al., 1985, fig. 5; Jim6nez de Cisneros et al., 1991, fig. 12; Vera, 1988, fig. 4; 1989, fig. 2; 1994, fig. 22.19; Garcia- Hernandez et al., 1987a, fig. 2; 1987b, fig. 3; 1988a, fig. 1; 1989, fig. 2) appears to have been ignored in fig. 17(B) of Winterer & Sarti (1994).

The existence of emergence stages with sub- aerial dissolution cannot be considered as an ‘unnecessary complexity’, if the observational data suggest this ‘complexity’. Winterer & Sarti (1994) present a genetic model exclusively based on fracturing. However, to explain some dyke

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morphologies at Navazuelo and Las Angosturas, they hypothesize downslope removal and sliding of blocks despite the fact that ‘no occurrences of contemporaneous talus blocks or megabreccia formations are reported’. To explain this, they inferred that ‘the blocks disintegrated, or re- mained buried or were tectonically transported and then eroded’ (Winterer & Sarti, 1994, p. 1117). In our opinion this explanation is not simple or clear.

The search for definitive arguments in favour of or against subaerial emergence has been one of our principal areas of research. Below, we reiter- ate some of our essential arguments that favour at least local emergence related to the genesis of the neptunian dykes.

ARGUMENTS FAVOURING TEMPORAL AND LOCAL EMERGENCE

Bauxites

The best outcrop of Jurassic karst bauxites is located near Zarzadilla de Totana, and has been interpreted as the filling of karst cavities during the Jurassic by all previous authors (e.g. Seyfried, 1978: Vera et al., 1987: Molina et al., 1991), with the only exception of Winterer & Sarti (1994, p. 1116) who ‘suggest that the bauxite may be of Cenozoic rather than of Liassic age, and to have been deposited in a cave (sinkhole) dissolved by waters circulating down along a joint cutting the host Liassic strata’. This suggestion is intended to negate one of the main arguments supporting our interpretation in which palaeokarst plays an important role in the genesis of some neptunian dykes in the Subbetic.

The Jurassic age of the bauxites and the karstic nature of the cavity in which they appear is suggested by the following. (1) The detailed obser- vation of the outcrop and adjacent areas (Mina del Hierro, Solana de la Higuerica) in which we can observe some accumulations of iron and alu- minium oxides-hydroxides in cavities with flat bottoms, parallel to the stratification and system- atically located 35 m below the palaeokarst sur- face (Molina et al., 1991). (2) The fractures in this outcrop belong to a set of faults clearly of Jurassic age (before the Oxfordian) because they are covered by the Ammonitico Rosso Fm. (Upper Jurassic: Molina et al., 1991). The inset to fig. 7 in Winterer & Sarti (1994) is not correct because the bauxite is not filling a palaeosinkhole linked to a steep Cenozoic joint, but a stratiform cave with an

important bedding control. (3) Identification in another outcrop (Tornajo) of cavities filled with iron and aluminium oxides-hydroxides in a simi- lar stratigraphic location (Molina et a]., 1991). In these outcrops a demonstrable connection with the Jurassic unconformities on top of the Lower Liassic Gavilan Fm. also exists. (4) The opinion of experts in karst bauxites that have visited the outcrops (Dres. Bardossy and Korpas). (5) The similarity with analogous Jurassic bauxite out- crops in other studied regions (e.g. Parnassos Mountains in Greece).

On the other hand, we think that the Cenozoic age proposed by Winterer & Sarti (1994) for the bauxites is ambiguous because: (a) it is not specified if the deposit is pre-orogenic or post- orogenic; in the first case it would be palaeogeo- graphically very improbable because it would correspond to the interval with deeper deposits and in the second case it is also improbable because the present relief is the result of post- Miocene erosion of post-Jurassic material, the Jurassic material appearing in the core of an anticline. (b) From the Miocene to the present, favourable conditions for bauxitization were not reached in the Mediterranean area: the rare bauxites of this age are reworked. Therefore, it is simpler to infer emergence of a previous shallow- marine area, during an interval (Upper Liassic to Callovian) for which we have no deposits.

Calcretes

The systematic research in the lower parts of the sinkholes of the Jurassic palaeokarst has allowed the discovery of Jurassic calcretes in a locality near Castillo de Locubin (Molina et al., 1992), initially identified by their textural and geo- metrical aspects and later confirmed by their isotopic composition (Jimhez de Cisneros et al., 1993).

Geochemistry of speleothems

Recent geochemical studies of speleothems cover- ing the walls of neptunian dykes (Jim6nez de Cisneros et al., 1991, 1993) show, with the excep- tion of the calcretes cited above (Jim6nez de Cisneros et al., 1993), that the speleothems have an isotopic composition like the marine sedi- ments, coincident with the data of Winterer & Sarti (1994). Cathodoluminescence, however, shows an alternation of luminescent and non- luminescent cements, interpreted as the result of hydrodynamic changes in the cementation

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Neptunian dykes, southern Spain 959

1988b), in a small quarry in the Upper Rosso Ammonitico Fm. and in the Sierra de Estepa. At Cuillas, over a karstic surface with kamenitzas there are sedimentary structures (mudcracks, algal mats, cross-bedding, etc.), indicating very shallow-water deposition (Garcia-Hernandez e f al., 1988b) far from the continent. In the Sierra de Estepa, the karstic cavities are filled with shallow- marine sediments with ferruginous ooids; algal laminations and mudcracks occur in the upperly- ing Upper Ammonitico Rosso Fm. (Castro et al., 1990). In addition, tempestites have been described in the Upper Rosso Ammonitico Fm. (Molina e f al., 1987); therefore, in many External Subbetic areas there is clear evidence of a shallow-marine origin, with very different features from a ‘classic’ pelagic deposit.

The rocks above and below the stratigraphic discontinuities with associated neptunian dykes are shallow-marine platform facies or littoral facies organized in shallowing-upward sequences (Ruiz-Ortiz et al., 1985; Molina, 1987; Garcia- Hernandez e f al., 1988b). At these locations small fluctuations in sea level (some metres or some tens of metres) would be enough to produce emergence. Thus, the morphologies of the cavities and the shallow-water origin of the fill and the host sediments provide strong evidence against the argument of Winterer & Sarti (1994, p. 1130) that substantial relative changes in sea level (‘hundreds of metres’) were needed to explain the emergence. If we take into account the presence of calcrete levels (Molina et al., 1992; Jim6nez de Cisneros et al., 1993) and the existence of bauxites (Molina et al., 1991), the evidence for emergence appears indisputable.

environments as a consequence of the alternation of a very shallow environment with vigorous wave action (non-luminescent speleothems) and a deeper environment with calm water (lumines- cent speleothems; Garcia-Hernandez et al., 1988b; J imhez de Cisneros et al., 1991). A plot of 6l80 vs. 613C shows a pattern of positive covariance, suggesting a readjustment of the values in a dia- genetic environment with mixing of marine and fresh waters (JimBnez de Cisneros et al., 1991).

Cavity morphologies and related shallow-marine facies

Any interpretation of the morphology of the nep- tunian dykes must accept dissolution from previous fractures. The possible discrepancy comes from the specific dissolution environment. Winterer & Sarti (1994) consider that the dissolu- tion was exclusively submarine, whereas we think that, in some places, there was also tem- poral emergence and karstification. We have recognized cavities with karstic geometries at numerous localities in the External and Internal Subbetic (Vera et al., 1984, 1988; Molina, 1987; Molina et al., 1985, 1989, 1992; Ruiz-Ortiz et al., 1990; Castro et al., 1990; Garcia-Hernandez ef al., 1987a,b, 1988a). At these localities it is possible to recognize irregular morphologies of the cavity walls. They are rounded and fluted, rather than sharply angular wall forms, and they cannot be fitted back together because of significant dissolution.

We made a statistical analysis of the neptunian dyke and cavity morphologies in more than 20 outcrops in the Camarena-Lanchares unit. Neptunian dykes and large cavities with irregular walls are the predominant type (46%). Morpholo- gies clearly linked to fracturing (Q type) comprise 31% and those parallel to bedding (S type) com- prise 23% (Vera et al., 1984; Molina, 1987, pp. 141-142, fig. 44). This statistical distribution seems to establish the process of chemical disso- lution as unquestionable in the genesis of the neptunian dyke cavities.

In some places, we have found excellent ex- amples of palaeosinkholes with a perfect circular morphology, up to 180m in diameter (Fuente Rebola, Cortijo de las Melladas) or more irregular in shape (up to 130m in maximum length in Fuente del Espino). Molina (1987, fig. 43 and pp. 138-148) describes other clear karstic morphologies on the top of the Camarena Fm.

There are also clear karstic morphologies in the locality of Cuillas (Garcia-Hernandez et al.,

SOME SPECIFIC POINTS

There are some mistakes in the references of the paper by Winterer & Sarti (1994). Thus, Vera et al. (1987) on pp. 1109,1118 and 1119 and Vera et (11. (1984b) on pp. 1110, 1123,1129 and 1132 should be cited as Vera et al. (1988). Molina (1989) on p. 1118 is Molina (1987). Garcia-Hernandez et al. (1987) on p. 1126 is Garcia-Hernandez et al. (1988~). Molina et al. (1989) on p. 1112 did not describe the locality mentioned; this was, in fact, described in Garcia-Hernandez et al. (1988b) and Molina (1987).

Figure 17(A) is not accurate from a palaeogeo- graphical point of view. Palaeogeographically, Zafarraya is on the Southern Ridge and not on the southern margin of the Northern Ridge as is

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proposed in this figure. Also, the relative location of Las Angosturas with respect to Castillo de Locubin (the former to the south of the latter) and Zafarraya (east of Las Angosturas and Castillo de Locubin) is not correct, if according to the domi- nant direction of downslope displacement we suppose that south is to the right margin of the figure. Castillo de Locubin and Las Angosturas are in the same palaeogeographical realm (southern margin of the External Subbetic) but Zafarraya is in a different palaeogeographical realm (Internal Subbetic) more than 100 km to the south.

The location of Cuillas on p. 1112: ‘. . . was near the southern margin of the Northern Ridge (or Central Ridge?)’ is in error because Cuillas was not near this southern margin. Palaeogeographi- cally, it belongs to the Camarena-Lanchares Unit (the northern unit of the External Subbetic) and to the south other units belonging to the External Subbetic or Northern Ridge occur (Gaena and Lobatejo-Pollos Units; see Molina, 1987, fig. 142; Molina, 1993). On p. 1113 the locality of Navazuelo was given as ‘near the south side of the Northern Ridge’ but it also belongs to the Camarena-Lanchares unit. Also, on p. 1117 Winterer & Sarti (1994) introduce some confusion by referring to Cuillas, Navazuelo, Las Angosturas and Zarzadilla de Totana with similar locations in ‘a slope close to the south edge of the Central (or Northern?) ridge’. In fact, Las Angosturas is palaeogeographically the only one of the four localities placed correctly. The other three locali- ties are not on the south edge of the Central Ridge (External Subbetic).

The only ‘analogous’ modern example pre- sented by Winterer & Sarti (1994, p. 1117) is not so similar. The submarine canyons described by McHugh et al. (1993) are very deep on the lower slope (water depths of 1500-2500m), with two alternating rock types (porcellanites and chalks)

with different physical and diagenetic properties from the wallrocks of the Subbetic neptunian dykes. The described morphologies, ‘stepped, rectangular scarps with nearly vertical walls and floors of the canyons are flat and broad up to 2 km wide’, are also different to those observed by us.

In p. 1129 Winterer & Sarti (1994) stated that ‘No single example of a shallowing upward suces- sion that is cut by dykes is known to us from the Betic region’, but the Camarena Fm. on which neptunian dykes appear is a shallowing-upward succession, with the development of ooid shoals, corals, tide-dominated bioclastic facies with her- ringbone structures and mudstone with fenestral fabrics towards its upper part (Ruiz-Ortiz et al., 1985; Molina, 1987).

FINAL CONSIDERATIONS

The most important wallrocks of the neptunian dykes (Gavilgn Fm., Lower Liassic, and Camarena Fm., Middle Jurassic) are limestones or diagenetic dolomites deposited in shallow-water environ- ments that were prone to subaerial exposure as a result of sea-level changes. Where the wallrocks are ‘pelagic’ facies (Upper Rosso Ammonitico Fm.) they nevertheless commonly show features typical of shallow-marine environments. Thus, relatively minor changes in sea level would have been necessary to produce emergence. On the other hand, we recognize that other Subbetic Jurassic and Cretaceous formations consisting of deeper-water sedimentary deposits lack neptu- nian dykes. In our model, emergence was caused by tilting related to movement on listric faults. The different genetic stages of neptunian dykes can be related to repeated movement of these faults.

A. MARTiN-ALGARRA and J. A. VERA Departamento de Estratigrafia y Palaeontofogia, Facultad de Ciencias, Universidad de Granada, 18071 Granada, Spain

We welcome the paper by Winterer & Sarti (Sedimentology, 41, 1109- 1132, 1994) who, by reopening an old debate (formerly posed by Fuchtbauer & Richter, 1983, among others) about the origin of the neptunian dykes and associated features of stratigraphic discontinuity surfaces in the Mesozoic of the Alpine Mediterranean regions, give us the opportunity to synthesize

and communicate to Sedimentology readers some of our conclusions, the result of many years of field research and complementary studies in laboratories. Winterer & Sarti (1994) conclude that the origin of the neptunian dykes that we have studied is ‘exclusively’ tectonic, whereas we maintain that subaerial exposure and karstification can be inferred from many of

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Neptunian dykes, southern Spain 961

previous papers, mostly written in Spanish; and (c) the lack of appreciation of the regional magni- tude and lateral evolution of the stratigraphic discontinuity surfaces of the Penibetic of which the neptunian dykes are just one type of evidence. Contrary to the contention of Winterer & Sarti (1994), we have never underestimated the role of synsedimentary tectonics in the genesis of the stratigraphic discontinuity surfaces and associ- ated neptunian dykes of the Penibetic. We have always emphasized its importance in order to explain the genesis of both submarine and sub- aerial discontinuity surfaces, and of associated pelagic facies, both in the Penibetic (Company et al. 1982, pp. 556 & 559; GonzBlez-Donoso et al., 1983, pp. 104, 111 & 112 ; Vera & Martin-Algarra, 1994, pp. 338-339; Martin-Algarra & Vera, 1994, p. 350) and in many other sites of the betic Mesozoic (e.g. Garcia-Hernandez et al., 1988a, 1989). Moreover, we explicitly stated that the origin of the neptunian dyke system in Grazalema, Villaluenga del Rosario and other Penibetic sites must be interpreted as a conse- quence of the tectonic fracturing and later widen- ing of the fissures by dissolution (Martin-Algarra, 1987, p. 128, lines 18-20; p. 132, lines 23-30; pp. 135-136; see also pp. 153-157 and 213-217, and figs 42-45 and 62-67, especially fig. 65, block 9, where the interaction between tectonism and eustasy is clearly presented).

The Penibetic is the westernmost tectonic and palaeogeographical unit of the External Zones of the Betic Cordillera. It constitutes three litho- stratigraphic units (Martin-Algarra, 1987; Martin- Algarra & Vera, 1989, 1994). These units are: the Hidalga Group (Triassic of germanic facies), the Libar Group (Jurassic to Lower Valanginian, neritic to pelagic limestones and dolomites) and the Espartina Group (Lower Cretaceous to Lower Miocene pelagic marls and marly limestones). The upper limit of the Libar limestones (Torcal Formation) is determined by an abrupt, clearly erosional surface that can be recognized all over the extension of the Penibetic, more than 100 km along the regional strike and 40 km across (from NW to SE). This surface is very complex in its details because it constitutes at least four different superimposed stratigraphic discontinuity sur- faces, separated by thin and condensed but fossiliferous pelagic sediments of the Lower Cretaceous (Gonztilez-Donoso et a]., 1983). We have interpreted only one of these four surfaces, that dated as Hauterivian, as karstic in origin. This dissolution surface, which is the most evi- dent stratigraphic discontinuity of the Penibetic,

the examples that they have reinterpreted as exclusively submarine.

We thank the authors for acknowledging our ‘detailed descriptive publications’ (p. 1110), but we want to add that, in our papers, after a detailed presentation of our observations and data and after a careful review of the available literature, we also made very prudent and serious interpre- tations of the observed facts, among them the proposal of the karstic hypothesis for some (but not all) neptunian dykes. Figure 17(A) of Winterer & Sarti (1994) seems to us erroneous, because it tries to unify observations made in outcrops belonging to different tectonic units, of different ages, sometimes separated by wide, deep basins. Neptunian dykes of the Angosturas, which belongs to the External Subbetic, are of Upper Jurassic age; those of Castillo de Locubin are Middle Jurassic and are located in the northern border of a Median Subbetic tectonic unit; finally the Zafarraya outcrop belongs to the southern part of the Internal Subbetic and the dykes described are, mainly, Middle and Late Liassic. Winterer & Sarti (1994) relate outcrops which are not corre- lated either in space or in time, and which, at the time of deposition, were situated in very different and distant areas of the South Iberian Mesozoic palaeomargin. We wish to point out that their fig. 17(B) is their interpretation of ideas presented by Vera et al. (1984), but that such a model has never been published in any of our papers.

THE HAUTERIVIAN PALAEOKARST OF THE PENIBETIC

We will concentrate now on the Cretaceous strati- graphic discontinuity surfaces of the Penibetic, not only in Grazalema and Villaluenga del Rosario (localities cited by Winterer & Sarti, 1994), but also in neighbouring areas, where excellent and unique outcrops bearing, in our opinion, clear evidence of Cretaceous subaerial palaeokarst can be recognized everywhere. A catalogue of many of these localities, with indica- tion of U.T.M. coordinates, can be found in Gonzalez-Donoso et al. (1983) and Martin-Algarra (1987), but there are many other sites where similar observations are possible. In our opinion, their conclusions relative to the Grazalema and Villaluenga del Rosario outcrops are partially erroneous, and result from: (a) the incomplete, and slightly biased revision of just some of the numerous outcrops previously studied by us; (b) incomplete reading and misunderstanding of our

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962 A. Martin-Algarra and J. A. Vera

is clearly exposed at many localities, revealing the palaeorelief in three dimensions, because recent erosion has exhumed the palaeokarstic morpholo- gies carved in the Libar limestones by removing the marly Cretaceous sediments that covered them. The erosion associated with this surface diminishes from the NW, where it reaches deeper levels, towards the SE, where only small-scale (decimetres to centimetres of dissolution) features are visible and the stratigraphic succession is more complete and better stratified, sometimes ‘paraconformable’. The morphology is, however, rather similar (if not identical) in most outcrops, the essential differences being the size of the dissolution features.

The palaeokarstic origin of this surface is appar- ent in many outcrops, and karstic landforms similar to those developed on recent karst are extremely abundant. The most typical features are decimetre- to metre-scale dissolution pits and hollows (solution pans or kamenitzas) with sinu- ous and very irregular lateral boundaries and flat bottoms, which isolate many residual, flat-topped (coinciding with the stratification) and frequently stepped prominences (mogotes) that are not later- ally limited by any kind of fracture in most cases. Nevertheless, when fractures are locally present, they have been exploited as sites of accelerated dissolution. The dissolution structures show many solution flutes (and even runnels in out- crops where the palaeokarstic relief is more devel- oped, as in the Grazalema area) that can be identified as rillenkarren and rinnenkarren. Most of these dissolution features are orientated per- pendicular to the stratification of the karstified limestones regardless of tectonic dip. These typi- cal karstic morphologies were described and illustrated by GonzAlez-Donoso et al. (1983, figs 2, 6-8, 13 and 14), Company et al. (1982, figs 3 and 4), Martin-Algarra & Vera (1994, figs 3, 5 and 6) and, especially, Martin-Algarra (1987, figs 31, 32, 34, 36 and 37, and plates 1 2 , 13 and 14).

This field evidence demonstrates: (1) that the dissolution morphologies are not a local but a regional feature of the top of the Libar Group; (2) that they were formed before folding of the Penibetic, when the bedding of the limestones of the Libar Group was horizontal, which is also obvious from their relations with the overlying pelagic marly sediments (Espartina Group); and (3) that the Hauterivian dissolution followed a vertical, gravitationally determined tendency, which is rather difficult to explain by submarine dissolution or erosion, except if the sediment was unconsolidated during submarine erosion and

had been mechanically eroded along nearly verti- cal walls. This does not seem to have been the situation during the formation of the Cretaceous neptunian dykes and associated features, as can be concluded even from the partial obser- vations made by Winterer & Sarti (1994) in the Villaluenga del Rosario area. Their fig. 16 (com- pare with our previous sketch of the outcrop, in Company et al., 1982, fig. 4; Martin-Algarra, 1987, fig. 37) shows that the oolitic limestones with associated coral reefs (typical shallow-water, neritic platform facies) of the Endrinal Formation (Dogger) are unconformably covered by the nodu- lar, pelagic limestones rich in ammonites and tethyan pelagic microfossils (Protoglobigerina, Saccocoma and Calpionellidae) of the Torcal Formation (Middle Oxfordian to Berriasian in this outcrop). This indicates that platform limestones were indurated before the beginning of the Late Jurassic pelagic sedimentation. The same can be concluded from observations in Grazalema, where very scarce information is given by Winterer & Sarti (1994) although this outcrop was described in great detail by Martin-Algarra (1 987). In the Grazalema region the contact between the Endrinal Formation and the Torcal Formation is full of small-sized neptunian dykes filled with pelagic limestones sometimes bearing a rich fauna of Upper Oxfordian dwarf ammonites (Martin- Algarra, 1987, fig. 36B, photos 3 & 4 of plate 5; see also Martin-Algarra & Vera, 1994, fig. 3B,C). The Endrinal (Dogger) limestones were clearly indurated and cemented before deposition of the Torcal Formation.

Throughout the Penibetic, the Cretaceous dis- continuity surface, with dissolution features on top of the Libar Group, post-dates deposition of the Lower Valanginian (top of the pelagic lime- stones of the Torcal Formation) and sometimes a thin bed dated as Late Valanginian to Lowermost Hauterivian (Gonzalez-Donoso et al., 1983). In the Grazalema and Villaluenga del Rosario region, this discontinuity surface is laterally very irregu- lar with spectacular palaeorelief of tens of metres. Because of the palaeorelief and the thinness of the Torcal Formation in these outcrops, Cretaceous erosion locally eliminated the pelagic Torcal For- mation, so that Cretaceous marly sediments rest directly on dissolutional features in the shallow platform limestones of the Endrinal Formation. This is evident in many outcrops, but especially in Grazalema, where (originally vertical) dissolu- tion flutes such as those described above dissolve both the Torcal and the Endrinal limestones and cross-cut the contact between them (fig. 3B,C in

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Neptunian dykes, southern Spain 963

is evident after reading the text since no breccias are mentioned for Villaluenga, and from the fact that the ornamentation for box 7 is not typical for breccias, but rather for crudely bedded ‘sandy or silty’ (actually in this case pseudonodular and microsparitic) limestones. Nevertheless, excellent outcrops of autoclastic and collapse breccias, the matrix of which is dated by fossils, occur at many localities in the area, especially near Grazalema (Company et al., 1982, fig. 2 & p. 551; Martin- Algarra, 1987, p. 132), but also near Villaluenga del Rosario. That Winterer & Sarti (1994) had not recognized these Cretaceous breccias is under- standable, since they are very similar to Recent breccias associated with the Quaternary karst, which is strongly developed in the area. Only after careful examination of these outcrops and systematic sampling and dating by fossils is it possible to avoid confusion.

Martin-Algarra & Vera, 1994); moreover, these solution pipes are filled with pelagic sediment, here dated as Late Aptian. The mechanical, verti- cal erosion of a semi-indurated deep pelagic sedi- ment, such as described by McHugh et al. (1993), seems an unlikely explaination for the features of the Torcal Formation in the Grazalema outcrop.

When describing the remarkable palaeorelief at Villaluenga del Rosario, Martin-Algarra (1987, p. 135 and fig. 37) remarked on ‘the absence of conglomerates and breccias in the palaeocavity’. We were therefore surprised that Winterer & Sarti (1994) should write (pp. 1127-1128) ‘We observed no true “collapse” breccia (Martin- Algarra, 1987)’, when we specifically state that these breccias were not observed by us in the outcrop! Perhaps they were confused by the key to fig. 4 in Company et al. (1982), where box 7 is erroneously annotated as ‘breccia’, but this error

REPLY TO MOLINA El’ AL.

E. L. WINTERER* and M. SARTIt *Scripps Institution of Oceanography, La Jolla, CA 92093, USA tFacoltu d i Scienze, Universitu di Ancona, Ancona 60132, Italy

At the localities at issue in our differences with Molina et al., neptunian dykes of pelagic sedi- ment are hosted by shallow-water carbonate strata and are overlain by sediments of pelagic facies. We are acutely aware of the difficulties in assign- ing the formation of the dykes and other cavities in the host platform carbonates to either a sub- aerial or a submarine environment. Indeed, one of us has assembled evidence for a subaerial environment of formation of large depressions on the surface of now-sunken mid-Cretaceous shallow-water carbonate platforms (guyots) in the north-west Pacific (van Waasbergen & Winterer, 1993; Winterer et al,. 1995). This is based on the three-dimensional morphology of the features as imaged in multibeam and seismic reflection pro- filer records, and on the occurrence of rounded pelagic-sediment-filled cavities in drill cores of the limestones. Only weak indications in the stable-isotopic data give evidence of meteoric waters, the open cavity system having been mainly still empty until submergence and pre- cipitation of typical marine cements in the cavities. The localities we described in Spain, where dykes and other cavities are hosted by platform carbonates, pose equal challenges for interpretation.

For the localities we described in our paper, the important issue between us and Molina et al. is mechanical fracturing vs. chemical dissolution in a subaerial environment. We are familiar with the papers in which Vera and his associates noted the role of fractures in creating neptunian dykes, and in this we are in entire agreement. Indeed, the Spanish workers have been able in some places to relate the fractures to regional tectonics. However, at the localities that we described in our paper (except Villaluenga del Rosario and Grazalema), we discovered no evidence for significant disso- lution in forming the cavities filled by younger pelagic sediments and calcite precipitates, and argue that the cavities are of mechanical origin, by fracturing that created fissures open to the sea floor. Our main point of difference is with the interpretation by Molina et al. and their associates that subaerial dissolution and the formation of karstic cavities have played a major role in the formation of the neptunian dykes.

In their discussion, Martin-Algarra and Vera, and by implication Molina et al., appear to have misunderstood some of our words: we do not say that the dykes are tectonic, but rather that the dyke and sill cavities are of mechanical origin, while some other cavities were formed by

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964 E. L. Winterer and M. Sarti

submarine, as opposed to subaerial, dissolution. Tectonic implies to us deep-seated, whereas mechanical includes both deep-seated and more surficial processes, such as slumps and slides. We believe the latter are the more important in fissure formation.

EMERGENCE AND PALAEODEPTHS

We are admirers of the works of the Spanish geologists documenting the history of block fault- ing during the evolution of the region, but we do not accept as proven, in the absence of the types of evidence cited in our reply to Martin-Algarra and Vera, that this tectonic mechanism, even in combination with eustatic fluctuations in sea level, can ensure that all neptunian dyke locales were emergent. Many of the discontinuities cited by Garcia-HernBndez et af. (1989) are in our opinion classic submarine ferromanganese hard- grounds, e.g. the ammonitic ferromanganese ‘kamenitzas’ at Illora (Garcia-Hernandez et al., 1986-87) and at the intra-Rosso Ammonitico sculptured surface in the quarry near the Cortijo de Las Cuillas (Garcia Hernandez et al., 1988), which we studied in detail but did not include in our article as a result of lack of space.

Molina et al. have misunderstood our conten- tion that none of the neptunian dike localities we studied is associated with shallowing-upward sequences. We were pointing out that at none of our localities are the strata overlying the dykes of shallower aspect than the underlying host rocks for the dykes. Where the host strata show evi- dence for shallowing-upward environments and good evidence for emergence (e.g. tepees, palae- osols, etc.), then a partial case may be made for a subaerial environment for the dykes. We would be convinced if there were also indications in the overlying strata of non-marine or shallow-water environments (as at Marroqui hill; see below).

BAUXITE

We stand by the essential correctness of the sketch geological map (our fig. 7) of the bauxite quarry near Zarzadilla de Totana. Our map and section of the quarry are completely at odds with the geometric relations shown in the cartoon in Vera et a f . (1987) and on the generalized map and sections of Molina et al. (1991). The main contacts between bauxite and host rocks are cross-cutting buttress unconformities. The obvious steep fault

with breccia that bounds the east side of the bauxite body (not shown at all on the Molina et al. map) is far from supposed Liassic faults shown on their map (we note they show these faults cutting the Upper Jurassic and Lower Cretaceous). A small cave opening into the upper west quarry wall and descending west parallel to Liassic bed- ding planes for at least a few metres is in fact shown on our map. The floor of the cave is covered by bauxite up to a level 1 m or so from the roof. The upper 15 cm of bauxite in this cavern includes shells of modern land snails, and the roof is decorated with dripstone. If the upper, open part of this branch cave is not simply a mined-out space, then it gives further credence to the hypothesis of a late Cenozoic origin for the cave. The cited thesis of Rey is unavailable in research libraries in the U.S. or Italy.

The supposed connection between the bauxite body and the Rosso Ammonitico, some 35m above the bauxite, is in our opinion non-existent. The tiny patches of red material enveloping shattered limestone half-way between, reported in Vera et af. (1987) and Molina et al. (1991), is a stain of iron oxide on fractures, and is not bauxite. Besides, the unconformity between the Liassic platform carbonates and the pelagic Rosso Ammonitico is a submarine hardground, locally plastered with ferromanganese oxides. It is not a karstic surface, but a ‘stepped’ unconformity developed by sliding away of joint-bounded blocks of platform carbonates along joints in the Liassic strata. The Rosso Ammonitico is not a viable candidate as a subaerial source for the bauxite.

CALCRETES AND GEOCHEMISTRY OF ‘SPELEOTHEMS’

JimBnez de Cisneros et al. (1991) had recourse to diagenetic re-equilibration to explain the marine signatures in the calcites on neptunian dyke cav- ity walls, an explanation that assumes from the outset that the calcite was deposited from mete- oric rather than from marine waters. We, of course, accept that cavities may be formed in a subaerial setting and later be filled by calcite in a submarine environment (van Waasbergen & Winterer, 1993). We also accept the strong iso- topic and textural evidence (JimBnez de Cisneros et al., 1993) for subaerial environments of forma- tion of the calcretes on Marroqui hill, at the top of Liassic platform carbonates. We regret this paper was unavailable to us at the time we submitted our paper.

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Neptunian dykes, southern Spain 965

the dykes were open for at least a time in water of the depth appropriate to the infilling facies, which in no case known to us from the Mesozoic of southern Spain are either subaerial or shallow- water facies. In examining the walls of dykes for cross-dyke fits, it is essential to keep in mind the possibility of strike-slip as well as simple tensional opening, which can create apparent mismatches in cross-section. Our examples from Castillo de Locubin illustrate this situation.

The J imhez de Cisneros thesis data on thermo- luminescence are unavailable to us. The extensive literature on thermoluminescence suggests great caution in interpretation, as, for example, to determine relative depths or degree of water turbulence.

CAVITY MORPHOLOGY AND RELATED SHALLOW-MARINE FACIES

We studied the outcrops in the small quarry by the farmhouse at Cuillas and saw the ‘karstic surface with kamenitzas’, which in our opinion is a classical submarine ferromanganese-encrusted hardground, with the typical concentric- mounded and cracked layering of manganese crusts (which may well be in part the product of bacterially mediated accumulation). Molina et al. will find descriptions of such hardgrounds in Jenkyns (1986). Current bedding, cited by Molina et al., is no indication of water depth, since, as has been known for decades, vigorous currents stir the sea floor at all depths, producing current ripples and even dunes (Heezen & Hollister, 1971, esp. chapter 9; Lonsdale et al., 1972). We have not seen the outcrops described by Castro et al. (1990), although we note that the stratigraphic relations they show (two-dimensional views only) strongly resemble those we described at Las Cuillas and Navazuelo, with a hardground at the contact between carbonate platform and pelagic facies. We did study in detail the outcrops in the vicinity of Illora (Garcia-Hernandez et al., 1986- 87) where we observed a ferromanganese hard- ground at the contact between Liassic platform limestone and overlying pelagic facies.

We reiterate our faith in the observations of Molina et al. that karstic features have indeed been observed, as, for example, the sinkholes they cite at Fuente Rebola and elsewhere, where the depressions are apparently visible in three di- mensions rather than only the two dimensions available at most outcrops. We do note that the same authors labelled as karstic depressions the stepped unconformities at Las Angosturas, Navazuelo and Zarzadilla de Totana, which we have shown to be of different origin.

Finally, although we did not discover any examples other than at Villaluenga del Rosario and Grazalema, we accept in principle that the walls of dykes may be modified by dissolution, but note that this can easily take place in the submarine environment. It is clear from the pelagic nature of the infill of the dykes that

SOME SPECIFIC POINTS

Molina et al. are quite correct in calling attention to the errors in our references, and we stand chastized and embarrassed in not having sorted out all the specific references to localities described by Vera and his associates. The readers of this journal will be grateful for their corrections.

We attempted to help readers understand the actual field evidence by making detailed maps and cross-sections at our most important locali- ties, rather that relying on depicting relations by showing dykes, for example, as merely conven- tional ‘lightning-strokes’ into the host strata. This effort to stick close to the field facts may have led our critics astray when they arrived at the sum- mary diagrams in our fig. 17 . These are clearly cartoons, combining features from many localities of different ages and from different tectonic units. Their aim was to contrast the subaerial- dissolution and the submarine-mechanical hypotheses by drawing together the main features at representative localities, and to compress them into a model physiography, with the vertical scale exaggerated for illustrative purposes. We are aghast that any reader would take the cartoons for realistic palaeogeography at some one time and place. Similarly, the diagrammatic stratigraphic columns in our fig. 3 are meant to convey the essential geometric relations, and the scales are exaggerated to show details at contacts.

As to the internal subdivisions of major tectonic units in the region, we readily concede to Molina et d. the arguments they present about the details - we do not pretend to their knowledge of local structural relations, and have manifestly assigned some of the outcrops we studied to the wrong subunit, and hence to a wrong particular position in the overall Subbetic palaeogeography. We are concerned, rather, with the local slope relations that influence processes of slope failure and fis- sure opening, and we think we have got these

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966 E. L. Winterer and M. Sarti

right. We thank Molina et al. for pointing out the position of the outcrops at Las Cuillas as belong- ing to a tectonic unit in the interior instead of along the southern part of the Northern Ridge, but this does not change the fundamental top-of-slope position we ascribed to these outcrops, based on the presence of a ‘stepped’ unconformity with preserved detached blocks. Indeed, Molina (1987, fig. 142, panel D) and Molina & Ruiz-Ortiz (1990) show a palaeogeography for this unit at the end of the Middle Jurassic that depicts a south-facing escarpment at the edge of a plateau, with a still- exposed breccia of displaced Middle Jurassic platform oolite blocks in an Upper Jurassic red nodular limestone matrix along the base of slope, in exactly the manner we hypothesized.

REPLY TO MARTIN-ALGARRA & VERA

We welcome the opportunity to clarify both the points of difference between ourselves and Vera and his associates and possible misreading of what we tried to set forth in our paper.

SUBMARINE VS. SUBAERIAL DISSOLUTION OF LIMESTONE

Many of the supposed subaerial karst features of the Penebetic region, exemplified by the outcrops at Villaluenga del Rosario and Grazalema, are in a particular stratigraphic setting, namely that the dissolution features are carved into underlying pelagic sediments and are in turn overlain by younger pelagic sediments. A main point of our paper is that we found no evidence for subaerial dissolution as an agent in the formation of the erosional cavities and, by implication, no basis for requiring that the strata hosting the cavities were subaerially exposed by a relative drop in sea level. We explicitly indicated the probable disso- lution origin of the grooves and cavities at Grazal- ema and at Villaluenga del Rosario, but also indicated the evidence that these formed by sub- marine processes in a pelagic environment. The literature of marine geology is rich in documented examples of dissolution of calcium carbonate in the sea at depths beneath the lysocline, where submarine karst may develop (e.g. Berger et al., 1979; Malfait & van Andel, 1980). It is also a well-established feature of ocean basins that dis- solution levels tend to be significantly shallower on or near continental margins than in the open ocean, because of CO, released from decay of organic components in near-continent sediments

(Berger & Winterer, 1974). Abyssal depths are not required. Dissolution effects are enhanced where bottom currents keep undersaturated waters in contact with the sea bed and disperse the dis- solved ions. Submarine dissolution is also capable of producing erosional features in well- indurated limestone (Konishi, 1989). Submarine dissolution unconformities can be very wide- spread, as, for example, in the Cenozoic pelagic carbonate sediments of the equatorial Pacific, where some dissolution horizons can be mapped over regions at least as large as 400000km2 - nearly the size of Spain (Mayer et al., 1986).

In ascribing dissolution features - flutes, runnels, pits, hollows, cavities, prominences and collapse breccias - to a subaerial origin, more than morphology is required: material evidence of a subaerial phase must also be adduced. This might include, for example, stable-isotopic data from the exposed rocks, or evidence of palaeosols, tepees, birdseyes, desiccation cracks, non-marine fossils, or dripstone features such as stalactites and stalagmites. Evidence of shallow-water con- ditions in the strata immediately above the disso- lution features is evidence at least pointing in the direction of possible emergence. On the other hand, where the immediately overlying strata are pelagic sediments, and especially where the underlying strata are also pelagic, then a particu- larly heavy burden of proof is necessary to estab- lish a subaerial, as opposed to a submarine, origin for dissolutional features at the contact. Is it reasonable that every trace of shallow-water con- ditions has been removed by erosion, at every outcrop? The wider the extent of the unconform- ity, the less tenable is this erosional mechanism.

To accommodate emergence of pelagic sedi- ments by reason of eustatic falls in sea level into their scenarios, the Vera team has had to invoke relatively shallow (<Zoo m) depths of accumula- tion for the pelagic sediments. There are many documented depth histories for continental mar- gins and oceanic basins in the Atlantic (Initial Reports, Deep Sea Drilling Project, 1972-87; Scientific Results, Ocean Drilling Program, 1988- 91), in which Jurassic and Cretaceous pelagic sediments are similar to those cropping out on the now-exposed circum-Mediterranean Tethyan margins (e.g. Bernoulli & Jenkyns, 1974; Hsu, 1976; Bosellini & Winterer, 1975). We therefore believe that most of the pelagic sediments associ- ated with the neptunian dykes in southern Spain, e.g. the red nodular limestone, the planktonic foraminifera1 limestones and marlstones, without remains of benthic organisms limited to the

0 1995 International Association of Sedimentologists, Sedimentology, 42, 957-969

Neptunian dykes, southern Spain 967

involved, though these might have played a role in enhancing dissolution.

photic zone, were deposited in depths greater than the reach of eustatic fluctuations in sea level during Jurassic and Cretaceous time.

VILLALUENGA DEL ROSARIO AND GRAZALEMA LOCALITIES

We are aware of the many other localities cited by GonzAlez Donoso et al. (1983), and we visited and studied a number of them. We chose to describe the outcrops at Villaluenga del Rosario and Grazalema because the Spanish literature per- suaded us that the authors viewed these as par- ticularly illustrative. At Villaluenga del Rosario, as shown in our detailed drawing of the outcrop (our fig. 16), the dissolution cavity and the dykes truncate not only the shallow-water Endrinal Formation, but also the overlying pelagic Torcal Formation (both of Jurassic age). The infilling sediments are pelagic and of Late Cretaceous age. Thus, the cavities cut into pelagic sediments, are filled with pelagic sediments and are overlain by pelagic sediments. We do not disagree that some of the fissures in the Endrinal Formation may be of mechanical (fracture) origin, later widened by dis- solution. Nor do we disagree that the Endrinal Formation was indurated when Torcal Formation deposition began. Submarine dissolution, like subaerial dissolution, attacks indurated rock. At Grazalema, a very similar situation is present, with Aptian pelagic sediments resting on a pro- nounced dissolution unconformity on pelagic Torcal Formation rocks, which is underlain by shallow-water Endrinal Formation rocks.

Thus, at neither locality is there any material evidence that subaerial or even shallow-water conditions were associated with the formation of the cavities. Neither the morphology of the cavi- ties nor the areal extent of the unconformity is sufficient evidence for emergence. The argument of Martin-Algarra and Vera that the near-vertical joint-controlled (Company et a]., 1982, fig. 2) dissolution grooves at Grazalema were cut by gravity-driven drainage, and hence are of sub- aerial origin, is pure speculation, and no argu- ment against their formation by submarine dissolution is offered. We are aware of the regional extent of the dissolution features at the Hauterivian unconformity, and would expect that any regional joint pattern developed at the time of deformation would be the locus of dissolution at depth during the interval of non-deposition. For neither Villaluenga del Rosario nor Grazalema did we state that physical erosion processes were

REFERENCES

Berger, W.H., Ekdale, A.A. and Bryant, P.P. (1979) Selective preservation of burrows in deep-sea carbon- ates. Mar. Geol., 32, 205-230.

Berger, W.H. and Winterer, E.L. (1974) Plate stratigra- phy and the fluctuating carbonate line. In: Pelagic Sediments: on Land and Under the Sea (Ed. by H. C. Jenkyns and K. J. Hsii), Spec. Pub. int. Ass. Sedimen- tol., 1, 1148.

Bernoulli, D. and Jenkyns, H.C. (1974) Alpine, Mediter- ranean, and Central Atlantic Mesozoic facies in relation to the early evolution of the Tethys, pp. In: Modern and Ancient Geosynclinal Sedimentation (Ed. by R. H. Dott andR. H. Shaver), Spec. Publ. SOC. econ. Paleont. Miner., 19, 129-160.

Bosellini, A. and Winterer, E.L. (1975) Pelagic lime- stone and radiolarite of the Tethyan Mesozoic: a genetic model. Geology, 3, 279-282.

Castro, J.M., Checa, A. and Ruiz-Ortiz, P.A. (1990) Cavidades kkrsticas con relleno de Calloviense supe- rior y Oxfordiense inferior (SubbBtico externo; Sierra de Estepa, prov. de Sevilla). Geogaceta, 7, 61-63.

Company, M., Gonzilez-Donoso, J.M., Linares, D., Martin-Algarra, A., Rebollo, M., Serrano, F., Tavera, J.M. and Vera, J.A. (1982) Diques neptlinicos en el Cretacico del PenibBtico: Aspectos genBticos y etapas de relleno. Cuad. geol. IbBrica, 8, 547-564.

Fuchtbauer, H. and Richter, D.K. (1983) Relations between submarine fissures, internal breccias and mass flows during Triassic and earlier rifting periods. Geol. Rdsch., 72, 53-66.

Garcia-Hern&ndez, M., LBpez-Garrido, A.C., Martin- Algarra, A., Molina, J.M., Ruiz-Ortiz, P.A. and Vera, J.A. (1989) Las discontinuidades mayores del Jur6 sic0 de las Zonas Externas de las Cordilleras BBticas: anilisis e interpretacion de 10s ciclos sedimentarios. Cuad. geol. IbBrica, 13, 35-52.

Garcia-Hernhdez, M., Lupiani, E. and Vera, J.A. (1987a) La sedimentacion liisica en el sector central del Subbetico Medio: registro de la evolucih de un rift intracontinental. Acta geol. Hispanica, 21-22,

Garcia-Hernindez, M., Lupiani, E. and Vera, J.A. (1987b) Discontinuidades estratigrificas en el Jurisico de Sierra Gorda (SubbBtico interno, Provincia de Granada). Acta geol. Hispanica, 21-22, 339-349.

Garcia-Hernandez, M., Martin-Algarra, A., Molina, J.M., Ruiz-Ortiz, P.A. and Vera, J.A. (1988a) Umbrales peligicos: Metodologia de estudio y significado de las facies. 11 Congr. Geol. Espaiia, Simposios, pp. 231-241. S. G. E., Granada.

Garcia-Herniindez, M., Mas, J.R., Molina, J.M., Ruiz- Ortiz, P.A. and Vera, J.A. (1988b) Episodio de karsti- ficaci6n en litorales insulares del Jurasico superior (Fm. Ammonitico Rosso, SubbBtico externo, Provin- cia de Cordoba). I l l Col. Estrat. Paleog. Jurasico de Espaiia, Logroiio, Abstracts, pp. 32-35. G.E.M.

3 29-3 37.

0 1995 International Association of Sedimentologists, Sedirnentology, 42, 957-969

968 E. L. Winterer and M. Sarti

Garcia-Hernandez, M., Molina, J.M., Ruiz-Ortiz, P.A. and Vera, J.A. (1988~) Acuiiamientos y geometrias sigmoidales en calizas pelagicas rojas del Jurasico de la Sierra de Reclot (provincia de Alicante). II Congr. Geol. Esparia, SGE, Granada, Comunicaciones, 1,

GonzBlez-Donoso, J.M., Linares, D., Martin-Algarra, A., Rebollo, M., Serrano, F. and Vera, J.A. (1983) Discon- tinuidades estratigriificas durante el Cretacico en el PenibBtico (Cordillera BBtica). Est. geol., 39, 71-116.

Heezen., B.C. and Hollister, C.D. (1971) The Face of the Deep. University Press, New York.

Hsii, K.J. (1976) Paleoceanography of the Mesozoic Alpine Tethys. Spec. Pap. geol. SOC. Am., 170.

Initial Reports, Deep Sea Drilling Project. (1971-1987)

83-86.

14, 39-41, 43, 44, 47, 50, 72-77, 79, 80, 93-95. Government Printing Office, Washington, DC.

Jenkyns, H.C. (1986) Pelagic environments. In: Sedi- mentary Environments and Facies (Ed. by H. G. Reading), pp. 343-397. Blackwell Scientific Publica- tions, Oxford,

JimBnez de Cisneros, C., Mas, J.R. and Vera, J.A. (1991) Geochemistry of speleothems from Jurassic palae- okarst (Subbetic, Southern Spain). Sediment. Geol.,

JimBnez de Cisneros, C., Molina, J.M., Nieto, L.M., Ruiz-Ortiz, P.A. and Vera, J.A. (1993) Calcretes from a palaeosinkhole in Jurassic palaeokarst (Subbetic, Southern Spain). Sediment. Geol., 87, 13-24.

Konishi, K. (1989) Limestone of the Daiichi Kashima Seamount and the fate of a subducting guyot: fact and speculation from the Kaiko ‘Nautile’ dives. Tectono-

Lonsdale, P., Normark, W.R. and Newman, W.A. (1972) Sedimentation and erosion on Horizon Guyot. Bull. geol. SOC. Am., 83, 289-316.

Malfait, B.T. and van Andel, T.J. (1980) A modern oceanic hardground on the Carnegie Ridge in the eastern Equatorial Pacific. Sedimentology, 27, 467-496.

Martin-Algarra, A. (1987) Evolucidn geologica alpina del contact0 entre las Zonas Internas y las Zonas Externas de la Cordillera Betica (sector central y occidental. Doctoral thesis, University of Granada.

Martin-Algarra, A. and Vera, J.A. (1989) La serie estrati- grhfica del Penibbtico. In: Libro Homenaje a R. Soler (Ed. by A.G.G.E.P., A.G.G.E.P. Madrid), pp. 67-76.

Martin-Algarra, A. and Vera, J.A. (1994) Mesozoic pelagic phosphate stromatolites from the Penibetic (Betic Cordillera, Southern Spain). In: Phanerozoic Stromatolites II (Ed. by J. Bertrand-Sarfati and C. Monty), pp. 345-391. Kluwer Academic, Dordrecht.

Mayer, L.A., Shipley, T.H. and Winterer, E.L. (1986) Equatorial Pacific seismic reflectors as indicators of global oceanographic events. Science, 233,

McHugh, C.M., Ryan, W.B.F. and Schreiher, B.C. (1993) The role of diagenesis in exfoliation of submarine canyons. Bull. A m . Ass. petrol. Geol., 77, 145 -172.

Molina, J.M. (1987) Analisis defacies del Mesozoico en el Subbetico Externo (Provincia de Cordoba y sur de laen). Doctoral thesis, University of Granada.

73, 191-208.

physics, 160, 249-265.

761-764.

Molina, J.M. (1993) Sobre la historia geol6gica del Subbbtico Externo en la provincia de Cordoba y sup de JaBn. Naturalia Baetica, 5, 77-90.

Molina, J.M., Nieto, L.M. and Ruiz-Ortiz, P.A. (1992) Paleokarst jurasico en la Unidad del Ventisquero (SubbBtico externo, Cordilleras BBticas). Geogaceta,

Molina, J.M. and Ruiz-Ortiz, P.A. (1990) Nuevos datos y modelo genetic0 sohre hrechas jurasicas generadas en relaci6n con fallas transcurrentes (SubbBtico Externo, provincia de C6rdoba). Geogaceta, 7, 56-59.

Molina, J.M., Ruiz-Ortiz, P.A. and Vera, J.A. (1985) Sedimentacidn marina somera entre sedimentos pelagicos en el Dogger del SuhhBtico externo (Sierras de Cahra y de Puente Genil, provincia de Cdrdoba). Trab. Geologia, 13, 127-146.

Molina, J.M., Ruiz-Ortiz, P.A. and Vera, J.A. (1987) Capas de tormentas (tempestitas) en el JurBsico del SubbBtico externo (Cordilleras BBticas). Acta geol. Hispanica, 21-22, 167-175.

Molina, J.M., Ruiz-Ortiz, P.A. and Vera, J.A. (1989) Escarpes de falla jurasicos karstificados: un posible margen bypass de umbra1 pelBgico. SubbBtico externo. XII Congr. ESP. Sediment., Comunicaciones, Bilbao, 1, 131-134.

Molina, J.M., Ruiz-Ortiz, P.A. and Vera, J.A. (1991) Jurassic karst bauxites in the Subbetic. Betic Cordillera, Southern Spain. Acta geol. Hungarica, 34,

Ruiz-Ortiz, P.A., Checa, A,, and Molina, J.M. (1990) Paleofosa tect6nica con relleno de Ammonitico Rosso del Jurasico superior (SubbBtico externo, provincia de C6rdoba). Geogaceta, 7, 59-61.

Ruiz-Ortiz, P.A., Molina, J.M. and Vera, J.A. (1985) Coral-ooid-oncoid facies in a shallowing-upward sequence of the Middle Jurassic. (External Subbetic. Southern Spain.) In: 6th Eur. Meet. Sedim., I.A.S., Abstracts, Lleida (Ed. by J. Rossell, E. Ramacha, and M. Zamorano), pp. 403-406. Univ. Autdnoma, Barcelona.

Scientific Results, Ocean Drilling Program. (1988) 102, 103. College Station, TX.

Seyfried, H. (1978) Der Suhbetische Jura von Murcia (Siidost-Spanien). Geol. Jb., 29, 1-201.

Vera, J.A. (1988) Evolucidn de 10s sistemas de depdsito en el margen ib6rico de las Cordilleras BBticas. Rev. SOC. geol. Espaiia, 1, 373-392.

Vera, J.A. (1989) Diferenciaci6n de unidades estratigrh- ficas en materiales pelhgicos. Rev. SOC. geol. Esparia, 2,335-374.

Vera, J.A. (1994) Estratigrafia. Principios y metodos. Rueda, Madrid.

Vera, J.A. and Martin-Algarra, A. (1994) Mesozoic stratigraphic breaks and pelagic stromatolites in the Betic Cordillera (Southern Spain). In: Phanerozoic Stromatolites II (Ed. by J. Bertrand-Sarfati and C. Monty), pp. 319-344. Kluwer Academic, Dordrecht.

Vera, J.A., Molina, J.M., Molina-Diaz, A. and Ruiz- Ortiz, P.A. (1987) Bauxitas karsticas jurBsicas en la Zona SubbBtica (Zarzadilla de Totana, Prov. de Murcia, SE de Espaiia): Interpretaci6n paleogeogrg- fica. Acta geol. Hispanica, 21-22, 351-360.

11, 74-76.

163-178.

0 1995 International Association of Sedimentologists, Sedimentdogy, 42, 957-969

Vera, J.A., Molina, J.M. and Ruiz-Ortiz, P.A. (1984) Discontinuidades estratigrAficas, diques neptiinicos y brechas sinsedimentarias en la Sierra de Cabra (Mesozoico, Subbetic0 externo). In: Lib. Homen. L. Sanchez de la Torre (Ed. by A. Obrador), Publ. Geologia, University of Aut. Barcelona, 20, 141-162.

Vera, J.A., Ruiz-Ortiz, P.A., Garcia-HernAndez, M. and Molina, J.M. (1988) Paleokarst and related sediments in the Jurassic of the Subbetic Zone, Southern Spain. In: Paleokarst (Ed. by N . P. James and P. W. Choquette), pp. 364-384. Springer, New York.

van Waasbergen, R. and Winterer, E.L. (1993) Summit geomorphology of western Pacific guyots, The Meso- zoic Pacific, Sliter, W.V. and Pringle, M., eds., AGU Geophys. Mon., 77, 335-366.

Winterer, E.L. and Sarti, M. (1994) Neptunian dykes and associated features in southern Spain: mechanics

Neptunian dykes, southern Spain 969

of formation and tectonic implications. Sedimentol-

Winterer, E.L., van Waasbergen, R., Mammerickx, J. and Stuart, S. (1995) Karst morphology and diagen- esis of top of Albian platforms, Mid-Pacific Moun- tains. In: Proc. Ocean Drilling Program, Scientific Results, 143 (in press).

Wright, V.P. and Smart, P.L. (1994) Paleokarst (Disso- lution diagenesis): its occurrence and hydrocarbon exploration significance. In: Diagenesis N (Ed. by K. H. Wolf and G. V. Chillingarian), Develop. Sedi- ment., 51,477-517.

OW, 41,1109-1132.

Discussions received 28 March and 2 April 1995; Replies received 1 7 April 1995

0 1995 International Association of Sedimentologists, Sedimentology, 42, 957-969