Pre‒volcanic sedimentation in the MJ‒1 Cycle started with grayish to reddish bioclastic wackestone‒packstone limestones, 2 m thick in their maximum thickness, which contain occasionally phosphatic or ferruginous oolites and usually firmgrounds or hardgrounds developed at the top of beds that present signs of bioturbation (Thalassinoides). Resedimented and reelaborated ammonite specimens have enabled the identification of the Bradfordensis and Concavum chronozones (Brasilia sp., Apedogyria sp., Vacekia sp., Erycites sp., Abbasitoides sp., Abbasites sp., Rodaniceras sp., Graphoceras sp., Ludwigella sp.). No specimens belonging to the Murchisonae Chronozone in the El Pedregal Formation have been found.

Volcanic rocks were emplaced on the carbonate platform at the early stages of the MJ‒1 Cycle, overlying the Aalenian (Concavum Chronozone) limestones. The volcanic products consist almost exclusively of explosive volcaniclastic deposits with abundant clasts of sedimentary rocks, although effusive lavas may be a minority component. Lava flows (Fig. 5A) grade vertically and laterally into volcaniclastic deposits (Fig. 5B), which, in turn, pass laterally into epiclastic accumulations. Here the term ‘volcaniclastic’ is used as a descriptive term for fragmental volcanic rocks with no genetic implications, and the term ‘epiclastic’ is used when post‒eruptive sedimentary activity can be identified with certainty. Lava lobes coincide with, or are near to, the maximum thickness of the mound; however, feeder dykes linked to vent sites have not been found.

The post‒volcanic carbonate sediments present variable thicknesses that range from 0 on the volcanic flanks up to a maximum of 20 m in CA‒12 stratigraphic log. Three main types of carbonate lithofacies from the El Pedregal Formation are identified in the post‒volcanic succession during the early Bajocian MJ‒1 Cycle, based on field observations (grain size, bedding characteristics or sedimentary structures) and petrographic analysis (texture, allochem types). These lithofacies are: A) bioclastic wackestone‒packstone limestones, B) crinoidal wackestone to grainstone limestones, and C) Cross‒bedded bioclastic grainstone limestones.

Lithofacies A is a grayish bioclastic wackestone‒packstone with centimetric to decimetric irregular chert nodules (Fig. 6A) and abundant macrofossils of cephalopods (belemnites and ammonites). Under petrographic microscope, it shows a mud‒ to grain‒supported fabric with sectorally packed allochems embedded into a micritic to microsparitic, even pseudosparitic, matrix (Fig. 6B). Skeletal grains are basically composed of echinoderm fragments (almost all of them crinoids), minor thin‒shelled (microfilaments) and thick‒shelled bivalves, punctate brachiopods, foraminifera, bryozoans, ostracods, and serpulids. Non‒skeletal grains consist of rounded to subangular intraclasts and peloids of different sizes, as well as fine subhedral or anhedral crystals of terrigenous quartz (<1%). Blocky sparry cement is occasionally present inside intergranular voids, whereas syntaxial overgrowth cements on echinoderm plates are very common. Silicification is manifested both by partial silica replacement of thick‒shelled bivalves and intergranular microcrystalline aggregates of authigenic quartz.

The thin‒bedded to thick‒bedded lithofacies A (ranging from 5 to 80 cm) is organized into thickening‒, coarsening‒ and shallowing‒upwards sequences, showing remobilization surfaces with reworked ammonites (both resedimented and reelaborated) in the uppermost beds. Firmgrounds and hardgrounds with biogenic trace fossils (usually Thalassinoides) and ferruginous crusts are common across the sequence boundaries. Resedimented ammonoid taxa collected from lithofacies A have allowed the recognition of the Propinquans and Humphriesianum chronozones: Bradfordia sp., Nannina sp., Dorsetensia sp., Strigoceras sp., Emileia sp., Stemmatoceras sp., Itinsaites sp., Stephanoceras sp., Normannites sp., Oppelia sp., Skirroceras sp., Paulostephanus sp., Chondroceras sp., Poecilomorphus sp., Teloceras sp.

Lithofacies B is a grayish to bluish gray massive and, normally, coarse‒grained wackestone to grainstone with no internal structure or faintly laminated (Fig. 6C). The petrographic microscope reveals a mainly bioclast‒supported and densely packed fabric. Microcrystalline micritic matrix is scarce, scattered, and sometimes appears as a fine‒bioclastic micrite. Patchy recrystallization of micrite to microspar and even to pseudospar is frequent (Fig. 6D). Skeletal allochems consist almost entirely of fragmented crinoids and, less commonly, fragmented thick‒shelled bivalves, punctate brachiopods or foraminifera. Non‒skeletal allochems, which are variously sized and shaped, are composed of partly recrystallized micritic intraclasts, very abundant rounded or ellipsoidal mud peloids, and subhedral or anhedral crystals of terrigenous quartz characterized by undulose extinction. Primary intergranular porosity was reduced both by sintaxial overgrowth cement on crinoid fragments and intergranular or shelter inequant blocky mosaics. Cement rims of bladed calcite crystals can also be seen coating shells fragments.

The thick‒bedded (up to 2 m thick) massive lithofacies B shows sedimentary structures such as erosional surfaces within beds and occasionally a faint tractive lamination. Bioturbated (Thalassinoides) and early cemented firmgrouds/hardgrounds are developed at the top beds, which are around 1 m thick, whereas more massive and thicker intervals of lithofacies B, with no hardground surfaces, do not show a clear cyclic organization. Moreover, centimetric and sharp‒based episodes of lithofacies B can also appear interbedded within the thickest (decimetric) beds of lithofacies A.

Although belemnites are common, the ammonite content is virtually absent in this coarse‒grained lithofacies. However, Fernández‒López et al. (1985) identified the Propinquans Chronozone in their CAUDIEL‒XXVI stratigraphic log, in a lenticular bed with a maximum thickness of 0.5 cm located immediately above the Aalenian beds, based on the presence of Skirroceras sp. and Kumatostephanus perjukundus.

Lithofacies C is a grayish to reddish gray cross‒bedded bioclastic grainstone (Fig. 6E). The microfacies analysis shows a grain (bioclast)‒supported fabric with very closely packed grains and absent micritic matrix. Blocky and syntaxial rim calcite cements infill the scarce primary intra‒particle porosity (Fig. 6F). The most common bioclasts are fragmented crinoids (plates and stems) and thick‒shelled bivalves, with lower percentages of prismatic bivalve shells, punctate brachiopods fragments, and foraminifera. Angular and subrounded micritic intraclasts, sometimes bioclastic wackestone intraclasts, and smaller rounded mud peloids formed by fragmentation of intraclasts are common non‒skeletal constituents. Fine‒sized subhedral or anhedral crystals of detrital quartz characterized by undulose extinction are also present. The compaction and pressure solution of alloquems is evident along the irregular stylolitic contacts intersecting them. The non‒stratified and coarse‒grained lithofacies C do not reflect any cyclic pattern and evinces a complete absence of ammonite content.

In well‒expanded carbonate successions of the Iberian Basin, the MJ‒1 Cycle began with El Pedregal Formation sediments resting on the basinal‒scale intra‒Murchisonae unconformity which marked the lower boundary of this second‒order MJ‒1 Cycle (Fernández‒López, 1997a,b; Fernández‒López & Gómez, 2004; Gómez & Fernández‒López, 2004a,b, 2006). In the Caudiel outcrop, however, the sedimentation began during the Bradfordensis Chronozone. No evidence of the post‒unconformity Murchisonae Chronozone has been found, which enables the inference of regionally wider gaps in shallower and poor‒expanded successions like this one.

Aalenian sediments (Bradfordensis and Concavum chronozones) represent successions deposited under low sedimentation rate conditions (stratigraphic condensation), containing mixed fossil assemblages (taphonomic condensation). However, they constitute, probably, expanded sediments (with no sedimentary condensation) deposited under high accumulation rates and separated by non‒depositional or erosional gaps (Gómez & Fernández‒López, 1994). Even so, Aalenian deposits can be found in the whole outcrop with non‒substantial variations in thickness and, even, in sedimentary distinctive features. As previously stated, volcanic accumulation was emplaced around the Aalenian‒Bajocian boundary, and it is only later (Bajocian) that non‒uniform variations in both thickness and facies of the sedimentary infill are appreciated.

To begin with, a description of post‒volcanic sediments on the north part of the volcanic mound will be made. Firstly, a significant hiatus was identified along which erosional and/or non‒depositional steady conditions were placed on the depositional surface during the Discites and Laeviuscula chronozones (Fernández‒López et al., 1985), probably over virtually the entire outcrop. This omission suggests a late Concavum‒early Propinquans uplift (lasting about 400 ka, according to Ogg & Hinnov, 2012) that suppresses the accommodation space and precludes sedimentation. It was along this interval that the volcanic edifice was more likely to be eroded at the top and even to be emerged. In fact, lateral epiclastic landslides driven by the wave effect occurred at some point in the time interval between the end of the Concavum Chronozone and the onset of the Propinquans Chronozone. Nevertheless, as explained above, this must have happened relatively shortly after the volcanic accumulation.

On the other hand, lithofacies A, B, and C of post‒volcanic Bajocian sediments exhibit similar components, but they differ in whether intra‒particle porosity has been infilled by micritic matrix or calcite cement, and in their distinctive sedimentary structures. All these features seem to point to variable energy conditions and distinct bathymetric locations on the platform. Lithofacies A (bioclastic wackestone‒packstone limestones with chert nodules) is interpreted to have been deposited in a relatively shallow open platform. The ammonite content in lithofacies A is probably restricted only to adult forms which could have reached these shallow areas as a result of the dispersion that affects the floating shells of dead specimens. Taphonomic‒resedimented taxa have characterized the Propinquans and Humprhiesianum chronozones. Lithofacies B (massive wackestone to grainstone, mainly crinoidal limestones) is interpreted to be originated by gravity flow processes. The triggering mechanism for gravity flow deposits was probably the sweeping effect of waves and currents over the upper parts of the volcanic edifice (Fig. 9A). Sessile crinoids colonized the summit and flank environments of the mound, and, once they died, their remains were transported down the slope and deposited as successive avalanche bodies at both the lower part and the base of the flanks (Gómez, 1979; Cortés & Gómez, 2016). The numerous internal erosional surfaces suggest multiple and successive events. Ammonoids are virtually absent in the coarse lithofacies B, though Fernández‒López et al. (1985) were able to identify the Propinquans Chronozone at the base of a lithofacies B set, immediately above the Aalenian sediments and beyond the point at which the volcanic mound is no longer present. Lithofacies C (bioclastic grainstone limestones), with high‒energy features such as cross‒stratification, is interpreted as the product of migrating shallow subtidal shoals (Fig. 9A). The lack of ammonites throughout the whole lithofacies C suggests inhospitable living conditions and/or unfavorable conditions for their preservation.

As stated above, the MJ‒2 Cycle has not been recorded in the Caudiel outcrop. The sedimentation in the Bajocian time ceased abruptly towards the end of the Humphriesianum Chronozone. Since it is assumed that the position of the platform bottom had not fundamentally changed from the onset of the Niortense Chronozone until the end of the Parkinsoni Chronozone (length of time the MJ‒2 Cycle) in the Caudiel outcrop, the top of the El Pedregal Formation, concurrent with the upper boundary of the MJ‒1 Cycle, is assessed as the most appropriate surface to become the reference datum of this cycle for schematic representations. Figures 8A and 9B schematically illustrate the time‒space distributions and relationships between lithofacies A, B, and C along a cross‒section constructed through the northern flank of the volcanic mound. When the flat and uniform surfaces at the top are used, the tectonostratigraphic relationships of the units below can be evidenced by the observation of uneven bottoms, differential subsidence and variations in infilling thickness, despite the fact that the vertical scale has been strongly exaggerated. The thicknesses of Bajocian sediments vary quickly depending on the sector considered, suggesting an influence of the substrate movement on the thickness variation. It is obvious that the volcanic mound implied a significant relief on the sea bottom that reduced, if not precluded, the post‒volcanic sedimentation. However, a flat‒topped reconstruction reveals that the mound was not the only relief present during the Bajocian deposition. A topographic high of similar magnitude appears to be developed towards the northernmost part of the outcrop, so that the sedimentation fills the small basin‒like space formed between the ramp that dips gently off the northern high and the north flank of the mound. Lithofacies B deposits extend throughout both slopes and the merging area, which is consistent with downdip gravitational deposition derived from the two areas of high topography.

As can be seen in Figures 8A and 9B, lithofacies B sediments usually are slightly older (base of the Propinquans Chronozone) than those of lithofacies A (top of the Propinquans Chronozone‒top of the Humphriesianum Chronozone) except in the northern basin margin. At this site, the contact between a relatively lower‒energy lithofacies A and a higher‒energy lithofacies B takes place through a lateral and jagged facies change within a section of comparable age. Therefore, it seems that lithofacies B sediments coming from the volcanic mound are limited to the areas near the flank and the foot of the slope, while lithofacies B sediments that originate from the northern topographic high are far more laterally expansive.

High‒energy lithofacies C environments are restricted to the top of the northern structural high, constituting the source area for gravity‒induced coarse‒grained lithofacies B on the northern slope. Storm waves and currents are interpreted to be the dominant triggering mechanism by which remobilized parts of banks and shoals overstep the margin of the structural high, shedding off and tumbling down the slope under the influence of gravity. To be more precise, the cross‒bedded bioclastic grainstones lying on the Aalenian substrate to the north of the Caudiel outcrop do not undergo vertical facies changes along the total thickness of the section until the base of the next overlying Domeño Formation. Due to the absence of ammonites, the boundary Bajocian‒Bathonian cannot be traced with certainty within the stratigraphic interval. However, an undetermined lower portion of the cross‒bedded bioclastic grainstones must be Bajocian in age to constitute the device formed by shoal facies located at the top of the topographic high and by gravitational sliding facies on the slope (Figs. 9B, 10). Therefore, the gravitational sliding deposits, which are coeval with the well‒dated lithofacies A sediments form the Bajocian lithofacies B, and the lower portion of the cross‒bedded bioclastic grainstones, presumably Bajocian in age, composes the lithofacies C (Figs. 9B, 10).

The concurrence of nearly 50 m‒thick non‒emerged volcanic deposits compared to a very reduced marine depth, represented by the bioclastic shoal complex to the north, is better explained when the subsidence affecting the volcanic mound is considered. Such configuration requires the existence of two domains which had different subsidence rates and were controlled by an inferred synsedimentary fault. The hanging wall block comprising the volcanic mound moves downward relative to the northern structural high represented by the footwall block.

On the other hand, the lateral distribution of unconformities (firm‒ and hardgrounds) between CA‒7 and CA‒24 stratigraphic logs (Fig. 8A) is also significant. The shallowing‒upward sequences formed by lithofacies A, as well as the non‒cyclic massive intervals of lithofacies B, are bounded by firmgrounds or hardgrounds. In Figure 8A, lateral correlations between firmgrounds and hardgrounds have been drawn within the Bajocian sedimentary succession on the northern flank of the volcanic mound. As can be seen, the lines of correlation tend to converge and overlap until their pinching out on the updip flank of the mound. The form described by the correlation lines, converging upwards to the highs and flexing downwards to the trough, suggests that the bottom subsided favored by synsedimentary faulting. This subsidence resulted in the creation of accommodation that was progressively and simultaneously filled up with sliding sediments coming from the highs. The confluence of the correlation lines towards the northern high reveals how the bedding planes tend to be slightly deformed (normal drag folding near the fault) resulting in a gentle hanging wall syncline (Fig. 8A). The dip of the slopes (flank of the mound and wall of the structural high) is smooth; nevertheless, gravity‒flow sediments do not seem to need high slope gradients to slide. Submarine slides happen on modern slopes of less than 4º (Shanmugam, 2016). In the slopes that connect the shallow‒water carbonate platforms of the Bahamas with the deeper water areas, Eberli (1988) reported that carbonate turbidites start to accumulate on slopes with declivities of less than 3º. In the margin of the Upper Devonian Ancient Wall carbonate complex of Alberta (Canada), Cook & Mullins (1983) described a 1 m‒thick bed that was interpreted as a probable grain‒flow deposit. This bed may have been initiated on slopes of 5 to 10º, but after about 1 km it moved across gradients of probably less than 2º.

Later (during the Humphriesianum Chronozone), litofacies A arranged into shallowing‒upward sequences in the central part of the basin‒like space, away from the mound influence. Meanwhile, the northern mechanism continued to operate and to provide litofacies B sediments around the synsedimentary fault.

In the southern part of the volcanic mound, substantial thickness reductions of the post‒volcanic sediments belonging to the MJ‒1 Cycle can be observed as compared to thicknesses measured on the north flank (Figs. 7, 8B). The thickness of the volcanic rocks is also smaller in this southern flank. Post‒volcanic sediments of the MJ‒1 Cycle have not been able to be accurately dated as no ammonoids have been found. They are assigned to the early Bajocian because the sedimentary facies are similar to those of the north flank, especially to lithofacies B, but basically because they are stratigraphically positioned above the well‒dated Aalenian succession and below several thin beds that are late Bajocian (Niortense Chronozone) in age (CA‒65 stratigraphic log). Lithofacies B sediments deposited on the south volcanic flank must come from the sweeping of dead crinoid remains on the summit and slope, as in the case of the north flank. Central parts corresponding to the summit and upslope areas of the volcanic mound have remained non‒covered by sediments at the end of MJ‒1 Cycle, to be covered later by Bathonian and Callovian strata.

The highest rates of subsidence and the greatest sedimentary thickness occurred around the north flank of the volcanic mound, while lower rates of subsidence appear to have led simultaneously to smaller sedimentary accumulations on the south flank of the volcanic mound. All these features are compatible with a half‒graben‒like depression structure, where the downthrown block is north‒dipping against the surface of the synsedimentary fault. A pivoting zone has been tentatively located towards the middle part of the volcanic mound to account for the rotating motion of the down‒dropped ground, probably favored by not a planar, but rather a curved, fault plane (Fig. 11A).

In the southernmost point of the platform under the volcanic mound, there must exist a new hinge zone that worked against the northward dipping in order not only to prevent the emersion of the most distal parts of the southern seafloor, but also to implement the southward creation of accommodation (Fig. 11A).

There is virtually no sedimentary record throughout the whole MJ‒2 second‒order Cycle in the Caudiel outcrop. Two alternative approaches may be envisaged concerning the null or minimum accommodation that occurred at the time when this sedimentary cycle developed: (1) if tectonism was the only mechanism for accommodation generation on a basinal scale, then it can be claimed that no subsidence took place in the Caudiel outcrop from the onset of the Niortense Chronozone to the end of the Parkinsoni Chronozone, (2) if the creation of accommodation was mainly eustatic in origin, the Caudiel outcrop had to undergo uplift able to compensate the global accommodation that was created along this time interval.

The MJ‒3 Cycle is characterized by the alternation of subsidence‒uplift. After an extended sedimentary gap (MJ‒2 Cycle), the sedimentation resumed during the early Bathonian Zigzag Chronozone with coarse‒grained lithofacies of the Moscardón Formation. The shoals field/gravitational flows system induced by the half‒graben activity remained active at the beginning of the MJ‒3 Cycle (Bathonian Zigzag Chronozone) just like in the early Bajocian (Propinquans and Humphriesianum chronozones). This happened to such an extent that Bajocian lithofacies B sediments (MJ‒1 Cycle) are indistinguishable from the overlying limestones of the Bathonian Moscardón Formation (MJ‒3 Cycle, CA‒7 to CA‒10 stratigraphic logs). Similarly, the Bajocian lithofacies C (MJ‒1 Cycle) and the beds of the overlying Bathonian Moscardón Formation (MJ‒3 Cycle) cannot be distinguished on the northern topographic high (CA‒4 to CA‒6 stratigraphic logs) (Fig. 10). It is therefore likely to include Bajocian litofacies B and C within the Moscardón Formation. Its lower boundary is dated, consequently, as Propinquans Chronozone in the northern part of the Caudiel outcrop. It is unclear whether the still lifted and uncovered parts of the volcanic mound could provide bioclastic input, but it is a fact that sediments of the Bathonian Moscardón Formation pinch out onto El Pedregal Formation beds instead of overlying the volcanic slope (Figs. 9B, 11B).

In the southernmost point studied, 3 m of sediments belonging to the Moscardón Formation (above the well‒dated beds as late Bajocian in CA‒65 stratigraphic log) have been observed, but their age is uncertain, ranging from late Bajocian to early Bathonian. In any case, as the northward tilted ground persisted to favor a renewed shoals/slides system, the hinge zone of the south flank had also been activated both to prevent the most distal parts of the southern seafloor from being subaerially exposed, and to place the platform ground around the submarine erosional‒depositional boundary (Fig. 11B).

Later, still during the Zigzag Chronozone, the high‒energy and coarse‒grained sediments of the Moscardón Formation were replaced abruptly by finer limestones belonging to the Domeño Formation. This indicates a rapid and significant deepening of the depositional environment. The northern structural high sank and ceased to be an important supply source paleogeographic element. The half‒graben and its related synsedimentary fault will no longer act.

In the northern flank, the Domeño Formation (MJ‒3 Cycle) has been found now to be much more expanded than the Moscardón Formation, since it overlies practically the entire northern volcanic flank that had remained uncovered until that time. In addition, the infilling of the accommodation space seems to be indicative of a homogenization in subsidence patterns (Figs. 7, 11C).

However, in the southern flank, the Domeño Formation shows less expansion as it pinches out onto the Bajocian Moscardón Formation and does not overlie the volcanic rocks. This points to lower rates of subsidence than in the northern flank, even to a slight uplifting. Nevertheless, increasing thickness can be observed farther southward from the southern hinge zone (Figs. 7, 11C).

The upper part of the Moscardón and the lower part of the Domeño Formation have been deposited during early Bathonian Zigzag Chronozone times with almost no record of subsequent Bathonian chronozones. A generalized uplifting seems to have taken place once again, competing with global or regional creation of accommodation throughout the middle and late Bathonian.

It has not been possible to determine an accurate chronostratigraphy of the Callovian (Domeño Formation, MJ‒4 Cycle) in the Caudiel outcrop. However, Fernández‒López et al. (1985) assigned an early Callovian age to the upper part of the Domeño Formation, below the Arroyofrío Bed, in their CAUDIEL‒VI and CAUDIEL‒XXVI stratigraphic logs. Thus, it is very likely that tectonic patterns operated in a similar way to that of the previous MJ‒3 Cycle; that is, an uplift following the initial subsidence. In any case, a homogeneous subsidence pattern can be identified by comparing the thicknesses of the Callovian Domeño Formation observed in both flanks of the volcanic mound. However, the greater thickness on the northern flank could be linked to a possible tilting northward of the ground (Fig. 11D), perhaps related to some normal fault located away of the area studied.