The provenance of a turbidite system within a tectonically active wrench basin: Insights from heavy mineral characteristics of Miocene sandstones in the Tabernas Basin, south‐east Spain

This paper provides insight into the provenance of the Late Miocene turbidite succession of the Tabernas Basin. Although this area has been extensively studied, only limited attention has been paid to sediment provenance. Through heavy mineral analysis, it has been possible to identify provenance‐related signatures from the adjacent Sierra de los Filabres and Sierra Alhamilla uplifts. Stable mineral ratio data confirm that the Sierra de los Filabres provided sediment with generally higher chloritoid:tourmaline and higher Type Bii garnet abundances than those derived from the Sierra Alhamilla. By comparison, modern sediments derived from the Sierra Alhamilla have garnet compositions with larger proportions of Types A and C, suggesting that the basinal sediments were not sourced from the incipient Sierra Alhamilla Uplift. Heavy mineral analysis confirms that the Sierra de los Filabres was the primary source for the Tabernas succession, with minor variations indicating that the erosive part of the system migrated across the uplift. Input was predominantly from the Nevado–Filábride Complex, with minor amounts from the small remnant of the Alpujarride Complex attached to the southern margin of the Sierra de los Filabres. Evidence strongly suggests a single sediment routing system but identifies some subtle provenance variations. In particular, there was a shift in detrital garnet composition between the Sartenella Formation and the Verdelecho Formation, Solitary Channel and El Gordo Megabed, which is attributed here to a shift in catchment within the Sierra de los Filabres. This shift appears to have occurred during the deposition of the Sartenella Formation, since the garnet compositions of the Verdelecho Formation and Solitary Channel are similar to each other and differ from the preceding part of the Sartenella Formation. The Solitary Channel displays marked heterogeneities in provenance character, manifested by changes in chloritoid abundance, consistent with previous studies that suggest the depositional architecture in the channel was influenced by high‐frequency changes in sediment flux and sea level.

Stable mineral ratio data confirm that the Sierra de los Filabres provided sediment with generally higher chloritoid:tourmaline and higher Type Bii garnet abundances than those derived from the Sierra Alhamilla.By comparison, modern sediments derived from the Sierra Alhamilla have garnet compositions with larger proportions of Types A and C, suggesting that the basinal sediments were not sourced from the incipient Sierra Alhamilla Uplift.Heavy mineral analysis confirms that the Sierra de los Filabres was the primary source for the Tabernas succession, with minor variations indicating that the erosive part of the system migrated across the uplift.Input was predominantly from the Nevado-Filábride Complex, with minor amounts from the small remnant of the Alpujarride Complex attached to the southern margin of the Sierra de los Filabres.Evidence strongly suggests a single sediment routing system but identifies some subtle provenance variations.In particular, there was a shift in detrital garnet composition between the Sartenella Formation and the Verdelecho Formation, Solitary Channel and El Gordo Megabed, which is attributed here to a shift in catchment within the Sierra de los Filabres.This shift appears to have occurred during the deposition of the Sartenella Formation, since the garnet compositions of the Verdelecho Formation and Solitary Channel are similar to each other and differ from the preceding part of the Sartenella Formation.The Solitary Channel displays marked heterogeneities in provenance character, manifested by changes in chloritoid abundance, consistent with previous studies that suggest 1

| INTRODUCTION
The Tabernas Basin in Andalucía, south-east Spain (Figure 1) hosts a well-exposed turbidite succession of Late Miocene (Tortonian-Messinian) age.These deepwater sediments are frequently visited on educational field trips, especially by geologists investigating potential hydrocarbon reservoir analogues.Extensive sedimentological, stratigraphic and structural studies of the basinal succession (Kleverlaan, 1987(Kleverlaan, , 1989a(Kleverlaan, , 1989b;;Cronin, 1995;Haughton, 2000;Pickering et al., 2001;Hodgson & Haughton, 2004;Koopmans, 2012;Baudouy et al., 2021) have led to the identification of two lobe systems, informally the termed Sandy System (Sartenella Formation) and Muddy System (the confined Loma de Los Baños Formation and the unconfined Verdelecho Formation), a channel unit within the Sartenella Formation (Solitary Channel) and a basin-wide seismite (El Gordo Megabed).Nevertheless, there remains some doubt over the provenance of the sandstones and of the stratigraphic relationships between the lobe and channel systems.Kleverlaan (1989aKleverlaan ( , 1989b) invoked a single source, draining the Sierra de los Filabres to the north (Figure 1).Haughton (2000) and Hodgson and Haughton (2004), who examined the succession in the Alfaro Sub-basin (the southern extension of the basin), agreed that the Sierra de los Filabres was the source for the early part of the succession but proposed a subsequent second source from the south-west, possibly the Sierra Gador, for the calciturbidites that include detritus from the Alpujarride-type basement (Figure 1).Pickering et al. (2001) agreed with Haughton (2000) that the Solitary Channel flowed to the east and northeast and believed it was connected to the channelised the depositional architecture in the channel was influenced by high-frequency changes in sediment flux and sea level.

K E Y W O R D S
heavy mineral analysis, provenance, Tabernas Basin F I G U R E 1 Regional tectonic elements with the location of the study area in south-east Spain and the relationship of the Tabernas Basin to the Sorbas Basin, Vera Basin and Cerro Alfaro Sub-basin along the Alpujarran Corridor.Potential sediment source areas are the Sierra de los Filabres to the north and the Sierra Alhamilla to the south.
sandstones of the Sandy System.Kleverlaan (1989a) and Cronin (1995), however, interpreted a westerly flow for the Solitary Channel.
Despite extensive and prolonged research into the sedimentology and structural history of the Tabernas Basin, until recently, detailed provenance studies have been conspicuous by their absence, although abundant basement clasts have enabled relationships to be established with the bordering basement highs.The scarcity of provenance information has recently been addressed by the detailed petrographic study of Koch and McCann (2020), which investigated whether the sandstones were derived from a single source or multiple sources on the basis of variations in framework constituents.They concluded that the Molinos and Verdelecho formations were purely sourced from local Nevado-Filábride basement (with the Verdelecho Formation showing evidence of internal variation within the Nevado-Filábride Complex), while a combination of the Nevado-Filábride Complex and the Alpujarride Complex contributed to the Sartenella and Loma de los Baños formations.See below for more context regarding the Nevado-Filábride and Alpujarride basement complexes.
The current paper presents complementary provenance information acquired from conventional heavy mineral analysis, the determination of provenancesensitive heavy mineral index parameters and the geochemistry of detrital garnet and chloritoid, and discusses their implications in terms of the palaeogeographical setting of the basin succession and the stratigraphic relationships within the turbidite system.The data presented here form part of a larger data set, including biostratigraphy, which is currently in preparation for additional publication.

| PRINCIPLES AND METHODS
Heavy mineral assemblage compositions are controlled not only by provenance but also by other processes that operate during the sedimentary cycle (weathering, transport, deposition and diagenesis; see Morton, 2012, and references therein).One approach to reduce the effects of these processes on the provenance signal is to determine ratios of minerals that have similar hydraulic behaviour, minimising hydrodynamically induced variations and are stable in the context of the study, eliminating the effects of diagenesis (Morton & Hallsworth, 1994).Of the indices considered most useful by Morton and Hallsworth (1994), apatite: tourmaline (ATi) and garnet: zircon (GZi) have the greatest potential for examining provenance variations in the Tabernas Basin.The rutile: zircon, monazite: zircon and chrome spinel: zircon indices, which were regarded as useful by Morton and Hallsworth (1994), are difficult to apply owing to the general scarcity of these components in the assemblages.However, Knox et al. (2007) noted that chloritoid:tourmaline (CtTi) is a useful index in the Palaeozoic of Saudi Arabia, and given that chloritoid abundances show significant variations in the Miocene of the Tabernas Basin, this parameter has also been determined.
Sandstone samples were collected at outcrop, aiming to cover as complete a stratigraphic coverage as possible, without bias in terms of facies (structured or structureless) or grain size (fine to coarse sand).Sample preparation involved disaggregation using a mortar and pestle, followed by the use of an ultrasonic probe.The samples were then wet-sieved to extract the 125 to 63 μm grain-size fraction, dried and placed into a flask of bromoform, a heavy liquid of specific gravity 2.89, in order to separate the heavy minerals from the less dense framework minerals such as quartz and feldspar.The narrow grain-size window approach is necessary when applying the provenance-sensitive index method, in order to avoid bias by differences related to inherited grain-size distributions from the source lithologies (Morton & Hallsworth, 1994).The heavy mineral separates were dried and mounted onto glass slides using Canada Balsam as the resin.Coverslips were applied over the top and depressed in order to create an even layer of grains to allow for clear optical identification.The slides were then heated at ca 60°C for several hours for the mounting medium to set solid, after which the slides were ready for conventional petrographic analysis.Where possible, splits of the separates were retained for additional study.
Conventional heavy mineral analysis was conducted using a petrographic microscope to determine assemblage compositions and to acquire stable mineral index data, by means of the ribbon counting technique (Galehouse, 1971).Mineral identifications were made on the basis of optical properties as described by Mange and Maurer (1992), and the data set that was acquired is shown in supplementary material (S1).Analyses of garnet and chloritoid compositions (Morton, 1985;Lonergan & Mange-Rajetzky, 1994) were carried out by energy-dispersive X-ray analysis using a Microscan MK56 (Cambridge Scientific Instruments Ltd) electron microprobe, with data acquisition and processing by a Link Systems AN10/25S analyser using the ZAF4/FLS programme.The conditions for the analysis were: accelerating voltage of 15 kv, take off angle of 75°, probe current approximately 3.0 nA (ca 2.2 nA on the cobalt standard), beam diameter of ca 5 μm and a livetime of 30 s.

| REGIONAL SETTING
The Tabernas Basin is one of a series of Miocene wrench basins located in the eastern end of the Alpujarran Corridor, within the Betic Internal Zone of south-east Spain (Sanz de Galdeano et al., 2010;Martinez-Martos et al., 2017;Williams & Platt, 2018).The Tabernas Basin is on trend with the Alpujarran basins to the west and the Sorbas Basin to the north-east (Figure 1).The basin is bounded by the metamorphic basement of the Sierra de los Filabres to the north and the Sierra Alhamilla to the south.The Sierra de los Filabres is primarily formed of Nevado-Filábride Complex basement rocks.These also form the core of the Sierra Alhamilla, where they are surrounded by Alpujarride Complex basement rocks (Martinez-Martinez et al., 1995).Alpujarride Complex rocks also outcrop in small regions along the southern margin of the Sierra de los Filabres (Figures 1 and 2).
The Nevado-Filábride Complex primarily consists of Palaeozoic to Mesozoic metasediments, present in three structural units, from bottom to top, Ragua, Calar-Alto and Bédar-Macael (Santamaría-López et al., 2019).The contacts between the units are believed to correspond to ductile shear zones.All three units were subjected to high-pressure, low-temperature metamorphism during the Alpine Orogeny, with the highest temperatures experienced by the upper (Bédar-Macael) unit (Santamaría-López et al., 2019).Subsequent exhumation (dated by U-Th-Pb on allanite as taking place at ca 13 Ma; Santamaría-López et al., 2019) was associated with an increase in metamorphic temperature of ca 130°C.
The Alpujarride Complex comprises Triassic metacarbonates, phyllites and quartzites, including chloritoidbearing metapelites similar to those of the Nevado-Filábride Complex.However, the metamorphic grade in the Alpujarride Complex is lower than in the majority of the Nevado-Filábride (Egeler & Simon 1969;Azañón & Goffé, 1997).
The metamorphism of both the Nevado-Filábride and Alpujarride complexes took place during the Alpine orogeny (Sanz de Galdeano & Garrido, 2016).Recent geochronological studies on white mica, apatite and zircon indicate the earlier high-pressure, low-temperature metamorphism took place during the Eocene, with higher temperature metamorphism related to exhumation in the Miocene (Bessière et al., 2022;Poulaki et al., 2023).

| STRATIGRAPHIC AND SEDIM ENT OLO GICAL CONTEXT
The basal part of the Tabernas Basin fill succession consists of lower Tortonian continental alluvial redbeds that grade up into blue-grey bioclastic sandstones and conglomerates.This part of the succession is assigned to the Molinos Formation and reflects the onset of tectonically controlled basin subsidence, followed by flooding and deepening during the Middle Tortonian (Hodgson & Haughton, 2004).The continental red beds of the Molinos Formation crop out on the north side of the basin on the Sierra de los Filabres margin and are exposed in the core of the Serrata del Marchante anticline in the basin axis (Figure 2).The red beds contain large boulders and clasts of schistose metamorphic rocks (Nevado-Filábride Complex) in a chaotic proximal assemblage, locally shed off the Sierra de los Filabres basement.
The overlying deep-water sediments have been assigned to the Sartenella, Loma de Los Baños and Verdelecho formations (Figure 3), which are believed to be Tortonian to Early Messinian in age (Kleverlaan, 1989a(Kleverlaan, , 1989b;;Cronin, 1995;Koopmans, 2012) and deposited within ca 2 Myr.Kleverlaan (1987Kleverlaan ( , 1989aKleverlaan ( , 1989b) suggested these deposits are broadly coeval, but Hodgson and Haughton (2004) considered that the Sartenella Formation pre-dates the Loma de Los Baños and Verdelecho formations.The Sartenella Formation consists of confined, wide and extensive channel sandstones and conglomerates (the Sandy System of Kleverlaan, 1987Kleverlaan, , 1989aKleverlaan, , 1989b; Figure 4A) overlying massive, light-coloured deep-water marls and includes the Solitary Channel sandstone at the top of the unit (Figure 4B,C).The Loma de Los Baños (confined) and Verdelecho (unconfined) formations, which together equate to the Muddy System of Kleverlaan (1987Kleverlaan ( , 1989aKleverlaan ( , 1989b)), comprise of confined followed by unconfined turbidites deposited as sheet sandstones with narrow feeder channels in a distinctive dark-coloured mudstone sequence (Figure 4D).The Verdelecho Formation is capped by the El Gordo Megabed (Figure 4E,F), which is a seismite feature that extends across the basin from Buho Canyon in the north to Cerro Pedro 10 km to the south (Figure 2), with additional less voluminous megabeds at higher stratigraphic levels.Baudouy et al. (2021) refer to the Molinos Formation and equivalents as Phase 1, the Sartenella Formation as Phase 2, the Loma de Los Baños Formation as Phase 3 and the Verdelecho plus El Gordo Megabed as Phase 4 (Figure 3).In this paper, the lithostratigraphic nomenclature of Haughton (2000) and Hodgson and Haughton (2004) is followed, but the Solitary Channel is separated from the remainder of the Sartenella Formation in view of its depositional history (Pickering et al., 2001) and the discrepancies concerning its inferred palaeoflow direction.To avoid confusion, in the following text, samples from the Sartenella Formation (excluding the Solitary Channel sandstones) will be called the Sartenella sandstones, and samples from the Solitary Channel sandstone unit of the Sartenella Formation will be referred to as the Solitary Channel.

| HEAVY MINERAL PROVENANCE
A key question concerning the Tabernas Basin fill is the provenance of the sediment.Although the Sierra de los Filabres to the north has been considered the main source (Kleverlaan, 1987(Kleverlaan, , 1989a(Kleverlaan, , 1989b)), the possibility of southwest to north-east transport has been proposed for parts of the Sartenella Formation and the Solitary Channel (Haughton, 2000;Pickering et al., 2001), and palaeoflow from east to west has also been proposed for the Solitary Channel (Kleverlaan, 1989a;Cronin, 1995).The possibility of provenance variations has been investigated using a combination of conventional heavy mineral analysis, determination of provenance-sensitive heavy mineral indices (Morton & Hallsworth, 1994;Knox et al., 2007) and garnet and chloritoid compositional analysis (Morton, 1985;Lonergan & Mange-Rajetzky, 1994).The data set covers the Sartenella sandstones (undifferentiated), the Solitary Channel, the Verdelecho Formation and the El Gordo Megabed, as well as the underlying Molinos Formation redbeds and modern stream sediments draining the two possible source areas (Sierra de los Filabres and Sierra Alhamilla).Heavy mineral F I G U R E 2 Geological map of the Tabernas Basin showing locations of sites discussed in the text and samples used in the heavy mineral provenance study, adapted from Kleverlaan (1987) and Baudouy et al. (2021).Locations 4A through F refer to illustrations of sedimentological elements shown in Figure 4.
signatures of the Loma de los Baños Formation were not acquired owing to its relatively small outcrop area, but could form a focus for future work.Sample locations are shown in Figure 2. Details of the analysed samples, the conventional heavy mineral data set, and provenance-sensitive index measurements are provided in Table S1.

| Heavy mineral assemblages
Six detrital heavy minerals (apatite, chloritoid, garnet, rutile, tourmaline and zircon) comprise the vast majority of the assemblages (Figure 5; Table S1).Other minerals (calcic amphibole, epidote and staurolite) are present sporadically and in minor amounts.Garnet, which is ubiquitous, is the dominant component in the great majority of assemblages.Chloritoid is also abundant, but in a small number of cases (notably in some Molinos Formation, Verdelecho Formation and Solitary Channel samples), this distinctive phase is scarce or absent.Apatite and tourmaline are generally minor, but some samples have higher proportions of these minerals, especially in the sands derived from the Sierra Alhamilla and the Molinos Formation red beds in the Serrata del Marchante Ridge.Zircon and rutile are uniformly minor, but nevertheless ubiquitous, components of the assemblages.

| Provenance-sensitive indices
Variations in provenance-sensitive parameters are shown in Figures 6 and 7.The GZi-ATi plots show that the great majority of samples have similar characteristics, with extremely high GZi and generally low ATi.The only exceptions are a single Sartenella sandstone sample (10.1), which has distinctly higher ATi, and two Verdelecho Formation samples (15.3 and 15.4) that have significantly higher ATi, though not to the same extent as the Sartenella sandstone sample.
By contrast, the CtTi-ATi plots display significantly greater variation.The Sierra de los Filabres source region has high CtTi and low ATi, whereas the Sierra Alhamilla yields sand with lower CtTi and marginally higher ATi.The Molinos Formation displays even more extreme differences: the samples on the northern margin have very similar character to the adjacent Sierra de los Filabres (high CtTi and low ATi), whereas the samples from the Serrata del Marchante uplift in the basin centre have very low CtTi and higher ATi.
For the most part, the Verdelecho Formation and El Gordo Megabed samples have very similar parameters, with high CtTi and low ATi.However, the two Verdelecho Formation samples that have relatively high ATi have distinctly lower CtTi (15.3 and 15.4) and therefore plot at a significant distance from the main Verdelecho Formation cluster.Most Sartenella sandstone samples plot in the same area as typical Verdelecho Formation and El Gordo Megabed samples, but the atypically high ATi sample (10.1) has markedly lower CtTi, similar to the high ATi and low CtTi samples from the Verdelecho Formation.
The greatest complexity on the CtTi-ATi plot is shown by the Solitary Channel, despite the close similarity on the GZi-ATi plot.There is a strong clustering in the same area as the Verdelecho Formation, El Gordo Megabed and Sartenella sandstone samples, but samples from two outcrops deviate from this group towards lower CtTi.Samples 3.1 and 3.2 have moderate to high CtTi, and samples from locality 5 have very low to moderate CtTi.The samples with low to moderate CtTi from the Solitary Channel differ from those in the Verdelecho and Sartenella formations on the basis of their lower ATi.

| Garnet compositions
All of the analysed garnet assemblages (Figure 8; Table S2) are dominated by grains with low-Mg and variable-Ca contents that correspond to Type B of Mange and Morton (2007).The only significant deviation from this character are shown by the two modern samples derived from the Sierra Alhamilla (sample 6.1 having 14% garnets falling in Field A and sample 20.6 having 6% Type C).This suggests that the Sierra Alhamilla presently yields garnet assemblages that do not directly match with any seen in the Miocene Tabernas Basin fill.
Within the dominant Type B garnet group, there are significant variations in the relative proportion of low-Ca (Type Bi) and high-Ca (Type Bii) garnets (Figure 8).Variations in garnet composition, ATi and CtTi (Figures 9 and 10), illustrate further differences between the Sierra de los Filabres and the Sierra Alhamilla, the former having higher Type Bii abundances.There is also a difference between the Molinos Formation at the northern margin compared with the Serrata del Marchante Ridge at the basin centre, the latter having lower Type Bii abundances.
Most Sartenella sandstone garnet assemblages have relatively low Type Bii contents (Figures 9 and 10), the exception being sample 10.1, which has higher Type Bii contents, providing further confirmation that this sample has different provenance characteristics along with its atypically high ATi and low CtTi values.By contrast, Solitary Channel samples have uniformly high Bii garnet contents.In this regard, they are similar to the majority of Verdelecho Formation and El Gordo Megabed samples, which have closely comparable Bii-rich garnet assemblages (Figures 9 and 10).There are two Verdelecho Formation samples that plot away from the main group.Sample 15.4 has lower Type Bii contents in association with atypically high ATi and low CtTi.Sample 15.1 also has low Type Bii contents but has low ATi and high CtTi (Figures 6 and 7), and therefore bears close similarities with Sartenella sandstones (Figures 9 and 10).

| Chloritoid compositions
Chloritoid compositions are believed to depend on the metamorphic grade of the metapelites in which the mineral formed (Lonergan & Mange-Rajetzky, 1994), with low to medium-grade rocks tending to have lower Mg/ Fe ratios compared with high-pressure environments.All the samples have similar detrital chloritoid compositional ranges (Figure 11; Table S3), with most chloritoids falling in the low to medium-grade field.However, a significant subsidiary number of chloritoids from two samples (Sartenella sandstone sample 10.1 and Verdelecho Formation sample 15.3) fall within the range shown by chloritoids originating in high-pressure metamorphic environments.These two samples are also distinctive in having lower CtTi values than all other samples with chloritoid compositional data.The two potential source areas, Sierra de los Filabres and Sierra Alhamilla, show very similar chloritoid signatures to one another (and to the Miocene basin fill).
The great majority of the samples analysed in this study have closely comparable heavy mineral and mineralchemical provenance characteristics that indicate the sediments have the same provenance.Most samples are characterised by very high GZi, high CtTi and low ATi values, in conjunction with garnet assemblages rich in Type Bii and chloritoids with low-pressure metamorphic affinities.This character is found in (i) modern sands shed from the Sierra de los Filabres; (ii) the Molinos Formation at the northern basin margin; (iii) most Verdelecho Formation samples; the El Gordo Megabed samples; and (v) some of the Solitary Channel samples.These sandstones are interpreted as sourced from the Nevado-Filábride Complex, which comprises most of the Sierra de los Filabres to the north of the Tabernas Basin and the Sierra Nevada to the west (Figure 2).Confirmation that sediment was supplied predominantly from the Nevado-Filábride Complex ties in with evidence that exhumation took place at ca 13 Ma, as indicated by the U-Th-Pb dating of allanite (Santamaría-López et al., 2019).
Derivation of sediment from the Sierra Alhamilla can be ruled out on the basis of garnet assemblages, since modern stream sediments draining this area have larger proportions of types A and C garnets compared with all the basinal sediments and the Sierra de los Filabres.Modern sediment from the Sierra Alhamilla has lower CtTi than the Sierra de los Filabres, suggesting that the Sierra Alhamilla provides sediment that is less rich in chloritoid, despite the fact that both Nevado-Filábride and Alpujarride metamorphic rocks are chloritoid-bearing (Azañón & Goffé, 1997).The lack of evidence for sediment input from the Sierra Alhamilla supports the conclusions of Weijermars et al. (1985) and Braga et al. (2003) that this massif did not become emergent until the end of the Tortonian.Sartenella sandstones differ from the Verdelecho Formation, Solitary Channel and El Gordo Megabed samples in terms of garnet geochemistry since, with one exception, the Sartenella sandstones have significantly lower F I G U R E 6 Variations in apatite: tourmaline index (ATi) and garnet: zircon index (GZi) for the Tabernas Basin succession.ATi and GZi, as defined by Morton and Hallsworth (1994).For sample locations, see Figure 2.
Type garnet contents.This difference is interpreted as related to a change in catchment on the Sierra de los Filabres, since in all other respects, the Sartenella sandstone heavy mineral assemblages are closely comparable to the other turbidite sandstones.The lack of correspondence between the Solitary Channel and other Sartenella Formation samples suggests the preserved Solitary Channel deposits are from a different phase of deposition F I G U R E 7 Variations in chloritoid:tourmaline index (CtTi) and apatite: tourmaline index (ATi) for the Tabernas Basin succession.ATi and CtTi, as defined by Morton and Hallsworth (1994) and Knox et al., (2007), respectively.For sample locations, see Figure 2.
to that responsible for the Sartenella sandstones.The similarity between the Solitary Channel and Verdelecho Formation garnet assemblages suggests the change in catchment occurred before deposition of the Solitary Channel, that is during Sartenella Formation deposition (Figure 3), which corresponds to the later part of basin development Phase 2 according to Baudouy et al. (2021).The change in provenance identified herein could be an early of processes set in motion to rearrange the basin geometry.
The Solitary Channel has greater mineralogical heterogeneity than the majority of Verdelecho and Sartenella sandstone samples, as expressed by major variations in chloritoid contents and CtTi.All other parameters (ATi, GZi, garnet and chloritoid compositions) remain consistent, with continued supply from the Sierra de los Filabres being indicated.The variation in chloritoid supply is linked with lithological heterogeneity in the source region and suggests that there was a difference in the catchment for the Solitary Channel compared with the preceding units.One possibility is that the heterogeneities relate to variable input from the orthogneisses and associated lithologies found in the upper part of the Nevado-Filábride Complex, which are rich in tourmaline (Gómez-Pugnaire et al., 2004) and thus are probably to be characterised by low CtTi ratios.Pickering et al. (2001) interpreted the internal channel architecture of the Solitary Channel as resulting from fluctuating relative base levels.They attributed the change in base level throughout the history of the channel to regional tectonism, with higher-frequency variations resulting from fluctuations in sediment supply and calibre from the source area, with sea-level changes possibly also being involved.The heterogeneity associated with the Solitary Channel heavy mineral assemblages also testifies to tectonism and fluctuations in the type of sediment supplied from the Sierra de los Filabres source area.
One Sartenella sandstone and two Verdelecho Formation samples have distinctly different character to other samples of the deep-water succession.They have higher ATi, lower CtTi, lower contents of Type Bii garnet and more diverse chloritoid compositional assemblages, including some with high-pressure metamorphic origin.The provenance of these samples is interpreted as including high-pressure metamorphic rocks found in the Sierra de los Filabres (Gómez-Pugnaire & Franz, 1988).
The source for the Lower Tortonian Molinos Formation red bed succession in the Serrata del Marchante Ridge area is evidently different to that on the northern margin, which was supplied by the Sierra de los Filabres.One possible source is the Alpujarride basement on the adjacent Sierra Alhamilla, but the scarcity of chloritoid is difficult to reconcile with the presence of this mineral in Alpujarride phyllites (Azañón & Goffé, 1997).Furthermore, it is unlikely that the Sierra Alhamilla was emergent in the Early Tortonian (Weijermars et al., 1985;Braga et al., 2003).The origin of this detritus, therefore, remains speculative.
Variations in heavy mineral provenance are mirrored by differences in framework constituents, in particular by the nature of the lithic component (Koch & McCann, 2020).On the basis of petrographic data, the Molinos Formation is interpreted as being solely derived from the Nevado-Filábride Complex, as is the Verdelecho Formation.The Sartenella sandstones have both Nevado-Filábride and Alpujarride detritus.It is therefore possible that the observed difference in garnet geochemistry between the Sartenella sandstones and Verdelecho Formation relates to the greater input from Alpujarride metamorphics recognised on the basis of the petrography (Koch & McCann, 2020).Koch and McCann (2020) also recognised differences in provenance between the Solitary Channel and other Sartenella sandstone samples, consistent with the heavy mineral evidence.
The heavy mineral data provide evidence for heterogeneities in the nature of the source, with variations in metamorphic grade being responsible for changes in chloritoid and garnet geochemistry.This conclusion is supported by the variable nature of the lithic component within the Verdelecho Formation sandstones, indicating that heterogeneities within the Sierra de los Filabres are reflected in the nature of the sediment supplied to the basin (Koch & McCann, 2020).
The petrographic data also indicate the involvement of additional components, notably carbonate intrabasinal material from the coeval shelfal areas, as well as wavereworked material of both extrabasinal and intrabasinal origin (Koch & McCann, 2020).
F I G U R E 8 Garnet compositions in sandstones from the Tabernas Basin succession displayed on Fe + Mn-Mg-Ca ternary plots, with all Fe determined as Fe 2+ .The key ternary diagram illustrates the compositional fields of garnets from potential source lithologies, after Mange and Morton (2007).For sample locations, see Figure 2. Type A-high-Mg, low-Ca, usually found in high-grade metasedimentary rocks and charnockites.Type B-low-Mg, variable-Ca, often rich in Mn, commonly found in amphibolite facies metasediments and intermediatefelsic metaigneous rocks.Type Bi is commonly associated with granitoids, especially if the garnets are Mn-rich.Type C-high-Mg, high-Ca, typical of high-grade mafic and ultramafic gneisses.Type D-Fe 3+ -Ca-rich, generally derived from metasomatic rocks such as skarns, from very low-grade metabasic rocks, or from ultrahigh-temperature metamorphosed calc-silicate granulites.Filled circles-X Mn <5%, open circles-X Mn >5%.

| CONCLUSIONS
Heavy mineral provenance analysis of the Tabernas Basin succession confirms a single dominant source, located in the Sierra de los Filabres to the north, consistent with evidence from sandstone petrography (Koch & McCann, 2020).Variations within the samples are explained by the erosive part of the system moving F I G U R E 9 Variations in apatite: tourmaline index (ATi) and abundance of Type Bii garnet for the Tabernas Basin succession.ATi as defined by Morton and Hallsworth (1994); see Figure 8 for the definition of Type Bii garnet.For sample locations, see Figure 2. across the Sierra de los Filabres uplift, providing sediment from the Nevado-Filábride Complex.The dominant supply was from low to medium-grade chloritoid-rich metapelites, with variable input from high-pressure metapelites and orthogneisses.There was also some input from the remnants of the Alpujarride Complex attached to the southern margin of the Sierra de los Filabres.Supply from the Sierra Alhamilla on the southern border of the basin is unlikely on the basis available data.A single sediment routing system fits with previous sedimentological observations, including those of Kleverlaan (1989aKleverlaan ( , 1989b) ) and Cronin (1995), who both suggest a single sediment routing system from the north.Provenance characteristics of the Solitary Channel differ from those of the Sartenella Formation, suggesting that the sediments preserved represent a later phase of deposition.The Solitary Channel has greater affinities with the Verdelecho Formation, suggesting that a change in provenance took place within the Sartenella Formation.Variations in provenance characteristics within the Solitary Channel are probably due to reflect high-frequency changes in sediment flux and sea level that exerted strong influences on the depositional architecture in the channel (Pickering et al., 2001).

ACKNO WLE DGE MENTS
The authors would like to thank Lee Clark for the sample preparation and John Still at the University of Aberdeen for help with microprobe analysis.A special thanks must also be given to the referees of this paper, their feedback proving supportive and essential in preparing the final version of this manuscript.

DATA AVAILABILITY STATEMENT
Details of the analysed samples, the conventional heavy mineral data set, and provenance-sensitive index measurements are provided in the Supplementary Publication.

ORCID
Paula McGill https://orcid.org/0009-0002-3334-7038F I G U R E 1 1 Bivariate plots illustrating chloritoid compositions in sandstones from the Tabernas Basin.Line dividing low-pressure and high-pressure chloritoid taken from Lonergan and Mange-Rajetzky (1994).For sample locations, see Figure 2. Manganese (Mn), magnesium (Mg) and iron (Fe) (represented on the axes) are the numbers of ions in the chloritoid formula on the basis of 12 oxygens.

F
Illustrations of the main sedimentological elements in the Tabernas Basin fill.For locations, see Figure 2. (A) Massive stacked channel sandstones of the Sartenella Formation, Rambla de Sierra.The sandstones are erosional and anastomosing, within a channelised sandstone sequence.(B) Solitary Channel outcrop in the Rambla de Lanjuar.(C) Solitary Channel equivalent outcrop forming a resistant top to the Cerro Alfaro.(D) Verdelecho Formation sandstone beds with aligned schistose blocks (Nevado-Filábride Complex), top of section, proximal, near the northern margin.(E) El Gordo Megabed outcrop in Cerro Pedro, to the south of Cerro Alfaro.(F) El Gordo Megabed outcrop in Rambla de Tabernas.

F
Bar chart showing heavy mineral assemblage compositions.'Others' = calcic amphibole, epidote and staurolite.Sample order does not imply relative stratigraphic position.For sample locations, see Figure 2.

F
Variations in chloritoid:tourmaline index (CtTi) and abundance of Type Bii garnet for the Tabernas Basin succession.CtTi as defined byKnox et al. (2007); see Figure8for the definition of Type Bii garnet.For sample locations, see Figure2.