Mid-Cretaceous paleogeography and paleoceanography of the Betic Seaway (Betic Cordillera, Spain)

Palaeogeography, Palaeoclimatology, Palaeoecology, 107 (1994): 1-33

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Elsevier Science B.V., Amsterdam

Mid-Cretaceous paleogeography and paleoceanography of the Betic Seaway (Betic Cordillera, Spain) K. Reicherter a, T. Pletsch a, W. K u h n t a, J. Manthey", G. Homeier a, J. Wiedmann a and J. T h u r o w b a Institutfiir Geologie und Paliiontologie, Universitdt Tfibingen, Sigwartstr. 10, W-7400 Tiibingen, Germany b lnstitutfiir Geologie, Ruhr-Universitiit Bochum, Postfach 102148, W-4360 Bochum 1, Germany (Received March 11, 1993; revised and accepted July 14, 1993)

ABSTRACT Reicherter, K., Pletsch, T., Kuhnt, W., Manthey, J., Homeier, G., Wiedmann, J. and Thurow, J., 1994. Mid-Cretaceous paleogeography and paleoceanography of the Betic Seaway (Betic Cordillera, Spain), Palaeogeogr., Palaeoclimatol., Palaeoecol., 107: 1-33. Sedimentary and micropaleontological features of Cretaceous formations in the Betic Seaway have been examined. In the External Zone of the Betic Cordillera (Southern Spain) planktic and benthic foraminiferal assemblages were studied to establish a biostratigraphic framework and to provide estimates of paleo-waterdepth. Further environmental interpretations are based on the analysis of clay minerals, sedimentary petrography and organic geochemistry. We suggest the existence of several subbasins with differing subsidence histories created by transform tectonics along the axis of the Betic Seaway. A comparison with mid-Cretaceous sequences of adjacent DSDP/ODP holes indicates that the general paleoceanographic conditions within the seaway were similar to the North Atlantic. Our results are integrated in a paleogeographic reconstruction for the Western Mediterranean during the late Albian.

Introduction and methods

Fallot (1948) and Durand Delga (1972, 1980b) proposed a division of the western Mediterranean realm into two margin/trough settings north and south of the Alboran Block (Mesomediterranean subplate of Andrieux et al., 1971). The northern basin (Betic Seaway of Thurow and Kuhnt, 1989) is regarded as an eastward shallowing marginal basin of the North Atlantic (Dercourt et al., 1985, 1986). Leblanc and Olivier (1984) proposed major transcurrent movements along the northern margin of the Alboran Block at least since the Oligocene. The role of lateral movements during the formation of the Betic Seaway in the Mesozoic is still a matter of discussion. Torres-Roldfin (1979), Comas et al. (1982) and Vera (1988) proposed basin formation in a pure stretching regime with classic passive continental margins for the Jurassic and Early Cretaceous. However, several geometric features in facies distribution are difficult to explain

by a passive margin model and strike-slip movements may have played a more important role than previously assumed. Considerable difficulties exist in recognizing ancient marine strike-slip systems and related basins because unambiguous evidence is rarely preserved. Several characteristic features of strikeslip basins have been established (Mitchell and Reading, 1986; Ben-Avraham, 1992; Einsele, 1992): strike-slip basins are usually elongate along the major transcurrent fault and do only rarely contain any record of syn-depositional volcanism and no plutonism, but diapirism is often observed. Individual facies have a limited lateral extent and there is usually evidence for a nearby active source area, frequently indicated by restricted deposition of locally derived conglomerates and breccias. The basin fill is characterised by abundant synsedimentary deformation, possibly in response to seismicity along the basin margins. Sediment distribution shows a complex geometry and sediment

0031-0182/94/$07.00 © 1994 - - Elsevier Science B.V. All rights reserved. SSDI 0031-0182(93)E0119-E

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composition reflects multiple sources. The characteristic size of a marine strike-slip basin ranges from 10 x 20 km to about 30 x 100 km, reaching depths of more than 1000 m. The ratio of depth to surface is thus considerably higher than in other types of extensive basins. In this paper we examine sedimentary, mineralogic and micropaleontological features of Cretaceous sedimentary formations in the Betic Seaway, which now forms the External Zone of the Betic Cordillera in southern Spain. This zone, comprising the Prebetic, Intermediate Units, Subbetic and Penibetic units (Blumenthal, 1927; Fallot, 1948) has been the object of geological investigations for more than 100 years (Kilian, 1889). An overview of the modern tectonosedimentary subdivision is given in Azrma et al. (1979) and is depicted in Figs. 1 and 2. Our studies concentrate on the deep-water facies within the Subbetic and on pelagic swell facies of the Penibetic units. Methods include clay mineralogy, organic geochemistry, sedimentary petrography of redeposited material, and micropaleontology. Methods

Provenance of redeposited material was examined using standard sedimentary petrographic techniques (e.g. point-counting and semi-quantitative studies of thin-sections, SEM and EDX analyses) and was supplemented by micropaleontological studies of redeposited microfossil assemblages. Clay minerals were studied by X-ray diffraction of oriented pastes. Preparation, measurement and interpretation of the < 2 ~tm-fraction were done according to the standard procedures used at Lille University (Holtzapffel, 1985). Results are therefore readily comparable to DSDP/ODP and onshore data from adjacent Atlantic sites obtained at the same laboratory. Error range of mineral percentages can be assumed to be in the order of + 5 % in an assemblage (Holtzapffel, 1985). Selected samples were investigated by SEM with combined EDX to study texture and associated non-clay minerals. Pelagic claystones were analyzed for the content and type of organic matter using the Rock-Eval II devices at the Institut Franqais du P&role as well

K. REICHERTER ET AL.

as standard and fluorescence microscopy for petrography and reflectance measurements of selected samples. Autochthonous foraminiferal assemblages were studied to establish a biostratigraphic framework and provide estimates of paleo-waterdepth and depositional environment. Subsidence analysis was carried out using BasinWorks TM by Marco Polo Software (1991) based on Bowmann and Vail (in press).

Geological setting The investigated sections are located in the Subbetic Zone between the cities of Granada and Jarn and include Subbetic and Penibetic localities in the westernmost part of the Betic Cordillera (Fig. 1). The Subbetic series strike NE-SW and commence with Upper Triassic rocks of GermanoAndalusian facies comprising shales, evaporites and basic volcanic rocks. Its Mesozoic and Tertiary series are part of a nappe system created by Oligo/ Miocene continental collision of the Iberian and African plates (Garcia-Hernandez et al., 1980). The Subbetic is bound to the North by the Prebetic (Blumenthal, 1927), the Neogene Guadalquivir complex and further north by the Variscan series of the Iberian Meseta. To the South a pile of nappes with varying intensity of metamorphism forms the Internal Zone of the Betic Cordillera. The Subbetic Zone is subdivided into three structural units, which roughly correspond to three major Mesozoic paleogeographic zones (GarciaHernandez et al., 1980). These are the External Subbetic to the North, the Median Subbetic in the central part of the basin and the Internal Subbetic to the South. The External Subbetic formed an intra-basinal swell (Molina, 1987), whereas the Median Subbetic includes basinal sequences with the deepest depositional environments in the Subbetic Zone. The Internal Subbetic is regarded as a basinal high and may be the eastern equivalent of the Penibetic Zone (Blumenthal, 1927) of the Campo de Gibraltar near Ronda. Our studies were mainly concerned with the Cretaceous Median Subbetic and the Penibetic. The following depositional history can be reconstructed (Azrma et al., 1979):

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MID-CRETACEOUS PALEOGEOGRAPHY AND PALEOCEANOGRAPHY OF BETIC SEAWAY (BETIC CORDILLERA. SPAIN)

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Fig. I. Structural units of the central part of the Betic Cordillera. Compiled using data of Az(~maet al. (1979) and Mapa Geol6gicoMinero de Andalucia, Consejaria de Economia e Industria, Junta de Andalucia (1985). Locality of the sections: 1~ Rio Fardes; 2 = Benalfla de las Villas; 3 = Sarinas; 4 = SW of Rute; 5 = Benameji; CdG = Campo de Gibraltar.

Platform carbonates were deposited in the Western Tethyan sea between the Iberian and African plates during the early Liassic. Individual facies zones developed after the collapse of the shallow marine platform in the Late Pliensbachian due to the separation of areas with different subsidence. The Middle and Late Jurassic are characterised by the formation of half-graben structures which are delineated by condensed pelagic red limestones on the inferred swells and by calcareous turbidites and radiolarites (Ruiz-Ortiz et al., 1989) in the basins. Basic volcanic rocks (tboleiitic and alkaline) of partly submarine origin are intercalated in pelagic sediments which range in age from the late Liassic to the Jurassic/Cretaceous boundary. Geochemical analyses (Comas et al., 1986; Puga et al., 1989b; Reicherter, unpublished data)

indicate intra-plate type volcanism. No mid-ocean ridge basalts have been described so far. Pelagic limestones and marl/limestone alternations make up the Lower Cretaceous sequence. Debris flow deposition and intense slumping may indicate synsedimentary tectonic movements. The Albian sedimentation is characterised by dark claystones, siliciclastic and calcareous turbidites and channelfills. Calciturbidite sequences of Cenomanian to Turonian age are often interrupted by organic-rich sediments at the Cenomanian-Turonian boundary. Overlying the calciturbidites is the CouchesRouges facies from the upper Turonian onwards. The Couches-Rouges facies is typically developed as pink to red, alternately white marly limestones mainly consisting of planktic foraminifera and calcareous nannoflora. Clastic influx increases sig-

4

K. REICHERTERET AL.

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nificantly above the Cretaceous/Tertiary (K/T) boundary. A Paleogene "flysch"-facies first comprises nummulite-bearing calciturbidites, later gravity mass flow-deposits with fragments of metamorphic basement rocks. The development of the Penibetic Zone is mainly distinguished from the Median Subbetic and the more internal Predorsalian units by a final drowning of the carbonate platforms as late as in the Albian. Lower to Middle Jurassic sediments are dominated by shallow-water limestone deposits (Martin-Algarra, 1987); uppermost Jurassic and Lower Cretaceous is characterised by hiati, emersion, karstification and condensed pelagic swell deposits (Gonzalez-Donoso et al., 1983). Pelagic deep water limestones and marlstones persist

throughout the entire Upper Cretaceous sequence, locally interrupted by an organic-rich, biosiliceous layer at the Cenomanian-Turonian boundary. Observations

Sedimentaryfacies In the Median Subbetic we examined five sections in the vicinity of Granada (Fig. 1). These observations were compared to data from the westernmost exposure of the Median Subbetic Zone (Sierra de las Cabras, near Arcos) and to a reference section in the eastern part of the Median Subbetic near Vel6z R6bio. These sections were chosen not on a transect through the Subbetic

MID-CRETACEOUS

PALEOGEOGRAPHY

AND PALEOCEANOGRAPHY

OF BETIC

trough but on a W - E line along the basin axis to detect facies variations in the deepest parts of the Betic Seaway. According to previous paleogeographic reconstructions (Garcia-Hernandez et al., 1980; Thurow, 1987; Martin-Algarra, 1987; Martin-Algarra et al., 1992), we envisaged a general trend of westward deepening of the basin. The observed stratigraphic sequences and inferred paleoenvironmental position of these sections are summarised in Fig. 3. Section 1 (Fig. 3: 1), situated 30 km north of the city of Guadix and comprises the FardesFormation (Comas, 1978; Comas et al., 1982b).

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5

The mid- to Upper Cretaceous sequence reaches a thickness of about 300 m, which reflects the highest sedimentation rates in the Median Subbetic (Schuster, 1991; Homeier, 1993). The autochthonous Albian black and dark green claystones yielded assemblages of agglutinated foraminifera of peculiar taxonomic composition, which point to sub-CCD conditions. Oxygen-depleted interstitial water conditions can be deduced from dispersed pyrite and abundant baryte concretions. Detrital influx is made up by coarse debrites, channelised conglomerates and fine-grained turbidites. Red claystones were deposited in

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Fig. 3. Stratigraphy and paleobathymetric interpretation of Albian to Maastrichtian sequences in the Median Subbetic (GranadaJa6n region, for numbering of sections see Fig. 1), one section near Vel6z Rfibio in the eastern Median Subbetic, the Sierra de las Cabras-section in the westernmost Subbetic and adjacent sequences in the eastern North Atlantic (DSDP Hole 398D). Different shades of the Albian portions refer to the paleobathymetric positions as indicated in the lower part of the figure; white= Cenomanian-Turonian limestones and claystones; hatched = Couches Rouges facies.

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the Cenomanian. Oxygen-depletion increased throughout the Cenomanian, culminating at the Cenomanian-Turonian boundary with the occurrence of black shales and organic-rich chert layers. The onset of the Couches-Rouges with red or light red limestones indicates the return of oxygenated conditions in the Fardes region in the early Coniacian. Sub-CCD conditions persisted until the early Campanian. A similar section was encountered near Benameji (Prov. of Cordoba) in the western part of the investigated area (Fig. 1: 5). It shows the same Albian sub-CCD fauna as in section 1. Siliceous sandy turbidites and fine-grained turbidites with calcareous foraminifera occur in the Albian. A stratigraphic gap including the Cenomanian to Lower Campanian is probably related to younger tectonic events. The Couches-Rouges comprise calciturbidites and hemipelagites. The stratigraphic column of section 3 (Sarinas, Fig. 3: 3), near Alcal/t la Real (Prov. of Ja6n), differs in many points from the former ones. Within the Albian green claystones fine-grained turbidites and some clay debrites indicate redeposition. From the uppermost Albian (Rotalipora appenninica-Zone) sediments become progressively calcareous, often with signs of synsedimentary movements. The Cenomanian-Turonian calciturbidites with black chert nodules are interrupted by black shales. From the upper Turonian onwards we observe deposits of red, alternately white marly limestones. The foraminiferal assemblages in the Couches-Rouges indicate a shallower slope environment. The depositional environment of the whole section never descended below the CCD during its Mesozoic history. A transition between deep basins (sections 1 and 5) and topographic highs (section 3) may be exposed in a section near Rute (Fig. 3: 4). Albian claystones contain planktic foraminifera with signs of dissolution of the tests indicating deposition below the carbonate lysocline. The depositional environment is interpreted to be the lower slope during the Albian. The younger part of the section is similar to section 3, comprising CenomanianTuronian calciturbidites, black shales, and later Couches-Rouges facies. A comparable sedimentary sequence (Fig. 3: 2)

K. REICHERTER ET AL.

crops out in the vicinity of Benalfia de las Villas (Prov. of Granada). Several distinct outcrops in the Arroyo de Balagar have been composed to a synthesised section. The faunal composition within the Albian and the Couches-Rouges is identical to section 4, interpreted as a lower slope setting. It is possible to trace Albian deep-water facies to the East in the Vel6z Rfibio region (Fig. 1) and to the West (Las Cabras Section south of Arcos de la Frontera, Fig. 2). In the Sierra de las Cabras area (Figs. 1 and 3), a thick early Cretaceous pelagic marlstone and limestone sequence is developed which is comparable to the Maiolica facies of the Italian Apennines. Aptian to middle Albian sediments are characterised by greenish-gray claystones and marlstones with some intercalations of thin-bedded siliciclastic turbidites in the uppermost Aptian. Upper Albian and Cenomanian sediments are more calcareous marlstones with increasing abundance of calciturbidites during the earlymiddle Cenomanian. The Barranco Salada section (Fig. 3) of the Vel6z Rfibio area is intensely tectonised, but nevertheless the reconstructed and balanced section exhibits a similar succession as observed in section 3. A detached sequence of Albian dark claystones and marlstones near Zarcilla de Ramos (Paquet et al., 1977) is regarded as the older stratigraphic continuation of the Barranco Salada. In the Penibetic, outcrop sections (Fig. 2) have been examined near Manilva (Kuhnt, 1987), along the western flank of the Cerro del Pander6n (D/irr, 1967), and at the Hacho de Montejaque near Grazalema (Bourgois, 1978). Within the Internal Subbetic, isolated localities of Albian marlstones were encountered in the Sierra Harana NE of Granada (Wielandt, 1991). The Albian sediments of the Penibetic and Internal Subbetic comprise pelagic marlstones which differ from those described from the Median Subbetic. Rhythmic marl-limestone alternations point to generally oxic water-masses, only locally thin layers of dark shales with preserved organic carbon (up to 1.2%) of mixed marine and terrestrial origin are observed. Condensed sedimentation (1-5 m/Ma) and/or major hiati have been found in several sections. Neptunian dikes and karstic cavities contain a shallow-water micro-

MID-CRETACEOUS PALEOGEOGRAPHY AND PALEOCEANOGRAPHY OF BET1C SEAWAY (BETIC CORDILLERA, SPAIN)

fauna, which indicates an open marine (middle to lower neritic) paleoenvironment. Albian deep-water facies which probably were deposited within the Betic Seaway are known from several localities outside the Median Subbetic Zone. In the western part of the Betic Cordillera the strongly tectonised Paternas Unit (Chauve, 1968) yielded Albian deep-water sediments with a faunal composition comparable to the Median Subbetic (Table 2). In the Boyar region (Fig. 2), the Neocomian is constituted by calcareous and siliciclastic turbidites intercalated within varicolored deep-water claystones (Bourgois, 1978). Calcareous detrital input strongly decreases in the Aptian, where darkgreen claystones dominate. An Albian siliciclastic turbidite sequence is overlain by pelitic and biosiliceous deep-water sediments of Late Albian to Cenomanian age (Thurow, 1987). The Facinas Unit (Didon, 1969) (Fig. 2) is made up of an Aptian-Albian sandstone-shale alternation ("flysch" of the French authors) with a very low sand-mud ratio. The Aptian-Albian shales are poor in calcite and display a variety of concretionary phenomena ranging from siderite layers to cow pat-shaped baryte concretions. Both lithoand biofacies led Thurow (1987) to conclude that the Facinas Unit forms part of the "Massilian flysch family" of Morocco and Algeria.

Distribution and composition of coarse-grained detritus Coarse-grained redeposited sediments were examined for components of known or presumed provenance either from the margin of the Alboran Block or the Iberian Meseta. Typical sedimentary facies of these continental margins were discriminated by Thurow (1987). According to this definition, sediments originating from the margin of the Alboran Block ("Austro-Alpine resedimentfacies") are characterised by components of a marine Triassic and Jurassic deep-water facies. Detrital components originating from the Iberian Meseta ("Urgonian resediment-facies") are dominated by shallow water biogenous material and limestone fragments of predominantly Early Cretaceous age. A third resediment-facies, which is characterised by pelagic limestones of Middle

7

Jurassic to Early Cretaceous age, radiolarites, and volcanic rock fragments may originate from intrabasinal highs within the Betic Seaway. During the Albian large parts of Iberia were covered by the Utrillas facies, consisting of terrestrial, siliciclastic debris, which was a probable source for coeval marine clastics. In our sections we observe the following distribution pattern of these resediment facies. Coarse-grained channel-fills within the Albian claystones of the central part of the Median Subbetic (Rio Fardes area, Fig. 3, section l) are dominated by carbonate components (70-85%). They consist of dolostones, Lower Jurassic o6id limestones, Upper Jurassic Calpionella limestones, Bositra (a bivalve) and radiolaria limestones and additionally basaltic volcanic rocks. Other components encountered were Albian rudist fragments and single pelagic o6ids, for which the shallowmarine Prebetic (Az6ma et al., 1979) is a possible source region. High amounts of euhedral quartz crystals, which are typical for the underlying Keuper facies may indicate a beginning diapirism and/or redeposition of these materials into the deep sea (L6pez-Galindo, 1986). Generally, this facies is composed of a mixture of the "Urgonian" and the intrabasinal resediment-type in the sense of Thurow (1987). The derivation from multiple sources was changing through time. Paleocurrent directions, indicated by imbrication within conglomerates, cross-bedding and sole marks, indicate both N- and S-directed transport. Possible source areas may have been the Iberian Meseta and shallower units of the Subbetic; detrital input from earlier stratigraphic units of the Alboran margin is still doubtful for the Albian. Fine-grained turbidites consisting predominantly of well-sorted Albian planktic foraminifers are intercalated within coeval deep-water sediments of the Fardes area. The faunal composition indicates a shallower, pelagic environment (upper slope) with similarities to the Albian of the External Subbetic, Penibetic and Internal Subbetic. One argument for an internal (Alboran margin) derivation of parts of the calciturbidites may be their low content in quartz and feldspar never surpassing a total of 5%. In contrast to this, the Lower Cretaceous series of the more

8

external Intermediate Units (Ruiz-Ortiz, 1980) are dominantly siliciclastic. During the Cenomanian-Turonian, calciturbidites are dominantly composed of micritic lithoclasts and single orids, peloids and oncoids. Quartz, chert, feldspar, glauconite, basic volcanics and opaques account for about 20%. Huge blocks of Jurassic red nodular limestone are contained in Coniacian mass-flows, whose speculative source region is the Internal Subbetic, the External Subbetic or the Predorsalian Units of the Alboran margin. Within the Rute Section (Fig. 3, section 4) redeposited rock fragments are observed only as rare exceptions. Small scour-fills contain single o6ids, Orbitolina fragments, smaller benthic foraminifers, echinoid debris and peloids, cherty fragments, quartz, microcline and plagioclase. The detrital components within this section differ significantly from the Fardes area. Main differences are the lack of volcanic clasts, Calpionella limestones, radiolarites and other reworked deep-water facies. The main detrital component within the Albian of Rute is shallow-water biogenic debris of the same age and fine-grained terrigenous detritus in thin layers. The source area for this type of resediments is most probably the Iberian shelf. The resediments of the Benalua (Fig. 3, section 2), Sarinas (Fig. 3, section 3) and Benameji (Fig. 3, section 5) sections are exclusively composed of the fine-grained terrigenous component, which may be a redeposited Utrillas facies. Within the Sarinas section marly debrites of several meters thickness, which are mainly composed of claystone granules, additionally occur. The washed residues of both matrix and clay clasts consist of echinoderm debris, radiolaria and foraminifera. Within the Albian of the Sierra de las Cabras section, redeposits are not observed. Calciturbidites within the lowermost Cenomanian are entirely composed of pelagic material, mainly tests of planktic foraminifera, which do not fundamentally differ from the autochthonous layers. Redeposited components within the Albian of the Paternas section, south of Medina Sidonia, consist of single orids, fecal pellets, shallow-water foraminifers (miliolids, textulariids), coated grains, crinoid debris, bivalve fragments and small

K. REICHERTER ET AL.

amounts of quartz. This redeposit facies may be compared to the "Urgonian" redeposit facies of Thurow (1987). Conglomerates contain Middle Jurassic filament limestones, as well as claystone fragments and sandstones of possible Triassic age. We conclude that within different subbasins in the Median Subbetic detrital input came from different sources during the Albian. The composition was highly dependent on the paleotectonic evolution of the source regions. Some source areas undoubtedly underwent uplift prior to the late Albian, whereas others may have remained stable or continuously subsiding. It still remains ambiguous whether or not the influence of salt diapirism played a major role in the uplift of certain source areas.

Clay minerals Previous clay mineral (CM) studies in Cretaceous sediments of the Subbetic and Gibraltar Arch area include the qualitative results of Paquet et al. (1977) and semi-quantitative data of the Malaga (Rodriguez Jimenez and Ruiz-Cruz, 1989) and Granada working groups (summarised partly in Lrpez-Galindo, 1987 or Lrpez-Galindo and Martin-Algarra, 1992). Paquet et al. (1977) recognised a striking difference between illitedominated CM assemblages of the Subbetic and smectite- and glauconite-dominated assemblages of an internal Malaguid Unit in the Murcia Province. While the M~ilaga working group focused on the "flysch" Units of the Campo de Gibraltar, the work of the Granada group is based on a geographically extended sample set including data from the External, Median and Internal Subbetic, Penibetic (Lrpez-Galindo, 1986, 1987) and "flysch" Units of the Boyar and Ubrique area (Lrpez-Galindo and Martin-Algarra, 1992). Going from Albian formations in the northern Prebetic Unit, adjacent to the Iberian Meseta to those of the South (Median Subbetic), a strong increase in smectites and a correlative decrease in illite, chlorite and kaolinite was observed (Lrpez-Galindo and Lrpez-Garrido, 1990). Our sampling strategy was mainly designed to complement this data base including stratigraphically well-defined sections. For our study we analyzed 140 samples of

MID-CRETACEOUS PALEOGEOGRAPHY AND PALEOCEANOGRAPHY OF BETIC SEAWAY (BETIC CORDILLERA, SPAIN)

Barremian to Early Cenozoic sediments with varying lithologies. Most samples presented here are Aptian to Turonian claystones of five sections in the Median Subbetic and the Sierra de las Cabras, two sections in the External Subbetic, two sections in the Penibetic and reference sections from the Boyar and Facinas "flysch" series (Table l). Preliminary CM data for the Late Cretaceous to Cenozoic are integrated into Fig. 4. Because clay minerals in ocean margin basins are mainly terrigenous, their assemblage reflects paleoenvironmental conditions on the continents. Secondary influences during transport and deposition are restricted to a specific density/surface related differential settling (Gibbs, 1977) of the various CM species. Thus, paleoenvironmental factors (climate, tectonics, source rock composition, transport systems, etc.) essentially determine the clay mineral assemblage encountered in a sediment (Chamley, 1989). Effects of weathering and burial diagenesis on our CM results can be largely excluded, as samples were removed from fresh outcrops such as rivers and road cuts and potentially diagenetic minerals (chlorite, illite, mixed-layers) only rarely show a systematical increase downsection. In the "flysch" sections, where chlorite (Facinas) and illite (Boyar) amounts are high, good preservation of reworked palynoflora and radiolaria (Thurow, 1987) support the interpretation of Rodriguez Jimenez and RuizCruz 0989) that a potential diagenetic signal of these CM is at least partly inherited. Except for the "flysch" samples, the clay fraction ( < 2 gm) is mainly composed of illite and illitesmectite mixed layer minerals (also referred to as "smectite"). Kaolinite, chlorite and diverse regular and irregular mixed-layer species occur in lesser amounts. Palygorskite seems to be restricted to certain stratigraphic levels. Generally, two types of CM assemblages are distinguished: (1) "smectite assemblages" (SA) dominated by itlite-smectite mixed-layer minerals (I-S), often with an elevated portion of smectite sheets and occasionally palygorskite (2) "illite assemblages" (IA) dominated by illite, chlorite, kaolinite and diverse mixed-layer minerals.

9

In each assemblage the defining minerals make up more than 50% of the detectable clay minerals. The time-related distribution of clay mineral assemblages for the Median Subbetic is summarised in Fig. 4. Data for the other units studied are given in Table 1. Prior to the Albian, all samples show relatively high amounts of IA minerals. Notably, kaolinite accounts for up to 20%, while this mineral is very rare between the late Albian and the late Turonian of the Subbetic sections. During the Albian two trends can be distinguished: - - a change from IA to SA during or prior to the middle Albian in the Median Subbetic and the Penibetic. Palygorskite occasionally occurs. --constant IA until at least the late Albian in the External Subbetic and the "flysch" Units. No palygorskite was detected. From the Cenomanian onwards, a pronounced "smectite assemblage" (around 90% I-S) characterises the Median Subbetic and Penibetic. A renewed increase of illite assemblages, especially of kaolinite occurs in the Senonian. Palygorskite was detected in the Late Albian to Cenomanian of Estepa (External Subbetic), Rio Fardes (Schuster, 1991) and Sarinas and in the Campanian to Eocene samples from Benahia, Sarinas and Benameji (Fig. 3, sections 2, 3 and 5). It probably occurs also in the early Aptian of Sierra Martina (External Subbetic) and the late Albian of Paternas. Other occurrences of palygorskite in the Cretaceous of the Subbetic were described by Ldpez-Galindo (1986, 1987) and Lbpez-Galindo and L6pez-Garrido (1990). In contrast to these authors we found palygorskite unrelated to paleobathymetry or confinement of the site of deposition and even detectable in coarse detrital facies. The main paleogeographic pattern in CM distribution within the Betic Seaway is a decrease of the IA percentage from North to South, while SA increases (Fig. 5). The decrease of the illite and kaolinite in more distal settings seems to be related to their preferred settling on the shelf (Gibbs, 1977). This mechanism seems to have acted very efficiently during the Mesozoic probably due to the development of wide carbonate platforms that acted as traps for the IA minerals (Deconinck et al., 1985). Another distribution pattern is observed in a N-S extending area between Ja~n

10

K. REICHERTER ET AL TABLE 1 R o u n d e d percentages o f clay minerals in the < 2 ~tm size fraction o f Subbetic a n d C a m p o de G i b r a l t a r samples. C: chlorite; I: illite; I - S : i l l i t e - s m e c t i t e mixed-layer minerals; K: kaolinite; P: palygorskite; tr: traces; *: presence unsure. Values for clay m i n e r a l s are r o u n d e d percentages w i t h indications for a subjectively higher ( + ) or lower ( - ) tendency.

Sample

Age

NAV-13 NAV-12b NAV-9 NAV-5 NAV-3

Turonian Turonian Cenomanian Cenomanian late Albian

S 7-6 S 7-5A S 7-5 S 7-4 MAN 1-9 S 7-3 S 7-2 S 7-1 S 7-0

Cenomanian late Albian middle Albian middle/late Aptian early Aptian early Aptiaa early Aptian Barremian Barremian

Grazalema

GRA 2 GRA 1

late Albian late Aptian

Paternas Alamedill

PAT 3 ALA 4-1 ZDT 1

Albian Albian Albian

BMJ 7 BMJ 9 BMJ 3 BMJ 10 BMJ 8

late Albian late Albian late Albian middle Albian middle Albian

SA 12 SA 11-1 SA 8 SA 8-1 SA 7 SA 0a SA 5 SA 4 SA 1-2

late Turonian (early) Turonian Cenomanian Cenomanian late Albian late Albian late Albian late Albian (middle) Albian

BEN 19-5 BEN 17 HAB 27B BEN 20-1 BEN 20-5 BEN 21-2

late Albian late Albian Albian Albian early Albian early Aptian

EST 4 EST 6 PUV 1

late Albian Albian late Albian

MA 8 MA 7 MA 6 MA 5 MA 4 MA 3 MA 1

late Albian late AIbian (middle) Albian Albian Aptian Aptian Barremian

Cortijo de los Navazos

,

0 i

o JO cO = i

_>

a.

a

E c

0

I11

= i

0

.0 JO

u) e-

c

= m

10 0

=E

,::=> I10 "0

o .£2 J~ :3

t~

E o

>¢

tlJ

Estepa Pto. Viejo

Remarks 11 C

I

I/S

10+ 5 10+ 30-

9095 I008065

5 10 15 30 4550 60 55 65-

95 90 85 70 55 50 40 45 30

30 40-

6555

5 5

20+ 2030-

70 80 55+

10-

10 15 15 10 10

85 85 75+ 85 85

5

tr

tr

I%TOC

Qz-sandy

tr tr

opal C T

K

opal C T

clay debrite

tr 5+

opal CT u 5

20

303030+ 35 40+ 25-

50+ 50 70656075

15 1515+

6565 75

7555+ 60 60 70+ 70 60

2520 3535 20 20 20

P

105+

,_

5+

15-

105 5

lO0notenoagh clay minerals 955 95 10 755+ 75 10 80 5 85 15 75+ 10-

opal C T

Qz-smady

14

15+ 2010 10

2015

2O 20+ 1015

105 1010

"-

11

M I D - C R E T A C E O U S P A L E O G E O G R A P H Y A N D P A L E O C E A N O G R A P H Y O F BETIC SEAWAY (BETIC C O R D I L L E R A , SPAIN)

T A B L E 1 (Continued)

t~ t~

,'-o

O 03

0~

F

c t~ tl

Sample

Age

I5-11 LCB-2 14-7 K 3-22 K 3-21 K3-19 K3-18 K 3-13 K3-11 K 3B-2 K 6-3 K 7-8a K 7-4 K7-1 K I-7 K 3-C3 K 3-C2 K 2-3 K2-1 K 3-C1 K 3-Cla LCb 1 IV 1-43 K 15-6 K 15-3 K 15-2 K 16-4 K 16-1 K 5-4 K 5-2 K 4 top K 4-21 K 4-3

middle Tttronian middle Turonian late Cenomaman early Cenomanian early Cenomanian early Cenomanian early Cenomanian early Cenomanian early Cenomanian early Cenomanian late Albian late Albian late Albian late Albian late Albian late Albian late Albian middle Albian middle Albian middle Albian middle Albian middle Albian early Albian middle Aptian middle Aptian middle Aptian middle Aptian early Aptian early Aptian early Aptian early Aptian early Aptian late Barremian

E 14-12 E 12-13B E 12-13A E 12-11 A 85-28 A 85-20

middle/late Albian middle/late Albian middle/late Albian Albian Albian early Aptian?

D 70-1 D 36-34b

1. Alb./e. Cenom. 1. Alb./e. Cenom.

$5-1

Remarks

C

coarse turbidit¢

I

I/S

5 tr tr 10-

95 90 10090+ 10090+ 9510095+ 959085 85857560+ 6575 60+ 6O7590 55+ 7070 70 553545+ 45 6560 60-

tr

105+ tr

1,2% T ( ~ 4,2% T ( ~

5 5+ 5tr

Ix

well preserved palynofloras

5 ff 5 U 15+

55+ 10 15 15 15 15+ 3025+ 202530 20 102525+ 25+ 3030+ 40+ 35 35 25 4030 4540+ 4045 4055-

14

K

10-

tr

tr

"-

5 5

30 35 u 35 30

20 105010 15 25-

5

20+

tr 10 10 10 5 1010+ 5+ tr 15 5 5tr 10 2015 155 tr 10 1510 5 15 5+

40

20

very well to

10

40-

late Albian

to

25

65

10

S 5-2 S 11-64 D 37-1

late Albian

moderately preserved

40

40+ 25

middle/late Albian

4530

3015 20+

S 10-18

15 10

30 20 20 30

30

S 10-2

middle/late Albian

40

35

20

5

S 10-1

middle/late Albian

30

40-

15+

15

S 10-9 S 10-10

middle/late Albian

4570-

30 15

20

5+

late Albian late Albian

middle/late Albian

and Iznalloz with pronounced IA which may trace one of the conduits of fine-grained terrigenous material from the Iberian shelf to the basin. Deposits of the Internal Subbetic and the

palynofloras

P

40 25

15

Penibetic which are related to the Alboran margin (Table 1 and data in L6pez-Galindo, 1986) are poor in IA-minerals and might point to a second, smectite-rich sediment source on the Alboran

12

K. REICHERTERET AL.

AGE

LITHOLOGY

Paleogene

calciturbidites

Maastrichtlan

red/pinkpelagic marl-limestone alternations

Conlaclan

Turonlan

calciturbidites

Cenomanlan

biosilicaousshale white pelagic limestone

Alblan

coarseclasticsin dark claystone

CLAY MINERAL PERCENTAGES

7

I

ApUan grey pelagic marl-limestone alternation

Barremlan Lower Cretaceous

submarine volcanics calciturbidites and radioladtes

Upper Jurassic

14,14mixedIsyera r---1 Illite-Smectite Palygorskite

not to scale

Fig. 4. Simplified lithological column and averaged clay mineral distribution of the Median Subbetic. Partly based on unpublished results for the Late Cretaceous.

External Subbetic Median Subbetic ILLITE A S S E M B L A G E Palygors-~ ~ kite ~

SMECTITE A S S E M B L A G E

Fig. 5. Distribution of middle to late Albian clay mineral assemblages in the central part of the Betic Cordillera. Partly based on data in L6pez-Galindo (1986) and Schuster (1991). CdG = Campo de Gibraltar. B M J = Benameji, S A = Sarinas, M A = Sierra Martina, B E N = Benalfia de las Villas, A L A = Alamedilla, F A R = Rio Fardes.

MID-CRETACEOUS PALEOGEOGRAPHY AND PALEOCEANOGRAPHY OF BETIC SEAWAY (BETIC CORDILLERA. SPAIN)

Block. However, known occurrences of these deposits are volumetrically unimportant or indicate sediment starvation (Paquet et al., 1977). The CM contribution from the Alboran Block is thus probably low. We suggest that the clay minerals of the Subbetic mainly represent the fine-grained detritus of the Iberian microcontinent. Reviewing clay mineral data from the North Atlantic, De Graciansky et al. (1987) outline an evolution of the Eastern Atlantic margin which is characterised by the following periods: --diverse CM assemblages until the early Aptian; --dominance of illite and kaolinite from Aptian to middle Albian; --assemblages become progressively smectiterich with additional palygorskite during the late Albian to early Cenomanian and remain constant until at least the Turonian; --renewed increase of the "illite assemblage" in the Senonian. We clearly observe these trends in the Subbetic suggesting that the evolution of CM assemblages of the Betic Seaway were controlled by the same mechanisms as those of other Eastern Atlantic basins. It is therefore unlikely that small-scale source rock differences or any other local process exerted a significant effect on the overall evolution of CM assemblages in the Betic Seaway. Illite-rich assemblages in the Aptian to Albian Betic Seaway seem to result from the erosion of source regions with a well-developed topography thus pointing to a regional tectonic cause. Shorter periods with elevated amounts of kaolinite may either represent an increased humidity or a decrease in the efficiency of kaolinite entrapment on the shelf. The latter could be the result of sealevel lowstands. The prevalence of SA from the middle Albian onwards may have several converging causes according to Chamley et al. (1990): --erosion of soils on a leveled topography in the source region; - - a more arid climate favoring smectite and palygorskite formation; --efficient entrapment of 1A on a wide shelf due to high sea-level;

13

--dilution with altered volcanic ashes, hydrothermal smectites and early diagenetic modifications of preexistent CM due to generally low sedimentation rates or higher production of these materials during periods of enhanced volcanic activity. While the relative effects of these causes is impossible to quantify it can be said to some degree of certainty that tectonic rejuvenation of terrestrial source-areas is low from the late Albian until the end of the Turonian. Moreover, no vestiges of coeval volcanism or hydrothermal alterations have yet been found in the study area. As both tectonic and volcanic activity are of subordinate importance in the mid-Cretaceous of the study area it is mainly eustacy and climate that control composition and distribution of the fine-grained sediments. The Albian to Turonian smectite-rich CM assemblages in the Betic Seaway region seem to reflect the long-term sea-level highstand (Haq et al., 1987) during that time. After the Turonian, illite, chlorite and kaolinite increase again possibly caused by a lowering sea level.

Organic matter Type and content of organic matter were studied for selected Aptian to Turonian dark-colored claystones from several localities in the Subbetic and Penibetic (Figs. 1 and 2), e.g. Rio Fardes (central Median Subbetic, Fig. 3: 1), Sarinas (central Median Subbetic, Fig. 3: 3), Sierra de las Cabras (western Median Subbetic), Vel~z Rt~bio (eastern Median Subbetic), Hacho de Montejaque (central Penibetic), Cerro del Pander6n (southwestern Penibetic) and Manilva (southwestern Penibetic). Kerogen characterisation was carried out using Rock-Eval analyses. Results were plotted in the HI-Tmax diagram of Espitali6 et al. (1977, 1985) (Fig. 6). This diagram discriminates between different maturation paths of kerogen types, that can be related to paleoenvironmental conditions. Aptian samples plot in the fields of both typeII and type-III kerogen while Albian samples are predominantly of type-III. Cenomanian-Turonian boundary (CTB) samples display a wide range of hydrogen indices most of which scatter around

14

K. R E I C H E R T E R

CENOMANIAN

/ TURONIAN

900-

APTIAN / ALBIAN

800 -

Maturation paths

900

Maturation paths

- -

Vitrinite reflectance

- -

•

ET AL.

700

X

X

ttl

141

a Z 6o0

za

Aptian Albian

•

800

CTB

Vitrinite reflectance

700 1~%

600

-

Z 500I¢1

o a >,, "1-

Z

•

4o0-

•

~

OOj

w 5oo-

/ , (3

•

w, a >•I"

Q

300-

400-

30o-

i

200

.'N

100

! 4110

450

Tm~ ( o e )

100

50~

i

i

5s0 =

5d0

Tmax(°C)

5 5'0

,.

Fig. 6. IH-Tmax diagram (Espitali6 et al., 1977; 1985) from Aptian (triangles), Albian (squares), and Cenomanian-Turonian boundary (CTB; circles) samples of the Subbetic based on Rock-Eval analyses. Maturation paths (I, II, III) for the three kerogen types. Note good correlation of measured vitrinite reflectance of Rio Fardes samples (0.5 Rrn%) with CTB maturation path.

500 mg HC/g TOC which is typical for type-II kerogen. Kerogen analysis is supplemented by an organic petrography study of an Albian jet (bitumenimpregnated wood) and two CenomanianTuronian black shales from the Fardes Formation (Fig. 1: 1). CTB samples contain some terrestrial macerals (vitrinite, fusinite, sporinite) and additional alginite and bituminite which are indicative of a marine contribution. Maturity, as indicated by maximum pyrolysis temperature (Tmax) and vitrinite reflectance (Rm%) is comparatively low in all studied samples. Tmax values vary between 405°C and 425°C for type-II kerogen and 420°C and 455°C for type-III kerogen (Fig. 6). Higher values (around 430°C to 440°C for type-II kerogen and around 470°C for type-III kerogen) are restricted to samples with low TOC (below 1%) and/or strong secondary silicification.

Reflectance is 0.5 Rm% in vitrinite from a laminated blackshale of the CTB which corresponds well with the Tma~data (Fig. 6). Lower reflectance values (0.35 Rm%) occur in the Albian jet (gymnosperm driftwood) due to a secondary bitumen impregnation. The mid-Cretaceous organic facies of the Median Subbetic and Penibetic is still immature. Temperature, the most important factor with regard to increase immaturity must have been moderate (50-80°C assuming a normal thermal gradient). Occurrence of opal-CT in radiolarian skeletons of Aptian-Turonian strata further supports low maximum temperatures: the age dependent transformation from christobalite to quartz takes place around 80°C (Tada, 1991). These data allow an estimate for the maximum burial depth of mid-Cretaceous sediments of less than 1000 m.

MID-CRETACEOUS PALEOGEOGRAPHY AND PALEOCEANOGRAPHY OF BETIC SEAWAY (BETIC CORDILLERA, SPAIN)

Albian foraminiferal assemblages Autochthonous and redeposited benthic foraminiferal assemblages from ten Albian localities in the Median Subbetic are compared to coeval assemblages from the Internal Subbetic, Penibetic and "flysch" units of the Campo de Gibraltar (Table 2). Five different assemblages of benthic foraminifera are discriminated according to their quantitative composition. Two of these assemblages are purely composed of agglutinated foraminifera. These faunas probably indicate a depositional environment below an at least local CCD. Assemblage 1 is characteristic of the Facinas "flysch"-Unit within the Campo de Gibraltar and is here interpreted as the paleobathymetrically deepest Albian environment within the Betic Cordillera. Assemblage 2, which is also completely composed of agglutinated forms with organic cement is observed in the Fardes formation in the central part of the Median Subbetic. The differences to assemblage 1 are a certain dominance of

Ammodiscus, Glomospira, Glomospirella, Haplophragmoides and Recurvoides. Most of these forms are common inhabitants of mildly dysaerobic environments and the main difference to the "flysch" environment of the Campo de Gibraltar may be higher organic flux rates and/or a more restricted bottom circulation in the Fardes subbasin. Assemblage 3 contains in addition to the "flyschtype" assemblages several species of agglutinated foraminifera that use calcareous cement, and some robust calcareous benthic deep-water foraminifera such as Gyroidinoides ex gr. nitidus and pleurostomellids. Assemblage 4 is characteristic of "shallower" sites within the Median Subbetic, and occurs as redeposited assemblage in the Fardes subbasin. It is dominated by planktic foraminifera with a minor number of deep-water benthic foraminifera such as Clavulinoides gaultinus, Dorothia oxycona and Gavelinella spp. Gyroidinoides ex gr. nitidus and Pleurostomella. These benthic assemblages are similar to biofacies 5, which characterises the Albian sections of the Penibetic and Internal Subbetic. This biofacies is defined by a low plankton/benthos-ratio and a large diversity of shelf-forms of benthic foraminifera (Fig.7).

15

The composition of these biofacies is controlled primarily by carbonate availability, flux rates of organic particles as food and environmental stability. All these factors are waterdepth dependent and consequently, the distribution of benthic foraminiferal biofacies can be used as a paleobathymetric indicator. Using the paleobathymetric zonations of Gurrin (1981), Moullade (1984) and Sikora and Olsson (1991), we roughly assign our assemblages to the following paleobathymetric zones: assemblage 1: abyssal (> 2500 m); assemblage 2: lower bathyal or abyssal (25001500 m); assemblage 3: lower-middle bathyal (1500500 m); assemblage 4: upper bathyal (500-200 m); assemblage 5: middle-outer neritic (200-100 m). The distribution of these assemblages along the axis of the Betic Seaway (Median Subbetic) is of special interest. There is no clear trend of shallowing towards the east as indicated by previous reconstructions, but a highly complicated pattern of shallower (upper bathyal) to deeper (lower bathyal to abyssal) environments. The paleogeographic consequences of this distribution pattern are discussed in the following chapter. Discussion

Subsidence history We established five sections for the Jurassic to Cretaceous sedimentary infill of the Betic Seaway at different locations (Fig. 3). Subsidence was calculated using standard backstripping methods (sediment accumulation rates with porosity correction after Bowman and Vail, in press) and paleowaterdepth estimates based on micropaleontological and sedimentological data (Fig. 8). In the Median Subbetic five stages with different subsidence rates can be discriminated and ascribed to distinct tectonic phases. The evolution of a carbonate platform during the latest Triassic to the early Liassic is characterised by a slow subsidence rate. The collapse of the platform is depicted by a moderate increase of subsidence. The Jurassic rifting is related to extensional movements with the

16

K. R E I C H E R T E R ET A L

TABLE 2

Albian benthic foraminifers of the Penibetic Zone, different subbasins of the Median Subbetic and the Facinas "flysch" Unit of the Campo de Gibraltar

Section Sam~le

Ammobaculites Ammodiscus creta ceus / t ~n uissimus Ammodiscus infimus Ammodiscus cf. peruvianus Ammolagena sp. ~a'oaobulimina spp. 8ulbobaculites sp. Elavulinoides gauliinus C.lavulinoides sp. Dendrophrya / Rhabdammina Dorothia filiformis group Dorothia gradata Dorothia oxycona Egg~dlina sp. 3audryina spp. 31omospira charoides 3lornospira gordialis ~,lomospira irregularis 31omospira serpens 31omospirena gaultina Haplophragmoides concavus Haplophragmoides falcatosuturalis Haplophragmoides nonioninoides Haplophra gmoides spp. iHippocrepina depressa Hormosina ovulum/crassa Hyperammina Kalamopsis Lagenammina Pseudobolivina Recurvoides spp. geophax minutus ;Reophax spp. Rhizammina indivisa Saccammina grzybowskii Saccammina cf. placenta Spiroplectammina cretosa Spiroplectammina (?) sp. Spirop|ectinata gr. annectens Spiropleclinata Subreopha x scalaris Textularia Thurammina papiUata Tfihaxia Trochammina spp. Uvigerinammina moesiana Verneuilinoides Fissurina Gavelinella group Globorotalites Gutt ulina/Globulina Gyroidinoides ex gr. nitidus Leniiculina Lingulina Marginulina group qodobacularia noddosa Nodosariids Osangularia cL utatur~'~sis P]eurostomella Praebulimina group Quinqueloculina antiqua Ramulina globotubulosa Ramulina spp. Spirinina sp. Tristix excavatus % calcareous benthics % organic c~a'nented a~;lutinates ASSEMBLAGE

:.;

s,,, 7 3

12

7

6

2 4

PENIBETIC

^.,,,,,i

c.o, ,v.I, 28

20

3 5

2

1 8

4 13

1

7

10

12

BEN

4-2

14

4

17

14

8

2

12

3

49

23

15 18

1 5 21 4 4 11

8 6

1

11

ALA

6

5

6,5 3

1 4 38 5 2 1

9

1 13 2

6 26

31

1

6 31 1 2

25

1 1

1 12 40 10 6

18

6

1 24 1 4

1

7

65

8 14

3 8

4

2 1

1

36 2 8 1

5

14

1

1

2 15 5

1

1

1 1

1

3

4

11 31

1 11 5

4

1

9

4

5

3

16

1

1

1 13

16

4

1 1

23

11

5

2 1

29

31

6

1

l

3

11

1

5

2

3

4

1

36

1

13

3 2

18 4

44 4

4

123 3

38 1

60 2

68 3

82

11

42 6

4 22

24 4

40 4

14 14

2

1

2

4

1

6 1

3 5

49 7

15

22 1

7 1

17 1

305

39

22

21

3 27 14

5 6

11 9

4 2

6 3

17 9

43 11

240

12 2

2

8

7

2

3

1

12

147 48 6 28

44

11

25

6

11

43

26

12

4 2

25 3

22 2

6 1

3 9

47 3

27 2

10

1

4 8 3

4 8

3 3

57 23 5

5 3

3 1

2

70 2

65 12

77 6

62 3

75 7

1 6 3 1 51 31

3

5

S

5

5

5

1 6

4 8

2

7

14

17

47 10 14

37 9

6 1 42 10

58 28

64 16

5 73 1

63 6

63 18

44 36

4

4

5

5

5

5

3

3

17

MID-CRETACEOUS PALEOGEOGRAPHY AND PALEOCEANOGRAPHY OF BETIC SEAWAY (BETIC CORDILLERA, SPAIN) TABLE 2

(Continued)

MEDIAN SUBBETIC 2 1

15

3

34 2 5

2 7

4 1

2 1 1

8

8

16

3

2 17

24

2

1

4

3

1 4

7

4

7 15 1 1 6

1

1

4

7

3

16 22 8 9

3

6 12 12

1

9 12 3 7 1

17 3 1 3 1

26

20

1

47

2

7

29

6

17

21 14 5

4 27 3

5 1

2

5 12 5

12

1 44 3

16 5

10

2

33 7 12

28

4 4 1 71 3 3

2

7

1 2

2

2

7

5 7

4 3

1 3

2

1 1

1

1 1 1 3

29

3

5

8 1

4

3

2

3

7

4

5

2

4 1

9

10

16

6

2 2

15

1

8

4

23

3

9 1

12 6

1 19 2 1 17 13

2

1

3

12

11

2

7

6

8

5

24 2 11 1 2 5 7

37

3

55 6 11 49 2 8 11

6

15 2

2

45 16

27 4

2 1

4

6

7

10 7 10 1 1 1

2

0 100 2

57 43 3

49 36 3

50 10 3

5

2 1

5

0 100 2

1

8 3

9 1

0 100 2

48

1

3 1

3 5 2

53 2 3

14

5

8 6 3

12

3 2

7

1

4 22

2 2

1

4

12

7

20

1

9

2

4

4

1

1

2 2 1

10

21

1 2

21

1 2

21 6

1 1

6 2

3

11 19 22

3

1

4 1

17 1

2

34 34 3

51 15 3

formation of a halfgraben morphology and facies differentiation in the Betic Seaway (Comas et al., 1982a). Relatively constant subsidence rates for the Median Subbetic of the entire Betic Seaway

43 0 4

57 4 4

18

22 2

12

153 10

132 12

73

95

8

11 4

24 5

36 17

47 11

11 11 12

14 14 3 4

6 5

7

106 44 2 15

5

5

9

30

17

8

3

12 1 10

6 11 3

36

8

16

33 2 73 6 5

24 78 1 3 7 1 81 1 4

74 3 4

5

55 38 4

8 3 1 10

2

2

79 10 5

95 0 5

98 0 5

52 32 4

73 27 4

can be observed during the Jurassic. Significantly increased and differing subsidence rates are observed above the Jurassic-Cretaceous boundary (145 Ma). Subsidence and waterdepth increase

18

K. R E I C H E R T E R ET AL.

TABLE 2

(Continued) FARDES

1

3

37

2 28

^,l 18

17

1 23

28

2 11

2 1 10

1 12

11 2 1 3

1 3 4

2 5 21

3 14 19

16

22

39

1

1 2 5

1 8 33 7 7 7 3

9 5 22 6 I0 13 3

6

1 16

1 30

1 2

7 1

,,,5 [ ^,4 I 14

38 3

3 20

I ^, I ^9. I ^,ol A-I 3 41

3 11

2 20

16

37

13 38

2 2

8 1

1

2

4

8

29 4 3 1

156

23 8 2

2

11 4

28

5

16

7 17

1 I0 29

7

32 6 1

12

1 1 9

1

-I

FORMATION

2

5

2 2

1

39 7 2 1

28 4

4 7 5

3 1 2

3

2

1

2

2

3

3

59

28 5 2 12

85 5 2 3 4 2 8 2

32 4 3 1 1 3 7

30 2 3 4

76 5

1 3

1 9 1

6 3

4

1

2

7

1 2

3 7

5

3 2

5

24

60 3

2 2

2 13 1

41 5 1 3

12 2 1

3 3

3

1

4

12

12 1

8

1 18

22

5

6

8

13 54

10 11

7 1

5 3 4 53

33

10 41

4

3

6

5

106 1

130 3

66

56 1

112

53 2

96 5

88 1

178 2

43 1

45

48

134 2

204 3

23

14

24

24

14

I0

5

15

4

8

9

4

55

2

4

4

47

9

58

7

339

1

3

26

10

0 100 2

0 100 2

4 1

2 9

1

1 1

2

19

1 12

98

5

5

1 1 4 33

1 30

20 9

2 6 7

34

1

2

103

36 2

44

8 57 12

5 16

3 27 1 8 8 10

5

5

12

5

72 2 20

59

2 22 24

42

4

62 7 4

36

21

36

45

4 4

1

61 31 4

31 57 4

3 4 11 5 4 44 34 4

7 3 17 6 47 37 4

13

10

14

7

12

5

54

16

23

17

2

1

0 99 2

0 100 2

0 100 2

0 100 2

0 100 2

0 100 2

0 100 2

0 100 2

0 100 2

0 100 2

0 100 2

0 I00 2

4 1 50 34 4

block dependent (Fig. 3) along the axis (Median Subbetic) of the Betic Seaway. Between the Albian and the Coniacian (110-87 Ma) remarkable differences in paleo-waterdepth and subsidence

0 100 2

rates of the strongly subsiding blocks and relative highs are obvious. The lack of coarse-grained debris in the described western sections (Fig. 3: 2-5) may be due to the proximity of the opening

M I D - C R E T A C E O U S P A L E O G E O G R A P H Y A N D P A L E O C E A N O G R A P H Y O F BETIC SEAWAY (BETIC C O R D I L L E R A , SPAIN)

[9

TABLE 2 (Continued) FACINAS

PATERNAS PAT

PAT3 PAT6 r

58

9 4

8

r r

f

r

r

r

r

r

r r

r

a

r

2

c

a

c

f

6

2 1

2

r r

r

a

c

r

f

c

f

r

r

f

r

c

r

I

r

f f

r

f

r r

r

r r

r

r

r

r

r

2 5 13 1 11 3 5 50 7 9 154 11 19

f

3 4 1

r

f

r r

r

c

c

f

r

r

f r

5 1 9 9 3 85 1 16

r r r 1 24

f

r

a f r f f

r

a

f

c

f

f

f f f f c f

r

f

r c r

c f

c f

f

c

f c

c

c

c

r r

f c

~on Sample Ammobaculites Ammodiscus cretaceus / tenuissimus Ammodiscus lnfimus Ammodiscus cir. peruvtanus Ammolagena sp. Arenobulimina spp. Bulbobaculites sp. Clavulinoides gauRinus Cla vulinoides sp. Dendrophrya / Rhabda mmina Dorothia filiformis group Dorothia gradata Dorothia oxycona Egge*eUina sp. Gaudryina spp. Glomospira charoides Glomospira gordialis Glomospira irregularis Glomospira serpens Glomospirella gaultina

Haplophragmoides concavus Haplophragmoides falcatosu turalis Haplophragmoides nonioninoides Haplophragmoides spp. Hip~ina depressa Hormosina ovulum/crassa H yperammina Kalamopsis Lag Pseudobolivina Recurvoides spp. Reophax minutus Reophax spp. Rhizammina indivisa Saccammina grzybowskii Saccammina cf. phcenta Spiroplectammina cretosa Spiroplectammina (?) sp. Spiroplecfinata gr. annectens Spiroplectinata

2

2 f

18

r

33

c

a

2

r

c

f

c

f c

f

f

c

f

c

c

c

!Subreophax scalaris rextularia Fhurammina papillata rritaxia rrochammina spp. Uvigerinammina mcesiana Verneuilincddes Fissurina ~avelinella group 3Ioborotalites

C,ut tulina/Globulina C,yroidinoides ex gr. nitidus L,mticulina Lmgulina

rare: 1-3 s p e c i m e n s few: 4 - 1 0 s p e c i m e n s c o m m o n : 11-50 specimens a b u n d a n t : >50 soecimens

0 100 2

0 100 2

0 100 Z

0 1(30 1

0 100 1

0 100 1

0 100 1

0 100 1

0 100 1

0 leo I

Atlantic and a widening o f the Betic Seaway towards the west. Sections 2 and 3 are seen to be the intrabasinal highs. They show a reduction in coarser grained redeposits. We interpret the upper

0 100 1

0 100 1

Marginu]ina group

0 1(30 I

0 100 1

Nodobacularia nodulosa Nodusariids Dsangularia d . utaturensis Pleurostomella Praebulimina group Quinqueloculina antiqua Ramulina globotubulosa Ramulina spp. Spirillina sp. Tristix excava~as % calcareous be~thics 0 100 % organic cemented agglutinates 1 ASSEMBLAGE

to middle slope setting to be the source region for fine-grained turbidites consisting of planktic foraminifers. Synchronous transtensional and transpressional tectonic movements may be responsible

20

K. REICHERTERET AL.

Fig. 7A. Environmentally significant benthic foraminifera from the Albian of the Betic Seaway. Albian deep water agglutinated foraminifera with organic cement--characterizing sub-CCD environments of the Median Subbetic and Facinas "flysch" Unit of the Campo de Gibraltar (assemblages 1 and 2). A-D: characterise slightly oxygen-deficient environments with enhanced organic carbon content.

A. Ammodiscus cretaceus, sample ALA4-2, x 80 B. Glomospira charoides; Rio Fardes, x 80 C. Glomospira gordialis, Rio Fardes, x 88 D. Glomospira irregularis, sample ZDT1, x 48 E-F. Hippocrepina depressa, sample BMJ3, x 48 G-H. Arnmodiscus infimus, Rio Fardes, x 36 I. Pseudobolivina variabilis, sample BMJ8, x 56 J-K. Hormosina crassa, sample BMJ3, x 72 (10), × 88 (11) L. Haplophragmoides nonioninoides, sample ALA4-2, x 48 M. Haplophragmoides nonioninoides, Rio Fardes, x 56 N. Haplophragmoides nonioninoides, sample ALA4-2, x 48 0. Reophax minutus, sample BMJ3, × 64 P. Reophax minutus, Rio Fardes, x 56 R. Plectorecurvoides alternans, Rio Fardes, x 60 S. Trochammina sp. A (large), sample ZDTI, x 36 T. Trochammina sp. A (large), Rio Fardes, x 56

(see p. 21)

Fig. 7B. Albian deep water agglutinated foraminifera with organic cement--characterizing sub-CCD environments of the Median Subbetic and Facinas "flysch" Unit of the Campo de Gibraltar (assemblages 1 and 2). A-I: are more abundant in slightly oxygendeficient dark-green or black claystones, K-L: are infaunal morphotypes, which preferably occur in better oxygenated environments. A. Haplophragmoides concavus, sample BMJ3, x 36 B. Haplophragmoides sp., sample BMJ3, x 92 C. Haplophragmoides concavus, sample BMJ3, x 40 D. Haplophragmoides sp.; sample BMJ3, x 104 E. Haplophragmoides falcatostuturalis, Rio Fardes, x 36 F. Haplophragmoides cf. falcatosuturalis, sample GAL2-1, x 48 G. Saccamina grzybowskii, sample BMJ3, x 80 H. Saccamina cf. placenta, sample BMJ3, x 64 I. Saccamina cf. placenta, Rio Fardes, x 88 J. Dorothiafiliformis, sample BEN14, x 72 K-L. Dorothia oblonga, sample ZDT1, x 36 (included in Dorothiafiliformis group in Table 2) M-N. Verneuilinoides sp., sample BEN20-1, x 48 0. ?Gaudryinella sherlocki, sample BEN20-1, x 48 (included in Dorothiafiliformis group in Table 2) P. ?Gaudryinella sherlocki, sample ALA4-2, x 48 R. Textularia sp., sample HAB27b, x 48 S. Bulbobaculites sp., sample BEN14, x 88 (see p. 22) Fig. 7C. Albian agglutinated foraminifera using calcareous cement (main component of assemblage 3). These forms are restricted to environments above the CCD and characterise middle to upper bathyal and outer neritic environments (e.g. elevated blocks of the Subbetic and Penibetic). A. Arenobulimina conoidea, sample ALA4-2, x 72 B. Arenobulimina conoidea, sample ALA4-2, x 48 C. Arenobulimina sp. 1, sample EST3, x 72 D. Arenobulimina sp. 1, sample EST3, x 104 E. Gaudryina aft. pyramidata, sample BENI9-3, x 48 F. Dorothia trocha, sample BMJ10, x 48 G. Dorothia oxycona, sample BENI4, x 40 H. Dorothia oxycona, sample BEN14, x 52 I. Spiroplectammina cretosa, sample BEN19-3, x 48 J. Spiroplectinata ex gr. annectems, sample EST3, x 80 K. Spiroplectinata ex gr. annectems, sample EST3, x 104 L. Spiroplectinata ex gr, annectems, sample EST3, x 88 M. Spiroplectinata ex gr. annectems, sample ZDTI, x 36 N. Spiroplectinata ex gr. annectems, sample ZDT1, x 48 0. Clavulinoides/Tritaxia, sample BEN16, x 48 (see p. 23)

MID-CRETACEOUS

PALEOGEOGRAPHY

Fig. 7A (for explanation

see p. 20)

AND PALEOCEANOGRAPHY

OF BETIC

SEAWAY

(BETIC

CORDILLERA,

SPAIN)

21

22

Fig. 7B (for explanation see p, 20)

K. REICHERTERET AL.

MID-CRETACEOUS

PALEOGEOGRAPHY

Fig. 7C (for explanation

see p. 20)

AND

PALEOCEANOGRAPHY

OF BETIC SEAWAY

(BETIC CORDILLERA,

SPAIN)

23

24

Fig. 7D (for explanation see p. 26)

K. REICHERTERET AL.

MID 1.CRETACEOUS

Fig

PALEOGEOGRAPHY

7E (for explanation

see p. 26)

AND PALEOCEANOGRAPHY

OF BETIC

SEAWAY

(BETIC

CORDILLERA,

SPAIN)

25

26

K. REICHERTER ET AL.

(Figure 7 - - caption continued) P. Clavulinoides/Tritaxia, sample BEN16, x 48 R. Clavulinoides gaultinus, sample BEN14, x 48 S. Clavulinoides gaultinus, sample BEN19-3, x 28 T. Clavulinoides sp., sample BENI9-3, x 36 U. Clavulinoides mendrisiensis, sample BEN19-3, x 36 V. Clavulinoides sp. (juvenile), sample BENI4, x 72 W. Dorothia gradata, sample GALl-6, x 18 X. Dorothia gradata (rough), sample GALl-6, x 18 Y. Textularia, sample BEN14, x 72 Z. Textularia, sample BEN14, × 44

(see p. 23)

Fig. 7D. Albian calcareous benthic foraminifera of the Median Subbetic (assemblages 3-5). Most species are restricted to neritic and upper bathyal environments (assemblages 4-5). Gyroidinoides ex gr. nitidus (A-C), Pleurostomella spp. (I-K), Ramulina globotubulosa (L) and Osangularia cf. utaturensis (P-T) may also occur in deeper (middle bathyal?) environments (assemblage 3, ALA, BEN, HAB, BMJ). A-C. Gyroidinoides ex gr. nitidus, sample ALA4-2, x 72 D. Globorotalites sp., sample SA4-1, x 72 E. Trocholina sp., sample EST3, x 160 F. Tristix excavatus, sample BEN14, ×44 G. Fissurina sp., sample SA4-1, x 80 I. Pleurostomella sp. I, sample GAL2-1, x 40 J. Pleurostomella sp. 2, sample BENI4, x 44 K. Pleurostomella nodosa, sample GAL2-1, x 48 L. Ramulina globotubulosa, sample BEN16, x 80 M-N. Ramulina sp. 1, sample ZDT1, x 120 (M), x 64 (N) O. Spirillina sp., sample EST4, x 64 P-R. Osangularia cf. utaturensis, sample BEN14, x 72 (P), × 86 (R) S-T. Osangularia cf. utaturensis, sample ALA4-2, × 72 (see p. 24) Fig. 7E. Albian calcareous benthic foraminifera of the Median Subbetic. Characteristic forms of neritic environments (assemblage 5). "Buliminid" morphotypes (N-X) are generally more common in environments with enhanced flux of organic particles--in areas of normal primary productivity they are consequently restricted to comparatively shallow waterdepths. A. Marginulina sp., sample EST5, x 56 B. Nodosaria sp., sample EST5, x 96 C. Lingulina sp., sample EST6, x 92 D. Lingulina sp., sample EST5, x 120 E. Quinqueloculina antiqua, sample BEN14, x 92 F. Frondicularia sp., sample EST5, x 36 G. Lenticulina sp., sample SA6, x 64 H. Planularia complanata, sample BEN19-3, x 48 I. Vaginulina sp., sample EST5, x 56 J. Gavelinella sp., sample EST3, x 56 K. Osangularia sp., sample EST3, × 72 L-M. Gavelinella intermedia, sample SA4-1, x 48 N-R. Neobulimina sp., sample SA5, x 120 S-T. Bolivina sp., sample EST4, x 120 U. indet, buliminid morphotype, sample BEN19-3, x 120 V-X. Praebulimina elata, sample SA6, x 120 (see p. 25)

for the c r e a t i o n o f s e d i m e n t t r a p s in d e e p b a s i n s a n d hiati o n i n t r a b a s i n a l highs ( M a r t i n - A l g a r r a , 1987), respectively. W e i n t e r p r e t this w i t h c h a n g e s in the s u p r a - r e g i o n a l t e c t o n i c c o n f i g u r a t i o n a n d transtensional movements. The Couches-Rouges facies was d e p o s i t e d d u r i n g a p e r i o d o f i n c r e a s e d

s u b s i d e n c e in t h e S e n o n i a n . A l e v e l i n g o f t h e d e e p basins a n d i n t r a - b a s i n a l h i g h s is o b s e r v e d d u r i n g this p e r i o d . N e v e r t h e l e s s differences in p a l e o b a t h y m e t r y c a n still b e p r o v e n to be in the o r d e r o f a b o u t 1000 m w i t h i n these series ( R e i c h e r t e r a n d M a n t h e y , u n p u b l , d a t a ) . T h e late C a m p a n i a n to

MID-CRETACEOUS PALEOGEOGRAPHY AND PALEOCEANOGRAPHY OF BETIC SEAWAY (BETIC CORDILLERA, SPAIN)

Q W

6 Q.

A

g 0 C

.Q ¢0

E 0

.12

205

185

165

145

125

105

85

65

Age (ma)

Fig. 8. Subsidence history of different subbasins within the Median Subbetic Zone. Shaded area indicates period (Early-Middle Cretaceous) of significant differencesin estimated paleo-waterdepthand subsidence. Paleocene is characterised by uplift of large parts of the Betic Seaway, caused by compression during the beginning convergence of the Iberian Plate and the Alboran Block (De Jong, 1990).

Paleoceanography The paleoceanographic evolution within the Betic Seaway exhibits striking similarities with the evolution of the eastern North Atlantic. Significant changes in detrital fluxes (CM assemblages), deep water mass oxygenation, lysocline- and CCDposition are observed coeval in both basins (Fig. 9). The position of the Albian CCD in the Atlantic is estimated to be at about 2500 m (Tucholke and Vogt, 1979). The CCD-position in the Betic Seaway may deviate from those of the Atlantic, because the narrow seaway was characterised by its own carbonate budget, due to limited exchange of water masses. Sections 1 and 5 reveal foraminiferal assemblages, indicating a sub-CCD environment during the Albian. Within the Fardes area (section 1) sub-CCD conditions prevail until the early

27

Campanian. Campanian and early Maastrichtian carbonate percentages (Fig. 9) and foraminiferal assemblages indicate deposition below the planktic foraminiferal lysocline. In the middle to late Maastrichtian carbonate values exceed 70% and planktic forms dominate the foraminiferal assemblages (up to more than 98% of the total assemblages). These changes in carbonate content and foraminiferal assemblages parallel almost precisely the CCD fluctuations in adjacent North Atlantic deep water settings such as the adjacent DSDP Site 398 at the Vigo Seamount (Fig. 9). Similarities in the paleoceanographic evolution of the Betic Seaway and the North Atlantic basin are also observed in the changing oxygenation of deep-water masses. The Albian to Middle Cenomanian rhythmic alternations of gray, green and black claystones within the Fardes Formation indicate oxygen-depleted deep-water masses. The oxygen depletion is similar or even more intense than the coeval "oceanic anoxic event 1" (Schlanger and Jenkyns, 1976) in the adjacent North Atlantic. After a short period of condensed deposition in the North Atlantic (e.g. Site 641A, Thurow et al., 1988) and clastic deposits in the Fardes Formation, a second intense anoxic phase is observed in both basins at the CenomanianTuronian boundary (Fig. 9). The deposition of red to light red claystones, marlstones and marly limestones of the Couches-Rouges from the upper Turonian onwards indicates the return of stable oxygenated pelagic conditions in the Betic Basin. Benthic biofacies and sedimentary environment exhibit striking similarities to the Plantagenet Formation in the Atlantic Basin, however, the Betic Basin was rapidly leveled by a high input of carbonaceous turbidites and hemipelagites during the Tertiary.

Albian paleogeography Plate tectonic reconstructions for the Cretaceous Quiet Zone are hampered by the lack of magnetostratigraphic control. Both northern and southern margins of Iberia were deformed and shortened in the Late Cretaceous and even more during the Tertiary (e.g. Comas et al., 1982a; De Smet, 1984; De Ruig, 1990). It is consequently difficult to

28

K. REICHERTER ET AL.

RIO FARDES (section 1)

DSDP HOLE398D contents (in %) of organic carbon and carbonate 2

4 6 8 100

RIO FARDES (section 2) contents (in %) of organic

contents (in %) of carbonate

20 40 60 80

.~,

.4°

carbon and carbonate

. 60 .e,0 .10,

0

4

8 12 16

corr~ponavm

]

t western Norm

II ~ I

I Atlantic Basin

]l

I formatlonslnthell N |

f

20 40 60 80

800 ~" " ' " ' " ' " ' " ' " ' " ' PEAKS ..........

I 900

4( 6 .m E 2(

...,..,,,,

MAA

PAM

/ ' ~ ' ~ redeposited carbonate

~ r~po~ted cetbor~e

~ ~ redeposited ~ ~" carbon~e

I

PI.ANTAGENET

..,ON TUR DEN

g. • cacos

• c~o

ALB 3

1000

Fig. 9. Comparison o f sedimentary formations, carbonate-content and T O C in DSDP Hole 398D and the composite sections o f the Rio Fardes area (Fig. 3: section 1).

locate the latitudinal plate position of Iberia during the mid-Cretaceous (Malod and Mauffret, 1990). Our approach to constrain the relative positions of crustal blocks and marine basins at the southern margin of Iberia is based on a regional paleogeographic reconstruction using paleobathymetric, sedimentologic and sedimentary petrographic data (Fig. 10). Former paleogeographic reconstructions of the Mesozoic western Mediterranean area suggested ocean floor spreading either to the north (Ziegler, 1990) or to the south (Dercourt et al., 1985, 1986) or even both to the north and the south (Favre and Stampfli, 1992) of the Alboran microplate. However, no undoubted vestiges of coeval oceanic volcanism were described from either seaway. The Jurassic volcanism within the Betic Seaway is related to an individualization of small-scale blocks (Garcia-Hernandez et al., 1980; Ruiz-Ortiz et al., 1989) on attenuated continental crust without the formation of oceanic lithosphere. We favour a setting entirely based on transform faults bounding the Alboran microplate. Absence of Cretaceous volcanics and the lack of true ophiolitic remains in the Subbetic Zone point to an interpretation of the Betic Seaway as a small rifted basin, underlain by thinned continental lithosphere.

Median Subbeticof two

Andrieux et al. (1971) explained the Gibraltar "Arch" with a westward moving Alboran microplate. This would imply a conjugate couple of a (northern) dextral and a (southern) sinistral set of transform faults. Paleomagnetic studies (Vandenberg, 1980; Platzman, 1990, 1992)indicate anti-clockwise rotation of the Iberian Peninsula of about 35° with respect to the Alboran Block between the late Jurassic and late Cretaceous. The rotation of Iberia was caused by the formation of oceanic crust and spreading in the Bay of Biscay (Malod and Mauffret, 1990). The opening of the Bay of Biscay in the early mid-Cretaceous (Ries, 1978) must have induced transform movements along the southern Iberian margin. The result probably was transform movement with a dextral sense of shear within the Betic Seaway leading to a tectonic configuration comparable to Riedel shears in the direction of the Betic Seaway. The dextral sense of displacement probably was the same as along the major fault in the southern Mauretanian seaway connecting the Atlantic and Tethys (see Fig. 10). Puga et al. (1989a) suggested an ophiolitic nature for the Upper Jurassic volcanics and metavolcanics of the Internal Zone of the Betic Cordillera. These debatable "ophiolites" were considered to repre-

MID-CRETACEOUS

PALEOGEOGRAPHY

AND

&

transform fault

/

;z;;;i

‘A’

volcanism

PALEOCEANOGRAPHY

OF BETIC

Iberia

SEAWAY

(BETIC

CORDILLERA,

SPAIN)

29

,

D

emerged land

@j

pelagic swell

:-I-: :

clays

Z

marls

e

carbonates

.::.;.,:j.,:,: y... .;.,. i” sandstones %. . elastic supply

Fig. 10. Middle to late Albian paleogeography of the Western Mediterranean based on an interpolation of the 1 10 Ma (Aptian) and 80 Ma (Campanian) maps presented by Dercourt et al. (1985, 1986) and data from the northern Iberian Margin (Schwentke, 1990; Boillot and Malod, 1988). The time interval comprises the primula-, roberti-, breggiemis-. subticinensis- and lirinensis foraminiferal zones [ = 5 m.y. according to the time scale of Haq et al. (1987)]

sent the oceanic basement of a hypothetical southern seaway within the Internal Zone. Additionally, production of oceanic lithosphere can not be totally excluded for the Mauretanian basin during the late Jurassic and Cretaceous, although some of the Cretaceous “roches vertes” in the “flysch” Nappes of the Moroccan Rif (Durand Delga, 1980; Giibeli, 1983) have been proven to be sedimentary in origin (Thurow, 1987). However, submarine volcanism, including pillow-basalts undoubtedly exists in the uppermost Jurassic and Lower Cretaceous Mauretanian “tlysch” sequences of the Algerian Tell Atlas (Bouillin, 1979). The observed phenomena in the Betic Seaway, such as the derivation of the redeposited sediments, clay mineral distribution and basin morphology estimated from the distribution of benthic foraminifera assemblages point to a complex pattern of subbasins in the Betic Seaway. We interpret these subbasins as strike-slip basins which formed during the early Cretaceous and reached their maximum depth and facies differentiation during

the Albian. The transform movements in the Betic Seaway probably started around the Jurassic/ Cretaceous boundary and may have ceased in the late Albian. Kinematic reconstructions (Malod and Mauffret 1990; Srivastava et al., 1990) postulate that Iberia moved after chron MO (Early Aptian) in the same direction as Africa though with different velocities. The resulting dextral shear movements between Africa and Iberia at least until the late Albian are a consequence of these different velocities. A considerable problem in the regional paleogeographic reconstruction of the western Mediterranean is the paleo-position of the Internal Subbetic and Penibetic basinal highs. Wildi (1983) proposed a transform setting placing the Internal Subbetic on the Iberian side. These units display a pelagic swell facies until their drowning as late as in the Albian (Martin-Algarra, 1987; Kuhnt, 1987). They are bordered by deeper basins, the Median Subbetic to the North and a poorly preserved “flysch” basin to the South, which already

30

subsided in the late Jurassic. We consequently see this "Penibetic High" in a similar position as the Alboran Block between the two dextral transform faults. This situation within a fault junction with both releasing and restraining characteristics may explain its elevated topography (Christie-Blick and Biddle, 1985).

Conclusions Distribution patterns of coarse detritus, clay minerals, organic matter and benthic foraminiferal biofacies allow us to speculate about the basin morphology of the Betic Seaway. According to these observations the mid-Cretaceous Betic Seaway can be characterised as follows: (1) generally asymmetric basin geometry; (2) terrigenous sediment supply mainly from Iberia; (3) significant intra-basinal topographic highs and subbasins; (4) possible restricted circulation within deep subbasins; (5) open deep water connection to the North Atlantic. The evolution of the Betic Seaway was dominated by extension during late Triassic to late Jurassic rifting. The Alboran Block and the "Penibetic High" are regarded as crustal parts of Iberia, which incompletely separated from the Iberian Plate. Rifting may have failed because of the extensional movements in the Bay of Biscay, which increased around the Jurassic-Cretaceous boundary. This pulse caused a change in the dynamics of the Betic Seaway. Early to midCretaceous sedimentary features suggest a complex strike-slip basin configuration for the Betic Seaway on thinned continental crust. Deep basin and intrabasinal high formation are thought to be induced by strike-slip tectonics during the early Cretaceous. Several small subbasins developed during the midCretaceous. Decreasing subsidence rates and beginning compression are observed since the Campanian. Finally, convergence of the Iberian and African plates during the late Cretaceous and Cenozoic closed the basins between Iberia and Africa.

K. REICHERTER ET AL.

Acknowledgements This paper benefitted from the reviews by W.A. Berggren, P. Olivier and T. Peper. We thank J.P. Herbin (Rueil-Malmaison) for Rock-Eval analyses, and B. Ligouis (Tfibingen) for his review of the organic geochemistry section. Clay mineral analyses were done at USTLFA, Villeneuve d'Ascq. T.P. thanks J.-F. Deconinck (Lille) for a critical review of the clay mineral data and interpretations. SEM work was done with the help of H. Hiittemann (T~ibingen). U. Wielandt and F. Schuster (Tiibingen) supplied field data and samples. K.R. wants to thank J.P. Platt (Oxford), P.A. Ruiz-Ortiz and J.M. Molina (Jarn) for fruitful discussions and constructive reviews. This project was funded by the G e r m a n Research Council (DFG), project number WI-127/2.

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