Facies (2005) 50:477–503DOI 10.1007/s10347-004-0025-6

O R I G I N A L P A P E R

Khalil El Kadiri · Francisco Serrano · Rachid Hlila ·Hoda Liemlahi · Ahmed Chalouan ·Angel Carlos L�pez-Garrido ·Antonio Guerra-Merch�n · Carlos Sanz-de-Galdeano ·Karima Kerzazi · Abdelaziz El Mrihi

Lithostratigraphy and sedimentology of the latest Cretaceous-earlyBurdigalian Tamezzakht succession (Northern Rif, Morocco):consequences for its sequence stratigraphic interpretation

Received: 4 March 2003 / Accepted: 22 July 2004 / Published online: 24 November 2004� Springer-Verlag 2004

Abstract The Tamezzakht succession (Maastrichtian–middle Burdigalian), situated at the fringe between theInternal and the External zones, displays contrastinglithologies with abrupt facies changes, discontinuities,and/or coarse-grained calciturbidite in between. Thesecriteria allow the definition of seven main lithostrati-graphic formations.

Depositional environments (oxygenation levels, tro-phic conditions, omission histories, among others) and/ortransgressive/regressive trends are inferred from inte-grated sedimentologic data including facies change,cyclicity pattern and the textural composition of the tur-bidite facies tracts. Special emphasis is given to the ich-nological features.

Taking into account the extended time-range, the po-sition between the internal zones and the external ones, aswell as the clear differentiation into several contrastingsedimentary formations, the Tamezzakht succession isexpected to provide useful stratigraphic data for the re-gional correlations.

Keywords Ichnofacies · Omission surface · Sequencestratigraphy · Cretaceous-Tertiary boundary ·Eocene-Oligocene · Early Burdigalian · Morocco

Introduction

As is the rule in the Alpine Mediterranean mountains,paleogeographic reconstructions of the northwestern RifBelt during the early-middle Jurassic show its internaldomain bordered by a stable continental paleomargin (ElKadiri 1984, 1991; Olivier 1984; El Hatimi 1991; ElKadiri et al. 1992), the collapse of which during the lateJurassic-early Cretaceous times resulted in a deep flyschbasin (i.e. the Maghrebian Flysch Trough, Didon et al.1973; Raoult 1974; Bourgois 1978; Durand-Delga 1980;Chalouan et al. 2001; Michard et al. 2002). Among theissues and questions currently addressed are the origin ofthe clastic material and the factors controlling the calci-turbidite versus the sandstone flysch episodes, i.e., tec-tonics versus eustasy and the related environmentalchanges. These uncertainties are due to (i) the fact that thepioneer authors (e.g., Durand-Delga 1972, 1980; Didon etal. 1973; Raoult 1974; Bourgois 1978; Hoyez 1989) fo-cused their attention mostly on the stratigraphy of thethick sandstone bodies, and (ii) the scarcity or lack ofsubsequent detailed studies dealing with the sedimentol-ogy, sequence stratigraphy and environmental controllingfactors of the Rifian turbidite successions.

K. El Kadiri ()) · R. Hlila · H. Liemlahi · A. El MrihiFaculty of Sciences, Dep. Geology,Univ. Abdelmalek Essaadi,M’Hannech II, BP. 2121, 93003 Tetuan, Moroccoe-mail: khkadiri@fst.ac.ma

F. Serrano · A. Guerra-Merch�nDep. Ecologia & Geologia,Univ. of Malaga,Teatinos, Malaga, Spain

A. C. L�pez-Garrido · C. Sanz-de-GaldeanoFacultad de Ciencias,Dep. Geodinamica,Av. Fuente Nueva, 18002 Granada, Spain

K. KerzaziMinist�re Energie and Mines, Div. Geology,Rabat-Institut,Morocco

A. ChalouanFaculty of Sciences, Dep. Geology,Univ. Mohamed V,BP. 703, Rabat, Morocco

The present paper attempts to give new insights intothis second line of research in undertaking an integratedanalysis embracing stratigraphy, sedimentology and ich-nology of a key stratigraphic series lying at the fringebetween the internal and external Rifian domains (Fig. 1).

Purpose

The Tamezzakht succession (late Cretaceous–early Bur-digalian) displays, from the base onwards, distinct sedi-mentary units, the facies of the majority of which areclearly contrasted in the field. The sharp contact betweenthem suggests regional events resulting in abrupt changesof the factors controlling the clastic material produced atthe source area.

The purpose of this paper is to shed light on the natureof these events based upon an integrated sedimentologicdescription focused on four key issues, namely:

– the description and inventory of turbidite divisionsbuilding the successive facies tracts (in the sense ofMutti 1992). Precisely, the clastic composition, grainsize and thickness of each of these divisions dependprimarily upon the textural composition of the originalparent flow, and secondarily on the downslope grain-segregation processes (Mutti 1992), which result in afacies tract composed of vertically stacked grain-seg-regated intervals (i.e., future grain divisions). Becauseof their distinct hydrodynamic behaviour, detachmentplanes may be partly or fully activated between these

intervals, so an individual bed considered separately ina stratigraphic column (i.e. a completely detached di-vision) can no longer be regarded as representing alonethe original turbidite event. A facies sequence (FS) ishere used in a sense slightly modified from Mutti(1992:49, FS: “vertical expression of a facies associ-ation”) as corresponding to a stratigraphic intervalmade up of successive turbidite strata deriving fromparent flows of the same textural composition. Thus, afacies sequence may reflect a sedimentary episodeduring which the paleogeographic conditions prevail-ing at the source area remain near constant. In thiscontext, facies sequence can have an important bearingon the tectonic and/or eustatic interpretation;

– the cyclicity pattern, which may involve the mainturbidite and non-turbidite components. Hence, facieschange across two distinct stratigraphic intervals maybe regarded also on the scope of the change affectingthe cyclicity pattern and not strictly as a consequenceof the change in the lithologic composition;

– the ichnological features that help to delineate keysurfaces and enable us to understand the sea-level-,climate- and/or tectonics-mediated paleoenvironmen-tal changes (sedimentation rate, omission duration,oxygen fluctuations, benthic food contents, and sub-strate consistency);

– the nature of the discontinuity surfaces between dis-tinct stratigraphic intervals. These merit a more fo-cused attention, especially in the case where they arepaired with the main gravity flow events and/or thefacies changes. Discontinuity surfaces classically point

Fig. 1 Simplified geologic mapof the northwestern Rif belt.The Tamezzakht area is locatedat the boundary between theInternal zones (Sebtides, Gho-marides and Dorsale Calcaire)and the External ones (flyschnappes and the underlying para-autochthonous units, mainly)

478

to the role played by the tectonic, paleoenvironmentaland/or eustatic controls and can serve to monitor re-gional correlations with coeval successions of theneighbouring Dorsale Calcaire and throughout theBetico-Rifian internal zones.

We will emphasize hereafter these approaches differ-ently, depending on the sedimentologic features domi-nating each formation. For convenience, some well-known interpretative comments, will be given concur-rently with the description of some sedimentological andichnological key data, which allows us to focus the finaldiscussion on the sequence stratigraphic and some re-gional interpretations.

Geological framework

The Tamezzakht succession is located 6 km southwest ofthe city of Tetuan (Fig. 2), in an area of about 3 km2,which is extensively quarried for building purposes. It isentirely exposed in a great quarry at the northern part ofthis area. It consists of a 200-m-thick calciturbidite- andmarl-dominated “continuous” series that spans the lateSenonian–early Burdigalian time interval.

Regionally, it belongs to the Predorsalian zone, whichacted as a narrow, transitory paleogeographic zone (Di-don et al. 1973; Olivier 1984; Martin-Algarra 1987; BenYa�ch et al. 1988) lying between a carbonate platform(i.e., Dorsale Calcaire) and an adjacent basinal zone(Maghrebian Flysch Trough).

Tectonically, the Tamezzakht section is overthrust bythe Kobat el Keskasse olistostrome located on thenortheastern side of the studied area. It includes de-cametre- to hectometre-scale blocks derived from an ex-ternal-Dorsale-type unit, probably from the neighbouringHafat Nator unit (Fig. 2). These are embedded within thePredorsale matrix made up of the classical and wide-spread variegated marls of the late Eocene – middleOligocene. Near the village of Dar Zkiek, thick-beddedholoquartzous sandstones of Aquitanian–early Burdi-galian age stratigraphically overlie this unit. The lattersandstones correspond to the so-called “B�liounis” sand-stones. They also occur in the uppermost part of theTamezzakht stratigraphic succession, which indicates acertain relationship of the latter with the Predorsale do-main and/or the Tariquide Ridge units (Fig. 1; Durand-Delga 1972; Didon et al. 1973). It is noteworthy that thereworked blocks are embedded also in the Tamezzakhtsuccession, within time-equivalent levels (precisely closeto the Eocene–Oligocene transition), but the Tamezzakhtones are inherited from underlying strata of the samesuccession.

The Tamezzakht area, in turn, overthrusts the Tangiersunit that is represented here by its internal-type faciesmainly made up of the widespread early Senonian greento grey monotonous pelites (Fig. 3). Metre- to decametre-thick slices made up of the B�ni Ider sandstones maydiscontinuously be trapped in between.

Cartographically, a very similar succession crops outnorthwards in the B�ni Imrane area close to the external-Dorsale/internal-Tangiers-unit fringe. It is also developedmore northwards in the Andjra area upon the internalTangiers unit (Durand-Delga and Didon 1984a, b). Alongthese areas, metre- to decametre-scale, Jurassic sedi-mentary blocks sparsely emerge from this succession.They strongly recall the Tariquide-Ridge units (i.e. J.Moussa Group Jurassic successions, Fig. 1), a fact that isin agreement with the presence of the above-mentioned“B�liounis”-type sandstones in the Tamezzakht succes-sion.

Stratigraphy and sedimentology

Figure 3 presents the main sedimentary formations of theTamezzakht succession and shows the sampling levelsthat had yielded planktonic foraminifera and calcareousnannoplankton. Biostratigraphic data are summarized inTable 1. Bed-by-bed columns are presented in Figs. 4, 5and 6. From the base onwards, the contrasting formationswe have recognized are as follows.

Black Shale Formation (BSF, late Campanian–earlyMaastrichtian)

Black shales represent the basal formation of theTamezzakht succession (5–10 m in thickness, Fig. 3).They consist of decimetre- to metre-scale mud-dominatedgravity flows, which are developed in poorly graded,black, calcareous, fine-grained sandstones and blackshales. They are extremely rich in wood debris, trapped asfloating clasts within both sandstones and shales. Thisfact may indicate that the corresponding flows were ac-tive only over short distances so that no significant seg-regation within the suspension occurred. Accordingly,they cannot be interpreted in terms of the Bouma’s se-quence, but may be more or less compared to a small-scale F1 facies-type of Mutti (1992), in which no pebblesare present in their fine-grained matrix.

Glaucony-bearing, clean calciturbidites are embeddedwithin the upper part of the black shales as centimetre- todecimetre-thick channellized beds or as metre-scalelenses and blocks. All consist mostly of large benthic-foraminifera debris (mainly Orbitoids) and testify thatthey were produced on a shallow-water carbonate plat-form, which episodically operated during transgressivepulses as coarse-grained basal division developed in fa-cies F3 of Mutti (1992) or in facies R1 of Lowe (1982). Itmay be attached to these bioclastic grainstones. Theytypically point to steep slopes bordering the supplyingplatform.

479

Green Pelite Formation (GPF, late Maastrichtian)

The preceding formation is followed, with an abrupt fa-cies change, by 5–10 m of carbonate-free green peliteswith spaced intercalations of sandstone beds. No pro-gressive grading is observed between these two compo-

nents, so the sedimentation regime may be regarded asrepresenting a true rhythmic alternation. Lending supportto this is the common observation on the soles of sand-stone beds of graphoglyptid (e.g., Helminthorhaphe,Cosmorhaphe). They testify to starved deep-water set-tings experiencing both very low bottom-current and very

Fig. 2 Geologic map of the Tamezzakht area (this work). A, BDetailed geologic map for two selected sectors wherein the strati-graphic column shown in Figs. 4, 6 and 10 were established. CStructural cross section showing the stacking pattern of the mainformations distinguished herein. HNU northernmost side of HafatNator unit (External Dorsale, bordering westwards the Internaldomain); JM a decametric olistolite displaying a Jurassic succes-sion (Rosso-Ammonitico, radiolarite facies, etc.) of Jbel Moussa-Group type (i.e. Tariquide Ridge, Durand-Delga 1972); ITU greenpelites of the internal Tangiers unit; BSF Black Shale Formation(late Campanian–early Maastrichtian); GPF Green Pelite Forma-

tion (late Maastrichtian); SCF Slope Calcarenite Formation (latestMaastrichtian–early Paleocene); CF Calciturbidite Formation(middle to late Paleocene); RSF Red Shale Formation (Eocene–earliest Oligocene); MSF Marlstone-and-Sandstone Formation withfour members (early Oligocene–early Burdigalian). THM Transi-tional Hemipelagic Member (early Oligocene); MM Marly Mem-ber (middle Oligocene?); SM Sandstone Member (late Oligocene–Aquitanian?); SMM Siliceous Marly Member (early Burdigalian);HF Holoquartzous Formation (latest early Burdigalian). Note thehidden discontinuity at the base of SCF (HD.1), CF (HD.2), RSF(HD.3) and MSF (HD.4)

480

low benthic-food input (Uchman 1995; Wetzel 1991;Bromley 1996; Tunis and Uchman 1996a).

The sandstone beds consist nearly exclusively of amixture of fine-grained quartz and rare planktonic for-aminifera, within a black ferruginous carbonate matrix.These quartz grains are limpid, very angular and most ofthem are elongated. They recall the so-called “quartz en�charde” described by Meyer (1987) as originated in thepedogenic realm.

Centimetre-sized pyrite aggregates are common andtestify to oxygen-depleted conditions beneath the sedi-ment–water interface. Both Chondrites targionii(BRONGNIART) and Chondrites intricatus (BRONG-NIART) may abundantly occur within the shaly laminatedhorizons of the sandstone beds. These trace fossils are

known to occur preferably in oxygen-poor environments(e.g., Bromley and Ekdale 1984; Ol�riz and Rodr�guez-Tovar 1999), which is in accordance with the green colourof pelites, a result of the reduced state of iron pigments.

This formation ends with a 2.5-m-thick bed dominatedby structureless yellowish mudstone rich in cm-sized,green mud clasts. They are rich in planktonic for-aminifera, which reveals that these clasts were reworkedfrom hemipelagic deposits. The bed displays a 30-cm-thick, slightly graded, well-sorted coarse-grained basaldivision, in which the clasts are cm-sized and supportedby the same carbonate muds. As we shall see below, thisclastic mixture strongly recalls an Internal-Dorsale-typesource.

Fig. 3 Stratigraphic column ofthe Tamezzakht succession andits possible sequence strati-graphic interpretation (see alsochapter results and discussions).The transgressive–regressivecycles T1/R1–T6/R6 are notconsidered here in limited time-scale (see recommendations byPosamentier and James 1993, 8-9) and may fit well with Vail’sclassical depositional se-quences, 3rd order, 0.5–3 my,Duval et al. 1998) or with the T/R facies cycles, which is thecase of the majority of them(2nd order, 3–30 to 50 my,Duval et al. 1998; Jacquin andDe Graciansky 1998). They arerecognized here based on theirbasal discontinuities and theirlithological signal (lithologicprediction method, Posamentierand James 1993, 7; “m�thodedirecte”, Vail et al. 1987). SeeTable 1 for the nannoplanktonand planktonic-foraminiferadates. Abbreviations as in Fig. 2

481

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Slope Calcarenite Formation(SCF, latest Maastrichtian–early Paleocene)

The Slope Calcarenite Formation (SCF) consists of slopeto base-of-slope deposits arranged in condensed sedi-mentary packages, with numerous omission surfaces inbetween (see below).

The textural composition of attached facies tracts (inthe sense of Mutti 1992) allows distinguishing two mainmembers (facies tracts II and III, Fig. 4). The first onedisplays four distinct divisions, among which division c.3is commonly detached and results in distinct individualbeds. This may be explained by activation of laminationplanes, a common feature in this division. The c.1-bearingbeds occur preferentially in the lower third of the for-

mation, whereas c.4 beds are rather common in the upperpart of the facies tract II interval (Fig. 4). Hence, memberII fits well Mutti’s definition of a facies sequence (Mutti1992).

The division c.1 is dominated by heavily altered do-lomite lithoclasts, the majority of which show pedogenichematite coating. Lending support to this are the commonpaleosoil-derived silcrete clasts. The hematite coating islikely to have partly hindered the diagenetic cementationand also explains why the basal coarsest division easilyweathers (then termed calcarenite). Other lithoclasts areinherited from white massive packstones/grainstones,Calpionella- and/or Saccocoma-rich mudstones and fromfilament-rich mudstones. Albeit these lithoclasts are rep-resented in low proportions, they have an important

Fig. 4 Bed-by-bed stratigraphiccolumn of the latest Maas-trichtian–Paleocene strata out-cropping on the northern side ofthe Tamezzakht area (see de-tailed geologic map, sector A,Fig. 2) and photographic illus-tration of some key surfaces(S1-S5) and key facies (see alsoFig. 11). The S2 surface is ex-pected to correspond to the K/Tboundary (see also Fig. 5). Themajority of calciturbidites dis-play graded-bedding and well-developed Bouma-sequence di-visions. However, we prefer touse the facies-tract scheme asdescribed by Mutti (1992, hisFig. 31) and to adopt for this anopen nomenclature (e.g., c.1-c.4) in order to take into ac-count the change affecting thematerial delivered at the sourcearea. Photograph legend: Zo:Zoophycos, Th: Thalassinoides,Cht: Chondrites targionii(BRONGNIART), Chi: Chon-drites intricatus (BRONG-NIART)

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bearing on the paleogeographic reconstructions (see be-low).

In thin-section, the c.1 division exhibits millimetric tocentimetric clasts of glaucony crusts and abundant glau-conite grains. In contrast to the lithoclasts, which hadsuffered alteration in paleosoils, these grains are rounded,limpid and show no sign of weathering. They are likely tobe derived from adjacent shelves. Most of them may beassigned to the shallow-water, mature highly evolved–type grains (Odin and Matter 1981; Hesselbo and Hugget2001), which are well known to develop during trans-gressive phases and under suboxic, sediment-starved en-vironments (e.g., Kitamura 1999; Hesselbo and Hugget2001). This result is consistent with that obtained fromichnological data.

A conspicuous c.2 bed, lies just below the surface S2(possible K/T boundary, Figs. 4, 5). This division consistsexclusively of near-equigranular, red and green, centi-metric mud clasts (“kaleidoscopic” breccia, Fig. 4), whichare likely derived from the underlying strata or from thesame formation. Generally, muddy sediments resist cur-rent reworking due to their high shear strength, a fact that

leads us to suggest seismic instability and/or huge stormevents as the possible triggering mechanisms for c.2 beds.

The division c.3 is made up of parallel- to cross-lam-inated, fine-grained sandstones. It consists of a mixture ofangular fine-grained quartz and lithoclasts, within a fer-ruginous carbonate matrix. The c.4 division consists ofyellowish to light-coloured, structureless carbonate mud,with a more or less important amount of fine-grainedquartz. Thus, it recalls the key bed 1 intercalated in theupper part of the underlying formation (GPF).

Ichnofabric features allow distinguishing four maintypes of surfaces (S1-S4, see Fig. 4 for their verticaldistribution).

S1-type surfaces

Nearly exclusive assemblages of Chondrites isp. (bothlarge and small forms) dominate S1-type surfaces andmedium Zoophycos ranging from 10 to 30 cm in diameter.The former ichnotaxa occur densely in near-surface po-sition, whereas the second may extend down for about

Fig. 5 Upper half of the Slope Calcarenite Formation (SCF, com-pare with Fig. 2) showing from the base onwards: a The strati-graphic interval (rectangle) assumed to enclose the Cretaceous–Tertiary boundary (K/T). The bed K (Cretaceous) has yielded aspecimen of Abatomphalus mayaorensis (BOLLI) (in thin-section),whereas the red and greenish marls immediately underlying the bedT (Tertiary) have yielded planktonic foraminifera of early Pale-ocene in age (see Table 1 for additional dating below the bed K); bEastward-thickening bed set (dashed lines) giving evidence of de-position in slope settings. The majority of beds consist of the threelower divisions distinguished in Fig. 3 (c1-c3, interval III); c Thekey bed 3 (KB.3), which is a graded, metre-thick, turbidite event

dominated by a conspicuous red sandy division (see Fig. 3: intervalIII, c3 division). The top surface of the latter is of the S3-type,finely and densely bioturbated (Fig. 11, 4). Numerous Zoophycossubsequently penetrated this upper division (see also the corre-sponding photo in Fig. 3). B Close-up view of the interval enclosingthe K/T boundary (rectangle in photo A). Hammer indicates thestratigraphic level possibly corresponding to the K/T boundary.This level is a distinctly Fe-coated hardground (S2 surface in thetext) that fossilizes strange ripple-like structures originating fromsmall-scale slumping (see photographs in Fig. 3). These strangestructures allow to recognize this surface laterally along the quarrylocated in the northwestern part of the Tamezzakht area

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10–20 cm and generally maintains a near-vertical con-nection with the bed surface. It is striking to note thatnearly all the specimens observed are Spirophyton-likeforms (as described by Gaillard and Olivero 1993; Uch-man 1998), which are believed to preferentially developin firm substrates (Gaillard and Olivero 1993; Olivero1996; MacEachern and Burton 2000). Chondrites isp. iswell known to colonize organic-rich sediments in oxygen-poor, quiet, deep-water environments (e.g., Ekdale andMason 1988; Vossler and Pemberton 1988; Wetzel 1991).Otherwise, the association of these two ichnotaxa recallsthe Chondrites/Zoophycos ichnoguild, which has beenassigned to near-inhospitable environmental extremes(Bromley 1996). It may indicate that oxygen-poor con-ditions developed rapidly after the turbidite deposition(Wetzel and Uchman 2001:180). This satisfactorily ex-plains why forms that require fully oxygenated conditionssuch as Thalassinoides are absent (e.g., Savrda et al.1991; Ozalas et al. 1994; Savrda 1995). Bed-by-bed sur-vey shows that S1-type ichnofabric commonly occurs inthe muddy upper division of the graded decimetre-thickbeds (Fig. 4, division c.4 of the facies tract II), which isknown to have been derived from nutrient-rich, upperslope pelagic oozes (see synthetic model developed byWetzel and Uchman 2001). Nutrient availability in thesediment, if not pre-consumed by “bulldozing” pascichnia(see below), seems to be the most required condition forthese sessile chemichnia/fodinichnia (large Chondrites,Zoophycos). We know also, that such a condition is met inoxygen-poor deep-water environments where no “burn-down” phenomenon occurs (Wetzel and Uchman 2001).

S2-type surface

The S2-type surface corresponds to the surface confinedwithin the Cretaceous–Tertiary transition zone (ca 50 cm)or possibly to represent the K/T boundary itself (see Fig. 4and biostratigraphic data in Table 1). It is light-grey co-loured and displays conspicuous synsedimentary “slump-head” structures covered with patchy, rust-coloured Fe-coating. These omission features show that the surfacereached at least the firmground stage. Strikingly, it con-tains a dense, homogeneous grazing ichnocoenosis rep-resented near-exclusively by very small Planolites innear-surface position. They never exceed 1 mm in di-ameter and are not compacted. All tubes are unlined, witha smooth surface and a structureless filling. They arestraight or gently curved and consist of the same mud-stones as the surrounding matrix. Thin-sections show nodistinct internal structure, which indicates softgroundbioturbation that occurred immediately after turbiditedeposition. Scarce small Zoophycos are overprinted onthe Planolites, with their spreiten being sharply markedby ochre-red shales. This clearly points to a further stageof colonization. The S2-type surface also contains spacedlong tubes of Ophiomorpha isp. in sharp epichnial posi-tion filled up with coarse grainstone, which points to asubsequent burrowing stage piping down from the over-

lying strata, since the corresponding producers are wellknown to commonly act as multi-layer colonizers (Uch-man 1995, 1999; Wetzel and Uchman 1998, 2001).

According to Wignall (1991:268) small Planolitesrepresents the last oxygen-deficiency – resistant ichno-coenosis occurring close to the extreme levels of O2-de-pletion. Savrda (1998a, b) showed that the small Plano-lites ichnocoenosis (ichnocoenosis 2 of Savrda 1998b:142) ranges close to the Chondrites ichnocoenosis withinpoorly oxygenated environments. Ol�riz and Rodr�guez-Tovar (1999) have come to a similar conclusion in upperJurassic pelagic sediments. Planolites ichnoguild alsopoints to quiet water settings (Bromley and Ekdale 1986;Bromley 1996). Accordingly, the S2-type surface wouldrecord rapid oxygen depletion achieved as early as duringthe softground stage, like in the case of the precedingsurface (S1).

S3-type surfaces

S3-type surfaces are by far the richest in trace fossils.They developed on ochre-red, shaly sandstones (top ofdivision c.3 of facies tract III, Fig. 4), and record verydense and thin biodeformational structures with no dis-tinct outlines, probably because they were produced in asoft substrate (Fig. 11, Pictures 1–4, 6). Cross-cuttingrelationships indicate that this stage of dense churningwas followed by spaced grazing trace fossils of mainlyechinoids (Scolicia). These are, in turn, commonly cross-cut by tracemakers producing numerous simple or pairedholes ranging from 0.5 up to 4 mm in diameter (probableArenicolites isp. and/or Diplocraterion isp., respectively).These dwelling structures were produced after the bull-dozer effect of the churning tracemakers has ceased.Thalassinoides isp. tunnels (probably Th. suevicus (RI-ETH) see Uchman 1995) represent the latest stage ofcolonization and show a muddy filling that sharply con-trasts with the surrounding sandy matrix. It gives evi-dence that subsequent colonization occurred during fir-mground conditions (see Savrda et al. 2001a, b as well asMacEachern and Burton 2000 for similar depositionalslope settings). Other epichnial Thalassinoides exhibit acoarse-grained calcarenite filling, that commonly derivefrom by-passing sediment, which fill open burrows al-ready preserved in relatively stiff substrates. This factprovides additional support for the attribution of theseThalassinoides to the Glossifungites ichnofacies (as em-phasised also by e.g., Savrda 1995; MacEachern andBurton 2000; Savrda et al. 2001a, b).

Ichnofabric of this surface type may be interpretedbased upon the presence of Thalassinoides, which clas-sically points to well-oxygenated environments. Sinceoxygenation did not exert a limiting control, dense andthin bioturbation in near-surface position could be relatedto the competition for nutrients, probably under oligo-trophic to poorly trophic conditions, a fact that may besuggested from the ochre-red colour of the sediment.

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S3-type surfaces also record a post-colonisation stagemarked by Fe-coating, a feature testifying to inhospitableconditions due to extreme oxygen depletion.

S4-type surfaces

S4-type surfaces lie in the upper part of the formation (ca.1.5 m) and terminate grey to dark-coloured, centimetre-thick beds. They display dense, small grazing trace fossilsof unknown ichnotaxa, which cross-cut each other andrecall the small Planolites-dominated ichnocoenosis ofthe S2 surface in being produced by the same tracemaker.Trace fossils are straight to gently curved, and correspondto dragging structures (1 to 4 mm in width and 5 to 15 cmin length) printed in a more or less firm substrate. Theyindicate an opportunistic colonizer rapidly invading thesubstrate during a specific stage of omission history.

Interpretation of these surfaces in terms of oxygen and/or food availability seems to us difficult, owing the ab-sence of the preceding marker ichnotaxa. Nonetheless,absence of a Fe-crust suggests that they have not expe-rienced a protracted omission history, as was the case forthe preceding ones.

Calciturbidite Formation (CF, middle–late Paleocene)

The CF consists of about 20 metric calciturbidite bedsseparated by thin intercalations of green marls. It startswith a sudden gravity-flow event reworking decimetric,red mud-pebbles (out-sized mud pebbles, Fig. 4) and amixture of carbonate clasts. Outcrop survey shows thatthis first bed ravines the preceding Green Pelite Forma-tion (GPF) in the northwestern side of the Tamezzakhtarea, with the SCF being missing.

As in the case of the underlying strata (SCF), petro-graphic evidence shows that these clasts were inheritedfrom the Triassic–early Jurassic, massive carbonate for-mations, mainly dolomites and white massive limestones,as well as from late Jurassic pelagic units, namely Cal-pionella- and/or Saccocoma-rich mudstones. The abun-dance of rust-coloured, pedogenic clasts is noteworthy. Itmay indicate that this clastic material was derived from anadjacent emerged area during an incipient flooding stage(i.e., “transgressive washing” concept of El Kadiri et al.2003; “shelf sweep” process discussed by Carannante etal. 1999). Attached facies tracts show that the coarsestbasal division (division Cg in the facies tract IV interval,Fig. 4) grades up into a greenish, glaucony-rich, bioclast-dominated grainstone (division c.1, facies tract IV), whichin turn sharply passes upwards to black mudstones rich inMicrocodium fragments, fine-grained quartz and smallplanktonic foraminifera. In spite of this sharp grading, nodetachment plane has been activated between divisionsc.1 and c.3. Thus, they recall the F4-F5 couplet of Mutti(1992) i.e., S2-S3 couplet of Lowe (1982), and allows usto interpret this thick-bedded formation as resulting fromrelatively proximal gravity flows, the travelling distances

of which were too short to allow their grain populations tobe laterally detached. This phenomenon may also be ex-plained with respect to the initial volume of the parentflows, since generally the greater the volume of reworkedsediment, the more travelling distance is required for thedetachment of the parent-flow divisions.

Bed-by-bed analysis shows that this formation can besplit into four distinct bed sets with decimetre green-shaleintervals in between. Surface analysis shows that eachbed-set is punctuated by a heavily bioturbated omissionsurface (e.g., S5a and S5b, included in Fig. 4), with itsinternal bed surfaces being either amalgamated or non-bioturbated to poorly bioturbated and having experiencedno significant omission history. Thus, considered sepa-rately, each of these depositional packages resulted fromhigh frequency turbidite events. This formation displaysan overall thinning-upward trend of the bed sets and theshaly intervals in between (bed sets: 5, 3, 1, 0.5 m andshaly intervals: 1, 0.25, 0.1 m, respectively).

S. 5a and S. 5b surfaces exhibit near-identical ichno-fabrics that, at first sight, recalls the preceding S3-typesurfaces. Cross-cutting relationships help to recognize thefollowing colonization suite: (1) A softground to earlyfirmground stage with dense, thin biodeformationalstructures, which are overprinted by Scolicia s.l. (Uchman1995, 1999), Chondrites targionii (BRONGNIART),Zoophycos (Spirophyton-like form), and spaced Rhizo-corallium. Spreiten of these are, in turn, partly destroyedby fine tangled fodinichnia produced by a near-surface,small tracemaker. The surface S5a lies on a centimetricbed, on the sole of which dense Halopoa imbricataTORELL are preserved in hypichnial semi-relief (near-identical trace fossils are presented by Uchman 1998:115,his Fig. 9A). (2) A firmground stage with numerous singleor paired holes (probable Arenicolites) and spaced Tha-lassinoides suevicus (RIETH) in epichnial positive semi-relief. Some of the latter trace fossils show a coarse-grained filling sharply contrasting with the surroundingshaly matrix. (3) Small patches of Fe-coating indepen-dently cover the previous traces, a feature that give ad-ditional evidence that these surfaces attained at least thefirmground stage (incipient hard-ground of Kennedy andGarrison 1975).

As stressed above for S3-type surfaces, S5a-b ichno-fabrics may be assigned to the Glossifungites ichnofacies,which is pointing here to a more or less prolongedomission phase immediately following minor transgres-sive pulses. Thus, it may be assumed that such calcitur-bidite events might be tied to the transgressive-inducedexport (e.g., Savrda et al. 2001b). Lending support to thisis the concomitant reworking of glaucony-bearing bio-clastic material (division c.3, facies tract interval IV,Fig. 4), which is well known to be produced by healthyplatforms, in which the carbonate production is com-monly favoured during the transgressive regime (manyauthors, e.g., Swift 1968; Droxler and Schlager 1985;Nummedal and Swift 1987; Baum and Vail 1988; Plint1988; Frsich et al. 1991, 1992; Glaser and Droxler 1991;Schlager 1991; El Kadiri 2002a, b). Such an assumption

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may also be extended to certain gravity-flows at the re-gional scale, since they may act as the basal conglomerateof transgressive marine formations, a phenomenon thatmight be interpreted in terms of the “shelf sweep” processas discussed by Carannante et al. (1999) or the trans-gressive washing concept presented by El Kadiri et al.(2003).

Ochre green, carbonate-free siliceous shales, of about3 metres in thickness, overlie the CF. They contain threespaced centimetric black sandstone intercalations. Theseshow dense Chondrites intricatus (BRONGNIART) closeto the bed surfaces, a position that points to an oxygen-poor to -deficient environment. This shaly intervalstrongly recalls the above-described late MaastrichtianGPF, which occurred during a regressive regime.

Red Shale Formation (RSF, Eocene–earliest Oligocene)

The Calciturbidite-Intercalated Red Shale Formation(RSF) starts with five decimetric, amalgamated, calcare-ous sandstone beds, which indicates high-frequency tur-bidite events. By contrast to the preceding formations(BSF and GPF), wherein the quartz grains correspondedto the angular and very fine pedogenic “quartz-en-�charde” (as witnessed by the paleo-silcrete fragmentsobserved in thin-sections), the present sandy facies con-sists of the filonian-type quartz, whose appearance is herethe first in the studied succession. These are millimetre-sized, rounded and may be red, white, or black in colourand correspond to the quartz grains classically derivedfrom crystalline basements.

Lending support to this distinction is the commonobservation that this basement-rock-derived quartz isclassically accompanied by a mixture of clasts derivedfrom other older strata, namely carbonates and/or theschists (see below). Petrographic evidence shows that themajority of the reworked lithoclasts were inherited fromLiassic strata, particularly from white massive grainstonesand light-coloured pelagic mudstones, whereas lithoclastsin the underlying formations were represented chiefly bythe Triassic dolomites.

Both the quartz grains and the reworked lithoclastsclearly show that the onset of this formation coincidedwith an important change in the source area (see inter-pretation below). Outcrop survey and detailed mappingreveal that this thick-bedded sandy interval as well as theunderlying green shales may laterally be missing so thatthe overlying ochre-red shales rest directly onto the pre-ceding Calciturbidite Formation (CF). A low angle inbetween delineates this unconformity, which is likely tobe generated by slope failure processes.

Attached facies-tracts from the downslope grain-seg-regation processes exhibit four divisions (see details inFig. 6, facies tract interval V), with the coarse-grainedbasal one (division Cg) being poorly graded and generallysmall (1–10 cm in thickness), and the sandy one (divisionQ.2, 30–70 cm in thickness) being structureless to faintlylaminated. This contrasts with the overlying c.3 division

that is wavy to parallel laminated. Twenty to 50-cm-thickparallel-laminated green marls represent the uppermostdivision (c.4).

A decimetre-thick, pink marlstone bed overlies thefifth sandy bed and immediately precedes the first level ofthe ochre-red, carbonate-free shales. Identical pink marl-stones (background sedimentation b.3, Fig. 6) reappearthroughout the lower half of this formation, onto thecalciturbidite intercalations. They may also rhythmicallyalternate with decimetric-scale intervals dominated by theochre-red, carbonate-free shales, without calciturbiditeflows (Fig. 7, i.e., interval between the Fe-crust and bedKb4a). Additionally, these red intervals may in turncontain, at a smaller-scale, millimetric- to centimetric-scale horizons of pelagic green marls (background sedi-mentation b.4).

Analysis of the ichnological signature within thesecomponents and at levels in between helps elucidate thestacking pattern of this alternation:

– The pelagic green marly horizons lie with sharp con-tact onto the ochre-red shales. The sole of the formercommonly records well-preserved predepositionalgraphoglyptids, namely Paleodictyon isp. and Spir-orhaphe involuta (DE STEFANI) (see Uchman1998:182, his Fig. 88; see also Fig. 12, Picture 4).Interestingly, these trace fossils, preserved thanks todelicate scouring and casting, testify to very low sed-imentation episodes punctuating deposition of the redshales. In addition, they are well known to colonizeoligotrophic to super-oligotrophic sediments instarved, quiet deep-water settings (e.g., Wetzel 1991;Uchman 1995; Bromley 1996; Tunis and Uchman1996a). Internally, the green marly horizons showvarve-like laminations and exhibit rare trace fossils.They are opportunistic colonizers favoured by foodflux related to short “eutrophic” periods (Fig. 12,Pictures 1, 2 ). These green horizons progressivelypass upwards into the ochre-red shales. Thus, thesetwo components are likely to have originated during asimilar sedimentary event.

– The pink marlstone beds are homogeneous, non-lam-inated hemipelagite deposits. They are heavily bio-turbated by mm- to cm-sized Phycosiphon hamatum(FISCHER-OOSTER) and Phycosiphon geniculatum(STERNBERG) (no Ph. incertum is observed; Fig. 12,Picture 3). Spaced Chondrites intricatus (BRONG-NIART) cross-cut the former during a subsequentstage probably of oxygen-depleted conditions. Phy-cosiphon is randomly inclined and its density pro-gressively decreases downwards. As emphasized byWetzel and Uchman (2001) this vertical pattern indi-cates sediments, which are both fully oxygenated andrich in food material. Such a condition is met whenhemipelagic mud-flows originating from the conti-nental slope undergo both mixing with the oxygenatedwater-column and deposition sudden enough to trapoxygen and food material. The homogeneous aspect ofthe present facies duly confirms this phenomenon.

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These dense occurrences of Phycosiphon are likely toreflect an opportunistic behaviour by virtue of whichthe tracemaker rapidly colonized the sediment duringthe pre-omission stage.

Diverse intercalations of this facies within the lowerhalf of this formation (background sedimentation b.3,Fig. 6), show that it constantly bears this same ichnofabricand might be originated from specific pelagic, carbonate-mud flows independent of that carrying the calciturbiditeones and the green horizons/red shales couplets.

– The calciturbidite flows exhibit centimetre-scale, well-sorted, nummulite-rich arenites (division c.1, facies-sequence intervals VI and VII, Fig. 6) passing upwards

into faintly laminated green marlstones (division c.4,1–2 cm in thickness). These commonly exhibit densebiodeformational structures (i.e., dense bioturbationwith no distinguishable trace fossils) that may beoverprinted by spaced Scolicia and Chondrites intri-catus (BRONGNIART) during a subsequent soft-ground stage. The soles of these arenites commonlyexhibits both: (i) predepositional graphoglyptids (e.g.,Desmograpton alternum (KSIAZKIEWICZ), whichare cross-cut by Protovirgularia vagans (KSIAZKIE-WICZ), and (ii) post-depositional Thalassinoides andPlanolites. At the sole of many arenite beds, Tha-lassinoides has a sharp contact with the surroundingarenite matrix, and is filled with the overlying ochre-red shales (Fig. 12, Picture 5). This is a firmground

Fig. 6 Bed-by-bed stratigraphiccolumn of the Eocene strataoutcropping on the northernside of the Tamezzakht area(see detailed geologic map,sector A, Fig. 2) and photo-graphic illustration of thecyclicity pattern and of somekey facies (see also Figs. 12,13). Facies tracts and facies se-quences as mentioned forFig. 4. KB4a-c: Key Beds 4a-c;FS (V-IX)/FTD: facies se-quences (V-IX) and facies tractdivisions Cg, c.1-c.4

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signature that points to the Glossifungites ichnofacies.Fe encrusting may subsequently occur.

– The ochre-red shales are free of carbonate, structure-less and generally lack bioturbation (except some rareclusters of Chondrites intricatus (BRONGNIART),Fig. 12, Picture 6). This indicates that they were barrenof organic matter (as indicated by graphoglyptid atomission surfaces within these shales). They show noevidence of transportation as gravity mud flows, whichpoints to deposition from suspension. It may be as-sumed that they originated from wind-blown dusts.Commonly such environmental conditions are knownto trigger nutrient-bearing upwelling currents andhence eutrophic conditions, which in turn would resultin the deposition of green marls. The greenhemipelagic marly horizons lying at the base of themajority of the red-shale–dominated cycles are con-sistent with this assumption, since they may reflect theshort period during which the minor amount of avail-able organic matter was rapidly consumed.

Within the upper third of the present formation threeconspicuous, channelled and normally graded calcitur-bidite beds occur (ca. 100–70 cm in thickness, Fig. 7, beds

KB4 a, b, c). The two lower ones consist of five distinctdivisions (see attached-facies tract-interval VIII, Fig. 6).Unsorted, poorly graded, grain-supported conglomeratesdominate their lower half (division Cg) that abruptlypasses up into a nummulite-rich grainstone division (c.2).A similar sharp contact (potential detachment plane) ex-ists between divisions c.2 and c.3, which consist ofnummulite-rich, structureless arenites and finely lami-nated mudstones, respectively.

The first bed ends with a very thin green marly division(1 – 3 cm in thickness). This displays dense biodeforma-tional structures overprinted by spaced Scolicia prisca DEQUATREFAGES, before being covered with a thin Fe-crust. The second ends with near-planar, laminated shalyhorizons, the topmost of which shows patchily distributedPhycosiphon incertum FISCHER-OOSTER and spacedcylinders of Thalassinoides suevicus (RIETH). The un-derlying horizons are dominated by Chondrites intricatus(BRONGNIART) that were preceded by large circularRotundusichnium zumayaensis (GOMEZ DE LLARENA).In some cases, Naviculichnium marginatum KSIAZKIE-WICZ may cross cut the latter trace fossil. No Fe crustoccurs.

These ichnological features show that the first surfaceunderwent a more rapid oxygen-depletion than the second(and probably also a more prolonged one as witnessed bythe Fe-crust). This exhibits a progressive ichnologicalevolution between two end-members, namely Phy-cosiphon, the most demanding in terms of both food andoxygen, and Chondrites, which resists restricted ones.

The third bed is a remarkable debris flow with out-sized, ochre-red mud clasts, derived certainly from un-derlying strata of the same formation. This bed contrastswith the two preceding clean grain-flows in being free ofcoarse-grained carbonate lithoclasts, but recalls them bythe texture of c.1 and c.2 divisions. Outcrop survey of thiskey level shows that it may laterally be coarser andtransform into an olistostrome-like gravity event(Fig. 8B), precisely in the southern part of the Tamez-zakht area, where it contains meter-sized boulders inher-ited from the Calciturbidite Formation (CF). Here, theoverlying ochre-red shales may independently rest ontothe Green Pelite Formation (GPF) or the Black Shales one(BSF). Both the low-angle and the important hiatus inbetween (RSF/GPF-CF-BSF) led us to assign such anunconformity to the “hidden discontinuity” in the sense ofClari et al. (1995:108), the genesis of which is linked toslope-failure processes. At some localities where no de-bris flow delineates it, this discontinuity passes unnoticedbetween the monotonous ochre-red shales and the Calci-turbidite Formation (CF).

Marlstone-and-Sandstone Formation(MSF, early Oligocene–early Burdigalian)

The Marlstone-and-Sandstone Formation (MSF) overliesthe RSF with an abrupt change in colour, well delineatedin the field (Fig. 8A). It consists of well-developed

Fig. 7 General view of the Red Shale Formation (RSF) along a N/S-oriented quarry (compare with Fig. 4). The “double-bed” on thelower left corresponds to the top of the underlying formation (CF).It is covered by siliceous green shales, which are completely erodedon the lower right (south) by the early Eocene amalgamatedsandstone-beds. These may unconformably rest onto the Calcitur-bidite Formation (CF) through a hidden discontinuity (HD). Thered-shale – dominated middle interval (interval VII, Fig. 6) ispreceded by a well-delineated Fe-horizon (Fe-crust) resulting fromthe iron-staining of the upper half of a decimetre-thick calcitur-bidite bed. Three channelled, coarse-grained calciturbidite eventsoccur in the upper part of this formation (interval VIII, Fig. 6):KB4a, KB4b and KB4c, with the latter being poorly contrasted inthe field due to the red colour of its coarse-grained mud-clast-reworking division (MCg, Fig. 6). Total height of the quarry: 30 m

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rhythmic alternations of fine-grained sandstones, yellowmarls and light-green marlstones (ca. 80 m in thickness).While the thickness of these alternating facies remainsvertically thoroughly constant, it undergoes a significantchange within individual cycles. In addition, the stackingpattern of the latter allows three main members to bedistinguished (Fig. 9, cyclicity pattern change throughoutthe MSF).

Transitional Hemipelagic Member(THM, early Oligocene)

The Transitional Hemipelagic Member (THM) consists ofcentimetric- to decimetric-scale (mainly) cycles domi-nated by homogeneous to faintly laminated, light-greenmarlstones. Each of these cycles starts with a centimetricsandstone bed, which is immediately followed by a yel-low, marly millimetric horizon (Fig. 9). The lower cycles

Fig. 8 General view of the distinct facies change across theboundary between the Red Shale Formation (RSF, Eocene–earlyOligocene) and the yellowish Marl-Sandstone Formation (MSF,middle Oligocene–early Burdigalian), with the TransitionalHemipelagic Member (THM) at the base of the latter. Along thesouthwest side of this same outcrop the MSF unconformably restson distinct levels of the RSF and then on the two basal formations(GPF, BSF, see also Fig. 1A). B Example of a chaotic-breccia lens

derived from the underlying CF (late Paleocene) and embeddedwithin the upper part of the RSF (late Eocene levels). This resed-imentation event may be correlated with coeval coarse-graineddebris-flows occurring in the Dorsale Calcaire and in equivalentsuccessions in the Predorsale domain close to the Eocene–Oligo-cene boundary. It also may be correlated with the turbidite eventKB4c (see Fig. 7)

Fig. 9 Evolution of the cyclicity pattern throughout the main for-mations of the Tamezzakht succession and possible facies-corre-lation between their components. Change affecting the cyclicitypattern might be an alternative useful tool of interpreting facieschanges and the factors controlling the material delivered at thesource area, especially in the case of hemipelagite-dominated

successions wherein the reduced volume of the turbidite flows donot allow the facies sequence/facies tract concept to be fully used asa predictive method. RS-1: lower half of the Red Shale Formation;RS-2: upper half of the Red Shale Formation (other abbreviationsas in Fig. 2)

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still show patchy red-coloured levels resulting in a var-iegated, purple colour at the outcrop scale. This factsuggests that these green marlstones derived from thepreceding ochre-red shales via “discolouration” (partly,due to Fe-pigment–reduction). By comparison with thecyclicity pattern in the underlying formation, it may beassumed that the ochre green shales would correspondprecisely to the expansion of the green hemipelagichorizons lying at the base of the ochre-red shales.

Surface analysis shows scarce trace fossils, representedby rare post-depositional Planolites on the sole of sand-stone beds and rare Phycosiphon incertum FISCHER-OOSTER on or near their top. Both do not record sig-nificant omission surfaces, but may indicate that thesandstone-bed events were punctuating the marly ones. Apossible interpretation of this marl/sandstone cyclicitypattern is proposed hereafter based on much more com-plete ichnological data (see below the Siliceous MarlyMember). The yellow/green marl boundary is either dif-fuse or planar and shows no trace fossils. The absence orscarcity of trace fossils within the marly intervals andbetween them are likely to be linked to the followingcontrolling factors:

(i) The negative impact of the abrupt increase of sed-iment input on the benthic food resources (Savrda et al.2001b: 54) and/or, (ii) the muddy substrate that is here toothick to favour sandy-substrate burrowers (as stressed byTunis and Uchman 1996b: 185), and/or (iii) the relativeshortage of dissolved oxygen, which is a common featurein “eutrophic” green shales.

Marly Member (MM, Middle Oligocene?)

The Marly Member (MM, ca. 25 m in thickness) developfrom the underlying one through a rapid decrease inthickness of the green-marlstone, with a slight increase inthe thickness of the yellow one, which results in a yel-lowish centimetric-scale, sandstone/marl alternation. Thisfacies change coincides with the onset of a second type ofdark green shales that are randomly interlayered asdecimetre- to metre-spaced, dm-thick intercalationswithin the whole of this member. Contrary to the formershales, the dark green shales are highly laminated andshow a slight grading from their very base. This is thor-oughly planar and strongly suggests that the dark lami-nated shales were detached from a different kind of par-ent-flow, whose textural composition is independent ofthat resulting in the general marl/sandstone-alternationregime.

As was the case for the preceding member, no tracefossils are preserved within the homogeneous marly in-tervals, whereas the sandstone beds commonly display ontheir sole pre-depositional trace fossils corresponding toeither Scolicia strozzi (SAVI & MENEGHINI) orPlanolites isp. The corresponding bed surfaces may besparsely colonized by Phycosiphon incertum FISCHER-OOSTER. In comparison with the underlying member,such an ichnological signature points to a relatively more

lowered sedimentation rate, a fact that may otherwise bewitnessed by the marked thinning of the marl/sandstonecycles. Importantly, the presence of Ph. incertum indi-cates a certain tendency towards better bottom-wateroxygenation (e.g., Tunis and Uchman 1996b: 184).

Sandstone Member (SM, late Oligocene Aquitanian?)

Five-m-thick couplets of micaceous sandstone/shale splitinto four intervals the background marl/sandstone alter-nation (Fig. 10 presenting the bed-by-bed column of thelast interval). These are 5 to 10 m in thickness and differfrom the underlying member by the sandstone beds,which become thicker (Fig. 9). Strikingly, the majority ofthe sandstone beds are not graded to poorly graded, ho-mogeneous to faintly laminated. The lack of the parallel-to cross-laminated structures (the classical “Tc” and “Td”Bouma divisions) that typify the outer fan deposits, doesnot allow us to consider them as detached from the upperpart of low-density turbidity currents. Wood debris isfrequently trapped within the sandy matrix, which re-quired moderate to weak suspension-segregation. Such atype of fine-grained sandy deposits likely derives frombed loads that underwent a mechanism of depositionsimilar to grain-flow frictional-freezing (Lowe 1982).They should be distinguished from the classical base-missing Bouma’s sequences that originate from low-density turbidite flows (i.e., suspension loads). Ichnolog-ical features presented below lend support to this inter-pretation (see bed-types 2 and 3).

Bed surfaces exhibit a more pronounced ichnologicalrecord, which provides evidence for very low sedimen-tation regime occurring both before and just after thesandstone turbidite events. Ichnological signature on boththe top surface and on the sole of the successive sandstonebeds, allows the comparison of the pre- and post-depo-sitional ichnological record. This leads to the recognitionof six main types of beds within each sandstone/marlinterval. Depending upon their relative occurrence fromthe base onwards, these bed types are as follows:

1. The first type corresponds precisely to those beds thatdirectly overlie the metric-scale micaceous shales.Their sole casts giant winding, semi-relief structures(ichnotaxon indet. A, Fig. 14, Picture 5), which areabout 12 cm in diameter and 5 cm in height. A well-developed Fe-coating on these trace fossils shows thatthere was a notable omission phase after deposition ofthe micaceous sandstones. The corresponding bed topappears relatively smooth with rare or no trace fossils.

2. The second type dominates the two lower marl/sand-stone intervals and occurs in the lower half of the twolast sandstone/marl intervals (Fig. 14, Picture 1). Bedsurfaces show dense Phycosiphon incertum FISCHER-OOSTER, which may be subsequently cross-cut byspaced Nereites irregularis (SCHAFH�UTL). Later,Ophiomorpha rectus (FISCHER-OOSTER) and/orOphiomorpha annulata (KSIAZKIEWICZ) overprint

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independently the two former trace fossils. No Scoliciaare found here. The corresponding soles are dominatedby other post-depositional Ophiomorpha isp.

Phycosiphon (produced by a single-layer colonizer) isknown to require both well-oxygenated and nutrient-richsediments; a double condition met when the originalgravity flow undergoes deposition sudden enough to trapnutrient particles and dissolved oxygen (see referencesabove). Additionally, Ophiomorpha is a bulldozing(Uchman 1999:160), multi-layer colonizer that prefersplant detritus and survives moderate- to high-frequencyturbidite events. It occurs in unstable, moderate to rela-tively high sedimentation-rate environments (Uchman1995, 1999).

3. The third type is common in the upper half of the foursandstone/marl intervals (Fig. 14, Pictures 3, 6). It isalso typified by near-surface, dense Phycosiphon in-certum FISCHER-OOSTER that are commonly cross-cut by Nereites irregularis (SCHAFH�UTL) and

during a subsequent stage of colonization by Scoliciavertebralis KSIAZKIEWICZ. The soles of the samebeds are dominated by pre-depositional domichniarepresented by numerous mm-sized mound structures,that may be either paired (Saerichnites ? isp.) orclustered traces (Parahaentzschelinia ? isp., Uchman1995; Tunis and Uchman 1996a). They testify to rel-atively quiet deep-water before the onset of a turbiditeevent.

Producers of Scolicia vertebralis (solely epichnial;Uchman 1995, 1999) are known as single-layer colonizersthat also preferred plant detritus, but may have been ableto survive oxygen-poor conditions. Likely, this is thecause behind the disappearance of Ophiomorpha (aspointed out by Uchman 1995, onset of low oxygenationconditions generally results in the replacement ofOphiomorpha by Scolicia).

4. The fourth type of bed occurs near the topmost of thetwo last sandstone/marl intervals (Fig. 13, Pictures 3,

Fig. 10 Bed-by-bed column of the last marl-sandstone interval ofthe Sandstone Member (SM) and the lower part of the SiliceousMarly Member (SMM). Between two given micaceous-sandstoneintercalations, hemipelagic marls and rust-coloured sandstones

make up a metre-scale interval, that considered alone, records adepositional regime during which both omission duration andoxygen-depleted conditions progressively increase upwards (seetext for additional explanation)

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Fig. 11 1–3 Example of S3-type surfaces of the Slope CalcareniteFormation. Cross-cutting relationships allow distinguishing threemain stages of colonization: 1 Surficial dense churning (finebiodeformational structures) produced during an early stage ofprobably good oxygenation. It reflects a competition for the foodflux. Later, this diffuse bioturbation is “peacefully” cross cut byechinoid grazers (the winding trace fossil: Scolicia (Sc.) in thesense of Uchman 1998:153). 2 Small vertical tubes produced bydomichnia tracemakers (Arenicolites and/or Diplocraterion) duringa further stage of colonization when the bulldozing effect of thegrazers ceased, probably because the substrate entered the firm-ground stage (i.e. Arenicolites and Diplocraterion are commoncomponents of the Glossifungites ichnofacies, e.g.; MacEachernand Burton 2000). Note the small holes penetrating previous pas-cichnia. 3 The preceding domichnia become so dense as to producenew diffuse bioturbation. 1–3 shows that this colonization suite isonly the first step of a protracted omission history. This step wasfollowed by a post-colonization stage marked by Fe-coated, rust-coloured, large areas, a fact that testifies to inhospitable conditionsdue probably to lethal levels of oxygen depletion (e.g., El Kadiri

2002a, b). 4 Example of S3-type surface of the Slope CalcareniteFormation, showing a filled tunnel of Thalassinoides suevicus(RIETH) (Th.s.), another domichnion that followed the first stage ofdense churning. Note its distinct muddy filling, sharply contrastingwith the ochre-red “ background ” facies. 5 Horizontal U-tube of aRhizocorallium isp. (Rh) on a S1-type surface, which is markedlyless bioturbated than the preceding ones. Rhizocorallium crossesclusters of small Chondrites (scarcely visible in the photograph)and is in turn cross-cut by spaced small domichnia (simple holes).The S1-type surface is interpreted as undergoing relatively rapidoxygen-depletion preventing intense bioturbation as early as at thesoftground stage. This is in accordance with the presence of bothRhizocorallium and Chondrites. 6 Another example of S3-typesurface (typified by fine biodeformational structures + perforatingdomichnia) showing a tunnel of Thalassinoides suevicus (RIETH)(Th.s.), subsequently filled with coarse grainstones piped downfrom the basal coarse division of the overlying stratum. This dis-tinct burrow fill testifies that the corresponding excavator was ca-pable of penetrating firm substrates

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Fig. 12 1–2 Sole of a thin horizon of hemipelagic green marls (seeFig. 6, term b4) interlayered within the carbonate-free ochre-redshales of the middle interval of the RSF (Eocene). Contrary to the“oligotrophic” ochre-red shales, the green horizons point to short“eutrophic” periods resulting in phases of abrupt food flux. Thesefavoured rapid colonization by opportunists, which are representedhere by Thalassinoides suevicus (RIETH) and/or Planolites. In 1,the green cylinders show that the corresponding tracemaker pipeddown into the underlying red shales without reworking them. In-terestingly, this gives evidence that the ochre-red shale depositionwas punctuated by omission plus consolidation before being cov-ered by an “eutrophic” marly horizon. This also may be evidencedby the mud-crack – like structures, which are commonly printed onthe sole of the green marly horizons. 2 Close-up view of a similargreen surface (sole of a green marly horizon) showing a smooth,branched cylinder of Thalassinoides suevicus (RIETH). 3 Anotherexample of the “eutrophic” marls punctuating the “oligotrophic”red shale deposition: pink marlstones, which are characteristically

colonized by Phycosiphon incertum FISCHER-OOSTER (arrows,see also a similar photograph in Fig. 6, interval VI). 4 Thegraphoglyptid Spirorhaphe involuta (DE STEPHANI) on the soleof a centimetre to millimetre green shale horizons interlayeredwithin the middle part of the Red Shale Formation. Such highlypatterned traces are known to require stable conditions and to resistlong-lasting food-shortage episodes. It gives additional evidencethat the red shale deposition was punctuated by omission histories.5 Light-coloured sole of a calciturbidite bed lying near the upper-most level of the Red Shale Formation (above the three turbiditeevents, see Fig. 7 in the text). It shows post-depositional Tha-lassinoides isp. and/or Ophiomorpha tunnels, both produced bycrustaceans that require good benthic oxygenation. Their contrast-ing muddy infilling points to colonization during firmground con-ditions. 6 Sole of a thin horizon of green marls (on the upper right)with sparsely visible burrowing, and a cluster of Chondrites intri-catus (BRONGNIART) in the basal levels of a decimetric red shaleinterval

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Fig. 13 1 Paleogene cover of the Internal Dorsale outcroppingalong the road to television aerial. The yellow sandstones (Middle(?)–late Oligocene to Aquitanian (?) on the left side, correspond tothe so-called “Gr�s Roux”. They sharply overlie green and pinkhemipelagic marls of the early to middle Oligocene (Maat� et al.1993). This sandstone event may tentatively be correlated with theonset of near-identical sandstones from middle Oligocene levels(MM) of the Tamezzakht succession. 2 Close-up view of dm- to m-sized synsedimentary faults affecting the base levels of the “Gr�sRoux”, a fact showing that the onset of this facies coincided with atectonic collapse event. 3 General view of the last marl/sandstoneinterval at the uppermost part of the SM (just below the SiliceousMarly Member, SMM). Note the thickening-upward trend of thesandstone beds and their rhythmic alternation with yellowish andgreen marls. From the base onwards, each cycle is made up of: (i)yellow soft marls (YSM), which rest on a sandstone bed via anomission surface (OS), (ii) Vi�uela-like Siliceous Marls (VLM),(iii) “Gr�s Roux”-type sandstone bed (GR) (see also Fig. 9 for

comparison with the cyclicity pattern in the underlying members).The thickest brown bed (BB) capping this interval is the first at thebase of the overlying member (Siliceous Marly Member). The latteris typified by both the abrupt change of bed colour and the increaseof thickness of the bed sandstones and green marlstone interval. 4example of a Scolicia surface, which typifies the last rust-colouredsandstone beds of the Sandstone Member. This meandering form isa post-depositional variant of the echinoid-produced trace fossil:Scolicia vertebralis KSIAZKIEWICZ (Sc.v) (e.g., Uchman 1998,p. 155, his Fig. 58B). For another example see Fig. 14 (4). 5–7Examples of trace fossils observed on top surfaces of the light grey-coloured beds of the Siliceous Marly Member. They are poorly tomoderately bioturbated. 5: cluster of Phycosiphon incertum FI-SCHER-OOSTER; 6 Ophiomorpha isp. tube with casting of itspelletal wall structure (Ophiomorpha is commonly lined with verysmall muddy pellets); 7 Tube of Palaeophycus (?) tubularis withlining consisting of the material of the host rock itself

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4; Fig. 14, Picture 4). It is entirely dominated byabundant pre-depositional bulldozing pascichniarecorded on the bed sole, namely Scolicia plana(KSIAZKIEWICZ) (mainly), Scolicia strozzii (SAVI& MENEGHINI) and Planolites isp. The correspond-ing bed surfaces display other bulldozing echinoid-produced trace fossils, namely post-depositional Scol-icia vertebralis KSIAZKIEWICZ. Fe-coating com-monly covers such a type of Scolicia-dominated bed.

5. The fifth type is found only in the topmost of thesecond and the third sandstone/marl interval (insofar asobserved). The beds are rust-coloured and topped witha Fe-coating. They show near-surface, dense coloniesof Chondrites intricatus (BRONGNIART), which canbe ascribed to both oxygen-poor (e.g., Bromley andEkdale 1984; Ol�riz and Rodr�guez-Tovar 1999) andnutrient-rich sediments (Vossler and Pemberton 1988).

6. The sixth type corresponds to centimetric micaceous-sandstone beds, which are interlayered with yellow

marlstones. They occur in the top of this member,precisely just after the deposition of the last and thegreatest micaceous sandstone event (4 m thick). Theirupper surface is smooth and shows no trace fossils. Incontrast, their sole casts dense, strange centimetricmound structures (Fig. 14, 2). This bed type stronglysuggests that the preceding ecologic niche becameliberated after the preceding oxygen-depletion peakand the subsequent onset of an important turbiditeevent (i.e., the 2-m-thick, micaceous sandstone bed,immediately underlying the stratigraphical top of thismember). The latter is known to kill the majority of thesingle-layer colonizers (Uchman 1995:65). Important-ly, this ichnological event coincides with the facieschange resulting in the deposition of the followingmember.

Fig. 14 (All the beds are fromthe Sandstone Member, SM). 1,3 Top surface of centimetretype-2 and type-3 beds, respec-tively. They are intensely colo-nized by Phycosiphon incertumFISCHER-OOSTER (Phy),which is subsequently cross-cutby Ophiomorpha (Oph) and/orThalassinoides (1) or by Nere-ites irregularis (SCHAF-H�UTL) (3). 2 Strange moundstructures on the sole of a mi-caceous, centimetric type-6 bedat the uppermost part of theSandstone Member (biogenicorigin?). 4 Scolicia vertebralisKSIAZKIEWICZ (Sc.v) on thetop surface of a type-4 bed atthe upper part of the SandstoneMember (see also Fig. 13, 3). 5Giant biodeformational struc-tures (ichnotaxon indet. A) onthe sole of the basal bed of thelast sandstone interval, whichdirectly overlies a 3-m-thickmicaceous sandstone turbiditeevent. These giant structures arecast from the stratigraphic topof the micaceous shales (this isalso true for the strange moundstructures shown in 2 above). 6Scolicia vertebralis KSIAZ-KIEWICZ (Sc.v) crossingOphiomorpha and/or Thalassi-noides (type-3 bed) probablyduring a subsequent stage ofrelative oxygen depletion

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Siliceous Marly Member (SMM, early Burdigalian)

The Siliceous Marly Member (SMM, ca. 30 m) is typifiedby metre-scale intercalations of homogeneous, light-greensiliceous marlstones. The latter facies strongly recalls theVi�uela Formation, a widespread transgressive pelagic-dominated succession well known in the Betico-Rifianinternal zones, especially during the early Burdigalian(Bouillin et al. 1973; Sanz de Galdeano et al. 1993;Serrano et al. 1995; L�pez-Garrido and Sanz de Galdeano1999; El Kadiri et al. 2001). Here, it derives from theunderlying member (SM) through both the reduction ofthe yellow marl cycle-component and the simultaneousexpansion of the green marlstone ones (Fig. 10). In ad-dition, sandstone beds become thicker than previously,i.e. from 30 to 60 cm in thickness. They exhibit more orless pronounced graded bedding and a wavy to convo-luted silty upper division. This gives evidence that theoriginal flows underwent deposition sudden enough totrap the interstitial water. Some beds in the lower part ofthis member show that the laminated division grades intoa yellow muddy one. The vertical stacking of these threedivisions (non-graded sandstones\laminated silts\yellowmuds) in a single turbidite bed lends additional evidencefor sudden deposition processes, since they clearly showthat detachment cannot often occur between the divisionsof the corresponding mature facies-tract.

On the contrary, a number of other beds show a bur-rowed omission surface between the laminated divisionand the yellow marls, which indicates that these twocomponents can pertain to two distinct depositionalevents. This recalls the cyclicity pattern shown in theunderlying member.

These surfaces exhibit two kinds of ichnoassemblagesdepending on facies and bed-thickness: (i) dense Phy-cosiphon incertum FISCHER-OOSTER may dominatethe surface of certain centimetric sandstone beds (Fig. 13,5), whereas (ii) spaced small clusters of the same tracefossils and abundant Ophiomorpha isp. and Paleophycus(?) tubularis HALL may occur on the laminated siltydivision of decimetric beds (Fig. 13, 6,7).

Thin-sections from the coarser basal division reveal amixture of metamorphic-rock-derived lithoclasts, mainlyschist, quartzite, feldspar, micas. But none of these seemto come from the metamorphic and/or crystalline base-ment presently known in the Ghomaride and Sebtide units(ultramafite rocks, garnet schists, etc., see Fig. 1 for lo-cation).

Holoquartzous Formation (HF, latest early–Burdigalian?)

The Holoquartzous Formation (HF, ca. 10 m) consists of apure siliciclastic interval, which ended the preceding pe-lagic–marl–dominated regime. Tobacco-brown pelitesmake up its lower part wherein decimetric micaceous-sandstone beds may be still interlayered. The upper oneconsists entirely of the classical brown-coloured B�liou-nis-type sandstones (Didon et al. 1973). These were used

by Didon et al. (1973), Durand-Delga (1980) and Olivier(1984) to define the Predorsale units as corresponding to adistinct paleogeographic domain along the fringe of theBetico-Rifian internal zones. In the present work, we dulynote the presence of this facies as part of the Tamezzakhtstratigraphic succession, a fact that may have an impor-tant bearing on the paleogeographic reconstruction, butthe outcrop conditions do not allow us to present a de-tailed description.

However, we note that these two facies strongly recallsthe Talembote succession described by El Kadiri et al.(2001) in the Ghomaride transgressive cover.

Results and discussion

Sedimentological data, bed surfaces, turbidite-flow com-position, sediment colour and ichnological features evi-denced above, provide important clues for the interpre-tation of the distinguished formations in terms of bothenvironmental and relative sea-level changes. The mainresults can be drawn as follows:

Glaucony-bearing, clean calciturbidites and theircoarse-grained basal division allow the interpretation ofthe BSF (late Campanian – early Maastrichtian) as relatedto a transgressive trend. Indeed, glaucony-bearing bio-clastic grainstones and/or wood-debris-rich sediments arewell known as being the typical sedimentary response tothe onset of a transgressive regime onto a healthy, shallowcarbonate platform (e.g., Baum and Vail 1988; Loutil etal. 1988; Galloway 1989; Vail et al. 1991; Ghibaudo et al.1996; Robaszynski et al. 1998; Kelly and Webb 1999;Bombardi�re and Gorin 2000; Hesselbo and Huggett2001; Savrda et al. 2001a), or onto a continental area(e.g., Posamentier and Vail 1988; Savrda 1991; Vail et al.1991; Savrda et al. 1993), respectively. For both cases,transgression-induced winnowing and polishing/spill-overprocesses may be envisaged, since they are now thoughtto be the major shelf-to-basin exporting mechanisms(Einsele 1992; Stow and Mayall 2000; Viana and Stow2000; Savrda et al. 2001b). This line of reasoning mayalso be followed to understand the gravity flow events andthe cyclicity pattern within the overlying calciturbiditeformations.

Compiled data by Leszczynski (1993) showed that thecolour of sediment is mainly controlled by the Fe3+/Fe2+

ratio, i.e. the oxidation state of Fe-pigments. Kuhnt et al.(1996) stated, on the basis of deep-sea agglutinatedbenthic foraminifera, that the colour of the backgrounddeposition commonly reflects trophic conditions. Greenshales may generally coincide with eutrophic ones duringwhich specific planktonic blooms could result in thedrastic reduction of dissolved oxygen throughout thewater column (see also Uchman 1995:62). In the GreenPelite Formation (GPF, latest Maastrichtian) this phe-nomenon may be otherwise confirmed by the above-mentioned pelagic mudstone bed, whose lateral continuityhas been controlled in the field (key bed 1 in Figs. 3, 4). Itis rich in dust-sized quartz grains, a common feature in

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planktonic oozes (e.g., Shimmield 1992). By contrast, redand pink shales may correspond to oligotrophic periodsduring which oxygen consumption is lowered and Fe-pigments remain in the oxidized state (see also discussionby Sarmiento et al. 1988 on the causal link between an-oxia and eutrophic conditions).

This line of reasoning may tentatively be completedwith the possible relationship between sediment colourand relative eustatic changes, since eutrophic conditionsare generally favoured by the intensification of oceancirculation, which is well known to be intensified duringlowstand-related cold climates (many authors, e.g., Haq1991, 1993 and compiled data by Martire 1992). Bycontrast, oligotrophic conditions may partly be linked toperiods of thermohaline water stratification (e.g., warmsaline bottom waters, Brass et al. 1982; Kennett and Stott1990) and/or sluggish ocean circulation (as emphasizedby Martin 1995, 1996), both are the two common effectsof flooding episodes (Haq 1991, 1993; Hallam andWignall 1999). These considerations seem to us alsoconsistent with the facies change resulting in the depo-sition of the overlying reddish formation (see below).

Therefore, it may be assumed that the facies changeacross the BSF-GPF boundary would be related to theonset of an abrupt regressive regime, a fact that may beotherwise supported by both the sudden siliciclastic inputand the disappearance of the carbonate-platform-derivedflows. Considering its age (late Maastrichtian, Abatom-phalus mayaroensis Zone) and its stratigraphic positionimmediately below the levels including the K/T transi-tion, this regression may be the expression of the sea-levelfall well documented just below the K/T boundary (Bar-nes 1999; Hallam and Wignall 1999).

The preceding bioclastic–material–delivering source(BSF) is likely to be emerged and/or drowned under ter-rigenous deposits of the Green Pelite Formation. Hence,the abrupt facies change from black to green pelites maycorrespond to a drowning discontinuity (in the sense ofSchlager 1989:17), which is known to occur during latehighstand/lowstand regimes.

The most striking feature of the Slope CalcareniteFormation (SCF, ranging from the latest Maastrichtian upto the early Paleocene) is the scarcity of biogenic com-ponents (both shallow-water and planktonic ones), a factuncommon in glaucony-rich, shallow-water-derived cal-citurbidites. Superoligotrophic conditions due to impor-tant flooding episodes and the concomitant water columnstagnation (and hence spreading of ocean anoxia) areconsidered as the more efficient environmental conditionin killing both planktonic and benthic biota during themajor bioevents (see data compiled by Barnes 1999;Hallam and Wignall 1999). In this formation (SCF),which includes the K/T boundary, the scarcity of bio-clasts, the red colour and the protracted omission surfaces(see below) may tentatively be considered as evidence fora similar scenario.

Dolomite, white limestones and thin-shelled-bivalve-rich mudstones, Calpionella-and/or Saccocoma-richmudstones compose the carbonate lithoclasts reworked in

the Slope Calcarenite Formation (SCF). These facies arewell known in the late Triassic and Jurassic successions ofthe Internal Dorsale units (e.g., Griffon 1966; Raoult1966; Nold et al. 1981; El Kadiri et al. 1989; Maat� 1996)and in the Jbel Moussa Group (e.g., El Kadiri et al. 1990),and thus may give a first impression about their possiblesource. However, the well-developed slump-like struc-tures in the surface S2, as well as measurements of pa-leocurrent directions in this formation and in the overly-ing ones, indicate currents travelling towards N70E–N85E, mainly N80E. Thus, calciturbidites of theTamezzakht succession are likely to have originated froman external shallow-water high area and not from theneighbouring Dorsale Calcaire. The absence of clasts in-herited from key facies belonging to the external Dorsaleunits (e.g., radiolarites, cherty limestones), lends supportto this important result. It is in accordance with Durand-Delga’s (1972) “ Tariquide Ridge ” hypothesis that statedthe existence of a lost external carbonate platform duringthe pre-paroxysmal history.

The ichnological features of the SCF, albeit brieflydescribed, lead to the assignment of its ichnoassemblagesto both: (i) the Zoophycos ichnofacies (in the sense ofFrey et al. 1990; Seilacher 1967), a bathymetry-relatedassemblage colonizing the slope and base-of-slope set-tings, and (ii) the Glossifungites ichnofacies, which is asubstrate-consistency-controlled assemblage. It was ini-tially defined in non-marine and shallow-water settings(Seilacher 1967). Later, Bromley and Allouc (1992),Bromley and Asgaard (1991), MacEachern and Burton(2000), Pemberton and Frey (1985) and Savrda et al.(2001a, b) pointed out that the latter assemblage has nobathymetric restriction and can develop on the base-of-slope omission surfaces and even on bathyal firmgrounds.

Since the Glossifungites ichnofacies can serve to de-lineate key stratigraphic surfaces, many authors empha-sized its sequence-stratigraphic significance (MacEachernet al. 1992, 1999; Bromley 1996; Pemberton andMacEachern 1995; Savrda 1995; MacEachern and Burton2000; Savrda et al. 2001a, b). Depending on the time scaleconsidered, it is now thought to mark minor or majortransgressive pulses, namely: (i) parasequence-boundingminor flooding surfaces (Van Wagoner et al. 1988) or (ii)the omission surfaces within the amalgamated condensedsection, respectively (e.g., Loutil et al. 1988; Jacquin andDe Graciansky 1998). Cross-cutting relationships andhence the colonization suites inferred above showed thatthe S1–3-type surfaces experienced a protracted omissionhistory. Furthermore, Fe-coating (especially on the S2surface) indicates that some of them had possibly reachedthe late firmground (to hardground?) stage (i.e., thepolygenic omission surfaces of Clari et al. 1995, “truehardgrounds” of Kennedy and Garrison 1975). El Kadiri(2002a, b) and Pr�at et al. (2000), showed that ferruginouscrusts on hardground surfaces will be of bacterial originand occur when the environmental stresses, induced bytransgressive pulses, attained lethargic conditions.

Ichnological features of S1-S3- surfaces showed thatsuch environmental extremes may be attained more or

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less rapidly. Their vertical distribution within the SCFmay be ascribed to a transgressive regime, the peak ofwhich is confined in the surface S2 (possible K/Tboundary). This conclusion is consistent with the onset ofthe carbonate-poor ochre-red shales from the very base ofthis formation.

In comparison with the preceding formation, the Cal-citurbidite Formation (CF, late Paleocene) is typified bythe sudden disappearance of the red colour and an in-crease in the volume of parent flows; both events coin-cided with the sudden proliferation of benthic largerforaminifera (i.e., division c.1, facies sequence intervalIV, Fig. 4). Thus, the base of this formation possiblycoincides with the first restoration of the supplier car-bonate platforms, after the K-T transition crisis, and thusmay point to an important paleoenvironmental change.Amongst its controlling factors, which could better bedeciphered based upon regional and/or global data, theTamezzakht section allows us to quote here the evidencefor the onset of a transgression (sensu lato, of tectonicand/or eustatic origin).

Oligotrophic (to super-oligotrophic) red ochre shales,barren in organic matter dominate the Red Shale For-mation (RSF, Eocene – early Oligocene). Compiled datafrom, e.g., Barnes (1999), Hallam and Wignall (1999),Kuhnt et al. (1996), Leszczynski (1993), Leszczynski andUchman (1993), Pletch (1998, 2000), Samtleben et al.(2000) and Tunis and Uchman (1996a, b) help elucidatethe possible origin of this facies. Thus, the Eocene time ischaracterized by extreme warm episodes during whichprotracted arid periods (A-periods of Bickert et al. 1997)lowered the input of nutrients transferred by rivers. Si-multaneously, the intense evaporation in the epeiric arearesulted in the formation of dense warm saline waters(Brass et al. 1982). Once transferred to the deep settings,these cause stagnation and allow upwelling currents tostart only from nutrient-poor shallow depths. These twophenomena may act separately or in concert to causeoligotrophy. Analysis of the cyclicity pattern in theoverlying formation showed that a yellow-marl cycliccomponent substituted the “oligotrophic” red shales dur-ing the restoration of the eutrophic regime (Fig. 9).

The ochre-red shales are sharply overlain by a well-developed yellow Marlstone-Sandstone Formation (MSF,middle Oligocene – early Burdigalian). Although nostratigraphic gap is clearly evidenced at its very base,mapping and outcrop survey show the presence, in twolocalities of the study area (the northwestern and south-western sides), of a hidden discontinuity in the sense ofClari et al. (1995), along which the yellow marls maynear-conformably overlie independently the green pelites(GPF) and the black shales (BSF).

Worth noting is the disappearance of the bioclastic,shallow-water-derived calciturbidites from the base of theMSF. The preceding supplying carbonate platform waslikely destroyed and/or drowned under the siliciclasticaccumulations. In both cases, the sharp contact betweenthe Red Shale Formation (RSF) and the siliciclastic onecan be assigned to the depth-equivalent of the drowning

discontinuity in the sense of Schlager (1989). Petro-graphic evidence from the very base of the graded-sand-stone beds shows a mixture of basement-derived grains,namely, filonian-type quartz, schist, feldspar, and micas.They are possibly related to a tectonically raised, newsource-area. If so, regional tectonics may be consideredamong the controlling factors behind the abrupt facieschange well delineated in the field across the red-shale/yellowish-marl boundary (see Fig. 8A), which primarilyrecords an important paleoenvironmental event (climate-and/or eustasy-mediated global environment change, e.g.,synthesis by Bestland 2000).

The Fe-encrusted surfaces, well delineated in the fieldin the upper half of the Sandstone Member (SM, probablyof late Aquitanian in age) may be interpreted based uponthe ichnological record on both the upper bed surfacesand the soles of the successive sandstone beds. A moreadequate interpretation of the six burrowing patternsrecognized in this member requires a more precise bed-by-bed survey and regional-scale correlations, which isbeyond the scope of this paper. For instance, we note aprecise double trend (throughout the whole member andwithin each sandstone/marl interval) towards increasingof both oxygen-depletion and duration of the omissionphase just before and after each turbidite sandstone event.This sedimentation regime deduced from ichnologicalevidence does not necessarily mean that there was alowering of the sedimentation rate, since it coincided witha clear-cut thickening-upward trend, which directly re-flects an increase in the sedimentary volume of the suc-cessive parent flows (tectonic and/or eustatic influences).Chondrites, Scolicia surfaces and Fe-crusts express thepeak of this evolution that tentatively may be explained inthe context of sea level – mediated climatic changes. Sucha sedimentary regime fits very well the remark by Savrdaet al. (2001b: 47) that most of the sand-rich accumulationscoincide with warm, transgressive/highstand phases. Theyalso showed the presence of Phycosiphon, amongst othertrace fossils, in the sandy facies.

The total lack of graphoglyptid is striking in the SM.Commonly, these highly patterned trace fossils requirelong-term, stable conditions characterized by food-short-age episodes and relatively quiet bottom waters. In theturbidite realms this double condition may be possible indistal fan areas or in interchannel ones (e.g., Crimes et al.1981) where only small-scale, low frequency, deep-seaturbidites occur. Therefore, it seems that such distal en-vironments were not present in the case of the Tamez-zakht depositional area (the micaceous sandstones inter-calated as metre-scale gravity-flows within the successionsupport this deduction).

The carbonate clastic material, reworked during theMaastrichtian-early Oligocene, derived from an externalshallow platform (Tariquide-type Ridge) and not from theneighbouring internal areas (Dorsale Calcaire). They re-sulted in calciturbidites interbedded successively betweenblack, green and ochre-red shales. By contrast, coevalsuccessions in the Dorsale Calcaire chiefly consist ofcalciturbidite-free, reduced hemipelagite deposits and

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point to a distant paleogeographic area with respect ofthat studied herein.

The upper half of the Tamezzakht succession is char-acterized by the alternation of yellowish to pink sand-stones (the so-called “Gr�s Roux”; Fallot 1937; Griffon1966) and micaceous sandstones (the so-called “Gr�so-Micac�”), with decimetric to metric marlstone intervals inbetween. The latter facies corresponds to the classicalVi�uela-type facies, which was widespread in the Betico-Rifian internal zones during the early Burdigalian times.Micropaleontological evidence from the studied sectionshows that the onset of this key facies may start as earlyas the late Oligocene. Moreover, the “Gr�s Roux” faciesis also well known in the late Oligocene-Aquitaniansuccessions of the Dorsale Calcaire, whereas the mica-ceous sandstones are typically the facies that define theB�ni Ider sandstone flysch during the same time interval.As a result, the upper half (late Oligocene-early Burdi-galian) of the Tamezzakht succession strikingly combinesin a single stratigraphic column, facies that characteriseseparately the Internal-domain transgressive cover and theExternal-domain flysch successions. This fact might ten-tatively be explained in terms of a tectonic shorteningpreceding the major thrusting of the Internal domain ontothe External one, which is well known to have occurredduring the middle-late Burdigalian times.

Conclusion

An integrated sedimentologic approach including faciestract/facies sequence description, ichnologically-basedsurface and depositional environment analyses and se-quence-stratigraphic interpretation (via lithologic predic-tion method), allowed us to distinguish seven main for-mations from the latest Cretaceous up to the early Bur-digalian. These may parallel six main transgressive/re-gressive cycles and the regionally correlatable time-equivalent strata known in the neighbouring zones (workin progress).

Acknowledgements The authors express their sincere thanks toAlfred Uchman and Franz Frsich for their thorough reviews andconstructive criticisms. This study was financially supported by the“Junta de Andalucia” Project N A49/02 (M): “Las Formacionescenzoicas de la zona interna ...” (Spain) and by the PARS SDU.72Program: “Les bassins s�dimentaires et leurs ressources...” (Mo-rocco).

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