Palaeocene–Eocene deep water agglutinated foraminifera from the Numidian Flysch (Rif, Northern Morocco): their significance for the palaeoceanography of the Gibraltar gateway

A lower bathyal to abyssal agglutinated foraminiferal fauna (over 78 taxa belonging to 31 genera) is documented from Palaeocene–Eocene deep-water sediments of the Numidian Flysch (Talaa Lakrah Unit) in Northern Morocco. The sample locality is adjacent to the Strait of Gibraltar, which comprised an oceanic ‘gateway’ between the Tethys Ocean and the North Atlantic during the Palaeogene. The chronostratigraphy of the section is based upon long-distance comparisons with the stratigraphic ranges of identified species in the North Atlantic region and the Polish Carpathians. Although no major evolutionary turnover among deep-water agglutinated foraminifera (DWAF) is observed across the Palaeocene/Eocene boundary, a change from Palaeocene Aschemocella- and Trochamminoides-dominated assemblages to an early Eocene Glomospira assemblage is recognized. This Glomospira biofacies occurs throughout the North Atlantic and western Tethys and may indicate lowered productivity and widespread oxygenated deep-water conditions during the early Eocene greenhouse conditions. A change to an overlying Reticulophragmium amplectens biofacies in green claystones reflects renewed higher productivity. Taxonomic affinities and the succession of benthic foraminiferal assemblages from the Gibraltar gateway display greater affinities to Tethyan assemblages than North Atlantic assemblages. This is interpreted as faunal evidence for a late Palaeocene to early Eocene equivalent of ‘Mediterranean outflow water’, flowing from the western Tethys into the Atlantic.


INTRODUCTION
The Palaeocene/Eocene boundary witnessed the greatest turnover in the taxonomic composition of deepwater benthic foraminiferal faunas of any time during the last 80 million years. At this time, the last of the typically Cretaceous benthic foraminifera became extinct. and the new deep-sea faunas of the Eocene migrated down into the ocean basins from the continental margins (Berggren & Olsson,195%). I~Jnfortunately, few continuous oceanic Palaeocene-Eocene records with deepwater agglutinated foraminifers (DWAF) are available from the North Atlantic area. In the northeastern North Atlantic, lithofacies changes associated hith the Thulean volcanism and the onset of biosiliceous sedimentation render the sediments unfavourable for foraminiferal preservation, and many of the exposed sediments in passive margin settings in the Atlantic area are complicated by sequence boundaries.
One of thc few land sections containing well-preserved assemblages of DWAF across the Palaeocene/Eocene boundary is in the Numidian Talaa Lakrah Flysch of northern Morocco. This series cornprises a succession of distal deep-sl,a turlbiditic sediments with thick hemipelagic layers that was deposited within the oceanic gateway between the North Atlantic and the western Tethys. This section enables us to examine faunal changes in a continuous deep-sea setting below the CCD. The main objective of this study is to investigate the nature of the Palaeogene turnover in DWAF in the Talaa Lakrah Flysch and assess their biostratigraphic and palaeoecological significance in light o f palaeoceanographic changes that took place in the early Palaeogene.
We sampled a continuous section within the lower part of the Numidian Flysch sequence in a Numidian subunit known as the Talaa Lakrah Flysch. The Talaa Lakrah Flysch Unit was first defined by Didon et ul. (1973), based on the Miocene turbiditic sandstone unit exposed in the Strait of Gibraltar on the northern coast of Morocco approximately 18 km ENE of Tangier, near the village of Talaa Lakrah (Fig. 1). The unit consists of Campanian to Miocene deepwater sediments, and has been included in the Numidian Flysch, which is a geographically widespread unit extending from Sicily along the coast of North Africa to the Strait of Gibraltar. The Numidian Flysch represents the compressional phase of tectonics between the North African and European continents. The flysch unit is overthrust onto Cretaceous deep-water sequences that were probably based on oceanic substratum. The sediments comprising the Numidian Flysch are generally believed to be derived from the North African continent. However, a part of the detrital input to the Talaa Lakrah Unit may have been derived from the Alboran microplate.
The outcrop of the Palaeogene portion of the Talaa Lakrah IJnit sampled in this study is situated above a retaining wall behind a Moroccan military outpost, immediately west of the mouth of the Lediane valley. The section is overturned, and consists of steeply dipping turbidite sandstones and interbedded claystones. The base of the sampled section is identified by a c. 1 m thick sandstone ledge. overlain by dark bluish-grey, tectonically disturbed claystones. The sandstones in the sequence thin upwards, and the sand/shale ratio decreases. The colour of the hemipelagic claystones changes from bluish-grey at the base to reddish-brown, and then to greenish-grey at the top. The colour changes may reflect changing oxygenation of the bottom waters and sediment surface rather than sediment input, and invites comparisons to the coeval oceanic sequences of the North Atlantic.

MATERIAL AND METHODS
Fifteen large samples ( Table 1) were collected from the Talaa Lakrah outcrop (Fig. 2). Samples wcrc dried. weighed, and disaggregated by repeated boiling and drying using sodium carbonate solution. Samples were washed over a 63 p m screen. All foraminifera from the > 125 p m fraction were picked and mounted onto cardboard microscope slides. In this material, the 63-125 pin fraction did not yield identifiable foraminifera.
Smear slides were made of each sample, but all samples were barren of nannofossils. The green samples were tested for palynomorphs and found to be barren.

BIOSTRATIGRAPHY
Because the Palaeogene autochthonous claystones were all barren of calcareous nannofossils, and palynomorphs were probably oxidized, the DWAF provide the only stratigraphic control to constrain the age of the sediments. The chronosl ratigraphy is necessarily based upon long-distance comparisons will the stratigraphic ranges of identified species in the North Atlantic region and thc Polish Carpathians (Fig. 3).
The Palaeocene to Eocene benthic foraminiferal biostratigraphy of the North Sea region has been calibrated to the standard chronostratigraphy by the use of dinoflagellate zones (C'harnock & Jones, 1YYO). In the Zumaya section of northern Spain, the stratigraphic ranges of D W A F are calibrated to planktonic foraminiferal zones in the Palaeocene to lower Eocene (Fig. 3). The DWAF biostratigraphy at Site 647 in the southern Labrador Sea is calibrated by the use of standard nannofossil zones (Kaminski et al.,198Y), but this record only extends upward from lower Eocene Zone NPl I . Although nearby DSDP Site 112 penetrated into the Palaeocene. the hole was spot-cored, and did not recover the Palaeocene/Eocene boundary (Miller et ul., 1982). The biostratigraphy of DWAF in Trinidad was calibrated to the standard, low-latitude planktic foraminifera1 zonation by Kaminski et al. (1988). This biostratigraphic scheme was based upon isolated samples from Zones Plc to P8. However, the I'alaeocene/Eocene boundary in Trinidad is represented by  (Geroch & Nowak,19X4), the Basque Basin of northern Spain (Kaminski. 1988). Trinidad (Kaminski CI id., 1988). and thc North Sea (Charnock & Jones, 1990). Calibration to planktonic zones applies only 10 Trinidad and Zumaya. Notes: ( I ) FO of K. rrmp/ecrms is in Zone PX in the North Sea (M.A. Charnock. pcrs. comm., 1994): (2) reported a s ('onglophrrrgniirrni coronrr1um by Charnock & Jones, 1990 an unconformity (Bolli, 1957). In the abyssal North Atlantic, Palaeocene claystones are extremely poor in agglutinated foraminifera. Assemblages consist generally of few longranging forms which d o not allow any biostratigraphic zonation. Near the Palaeocene/Eocene boundary there is a major change in lithology with lower Eocene sediments bccoming increasingly biosiliceous. Normal deep-sea claystones with diverse agglutinated foraminiferal assemblages have been described only from the Labrador and Norwegian Seas (Kaminski rt ul., 1990). The Palaeogene DWAF biostratigraphy for the westcrn Tethys is based on the zonation of Geroch & Nowak (1984). This zonation is based upon composite sections from the Silesian flysch basin in Poland. Because these sediments are largely noncalcareous, direct calibration to the standard plankton zones is not possible, and benthic foraminiferal assemblages were determined based largely on their superposition. The Geroch & Nowak zonation, while providing an excellent framework for correlation in flysch sediments, is a scheme that still requires direct calibration to the geomagnetic polarity time scale.
The Palaeogene foraminiferal micropalaeontology of the Gibraltar seaway has not been formally described. The only previous micropalaeontological study from the north coast of Morocco is a preliminary note by Morgiel & Olszewska (1982). In the Talaa Lakrah section, the interval from approximately the middle Palaeocene to middle Eocene is exposed in a continuous stratigraphic succession. In contrast to the Zumaya section which is a shallowing-upward sequence across the Palaeocene/Eocene boundary, the Talaa Lakrah Flysch remains a distal turbidite depositional environment throughout the Palaeogene with a more or less continuous record of hemipelagic deposition (Fig. 4). All the hemipelagic claystones we sampled yielded well-preserved DWAF.
The DWAF assemblages recovered from the Talaa Lakrah samples are generally diverse and show no signs of size sorting. Rare abraded specimens of calcareous benthic foraminifera in Samples 2. 5 , 14, and 15 are considered to be redeposited from a shallow bathymetric setting. We recognized a total of 78 species and taxonomic groups in our samples (Table 2), but because a number of our counting groups include more than one species, our estimates of the faunal diversity must bc rcgarded as a lowcr limit. Changes in relativi. percentages of selected species and morphogroups are compiled in Fig. 5.
We discriminate five assemblages within the sampled interval based on the total ranges and relative abundances (Fig. 5 ) of characteristic species and taxonomic groups:

Aschemocella-Saccamminu placenta assemblage
Samples ai. the base of the studied section (samples [1][2][3][4][5][6] are characterized by common occurrence of A.schemocc~llri spp. and Saccamniinu placenta. The abundance of the former taxon reaches 30% in sample 6. Other common forms include species o f Rhabrlamniinn and Pmrurrochcinzmirzoide,s. In the modern deep ocean, tubular taxa are common in turbulent settings affected by deep currents (Kaminski,19x5). The species A. carpathicci was first described from the upper surfaces of turbidite mudstoncs in the Romanian Flysch C,arpathians (Neagu,1 Y64). Late Cretaceous A.schrmocc.1lu-dominated assemblages occur mainly in areas with large amounts of fine-grained detrital supply provided by mud-turbidites. High abundances of Aschemocella may reflect high amounts of organic detritus from terrigenous sources, which provide nutrients for these large taxa.

Trochamm inoidesl Paratrochamm inoides -Recurnoides assemblage
Samples 7-8 are dominated by the Parcitroclzaniniirioidr,s and Rcuruoidrs groups. Ammodiscids are also significant, but less dominant than in samples 9-14 (see below). The assemhlagc consists of numerous individuals and species, many of which are yet undescribed. The abundance o f diverse Prirntrochurriininoid~~s in the lower half of the studied section invites comparison to the Upper Cretaceous red clay environments of abyssal turbidite basins ( = Flyschtype. high diversity, Parutrochaniminoides-faunas of Kuhnt . These Late Cretaceous Puratrochanzniinoides assemblages probably characterized more oligotrophic environments. The Maastrichtian part of the Talaa Lakrah section also contains numerous Parrrtrochaninziiioine.c (Kuhnt & Kaminski, 1989). Although much of the Palaeocene to lower Eocene part of the Talaa Lakrah section does consist of reddish-brown sediments. there is a significant influence of dctrital material.
The taxonomic composition and stratigraphic position o f this assemblage is reminiscent of the 'Trochamminoidcsschichten' of Majzon (1 943) (1978) correlated this acme to the lowermost Eocene. Reddish claystoncs containing common flattened P(~rarocharrzniirioides are also known from the lower Eocene S'irhhotina parugonica Zone (= Zones P7-P8) o f the North Sea.

Glomospira-Ammodiscus assemblage
Samples 9 and 10 contain more than 60% ammodiscids (Gloniospira. Ammodisciis, and Gloniospirella). This assemblage corrclatcs with Gloniospiru-dominated asscmblages observed in other parts of the Atlantic (Kaminski e/ a/.. 1989) and western Tethys (Winkler, 1984). The interval is characterized by numerous small specimens of Glomospirn spp. and Anznzo&ciis /eniris.sinzir.s. A distinctive taxon in this interval is an undescribed species o f Gloniospiru that has very irregular coiling. Our species Gloniospira sp. 5 is a form that is probably new. and appears to be related to the Palaeogene species Amniociiscits p w z v i .
The faunal abundance and the average size of specimens in this interval diminishes upsection, attaining minimum values in samples 10 and 11 (Fig. 4). This agrees with trends in calcareous benthic assemblages in the lower Eocene o f the North Atlantic, which are reported to be depauparate (Berggren CG Olsson. 1986).

Karrerulina conijormis assemblage
The tirst occurrence of K. conif0rnii.c is observed in sample 1 I, which also contains the maximum abundance of the genus (Fig. 5). In Trinidad the first occurrence (FO) of this species was observed in the lower Eocene (Zone P6b), at Site 647 its FO was observed within Zone NP11, below the Gloniospira horizon. The stratigraphic distribution of Kurrerirlina species may be controlled by palaeoceanog-  raphic factors such as organic matter flux, since modern representatives of this group live infaunally.

Reticulophragmoides amplectens assemblage
Samples 12 to 15 are characterized the common occurrence of R. amplectens, which is a typical form of middle to upper Eocene sediments in the Atlantic and 6 western Tethys. Other characteristic forms in the uppermost part of the section are Reophax elongaius and Karrerinlinu coniforrnis. Geroch & Nowak (1984) reported the range of Reophax elongatus as middle to upper Eocene in the Polish Carpathians. The ranges of all of these taxa extend to the Eocene/Oligocene boundary in the North Atlantic (Kaminski a[,, 1ygy). Reticiil~)phragmiiin?n rimplectrws is believed t o have evolved from an early Emene ancestor by the acquisition of additional chambers and advancing the development of alvcoles with ontogeny. Jurkiewicz ( 1 967) had already reported that alveolar structure usually begins closer to thc proloculux in specimens from younger stratigraphic horizons. Alveoles first appear between the 10"' and 17"' chamber in the microspheric generation cif primitive individuals, and between the 5'" and 13'" chambers in more advanced individua1:i. Myatlyuk (1970) considered the smaller early Eocene niorphcitype of R. anzplectens with 10 chambers in the last whorl and few alveoles to be a separate species, and named it Cycluniniinu internaediu. Although lower Eocene assemblages from the North Sea and the Carpathians undoubtedly contain the 'Cyclurnrnina intermedia' morphotype, this form is absent from our samples of the Numidian Flysch. In this regard, they are more similar to early Eocene specimens from Labrador. which consist of 'advanced ' f o r m of R. urnplectens with well-developed alveoles.

FAUNAL, TURNOVER AT TlHE PALAEOCENE/EOCENE BOUNDARY
A major turnover of deepwater calcareous benthic foraminiferal ta:ra at the Palaeocene/Eocene boundary has bcen ohscrved in all the world's oceans (Tjalsma, 1977: Schnitker. 1979: Tjalsma & Lohmann, 19x3: Thomas & Shackleton, 1991: Pak & Miller, 1992. lJtilizing benthic foraminifera1 oxygen isotope records. Shackleton ( I 986) suggested that deep oceanic waters had a temperature of approximately 1'0°C in the earliest Palaeogene, increasing to 12°C in the early Eocene and thcn decreasing again. Miller ('r ul. (1Y87a) suggested that the world ocean was ice-free throughout most of the Palaeocene and Eocene. Their oxygen isotope studies on calcareous benthic foraminifera also indicate rapid warming of sea water from mid-Palaeocene to early Eocene times, followed by a step-wise deterioration culminating in the late Eocene glaciations. Superimposed on this first-order trend are fluctuations that correspond to rapid climatic change. Kennett & Stott (1991) documented a rapid c. 8°C warming of Antarctic surface waters that coincided with a 4% drop in foraminiferal d"C and the extinction of about half of the calcareous benthic taxa. These authors suggested that deep water circulation was reduced resulting in lowered oxygenation of the deep sea. These isotopic changes have been confirmed in all the ocean basins (Stott, 1992), and show that the deep sea warmed to about 10°C. These unusually warm temperatures persisted for about 100 000 years. More importantly, the surface-to-deep foraminiferal d ' 'C gradient decreased from about 1.7% in the Palaeocene to near zero at Site 690 (Stott,1 992), which suggests that marine organic productivity was severely diminished. This observation corroborates the findings of Miller ev nl. (1987b) who noted decreased sediment grain size in the Pacific, which implies weaker trade winds and consequently reduced upwelling. The Palaeocene/Eocene warming has been attributed to increased supply of C 0 2 , as a consequence of global tectonic activity (e.g. opening of the Norwegian-Greenland Sea) and volcanism in the North Atlantic region (Owen & Rea, 1985).
The impact of climatic changes at the Palaeocene/Eocene (P/E) boundary on DWAF is still poorly documented. While all DWAF localities studied so far display a reduction in both abundance and taxonomic diversity from the upper Palaeocene to the lower Eocene, this turnover cannot be attributed to a single environmental cause (Kaminski. 1991). The bathyal foraminiferal assemblages of Zumaya Spain and the West Greenland, Labrador, and Norwegian continental shelves occur in shallowing-upward sequences. In these areas, Palaeocene agglutinated faunas are replaced by calcareous assemblages, or barren intervals. In the North Sea and Norwegian Sea regions, the boundary is contained within volcanoclastic sediments. In the central North Atlantic the P/E boundary occurs within a lithologic change from claystones to radiolarites that are barren of foraminifera. Biostratigraphic data from the upper Maastrichtian to middle Eocene Gurnigel-Schlieren flysch of Switzerland (Winkler, 1984) reveal the last occurrences of six species of D W A F at or just below the P/E boundary. No taxa with first occurrences near the boundary were recorded. In the Polish External Carpathians (Geroch & Nowak, 1984), five species have last occurrences approximately at the P/E boundary and two species have first occurrences just above the boundary. In the Guayaguayare and Lizard Springs Formations of Trinidad 15 species display LOs at or just below the boundary and only one incoming species occurs just above the boundary (Kaminski et ul., 1988). The most dramatic faunal turnover of DWAF near the P/E boundary has been observed in the North Sea. As many as 20 species display LOs immediately below the P/E boundary and 35 species have FOs just above the boundary (Charnock & Jones, 1990). However, the effects of local palaeoenvironmental change in the North Sea area have probably amplified the magnitude of the faunal change.
At Talaa Lakrah, the following taxa have last occurrences between samples 5 and 9 (broadly coincident with the P/E boundary): Saccummiria Ascheniocella assemblages appear to comprise a statistically independent end-member of Late Cretaceous DWAF assemblages that are typically developed in fine-grained turbidite environments, such as the Maastrichtian flysch of the Carpathians and the lower bathyal turbidite units in the Campo de Gibraltar. In the Talaa Lakrah section, the occurrence of A.schemocellu is restricted to samples from the Palaeocene that are associated with thick-bedded sandstones. Their disappearance across the P/E boundary may result from reduced amounts of organic detritus from terrigenous sources as well as marine organic productivity.
The majority of first and last occurrences across the P/E boundary in this section are among species that are known from the Palaeocene and Eocene at other localities. At Talaa Lakrah, these constitute local biostratigraphic events. In general, it appears that calcareous-cemented agglutinated taxa were especially prone to extinction at the Palaeocene/Eocene boundary. Therefore, the magnitude of the faunal turnover of agglutinated taxa is more pronounced at the marginal North Atlantic sites and is less important in the Tcthyan sites below the CCD.

EARLY-MIDDLE EOCENE GLOMOSPIRA EVENT
Assemblages with common Ammodisciis and Glomospira have been found in the lower Eocene of the Alpine-Carpathian region (Jurkiewicz, 1967;Morgiel & Szymakowska, 1978;Morgiel & Olszewska, 1981 and the Moroccan flysch (Morgiel & Olszewska, 1982). Winkler (1984) discovered a level with common Glomospira in the lower part of Zone  in the Schlieren flysch of the Alpine Flysch Zone of Switzerland. In the southern Labrador Sea, Glornospira spp. range throughout the Eocene and basal Oligocene at Site 647, but display a distinct acme in Zones NP13-NP15 (Kaminski ef a/., 1989). Characteristic species of this assemblage consist of Glomospira irregularis, Glomospiru churoides, Ammodiscus cretaceus. Karrerulina coniformis, Trochamminoides spp. and Haplophragmoides walteri. At Site 643 in the Norwegian Sea the total range of Glomospiru spp. is confined to the lower Eocene . The so-called 'Glomospira Event' is consequently of biostratigraphic use in the North Atlantic and western Tethys, bearing in mind the observation that it may be diachronous from east to west. In the Tellien Units in northern Morocco, we also observed a lower Eocene biosiliceous lithofacies which may correlate with the Glomospiru Event in the Numidian Flysch. Immediately above these biosiliceous sediments are cl aystoncs with Reticulophragmoides amplectens.
Kuhnt  noted increased abundances of ammodiscids, especially the genus Glomospirellu, in lower Campanian green claystones reflecting poorly oxygenated benthic conditions in the North Atlantic. This distinct assemblage, termed 'Biofacies B', was subsequently found at different Cretaceous horizons at other deep sea localities such as in the Barremian at O D P Site 765 on the Argo Abyssal Plain (Kaminski et al., 1991). In the lower-middle Eocene at O D P Site 647, an interval with abundant Glomospira is characterized by an increase in deposition of biogenic silica (Bohrmann & Stein, 1989) and organic carbon , which is consistent with a scenario of increased biogenic productivity. Some modern species of Glomospira appear to be environmentally tolerant, and thrive in environments where oxygen and salinity levels are low. They have the ability to survive on organic-rich substrates, such as in an area of active petroleum seepage in the Gulf of Mexico. Alve (1990) recognized an Ammodiscus? [ = Glomospirella] gullmarensis assemblage in temperate water masses in Drammensfjord, southeast Norway, characterized by reduced salinity and very low dissolved oxygen content. Kaminski et a/. (1989) speculated that Glomospira feed epifaunally on organic detritus, and was consequently well-adapted to areas of high productivity.
However, other aspects of the DWAF assemblages in the Talaa Lakrah section question the validity of this model for the lower Eocene reddish claystones. Both the abundance and relative size of DWAF decline steadily from the Palaeocene, reaching minimum values in the Glornospira acme (Fig. 4). The environmental significance of size and abundance trends in deep-sea benthic foraminifera has been examined by Pederson et a/. (1988) and Herguera & Berger (1991) in their studies of modern and Pleistocene productivity in the Pacific. These studies demonstrated that both the average size of certain benthic foraminifera as well as benthic foraminifera1 accumulation rates are positively correlated with the flux of organic matter to the sea floor, and can serve as good proxies for palaeoproductivity. At the same time, the relative proportion o f tubular forms reaches a minimum (Fig. 5). Because modern tubular taxa such as Rhmhtkaimminri and Saccorhizn have been found to be suspension feeders (Altenbach ei a/., : Linke & Lutze. 1993, the decline in tubes over this interval may be related to the reduction in food particles carried in suspension by bottom currents. It may simply be the case that Gloniospiru is an opportunist, inhabiting environments that have undergone rapid change, or occupying niches that have been left vacant by other species.

RETICULOPHRAGMOIDES AMPLECTENS ACME
Deep-water clastic sediments containing large proportions of Reticulophrugmiunz ampleciens are typically referred to thc middle Eocenc in the Polish Carpathians. In Poland, its first occurrence was reported in the lower Eocene (Zone NP12) by Olszewska & Smagowicz (1977). Its total range in the Polish Carpathians was given as lower to upper Eocene by Morgiel & Olszewska (1981), and its partial range and optimum occurrence characterizes the middle Eocene C.yclamwtinu ampleciens Zone of Geroch & Nowak (1984). In the Austriain Alps, R. ampleetens was reported from the lower to lower middle Eocene Buntmergelserie (Rogl ei a/., 1086). In the Central North Sea the R. umplecteris acme is observed immediately above the lowcr/middle Eocene boundarq as determined by palynological and micropalaeontological evidence, occurring in a unit of high gamma ray values ( M A . Charnock. pers. comm., 1994). At Site 647 in the southern Labrador Sea its FO occurs in the upper part of Zone N P I I (below the Glomospira event), and its greatest abundance occurs in the middle Eocene. However. at Talaa Lakrah its first occurrence is above the Glomospira event, which is consistent with its occurrence in the Carpathians.
The palaeoecology of R. ampleetens is not well understood, however, its symmetrical shape and circular outline recalls ihat of the modern deep-sea species Mr1oni.s harle~wntcm, a mobile infaunal detritivore (Corliss, 1985). Moreover, R. aniplecrens is one of the dominant taxa in the Eocene o f the Labrador margin (beneath the oxygen minimum zone) but only comprises S-IO% o f the assemblage at abyssal Site 647. 'This agrees with findings of Corliss & Chen (1988) and Corliss & Fois (1991), who observed a shift from dominant infaunal taxa in the upper-middle bathyal zone to dominant epifaunal taxa in the lower bathyal t o abyssal zone. This changeover is related to the amourit of food available to the infauna. If R. umplccfens was inderd infaunal, then its dominance in the greenish claystones above the Glomo.spira event indicates a return to the more productive and/or less well oxygenated oceanographic conditions that favour significant proportions of infauna.

PALAEOENVJRONMENT AND PALAEOCEANOGRAPHY OF THE PALAEOGENE NUMIDIAN FLYSCH BASIN
The Palaeogene of the Talaa Lakrah Flysch is charactcrized by diverse flysch-type agglutinated foraminifera and a lack of autochthonous calcareous forms. They are interpreted as autochthonous assemblages and can be vicwed as remnants of former benthic communities that flourished beneath the CCD.
It is surprising that two otherwise common early Palaeogene species are absent entirely (Spiropleciunzmina speciahilis) or extremely rare (a single specimen of Rzchakina epigotia in sample 3) in our material from the Talaa Lakrah Flysch. Spiroplectammin~~ .speciuhilis and R. rpigona are among the most common and characteristic species of DWAF in Palaeocene deep-water sediments deposited along the North African continental margin, in Trinidad, and in the Central North Sea. Both species preferably occur in dark greenish shales with enhanced content of organic carbon and may characterize environments with high organic flux rates. Consequently, the absence of these species at Talaa Lakrah might reflect low abundanccs of organic matter or other nutrients.
Although the assemblages consist mainly of cosmopolitan species, the relative succession of benthic foraminifera1 assemblages from the Gibraltar gateway displays a greater affinities to Tethyan assemblages than to assemblages from the North Atlantic. In particular the presence of an assemblage consisting of diverse species of Porutrochun7nzinoidr.s and Trochamnzinoiries overlain by a Glorno.rpira-dominated assemblage provides evidence of strong links with the Carpathian Palaeocene-Eocene deposits. This gives us some insight into the nature of the deep water masses. For example, studies of carbon isotopes (Katz & Miller, 1991) have revealed that the Southern ocean was a source of deep water during the late Palaeocene and again during the early Eocene, but that the supply of deep water decreased near the Palaeoccne/Eocene boundary. This interpretation is supported by the observation of a late Palaeocene erosional hiatus on the Bermuda Rise, indicating strong bottom currents flowing into the North Atlantic from the south (Mountain & Miller, 1992). Sediment deposition resumed on the Bermuda Rise during the latest Palaeocene, a result of the reduction in deepwater circulation. General ocean circulation models have suggested that the eastern Tethys was a likely zone o f high evaporation and therefore a prime site for the formation of warm, saline deep water (WSDW) (Barron & Peterson, 1990). It is possible that the change in the oxidation state of the sediments at Talaa Lakrah and the loss of large specimens is a reflection of differing bottom water sources. We suggest that the appearance of lower Eoccne reddish shales reflects a proximal WSDW source which was well oxygenated and nutrient depleted.
The abrupt appearance of an K. ampleetens dominated assemblage above the Glomospira event horizon may have palaeoccanographic significance. At DSDP Site 401 in the Bay of Biscay, Pak & Miller (1992) noted a change from an earliest Eocene Niittu1ide.s trirempyi assemblage to an assemblage dominated by Bitlirninella grata, Siilostomella gracilliniu and Bziliniina .sen7icostai~i in Zone P6c. In Zones P8-P9 Siilostornellu (an infaunal form) was dominant. This shift from epifaunal-dominated assemblages to ones dominated by infauna in the middle part of the early Eocene also points to similar changes in oxygenation and/or palaeoproductivity. Because the Bay of Biscay is distal to any proto-Mediterranean outflow water flowing northward around Portugal as an eastern boundary current, perhaps the assemblage changes in the Gibraltar and Biscay regions are linked. Indeed, based on their comparison of stable isotopic data, Pak & Miller believed that Site 401 monitored deep water of a western Tethyan origin.

CONCLUSlONS
The diverse (>78 taxa) D W A F assemblages of the Talaa Lakrah Flysch compare well with the diverse cosmopolitan flysch-type agglutinated assemblages in the sense of Gradstein & Berggren (1981). The depositional environment of the Palaeogene Talaa Lakrah turbidites was lower bathyal or abyssal, and below the calcium carbonate compcnsation depth.
The taxonomic affinities and relative succession of benthic foraminifera1 assemblages from the Gibraltar gateway are more Tethyan than Atlantic. In particular, diverse Paratrochamminoides and Trochumminoides and the presence of an interval of reddish claystones with Glomospiru provide strong links with the Palaeocene-Eocene assemblages of the Carpathians. We interpret this as faunal evidence for a late Palaeocene to early Eocene equivalent of 'Mediterranean outflow water', with bottom water flowing from the western Tethys into the Atlantic as it does today.
Despite the now well-documented Palaeocene/Eocene boundary extinction event among calcareous benthic foraminifera, there is surprisingly little taxonomic turnover among DWAF in the Talaa Lakrah section (in terms of species extinctions and originations). However, changes in the size, abundance, and relative proportions of agglutinated foraminifera across the Palaeocene/Eocene boundary interval undoubtedly reflect environmental changes that took place in the western Tethys. Reductions in the abundance and size of DWAF from the Palaeocene to the lower Eocene indicate decreasing nutrients and/or palaeoproductivity. An early Eocene Gfornospira-dominated hiofacies can be attributed to a period of well-oxygenated, oligotrophic conditions, probably caused by reduced particulate organic matter flux. The sparse assemblages from oxygenated sediments may be linked to lowered surface water productivity during the early Eocene climatic optimum and/or warm, well-oxygenated deep water masses of possible Tethyan origin. The return to greenish-grey, biosiliceous claystones with successive Karrerulinudominated and R. amplectens-dominated assemblages signalled the return to a more eutrophic environment.