Planktonic foraminiferal biostratigraphy and paleoecology of Upper Cretaceous deposits from the Palmyride Region , Syria

This study represents a detailed micropalaeontological investigation of the composition and diversity of planktonic foraminiferal assemblages from the upper Turonian to Maastrichtian interval of two deep exploration wells (Al Mahr-1 and Palmyra-1) in the Palmyride area of Syria. In combination with lithostratigraphic analysis, this detailed biostratigraphic study provided important new palaeoecological and palaeoclimatic interpretations and insights into the nature of deposition along the northern passive margin of Gondwana during the Late Cretaceous. The investigated strata belong to three lithostratigraphic units (from base to top): the upper part of the Judea Formation (upper Turonian–lowermost Santonian), the Soukhne Formation (Santonian–lower Campanian), and the Shiranish Formation (upper Campanian–Maastrichtian). The results represent the fi rst detailed determination of planktonic foraminifera from the Palmyride region. The presence of rich and diverse foraminiferal associations enabled the establishment of the following nine late Turonian to Maastrichtian biostratigraphic zones, based on documented indextaxa and/or the entire microfossil assemblages: I) Biozone I; II) Biozone II; III) Biozone III; IV) Contusotruncana plummerae Zone; V) Biozone V; VI) Globotruncanella havanensis Zone; VII) Pseudoguembelina palpebra Zone; VIII) Racemiguembelina fructicosa Zone; and IX) Abathomphalus mayaroensis Zone. The late Turonian to early Campanian foraminiferal assemblages (biozones I–IV) are dominated by opportunistic taxa (r-strategists) and suggest a generally fl uctuating subtropical climate and deposition an outer shelf environments. The well­preserved and highly diversifi ed late Campanian to Maastrichtian foraminiferal assemblages (biozones V–IX) imply the presence of a well­stratifi ed water column, tropical to subtropical climate, and deposition in outer shelf to upper bathyal envi­ ronments. A decrease in the number of globotruncanid species during the late Maastrichtian indicates a less stratifi ed water column and unfavourable environmental conditions for K-strategists. The common occurrence of phosphate grains in the Soukhne Formation (Santonian–lower Campanian) represents an important indicator of specifi c geological and palaeoenvironmental conditions, such as oxygen defi ciency, up­ welling and transgression. These conditions support the interpretation of the domination by opportunistic planktonic foraminiferal taxa (heterohelicids and muricohedbergellids) in Biozone II.


INTRODUCTION
The Palmyride area is part of the northern Arabian platform (Fig. 1). The Arabian platform was located on the northern passive margin of Gondwana bordering the Tethys Ocean for most of the Phanerozoic. The Palmyride fold belt was established at the site of an inverted Mesozoic rift basin and developed as a linear trough genetically related to the Levantine margin rift system, which formed along a Gondwana Proterozoic suture zone (BREW, 2001). Ongoing extension produced a 6 km thick and 200 km laterally extensive Palaeozioc and Mesozoic sedimentary succession (BREW, 2001). Tectonic evolution of the area has been strongly influenced by geological activity along the Arabian plate boun daries: the Dead Sea transform fault to the west, the Bitlis suture and East Anatolian fault to the north, and the Zagros suture to the east (Fig. 1).
This study focuses on the Upper Cretaceous (upper Turonian-Maastrichtian) succession from two deep exploration wells Al Mahr-1 and Palmyra-1, and was aimed at age determination and correlation (litho-and biostratigraphic) of strata based on their microfossil assemblages (mainly planktonic and some benthic foraminifera). Planktonic foraminifera have been abundant in most oceanic environments since their appearance in the Middle Jurassic and are the most commonly used microfossil group for biostratigraphic zonation and reconstruction of past sea surface-water conditions and palaeoclimate (HEMLEBEN et al., 1989;MURRAY, 1991).
The main purpose of this paper is to establish planktonic foraminiferal zonation of the upper Turonian-Maastrichtian succession of the Palmyride area based on the microfossil assemblages and/or index taxa present in order to improve palaeoenvironmental interpretations of deposition in the Palmyride basin during the late Cretaceous. The biostratigraphic zonation is compared with the regional Tethyan zo-  LITAK et al., 1998) and the study area in the Palmyride region. A circle represents the approximate location of the Hayan block with the Al Mahr-1 (1) and Palmyra-1 (2) exploration wells; distance between the wells is about 50 km.
nation. Documenting variations in planktonic foraminiferal assemblages and any associated lithological changes are critical for making palaeoclimatic and palaeoceanographic interpretations. Santonian to early Campanian sediments rich in phosphate grains are examined here as an important indicator of specific geological and palaeoenvironmental conditions. The data obtained are compared to those from other coeval regional successions in order to establish the significance of the Palmyride strata, as part of the Arabian platform, for better understanding of the sedimentary evolution of the broader Tethyan region and its response to global environmental changes.

GEOLOGICAL SETTING
Regionally the investigated area is also known as the Hayan exploration block (Fig. 1), which is located in the Palmyride area, an intracontinental transpressive mountain range (LUČIĆ, 2001). The Palmyrides represent the most distinct tectonic and structural unit in central Syria as a zone of subdued topography that extends from the Dead Sea Fault Zone to the west, and disappears to the east at the Euphrates Graben or depression (Fig. 1). The Palmyrides are 400 km long and 100 km wide, stretching southwest-northeast across Syria with a maximum altitude of around 1300 m (LUČIĆ & FORŠEK, 2000;BREW, 2001;BREW et al., 2001;HER-NITZ KUČENJAK et al., 2006;WOOD, 2011).
In the Palmyride area, Mesozoic deposits of Early Triassic to Late Cretaceous age were observed in all deep wells (LUČIĆ et al., 2002). Unlike the Upper Triassic and Jurassic deposits (maximum 700 m thick), which can either exhibit substantially reduced thickness (to 200 m minimum) or be absent in some places due to erosion or non-deposition, the Cretaceous strata are present throughout the region (approx. 800 m thick). The oldest deposits exposed on the surface are Upper Triassic evaporites interbedded with shales. Jurassic deposits are represented by different varieties of carbonate rocks, and Lower Cretaceous deposits consist of dolomites and limestones with rare interbeds of anhydrite and shale. In the Late Cretaceous there was a deepening of the depositional system, which resulted in the deposition of shales and marly limestones with a gradual increase in the amount of marl upsection (PONIKAROV, 1966a, b;LUČIĆ et al., 200. For the purpose of the Syrian Petroleum Company (SPC), the investigated Upper Cretaceous succession is subdivided into three lithostratigraphic units (Figs. 2,3): 1) the upper part of the Judea Formation (upper Turonian-lowermost Santonian); 2) the Soukhne Formation (Santonianlower Campanian); and 3) the Shiranish Formation (upper Campanian-Maastrichtian); (MOUTY & AL-MALEH, 1983). The Judea Formation is represented by limestones and dolomitic limestones with thin intercalations of yellow to brownish yellow marl. The Soukhne Formation is characterized by calcareous horizons in the lower part, and by clayey limestones, marls and phosphatic deposits in the upper part. Argillaceous limestones, marls, chert and ovoid calcareous concretions (10-30 cm in diameter) are present in the Shiranish Formation.

MATERIAL AND METHODS
The foraminiferal study is based on analyses of 81 samples of Upper Cretaceous deposits obtained as drill cuttings from two deep exploration wells (Al Mahr-1 and Palmyra-1) drilled in the Hayan exploration block in the Palmyride area. Samples of drill cuttings from mud samples were collected every 5-10 metres. Most of the analyzed samples contain very well preserved planktonic and benthic foraminifera.
Samples for micropalaeontological analyses were disaggregated in tap water and diluted with hydrogen peroxide, then washed through 63 mm, 125 mm, and 160 mm sieves, dried and examined on an Olympus SZX16 stereomicroscope. Representative aliquots of approximately 300 planktonic foraminiferal specimens were counted for quantitative planktonic foraminiferal analyses. The term ""dominant" was used for species that constitute more than 10% of the planktonic foraminiferal assemblage, whereas the terms ""common", ""fewand ""rare" refer to species comprising 3-10%, 1-3%, and <1% of the assemblage, respectively. Plankton/benthic ratios were determined for each biozone on at least 300 specimens from the entire foraminiferal assemblages in >63 mm grain fraction and were used for palaeoecologic and palaeoenvironmental interpretations.
Petrographic thinsections were made of 35 samples throughout the Upper Cretaceous interval for the purpose of lithological interpretation. Prepared petrographic thin-sections were stained with Alizarin red -S after the method of EVAMY & SHEARMAN (1962) in order to distinguish carbonate minerals. A detailed study of foraminiferal morphology was performed on a scanning electron microscope (SEM). The overall preservation of foraminifera is good although their original calcite shells have been recrystallized.
Phosphatic grains of the Soukhne Formation deposits were also analyzed using SEM back-scattered electron imaging (BSE) and energy dispersive X-ray analysis (EDX). The semi-quantitative X-ray elemental mapping of P, F, Cl

BIOSTRATIGRAPHY
Biostratigraphic subdivision of the investigated Upper Cretaceous successions is based on planktonic foraminifera. Stratigraphic ranges of the identified microfossil assemblages indicate a late Turonian to Maastrichtian age. Stratigraphic relationships between the identified planktonic foraminiferal species are shown in Figs. 2 and 3, whereas the lithostratigraphic and biostratigraphic biozonation correlation between Al Mahr1 and Palmyra1 are presented in Fig. 4.
The upper Turonian to lowermost Santonian deposits contain planktonic and benthic foraminiferal assemblages characteristic of this stratigraphic range. These poorly diversified microfossil assemblages have equal proportions of small benthic and planktonic foraminifera. The Santonian to lower Campanian strata, on the other hand, are characterized by a moderately diversified microfossil assemblage with increased abundance and diversity of planktonic foraminifera, and the absence of nominal taxon/zonal markers. High diversity microfossil assemblages with a dominance of planktonic foraminifera and well-preserved index taxa are present in the upper Campanian to upper Maastrichtian deposits.
Nine biozones have been identified in the upper Turonian to Maastrichtian succession: Biozone I, Biozone II, Biozone III, IV Contusotruncana plummerae Zone, Biozone V, VI Globotruncanella havanensis Zone, VII Pseudoguembelina palpebra Zone, VIII Raceemiguembelina fructicosa Zone, and IX Abathomphalus mayorensis Zone. A list of taxa together with author names and year of publication are provided in the Appendix. All of the diagnostic species and some additional taxa typical of the studied foraminiferal assemblages are illustrated in Figs. 6-9. Assemblage characteristics. As index taxa were not observed, the lowest occurrence (LO) of Contusotruncana fornicata and Globigerinelloides bollii has been used to define the lower boundary of this Zone. This biozone may correspond to the Dicarinella concavata Zone (PREMOLI SILVA & SLITER, 1994;ROBASZYNSKI & CARON, 1995;RO-BASZYNSKI et al., 2000;PREMOLI SILVA & VERGA, 2004;SARI, 2006SARI, , 2009. The foraminiferal assemblage of this interval is composed of rare non-keeled planktonic foraminifera with a wide stratigraphic range: Archaeoglobigerina blowi, A. cretacea (Figs. 6C,D), Whiteinella balthica, Whiteinella sp., Dicarinella sp. (Fig. 6A) and Marginotruncana sp. (Fig. 6B). In the middle of the biozone Muricohedbergella holmdelensis and Pseudotextularia nuttalli have their lowest occurrence. The most abundant species in the assemblage are Heterohelix reussi, H. moremani, and H. globulosa, comprising 38% of the total planktonic association. Biozone I is also characterized by very common Pseudotextularia nuttalli, Muricohedbergella holmdelensis, Muricohedbergella flandrini, marginotruncanids and whiteinellids. In addition, the following small calcareous benthic foraminifera are present and account for up to 50% of the total foraminiferal association: Bulimina ovulum, Gyroidinoides globosus, Bulimina sp., Gavellinela sp. (Figs. 9A, B), Lenticulina sp., and Nodosaria sp.
Lithology and palaeoenvironment. Brownish grey to grey limestone (mudstone/wackestone to foraminiferal wacke stone), dolomitic limestone and marl with equal proportions of planktonic and calcareous benthic foraminifera indicate accumulation within outer shelf environments.

Biozone II (Figs. 6E-I)
Age.  Assemblage characteristics. The main characteristic of the microfossil assemblage is the disappearance of marginotruncanids at the base of this biozone while Pseudoguembelina costulata has its lowest occurrence. Rugoglobigerina rugosa first occurs in the middle part of Biozone III, whereas Heterohelix reussi has its highest occurrence (HO). This bi-not present in every sample. In the upper part of this biozone Globotruncanita stuartiformis appears for the first time, while Heterohelix moremani and Muricohedbergella flandrini have their highest occurrence. The genus Heterohelix is very abundant and diverse (6 species), and comprises a very high percentage (46%) of the planktonic association. Among calcareous benthic foraminifera, common taxa with a wide stratigraphic range include: Bulimina ovulum (Fig.  9D), Praebulimina reussi, P. kickapoensis, Gyroidinoides globosus, Bulimina sp., and Lenticulina sp. Small benthic foraminifera make up to 40% of the microfossil assemblage.

Biozone V (Figs. 7C-G)
Age  . 7C), and Rugoglobigerina rugosa (Fig. 7D). The genus Heterohelix constitutes 38% of the assemblage and remains the most abun dant group in the planktonic association. In comparison with previous biozones, the diversity of Biozone V increases and the total number of planktonic foraminifera reaches 27 species.
Lithology and palaeoenvironment. Marl and argillaceous limestone (mudstone/wackestone) with abundant planktonic foraminifera (85%) suggest outer shelf to upper bathyal depositional environments. Assemblage characteristics. Pseudoguembelina palpebra (Fig. 7N) is consistently present in this biozone. The first occurrence of Globotruncanella pschadae, Pseudoguembelina kempensis and Racemiguembelina powelli is recorded in the lower part of this biozone. Gansserina gansseri (Figs. 7O, P) is present, but very rare, throughout this interval.Very common species in the assemblage include Heterohelix globulosa, Pseudoguembelina costulata (Fig. 7M) (Fig. 7K), and R. macrocepha la. The middle part of Biozone VII is characterized by the lowest occurrence of Abathomphalus intermedius, Globotruncanella minuta and Globotruncanita pettersi, while Globigerinelloides bollii become extinct. The upper part of this Biozone is also characterized by the lowest occurrences of Pseudotextularia intermedia and Globotruncanita conica. In comparison with Biozone VI, biodiversity significantly increases throughout Biozone VII and reaches the maximum of 41 species. This increase is partly related to speciation of globotruncanids, (represented by 12 species). The genus Heterohelix remains the dominant group with 34% abundance, whereas pseudoguembelinids remarkably increase up to 17%. Globotruncanids, despite numerous species, represent 15% of the planktonic foraminiferal population.
Small benthic foraminifera comprise less than 10% of the assemblage and include A large overturn in planktonic fauna occurred within Bio zone IX due to the extinction and disappearance of many species at the base of the biozone, including: Archaeoglobigerina blowi, A. cretacea, Globotruncana bulloides and Globigerinelloides prairiehillensi.Furthermore, species such as Abathom phalus intermedius (Fig. 8O), Gansserina gansseri, Glo botruncana linneiana, Pseudoguembelina costulata and Racemiguembelina powelli become rare and then disappear in the middle part of Biozone IX. Species of the genus Heterohelix remain the dominant group in the planktonic assemblage with the same abundance of 36%, whereas globotruncanids and rugoglobigerinids have almost the same abun dance as in the underlying Biozone VIII. The very high overall diversity (40 species) of Biozone IX, although somewhat lower than in Biozone VIII, dramatically decreases at the end of the zone when most planktonic foraminiferal species become extinct. Only a few species such as Muricohedbergella holmdellensis, M. monmouthensis and Guembelitria cretacea cross the Cretaceous/Palaeogene boundary.

INTERPRETATION AND DISCUSSION
This detailed study of the Late Turonian-Maastrichtian planktonic and benthic foraminiferal assemblages provides the ba sis for biostratigraphic and palaeoenvironmental interpretations of the successions examined. A total of 56 planktonic foraminiferal species belonging to 20 different genera have been identified. Abundant and moderately to highly diverse and generally well preserved planktonic foraminiferal assemblages enabled biozonation and identification of the following biozones: Biozone I, Biozone II, Biozone I, IV Contusotruncana plummerae Zone, Biozone V, VI Globo truncanella ha va nensis Zone, VII Pseudoguembelina palpebra Zone, VIII Racemiguembelina fructicosa Zone and IX Abathomphalus mayorensis Zone. Identification of possible stratigraphic gaps in the Upper Cretaceous successions examined here was very difficult because the drill cuttings were sampled every 5-10 metres. According to BREW (2001), the Upper Cretaceous strata succession of the Palmyride area is characterized by progressively deeper water environments. Evidence for some minor compression and uplift has been documented for the latest Cretaceous of this area, together with an associated minor sedimentary hiatus at the Creta-  ceous/Palaeogene boundary (BREW, 2001). To the northeast of the Palmyride area, however, a widespread unconformity has been documented for the Turonian-Coniacian. According to BREW (2001), during the Campanian and early Maastrichtian in the Palmyride area of Syria, progressively deeper water carbonate facies and pelagic marly limestones of the Shiranish formation were deposited. A significant period of Late Cretaceous deformation in northeastern Syria began in the latest Campanian or earliest Maastrichtian (BREW, 2001). The boundary between the Soukhne (massive limestone) formation and the syn-extensional Shiranish formation is unconformable, suggesting a major pre-extensional stratigraphic hiatus in that area.
On the other hand, the occurrence of K-strategists (Dicarinella and Marginotruncana), although present in a smaller percentage in the planktonic assemblage, indicates warm stable episodes with oligotrophic oceanic conditions and well developed water column stratification, which are favourable for these two groups with more complex test architecture (PETRIZZO, 2002). Almost equal proportions of small benthic and planktonic foraminifera in limestones (mudstone/wackestone to foraminiferal wackestone) and marl suggest deposition in outer shelf environments (OLS-SON & NYONG, 1984;BOERSMA, 1988;MURRAY, 1991;GRÄFE, 2005 The most important characteristic of Biozone II (middle-late Santonian, the Soukhne Formation; Figs. 2-5 and 10) is the high level of speciation of planktonic foraminifera. This Biozone is determined by the first appearance of several new taxa including Globotruncana linneiana, G. arca, G. bulloides, G. hilli, Hendersonites carinatus, Heterohelix planata, H. punctulata, H. striata, Globigerinelloides prairiehillensis, and Globotruncanita stuartiformis, which may suggest the Dicarinella asymetrica Zone. The foraminiferal assemblage is moderately diverse and better preserved rela-tive to biozone I. Heterohelicids experienced speciation during this Biozone; their abundance increased to 46.5%, and they remained a dominant group until the end of the Cretaceous. As opportunistic planktonic foraminifera heterohelicids inhabit more nutrient-rich waters and are indicators of cooler and unstable environments (NEDERBRAGT, 1991;NEDERBRAGT et al., 1998;PETRIZZO, 2002). Their speciation is most likely induced by a somewhat cooler but variable climate and anoxic events during the middle Santonian. Beside heterohelicids, other small-sized forms with simple test-morphology, such as muriciohedbergellids, archeoglobigerinids and globigerinelloids, are very common in the planktonic assemblage. All of these groups belong to opportunistic taxa that have a great reproductive potential in eutrophic and somewhat mesotrophic environments with a very well developed oxygen minimum layer (NEDERBRAGT, 1991). Small-sized heterohelicids indicate expansion of the oxygen minimum zone (OMZ) due to increased surface water productivity and depletion of oxygen in subsurface waters by oxidation of organic carbon (LECKIE, 1987;LECKIE et al., 1998;KELLER & PARDO, 2004;PARDO & KEL-LER, 2008;ASHCKENAZIPOLIVODA et al., 2011). Heterohelicidae were found to be very common in most of the OMZ suggesting high productivity and/or some tolerance to subsurface oxygen depletion (ASHCKENAZI-POLIVODA et al., 2011). In addition, abundant phosphate grains in the upper part of this zone, support the interpretation that Biozone II was characterized by high palaeoproductivity, relatively constant and high food supply and moderate increase in bottom water aeration. Very high productivity during this biozone was supported by a fluctuating climate and upwelling cycles, which brought nutrient-rich water into the environments inhabited by heterohelicids and upper-middle bathyal benthic foraminifera. At the upper boundary of Biozone II all dicarinellids and whiteinellids became extinct. The proportion of planktonic species increased and reached up to 60% of the microfossil assemblage present in foraminiferal mudstone/wackestone, marl and dolomitic limestones that represent an open marine, most probably outer shelf environments (OLSSON & NYONG, 1984;BOERSMA, 1988;MURRAY, 1991;GRÄFE, 2005).
Biozone III (early Campanian, the Soukhne Formation; Figs. 2-5 and 10) is marked by the disappearance of marginotruncanids in its base and by the LO of Pseudoguembelina costulata and Rugloglobirerina rugosa. This planktonic assemblage may correspond to the Globotruncanita elevata Zone. Planktonic and benthic foraminiferal assemblages are rich and moderately to well preserved. The proportion of planktonic species reaches up to 65% and indicates further deepening of this realm (BOERSMA, 1988;MURRAY, 1991;GRÄFE, 2005;DARVISHZAD & ABDOLALIPOUR, 2009). The most common species are opportunistic (rstrategists) taxa: Hendersonites carinatus, Heterohelix punctulata, H. striata and Pseudotextularia nuttalli. Although characterized by different deposits, i.e., limestone (foraminiferal mudstone/wackestone) and calcareous marl, relative to Biozone II, the deposition of these strata continued within the same open marine, probably outer shelf settings.
Phosphate grains are very common in dolomitic limestones from the upper part of Biozone II in Al Mahr-1 (Figs.  2 and 4), and in the uppermost part of Biozone II and the lowermost part of Biozone III in Palmyra1 (Figs. 3, 4). Abundant phosphate grains generally indicate some very specific geological and palaeoenvironmental conditions, such as oxygen deficiency, upwelling conditions, and transgressive intervals (HAQ et al., 1987;REISS, 1988;AL-MOGILABIN et al., 1993;WIDMARK & SPEIJER, 1997;JARVIS et al., 2002;PUFHAL et al., 2003;SOUDRY et al., 2006;ASHCKENAZIPOLIVODA et al., 2011). It is possible that such palaeoceanographic conditions, especially upwelling, increased food supply and primary production in the surface and subsurface marine environments, and thus also indirectly affected higher production and domination of oportunistic (r-strategists) planktonic foraminiferal species during Biozones II and III.
The lowest occurrence of Laeviheterohelix glabrans and Muricohedbergella mounmouthensis and rare Contusotruncana plummerae in the planktonic foraminiferal assemblage of Biozone IV (middle-late Campanian, the Shiranish Formation; Figs. 2-5 and 10) suggest the Contusotruncana plummerae Zone. This biozone has been appointed by PETRIZZO et al. (2011) for the lower-middle Campanian of tropical and subtropical areas because of the difficulties in using the first occurrence datum of Globotruncana ventricosa in low latitude successions from the Tethyan Realm. Species of the genus Heterohelix dominated in the previous Biozone III but decrease to 32.5% in Biozone IV, whereas the abundance of two genera Muricohedbergella and Pseudoguembelina significantly increases up to 15% and 10.5%, respectively. Although the opportunistic (r-strategists) species are still dominant, the specialized taxa (K-strategists) such as globotruncanids (PREMOLI SILVA & SLITER, 1999;PETRIZZO, 2002;DUBICKA & PERYT, 2012) increase in the overall number of species and also slightly increase in abundance within this planktonic assemblage. This indicates mesotrophic to more oligotrophic environmental conditions that are favorable for keeled globotruncanids. The well-preserved foraminiferal assemblage and high proportion of planktonic foraminifera (70%) in the argillaceous limestones marl and calcareous marls of Biozone IV suggest an open marine, probably outer shelf to upper bathyal environment (BOERSMA, 1988;MURRAY, 1991;GRÄFE, 2005).
The zonal marker Globotruncanella havanensis is relatively rare in Biozone VI (late Campanian, the Shiranish Formation; Figs. 2-5 and 10), and the base of this Biozone is indicated by the LO of Pseudoguembelina excolata, Planoglobulina carseyae and Rugoglobigerina hexacamerata. The foraminiferal assemblage is rich and well preserved. Although the opportunistic group heterohelicids stay dominant group in the planktonic assemblage with 37.5% abundance, K-strategists, such as keeled globotruncanids, become an important component in the planktonic foraminiferal assemblage with 9 species and 13.5% abundance. These point to stable environmental conditions, such as an oligotrophic ocean with a tropical to subtropical climate, well stratified water column, stable thermocline and other favourable palaeoceanographic parameters for r/K and K-selected group of planktonic foraminifera (LECKIE, 1989;MURRAY, 1991;DARVISHZAD & ABDOLALIPOUR, 2009). Abundance of species from the genus Globigerinelloides and Muricohedbergella (r-selected forms) show inverse trends in comparison with the previous biozones and decrease to 7.5% and 6%, respectively (Fig. 10). The proportion of planktonic species increased and reached up to 85% of the microfossil assemblage present in marl and argillaceous limestone (mudstone/wackestone) that represent an open marine, outer shelf to upper bathyal environments (OLSSON & NYONG, 1984;BOERSMA, 1988;MURRAY, 1991;GRÄFE, 2005).
The Pseudoguembelina palpebra Zone (Biozone VII, late Campanian-early Maastrichtian, the Shiranish Formation; Figs. 2-5 and 10) is characterized by the LO of P. palpebra, which is consistently found throughout the interval in moderate abundance. Also, the lowest occurrence of Globotruncanella pschadae, Pseudoguembelina kempensis and Racemiguembelina powelli is recorded in the lower part of this biozone. Gansserina gansseri is very rare and poorly preserved in the investigated samples, and therefore P. palpebra serves as a better zonal marker for the uppermost Campanian, as also reported by HUBER at al. (2008) from subtropical North Atlantic (Blake Nose). The planktonic foraminiferal assemblage of Biozone VII is rich, very well preserved and in comparison with Biozone VI, biodiversity throughout this interval significantly increases (to 41 species). Opportunistic representatives of the genus Heterohelix are still the dominant group in the planktonic assemblage with 34% abundance. Also, the genus Pseudoguembelina, known as a successful surface and subsurface dweller in tropical and subtropical open ocean (NEDERBRAGT, 1989;HUBER, 1992;ABRAMOVICH et al., 2003), significantly increased in abundance up to17%. Species of the genus Pseudoguembelina are strongly photosymbiotic and their expansion is related to favourable palaeoecological conditions in the Late Cretaceous ocean, such as the presence of warm and oligotrophic surface ocean waters (D´HONDT & ZACHOS, 1998;ABRAMOVICH et al., 2003). The proportion of planktonic foraminifera accounts for up to 90% of the microfossil assemblages found in marl and argillaceous lime-stone (mudstone/wackestone), which implies further deepening of this realm and deposition in outer shelf to upper bathyal environments (BOERSMA, 1988;MURRAY, 1991;GRÄFE, 2005;DARVISHZAD & ABDOLALIPOUR, 2009).
The lowest occurrence of planktonic foraminifera Planoglobulina acervulinoides and Peudotextularia elegans in association with the rare zonal marker Racemiguembelina fructicosa, is indicative of Biozone VIII (early-late Maastrichtian, the Shiranish Formation; Figs. 2-5 and 10). This biozone is characterised by a diverse and very well preserved planktonic foraminiferal assemblage with 41 species, similar to that from Biozone VII. Rugoglobigerinids increased in abundance and reached up to 14% of the assemblage, while representatives of the genus Heterohelix still dominate the assemblage with 38%. Species of the genus Rugoglobigerina inhabit surface and subsurface habitats (ABRAMOVICH et al., 2003), and are known as symbiotic organisms (D´HONDT & ZACHOS, 1998). Speciation of planktonic foraminifera in this biozone is likely supported by good water column stratification and opening of new niches favourable for all groups of planktonic foraminifera. Many subsurface dwellers, such as several species of the genus Globotruncana, acquired adaptation to the thermocline habitat (ABRAMOV-ICH et al., 2003). All of these changes correspond very well to the documented global sea level fluctuations and alternating cooler and warmer periods in the early to late Maastrichtian (HAQ et al., 1987;Fig. 5). During Zone VIII the sedimentary setting was a deep sea environment (upper bathyal), as a result of further deepening of this sedimentary realm.
The planktonic foraminiferal assemblage of the latest Cretaceous Abathomphalus mayaroensis Zone (Biozone IX, late Maastrichtian, the Shiranish Formation; Figs. 2-5 and 10) is very similar to those in Biozone VIII and is rich in the overall number of species (39) as well as in the number of individuals. An important characteristic of this biozone is the increased number of K-strategist species of globotruncanids (15.5%), and planoglobulinids (4%), whereas rugoglobigerinids retained their abundance (14%). Some opportunistic species of the genus Muricohedbergella also show an increase and constitute 9% of the assemblage, while members of the genus Globigerinelloides (2%) decrease in abundance (Fig. 10). Species of the genus Heterohelix have an almost equal abundance (36%) compared to Biozone VIII.
Composition of the planktonic foraminiferal assemblage with a significantly higher percentage of Kstrategist specialists, which inhabit subsurface and thermocline layers, indicates an oligotrophic ocean with a very well stratified water column supported by a stable thermocline (PREMOLI SILVA & SLITER, 1999;PEARSON et al., 2001;ABRAM-OVICH et al., 2003). On the other hand, the symbiontbearing taxa Rugoglobigerina, Pseudoguembelina and Heterohelix were very well adapted to surface and subsurface oligotrophic ocean water (D´HONDT & ZACHOS, 1998;PEARSON et al., 2001;ABRAMOVICH et al., 2003). In the upper part of Biozone IX, the decreased numbers of globotruncanid species indicate fluctuating climate, sealevel changes and up-welling cycles which could cause instability in the water column and unfavourable environmental conditions for Kstrategists (ABRAMOVICH & KELLER, 2002;HAQ et al., 1987). This high diversity abruptly decreases at the end of the Biozone, when most planktonic foraminiferal species became extinct. Marl, argillaceous limestone (mudstone/wackestone), and slightly dolomitized limestone (foraminiferal wackestone) contain rich and very well preserved foraminiferal assemblages, whereas planktonic foraminifera reach over 90% of the entire community suggesting deposition in upper bathyal environments (BOERSMA, 1988;MURRAY, 1991;GRÄFE, 2005;DARVISHZAD & AB-DOLALIPOUR, 2009). All these facts indicate the Late Cretaceous as being a long, warm and relatively stable period with palaeoceanographic conditions favourable for all groups of planktonic foraminifera which inhabited different niches in a well stratified water column (LECKIE, 1989;HUBER et al., 1995;PREMOLI SILVA & SLITER, 1999;PETRIZZO, 2002, PEARSON et al., 2001ABRAMOVICH et al., 2003;DUBICKA & PERYT, 2012).
The Soukhne Formation (Santonian-Early Campanian, Biozones II and III, Figs. 2-4) contains phosphate grains. Similar phosphate deposits are widespread in many parts of the Levantin region (i.e., Israel, Jordan, Iraq, Turkey and Egypt; AL MALEH & MOUTY, 1994;PUFHAL et al., 2003;ABED at al., 2005;BAIOUMY & TADA, 2005;SOUDRY et al., 2006;ASHCKENAZIPOLIVODA et al., 2011;SCH-NEIDERMOR et al., 2012). The phosphate deposits in Syria formed in response to a high-productivity upwelling regime that persisted on the southern margins of the Tethys during the Late Cretaceous (AL MALEH & MOUTY, 1994). The planktonic assemblages associated with phosphate grains in the Palmyride strata are characterized by domination of opportunistic (r-strategists) taxa such as the genus Heterohelix (Biozone II and III, Figs. 2, 3), which indicates a highly productive photic zone (REISS, 1988;ALMOGI-LABIN et al., 1993;WIDMARK & SPEIJER, 1997;PUFHAL et al., 2003) and a low oxygen environment (ASHCKENAZI-POLI- VO DA et al., 2011). The benthic assemblages found with phosphates have abundant specimens of the genus Bulimina, which are commonly documented from highly productive, low-oxygen settings from around the world, including for example South America, Morocco, Egypt, Jordan, Iraq and Israel (PUFHAL et al., 2003;ASHCKENAZIPOLIVODA et al., 2011). An additional factor that contributed to the formation of phosphate was the enrichment in phosphorous from P-rich deep waters that upwelled in the Palmyrida Basin by currents flowing along the northern edge of the Arabian platform (SOUDRY et al., 2006). Warming of the upwelled water and the abundance of nutrients caused the proliferation of plankton, which assimilated, stored and concentrated phosphate. After the deposition of plankton, a large amount of phosphate dissolved and became concentrated in the seafloor sediments (AL MALEH & MOUTY, 1994).
Such high primary productivity and sea floor phosphogenesis prevailed mainly on the southeastern Tethyan margins as a result of persistent upwelling circulation that recycled dissolved phosphorous from the intermediate-depth waters and distributed it to the photic zone (SOUDRY et al., 2006). The phosphates developed during transgressive periods that promoted carbonate sediment starvation. Simple (internally homogenous) P 2 O 5 -enriched phosphate nodules probably replaced calcite nodule precursors in suboxic conditions as a result of processes that involved oceanic upwelling, exhumation and burial coupled with alternating oxic and suboxic conditions (MARSHALL-NEILL & RUFFELL, 2004). The presence of phosphate is an important indicator of oxygen deficiency, upwelling conditions, transgressive intervals, and omission surfaces (TRAPPE, 2001), and any future studies of this Cretaceous stratigraphic interval should also include detailed analyses of the associated phosphate grains.

CONCLUSIONS
The stratigraphic analysis of the Upper Cretaceous strata from the Palmyride area in Syria included a detailed micropalaeontological investigation of foraminferal assemblages and rock types obtained from drill cuttings in two deep exploration wells (Al Mahr-1 and Palmyra-1).
During the late Turonian to early Campanian (Biozone I to III) in the investigated Palmyride strata, domination of opportunistic taxa (Heterohelix, Globigerinelloides, Archaeoglobigerina, and Muricohedbergella) implies upwelling, low oxygen conditions and subtropical climate. On the other hand, the rich and highly diversified planktonic assemblages (Biozone IV to IX) with many K-selected taxa (i.e., ornamented keeled globotruncanids, rugoglobigerinids, planoglobulinids, pseudoguembelinids) indicate a tropical to subtropical climate and wellstratified water column during the late Campanian and into the Maastrichtian. In the upper part of Biozone IX, the decreased numbers of globotruncanid species indicate a less stratified water column and unfavourable environmental conditions for K-strategists. A dramatic faunal turnover at the end of this Biozone is marked by the extinction of most planktonic foraminifera, with only a few species (e.g., Muricohedbergella holmdelensis, M. montmouthensis and Guembelitria cretacea) present across the Cretaceous/Palaeogene boundary.
Phosphate grains are very common in dolomitic limestone of the upper part of Biozone II in Al Mahr-1 and in the uppermost part of Biozone II and lowermost part of Biozone III in Palmyra-1 (Soukhne Formation). The phosphate occurrence helps improve the late Santonian-early Campanian stratigraphic interpretation of this interval because similar deposits occur during this time period elsewhere along the southeastern margins of Tethys (Israel, Jordan, Iraq, Turkey and Egypt). The presence of phosphate in the study area indicates oceanic upwelling that caused increased food supply and influenced higher primary marine production, and thus indirectly affected higher production and domination of oportunistic planktonic foraminifera in Biozones II and III.

ACKNOWLEDGMENT
We thank Bosiljka GLUMAC (Smith College) whose comments and suggestions improved this paper, Morana HER-NITZKUČENJAK (INAindustrija nafte d.d.) for discussion and tehnical support, Robert KOŠĆAL (University of Zagreb) for technical assistance, Renata SLAVKOVIĆ (INA-industrija nafte d.d.) for SEM photomicrografs of foraminifera, Vladimir VESELI and Ivan A. MESIĆ (INAindustrija nafte d.d.) for sharing well report data. We are grateful to Brian T. HUBER (Smithsonian Institution) and Bilal SARI (Dokuz Eylül University) for carefully reviewing the manuscript and enabling us to significantly improve it. This research was supported by INA-Industrija nafte d.d. Zagreb, who also provided samples from the Syrian wells.