Biostratigraphy and palaeoceanography of the early Turonian–early Maastrichtian planktonic foraminifera of NE Iraq

The Upper Cretaceous Kometan and Shiranish formations of the Kurdistan region, NE Iraq, yield diverse planktonic foraminiferal assemblages, with a total of 93 species, which enable recognition of nine biozones and two subzones spanning the early Turonian to late early Maastrichtian. Sequential changes in planktonic foraminiferal assemblages map discrete intervals within the Kometan and Shiranish formations that suggest dominantly warm, nutrient-poor marine surface and near-surface conditions during the mid-Turonian to late Coniacian, latest Santonian, and late Campanian, and cooler more nutrient-rich surface and near-surface waters in the early Turonian, early to late Santonian, early Campanian and early Maastrichtian. These intervals appear to correlate with changes in water masses from other regions of the Cretaceous palaeotropics, and with a phase of global, early Maastrichtian climate cooling. The major intra-Campanian truncation surface between the Kometan and Shiranish formations, recognized from the foraminiferal biostratigraphy, represents a lowstand that appears to equate with regional tectonics and ophiolite obduction across the NE margin of the Arabian Plate.

. Without a new geological survey the boundary between these two formations remains ill defined.
a supersaturated solution of sodium sulphate decahydrate until the rock disaggregated. The disaggregated sediments were then washed thoroughly through a 63 µm sieve and the residues separated by filtration and dried overnight with an oven temperature of 50°C. Dried residues were sorted using sieves from 500 µm to 63 µm. All foraminifera were picked and studied from the residue in the 63-300 µm size fraction, but planktonic foraminifera were not recorded in the >300 µm sieve. The foraminifera were imaged using a Hitachi S-3600N scanning electron microscope (SEM) at the University of Leicester, UK. Identifications of foraminifera largely follow the work of Smith & Pessagno (1973), Robaszynski et al. (1984), Caron (1985), Sliter (1989), Nederbragt (1989Nederbragt ( , 1991, Premoli Silva & Sliter (1994), Premoli Silva & Verga (2004) and Petrizzo et al. (2011). The specimens illustrated in this paper are deposited in the collections of the British Geological Survey, Keyworth, Nottingham, UK.

lIthostratIgraPhy
The Upper Cretaceous (early Turonian to early Maastrichtian age) strata of NE Iraq comprise two marine-deposited formations: the pelagic limestone of the Kometan Formation (early Turonianearly Campanian) and the marly limestones and marlstones of the Shiranish Formation (late Campanian-early Maastrichtian).

Kometan Formation
The type section of the Kometan Formation was first described in an unpublished report by H. V. Dunnington (1953, fide Van Bellen et al., [1959 2005) from the village of Kometan near Endezeh in NE Iraq. At Endezeh, the formation comprises some 36 m of light grey, thinly bedded, globigerinal-oligosteginal limestone, locally silicified, with chert nodules, and glauconite especially at the base of the formation. According to a number of authors (e.g. Kaddouri, 1982;Al-Jassim et al., 1989;Al-Sheikhly et al., 1989;Abawi & Hammoudi, 1997;Hammoudi & Abawi, 2006;Haddad & Amin, 2007) the age of the Kometan Formation is late Turonian at its base and extends to the early Campanian at the top. The Kometan Formation is interpreted to be an outer shelf or basinal deposit (Jassim & Goff, 2006), becoming increasingly argillaceous to the west and SW of Iraq. The base of the Kometan Formation is unconformable on the underlying Balambo and Qamchuqa formations (which are early Cenomanian; Buday, 1980;Van Bellen et al., [1959] 2005; Jassim & Goff, 2006;Ameen & Gharib, 2014;Fig. 2). The Kometan Formation has thicknesses of approximately 158 and 96.5 m in the Dokan and Azmer areas, respectively. In the Dokan area the formation is composed of well-bedded, light grey or white limestone with common chert nodules ( Fig. 3a and d). The top of the Kometan Formation records a local extinction of large ammonites ( Fig. 3i and j). This extinction might be related to the termination of pelagic limestone facies and a significant sea-level fall evident from examination of the top of the Kometan Formation. Moreover, the top of the Kometan Formation is extensively bioturbated with Planolites and Thalassinoides, which may indicate a period of slow or non-deposition (Fig. 3f). In the Azmer area the Kometan Formation is composed mainly of light grey, medium-bedded limestone (Fig. 3b): the lower part of the formation is associated with small, centimetre-scale ammonites, but towards the upper part of the formation there is a notable increase in the size of the ammonites, which also become more common. In the Azmer area the formation lacks chert nodules.

shiranish Formation
The Shiranish Formation was first defined in an unpublished report by F. R. S. Henson (1940, fide Van Bellen et al., [1959 2005) from the 'High Folded Zone' of northern Iraq, near the village of Shiranish Islam, NE of Zakho. The formation in its type section is about 228 m thick, and is informally subdivided into a 'lower unit' characterized by alternating marly limestone and calcareous marlstone that is rich in foraminifera, and an 'upper unit' that is dominated by blue-coloured marlstone (Aqrawi et al., 2010). According to several authors (Kennedy & Lunn, 2000;Al-Banna, 2010;Aqrawi et al., 2010;Jaff et al., 2014) the age of the Shiranish Formation is late Campanian to Maastrichtian, but it does not extend to the late Maastrichtian (Kassab, 1973;Jaff et al., 2014). The formation in its type area is interpreted to be an outer shelf to basinal deposit (Jassim & Goff, 2006) that unconformably overlies the Kometan Formation, and is succeeded conformably by marine clastic deposits of the Tanjero Formation (which is of late Maastrichtian age; Fig. 2).
The Shiranish Formation is well exposed in the localities studied and is about 260 and 144 m thick in the Dokan and the Azmer areas, respectively. In the Dokan area there is a glauconitic pebbly sandstone bed of around 0.5 m at the base of the 'lower unit' that may indicate a very slow rate of deposition or period of nondeposition ( Fig. 3g and h). In the Dokan area the uppermost part of the 'upper unit' of the Shiranish Formation also develops a massive bed of marly limestone that is about 1 m thick and bears a mass of rudist bivalves near the contact with the overlying Tanjero Formation. This rudist bed is developed only locally and hence is not recognized as a separate member in the Shiranish Formation.

PlanKtonIc ForaMInIFeral BIozonatIon
Some 93 planktonic foraminiferal species belonging to 23 genera have been identified in the Kometan and the Shiranish formations during the present study (Appendix A; Pls 1-5). The stratigraphic distribution of these foraminifera permits the recognition of nine biozones and two subzones in the Upper Cretaceous (early Turonian-early Maastrichtian time interval) succession. Five of the biozones are identified as interval zones (IZ): the Dicarinella primitiva IZ, the Dicarinella concavata IZ, the Globotruncana aegyptiaca IZ, the Gansserina gansseri IZ (which can be subdivided into the Pseudoguembelina excolata and Planoglobulina acervulinoides subzones) and the Contusotruncana contusa IZ. Two biozones are total range zones (TRZ): the Helvetoglobotruncana helvetica TRZ and the Dicarinella asymetrica TRZ. Two biozones are partial range zones (PRZ): the Marginotruncana schneegansi PRZ and the Globotruncanita elevata PRZ. The definitions of the biozones follow Caron (1985), Sliter (1989), Premoli Silva & Sliter (1994), Robaszynski & Caron (1995), Premoli Silva & Verga (2004) and Sari (2006Sari ( , 2009. helvetoglobotruncana helvetica total range zone, early turonian This biozone is defined by the lowest and highest occurrences (Lo, Ho) of Helvetoglobotruncana helvetica (see Dalbiez, 1955) and represents the oldest foraminiferal biozone identified in the lower part of the pelagic limestones of the Kometan Formation. The lower limit of this biozone in NE Iraq coincides with the facies change at the unconformable contact with the underlying Balambo and Qamchuqa formations. It is uncertain, therefore, whether the base of the biozone as defined equates to the global Lo of H. helvetica. In the Azmer section the H. helvetica biozone is identified through about 5.5 m of strata, from sample numbers AK-1 to AK-3, and in the Dokan section through about 8 m of strata, from sample numbers DK-01 to DK-04 ( Fig. 4): the eponymous biozonal species occurs rarely in both sections. Although previous work suggested that H. helvetica is indicative of the mid-Turonian (Salaj, 1980(Salaj, , 1997Wonders, 1980;Robaszynski et al., 1984;Caron, 1985;Sliter, 1989;Abdel-Kireem et al., 1995;Premoli Silva & Verga, 2004;Abawi & Mahmood, 2005), it is now considered to denote an interval in the early Turonian (Caron et al., 2006;Desmares et al., 2007;Gebhardt et al., 2010;ogg & Hinnov, 2012;Vahidinia et al., 2014;see Fig. 5). The H. helvetica biozone also represents the maximum abundance and diversity of whiteinellid planktonic foraminifera, with five species recorded. The most abundant planktonic foraminiferal species in this biozone are Heterohelix moremani and H. globulosa (see Figs 6 and 7).

globotruncana aegyptiaca interval zone, late campanian
This is an interval zone from the Lo of the eponymous species to the Lo of Gansserina gansseri (see Caron, 1985) and it represents the oldest foraminiferal biozone identified in the lower part of the Shiranish Formation. At the base of the Shiranish Formation there is an unconformity, and the local Lo of G. aegyptiaca may not equate to the global Lo of this species. The biozone is recognized through some 47.5 m of rock in the Azmer section, from sample numbers ASH-01 to ASH-33, and in the Dokan section is about 121 m, from sample numbers DSH-03 to DSH-67 ( Fig. 8). Some publications (e.g. Robaszynski et al., 1984;Caron, 1985;Sliter, 1989;Ayyad et al., 1996;Mancini et al., 1996) have equated the first appearance of G. aegyptiaca with the early Maastrichtian, whilst later works have documented a first occurrence within the late Campanian (Premoli Silva & Sliter, 1994, 1999Li & Keller, 1998a, b;Robaszynski, 1998;Li et al., , 2011Özkan-Altiner & Özcan, 1999;Abdelghany, 2003
Succeeding foraminiferal biozones cannot be recognized in NE Iraq, due to the absence of planktonic foraminifera in a rapidly shallowing marine succession. This is indicated by the presence of a massive bed of marly limestone about 1 m thick, bearing a mass of shallow-marine rudist bivalves near the contact with the overlying Tanjero Formation.
the MId-to early late caMPanIan unconForMIty The unconformity between the Kometan and Shiranish formations is demarcated by Globotruncanita elevata as the youngest biozone in the pelagic limestones of the uppermost Kometan Formation, and Globotruncana aegyptiaca as the earliest biozone in the overlying Shiranish Formation. on the basis of the most recent Upper Cretaceous planktonic foraminiferal biozonation compiled by ogg & Hinnov (2012), the successive biozonal planktonic foraminiferal species Contusotruncana plummerae (=Globotruncana ventri cosa) proposed by Petrizzo et al. (2011), Radotruncana calcarata (Cushman, 1927) and Globotruncanella havanensis (Voorwijk, 1937) are absent in the sections studied in NE Iraq. It is likely, therefore, that the mid-and early late Campanian is not represented (see Fig. 5). Based on calibration for the Cretaceous time-scale proposed by ogg & Hinnov (2012) for the Lo and Ho of the index Upper Cretaceous planktonic foraminiferal biozones, the estimated age for the end of the Globotruncanita elevata biozone and the beginning of the succeeding Contusotruncana plummerae biozones is 79.2 Ma, while the Globotruncana aegyptiaca biozone begins at 74.0 Ma. These suggest that the time gap in the sections studied is at least 5.2 Ma (79.2-74.0 Ma): this gap may represent components of both non-deposition and erosion prior to the deposition of the Shiranish Formation. The unconformity surface at this stratigraphic level has been identified in several areas of Iraq and is a regional feature (Buday, 1980;Abawi et al., 1982;Kaddouri, 1982;Abdel-Kireem, 1986;Van Bellen et al., [1959] 2005Jassim & Goff, 2006;Aqrawi et al., 2010). It may represent a response to regional tectonics. In late Campanian time ophiolites were obducted across the NE margin of the Arabian Plate (Ziegler, 2001;Jassim & Goff, 2006), and the compression associated with this obduction caused uplift (Numan, 1997;Ziegler, 2001;Jassim & Goff, 2006; see Fig. 2), during which a considerable thickness of early Turonian-early Campanian sedimentary deposits of the Kometan Formation may have been eroded (Jassim & Goff, 2006). The unconformity also appears to correlate with a major regional unconformity evident in Iran (Babazadeh et al., 2007), Turkey (Sari, 2006(Sari, , 2009, Kuwait, Qatar and Saudi Arabia (Al-Naqib, 1967; see Fig. 2), and with Arabian Plate sea-level fall recorded by Sharland et al. (2001).

PalaeoceanograPhIc sIgnIFIcance
Planktonic foraminifera are widely used for palaeoceanographic reconstruction and to provide estimates of past sea surface temperatures for the calibration of General Circulation Models of palaeoclimate (e.g. Dowsett et al., 2013). The composition of extant planktonic foraminiferal assemblages is influenced by water properties including temperature, density and salinity, by nutrient supply, and by the degree of stratification of the water column (Bé & Hamilton, 1967;Bé & Tolderlund, 1971;Bé, 1977;Hart, 1980;Caron & Homewood, 1983;Hallock et al., 1991;Huber, 1992;Pflaumann et al., 1996;Mulitza et al., 1997;Leckie et al., 1998;Keller et al., 2001;Malmgren et al., 2001). These characteristics vary both spatially and by water depth. Temperature appears to be the most important single factor controlling assemblage composition (Morey et al., 2005), diversity (Rutherford et al., 1999) and test size (Schmidt et al., 2004). The highest diversity and largest sizes of planktonic foraminiferal assemblages are found in oligotrophic subtropical waters (Huber, 1992;Kucera, 2007). Most likely a combination of higher light intensity, higher carbonate saturation and greater niche diversity encourages growth to larger and heavier test sizes in warm subtropical and tropical oceans (Schmidt et al., 2004). Temperature effects appear to control test size in planktonic foraminifera even at the species level (Kucera, 2007). other authors have emphasized the importance of nutrient supply on foraminiferal assemblage structure (Hallock, 1987;Almogi-Labin et al., 1993;MacLeod et al., 2001;Petrizzo, 2002).
Based on the known palaeo-latitudinal and environmental distribution of Cretaceous planktonic foraminifera, and possible links with overall morphology, three major groups have been identified (following Premoli Silva & Sliter, 1994, 1999Keller et al., 2001;Petrizzo, 2002;see Fig. 11). These groups are considered, tentatively, to signal ambient environmental regimes ranging from nutrient-rich to nutrient-poor, coupled with prevailing cooler or   Fig. 11. Scheme showing suggested planktonic foraminifera reproductive strategy. The r-, k-or r/k-strategists are identified according to morphology (for methodology, see Premoli Silva & Sliter, 1999). Patterns of foraminiferal relative abundance are shown in Figures 12 and 13.   Fig. 12. Relative abundance and species diversity for planktonic foraminifera in the Kometan Formation. Numbers in the right-hand column indicate five assemblages that are distinguished on the basis of abundance of particular foraminifera displaying reproductive strategies interpreted as r-, k-or r/k-intermediate (for these groups, see Fig. 11). Assemblages 1, 3 and 5 are interpreted as indicative of less warm and more nutrient-rich sea surface conditions. Assemblages 2 and 4 are interpreted to represent warmer, more nutrient-poor intervals. The number of specimens counted for each sample ranges from 90 to 215; all from thin-section analysis.  Fig. 13. Relative abundance and species diversity for planktonic foraminifera in the Shiranish Formation. Numbers in the right-hand column idicate two assemblages that are distinguished on the basis of abundance of particular foraminifera interpreted as displaying r-, k-or r/k-intermediate strategies (for these groups, see Fig. 11). Assemblages 6 and 7 are interpreted as the warmest and coolest intervals of the Late Cretaceous analysed for this study. The number of specimens counted for each sample ranges from 180 to 300; this represents specimens recovered from both picked residues and thin sections. The percentage of more r-selected r/k-intermediates includes species of Archaeoglobigerina, Pseudoguembelina, Globigerinelloides, Globotruncanella, Rugoglobigerina and Rugotruncana; whilst the percentage of more k-selected r/k-intermediates includes species of Gansserina, Planoglobulina, Gublerina and Pseudotextularia. warmer seawater temperatures. Species recorded in NE Iraq can be tentatively assigned to these biological groups (Fig. 11). Where possible, the interpreted ecological preferences for planktonic foraminifera are quantified by reference to published stable isotope analyses of comparable foraminiferal assemblages.
(2) Low-nutrient/oligotrophic Cretaceous marine environments that are also stable may be indicated by 'k-selected specialists' (Premoli Silva & Sliter, 1999;Keller et al., 2001;Petrizzo, 2002). The k-strategists are interpreted as including species of the single-keeled Globotruncanita and double-keeled Marginotruncana, Contusotruncana and Globotruncana. Specialist taxa, characterized by long-lived individuals, low reproductive potential (and usually larger size), prefer lower and middle latitudes and, consequently, they are considered indicators of warmer-water environments (Emiliani, 1971;Caron & Homewood, 1983;Leckie, 1987Leckie, , 1989Huber, 1988Huber, , 1992Hallock et al., 1991;Keller et al., 2001;Petrizzo, 2002;Falzoni et al., 2013). (3) Between these end-members, foraminifera tolerant of Cretaceous mesotrophic environments exhibit a range of strategies and are termed 'r/k intermediates' and have been further subdivided into two subgroups: Subgroup 1 are the more k-selected r/k intermediates and include those with high trochospires, hemispherical chambers with marginal keel(s), flaring heterohelicids with more than two chambers per row, and medium-sized heterohelicids with chambers arranged from biserial to annular; these have been interpreted as occupying the oligotrophic portion of the mesotrophic spectrum (Premoli Silva & Sliter, 1999;Petrizzo, 2002;see Fig. 11). Subgroup 2 is the more r-selected r/k intermediates which have been interpreted as occupying the eutrophic part of the mesotrophic spectrum, and comprise forms with planispiral, low to medium trochospiral tests with sub-globular chambers and include biserial heterohelicids with a supplementary aperture (Premoli Silva & Sliter, 1999;Petrizzo, 2002;see Fig. 11). Most of these r/k intermediate foraminifera can be recognized in the Shiranish Formation, with the exception of species of Dicarinella, Helvetoglobotruncana and Whiteinella that are only found in the Kometan Formation.
The NE Iraqi sector of the Cretaceous Tethys ocean represents tropical waters in an epicontinental sea setting. Interpreted water depths for the Kometan Formation are estimated at c. 200 m (Jassim & Goff, 2006), whilst water depths for the Shiranish Formation are estimated at greater than 600 m, based on associated benthonic foraminiferal assemblages (Jaff et al., 2014). However, in both formations there is a shallowing-upwards marine succession, and in the upper part of the Shiranish Formation planktonic foraminifera disappear, signalling a shallow shelf setting (Jaff et al., 2014). Using morphology as a tentative basis for interpreting water properties, and coupled with detailed abundance data, seven temporally distinctive assemblages are recognized in the succession of NE Iraq (Figs 12 and 13). These are interpreted as indicating possible changes in near-surface and sea surface temperatures and nutrient availability. In assessing relative sea temperatures as 'warmer' or 'cooler', Sellwood & Valdes (2007) used a General Circulation Model to interpret sea surface temperatures of about 28ºC for the Late Cretaceous in the Arabian sector of the Tethys ocean. These results have not been tested with precise proxy data in this region and, indeed, the planktonic foraminifera studied here are recrystallized and not suitable for geochemical analysis. It is notable, however, that the foraminiferal assemblages suggest temporal variation in sea temperature through the interval of the Late Cretaceous, and this variation is compared with changes noted in other Cretaceous palaeotropical settings.

assemblage 1
Planktonic foraminiferal Assemblage 1 is present through the basal part of the Kometan Formation, and occurs through an interval equivalent to the early Turonian Helvetoglobotruncana helvetica biozone. This assemblage is numerically dominated by simple test morphotypes, particularly those interpreted as r-strategists, such as species of Muricohedbergella (M. planispira and M.

delrioensis) and
Heterohelix (H. globulosa and H. moremani), together with more r-selected r/k intermediates such as Whiteinella (Fig. 12). The dominance of opportunistic species (of Heterohelix and Whiteinella) in the early Turonian has previously been widely recorded from Tethyan successions (Bauer et al. (2001) in Egypt, Caron et al. (2006) in Tunisia and Gebhardt et al. (2010) for the northern Tethyan margin). In NE Iraq the maximum abundance and diversification of whiteinellids and Heterohelix moremani are recorded through this interval. The more r-selected r/k intermediate Helvetoglobotruncana helvetica is rare in this interval in NE Iraq, and this is typical for a number of localities of this age world-wide (Kuhnt et al. 1997;Petrizzo, 2001;. The first k-strategists Marginotruncana renzi and M. sch neegansi appear in this interval but are rare. Based on analyses of stable oxygen and carbon isotopes from foraminiferal tests,  have interpreted helvetoglobotruncanids, including H. helvetica, as living in the surface mixed layer together with whiteinellids and biserial foraminiferal species. Moreover, stable isotope analysis confirms that species of Muricohedbergella and biserial taxa such as Heterohelix, including H. moremani, are typical of the shallowest part of the water column (Leckie, 1987(Leckie, , 1989Leckie et al., 1998;Nederbragt et al., 1998;Hart, 1999;Premoli Silva & Sliter, 1999;Keller et al., 2001;Coccioni & Luciani, 2004;Bornemann & Norris, 2007;Friedrich et al., 2008;Falzoni et al., 2013). overall, the numerical dominance of Muricohedbergella, Heterohelix and Whiteinella species suggests the influence of cooler sea surface temperatures (SSTs) (Petrizzo, 2002) relative to the succeeding stratigraphic interval.
Species of whiteinellids are interpreted as taxa with a high tolerance toward eutrophic environments (Leckie, 1987(Leckie, , 1989Leckie et al., 1998;Huber et al., 1999;Keller et al., 2001;Coccioni & Luciani, 2004;Bornemann & Norris, 2007;Friedrich et al., 2008). Therefore, the abundance of foraminifera interpreted as r-strategists, together with whiteinellids, suggests that near-surface waters experienced high nutrient levels (possibly mesotrophic to eutrophic; see also Premoli Silva & Sliter, 1994, 1999Keller et al., 2001;Petrizzo, 2002;Friedrich et al., 2008). Biotic evidence for high surface productivity coupled to a major expansion of the oxygen minimum zone is seen in the low speciesrichness in planktonic foraminifera, near absence of deeper-marine dwellers, dominance of Heterohelix, and the relatively high abundance of surface dwellers (species of Muricohedbergella and Whiteinella). assemblage 2 Planktonic foraminiferal Assemblage 2 is present in the Kometan Formation through the interval of the Marginotruncana schneegansi biozone, to the top of the Dicarinella concavata biozone, and this is equivalent to the mid-Turonian to late Coniacian time interval. Assemblage 2 suggests warmer, nutrient-poor waters relative to the preceding interval, with Marginotruncana species interpreted as k-strategists becoming more abundant and more diverse (maximum abundance and diversification with seven species), suggesting warmer surface waters (Petrizzo, 2002;Fig. 12).
Foraminiferal Assemblage 2 is also characterized by more k-selected r/k intermediates, such as species of Dicarinella. The interval is also characterized by an abrupt decrease in species of Whiteinella, which disappear at the top of this interval, with the exception of Whiteinella brittonensis. The reduction of whiteinellids is associated with the increase in abundance of Marginotruncana and the first appearance of Globotruncana (G. angusticarinata). This suggests that the mesotrophic to eutrophic environment interpreted for the preceding (Assemblage 1) interval gave way to a well-stratified water mass with a reduced oxygen minimum zone (Premoli Silva & Sliter, 1999;Keller et al., 2001;Petrizzo, 2002); this is also suggested by the increasing size of Dicarinella and Marginotruncana species compared to the preceding interval. According to Leckie (1987Leckie ( , 1989, Keller et al. (2001), Petrizzo (2002) and Falzoni et al. (2013), the greater diversity and abundance of Dicarinella and Marginotruncana species may relate to greater stratification of surface and near-surface waters that provided a wider range of ecological niches for specialist foraminifera to colonize. The apparent increase of tropical SSTs in the Arabian sector of the Tethys ocean during this interval coincides with the mid-Turonian to Coniacian SST maximum recorded by Boersma & Shackleton (1981) in the Central Pacific, at IoDP (DSDP) sites 463 and 465, and with maximum SSTs in the eastern Indian ocean during the Coniacian recorded at IoDP (oDP) sites 762 and 763 (Petrizzo, 2002). k-strategists, especially a rapid decline in the number of Marginotruncana species: only M. coronata and M. marginata are present throughout the interval. The top of this interval coincides with the disappearance of marginotruncanids. overall, Assemblage 3 suggests cooler, more nutrient-rich waters relative to the preceding interval. The decrease in the diversity and abundance of Marginotruncana is associated with: (1) the Lo of Contusotruncana (C. fornicata), (2) increases in abundance of the r-strategist Heterohelix (including the Lo of H. planata), and (3) the Lo of the r-strategist Laeviheterohelix (L. pulchra, Fig. 12).
Based on evaluation of stable isotope data from the carbonate test (Abramovich et al., 2011), H. planata is inferred to be a mixed-layer planktonic foraminifera that occupied subsurface waters. This species was most abundant in high palaeolatitudes of the Cretaceous (Nederbragt, 1998), and therefore its appearance, when abundant, at lower palaeolatitudes may signal cooler sea temperatures (MacLeod et al., 2001). Falzoni et al., (2013) also used stable isotope data to interpret Contusotruncana fornicata as a mixed-layer planktonic species. They suggested that both Marginotruncana coronata and M. marginata were adapted to water masses with the same or very similar ecological characteristics as those occupied by C. fornicata. The disappearance of most species of Marginotruncana and Dicarinella can also be interpreted as reflecting a decrease in near-surface sea temperature and development of more nutrient-rich conditions (Petrizzo, 2002;Friedrich et al., 2008;Falzoni et al., 2013), and may be the result of a shallowing thermocline that resulted in the progressive removal of ecological niches occupied by the most specialized taxa (Petrizzo, 2002;Falzoni et al., 2013). Increased surface productivity may be consistent with the abundance of L. pulchra through this interval, which may signal low oxygen and high productivity environments (Friedrich et al., 2008).
Assemblage 3 occupies an interval of time that is equivalent to the Santonian faunal turnover (Sliter, 1989;Petrizzo, 2002;Sari, 2006Sari, , 2009 which is ascribed to a cooling event strong enough to cause the extinction of the marginotruncanids, and the extinction of most of the specialized intermediate r/k taxa, such as species of Dicarinella.

assemblage 4
Planktonic foraminiferal Assemblage 4 of the Kometan Formation occurs through the interval of the top of the Dicarinella asymetrica biozone, and represents the latest Santonian time interval. The interval is associated with the disappearance of Margino truncana (see also Petrizzo, 2003;Kochhann et al., 2014;Vahidinia et al., 2014), which coincides with the earliest diversification of the double-keeled Globotruncana and the first occurrence of the single-keeled Globotruncanita (G. elevata and G. stuartiformis). Assemblage 4 is interpreted as signalling warmer surface waters, stronger stratification and an overall nutrient-poor environment relative to the preceding interval. Species of the r-strategist Heterohelix and Muricohedbergella are present as a rare component of the assemblage. only Dicarinella asymetrica of the more k-selected r/k intermediates survives through this interval.
The progressive diversification and increasing abundance of globotruncanids through the latest Santonian, seen also in the Kometan Formation, probably relates to an increase in tropical SSTs (Petrizzo, 2002;Ando et al., 2013;Falzoni et al., 2013). Falzoni et al. (2013) used stable isotope records to deduce that Globotruncana bulloides inhabited surface waters; whereas G. arca inhabited cooler/deeper waters at the depth of the thermocline. Globotruncana linneiana, Globotruncanita stuartiformis and G. elevata occupied intermediate levels between these end-members. The abundance and diversity of these species in the Kometan Formation indicates the development of a well-stratified water column, with a warm sea surface and a well-developed thermocline (see also Premoli Silva & Sliter, 1999;Petrizzo, 2002;Falzoni et al., 2013;Fig. 12).

assemblage 5
Planktonic foraminiferal Assemblage 5 occurs through the uppermost part of the Kometan Formation and spans the Globotruncanita elevata biozone, being time-equivalent to the early Campanian. The numerically dominant planktonic foraminifera are heterohelicids and globotruncanids (Fig. 12). overall, Assemblage 5 suggests cooler, more nutrient-rich waters relative to the preceding interval. In the k-strategist group, Globotruncana arca and Globotruncanita elevata were the most abundant species; Globotruncana bulloides, Globotruncanita stuartiformis and Contusotruncana fornicata were also common but occur intermittently. Based on wide geographical distribution, Premoli Silva & Sliter (1999) and Falzoni et al. (2013) concluded that G. bulloides was a generalist species, being adaptable to changing surface environments. This interval of the Kometan Formation is also characterized by abundant benthonic Lenticulina and Textularia. Lenticulinids, in particular, are considered to be dominant in low-oxygen seabed environments (Honigstein et al., 1986;Friedrich et al., 2003Friedrich et al., , 2005a, where they may be adapted for utilizing degraded organic matter as a food source (Friedrich et al., 2006). Therefore, their abundance in the Kometan Formation might signal increased organic input from the overlying water column, and would be consistent with a more nutrient-rich water column and higher productivity. Decreased abundance of Globotruncana species relative to the preceding interval may signal cooler SSTs (Petrizzo, 2002;Falzoni et al., 2013). This possible decrease of SSTs in the Arabian sector of the Tethys ocean during this interval coincides with a recorded SST drop in the eastern Indian ocean during the early Campanian recorded at IoDP (oDP) sites 762 and 763 (Petrizzo, 2002). Moreover, Ando et al. (2013) reported that the mid-Cretaceous hothouse persisted to the latest Santonian at the Shatsky Rise in the Pacific ocean, and then switched to a cooler state during the early Campanian.

assemblage 6
Planktonic foraminiferal Assemblage 6 occurs through the lower part of the Shiranish Formation immediately post-dating the mid-Campanian unconformity, and represents the interval of the Globotruncana aegyptiaca biozone to the lower part of the Gansserina gansseri biozone (time-equivalent to the late and latest Campanian). The numerically dominant planktonic foraminiferal taxa are those interpreted as k-strategists (Fig. 13), including Globotruncana, Globotruncanita and Contusotruncana species. The maximum species diversity and abundance of globotruncanids occurs in this interval, and coincides with the global diversity peak of globotruncanids world-wide (Premoli Silva & Sliter, 1999). Based on stable isotope records by Abramovich et al. (2003), most keeled globotruncanids occupied warm shallow subsurface habitats during the late Campanian. Almogi-Labin et al. (1993), MacLeod et al. (2001) and Frank et al. (2005) stated that globotruncanids are relatively abundant during times of low surface productivity.
Within those taxa interpreted as r/k intermediates, species of the genera Rugoglobigerina (R. rugosa and R. macrocephala), Pseudotextularia (P. elegans) and Pseudoguembelina (P. costu lata) become abundant in this interval. According to Abramovich et al. (2003Abramovich et al. ( , 2011, these assemblages are characteristic of subsurface water masses, except for P. costulata which is an index taxon for upper surface waters. Stable isotope analyses suggest that Rugoglobigerina species probably lived in the mixed layer and inhabited relatively warm waters (MacLeod et al., 2001;Abramovich et al., 2003;Falzoni et al., 2013Falzoni et al., , 2014contra Zepeda, 1998). According to Malmgren (1991) andolsson et al. (2001), the abundances of P. elegans and P. costulata are also good indicators for warm waters.
Based on stable isotopic analyses of a range of planktonic foraminifer tests, including globotruncanids (Abramovich et al., 2003(Abramovich et al., , 2011, the planktonic foraminiferal assemblages in this interval of the Shiranish Formation also suggest well-developed stratification of surface and near-surface waters that provided a greater range of ecological niches for specialist foraminifera to colonize. Warmer SSTs relative to the preceding interval of the uppermost Kometan Formation are also consistent with a warm late Campanian climate (see Abramovich et al., 2003;Friedrich et al., 2005b;Zakharov et al., 2007;Darvishzad & Abdolalipour, 2009;Linnert et al., 2014).
Benthonic foraminiferal assemblages in this interval suggest gradual deepening of the marine basin throughout the late Campanian (Globotruncana aegyptiaca biozone).  Jaff et al., 2014). According to Jaff et al. (2014), water depths of c. 600 m can be interpreted for this part of the Shiranish Formation.

assemblage 7
Planktonic foraminiferal Assemblage 7 occurs through the middle and upper part of the Shiranish Formation, being the interval of the upper part of the Gansserina gansseri biozone and the Contusotruncana contusa biozones (early Maastrichtian age).
Towards the top of this interval the percentage abundance of globotruncanids decreases sequentially until all foraminifera disappear (Fig. 13). Abramovich et al. (2003) stated that most keeled globotruncanids occupied the deeper thermocline layer during the cool early Maastrichtian. The decrease in globotruncanids through this interval is associated with the maximum diversification and abundance of taxa interpreted as r-strategists, including Heterohelix, Laeviheterohelix and more r-selected r/k intermediate Globigerinelloides. overall, Assemblage 7 suggests cooler, more nutrient-rich waters relative to the preceding interval.
Benthonic foraminiferal assemblages in this interval suggest a shallowing trend for the Shiranish Formation in the early Maastrichtian. In the upper part of the Gansserina gansseri and the Contusotruncana contusa biozones, common benthonic foraminifera are species of Coryphostoma, Dentalina, Fissurina, Laevidentalina, Lagena, Nodosaria, Oolina and Reussoolina. According to Jaff et al. (2014), water depths of 200 m are suggested for this part of the Shiranish Formation. Shallowing in NE Iraq might be related to the closure of southern Neo-Tethys (Jassim & Goff, 2006).

conclusIon
In this study 93 species of early Turonian to late early Maastrichtian planktonic foraminifera have been identified. The index planktonic foraminifera demarcate nine biozones and two subzones for the Kometan and Shiranish formations of the Kurdistan region, NE Iraq. Most previous studies suggested that the base of the Kometan Formation is late Turonian; however, based on the appearance of Helvetoglobotruncana helvetica, the base of the Kometan Formation is here interpreted as early Turonian. The distinct intra-Campanian unconformity between the Kometan and overlying Shiranish Formation is seen in other parts of the Arabian Plate, and is ascribed to regional Arabian tectonics. on the basis of planktonic foraminiferal assemblages, 7 temporally distinct intervals within the Kometan and Shiranish formations can be distinguished that reflect evolving surface ocean conditions with dominantly warm, nutrient-poor marine surface and near-surface conditions during the mid-Turonian to late Coniacian, latest Santonian, and late Campanian, and cooler more nutrient-rich surface and near-surface waters in the early Turonian, early to late Santonian, early Campanian and early Maastrichtian. These intervals appear to correlate with changes in water masses from other regions of the Cretaceous palaeotropics. thin section preparation at the University of Leicester. IPW publishes with permission of the Executive Director of the British Geological Survey (NERC).

Manuscript received 16 July 2014 Manuscript accepted 25 november 2014
Scientific Editing by Bridget Wade and Sigal Abramovich.