Ammonites and Foraminifera of Shiranish Formation (Late Campanian- Maastrichtian) from Sulaimaniya and Erbil Governorates, Northern Iraq

This study deals with the biostratigraphy of Shiranish Formation (Late Cretaceous), depending on the Ammonite and associated Foraminifera in four outcrop sections, three of which are located in Al-Sulaimaniya governorate (Dokan, Esewa and Kanny dirka sections) and one in Erbil governorate, northern Iraq (Hijran section). Fourteen species of Ammonite belonging to fourteen genera were determined, which are: Dsemoceratidae, Gaudryceras, Gunnarites, Hoplitoplacenticeras, Kitchinites, Kossmaticeratinae, Neancyloceras, Neokossmaticeras, Nostoceras, Paratexanites, Partschiceras, Phylloceras, Pseudophyllites and Yubariceras. Also, thirtyfive species of Foraminifera belonging to thirteen genera were determined, which are: Cibicides, Cymopolia, Eggellina, Elphidium, Globigerinelloides, Globotruncana, Hedbergella, Heterohelix, Marginulina, Miliolid, Neobulimmina, Nodosaria and Textularia. Seven range zones were determined, three of which are of Ammonite, which are: Desmophyllites larteti (Seunes, 1892), Nostoceras (Nostoceras) hyatti and Pseudophyllites teres (Van Hoepen, 1920), whereas the others are of Foraminifera species, which are: Glt. gagnebini Tilev, Glt. tricarinata lapparenti Brotzen, Glt. tricarinata tricarinata (Querean) and Glt. Stuartiformis Dalbiez. According to these findings, the age of Shiranish Formation was determined as the Late CampanianMaastrichtian.


Introduction
Starting from earlier studies, Ammonites have been considered as prime biostratigraphic indicators in marine sediments [1][2][3][4][5][6]. The group generally possesses many of the characteristics of the ideal index fossil: wide, rapidly attained geographic distribution, high degree of facies independence, rapid evolutionary rates, and high preservation potential. Ammonites are conspicuous and commonly determinable even when fragmentary. These factors allow the recognition of fine biostratigraphic subdivisions that are correlatable over long distances [7].
As for planktonic Foraminifera, their use as guide fossils is generally accepted today. The Planktonic Foraminifera, being of practical use in biostratigraphy, first occurred during the Early Cretaceous. They have continued to distribute on a worldwide scale, and in a rapid succession of species, to the recent time [8]. Comprehensive studies dealing with the Late Cretaceous Ammonite-Foraminifera association within Shiranish Formation are limited. However, the present study of Shiranish Formation was conducted at four selected geological sections, which are Dokan, Hijran, Esewa and Kanny dirka (Figure 1). The current study aims to determine the biostratigraphy of the formation depending on the Ammonite fossils with Foraminifera associations.

Results and Discussion
According to the fossil associations of the Ammonites and Foraminifera, seven biozones were determined; three are related to the Ammonites and the other four are related to the planktonic Foraminifera. The following is a description of the recorded fossils in each section.

Biostratigraphy of Dokan Section
Various macrofauna were identified in the sediments of Shiranish Formation at the Dokan section ( Figure 2). These include the following Ammonite species:  Figure 1). Other microfossils were also identified, such as Ostracoda shells (Pl.8, Figure 1).

Biostratigraphy of Hijran Section
Different types of macrofauna were identified in the sediments of Shiranish Formation at the Hijran section (Figure3). These include the following Ammonites: Desmophyllites larteti (Seunes, 1892) (Pl., Figure),

Biozones of the studied area Ammonite biozones
The ranges of Ammonites were studied through the stratigraphic sections to determine their biostratigraphic zones. Accordingly, each of the Dokan and Hijran sections were divided into three main biozones, which are pseudophyllites teres (Van Hoepen, 1920) biozone, Desmophyllites larteti (Seunes, 1892) biozone, and Nostoceras (Nostoceras) hyatti, Stephenson, 1941 biozone. While Esewa section was divided into two biozones, which are Desmophyllites larteti (Seunes, 1892) biozone and Nostoceras (Nostoceras) hyatti (Stephenson, 1941) biozone. Pseudophyllites teres (Van Hoepen, 1920) rang zone The lower limit of this biozone is set in accordance with the first appearance of Pseudophyllites teres species, whereas its upper limit coincides with the disappearance of this species. The thickness of the zone is 60 m in Dokan section and 34 m in Hijran section. This biozone is coincident with two biozones of Foraminifera within Dokan section, which are Glt. tricarinata lapparenti (Brotzen) biozone and Glt. tricarinata tricarinata (Querean) biozone. In addition, the presence of Nostoceras (

Age of Pseudophyllites teres (Van Hoepen, 1920) rang zone
The age of this zone is dependent on the recorded age of the species Pseudophyllites teres in other countries [9], which showed that the range of this species is from the late Santonian to the early Campanian. This range has to be extended to the late Campanian, on the basis of the Gschliefgraben specimen. The geographic range of the species involves Pondoland (South Africa), Madagascar, and possibly Brazil. In the percent study, the age of this zone was determined to be the late Campanian-early Maastrichtian in Dokan and Hijran sections. Desmophyllites larteti (Seunes, 1892) rang zone The lower limit of this zone is determined based on the first appearance of this species. Its upper limit coincides with the disappearance of the species (until the sections end). The thickness of the zone is 82 m in Dokan section, 66 m in Hijran section, and 28 m in Esewa section. This biozone is coincident with Glt. stuartiformis Dalbies biozones of foraminifera, along with the presence of foraminfera biozones within Dokan section, which are Glt. tricarinata lapparenti Brotzen biozone, Glt. tricarinata tricarinata (Querean) biozone and Glt. gagenbini Tilev biozones. In addition, we recorded the presence of Nostoceras ( As for Hijran section, it is coincident with the appearance of Glt. Stuartiformis Dalbies biozone of foraminifera and with the disappearance of Pseudophyllites teres (Van Hoepen, 1920) ammonite biozone and Glt. tricarinata tricarinata (Quereau) foraminfera biozone. In addition, the presence of the fossils of Partschiceras? Japonicum (Motsumoto) and Yubariceras yubarense (ex yabe ms.) sp. nov. was observed within this biozone.
As for Esewa section, it is coincident with the appearance of Glt. gagnebini Tilev foraminifera biozone and with the disappearance of Nostoceras (Nostoceras) hyatti ammonite biozone. It also contains the fossil Neancyloceras bipunctatum. Age of Desmophyllites larteti (Seunes, 1892) rang zone The age of this zone was determined depending on the occurrence of this species within sediments belonging to Campanian-Maastrichtian age in Iraq and other countries. This zone was recorded to belong to the late Campanian to late Maastrichtian in Pyrenees-Atlantiques and Landes in France, the coastal sections of the Biscay region of France and NW Spain, the Gschliefgraben, Austria, and possibly Madagascar [10]; it also ranges from early Maastrichtian to late Maastrichtian of Madagascar [11]. In the present study, it was determined to the late Campanian-late Maastrichtian within Dokan section, middle Maastrichtian-late Maastrichtian within Hijran section, and Maastrichtian within Esewa section.

Nostoceras (Nostoceras) hyatti Stephenson, 1941 rang zone
The lower limit of this zone was determined based on the first appearance of this species and its upper limit coincides with the disappearance of the species. The thickness of the zone is 30 m in Dokan section, 16

Age of Nostoceras (Nostoceras) hyatti Stephenson, 1941 rang zone
The age of this zone is dependent on the age of the species Nostoceras (Nostoceras) hyatti in Iraq and other countries. This species is widespread worldwide and represents the last range of the Campanian age, where the period after its last appearance was that of the beginning of the Maastrichtean [12]. These countries include France, the United States of America, Spain, Belgium, Poland, Angola, Madagascar, Palestine, and Iraq [13,14]. Also, it was recorded to belong to the late Campanian age in the lower part of Shiranish Formation, NW Iraq [15]. In the percent study, the age of this zone was determined to be the late Campanian within each of Dokan, Hijran, and Esewa sections, depending on the age of the species Nostoceras (Nostoceras) hyatti.

Age of the Globotruncana stuartiformis Dalbiez rang zone
The age of this zone was determined to be dependent on the age of the species Glt. stuartiformis in Iraq and other countries. In north-east Iraq, Glt. stuartiformis is one of the abundant species of Globotruncana, observed in the Shiranish Formation (Campanian-Maastrichtian) [16] and Maastrichtian within Sinjar area [17]. The species was originally described to be from the Campanian-early Maastrichtian strata of Tunisia. It is also known from the strata of similar ages in Texas and Puerto Rico [18][19][20], New Jersey [21], and the Maestrichtian of Egypt [22]. Glt. stuartiformis was also recorded from the Campanian-Maastrichtian of Europe and Russia. Dalbiez [23] described Glt. stuartiformis as a subspecies of Glt.elevata (Brotzen) from the Campanian-Lower Maastrichtian of Tunisia [24]. In the present study, it was determined to belong to the late Campanian-late Maastrichtian in Dokan section and middle Maastrichtian-late Maastrichtian within Hijran section.

Globotruncana tricarinata lapparenti Brotzen rang zone
This zone is identified depending on the range of extension of Glt. tricarinata lapparenti subspecies. The lower limit of this zone is determined based on the first appearance of this species and its upper limit coincides with disappearance of the species. The thickness of the biozone is 50 m in Dokan section and 32 m in Hijran section. In Dokan section, this biozone is within Glt. stuartiformis Dalbies biozone and includes Glt. tricarinata tricarinata Brotzen biozone along with the fossils of Glt. concavata cyrenaiea, Glt. marginata (Ruess) and Globigerinelloides bollii Passagno. Within Hijran section, the appearance of this biozone is coincident with the appearance of Glt. gagnebini Tilev biozone and includes the fossils of Globigerinelloides multispina (Lalicker) and Glt. Stuartiformis (de' lapparent).

Age of Glt. tricarinata lapparenti Brotzen rang zone
This biozone is recorded depending on the occurrence of this species within sediments in Iraq and other countries, as in the following: This species is recorded from the Campanian portion of the Shiranish Formation where it occurs rather commonly [16]. De Lapparent's original figures are of specimens from strata within the Turonian to Campanian interval in Europe. The subspecies is also recorded from strata of early Santonian to early Maastrichtian age of Mexico and Texas [20], Santonian-Campanian of Puerto Rico [18,19], and Santonian-Lower Maestrichtian of Trinidad [25]. It is also known in the strata of the similar age in Russia [26], Australia [16,27,28], and North Africa [29]. In the present study, it was determined in the late Campanian-early Maastrichtian within Dokan section and early Maastrichtian-middle Maastrichtian within Hijran section.

Globotruncana tricarinata tricarinata (Querean) rang zone:
The lower limit of this zone is set in accordance with the first appearance of this species and its upper limit coincides with the disappearance of the species. The thickness of the biozone is 42 m in Dokan section and 36 m in Hijran section. In Dokan section, this biozone is within Glt. stuartiformis Dalbies biozone and Glt. tricarinata lapparenti Brotzen biozone. Within Hijran section, the disappearance of this biozone coincides with the appearance of Glt. stuartiformis Dalbies biozone and includes the fossils of Globigerinelloides multispina (Lalicker) and Glt. Stuarti (de' lapparent).

Age of Glt. tricarinata tricarinata (Querean) rang zone
The age of this zone was determined depending on the occurrence of this species within sediments recorded in Iraq and other countries, as follows: Glt. tricarinata tricarinata occurs rather commonly in Campanian portions of the Shiranish Formation [16]. The species was originally described from Campanian to early Maestrichtian strata of Switzerland. Bolli [25] and [30] used the subspecies as a distinctive zonal marker for the Campanian-early Maastrichtian strata of Trinidad and the subsurface Campanian-early Maastrichtian. Strata uncounted in Leg 15 sites in the Caribbean Sea. It is also described from the Campanian of the Carnarvon Basin, north-west Ausralia [27], the Santonian of England [31], and the Campanian-early maestrichtian of Libya [29,32]. According to previous reports [16,33], the subspecies is also recorded from the type Campanian section at Aubeterre in the Aquitain Basin. It is also known in the strata of lower Maastrichtian age in New Jersey [21]. Turonian-Maastrichtian worldwide [24,34]

Age of Globotruncana gagnebini Tilev rang zone
The age of this zone was determined depending on the occurrence of this species within sediments belonging to the Maastrichtian age in Iraq and other countries. The specimens are identical to the specimen figured by an earlier study [21] from the Maastrichtian strata of New Jersey. In the present study, it is determined in the early Maastrichtian-late Campanian within Dokan and Hijran sections and the Maastrichtian within Esewa and Kanny dirka sections.