Microfacies Analysis and Paleoenvironment of Baba Formation, Anah Area Westren Iraq

Microfacies analysis and Paleoenvironment of Baba Formation were investigated in Anah area, Anbar Governorate, Western Iraq. Baba Formation was cropped out in Wadi Al-Khazgah section with 9 meters thick, consisting of white to creamy, chalky, coralline, high fracture Limestone. Five Microfacies types were recognized Coral Lime Boundstone, Lepidocyclina Lime Packstone, Nummulitids Lime Packstone, Miliolids Lime Packstone - Grainstone, and Coraline Algae Lime Wackestone described in 10 samples collected from one section (Wadi Al-Khazgah Al-Gharbi section). These Microfacies described on the basis of the presence of the Benthic Large Foraminifera (BLF) as Miliolids, Lepidocyclinide, Rotalide and skeletal fragments of brachiopod, coral, and algae shell. The paleoenvironment of Baba Formation was determined fore-Reef and Reef environments.


Introduction
The studied section was located near Anah village within Anah Anticline, at latitude N: 34° 25' 44" and longitude E: 41° 42' 12" (Fig. 1).The area was about 130 Km Northwestern of Al-Ramadi town within Anbar Governorate.This area is characterized by the presence of various forms of karst that are distinguished by their picturesque appearance, making them tourist areas visited by many communities [1].Wadi Al-Khazka is considered one of the most important seasonal valleys in this region, and its waters flow into the Euphrates River [2].This study focused on Microfacies analysis and Paleoenvironment of Baba Formation (Middle Oilgocene) of Kirkuk Group.Baba Formation was determined by [3] for the first time, on Kirkuk well-10, within Baba structure by 20 meters thick, it composed from porous dolomitized and chalky limestone, he found many types of fossils which were: Lepidocyclina s. i. spp., Nummulites intermedius, Nummulites fichteli, Operculina sp., Rotalia viennoti and Heterostrgina cf.assilinoides of fore-reef environment.
The upper contact of this formation in type section is conformable with Bajwan Formation, and lower contact is unconformble with Shurau Formation [4].This formation recorded as sub surface in Bai Hassan well-25, and distinguished Lepidocyclina -Nummulites Assemblage Zone and three Microfacies types and the environment was attached platform sitting [5].Also Baba Formation exposed in Darsila section, northeastern Iraq, was composed from nine meters thick of creamy, massive and fossiliferous Limestone, the formation overlies Sheikh Alas Formation conformably and underlies by Bajwan Formation unconformable [6].Aims of this study was conducted a Lithostratigraphic study and boundaries of Baba Formation, and distinguishing the paleoenvironment based on determining a number of Microfacies types Fig. 1.Location map of study area

Samples and Methods
This study was based on 10 samples collected from 9 meters thick outcrop section of the Baba Formation in Anah anticline, near Anah village, Wadi Al-Khazgah section (Fig. 2).The samples are collected on the basis of lithology change and type of fossil content.The lithology of the sequence was described based on field observations.Most of the samples contain well preserved and abundant Benthic Large Foraminifera, coral, algae and other skeletal grains of microfossils.
The laboratory work included preparation of 2 thin-sections, for each sample in workshop of Geology department, Anbar University.The thin sections were examined using polarized microscope to identify different types of Microfacies.Adigital camera was used to tack photo the microfossils in thin sections.The first part of this paperis assigned to Microfacies analysis of the Baba Formation, based on benthic foraminifera described.The second part is focused on Microfacies and Paleoenvironment.

Geological Setting and Lithostratigraphy
The study area located in northeastern part of the Arabic Platform and within Rutba subzone of Stable Shelf in western Iraq (Fig. 3).The area is surrounded by two types of transverse fault Sirwan and Anah Qalat -Dhizah [7].The folds within the Stable Shelf are buried, except Anah Anticline, which was exposed on the surface, and sequence stratigraphy from the core was Baba Formation ( Middle Oligocene) and the limps were (Lower Miocene) Euphrates Formation.

Fig. 3 Map of divisions tectonic of Iraq [7]
4 Baba Formation is oldest formation exposed in Wadi Al-Khazgah section, it is comprise of whitish gray to creamy, homogeneous, fine crystalline, medium tough, massive into thickly bedded, chalky, highly jointed, fossiliferous, and coralline Limestone (Fig. 4).The lower contact not exposed in this section and the upper contact consist of milky, thick bedded, highly jointed, medium tough, and fossiliferous Limestone of the Azkand Formation.The thickness of the Baba Formation in the studied section is about 9 meters.(Fig. 5).
The lower bed of the Baba Formation is contains the Lepidocyclina Eulepidina clearly visible to the naked eyes, and it is consider indicate of the beginning this formation, this bed also is reappear, but with a less percentage of fossils.The upper contact of Baba Formation point to disappear of Lepidocyclina Eulepidina, while Lepidocyclina Nephrolepidina appear in lower contact of Azkand Formation.(Fig. 5).

1-Coral Lime Boundstone
This Microfacies appeared in middle part of Baba Formation above Nummulitide Lime Packstone, that appear micarization in this facies is point earliest diagentic process development during post deposion by algae and bacterea activety [8].The thickness of this facies was two meters.It mainly consists of coral plate 1(fig: 1, 2).
Coral complex reef reflected of Boundstone rocks at good water circulation, high energy condition in depth 1-30 meters [9].This facies usually deposited in organic reef coral and algae, and it found on platform margine [10], which was similar to the SMF.7 by [11] and FZ.5 [12].The presence of Nummulite in open marine with high energy within fore-reef and may extend to the deepest point in the light zone [15], while [16] suggested this facies was deposited at the bottom of the waves in the conditions of the moderate environment.This facies was suggested to be similar to SMF.4 and FZ.4.
The high diversification of miliolids tests indicated on lagoon in tropical shallow, clean of normal salinity water [17].Occur miliolids in sallow sea of barrier reef [18], while [11] regarded the present miliolids reflected the shallow, restricted lagoon environment.This Microfacies was similar to SMF.8 and FZ.6.

5-Coralline Algae Lime Wackstone
This Microfacies appeared in upper part of Baba Formation, the thickness of this facies is one meter.It consists of Lithophylum sp.,and Algae cell plate 2 (Fig: 5 and 6).Neomorphism is appear in this facies that cover the combined processes of inversion and recrystallization [19].
The present coralline algae in this Microfacies indicated on depositional in reef sitting which was located in deeper, and algae and coral live in a symbiotic where appropriate lighting is available [20].This Microfacies equivalent to SMF.

Paleoenvironment
Depending on the thin sections and their fossil content and their comparision with Standard Microfacies (SMF) of [11] and Facies Zone of [12], five sub Microfacies were identified.This study showed that Baba Formation deposited within these FZ.4,5,6, which explains following  The present coral and algae which are grow in shallow tropical and subtropical water, which is require conditions for its construction, such as warmth and lack of water currents [21]. It also explained the existence of the Corall Lime Boundstone to warm, shallow sitting and normal salinity during the Oligocene period, and it was deposited in the coral reef environment [22]. The presence of large size of Lepidocyclina with packstone texture within this formation was evidenced of sedimentation in fore-reef environment [23]. The occurrence of Nummulites within Baba Formation was indicated of relatively deep sitting to move away from high light and to preserve its test from the high kinetic energy of currents and sea waves [24]. The presence of Miliolids within this formation explains that deposition occurred within shallow environment with limited circulation of water movement [25].

Conclusion
Through this study, the following was achieved: 1-According to Lepedocyclina Eulepidina dilalata, L. Eulepidina elephantine the collection, it was indicated the age of the Middle Oligocene.2-The upper contact of the Baba Formation within the study area are conformable and gradual, and indicated by the emetgence of a bed eich in Lepidocyclina, while the lower contact didn't appear within this section.3-Five types of Microfacies had been distinguished within Baba Formation, and they are arranged from the bottom of the formation to the top were: Lepidocyclina Lime Packstone,

6 )
Fig (1 and 2) facies Coral Lime Boundstone.Fig (3, 4 and 5) Eulepidina dilalata from facies Lepidocyclina Lime Packstone.Fig (6) Nephrolepidina sp., from facies Lepidocyclina Lime Packstone.3-Nummulitids Lime Packstone This Microfacies appeared in lower part of Baba Formation above Lepidocyclina Lime Packstone, the thickness of this facies is one meter.It consists of Rotalia viennoti Greig, Amphistegina bohdanowiciz Bieda, Miogypsinoides sp., Nummulits fichteli plate 2 (Fig: 1,2 and 3).The presence of Nummulite in open marine with high energy within fore-reef and may extend to the deepest point in the light zone[15], while[16] suggested this facies was deposited at the bottom of the waves in the conditions of the moderate environment.This facies was suggested to be similar to SMF.4 and FZ.4.4-MiliolidsLime Packstone -GrainstoneThis microfacies appeared in upper part of Baba Formation above Coral-Algae Lime Wackestone, with nonfabric selective porosity vug fiiie with calcite cement, the thickness of this facies was one meter.It consists of Quenquoloculina sp., and Triloculina trigonula Lamarck, plate 2 (Fig:4).The high diversification of miliolids tests indicated on lagoon in tropical shallow, clean of normal salinity water[17].Occur miliolids in sallow sea of barrier reef[18], while[11] regarded the present miliolids reflected the shallow, restricted lagoon environment.This Microfacies was similar to SMF.8 and FZ.6.5-CorallineAlgae Lime WackstoneThis Microfacies appeared in upper part of Baba Formation, the thickness of this facies is one meter.It consists of Lithophylum sp.,and Algae cell plate 2 (Fig:5 and 6).Neomorphism is appear in this facies that cover the combined processes of inversion and recrystallization[19].The present coralline algae in this Microfacies indicated on depositional in reef sitting which was located in deeper, and algae and coral live in a symbiotic where appropriate lighting is available[20].This Microfacies equivalent to SMF.5 and FZ.4.

7 Fig ( 1 )Fig ( 2 )Fig ( 3 )Fig ( 5 ) 6 )
Fig (1 and 2) facies Coral Lime Boundstone.Fig (3, 4 and 5) Eulepidina dilalata from facies Lepidocyclina Lime Packstone.Fig (6) Nephrolepidina sp., from facies Lepidocyclina Lime Packstone.3-Nummulitids Lime Packstone This Microfacies appeared in lower part of Baba Formation above Lepidocyclina Lime Packstone, the thickness of this facies is one meter.It consists of Rotalia viennoti Greig, Amphistegina bohdanowiciz Bieda, Miogypsinoides sp., Nummulits fichteli plate 2 (Fig: 1,2 and 3).The presence of Nummulite in open marine with high energy within fore-reef and may extend to the deepest point in the light zone[15], while[16] suggested this facies was deposited at the bottom of the waves in the conditions of the moderate environment.This facies was suggested to be similar to SMF.4 and FZ.4.4-MiliolidsLime Packstone -GrainstoneThis microfacies appeared in upper part of Baba Formation above Coral-Algae Lime Wackestone, with nonfabric selective porosity vug fiiie with calcite cement, the thickness of this facies was one meter.It consists of Quenquoloculina sp., and Triloculina trigonula Lamarck, plate 2 (Fig:4).The high diversification of miliolids tests indicated on lagoon in tropical shallow, clean of normal salinity water[17].Occur miliolids in sallow sea of barrier reef[18], while[11] regarded the present miliolids reflected the shallow, restricted lagoon environment.This Microfacies was similar to SMF.8 and FZ.6.5-CorallineAlgae Lime WackstoneThis Microfacies appeared in upper part of Baba Formation, the thickness of this facies is one meter.It consists of Lithophylum sp.,and Algae cell plate 2 (Fig:5 and 6).Neomorphism is appear in this facies that cover the combined processes of inversion and recrystallization[19].The present coralline algae in this Microfacies indicated on depositional in reef sitting which was located in deeper, and algae and coral live in a symbiotic where appropriate lighting is available[20].This Microfacies equivalent to SMF.5 and FZ.4.