ORIGINAL PAPER

Contribution to the stratigraphy of the Walash Group,Sulaimani area, Kurdistan, Iraq

Basim Al-Qayim & Imad Ghafor & Rawand Jaff

Received: 27 September 2012 /Accepted: 11 December 2012 /Published online: 3 January 2013# Saudi Society for Geosciences 2012

Abstract The Walash Group represents sequences of silici-clastic sediments with alkaline volcanics at the upper part. Itforms the lowermost thrust sheet of the Zagros Suture Zone.Three localities around Sulaimani area of Kurdistan regionof north Iraq were chosen for sedimentological and strati-graphic review of this group. Examination includes fieldmeasurements, description, and correlation, and petrograph-ic and biostratigraphical analyses. The Walash Group se-quence in the study area has variable thickness, with thehighest reaching 150 m, and generally consists of greenishgray silty calcareous shale which alternates with thin- tothick-bedded, coarse-grained sandstone and limestone.Sandstone beds show sedimentological evidences of turbi-dite origin. Based on occurrences of volcanic admixtures,the group is subdivided into two basic lithostratigraphicunits: lower sedimentary unit and upper sedimentaryvolca-nic unit. Petrographic analysis shows that the sandstonesinclude two basic types: lithicarenites which is dominatedby carbonate, quartz, chert, and volcanic rock fragments,and calcarenite with bioclasts and benthic forams as themain type of grains. Biostratigraphic analysis of the shaleinterlayer samples near Kinjurine Village reveals the occur-rence of both benthonic and planktonic foraminifera. Strati-graphic ranges of the identified planktonic foraminiferashow occurrence within the Paleogene biozones P5P9which indicate Ypresian age (Lower Early Eocene). Similarage inferences were reached from benthic foraminiferalassemblages. Based on correlation with other areas, thestudy calls attention to a review of the stratigraphic statusof the group by renaming the upper part and introducingnew name for the lower part.

Keywords Stratigraphy .Walash Group . Sulaimani area .

Iraq . Kurdistan Region

Introduction

The Walash Volcanic Series was first introduced by Bolton(1958) to denote the lower major thrusted sheet of theZagros Suture Zone formerly known as the Thrust Zoneof northeast Iraq. The name is taken after measuring a typesection of the series at Walash village in the Rowanduz rivervalley of northeastern Iraq. The name changed into theWalash Rock Group when it appeared in the generalgeologic map of Iraq (1/1,000,000 scale) of 1960. The groupin the type section area is composed of volcanic rockspassing laterally into sedimentary rocks. The type section,however, as compared to other localities, represents onlyone relatively small part of the group (Buday 1980). Acompiled reference section based on unpublished reportsof the Geological Survey of Iraq (Bolton 1958; Smirnovand Nelidov 1962; Polnikov- Nikolajev 1962) is constructedby Buday (1980) and approved by Jassim and Buday (2006)for the group. This section includes five major divisions.These divisions are, from bottom:

(a) Lower Red Beds UnitRed mudstone with cherty siltstone and shales.

(b) Lower Volcanics UnitBasic and less frequently acidic lava and pillow lava

which are associatedwith pyroclasts. Volcanics often occuras volcanic coneswhich pass laterally into tuffaceous rockswith radiolarite and white chemical limestone.

(c) Middle Red Beds UnitSiliciclastic sequence passes laterally into tuffaceous

rocks. Sedimentary rock types include: red mudstone,red and gray shales, sandstone, conglomerate, andlimestones.

B. Al-Qayim (*) : I. Ghafor : R. JaffDepartment of Geology, Sulaimani University, Sulaimani,Kurdistan, Iraqe-mail: alqayim@yahoo.com

Arab J Geosci (2014) 7:181192DOI 10.1007/s12517-012-0809-x

(d) Upper Volcanics UnitIt is composed mainly of basalt and andesitic flows,

pyroclastics, and associated sediments. Volcanic conesalso occur and pass laterally into marine sequence withlimestone.

(e) Upper Red Beds UnitRed mudstone and conglomerate near the base, and

brownred mudstone and greywacke sandstone higherup.

Large benthic forams collected from the limestones of theWalash Group (Nummulites and Alveolina) indicate that theage of this unit is generally Paleogene (Buday 1980).

The thickness of the group is highly variable andreaches 3,500 m near Chia-Sefid-Darband of Rowanduzarea (Bolton 1958, p. 106). At the type locality, themeasured thickness of about 1,000 m made Buday(1980) believe that the type locality represents a rela-tively small part of the sequence. However, due to thetectonic complication of the area, it is possible that thehigh thickness of the group might be the result ofrepetition due to multiple thrusting with the group.

At the Sulaimani area, specifically the Mawat region, thegroup is examined in detail for the first time by Al-Mehaidi(1975). The group consists of an unmetamorphosed com-plex sequence of volcanic rocks of tuff, basaltic rocks, andlava flows of basic to intermediate composition, which isassociated with red shale, greywacke, and red limestone. Itpasses laterally into a flysch unit with nummulitic lime-stone. The flysch unit shows rhythmic alteration of graysilty shale, greywacke, sandy limestone, and conglomerate.He believed that this flysch unit belongs to the NaopurdanGroup. The reason for that is the occurrence of the associ-ated recrystallized sheared and fossiliferous limestone,which is similar to a middle limestone unit recognized inthe type locality of the Naopordan Group (Bolton 1958).The limestone unit is gray in color, medium to thick bedded,and of bioclastic calcarenites. It is rich in Nummulites andother benthonic foraminifera (Al-Mehaidi 1975). The age ofthese Nummulite assemblages is determined by Al-Hashimi(1975) as Lower to Middle Eocene. Similar results (M.Eocene) using planktonic foraminiferal assemblages fromthe group were assigned by Al-Banna and Al-Mutwali(2008). The depositional environment of these limestonesis believed to represent an outer shelf to slope margin(Surdashy 1997; Al-Banna and Al-Mutwali 2008).

The purpose of this study is to investigate the sedimen-tological characters, facies type, and microfossil assemb-lages of the Walash Group at the Sulaimani area in orderto determine its stratigraphic status and age. Examination ofthese rocks as a part of the Zagros Suture Zone wouldcontribute to the integrated evolution of the Zagros orogeny(Fig. 1).

Material and methodology

Three localities in Sulaimani area with Walash Group out-crops were visited and examined for different stratigraphiccharacters. The first is selected along an unpaved road to theserpentinite quarry, about 1 km to the northwest of Kinjurine(Fig. 2). This locality is taken as a master section for thestudy for its complete and well exposed strata. Detailedstratigraphic section is measured focusing on lithologic var-iations and facies associations. Systematic sampling wasconducted for the sandstones, conglomerate, and limestonefor petrographic analysis. The second section is located tothe north of Bardazard about 3 km to the north of Chwarta.The third locality is an incomplete section of the groupsituated along the road to Penjwin about 1.5 km to thenortheast of Kani Manga (Fig. 2).

To evaluate type and origin of the dominant rock types ofthe Walash Group, 30 samples of sandstone and limestonewere thin sectioned for petrographic analysis. Several sam-ples were treated with Alizarin Red-S stains to differentiatedifferent carbonate minerals following Dickson (1966). Pet-rographic examination includes type and abundance of ma-jor components as well as textural characters. Classificationnomenclatures for sandstones followed Pettijohn et al.(1973) and for carbonates, Dunham (1962).

Marly shale and calcareous shale samples were selectedfrom Kinjurine sections for biostratigraphic analysis. About200300 g of each soft sample was dried out and processedby a repeated freezing and thawing method until the sedi-ments disaggregated in a supersaturated solution of sodiumsulfate. Disaggregated sediments were washed thoroughlythrough a 63-m sieve; the residues were separated byfiltration and dried overnight. Dried residues were then sizesorted through sieves from 500 down to 63 m. Foraminif-era were picked from the residue in the 63200-m-sizefractions and examined under a binocular microscope. Fo-raminifera were cross examined and photographed by usingS520 Hitachi Scanning Electron Microscope at LeicesterUniversity, UK, after particular treatment.

Geologic setting

Sulaimani area is located in the heart of the ZagrosOrogenic belt which runs from SE Turkey to Oman.The tectonic evolution of this belt resulted from a longconvergence history between the Arabian Plate from oneside and the Iranian block of SanandajSirjan from theother side (Beydoun 1991). This tectonic history yield aNWSE trending suture zone of Tethyan componentsand adjacent folded belt. The Walash Group is part ofthe Zagros Suture Zone which consists of overthrustedsheets of Tethyan accretionary prism developed in two

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different stacking episodes (Al-Qayim et al. 2012). Theearly stacking is related to the ConiacianCampanianophioliteradiolarite obduction and includes: the Qulqula

Group, the Triassic platform carbonate (Avroman Lime-stone Formation). The second and succeeding stackingis related to the accretionary prism of the remnant

Fig. 1 General physiographicmap of northeast Iraq showinglocation of the study area

Fig. 2 General geologic map of the study area showing location of the studied sections. (1) Kinjurine, (2) Chwarta, and (3) Penjwin section.(Geology after Maala 2008)

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Tethyan ocean and includes the volcano-sedimentary se-quence of the WalashNaopordan Series, and ophiolitemasses (Mawat and Penjwin complexes). The emplacementof this package is associated with Mid-Miocene continentalcollision of the Arabian plate with the Sanandaj-Sirjan Block(Al-Qayim et al. 2012). The Walash sheet always bottoms theophiolite masses with a tectonic boundary zone marked by theoccurrence of serpentinite horizon. Emplacement of thesemasses overlay the foreland sequence which was developedover the Arabian plate margin during the Late Cretaceous anddue to the ophioliteradiolarite obduction (Al-Qayim 2012).The Red Beds Series bottom the Walash Group immediatelyas it forms the Paleogene coastal sediments of the forelandbasin (Al-Qayim 2000; Karim et al. 2007). Further southwest,the proper sequence of the foreland basin (i.e., ShiranishTanjeroAqra formations) is exposed successively below theSuwais Red Beds. The Zagros Suture Zone is bounded fromthe northeast by a regional reverse fault known as the MainZagros Reverse Fault (Fig. 3) and from the southwest by asegmented fault line called the Zagros Thrust Front (Al-Qayim et al. 2012).

To the southwest of the Zagros Suture Zone, the fold beltevolved during the final collision and accompanying short-ening and deformation of the foreland sequence. The foldingintensity decreases southwestward leading to segmentation

of the Folded Zone into the High Folded Zone and the LowFolded Zone. The separating boundary is a master fault lineknown as the Zagros Mountain Front Fault. It runs in thestudy area as a tectonic contact between the Walash Groupand the Suwais Red Beds (Al-Qayim et al. 2012). It isrecognized by a linear valley, often covered by recent sedi-ments and hard to trace. It separates the soft olive grayclastic sediments of the Walash from the underlying redsiliciclastic sediments of the Suwais Red beds (Fig. 3).

The outcrop of the Walash Group usually forms a narrowbelt swing around the ophiolite complexes as the case inMawat and Penjwin areas (Fig. 1), and due to the softsediment of the group, it always forms a low-relief area infront of the ophiolite masses. The section generally consistsof cyclic alternation of sandstone and olive gray silty shale.Conglomerate lenses and limestone are subsidiary. The vol-canicity of the Walash Group in the study area is of limiteddistribution. It is usually noticed as small size sills or pyro-clasts of different sizes. Their composition is found to be ofbasic dykes of spilitic diabase, spilitic basalt, spilites, andintermediate volcanic of pyroxene andesite, pyroxene-amphibole andesite, and altered andesite (Aziz 1986; Jassimand Buday 2006). The group is generally overlain by aserpentinite horizon of variable thickness. The lower bound-ary of the Walash Group is tectonic and usually covered by

Fig. 3 Major tectonicsubdivision of NE Iraq and theirboundaries overlie the generaltectonic map of Iraq (tectonicmap after Al-Kadhimi et al.1996; tectonic boundariesnomenclature after Al-Qayim etal. 2012). A Shalair Zone, BZagros Suture Zone, C ZagrosImbricate Zone, D High FoldedZone, E Low Folded Zone, FMesopotamian Zone. MZRFMain Zagros Reverse Fault,ZTF Zagros Thrust Front,HZRF High Zagros ReverseFault, ZMFF Zagros MountainFront Fault, ZFF ZagrosForedeep Fault

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recent sediments due to the soft sediments of both units. Thegroup displays different shearing and deformation featureswhich appear as local foliation, imbrications, multiple fault-ing, sliding, folding, as well as flowage structures (Fig. 4a).

Lithostratigraphy and sedimentology

Due to the tectonic emplacement of the Walash Group,thickness is quite variable as a result of thrusting and inter-nal faulting. This thickness variation is reflected on the localpreservation of lithofacies and sedimentological charactersof the cropped-out Walash group sections. The total thick-ness of the section at Kinjurine reaches 110 m with theupper sharp contact with the serpentinite horizon seeminglyas thrust boundary (Fig. 4b). The lower contact with SuwaisRed Beds is sharp but obscured by the valley and its recentsediment running at the boundary zone.

The thickness of the group is slightly higher at Chwartaarea. It reaches 140 m. The uppermost unit is characterizedby a large volcanic body where no serpentinite is recog-nized. The lower boundary with the Suwais Red Beds Seriesis assumably tectonic and, as usual, hard to depict due to thesoft sediment on both sides of the contact. At Penjwin, only20 m of the Walash Group is exposed. The upper boundaryat this locality is sharp and tectonic with the thick serpen-tinite horizon (Fig. 4c), whereas the lower boundary withthe Suwais Red Beds is hidden under a thick cover of recentsediments (Fig. 5). Based on the lithologic variations andassociation with volcanic rocks, the Walash Group can besubdivided into two basic lithostratigraphic units. A lowersedimentary unit which lacks any obvious volcanicity andan upper unit which consists of a similar sedimentary se-quence but with conspicuous volcanic rock association.Below is the description of these units in the study area.

Lower sedimentary unit

The Lower Unit is generally a sedimentary sequence of80 m thick at Kinjurine and 40 m at Chwarta area, and only20 m of this unit is exposed at Penjwin section and occursimmediately below the serpentinite horizon (Fig. 4c). It isgenerally characterized by cyclic alternation of buff to gray,hard, occasionally sheared, thin (510 cm) to thick (up to80 cm) sandstones beds with greenish gray, fissile, silty, andcalcareous to marly shale interlayers (Fig. 6a). These shaleinterlayers can exceed 5 m in thickness and yield benthonicand planktonic foraminifera. The sandstone beds becomethicker and more frequent upward the unit. Their lowerboundary is sharp, and its upper boundary is often grada-tional to the shale interlayer (Fig. 6b). Sandstone beds aremedium to coarse grained and often display graded beddingand occasional cross and or parallel bedding (Fig. 6c). Inother cases, medium and graded-bedded sandstones displayamalgamation which makes them appear as thick-beddedunits (Fig. 6d). Other beds which are infrequently recog-nized include lenses of conglomerate and thin limestonebeds. These are specially noticed at Kinjurine section.

Upper sedimentaryvolcanic unit

This unit is only appearing in the Kinjurine and Chwartasections with thickness ranging between 80 and 40 m, re-spectively. The basic character of this part is the associationwith different forms of volcanic material. The sedimentarysequence is almost the same as in the lower unit. Thesandstone beds, however, are often thicker and denser. Cal-carenite sandstones become thin fossiliferous limestonebeds with components of shallow marine environment.The shale part displays shearing and even foliation especial-ly in the upper part (Fig. 6e). The volcanic rocks are variable

A

B

C

Fig. 4 a Highly sheared and deformed (arrows) shale and sandstone ofthe Walash Group, Kinjurine section, Upper Unit. b Sharp and striatedthrust boundary between Walash sediments and the serpentinite hori-zon, Kinjurine section. c Irregular tectonic upper boundary of WalashGroup with the overlaying serpentinite horizon, Penjwin section

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in size and origin. These are ranging in forms from tuffs,lapillis, pyroclasts , irregular sills, and dykes. These bodieswere weathered to pinkish, reddish brown and light graysofter rocks (Fig. 6e and f). Petrographic examination ofthese units shows that these volcanics are classified intobasic and intermediate dykes, lava flows of spilitic diabase,and pyroxene-bearing spilitic basalt, spilite, and intermedi-ate volcanic of pyroxene andesite, pyroxene-amphibole an-desite, and altered andesite (Al-Mehaidi 1975; Aziz 1986;Jassim and Goff 2006). The volcanic inclusions are distrib-uted through the whole section of the unit. However, itshows conspicuous concentration towards the top of theunit.

The Chwarta section shows the occurrence of a massive ,whitish gray, fractured and sheared, and recrystallized bodylimestone of up to 40 m in dimension. These limestonesyield benthic foraminifera assemblages with different abun-dance including: Nummulites, Alveolinds, Orbitolites, Mio-gypsina, Lepidocyclina, Discocyclina, Milliolids, andTextularid assemblages (Al-Hashimi 1975; Surdashy 1997;Al-Banna and Al-Mutwali 2008).

Petrography and microfacies

Sandstones and limestones are selected for the petrographicstudy to define their compositional components and texture

in order to classify them and to evaluate type and origin ofthe dominant rock types of the Walash Group.

Sandstones

Sandstones of the Walash Group are of two basic types. Thedominant type is Litharenite. It is generally noticed in thelower and middle part of the lower unit. It ranges frommedium (Fig. 7a) to coarse grained (Fig. 7b) in size. Grainsare dominated by lithic fragment of carbonate (limestoneand dolostone), chert, and igneous origin (Fig. 7b and c).Igneous rock fragments are rich in volcanic fragments(Fig. 7b). Other secondary grains such as mudstone andmetamorphic rock fragments are less frequent (Fig. 7c).Quartz and feldspar are common especially in themedium- to fine-grained sandstones (Fig. 7a). Other lessfrequent grains are bioclasts and foraminifera. Grains areoften packed and likely to lack matrix especially in coarsegrain sandstone (Fig. 7a and b). Sorting for the medium-grained size is much better than in the coarse grained(Fig. 7a and b). This type of sand becomes replaced by thecalcarenite of the limestone beds upward the section (i.e.,Upper SedimentaryVolcanic Unit). The second sandstonetype is Calcarenite. This type is dominated by calcareousgrains of different sizes. It is generally of bioclastic originderived from shelf fauna especially forams (Fig. 7d). Mud-dy, occasionally fossiliferous intraclasts are also common.

Fig. 5 Stratigraphic sectionsand lithologic units of theWalash Group at the studiedlocalities of Sulaimani area

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Sometimes, large grains of dolostone are also recognized.Benthonic foraminifera of different species can also be seen(Fig. 7d). Micritic matrix disseminated in between grains inlow percentage. Other lithic grains occur in low percentageand include quartz, chert, and volcanic rock fragments.

Limestone

These beds are frequent in the upper part of the sectionespecially in the Upper SedimentaryVolcanic Unit(Fig. 5). They are usually thin (

Micropaleontology and biostratigraphy

The examined samples are rich in foraminifera (planktonicand benthonic) with moderate mode of preservation (Figs. 8and 9). The following species of planktonic foraminifera areidentified: Acaranina intermedia, Anomalinides sp., Subbo-tina eocaenica, Subbotina inaequispira, Subbotina velas-coensis, Subbotina sp., Parasubbotina sp. 1, Parasubbotina

sp. 2, Globonomalina ovalis, Globonomalina sp., Turborota-lia prolata, Turborotalia sp., Chilogumbelina trinitatensis,Chilogumbelina crinita, Chilogumbelina sp.

Identification is assisted by referring to internationalstudies of similar chronostratigraphic units such as: Silvaet al. (2003) and Luciani et al. (2007). The recognizedspecies of benthonic foraminifera are less abundant andinclude the following : Siphogenerinoides elongata,

A B

C D

E F

Fig. 7 a Medium sand-size litharenite, Lower Unit, Kinjurine section.b Coarse-grained litharenite of lower part of Lower Unit, Kinjurinesection. c Packed, coarse-grained litharenite, lower unit, Kinjurinesection. d Coarse-grained calcarenite, Lower Unit, Kinjurine section.

e Nummuliticbioclastic grainstone, Upper Unit, Kinjurine section. fMiloilidbioclastic grainstone. Bar is 0.5 mm. Q quartz, V volcanic RF,ch chert, C carbonate RF, F feldspar, M metamorphic RF, B bioclast, FForaminifera, I intraclast, N nummulite

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Fig. 8 ac Acaraninaintermedia (a ventral view, bdorsal view, c side view). df S.velascoensis (d ventral view, edorsal view, f side view). giParasubbotina pseudobulloides(g ventral view, h dorsal view, iside view). jl T. prolata (jventral view, k dorsal view,l side view)

Fig. 9 ac S. inaequispira (aventral view, b dorsal view, cside view). df A. intermedia (dventral view, e dorsal view, fside view). gh S. elongata. ijG. danica. kl C. trinitatensis.mn C. crinita

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Siphogenerinoides sp., A. intermedia, Anomalinides sp.,Cibicidoides alleni, Cibicidoides sp., Gavelinella danica,Gavelinella semitenes, and Gavelinella sp. The identifica-tion of these species and their age determination are inferredwith the help of reference to international studies such as:Kaiho et al. (1993), Ortiz (1995), and Alegret and Ortiz(2007).

Walash Group chronology is studied by different authorsfrom 1958 to 2008. The most recent one is the study by Al-Banna and Al-Mutwali (2008). They studied the microfaciesand age determination of Walash Group in Northeastern Iraqand gave the age as Lutitian stage of Middle Eocene by thespecies of planktonic Foraminifera dominated within thebiozones (P10P11) with absolute time ranging between42.5 and 48 MY. But Azizi et al. (2011) studied the mag-matic rocks along the Zagros Thrust Zone, northwest Iran,and assigned the age to Early Eocene with absolute timeranging between 54 and 36 M.

A biostratigraphic study was conducted of the studiedarea of the Walash formation which is rich in planktonicforaminifera and benthonic foraminifera based on the geo-logical range of the identified foraminifera. The biostrati-graphic studies of the Walash Group in Kinjurine sectionyielded planktonic Foraminifera assemblages of bad preser-vation which is affected by diagenesis processes. The bio-stratigraphic ranges of the identified species extended withinbiozone P5P9, which are, from bottom to top: A. esnaensis(part P5), S. inaequispira (P6), S. velascoensis (P7), Para-subbotina (P8), and Chilogumbelina (P9). This indicatesYpressian stage (Lower Early Eocene) with absolute timeranging between 54 and 48 MY. The benthonic Foraminif-era show similar ranges of biozones (P5P9) and thus con-form the assigned age (Fig. 10).

Discussion

The similarities of the sedimentological characters andlithologic association of both lithostratigraphic units ofthe Walash Group indicate a continuous section of adeep marine setting. The litharenite type, the occurrencegraded, parallel and cross bedding in these sandstones,its directional sole marks, and commonly sharp lowercontact indicate turbidite suites (Walker 1967). The lim-ited occurrence of the channel conglomerate suggests adistal location of the studied sections from the sedimentsource. The association of these sandstones with deepmarine foraminiferal shale indicates a flysch origin assuggested earlier by Al-Mehaidi (1975) and Buday(1975). The general replacement of the siliciclastic bedsof the lower part by calciturbidites upwards the sectionimply shallowing of depositional environment with timeand the increase of carbonate-producing shoal

communities. The only basic difference between thetwo units is the occurrences of volcanicity in the upperunit. Correlation of these two units with the tripartitefacies classification of the NaopordanWalash Series,suggested by Buday (1975), shows close similarities.The lower unit in the study area is quite similar to theouter purely clasticflysch-type facies. The upper uniton the other hand is well correlated with central faciesof Buday (1975) which is composed of flysch-typesediments with several volcanogenic inlayers. Heassigned this unit as the typical Naopordan unit. Histhird (innermost) and upper unit which is prevalentlyvolcanogenic is either missing or poorly represented inthe area. The latter, which is not reported in the Sulai-mani area, is assigned by Buday (1975) as the WalashGroup. Therefore, a revision of the stratigraphic nomen-clature of the Walash Group in the studied area isrequired to name the lower pure flysch-type unit by anew stratigraphic name and to rename the WalashGroup in the area as the Naopordan Formation.

The age of the Walash Group sediments using foraminif-era collected from the carbonate rocks of certain intervalfrom the studied area is previously determined by Al-Bannaand Al-Mutwali (2008) to be of Middle Eocene (Lutetian).However, the systematic biostratigraphic analysis of thisstudy for the Kinjurine section sediments using planktonicand benthonic foraminiferal biozones, supported by ben-thonic foraminifera assemblages range zones, shows closeresults of Early Eocene (Ypresian). The noticed slight dif-ference might be related to the analyzed parts of the studiedsection in the two studies.

Age determination of the volcanogenic rocks of theWalash Group in the study area shows wider and youngerrange of age. Koyi (2006) using the Ar40/Ar39 method forage determination for volcanic samples within the WalashGroup of the Mawat area shows age ranges from MiddleEocene to Early Oligocene (43323 Ma). These volcanicsare believed to represent arc volcanic suites (Jassim et al.1982; Aziz 1986). Their association with flysch basin in aconverging plate margin suggests development in a remnantoceanic basin developed in a fore-arc sedimentary setting(Al-Qayim et al. 2012). However, Ali (2012) in his regionalstudy of the WalashNaopordan Series of northeast Iraqshows that the volcanics of the series are developed in aback-arc basin with signatures of subduction setting.

Conclusions

Examination of the Walash Group rocks in three localitiesfrom Sulaimani area reveals important contributions to itsstratigraphic status. These are summarized below:

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1. Thickness variation of the group is common. It is relatedto the tectonic emplacement of the group and contributeto the complication of its facies architecture.

2. Two basic lithostratigraphic units are clearly recog-nized: the Lower Sedimentary Unit (volcanic free) andthe Upper Volcano-sedimentary unit.

3. Both consist of flysch sequence of cyclic alternationof litharenite to calcarenite sandstone, foraminiferalbioclastic limestone, and dominant marine shaleinterlayers. The sequence is contaminated in laterstages by volcanic activities which are increasedupwards.

Fig. 10 Biostratigraphic range chart of the Walash Group at Kinjurine Section

Arab J Geosci (2014) 7:181192 191

4. The occurrence of shallow marine carbonates upwardsthe section indicates overall shallowing of the basin.

5. The exceptionally recrystallized and sheared limestonebodies are shelf carbonates subjected to deformation dur-ing transportation and tectonic emplacement of the group.

6. Biostratigraphic analysis using planktonic foraminiferalzonation and benthonic foraminiferal assemblages pick-ed from shale interlayers show that the age of the groupat the studied area is of Lower Early Eocene (Ypresian).

Acknowledgments We would like to thank Dr. Azad Omer and Dr.Salim Hakari of the Department of Geology of Sulaimani Universityfor their assistance during field work. The help of Mr. Rob Wilson ofthe SEM Laboratory at the University of Leicester, UK, in SEMphotography of the foraminiferal specimens is sincerely appreciated.

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192 Arab J Geosci (2014) 7:181192

Contribution to the stratigraphy of the Walash Group, Sulaimani area, Kurdistan, IraqAbstractIntroductionMaterial and methodologyGeologic settingLithostratigraphy and sedimentologyLower sedimentary unitUpper sedimentaryvolcanic unit

Petrography and microfaciesSandstonesLimestone

Micropaleontology and biostratigraphyDiscussionConclusionsReferences