Transcript

Arab J Geosci (2014) 7:181–192

DOI 10.1007/s12517-012-0809-x

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 siliciclastic sediments with alkaline volcanics at the upper part. It
forms the lowermost thrust sheet of the Zagros Suture Zone.
Three localities around Sulaimani area of Kurdistan region
of north Iraq were chosen for sedimentological and stratigraphic review of this group. Examination includes field
measurements, description, and correlation, and petrographic and biostratigraphical analyses. The Walash Group sequence in the study area has variable thickness, with the
highest reaching 150 m, and generally consists of greenish
gray silty calcareous shale which alternates with thin- to
thick-bedded, coarse-grained sandstone and limestone.
Sandstone beds show sedimentological evidences of turbidite origin. Based on occurrences of volcanic admixtures,
the group is subdivided into two basic lithostratigraphic
units: lower sedimentary unit and upper sedimentary–volcanic unit. Petrographic analysis shows that the sandstones
include two basic types: lithicarenites which is dominated
by carbonate, quartz, chert, and volcanic rock fragments,
and calcarenite with bioclasts and benthic forams as the
main type of grains. Biostratigraphic analysis of the shale
interlayer samples near Kinjurine Village reveals the occurrence of both benthonic and planktonic foraminifera. Stratigraphic ranges of the identified planktonic foraminifera
show occurrence within the Paleogene biozones P5–P9
which indicate Ypresian age (Lower Early Eocene). Similar
age inferences were reached from benthic foraminiferal
assemblages. Based on correlation with other areas, the
study calls attention to a review of the stratigraphic status
of the group by renaming the upper part and introducing
new name for the lower part.
B. Al-Qayim (*) : I. Ghafor : R. Jaff
Department of Geology, Sulaimani University, Sulaimani,
Kurdistan, Iraq
e-mail: [email protected]

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 the
Zagros Suture Zone formerly known as the “Thrust Zone”
of northeast Iraq. The name is taken after measuring a type
section of the series at Walash village in the Rowanduz river
valley of northeastern Iraq. The name changed into the
“Walash Rock Group” when it appeared in the general
geologic map of Iraq (1/1,000,000 scale) of 1960. The group
in the type section area is composed of volcanic rocks
passing laterally into sedimentary rocks. The type section,
however, as compared to other localities, represents only
one relatively small part of the group (Buday 1980). A
compiled reference section based on unpublished reports
of the Geological Survey of Iraq (Bolton 1958; Smirnov
and Nelidov 1962; Polnikov- Nikolajev 1962) is constructed
by 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 Unit
Red mudstone with cherty siltstone and shales.
(b) Lower Volcanics Unit
Basic and less frequently acidic lava and pillow lava
which are associated with pyroclasts. Volcanics often occur
as volcanic cones which pass laterally into tuffaceous rocks
with radiolarite and white chemical limestone.
(c) Middle Red Beds Unit
Siliciclastic sequence passes laterally into tuffaceous
rocks. Sedimentary rock types include: red mudstone,
red and gray shales, sandstone, conglomerate, and
limestones.

Geologic setting Sulaimani area is located in the heart of the Zagros Orogenic belt which runs from SE Turkey to Oman.5 km to the northeast of Kani Manga (Fig. Examination of these rocks as a part of the Zagros Suture Zone would contribute to the integrated evolution of the Zagros orogeny (Fig. The second section is located to the north of Bardazard about 3 km to the north of Chwarta. He believed that this flysch unit belongs to the Naopurdan Group. The reason for that is the occurrence of the associated recrystallized sheared and fossiliferous limestone. which is associated with red shale. and microfossil assemblages of the Walash Group at the Sulaimani area in order to determine its stratigraphic status and age. Arab J Geosci (2014) 7:181–192 Material and methodology Three localities in Sulaimani area with Walash Group outcrops were visited and examined for different stratigraphic characters.500 m near Chia-Sefid-Darband of Rowanduz area (Bolton 1958. due to the tectonic complication of the area. The purpose of this study is to investigate the sedimentological characters. Marly shale and calcareous shale samples were selected from Kinjurine sections for biostratigraphic analysis. 30 samples of sandstone and limestone were thin sectioned for petrographic analysis. At the Sulaimani area. and associated sediments. Dunham (1962). Several samples were treated with Alizarin Red-S stains to differentiate different carbonate minerals following Dickson (1966). Dried residues were then size sorted through sieves from 500 down to 63 μm. after particular treatment. Detailed stratigraphic section is measured focusing on lithologic variations and facies associations. However. This locality is taken as a master section for the study for its complete and well exposed strata. (1973) and for carbonates. Classification nomenclatures for sandstones followed Pettijohn et al.182 (d) Upper Volcanics Unit It is composed mainly of basalt and andesitic flows. The tectonic evolution of this belt resulted from a long convergence history between the Arabian Plate from one side and the Iranian block of Sanandaj–Sirjan from the other side (Beydoun 1991). specifically the Mawat region. It passes laterally into a flysch unit with nummulitic limestone. about 1 km to the northwest of Kinjurine (Fig. 2). 2). the measured thickness of about 1. and conglomerate. Disaggregated sediments were washed thoroughly through a 63-μm sieve. medium to thick bedded. Similar results (M. Al-Banna and Al-Mutwali 2008). the group is examined in detail for the first time by Al-Mehaidi (1975). About 200–300 g of each soft sample was dried out and processed by a repeated freezing and thawing method until the sediments disaggregated in a supersaturated solution of sodium sulfate. which is similar to a middle limestone unit recognized in the type locality of the Naopordan Group (Bolton 1958). The age of these Nummulite assemblages is determined by Al-Hashimi (1975) as Lower to Middle Eocene. and brown–red mudstone and greywacke sandstone higher up. The first is selected along an unpaved road to the serpentinite quarry. 1). Petrographic examination includes type and abundance of major components as well as textural characters. p. (e) Upper Red Beds Unit Red mudstone and conglomerate near the base. Large benthic forams collected from the limestones of the Walash Group (Nummulites and Alveolina) indicate that the age of this unit is generally Paleogene (Buday 1980). pyroclastics. sandy limestone. conglomerate. It is rich in Nummulites and other benthonic foraminifera (Al-Mehaidi 1975). Eocene) using planktonic foraminiferal assemblages from the group were assigned by Al-Banna and Al-Mutwali (2008). Volcanic cones also occur and pass laterally into marine sequence with limestone. The third locality is an incomplete section of the group situated along the road to Penjwin about 1. Systematic sampling was conducted for the sandstones. and red limestone. The flysch unit shows rhythmic alteration of gray silty shale. The depositional environment of these limestones is believed to represent an outer shelf to slope margin (Surdashy 1997. the residues were separated by filtration and dried overnight. and lava flows of basic to intermediate composition. The group consists of an unmetamorphosed complex sequence of volcanic rocks of tuff. 106). and of bioclastic calcarenites. basaltic rocks. facies type. This tectonic history yield a NW–SE trending suture zone of Tethyan components and adjacent folded belt. UK. Foraminifera were cross examined and photographed by using S520 Hitachi Scanning Electron Microscope at Leicester University. greywacke. The thickness of the group is highly variable and reaches 3. To evaluate type and origin of the dominant rock types of the Walash Group. At the type locality. The Walash Group is part of the Zagros Suture Zone which consists of overthrusted sheets of Tethyan accretionary prism developed in two . The limestone unit is gray in color. Foraminifera were picked from the residue in the 63–200-μm-size fractions and examined under a binocular microscope. it is possible that the high thickness of the group might be the result of repetition due to multiple thrusting with the group.000 m made Buday (1980) believe that the type locality represents a relatively small part of the sequence. and limestone for petrographic analysis. greywacke.

The early stacking is related to the Coniacian–Campanian ophiolite–radiolarite obduction and includes: the Qulqula Group. 1 General physiographic map of northeast Iraq showing location of the study area different stacking episodes (Al-Qayim et al. the Triassic platform carbonate (Avroman Limestone Formation). 2012). (1) Kinjurine. 2 General geologic map of the study area showing location of the studied sections.Arab J Geosci (2014) 7:181–192 183 Fig. The second and succeeding stacking is related to the accretionary prism of the remnant Fig. (Geology after Maa´la 2008) . and (3) Penjwin section. (2) Chwarta.

The group is generally overlain by a serpentinite horizon of variable thickness. ZFF Zagros Foredeep Fault Arab J Geosci (2014) 7:181–192 of the Folded Zone into the High Folded Zone and the Low Folded Zone. To the southwest of the Zagros Suture Zone. It is recognized by a linear valley. often covered by recent sediments and hard to trace. 1). B Zagros Suture Zone. The outcrop of the Walash Group usually forms a narrow belt swing around the ophiolite complexes as the case in Mawat and Penjwin areas (Fig. C Zagros Imbricate Zone. HZRF High Zagros Reverse Fault. the fold belt evolved during the final collision and accompanying shortening and deformation of the foreland sequence. The folding intensity decreases southwestward leading to segmentation Fig. 2012). it always forms a low-relief area in front of the ophiolite masses. Emplacement of these masses overlay the foreland sequence which was developed over the Arabian plate margin during the Late Cretaceous and due to the ophiolite–radiolarite obduction (Al-Qayim 2012). ZMFF Zagros Mountain Front Fault. Their composition is found to be of basic dykes of spilitic diabase. MZRF Main Zagros Reverse Fault. The lower boundary of the Walash Group is tectonic and usually covered by . 2012).184 Tethyan ocean and includes the volcano-sedimentary sequence of the Walash–Naopordan Series. The volcanicity of the Walash Group in the study area is of limited distribution. the proper sequence of the foreland basin (i. Conglomerate lenses and limestone are subsidiary. The emplacement of this package is associated with Mid-Miocene continental collision of the Arabian plate with the Sanandaj-Sirjan Block (Al-Qayim et al. spilitic basalt.e.. and intermediate volcanic of pyroxene andesite. It separates the soft olive gray clastic sediments of the Walash from the underlying red siliciclastic sediments of the Suwais Red beds (Fig. The separating boundary is a master fault line known as the Zagros Mountain Front Fault. It is usually noticed as small size sills or pyroclasts of different sizes. Shiranish– Tanjero–Aqra formations) is exposed successively below the Suwais Red Beds. and altered andesite (Aziz 1986. The section generally consists of cyclic alternation of sandstone and olive gray silty shale. and ophiolite masses (Mawat and Penjwin complexes). The Red Beds Series bottom the Walash Group immediately as it forms the Paleogene coastal sediments of the foreland basin (Al-Qayim 2000. The Walash sheet always bottoms the ophiolite masses with a tectonic boundary zone marked by the occurrence of serpentinite horizon. ZTF Zagros Thrust Front. The Zagros Suture Zone is bounded from the northeast by a regional reverse fault known as the “Main Zagros Reverse Fault” (Fig. 2012). and due to the soft sediment of the group. 1996. It runs in the study area as a tectonic contact between the Walash Group and the Suwais Red Beds (Al-Qayim et al. Jassim and Buday 2006). 2012). 3). 3) and from the southwest by a segmented fault line called the “Zagros Thrust Front” (AlQayim et al. 2007). Further southwest. Karim et al. spilites. pyroxeneamphibole andesite. tectonic boundaries nomenclature after Al-Qayim et al. D High Folded Zone. E Low Folded Zone. 3 Major tectonic subdivision of NE Iraq and their boundaries overlie the general tectonic map of Iraq (tectonic map after Al-Kadhimi et al. A Shalair Zone. F Mesopotamian Zone.

as usual. The volcanic rocks are variable . occasionally sheared. 4 a Highly sheared and deformed (arrows) shale and sandstone of the Walash Group. 6b). Upper sedimentary–volcanic unit C Fig. 6a). silty. The total thickness of the section at Kinjurine reaches 110 m with the upper sharp contact with the serpentinite horizon seemingly as thrust boundary (Fig. The upper boundary at this locality is sharp and tectonic with the thick serpentinite horizon (Fig. 4c). c Irregular tectonic upper boundary of Walash Group with the overlaying serpentinite horizon. Kinjurine section. respectively. thin (5–10 cm) to thick (up to 80 cm) sandstones beds with greenish gray. The sandstone beds become thicker and more frequent upward the unit. The lower boundary with the Suwais Red Beds Series is assumably tectonic and. 6c). In other cases. 6e). however. Kinjurine section. sliding. only 20 m of the Walash Group is exposed. Below is the description of these units in the study area. 4b). The group displays different shearing and deformation features which appear as local foliation. and calcareous to marly shale interlayers (Fig. The lower contact with Suwais Red Beds is sharp but obscured by the valley and its recent sediment running at the boundary zone. and its upper boundary is often gradational to the shale interlayer (Fig. 6d). Based on the lithologic variations and association with volcanic rocks. Sandstone beds are medium to coarse grained and often display graded bedding and occasional cross and or parallel bedding (Fig. 4a). 4c). Upper Unit. 5). Lithostratigraphy and sedimentology Due to the tectonic emplacement of the Walash Group. Their lower boundary is sharp. thickness is quite variable as a result of thrusting and internal faulting. b Sharp and striated thrust boundary between Walash sediments and the serpentinite horizon. fissile. multiple faulting. Other beds which are infrequently recognized include lenses of conglomerate and thin limestone beds. The shale part displays shearing and even foliation especially in the upper part (Fig. hard. as well as flowage structures (Fig.Arab J Geosci (2014) 7:181–192 recent sediments due to the soft sediments of both units. imbrications. whereas the lower boundary with the Suwais Red Beds is hidden under a thick cover of recent sediments (Fig. A lower sedimentary unit which lacks any obvious volcanicity and an upper unit which consists of a similar sedimentary sequence but with conspicuous volcanic rock association. These are specially noticed at Kinjurine section. It reaches 140 m. the Walash Group can be subdivided into two basic lithostratigraphic units. It is generally characterized by cyclic alternation of buff to gray. At Penjwin. The sandstone beds. These shale interlayers can exceed 5 m in thickness and yield benthonic and planktonic foraminifera. medium and graded-bedded sandstones display amalgamation which makes them appear as thick-bedded units (Fig. The sedimentary sequence is almost the same as in the lower unit. are often thicker and denser. and only 20 m of this unit is exposed at Penjwin section and occurs immediately below the serpentinite horizon (Fig. folding. hard to depict due to the soft sediment on both sides of the contact. Lower sedimentary unit The Lower Unit is generally a sedimentary sequence of 80 m thick at Kinjurine and 40 m at Chwarta area. The uppermost unit is characterized by a large volcanic body where no serpentinite is recognized. The basic character of this part is the association with different forms of volcanic material. Calcarenite sandstones become thin fossiliferous limestone beds with components of shallow marine environment. Penjwin section This unit is only appearing in the Kinjurine and Chwarta sections with thickness ranging between 80 and 40 m. This thickness variation is reflected on the local preservation of lithofacies and sedimentological characters of the cropped-out Walash group sections. A B 185 The thickness of the group is slightly higher at Chwarta area.

Igneous rock fragments are rich in volcanic fragments (Fig. 7a) to coarse grained (Fig. and altered andesite (Al-Mehaidi 1975. 7b and c). and recrystallized body limestone of up to 40 m in dimension. occasionally fossiliferous intraclasts are also common. Al-Banna and Al-Mutwali 2008). Discocyclina. Alveolinds. 7a and b). Other less frequent grains are bioclasts and foraminifera. 6e and f). Aziz 1986. 7b) in size. Orbitolites. Miogypsina. These are ranging in forms from tuffs. chert. and intermediate volcanic of pyroxene andesite. It ranges from medium (Fig. However. The dominant type is Litharenite. lapillis. spilite. and dykes. These limestones yield benthic foraminifera assemblages with different abundance including: Nummulites. pyroclasts .to fine-grained sandstones (Fig. Milliolids. This type of sand becomes replaced by the calcarenite of the limestone beds upward the section (i. Petrography and microfacies Sandstones and limestones are selected for the petrographic study to define their compositional components and texture in order to classify them and to evaluate type and origin of the dominant rock types of the Walash Group. Other secondary grains such as mudstone and metamorphic rock fragments are less frequent (Fig.. 7a and b). 7b). 7d). It is generally of bioclastic origin derived from shelf fauna especially forams (Fig. Sorting for the mediumgrained size is much better than in the coarse grained (Fig. Grains are often packed and likely to lack matrix especially in coarse grain sandstone (Fig. reddish brown and light gray softer rocks (Fig. The Chwarta section shows the occurrence of a massive . 7a). The volcanic inclusions are distributed through the whole section of the unit. This type is dominated by calcareous grains of different sizes. Jassim and Goff 2006). and pyroxene-bearing spilitic basalt. It is generally noticed in the lower and middle part of the lower unit. Lepidocyclina. 5 Stratigraphic sections and lithologic units of the Walash Group at the studied localities of Sulaimani area in size and origin.e. Sandstones Sandstones of the Walash Group are of two basic types. it shows conspicuous concentration towards the top of the unit. The second sandstone type is Calcarenite. fractured and sheared. Upper Sedimentary–Volcanic Unit). Quartz and feldspar are common especially in the medium. . whitish gray. Petrographic examination of these units shows that these volcanics are classified into basic and intermediate dykes. Grains are dominated by lithic fragment of carbonate (limestone and dolostone). Muddy. lava flows of spilitic diabase. irregular sills. and igneous origin (Fig. pyroxene-amphibole andesite.186 Arab J Geosci (2014) 7:181–192 Fig. 7c). and Textularid assemblages (Al-Hashimi 1975. Surdashy 1997. These bodies were weathered to pinkish.

7e and f). miliolids are common (Fig. Non-carbonate grains include quartz. Petrographic components are basically bioclasts and foraminifera. b Laminated medium-bedded sandstone with gradational upper boundary with overlying fissil shale.Arab J Geosci (2014) 7:181–192 187 A B C D E F Fig. Benthic forams include . chert. Benthonic foraminifera of different species can also be seen (Fig. and volcanic rock fragments. d Amalgamated graded sandstone beds forming thick horizon. 7e). They are usually thin (<30 cm). f Variable forms of pyroclasts (V) in sandstone and shale of the upper unit of Chwarta section Sometimes. Other lithic grains occur in low percentage and include quartz. Kinjurine Section. Association with deep marine shale and turbidite sandstone imply that these beds could be a type of calciturbidite derived from carbonate-punctuated sandy shelf. Lower Unit at Kinjurine section. whole Nummulite. Other non-skeletal grains are intraclasts of micritic limestone and/or dolostone (Fig. Discocyclina. and volcanic fragments (Fig. All components of these limestone indicate shallow marine environment with silicicalstic admixture. 6 a Cyclic alternation of thick-bedded sandstone with gray calcareous marine shale of the Lower Unit at Kinjurine section. Micritic matrix disseminated in between grains in low percentage. In other cases. chert. 5). e Sheared and foliated shale (sh) and deformed sandstone (ss) with brown color sill (v) of the upper unit of Kinjurine section. grain supported (grainstone) with micritic matrix is nil. 7f). and sometimes sandy or marly. Lepidocyclina. Limestone These beds are frequent in the upper part of the section especially in the Upper Sedimentary–Volcanic Unit (Fig. 7e). large grains of dolostone are also recognized. and Miogypsina (Fig. The rest of the groundmass is made of debris and fragments of these and other bioclasts. massive. 7d). c Graded bed of sandstone of Lower Unit at Kinjurine section. Texture is packed.

lower unit. e Nummulitic–bioclastic grainstone. Chilogumbelina sp. ch chert. coarse-grained litharenite. The recognized species of benthonic foraminifera are less abundant and include the following : Siphogenerinoides elongata.5 mm. Kinjurine section. Globonomalina sp. Lower Unit. The following species of planktonic foraminifera are identified: Acaranina intermedia. Kinjurine section. M metamorphic RF... f Miloilid–bioclastic grainstone.. Q quartz. Lower Unit. (2007). Kinjurine section. Anomalinides sp. Turborotalia prolata. F feldspar. N nummulite Micropaleontology and biostratigraphy sp. F Foraminifera. (2003) and Luciani et al. c Packed.188 Arab J Geosci (2014) 7:181–192 A B C D E F Fig. Kinjurine section. Turborotalia sp. Subbotina inaequispira. 7 a Medium sand-size litharenite. Subbotina eocaenica. Parasubbotina sp. The examined samples are rich in foraminifera (planktonic and benthonic) with moderate mode of preservation (Figs. Chilogumbelina trinitatensis. Parasubbotina . B bioclast. V volcanic RF. 1. Globonomalina ovalis. C carbonate RF. Kinjurine section. Identification is assisted by referring to international studies of similar chronostratigraphic units such as: Silva et al. Subbotina velascoensis. b Coarse-grained litharenite of lower part of Lower Unit.. I intraclast. Upper Unit. d Coarse-grained calcarenite. Chilogumbelina crinita. Bar is 0. Subbotina sp. 8 and 9). 2.

elongata. f side view). k dorsal view. h dorsal view. c side view). b dorsal view. d–f S. c side view). prolata (j ventral view. g–i Parasubbotina pseudobulloides (g ventral view. j–l T. l side view) Fig. velascoensis (d ventral view. g–h S. trinitatensis. m–n C. crinita 189 . intermedia (d ventral view. f side view). i side view). 8 a–c Acaranina intermedia (a ventral view. d–f A. k–l C.Arab J Geosci (2014) 7:181–192 Fig. 9 a–c S. inaequispira (a ventral view. e dorsal view. b dorsal view. i–j G. danica. e dorsal view.

. The only basic difference between the two units is the occurrences of volcanicity in the upper unit. supported by benthonic foraminifera assemblages range zones. which are. The identification of these species and their age determination are inferred with the help of reference to international studies such as: Kaiho et al. The biostratigraphic ranges of the identified species extended within biozone P5–P9. is assigned by Buday (1975) as the Walash Group. inaequispira (P6). Their association with flysch basin in a converging plate margin suggests development in a remnant oceanic basin developed in a fore-arc sedimentary setting (Al-Qayim et al. Discussion The similarities of the sedimentological characters and lithologic association of both lithostratigraphic units of the Walash Group indicate a continuous section of a deep marine setting. However. velascoensis (P7). Gavelinella semitenes. The biostratigraphic studies of the Walash Group in Kinjurine section yielded planktonic Foraminifera assemblages of bad preservation which is affected by diagenesis processes. Koyi (2006) using the Ar40/Ar39 method for age determination for volcanic samples within the Walash Group of the Mawat area shows age ranges from Middle Eocene to Early Oligocene (43–32±3 Ma). The limited occurrence of the channel conglomerate suggests a distal location of the studied sections from the sediment source. However. He assigned this unit as the typical Naopordan unit. the occurrence graded. Parasubbotina (P8). intermedia. shows close similarities. a revision of the stratigraphic nomenclature of the Walash Group in the studied area is required to name the lower pure flysch-type unit by a new stratigraphic name and to rename the Walash Group in the area as the Naopordan Formation. These volcanics are believed to represent arc volcanic suites (Jassim et al. shows close results of Early Eocene (Ypresian). 10). Conclusions Examination of the Walash Group rocks in three localities from Sulaimani area reveals important contributions to its stratigraphic status. parallel and cross bedding in these sandstones. Therefore.190 Siphogenerinoides sp. S. esnaensis (part P5). S. The association of these sandstones with deep marine foraminiferal shale indicates a flysch origin as suggested earlier by Al-Mehaidi (1975) and Buday (1975). Correlation of these two units with the tripartite facies classification of the Naopordan–Walash Series. The most recent one is the study by AlBanna and Al-Mutwali (2008). The latter.5 and 48 MY. Cibicidoides alleni. A. and commonly sharp lower contact indicate turbidite suites (Walker 1967). His third (innermost) and upper unit which is prevalently volcanogenic is either missing or poorly represented in the area. Aziz 1986). The benthonic Foraminifera show similar ranges of biozones (P5–P9) and thus conform the assigned age (Fig. (2011) studied the magmatic rocks along the Zagros Thrust Zone. This indicates Ypressian stage (Lower Early Eocene) with absolute time ranging between 54 and 48 MY. The age of the Walash Group sediments using foraminifera collected from the carbonate rocks of certain interval from the studied area is previously determined by Al-Banna and Al-Mutwali (2008) to be of Middle Eocene (Lutetian). Ortiz (1995). These are summarized below: . northwest Iran. (1993). which is not reported in the Sulaimani area. and assigned the age to Early Eocene with absolute time ranging between 54 and 36 M. Gavelinella danica. A biostratigraphic study was conducted of the studied area of the Walash formation which is rich in planktonic foraminifera and benthonic foraminifera based on the geological range of the identified foraminifera. its directional sole marks.. and Alegret and Ortiz (2007). The upper unit on the other hand is well correlated with central facies of Buday (1975) which is composed of flysch-type sediments with several volcanogenic inlayers. Ali (2012) in his regional study of the Walash–Naopordan Series of northeast Iraq shows that the volcanics of the series are developed in a back-arc basin with signatures of subduction setting. Age determination of the volcanogenic rocks of the Walash Group in the study area shows wider and younger range of age. suggested by Buday (1975). Walash Group chronology is studied by different authors from 1958 to 2008. Cibicidoides sp. The general replacement of the siliciclastic beds of the lower part by calciturbidites upwards the section imply shallowing of depositional environment with time and the increase of carbonate-producing shoal Arab J Geosci (2014) 7:181–192 communities. The lower unit in the study area is quite similar to the outer purely clastic–flysch-type facies. The litharenite type. Anomalinides sp. 1982. They studied the microfacies and age determination of Walash Group in Northeastern Iraq and gave the age as Lutitian stage of Middle Eocene by the species of planktonic Foraminifera dominated within the biozones (P10–P11) with absolute time ranging between 42. and Gavelinella sp. from bottom to top: A. The noticed slight difference might be related to the analyzed parts of the studied section in the two studies. 2012). and Chilogumbelina (P9).. But Azizi et al. the systematic biostratigraphic analysis of this study for the Kinjurine section sediments using planktonic and benthonic foraminiferal biozones.

foraminiferal– bioclastic limestone. 3. and dominant marine shale interlayers. 10 Biostratigraphic range chart of the Walash Group at Kinjurine Section 1. The sequence is contaminated in later stages by volcanic activities which are increased upwards.Arab J Geosci (2014) 7:181–192 191 Fig. Both consist of flysch sequence of cyclic alternation of litharenite to calcarenite sandstone. 2. Thickness variation of the group is common. Two basic lithostratigraphic units are clearly recognized: the Lower Sedimentary Unit (volcanic free) and the Upper Volcano-sedimentary unit. . It is related to the tectonic emplacement of the group and contribute to the complication of its facies architecture.

The exceptionally recrystallized and sheared limestone bodies are shelf carbonates subjected to deformation during transportation and tectonic emplacement of the group. Koyi H (2012) Tectonostratigraphic overview of the Zagros suture zone. Northeast Iraq. J Mar Micropaleontol 23:51–86 Karim K. Waldhausrova J. p 32. Al-Kadhimi JAM.000 sheet K5. 1. GeoArabia 17:109–156 Aziz NR (1986) Petrochemistry. Surv. PhD thesis. NE Iraq. Rob Wilson of the SEM Laboratory at the University of Leicester. p37 Silva I. NE Iraq. Potter P. J Sediment Res 36:491–505 Dunham RJ (1962) Classification of carbonate rocks according to depositional texture. Goff T (2006) Phanerozoic development of the northern Arabian Plate. Baghdad. Dolin. J Geol Soc Iraq Spec Issue. 1. Ltd. Turkey. Abstract with program Al-Qayim B. Unpub.Penjwin area. petrogenesis and isotope dating of Walash volcanic rocks at Mawat-Chowarta area. 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