Palynological Study of Ora and the Upper Part of Kaista Formation in Zakho area, Iraqi Kurdistan Region

Palynological investigations of Ora Formation and the upper part of Kaista Formation (Late Devonian – Early Carboniferous) in the Northern Thrust Zone were conducted in Kiasta exposures about 2km away to the north west of Kaista village Zakho District, Northern Iraq. The upper part of Kaista Formation is mainly composed of dolomitic limestone interbedded in the lower part with black shale, fine sandstone, and sometimes with lime mudstone, but in the upper part the facies is dominantly fossiliferous limestone. Ora Formation is composed of black shale and silty shales interbedded with siltstones and thin fossiliferous limestone. Based on available organic matter, ( phytoclasts, amorphous organic matters, and palynomorphs). Kaista section divided into five different palynofacies (PF1, PF2, PF3, PF4 and PF5). The detailed palynological study in Kaista section, having both Ora and Kaista Formations, enabled their division into five palynozones (P.Z1, P.Z2, P.Z3, P.Z4 and P.Z5). The basic index for this division is the miospores studied in the sum of 15 samples. The palynological analysis has confirmed the previously determined age of the studied formations, as (Late Devonian – Early Carboniferous) for the Kaista Formation and Early (StrunianLate Tournaisian) for Ora Formation. The palynomorphs and the organic matters indicate that the depositional environment of Ora Formation is shallow marine to near shore. However, the depositional environment of the Kaista Formation was not established owing to scarcity of diagnostic palynomorphs. Introduction The studied formations are the upper part of Kaista Formation and all Ora Formation. Both formations crop out in the Northern Thrust Zone, very close to the Iraqi – Turkish boarder. The Kaista Formation was first introduced by Wetzel and Morton (1952) in Bellen et. al., (1959) in the Northern Thrust Zone region of Iraq to be of Late Devonian (Famennian) age, whereas the Ora Formation was first introduced by Wetzel (1952) in Bellen et. al. (1959) from the same area to be of Early Carboniferous or Late Devonian – Early Carboniferous. There are only few studies on the Scientific Studies , vol.5, No.1,2010 – Journal of Kirkuk University 51 Paleozoic sequence in this area. The most important studies are Hasson, (1999),Al-Lami(1998) and Baban(1996). AlLami (1998) conducted a palynology study of the interval 1295-1394 m. in Akkas-1 borehole which is nearly coincident with the entire Ora Formation. He gave late Devonian age to the studied section in his study. AlHasson (1999) studied the palynomorphs of the Late Devonian – Early carboniferous in Khleisia wel1. She gave Late Devonian-Early Carboniferous age for the studied section Fig.1. The Kaista section is about 2 kilometers northwest of Kaista village (Latitude 37 o 17' 45" and Longitude 43 o 10' 00"), in the core of Chia Zinnar fold where Paleozoic formations are successively well exposed. The area of the Kaista section(studied area) Fig.1 is affected by several faults which led to some distortion of the stratigraphic section to some interruption and repetition of strata. However, impact of faulting is much greater. Aim of the study The main aims are to check the content of different types of palynomorphs and organic matters, then making use for dating and comparison with their equivalent units in other places in the world in order to determine the palynofacies, the real age, and environment of deposition of the studied formations. Geological setting The studied area is part of the Northern Thrust Zone of Buday (1980) which corresponds to the Zone of Imbrications of the foreland basin of Numan (2000). The structural pattern of the Thrust Zone is characterized by relatively long east – west trending anticlinorium with three dome shaped culminations, where the oldest Paleozoic rocks are cropping out. The southern limbs of the anticlinorium are the steeper ones; the northern flanks are less disrupted by faults. The main movement that took place at that time is Caledonian – Hercynian movement (Buday,1980). The age proposed by the original authors for the Kaista Formation was Late Devonian (Famennian). Other researchers favored Late Devonian – Early Carboniferous (Gaddo & Parker, 1959; Ditmar, 1971). The age of the Ora Formation was proposed by the original author as Early Carboniferous or Late Devonian – Early Carboniferous (Wetzel, 1952, in Bellen et al., 1959). This was later disputed by Hasson (1999) on the basis of palynological evidence and Late Devonian – Early Carboniferous age was proposed. The Kaista Formation overlies the Scientific Studies , vol.5, No.1,2010 – Journal of Kirkuk University 52 Pirispiki Formation with disconformable contact and underlies the Ora Formation with conformable and gradational contact (Bellen et al., 1959). Near the latter contact, the carbonate rock decrease with increase of clastic rock toward the Ora Formation, with few interbedding of limestone with shale near the contact. The Ora Formation is overlain by Harur Formation with conformable and gradational contact. Near this contact the thickness of carbonate rock increases with decrease of shale towards the contact with Harur Formation.


Introduction
The studied formations are the upper part of Kaista Formation and all Ora Formation. Both formations crop out in the Northern Thrust Zone, very close to the Iraqi -Turkish boarder. The Kaista Formation was first introduced by Wetzel and Morton (1952) in Bellen et. al., (1959) in the Northern Thrust Zone region of Iraq to be of Late Devonian (Famennian) age, whereas the Ora Formation was first introduced by Wetzel (1952) in Bellen et. al. (1959) from the same area to be of Early Carboniferous or Late Devonian -Early Carboniferous. There are only few studies on the

Aim of the study
The main aims are to check the content of different types of palynomorphs and organic matters, then making use for dating and comparison with their equivalent units in other places in the world in order to determine the palynofacies, the real age, and environment of deposition of the studied formations.

Geological setting
The studied area is part of the Northern Thrust Zone of Buday (1980) which corresponds to the Zone of Imbrications of the foreland basin of Numan (2000). The structural pattern of the Thrust Zone is characterized by relatively long eastwest trending anticlinorium with three dome shaped culminations, where the oldest Paleozoic rocks are cropping out. The southern limbs of the anticlinorium are the steeper ones; the northern flanks are less disrupted by faults. The main movement that took place at that time is Caledonian -Hercynian movement (Buday,1980). The age proposed by the original authors for the Kaista Formation was Late Devonian (Famennian). Other researchers favored Late Devonian -Early Carboniferous (Gaddo & Parker, 1959;Ditmar, 1971).
The age of the Ora Formation was proposed by the original author as Early Carboniferous or Late Devonian -Early Carboniferous (Wetzel, 1952, in Bellen et al., 1959. This was later disputed by Hasson (1999) on the basis of palynological evidence and Late Devonian -Early Carboniferous age was proposed. The Kaista Formation overlies the Pirispiki Formation with disconformable contact and underlies the Ora Formation with conformable and gradational contact (Bellen et al., 1959). Near the latter contact, the carbonate rock decrease with increase of clastic rock toward the Ora Formation, with few interbedding of limestone with shale near the contact. The Ora Formation is overlain by Harur Formation with conformable and gradational contact. Near this contact the thickness of carbonate rock increases with decrease of shale towards the contact with Harur Formation.

Methodology
Palynological analysis was carried out on 15 samples taken from kiasta section Fig.2. The usual procedure of the preparation of sample was followed (Traverse, 1988).

Palynostratigraphy
Fifteen samples were studied palynologically for both formation, one sample for Kaista Formation, and fourteen for Ora Formations, this is due to rareness of palynomorphs in Kaista Formation if compared with Ora Formation, and only two species were observed in Kaista Formation during this study. A total of 88 miospore species belongs to 40 genera and some acritarch species were identified. The distribution of spores was established by making the range of stratigraphic important species as given in the range chart Fig.2. The range chart shows the following miospore assemblage palynozones Fig.2: -Palynozone 1 (P .Z1): This assemblage palynozone is represented in the present study by samples (Kk6, KkOr1). This palynozone is equivalent to the (LL) palynozone of Higgs et al. (1988) (Fig. 3). This palynozone is characterized by an association species in the bottom of this palynozone such as, Retispora lepidophyta, Apiculiretusispora multiseta, A.  Clayton et al. (1978), and to the (LE) palynozone of Higgs et al. (1988) Fig.3. The base of the palynozone is characterized in the bottom by Hymenozonotriletes explanatus, with several taxa that make their first appearance within this palynozone such as, Ancyrospora furcula, Aurospora cf. asperella, Azonomonoletes sp., Cymbosporites cyathus, Cymbosporites sp. cf. magnificus, Dictyotriletes reticosus, Endoculespora setacea, Leiotriletes platyrugosus, Lophozontriletes proscurrus, Spelaeotriletes gigantus. Species such as Cymbosporites magnificus, Retusotriletes crassus, ranged down in this study from younger palynozone into the PZ 2 , together with the most of the diagnosis species of the preceding P.Z1 palynozone, (Fig 2).This palynozone is ends with the first appearance of (Corbulispora vimineus, Dictyotriletes (KOr14s 1 , KOr15s 1 ). This palynozone is equivalent to the VI, HD and BP Palynozone of Higgs et al. (1988), (Fig. 3). This zone is characterized by disappearance of Retispora lepidophyta a world wide marker species for latest Devonian (Upper Strunian), which is extending in LL to LN palynozone of Higgs et al. (1988). McGregor and McCutheon (1988) stated that Retispora lepidophyta is a worldwide marker species for the latest Devonian (Strunian). This zone is characterized along most palynozones some of those species are diagnostic species for the (P. Z 4 ) zone such as Vallatisporites vallatus, Densosporites variomarginatus, Spelaeotriletes obstrusus. Higgs et al. (1988), placed the first occurrence of Vallatisporites vallatus at the base of the BP zone, or ranged below (VI) palynozone after Higgs et al. (1988). This zone is characterized by the disappearance of species in the base of this zone, such as, Verrucasisporites irrgularis, Corbulisporites vimineus, Camarazonotriletes sextantii, Brochotriletes diversifoventus, Radiizonate geniunus. The top of this zone is characterized by the disappearance of Lophotriletes lebediansis, Spelaeotriletes triangulatus, with continue of ranges of many species in the preceding and younger zone. Age of (P.Z4) -The age of this palynozone extends from Devonian -Carboniferous boundary (Upper -Lower Tournaisian) to Middle Tournaisian, within the Courceyan stage. -Palynozone 5 (P.Z5): The P.Z 5 assemblage palynozone is represented in this study by the samples, (KOr15s 2 , KOr16s 1 , & Or-Hr.contact). This palynozone is equivalent to (PC) palynozone after Higgs et al. (1988), (Fig.  3). Many of the taxa from the preceding palynozones are common element of this zone (P.Z5); these taxa are ranged along this palynozone, which is the final palynozone of the present study. These taxa are, Vallatisporites vallatus, V. verrucosus, Densosporites sptibergensis, Retusotriletes minutus, Spelaeotriletes owensii, Prolycospora rugulosa, Aratrisporites saharaensis, Spelaeotriletes balteatus, Aurorospora solisortus, Vallatisporites agadesi. (Fig.2). Age of (P. Z5) -The age of this zone is Upper-Middle Tournaisian -Upper Tournaisian.

Palynofacies
The term palynofacies was first introduced by Combaz (1964), to indicate the total assemblage of particulate organic matter contained in the sediment after the removal of the sediment matrix, by the standard techniques of palynological separation. Palynofacies used as a good tools for concluding paleoenvironment, sea level fluctuations and palaeoclimate in Naqishbandi (1999). The main studied components are spores, acritarchs and sedimentary organic matters. Acritarchs was not used in establishing the palynofacies, due to their scarcity, whilst spores and sedimentary organic matters are common enough to be used as good indicators for this purpose. The main organic matters in the present study are the followings. Fig. 4. 1-Palynomorphs -This type of organic matter, include phytoplankton group, freshwater algal colonies and some types of bacteria. Commonly palynomorphs are spores, pollen grains, dinoflagellates and acritarchs 2-Phytoclasts -Those particles are originally fragments of plants, sometimes called "phytoclasts", or they are biostructures of Gymnosperm trachieds .Marsan and Pocock (1981) devised a classification for phytoclasts based largely on botanical and coal petrologic of particulate palynodebris. Increasing of these particles is a good indicator for nonmarine environment. The particles are of different forms (Vascular plant remains, woody and membranous, plant cuticles, root cortex tissues, gymnosperm xylem).

3-Amorphous organic matter:
They are structurless and dark matters. This type of particles likely to be associated with hydrocarbon generation (Traverse, 1988

Palynofacie description:
Depending on the data we got from the current study Table 1, the following palynofacies were recognized Fig.4: Palynofacies 1 (PF1): It is located in Kaista Formation and lower part of Ora Formation , limited between sample Kk6,and Kor.1.The amount of organic matters is different in the upper part of Kaista Formation, the spores is between 1-5 % , while other organic components are different in amount . In the sample Kk6 the amount of amorphous organic matter is 46,9% ; but spores are increased observably into 50% in the lower part of Ora Formation , which is of silty facies mainly, in this facies palynomorphs are 19% , amorphous 17.4% , and phytoclasts 18.9%, with no or rare acritarchs. Palynofacies 2 (PF2): This facies is appeared in the lower part of Ora Formation limited between sample (Kor.2, Kor.4, ….Kor.7), which is mainly shale interbedded thin bedded fossiliferous limestone in the upper part of the facies .The range of the spores is between 7.8-41.8%, while palynomorphs and amorphous organic matter decrease, with increasing of spore amount to the upper part of this facies. Phytoclasts in this facies is ranged between 2.3 -6.8%. Palynofacies 3 (PF3): It is observed near the middle part of Ora Formation ; which includes samples Kor.8,Kor.10 and Kor.12. In this facies the P.Z=palynozone numbers=1,2,3,4,5