Geo log i cal Quar terly, 2018, 62 (1): 90–99 DOI: http://dx.doi.org/10.7306/gq.1394
Ma rine palynology and en vi ron men tal in ter pre ta tion of the Lower Cre ta ceous (Barremian?–Aptian) rock units in the Koppeh-Dagh Ba sin, NE Iran
Mohammad SHARIFI1, Ebrahim GHASEMI-NEJAD1, *, Mehdi SARFI2, Mohsen YAZDI-MOGHADAM3, Mostafa TARJANI SALEHANI1 and Maryam AKHTARI3
1 Uni ver sity of Teh ran, Uni ver sity Col lege of Sci ence, De part ment of Ge ol ogy, Teh ran, Iran
2 Damghan Uni ver sity, School of Earth Sci ences, Damghan, Iran
3 Na tional Ira nian Oil Com pany, Ex plo ra tion Di rec tor ate, Sheikh Bahayi Square, Teh ran, Iran
Sharifi, M., Ghasemi-Nejad, E., Sarfi, M., Yazdi-Moghadam, M., Tarjani Salehani, M., Akhtari, M., 2018. Ma rine palynology and en vi ron men tal in ter pre ta tion of the Lower Cre ta ceous (Barremian?–Aptian) rock units in the Koppeh-Dagh Ba sin, NE Iran. Geo log i cal Quar terly, 62 (1): 90–99, doi: 10.7306/gq.1394
The Sarcheshmeh and Sanganeh for ma tions are the Lower Cre ta ceous deep ma rine se quences of the Koppeh-Dagh sed i - men tary ba sin, which re vealed a di verse as sem blage of dinoflagellates. The pa per dis cusses palynostratigraphy, palynofacies and palaeoenvironment of these rock units in a bore hole drilled in the east ern part of this ba sin. Ninety-five ditch-cut ting sam ples were pre pared and stud ied paly no logi cal ly, which re sulted in rec og ni tion of 76 spe cies of dinoflagellate cysts be long ing to 29 gen era. The re corded as sem blages are in ac cor dance with the Odontochitina operculata Zone sug - gest ing a Barremian?–Aptian age for the for ma tions. Palynological data ex tracted led to iden ti fi ca tion of five palynofacies types based on the cat e go ries of Tyson (1995). These in di cate a mar ginal, prox i mal and dis tal shelf en vi ron ment of de po si - tion. The ob tained data from cal cu lated palaeo eco logi cal fac tors re vealed a grad ual sea level rise dur ing the de po si tion of these rock units, re sult ing in re place ment of the oxic/dysoxic Sarcheshmeh For ma tion by the dysoxic/anoxic Sanganeh For - ma tion.
Key words: Koppeh-Dagh, palynostratigraphy, palynofacies, palaeo ec ol ogy, palaeoenvironment.
INTRODUCTION
The Cre ta ceous pe riod is as so ci ated with spread ing of low-ox y gen con di tions in oce anic bas ins due to mas sive sub - ma rine vol ca nic ac tiv ity and oce anic crustal pro duc tion. These oce anic anoxic events (OAEs) led to de po si tion of large amounts of or ganic mat ter in many parts of the world es pe cially in the Tethys Ba sin (Ar thur et al., 1990; Leckie et al., 2002;
Baudin, 2005; Steuber et al., 2005; Ando et al., 2008; Föllmi, 2012). The Koppeh-Dagh sed i men tary ba sin, as part of the north ern Tethyan realm (Glen nie, 2000), stretches in an area cov er ing north east ern Iran, south ern Turkmenistan and north Af ghan i stan (Fig. 1A). It is known for high hy dro car bon po ten tial and huge gas res er voirs (Kavoosi et al., 2010). The Aptian - -Albian deep-ma rine suc ces sions of this ba sin, in tro duced as the Sarcheshmeh and Sanganeh for ma tions, are rich in ma rine palynomorphs (dinoflagellate cysts). These ma rine el e ments are a ma jor mem ber of the Cre ta ceous microflora in the Tethyan realm and eval u a tion of their strati graphic and en vi ron -
men tal dis tri bu tion is broadly ap plied in ma jor hy dro car bon ex - plo ra tion pro jects (Kimyai, 2000; Torricelli, 2000; Pavlishina and Feist-Burkhardt, 2004; Oosting et al., 2006; Back house, 2006;
Quattrocchio et al., 2006; Pestchevitskaya, 2007). The cur rent study in ves ti gates palynology, palynostratigraphy and depositional set ting of the Sarcheshmeh and Sanganeh for ma - tions in a bore hole lo cated in the east of the Ira nian part of the ba sin. For con fi den tial rea sons of Na tional Ira nian Oil Com pany (NIOC), the real name of the stud ied well is not cited. There fore, the subsurface sec tion is re named here as bore hole A.
GEOLOGICAL SETTING
The Koppeh-Dagh Ba sin is an in verted struc ture formed in the Early to Mid dle Ju ras sic (Garzanti and Gaetani, 2002; Allen et al., 2003). A rel a tively con tin u ous sed i men ta tion from the Ju - ras sic through the Eocene in the east ern parts of the ba sin (Afshar-Harb, 1994) ren dered the thick est Cre ta ceous de pos its of Iran (Berberian and King, 1981; Raisossadat and Moussavi - -Harami, 2000; Raisossadat, 2006). The Early Cre ta ceous sea level rise re sulted in a transgressive sed i men tary mega se - quence that con sists of four for ma tions. The suc ces sion be gins with the Neocomian terrigenous Shurijeh For ma tion pass ing into shal low-shelf strata of the car bon ate Tirgan For ma tion of
* Corresponding author, e-mail: eghaseminejad@gmail.com Received: July 8, 2017; accepted: November 2, 2017; first published online: January 4, 2018.
Barremian–Early Aptian age. These car bon ates are in turn fol - lowed by rel a tively deep-ma rine strata of the Sarcheshmeh and Sanganeh for ma tions (Fig. 1B; Rob ert et al., 2014). Fig ure 1D shows the struc tural re la tion ships be tween the rock units across the AB pro file (Fig. 1C) in the study area.
At the type sec tion, the Sarcheshmeh For ma tion con sists of marls and shales and the Sanganeh For ma tion is rep re sented mainly by dark grey to black shales (Afshar-Harb, 1994). In bore - hole A, the thick ness of the Sarcheshmeh For ma tion is 177 m, and the unit con sists mainly of marls, shales and shaly lime - stones. The Sanganeh For ma tion is a 348 m thick suc ces sion of claystones and shales interbedded by lime stones (Fig. 2).
MATERIAL AND METHODS
Ninety-five ditch-cut ting sam ples from both the Sarche - shmeh and Sanganeh for ma tions were col lected and ana lysed
for palynology. Of these, 48 sam ples were from the Sarche - shmeh For ma tion and 47 sam ples from the Sanganeh For ma - tion (Ap pen dix 1*).
Palynological slides were pre pared in a con ven tional mac - er a tion pro ce dure (Tra verse, 2007). Cold hy dro chlo ric (20%) and hy dro flu oric (50%) ac ids were used to dis solve car bon ates and sil i cates. No ox i dants or al ka lis were ex erted. The res i due was neu tral ized and cen tri fuged in aque ous so lu tion of ZnCl2
(spe cific grav ity 1.9 g/cm3), then sieved at 15 µm via a ny lon mesh, and mounted on mi cro scope slides us ing liq uid Can ada bal sam. Pre pared palynological slides were stud ied by a trans - mit ted light mi cro scope and the in dex spe cies were pho to - graphed and pre sented in Fig ure 3. In this study, we also count and cal cu late per cent ages of the three main groups of palyno - logical el e ments in clud ing amor phous or ganic mat ter (AOM), ter res trial el e ments (phytoclasts) and ma rine palynomorphs in all sam ples. The data gained are plot ted on Tyson‘s ter nary di a - gram (Tyson, 1995) for palaeoenvironmental in ter pre ta tions Ma rine palynology and en vi ron men tal in ter pre ta tion of the Lower Cre ta ceous (Barremian?–Aptian) rock units... 91
Fig. 1A – lo ca tion map of the stud ied bore hole; B – Cre ta ceous lithostratigraphic chart of the Koppeh-Dagh sed i - men tary ba sin; C – geo log i cal map of the study area (mod i fied from Afshar-Harb, 1982); D – geo log i cal cross-sec - tion A–B shown in Fig ure 1C (mod i fied from Afshar-Harb, 1982)
* Supplementary data associated with this article can be found, in the online version, at doi: 10.7306/gq.1394
(Fig. 4). The spore col our in dex (SCI) is also used here as an - other method in or der to es ti mate the de gree of or ganic ma tu - rity. It ranges from 1 to 10 re flect ing a col our gra da tion from yel - low to black (Mar shall, 1990; Utting and Hamblin, 1991).
RESULTS AND DISCUSSION
PALYNOLOGY AND PALYNOSTRATIGRAPHY
Cre ta ceous dinoflagellate cysts have been stud ied by many re search ers and widely used for biostratigraphy and age dat ing in the Tethyan Realm (Davey and Verdier, 1974; Hoedemaeker and Leereveld, 1995; Leereveld, 1997; Ibrahim et al., 2002).
The Neocomian dinocyst as sem blages re vealed low-di ver sity com mu ni ties (Stover et al., 1996) usu ally marked by the pres - ence of Cribroperidinium, Circulodinium, Muderongia, Pseudoceratium, Phoberocysta and Oligosphaeridium gen era (Davey, 1979; Raw son and Riely, 1982; Woollam and Rid ing, 1983; Helby et al., 1987; Stover et al., 1996). Dur ing the Barremian and Aptian, dinoflagellates in creased in num ber and di ver si fied (Stover et al., 1996). The first ap pear ance of Odon - to chitina operculata and Palaeoperidinium cretaceum are re - corded in the Barremian stage (Har ding, 1990; Costa and
Davey, 1992). The Aptian dinocyst as sem blages are char ac ter - ized by the co-oc cur rence of Oligosphaeridium, Spiniferites, Kiokansium, Pseudoceratium, Hystrichodinium, Odontochitina and Florentinia gen era (Davey and Verdier, 1974; Costa and Davey, 1992; Torricelli, 2000; Helby et al., 2004).
In this study, palynological in ves ti ga tions re vealed that the Sarcheshmeh and Sanganeh for ma tions are dom i nated by dinoflagellate cysts. Thirty-two spe cies of dinoflagellate cysts be long ing to 19 gen era were re corded in the Sarcheshmeh For - ma tion. The Sanganeh For ma tion was richer and more di verse, yield ing 53 spe cies be long ing to 28 gen era. Spore and pol len grains and acritarchs were also pres ent in both for ma tions. Ex - cept for the basal in ter vals of the Sarcheshmeh and the up per parts of the Sanganeh for ma tions in which dinoflagellate cysts pres er va tion is poor, they are gen er ally pre served mod er ate to good in the rest of the two rock units stud ied. The as sem blages de tected in the Sarcheshmeh and Sanganeh for ma tions are dom i nant and char ac ter ized by the pres ence of Achomo - sphaera neptuni, Callaiosphaeridium asymmetricum, Cerbia tabulata, Circulodinium distinctum, Coronifera oceanica, Kleithria sphaeridium eoinodes, Cribroperidinium edwardsii, Cr.
orthoceras, Florentinia abjuncta, Fl. cooksoniae, Hystricho - dinium pulchrum, Hy. ramoides, Hystrichosphaerina schinde - wolfii, Kiokansium polypes, Muderongia pariata, Mu. sim plex, Odontochitina operculata, Oligosphaeridium com plex, Ol.
92 M. Sharifi, E. GhasemI-Nejad, M. Sarfi, M. Yazdi-Moghadam, M. Tarjani SalehanI and M. Akhtari
Fig. 2. Re corded ma rine palynomorphs and their dis tri bu tion through out the stud ied in ter val
Ma rine palynology and en vi ron men tal in ter pre ta tion of the Lower Cre ta ceous (Barremian?–Aptian) rock units... 93
Fig. 3. Some of the re corded palynomorphs from the stud ied bore hole (scale bars are 10 mm), A, B, G, J, L, M, P–T – Sarcheshmeh Fm.; C–F, H, I, K, N, O – Sanganeh Fm.
A – Achomosphaera ramulifera (Deflandre, 1937) Evit, 1963; B – Callaiosphaeridium asymmetricum (Deflandre and Courteville, 1939) Davey and Wil liams, 1966; C – Cerbia tabulata (Davey and Verdier, 1974) Be low, 1981; D – Circulodinium distinctum (Deflandre and Cookson, 1955) Jansonius, 1986; E – Cribroperidinium edwardsii (Cookson and Eisenack, 1958) Davey, 1969; F – Cr. orthoceras (Eisenack, 1958) Davey, 1969 emend. Sarjeant, 1985; G – Hystrichodinum ramoides Al ber ti, 1961; H – Hystrichosphaerina schindewolfii Al ber ti, 1961; I – Kiokansium polypes (Cookson and Eisenack, 1962) Be low, 1982 emend.
Duxbury, 1983; J – Muderongia sim plex Al ber ti, 1961; K – Odontochitina operculata (Wetzel, 1933) Deflandre and Cookson, 1955;
L – Oligosphaeridium com plex (White, 1842) Davey and Wil liams, 1966; M – Ol. totum Brideaux, 1971 emend. Dörhöfer and Davies, 1980; N – Petrospermella sp.; O – Pseudoceratium pelliferum Gocht, 1957; P – Palaeoperidinium cretaceum (Pocock, 1962) Lentin and Wil liams, 1976; Q – Pseudoceratium polymorphum (Eisenack, 1958) Bint, 1986 emend. Dörhöfer and Davies, 1980; R – Spiniferites ramosus (Ehrenberg, 1838) Mantell, 1854; S – Kleithriasphaeridium eoniodes (Esienack, 1958) Davey, 1974 emend. Sarjeant, 1985; T – Subtilisphaera perlucida (Al ber ti, 1959) Jain and Millepied, 1973
totum, Palaeoperidinium cretaceum, Pseudoceratium poly mor - phum, Ps. securigerum, Spiniferites ramosus and Subtili spha - era perlucida (Figs. 2 and 3).
The last oc cur rences of spe cies such as Achomosphaera neptuni, Cerbia tabulata and Hystrichosphaerina schindewolfii proved the Aptian age in the Tethyan realm (Davey and Verdier, 1974; Leereveld, 1995; Stover et al., 1996). More over, high fre quency and abun dance of Odontochitina operculata, Oligosphaeridium com plex and Circulodinium distinctum were used for sub di vid ing the Aptian stage (Kimyai, 2000), and the pres ence of Coronifera oceanica and Surculosphaeridium longi furcatum in di cates Aptian age in West ern Eu rope (Torricelli, 2000; Heimhofer et al., 2005). Helby et al. (1987) in - tro duced a com pre hen sive palynozonation for the Aus tra lian Ba sin. Our dinocysts re corded from the Sarcheshmeh and Sanganeh for ma tions are in rea son able ac cor dance with the Odontochitina operculata Oppel Zone. This palynozone and part of the Muderongia superzone (Helby et al., 1987) are de - fined be tween the first oc cur rences of Odontochitina operculata and the first oc cur rence of Psedoceratium turneri (Helby et al., 1987). There is no con sen sus about the lower bound ary of this zone, as in Aus tra lia it is dated Aptian (Mor gan, 1980; Helby and McMinn, 1992; Helby et al., 1987, 2004; Ooisting et al., 2006) or Barremian-Aptian (Back house, 1988). In Eu rope, this zone has been re garded as the marker of the Barremian (Davey, 1979; Heilmann-Clausen, 1987; Har ding, 1990; Costa and Davey, 1992).
Ac cord ing to the palynomorphs re corded here, the as sem - blages could be as signed to the Barremian?–Aptian, and the Odontochitina operculata palynozone is con strained.
PALYNOFACIES
Palynofacies has an im por tant ap pli ca tion in palynological stud ies that are widely used for palaeoenvironmental re con - struc tion, ba sin anal y sis, pe tro leum ex plo ra tion, and eval u a tion of source rocks po ten tial. Var i ous con cepts, such as: es ti mat - ing dis tance to shore line, wa ter depth, se quence stra tig ra phy, re con struc tion of palaeoenvironment and its ef fect on palaeo - eco logi cal fac tors, can be un der stood from palynofacies stud - ies (Tyson, 1995; Bom bar dier and Gorin, 2000; Oboh-Ikuenobe and de Villiers, 2003). One of the most use ful ap pli ca tions is the use of palynofacies anal y sis as a proxy to eval u ate source rock
ho ri zons that are of im mense prac ti cal sig nif i cance in hy dro car - bon sys tems (Bat ten, 1996; Bat ten and Stead, 2005). To tal or - ganic car bon (TOC) val ues are in di rect re la tion with the amount of AOMs in palynofacies stud ies (Tyson, 1995; Zobaa, 2011).
The AOM-rich zones are char ac ter is tic of highly oil-prone kerogen type I, while kerogen types II and III are con trolled by both phytoclasts and AOM and in di cate oil- to gas-prone ho ri - zons (Tyson, 1993, 1995; Ibrahim et al., 1997).
Dur ing the past de cades, dif fer ent types of palynofacies char ac ter iza tions for palaeoenvironmental in ter pre ta tion have been pub lished (e.g., Tyson, 1993, 1995; Bat ten, 1996; Bat ten and Stead, 2005). Tyson (1995) de scribed a ter nary kerogen plot based on three ma jor groups of or ganic mat ter re mains and de fined nine dif fer ent palynofacies zones, each show ing a spe - cific palaeoenvironmental con di tion. In the cur rent study, per - cent ages of the three main kerogen types were cal cu lated (Ap - pen dix 1) for de tailed palynofacies anal y sis. Re sults show abun dance of phytoclasts in most parts of the Sarcheshmeh For ma tion and in the basal sec tion of the Sanganeh Forama - tion. Mean while, up wards in the Sanganeh For ma tion, the amount of phytoclasts de creased and the fre quency of AOM and palynomorphs in creased, which is gen er ally in ter preted as re flect ing a sea level rise (trans gres sion) (Eshet et al., 1988a, b;
Habib and Miller, 1989; Gorin and Steffen, 1991; Greg ory and Hart, 1992; Carvalho et al., 2006). Us ing the Tyson ter nary di a - gram, five types of palynofacies have been iden ti fied based upon the dis tance from the source re gion. The palynofacies are of types II, IV, V, VI and VII. They rep re sent mar ginal, prox i mal and dis tal shelves and are used to study depositional set ting (Figs. 4 and 5).
Palynofacies II. This palynofacies en com passes enor - mous amounts of phytoclasts vary ing from 65 to 95%. AOM and ma rine palynomorphs were <30 and 10%, re spec tively. These phytoclast-rich fa cies is de pos ited in a mar ginal dysoxic-anoxic ba sin and its kerogen is of III type, which is gas-prone. This palynofacies is dom i nant within the Sarcheshmeh Fm., while it is lim ited only to the lower parts of the Sanganeh Fm. (Fig. 6).
Palynofacies IV. Ter res trial el e ments vary be tween 42–75%, AOM from 5 to 41.1%, while ma rine palynomorphs vary from 10 to 32%. These char ac ter is tics are in dic a tive of palynofacies IV of Tyson (1995), re veal ing a tran si tional, shelf- to-ba sin en vi ron ment, and, it is mainly gas-prone due to its high ter res trial kerogen con tent (Tyson, 1995). Palynofacies type IV in the Sarcheshmeh For ma tion re flected a sea level fluc tu a tion 94 M. Sharifi, E. GhasemI-Nejad, M. Sarfi, M. Yazdi-Moghadam, M. Tarjani SalehanI and M. Akhtari
Fig. 4. The di a grams of Tyson (1995) for (A) Sarcheshmeh For ma tion and (B) Sanganeh For ma tion
from shal lower to deeper con di tions in the ba sin. Sim i lar to palynofacies type II, this fa cies,was re corded mainly in the lower parts within the Sanganeh For ma tion.
Palynofacies V. In this palynofacies, dinoflagellate cysts sig nif i cantly in creased and reached their high est per cent age (45–65%) in the stud ied se quences. Other or ganic mat ter clasts, such as phytoclasts, were be tween 25 and 46% and AOMs vary from 10 to 30%. This palynofacies is re ferred to kerogen type II and is de pos ited on an oxic dis tal shelf (Tyson, 1995). The fre quency and good pres er va tion state of dinocysts could be at trib uted to high sed i men ta tion rate. Pres ence of palynofacies V in the stud ied se quence is in ter preted as cor re - spond ing to the max i mum flood ing (trans gres sion) in a shelf and co in cided with de vel op ment of a proper con di tion for de po -
si tion of or ganic-rich shales. This fa cies is con fined to the up per parts of the Sanganeh For ma tion and is not known from the Sarcheshmeh For ma tion.
Palynofacies VI. Tyson (1995) pro posed a prox i mal suboxic -anoxic shelf sed i men tary en vi ron ment for this palyno - facies. Amor phous or ganic mat ter and ter res trial phytoclasts were the ma jor con sti tu tive com po nents of the palynological kerogens, and ma rine palynomorphs con sti tuted <10%. Ac - cord ing to Tyson (1995), kerogen of palynofacies VI is of oil-prone type (kerogen type II) due to its high AOM con tent. In con trast to palynofacies V, this palynofacies is not found in the Sanganeh For ma tion and scat tered at low fre quency only in the Sarcheshmeh For ma tion.
Ma rine palynology and en vi ron men tal in ter pre ta tion of the Lower Cre ta ceous (Barremian?–Aptian) rock units... 95
Fig. 5. Ex am ples of rec og nized palynofacies within the Sarcheshmeh and Sanganeh for ma tions A – palynofacies II (2932 m); B – palynofacies VI (2862 m); C – palynofacies IV (2752 m);
D – palynofacies VII (2616 m); E – palynofacies V (2552 m)
Palynofacies VII. The kerogen com po si tion of this palyno - facies, in sim i lar with palynofacies VI, is char ac ter ized with the dom i nance of AOMs and phytoclasts; how ever, the fre quency of ma rine palynomorphs in creased (up to 10%). Palynofacies VII re fers to oil-prone kerogen of type II de pos ited in a dis tal dysoxic–anoxic shelf (Tyson, 1995). This fa cies is not com mon and has only been de tected from small in ter vals in both for ma - tions.
DEPOSITIONAL SETTING AND ENVIRONMENTAL RECONSTRUCTION
In or der to re con struct the palaeoenvironment and its prev a - lent con di tions, palynofacies data com bined with prom i nent palaeo eco logi cal re sults, ob tained from some cal cu lated palaeo - eco logi cal fac tors, have been used (Fig. 6). The palaeo eco logi - cal fac tors used are the ra tios of brown to opaque phytoclasts (Lability), light AOM to dark AOM, AOM to brown phytoclasts, AOM to ma rine palynomorphs, and, fi nally, cu bic to bladed phytoclasts. These palaeo eco logi cal pa ram e ters are di versely used to de ter mine sea level changes, sed i men ta tion rates, palaeoproductivity and dif fer en ti a tion of ox i dant, dysoxic and anoxic en vi ron ments (Tyson, 1993; Van-Waveren and Visscher, 1994; Bom bar dier and Gorin, 2000). Gen er ally, phyto clasts de -
pend on land plants. Their abun dance shows an en vi ron ment close to the shore lines; how ever, high val ues of bladed phyto - clasts along with dom i nance of ma rine palyno morphs (in com - par i son with ter res trial ma te ri als) mark off shore en vi ron ments (Boul ter and Riddick, 1986; Bom bar dier and Gorin, 2000;
Schioler et al., 2002). The amount of ox y gen in the depositional en vi ron ments is usu ally es ti mated us ing the AOMs con tent of rock units. Based on this, high val ues of AOMs, es pe cially light AOMs (the light AOM to dark AOM ra tio >1), re flect dom i nance of an anoxic con di tion (Bom bar dier and Gorin, 2000). In con trast to this, black col our clasts (dark AOMs and opaque phytoclasts) show a rel a tively oxic en vi ron ment (Van -Waveren and Visscher, 1994). The sed i men ta tion rate could also be eval u ated by use of palynomorphs pres er va tion. In these cases, the max i mum per - se ver ance of dinoflagellate cysts oc curs in an anoxic con di tion with high sed i men ta tion rate (Van-Waveren and Visscher, 1994;
Bom bar dier and Gorin, 2000).
Ac cord ing to the ob tained data (pre sented in Fig. 6), a mar - ginal ba sin ex tended dur ing de po si tion of the Sarcheshmeh For ma tion. It was more sta ble dur ing de po si tion of its lower part, re flect ing some sea level fluc tu a tions in the up per part of the for - ma tion. A grad ual sea level rise can be in ter preted. Due to this, a dysoxic/anoxic dom i nance with low sed i men ta tion rates can be de tected in the up per part in con trast to the oxic/dysoxic con - di tion in the lower sec tion of the for ma tion. The sea level rise, 96 M. Sharifi, E. GhasemI-Nejad, M. Sarfi, M. Yazdi-Moghadam, M. Tarjani SalehanI and M. Akhtari
Fig. 6. Vari a tions in prox ies used for palaeoenvironmental in ter pre ta tions in the stud ied rock units
the start of which is re corded in the up per part of the Sarcheshmeh For ma tion, ex tended up into the lower part of the Sanganeh For ma tion re veal ing a tran si tional zone be tween shelf and ba sin. In the up per part of the Sanganeh For ma tion, palynofacies types V and VII are dom i nant, in di cate a neritic ma rine en vi ron ment, and re sult from a grad ual sea level rise.
These palynofacies form the kerogen type II/III, which is an oil and gas-pro duc ing com po nent, and en rich hy dro car bon gen er - a tion pos si bil i ties of this sec tor. The grad ual sea level rise can also be un der stood from a grad ual in crease in the num ber of chorate dinocyst forms (Brinkhuis and Zachariasse, 1988;
Carvalho, 2004). The bloom of Cribroperidinium ge nus in the up per part of the Sanganeh For ma tion (Fig. 5E) also con firms the neritic en vi ron ment (Leereveld, 1995). The palaeo eco logi - cal fac tors show ex ten sion of an anoxic/dysoxic con di tion with higher sed i men ta tion rates (due to high pres er va tion of ma rine palynomorphs) in the up per parts of the Sanganeh For ma tion in com pare with other parts of the stud ied col umn. More over, in the Sanganeh For ma tion the Peridinioids to Gonyalacoids (P/G) dinocysts ra tio (Harland, 1973) was also hired to gain more pre cise palaeoenvironmental in ter pre ta tions. The re - corded peridinioid forms in the Sanganeh For ma tion in clude Cribroperidinium, Eucladinium, Palaeoperdinium and Subtilis - phaera gen era. Prom i nent in creas ing of P/G ra tio in the up per
parts of the Sanganeh For ma tion em pha sized ex ten sion of the anoxic con di tions and high palaeoproductivity due to the pres - ence of upwelling cur rents (Reid, 1977; May, 1980; Costa and Davey, 1992) that may led to ex pan sion of the oce anic anoxic events (OAEs) that re sulted de po si tion of source rocks. As a re - sult, ex ten sion of anoxic con di tion, high sed i men ta tion and high palaeoproductivity and in crease in AOMs val ues, give us valu - able keys to con clude a fair po ten tial pro duc tion zone in the up - per parts of the Sanganeh For ma tion. Based on the mi cro - scopic ob ser va tions, the spore col our in dex (SCI) prac ticed on the sam ples col lected from the Sanganeh Fm. (Fig. 7). The SCI val ues var ies from golden yel low to dark brown (SCI 4-8, depth ranges 2496–2824 m) for the ma jor ity of the grains. The SCI 4-8 is in ac cord with the ther mal al ter ation in dex (TAI) 2-3 of Utting and Hamblin (1991) (Fig. 7A, B) that in di cate a ther mally ma ture to hy dro car bon gen er a tion zones (oil and gas win dows).
CONCLUSIONS
The palynological stud ies were per formed on the Lower Cre ta ceous shaley suc ces sion of the Sarcheshmeh and San - ganeh for ma tions in the Koppeh-Dagh Ba sin of north east ern Ma rine palynology and en vi ron men tal in ter pre ta tion of the Lower Cre ta ceous (Barremian?–Aptian) rock units... 97
Fig. 7A – spore col our in dex (SCI) and col our changes within spores and pol len (mod i fied from Mar shall, 1990); B – cor re la tion be tween col our changes in spores and pol len, ther mal al ter ation in dex (TAI) and pe - tro leum gen er a tion zones (Utting and Hamblin, 1991); C – some of the re corded spore and pol len grains in the Sanganeh For ma tion
Iran. They have led to the rec og ni tion of 32 spe cies of dinocysts from the Sarcheshmeh For ma tion. The re corded as sem blages from the Sanganeh For ma tion re vealed a richer ma rine as sem - blage with 53 dinocyst spe cies. These palynomorph as sem - blages sug gest a Barremian?–Aptian and Aptian age for the Sarcheshmeh and Sanganeh for ma tions, re spec tively. Based on these palynoflora as sem blages, the stud ied suc ces sion is also as signed to the Odontochitina operculata Oppel Zone.
Moroever, per cent ages of the three main types of kerogen from palynological slides were cal cu lated for de tailed palynofacies stud ies, and five dif fer ent fa cies types (palynofacies types II, IV, V, VI and VII of Tyson, 1995) are char ac ter ized rang ing from mar ginal to dis tal shelves. Palynofacies data com bined with palaeo eco logi cal ev i dence show a grad ual rel a tive sea level
rise up ward in the sec tion, and dom i nance of an anoxic en vi ron - ment es pe cially in the up per part of the Sanganeh Fm. The abun dance of palynofacies types V and VII, pres ence of anoxic con di tion, ac cu mu la tion of hy dro car bon-prone kerogen (type II/III) and SCI val ues (that sug gested ther mally ma tured com po - nents) in the up per part of the Sanganeh Fm. in di cate po ten tial for pe tro leum (mainly gas) pro duc tion.
Ac knowl edge ments. The au thors thank the ex plo ra tion di - rec tor ate of the Na tional Ira nian Oil Com pany (NIOC), Uni ver - sity of Teh ran and Damghan Uni ver sity for their sup port. Prof.
M. Fabiañska and an Anon y mous re viewer are thanked for re - view ing the manu script and giv ing many com ments that im - proved qual ity of this pa per.
REFERENCES
Afshar-Harb, A., 1982. Geo log i cal quad ran gle map of Iran, No. L4, (1:250 000 geo log i cal map of Sarakhs). Geo log i cal Sur vey of Iran, Teh ran.
Afshar-Harb, A., 1994. Ge ol ogy of Kopet Dagh (in Per sian). In:
Trea tise on the Ge ol ogy of Iran (ed. A. Hushmandzadeh). Geo - log i cal Sur vey of Iran, Teh ran.
Allen, M.B., Vin cent, S.J., Alsop, G.I., Ismail-zadeh, A., Flecker, R., 2003. Late Ce no zoic de for ma tion in the South Cas pian re - gion: ef fects of a rigid base ment block within a col li sion zone.
Tectonophysics, 366: 223–239.
Ando, A., Kaiho, K., Kawahata, H., Kakegawa, T., 2008. Tim ing and mag ni tude of early Aptian ex treme warm ing: un rav el ing pri - mary d18O vari a tion in indurated pe lagic car bon ates at Deep Sea Drill ing Pro ject Site 463, cen tral Pa cific Ocean. Palaeo ge - ogra phy, Palaeoclimatology, Palaeo ec ol ogy, 260: 463–476.
Ar thur, M.A., Jenkyns, H.C., Brumsack, H.J., Schlanger, S.O., 1990. Stra tig ra phy, geo chem is try and paleoceanography of or - ganic-car bon rich Cre ta ceous se quences. NATO ASI Se ries, 304: 75–119.
Back house, J., 1988. Late Ju ras sic and Early Cre ta ceous palynology of the Perth Ba sin, West ern Aus tra lia. Bul le tin of the Geo log i cal Sur vey of West ern Aus tra lia, 135: 1–233.
Back house, J., 2006. Albian (Lower Cre ta ceous) dinoflagellate cyst biostratigraphy of the Lower Gearle siltstone, South ern Carnarvon Ba sin, West ern Aus tra lia. Palynology, 30: 43–68.
Bat ten, D.J., 1996. Palynofacies and pe tro leum po ten tial. Amer i can As so ci a tion of Strati graphic Paly nolo gists Foun da tion, 3:
1065–1084.
Bat ten, D.J., Stead, D.T., 2005. Palynofacies anal y sis and its strati - graphic ap pli ca tion. In: Ap plied Stra tig ra phy (ed. E.A.E. Kout - sou kos): 203–226. Springer, Dordrecht.
Baudin, F., 2005. A late Hauterivian short-lived anoxic event in the Med i ter ra nean Tethys: the Faraoni event. Comptes Rendus Geosciences, 337: 1532–1540.
Berberian, M., King, G.C.P., 1981. To ward a paleogeography and tec tonic evo lu tion of Iran. Ca na dian Jour nal of Earth Sci ences, 18: 210–265.
Bom bar dier, L., Gorin, G.E., 2000. Strati graphi cal and lat eral dis - tri bu tion of sed i men tary or ganic mat ter in Up per Ju ras sic car - bon ate of South east France. Sed i men tary Ge ol ogy, 132:
177–203.
Boul ter, M.C., Riddick, A., 1986. Clas si fi ca tion and anal y sis of palynodebris from the Paleocene sed i ments of the For ties Field.
Sedimentology, 33: 871–886.
Brinkhuis, H., Zachariasse, W.J., 1988. Dinoflagellate cysts, sea level changes and plank tonic foraminifers across the Cre ta - ceous-Ter tiary bound ary at El Haria, north west Tu ni sia. Ma rine Micropaleontology, 13: 153–191.
Carvalho, M.A., 2004. Palynological as sem blage from Aptian/Albian of the Sergipe Ba sin: paleoenvironmental re con - struc tion. Revista Brasileira de Paleontologia, 7: 159–168.
Carvalho, M.A., Filho, J.G.M., Menezes, T.R., 2006. Palynofacies and se quence stra tig ra phy of the Aptian–Albian of the Sergipe Ba sin, Brazil. Sed i men tary Ge ol ogy, 192: 57–74.
Costa, L.I., Davey, R.J., 1992. Dinoflagellates cysts from the Cre ta - ceous Sys tem. In: A Strati graphic In dex of Dinoflagellate Cysts (ed. A.J. Powell): 99–154. Brit ish Micropalaeontological So ci ety Pub li ca tion Se ries/Kluwer Ac a demic Pub lish ers.
Davey, R.J., 1979. The strati graphic dis tri bu tion of dinocysts in the Portlandian (lat est Ju ras sic) to Barremian (Early Cre ta ceous) of north west Eu rope. Amer i can As so ci a tion of Strati graphic Paly - nolo gists, Con tri bu tions Se ries, No. 5B, 2: 48–81.
Davey, R.J., Verdier, J.P., 1974. Dinoflagellates cysts from the Aptian type sec tions at Gargas and La Bedoule, France. Palae - on tol ogy, 17: 623–653.
Eshet, Y., Cousminer, H.L., Habib, D., 1988a. A model for us ing re - worked palynomorphs as sedimentological and en vi ron men tal in di ca tors. Palynology, 12: 236–237.
Eshet, Y., Druckman, H.L., Cousminer, Y., Habib, D., Drugg, W.S., 1988b. Re worked palynomorphs and their use in the de - ter mi na tion of sed i men tary cy cles. Ge ol ogy, 16: 662–665.
Föllmi, K.B., 2012. Early Cre ta ceous life, cli mate and an oxia. Cre ta - ceous Re search, 35: 230–257.
Garzanti, E., Gaetani, M., 2002. Unroofing his tory of Late Pa leo zoic mag matic arcs within the Turan Plate (Tuarkyr, Turkmenistan).
Sed i men tary Ge ol ogy, 151: 67–87.
Glen nie, K.W., 2000. Cre ta ceous tec tonic evo lu tion of Ara bia east - ern plate mar gin ing: a tale of two oceans, in Mid dle East mod els of Ju ras sic/Cre ta ceous car bon ate sys tems. SEPM Spe cial Pub - li ca tion, 69: 9–20.
Gorin, G.E., Steffen, D., 1991. Or ganic fa cies as a tool for re cord ing eustatic vari a tions in ma rine fine-grained car bon ates – ex am ple of the Berriasian stratotype at Berrias (Ardeche, SE France).
Palaeo ge ogra phy, Palaeoclimatology, Palaeo ec ol ogy, 85:
303–320.
Greg ory, W., Hart, G.F., 1992. To wards a pre dic tive model for the palynologic re sponse to sea-level changes. Palynostratigraphy and So ci ety of Sed i men tary Ge ol ogy, 7: 3–33.
Habib, D., Miller, J.A., 1989. Dinoflagellate spe cies and or ganic fa - cies ev i dence of ma rine trans gres sion and re gres sion in the At - lan tic coastal plain. Palaeo ge ogra phy, Palaeoclimatology, Palaeo ec ol ogy, 74: 23–47.
Har ding, I.C., 1990. A dinocyst cal i bra tion of the Eu ro pean Bo real Barremian. Palaeontographica Abt. B, 218: 1–76.
Harland, R., 1973. Dis tri bu tion maps of re cent dinoflagellate cysts in bot tom sed i ments from the North At lan tic and ad ja cent seas.
Palae on tol ogy, 26: 321–387.
98 M. Sharifi, E. GhasemI-Nejad, M. Sarfi, M. Yazdi-Moghadam, M. Tarjani SalehanI and M. Akhtari
Heilmann-Clausen, C., 1987. Lower Cre ta ceous dinoflagellate bio - stratigraphy in the Dan ish Cen tral Trough. Danmarks Geolo - giske UndersÝgelse, 17: 1–90.
Heimhofer, U., Hochuli, P.A., Herrle, J., Weissert, H., 2005. Con - trast ing or i gins of early Cre ta ceous black shales in the Vocontian ba sin: ev i dence from palynological and cal car e ous nannofossil re cords. Palaeo ge ogra phy, Palaeoclimatology, Palaeo ec ol ogy, 235: 93–109.
Helby, R., McMinn, A., 1992. A pre lim i nary re port of early Cre ta - ceous dinocyst flo ras from Site 765, Argo Abys sal Plain, North - west Aus tra lia. Pro ceed ings of the Ocean Drill ing Pro gram, Sci - en tific Re sults, 123: 407–420.
Helby, R., Mor gan, R., Par tridge, A.D., 1987. A palynological zonation of the Aus tra lian Me so zoic. Mem oir of the As so ci a tion of Australasian Palaeontologists, 4: 1–49.
Helby, R., Mor gan, R., Par tridge, A.D., 2004. Up dated Ju ras sic – Early Cre ta ceous dinocyst zonation NWS Aus tra lia.
Geoscience Aus tra lia Pub li ca tion.
Hoedemaeker, P.J., Leereveld, H., 1995. Biostratigraphy and se - quence stra tig ra phy of the Berriasian-low est Aptian (Lower Cre - ta ceous) of the Rio Argos suc ces sion, Caravaca, SE Spain.
Cre ta ceous Re search, 16: 195–230.
Ibrahim, M.I.A., Aboul Ela, N.M., Kholeif, S.E., 1997. Paleo - ecology, palynofacies, ther mal mat u ra tion and hy dro car bon source-rock po ten tial of the Ju ras sic-Lower Cre ta ceous se - quence in the subsurface of the north East ern Desert, Egypt.
Qa tar Uni ver sity Sci ence Jour nal, 17: 153–172.
Ibrahim, M.A.I., Aboul Ela, N.M., Kholeif, S.E., 2002. Dino fla - gellate cyst biostratigraphy of Ju ras sic-Lower Cre ta ceous for - ma tion of the North East ern Desert, Egypt. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, 224: 255–319.
Kavoosi, M.A., Daryabandeh, M., Jamali, A.M., Bagheriy - -Tirtashi, R., Ebadian, H., Sherkati, Sh., 2010. Un con ven - tional shale gas res er voirs in Iran, NIOC. Ex plo ra tion di rec tor - ate, TR 1914.
Kimyai, A., 2000. Palynology and biostratigraphy of the Lower Cre - ta ceous sed i ment in the South Bar row Test Well. No. 1, Point Bar row, Alaska. Palynology, 24: 201–215.
Leckie, R.M., Bralower, T.J., Cashman, R., 2002. Oce anic anoxic events and plank ton evo lu tion: bi otic re sponse to tec tonic forc - ing dur ing the mid-Cre ta ceous. Paleoceanography, 17: 13–29.
Leereveld, H., 1995. Dinoflagellate Cysts from the Lower Cre ta - ceous Rio Argos Suc ces sion (SE Spain). LPP Con tri bu tions Se - ries, B.
Leereveld, H., 1997. Hauterivian-Barremian (Lower Cre ta ceous) dinoflagellate cyst stra tig ra phy of the west ern Med i ter ra nean.
Cre ta ceous Re search, 18: 421–456.
Mar shall, J.E.A., 1990. De ter mi na tion of ther mal ma tu rity. In:
Palaeo bi ol ogy – a Syn the sis (eds. D.E.G. Briggs and P. Crow - ther): 511–515. Blackwell Sci en tific Pub li ca tions, Ox ford.
May, F.E., 1980. Dinoflagellate cysts of the Gymnodiniaceae, Peridiniaceae, and Gonyaulacaeae from the Up per Cre ta ceous Monmouth Group, At lan tic High lands, New Jer sey. Palaeonto - graphica, Abt. B, 172: 10–116.
Mor gan, R., 1980. Palynostratigraphy of the Aus tra lian Early and Mid dle Cre ta ceous. Mem oirs of the Geo log i cal Sur vey of New South Wales, Palae on tol ogy, 18.
Oboh-Ikuenobe, F.E., de Villiers, S.E., 2003. Dis persed or ganic mat ter in sam ples from the west ern con ti nen tal shelf of South - ern Af rica: palynofacies as sem blages and depositional en vi ron - ments of Late Cre ta ceous and youn ger sed i ments. Palaeo ge - ogra phy, Palaeoclimatology, Palaeo ec ol ogy, 201: 67–88.
Ooisting, A.M., Leereveld, H., Dick ens, G.R., Henderson, R.A., Brinkhuis, H., 2006. Cor re la tion of Barremian-Aptian (Mid-Cre - ta ceous) dinoflagellates cyst as sem blages be tween the Tethyan and Aus tral realms. Cre ta ceous Re search, 27: 792–813.
Pavlishina, P., Feist-Burkhardt, S., 2004. Berriasian and Valanginian dinoflagellate cysts from three bore holes in North - east Bul garia. Re view of the Bul gar ian Geo log i cal So ci ety, 65:
107–114.
Pestchevitskaya, E.B., 2007. Dinocyst biostratigraphy of the Lower Cre ta ceous in North Si be ria. Stra tig ra phy and Geo log i cal Cor re - la tion, 15: 577–609.
Quattrocchio, M.E., Mar ti nez, M.A., Carpinelli, P.A., Volkheimer, W., 2006. Early Cre ta ceous palynostratigraphy, palynofacies and palaeoenvironments of well sec tions in north east ern Tierra del Fuego, Ar gen tina. Cre ta ceous Re search, 27: 584–602.
Raisossadat, S.N., 2006. The fam ily Parahoplitidae in the San - ganeh For ma tion of the Kopet Dagh Ba sin, north-east ern of Iran. Cre ta ceous Re search, 27: 907–922.
Raisossadat, S.N., Moussavi-Harami, R., 2000. Lithostratigraphic and fa cies anal y ses of the Sarcheshmeh For ma tion (Lower Cre - ta ceous) in the east ern Kopet Dagh Ba sin, NE Iran. Cre ta ceous Re search, 21: 507–516.
Raw son, P.E., Riley, L.A., 1982. Lat est Ju ras sic – Early Cre ta ceous events and the “Late Cim mer ian Un con formity” in the North Sea area. AAPG Bul le tin, 66: 2628–2648.
Reid, P.C., 1977. Peridiniacean and glenodiniacean dinoflagellate cysts from the Brit ish Isles. Nova Hedwigia, 24: 429–63.
Rob ert, A.M.M., Letouzey, J., Kavoosi, M.A., Sherkati, Sh., Müller, C., Vergés, J., Aghababaei, A., 2014. Struc tural evo lu - tion of the Kopeh Dagh fold-and-thrust belt (NE Iran) and in ter - ac tions with the South Cas pian Sea Ba sin and Amu Darya Ba - sin. Ma rine and Pe tro leum Ge ol ogy, 57: 68–87.
Schioler, P., Crampton, J.S., Laird, M.G., 2002. Palynofacies and sea level changes in the Mid dle Coniacian–Late Campanian (Late Cre ta ceous) of the East Coast Ba sin, New Zeland. Palaeo - ge ogra phy, Palaeoclimatology, Palaeo ec ol ogy, 188: 101–125.
Steuber, T., Rauch, M., Masse, J.P., Graaf, J., Malkoc, M., 2005.
Low-lat i tude sea son al ity of Cre ta ceous tem per a tures in warm and cold ep i sodes. Na ture, 437: 1341–1344.
Stover, L.E., Brinkhuis, H., Damassa, S.P., de Verteuil, L., Helby, R., Monteil, E., Par tridge, A.D., Powell, A.J., Rid ing, I.B., Smelror, M., Wil liams, G.L., 1996. Me so zoic-Ter tiary dino - flagellates, acritarchs and prasinophytes. Amer i can As so ci a tion of Strati graphic Paly nolo gists Foun da tion, 2: 641–750.
Torricelli, S., 2000. Lower Cre ta ceous dinoflagellate cyst and acritarch stra tig ra phy of the Cimon APTICORE (South ern Alps, It aly). Re view of Palaeobotany and Palynology, 108: 213–266.
Tra verse, A., 2007. Paleopalynology. 2nd Edi tion, Springer.
Tyson, R.V., 1993. Palynofacies anal y sis. In: Ap plied Micro - paleonto logy (ed. D.G. Jenkins): 153–191. Kluwer Ac a demic Pub lish ers, Neth er lands.
Tyson, R.V., 1995. Sed i men tary Or ganic Mat ter, Or ganic Fa cies and Palynofacies. Chap man and Hall, Lon don.
Utting, J., Hamblin, A.P., 1991. Ther mal ma tu rity of the Lower Car - bon if er ous Horten Group, Nova Sco tia. In ter na tional Jour nal of Coal Ge ol ogy, 13: 439–456.
Van-Waveren, I., Visscher, H., 1994. Anal y sis of the com po si tion and se lec tive pres er va tion of or ganic mat ter in surficial deep-sea sed i ment from a high-pro duc tiv ity area (Bandasa, In - do ne sia). Palaeo ge ogra phy, Palaeoclimatology, Palaeo ec ol - ogy, 112: 85–111.
Woollam, R., Rid ing, J.B., 1983. Dinoflagellate cyst zonation of the Eng lish Ju ras sic. In sti tute of Geo log i cal Sci ences Re port, 83/2:
1–42.
Zobaa, M.K., 2011. Ap plied palynology: multidisciplinary case stud - ies from Egypt, Gulf of Mex ico and USA. Ph.D. the sis, Mis souri Uni ver sity of Sci ence and Tech nol ogy.
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