Scientific Quarterly Journal of Geosciences

Scientific Quarterly Journal of Geosciences

Deliberation of Cenomanian- Coniacian Boundary based on Biostratigraphic and Lithostratigraphic Studies in Bahregansar Field, Presian Gulf

Document Type : Original Research Paper

Authors
K. Kiarostami 1
S. H. Vaziri 1
B. Noori 2
S. Allahmadadi 3
F. Vakilbaghmisheh 3
1 Islamuc Azad University (IAU) , North Tehran Branch, Tehran, Iran
2 National Iranian Oil Co., Tehran, Iran
3 Geological Survey of Iran, Tehran, Iran
10.22071/gsj.2011.54447
Abstract
In order to investigate lithostratighraphical and biostratigraphical as well as determination of exact contact between the Sarvak and Ilam formations in oil well X-01 of Bahregansar field thin microscopic sections, final well reports and its illustrative diagram were studied. The Sarvak Formation with a thickness of 206 m overlies the black to dark-green marls of Kazhdomi Formation with a gradual contact. This formation can be divided into 2 members and consist mainly of dolomite and dolomitic limestone. The Ilam Formation is considered in a depth ranging from 2672 to 2678 m in the studied well based on studied section and is mainly formed of clay limestone and thin-bedded limestone. This formation is covered by Gurpi Formation with a gradual contact and has a disconformity contact with the Sarvak Formation. Moreover, the age of the Ilam Formation has been considered as Coniacian - Early Campanian which is formed of pelagic facies in the studied area. A number of 22 species belonging to 23 genera have been identified that 6 genera and 11 species belong to the Ilam Formation and 11 species of 17 genera belong to the Sarvak Formation. Considering the identified fauna in the Sarvak Formation, the three following biozones were identified conforming to biozones presented by Wind (1965):1-Nezzazata - Alveolinids Assemblage Zone # 25; 2-Rudist debris # 24; 3-"Oligostegina"facies # 26. Presented biozones and principle of super position indicate Cenomanian age for the Sarvak Formation that consist of pelagic and neretic facies. Moreover, the age of the Ilam Formation has been considered as Coniacian - Early Campanian which is formed of pelagic facies in the studied area.
Keywords
Cenomanian
Coniacian
Sarvak& Ilam Formations
Bahregansar
Persian Gulf
References
 
Boli, H. M., 1945- Zur stratigraphic der Oberen kreide in den hoheren Helvetisehen Dechen. Eclog.  Helv., 37, pp. 217-328.
Boli, H. M., 1966- Zonation of Cretaceous to Pliocene marine sediments based on planktonic foraminifera Bole thin Informative Asociacion Venezolana De Geologia.Mineriay peteroleo, No.9, pp.3-32
Boli,H. M., 1959- Planktonic forminofera from the Cretaceous of Trinidad., W.I., Bull., Amer.paleonto.Vol.39
Bolz, H., 1978- The paleogeographical evolution, during The Cretaceous in the operating area, O.S.C.O. (Oil Services Company Of Iran).
Caron, M., 1983- Taxonomic et.phylogenic dela famille des Globotruncanidae. 2nd kreide symposium, Munchen ,1982, Zitteliana Munchen, No.10, pp.667-81
Caron ,M., 1989- Cretaceous Plankton.Foraminifera, and Boli, H.M., et at.(editors). Planktonic Stratigraphy, Vol.1, Cambridge University press.
I.O.O.C (Iranian Off Shore Oil Co.), 2005 - Bahregansar Geosience Study.
P. P.Z.Pars Petro Zagros Co., 2005- Hendijan Field Study.
Postuma, J., 1971- Manual of Planktonic foraminofera,Elsevier publishin  Company A mesterdom, 420p
T. E. (Tehran Energy) Co., 2000- Bahregansar Field Study.
Wynd, J. G., 1965- Biofacies of Iranian Oil Consorticsm agreement area, I.O.O.C. rep., No.1082
 
Scientific Quarterly Journal of Geosciences
Volume 21, Issue 82
Autumn 2011
Pages 113-120