JOURNAL OF GEOTECHNICAL GEOLOGY (APPLIED GEOLOGY)
Year:2010 | Volume:6 | Issue:2|Papers Count:11

In the present research biostratigraphic studies of the Abtalkh Formation at the Kopeh-Dagh basin have been investigated. The study of foraminifera content of the Abtalkh Formation showed that there are 6 biozones in the Mozduran section (Kopeh-Dagh). These biozones indicate the age of Early Campanian-Late Maastrichtian. Most of the lithology of the Abtalkh Formation includes gray marls with a thickness of 793.5 meters. Its lower boundary with the Abderaz Formation and upper boundary with the Neyzar Formation are conformable. In this study 24 planktonic species of 11 genera have been identified and presented.

The Surmeh Formation of the Khami Group (Early-Late Jurassic) is composed of carbonate rocks and is separated from its lower and upper formations disconformably. The lower part of the Formation is composed of limestone facies containing Lithiotis zone. The upper limit of the Middle Jurassic in Fars is determined at the top of Pfendrina zone. The red-coloured vein of sandstone in the studied area (Gadvan Mountain) can be identified as the cause of the operation of the Mid-Cimmerian phase. The microfacies belong to the shallow and deep open marine (O), barrier (B) and lagoon (L) environments. In the section of Gadvan Mountain, it is determined that a soluble surface of solution breccias exists in the Surmeh Formation terminal. So, the Jurassic-Cretaceous boundary at Gadvan Mountain is discontinuous.

Bozorgniella qumiensis is one of the determined species from sediments of the Asmari Formation at Alamdar stratigraphic section located in northeastern Behbahan, Khuzestan province. This species was recognized in eleven from 109 collected samples. The Asmari Formation in the studied section is composed of limestone with a thickness of 256.6m overlying unconformably the Pabdeh Formation and underlying the Gachsaran Formation. On the basis of the assemblage and stratigraphic distribution of determined benthonic foraminifera, the age of the Asmari Formation is Oligocene (Late Rupelian-Chattian) to Early Miocene (Aquitanian-Burdigalian). Bozorgniella qumiensis was introduced from Aquitanian sediments of the Qom Formation in Qom region, central Iran. However, the age of this species in Alamdar section is Oligocene (Late Rupelian-Chattian) to Early Aquitanian.

The nannofossils and planktonic foraminifera have a short range stratigraphy and a vast geographical extension. As a consequence, the two fossil groups can be used for biostratigraphic subdivision and correlation. Therefore, and due to the lack of any correlation study, the nannofossils of the Gurpi Formation have been investigated in western Shiraz. The Gurpi Formation has been formed of shale and few marly limestones. As a result of this study, based on the obtained nannofossils and the planktonic foraminifera, the studied section is of Early Santonian to Late Maastrichtian age, which is corresponding to the CC14-CC26 of the Sissingh zones (Sissingh, 1977) and the biozones of Dicarinella concavata-Dicarinella asymetrica to Abathomphalus mayaroensis (James&Wynd, 1965).

The Lower Miocene Asmari Formation in Lali oil field, 40 kilometers NW of Masjed-e-Soleyman, is a thick sequence of limestone, argillaceous limestone and dolomitic-anhydritic limestones. At the mentioned area, it lacks the Lower Asmari but contains the Kalhur member and basal anhydrite. The study of the Asmari thin sections from available cores and cuttings at wells no. 20 and 22 of Lali oilfield led to the recognition of 10 microfacies, related to six facies zones, including: supratidal, intertidal, shelf lagoon, barrier or shoal, shallow open marine and basin margin. The Asmari Formation represents sedimentation on a homoclinal carbonate ramp. Diagenetic processes in the Asmari Formation are: physical and chemical compaction, cementation, dissolution and production of mainly vuggy and channel porosities, neomorphism, dolomitization, anhydritization, fractures, micritization and biogenic processes. Fractures have had major effect on the quality of the Asmari reservoir, but vuggy and channel porosities, having less development, have played a less important role in reservoir quality. Results from this study have led to the recognition of marine, meteoric and burial diagenetic environments.

During the studies on vertebrate fossils, no sample of finger bones and metacarpal of ancient horses (Hipparion) were discovered. So there were different ideas about Hipparion existence in Iran. According to the excavations and the new findings, a sample of metacarpal belonged to this species was found, which with 3 separated and definite fingers (the 3rd finger is bigger than the side ones) proved the existence of Hipparion in Iran.

The clastic nannofossils in the Sephidan section of the Gurpi Formation have been studied. Based on these study 12 families, 18 genera and 45 types have been identified. As for stratigraphic spread of clastic nannonectons, this formation has compliance with the universal zonation of Sisingh (1979) of CC26 to CC14. Based on this study, the age of the Gurpi Formation in this section is the Santonian to Maastrichtian.

The fossil vertebrate localities of the informal Maragheh Formation in Azerbaijan, northwestern Iran are among the most renowned late Miocene localities in Eurasia .The fossiliferous beds are found to the north and east of the town of Maragheh on the southern and eastern slopes of the Sahand massif. Connecting with other Savanna-like faunas in the Pontian and its similarity to European Mammalian faunas, from the viewpoint of the paleoecology and paleogeography, make it an important fauna. The environment was like a forest. The Formation is divided into two parts, the upper subformation, which hasn’t any Mammalian fossils, consists of silt with Diatom, tuff with fossils of fish, pyroclastic sand and gravel. This part is located between NW of Sahand massif and Tabriz. The lower subformation consists of alternative marl, tuff and tuffy sand with occasionally layers of conglomeratic sand, which is thinner than the upper part and consists of Mammalian fossil fragments. Fossil fragments have been found in the lenses like puddles which were fluvio-lacustrine in their origin. The lower subformation according to phylogeny of Hipparion and isotopic studies is divided into three divisions. Although in some cases the upper subformation is detached from the informal Maragheh Formation, Prostrepsiceros aff. rotundicornis, Oioceros atropatenes, Protragelaphus skouzesi (Artiodactyls, Bovidae, Mammalians) are introduced by Horn-cores and several teeth rows.