Document Type : Original Research Paper
Authors
1 Associate Professor, Geology Department, Earth Sciences Faculty, Kharazmi University, Tehran, Iran
2 Assistant Professor, Research Institute of Petroleum Industry of Tehran (RIPI), Tehran, Iran
3 M.Sc. Student, Geology Department, Science Faculty, Kharazmi University, Tehran, Iran
Abstract
In this research, the Sarvak Formation and lower part of the Surgah Formation in Kabirkuh anticline, southeast Ilam with thickness of 897 m were studied. Prospect of changes in umbilical structures of planktonic foraminifera such as lip, ortico throughout of Albian to Turonian were investigated. The phylogenic trend shows that lip structure in primary morphogroups gradually replaced by ortico in more developed forms. The statistical analyses showed that the trend of the mentioned changes is comparable with increasing the water depth while a decrease in depth result in the development of lip in studied planktonic foraminifera. According to foraminifera and Oligosteginids, the age of examining succession is late Middle Albian to Late Turonian. The study of different type of morphotype groups in this section indicates that the fauna mostly belong to morphotypes number two and one, and then rarely number three. The studied morphotypes show that the main part of sedimentation carried out in relatively deep marine condition The results show that the Muricohedbergella frequency at lower and middle parts of the Sarvak Formation incompatible with the basin depth decrease that is specified with two decreasing peaks (sea regression). Also Favusella frequency in line with three increasing peaks (sea Transgression), and is a good index for showing the basin depth. In the final part of the sequence, the presence of Whiteinella to increase peaks which are compatible with the basin increasing depth and sea transgressive in studied section.
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