حسن رامه

Morphogroup analysis, due to independence of species level taxonomy, as wel as permit to comparison of assemblages of differing ages, is a useful tool for ecological and palaeoecological interpretation. Foramniferal study of the Qom Formation in the Natanz (with Rupelin-Chattian?-Aquitanian in age and 330 m thickness) and Khorabad (southeastern Qom; with Rupelin-Burdigalian in age and 260 m thickness) sections resulted in identification of 8 morphogroups. The morphogroups were distinguished according to test/shell morphology and architecture (general shape, mode of coiling, and arrangement and number of chambers), inferred life habitat either living on the surface of the sediments or within the sediments (epifaunal and infaunal), and feeding strategy. Generaly, epifaunal morphogroups were dominated in both study sections. The lower 200 m of the Natanz section, are dominated by calcareous porcelaneous morphogroups; while the upper layers are dominated by hyaline morphogroups, which indicates the lower and upper parts were deposited in inner ramp (lagoonal environments) and open sea, respectively. This significant change through time reffers to gradual increasing of the basin depth, decreasing the light intensity, reducing the salinity and decreacing the nutrient level. The distribution of morphogroups in the Khorabad section follows a reverse pattern; so that, despite the minor fluctuations, the lower 200 m of the Khorabad section, are dominated by hyaline morphogroups; while the upper layers are dominated by porcelaneous morphogroups, which indicates the lower and upper parts were deposited in open sea and inner ramp (lagoonal environments), respectively.

In this study biostratigraphy of the Upper Cretaceous deposits (Gurpi Formation) in Sepidan section located in the Interior Fars basin (SW Iran) was studied. The Gurpi Formation in this section consists of 360 m lime shale, argillaceous limestone and shale laid continuously on the Ilam Formation and with a paraconformity under the Pabdeh Formation. Nine genera and 27 species of planktonic foraminifera have been identified in the section. On this basis, the Gurpi Formation here includes nine biozones with an age of Santonian to Maastrichtian. The biozones identified resemble considerably those of the other parts of the world.

The Qom Formation in Talenkuh section with 605 meters thick is located 50 kilometers west of Semnan and includes six rock units which mainly consists of limestone, alternating of limestone and marl, marl, marly limestone, and gypsum. Lower boundary of the Qom Formation in this section with Lower red Formation is unconformable and its upper boundary is missing by faulting or erosion. By biostratigraphic studies, 34 genera and 18 species of benthic foraminifera were identified. Three assemblages have been recognized by distribution of these benthic foraminifera in the studied section that indicate Chattian? – Burdigalian age. Field evidences and petrographic studies together with microfacies analysis, led to recognition 1 conglomerate lithofacies, 1 evaporite facies and 10 microfacies that deposited in 5 sedimentary environments consists of: supratidal, tidal flat, lagoon, shoal and shallow open marine. Therefore, for the Talenkuh section, a carbonate platform in the homoclinal ramp has been suggested.