List of Articles Oligo-Miocene

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  1 - Sequence Stratigraphy of Oligo-Miocene deposits at Ahmadi anticline, southeast of Shiraz
  Jahanbakhsh Daneshian Mohsen Yaghoobi Alireza Tahmasbi Sarvestani
  The sequence stratigraphic studies can be of great help in understanding and analysis of sedimentary basins. For this purpose, Oligo-Miocene sediments (Razak and Asmari formations) at the Tang-e-Abdi section (southern flank of Ahmadi anticline) located in Fars province More

  The sequence stratigraphic studies can be of great help in understanding and analysis of sedimentary basins. For this purpose, Oligo-Miocene sediments (Razak and Asmari formations) at the Tang-e-Abdi section (southern flank of Ahmadi anticline) located in Fars province was selected and investigated. The Asmari Formation overlies paraconformably on the Jahrum Formation, and it is overlain by the Razak Formation. The lithologic column of this section includes a succession of the Jahrum (10m), Asmari (35m) and Razak (172.5m) formations, and consists mainly of limestone, argillaceous limestone, marl, sandstone, conglomerate, shale and dolomitic deposits. Totally, 84 samples were investigated, and their age is suggested as Late Eocene for the Jahrum Formation to Rupelian for the Asmari sediments, and Rupelian to Aquitanian for the Razak Formation based on the benthic foraminiferal stratigraphic distribution. The microfacies studies were led to recognition of four facies belts including tidal flat, lagoon, sand shoals and open marine. According to field & laboratory studies, four sequences and sequence boundaries were recognized. Two sequence boundaries are of type one and the other two are of type II sequence boundaries. Manuscript profile
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  2 - Foramniferal morphogroups of the Qom Formation in E Sirjan and SW Kashan: implication for paleoenvironmental and paleoecological interpretations
  Ebrahim  Mohammadi
  The Qom Formation is the main reservoir and source rock of hydrocarbons in central Iran. Foraminifera are now central to our ability to date, correlate and analyse the sedimentary basins that are currently key to the economic wellbeing of the world. Morphogroup analysis More

  The Qom Formation is the main reservoir and source rock of hydrocarbons in central Iran. Foraminifera are now central to our ability to date, correlate and analyse the sedimentary basins that are currently key to the economic wellbeing of the world. 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. It is independent of species level taxonomy and is thus relatively elementary to translate from one worker to another. Foramniferal study of the Qom Formation in the Bujan (eastern Sirjan; with Rupelin-Chattian in age and 156 m thickness) and Varkan (southwestern Kashan; with Rupelin in age and 190 m thickness) sections resulted in identification of seven 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 (suspension-feeder, herbivore, etc.). Generaly, epifaunal morphogroups were dominated in both study sections. The morphogroup analyses showed variations in the percentage of the dominant morphotypes, suggesting fluctuations in the paleoecological conditions. In the Bujan section, the Rupelin deposits are dominated by calcareous porcelaneous morphogroups; while the Chattian deposits are dominated by hyaline morphogroups, which indicates the lower and upper parts were deposited in inner ramp (lagoonal environments) and middle ramps, 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. De dominance of the hyaline morphogroups throughout of the Varkan section is indicative of the deposition in middle ramp environments with normal salinity under meso-photic to oligo-photic conditions. Manuscript profile