Epifauna

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1 - Foramniferal morphogroups of the Qom Formation in E Sirjan and SW Kashan: implication for paleoenvironmental and paleoecological interpretations
Ebrahim Mohammadi
20.1001.1.22518738.1399.10.20.2.1

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
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2 - palaeoechology and taphonomy of Albian-Cenomanian Echinoids of Kazhdumi Formation in Firouzabad section, Zagros Basin
Babak Sedghi Ali Bahrami Yazdi Yazdi

Kazhdumi Formation deposits in Firouzabad section were investigated regarding the postmortem and burial events of echinoderms, from about 150 echinoderm fossils which include 10 genera and 13 species of Coenholectypus neocomiensis, Phymosoma binexilis, Dorocidaris taouz More

Kazhdumi Formation deposits in Firouzabad section were investigated regarding the postmortem and burial events of echinoderms, from about 150 echinoderm fossils which include 10 genera and 13 species of Coenholectypus neocomiensis, Phymosoma binexilis, Dorocidaris taouzensis, Cottaldia aff. Benettiae, Leptosalenia sergipensis, Phymosoma baylei, Micropedina olisiponensis, Tetragramma deshayesi, Macraster douvillei, Mecaster batnensis, Macraster obtritus, Pliotoxaster comanchei, Macraster sp., Hemiaster sp. most part of them suffer from disarticulation and fragmentation, radial cracks and shell deformation (test outline distortion and radial cracking) and volume change and biological erosion (bioerosion) and perforation by living worms (microboring). Of course, after volume changes, fractures or taphonomic compression, the existing solutions (hydrocarbon and solutions rich in iron, manganese and sometimes silica) hydroxides have been replaced in the cracks. The test of these echinoderms has been used by symbiotic epifauna such as Osterids and Gryphaes as food and attachment points and shelter after their death and burial. It seems that the volume change, crushing, solution injection and fauna bending are influenced by the tectonic pressure of the salt domes of the region and the soft lithology (high plasticity) of the Kazhdami formation between the Darian and Sarvak formations. Manuscript profile

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