نشریه رخساره های رسوبی
سال دوم شماره 2 (پیاپی 3، زمستان 1388)

The Nayband Formation sediments contains of abundant macrofossils such as corals, sponges, gastropods, bivalves, foraminifera and microproblematic fossils. Less attention has been given to these microproblematic fossils. In this research, Hasan-Abad stratigraphic section, northwest of Ferdows city, was selected. The Nayband Formation in this area has the Bidestan Member patch reef limestone within this formation. Study of mentioned limestone is led to identification of some microproblematic fossils such as Baccanella floriformis, Bacinella sp., Gosaukamerella eomesozoic, Lithocodium sp., Microtubs communis, Tamatophorella parvovesicuifer, Tubiphytes sp. and some Late Triassic index foraminifers. Scrutiny on microproblematic fossils and their association with foraminifers are important in paleontological studies and explanation of Late Triassic reefal – lagoonal environments. These species belong to shallow marine reef or carbonate platform and suggest a shallow reefal environment in photic zone with clear water in the inner ramp platform. Sedimentation during deposition of the Bidestan Member in the Late Triassic time may have taken place in low latitude.

Qom Formation deposits in the Chenar area, about 50 km northwest of Kashan, has 147 m thickness and consists of sandy limestone, thin to thick bedded massive limestone and shale. They unconformably overlain the Eocene volcanic rocks and the upper boundary is covered by alluvium. 8 carbonate microfacies and 1 silisiclastic facies, related to semi- restricted lagoon and open marine (slop and basin) environment, were identified. Based on 112 thin section studied, microfacies analysis and field observation, the Qom Formation at the study area deposited on open- shelf setting.

Four stratigraphic sections of the Qom Formation were measured and sampled at Kuh-e-khavich, Chah Qaleh No.1&2 and Baghat, south of Sirjan, to study the biostratigraphy characteristics of this formation according to benthonic foraminifers. Biostratigraphical studies indicated that this exposure is belonging to Burdigalian stage (Early Miocene) and is composed of the youngest strata of Qom Formation in Central Iran.

To study the Paleoecology of Oligo – Miocene Ostracods in north east of Sirjan, a suitable section has been measured and sampled. 12 genera of ostracods have been identified and are reported for the first time from this area. The specimens are well – preserved and both platycopids and podocopids are present. The assemblage consists of Aurila spp., Actinocythereis, Baidoppilata, Bairdia, Cytherideis, Propontocypris, Henryhowella, Krithe spp., Paradoxostoma, Trachyleberis, Tenedocythere, Xestoleberis, Cytherella, and Cytherelloidea. Constituents of this assemblage of ostracods community confirm a favorable condition during the deposition of the strata, specially well-oxygenated environment. These ostracods and associated foraminifers are representing an Early Miocene age for this succession.

For age determination of detrital sediments that have been deposited on metamorphic rocks in 1:25000 map of Shandiz, several macrofossils are collected. In this study, 22 genus and 39 species are identified and presented. They consist of Horsetails; natural Ferns seed Ferns & Gymnosperms and consist of Cycades, Gynkgoes & Conifers. Seven genus consist of Carpolithes, Cycadocarpidium, Pacypteris, Phoenicopsis, Pseudoctenis, Ptilophyllum & Sphenarion and five species consist of Dictyophyllum nervulosum, Ginkgoites baieraformis, Neocalamites ishpushtensis, Nilssonia ingens & Nilssonia undulate are report for the first time from Binaloud zone. Mesozoic detrital sediments in this map consists of 4 members (from base to top) including Conglomerate beds Jc1 (without plant fossil), Conglomerate beds Jc2, Shaly – Sandstone bed sh.s and Conglomerate beds Jc3. According to their stratigraphical distribution and assemblage of two genus Coniopteris and Phoenicopsis in Conglomerate beds Jc2 and stratigraphical position of this beds and also presence of species such as Cladophlebis denticulate, Dictyophyllum nervulosum, Ginkgoites baieraformis, Ginkgoites cordilobata, Klukia exilis, Nilssona ingens & Nilssonia feriziensis in Shaly – Sandstone bed sh.s, latest Late Liassic (Toarcian) to Early Dogger (Aalenian) age are suggested for both of Jc2 and sh.s beds. Based on the presence of index species from Conglomerate beds Jc3 such as Cladophlebis cf. feriziensis, Cladophlebis denticulate, Coniopteris hymenophylloides, Klukia exilis, Neocalamites ishpushtensis & Sagenopteris cf. Iranica and abundance of 3 genus consist of Coniopteris, Klukia and Phoenicopsis that are present in the sh.s bed, Early Dogger (Aalenian – Bajocian) age are suggested for this bed.

Abderaz Formation has a widespread exposure in eastern Kopet-Dagh basin. This formation is mainly composed of gray to bluish-gray marl, marly limestone and limy marl with 3 bands of chalky limestone. Measured thickness of the Abderaz Formation in this section is about 583 m. 109 samples including 83 soft, infirm samples and 26 hard, firm samples were collected. In this study, 80 species of 40 genera of planktonic and benthic foraminifera, 3 genera and 3 species of nonforaminifera were identified. Based on these fossils, 5 biozones was determined; therefore the age of the Abderaz Formation is partly of Early Turonian - Late Santonian. In this study, three fauna composed of Heterohelix fauna of epicontinental sea, Globigerinelloides and Hedbergella fauna of shallow marine and keeled Globotruncana fauna of deep open marine were identified.

Gurpi Formation has a wide exposure in the Zagros sedimentary basin and has received considerable attention due to its unique stratigraphic position, choronostratigraphic situation, and flora and faunal diversity and abundance. Based on abundance, short biostratigraphy range and geographic distribution of nannofossils, these groups of planktonic fossils are very good biostratigraphic tools especially in the Late Cretaceous time. For the biostratigraphica studies of the Gurpi Formation in Kavar, 117 samples were taken and prepared. A total of 51 species belong to 21 genera were determined and photograph. The distribution of nannofloral assemblage of Gurpi Formation in Kavar section reveals the presence of CC18 to CC26 zones of Sissingh (1977) and NP1-NP2 zones of Martini (1971) that is indicating an Early Campanian to Early Danian age for the studied section.