Geopersia
Volume:7 Issue: 2, Summer- Autumn 2017

The Upper Cretaceous strata were studied in a composite stratigraphic section named here Padeha-Baghak section in east of Koppeh- Dagh basin, north east of Iran. In this study, palynostratigraphy, palynofacies and depositional environment history of Abderaz Formation were integrated with sequence stratigraphy. Determination of sea level history and sequence units of the Abderaz Formation using sedimentology data is accompanied with many problems due to uniform deposition of this formation in moderately deep parts of the basin. Hence, using the fossil evidences together with sedimentology information, sequence units of this formation have been splitup. For this purpose, 127 rock samples were collected and studied. Studies of planktonic foraminifera and dinoflagellate cysts suggested a late Turonian-early Campanian age for this formation. Palynofacies parameters such as frequency and diversity of dinoflagellate species and the ratio of continental to marine constituents (CONT/MAR ratio) have been used for interpretation of the sequence stratigraphy of the formation. The ratios of amorphous organic matter to Marine Palynomorphs (AOM/MP), and Chorate to Proximate, Proximochorate, Cavate (C/PPC) and peridinioid to gonyaulacoid dinocysts (P/G) reflect the changes in sea level throughout the studied section. According to these studies, five palynofacies have been recognized. The record of sea level changes in the shales and marls of this section shows seven third – order sequence with six sequence boundary (type II), The interpreted sea-level curve in the Koppeh-Dagh basin can be correlated with late Cretaceous global curves.

The Gurpi Formation, one of the geologycal units of the Zagros Basin, stretches with in the Folded Zagros in the provinces of Khuzestan, Lorestan, and Fars,in southwest Iran. In all 525 samples were collected from five stratigraphic sectiones of the Gurpi Formation in Dezful embayment Zone for studying biostratigraphy. Totally 47 species from 23 Planktonic foraminifera genera were recognized in this study. From a biochronostratigraphic point of view, eight of the identified biozones are typically restricted to the Late Santonian to Late Maastrichtian. To examine the paleoecology of the formation, some important ecological factors including water level, salinity, and oxygen regime changes during the depositional courses of the formation were analysed.

This study includes a thorough systematic analysis of the ichnological record in the Late Triassic siliciclastic Nayband Formation of the Tabas Block, Central Iran. A total of 48 ichnospecies representing 28 ichnogenera are identified and their preservation aspects, paleoecological aspects, producers and behavioral aspects are discussed. The ichnofauna includes Arenicolites, Asterosoma, Bergaueria, Chondrites, Cochlichnus, Cylindrichnus, Diplocraterion, Helminthopsis, Gordia, Gyrochorte, Lockeia, Macaronichnus, Monocraterion, Ophiomorpha, Palaeophycus, Paleodictyon, Phycodes, Phycosiphon, Planolites, Protovirgularia, Rhizocorallium, Rosselia, Scolicia, Skolithos, Taenidium, Teichichnus, and Thalassinoides. The high ichnodiversity and bioturbation intensity of the Nayband trace fossil suite seem to represent proliferation of epifaunal and infaunal habits, experiencing a high diversification of marine communities after the drastic reorganization of marine ecosystems during the Late Triassic. Further studies focused on the ichnological
signatures of these deposits will provide more detailed information to improve the current paleoecologic and paleoenvironmental interpretations of the Nayband Formation deposits.

Analysis of benthic foraminiferal assemblages was performed in Callovian deposits of the Farsian Formation Northeastern Alborz; Iran. The sequence of Callovian at the Goznawwi area consists mainly of soft marls , which contain high-diversity calcareous assemblages. In this foraminiferal succession nine morphogroups were differentiated according to shell architecture (general shape, mode of coiling and number of chambers), integrated with the supposed microhabitat (epifauna, shallow infauna and deep infauna) and feeding strategy (suspension-feeder, herbivore, bacterivore, etc.). Based on foraminiferal assemblage, we have distinguished nine type of morphogroups, including seven calcareous benthic and two agglutinated benthic morphogroups. The environmental evolution of the analyzed section is interpreted by using the stratigraphic distribution of morphogroups, combined with species diversities and sedimentary data, in a sequence stratigraphic framework. Palaeoecological analysis of the foraminiferal assemblages based on morphogroups analysis and macroinvertebrate has shown that this sediment was deposited on the open marine, deeper of the shelf water, with normal saline (euhaline), with sub-oxyed (or dysoxic) condition and eutrophic environment.

The Aitamir Formation is divided into two members the lower sandstone and the upper shale. 32 genera and 57 species of foraminifera have been recognized. According to identified foraminifera Rotalipora appenninica Interval Zone, Rotalipora globotruncanoides (Rotalipora brotzeni) interval zone and Whiteinella aumalensis-Dicarinella canaliculata assemblage zone are proposed and a l Albian-l Cenomanian age is attributed for upper shale member of the Aitamir Formation. Palaeoecological studies led to recognition of three calcareous, two agglutinated benthic and three planktonic foraminifera morphogroups. In the lower one third of shale member, the planktonic foraminifera are more abundant than agglutinated benthic foraminifera, while in the upper one third, the frecuency of all morphogroups increase. Calcareous benthic morphogroups could be attributed to aerobic, shallow to slightly deep water, oligotrophic environment; while the agglutinated benthic morphogroups show aerobic, mesotrophic to eutrophic condition that are characterized by a dominance of arenaceous shallow infaunal specimens which are active deposit feeders. Planktonic foraminifera morphogroups with trochospiral and smooth test show that may have lived near the surface water in the aerobic to semi aerobic environmental conditions. The increasing number of planktonic foraminifera and specially keeled species could suggest recovery in paleoenvironmental conditions.

In this paper, 2D seismic data and petrophysical logs of the Pabdeh Formation from four wells of the Mansuri oil field are utilized. ΔLog R method was used to generate a continuous TOC log from petrophysical data. The calculated TOC values by ΔLog R method, used for a multi-attribute seismic analysis. In this study, seismic inversion was performed based on neural networks algorithm and the resulting acoustic impedance was utilized as an important predictor attribute. Afterward, a probabilistic neural network was trained by using a set of predicting attributes derived from multiple regression. Subsequently, TOC was estimated by using seismic attributes with a correlation coefficient of 75%. In the next step of the study, the nonlinear ant colony optimization technique was utilized as an intelligent tool to generate a 2D TOC section from seismic attributes. Nonlinear ant colony optimization proposed an intelligently derived equation for which weight factors of each predictor seismic attribute in TOC estimation model were derived by using stochastic optimization. The results show that nonlinear ant colony equation (stochastic optimization) outperforms the probabilistic neural network model (gradient optimization).

The Oligocene–Miocene deposits of the Asmari Formation are located in SW of the Zagros Mountains of Iran. The lower part of the Asmari Formation consists of an evaporite bed that is termed Basal Anhydrite. Seven sections from four different anticlines were selected and sampled for petrographic and mineralogical analyses .The petrographical examinations were carried out using an optical polarized light microscope and SEM analyses. To determine the mineralogical composition, evaporite samples were analyzed by X-Ray Diffraction. Particular petrographic characteristics, at the macro- and microscales, especially common pseudomorphic features and mineralogical analysis of the Basal Anhydrite showed that anhydrite was transformed to gypsum during exhumation. Diagenetic processes caused an increase in the pure gypsum and a simultaneous decrease in the residual anhydrite. Two main textures, fine- crystalline (alabastrine) and coarse crystalline (porphyroblast), were distinguished in samples indicating replacement of anhydrite by gypsum. The textures related to the tectonic movements in evaporite rocks were observed in the thin sections. The effect of tectonic varies due to the type of gypsum texture. Microcrystalline gypsum is mostly recrystallized to form coarse-crystalline and aligned-flowing texture. Coarse crystalline gypsum which contains anhydrite is more resistant against the tectonic effects because it shows only a little rotation.

In this research, different experimental techniques have been used to determine the strength of four types of travertines, selected from Hamedan and Markazi Provinces, west and central parts of Iran respectively. For this purpose, after sample preparation and assessment of mineral properties, the selected samples were subjected to physical and mechanical tests with special reference to two major anisotropic angles (i.e. perpendicular (⊥) and parallel (∥)) between bedding/lamination planes and the major loading directions. Based on the test results, it can be concluded that the percentage/type of matrix and porosity have a more important effect on the physical and mechanical properties than the rock structure. Statistical analyses, including simple and multiple linear regressions, were applied to identify those physico-mechanical parameters that are more appropriate to predict uniaxial compressive strength (σ_(c⊥) and〖 σ〗_(c∥)) and to establish some new equations. Data analysis in simple regression shows that bulk specific gravity (saturated surface dry, SSD) and Brazilian tensile strength are the most and the least influential factors on σ_(c⊥) and〖 σ〗_(c∥), respectively. Based on multiple regression method, equations with only two parameters (a physical and a mechanical parameter) were extracted for calculating σ_(c⊥) and σ_(c∥).

The North Tabriz Fault is seismologically an active fault with current right lateral strike-slip movements. Restricted mafic to intermediate Late Cretaceous igneous rocks are exposed along the North Tabriz Fault. Whole rock samples and clinopyroxene phenocrysts geochemistry were studied in order to characterize the petrogenesis of these mafic rocks and their possible relation to an oceanic crust. The results indicate a tholeiitic parental magma that formed in an evolved mid- ocean ridge tectonic setting similar to the Iceland mid-Atlantic ridge basalts. The ocean floor basalt characteristics give evidence of an oceanic crust along the North Tabriz Fault. Therefore, the trend of the North Tabriz Fault more likely marks a suture zone related to the closure of a branch of the Neo-Tethys Ocean in the NW Iran. This fault, in addition to the Caucasus and Zagros suture zones, compensates an important part of the convergence between the Arabian and Eurasian plates resulting from the Red Sea divergence. It is concluded that the North Tabriz Fault appears to be possible southeastern continuation of the North Anatolian suture zone.

Aghdarband coal mine, located in NE of Iran, with annual coal and waste production capacity of about twenty million and six thousand tons, respectively, causes the increase of the concentration of some heavy metals in the soil and surrounded sediments. This paper deals with geochemical distribution and environmental effects of the heavy metals on the sediments around the mine, using geochemical data and statistical analysis. Investigation of the correlations of soil chemical parameters based on Pearson correlation coefficients, cluster analysis and principal component analysis suggested that sulfur, arsenic, molybdenum and copper were distributed in the region under the effect of anthropogenic origin (coal washing plant). Also, magnesium, nickel, cadmium and chromium were caused by the lithogenic origin effect (ultramafic rocks) in soil and sediment of the region. These studies also revealed that the concentration and geochemical distribution of aluminum, manganese, antimony, cobalt, iron, zinc and lead was controlled by the acidic rocks (rhyolites, metamorphosed acidic tuffs) and the metamorphosed politic sediments (slate and phyllite) and the calcium element by the carbonate rocks. Calculation of the enrichment and geo-accumulation factors also shows that the soil of the region is polluted by the elements such as sulfur, arsenic, copper and lead. Zoning maps of elements concentration also showed that these elements have the highest concentration at the place of coal washing and coking plan, as the concentration was gradually decreased by moving away from these locations.