APPLIED SEDIMENTOLOGY
Year:2016 | Volume:3 | Issue:6|Papers Count:7

The Fahliyan Formation contains relatively thick carbonate sequence which belongs to the Khami Group with Neocomian-Barremian age. This study investigated this unit in Lar anticline in Izeh Zone, which led to the identification of 25 microfacies in 4 facies belts. In the Fahliyan Formation, the remains of the framework builders such as hermatypic corals and algaes are scarce, while grain-supported shoal facies show good deveolpment. Suggested depositional environment for this carbonates in the Lar anticline is a homoclinal carbonate ramp and dominantion of grain-supported facies indicates windward side of a ramp. Seemingly, barrier-bank complexes were developed in this area along the ramp shoreline which lead to dominance of bioclastic grainstone, bioclastic-peloidal wackestone-packstone facies, and calcareous sandstones. In addition, presence of stromatoporoid along with thick shoal facies may indicate a wave-dominated ramp. The most significant and effective diagenetic processes in the studied unit in the Lar anticline include micritization, compaction, dolomitization, dedolomitization, silicification, pyritization, cementation, and fracturing that occured in different stages of marine, meteoric, burial and telogenetic diagenesis.

In this study, petrological and geochemical characterizes of major elements of the Dahu Formation sandstones (lower Cambrian) in Abyaneh section which in west of Natanz, Central Iran have been investigated to specify the origin, tectonic setting and pale weathering condition. According to petrological studies, sandstones in this region are fine to coarse grained with intermediate to good sorting. Generally these sandstones are identified as litharenite, sub-litharenite, quartz-arenite and partially pheldesphtic litharenite. By comparing major elements with UCC shows that all elements (except CaO and MnO) have depleted with respect to upper continental crust (UCC). Geochemical data in tectonic setting discernment diagrams show that sandstones were deposited in active continental margin mainly. High value (93) of chemical weathering index (CWI) suggests an intermediate igneous source rocks with wet and warm condition.

The combination of petrography and geochemistry data of sedimentary rocks can reveal the nature of source regions, the tectonic setting of sedimentary basins, and paleo-climate conditions. With this goal, the Oligocene Upper Red Formation clastic rocks with a thickness of 220 m outcrop in the southern region of Hasan Abad- Tehran were studied. Using thin sections and point counting of minerals and components and geochemical analysis of major and minor elements, the sequence were carefully investigated. This section is composed of repeating sequence of bright color Marl and Litharenite sandstone. Grain counts and geochemical evidence proved that most of these sandstones are volcanic-arenite. Maturity and sedimentary cycle index of these rock is equal to 1.722, which indicates the formation of deposits in the first cycle of sedimentation in active tectonic setting with relatively low maturity. Also, based on the results of the interpretation of geochemical data, felsic to intermediate source rock with a composition similar to continental crust is suggested for sandstone.

Marls produce the highest deposits in the catchment areas among lithological units. This property of marls can cause the reduced useful life of dams, river, and sedimentation of water channels, the destruction of road, utilities, and ultimately desertification phenomenon. Hence, understanding the characteristics influencing the erodibility and marls divergence can be a priority. In this thesis, marls located in the south of Tehran (south of Hassan Abad- Varamin) were evaluated in terms of shape and intensity of erosion, physical, chemical, engineering and divergence features. Marl unit studied includes the onshore marl of Upper Red Formation unit M3 and Pliocene marl of unit Plm. Sampling in the unit of red upper geology and Pliocene was conducted in slopes 5%, 20% and 40%. Tests such as gradation, Atterberg limits, chemical analysis such as cations and anions, SAR, TDS, EC and dual Hydrometry and pinhole were carried out to achieve the predetermined goals. Granulation distribution showed no significant difference in different slopes. Comparing the plasticity index among the different forms of erosion, it can be seen that the surface erosion plasticity index is greater than other forms of erosion.it is a factor in the postponement of erosion. But overall, it's not much different from many other forms of erosion. The cation exchange capacity in the samples is between 14.2 to 25.88 meq per liter. The mean of this variable is further in the stream erosion. the range of this variable in samples is between 0.9 to 2.17 meq per liter. The mean of this variable in the erosion of stream and ditch is more than the rest of upper red formation units. The results of the double hydrometer tests on 20 samples indicate the high non-divergence. The sample collected from Station 1 (in the form of gully erosion) and station 5 with a gradient of 5% (with stream erosion) shows the average divergence. According to the pinhole experiment conducted at different stations, station 5 (with single stream erosion M3) and station 7 (with a form of gully erosion M3) showed a moderate divergence.

For the purpose of interpretation of paragenetic sequence and post-depositional history of the carbonate rocks of Badamu Formation carbonate rocks (Lower-Middle Jurassic), a selected section (thickness=101 m) including grainstones to packstones in north of Tabas city (east of Iran) has been studied. The main diagenetic processes are micritization, cementation, compaction and dissolution, neomorphism, dolomitization, fracturing and pore-filling, bioturbation and geopetal fabric. The results of geochemical analysis reveal positive relationships between Fe, Mn, Sr and Na amounts, whereas Mg shows negative relation to the others. According to the petrographic and geochemical evidences, paragenetic sequence of the Badamu Formation carbonates has been purposed. Hence, it has been concluded that four different environments (i.e. marine, meteoric, burial and uplift) are recognizable and also the sediments have been affected during eogenesis, mesogenesis and telogenesis stages.

The Middle Jurassic scilisiclastic doposit has a good exposure in the East of the Binaload Zone and composed of conglomerate, sandstone and high amounts of fine grained sediments. The lower and upper boundaries of section are sharp respectively with Mashhad phylite and limestone. In this study lithofacies analysis in order to interpretation depositional environment and the origin of tectonic setting of Jurassic silisiclastic deposits in Binaload Zone were investigated in Baze hoz section, soth of Mashhad. Relying on the facies characteristics and stratal geometries the silisiclastic succession are divided into 10 lithofacies in the 160 meter thick. lithofacies are classified into 4 categories including coarse grain (Gcm, Gmm, Gh, Gp), medium grain (Sh, Sr, Sm), fine grain (Fl, Fm) and biochemical (C). Based on the following evidence, the Jurassic silisiclasic sediments have been deposited in Delta river system: Sedimentary facies: coarsening upward deposit, coal deposite, Leave fossils, syneresis crack and unidirectional sedimentary structures such as ripplemark, cross bedding, lack of Bi-directional structure. Petrographic studies led to the identification 6 petrofacies conglomerate and sandstone. Plotted data on Qt, F, L diagram, indicate recycled orogene for this deposits. Also plot data on Basu and Q, F, L diagrams, respectively shows low to medium grade metamorphic and hiumid climatic condition for sandstones of Jurassic sediments for these deposits at the time of formation. According to Turan and Iran clash pages and closing the Paleo-Tethys Sea in NE Iran Jurassic sediments in the study area composed of erosion of upland areas. These results indicate a wet weather conditions.

Depositional facies and diagenetic features are usually understood by their detailed petrographic studies and core or outcrop description. This study focuses on identification and interpretation of depositional and diagenetic facies from log facies concept in the Sarvak reservoir of a giant oil fields of the Abadan Plain, SW Iran. In order to achieve this, three step approach is used. Firstly core description and thin section study were carried out to determine sedimentary and diagenetic processes in one studied key well with 265 m core and 760 thin-sections. Facies analysis led to the recognition of 12 microfacies representing six facies belts, which are lagoon, shoal, rudist biostrome, slope, proximal and distal open marine. According to the results, it seem that studied interval have been deposited in a carbonate shelf platform. Diagenetic processes include micritization, bioturbation, recrystallization, cementation, dissolution, compaction and fracturing have been affected the Sarvak reservoir after deposition. In this study we introduced diagenetic facies as a method for effective comparison between diagenetic alterations and log facies distribution. Three diagenetic facies were recognized that coincide with intervals with low cementation and dissolution (facies 1), high dissolution (facies 2) and high cementation (facies 3). Secondly, five log facies were identified by hierarchical clustering method. The number of clusters were determined based on dendrogram tree and geological heterogeneity. Comparing the results of log facies distribution with depositional and diagenetic changes, show a good agreement between geological and petrophysical heterogeneity. Finally, identification of depositional facies belts and diagenetic facies after calibration of log facies with this geological properties, were carried out in un-cored wells by log facies approach. The presented approach in this study is effective in highlighting main depositional and diagenetic heterogeneity of the Sarvak reservoir in studied field.