JOURNAL OF STRATIGRAPHY AND SEDIMENTOLOGY RESEARCHES
Year:2012 | Volume:28 | Issue:3 (48)|Papers Count:6

Source rock intervals generally show a lower density, higher sonic transit time, higher porosity and higher resistivity than other sedimentary layers. Therefore wire-line logs have been used to identify source rocks and serve as an indicator for their potentiality. It is usually done using intelligent systems such as artificial neural network (ANN) and  DLogR techniques. Shaly-lime Pabdeh Formation with variable lithology and TOC has been used to make a comparison between results of these techniques and evaluate their validity. Regression analysis shows that correlation of ANN results with Rock-Eval pyrolysis outputs (99%) is more appropriate than DLogR results (60%). Calculation of mean square error (MSE) for mentioned procedures (used because MSE method has a better efficiency to determine real error) is in accordance with the said result. Here the MSE of ANN method (0.07) is much lower than that of DLogR technique (0.98). With an increase in TOC and clay content, DLogR accuracy will be increased. In this study, MSE of DLogR technique has been increased from 0.27 to 1.4 from shale to limestone lithology. TOC content of this formation vary from 0.5 to 4 wt. % based on ANN results. Pabdeh Formation can be divided into three members: A and C with lower than 1% and B with higher than 1% total organic carbon (TOC) values. Increase in formation thickness, clay percentage and TOC content toward the south-east of oilfield demonstrate that paleo-sedimentary basin had been deeper in this direction. Finally, since rush undulation response of gama-ray log with top of B member, therefore, this top can be used as an indicator of Eocene-Oligocene boundary and Pyrenean orogeny.

Two diagenetic processes of glauconitization and calcite cementation and relation those to sea level changes in the siliciclastic-carbonate sediments of the Aitamir Formation (Albian-Cenomanian) in Kopet-Dagh basin have studied. The lower sandstone unit consists of mainly sandstone intercalated with shale and limestone and the upper shale units are two major sediments of this formation. The sandstone of the lower unit based on composition and their relations with sea level change subdivided into two transgressive and regressive facies and in this relation, show different pathways of the diagenesis. In the transgressive facies display by high content of the shell remains, with development in diagenesis shows extensive cementation and a little compaction during burial stage. In the regressive sandstone, characterized by little skeletal elements, display little calcite cements and high burial compaction. The glauconitic grains and calcite cementation in the Aitamir Formation concentrated in the transgressive facies and especially in the maximum flooding surface and transgresive surface. Whereas, in the regressive facies the glauconitic grains and calcite cementation is principally low. Moreover, the transgressive system tract and maximum flooding surface is characterized by mature and high mature glauconitic grains.

The Shemshak Group is well-exposed and spread in the Baladeh area (Central Alborz). 22 macrofossil species allocated into 14 genera of various orders such as Equisetales, Filicales, Bennettitales, Cycadales, Ginkgoales, Czekanowskiales and Coniferales are identified. Two asseblage biozones are recognized. Assemblage zone I is established based on Ptilophyllum minor and Klukia exilis, and assemblage zone II is recognized according to Coniopteris hymenophylloides and Ptilophyllum harrisianum. Furthermore, on the basis of presence of index fossils such as Equisetites columnaris, Coniopteris hymenophylloides, Klukia exilis, Nilssonia macrophylla and Ptilophyllum minor the Early to Middle Jurassic age (?Hettangian-Toarcian to Bajocian) is suggested for these sediments.

Gavkhuni playa lake, located 130 km southeast of Isfahan, comprises of sand, mud and salt flats. This playa includes two environments as delta and playa lake. Sand dunes, 45 kilometers long, extend in the west of the playa. Rock fragments of andesite, dacite, tuff, granite, schist, gneiss, fossil bearing limestone, sandstone and also quartz and feldspar minerals form the alluvial and aeolian sediments. Heavy minerals including idocrase, tourmaline, biotite, wollastonite, magnetite, hematite, goethite and pyrite were also identified. Fesharak skarns located in northeast of the region are the sources of spinel, idocrase and wollastonite minerals. Silicate heavy minerals like hornblende, pyroxene, epidote, zircon, garnet, tourmaline, biotite and also magnetite are mainly originated from Urumieh-Dokhtar volcanic belt located in northeast of the area and different iron bearing rocks are the sources of pyrite, hematite and limonite. Therefore, lithology and its variation within the drainage basin and Zayandehrud River are important factors in the determination of kind and distribution of the alluvial and aeolian sands in the study area.

Litnology and sedimentology factors affect on downstream changes in bed load shape and can be useful to detect watershed hydrological processes as they are very important to design hydraulic structures and reservoir management. This research was conducted in Qalesar River in Mazandaran Province with main river length of 24 Kilometers. After recognition of the study area, 11 sections were selected toward downstream for bed load sampling. Laboratory analysis were done using gravel meter and sieving method to measure and calculate some bed load shape characteristics. Also physical properties of each sub-watershed were extracted using Arc/GIS 9.2 software. Finally, in order to determine most effective physical characteristics on bed load shape, data were analyzed using SPSS 16. Results of statistical analysis indicate the best model between D50 and length of 1 order channel in bivariate regression equations and between D50 and distance from upstream in multi-variate regression equations.

Permian deposits (Kubergandian-Lopingian) at Il-e Beyk section located in Bakhtiyari Zard Kuh, High Zagros, was studied comprehensively in regard to its fusulinids faunas for the first time. In this study 30 species belong to 14 genera were recognized and in addition one species (Rugososchwagerina zagroensis) was described systematically. Five Zones were distinguished in the studied section. The oldest one is Praeskinerella parviflucta-Chusenella? pseudocompacta is situated in the lower 120 m of the succession and is assignable to Kubergandian. The second zone is Eopolydiexodina persica occurs from 120 through 320 meters in the section and is referable to Early-Middle Murgabian. The Third zone is Chusenella schwagerinaeformis-Rugososchwagerina zagroensis that is found in a very narrow horizon within 320-350 m of the succession and yield late Murgabian-Early Midian age. The fourth zone is Parafusulina crassispira established from 360 to 435 m in the succession and is dated to Early Midian. The fifth zone is Afghanella schencki extended from 438 through 687 m and of latest Midian age. The strata rested in 920 m above the base of the section contain small foraminifers including Paraglobivalvulina sp. and Dagmarita sp. that can be considered Lopingian in age. The interval from 687 through 920 m yield no fossil and can be assigned to either Guadalupian or Lopingian age. Fusulinids studied in this paper demonstrate western Tethyan affinity.