APPLIED SEDIMENTOLOGY
Year:2017 | Volume:5 | Issue:9 |Papers Count:7

Sediment constituents, total organic carbon contents, redox-sensitive trace-metals concentrations, and organic matter (OM) types have been analyzed on fifteen sediment cores (73cm-165cm long) taken from the southern part of the South Caspian Basin (SPSCB). 257 samples for sedimentological studies (particles size analysis, mineralogy and biota contents) and 120 samples for organic-inorganic geochemistry studies (TOC, S2 and RSTM concentrations) were analyzed. Sediments on the distal parts of shelf are mud dominated, while slope and proximal parts of the basin plain comprise interbedded debrite, and pelagic-hemipelagic sediments. Several factors (e. g. bottom dissolved oxygen (BDO), TOC, biota content, faecal pellets, and RSTM) suggest that these sediments were deposited under markedly different redox conditions, namely: (1) Shelf and slope settings (oxic sediments), and (2) intraslope basins and basin plain settings (dysoxic sediments). Observations suggest that basin plain and intraslope basins sediments were deposited under oxygen-depleted (oxygen minimum zone) conditions. The dysoxic sediments are enriched in RSTM (V, Zn, Cr, Cu, Ni), with high TOC values, with mud peloids, and contain type II OM, while the sediments of the oxic sediments are enriched in infaunal organisms, faecal pellets, and contain types III and mixture II/III OM.

The Ilam Formation with Coniacian-Santonian ages is one of the petroleum reservoir in the Zagros basin and wide area of Khozastan plain, which mainly composed of carbonate rocks. In this study, the Ilam Formation in 3 subsurface sections with total thickness of 274 m was studied in one of the southwest Iranian oilfields. The lithology of this formation in studied wells is limestone with interbedded shale and clayey limestone. Sedimentological studies and facies analysis of 230 thinsections of drilling cutting lead to recognition of 11 microfacies and one shale petrofacies in 3 facies belts. These microfacies were deposited in lagoon, shoal and open marine facies belts. According to recognised microfacies and comparing them with same carbonate deposits in other places, absent of reef structures, sliding and slumping facies, the sedimentary envirnment of this carbonate sequence was recognised as a homocline ramp which consist outer, middle and inner ramps. The main diagenetic features of the Ilam Formation in studied oilfield are bioturbation, micritization, cementation, dissolution and porosity, dolomitization, stylolitization, pyritization and fractures. Main cement types in this formation are equant, drusy, blocky, syntaxial and vein filling cements which formed in marine, meteoric and burial diagenetic environments.

The Asmari Formation in Gachsaran oil field has a low lithological diversity and including of limestone in the lower parts and dolostone in the upper parts of the reservoir. The goal of this study is determination of facies, depositional environment, diagenetic processes and their effect on the reservoir quality of this formation. Microscopic studies of 478 thin sections of cores led to the identification of 11 microfacies belong to 3 facies belts including inner (tidal flat, lagoon, shoal), middle and outer ramps. This study also revealed diagenetic processes including micritization, bioturbation, neomorphism, compaction, dissolution, cementation and replacement. In order to investigation of reservoir characterization, the effects of diagenetic processes and sedimentology used on the distribution of porosity and permeability. Based on the results, dolostones with intercrystaline-vuggy porosity, wackeston/dolowackestone with vuggy-channel porosity and Porous grain-dominated Packstone are the best reservoir facies comparsion with other facies in the Gachsaran oil field. Key words: Asmari Formation, Gachsaran Oil Field, depositional environment, diagenesis, Reservoir quality.

The Khanik titanium deposit is located at 82 km northwest of Urmia city in Sanandaj-Sirjan structural zone. This deposit is a part of Qazan mafic-ultramafic intrusive complex bearing two types of mineralization: 1) magmatic ilmenite and 2) sedimentary type of alluvial placer. The main minerals of placer is consist of ilmenite, titanomagnetite, magnetite, hematite, albite, hornblende and its secondary minerals include augite, clinozoisite, actinolite, goethite, montmorillonite and some forsterite. Microscopic studies of placer samples show the ilmenite as of individual grains and lamella inside the magnetite. The chemical composition of placer samples the diagrams of Al2O3/TiO2 versus SiO2 and (Hf/Yb) × 10 versus La/Th indicates the protolith of source rock as an igneous mafic rock. The REEs distribution, normalized in respect to chondrite shows lower distribution of LREEs in respet to HREEs with low negative anomalyof Eu in the Khanik sediments implying a mafic source rock. Ni/Co, Cu/Zn, U/Th indexes and authigenic U represents oxidizing environment at the time of deposit formation. Chemical weathering index (CIW') also indicates a high degree of weathering processes during the development of this placer.

The lower part of Niur Formation is located in SW Kashmar in Central Iran microplate. This Formation consists of limestone and sandstone in the study area. Petrography and field observations including texture, structure and other properties such as hummocky cross-stratification (HCS), conglomerate with erosion base (storm erosion), intraclasts particles in the conglomerate and graded beddings, which were the most important documented sedimentary structures in the succession, led to identification of the storm wave deposits in the Niur Formation. A proximal tempestite model was proposed for sedimentary deposits in this area based on above mentioned evidence and also vertical facies variations in the sedimentary sequence. Tropical storms (cyclone) affected the sedimentation pattern in studied area due to paleo-latitude position of the Central Iran microplate (about 25o to 30 south paleo-latitude). These tempestites were deposited on a ramp setting in north of supercontinent Gondwana. Identification of the Silurian tempestite in north of Tabas block is significant in the paleogeography and paleoclimate interpretations.

The upper part of the Sarvak Formation is one of important hydrocarbon reservoirs in the Middle East and Persian Gulf. This part of the Sarvak Formation is equivalent to the Mishrif Formation (with mid-Cenomanian age) in Persian Gulf and neighboring countries. In this study, investigation of a set of well log data and their clustering based on mathematic and statistical rules resulted in determination of reservoir electrofacies (EF1, EF2, EF3 and EF4) for the Mishrif Formation in three wells of Sirri fields in the Persian Gulf. Then, by using of core porosity and permeability data and flow zone indicator (FZI) method, flow units (A, B, C and D) were identified. With integration of the results from these two methods, reservoir zone thickness of Sirri Esfand, Dena and Civand 62 ± 0. 5m, 91± 0. 5m and 39 ± 0. 5m was determined, respectively. Finally, by utilization of water saturation factor, hydrocarbon column thickness in Sirri Esfand, 34. 5m; in Sirri Dena, 8. 5m and in Sirri Civand, 39. 5m was calculated. Based on these results, hydrocarbon column thickness from Sirri Esfand to Dena decreases, and it increases from Sirri Dena towards Sirri Civand.

Sediment transport from continents to oceans and seas via rivers is one of the most important processes regulating river-bank stabilization, soil formation, biogeochemical cycling of elements, crustal evolution and many other earth-related processes. Shahroud catchment is a part of Caspian Sea great drainage basin, located in North of Qazvin Province; its main tributaries are Alamoutrud and Taleghanrud rivers. As a structural point of view, the study area is part of Southern-Central Alborz structural zone which is mostly composed of Eocene volcanic units and Miocene terrigenous sedimentary rocks. In this research, water and sediment discharges (2013-2014 water year), grain size and mineralogical analysis of the sediment load were studied. Cyclic variation of discharge indicate a flood-dominated river; both water discharge and sediment load are controlled by the river tributaries and lithology of the catchment. This research shows (for the first time) that suspended load constitutes (mainly silt-size grains, composed of quartz, calcite, feldspar, muscovite/kaolinite) more than 99% of the sediment load. Bed-load materials are mainly volcanic-and carbonate-rock fragments. Erosion is the main process in upstream and transport/sedimentation is dominant in the river mid and downstream.