JOURNAL OF SEDIMENT AND SEDIMENTARY ROCK
Year:2010 | Volume:2 | Issue:7|Papers Count:8

A thick volume of the Lower Cretaceous deposits outcrop lies in the northeast of Mahallat in Markazi Province.These deposits are mostly composed of carbonate and siliciclastic rocks which are totally 332 meters thick. The lower contact of these deposits is an angular unconformity with Shemshak Formation and its upper contact is a fault with Jurassic limestone. In order to study and distinguish facies, recognize the sedimentary environments and evaluate the diagenetic processes, one stratigraphic section was selected and measured in the study area and 140 samples were taken out of it. Microscopic and field examination of the cross carbonate section led to the recognition of three facies belts containing lagoon, barrier and open marine. These facies groups have deposited on a rimmed shelf type of a carbonated platforms.

For petrophysical evaluation, using wireline logs (such as, Nphi, Density, Sonic, Gr logs) resulted in achieving petrophysical parameters such as, shale volume, porosity, water saturation and lithology in Bandubast well#1 of Kangan and Dalan Formations (in Bandubast Anticline).In this study, the probabilistic method has been used for log interpretations. For this purpose, after editing and applying proper corrections on wireline logs, the petrophysical parameters have been generated, investigated and interpreted. PHIE and PHIT are approximately the same in most parts of well#1. This volume of shale is low.

Triassic rocks in Zagros zone, consisting of limestones, dolostones and shale (ca.324 m thick), were examined in Eghlid area (near Nezamabad Village). A lithofacies (shale/marl) and 13 carbonate microfacies, consisting of: 1) paleosol, 2) supratidal mudstone, 3) algal mat boundstone, 4) intertidal mudstone, 5) intertidal breccia, 6) lagoonal mudstone, 7) shale/marl, 8) lagoonal mudstone/wackstone, 9) lagoonal wackstone, 10) lagoonal wackstone/packstone, 11) lagoonal packstone 12) sand shoal packstone, 13) sand shoale grainstone, and 14) open marine mudstone were recognized. All of them have been taken place in the inner part of a ramp. Microfacies 1 to 5 belong to intertidal zone; Microfacies 6 to 11 (and shale) occurred in the lagoon site; Microfacies 12 and 13 referred to the sand shoal and bar; and Microfacies 14 was deposited in the open marine belt of the sedimentary basin.

The fahliyan formation (lower cretaceous) is composed of carbonate reservoir Rocks, in south and westsouth of Iran. In order to study facies, depositional environment diagenesis processes and sequence stratigraphy in subcoastal fars and coastal fars two subsurface section Nar-2 and west Aghar have been studied petrographic and geophysical logs studies indicate that the fahliyan formation deposited in four faeied belts: Tidal flat (A), Lagoon (B), Barrier (C) and open Marine (D).Study of facies, their vertical and Lateral changes and comparison with modern and ancient environments indicate that the fahliyan formation deposited in a shelf carbonate platform with shallow environments.Sequence stratigraphy of the fahliyan formation in the aera indicates on the existence of two depositional sequence (3rd- order cycles).In the studies sections, the lower and upper boundary of the first sequence and the top boundary of the second sequence are type one unconformity . The main diagenetic processes include cementation, micritization, neomorphism, dissolution, compaction, dolomitization and bioturbation that belong to marine phreatic, meteoric phreatic and burial environments.

The Gadvan Formation is a lithostratigraphic unit which is composed of limestone, shale, and marl. The boundary between Fahlyian and Gadvan Formations is gradual which is characterized by evidences of petrographic and isotopic analysis.No sharp fluctuation was witnessed in carbon and oxygen isotopic samples around the boundary and paleotemperature of Gadvan Formation using isotopic studies based on was estimated 27.5° C.Three depositional sequences have been identified in Gadvan Formation. These three sequences are bounded by type two boundary (SB2).

In order to study facies and sedimentary environment of Mobarak Formation in Kiasar, 75 km Southeastern Sari, a stratigraphy section, 250 m thick, was selected, which included thin to thick layers of limestone and of dolomite, shale and marl. Its lower contact includes shale and thin to thick layers of limestone with hemoclinal conformity overlies Geirud Formation (Upper Devonian) and its upper contact includes thick beds of shale covered by disconformity with sandstone of Dorud Formation (Lower Permian). For field sampling, the best path was chosen, and following sampling and studying the petrographic characteristics, thin sections were supplied from samples, and the microscopic features of the samples were studied. This study shows that these sediments may have been deposited in hemoclinal ramp that consists of 4 microfacies assemblages and 19 subfacies. These lithofacies indicate that sedimentation must have occurred in open marine, bar, lagoon and tidal flat subenvironments.

Vardeh Drainage Basin is located in the north of Karaj.This basin belongs to the Central Alborz structural zone and its climate is semi-humid. The area of Vardeh basin is 68, 97 km2. Formations in this basin relate to Paleozoic, Mesozoic and Cenozoic that mainly include shale, tuffaceous shale, tuffaceus sandstone and limestone. Kahar Formation dating to Precambrian is the oldest and quaternary alluvial deposits are the youngest deposits at this basin. The aim of this study is to investigate erosion processes, erosion landforms and erodibility of formations using MPSIAC model in ILWIS environment. One of the methods for doing this study is classifying rocks of this basin in 5 erosion categories. dolomitic limestone of Soltaniyeh Formation have low erosion and Quaternary alluvial deposits have high erosion. Common shapes of erosion were identified by interpreting aerial pictures and conducting field studies. In Vv-4, sub-basin minimum shapes of erosion and in V-int sub-basin maximum erosion shapes of Rill, Sheet and Rock fall erosion are available. In MPSIAC model the effect of nine important factors on soil erosion and sediment yield were evaluated and numerical values were assigned to them in terms of intensity and weakness of each factor. Using the sum of those values for different factors, the level of deposit in the basin was calculated as Qs=0.253e0.036R and finally the map for each of the 9 factors was prepared in ILWIS environment. Considering identifying sub-basins with high severity of erosion and sediment yield V2and V3 sub-basins deposit, this basin has to be the first priority for soil protection programming.

In this research, a stratigraphic section called Kaftarak Section related to Jahrum and Asmari Formations was selected. The sediments in this section are 286 m thick.Generally, index mirofacies of the studied thin section in Jahrum Formation includes wackestone, packestone, Grain stone, Dolomite microfacies and Dolomite Limestone, which lie in environmental groups of Intertidal (A), lagoon (B) and shoal (C). Index mirofacies of the studied thin section in Asmari Formation include Mud stone, wackestone, packestone and grainstone, that lie in environmental groups of Intertidal (A), lagoon (B), shoal (C) and open marine (D). Allochem and clastic elements of the mentioned microfacies could be Intraclast, Bioclast, Extraclast and ploeid. Based on the Sequence Stratigraphic studies, Jahrum Formation sediments include a 3rd order sediment sequence and Asmari Formatin sediments include two 3rd order sediments sequence.