APPLIED SEDIMENTOLOGY
Year:2018 | Volume:5 | Issue:10 |Papers Count:7

The Aitamir Formation (Albian-Cenomanian) consists of sandstone, shale, siltstone and several limestone beds. Artenj and Ghorghoreh sections have studied in east of basin for determination of the ichnofacies. In this research, trace fossils types and ichnofacies are recognized and their relation with depositional environment has interpreted. Trace fossils in studied sections consist of Arenicolitesisp., Cylinderichnous concentricus, Ophiomorpha isp., Palaeophycus heberti, Paleophycus tubularis and Thalassinoidesisp. that can be placed in glossifunjites and Cruziana ichnofacies. Glossifunjites ichnofacies with low diversity of trace fossils and oblique to vertical orientation of the Y branched Thalassinoides, Paleophycus and Arenicolites in trough and planar cross-bedded were formed in high-energy barrier complex. Whereas Cruziana ichnofacies with higher diversity and mainly oblique to horizontal trace fossils in sandy substrate with low to moderate sorting are formed in low energy condition in shoreface environment.

This investigation focues on the diagenesis events of the siliciclastic and carbonate rocks of the Upper Triassic and Lower Cretaceous strata in Kuh-e-Bejareh section of northeast Isfahan. The method of study include fieldwork, systematic sampling and thin section petrography of the siliciclastic and carbonate specimens with polarized and cathodoluminescence microscopes. The studied intervals with 167 meter thick includes the upper Qadir Member of Nayband Formation and the siliciclastic (K1) and carbonate rocks (K2) of Lower Cretaceous sequence. The diagenetic studies of siliciclastic petrofacies led to recognition of the bioturbation, alteration of feldspar, type of grain contacts, different cement types include calcite, iron oxide and clay mineral (related to eogenetic stage), chemical compaction, dolomite, overgrowth silica and clay cements (related to the mesogenetic stage). Iron oxide cement and clay minerals, fracturing and vein filling by dolomite are related to telogenetic stage. Studies have shown the effect of sandstone composition on the trend and formation of diagenetic process. Some impact of siliciclastic composition on diagenetic event includes the frequency of clay mineral cement as well as feldspar alteration which are high in the feldspar rich petrofacies of the Qadir Member. Diagenetic studies also shows abundant overgrowth silica cement in quartz-rich petrofacies in the Lower Cretaceous (K1 unit) sequences. Diagenesis study of carbonate rocks (K2 unit) led to recognition of different process such as micritization, bioturbation, fibrous isopachous cement in marine diagenesis stage and pendent and iron oxide cements are related to vadose stage. The pendant, drusy calcite and iron oxide cements are related to pheriatic stage. Burial diagenetic process are prismatic bladed, dolomitic, blocky calcite, syntexial overgrowth cements, compaction and fracturing. Luminescence intense of cements ranging from dark red to non-luminescence that led to the separation of the different phases of cementation in carbonate deposits. During uplift stage iron oxide cement and vein filling fractures occurred. Investigation of all diagenetic events in siliciclastic and carbonate rocks of this study shows that deposits has gone under different stage of diagenesis including early, intermediate and deep burial and uplift under the influence of sediment composition.

The middle-late Eocene Shahbazan Formation is extended in the Lurestan zone. It is underlain by Asmari Formation and overlaying the Kashkan Formation, however to the southwest of the Lurestan, it overlying the Pabdeh Formation with some interfingering lateral changes. Five surface sections and four well which are located in east of the Lurestan zone were sampled to investigate the depositional setting of the Shahbazan Formation. These sections were tentatively selected to survey across and normal to the basin as well. Petrographic examinations on 700 thin sections revealed 17 microfacies which are deposited in tidal flat (3 microfacies), lagoon (4 microfacies), shoal (4 microfacies), reef (1 microfacies) and shallow open marine (5 microfacies). Tidal flat and lagoon facies associations are extended in the north and east, whearas shoal and shallow open marine facies are more frequent in the south and west of the study area. Lack of barrier and also turbidite deposits suggest a NE-SW trending distally steepened ramp in studied area at middle-late Eocene. It is belived that the Shahbazan Formation in Dezful Embayment was deposited on a shelf type carbonate platform in middle Eocene and ramp in late Eocene. This variation could be explained as the consequence of activity of the Mountain Front Fault which was active since late Cretaceous.

The Fahliyan carbonate formation (Neocomian in age) is one of the major reservoirs of the Khami Group in the southwest of Iran. In this study, the sedimentary succession of the Fahliyan Formation in Kilur Karim Oil Field well#B (520m thick), situated in the Dezful Embayment, was investigated for microfacies, paleoenvironmental, diagenetic and sequence stratigraphic analyses. Based on thin section studies (some 490 samples), 11 microfacies and 5 facies associations were identified. According to the characteristics of typical sedimentary environments, these facies were deposited in a homoclinal carbonate ramp. Due to the dominance of the inner ramp (especially lagoonal) facies in the studied subsurface section, it is deduced that this area, in Neocomian, has been located in the marginal shallow parts of the Zagros Basin. Petrographic studies showed that the main diagenetic features of the Fahliyan carbonates were micritization, neomorphism, cementation, dissolution, compaction, dolomitization, fracturing, and pyritization. Sequence stratigraphic investigations led to recognition of three third order depositional sequences (comprising transgressive and highstand systems tracts) in the Fahliyan Formation. The lower boundary of the first sequence is type-1 and the other sequence boundaries are type-2. Lack of reservoir quality effective diagenetic processes and high amount of lime mudstone facies in the well succession have caused a low reservoir quality for the Fahliyan Formation in Kilur Karim Oil Field well#B.

crops out in a few areas in southern Iran. This member consists of medium to thick-bedded, dark brown colored dolomites which form a distinct, feature-forming horizon on the top of the Khaneh Kat Formation (High Zagros carbonates) and Dashtak Formation (evaporite-carbonate facies of the folded Zagros). This paper is a study of the mineralogy, geochemistry and diagenetic history of the SDM outcrops in Kuh-e-Surmeh and Khaneh Kat anticlines in Fars region with a thickness of 30 and 20m respectively. Petrographic features and geochemical evidences of the studied sections indicated that the SDM dolomites were subjected to a complex diagenetic history, resulting to three different dolomite-rock textures including microcrystalline, medium-crystalline and baroque. In the first stage, microcrystalline dolomites were formed in the tidal zone (especially Sabkha) of an eperic platfom affected by evaporation and condensation of brines under normal temperature (25-35° C), near surface conditions. Increasing the size and stoichiometry and changes in geochemistry of moderate and coarse-crystalline dolomites suggest the role of diagenetic processes associated with burial, including recrystallization in shallow to deep-subsurface environments. These dolomites are the products of changes in a diagenetic system at a depth of 1 to 3 kilometers inside the earth and at temperatures of 54 to 108° C. Comparison of the changes in the amounts of some minor elements of the SDM including reduction of iron and manganese, and the increase of strontium in samples of Khaneh Kat section indicated the flow of dolomitization fluids from south to north. The major faults of the region such as Mountain Front Fault and High Zagros Fault (HZF) while controlling the geometry of the sedimentary basin, have played a major role in determining the direction of flow and the pathway of the transfer of dolomitization fluids. Despite the significant difference between the facies and the Triassic sedimentary sequences in different sub-areas of Zagros, the SDM has a wide areal extent and can be traced to Lurestan and across the Persian Gulf into Saudi Arabia with similar rock facies. This subject suggests significant changes in the geology of the southern continental shelf of the Neothetys Ocean, especially in the continuity of the basin and stablishing of the same sedimentary conditions in the areas in both sides of the HZF in the middle of the Late Triassic.

The aim of this study to detect the Cretaceous-Paleogene (K/Pg) boundary in Coastal Fars based on lithological and micropaleontological characteristics and also gamma-ray logs in outcrop exposure and borehole wireline. This study has been done on one surface stratigraphic section in north flank of Gavbast anticline and one exploratory well in the same region and correlation between them. A presumable interval from the top of the Gurpi and base of the Pabdeh formations with thickness of 50 m was measured where 195 samples were collected. Surface gamma-ray survey was performed a cross section by using a hand-held gamma-ray spectrometer in 30 cm intervals. To distinguish the K/Pg boundary in detail, the sampling and gamma-ray measuring interval was focused on 15 cm steps near the presumable K/Pg boundary. The sampling interval of cuttings in wildcat well at the drilling time was 2 m. The U (ppm), Th (ppm), K (%) and dose rate (nGy/h) were measured in every sampling site. The data was processed by Geolog software. Field gamma-ray was correlated with the wireline gamma-ray log from borehole by the CycloLog software. The results shows gamma radiation has wide range values (17. 02 nGy/h-81. 94 nGy/h). The increasing of gamma-ray is not coincident to K/Pg boundary and this is due to high frequency of glauconite and phosphate near to K/Pg boundary. The minimum value of U is 1. 36 ppm and maximum value is 13. 24 ppm. The planktonic foraminifera studied and photographed under thin section and also as washed samples. 25 genera and 50 species of planktonic foraminifera have been determined. The recognized biozones are Gansserina gansseri Zone, and Contusotruncana contusa Zone indicate latest Campanian to middle Maastrichtian age for upper part of the Gurpi Formation and Eoglobigerina edita Partial-range Zone (P1), Praemurica uncinata Lowest-occurrence Zone (P2) and Morozovella angulata Lowest-occurrence Zone (P3) assign Danian age for lower part of the Pabdeh Formation. Due to lack of Abathomphalus mayeroensis Zone, Pseudoguembelina hariaensis Zone, Pseudotextularia elegans Zone, Plummerita hatkeninoides Zone, Guembeliteria cretacea (P0) Zone and Parvularugoglobigerina eugubina (Pα )Total-range Zone, a paraconformity between the Gurpi and Pabdeh formations in the studied area was recognized, which encompasses since late Maastrichtian till earliest Danian. Presence of glauconite and phosphate near to top of the Gurpi Formation deposits reveals a hardground. From lithostratigraphic point of view, due to lack of purple shale informal member at the base of Pabdeh Formation in Coastal Fars, the Gurpi and Pabdeh formations boundary was inferred at the low weathered marlstones beds at the base of Pabdeh Formation which comprises reworked Cretaceous planktonic foraminifera.

In this research, the Tirgan Formation, Barremian-Lower Aptian in age, has been studied at two areas, Radkan and Geliyan, in the Kopet-Dagh Basin. Lab was focused on 57 samples for petrographic and porosity studies and 15 samples for estimation of permeability. The objectives of this study are depositional environment interpretation, recognition of diagenetic history, and estimation of porosity and permeability. Based on field and laboratory studies four facies associations are recognized. Most of the carbonate rocks were deposited in an open marine, barrier, lagoon and tidal flat setting. Using petrographic results, the main diagenetic processes that affected these rocks are micritization, cementation, neomorphism, compaction, fracturing, dissolution, silicification, and dolomitization, with eodiagenetic, mesodiagenetic and telodiagenetic effects evident. Fracturing, intercrystalline, interparticle and intraparticle porosity are the main types. The average porosity and permeability at Radkan are 8. 31% and 0. 574 md, and at Geliyan 4. 28% and 0. 212 md. Based on these results, the Tirgan Formation does not appear to have reservoir capability in the region.