M. H. Kazemzadeh; A. Sadeghi; M. H. Adabi; H. Ghalavand
Abstract
In order to determine biostratigraphy, depositional environment and sequence stratigraphy of the Kalat Formation in the Sheikh Syncline (north east of Bojnurd), Four stratigraphic sections including South Sheikh, North Sheikh, Qaleh Zu and Ziarat were selected and sampled. The thickness of the Kalat ...
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In order to determine biostratigraphy, depositional environment and sequence stratigraphy of the Kalat Formation in the Sheikh Syncline (north east of Bojnurd), Four stratigraphic sections including South Sheikh, North Sheikh, Qaleh Zu and Ziarat were selected and sampled. The thickness of the Kalat Formation in the South Sheikh, North Sheikh, Qaleh Zu and Ziarat sections were 25, 16, 25 and 5m respectively, and its lithology consists mainly of brown to yellow limestones. The reason of changes in thickness in studied sections is tectonic factors, subsidence and different rates of sedimentation. The layer of conglomerate in the base part of the Kalat Formation at South Sheikh and Qaleh Zu sections and the layer of sandstone in the base part of the Kalat Formation at Ziarat section were recognized. In the biostratigraphic studies, 15 species belonging 23 genera of foraminifera were recognized and one biozone including Siderolites calcitrapoides-Sirtina orbitoidiformis assemblagezone was identified. The age of the Kalat Formation in all of studied sections based on the above biozone and fossil contents Maastrichtian were determined. Petrographic analysis led to recognition two silliciclastic and eight carbonate facies belonging to four depositional environments including tidal flat, restricted and semi-restricted lagoon, shoal and open marine. Based on the recognized facies and its gradual trend, abundance of shoal facies, absence of reefs and sediment of turbidite flows such as Falling and sliding sediments, the sedimentation of the Kalat Formation was occurred on the homoclinal ramp setting. Based on the vertical changes of facies and recognized depositional environments, one third-order depositional sequences was represented. This depositional sequence consists mainly of shoal facies rich in bioclast, intraclast, benthic foraminifera, echinoid, rudist (Hyporite) and bivalve. MFS of this sequence is represented by open marine facies rich in echinoid.
P Gholami Zadeh; M.H Adabi; M Hosseini-Barzi; A Sadeghi; M.R Ghassemi
Abstract
The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two ...
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The Miocene sediments in Neyriz region crop out in Zagros Crushed Zone, between Zagros Main Fault and Zagros Ophiolite Zone. For paleoenvironmental studies of these sediments, two stratigraphic sections (Kuh-e Asaki and Horgan sections) have been measured and sampled. The thicknesses of these two sections are 424 and 440 m respectively and contain red and green sandstone, conglomerate and marl which are bounded unconformably between the Jahrum Formation and Bakhtiari conglomerate. Based on the field and petrographic studies, 14 sedimentary facies related to proximal, mid fan-delta; transition zone, delta slope and prodelta have been recognized for the Miocene succession. Due to the slope facies formed by the turbidity currents, grain fall and debris flows, the coarse grained clasts and poorly sorted texture, a fan-delta model is suggested for the succession. Also, the development of the slope facies indicates a paleo-slope and slope-type, deep-water fan-delta. The frequent intra-formational disconformities, irregular changes in grain size and present of gravity flows indicate an active tectonic sedimentary basin and reflux of coarse grained sediments (catastrophic events) to the proximal parts of Zagros Basin.
Sedimentology
A. Rahimi; M. H. Adabi; A. Nabati; M. R. Majidifard; A. M. Jamali
Abstract
Carbonate sequences of the Shotori Formations (Middle Triassic) with a thickness of 308 m, were deposited in the Kalmard region of the Tabas city in Central Iran basin. The lower contact of the formation gradually and conformably overlies the Sorkhshale Formation and upper contact is faulted. The Shotori ...
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Carbonate sequences of the Shotori Formations (Middle Triassic) with a thickness of 308 m, were deposited in the Kalmard region of the Tabas city in Central Iran basin. The lower contact of the formation gradually and conformably overlies the Sorkhshale Formation and upper contact is faulted. The Shotori Formation is mainly composed of thick to medium bedded fine-coarsely crystalline dolomites with a thickness of 250 m with interbeds of thin bedded limestone and sandstone. The Shotori Formation is mainly composed of fine-coarsely crystalline dolomite. Based on petrographic (size and fabric), and elemental studies (Ca, Mg, Na, Sr, Fe, Mn), five dolomite types were recognized. Variation in dolomite types is mainly related to early to late diagenetic processes, changing the composition of dolomitizing fluids. Geochemical studies also indicate that medium to coarse grain dolomites formed in meteoric diagenesis under reducing conditions. Mechanism of dolomitization for dolomite type 1 is sabkha model, for dolomite types 2 and 3 is mixing zone and is burial model for dolomite types 4 and 5.
P Gholami Zadeh; M.H Adabi; M Hosseini-Barzi; A Sadeghi; M.R Ghassemi
Abstract
Petrography and geochemistry of the Neyriz Miocene sediments at RoshanKuh and Kuh-e Asaki sections were carried out to determine their provenance, tectonic setting and paleoclimate conditions in the proximal part of Zagros Basin. The Miocene sediments are limited to the Zagros Main Fault at the northeast ...
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Petrography and geochemistry of the Neyriz Miocene sediments at RoshanKuh and Kuh-e Asaki sections were carried out to determine their provenance, tectonic setting and paleoclimate conditions in the proximal part of Zagros Basin. The Miocene sediments are limited to the Zagros Main Fault at the northeast and the Neyrizophiolite zone at the southwest in the Neyriz region. They contain about 700 m red and green sandstone, conglomerate and marl which overlay the Jahrum Formation with a disconformity and covered by Bakhtiari conglomerate with an angular unconformity.Petrography of thin sections indicates that the rock fragments are the most constituent, and then quartz and feldspar respectively. The low compositional and textural maturity of the studied samples (angular grains and poorly sorted sandstones) shows the proximity to the source area. Petrography of the rock fragments and the bulk chemical composition of samples display that their provenance is multiple and the sediments were derived from Sanandaj-Sirjan Zone (Cretaceous limestone- metamorphic rocks- Eocene volcanic) and Zagros Zone (ophiolite sequence- radiolarites- Eocene limestone). Also, point-count data plotted on the QFL and QmFLt triangles indicate the recycled orogen and magmatic arc provenance. Based on geochemical data tectonic setting of Neyriz Miocene sediments is continental island arc and active continental margin. The averages of Cullers' index, CIW΄ (for calculation of the chemical weathering), ICV Index (to determine the maturity source), and SiO2versus Al2O3 + K2O + Na2O diagram for these sediments show a poor weathering and dry climatic condition during their deposition which is supported by the high percentage of calcareous cement and frequency of the rock fragments. The results of this study suggest a sedimentlogical framework for the proximal part of Zagros Basin and the Miocene syn-depositional processes.
M yavari; M Yazdi; M.H Adabi; H Ghalavand
Abstract
Dariyan Formation deposited in two different sedimentary settings. In some places it consists of shallow Limestone with algae and Orbitolina and in the other places in addition to limestone, it represents black shales and marls associated with planktonic foraminifera and radiolarian. In this research ...
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Dariyan Formation deposited in two different sedimentary settings. In some places it consists of shallow Limestone with algae and Orbitolina and in the other places in addition to limestone, it represents black shales and marls associated with planktonic foraminifera and radiolarian. In this research Draiyan Formation was studied in order to microfacies, depositional model and sequences stratigraphy of two sections so called, Kuh-e Gadvan and Kuh-e Banesh in high Zagros belt. Detailed petrographic studies led to the recognition of five main facies belts including: lagoon, bar, shallow open marine, outer ramp and deep marine. According to the vertical and lateral variations of facies, the Dariyan Formation deposited on a carbonate ramp platform and intrashelf basin. Depositional sequences have been presented on the basis of analysis of facies, fauna assemblages, Gama and Neutron logs. Three 3rd orders depositional sequences have been recognized during deposition of sediments. There is Type I sequence boundary in the top of third sequence and the other two sequences was considered as Type II sequence. Sea level fluctuations of the studied area correlated with Arabian platform and these changes follow of regional factors.
Z Kalantarzadeh; M.H Adabi; H Rahimpour Bonab
Abstract
After Early Cimmerian orogenic stage, due to marine transgression, the Nayband Formation Norian_Rethian (Upper Triassic) in age deposited in the Central Iran Zone. Because of transforming of aragonite and high Mg calcite into low Mg calcite during diagenesis, recognition of original carbonate ...
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After Early Cimmerian orogenic stage, due to marine transgression, the Nayband Formation Norian_Rethian (Upper Triassic) in age deposited in the Central Iran Zone. Because of transforming of aragonite and high Mg calcite into low Mg calcite during diagenesis, recognition of original carbonate mineralogy based on petrographic studies is difficult. In this research, original carbonate mineralogy and type of carbonates (tropical, temperate and polar) of the Nayband Formation in Darbidkhoon, Tarz, Gitry and Kuhbanan stratigraghic sections have been studied using geochemical evidences. The trace elements (Na, Sr, Fe, Mn) and isotopes (and) data of the Nayband Formation carbonates is located inside or close to the aragonitic tropical Fahlian Formation (Lower Cretaceous), the Ilam Formation (Upper Cretaceous), the Kangane Formation (Lower Triassic) and the Mozduran Formation (Upper Jurassic) limestones, because of aragonitic original carbonate mineralogy. The results of elemental and isotopic analysis correlate with the petrographic evidences and paleogeographic map of the Upper Triassic.
N Etemad-Saeed; M Hosseini-Barzi; M.H Adabi; A Sadeghi
Abstract
The Kahar Formation at its type locality in the KaharMountain, 75 km NW of Tehran, consists of about 1000 m of siliciclastic rocks (mainly mudrocks). This study focuses on the mineralogical and geochemical composition of these mudrocks to identify possible source areas and their tectonic setting. The ...
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The Kahar Formation at its type locality in the KaharMountain, 75 km NW of Tehran, consists of about 1000 m of siliciclastic rocks (mainly mudrocks). This study focuses on the mineralogical and geochemical composition of these mudrocks to identify possible source areas and their tectonic setting. The optical microscopy and XRD studies suggest that the mudrocks are rich in quartz and feldspar (especially plagioclase) and have low phyllosilicates (mostly illite and chlorite). SEM-EDX petrographic investigation of mudrocks reveals that platy illite and chlorite may have formed during the diagenesis (illitization and chloritization). Classification of studied mudrocks based on the maturity index, indicate that they are tectic and phyllo-tectic types, deposited in basins related to an (continental) island arc tectonic setting. The Chemical Index of Alteration (average 70) and A–CN–K parameters indicate that a moderate chemical weathering has taken place in the source region of the Kahar mudrocks. In addition, the chemical composition of mudrocks suggests that the amount of sediment recycling is very low in the Kahar deposits. The geochemical discrimination diagrams, immobile trace element ratios and Rare Earth Elements of mudrocks suggest that the Kahar mudrocks were derived mainly from the felsic sources and deposited in the basins related to an island arc tectonic setting. The resulting model for the tectonic setting of the Kahar basin during the Late Neoproterozoic can be best explained by recently models that considered Iran as part of Peri-Gondwanan terranes, similar to the Avalonia and Cadomia arc terranes, occupying the northern margins of Gondwana.
E Asadi Mehmandosti; M.H Adabi
Abstract
The Sarvak Formation from the Bangestan Group, Late Albian to Cenomanian in age is an important petroleum reservoir in Iran. 5 outcrop sections in the Izeh zone, including the BangestanMountain as a type section with 831.5 m thickness, the MangashtMountain with 426 m thickness, the PayunMountain with ...
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The Sarvak Formation from the Bangestan Group, Late Albian to Cenomanian in age is an important petroleum reservoir in Iran. 5 outcrop sections in the Izeh zone, including the BangestanMountain as a type section with 831.5 m thickness, the MangashtMountain with 426 m thickness, the PayunMountain with 480 m thickness, the north flank of MishMountain with 252 m thickness and the south flank of MishMountain with 348 m thickness were studied geochemically. The major elements (Ca, Mg), trace elements (Sr, Na, Fe, Mn) and carbon and oxygen isotopes studies indicate that the geochemical characteristics of the Sarvak Formation have been changed in the Izeh zone. High amount of Sr/Mn ratio and Sr content normalized to Ca and heaviest oxygen isotope of the Sarvak Formation carbonates in the north flank of Mish Mountain and some of the Bangestan Mountain carbonate samples indicate low amount of solution and closed diagenetic system in these outcrops compare to the Sarvak Formation carbonates in the south flank of Mish and Payun Mountains. The oxygen and carbon isotopes variation illustrate marine pheriatic digenesis in the north flank of Mish and BangestanMountains and meteoric diagenesis in the south flank of Mish, Mangasht and PayunMountains. The geochemical difference, which observed in the studied sections at Izeh zone, could be related to the reactivation of deep seated structures such as the Hendijan and Bahregansar (Izeh) faults, which caused thickness, facies and diagenetic variations in these areas.
A Ghorbani; M.H Adabi; S Sohrabi
Abstract
The Sirri E (Esfand) and D (Dena) Oil Fields are located in the south of the Persian Gulf. The Upper Sarvak (Mishrif Member) Formation, late Cretaceous (Cenomanian-Turonian) in age, is underlain by the argillaceous limestone of Khatiyah and by the late Turonian unconformity overlain by the Laffan Shale ...
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The Sirri E (Esfand) and D (Dena) Oil Fields are located in the south of the Persian Gulf. The Upper Sarvak (Mishrif Member) Formation, late Cretaceous (Cenomanian-Turonian) in age, is underlain by the argillaceous limestone of Khatiyah and by the late Turonian unconformity overlain by the Laffan Shale in mentioned two oil fields. On the basis of petrographic and geochemical evidences (elemental analysis such as Mg, Ca, Sr, Mn) and oxygen and carbon isotope values, aragonite was original carbonate mineralogy for the carbonates of the Upper Sarvak (Mishrif Member) Formation in (Well A) in the Sirri E Field. The geochemical studies and δ18O and δ13C illustrate that these carbonates were affected by meteoric diagenesis in hot and arid climate and in semi-closed to open diagenetic system with thin soil layer. Temperature calculation based on the oxygen isotope value of the least-altered sample and δw around of -1 SMOW for Cretaceous, show that the seawater temperature was around 34˚C during the deposition of the Upper Sarvak (Mishrif Member) Formation. With regards to the highly altered samples and light oxygen values the temperature should be probably related to the shallow burial diagenesis. Petrographic studies of thin sections of the well A in the Sirri E Field and the well B in the Sirri D Field show the effect of diagenetic processes such as micritization, dissolution, cementation, neomorphism, pressure solution, physical compaction, fracture and dolomitization on the reservoir quality of the Upper Sarvak (Mishrif Member) Formation. The most important diagenetic factor that increased the reservoir quality is dissolution, which occurred in the meteoric diagenesis. However, the most important diagenetic factor that decreased the reservoir quality is the expansion of various kinds of cement especially large blocky cement, which occurred in the burial diagenesis.
