جستجوی مقالات مرتبط با کلیدواژه « حوضه رسوبی زاگرس » در نشریات گروه « زمین شناسی »

The Oligocene – Miocene Asmari reservoir with 400 meters thickness in the Shadegan Oil Field consists of limestones and porous dolostones associated with sandstones, and shales. Dolomitization, as the most important diagenetic process, affected the Asmari reservoir and thus played a major role in the formation of the pore spaces structure, final flow capacity and heterogeneity of the Asmari reservoir. Dolomite types based on geochemical and textural characteristics, especially crystal size and shape includes: (i) very finely-crystalline, fabric-retentive dolomite (D1), (ii) fine to medium-crystalline, fabric-retentive dolomite (D2); (iii) medium to coarse-crystalline, fabric-destructive dolomite (D3); and (iv) very coarsely-crystalline, non-planar saddle dolomite (D4).Two types of fabric named fabric selective dolomitization and pervasive dolomitization were identified in dolomite crystals. Based on textural classification, 6 different textures including idiotopic, hypidiotopic or (idiotopic-S), xenotopic or non-planar-A (anhedral), idiotopic-C or planar-C (cement), porphyrotopic and poikilotpoic texture for dolomite crystals is identified. The mean concentration of strontium in dolomite samples is 483 ppm and the mean concentration of sodium is 1618 ppm which indicates the enriched amounts of strontium and sodium in these samples. The mean values of iron in dolomite samples are 3111 ppm and the mean concentration of manganese is 111 ppm. Dolomites (D1) with low Fe and Mn content may have formed during the early stages of diagenesis in an oxidizing environment. High amounts of iron and manganese in D3 and D4 dolomites indicate deposition in a reducing environment during shallow to relatively deep burial.

Zagros Sedimentary basin is located in the south and southwest of Iran and Pabdeh Formation is one of the most important Cenozoic units of Zagros Sedimentary basin. In addition, Pabdeh Formation is of special importance as one of the source rocks of Zagros Sedimentary basin. In order to study the Lithostratigraphic and Biostratigraphic rocks of Pabdeh Formation, the section of Ilam dam in the northwest of Zagros sedimentary basin has been selected and sampled. 360 samples were taken, of which 260 washing samples and 100 thin section samples were prepared. Based on the studies performed on these samples, 25 genera and 105 species have been identified in the Ilam dam section. 26 biozones and 2 sub-biozones have been identified based on the biological zoning of Wade et al., 2011 in the Tethys area. Based on the identified biozones, the age of Pabdeh Formation in the Ilam dam section, Middle Danian-Early Aquitanian has been obtained. The deposits of Pabdeh Formation in the section of Ilam dam have a thickness of 764 m (beginning of Pabdeh to the beginning of Kalhor anhydrite) which includes purple shale units (2 Units), marl limestone with lower limestone, cherti limestone, marl limestone with upper limestone. The lower boundary of Pabdeh Formation in this section is conform and continuous with shales and marls of Gurpi Formation but its upper boundary with the gypsums of the Asmari formation is most likely accompanied by a disconform.

After the Late Cretaceous and during the Paleogene, with the sea level rising, the Zagros sedimentary basin is covered with a progressive sea in which the Pabdeh Formation is deposited. The dual function of this formation as a source of oil and its reservoir capacity due to the diversity of lithology and its location between the two reservoirs Asmari and Bangistan, and the age of this formation is one of the issues that has attracted the attention of geologists. In order to study the stratigraphic and biostratigraphic rock of the Pabdeh Formation, the Jahangirabad section in the northwest of Zagros sedimentary basin has been selected and sampled. 320 samples were taken, of which 230 samples were prepared by washing method, and 90 samples were prepared by thin section method and examined. Based on studies conducted in the Jahangirabad section, 25 genera and 110 species have been identified, and based on the identified fossils, 27 biozones and 7 sub-biozones have been identified. Based on the identified biozones, the age of the Pabdeh Formation in the Jahangirabad Danian Early-Late Chattian section has been obtained. Pabdeh Formation deposits in the Jahangirabad section have a thickness of 676 m (beginning of purple shale to anhydrite Kalhor) which includes units of purple shale (2 parts), marl limestone with lower limestone, limestone, and marl limestone with limestone It is high. In this section, the lower boundary of the Pabdeh Formation is continuous with shales and marls of Gurpi Formation, and its upper boundary is with continuous limestone of Asmari Formation.

In this study, the lower part of carbonate successions from the Shahbazan Formation in the Chenareh anticline of the Zagros sedimentary basin (SW of Iran) based on Large Benthic Foraminifera (LBF) was investigated. From this succession, five species of Alveolina are described including A. fornasinii (Checchia-Rispoli), A. schwageri (Checchia-Rispoli), A. distefanoi (Checchia-Rispoli), A. cremaea (Checchia-Rispoli), A. decastroi (Scotto Di Carlo) along with species of Rotaliids such as Gyroidinella cf. magna (Le Calvez), Lockhartia hunti (Ovey), Cuvillierina vallensis (Ruiz De Gaona), Granorotalia sp. These assemblages of large foraminifera based on the Shallow Benthic Zones (SBZ) indicate the Late Ypresian (SBZ10–SBZ11). Thus, the detailed studies on this group of foraminifera were representative of the aforementioned age from the lower part of the Shahbazan Formation (Tang-e-Leilam section) for the first time. Therefore, identifying some species, such as Alveolina along with Rotaliids of the Early Eocene (Ypresian)succession was expressive of the Shahbazan Formation into the older time units.

In this study Surgah Formation at Maleh-Kuh and Sarkan section in south west of Khoram Abad have been studied based on bio-event models. Surgah Formation at Sarkan well no.1and Maleh-Kuh has 46 and 82-meter thickness respectively and was placed on the Sarvak Formation and under the Ilam Formation. In this study Surgah Formation were composed of shale, limy shale with glauconite and pyrite. In this section two Turonian-Coniacian and Coniacian-Santonian boundaries were recognized in Dicarinella concavata Interval Zone. Based of Heterohelix moremani and FODs Dicarinella concavata and Dicarinella primitiva were detected Turonian-Coniacian boundary. Finally based on LoDs Dicarinella primitiva and Marginotruncana marginata were distinguished Coniacian - Santonian boundary in this section.