JOURNAL OF STRATIGRAPHY AND SEDIMENTOLOGY RESEARCHES
Year:2010 | Volume:25 | Issue:2 (37)|Papers Count:9

The 50 meters thick Top Quartzite sediments in Kerman area is laid between siliciclastic red beds of the Oahu Formation and carbonate deposits of the Kuhbanan Formation. Three stratigraphy sections were measured at Gazuieh, Katkuieh and Oahuieh in eastern Zarand for analysis of depositional environment. Field and petrographic studies led to identification of a conglomerate petrofacies and three sandstone petrofacies (chert arenite, quartz arenite, sublitharenite) with high textural and compositional maturity. Lithofacies analysis resulted in recognition of three coarse grain (Gem, Gms, Gt), seven medium grain (Sp, St, Sh, S1, Sr, Sm, Se), one fine grain (FI) and three intermediate sand-mud lithofacies (Sr (F1), Sr/F1, F1 (Sr)) Structural and textural evidences as well as predominant bimodal paleo-currents in most facies show that these sediments have been deposited in the tidal flat environment. The coarse, medium and fine grain sediments are deposited in tidal channels, intertidal flats, supratidal flats, respectively. We hope represented data in the study improve the basin analysis and paleogeographical reconstruction of Cambrian sedimentation.

For petroleum potential evaluation of the Khazhdumi Formation in Nowrouz oil field north west of the Persian Gulf 59 ditch cutting samples obtained from two wells were investigated through petrographic and geochemical studies. Petrographical studies resulted in characterization and separation of four palynofacies. Palynofacies I (PF-l) containing 95-100 percent phytoclast and kerogen type III was recorded only in well 1. In palynofacies II (PF-2) values of phytoclast respect to previous palynofacies decreased and were in the range of 70-90 percent and included kerogen type III. This palynofacies contain majority of samples. Palynophacies III (PF-3) was composed of 40-50 percent phytoclast and 50-60 percent AOM and kerogen type III. Palynofacies IV (PF-4) included higher amount of AOM (in the range 65-80 percent) and kerogen type II. In the differentiated palynofacieses marine element were rarely observed. High values of dark AOM in the studied samples showed the domination of oxic conditions. The OI/HI ratios obtained from Rock-Evel pyrolysis showed the region between restrictions CD and D which confirmed rather oxic continental to marine environments. Also plotting hydrogen index values versus total organic carbons (TOC) a series of regressive and oxic conditions was concluded. Plotting data on Tyson's ternary diagrams and Van kervelen geochemical diagrams indicated that the kerogen is of type III, potentialy poor to fair in terms of hydrocarbon generation and type of petroleum is mainly gas except for a few samples are fairly oilgenerative. In well number 1 sample were on the boundary of immature and mature and in threshold of entrance to mature stage while in well 2 the samples were in early mature stage and or were in entrance threshold to this stage.

There are three oil families in west and southwest of Depul embayment. Tertiary oils which are derived from Pabdeh Formation. This petroleum system distributes in the'north edge of the area is distinctly identified in the Labe Sefid oil field. Whereas, the presence of Jurassic petroleum system is evident in the southwestern part of the area. This group is derived from Sargelu and distributed in Dalpari, Cheshmekhush, West Paydar and East Paydar oil fields in southwest of the Dezful embayment. The third oil family is identified in Qalenar oil field. The crude oil in the Qalenar oil field is of a special type in a sense this oil shows little correlation with any of two known source rocks. Based on their distribution in overlain reservoirs and it is concluded that these crude oils are mixtures of hydrocarbons sourced from Tertiary and Jurassic source rocks. Therefore, the crude oils in Qalenar oil field are produced mainly from Pabdeh source rock. But, thermal history profiles indicate that the organic-rich Pabdeh Formation encountered in most of the wells in the southwest of Dezful embayment is immature and has not yet yielded commercial quantities of hydrocarbons.

Entrainment of heavy metals into food chain is of main environmental problems. A big part of crude oil is exported to Western Europe and Japan through Strait of Hurmoz, thus this strait plays a strategic role in the world economy. This research dealt with some sedimentological characteristics and pollution degree of superficial sediment by As and Hg in Sirik and Jask ports, east of Strait of Hurmoz. Sediment samples were taken from 16 stations in Sirik and Jask harbors from depths of 5 and 10 m in January 2009. Sedimentological studies showed that the sediments in terms of size are very fine and close to clay particles. Average content of organic matter and calcium carbonate were 8.25 and 13.17 percent respectively. The pH varied from 8.6 to 9.2. The ICP-MS analysis showed that the average concentrations of As and Hg in Sirik were 5.28 and 0.027 ppm and were 4.52 and 0.038 in Jask respectively. Average values of enrichment factor for As and Hg were calculated as 16.77 and 1.93 in Sirik and, 11.36 and 2.14 in Jask respectively. These values indicate high and low enrichment for the measured elements as well as their non-crustal sources (agricultural and industrial wastewater and oil pollutions) in the sediments of the region. Neighboring agricultural land around Sirik and the oil spill event on 23 May, 2006 in Jask Harbor area justify the higher average pollution factor of As in Sirik (0.4) than in Jask (0.34). Comparison of Hg pollution degrees in Sirik and Jask stations (0.46 and 0.43 respectively) shows more contamination of sediments by As and Hg in Sirik stations.

Palaeoecology of the Shemshak Fonnatian (Rhaetian-Middle Jurassic) at the Khoshyeilagh section north of Ghoznavi Village was studied by using palynomorphs and organic matter contents. This section with a thickness of 1280m consists of shale, sandatone and coal layers. A total of 67 samples contain diverse and well-preserved palynomorphs such as spores, pollen grains, opaque and transparent AOM, opaque phytoclasts, phytoplankton (dinofelagellate cysts), woody debris (plant tissue) were collected. Seventy three species of spores (47 genera) and 17 species of pollen (12 genera) are identified. Inferred natural relationships of the miospores imply derivation from a diverse parental flora of Filicopsida, Bryopsida, Lycopsida, Coniferopsida, Cycadopsida and Sphenopsida growing under wann humid conditions during the Rhaetian - Middle Jurassic. The abundance of Ricciisporites tuberculatus testifies a wet and moist condition when the Shemshak Formation was deposited. The high abundance of equi-dimensional and sorted phytoclasts (up to %98) accompanied with well-preserved terrestrial palynomorphs (spore and pollen) indicates accumulation in a moderate or high level of energy with an aerobic deltaic condition. However, occurrence of rare marine palynomorphs testifies intermittent marine incursions.

To study biostratigraphy and paleoecology of Lower Cretaceous sediments in north of Kerman (Ravar) three sections have been chosen and sampled. The thicknesses of sections are measured 235 meters in Kaleh Gav section, ]62 meters in Ghadroon section and 229 meters in Markesh section. The sections have a divers assemblage of fossils such as macrofossils, ostracodes and foraminifera, among which the later is the most important one. The sediments are Barrernian?- Aptian - Albian in age. ]n benthic foraminifera, both the epifaunal and infaunal are present and eight morphogroups are recognized. High diversity and abundance of foraminifera and also presence of p]atycopid and podocopid ostracods in Markesh section, confirm that an oxygenated environment has been prevailed during the deposition of the strata. Also the proportion of planktonic foraminifera and consequently low PIB ratio suggests a shallow marine environment for the strata. The presence of some larger foraminifera such as orbitolinids and calcareous algae indicates a warm shallow and photic environment as well. Trophic strategies of foraminifera show that sufficient food have been available in these environments.

Diverse and well preserved palynoflora dominated by organic-walled marine microphytoplankton (acritarchs and prasinophyte phycomata) and radiosymmetrical spo?estogether with scolecodonts, cryptospores, and chitinozoans occurs in surface samples of the Geirud Formation at the Garmabdar section, northeast Tehran. Palynotaxa such as Dai/lydium pentaster, Gorgonisphaeridium ohioense, Papulogabata annulata, P. lobata, Cymatiosphaera perimembrana, C. radiosepta, Chomotriletes vedugensis, Deltotosoma intonsum, Crassiangulina tesselita, Tornacia sarjeantii, Unellium lunatum, U. piriforme, and Retispora lepidophyta appear to have well known Late Devonian (Frasnian-Famel}nian) vertical ranges. Of these, index taxa such as G. ohioense, D. pentaster, U. lunatum, U. piriforme, and T. sarjeantii are extensively used in dating and long-distance correlation of the Devonian strata. Tornacia sarjeantii range biozone (Frasnian-Famennian in age and 118m thick) is introduced herein on the basis of first and last observed occurrences (FOO and LOO) of the eponymous species and compared with local microphytoplankton-based biozones previously established in virtuaIly equivalent sequences elsewhere.

The Cretaceous Burgan Formation is one of the most important hydrocarbon producers in Persian Gulf, offshore Iran. To understand the lithofacies, depositional setting and depositional sequnces of the reservoir from Foroozan oil field in this area, detailed sedimentological study has been carried out on about 62.5 m of conventional core. The Burgan Formation in the studied oil field mainly consists of very fine to mediumgrained sandstone, claystone, carbonaceous shale and some limited carbonate intervals. The combined results of both macro and microscopic investigations indicate eight different depositional facies in the studied interval of Burgan reservoir. These facies are consecutively numbered from 1 to 8. These are: (1) Cross-bedded channel sandstones, (2) Silty/sandy claystone; mud flatlbay facies, (3) Finegrained sandstone with interlayers of shale; sand flat facies, (4) Alternation of fine-grained sandstone/siltstone and organic-rich shale; .sand flat/mud flat alternation, (5) Silty claystone with plant remains; marine-influenced mud flat/shore face facies, (6) Fine-grained glauconitic sandstone along with sandy dolostone layers; marine influenced sand flat/shore face facies, (7) Organic-rich dark shale; restricted bay/marsh facies and (8) Ooid grainstone; oolitic shoal facies.Based on sedimentary features such as rhythmic alternation of sandstone-shale couplets, thick-thin alternations of silt and clay layers, flaser bedding, lenticular bedding, marine trace fossils and deepening upward successions in the cored interval, it seems that the Burgan Formation has been deposited on a tidedominated estuary system. The studied interval of the Burgan Formation consists of several fining up-ward successions. These successions comprise four depositional sequences. Each sequence is started with lowstand channel sandstones and terminated with highstand shales and claystones.