Iranian Journal of Geology
Year:2011 | Volume:5 | Issue:18|Papers Count:7

Miospores retrieved from thirty-four rock samples collected from the uppermost beds of surface section of the Chamanbid Formation at its type section are used to investigate spore-plant relationships. The type section is located about 60 km southwest of Bojnourd and near Chamanbid. This rock unit conformably overlies the Bashkalateh Shale and with a sharp lithological break underlies the Mozduran Formation. Diverse and well preserved palynofloras, dominated by terrestrial palynomorphs including 39 species of spores (of 28 genera) and 13 pollen species (assigned to 11 genera), are identified. Other palynomorphs, in descending order of abundance, are dinoflagellates, fungal spores, and foraminiferal test linings. The miospores are assigned to Filicopsida, Lycopsida, Ginkgoopsida, Coniferopsida, and Bryopsida. Notable abundance, in the Chamanbid palynofloras of fern spores viz.: Klukisporites, Cicatricosisporites and Cyathidites is interpreted to imply that the host strata accumulated under moist warm climate during the Tithonian time. This can be seemingly confirmed with reference to co-occurrence of dinoflagellates such as Systematophora areolata, Tehamadinium spp., Cribroperidinium spp. and Kallosphaeridium spp. and fungal spores. Marked relative abundance of Corollina upward in the studied section seems to indicate progressive dominance of dry warm climate towards the Late Jurassic time.

Fell down particles (xenoliths) of garnet–biotite-kyanite schist cropped out in the northwest of the Qori regional metamorphosed complex, Neyriz, emplaced in the southern part of the Sanandaj-Sirjan metamorphic zone, when the Talle-Pahevani anorogenic magmatic intrusion, leuco-quartz diorite-anorthosite in composion, was injected into this part of the complex about 170 Ma years ago. These xenoliths underwent severe contact metamorphic event. Some schist xenoliths endured small degrees of partial melting; hence, migmatite textures were expanded in these xenoliths, and also extraction and accumulation of some partial melts were formed the small peraluminous granite patches.Field observations, microscopic studies, and chemical data show that there are close relation among the schist xenoliths, partial melting, and occurrences of the migmatites and small peraluminous granite patches. Decrease in SiO2, Na2O, and K2O contents, increase in Al2O3, TiO2, FeO*, and MgO contents, and relation of the elemental ratios such as Sr/Y, K/Sr, Lan/Ybn, Lan/Smn, and Gdn/Ybn, suggest that the formation of granite patches were extracted from diatexitic migmatite xenoliths. Therefore, muscovite and biotite-dehydration melting caused to be changed schist xenoliths to the migmatite and formation of the small granite patches.

Karanj anticline is an asymmetrical fold trending toward SW. The average thickness, parallel with the axial surface, of Asmari Formation in different parts of this anticline is 550 meters and its actual thickness is estimated to be 403 meters. Faulted detachment fold model is suggested as the mechanism of folding in Karanj oil field. Geological section and the epicenter of instrumental data along with the interpretations of 3D seismic profiles indicate the function of two thrust faults in northern and southern limb of this anticline and the function of a tear fault transverse with this anticline by which the curvature of the structural axis of it is influenced. The 3-D model prepared from the top of the Asmari Formation by the use of underground maps (UGC maps) and wells data showed that the morphology of the Asmari Formation is highly influenced by the function of these faults. Fractal analysis of the drainage patterns shows that different parts of this anticline has had different rate of tectonic activities during geological history, in a way that, the middle part in the northern limb shows more tectonic activities.

In the view of global plate tectonic reconstruction, Iran is a part of the Alpine-Himalayan folded range which is formed in relation to closure of the Tethys Ocean between two huge continents of Gondwana and Eurasia. There have been many studies concerning the formation and closure times of the Neo-Tethys, therefore different opinions have been presented in this regards. In the previous studies, the ages of closure of the Neotethys and collision of Arabian and Iranian continents have been considered to be from the Late Cretaceous to the Neogene. Based on the U/Pb zircon data from the leucosome of the mafic migmatites, and the 206Pb/238U age for migmatization processes in the Takht-e-Soleyman metamorphic complex, it is determined to be about ca. 24-32 Ma (corrected for 204Pb) and 25-29 Ma (corrected for 207Pb), corresponding to the Neotethys continental collision. In this regards, it can probably consider the extensive magmatic activities in the area in relation to Neogene extensional phases corresponding to the crustal thinning followed by the continental collision. The isotopic K-Ar data on shists from the Zarehshoran area, U-Th/He data on apatites from the Mahneshan area and 40Ar –39Ar isotopic ages on muscovite from pelitic shists from the previous studies support uplifting of the Takht-e-Soleyman metamorphic basement ca. 20 Ma (Early Miocene). Shortening of the crust and deepening of the Zagros thrust fault (probably to Moho depth) are more evidences for Miocene continental collision.

In this research, biostratigraphy and palaeoecology of the Sarvak Formation (208 meter thickness) in southwestern Firozabad, has been studied. Paleontological and biostratigraphical studies resulted in the identification of five faunal assemblages. The biostratigraphic study led to recognition of five biozones, in ascending order biozones are as follow: Conicorbitolina conica - Trocholina assemblage zone, Favusella washitensis range zone, Rudist debris zone, Nezazzata – Alveolinides assemblage zone, and Oligosteginids assemblage zone. According to these biozones, the Sarvak Formation is Late Albian-Cenomanian in age. Palaeoecological analysis yielded four assemblages. The first assemblage is composed of big conical and agglutinated foraminifera with low diversity. The second assemblage is mostly composed of large conical and agglutinated foraminifera and also small agglutinated foraminifera. This assemblage has diverse fossils. The third assemblage includes small agglutinated foraminifera and no large conical and agglutinated foraminifera are observed, the diversity in this assemblage is variable. The fourth assemblage is different from other three assemblages and includes oligosteginidae and planktonic foraminifers. The diversity in this assemblage is also variable. Differences between fossil assemblages are mainly interpreted and related to ecologic and biotic conditional changes such as: oxygen contents, depth, disappearance of symbiosis algae, sedimentation rate and type of bottom sediments (substrates).

Analysis of earth science data using different transform methods such as Fourier and wavelet transform, are useful for the extraction of hidden information imbedded in the data. Fortunately, the uses of such transforms have been expanding as reported in recent studies. Wavelets and wavelet transform in signal processing, offer important advantages that are highly useful in transient data analysis. These include multiresolution analysis of data for extraction of different information that reside in different frequency bands as well as extraction of localized features, a distinct property of wavelet transform as compared with other transforms. Furthermore, in wavelet transform, availability of alternative mother wavelets each with its own distinct feature makes wavelets highly suitable for their usage in different application environment for maximal information extraction. Therefore selection of appropriate mother wavelet for maximal information extraction in a given data analysis, is considered to be an important and necessary step when working with wavelets. A review of literature in earth science on the subject of optimal wavelet selection reveals little work has been done on the subject. In this paper, we have attempted to overcome this shortcoming in which we have investigated various approaches and considerations for the selection of optimum mother wavelet. In this investigation the results of a case study for selection of optimum mother wavelet for decomposition of set of petrophysical logs gathered from one of the Iranian south oil fields are presented. The significance of optimum mother wavelet selection in this oil field is shown.

The study area is located in north-east of Lut block and in the western part of geological map of Basiran (1:100000). In this area, acid to intermediate plutonic and subvolcanic rocks intruded into Eocene-Oligocene volcanic rocks and is a suitable area for mineralization. Indication of probable mineralization does by using of Aster satellite data. Processing of data has shown propylitic, argillic and sericitic alteration and formation of iron oxides (Hematite). Based on these processing, geochemical data related to those parts that mineralization is more probable was studied. It was recognized that in the east and north-east of Bisheh village, there are anomalies of copper, zinc, lead, tin and gold, and in the south west of Bisheh, there are anomalies of tin, tungsten, zinc, lead, and iron. The highest values of Cu, Zn, Pb, Sn and W are 123, 149, 56, 11, 39 ppm respectively and Au is equal to 16 ppb. Tin and tungsten anomalies in the north-east of Bisheh are related to ilmenite series granitoids bodies.Airborne geophysical studies have shown a distinguished magnetic anomaly in the east of Bisheh. Ground magnetic survey shows intensive anomaly (49500 nT) and the existence of ferrimagnetic mineral. Mineralographic studies of core samples indicated that the source of magnetic anomaly is magnetite. Magnetite genesis is related to intruding of magnetite series granitoids bodies to Paleocene limestone and occurring skarn.