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Open Access Article
1 - Palaeoecology of Middle Jurassic deposits in central and eastern Alborz
Palynological data are used to draw palaeoecological inferences for the Dalichai Formation (Bajocian - Callovian) in two stratigraphic sections, Balu in central Alborz and Tapal in eastern Alborz. Diverse and reasonably well preserved palynofloras consisting of miospore MorePalynological data are used to draw palaeoecological inferences for the Dalichai Formation (Bajocian - Callovian) in two stratigraphic sections, Balu in central Alborz and Tapal in eastern Alborz. Diverse and reasonably well preserved palynofloras consisting of miospores, dinoflagellate cysts, acritarch cyst and foraminiferal test linings are present in the host strata. Miospores (spores and pollen) were used to interpret the palaeoecological and palaeoclimatical conditions of the Dalichai Formation at these stratigraphic sections studied. Affinities of the Dalichai Formation’s miospores at the Balu section in central Alborz appear to be with the Pterophyta 49%, Coniferophyta 23%, Ginkgophyta 15%, Lycophyta 8%, Sphenophyta 4%, and Bryophytes 1%. Similarly to the Balu section, Pterophyta exhibits remarkable percentage (49%) at the Tapal section in eastern Alborz, followed by Coniferophyta 26%, Ginkgophyta 19%, Lycophyta 4%, Bryophytes 2% and Sphenophyta 1%. Compared with the distribution of modern plants, spore-pollen assemblages of these two stratigraphic sections reflect a wet warm climate during the Middle Jurassic Dalichai Formation in central and eastern Alborz. Manuscript profile -
Open Access Article
2 - Devonian alkaline basic magmatism in Eastern Alborz, North of Shahrood: evidence for Paleotethys rifting
Basic igneous rocks as microgabbroic dykes and sills, and basaltic lava flows frequently have been outcropped in the Padha and Khoshyelagh formations in Devonian successions in eastern Alborz, north of Shahrood. The existence of these magmatic rocks as interbeded in sil MoreBasic igneous rocks as microgabbroic dykes and sills, and basaltic lava flows frequently have been outcropped in the Padha and Khoshyelagh formations in Devonian successions in eastern Alborz, north of Shahrood. The existence of these magmatic rocks as interbeded in silici-clastics, limestones and dolomites of the Padha and Khoshyelagh formations indicates their relations with an extensional tectonic regime of an intracontinental rift system governed on eastern Alborz in this time. Occurrence a rift-type sedimentary succession, Enrichment of igneous rocks in LREEs, relative depletion of them in HREEs, absence of negative anomaly in HFSEs, high amounts of P and Ti in these rocks and their plots in the discrimination tectonic diagrams indicate alkaline nature of parental magma which have been generated from 14-16% partial melting of an enriched sub-lithospheic garnet lherzolitic mantle source in 100-110 km depths. This scenario indicates the continuation of paleotethys opening extentional movements in eastern Alborz during Lower-Middle Paleozoic (Ordovician-Devonian). Manuscript profile -
Open Access Article
3 - Magmatic evolution of the Nasrand granitic in Petrology, intrusion and associated dikes
زهرا Hamzehie فاطمه Sarjoughian جمشید Ahmadian علی کنعانیانThe Nasrand granitoid intrusion, which is located at southeast of Ardestan, consists of granite and granodiorite that intruded Eocene volcanic rocks and cut by NW-trending doleritic dikes. The granitic rocks display granular, pertitic, granophyric and poikilitic texture MoreThe Nasrand granitoid intrusion, which is located at southeast of Ardestan, consists of granite and granodiorite that intruded Eocene volcanic rocks and cut by NW-trending doleritic dikes. The granitic rocks display granular, pertitic, granophyric and poikilitic textures. Plagioclase crystals in these rocks composed of two distinct generation (large phenocrysts along with inclusions of lath-shaped crystals) and often exhibit zoning patterns and sieve textures. The conspicuous disequilibrium textures in the granitoid rocks may suggest that magma mixing beside fractional crystallization play a significant role in the formation of the plutonic rocks. In confirmation of petrographic data, crystal size distribution (CSD) technique was also used to determine crystallization conditions and magmatic processes that lead to the formation of the rocks. Increasing of feldspar crystal size in a semi-logarithmic plot of population density versus size represents fractional crystallization, whereas disruption and curvature of cumulative density of plagioclase and orthoclase on the semi-logarithmic diagram, indicating the arrival of new magma into the magma reservoir and confirm the importance of magma mixing. Additional chemical features such as variation trends of Rb versus Rb/Sr and Nb versus Nb/Y in the samples can be regarded as an indicator of magma mixing processes. Manuscript profile -
Open Access Article
4 - The study of shortening and changes in structural geometry of the Pazanan anticline based on seismic reflection data (Dezful embayment, SW Iran)
In this research, shortening percent and changes in structural geometry of the pazanan anticline in Dezful embayment (SW Iran) have been studied based on seismic profiles. This anticline with NW-SE trend has about 60 km length and 4 to 6 km width in surface. The Hendiha MoreIn this research, shortening percent and changes in structural geometry of the pazanan anticline in Dezful embayment (SW Iran) have been studied based on seismic profiles. This anticline with NW-SE trend has about 60 km length and 4 to 6 km width in surface. The Hendihan high, that is located in NW parts of the Pazanan anticline, is the most important structure caused different deformation and change in geometry of anticline. In general, geometry of NW parts of the Hendijan high is existence of a main fore-thrust, exposed of shallow thrust and low thickness of the Gachsaran Formation in hinge area. Geometry of the anticline in the Hendijan high area is similar the northern part but the Gachsaran Formation in more thickened in hinge area. Geometry of the fold has been tighter in the SE parts of the Hendijan high and main part of middle section up to near the SE parts of anticline and shallow thrust is not formed in SE parts of anticline. Also, maximum shortening percent in anticline is about 11 to 11.1 percent in middle parts due to longitudinal axial bending in fold and minimum shortening is about 8.4 to 8.6 percent in SE parts possibly due to plunge of fold. Manuscript profile -
Open Access Article
5 - Probable Tsunami in the south Caspian Sea by a large earthquake!
The South Caspian basin is surrounded by the Central Alborz mountain range in South and Talesh Mountain in its south western side respectively. The Central Alborz with E-W and Talesh with NS trends which bounding the Caspian Sea to the south and south west, as an active MoreThe South Caspian basin is surrounded by the Central Alborz mountain range in South and Talesh Mountain in its south western side respectively. The Central Alborz with E-W and Talesh with NS trends which bounding the Caspian Sea to the south and south west, as an active terrain belonging to the Alpine-Himalayan seismic belt. The Khazar (Caspian) fault, with about 450 kilometres long, and Astara fault, 110km long appear as the northern border of the Central Alborz and eastern border of the Talesh chain where Mesozoic and Paleogene rock units overthrust on the young deposits of the South Caspian plain. Based on morphotectonics and paleoseismologic studies, we suggest that a major part of the present shortening in Alborz is concentrated on the northern face of the chain along the Khazar fault zone; it is however worth noting that this contact might be located further to the North under the sea. This border can be interpreted as frontal contact between Alborz and the South-Caspian basin. A recent stratigraphic study on the Holocene –Pleistocene in East of the Haraz valley, suggests an incision rate of 1.25 mm/yr as calculated for the last 12 Kyr. If it is assumed that the incision is related to the vertical component along the Khazar fault, the horizontal N-S shortening along this fault would be 2.5 mm/yr (for a 35° S-dipping fault). This is only 1/10th of the total shortening of Alborz, estimated 5 ± 2 mm/yr. The Astara fault as major active fault system in south west of the SCB, based on the seismic and geophysical observation it seems propagated under the sea as well as the Khazar fault. Many earthquakes may have been caused by the activity of various branches of these fault systems in land or sea parts of the SCB. On the basis of the basin geometry, propagated faults to north or east and their land slope, besides more than 20 km thickness of Neogene and Quaternary deposits in the south Caspian Basin in the scenario with the possibility of a seismic activity on the Khazar or the Astara faults or one of them propagated branches to the north and east with magnitude M ≥ 7, as the closest active faults to the great lake can trigger many large submarine earthquake ruptures or submarine landslides which is potential for generating Tsunamis in the steep southern coast. Manuscript profile -
Open Access Article
6 - Evaluation of coastal geomorphologic change in northern coast of Persian Gulf from Kangan Port to Ziyarat Estuary using remote sensing and GIS
hossein taghaviCoastal geomorphological changes in the short-term and long-term are observable in all coastal areas. The changes occur to reach the balance in this region. Aware of these changes is very important to geomorphologists, environmental planners to help them to solve coasta MoreCoastal geomorphological changes in the short-term and long-term are observable in all coastal areas. The changes occur to reach the balance in this region. Aware of these changes is very important to geomorphologists, environmental planners to help them to solve coastal problems. The purpose of this study is to assess the geomorphologic changes occurring in the region of coastal Bushehr Port Kangan place within the Ziarat estuary. In this study multi-temporal satellite images of Landsat were selected as the data base. The principal component analysis and fuzzy logic are used for monitoring and evaluating the geomorphological changes. Results of this research show that during the 21 year research period from 1986 to 2006 most important factor changing landforms and coastline in the region are changes water level of the Persian Gulf that cause to submerged about 46 square kilometers of the region's coastal zone land. The important part of this area is containing spits and low slope and delta. The result of this research can be used for infrastructure projects, port facilities, commercial and military activities. Manuscript profile -
Open Access Article
7 - Occurrence of Celestite in Kalhur evaporatic Member of the Asmari Formation, Garah Chegha Mountain, Mehran, Ilam Province
The occurrence of celestite in Kalhur evaporitic member of the Asmari Formation in Garah Chegha Mountain, Saleh-Abad, Mehran in the province of Ilam is documented through a field work, thin section petrography, fluid inclusion, X-ray diffractometry and whole rock geoche MoreThe occurrence of celestite in Kalhur evaporitic member of the Asmari Formation in Garah Chegha Mountain, Saleh-Abad, Mehran in the province of Ilam is documented through a field work, thin section petrography, fluid inclusion, X-ray diffractometry and whole rock geochemistry studies. The celestite can only be observed in thin sections of the dark gray colored limestone with fine to medium size grain, dolomitic limestone and dolostone impregnated with bitumen. Polarized light microscopic study shows that celestite occurs mainly as disseminated or an aggregate of crystals and in terms of modal percentage varies from 1 to 15. The crystal shows a variety of textures including replacement, disseminate, aggregates, void filling, fracture and radial-fibrous textures. X-ray fluorescence analyses indicate that the celestite bearing rocks contain 1.65-12.99 wt.% SrO, 31.73-50.52 wt% CaO, 0.27-15.74 wt% MgO and 0.9-10.07 wt% SO3 respectively. Average minor element contents in the studied samples are: 1.2 wt% SiO2, 0.7 wt% Al2O3, 0.2 wt% Fe2O3, and 0.1 wt% Na2O. Normative mineral recalculation shows that the content of celestite in the studied samples varies from 2 to 23 wt% with an average grade of 8 wt%. Strontianite, considered as an alteration product of celestite, is only seen in two specimens, probably resulting from celestite replacing. The most abundant homogenization temperatures of fluid inclusions in celestite crystals fall between 164 and 184 °C and the majority of calculated salinity values are restricted to 8.5 - 9.5 wt% NaCl. Petrographic, mineralogical, fluid inclusion and geochemical analyses indicate that carbonate-hosted celestite is diagenetic in origin implying its formation during the dolomitization and transformation of probably aragonite to calcite and then to dolomite. In contrast, vein and veinlet celestite postdate diagenesis of carbonate rocks and may imply epigenetic origin. Manuscript profile -
Open Access Article
8 - Assessment of interpretation methods to calculate aquifer transmissivity from single-well step drawdown aquifer test
Hatefi Etebari Delkhahi Gholam Abbas Fanaei Kheirabad ShahsavariSince the measured well drawdowns in a single well test does not reflect the aquifer head loss and covering linear and nonlinear well losses, the calculations based on the observed head loss from a pumping well, cannot get a precise estimate of the hydrodynamic paramete MoreSince the measured well drawdowns in a single well test does not reflect the aquifer head loss and covering linear and nonlinear well losses, the calculations based on the observed head loss from a pumping well, cannot get a precise estimate of the hydrodynamic parameters of the aquifer. But when an inexpensive and rapid estimation of aquifer transmissivity is required, using the collected data from a single pumping well is amongst the attractive options. Several methods for estimating borehole loss components has been proposed by various researchers. In this study, methods proposed by Eden-Hazel, Hantush-Biershenk, Kasinow, Miller-Weber and Karami-Younger; suggesting to calculate well loss component (CQn) were assessed to determine the transmissivity of the aquifer using measured head losses from both the pumping well and the adjacent piezometer from some aquifer tests conducted on a number of exploration wells of Khorasan (Razavi and Southern) provinces. The calculated well loss components using Eden-Hazel, Hantush-Biershenk, Kasenow and Miller-Weber methods has a significant difference to the simulated well losses using piezometric data. Karami-Younger method has been able to calculate the CQn value more accurately, about 25% to the simulated value. However, an accurate CQn estimate did not necessarily concluded to an acceptable aquifer transmissivity calculation. In the other words, the results of implementation of this method is more sensitive in sediments with high permeability and lower well losses. Manuscript profile
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