جستجوی مقالات مرتبط با کلیدواژه "tabas" در نشریات گروه "زمین شناسی"

Sporomorph EcoGroups data and the relevant plant communities are considered as a possible routine used to draw palaeoecological inferences for their host strata. Occurrence of high abundant and diverse miospores in the Qadir Member (Nayband Formation), from the exploratory well no. 954 (Exploratory Area of Parvadeh 4), south of Tabas, central Iran allows for this method to be used to obtain certain palaeoecological implications. By classifying spores and pollens (sporomorphs) in Sporomorph EcoGroups (SEGs), all six plant ecogroups (including plants adapted to Upland, Lowland, River, Pioneer, Coastal, and Tidally-influenced) were identified in examined material. The high ratio of warmer/cooler sporomorphs and the low ratio of drier/wetter sporomorphs suggests deposition under a moist, ±warm climate during the Late Triassic in south of Tabas. From the investigation of miospore parent plants, it was approved that, in descending order, pteridophyta (44%), cycadophyta (34%), coniferophyta (9%), lycophyta (8%), pteridospermophytes (2%), ginkgophytes (2%) and bryophyta (1%) were surrounded the environment of the studied formation. Notable abundance of fern spores (Kyrtomisporis and Foveogleicheniidites) and cycads pollen (Ovalipollis and Ricciisporites) in the palynofloras studied indicate the predominance of warm to semi-warm climate with high humidity. Paleogeographic position of Iran during the Late Triassic in the southern active margin of Eurasia (Turan Plate) tends to support this palaeoclimate generalization.

In the present study, biostratigraphy of calcareous nannofossils from the marl part of Farrokhi formation in the Central Iran basin, stratigraphic section of Farrokhi village, are investigated. In the studied section, Farrokhi formation mainly consists of limestone, marls, and marly limestone. 64 samples were investigated from the marl successions of Farrokhi formation with 118 m thickness. Calcareous nannofossil studies lead to identification of 35 species belong to 22 genus. Based on the recognized genus and species, CC22-CC25 of Sissingh zonation were determined. According to this, the age of the late Campanian- early late Maastrichtian proposed to marly part of the Farrokhi formation in the studied section. In this research paleoecological investigations of calcareous nanofossils shows that the studied area was deposited in relatively low latitude with warm surface water, low productivity and low fertility conditions. According to this, the age of the late Campanian- early late Maastrichtian proposed to marly part of the Farrokhi formation in the studied section. In this research paleoecological investigations of calcareous nanofossils shows that the studied area was deposited in relatively low latitude with warm surface water, low productivity and low fertility conditions.

Earthquakes with a large magnitude affect people, man-made buildings and environments. This information can be a dataset of the earthquake description consisting of people’s feelings, the building damages, and the effects on the earth. For the building damages, different types of buildings should be considered to find the best dataset of the earthquake. For the effects on the earth, various environmental effects such as the displacements, landslides, rock falls, liquefactions, surface and chemical changes on the rivers and springs, etc. should be considered; more information of more situations, more accurate exports of the earthquake. According to global research in this field, using this information can be useful to assess the macroseismic intensity of the affected areas and the epicentral earthquake. Moreover, having a good dataset of these descriptions, the macroseismic parameters of the earthquake can also be estimated. It can be useful especially for the earthquakes with low or/ and lack of information in the earthquake catalogs and also paleo-earthquakes. This study concentrates on the Tabas earthquake, which occurred on September 16, 1978, in the Tabas region located in eastern Iran. This was a shallow earthquake felt in a region with 1130000km2 total affected area. Such as every large earthquake, several phenomena were observed related to this event. For example, it destroyed 1500 building units and 30 Qantas. Although the epicenter of the earthquake was located in a situation with a poor population, it destroyed or severely damaged 90 villages and slightly damaged other 50 villages. The surface rupture of this event was extended for about 85km with no connection on the surface with a trust mechanism. Moreover, 150cm vertical displacement and 300cm horizontal displacement were reported for this event. According to these descriptions of Tabas earthquake with magnitude more than 6, occurring more earthquakes in the past can be usual for this region; then, more investigation on this field is necessary. Therefore, in this study, primarily investigation on this region was started using the available maps (e.g. geology map) and images (e.g. Landsat) and for the following researches the locations near Ali Abad in NW of Tabas were suggested for the field study and sampling to date their absolute ages.

The Baghamshah Formation (Middle Jurassic) at the Senj stratigraphic section, northeastern Tabas, central Iran, consists of diverse and relatively well-preserved palynomorphs, including spore and pollen of land plants, microscopic algae, acritarchs, Tasmanites, fungal spores, foraminiferal test linings and dinoflagellate cysts. The miospores are attributed to the Pterophyta (11%), Lycophyta (1%), Coniferophyta (80%), Cycadophyta (3%) and Pteridospermophyta (5%). Among the miospores, the maximum frequency is related to Classopollis from the Chirolpidiaceae family of conifers. The abundance of Classopollis in the studied samples may represent the abundance of Chirolpidiaceae in the composition of vegetation nearby the sedimentary environment, the abundance of produced pollen, and/or the vicinity of the habitat of the parent plants to the depositional environment. Previous investigations about the environment of the Chirolpidiaceae family indicate the predominance of hot and dry climates. The abundance of Botryococcus algae separately or attached to Classopollis also supports this type of weather. The dominant size of the miospores in the stratigraphic section (25–35 µm) indicates the transport by a wind from highland to lowland. Based on the model of Sporomorph EcoGroups (SEGs), miospores typifying all the six plant communities are present in the studied strata. The palaeoclimate study was determined by the pattern of relative abundance of drier/wetter and warmer/cooler elements. The consequences of these calculations approve the hot and dry climatic conditions during the accumulation of the strata examined.

Middle Jurassic sediments of the Hojedk Formation have been well-exposed in the Central East of Iran. In this study, plant macrofossils, which are collected from a coal exploratory well in the Mazino area, southwest of the Tabas were studied, so that 29 species of well-preserved plant macrofossils belonging to 15 genera of various orders such as Equisetales, Filicales, Caytoniales, Bennettitales, Cycadales, and Pinales were identified. One local biozone- Ptilophyllum harrisianum-Klukia exilis interval zone was recognized. The lower and the upper boundaries of this biozone were identified by the first and the last occurrences of index species. Based on the occurrences of the Equisetites sp. cf. E. beanii, Klukia exilis, Ptilophyllum harrisianum, Nilssonia macrophylla, and Elatides thomasii, an early Middle Jurassic age (Aalenian-Bajocian) was suggested for this plant assemblage. The relative abundance of Filicales (ferns), Cycadales, Pinales, and Equisetales are 43.18, 31.82, 13.63, and 4.64 percent, respectively. Moreover, the results of similarity indices of plant macrofossils indicate relatively strong value of similarity between the plant macrofossil assemblage of the Mazino area and elsewhere in the Tabas Block. Besides, the floral gradient score of this assemblage is 54.89. Based on the paleontological and lithological evidence, a humid ‘warm temperate biome’ is considered for this locality. Moreover, it is confirmed that a uniform vegetation and palaeoclimate occurred in Tabas Block during the Middle Jurassic and that Iran was located within Vakhrameev’s Euro-Sinian region, as Transcaspian subprovince.

In this research biostratigraphy of Baghamshah Formation based on calcareous nannofossills in the kalshaneh section was investigated. This section is located in northwest of Tabas. Baghamshah Formation in this section with 505 m thickness mainly consists of green- gray marl, very thin bedded shale with intercalation of fine sandstone and brown limestone abundant of brachiopodae and pelecypodae fragments and gerrn marl with interbedded of nodular limestone. Lower boundry with Parvadeh Formation is comformable and upper boundry with Kamar-e- Mehdi Formation is also marked. The study of nannofossils has been led to the identification of 44 species and belonging to 22 genera. According to stratigraphy distribution of calcareous nannofossils, CC3-CC5 biozones of Sissingh (1977) were determined. Nannofossil biozones indicate lateValanginian- late Haterivian age for the Baghamshah Formation in the Kalshaneh section.

This research has studied calcareous nannofossils of the Baghamshah Formation in Tabas Block (eastern Iran). Calcareous nannofossils are one of the most important fossil groups for biostratigraphical analysis. The earliest paleontological studies on the Baghamshah Formation have focused on ammonites (e.g., Seyed-Emami et al. 1988, 1991, 1997, 2001, 2002; Wilmsen et al., 2009). Kallanxhi et al. (2016) have also considered this formation's ammonites and nannofossil contents. The current study is the first investigation of calcareous nannofossils of the Baghamshah Formation in the Kharvan section and aims to discuss the possibility of using the standard nannofossil zones for the Baghamshah Formation.

The Kharvan section with 239 meters thickness is located 40 km northeast of Tabas near the Kharvan village. The formation has lithologically consisted of green and gray shales and marls. Generally, 75 samples from the Baghamshah Formation have been taken. Samples were prepared via the smear slide method (Bown & Young, 1998). All nannofossils were photographed in both cross-polarized light (XPL) and (PPL) and identified using Perch-Nielsen (1985) and Bown & Young (1998).

46 species belonging to 26 genera were identified in the studied section. Amongst them, 38 species belong to 21 genera of nannoliths and coccoliths, and 8 species from 5 genera belong to Didemnid ascidian spicules. Didemnid ascidian spicules are organisms with soft bodies and rigid spicules, which carbonate-rich seawaters and coral reefs are suitable environments for their colonization (Varol, 2006). The most dominant genera from the Baghamshah Formation are Watznaueria and Nannoconus. Among the nannofossil species, Nannoconus steinmannii, Retecapsa angustiforata, Calcicalathina oblongata, Tubodiscus verenae, Lithraphidites bollii, Cruciellipsis cuvillieri, and Nannoconus abundans are index species, used for biozonation. The Biostratigraphic studies in the Baghamshah Formation is led to the identification of calcareous nannofossils biozones CC1 to CC5 of Sissingh (1977) in the Kharvan section. Determined biozones represent the age of the early Berriasian - late Hauterivian for the investigated strata in the Kharvan section

The nannofossil assemblages of the Baghamshah Formation in the Kharvan section have average to pretty good preservation. In this section, the presence of CC1 at the lower part of the Baghamshah Formation and the presence of CC5 at the upper part of the formation shows that the age of the Baghamshah Formation is Early Berriasian - Late Hauterivian in the Kharvan section.

Early and Middle Jurassic, continental sediments of considerable thickness are widespread in the northern, central, and central-eastern Iran (Kilpper, 1964, 1968, 1971, Barnard and Miller, 1976, Sadovnikov, 1976, 1984, 1991, Corsin and Stampfli, 1977, Fakhr, 1977, Schweitzer and Kirchner, 1995, 1996, 1998, 2003, Schweitzer et al., 1997, 2000, 2009, Vaez-Javadi and Pour-Latifi, 2004, Vaez-Javadi and Mirzaei-Ataabadi, 2006, Vaez-Javadi, 2008, 2011, 2012, 2014, 2015a, b, 2018, Saadatnejad et al., 2010, Vaez-Javadi and Abbasi, 2012, 2018, Vaez-Javadi and Allameh, 2015). For a more detailed study, plant macrofossils from Chah-Rekhneh were considered here.
Material, metho

The plant fossils have been driven from a borehole in Chah-Rekhneh, 62km of SW Tabas city, 33˚17´56ʺ North latitude, 56˚24´01ʺ East longitude. A total of 84 specimens have been collected from a 240 m stratigraphic-core section. Some specimens yielded more than one fossil. The flora from this locality here is introduced for the first time. Material cited in this work (prefixed MJHCh; acronym for Mehdizadeh, Javadi, Hojedk, and Chah-Rekhneh) is held in the collection of the Palaeobotany Laboratory of the Department of Geology at the University of Ferdowsi, Mashhad. Biostratigraphy of the Chah-Rekhneh The Hojedk Formation consists of shale, siltstone, and fine-sandy silt alternating with thick medium-grained sandstone at the base of column. Several coal seams are present at the middle and upper part of the core column. One assemblage biozone was established in this section with lower and upper boundaries identified by FOO (First Observed Occurrence) and LOO (Last Observed Occurrence) of Coniopteris hymenophylloides and Klukia exilis, respectively. Furthermore, three informal subzones were recognized which are upward: I- Equisetites beanii- Ptilophyllum harrisianum Interval zone; II- Ptilophyllum harrisianum- Elatides thomasii Interval zone, III- Elatides thomasii - Nilssonia macrophylla Interval zone.Palaeoclimate Analysis In order to recognize palaeoclimate of the Chah-Rekhneh area during the Middle Jurassic, plant macrofossils relative abundance analysis and floral gradient method were used. Ziegler et al. (1996) assigned all Jurassic leaf genera to ten coarser morphological categories (or 'morphocats'). Rees et al. (2000) explained "Floral gradient" analysis. They show how this analysis can be used to interpret phytogeographic patterns based on the axis 1 scores of individual leaf genera and corresponding plant localities, due to their relative degrees of association. Then the climatical distribution in terms of the basic morphological characteristics of individual leaf genera and the palaeogeographic distribution of plant localities can be understood. By calculating the average of the scaled (0 to 100) axis 1 scores of the 32 genera common to all three intervals, a Jurassic 'floral gradient' has been derived. Floral gradient score of this flora in Chah-Rekhneh is 41.81. It shows that the flora assigned to the middle part of Floral Gradient table and suggests a humid and sub-tropical climate during early Middle Jurassic.

The Hojedk Formation in the Chah-Rekhneh area, south west Tabas contains 33 plant macrofossil species (21 genera) of various orders. On the basis of FOO and LOO of index species, one assemblage zone- Coniopteris hymenophylloides-Klukia exilis Assemblage zone and three informal subzones were recognized. These subzones are upward: I- Equisetites beanii- Ptilophyllum harrisianum Interval zone, II- Ptilophyllum harrisianum- Elatides thomasii Interval zone, and III- Elatides thomasii - Nilssonia macrophylla Interval zone. The occurrence of index fossils such as Klukia exilix and Elatides thomasii, Aalenian-Bajocian are assigned for this assemblage. Statistical analysis studies reveal that Order Filicales, Cycadales, Pinales and Equisetales with relative abundance of 46.31%, 23.50%, 12% and 9.26%, and Nilssonia, Klukia, Coniopteris and Equisetites were the most abundant genera with 22.81%, 13.38%, 8.40% and 8.40%, respectively in the Chah-Rekhneh area. Therefore, based on relative abundance of Filicales and Cycadales, the occurrence of Equisetites beanii as index species of climatic and ecologic, and average floral gradient score (41.81), a humid sub-tropical palaeoclimate was dominant in this area during the Aalenian-Bajocian interval.

Coral fossils of Jamal Formation Bagh-e-Vang member in Bagh-e-Vang and Shesh-Angosht stratigraphic sections (Tabas area of East-Central Iran) have been investigated in this research. Except the studies by Flügel (e.g.; 1964, 1968, 1972, 1995) and Ezaki (1991) Permian corals are poorly known from Iran. The Jamal Formation was firstly introduced by Stöcklin et al. (1965) for the Permian rocks of east central Iran consisting mainly of limestone and dolomite in Shotori and Shirgesht Mountain ranges of the Tabas Block. With 293 to 473 m thickness (Stöcklin et al., 1965; Ruttner et al., 1968; Leven and Vaziri Mohaddam, 2004), its succession confined unconformably upon eroded surface of siliciclastic rocks  belonging to the Carboniferous Sardar Formation and is conformably overlain by the Lower Triassic Sorkh Shale Formation (Partoazar et al., 2014). Jamal Formation in the studied sections is divided into 2 members, Bagh-e-Vang and Cherty Limestone member. The first one which is the main subject of the current research consists of shale and fossiliferous limestone with a siliciclastic rock unit of conglomerate and sandstone at the base, which is overlaid on the green shales of the Sardar Formation. The member is overlaid by cherty limestone of the Jamal Formation through a conglomeratic horizon. This study discuss paleontologically and paleobiogeographically the new material collected from the Jamal Formation in the mentioned localities, Bagh-e-Vang (coordinates of N33°58′27″ and E56°47′33″) on the southwestern flank of the Bagh-e-Vang Mountain and Shesh-Angosht (coordinates of N33°59′15″ and E56°46′50″) on the western flank of the Shesh-Angosht Mountain, at the north of Tabas.

Beside the lithostratigraphical studies in the field, we looked the whole succession of the Bagh-e-Vang member to investigate the coral contents. Totally more than 350 specimens of in situ and float solitary and colonial corals have been collected bed by bed. The specimens were immersed in cold water for one week for study to remove the soft sediment particles attached to them with a special brush. Subsequently, the descriptive characteristics of the specimens included external features such as overall shape, length, diameter, diameter, base and calyx diameter, presence or absence of transverse and longitudinal bands, preservation and wall thickness, rejuvenation, columella and its diameter and depth of calyx were recorded in the respective tables and photographed from various positions with a Canon XD60 camera. In addition, coral fossils serially sectioned in the transverse and longitudinal directions according to the size and conditions of the study. They were studied under normal light (PPl) binocular microscope with a magnification of 5. In the thin section studies, coral diameter, dissepimentarium thickness, number of dissepiment rows, their size and slope, types of dissepiments, central structure, number, shape and thickness of septa as well as their types (Alar septa, cardinal septa, etc.), granule, fossula, tabularium and their number in cm, tabular diameter, type of wall, its thickness and ornamentation, central area diameter and septotheca were investigated. The final determination is carried out based on the proper literatures such as Flügel (1964, 1972, 1990), Ezaki (1991), Flügel & Hubmann (1993), Fedorowski (2010), Berkowski (2012), Kossavaya et al. (2012), Somerville et al. (2012).

The stratigraphic interval in which all examined tabulate corals occur represents the lowest ca. 60 m part (＝ Bagh-e Vang Member in Partoazar, 1995), where carbonate facies are sandy to marly and contain interlayers of sandstone, shale, and olistolith. The Bagh-e-Vang member was dated by various taxa. These results are as follows: Bolorian (＝Kungurian; fusulinids; Leven and Vaziri Mohaddam, 2004), Yakhtashian (＝Artinskian) to Bolorian (fusulinids; Arefifad, 2006), Artinskian to Kungurian (bryozoans; Ernst et al., 2006), Bolorian to early Kubergandinian (＝early Roadian; fusulinids; Leven and Gorgij, 2011), and Sakmarian to Kungurian (conodonts; Voulo, 2014). Taking these information into consideration, the age of corals examined herein is best constrained as late early Permian. The Tabas Block forms the Central-East Iranian Microcontinent with the Yazd and Lut blocks, whose paleogeographic position is interpreted to have been part of northern margin of Gondwana during early Permian time (e.g. Berberian and King, 1981; Ruban et al., 2007). It is concluded that, therefore, habitat of the Jamal coral assemblage was on the southern shelves of the Paleotethys.The coral assemblage of the Bagh-e-Vang member comprises 27 genera, 2 subgenera, 35 species, and 6 subspecies belong to 20 families of solitary and cerioid-fasiculate colonial Rugosa and Tabulata corals. This fauna is similar to Early Permain (Sakmarian – Kungurian) assemblages of the Cimmerian blocks. They are categorized into two distinct Waagenophyllum and Cyathaxonia fauna; although the Cyathaxonian forms with more diversity and abundance are dominant in the studied sequences. The Fasciculat and cerioid colonial genera of the Waagenophyllum fauna approve the shallow warm water tropical realms of the Tethys Ocean, however the small solitary Cyathaxonia fauna mostly tends to cool - temperate antitropical, antiequatorial or bipolar realms of the northern and southern hemispheres in the Permian (Wang et al., 2013). It means the Cyathaxonia fauna of the Bagh-e-Vang member are comparable with the Pri-Gonwanan realm and the Waagenophyllum fauna are similar to those from North and South China in the tropical realm. Consequently, the Early Permian coral fauna in the Bagh-e-Vang member suggests a complex paleobiogeographic pattern consist of tropical Waagenophyllum and cool-temperate Cyathaxonia fauna.

In this paper, we investigated optimum height in upward continuation of potential field data to separate local anomalies from regional ones. Cross correlation of the data at different heights was used to achieve this goal. In order to obtain optimum height of upward continuation, two methods were introduced. In the first one, cross correlation of the known regional anomalies and upward continuation of the total magnetic field at different heights was used. In this method, the height at which maximum of correlation coefficient happens is the optimum height of upward continuation. The second method is based on cross correlation of upward continued of two consecutive heights of total magnetic field. The height at which the maximum deviation of the first point and the second point from the curve of cross correlation versus height occurs is the optimum of height. The second method is preferable as we always have total magnetic field data at different heights. We applied the second method on the magnetic data from Kalshaneh area in Tabas region. In this area, the optimum height for upward continuation is 60 m in which we can separate local anomalies from deep ones.

The Hojdek Formation in the Kale-shur area consists of alternation of fine quartz arenitic - arkosic sandstones with dark gray to green shales and coal seams. This formation includes relatively well-preserved plant macrofossils which are studied here for the first time. 15 species of 9 genera belong to different orders such as Equisetales, Filicales, Sycadales and Pinales have been determined in this study. Based on these species, one biozone called Nilssonia bozorga - Coniopteris hymenophylloides Assemblage zone and two subzones in ascending order called Klukia exilis Taxon Range zone (I) and Ferizianopteris undulata- Equisetites sp. cf. E. columnaris Interval zone (II) were recognized in this section. The mentioned biozones in the studied area are comparable with the correspondent biozones of the Middle Jurassic interval in the Tabas area. Thus, the Coniopteris hymenophylloides-Klukia exilis Assemblage zone is proposed as a widespread biozone for the Tabas area during the Middle Jurassic. According to occurrence of the index fossils such as Coniopteris hymenophylloides and Klukia exilix the age of Aalenian-Bajocian is considered for this assemblage. Analytical studies reveals the Filicales, Cycadales, Pinales and Equisetales respectively with relative abundance of 48.08%, 32.69%, 15.38% and 3.85% were the most plentiful orders in the Middle Jurassic succession of the Kale-shur area. In addition, Nilssonia, Podozamites, Ferizianopteris and Lobifolia were the most abundant genera with 32.69%, 15.38%, 11.54% and 11.54% abundance in this region. The relative abundance of Filicales and Cycadales established a humid sub-tropical climate for this region.

Qadir Member of Nayband Formation in the eastern part of central Iran have a wide outcrop. Investigating the lithofacies and sedimentary environment of Qadir Member of Nayband Formation (Upper Triassic) in east central Iran, Tabas Block, resulted in identifying the coastal plain, deltaic and open marine deposits. Based onfield evidences, the facies features and the geometry of beds, this member consists of two lithofacies include carbonate and siliciclastic facies. The siliciclastic facies were identified as having four sandstone facies (medium-grained), including Sr, Sh, Sp, St and three fine-grained lithofacies, including FI, Fm, Fl (Sr) / Sr (FI) and one coal facies (C). Also carbonate facies are calcirudite and calcarenite. Regarding the field, laboratory studies and identifying the lithofacies, the coastal plain, deltaic (including deltaic plain, proximal delta front, distal delta front, and prodelta) and open marine environments were identified for Qadir Member on which it is under the impact of tidal currents.

Hojedk Formation spreads well through the Tabas Block. Diverse and moderately preserved palynofloras occur in the Middle Jurassic sediments of the formation in south Kouchekali, southwest of Tabas, central-east Iran. The present investigation of the Hojedk Formation has revealed a diverse assemblage of dinoflagellate cysts in which 12 species allocated to 5 genera. Two acritachs were also recognized, permitting establishment of Nannoceratopsis triceras-Pareodinia ceratophora Assemblage zone, and Nannoceratopsis gracilis Total Rane Subzone in the upper part, lower and upper boundaries have been identified by the first and last observed occurrence (LOO) of these index species. These biozones are comparable to the other palynozones in Iran and elsewhere especially in the northern hemisphere (Greenland, Norway, Scotland, England, and Poland). Occurrence of various species of Nannoceratopsis is concluded that this locality was located at the south palaeocoastal line of the Tabas Block during the Aalenian-Bajocian.

Consumption of water contaminated with heavy metals can result adverse health effects in people. Standard value of drinking water was determined 10, 10 and 3µg/L for As, Pb and Cd in Iran. According to the determination of arsenic contamination in some parts of the country, Study of drinking water resources must be done in all regions of the country at once. The present study aimed to determine the amount of arsenic, cadmium and lead in groundwater resources of Ferdows and Tabas area.
A total of 4 wells of the city and the villages around Ferdows city and 5 wells and 3 mineral spring in Tabas city and its surroundings for supplying drinking water were sampled by standard method. Physicochemical parameters (EC, Eh, pH)were measured using a portable pH meter at the location. The heavy metals amount were determined by ICP-MS instrument. In studied samples, Cadmium and lead concentrations were less than limits of drinking water standards in the country and these metals pollutants do not exist in the waters of these areas, but arsenic concentrations exceeded from allowed level (10 μg/L) in two districts of Tabas and one area of Ferdows. The highest positive correlation of arsenic was found with pH and Eh. Due to high complication of arsenic contamination in drinking water and increasing use of groundwater as a source of drinking water in the country, it is necessary, in areas where arsenic contamination is higher than standard limit to replace by healthy sources as soon as possible and the periodic control should be on the agenda of responsible organizations for concentrations of arsenic in drinking water for residential areas.

Nayband Formation is composed of sandstone, coal bearing shales, siltstone, and fossiliferous limestone in the southwest Tabas section, east central Iran. In this section, it is 1410 m in thickness and Late Triassic in age. A divers trace fossils have been found in the middle parts of sequence as 400-600 m. These trace fossils include Lockeia isp., Palaeophycus tubularis, Palaeophycus striatus, Planolites beverleyensis, Rhizocorallium isp., Rosselia isp., and cf. Treptichnus isp. This ichnoassemblage is attributable to Cruziana ichnofacies with presence of Lockeia isp., Rhizocorallium isp., and, Rosselia isp. This part of Nayband Formation was deposited in low energy conditions below fair-weather wave base.

Hojedk Formation is well-exposed at the Kouchekali area, south western of the Tabas city. It consists of mainly grey-dark shale, siltstone and sandstone intercalating with coal seams. Here, the core number 169 was studied and plant macrofossils were collected. Thirty-two species of plant macrofossil remains allocated to nineteen genera of various orders such as Equisetales, Dicksoniales, Schizaeales, Caytoniales, Bennettitales, Cycadales, Ginkgoales and Pinales were identified. On the basis of the occurrence of index fossils such as Coniopteris hymenophylloides, Elatides thomasii, Klukia exilis and Nilssonia macrophylla, Aalenian-Bajocian age is suggested for this assemblage. One assemblage zone (Klukia exilis-Nilssonia macrophylla) and four sub-biozones were recognized in this formation. These subzones are: I) Sagenopteris nilssoniana-Equisetites columnaris Concurrent range zone, II) Equisetites beanii-Ptilophyllum harrisianum Concurrent range zone, III) Ginkgoites huttonii Taxon range zone and IV- Ferizianopteris undulata-Coniopteris hymenophylloides Assemblage zone. Biozones of the Hojedk Formation in the Kouchekali area were correlated to the similar age sediments of the Mazino area (Tabas Block), the Dansirit Formation in Baladeh and Rudbarak areas (Central Alborz Mountains) and Bazehowz Formation in its type section (south Mashhad, Binalud Mountains). Moreover, on the basis of relative abundance of Filicales and Cycadales in this area, a humid sub-tropical (warm temperate) climate or is suggested for this period of time.
Material, methods and geological setting
The plant fossils have been driven from the borehole number 169, North Kouchekali, W Tabas city, 33˚17´North, 56˚18´East. A total of 86 specimens have been collected from a 405 m stratigraphic-core section. Some specimens yielded more than one fossil. There were several coal seams among this core. The flora from this locality is here introduced for the first time. Material cited in this work (prefixed FJNK; acronym for Fatemeh, Javadi, Namjoo and Kouchekali) is held in the collection of the Palaeobotany Laboratory of the Faculty of Geology at University of Tehran.
Systematic palaeobotany
North Kouchekali core section, W Tabas city contains well-preserved plant macrofossils belonging to 32 species allocated to 19 genera. These fossils are: Anomozamites sp., Cladophlebis aktashensis, Cladophlebis whitbyensis, Coniopteris hymenophylloides, Ctenis sp. cf., Ctenis sulcicaulis, Dictyophyllum sp., Elatides thomasii, Elatocladus zamioides, Equisetites beanie, Equisetites columnaris, Ginkgoites huttonii, Klukia crenata, Klukia exilis, Lobifolia rotundifolia, Lobifolia sp., Neocalamites sp., Nilssonia feriziensis, Nilssonia macrophylla, Nilssonia orientalis, Nilssonia sp., Nilssonia sp. cf., Nilssonia tazarensis, Nilssonia tenuicaulis, Nilssonia undulate, Podozamites distans, Pterophyllum feriziense, Ptilophyllum harrisianum, Rhizomopteris rezaii, Sagenopteris nilssoniana and Sphenobaiera sp.
Biostratigraphy of the North Kouchekali
The Hojedk Formation consists of shale, siltstone and fine-sandy silt alternating with a thick medium-grained sandstone at the base of column. Several coal seams present at the middle and upper part of the core column. One assemblage biozone was established in this section with lower and upper boundaries identified by FOO (First Observed Occurrence) and LOO (Last Observed Occurrence) of Klukia exilis and Nilsssonia macrophylla respectively. Furthermore, four informal subzones were recognized which are upward: I) Sagenopteris nilssoniana-Equisetites columnaris Concurrent range zone; II) Equisetites beanii-Ptilophyllum harrisianum Concurrent range zone; III) Ginkgoites huttonii Taxon zone and IV) Coniopteris hymenophylloides-Nilssonia feriziensis Concurrent range zone.
Geographic and stratigraphic distribution of taxa
Floristic association described here is widespread in the Central-East Alborz Mountains, Kerman Basin and Tabas area in the early Middle Jurassic. Similar plant macrofossil assemblages have been distinguished from the Shemshak Group in the Alborz Mountains, the Bazehowz Formation in the Binalud Mountains and the Hojedk Formation in the Kerman Basin and in the Tabas area (e.g. Barnard & Miller, 1976; Fakhr, 1977; Schweitzer et al., 2000, 2003; Vaez-Javadi, 2011, 2012, 2014; Vaez-Javadi & Allameh, 2015).
Relative abundance of Taxa in North Kouchekali
Relative abundances of morphocats was studied in which the relative abundances of Filicales and Equisetales and macrophyllous cycadophytes were 38.5% and 37% respectively. It is noteworthy that variety of the species of Genus Nilssonia (six species) and species of Order Ginkgoales (two taxa), as a macrophyllous cycadophyte was high within the North Kouchekali core column. Therefore, a humid subtropical (warm temperate) climate is considered during this period of time in this area.
Floral gradient analysis of the flora of North Kouchekali
In order to recognized palaeoclimate of the Calshaneh area during the Middle Jurassic floral gradient and correspondence analysis was used. Ziegler et al. (1996) assigned all Jurassic leaf genera to ten coarser morphological categories (or 'morphocats'). These are sphenophytes, ferns, pteridosperms, microphyllous cycadophytes, unassigned (intermediate or morphologically variable) cycadophytes, macrophyllous cycadophytes, ginkgophytes, microphyllous conifers, unassigned (intermediate or morphologically variable) conifers and macrophyllous conifers. These groups parallel the major taxonomic subdivisions which in turn reflect the individual physiognomic strategies of their constituent plants. Rees et al. (2000) explained "Floral gradient" analysis. They show how this analysis can be used to interpret phytogeographic patterns based on the axis 1 scores of individual leaf genera and corresponding plant localities, due to their relative degrees of association. Then it can be understood these climatically in terms of the basic morphological characteristics of individual leaf genera and the palaeogeographic distribution of plant localities. By averaging the scaled (0 to 100) axis 1 scores of the 32 genera common to all three intervals, a Jurassic 'floral gradient' has been derived. In this case, microphyllous conifers and microphyllous cycadophytes have low scores, whereas macrophyllous conifers and ginkgophytes have high ones. Ferns and macrophyllous cycadophytes occupy the central portion of the gradient, along with sphenophyte genera such as Equisetites. Using the floral gradient, can assign a value to any Jurassic plant locality simply by averaging the scores of its constituent leaf genera. In this study I established this analysis. Floral gradient score of the North Kouchekali flora is 56.2. This shows that the flora assigned to the middle part of Table and suggests a humid and sub-tropical climate during early Middle Jurassic.

In this study, new data have been provided from the Hojedk Formation at the North Kouchekali, west of Tabas city, central-east Iran. Jurassic deposits in this core-column contains thirty-two species of plant macrofossil remains belonging to nineteen genera of various orders such as Equisetales, Dicksoniales, Schizaeales, Caytoniales, Bennettitales, Cycadales, Ginkgoales and Pinales. On the basis of the occurrence of index fossils such as Coniopteris hymenophylloides, Klukia exilis, Nilssonia macrophylla and Elatides thomasii, Aalenian-Bajocian age is suggested for this assemblage. One assemblage zone (Klukia exilis-Nilssonia macrophylla) and four informal sub-biozones were recognized in this formation. These subzones are upward: I) Sagenopteris nilssoniana-Equisetites columnaris Concurrent range zone, II) Equisetites beanii-Ptilophyllum harrisianum Concurrent range zone, III) Ginkgoites huttonii Taxon range zone and IV) Ferizianopteris undulata-Coniopteris hymenophylloides Assemblage zone.  This assemblage biozone is comparable to other biozones of the same age in Iran. Furthermore, relative abundances of taxa and morphocats were studied and relative abundances of Filicales, Equisetales, macrophyllous and cycadophytes were 38.5% and 37% respectively. It is noteworthy that variety of the species of Genus Nilssonia (six species) and species of Order Ginkgoales (two taxa), as a macrophyllous cycadophyte was high within the North Kouchekali core column. In addition, floral gradient score of this assemblage is 56.2. This shows that the flora assigned to a humid and sub-tropical climate (warm temperate biome) during the Middle Jurassic.

Jurassic deposits are well exposed in the Calshaneh area, north western of the Tabas city, Central-East Iran. It contains plant macrofossils belonging to seventeen species allocated to eleven genera of various orders such as of Equisetales, Filicales, Bennettitales, Cycadales, Caytoniales, Ginkgoales and Pinales. One biozone was recognized in the Hojedk Formation at Calshaneh section. According to occurrence of Klukia exilis and Coniopteris hymenophylloides a Middle Jurassic age is suggested for this biozones. One Assemblage zone, Nilssnonia sp. cf. N. bozorga-Klukia exilis Assemblage zone, and three subzones were recognized in this section. Subzones are from base to up 1- Ptilophyllum harrisianum Taxon range zone 2- Elatides thomasii-Sphenobaiera longifolia concurrent range zone and 3- Ginkgoites sp. cf. G. parasingularis - Coniopteris hymenophylloides concurrent range zone. This Assemblage biozone is comparable to other biozones of the same age in Iran. Furthermore, relative abundances of taxa was studied and relative abundances of order Nilssoniales, Ginkgoales, Filicales, and Equisetales were 44.44%, 20.64%, 15.87, and 7.94% respectively. It is noteworthy that variety and relative abundance of the species of Genus Nilssonia (six species and 42.27%) and species of Order Ginkgoales (two taxa and 17.46%), as a macrophyllous cycadophyte, was high within the Calshaneh area. Therefore, a humid subtropical to temperate climate is considered for this period of time in this area.

Parvadeh coalfield with an area of 1200 km2 is one of the largest coalfields in East-Central Iran. The coal-bearing clastic rocks of the coalfield belong to Ghadir Member of the Upper Triassic Naiband Formation and could be classified as bituminous coal, containing low volatile, high ash and medium to high sulfur. Pyritic sulfur is the main form of sulfur in the Parvadeh coals. Quartz, illite, kaolinite, pyrite, and calcite/dolomite are the principal mineral phases. Enrichment in major elements and depletion in minor elements were observed in studied samples when compared with those of the earth crust. The element contents of coal-bearing layers are similar to those of the US and world coals except for Cd, Li, As and Zn. Based on the calculated enrichment factor, the elements As, Co and Cd are the most pollutants in Parvadeh area. Strong correlations among ash contents and Si, K and Al values indicate that the coal ash is mainly composed of aluminosilicates. Meanwhile, Cd, Co, As, Fe, and S show that Cd, Co, As participated in pyrite lattice. These results were confirmed by factor and cluster analyses. The calculated recovery index shows that Li, Mo, Pb and Cu are bounded to maceral and organic matter thus are enriched in the cleaned coals. The other minor metals, however, are present in mineral part of the coal and enriched in ash.

Geomorphic characteristics of alluvial fans on the sides of the Shotori Mountains in east of Tabas represent two different groups. The first group is older and is more dominant with their heads near the Shotori Mountain's hillside and their toe spreading to the central parts of the plain. These alluvial fans on which no main recent channel sedimentation is occurring, are often consisted of old alluvial sediments with a thin cover of newer ones. The second group includes younger and active alluvial fans consisted of more recent sediments of stream bed, which are located at the termination of the first group or at the southern foothills of the Shotori Mountains. It can be said that in the first group, recent active sedimentation process by the main channel has been transferred to the lower parts and toe of the alluvial fan, but in the latter group sedimentation has been done on top of the alluvial fan and on older sediments. In other words, the first group consists of two obvious old and active (recent) parts, while the second group only includes recent and active alluvial fans. Our investigations indictaes that geomorphic pattern of these two alluvial fan groups has a clear relation with location and mechanism of active faults and geomorphic surfaces in the plain of Tabas and eastern slopes of the Shotori Mountains; in other words, it is related to the mechanism of structural evolution of this mountain. According to this pattern, ver there is the active fault of the catastrophic 1978 earthquake at the front of mountain along which the Shotori Mountains are being uplifted, the second type of alluvial fans is formed. the fault is located in central parts of the plain as a result of deformational front propagation, and the old part of the alluvial fan and mountain are being uplifted along it, the first type of alluvial fans (with two separate parts) is formed. This uplift is accommodated by active faulting and folding associated with bedding plane faulting. Migration of deformational front during geologic evolution of the Shotori Mountains has caused four different geomorphic levels along with three generations of alluvial fans. It is concluded that investigating on geomorphic pattern of alluvial fans will provide valuable data about the location of active Quaternary faults in alluvial plains. This pattern shows an active fault near Boshruyeh (east of the Shotori Mountains). Although no major earthquake has been reported the fault, all morphotectonic evidences show its activity and thus the occurrence of large earthquakes in the future is expected.

The (Early Carboniferous) Shishtu 2 Formation at the study area is composed of a shallowing upward sequence. Skeletal packstones consist of crinoids, brachiopods, bryozoans, trilobites, corals and rare foraminiferas. The carbonates of this formation have undergone a complex diagenetic history and the most diagenetic events are silicification and pyritization. The complexity of silicification in these limestones is further demonstrated due to selectivity of silicification of different faunas. Based on morphology, four fabric types are distinguished in silica including microcrystalline quartz, spherulitic chalcedony and slightly megaquartz and euhedral quartz. The observed correlation between skeletal fragments and quartz replacement types (QRT) shows that skeleton microstructure may control QRT. The silicification of the skeletal grains in this study occurred along thin solution films where skeletal calcite dissolved and silica precipitated. The brachiopods, corals and crinoids are the most susceptible organisms to silicification. The presence of impurity of Mg2+ in the composition of skeletal grains (e.g., brachiopods and crinoids) may be the controlling factor for their susceptibility for silicification. Diagenetic pyrite in the limestone of the Carboniferous in this area exhibit as euhedral pyrite which occurs as singular euhedral crystals. These may occur after the death of faunas and during burial diagenesis. This process is strongly dependent on the redox potential (dysaerobia to anaerobia) and availability of the required elemental ingredients (Fe and S) in the burial realm.