Sedimentology
Majid Khazaee; Mahbobeh Hosseini-Barzi; Abbas Sadeghi; Hossein Mosaddegh
Abstract
The provenance of Jeirud Formation deposits (upper Devonian) in central Alborz has been investigated from study of siliciclastic sandstones (petrography, modal analysis and Heavy minerals assemblage) and mudstones (major and minor elements geochemistry). An integration of results suggest a mixture of ...
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The provenance of Jeirud Formation deposits (upper Devonian) in central Alborz has been investigated from study of siliciclastic sandstones (petrography, modal analysis and Heavy minerals assemblage) and mudstones (major and minor elements geochemistry). An integration of results suggest a mixture of basic to acidic igneous rocks and recycling of older sedimentary rocks as the provenance that weathered under cold and arid to semi-arid climatic conditions. An integration of modal analysis and heavy minerals results into the geochemical studies including Roser and korsch diagram (Log K2O/Na2O versus SiO2) and Verma and Armstrong-Altrin Functional diagrams, indicate that, siliciclastic rocks of Jeirud, resulted from weathering of acidic-intermediate to basic rocks of collisional tectonic provenances (recycled orogens) and transporting on craton interior and have been deposited on a passive margin basin. Investigations and comparison with McLennan et al., studies, represent that geochemical results and proportions of study area are consistent with those of old upper continental crust (OUC) typical of collisional tectonic settings.
M Medadi; H Mosaddegh; S.H Aleali; M.R Majidifard
Abstract
Some paleobiodiversity indices such as total diversity, stand diversity, origination and extinction rates of Permian (Yakhtashian- Dzhulfian) small foraminifera were analyzed based from an outcrop in Abe-Garm area, Gazvin. Some important bizones that recognized by Taraz (1969), Taraz et al. ...
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Some paleobiodiversity indices such as total diversity, stand diversity, origination and extinction rates of Permian (Yakhtashian- Dzhulfian) small foraminifera were analyzed based from an outcrop in Abe-Garm area, Gazvin. Some important bizones that recognized by Taraz (1969), Taraz et al. (1981), Kobayashi (1997), Shabanian (2010), Stiger (1966), Davydov et al. (1996) were used for separation of stages, and biodiversity indices were calculated based on Foote (2000). The investigations are resulted in recognition of Two trends:1: Origination rate decrease rapidly from Yakhtashian to Murgabian and,2: two rapid increase in the extinction rate are recorded in Midian and Dzhulfian, the first comparable with End-Guadalopian mass extinction and the latter probably related to environmental condition.
H Mosaddegh; M Hadi; M Parandavar
Abstract
The Eocene marine deposits in the Chenarbu section in Torbat-e-Jam region (eastern part of Central Iran Zone) have been biostratigraphically studied based on large benthic foraminifera coincide with Shallow Benthic Zones (SBZ) and Calcareous Nannofossils, according to standard worldwide zones (NP). This ...
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The Eocene marine deposits in the Chenarbu section in Torbat-e-Jam region (eastern part of Central Iran Zone) have been biostratigraphically studied based on large benthic foraminifera coincide with Shallow Benthic Zones (SBZ) and Calcareous Nannofossils, according to standard worldwide zones (NP). This investigation has been conducted on carbonate sediments with a focus on large benthic foraminifera assemblage such as Eorupertia magna (La Calvaz), Fabiania cassis (Oppenheim), Eoannulariaeoconica (Cole ve Bermudez), Gypsina sp., Textularia sp., Nummulites perforatus (De Montfort) Nummulites sp., Discocyclina sp., Rotalia sp., Acervulina sp., and calcareous nannofossils such as Cribrocentrum reticulatum, Sphenolithus obtusus, Sphenolithus spiniger, Sphenolithus editus, Helicosphaera compacta, Coccolithus pelagicus, Coccolithus eopelagicus, Reticulofenestra sp., Discoaster sp., Discoaster siapanensis, Discoaster barbadiensis. Therefore, based on the determined index species, the SBZ15?- 17 biozones of large benthic foraminifera and the NP16 biozone of calcareous nannofossils in the studied section have been detected which both assign the Late Lutetian- Early Bartonian (Middle Eocene) age for the section.Also, the Lutetian- Bartonian boundary according to index calcareous nannofossil species was separated carefully, and the first appearance of the foraminifera species of N. perforatus (de Montfort) in the middle part of the deposited sequence was recorded during geological time of the Bartonian stage. Therefore, this fact points that in Iran alike western parts of the Tethys basin, the first appearance of N. perforatus (de Montfort) occurred in Early Barthonian (SBZ17). Systematic of Nummulites perforatus (de Montfort) was described based on typological and biometrical characterization.
M Khazaee; M Hosseini-Barzi; A Sadeghi; H Mosaddegh
Abstract
The Jeirud Formation (Upper Devonian) in Deh-Sufian section of northeast of Shahmirzad consists of siliciclastic and carbonate deposits. In the study area lower boundary of the Jeirud Formation with fine grain clastic deposits of the Mila Formation is erosional (Disconform) and has been conformably overlain ...
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The Jeirud Formation (Upper Devonian) in Deh-Sufian section of northeast of Shahmirzad consists of siliciclastic and carbonate deposits. In the study area lower boundary of the Jeirud Formation with fine grain clastic deposits of the Mila Formation is erosional (Disconform) and has been conformably overlain by dark carbonate deposits of the Mobarak Formation. The clastic deposits of the Jeirud Formation include conglomeratic, sandy and muddy facies. The conglomeratic deposits comprises three facies A1, A2 and A3 that are equivalent to Gcm, Gt and Gmm/Gmg of Miall facies respectively. Also, five sandy facies of B1, B2, B3 and B4 equivalent to St, Sh, Sm and Sr of Miall respectively and B5 (Shc) with hummocky cross stratification (HCS) sedimentary structure have been identified. Muddy facies including C1 and C2 are equivalents to Miall’s Fsm and Fl facies. Carbonate facies (D) comprising small amounts of the stratigraphic column is almost entirely dolomitized. Field and petrographic studies provide five facies association: fluvial, foreshore-backshore, shoreface, offshore transitional zone and offshore and carbonate facies interpreted as Proximal carbonate tempestites and distal carbonate tempestites based on evidences such as basal erosional surface, normal grading, HCS and coexisting clastic facies . In the study area, the Jeirud Formation deposits initiate with fluvial sequences that have been followed by storm dominated marine deposits as foreshore-backshore deposits and alternations of shoreface to offshore deposits. Study of sequence stratigraphic surfaces especially important subaerial unconformities and also stratal stacking patterns of the formation resulted in determination of three subaerial unconformity bounded depositional sequences plus transgressive part of the 4th sequence.
M Hadi; H Mosaddegh; N Abbassi
Abstract
Carbonate successionsof the Ziarat Formation with introduce the Baghdareh and Gheynarjehsections in the Soltanieh Mountains(southern Zanjan) are rare locality in the western Alborzzone,which are contains of great abundance oflarge benthic foraminifera (LBF), particularly species of Alveolina. In fact, ...
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Carbonate successionsof the Ziarat Formation with introduce the Baghdareh and Gheynarjehsections in the Soltanieh Mountains(southern Zanjan) are rare locality in the western Alborzzone,which are contains of great abundance oflarge benthic foraminifera (LBF), particularly species of Alveolina. In fact, from this succession described some of Alveolinaspecies and their comparative stratigraphic distribution with the Alveolina species in the Tethyanbasinwhich is represent close affinitieswith coeval Alveolinaassemblages described in diVerent studies from this province. Also, this correlation shows Ilerdian-Cusianstages of study area that characterized by A. ellipsoidalis, A. laxa, A. tumida, A.cemali, A.aragonensis, A. pisiformis,A.rotundata, A.subpyrenaica, A. cf. canavari, A. canavari, A.ex gr. cremae species.
K Mohammadi; N Taghipour; H Mosaddegh
Abstract
Due to some environmental variations such as sea level fluctuation and the Hangenberg mass extinction event, geochemical variations of elements have occurred in the Devonian-Carboniferous transition, which some of these elements are useful indicators to display the source of sediments and the sea level ...
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Due to some environmental variations such as sea level fluctuation and the Hangenberg mass extinction event, geochemical variations of elements have occurred in the Devonian-Carboniferous transition, which some of these elements are useful indicators to display the source of sediments and the sea level changes. In this transition, Sr is one of these elements has a reverse relation with sea level changing and a direct relation with amount of sediment deposition. Trace elements such as Sr, Fe, Mn, Mg, Al, and Ca display the depositional environment conditions and their changing is affected by indoor and outdoor environmental conditions such as pH, Eh, climate, etc. This study has focused on investigation of elemental changes at the Devonian-Carboniferous boundary in the Khoshyeilagh and Mobarak Formations in the Labnesar section, North of Damghan.
The elemental changing in Brachiopoda shells and its containing sediments has the same trend as they show the fossil samples are in situ. The environmental situation of fossil organisms and their involving sediments in the study section were semi close to open sea with anoxia conditions. The black shale at D-C boundary shows LREE richer than HREE that confirmed its continental source. The variation of some elements such as Mn, Fe, Na… at D-C boundary in the Labnesar section indicates of LMC (low magnesium calcite) in the Brachiopod shells and involving sediments. The quantity variations of Mn and Sr in D-C boundary are related to sea level fluctuations. These elements are influenced by the sea level changes and impress the amount of other elements such as Fe, Al, Ti, Mg, Ca, Na, and K. The median amount of Na at the boundary indicates a moderate salinity.