H Jahangir; M Ghobadi Pour; A.R Ashouri
Abstract
The Cambrian- Ordovician boundary strata in the Kalat section, western Koppeh-Dagh, comprise continuous succession of fine clastic sediments, mostly argillites with some shell beds, accumulated offshore. This interval contains analmost complete succession of conodont biozones, including the Cordylodus ...
Read More
The Cambrian- Ordovician boundary strata in the Kalat section, western Koppeh-Dagh, comprise continuous succession of fine clastic sediments, mostly argillites with some shell beds, accumulated offshore. This interval contains analmost complete succession of conodont biozones, including the Cordylodus intermedius, Cordylodus lindstromi and Cordylodus angulatus biozones. The first appearance of the planktonic graptolite Rhabdinopora cf. Flabelliformis flabelliformis (Eichwald, 1840) in black argillite of the upper part of the Cordylodus lindstromi Biozone indicates relatively precise position of the Cambrian- Ordovician boundary in the section. Cambrian- Ordovician boundary beds in the eastern Alborz Region can be subdivided into three lithological units: Furongian bioclastic limestone mainly replaced by fine clastic sediments in the upper part, the terminal Cambrian Cruziana sandstone representing a shoal complex and the Tremadocian grey argillite accumulated offshore. In this area the position of Cambrian- Ordovician boundary is situated somewhat below the base of the Asaphellus inflatus- Dactylocephalus trilobite Biozone.
S. Hemati; M. Taherpour Khalil Abad; A. Ghaderi; A. R. Ashouri
Abstract
Micropaleontological study on the carbonate successions of the Tirgan Formation at the Taherabad village and Eshlir anticline stratigraphic sections is led to identification of various taxa of the calcareous algae belong to the families Dasycladaceae, Triploporellaceae, Udoteaceae, Solenoporaceae and ...
Read More
Micropaleontological study on the carbonate successions of the Tirgan Formation at the Taherabad village and Eshlir anticline stratigraphic sections is led to identification of various taxa of the calcareous algae belong to the families Dasycladaceae, Triploporellaceae, Udoteaceae, Solenoporaceae and Gymnocodiaceae and also some specimens of small Gorgonacea. Based on the biometric measurements of morphological features, 16 genera and 20 species from the Taherabad section and 12 genera and 16 species from the Eshlir section have been recognized. Moreover, Permocalculus minutus and Permocalculus? halimedaformis have been found for the first time in the Tirgan Formation. Permocalculus? halimedaformis was introduced from the Minis Valley in Romania for the first time and its finding in this research is the second report around the world. According to this new finding, its geographic distribution is being extended more than 2800 km eastward on the northern margin of the Tethys ocean.
N Hashemi; A.R Ashouri; M Aliabadian; M.H Mahmoudi Gharaie
Abstract
Paleozoology of Yafteh and Kani Mikaiel caves in center and northwest of Zagros Mountains led to the identification of small mammals' assemblage. Taxonomic determination revealed inclusion of four orders of small mammals including: order Rodentia with families of Muridea, Cricetidae, Calomyscidae, ...
Read More
Paleozoology of Yafteh and Kani Mikaiel caves in center and northwest of Zagros Mountains led to the identification of small mammals' assemblage. Taxonomic determination revealed inclusion of four orders of small mammals including: order Rodentia with families of Muridea, Cricetidae, Calomyscidae, Dipodidae; order Lagomorpha with two families of Ochotonidae and Leporidae; order Soricomorpha with family Talpidae, and order Carnivores with family Mustelidae. These remains were recovered after systematic excavation in these caves. Radiocarbon analysis of these remains showed the oldest sample belonged to Yafteh cave with 35,000 BP. and Pleistocene period, whereas, Kani Mikaiel cave covered the periods from lat Pleistocene (19,000 BP.) to Holocene (17, 00 BP.). Geochronology analysis of Kani Mikaiel sediments showed that the lower layers of this cave belonged to the last glacial age in Pleistocene which gradually has been replaced by the warm weather in Holocene period. With continuing of this weathering varying, faunal spectrum of Pleistocene and Holocene periods has been migrated in cold and warm phases or more spread. The aim of this research, are the study of small mammal remains of Yafteh and Kani Mikaiel caves in center and northwest of Zagros mountains and the research about the study of paleobiodiversity, paleoenvironment conditions and the evolution of microvertebrate on the Iranian plateau.
M Badpa; K Khaksar; A Ashouri; M Khanehbad
Abstract
Rich assemblages of Carboniferous corals exist in the Zaladu stratigraphic section. After the identification of the corals, more than of 200 thin sections of coral fossils and microfacies were selected and studied for environmental parameters. This association belonging to Bashkirian age (the oldest ...
Read More
Rich assemblages of Carboniferous corals exist in the Zaladu stratigraphic section. After the identification of the corals, more than of 200 thin sections of coral fossils and microfacies were selected and studied for environmental parameters. This association belonging to Bashkirian age (the oldest stage of Late Carboniferous) and were found in two horizons. Based on the colonies geometry, the distance between them, the abundance and distribution of corals and microfacies study, the habitats of lower horizon is “ Coral meadows (subtype B1) “. The upper horizon made a “polyspecific Coral biostrome (subtype C2) “. These corals existed in a lagoon toward barrier and open marine toward barrier belonging to a shallow carbonate ramp environment. This association favored a shallow, warm, and clear marine environment with normal salinity and high oxygen, within the photic zone. The fasciculate rugose of Fomichevella and Heintzella, have the most abundance, and these colonies made main builders of the coral association. Colonial rugose corals of Fomichevella and Minatoa have maximum diversity. Michelinia tabulate corals, has the least abundance and diversity.
M Taherpour Khalil Abad; S.H Vaziri; A.R Ashouri
Abstract
Among the subfamily Orbitolininae, Palorbitolinalenticularis Blumenbach, 1805 is a common facies marker prevailed in shallow marine deposits of the Tethys during Late Barremian-Early Aptian time span. This speciesis a eurytopic taxon having the high ability of adaptation to wide range of environmental ...
Read More
Among the subfamily Orbitolininae, Palorbitolinalenticularis Blumenbach, 1805 is a common facies marker prevailed in shallow marine deposits of the Tethys during Late Barremian-Early Aptian time span. This speciesis a eurytopic taxon having the high ability of adaptation to wide range of environmental conditions. This study is based on measurements on embryonic chamber and test diameter of Palorbitolinalenticularis. The specimens were collected from three surface sections which are arranged in east-west direction.Our data show that, depth of environment controls the diameter of embryonic chamber and size of the test. Furthermore, size of embryonic chamber increases through time during the Late Barremian to Early Aptian.
M Nouredini; M Yazdi; A Ashouri; S Rahmati
Abstract
The Lower Carboniferous deposits (Shishtu II Formation) is exposed in the Banarizeh section, Southeastern Isfahan, Central Iran. The Shishtu II Formation is characterized by continental to shallow marine deposits, where it unconformably overlies the Alluvial deposits and is unconformably overlain by ...
Read More
The Lower Carboniferous deposits (Shishtu II Formation) is exposed in the Banarizeh section, Southeastern Isfahan, Central Iran. The Shishtu II Formation is characterized by continental to shallow marine deposits, where it unconformably overlies the Alluvial deposits and is unconformably overlain by the Sardar Formation. The thickness of Shishtu II Formation reach to 195m and contain moderate diversity, high richness Holothurian sclerites assemblages and other skeletal particles of scatter Crinoids, Brachiopods and Corals. The systematic studies and taxonomic investigation carried out on the collected samples from studies area led to recognition of 8 species belonging mainly to 4 families (Calclamnidae, Achistridae, Palaeocaudinidae, Theelidae). The Holothurian sclerites in Shishtu II Formation are dominantly as: Eocaudina subhexagona, Eocaudina ovalis, Microantyx permiana, Mercedescaudina langeri, Protocaudina hexagonaria, Achistrum monochordata, Thalattocanthus Consonus. Based on sratigraphical distribution of the Holothurian sclerites, Tournaisian- Visean age is suggested for Shishtu II Formation.
J Rabbani; E Ghasemi-Nejad; A.R Ashouri; M Vahidinia
Abstract
The basal unit of the Pabdeh Formation at Bisheh-Deraz section composes of 47m purple to green to grey shale and marl. These beds gradually change to shale and argillaceous limestone in the top of the section. In order to study paleoecology and paleoenvironment of these beds, palynological evidences ...
Read More
The basal unit of the Pabdeh Formation at Bisheh-Deraz section composes of 47m purple to green to grey shale and marl. These beds gradually change to shale and argillaceous limestone in the top of the section. In order to study paleoecology and paleoenvironment of these beds, palynological evidences including palynofacies, abundance and diversity of dinocysts and environmental index have been investigated. Four Palynofacies types including IV: shelf to basin transition, VII-VIII: distal dysoxic-anoxic shelf, IX: distal suboxic-anoxic basin) have been differentiated that propose a distal suboxic-anoxic basin as depositional setting. According to the microfacies of planktonic foraminiferal Wakestone/Packestone a deep environment is proposed as the depositional basin. Using such parameters as palynofacies evidences, C/PPC ratio, AOM/MP ratio, abundance and diversity of dinocysts and environmental index, three system tracts related to one sequence (3rdorder) with one sequence boundary type 2 and one maximum flooding surface have been determined. In general, the factors all together show a deepening upward trend through this rock unit.
A. H. Rahiminejad; M. Yazdi; A. R. Ashouri
Abstract
Shallow marine gastropod assemblages of the recently discovered marine sequence of the Bakhtiari clastic succession in the Zagros Basin are studied in the Shalamzar area. The systematic studies of the fauna yielded 21 genera and 9 species of gastropods from 20 families distributed in 7 facies. The molluscs ...
Read More
Shallow marine gastropod assemblages of the recently discovered marine sequence of the Bakhtiari clastic succession in the Zagros Basin are studied in the Shalamzar area. The systematic studies of the fauna yielded 21 genera and 9 species of gastropods from 20 families distributed in 7 facies. The molluscs are from the following families: Turritellidae, Cerithiidae,Volutidae, Ranellidae, Strombidae, Muricidae, Conidae , Naticidae, Mitridae(?), Olividae, Cancellariidae, Triforidae, Melongenidae, Aclididae, Plesiotrochidae,Cypredae Sorbeoconcha,Trochidae , Turbinidae and Buccinidae (?)indet. The abundant species and genera belong to the families of Cerithiidae, Strombidae, Turritellidae and Turbinidae. Detailed paleoecology interpretation was made based on the trophic habitats of the gastropods. The habitats are distinguished as four types of trophic categories including Carnivores, Herbivores, Omnivores and facultative mobile suspension feeders. The herbivorous gastropods dominate the faunal assemblages due to the high accumulation of detritus and plant organic matters within the sediments. The distribution of the gastropods is controlled by their trophic habitats that directly depend on the environmental changes such as water turbulence, sedimentation and suspension rates, detritus input, and water energy. The gastropod assemblages describe an environment ranging from the higher energy intertidal zone to the deeper and lower stage of an oligophotic zone within a middle ramp. The test size of the molluscs was also controlled by the ecological factors. Abundant nutrients as well as deeper basin conditions decreased the shell size of some groups of gastropods. The larger shells appeared in the shallower depth zones with a lack of nutrients. The occurrence of the mentioned gastropod taxa and Miocene faunistic relationship with adjacent bioprovinces represent a faunal exchange between the Zagros basin and Mediterranean and Parathethys seaway by a shallow pathway trough. A weak marine connectivity with Caribbean Sea and Indian Ocean is also reflected by the faunal groups.