Stratigraphy and Palaeontology
Fatemeh Vaez-Javadi; Mahdi Abbaszadeh
Abstract
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 ...
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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.
F. Vaez-Javadi
Abstract
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 ...
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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.
K. Seyed Emami; N. Behfar; M. R. Majidifard; A. Behfar
Abstract
Middle Jurassic strata are well developed northeast of Damghan (E Alborz). At the study section the Dalichai Formation has a maximum thickness of 156 m, consisting of an alternation of bluish-grey limestones and marls, being subdivided into 4 members. The lower boundary with the siliciclastics of the ...
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Middle Jurassic strata are well developed northeast of Damghan (E Alborz). At the study section the Dalichai Formation has a maximum thickness of 156 m, consisting of an alternation of bluish-grey limestones and marls, being subdivided into 4 members. The lower boundary with the siliciclastics of the underlying Shemshak Formation is unconformity, due to the Mid-Cimmerian tectonic event, whereas the upper boundary with the light and cliff-forming carbonates of the Lar Formation is gradational. The Dalichai Formation at the study section is very fossiliferous. Summing up 1750 fossil specimens were collected, among which the ammonoids with 1491 specimens clearly predominate. Altogether 27 genera, 33 species of ammonites, belonging to 6 biozones (Parkinsoni Zone, Zigzag-Aurigerus zones, Subcontractus Zone, Bullatus-Gracilis zones, Anceps-Coronatum zones, Athleta Zone) has been recognized. In addition 17 genera and 8 species of planktonic and benthic foraminifers are described.These can be divided into 2 biozones. The fossil-content is mainly concentrated within few meters of red and nodular limestone in the upper part of the section. Based on the ammonite fauna the age of the Dalichai Formation in the investigated area ranges from Upper Bajocian to Oxfordian. Paleobigeographically the fauna shows close relationship to western Europe and Sub-Mediterranean region. This indicates a paleogeographic position of the area at the northern Tethys during the Middle-Upper Jurassic.
M. Shams; K. Seyed-Emami
Abstract
The Dalichai Formation and its ammonite fauna is studied for the first time in the Parvar area, Central Alborz. At Parvar the Dalichai Formation, with a thickness of about 70 m, consist of an alternation of grayish silty marls, marlstones, marly limestone and limestone and is subdivided into 5 members. ...
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The Dalichai Formation and its ammonite fauna is studied for the first time in the Parvar area, Central Alborz. At Parvar the Dalichai Formation, with a thickness of about 70 m, consist of an alternation of grayish silty marls, marlstones, marly limestone and limestone and is subdivided into 5 members. A rich ammonite fauna (407 specimens) have been collected from the member 4 and 5, comprising the following families: Phylloceratidae, Lytoceratidae, Oppeliidae, Haploceratidae, Sphaeroceratidae, Parkinsoniidae, Morphoceratidae and Perisphinctidae. These indicate a Late Bajocian and Bathonian age. Member five consists of greenish to reddish, nodular and flaggy limestones and is a typical condensed horizon.
