Stratigraphy and Palaeontology
elahe zarei
Abstract
The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of ...
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The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of pollen are identified (Middle Jurassic) and presence of some index dinoflagellate species led to the identification of three biozones in the Dalichai Formation. These include in ascending order, Cribroperidinium crispum Total Range Biozone (late Bajocian), Dichadogonyaulax sellwoodii Interval Biozone (Bathonian - early Callovian), Ctenididinium continuum Interval Biozone (early to middle Callovian). Also, this Formation was divided into two biozone on the basis of Lenticulina varians-Ophtalmidium Assemblage zone and Globigerina bathoniana Taxon range zone. The close similarities of fauna assemblages of Dalichai Formation in this region (eastern Alborz ((dinoflagellate cyst, foraminifera, posidonia and radiolar) with assemblages recorded from different parts of Iran (such as central and eastern, western Alborz and Binalud and south of Iran) and other parts of world (northwest of Europe, and the northwestern Tethys and …) confirm the marine connection and faunal exchange between the mentioned basins during Middle Jurassic.
Stratigraphy and Palaeontology
maryam naderiyan; elahe zarei; khadijeh Mohammad-khani
Abstract
The Dalichai Formation in Darjazin section in NE Semnan with a thickness of 631 meters consisting of an alternation of bulish-gray was studied. This formation overlies the Shemshak formation disconformity with conglomerate bed and it has gradually been covered by the thick-beded limestones of the Lar ...
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The Dalichai Formation in Darjazin section in NE Semnan with a thickness of 631 meters consisting of an alternation of bulish-gray was studied. This formation overlies the Shemshak formation disconformity with conglomerate bed and it has gradually been covered by the thick-beded limestones of the Lar formation. In order to study paleoenviroment of the Dalichai Formation the authors examined many different factors including Microfacies and palynological data (abundance and diversity of Dinocyst, proximate to chorat Dinocyst, palynofacies analysis and "selective preservation of organic matter"). A high percentage of brown wood and sporomorphs and the dominance of cavate and proximate dinocysts such as Nannoceratopsis gracilis, and pareodinia ceratophora and fluorescent amorphous organic matter, as well as Miliolid benthic foraminifera are evidence of suboxic to anoxic condition, which favored accumulation and preservation of organic matter in open marine lagoon, in the lower part of Dalichai Formation. A decrease in the brown wood and abundance and species richness of marine palynomorph (mainly chorate dinocysts) reflects more offshore settings in the upper part of Dalichai Formation. On the other hand, Appearance and increase of planktonic foraminifera and Radiolar and posidonia indicate development of strong marine transgression and deposition in an open marine environment.
Stratigraphy and Palaeontology
faeze Amiri; E Zarei
Abstract
The Gurpi formation in Bishe-deraz Section, south of Ilam, consists of 201m marl with intercalations of limy marl with two formal members of Seymareh (Lopha) and Emam-Hasan. The formation overlies the Ilam Formation and is gradationally overlain by the purple shales of the basal part of the Pabdeh Formation. ...
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The Gurpi formation in Bishe-deraz Section, south of Ilam, consists of 201m marl with intercalations of limy marl with two formal members of Seymareh (Lopha) and Emam-Hasan. The formation overlies the Ilam Formation and is gradationally overlain by the purple shales of the basal part of the Pabdeh Formation. The Gurpi Formation was divided to 9 biozone on the basis of planktonic foraminifera which almost are cosmopolitan and consist of: 1- Radotruncana calcarata Taxon-Range Zone. 2- Globotruncanita stuartiformis Partial-Range Zone. 3- Globotruncana aegyptiaca Interval Zone. 4-Gansserina gansseri Interval Zone. 5- Contusotruncana contusa Interval Zone. 6- Abathomphalus mayaroensis Interval Zone. 7- Praemurica uncinata Interval Zone. 8- Morozovella angulata Interval Zone. 9- Globanomalina pseudomenardii Interval Zone. The formation was deposited from upper Campanian through late Paleocene (Selandian-Thanetian?) according to the planktonic foraminifera recorded. A distinct hiatus was confirmed at the Cretaceous-Paleogene boundary according to microbiostratigraphic and sedimentologic studies and also field work observation.