M Mohammadi; H Amiri Bakhtiar; F Amraee
Abstract
This study aimed to compare Asmari Formation in two sections in Maleh-Kuh and Amiran anticlines based on benthonic foraminifera. In this study, 26 species and 16 genera of benthonic foraminifera from the Maleh-Kuh section yielded 2 biozones of Elphidiumsp. 14 – Peneroplis, farsenensisandBorelismelocurdica ...
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This study aimed to compare Asmari Formation in two sections in Maleh-Kuh and Amiran anticlines based on benthonic foraminifera. In this study, 26 species and 16 genera of benthonic foraminifera from the Maleh-Kuh section yielded 2 biozones of Elphidiumsp. 14 – Peneroplis, farsenensisandBorelismelocurdica – Borelismelomeloweresuggesting an age of Aquitanian – Burdigalian for the formation. In Amiran anticline based on 27 species and 20 genera only the biozone of Borelismelocurdica – Borelismelomelo (Burdigalian)was recorded.Based on this study, the Asmari sequence in Maleh-kuh Section (with a thicknessof 310m) deposited earlier In Aquitanian. But in Amiran section (with a thickness 162m) deposition started in Burdigalian and ended synchronously in both sections. In both sections the Asmari Formation overlain Shahbazan Formation disconformably and is in turn under lain by Ghachsaran Formation concordantly-transitionally in Maleh-Kuh and by a sharp contact in Amiran Section.
T Sarbandi Farahani; M.R Majidifard; M.R Kebriaee- Zadeh; M Mohammadi
Abstract
The Middle Jurassic rocks are widely distributed and superbly exposed in the AlborzMountains (Northern Iran). In the central part of the mountain range, near Mahdishahr (Northern Semnan), the Dalichai Formation, from the underlying conglomerate and sandstones of Shemshak Formation to the limestones of ...
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The Middle Jurassic rocks are widely distributed and superbly exposed in the AlborzMountains (Northern Iran). In the central part of the mountain range, near Mahdishahr (Northern Semnan), the Dalichai Formation, from the underlying conglomerate and sandstones of Shemshak Formation to the limestones of the overlying Lar Formation, is completely exposed on the southern slopes of the kuh-e-Rahband. At this area, the sedimentary succession with nearly 122 m thickness subdivided into four members starting with marl and medium to thick-bedded grey limestones to marly limestones. The lower boundary with the siliciclastics of the underlying Shemshak Formation is disconformity, whereas the upper boundary with the light and cliff-forming carbonates of the Lar Formation is rather inconspicuous and transitional. The Dalichai Formation in the east of Mahdishar section is fossiliferous. The ammonite fauna consist of 5 families, 22 genera and subgenera and 40 species, among them 8 species are recorded for the first time from Iran. Based on the ammonite fauna, 9 biozones were recognized that indicated the age of the Dalichai Formation in the investigated area ranges from the Upper Bajocian? to Upper Oxfordian. Pleobigeographically, the fauna shows close relationship to west Europe and sub-mediterranean regions. This indicates a paleogeographic position of the area at the northern Tethys during the Middle Jurassic.
