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.
Z Kiadaliri; M.R Majidifard
Abstract
The Lower- Middle Jurassic strata are well developed in northeast of Jajarm (E Alborz). At the study section, the Shemshak Group has a maximum thickness of 585 m, consisting of grey silty sandstones and light- green siltstones with brown sandstones, subdivided into 3 formations ofAlasht, Shirindasht ...
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The Lower- Middle Jurassic strata are well developed in northeast of Jajarm (E Alborz). At the study section, the Shemshak Group has a maximum thickness of 585 m, consisting of grey silty sandstones and light- green siltstones with brown sandstones, subdivided into 3 formations ofAlasht, Shirindasht and Fillzamin.The lower boundary of the Shemshak Group at Golbini sectionwith the red bauxite horizon of the underlying Elikah Formation is disconformity due to the EarlyCimmerian tectonic event.Its upper boundary with marly limestone and marl of the Dalichai Formation is disconformity, too. In the Shemshak Group at the study section, summing up 186 fossil specimens were collected, among which the ammonoids with 67 specimens clearly predominate and belonging to 6 biozones (ThouarsenseZone, Pseudoradiosa Zone,Aalensis zone, Opalinum Zone, Murchisonaezone, ConcavumZone) have been recognized. Based on the ammonite fauna, the age of the Shemshak Group in the investigated area ranges from the Upper Toarcian to Upper Aalenian. Paleobiogeographically, the fauna shows close relationship to Northwestern Europe and Sub-Mediterranean regions. This indicates a paleogeographical position of the area at the northern Tethys during the Lower-Middle Jurassic.
M. Paknia; Habib Alimohammadian; M. R. Majidifard; J. Sabouri; A. Aghanabat
Abstract
The Golbini section comprising of continuous succession of sediments ranging in age from Triassic – Jurassic formations, is situated at 35 Km north – east of Jajarm city. On the bases of studies on Dalichai Formation at this section and at about Middle Jurassic (Bathonian–Callovian ...
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The Golbini section comprising of continuous succession of sediments ranging in age from Triassic – Jurassic formations, is situated at 35 Km north – east of Jajarm city. On the bases of studies on Dalichai Formation at this section and at about Middle Jurassic (Bathonian–Callovian boundary), 3 Member, 31 Genus and 13 species of Ammonite, has been identified. For paleomagnetic analysis, with the help of portable coring machine, the total number of 155 oriented core samples were collected from limestone and clayey– limestone of this section. Then the samples were prepared for paleomagnetic analysis at Environmental and Paleomagnetic Laboratory based at Geological Survey of Iran, Tehran, Iran. The conducted paleomagnetic analysis include measurement of NRM, Susceptibility, Thermal and AF demagnetizing, Virtual Geomagnetic Polarity (VGP), identification of normal and reversal magnetic polarities and calculation of sedimentation rate. The obtained paleomagnetic results then composed with GPTS and also with proposed Bathonian–Callovian boundaries in Russia and Germany. This comparison reveals that the magnetic polarity of Golbini section is co-relatable with GPTS and also with Bathonian–Callovian boundary in Russia and Germany.
A. R. Ashouri; M. R. Majidifard; M. Vahidinia; A. Raoufian
Abstract
A thick succession of Middle – Late Jurassic rocks in the western part of BinaludRange has been studied. This succession consists mainly of limestone, marly limestone and marl. The thickness of the succession in the study section (Baghi, north of Neyshabour) is 709 meters and is subdivided into ...
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A thick succession of Middle – Late Jurassic rocks in the western part of BinaludRange has been studied. This succession consists mainly of limestone, marly limestone and marl. The thickness of the succession in the study section (Baghi, north of Neyshabour) is 709 meters and is subdivided into 4 members. The lower boundary with the underlying dark shale and upper boundary with the overlying buff limestone are inconspicuous and transitional. Ammonites are the most important and abundant macrofossils in this section. 43 genera and 76 species have been identified among them 8 species are reported for the first time from Iran. Based on the ammonite fauna, Early Bathonian to Kimmeridjian ages are purposed for these rocks. The fauna show close relationship to Sub- Mediterranean province and there is a great similarity between ammonite fauna of the investigated area with Kope – Dagh and AlborzRange.
