Biostratigraphy of Mobarak Formation at Valyabad Section, Chaloos Road
Author(s):
Abstract:
The Mobarak Formation with 347.5 m, thickness is well exposed in Valyabad section, at the Karaj - Chalus road. The lower contact with underlying Laloon Formation is disconformable, whereas stratigraphic relation to the overlying Dozdeband formation is transitional. According to the lithological character, the studied section can be subdivided into  rock units. The lower part of the fm. consist of dark- gray to black limestone as well as marly limestone, while upper part consist mainly of sandy limestone with interbeds of marlstone. According to the microfossil investigation 14 genius and species have been recognized which leads 2 conodont biozones. The both conodont biozones correspond to the international standard conodont biozonation which suggest an Early Tournisian to Middle Visean time interval. in addition, a Namurian age is suggested for deposites of informal Dozdeband formation, based on foraminifers. Received conodont bizones are as: Neopriniodus peracutus - Polygnathus longiposticus Assemblage- ZoneHibbardella roundya - Gnathodus girtyi Assemblage- ZoneMore over, 5 Holotorian species as well as 6 genuse, 72 species Foraminifers in form of 5 biozone have been distinguished. These biozones are as: Eotuberitina retligener - Endothyra spirilloformis Assemblage- ZoneArchaediscus permodiscus - Archaediscus(Paraarchaediscus)mixtus Assemblage- ZoneEndostaffella parva - Brunsina pulchera Assemblage- ZoneTuberitina bulbacea - Kammaena sp. Barren Interval ZoneLipinella notata - Archaediscus planoarchaediscus Assemblage- ZoneThe studied foraminifers support the given age. Conodonts the Color Alteration Index(CAI) correspond 190 to 300 C◦ which indicate dry gas stage or empty of any hydrocarbon.
Language:
Persian
Published:
Geosciences Scientific Quarterly Journal, Volume:21 Issue:83, 2013
Page:
111
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