Writers : Aghadadashi Abhari,Fateme; supervisor:A. Aghanabati; advisor:M. Moussavi Roohbakhsh
Refference : M.Sc. Thesis _ Islamic Azad university,North Tehran Branch;330p.
Publishing Year : 1380
Abstract :
This study which has suggested by Dr.Aghanabati,11 stratigraphic sections of lower cretaceous sedimentary in Northeast Iran in Kopeh dagh sedimentary basin selected. These sections are between Lates 35 45 to 36 45 and longs 59 45 to 6115, in the vertical direction of basin folding The aim of this study is surveying the biofacies and lithofacies of Tirgan Formation and determining the lower and upper boundary of this formation in this area.
During this project seven stratigraphic sections that their names are Mozduran, Padeha, baghak shurijeh, Shurab, Natu, Derazab have sampled and studied and then correlated with Cenar .Artenj, Taherabad and Ghorghoreh sections
In the field we could see that the thickness of Tirgan Formation from West to East decreased. .The thickness of this Formation in Mozduran section which is the western section )about 37 meters and in the Shurab section which is near to Afghanestan and Iran frontier is only 10 meters and it shows that the depth of this sedimentary basin is decreased from West to East and the Carbonate facies of this Formation in the West is gradually changed to the detrital facies On the base of field evidence we could see a gradually limit between red sandstones of Shuridjeh and grey limestones of Tirgan Formation which has a lot of Ooids in all of the sections. and we have a sudden limit between Tirgan and Sarcheshmeh Formations.
For surveying of lithofacies we used of Daunham method and in this investigation about microfacieses ditermined in this project, those 9 microfacies of them were carbonate and the ohters (2 remained microfaciese) were detrital. According to studing of thin sections(174 samples and based on existence faunas and lithofacieses we proposed Aptian age for this Formation
Totally, the Formation sedimentary is done in the supratidal and intertidal and under tidal limits Ù„ Tot and gradually the basin has become deeper until the marble and shalely Formation ol Sarcheshmeh has been deposited,that shows the open see environment.
The following cases is considered for determining of Aptian age for Tirgan Formation.
he existence of Algal Bouenia hochstetteri that is belong to this stage
he existence of Dictyoconuc arabicus which is belong to this stage.
he existence of Pseudo chofatella sp. That is belong to this stage with some index fossils of this stage like Nautiloculina sp., Lenticulina sp. he absence of some fossils which is related to Aptiar in some samples that is belong to Shuridjeh Formation could help us to detemine the boundary between Shuridjeh and Tirgan Formations.
he existence of a lot of Ooids in the biginning part of Tirgan is the other evidence for beginning of Tirgan Formation. And the other evidence is that the red sandy colour of Shuridjeh Formatior ,is changed ti grey Oolithic limestone of Tirgan.
Subject List :
Biofacies 
E-mail : info [at] gsinet [dot] ir