|
Hassan Mohseni, Bu-Ali Sina University (Islamic Republic of Iran)
Mehdi Khoshnoodkya, Bu-Ali Sina University (Islamic Republic of Iran)
Mahmoud Hajian, NIOC (Islamic Republic of Iran)
Behrouz Rafiei, Bu-Ali Sina University (Islamic Republic of Iran)
|
|
Carbonate ¨C evaporites of Dashtak formation are important seal interval in Zagros basin. Dashtak formation was studied in (Aghar#1, West Aghar#1, Naura#1 boreholes) in a sequence stratigraphic framework. Data come from petrographic examinations five hundred of thin sections from cutting, in addition gamma ray and sonic logs interpereted and sea level change with eustacy. The Dashtak formation consists of dolomite, anhydrite, shale and limestone. It comprises of Aghar shale member, A member, B member, C member, Sepidar dolomite and D member. Dashtak formation has eight facies deposited in inner ¨C middle homocline ramp. Four sequences distinguished in the Dashtak formation and two surfaces sequence boundaries type I and three sequence boundaries type II : First sequence begins lowermost disconformity at the base of of Aghar shale up to massive anhydrite A. Lagoon and mid- ramp Facies are known a MFS at this sequence and apparently correlateable to Tr50 of Ladnian stage. Second sequence begins from the base of B member up to the top of B massive anhydrite. MFS the upper boundary is a sequence boundaries type II with brecciaed dolomite. At this level is known as lagoon, shoal and open marine facies correlateable to Tr60 of Carnian stage. Third sequence begins from base of C member up the to top of C massive anhydrite. Thoroughly comprises C anhydrite member. It's upper contact is interpereted a type II sequence boundary. MFS is characterized by lagoon, shoal and open marine facies and correlateable to Tr 70 of Late Carnian stage. Uppermost sequence begins from top of C member and Sepidar dolomite to the top of D member. MFS including is characterized by open marine and shoal facies correlateable to Tr 80 of Norian stage. Uppermost sequence boundaries type is atype I as the disconformity contact Dashtak Fm with Neyris Fm. Key Words: Dashtak formation, sequence stratigraphy, Ramp, Sub costal, Fars, Iran.
|
