HR: 1340h
AN: PP33B-0942    [Abstracts]
TI: Geochemistry and sedimentary environments of Permian deposits in Eastern-Central Iran
AU: * Arefifard, S
EM: (s_arefi49@yahoo.com )
AF: Shahid-Beheshti University, Geosciences faculty, Department of geology,, Evin, Tehran,, 1983963113 Iran (Islamic Republic of)
AU: Adabi, M H
EM: m-adabi@cc.sbu.ac.ir
AF: Shahid-Beheshti University, Geosciences faculty, Department of geology,, Evin, Tehran,, 1983963113 Iran (Islamic Republic of)
AU: Davydov, V I
EM: vdavydov@boisestate.edu
AF: Boise State University Department of Geosciences,, 1910 University Dr.,, Boise, ID 83725 United States
AB: Permian of Eastern-Central Iran is represents of Jamal and Khan Formations. These formations are studied in three areas named Kalmard, Shotori and Shirgesht. Khan Formation composed of predominantly delataic to eolian coarse to very coarse silisiclastics that interbedded with thin shallow limestone. Jamal Formation includes predominantly shallow, but sometimes deeper water carbonate sediments. The purpose of this study was to determine the depositional environment and diagenetic history of each of the facies that were recognized within the Permian succession. Sedimentological and microfacies study and advanced geochemical study have been performed in this project. Macroscopic and microscopic evaluations of hand samples taken at approximately 4-5 meter intervals allow determination of composition and extent of cementation and dolomitization. 900 samples for microfacies studies and 100 samples for geochemical analysis have been collected. The principal microfacies have been identified in thin sections. O$^{18}$ and C$^{13}$ isotopes were utilized for better understanding of diagenetic processes. Ca, Mg, Mn, Na, Sr and Fe amounts and ratios were used to compliment the isotopic studies and recognition of original mineralogy. Geochemical data regarding elemental compositions of Khan and Jamal formations represent lower Sr ( 840 ppm ) and Mg ( 4600 ppm ) values and higher Fe ( 1500 ppm ) and Mn ( 250 ppm ) contents compared with tropical carbonates. Therefore the existence of a cool- water conditions during sedimentation of Khan and Jamal formations and probable calcitic precursor for them can be considered. Variations in $\delta$$^{18}$ O (-4 to -10 PDB) and $\delta$$^{13}$C (1 to 4 PDB) values and their relationship with trace elements of carbonates suggesting influence of burial and meteoric diagenesis that are compatible with petrographic studies. Also plot of Sr/Ca ratios versus Mn values indicative of influence of diagenetic processes in a roughly mid-closed environment. Lower $\delta$$^{13}$C contents and higher values of Mn and Fe of Khan Formation bulk carbonates than that of Jamal formation can be explained by presence of siliciclastic components. These data confirm sedimentation of Khan and Jamal formations in two different basins in Permian time. Khan Formation was deposited near to shore while sedimentary environment of Jamal formation is a carbonate shelf.
DE: 9320 Asia
DE: 9614 Paleozoic
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 1055 Organic geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting