The Upper Permian Dalan Formation and the Lower Triassic Kangan Formation in the Persian Gulf area are mainly composed of shallow marine facies limestone and dolomite.Two subsurface-cored intervals were investigated i...The Upper Permian Dalan Formation and the Lower Triassic Kangan Formation in the Persian Gulf area are mainly composed of shallow marine facies limestone and dolomite.Two subsurface-cored intervals were investigated in order to understand the original mineralogy and paleoceanic conditions.The decreasing trend of Sr concentration in these deposits shows that aragonite was precipitated during the Late Permian and then gradually changed to calcite toward the Permian-Triassic boundary（PTB）.The dissolution rate of aragonite decreased from 60 m below the PTB toward the boundary,with the only exception at 10 m below the Permian-Triassic Boundary（PTB） due to the Permian-Triassic unconformity in this region.The increasing trend of Mg/Ca ratio in a global scale at the end-Permian time shows that the interpreted variation of mineralogy does not result from the change of this ratio.The increasing p（CO2） and decreasing pH are considered to be the main controlling factors.The increase of Ca2＋ at the end-Permian time due to the input of meteoric waters is too little to fully compensate this effect.A local maximum of the Si content just at the PTB confirms the input of runoff waters.展开更多
In the present study,the Lower-Middle Pliocene Cheleken Formation in the south of Ghaemshahr city was studied to determine the provenance of the comprising sediments,paleoclimatic conditions,and tectonic setting of th...In the present study,the Lower-Middle Pliocene Cheleken Formation in the south of Ghaemshahr city was studied to determine the provenance of the comprising sediments,paleoclimatic conditions,and tectonic setting of the rocks.Petrographic and geochemical analyses of major and minor elements of the samples were used for this purpose.This Formation is composed of three major facies including conglomerate,fine sandstone,and mudstone.The source formations which were recognized to be supplying sediments to the Cheleken Formation depositional basin include Lalun,Ziarat,Tizkuh,Dalichai,and Cretaceous formations.According to the discrimination diagrams and other ratios for minor elements of the studied samples,a complex of felsic to intermediate igneous rocks in the source region was deciphered.The depositional environment of the rocks experienced humid and semi-arid climatic conditions during deposition.According to the CIW index,the samples underwent a high level of weathering(97%)in the source area or during transportation.From a tectonic point of view,the Cheleken Formation was deposited in an Active Continental Margin setting.展开更多
基金supported by a grant from the University of Tehranthe vicepresident of the Research and Technology of the University of Tehran for the financial support+1 种基金extend our appreciation to the POGC(Pars Oil and Gas Company of Iran)MAPSA(Abdal Industrial Projects Management Company)for the sponsoring,data preparation,and also permission to publish this study
文摘The Upper Permian Dalan Formation and the Lower Triassic Kangan Formation in the Persian Gulf area are mainly composed of shallow marine facies limestone and dolomite.Two subsurface-cored intervals were investigated in order to understand the original mineralogy and paleoceanic conditions.The decreasing trend of Sr concentration in these deposits shows that aragonite was precipitated during the Late Permian and then gradually changed to calcite toward the Permian-Triassic boundary（PTB）.The dissolution rate of aragonite decreased from 60 m below the PTB toward the boundary,with the only exception at 10 m below the Permian-Triassic Boundary（PTB） due to the Permian-Triassic unconformity in this region.The increasing trend of Mg/Ca ratio in a global scale at the end-Permian time shows that the interpreted variation of mineralogy does not result from the change of this ratio.The increasing p（CO2） and decreasing pH are considered to be the main controlling factors.The increase of Ca2＋ at the end-Permian time due to the input of meteoric waters is too little to fully compensate this effect.A local maximum of the Si content just at the PTB confirms the input of runoff waters.
文摘In the present study,the Lower-Middle Pliocene Cheleken Formation in the south of Ghaemshahr city was studied to determine the provenance of the comprising sediments,paleoclimatic conditions,and tectonic setting of the rocks.Petrographic and geochemical analyses of major and minor elements of the samples were used for this purpose.This Formation is composed of three major facies including conglomerate,fine sandstone,and mudstone.The source formations which were recognized to be supplying sediments to the Cheleken Formation depositional basin include Lalun,Ziarat,Tizkuh,Dalichai,and Cretaceous formations.According to the discrimination diagrams and other ratios for minor elements of the studied samples,a complex of felsic to intermediate igneous rocks in the source region was deciphered.The depositional environment of the rocks experienced humid and semi-arid climatic conditions during deposition.According to the CIW index,the samples underwent a high level of weathering(97%)in the source area or during transportation.From a tectonic point of view,the Cheleken Formation was deposited in an Active Continental Margin setting.
