Stratigraphy and Palaeontology
Peiman Rajabi
Abstract
The Asmari carbonate formation in Lorestan is seen in the form of a medium to the thick limestone-rich layer of benthic foraminifera and often as a rock formation. In this study, the stratigraphic sequence of Asmari carbonate formation in the Chenareh Anticline section located in the south of Lorestan ...
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The Asmari carbonate formation in Lorestan is seen in the form of a medium to the thick limestone-rich layer of benthic foraminifera and often as a rock formation. In this study, the stratigraphic sequence of Asmari carbonate formation in the Chenareh Anticline section located in the south of Lorestan basin and Amiran Anticline section located in the middle part of Lorestan basin were studied in terms of lithology and micro biostratigraphy. The thickness of the Chenareh Section was 180 meters and the Section of Amiran Anticline was 158 meters. In total, more than 290 thin sections of both were prepared and examined in the laboratory. The results of fossil studies based on the expansion of foraminifera finally lead to the introduction and presentation of 1 Assemblage biozone in the Amiran anticline section and 3 Assemblage biozones related to the Chenareh anticline stratigraphic section. Accordingly, the age of the Asmari Formation is in the Chenareh section is Oligo-Miocene (Chattian-Bordigalian) and in the Amiran section is Miocene (Bordigalin). According to the lithostratigraphic studies, the border of the Asmari Formation in both sections of Chenareh and Amiran with Shabazan Formation is progressive-continuous and discontinuous, and in both sections of the upper boundary with Gachsaran Formation can be seen in the same way as evaporative sediments.
N. Hadavandkhani; A. Sadeghi; M. H. Adabi; A. R. Tahmasbi
Abstract
The Pabdeh Formation with a thickness of 797.2 m. and 4 lithological units (purple shale (144.25 m.), lower limestone and marl (221.75 m.), limestone (73.5 m.) and upper limestone and marl (357.7 m.) is stretched at Chahardeh village stratigraphic section in Izeh zone.. Biostratigraphic studies led to ...
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The Pabdeh Formation with a thickness of 797.2 m. and 4 lithological units (purple shale (144.25 m.), lower limestone and marl (221.75 m.), limestone (73.5 m.) and upper limestone and marl (357.7 m.) is stretched at Chahardeh village stratigraphic section in Izeh zone.. Biostratigraphic studies led to recognition of 30 genera and 150 species of planktonic foraminifera based on which 23 biozones were identified in Tethys realm. These biozones are well correlated with biozones of Tethys region. Based on the indicated biozones and fossil contents, the age of the Pabdeh Formation is Middle Paleocene (Selandian) - Late Oligocene (Chattian). In this study, Paleocene- Eocene boundary is located in Purple shale unit and Eocene- Oligocene boundary is placed in upper marl and limestone unit.
M Joudaki; D Baghbani; S.A Aghanabati; B Soleimani; H Asilian; B Ariafar
Abstract
In order to biostratighraphy and to discover relationships between biozones of the Oligocene and lower Miocene strata in Zagros foreland basin, Zagros simply folded belt and High Zagros area, 10 stratigraphic sections along a transect from well "A" in Persian Gulf to Semirum section in High Zagros ...
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In order to biostratighraphy and to discover relationships between biozones of the Oligocene and lower Miocene strata in Zagros foreland basin, Zagros simply folded belt and High Zagros area, 10 stratigraphic sections along a transect from well "A" in Persian Gulf to Semirum section in High Zagros were investigated. The study of more than 1500 thin sections resulted in identification of 32 genera and 54 species of benthonic foraminifera belonging to nine genera and 15 species of planktonic foraminifera. The recorded assemblages led to establishment of six biozones ranging in age from Oligocene to Early Miocene. Biostratighraphic correlation yielded clarification of relationship between biozones and sedimentary trends and discontinuities of the Oligocene and lower Miocene in Zagros basin in the areas.
M Karavan; A Mahboubi; H Vaziri-Moghaddam; R Moussavi-Harami
Abstract
The Oligocene Qom Formation deposits in NW Central Iran (NE Delijan) are widespread in NE-SW trend.Four members of the Qom Formation (unknown, a, b& c1) in the study area consist of mainly marly limestone, limestone, sandy limestone and a minor amounts of sandstone. It disconformablyoverliesthe Lower ...
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The Oligocene Qom Formation deposits in NW Central Iran (NE Delijan) are widespread in NE-SW trend.Four members of the Qom Formation (unknown, a, b& c1) in the study area consist of mainly marly limestone, limestone, sandy limestone and a minor amounts of sandstone. It disconformablyoverliesthe Lower Red Formation and the upper boundary is covered by the recent alluvium. Based on the benthic foraminifers assemblage, these deposits are attributed to Oligocene (Rupelian- Chattian). Petrographic considerationled to identification of 12 carbonatemicrofacies and one sandstone facies that may have been deposited in a homoclinal ramp and in 4 sub environments including tidal flat, lagoon, bioclastic bar and open marine. Sequence stratigraphy analysis led to identification of 8 3rdordersdepositional sequences bounded by type I and type II sequence boundaries. Comparison between interpreted relative sea level curve with global sea level curve showsreasonable correlation with the lower and upper sequence boundaries of this formation and also Rupelian- Chattianboundary and the differences in other sequence boundaries can be related to local tectonic activity in the sedimentary basin of Qom Formation and the local sea level changes.
D Dehnavi; S.R Moussavi-Harami; M.H Mahmudy Gharaie; F Ghaemi; F Ghaemi
Abstract
For understanding parent rocks, tectonics setting, paleoweathering condition and classification of Binalood’s Oligocene deposits, the petrography analysis was done, on samples from Damanjan and Baghshan-Gach sections, north of Neyshabour. 14 sandstones and 6 shale samples from both sections were ...
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For understanding parent rocks, tectonics setting, paleoweathering condition and classification of Binalood’s Oligocene deposits, the petrography analysis was done, on samples from Damanjan and Baghshan-Gach sections, north of Neyshabour. 14 sandstones and 6 shale samples from both sections were analyzed for major elements. Petrographic studies and geochemical data show that these sandstones are Litharenite to lithic arkose and have been deposited in tectonics setting including active continental margin for Damanjan section and continental island arc for Baghshan-Gach section with felsic to intermediate source. Based on elemental analysis, paleoweathering condition was relatively weak at the time of deposition in both sections; however, paleoweathering was stronger in Damanjan than Baghshan –Ghch sections. Also, using petrographic and elemental data, it can be concluded that the paleoclimate was semi-humid to semi-arid at the time of deposition.
Z.K. Mossadegh; M.H. Adabi; A. Sadeghi
Abstract
We studied the geochemistry of the Asmari Formation in two outcrop sections: Tang-e-Sapou a 260 m section near Dehdasht City (Kohgiluyeh va Bouyer Ahmad Province) and Tang-e-Ban a 214 m section near Behbahan City (Khozestan Province). Sampling included the complete Asmari Formation and the top of the ...
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We studied the geochemistry of the Asmari Formation in two outcrop sections: Tang-e-Sapou a 260 m section near Dehdasht City (Kohgiluyeh va Bouyer Ahmad Province) and Tang-e-Ban a 214 m section near Behbahan City (Khozestan Province). Sampling included the complete Asmari Formation and the top of the Pabdeh Formation. The Late Oligocene to Early Miocene Asmari Formation lies above the Pabdeh Formation and is overlain by the Gachsaran Formation. Elemental geochemistry (Fe, Mg, Na, Sr, Mn, Ca), and Oxygen and Carbon isotope analyses indicate that meteoric diagenesis affected carbonates of the Asmari Formation. The δ18O/δ13C data plots in an inverted J-trend suggesting that meteoric diagensis occurred in a closed to semi-closed system. The geochemistry also suggests that the original mineralogy was Aragonite. The boundary between the Pabdeh and Asmari Formations can be recognized by changes in the δ 18O and δ 13C. In the Pabdeh Formation the δ 18O and δ 13C values are mostly negative, but in the Asmari Formation values range from positive to negative. Strontium is much higher in the Pabdeh Formation than in the Asmari Formation. Changes in isotope and elemental geochemistry clearly show the Chattian-Aquitanian and Aquitanian-Burgidalian boundaries.
N. Abbassi; A. Amini
Abstract
The Thalassinoides bearing calcareous sandstone and sandy limestones of Oligocene age unconformably overlay the Eocene volcaniclastic rocks and gradually pass into the lacustrine sediments (Miocene? in age) in the study area. These layers are dominated by Thalassinoides ...
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The Thalassinoides bearing calcareous sandstone and sandy limestones of Oligocene age unconformably overlay the Eocene volcaniclastic rocks and gradually pass into the lacustrine sediments (Miocene? in age) in the study area. These layers are dominated by Thalassinoides suevicus (Rieth 1932) in the Y shaped boxwork cylindrical and bifurcating burrows, which are mainly filled actively by trace maker(s). The bioturbations in the layers are categorized into five ichnofabric classes, which are equal to standard ichnofabric indexes of 1 to 5. Frequency of the ichnofabric classes are 40.37, 15.9, 8.85, 4.97 and 29.9 percents, respectively. Ichnofabric variations of the studied layers are arranged in seven bioturbated upward cycles, which are divided into two groups. The first group shows low ichnofabric fluctuations and a constancy in the bioturbation, where the second group shows high ichnofabrics fluctuations and variability in the bioturbation. Results from the study show that the Thalassinoides in the studied section formed in conditions similar to those of Cruziana and Glossifungites ichnofacies.
