Stratigraphy and Palaeontology
marjan zadesmaeil; Mahmoud Reza Majidifard; Seyed Hamid Vaziri; Davood Jahani
Abstract
The Middle and Upper Jurassic sedimentary well successions is located in the northwestern Damghan, (eastern Alborz range). The Dalichai Formation with a thickness of 618 meters in the studied section consists of marl, limestone and marly limestone. The lower boundary with the siliciclastic of the underlying ...
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The Middle and Upper Jurassic sedimentary well successions is located in the northwestern Damghan, (eastern Alborz range). The Dalichai Formation with a thickness of 618 meters in the studied section consists of marl, limestone and marly limestone. The lower boundary with the siliciclastic of the underlying Shemshak Formation is unconformable and in the upper boundary is gradually covered by the Lar Formation. From studied section, altogether 371 fossile sample were collected of which 15 sample were related to other taxon (Bellemnite, Bivalve, Coral and Sponge). Altogether, 51 species of ammonites from the Dalichai Formations belonging to 25 genera and 9 families and 14 zones are described. The following families are reported: Phylloceratidae, Lytoceratidae, Haploceratidae, Oppeliidae, Parkinsoniidae, Morphoceratidae, Reineckeiidae, Perisphinctidae and Aspidoceratidae.Based on ammonites, the Dalichai Formation ranges from the Upper Bajocian to Lower Kimmeridgin and can be subdivided, from bottom to top, into six informal members.Palaeobiogeographically the ammonite fauna is closely related to that of the sub-Mediterranean Province of the northwestern Tethys.
Sedimentology
Elmira Shahkaram; Mohammad Hosein Adabi; Davood Jahani; Seyed Hamid Vaziri
Abstract
The Dalichai Formation is the first rock unit of the Middle Jurassic in the Alborz sedimentary basin that has occurred in a marine environment. The boundary of the Dalichai formation with Shemshak Formation is erosional unconformable while it is concordant with Lar formation. Due to lithological similarity, ...
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The Dalichai Formation is the first rock unit of the Middle Jurassic in the Alborz sedimentary basin that has occurred in a marine environment. The boundary of the Dalichai formation with Shemshak Formation is erosional unconformable while it is concordant with Lar formation. Due to lithological similarity, the boundary of the Dalichai formation with the Lar formation is unclear. It is also very difficult to identify the primary carbonates mineralogy, due to the effects of diagenetic processes solely on the basis of petrographic studies. We studied a section of Sharaf mountain with a thickness of 1420m and 149 samples was studied. The study of the major and minor elements, the Oxygen and Carbon isotopes, and plotting of these values against each other represents that the Dalichai formation have had original aragonite mineralogy, and the nonmarine diagenesis have had the highest impact on them. Plotting the Sr/Ca ratio versus Mn value, shows that these carbonates are affected in a semi-closed to open diagenetic system. Using Sr, Sr/Na, Sr/Ca, Oxygen and Carbon isotopes, the boundary of this formation with the Lar Formation is recognized in thickness of 1200m. The diagenetic environment temperature for this section limestones is 32.9ºC.
Seyed Hamid Vaziri; Mahmoud Reza Majidifard; Marc Laflamme
Abstract
The Precambrian Kushk Series in the Bafq and Behabad regions of Central Iran contains a diverse assemblage of latest Ediacaran fossils that showcase a fossil assemblage much more diverse than typically known from the latest Ediacaran systems worldwide. The Kushk Series reaches a thickness of >500 ...
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The Precambrian Kushk Series in the Bafq and Behabad regions of Central Iran contains a diverse assemblage of latest Ediacaran fossils that showcase a fossil assemblage much more diverse than typically known from the latest Ediacaran systems worldwide. The Kushk Series reaches a thickness of >500 m and consists of carbonate (sandy dolomitic limestone and dolomite) and siliciclastic (shale, sandstone, and siltstone) facies with extensive accumulations of volcanic rhyolite, microdiorite, and tuff, which its argillaceous shales contain an assemblage of abundant Ediacaran fossils including Kuckaraukia multituberculata,Persimedusites chahgazensis, Corumbella werneri, Cloudinasp., Chuaria sp., Kimberella persii, Gibbavasis kushkii, Erniettomorpha, Rangeomorpha and numerous tubular organisms. The discovery of classic terminal-Ediacaran index fossils Cloudina and Corumbella in this assemblage confirms a latest Ediacaran age (Nama-Assemblage ~545-539 Ma) for these deposits. These taxa help expand our understanding of the latest Ediacaran prior to the Ediacaran extinction and the Cambrian explosion of complex animals.
K. Kiarostami; S. H. Vaziri; B. Noori; S. Allahmadadi; F. Vakilbaghmisheh
Abstract
In order to investigate lithostratighraphical and biostratigraphical as well as determination of exact contact between the Sarvak and Ilam formations in oil well X-01 of Bahregansar field thin microscopic sections, final well reports and its illustrative diagram were studied. The Sarvak Formation with ...
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In order to investigate lithostratighraphical and biostratigraphical as well as determination of exact contact between the Sarvak and Ilam formations in oil well X-01 of Bahregansar field thin microscopic sections, final well reports and its illustrative diagram were studied. The Sarvak Formation with a thickness of 206 m overlies the black to dark-green marls of Kazhdomi Formation with a gradual contact. This formation can be divided into 2 members and consist mainly of dolomite and dolomitic limestone. The Ilam Formation is considered in a depth ranging from 2672 to 2678 m in the studied well based on studied section and is mainly formed of clay limestone and thin-bedded limestone. This formation is covered by Gurpi Formation with a gradual contact and has a disconformity contact with the Sarvak Formation. Moreover, the age of the Ilam Formation has been considered as Coniacian - Early Campanian which is formed of pelagic facies in the studied area. A number of 22 species belonging to 23 genera have been identified that 6 genera and 11 species belong to the Ilam Formation and 11 species of 17 genera belong to the Sarvak Formation. Considering the identified fauna in the Sarvak Formation, the three following biozones were identified conforming to biozones presented by Wind (1965):1-Nezzazata - Alveolinids Assemblage Zone # 25; 2-Rudist debris # 24; 3-"Oligostegina"facies # 26. Presented biozones and principle of super position indicate Cenomanian age for the Sarvak Formation that consist of pelagic and neretic facies. Moreover, the age of the Ilam Formation has been considered as Coniacian - Early Campanian which is formed of pelagic facies in the studied area.
S.H. Vaziri; D. Jahani; M. Safdari; F. Chegeni
Abstract
The Ilam Formation in southwestern Khorram Abad with a thickness of up to 204 meters consists of uniform limestones with Middle Turonian to Early Campanian age which were deposited in a continuous sedimentation process. In this section, the Ilam Formation has continuous ...
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The Ilam Formation in southwestern Khorram Abad with a thickness of up to 204 meters consists of uniform limestones with Middle Turonian to Early Campanian age which were deposited in a continuous sedimentation process. In this section, the Ilam Formation has continuous and transitional contacts with the Sourgah Formation in the lower boundary and the Gurpi Formation in the upper boundary. In the present study, 9 genera, 30 species and 2 biozones of the planktonic foraminifera have been recognized. The Ilam Formation in the studied section consists of a shaly facies and three carbonatic microfacies include mudstone, wackestone and packstone containing planktonic foraminifera. Shaly facies and mentioned microfacies were deposited in deep-open marine, which formed in a quiet environmental condition and increased environmental energy in microfacies with mudstone texture toward microfacies with wackestone and packstone textures. Whereas in the studied section recognized microfacies are not related to parts of continental shelf,such as ; bar, lagoon and tidal flat, therefore it could be said that, the studied area was part of profound depositional basin in Middle Turonian to Early Campanian.