Stratigraphy and Palaeontology
Fereshteh Sajjadi; Firoozeh Hashemi Yazdi; Hossein Hashemi
Abstract
Reasonably diverse and very well-preserved palynomorphs including miospores, dinoflagellate cysts, foraminiferal test linings, acritarchs (sensu lato) and fungal spores occur in the Dalichai Formation, Yonjehzar, northeastern Tehran, central Alborz. The assemblages embrace 40 species of spores (assigned ...
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Reasonably diverse and very well-preserved palynomorphs including miospores, dinoflagellate cysts, foraminiferal test linings, acritarchs (sensu lato) and fungal spores occur in the Dalichai Formation, Yonjehzar, northeastern Tehran, central Alborz. The assemblages embrace 40 species of spores (assigned to 29 genera), 18 species of pollen (distributed among 10 genera) and 54 species of dinoflagellates (assigned to 28 genera). According to the presence of such miospores species with known worldwide stratigraphic distribution as Klukisporites variegatus, K. scaberis, Concavissimisporites verrucosus, C. pricei, Osmundacidites senectus and Striatella spp. the host strata are conceivably dated as Middle Jurassic. Based on the stratigraphic distribution of miospores, Klukisporites variegatus-Araucariacites australis-Cerebropollenites macroverrucosus Assemblage Zone is recognized. Presence of some index dinoflagellate species led to identification of four biozones in the Dalichai Formation. These include in ascending order, Cribroperidinium crispum Total Range Biozone (late Bajocian), Dichadogonyaulax sellwoodii Interval Biozone (Bathonian - early Callovian), Ctenididinium continuum Interval Biozone (early - middle Callovian) and Subzone a (early - middle Bathonian). Co-ccurrence of dinoflagellate cysts with known vertical ranges, viz., Cribroperidinium crispum, Meiourogonyaulax valensii, Carpatodinium predae, Ctenidodinium combazii and Compositosphaeridium polonicum suggests a Middle Jurassic age (late Bajocian to middle Callovian) for the host strata corroborates the available miospores-based biostratigraphy. The miospores are attributed to the Pterophyta (69%), Coniferophyta (15%), Pteridospermophyta (7%), Cycadophyta (5%), Lycophyta (2%), Ginkgophyta and Bryophytes (1%). Considering the relative abundance of fern spores (69%) and their morphological diversity (19 genera), it can be concluded that fern and fern-allies dominated the coastal vegetation around the sedimentary environments of the studied strata and that they flourished under a warm climate with notable humidity. The study of paleoclimate using the Sporomorph EcoGroups model shows a high ratio of warmer/cooler sporomorphs and a low ratio of drier/wetter sporomorphs, which is another confirmation of this type of climate. Presece of such warm water dinoflagellate cysts as Gonyaulacysta centriconnata, G. jurassica, Nannoceratopsis pellucida, Tubotuberella apatela, Ctenidodinium continuum, Pareodinia halosa, P. ceratophora, paleogeographic reconstruction and geographical location of Iran in the Middle Jurassic supports the generalization proposed.
Stratigraphy and Palaeontology
elahe zarei
Abstract
The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of ...
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The Dalichai Formation in Ahvanu section in the north of Damghan city with a thickness of 78 meters consisting of an alternation of bluish-gray marls and limestone, was studied. Based on the presence and stratigraphic distribution of miospore, Klukisporites variegatus and Callialasporites dampieri of pollen are identified (Middle Jurassic) and presence of some index dinoflagellate species led to the identification of three biozones in the Dalichai Formation. These include in ascending order, Cribroperidinium crispum Total Range Biozone (late Bajocian), Dichadogonyaulax sellwoodii Interval Biozone (Bathonian - early Callovian), Ctenididinium continuum Interval Biozone (early to middle Callovian). Also, this Formation was divided into two biozone on the basis of Lenticulina varians-Ophtalmidium Assemblage zone and Globigerina bathoniana Taxon range zone. The close similarities of fauna assemblages of Dalichai Formation in this region (eastern Alborz ((dinoflagellate cyst, foraminifera, posidonia and radiolar) with assemblages recorded from different parts of Iran (such as central and eastern, western Alborz and Binalud and south of Iran) and other parts of world (northwest of Europe, and the northwestern Tethys and …) confirm the marine connection and faunal exchange between the mentioned basins during Middle Jurassic.
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.
T Sarbandi Farahani; M.R Majidifard; M.R Kebriaee- Zadeh; M Mohammadi
Abstract
The Middle Jurassic rocks are widely distributed and superbly exposed in the AlborzMountains (Northern Iran). In the central part of the mountain range, near Mahdishahr (Northern Semnan), the Dalichai Formation, from the underlying conglomerate and sandstones of Shemshak Formation to the limestones of ...
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The Middle Jurassic rocks are widely distributed and superbly exposed in the AlborzMountains (Northern Iran). In the central part of the mountain range, near Mahdishahr (Northern Semnan), the Dalichai Formation, from the underlying conglomerate and sandstones of Shemshak Formation to the limestones of the overlying Lar Formation, is completely exposed on the southern slopes of the kuh-e-Rahband. At this area, the sedimentary succession with nearly 122 m thickness subdivided into four members starting with marl and medium to thick-bedded grey limestones to marly limestones. The lower boundary with the siliciclastics of the underlying Shemshak Formation is disconformity, whereas the upper boundary with the light and cliff-forming carbonates of the Lar Formation is rather inconspicuous and transitional. The Dalichai Formation in the east of Mahdishar section is fossiliferous. The ammonite fauna consist of 5 families, 22 genera and subgenera and 40 species, among them 8 species are recorded for the first time from Iran. Based on the ammonite fauna, 9 biozones were recognized that indicated the age of the Dalichai Formation in the investigated area ranges from the Upper Bajocian? to Upper Oxfordian. Pleobigeographically, the fauna shows close relationship to west Europe and sub-mediterranean regions. This indicates a paleogeographic position of the area at the northern Tethys during the Middle Jurassic.
M Allameh; S Saadati Jafarabadi
Abstract
The Dalichai Formation is among marine deposits in Jurrasic period that has a geographic expansion in north of Iran. In order to palynological studies in eastern part of the BinaloudMountains an outcrop of this formation, in the bar village was selected. The thickness in bar village section is 255 meters ...
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The Dalichai Formation is among marine deposits in Jurrasic period that has a geographic expansion in north of Iran. In order to palynological studies in eastern part of the BinaloudMountains an outcrop of this formation, in the bar village was selected. The thickness in bar village section is 255 meters includes dark gray shales. The study of 112 slides of 28 samples taken from this formation showed that the most of the samples contain palynomorphs specifically dinoflagellates. 53 species belonging to 27 genera of dinoflagellates were identified. According to dinoflagellates, a middle Jurassic age was determined for the Dalichai Formation in the Bar village section. Based on the study of three main groups of phytoclasts, marine palynomorphs and amorphic organic matters and result of the statistical studies of different factors, sedimentary environment of the Dalichai Formation in studied section was open marine basin with shallow and low oxygen condition.
Z. Boroumand; E. Ghasemi- Nejad; M. R. Majidifard
Abstract
The Dalichai Formation at Talu section, 24 kilometers NE of Damghan is studied Palynologically. The Middle Jurassic sediments with a thickness of 168 meters in this section contain grey to green marl and grey marly limestone. A total of 35 samples were collected systematically and 200 palynological sildes ...
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The Dalichai Formation at Talu section, 24 kilometers NE of Damghan is studied Palynologically. The Middle Jurassic sediments with a thickness of 168 meters in this section contain grey to green marl and grey marly limestone. A total of 35 samples were collected systematically and 200 palynological sildes were prepared. Forty nine species of dinoflagellate cysts belonging to 30 genera were identified. A few fungal spores and foraminiferal test lining and spores and pollen grain were also recorded. Although, dinoflagellate species are abundant but all the species recorded were concentrated in lower parts of the section (0-110 meters). Two palynozones were identified; Cribroperidinium crispum Total Range Palynozone (Ccr), Dichadogonyaulax sellwoodii Interval palynozone (Dse). A local palynozoneof Ctenidodinium combazii/Ctenidodinium ornatum ornatum Acme Zone were also established in the succession. An age of Bajocian – Late Callovian was proposed for the succession studied.
K. Seyed Emami; N. Behfar; M. R. Majidifard; A. Behfar
Abstract
Middle Jurassic strata are well developed northeast of Damghan (E Alborz). At the study section the Dalichai Formation has a maximum thickness of 156 m, consisting of an alternation of bluish-grey limestones and marls, being subdivided into 4 members. The lower boundary with the siliciclastics of the ...
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Middle Jurassic strata are well developed northeast of Damghan (E Alborz). At the study section the Dalichai Formation has a maximum thickness of 156 m, consisting of an alternation of bluish-grey limestones and marls, being subdivided into 4 members. The lower boundary with the siliciclastics of the underlying Shemshak Formation is unconformity, due to the Mid-Cimmerian tectonic event, whereas the upper boundary with the light and cliff-forming carbonates of the Lar Formation is gradational. The Dalichai Formation at the study section is very fossiliferous. Summing up 1750 fossil specimens were collected, among which the ammonoids with 1491 specimens clearly predominate. Altogether 27 genera, 33 species of ammonites, belonging to 6 biozones (Parkinsoni Zone, Zigzag-Aurigerus zones, Subcontractus Zone, Bullatus-Gracilis zones, Anceps-Coronatum zones, Athleta Zone) has been recognized. In addition 17 genera and 8 species of planktonic and benthic foraminifers are described.These can be divided into 2 biozones. The fossil-content is mainly concentrated within few meters of red and nodular limestone in the upper part of the section. Based on the ammonite fauna the age of the Dalichai Formation in the investigated area ranges from Upper Bajocian to Oxfordian. Paleobigeographically the fauna shows close relationship to western Europe and Sub-Mediterranean region. This indicates a paleogeographic position of the area at the northern Tethys during the Middle-Upper Jurassic.
M. Shams; K. Seyed-Emami
Abstract
The Dalichai Formation and its ammonite fauna is studied for the first time in the Parvar area, Central Alborz. At Parvar the Dalichai Formation, with a thickness of about 70 m, consist of an alternation of grayish silty marls, marlstones, marly limestone and limestone and is subdivided into 5 members. ...
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The Dalichai Formation and its ammonite fauna is studied for the first time in the Parvar area, Central Alborz. At Parvar the Dalichai Formation, with a thickness of about 70 m, consist of an alternation of grayish silty marls, marlstones, marly limestone and limestone and is subdivided into 5 members. A rich ammonite fauna (407 specimens) have been collected from the member 4 and 5, comprising the following families: Phylloceratidae, Lytoceratidae, Oppeliidae, Haploceratidae, Sphaeroceratidae, Parkinsoniidae, Morphoceratidae and Perisphinctidae. These indicate a Late Bajocian and Bathonian age. Member five consists of greenish to reddish, nodular and flaggy limestones and is a typical condensed horizon.