S Abbasi; B Hamdi; M.R Majidifard
Abstract
Sampling and study of Devonian deposits in North West Iran has done in two separate sections. 1) Illangareh section, 20 km far from NE the Maku city 2) peyr-es-hag composite section, situated South Jufa (W of Peyr-es-hag and Chay kasan villages). Because less work has been undertaken in the cited sections, ...
Read More
Sampling and study of Devonian deposits in North West Iran has done in two separate sections. 1) Illangareh section, 20 km far from NE the Maku city 2) peyr-es-hag composite section, situated South Jufa (W of Peyr-es-hag and Chay kasan villages). Because less work has been undertaken in the cited sections, in this research, microremains (fish teeth, scales and bone fragments) of Cartilaginous fish (Chondrichtyes), Osteichtyes (Acanthodians), fauna are known from the Devonian deposits. Index microvertebrates obtained from the cited above sections are: Siberiodus mirabilis, Phoebodus gothicus, Phoebodus turnerae, , Body scale Holonema sp., Sarcopterygian scale, Ischnacanthid jaw, Cheiracanthus sp., Ertychius intermedius Cladodus wildungensis. According to biostratigraphy and paleogeography these microremains can be comparing with other parts of Iran, neighbors, other parts of world. This assemblage show spread of shallow shelf environment of the northern margin of Gondwana during Middle-Late Devonian time.
M Khazaee; M Hosseini-Barzi; A Sadeghi; H Mosaddegh
Abstract
The Jeirud Formation (Upper Devonian) in Deh-Sufian section of northeast of Shahmirzad consists of siliciclastic and carbonate deposits. In the study area lower boundary of the Jeirud Formation with fine grain clastic deposits of the Mila Formation is erosional (Disconform) and has been conformably overlain ...
Read More
The Jeirud Formation (Upper Devonian) in Deh-Sufian section of northeast of Shahmirzad consists of siliciclastic and carbonate deposits. In the study area lower boundary of the Jeirud Formation with fine grain clastic deposits of the Mila Formation is erosional (Disconform) and has been conformably overlain by dark carbonate deposits of the Mobarak Formation. The clastic deposits of the Jeirud Formation include conglomeratic, sandy and muddy facies. The conglomeratic deposits comprises three facies A1, A2 and A3 that are equivalent to Gcm, Gt and Gmm/Gmg of Miall facies respectively. Also, five sandy facies of B1, B2, B3 and B4 equivalent to St, Sh, Sm and Sr of Miall respectively and B5 (Shc) with hummocky cross stratification (HCS) sedimentary structure have been identified. Muddy facies including C1 and C2 are equivalents to Miall’s Fsm and Fl facies. Carbonate facies (D) comprising small amounts of the stratigraphic column is almost entirely dolomitized. Field and petrographic studies provide five facies association: fluvial, foreshore-backshore, shoreface, offshore transitional zone and offshore and carbonate facies interpreted as Proximal carbonate tempestites and distal carbonate tempestites based on evidences such as basal erosional surface, normal grading, HCS and coexisting clastic facies . In the study area, the Jeirud Formation deposits initiate with fluvial sequences that have been followed by storm dominated marine deposits as foreshore-backshore deposits and alternations of shoreface to offshore deposits. Study of sequence stratigraphic surfaces especially important subaerial unconformities and also stratal stacking patterns of the formation resulted in determination of three subaerial unconformity bounded depositional sequences plus transgressive part of the 4th sequence.
S Abbasi; B Hamdi; M.R Majidifard
Abstract
Study of conodont fauna from the Illanghareh Formation in Illanghareh, Illanlu and Pir-Eshag sections provide new data on the stratigraphy of this formation in the North West Iran. Illanghareh section is a terrigenous-carbonate rock sequence, consists mainly of quartzarenite sandstone, shale, and carbonate ...
Read More
Study of conodont fauna from the Illanghareh Formation in Illanghareh, Illanlu and Pir-Eshag sections provide new data on the stratigraphy of this formation in the North West Iran. Illanghareh section is a terrigenous-carbonate rock sequence, consists mainly of quartzarenite sandstone, shale, and carbonate rocks. This sequence generally represents shallow-water Polygnathid-Icriodid biofacies and yielded five biozones: varcus, Older than rhenana, rhenana – linguiformis, Middle triangularis – Late trachytera, postera – expansa. Tectonic activities and erosion caused the Middle Devonian strata in the base of Illanghareh section to be omitted and the varcus Biozone is not recorded. Upper Devonian (Upper Famennian) rock units change into Carboniferous strata with a sedimentary gap though it is not recognizable in the field and no evidence of erosional surface is recognized. It is however, shown between Late Famennian and Late Turnaisian via conodonts recorded. The biozone bilineatus- bolandensis was also recorded in lower part of Carboniferous strata studied here.
H. Gholamalian; S. M. Hosseini-Nezhad; Z. Khosravi; I. Turkzadeh Mahani
Abstract
Bahram Formation equivalent sequence in the Baghin area spans late Givetian to late Frasnian age. Thirty-two species and subspecies are identified. Ancyrodella alata, An. pristina, Polygnathus aspelundi, P. aequalis, P. subincompletus,P. politus, Icriodus alternatus alternatus, I. iowaensis iowaensis ...
Read More
Bahram Formation equivalent sequence in the Baghin area spans late Givetian to late Frasnian age. Thirty-two species and subspecies are identified. Ancyrodella alata, An. pristina, Polygnathus aspelundi, P. aequalis, P. subincompletus,P. politus, Icriodus alternatus alternatus, I. iowaensis iowaensis are of important species. The presence of An. pristina and An. alata in the lower part of Bahram Formation in this section shows the late Givetian marine transgression. Five conodont biozones are recognized on the basis of stratigraphic ranges of species: Lower to Upper falsiovalis zones; transitans to punctata zones; Lower hassi to jamieae zones; Lower rhenana Zone; and Upper rhenana to ?linguiformis zones.
M. Mohammadi; A. Ernst; M. Yazdi
Abstract
Two bryozoan species are described from the Geirud Formation (Upper Devonian) of Central Alborz. The Geirud Formation is a sequence of nearly 340 meters of alternating silisiclastics and limestone and 1-2 andesitic lava units, with extensive exposures in the Central Alborz mountains. ...
Read More
Two bryozoan species are described from the Geirud Formation (Upper Devonian) of Central Alborz. The Geirud Formation is a sequence of nearly 340 meters of alternating silisiclastics and limestone and 1-2 andesitic lava units, with extensive exposures in the Central Alborz mountains. The study comprises the Type Section of the Geirud Formation in the Geirud valley and two sections in Zaigun and Lalun valleys near the Type Section, all in northern Tehran (Fig.1). In some calcareous beds we found bryozoan species from Famennian. Trepostome Schulgina mutabilis Troizkaya, 1975 is known from the Upper Devonian (Famennian) of Central Kazakhstan. The Ascopora .sp. is the earliest known representative of habdomesine genus Ascopora Trautschold, 1876. This is the first study on the bryozoans of the Geirud Formation in Central Alborz.
S. M. Hosseini-Nezhad; M. Yazdi; M. Ghobadi-Pour; H. Gholamalian
Abstract
Geirud formation deposits of Kalariz in the Eastern Alborz start with a relatively thick sequence of sandstone, shale, and red, white and brown colored siltstone changing into yellow dolomitic layers, fossiliferous limestone and shaly or marly limestone. This formation ...
Read More
Geirud formation deposits of Kalariz in the Eastern Alborz start with a relatively thick sequence of sandstone, shale, and red, white and brown colored siltstone changing into yellow dolomitic layers, fossiliferous limestone and shaly or marly limestone. This formation lies over Mila formation with a disconformity and covered transitionally by limestones of Mobarak formation. In the above mentioned sequence, numerous and various conodonts and brachiopods were identified. Based on the distribution of brachiopoda, two assemblage zones and based on the conodonts, four assemblage zones were recognized with Famennian and Strunian age. The first brachiopoda biozone, equivalent to the first and second conodont biozones, belongs to early Famennian age (older than late crepida zone and romboidea to late trachytera zone) and the second Brachiopoda biozone which is equivalent to conodont biozone of number three and four has the late Famennian age (postera to late expansa zone and praesulcata zone). Paleontological and stratigraphical evidence indicates that Frasnian sediments are absent in the study area.
