جستجوی مقالات مرتبط با کلیدواژه « ammonite » در نشریات گروه « زمین شناسی »

To determine the relative age of the Sarcheshmeh Formation in the northeast of the Kopet Dagh Basin, a stratigraphic section (Hosein Abad) with a thickness of 90 meters is selected. Lithologically, Sarcheshmeh Formation is mainly composed of gray to green marls with muddy limestone beds. In this research, based on ammonites, 10 species attributed to 4 genera of ammonites were identified. Accordingly, three biological zones, Deshayesites consobrinus, Deshayesites deshayesi, and Dufrenoyia mackesoni, are proposed confirming the Early’s relative age Aptian (Early Cretaceous) for Sarcheshmeh Formation in Hosein Abad section. The identified biological zones were also compared with some previous studies in the Kopet Dagh, Caucasus, and Mediterranean basins and it was found that the Sarcheshmeh Formation in the study area (northeast of the Kopet Dagh) shows well correlation to biological zones in the late Early Aptian. While, some studies on this Formation have reported biological zones related to the early Early Aptian.

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.

The Binalud Mountains in the northeast of Iran is a limited structural unit between the central Iran, Kopet-Dagh, and Alborz Mountains, mainly considered as a southeastern extension of Alborz Mountains (Lammerer et al., 1983; Eftekhar-Nezhad & Behroozi, 1991; Alavi, 1992; Seyed-Emami & Schairer, 2011). Jurassic successions, which have very well extended outcrops in the eastern Alborz and Binalud Mountains, were the main topic of the publications by Seyed-Emami & Schairer (2010), Wilmsen et al. (2009a,b), Raoufian et al. (2011, 2014), Seyed-Emami and Raoufian (2017), Seyed-Emami et al. (2018). Dalichai Formation in the eastern Alborz and Binalud Mountains comprises a thickness of marl and marly limestone, with an abundance of ammonite fauna which is the most important characteristic of the formation in the Binalud Mountains. This fauna in the Alborz and Binalud has long been considered in different papers (e.g., Shafeizad et al., 2005; Seyed-Emami et al., 2008, 2013, 2015, 2018; Raoufian et al., 2011, 2014). In this research, an outcrop of Dalichai Formation in the Bāghi stratigraphic section, northwest of Esfarayen city, was lithostratigraphycally and biostratigraphically studied.

The base of the measured stratigraphic section is located in 37°11′45.34″ and 57°16′21.89″, 29 km northwest of Esfarayen city (Esfarayen to Jajarm route). After field studies, reviews of lithofacies in the field, and drawing the log, 540 in situ ammonite specimens were obtained from the section. They are kept in the Museum of the Geology Department at the Ferdowsi University of Mashhad. The biometric details of ammonite specimens, including the dimensions of the specimens, size, depth, and diameter of the umbilical area, the number, arrangement, and shape of ribs, marginal keels, nodes, suture lines, and apertural shape, have been studied. The studied ammonitic fauna are typically Northwest Tethyan and belongs to the Submediterranean Province with episodic Mediterranean and Subboreal affinities (Seyed-Emami et al., 2013). It reflects the relationship between these regions with other parts of the Paleotethys sidelines during the Jurassic time.

In the Baghi section, the Dalichai Formation unconformably overlies the siliciclastic Shemshak Formation and gradationally underlies the cliff-forming carbonate rocks of Lar Formation. The Dalichai Formation, with a thickness of 655 meters, is divided into ten separate informal members and is mainly composed of marls, limestone, and marly limestone. One of the most important features of the Dalichai Formation in this section is the abundance of ammonite fauna, especially in the lower half of the section. Due to the specific color, lithology, and abundance of ammonite fauna, the second member is a key member.Paleontological studies in this research is led to the determination of 96 species, 26 subgenera, 39 genera, 20 subfamilies, 14 families, and 6 superfamilies belonging to 3 suborders of Ammonitida. According to the mentioned assemblage, 17 standard biozones are recognized, consisting of Grantiana, Parkinsoni, Zigzag, Retrocostatum, Bullatus, Gracilis, Anceps, Coronatum, Athleta, Lamberti, Transversarium, Bifurcatus, Bimammatum, Planula, Platynota, Hypselocyclum, and Acanthicum. These biozones show the age of late Bajocian – late Kimmeridgian for the Dalichai Formation. The studied ammonitic assemblages are closely related to the other Middle-Late Jurassic fauna from Iran and further peri-Mediterranean regions, which correlates with the Sub-Mediterranean province.

Ammonite biostratigraphy could be used in age determination and correlation of rock units in different sedimentary basins. Qumenjan section with 125 meters thickness is mainly formed by grey sandy limestone with grey and thick-bedded limestone intercalations. The study area is located in the eastern margin of the Lut Block. For a stratigraphical study of Lower–Upper Cretaceous deposits in southwestern of Qayen area, a stratigraphic section was selected and measured. Eight ammonites, including Anisoceras, Calycoceras, Hypoturrilites, Hysteroceras, Mantelliceras, Puzosia, and Scaphites genera and thirteen representative species were identified. Based on the identified assemblage fossils and comparison with international biozones, Hysteroceras orbignyi subzone for Late Albian age, Mantelliceras mantelli biozone for the lower part of Early Cenomanian age, Mantelliceras dixoni biozone for the upper part of Early Cenomanian age, and Turrilites costatus biozone for Middle Cenomanian age is suggested. According to identified genera and species a Late Albian–Middle Cenomanian age is assigned for ammonite bearing of the section. The first occurrence of Mantelliceras mantelli is taken as the base of Cenomanian. Compression of the identified ammonites with other basins shows that the east Iran basin was a part of Tethys Realm during late Albian–middle Cenomanian.

The present study deals with the ammonites from the upper part of the Chaman Bid Formation, member 4 (Middle-Upper Jurassic) at the type locality. Lithostratigraphicall, it is consites alternation of limestone and marls.Following ammonite families are present: Perispinctidae, Ataxioceratidae, Haploceratidae, Oppeliidae and Aspidoceratidae, which indicate the Biozones: Hybonoticeras hybobotum , Semiformiceras semiforme , Semiformiceras fallauxi , Microcanthoceras ponti and Micracanthoceras micracanthum Zones. Paleobiogeographicall, the ammonite fauna is closely related with the Submeditteranean Provice, with few affinities to South Tethys (Ethiopian province ),migrated during the Tithonian. Following taxa are reported for the first time fromthe Tithonian strataNorth Iran: Zappalia cf. zapalensis, Paraulacosphinctes transitorios, P. seneoides.

The Middle and Upper Jurassic strata of the Alborz are named the Dalichai and Lar formations. The Dalichai Formation is introducing primary unites of Alborz Jurassic marine deposites and lithologically consist of a sequence of greyish limestones and marls that specially exposed in the south of Alborz Mountains. Most of the studies on the Dalichai Formation mainly focus on the ammonite fauna and their biostratigraphical importance (e.g. Seyed-Emami et al. 1985, 1989, 1995, 2013, 2015; Seyed-Emami and Schairer 2010, 2011a, 2011b; Dietze et al. 2014; Seyed-Emami and Raoufian 2017, Majidifard 2003, 2015; Schairer et al. 1991 and Raoufian et al. 2014, 2019). Ammonites are the most important fossils in the Dalichai Formation, they are of fundamental importance in determining the age and conditions of its paleoenvironment. In most area of the Alborz, the Dalichai Formation has marl, marly limestone, spary and thin bedded limestone with intercalation of marl and marly shale. In the sections studied this Formation consists of marl, marly limestone, sandy limestone and limestone. The aim of this study is to give an overview of the Oppeliidae fauna of the Dalichai Formation in Northern Alborz. The family of Oppeliidae has a high frequency as one of the Bathonian and Callovian index families in Alborz (e.g. Seyed-Emami et al. 2013). In the studied sections, this family has a frequency of 21.5%.

Lithostratigraphy and biostratigraphy of Middle Jurassic Dalichai Formation in Northern Alborz ranges have been studied for the first time. Three stratigraghical sections of Dalichai Formation in Northern Alborz ranges include Keriush in south of Babol, Kanefejar in south of Babol and Vana in Haraz road have been chosen for the paleontological studies. After field studies due to the abundance and importance of ammonite fauna in these sections, detailed sampling of ammonite fauna within the layers was done. After cleaning and preparing the ammonite samples and taking photograph of them, these samples were identified up to the species level and based on the international standard zonation (Cariou & Hantzpergue, 1997); zones of ammonites have been identified.

The studied ammonites come from three localities in northern Alborz Mountains. These are: 1. Keriush: 65 km south of Babol (N 36° 2'53.61", E 52°40'22.23"). The thickness of the Dalichai Formation at this section is 21/3 meters and can be subdivided into four members. The age of the Dalichai Formation is Upper Bajocian to Upper Callovian. 2. Kanefejar: 60 km south of Babol (N 36° 3'15.59", E 52°36'26.74"). The thickness of the Dalichai Formation is measured at this section 18/9 meters and can be subdivided, from bottom to top, into four members. The age of the Dalichai Formation is Upper Bajocian to Upper Callovian. 3. Vana: 75 km south of Amol (N 35°56'31.48", E 52°15'40.36"). The thickness of the Dalichai Formation is 70 meters and can be subdivided into four members. The age of the Dalichai Formation is Upper Bajocian to Upper Callovian. In this region, Dalichai Formation follows discontinuously on the dark, siliciclastic Shemshak Formation and is overlain gradationally by the light and cliff-forming carbonates of the Lar Formation. The biostratigraphy of the Dalichai Formation is discussed with special emphasis on the ammonite fauna (Oppeliidae family).

Palaeobiogeographically the middle Jurassic ammonite fauna in this area is closely related to that of the northwest-Tethyan, with relations to Subboreal / Submediterranean provinces. The study of ammonite fauna in this region led to identification of 48 genus, 18 subgenus and 26 species. Existing ammonite fauna indicates 8 ammonite biozones and Late Bajocian-Late Callovian ages for Dalichai Formation in Northern parts of Alborz ranges. The thickness of the formation in Northern parts of Alborz represents a much lower thickness of this formation than the southern parts of Alborz. The thickness changes of the Dalichai Formation in the northern and southern parts of the Alborz Mountains can be due to the tectonic conditions of the area and the existence of an extensional phase during its formation.

The Kazhdumi Formation is well exposed and accessible in Tang-e Maghar, northwest of Behbahan city, Zagros basin. In this area, this formation has a thicknees of 344 m and it mainly consists of alternation of black - gray shale with medium – thin-bedded cream – gray argillaceous limestone. The lower contact of the Kazhdumi Formation is disconformable with Daryan Formation and conformable with the Sarvack Formation at the top. A total of 220 ammonite bearing surface samples were collected including the uppermost part of the Daryan Formation (5m) and the whole thickness of the Kazhdumi Formation (344m). This investigation resulted in 21 species (15 genera) which belong to six families. The encountered ammonite species of the upper part of the Daryan Formation and the whole Kazhdumi Formation consist of Douvilleiceras sp., Douvilleiceras cf. mammillatum, Epicheloniceras subnodosocostum– buxtorfi, Hypacanithoplites cf. elegnas, Acanthohoplites cf. aschiltaensis, Nolaniceras nolani, Parahoplites cf. melchioris, Venezoliceras sp., Venezoliceras cf. venezolanum, Mirapelia cf. buarquianum, Mirapelia sp., Oxytropidoceras carbonarium, Oxytropidoceras cf. roissyanum, Hysteroceras cf. orbignyi, Hysteroceras sp., Tonohamites cf. aequicingulatus, Mortoniceras sp., Mortoniceras aff. inflatum, Dufrenoyia sp., Hemiptychoceras cf. gaultinum and Scaphites sp.Amongst these ammonite species, Scaphites sp. and Hemiptychoceras gaultinum are recorded for the first time and the remainder has previously been recorded from this rock unit in the Zagros basin. Likewise, based on stratigraphic potential of the encountered ammonite species the lower Aptian is suggested for the upper part of the Daryan Formation and upper Aptian –upper Albian for the Kazhdumi Formation.Therefore, a hiatus is present between the Daryan and Kazhdumi formations, encompassing the middle Aptian.

Considering importance of ammonite fauna in biostratigraphy and sedimentary basins and due to the lack of studies on the ammonite fauna in the Kazhdumi Formation, the Nar stratigraphic section was ed and studied in the coastal Fars, northeast of Kangan (East Bushehr). The formation with a thickness of 87 meters in the studied section contains alternation of cream to brown limestone and brownish red marl. The lower boundary with the carbonate of the underlying Dariyan Formation is unconformable and in the upper boundary is gradually covered by the Madoud Member of Sarvak Formation. In the present study, 110 ammonites have been collected which are belong to three genera and seven species. These include Knemiceras sp., Knemiceras persicum, Knemiceras dubertreti, Knemiceras syriacum, Knemiceras comperessum, Tegoceras camatteanum and Lyelliceras lyelli. Based on these one subzone was differentiated indicating a late Early to Middle Albian age for the formation.

In order to study the Stratigraphic of sedimentary deposits of the Cenomanian in Kopeh Dagh, the Taghiabad section was selected. In the eastern Kopeh Dagh, the upper part of Aitamir Formation has this time range characteristic. The upper part of this formation includes shale and glauconitic sandstones and contains variety of ammonite fauna. Ten genera and species of ammonites are found inside these sedimentary layers and are identified as Acanthoceras rhotomagense, Cunningtoniceras cunningtoni, Schloenbachia varians, Schloenbachia coupei, Hypoturrilites sp., Mantelliceras saxbii, Mantelliceras mantelli, Hyphoplites curvatus arausionensis, Placenticeras mediasiaticum and Placenticeras gaurdakense. These ammonites belong to 5 families of ammonites including Hoplitidae, Turrilitidae, Schloenbachiidae, Acanthoceratidae and Placenticeratidae. These ammonites represent the Early to Middle Cenomanian age and are of a Boreal environment.

The Lower- Middle Jurassic strata are well developed in northeast of Jajarm (E Alborz). At the study section, the Shemshak Group has a maximum thickness of 585 m, consisting of grey silty sandstones and light- green siltstones with brown sandstones, subdivided into 3 formations ofAlasht, Shirindasht and Fillzamin.The lower boundary of the Shemshak Group at Golbini sectionwith the red bauxite horizon of the underlying Elikah Formation is disconformity due to the EarlyCimmerian tectonicevent.Its upper boundary with marly limestone and marl of the Dalichai Formation is disconformity, too. In the Shemshak Group at the study section, summing up 186 fossil specimens were collected, among which the ammonoids with 67 specimens clearly predominate and belonging to 6 biozones (ThouarsenseZone, Pseudoradiosa Zone,Aalensis zone, Opalinum Zone, Murchisonaezone, ConcavumZone) have been recognized. Based on the ammonite fauna, the age of the Shemshak Group in the investigated area ranges from the Upper Toarcian to Upper Aalenian. Paleobiogeographically, the fauna shows close relationship to Northwestern Europe and Sub-Mediterranean regions. This indicates a paleogeographical position of the area at the northern Tethys during the Lower-Middle Jurassic.

The Middle Jurassic rocks are widely distributed and superbly exposed in the Alborz Mountains (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.

Upper Jurassic rocks are well developed at the western part of the Binalud Range (northeast Iran). These consist mainly of limestone, marlstone and marl with few intercalations of sandstone and conglomerate. The thickness of this succession in the study section (Bormahan, northwest of Neyshabour) is 1084 meters and can be subdivided into 6 members. The lower boundary with the dark siliciclasts of? Kashafrud Formation (Upper Bajocian / Lower4 Bathonian) is sharp. The upper boundary with buff and cliff-forming carbonates of the? Mozduran Formation (Upper Jurassic) is transitional. Ammonites are the most important and abundant macrofossils.Totally more than 300 specimens have been collected, comprising 21 genera and 36 species.The relative abundances at the family level are: Phylloceratidae (48%), Perisphinctidae (42%), Oppeliidae (6%), Haploceratidae (2%), Aspidoceratidae (1%) Based on the ammonite fauna 15 biozones are recognized which can be fairly good compared with the ammonite biozonation of Sub-Mediterranean Province. According to the ammonite fauna an Early Bathonian to Kimmeridjian age is proposed.The ammonite fauna is closely related to those of the Sub-Mediterranean Province, indicading a permanent faunal exchange.

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 unconformable 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-Mediterraneanregion. This indicates a paleogeographic position of the area at the northern Tethys during the Middle-Upper Jurassic.