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Stratigraphical column of the Ghoznavi section, Upper Devonian-Lower Carboniferous Khoshyeilaq Formation, Sarcheshmeh Member, showing the horizons of fossil localities and stratigraphical ranges of trilobite, brachiopod and conodont species.
Source publication
The Late Devonian (late Famennian) phacopid trilobites represented by Omegops tilabadensis sp. nov. are described and illustrated from the Khoshyeilaq Formation, eastern Alborz Mountains, North Iran. The species formed a monotaxic trilobite association inhabiting a shallow shelf together with diverse brachiopod communities dominated by the athyridi...
Contexts in source publication
Context 1
... base of the measured profile of the Ghoznavi section has geographical coordinates 36°55′24.6″ N and 55°27′22.8″ E. The observed succession in ascending order looks as follows (Fig. ...
Context 2
... upper 32 m comprises mainly calcareous argillite with subsidiary nodular limestone beds. The upper 16 m of the unit is rich in brachiopods and also contains a few trilobites (Fig 2; sample Gh-7A/30-32 m). ...
Context 3
... Gh-7B -33.5 m of dark grey nodular lime- stones with argillite intercalations. The unit contains abundant brachiopods, conodonts (Fig. 2, sample Gh-7B/0 m) and occasional trilobites ( Fig. 2; samples Gh-7B/5-12 m and Gh-7B/23-30 ...
Context 4
... Gh-7B -33.5 m of dark grey nodular lime- stones with argillite intercalations. The unit contains abundant brachiopods, conodonts (Fig. 2, sample Gh-7B/0 m) and occasional trilobites ( Fig. 2; samples Gh-7B/5-12 m and Gh-7B/23-30 ...
Context 5
... Devonian-Carboniferous boundary can be placed provisionally at the base of Unit Gh-8, at the top of the uppermost limestone beds. The only fossil in the lower part of the unit, which is a stratigraphical equivalent of Wendt et al. (2005 (Fig. 2). This distinctive shell bed is apparently traceable also in the Khoshyeilaq section (Wendt et al. 2005, fig. ...
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Citations
... The Devonian deposits exposed in the area were characterised in some detail by Brice et al. (1978). Subsequently, the geology of the area was outlined by Ghobadi Pour et al. (2018), who referred to the fossil locality as the Ghoznavi section. The brachiopod specimens used in the present study were sampled from the late Famennian deposits assigned to the Sarcheshmeh Member of the Khoshyeilagh Formation. ...
... The sample GR 365 of Brice et al. (1978;Figures 1, 6; Table 1) was probably taken from the same unit. A detailed stratigraphical log of the measured section was given by Ghobadi Pour et al. (2018), as shown in Figure 2. From the base, the sequence is as follows: Figure 1. Simplified geographical map of eastern Alborz Region showing position of fossil localities discussed in the paper: 1, Namaki; 2, Ghoznavi; 3, Khoshyeilagh; 4, Mighan; 5, area c. 36 km north-west of Dibaj with geographical coordinates 36º27'20'N, 54º08'29' E (after Baranov et al. 2018). ...
... Simplified geographical map of eastern Alborz Region showing position of fossil localities discussed in the paper: 1, Namaki; 2, Ghoznavi; 3, Khoshyeilagh; 4, Mighan; 5, area c. 36 km north-west of Dibaj with geographical coordinates 36º27'20'N, 54º08'29' E (after Baranov et al. 2018). Pour et al. (2018). Informal units Gh0-Gh9 are the same as in the main text and after Ghobadi Pour et al. (2018). ...
The late Famennian Sarcheshmeh Member of the Khoshyeilagh Formation contains a sizeable rhynchonel�lide component comprised of eight genera and ten species, including Golestanirhynchus golestanicus sp. nov.
Petasmaria sartenaeri sp. nov. Tilabadirhynchus azadshahrensis gen. et sp. nov. Tilabadirhynchus qeshlaqensis
gen. et sp. nov. and Megalopterorhynchus chanakchiensis giganteus subsp. nov. The characters of brachiopod
biostratigraphical distribution in the Sarcheshmeh Member and correlation with conodont biozonation
suggest that Megalopterorhynchus chanakchiensis giganteus does not cross the lower boundary of the
Bispathodus ultimus Zone, while Araratella anatolica is probably confined to it. The pugnacoidean genus
Petasmaria is reported for the first time outside of North America. The broad paleobiogeographic affinities of
the late Fammenian rhynchonellide assemblages from the Sarcheshmeh Member of the Alborz Region with
the contemporaneous brachiopod faunas of Central Iran, Afghanistan and Transcaucasia corroborate the
well-established pattern of increasing cosmopolitanism of the brachiopod faunas towards the end of the
Devonian Period.
... Trilobites with low vision abilities remained the most abundant in the praesulcata zone. Nonetheless, large-eyed trilobites still inhabited shallow places (Brauckmann et al., 1992;Pour et al., 2018). An important faunal turnover is observed with both high origination and extinction rates. ...
... Unlike the compound (holochroal) eyes of most trilobites, the eyes of the Phacopina are schizochroal, with surfaces that consist of numerous small lenses segmented by interlensar cuticles (sclerae); each lens is covered by a separated cornea (Clarkson, 1975;Clarkson et al., 2006). These lenses, in addition to providing members of the Phacopina with a more efficient visual system (Clarkson and Levi-Setti, 1975;Clarkson et al., 2006;Schoenemann, 2021), are used in systematic taxonomy, according to their number and arrangement (e.g., Clarkson, 1966Clarkson, , 1969Eldredge, 1972;Zhou and Campbell, 1990;McKellar and Chatterton, 2009;Ghobadi Pour et al., 2018). However, quantitative study of eye lenses in some members of the Phacopina has shown that the lens numbers of the same species were not stable; their numbers could change with individual ontogeny and evolution (Thomas, 1998;Crônier and Clarkson, 2001), and even members of the same species living in different environments could show changes in the number of eye lenses (Crônier et al., 2004). ...
... Omegops Struve, 1976, one of the last phacopid trilobites, is found only in the Famennian and persists to the Devonian-Carboniferous boundary in many sections (Xiang, 1989;Brauckmann et al., 1992;Feist et al., 2021). Although Omegops has been found in Europe (Richter and Richter, 1933;Struve, 1976;Weber, 2000), North Africa (Alberti, 1972;Belka et al., 1999), Kazakhstan (Struve, 1976), Iran (Feist et al., 2003;Ghobadi Pour et al., 2018), Afghanistan (Farsan, 1998), and China (Xiang, 1981(Xiang, , 1989Yuan and Xiang, 1998), the number of specimens reported in the past was small, and the eyes of some specimens were not completely preserved. Therefore, it was difficult to carry out quantitative study on the eye lenses, and it was unclear whether the eye lenses of this genus were as diverse as those of other members of the Phacopina (Ghobadi Pour et al., 2018). ...
... Although Omegops has been found in Europe (Richter and Richter, 1933;Struve, 1976;Weber, 2000), North Africa (Alberti, 1972;Belka et al., 1999), Kazakhstan (Struve, 1976), Iran (Feist et al., 2003;Ghobadi Pour et al., 2018), Afghanistan (Farsan, 1998), and China (Xiang, 1981(Xiang, , 1989Yuan and Xiang, 1998), the number of specimens reported in the past was small, and the eyes of some specimens were not completely preserved. Therefore, it was difficult to carry out quantitative study on the eye lenses, and it was unclear whether the eye lenses of this genus were as diverse as those of other members of the Phacopina (Ghobadi Pour et al., 2018). ...
The suborder Phacopina, characterized by schizochroal eyes, is among the most common groups of trilobites in Devonian strata. The marine sediments of the Famennian in western Junggar, Xinjiang, contain abundant low-disparity phacopids, which have previously been designated to Omegops accipitrinus mobilis , Phacops circumspectans tuberculosus , and Omegops cornelius on the basis of small numbers of poorly preserved specimens. In this study, these phacopids were identified as two new species of Omegops , O. honggulelengensis n. sp. and O. xiangi n. sp., on the basis of nearly 200 well-preserved specimens. The intraspecific variations of eye lenses of these specimens were quantitatively analyzed. On the basis of differences in the total number, number of dorsoventral files, and arrangement of the eye lenses, the absence of lenses in the middle part of the visual surface, and asymmetry of the number and/or arrangement of lenses in the two eyes, it was concluded that the reasons for intraspecific variation in eye lenses of Late Devonian Omegops from western Junggar were different from previously described factors but were likely genetic or embryological malfunctions or abnormalities caused by pathological conditions. Diversity of lenses in the schizochroal eyes shows that the number and arrangement of eye lenses was not stable in Phacopina. Therefore, many specimens are needed for quantitative study to determine the true characteristics of the number or arrangement of eye lenses when these features are used in the systematic taxonomy of Phacopina.
UUID: http://zoobank.org/6bd14390-05fe-45ad-8eeb-3bf397a46a68
... During the last decades, a number of sections in eastern Alborz were studied due to their high fossil content and excellent preservation (e.g. Bozorgnia 1973;Brice et al. 1974;Ahmadzadeh-Heravi 1975;Jenny 1977;Coquel et al. 1977;Ashouri 1990Ashouri , 2006Wendt et al. 2005;Ghavidel-Syooki and Owens 2007;Hashemi 2011;Falahatgar and Mosaddegh 2012;Falahatgar et al. 2018;Abadi et al. 2015Abadi et al. , 2017Pour et al. 2018;Valeryi et al. 2018;Parvizi et al. 2021). Recently, Devonian/Carboniferous boundary (DCB) sections became a focus of international research (Aretz et al. 2013;Corradini et al. 2016). ...
Devonian/Carboniferous conodonts from the Chelcheli section in the Alborz Mountains were investigated. Although conodonts are generally less abundant in the entire section, important zonal index taxa of the widely applied conodont standard zonation could be used for a precise conodont zonation. Forty-seven conodont species belonging to fifteen genera were identified and led to the discrimination of fifteen conodont zones, ranging from the Palmatolepis minuta minuta Zone into the Scaliognathus anchoralis-Doliognathus latus Zone. At the Devonian/Carboniferous boundary (DCB), characteristic lithologies such as black shales and massive sandstones represent equivalents of the Hangenberg Black Shale and Hangenberg Sandstone. Close to the DCB, there is a small stratigraphic hiatus in the conodont record which might be a result of facies (shallow-water succession with no conodont record and siliciclastic rocks) rather than a period of non-deposition as the sedimentological record seems continuous. Similar to other DCB sections in shallow-water facies in Iran the two biostratigraphically important species Protognathodus kockeli and Protognathodus kuehni do not occur.
The Late Devonian witnessed landscape evolution, increased atmospheric O2 level, intense organic and volcanic activities and initial expansion of earliest wildfires. This paper is focused on petrographic and geochemical studies of Famennian inertinite-bearing marine shale facies in northern Kerman (central Iran), a Late Devonian key area in north of Gondwana. Our studies point to a wildfire activity. During the Famennian, the wildfire activity occurred in lowland vegetation (covered by lycopods) under warm and humid conditions. The moderately hot burning temperature (446.7 °C to 487.9 °C) of the fire and the type of the land vegetation suggest prevalence of a surface wildfire. Following the burning of the land plants, the ground became exposed to weathering that could result in erosion of the soil. Inputs of terrestrial organic matter, nutrients (particularly phosphate) and detrital materials into a nearshore marine environment were mainly controlled by proximity of the depositional environment to the terrestrial source, intense continental weathering of rocks and the soil in the land, wildfire and continental runoff during rainfall. Generally, preservation and enrichment of organic matter and formation of macerals were controlled by wildfire activity, transportation, oxidation, bacterial/fungal degradation and detrital input.
In Iranian geology, ophiolite is a collection of mafic and ultramafic rocks that may be regular and layered or mixed with each other due to tectonic stresses. Accompanying sedimentary rocks in deep areas is called "ophiolite complex" or "melange ophiolite". Iranian ophiolites are mostly in the form of narrow and more or less continuous bands that are often exposed along the main longitudinal faults. Geological evidence, especially the study of the chemistry of these assemblages in terms of isotopic ratios of Sr 86 / Sr 87 and the distribution of rare earth elements, indicates that their chemical composition is similar to that of oceanic rocks, so it is accepted that the assemblage Iranian ophiolites are the remnants of intercontinental derivations formed by rift and their escape, and during the movement of continents and subcontinents, are located in the location and along the land of ancient Paleotte seams. Phenomena such as rift of the shell and its escape due to the collision of the plates and the retention of these assemblies in the place of seams are the basis for the formation of these structures. Due to the tectonic and geological situation of Iran, the role of rift phenomenon is more. Although the type of magma formed in this system or the type of sediments along with the Iranian ophiolite series show differences and discrepancies with other ophiolite bands in the world, but in the eastern regions of Iran, the presence of destructive sediments such as flysch Silica shales, which are not compatible with the deep oceanic environment, are the reason why the ophiolite formation environment is close to the continental margin. Examination of the Iranian ophiolite bands shows that these assemblages formed during two separate phases. The first phase, an extension regime, created a deep rift in the earth's crust. These fissures, which extend to the asthenosphere, have been a good route for the placement of basaltic magmas. The second stage involves a compression phase that closes the initial rift, pushing ophiolite assemblages to the edge of adjacent continents. In this paper, we try to deal with the conditions of melange ophiolite formation in the west of Zarghan village, which is affected by the Zamand-Zarghan fault.
