Some Late Triassic gastropods from the Nayband formation in Central Iran

Sponges, along with scleractinian corals, are among the main reef-building organisms in Triassic reefs. Hypercalcified groups, including the chambered sphinctozoans, and the unchambered inozoans, chaetetids, and spongiomorphids, represent the most abundant Triassic reef-building sponges. Earlier workers have described elements of the latter group as “hydrozoans.” Hexactinellid sponges, abundant in some Permian reefs (e.g., in Texas, Finks, 1960), are rarely known from similar Triassic deposits, in general (Tichy, 1975), and particularly from Upper Triassic stratigraphic units. Hexactinellid sponges have been sporadically reported from well-investigated Upper Triassic reefs in the western Tethyan region (e.g., Keupp et al., 1989). However, a variety of hexactinellid sponges have been reported from Upper Triassic deposits and reefal limestones of the northern and central Tethyan realm (Boiko, 1990; Wu, 1989; Wu and Xiao, 1989; Rigby et al., 1998).

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Permian–Triassic magmatism in response to Palaeotethys subduction and pre-Late Triassic arrival of northeast Gondwana-derived continental fragments at the southern Eurasian margin: Detrital zircon evidence from Triassic sandstones of Central Iran

Gondwana Research ◽

10.1016/j.gr.2020.02.001 ◽

2020 ◽

Vol 83 ◽

pp. 118-131

Author(s):

Guido Meinhold ◽

Seyyedeh Halimeh Hashemi Azizi ◽

Jasper Berndt

Keyword(s):

Detrital Zircon ◽

Central Iran ◽

Late Triassic

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An unusual Late Triassic nuculid bivalve with divaricate shell ornamentation, and the evolutionary history of oblique ribs in Triassic bivalves

Journal of Paleontology ◽

10.1666/10-013.1 ◽

2011 ◽

Vol 85 (1) ◽

pp. 22-28 ◽

Cited By ~ 4

Author(s):

Michael Hautmann ◽

Babak Aghababalou ◽

Leo Krystyn

Keyword(s):

Posterior Part ◽

Late Triassic ◽

General Increase ◽

New Subgenus ◽

Extinction Event ◽

Concentric Pattern ◽

History Of ◽

Nayband Formation ◽

Mass Extinction Event ◽

Permian Mass Extinction

The new nuculid bivalveTrigonucula(Gonionucula)aciloidesnew subgenus and species from the upper Triassic Nayband Formation of Central Iran is described.Gonionuculadiffers fromTrigonuculas.s. by the presence of oblique ribs, which either deviate from a concentric pattern at the anterior shell part, or, as in the newly described type species, consist of a complex pattern of chevron-like ribs on the central part of the flank, plus an additional set of opisthocline to more or less acline ribs on posterior part of the flank. The oblique ribs ofGonionuculaprobably aided energy-efficient burrowing, which was advantageous in competing for food resources with less efficiently burrowing detritus feeders. The number of burrowing bivalve species with oblique ribs generally rose towards the end of the Triassic, which probably reflects increasing competition at a time when most niches were re-occupied after the end-Permian mass extinction event. The fact that oblique ribs were rare in Paleozoic bivalves suggests that the level of competition was higher in post-Paleozoic biota, which is in accordance with a general increase in metabolic rates, predation pressure, and ecospace occupation in the course of the Mesozoic.

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Wildfire Events at the Triassic-Jurassic Boundary of the Tabas Basin, Central Iran

10.21203/rs.3.rs-97849/v1 ◽

2020 ◽

Author(s):

Majid M Alipour ◽

Bahram Alizadeh ◽

AmirAbbas Jahangard ◽

AhmadReza GandomiSani

Keyword(s):

Major Change ◽

Lower Jurassic ◽

Upper Triassic ◽

Central Iran ◽

Sharp Boundary ◽

Depositional Settings ◽

Run Off ◽

Clastic Sediments ◽

Nayband Formation ◽

Microscopic Charcoal

Abstract This paper presents organic geochemical evidence pointing to the occurrence of wildfire events at the Triassic-Jurassic boundary in Central Iran. The studied outcrop section (the Kamarmacheh Kuh section) is comprised of the Upper Triassic Nayband Formation which passes conformably into the Lower Jurassic Ab-e-Haji Formation with no sharp boundary. Organic petrographical studies reveal a higher concentration of semi-fusinite macerals and microscopic charcoal at the boundary between studied formations. This observation can be an evidence for widespread wildfire events at the Triassic-Jurassic boundary of the studied area. Following these fires, vast areas of land were exposed for erosion and large volumes of clastic sediments were provided due to increased run-off. This agrees well with previous sedimentological and stratigraphical studies suggesting a major change in the depositional conditions from marine to non-marine at the Triassic-Jurassic boundary of the Tabas Basin. These findings can have important implications about paleo-depositional settings of the studied formations and the nature of the associated organic matter.

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Sedimentary environment and provenance of sandstones from the Qadir member in the Nayband Formation, Tabas block, east-central Iran

Boletín de la Sociedad Geológica Mexicana ◽

10.18268/bsgm2021v73n1a140920 ◽

2021 ◽

Vol 73 (1) ◽

pp. A140920

Author(s):

Ehsan Zamaniyan ◽

Mohammad Khanehbad ◽

Reza Moussavi-Harami ◽

Asadollah Mahboubi

Keyword(s):

Continental Margin ◽

Chemical Weathering ◽

Sedimentary Environment ◽

Active Continental Margin ◽

Central Iran ◽

Geochemical Data ◽

Delta Front ◽

Field Evidence ◽

Nayband Formation ◽

The Impact

Qadir Member of Nayband Formation, located in East of Central Iran, has developed to a great extent. Investigation of the lithofacies and sedimentary environment, resulted in identification of the deltaic and marine deposits. Based on field evidence and facies features, Qadir Member consists of two lithofacies, including carbonate and siliciclastic facies. The siliciclastic facies were identified as having four sandstone facies including Sr, Sh, Sp, St, three fine-grained lithofacies, including FI, Fm, Fl (Sr) / Sr (FI) and one coal facies. Also, regarding the field, laboratory studies, and identification of lithofacies, the coastal plain, deltaic (including deltaic plain, proximal delta front, distal delta front, and prodelta) and open marine environments were identified for Qadir Member which is is under the impact of tidal currents. The chemical weathering index (71%) indicated semi-arid to semi-humid conditions and plotting the geochemical data showed the provenance of re-cycling and active continental margin and because of Chemical Index of Alteration, the weathering rate was found to be rather medium to high. The geochemical diagrams also showed a probable source of the intermediate igneous and sedimentary rocks. The active continental margin conditions for this deposit could suggest the Neotethys subduction under Iran’s plate and volcanic activity at the end of Triassic, which coincided with the early Cimmerian orogeny in Alborz and Central East Iranian Microcontinent.

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