Wyniki wyszukiwania - BazTech

Ograniczanie wyników

2 2019

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Geochemistry of shales of the Qadir Member (Nayband Formation, Upper Triassic), East Central Iran (Tabas Block) : implications for provenance and palaeogeography

Zamaniyan Ehsan, Khanehbad Mohammad, Moussavi-Harami Reza, Mahboubi Asadollah

Geological Quarterly

2019

Vol. 63, No. 3

603--618

The Upper Triassic shale of the Qadir Member of the Nayband Formation, East Central Iran has been analysed geochemically to evaluate provenance and palaeogeography. The Qadir Member in the Parvadeh Coal Mine section is 450 metres thick, and includes sandstone, shale, coal, siltstone, and fossiliferous limestone. XRD analysis of shale samples from the Qadir Member largely indicated the presence of illite and chlorite, with small amounts of kaolinite and montmorillonite. On binary and triangular diagrams the data suggests an intermediate igneous source rock for these shales. Plotting the geochemical data on binary diagrams also indicates the tectonic setting of an active continental margin, perhaps reflecting the Early Cimmerian tectonic event with Neothetys subduction under the Iran Plate, and collision of the Iran Plate with Turan during the Late Triassic. The Chemical Index of Alteration (CIA) and Plagioclase Index of Alteration (PIA) values for shale from the Qadir Member of Nayband Formation vary from 74.04 to 80.54 (average 78.02) and 84.31 to 91.85 (average 87.81), respectively, indicating moderate to high chemical alteration in the source area and suggesting a semi-humid climate during deposition. The geochemical data and palaeogeographical models indicate that the Qadir Member shale was deposited on an active margin in a shoreline to transitional-marine setting.

Sporadoceratid ammonoids from the Shotori Range (east-central Iran) - a case of putative gigantism caused by hydraulic sorting?

Korn Dieter, Ghaderi Abbas, Devaere Léa, Hairapetian Vachik, Khanehbad Mohammad, Belka Zdzisław

Acta Geologica Polonica

2019

Vol. 69, no. 1

27--49

The Shotori Range of east-central Iran (east of Tabas) has yielded Famennian ammonoid assemblages dominated by the family Sporadoceratidae. Four genera Maeneceras Hyatt, 1884, Iranoceras Walliser, 1966, Sporadoceras Hyatt, 1884 and Erfoudites Korn, 1999 are represented. The conodont assemblage of one sample containing Iranoceras revealed an Upper marginifera Zone age. The ammonoid assemblages are characterised by comparatively large specimens; they reach conch diameters of 300 mm (including the body chamber) and the mean size is larger than 100 mm. The preservation of the material from the Shotori Range and size comparison with sporadoceratid assemblages from the Anti-Atlas of Morocco and the Rhenish Mountains of Germany suggest that hydraulic sorting has resulted in a bias towards large conchs, explaining the size distribution, rather than latitudinal differences. The new species Maeneceras tabasense is described; the genus Iranoceras is revised with a new description of the two species Iranoceras pachydiscus (Walliser, 1966) and Iranoceras pingue (Walliser, 1966).