Sandstone petrography and geochemistry of the Nayband Formation (Upper Triassic, Central Iran): Implications for sediment provenance and tectonic setting

Abstract

The Upper Triassic (Norian–Rhaetian) Nayband Formation is situated at the southwestern margin of Central East Iranian Microcontinent and records Eo-Cimmerian events. The formation is composed of mixed carbonate-siliciclastic deposits. This study presents information on the tectonic reconstruction and palaeoclimate of the southwestern margin of Central East Iranian Microcontinent during the Late Triassic. Petrography and modal analyses of sandstones show a variety of quartz-rich petrofacies including subarkose, lithic arkose, sublitharenite, feldspathic litharenite and litharenite. The combined modal analysis and geochemical results of major and trace elements of the sandstone samples represents mixed sedimentary, intermediate, felsic igneous rocks and moderate- to high-grade metamorphic provenance areas. The major elements and modal analyses of the Nayband Formation sandstone samples suggest an active continental margin tec-tonic settings. The palaeoclimatic conditions were sub-humid to humid with relatively low to moderate weathering in the source area which is in agreement with the palaeogeography and palaeotectonic history of southwestern margin of Central East Iranian Microcontinent during the Late Triassic.

Magnetic Fabric and Paleomagnetic Analyses of the Zaghar and Tafresh Areas, Central Urumieh-Dokhtar Magmatic Arc, Iran

“…The samples are neither foliation nor lineation dominant (Figure 18b). According to [85], the investigated dyke The Upper Triassic (Norian-Rhaetian) Nayband Formation is situated at the southwestern margin of the Central East Iranian Microcontinent and records Eo-Cimmerian events [83]. Therefore, it seems the magnetic fabric orientations of the Nayband Formation (i.e., sub-horizontal K 1 and sub-vertical K 3 ) indicate that δ 1 was vertical and is representative of lithostatic compression (Figure 17a).…”

“…Magnetic lineations in extensional settings have been defined by the crenulation of the clay minerals (i.e., paramagnetic minerals) parallel to the stretching direction [80] or by the intersection axis resulting from the girdling of phyllosilicate basal planes parallel to the stretching direction [81,82]. The Upper Triassic (Norian-Rhaetian) Nayband Formation is situated at the southwestern margin of the Central East Iranian Microcontinent and records Eo-Cimmerian events [83]. Therefore, it seems the magnetic fabric orientations of the Nayband Formation (i.e., sub-horizontal K1 and sub-vertical K3) indicate that δ1 was vertical and is representative of lithostatic compression (Figure 17a).…”