Petrography and Provenance of Sandstones from the Aghajari Formation, Folded Zagros Zone, Southwestern Iran

Abstract

The Late Miocene-Pliocene Aghajari Formation is exposed throughout the Folded Zagros Zone and consists of fluvial sediments. Detailed petrographic studies of sandstone samples from the Aghajari formation contain abundant quartz and lithic grains with subordinate feldspars, accessory amounts of micas. The feldspar content mostly ranges from 0 to 5 %. The abundance of lithic grains shows a wide range of variation (5.9 to 69.8 %). Although the lithics are mainly sedimentary, but fragments of metamorphic rocks are observed. Micas, including both muscovite and biotite, are generally less than 5 % of the total detrital grains. On the basis of the framework composition (point counting), the sandstones are classified as lithic arenite and sublitharenite. The modal analysis data of 75 collected (medium size and well sorted) samples, imply a recycled orogen (quartzose and transitional recycled) tectonic provenance. Moreover, petrographic point count data indicate the sources of quartzs are low-grade and middle to high-grade metamorphic rocks. Also quartz-rich (sedimentary) and granitic/gneissic are parent rocks for the Aghajari Formation sandstones.

Geochemistry of Sandstones from the Aghajari Formation, Folded Zagros Zone, Southwestern Iran: Implication for Paleoweathering condition, Provenance, and Tectonic Setting

“…The upper contact with Bakhtyari Formation is sometimes gradual and conformable and occasionally abrupt and unconformable. In the study area, the lower contact with Razak Formation and the upper contact with Bakhtyari Formation are gradual [15].…”

“…In fact, the Zagros fold-thrust belt lies on the northeastern margin of the Arabian plate and has been divided into NW-SE trending structural zones (imbricated and simply folded belt) parallel to the plate margin separated by major fault zones such as the High Zagros and mountain front faults. In addition to the tectonic divisions parallel to the mountain belt, the belt has also been divided laterally to the Lurestan, Dezful embayment and Fars regions from northwest to southeast [15].…”

Sedimentology and palaeogeography of conglomerates from the Aghajari Formation in Zagros Basin, SW Iran

“…LCCSC Lithofacies (Aghajari Formation) are the products of alluvial systems, mainly bedload streams. These lithofacies can be interpreted as channel lags [8][9][10]18]. Horizontally stratified or unstratified conglomerates with clast imbrication record deposition on a flat bed with vigorous grain transport such as might occur on the top of a longitudinal bar or on a channel floor and textural variation may relate to water stage changes [19].…”

“…In order to present detailed information about this topic, one of the obvious outcrops of this formation in the southeast of Sarvestan was investigated, and thereby the palaeogeography of the region was determined. Analytical work on sedimentology shows that these coarse-grained clastic rocks were deposited as fluvial deposits by temporary or permanent rivers in response to uplift of the Zagros Mountain range in the Upper Miocene-Pliocene [1][2][3][4][5][6][7][8][9][10]. Tectonically the area is part of a foreland basin [5,11] filled with a thick sequence of predominantly coarse clastic sedimentary rocks.…”

“…Palaeoalluvial structures were examined in a wide range of tectonic settings, including foreland basins. Traditionally, the sediments of foreland basins, also the Aghajari Formation sediments, were considered as continental molasse [8][9][10]12]. …”