The Aghajari (Upper Fars) Formation in the Folded Zagros Zone, Iran: Insights to Identify Facies, Architectural Elements, Fluvial Systems, Petrography and Provenance

Abstract

Abstract:The Aghajari Formation, called also the Upper Fars, develops throughout the Folded Zagros Zone and its thickness in the type section in southwest of Iran is 2966 meters. To analyze the sedimentary basin of this Formation, lithofacies, architectural elements and petrofacies of the related deposits in a section in southeast of Sarvestan in Fars Province of Iran with a thickness of 2221.45 meters were examined. Microscopically studying thin sections, the petrography and the occurrence of the deposits were determined. In this section, 16 lithofacies, 10 architectural elements and 2 sandstone petrofacies were identified. The lithofacies were divided into two major and minor groups, in which the major lithofacies consist of coarse‐grained (Gh, Gp, Gt and Gm), medium‐grained (Sh, Sp, St, Sl, Sm, Sr and Ss and fine‐grained ones (Fm, Fl and Fsm), and the minor lithofacies were evaporative and mixed silisiclastic‐carbonate. The identified architectural elements are CH, SB, GB, LA, DA, CR, CS, LV, LS, CH (FF) and FF. By combining evidences from facies analysis and architectural elements together, the Aghajari Formation was divided into three parts in which the related sedimentation environments, from top to bottom, are gravel, gravel‐sand and fine‐grained meandering river respectively. There have also been playas and shoreface in the lower part. Based on petrography, the sandstones of this formation were classified into two groups: litharenite and sublitharenite. The origin of these deposits (sandstones) was appointed to the recycled orogeny and the source of quartz is low and medium to high metamorphic rank. Using the field evidences, the paleocurrent direction was achieved indicating the direction of the paleocurrent from northwest to southeast at the time of deposition. It is hoped that these data can be used in the interpretation of the basin and reconstruction of the paleogeography in the local and regional scales.

Lithofacies, architectural elements and tectonic provenance of the siliciclastic rocks of the Lower Permian Dorud Formation in the Alborz Mountain Range, Northern Iran

“…Accordingly, the studied lithofacies of the Dorud Formation are classified into the coarse-, medium-and fine-grained deposits ( Table 1). The textural and architectural changes of the gravels are the result of traction, variable to the flow and deposit transportation rate because gravels may be deposited and/or transported several times (Miall, 1985;Lowey, 2007;Ghazi and Mountney, 2009;Sahraeyan et al, 2013). The medium-grained deposits (sandstones) may be deposited alternatively during the traction mechanism (Miall, 2000;Boggs, 2006Boggs, , 2009Khalifa and Catuneanu, 2008).…”

“…Such primary structures are abundantly found in the sandstone facies of the Dorud Formation. The fine-grained sediments such as mud, may be deposited during the suspension process and tend to overlays coarser deposits Mountney, 2009, 2010;Sahraeyan and Bahrami, 2012;Sahraeyan et al, 2013).…”

“…The lower contact of this lithofacies is erosive. These coarse-grained deposits have been probably formed due to the destruction of the walls and floor of river channel and have remained in the deepest part of the channel (channel floor) (Reincks and Singh, 1986;Sahraeyan et al, 2013). The primary laminations have been preserved in some grains (rip-up clast).…”

“…4F). This lithofacies is more likely to have been formed in the upper rates of water flow and low sedimentary load (Miall, 1996(Miall, , 2000Mountney, 2009, 2010;Sahraeyan et al, 2013).…”

“…The continuation of this trend also causes lateral accretion of channel and forms point bar deposits (Boggs, 2006;Ghazi and Mountney, 2009;Sahraeyan et al, 2013). In this environment, finer deposits are placed on the coarser deposits.…”