Lithological interpretation
Lurestan arc stratigraphy documents the geological history of the northeastern Arabian margin, beginning with Paleozoic rifting and continuing through Mesozoic Neo-Tethys ocean opening and closure to continental collision in the late Eocene. According to balanced cross-sections within the Lurestan arc, the thickness covers about 6 to 10 km and 11 to 14 km in the Mesopotami foreland SW of the arc (Blanc et al., 2003; McQuarrie, 2004; Emami et al., 2010; Sadeghi and Yassaghi, 2016; Vergés et al., 2011).
Based on visual interpretation with the color combination of R G and B bands 5, 4, and 7, we identified three lithological divisions, which are Quaternary deposits (Qt), Bakhtyari (Bk), and Asmari Formation (As). Each lithological unit has a distinct texture, color, and relief. The Qt mainly comprises gravel, sand, silt, and clay along the river (coarse and fine grain). The Qt is characterized by blue, light red, and dark red colors (Figure 5.2). Blue represents the built-up areas, and light to dark red represents the agricultural areas and other vegetation covers. The Qt unit covers the majority area of the study area. It extends from the middle part near the Alvand River to the south area. This area extends approximately 45.62% of the study area.
The Bk is classified as a conglomerate, sandstone, and shale. Bk was found in the research region. According to the Landsat satellite image, Bk is dark and pale blue with a few dark red spots. The heavy red indicates the land is densely vegetated, whereas the light blue patch denotes open areas. Bk is also known for its small-height hills. This lithological unit accounts for approximately 3.45% of the studied area.
It consists of limestone and is the oldest rock formation in the study area. It was formed between the Oligocene and Miocene. The Landsat 8 image indicates a light green with a few light blue spots (Figure 5.2).
Figure (5.2): Interpreted of lithologic on Landsat OLI image RGB 567.
The light green color refers to the marks on the frontal outcrop, which has a rough texture. It is mainly distributed in the middle part of the study site. It is located in the core of the anticline. The total area is about 39.67% of the study area. Because both units have comparable visual morphology, color, texture, and relief, Qt and Bk are difficult to distinguish from Landsat 8. However, the Bk deposits can be located using the association notion. Qt primarily accumulates on the foot slope of denudation hills, where the denudation processes form it. As a result, the narrow flat zones that lie on the border between mountainous and flat lands are frequently referred to as Qt. Moreover, because of the alluvial processes close to the denudation hills, it has poor material sorting and a high clay concentration.
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