Fan morphology evidence on Late Quaternary deformation in the southern front of the Central and Eastern Alborz Mountains
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REVIEW PAPER
Fan morphology evidence on Late Quaternary deformation in the southern front of the Central and Eastern Alborz Mountains in the Eyvanekey, Garmsar, Semnan areas, Northern Iran Soheila Bouzari 1 Received: 29 August 2019 / Accepted: 3 September 2020 # Saudi Society for Geosciences 2020
Abstract Although numerous studies have been done on the Alborz Mountains, few have examined Quaternary events based on alluvial fans which are located in front of the southern limb of the Central and Eastern Alborz Mountains. This study analyzed the morphometric indexes for 131 alluvial fans (three generations) in the Eyvanekey, Garmsar, and Semnan areas (As, WLF, Bull, Fa, Fs, Fg, Fc, R) as well as for basins (Da, AF, T, Bs), mountain fronts (Fmf, Smf, Vf, Fd), and rivers (Sl). The morphometry results show that a young deformation in this area has caused on uplift in the crust along structures in the Alborz. The Garmsar area is more active than the Semnan area in which both are more active than the Eyvanekey area. All of the alluvial fan evolution in this area relate to the Quaternary events. The study on the information obtained from the exploitation wells and geoelectric profiles of the region shows that the Alborz uplift in the north is associated with the erosion and deposition of the new deposits in the form of alluvial fans. The bedrock behavior at the base of the fans has a direct effect on the formation of the second- and third-generation fans. The effect of the continual compressional tectonics in the Late Quaternary is associated with the uplifting evaporite masses, the uplifting hanging walls of the reverse faults, and the growth of the folded structures. Keywords Alluvial fans . Late Quaternary . Morphometry . Compressional tectonics . Alborz Mountains . Northern Iran
Introduction The intracontinental Alborz range in Northern Iran (Djamour et al. 2010) is an active deformation and seismic zone (Jackson et al. 2002). The Alborz Mountains, with ~ 600 km length, ~ 100 km width, and an almost eastern–western direction, is located on the southern margin of the Caspian Sea and the northern Central Iran. This range is extended from the Ararat Mountains in the west and joins the Hindu Kush Mountains in Afghanistan in the east, passing through the north of Iran (Allen et al. 2003). Alborz is divided into the three parts: Western, Central, and Eastern Alborz (Stöcklin 1974). The Central and Eastern Alborz are active orogenic Responsible Editor: François Roure * Soheila Bouzari [email protected]; [email protected] 1
Department of Geology, Islamic Azad University Tehran North Branch, Shahid Babaei Highway- Hakimiyeh exit- Shahid Abbaspour Boulevard, Tehran 1651153311, Iran
belts. They are located on the northern part of the Arabia– Eurasia collision zone. The deformation in these areas indicates that from the Late Cenozoic, they have been affected by oblique shortening in the NE direction (Jackson and Mckenzie 1984; Allen et al. 2003). Based on the tectonic observation (Allen et al. 2003; Ritz et al. 2006)
