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Pliocene growth of the Dowlatabad syncline in Frontal Fars arc: Folding propagation across the Zagros Fold Belt, Iran
GSA Bulletin ( IF 3.9 ) Pub Date : 2021-07-01 , DOI: 10.1130/b35748.1
Mahdi Najafi 1 , Elisabet Beamud 2 , Jonas Ruh 3 , Frédéric Mouthereau 4 , Alireza Tahmasbi 5 , Gilen Bernaola 6 , Ali Yassaghi 7 , Hossein Motamedi 5 , Shahram Sherkati 8 , Mohammad Ghasem Hassan Goodarzi 5 , Jaume Vergés 9
Affiliation  

The integration of biostratigraphy, strontium isotope stratigraphy, and magnetostratigraphy allowed for the precise dating of the >3.0-km-thick marine to non-marine foreland sedimentary succession within the Dowlatabad growth syncline along the Frontal Fars arc in the Zagros Fold Belt that extends from eastern Turkey to southern Iran. This area was the missing link to complete the dating of syntectonic deposits in the Fars arc and quantify the migration of sedimentary belts as well as the propagation of folding across the entire Mesopotamian foreland basin. Both are essential for defining the interplay of basin evolution and sequence of folding.Deposition of the foreland marine marls in the Mishan Formation started at ca. 11.5 Ma. The transition to a non-marine basin infill occurred at 4.9 Ma by the progradation of thick fluvial deposits of the Aghajari Formation with a fast accumulation rate of 63 cm/k.y. The beginning of growth strata deposition and thus the onset of folding in the Dowlatabad syncline is dated at 4.65 Ma. The first appearance of carbonate conglomerates sourced from the Guri limestone at 2.8 Ma marked the progressive dismantling of the nearby growing anticlines. The tectonic deformation in the front of the Fars arc was active for at least 2.85 m.y. and ceased at 1.8 Ma before the deposition of the discordant and slightly folded Bakhtyari conglomerates characterized by a clast composition derived from the Zagros hinterland.The compilation of magnetostratigraphic ages reveals that both the migration of the Aghajari-Bakhtyari sedimentary belts and the propagation of the folding front was in-sequence toward the foreland at a rate close to 20 mm/yr in the Fars arc and 15 mm/yr in the Lurestan arc, in the last 20 m.y. These high rates of folding propagation are about one order of magnitude larger than age equivalent shortening rates (∼4 mm/yr in Fars arc and ∼2 mm/yr in Lurestan arc) and thus imply an efficient detachment level at the base of the deformed Arabian sedimentary cover.Numerical experiments on both the cover and basement sequences are designed to test the influence of inherited basement structures on the deformation propagation within the cover sequence, providing clues on the partly coeval in-sequence deformation of the Zagros Simply Folded Belt and the local out-of-sequence Mountain Frontal Fault system as illustrated by regional and local geology.

中文翻译:

前法尔斯弧中多拉塔巴德向斜的上新世生长:穿越伊朗扎格罗斯褶皱带的褶皱传播

生物地层学、锶同位素地层学和磁地层学的整合允许对沿扎格罗斯褶皱带前缘法尔斯弧的 Dowlatabad 生长向斜内 > 3.0 公里厚的海相到非海相前陆沉积序列进行精确测年土耳其东部至伊朗南部。该地区是完成法尔斯弧同构造沉积物年代测定和量化沉积带迁移以及褶皱在整个美索不达米亚前陆盆地传播的缺失环节。两者对于确定盆地演化和褶皱序列之间的相互作用都是必不可少的。密山组前陆海相泥灰岩的沉积开始于大约 10 年。11.5 毫安 向非海洋盆地填充的过渡发生在 4。9 Ma 由 Aghajari 组的厚河流沉积物以 63 cm/ky 的快速堆积速率进积。生长地层沉积的开始以及 Dowlatabad 向斜的折叠开始时间为 4.65 Ma。源自古里石灰岩的碳酸盐砾岩在 2.8 Ma 的首次出现标志着附近生长背斜的逐步拆除。Fars 弧前部的构造变形活跃了至少 2.85 my,并在 1.8 Ma 停止,然后在以来自 Zagros 腹地的碎屑成分为特征的不协调和轻微折叠的 Bakhtyari 砾岩沉积之前。
更新日期:2021-06-30
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