Relative timing of uplift along the Zagros Mountain Front Flexure (Kurdistan Region of Iraq): Constrained by geomorphic indices and landscape evolution modeling
Relative timing of uplift along the Zagros Mountain Front Flexure (Kurdistan Region of Iraq): Constrained by geomorphic indices and landscape evolution modeling
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DOI：
10.5194/se-10-663-2019
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发表时间：
2019-05
期刊：
影响因子：
3.4
通讯作者：
Mjahid Zebari;C. Grützner;P. Navabpour;K. Ustaszewski
中科院分区：
文献类型：
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作者：
Mjahid Zebari;C. Grützner;P. Navabpour;K. Ustaszewski
摘要。山前弯曲标志着扎格罗斯褶皱冲断带前缘的一个主要地形台阶。它的特点是在基底断层上有许多活动背斜。到目前为止，人们对背斜的相对活动、它们的演化以及地壳变形如何随时间迁移知之甚少。我们对位于伊拉克库尔德斯坦地区山前弯曲上壁上的三个沿走向背斜（从东南到西北：Harir、Perat和Akre）的相对景观成熟度进行了评估，以确定最活跃的构造，并深入了解褶皱冲断带的演化。利用地形指数，如地形曲线、地形积分、地表粗糙度和地表指数来评价景观成熟度。随后，利用Harir背斜现今地形作为基础模型，运行数值景观演化模型来估计背斜开始生长的相对时间差。采用水流动力方程来引入河流侵蚀，采用斜坡扩散方程来解释泥沙输运。在模型演化的不同时间步长下，我们计算了由基础模型生成的地貌指数。虽然阿克雷背斜显示出深切的山谷和超前的侵蚀，但哈里和佩拉特背斜的表面相对光滑，并且被认为比阿克雷背斜更年轻。景观成熟度等级由西北向东南递减。将模型输出的地貌指标与佩拉特背斜和阿克雷背斜现今地形的地貌指标进行比较表明，假设沿三个背斜在恒定条件下的侵蚀和恒定的岩石隆升速率，哈里尔背斜分别需要80-100和160-200 kyr才能达到佩拉特背斜和阿克雷背斜的成熟水平。由于三个背斜的地貌控制因素（岩性、构造环境和气候）相似，在持续生长和侵蚀条件下，我们推断阿克雷背斜的隆升开始于哈里尔背斜的160-200 kyr，而佩拉特背斜则处于中等时期。哈里尔背斜本身向北西扩展，表明在不同的段内抬升是独立的。我们的相对年龄差估计方法可以应用于山前弯曲地区的许多其他背斜，以构建该带的时间演化模型。
Abstract. The Mountain Front Flexure marks a dominant topographic step in the frontal part of the Zagros Fold–Thrust Belt. It is characterized by numerous active anticlines atop of a basement fault. So far, little is known about the relative activity of the anticlines, about their evolution, or about how crustal deformation migrates over time. We assessed the relative landscape maturity of three along-strike anticlines (from SE to NW: Harir, Perat, and Akre) located on the hanging wall of the Mountain Front Flexure in the Kurdistan Region of Iraq to identify the most active structures and to gain insights into the evolution of the fold–thrust belt. Landscape maturity was evaluated using geomorphic indices such as hypsometric curves, hypsometric integral, surface roughness, and surface index. Subsequently, numerical landscape evolution models were run to estimate the relative time difference between the onset of growth of the anticlines, using the present-day topography of the Harir Anticline as a base model. A stream power equation was used to introduce fluvial erosion, and a hillslope diffusion equation was applied to account for colluvial sediment transport. For different time steps of model evolution, we calculated the geomorphic indices generated from the base model. While Akre Anticline shows deeply incised valleys and advanced erosion, Harir and Perat anticlines have relatively smoother surfaces and are supposedly younger than the Akre Anticline. The landscape maturity level decreases from NW to SE. A comparison of the geomorphic indices of the model output to those of the present-day topography of Perat and Akre anticlines revealed that it would take the Harir Anticline about 80–100 and 160–200 kyr to reach the maturity level of the Perat and Akre anticlines, respectively, assuming erosion under constant conditions and constant rock uplift rates along the three anticlines. Since the factors controlling geomorphology (lithology, structural setting, and climate) are similar for all three anticlines, and under the assumption of constant growth and erosion conditions, we infer that uplift of the Akre Anticline started 160–200 kyr before that of the Harir Anticline, with the Perat Anticline showing an intermediate age. A NW-ward propagation of the Harir Anticline itself implies that the uplift has been independent within different segments. Our method of estimating the relative age difference can be applied to many other anticlines in the Mountain Front Flexure region to construct a model of temporal evolution of this belt.