Assessing tectonic and climatic causal mechanisms in foreland‐basin stratal architecture: insights from the Alborz Mountains, northern Iran
Assessing tectonic and climatic causal mechanisms in foreland‐basin stratal architecture: insights from the Alborz Mountains, northern Iran
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DOI：
10.1002/esp.3480
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发表时间：
2014-01
影响因子：
3.3
通讯作者：
P. Ballato;M. Strecker
中科院分区：
文献类型：
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作者：
P. Ballato;M. Strecker
伊朗北部Alborz山脉南部前陆盆地的特征是一层厚约7.3 km的中新世沉积岩层序，构成了三个盆地范围内的粗化-上升单元，历时106年。我们评估了现有的磁地层学、古气候重建、地层构造、沉积环境记录和沉积物物源数据，以表征构造生成的可容纳空间(A)和沉积物供应(S)之间的关系。我们的分析允许对特定强迫机制的地层学进行反转，记录因果关系，并为解释构造和气候（推断降水变化）在控制前陆盆地沉积物供应方面的相对贡献提供基础。其中，各基单元（17.5 ~ 16.0、13.8 ~ 13.1和10.3 ~ 9.6 Ma）典型的A/S > 1与剧烈的相退有关，反映了明显的构造沉降。在这些时间间隔内，干旱的气候条件、沉积物来源的变化以及造山带的加速挖掘表明，沉积物的供应很可能是由高抬升速率驱动的。相反,A / S < 1(13.8和13.8 -11毫安,单位1和2)反映相前积在急剧下降的构造沉降引起的局部内部盆地隆起。在此期间，气候持续干旱，挖掘活动频繁，表明沉积物供应再次受到构造控制。A/S < 1，在11-10.3 Ma和9‐6-7.6 Ma（也可能是6.2 Ma；单元2和3的顶部），也与两次广泛的进积有关，但发生在湿润阶段。第一个事件似乎与降水增加导致的沉积物供应的脉动有关。第二阶段反映了气候引起的沉积物供应增加和近前陆合并到造山带中的沉降减少之间的平衡。这反过来又造成了集水区的扩大，从而进一步增加了沉积物的供应。版权所有©2013 John Wiley & Sons， Ltd
The southern foreland basin of the Alborz Mountains of northern Iran is characterized by an approximately 7.3‐km‐thick sequence of Miocene sedimentary rocks, constituting three basin‐wde coarsening‐upward units spanning a period of 106 years. We assess available magnetostratigraphy, paleoclimatic reconstructions, stratal architecture, records of depositional environments, and sediment‐provenance data to characterize the relationships between tectonically‐generated accommodation space (A) and sediment supply (S). Our analysis allows an inversion of the stratigraphy for particular forcing mechanisms, documenting causal relationships, and providing a basis to decipher the relative contributions of tectonics and climate (inferred changes in precipitation) in controlling sediment supply to the foreland basin. Specifically, A/S > 1, typical of each basal unit (17.5–16.0, 13.8–13.1 and 10.3–9.6 Ma), is associated with sharp facies retrogradation and reflects substantial tectonic subsidence. Within these time intervals, arid climatic conditions, changes in sediment provenance, and accelerated exhumation in the orogen suggest that sediment supply was most likely driven by high uplift rates. Conversely, A/S < 1 (13.8 and 13.8–11 Ma, units 1, and 2) reflects facies progradation during a sharp decline in tectonic subsidence caused by localized intra‐basinal uplift. During these time intervals, climate continued to be arid and exhumation active, suggesting that sediment supply was again controlled by tectonics. A/S < 1, at 11–10.3 Ma and 9‐6–7.6 Ma (and possibly 6.2; top of units 2 and 3), is also associated with two episodes of extensive progradation, but during wetter phases. The first episode appears to have been linked to a pulse in sediment supply driven by an increase in precipitation. The second episode reflects a balance between a climatically‐induced increase in sediment supply and a reduction of subsidence through the incorporation of the proximal foreland into the orogenic wedge. This in turn caused an expansion of the catchment and a consequent further increase in sediment supply. Copyright © 2013 John Wiley & Sons, Ltd.