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首页> 外文期刊>Geomorphology >Geomorphic and stratigraphic evidence of incision-induced halokinetic uplift and dissolution subsidence in transverse drainages crossing the evaporite-cored Barbastro-Balaguer Anticline (Ebro Basin, NE Spain)
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Geomorphic and stratigraphic evidence of incision-induced halokinetic uplift and dissolution subsidence in transverse drainages crossing the evaporite-cored Barbastro-Balaguer Anticline (Ebro Basin, NE Spain)

机译：横切蒸发成岩的Barbastro-Balaguer背斜（西班牙内布拉斯加州埃布罗盆地）的横向排水中，切口引起的盐岩运动抬升和沉降沉降的地貌和地层证据

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The evaporite-cored Barbastro-Balaguer Anticline, located in the northeastern sector of the Ebro Tertiary Basin, NE Spain, is traversed perpendicularly by several drainages coming from the Pyrenees, including the Cinca, Noguera-Ribagorzana and Segre rivers. The terraces associated with these discordant fluvial systems, deposited upon evaporitic and detrital formations across the anticline, allow the analysis of geomorphic and stratigraphic anomalies related to the soluble and ductile nature of the halite-bearing rocks in the core of the anticline. Geomorphological mapping reveals that the gravels discontinuously capping the evaporitic core of the anticline, together with some alluvial mantles disconnected from the present-day river valleys, constitute the oldest sediments deposited under exorheic conditions in this sector of the Ebro Tertiary Basin. These alluvial deposits inset into the basin fill record an early post-capture palaeogeographic stage during which the drainage was dominated by unconfined distributary channels developed on extensive alluvial fans fed by perennial rivers coming from the Pyrenees. The terraces associated with the present-day fluvial valleys correspond to a later palaeogeographic stage characterized by a well-integrated drainage confined to fluvial valleys entrenched in the basin fill. These terraces show evidence of both dissolution-induced subsidence and halokinesis restricted to areas underlain by the evaporites of the anticline core. The deposits of the highest terrace levels of the Noguera-Ribagorzana and Segre rivers and its tributaries, Lo Reguer Creek and Farfanya River, are locally thickened filling basins generated by dissolution-induced syn-sedimentary subsidence up to several kilometers long and more than 100 m deep. Subsidence caused by the karstification of the evaporites reached higher magnitude and extent during the early stages of development of the new external drainage network, when the more soluble halite-bearing units were closer to the new incisional base level. Most likely, the development of a thick caprock, rich in less soluble sediments, has hampered dissolution and subsidence processes in subsequent stages. Incision-induced halokinetic deformation is locally recorded by differentially uplifted terraces dipping away from the valley. The increasing differential loading caused by the entrenchment of the fluvial systems has driven the lateral and upward flow of salt-rich evaporites from the valley margins towards the valley bottom. A minimum long-term uplift rate of 0.3 mm/yr has been calculated for a titled OSL-dated Upper Pleistocene terrace of the Cinca River valley. The capture of the Ebro Basin and its change to exorheic conditions have played an instrumental role in the development of the Quaternary gravitational deformations associated with the evaporitic bedrock. The new incisional drainage network propitiated the karstification and evacuation of large amounts of evaporites, and its entrenchment has created adequate differential loading conditions for the salt to flow towards the valley floors.
机译：蒸发岩心的Barbastro-Balaguer背斜位于西班牙东北部埃布罗第三纪盆地的东北部，被比利牛斯山脉的多条排水渠垂直穿过，包括Cinca，Noguera-Ribagorzana和Segre河流。与这些不协调河流系统相关的阶地，沉积在整个背斜的蒸发和碎屑地层上，可以分析与背斜中心含盐岩的岩石的可溶性和韧性有关的地貌和地层异常。地貌图显示，不连续地覆盖在背斜的蒸发岩芯上的砾石，以及与当今河谷断开的一些冲积地幔，构成了在埃布罗第三纪盆地此区在高位条件下沉积的最古老的沉积物。这些冲积沉积物进入盆地填充物，记录了捕获后的早期古地理阶段，在此阶段，排水主要由比利牛斯山脉多年生河流域提供的广泛冲积扇所形成的无限制分布河道支配。与当今河谷相联系的阶地对应于后期的古地理阶段，其特征是排水良好，仅限于深陷于盆地填充物中的河谷。这些阶地显示出溶解诱导的沉陷和晕机现象的证据，这些现象仅限于背斜岩芯蒸发层所覆盖的区域。 Noguera-Ribagorzana河和Segre河及其支流Lo Reguer Creek和Farfanya河的最高阶地层沉积物是由溶解诱导的同沉积沉降产生的局部增厚的充填盆地，其沉降长达数公里且超过100 m深。在新的外部排水网络发展的早期阶段，当溶解度更高的含盐分岩的单元更接近于新的切开基础水平时，由蒸发岩的岩溶作用引起的沉陷达到了更高的幅度和程度。最有可能的是，厚的盖层的发展，富含难溶的沉积物，阻碍了后续阶段的溶解和沉降过程。切口引起的晕动作用变形是通过从山谷中倾斜的不同隆起的阶地局部记录的。由河流系统的纠缠所引起的不断增加的差异载荷驱使富盐蒸发物的横向和向上流动从山谷边缘向山谷底部流动。对于辛卡河谷地带OSL日期的上更新世阶地，已计算出最小长期上升速率为0.3毫米/年。埃布罗盆地的捕获及其对溢流条件的变化在与蒸发基岩有关的第四纪重力变形的发展中发挥了重要作用。新的切线排水网络促进了岩溶作用和大量蒸发岩的疏散，其固结为盐分流向谷底创造了足够的差异负载条件。

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