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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >100 kyr fluvial cut-and-fill terrace cycles since the Middle Pleistocene in the southern Central Andes, NW Argentina
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100 kyr fluvial cut-and-fill terrace cycles since the Middle Pleistocene in the southern Central Andes, NW Argentina

机译：自从中央安第斯山州南部的中央南部（NW Argentina）以来，100 kyr河切割露台周期

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Fluvial fill terraces in intermontane basins are valuable geomorphic archives that can record tectonically and/or climatically driven changes of the Earth-surface process system. However, often the preservation of fill terrace sequences is incomplete and/or they may form far away from their source areas, complicating the identification of causal links between forcing mechanisms and landscape response, especially over multi-millennial timescales. The intermontane Toro Basin in the southern Central Andes exhibits at least five generations of fluvial terraces that have been sculpted into several-hundred-meter-thick Quaternary valley-fill conglomerates. New surface-exposure dating using nine cosmogenic Be-10 depth profiles reveals the successive abandonment of these terraces with a 100 kyr cyclicity between 75 +/- 7 and 487 +/- 34 ka. Depositional ages of the conglomerates, determined by four Al-26/Be-10 burial samples and U-Pb zircon ages of three intercalated volcanic ash beds, range from 18 +/- 141 to 936 +/- 170 ka, indicating that there were multiple cut-and-fill episodes. Although the initial onset of aggradation at similar to 1 Ma and the overall net incision since ca. 500 ka can be linked to tectonic processes at the narrow basin outlet, the superimposed 100 kyr cycles of aggradation and incision are best explained by eccentricity-driven climate change. Within these cycles, the onset of river incision can be correlated with global cold periods and enhanced humid phases recorded in paleoclimate archives on the adjacent Bolivian Altiplano, whereas deposition occurred mainly during more arid phases on the Altiplano and global interglacial periods. We suggest that enhanced runoff during global cold phases - due to increased regional precipitation rates, reduced evapotranspiration, or both - resulted in an increased sediment-transport capacity in the Toro Basin, which outweighed any possible increases in upstream sediment supply and thus triggered incision. Compared with two nearby basins that record precessional (21-kyr) and long-eccentricity (400-kyr) forcing within sedimentary and geomorphic archives, the recorded cyclicity scales with the square of the drainage basin length. (C) 2017 Elsevier B.V. All rights reserved.
机译：跨门盆地的河流填充梯田是有价值的地貌档案，可以记录地面和/或气动变化的地面处理系统。然而，通常，填充露台序列的保存是不完整的和/或它们可以从他们的来源区形成远方，使迫使机制与横向响应之间的因果关系的识别复杂化，特别是在多千禧一代的时间表之间。中部南部的间歇班托罗盆地展示了至少五代的河梗梗，这已经雕刻成几百米厚的四元谷填充集团。使用九个宇宙的BE-10深度配置文件的新表面曝光约会揭示了在75 +/- 7和487 +/- 34 ka之间的100kyr循环的连续放弃这些露台。由4个Al-26 / BE-10埋下样品和U-PB锆石沉积的三个插入的火山灰床，范围为18 +/- 141至936 +/-170 ka，确定的沉积年龄和U-Pb锆石均测定，表明存在多个切割和填充集。虽然自CA以来类似于1 mA和整体净切口的初始发作。可以通过偏心驱动的气候变化最佳地解释，500 kA可以与窄盆地出口处的构造过程相关联，通过偏心驱动的气候变化，最好解释。在这些循环中，河切口的发作可以与全局冷时段相关，并且在相邻的玻利维亚Altiplano上的古平衡档案中记录的增强潮湿阶段，而沉积主要发生在Altiplano和全球间冰片时期的更多干旱期间。我们建议在全球冷阶段期间增强径流 - 由于区域降水率增加，降低蒸发或两者 - 导致托罗盆地中的沉积物运输能力增加，这超过了上游沉积物供应的任何可能增加，因此触发了切口。与两种附近的盆地相比，记录了预铸（21-Kyr）和长偏心（400-Kyr）强迫沉积和地貌档案中的迫使，记录的循环性与排水盆长的平方缩放。 （c）2017年Elsevier B.V.保留所有权利。

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