Pliocene orographic barrier uplift in the southern Central Andes
Pliocene orographic barrier uplift in the southern Central Andes
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DOI：
10.1130/g35538.1
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发表时间：
2014-08
期刊：
影响因子：
5.8
通讯作者：
H. Pingel;R. Alonso;A. Mulch;A. Rohrmann;M. Sudo;M. Strecker
中科院分区：
文献类型：
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作者：
H. Pingel;R. Alonso;A. Mulch;A. Rohrmann;M. Sudo;M. Strecker
沿着造山高原迎风侧翼的沉积盆地是古环境变化的宝贵档案，具有解决地表隆升和地形障形成历史的潜力。中安第斯山脉南部的山间盆地含有厚层的沉积物，通常与可确定年代的火山灰互层。我们涉及的氢同位素组成的变化，新第三纪的水化火山玻璃（三角洲D-g）第四纪填充在半干旱山间Humahuaca盆地（东部科迪勒拉，阿根廷西北部）的地形和相关的地形效应的时空变化。盆地地层中火山玻璃的δ D值（-117 ‰至-98 ‰）显示了研究区域内观察到的构造沉积事件的两个主要趋势。在6.0和3.5 Ma之间，三角洲D-g值减少了17个千分之一，这与汇水区的表面隆起有关。3.5 Ma后，三角洲D-g值显示氘突然富集，这与（1）达到阻止东部盆地边界范围内水分输送的阈值高程以及（2）盆地半干旱条件的开始有关。这种地形障碍在整个东部侧翼的中央安第斯山脉阻碍了水分输送到造山带内部，这可能有助于保持干旱和内部排水条件在邻近的安第斯高原。
Sedimentary basin fills along the windward flanks of orogenic plateaus are valuable archives of paleoenvironmental change with the potential to resolve the history of surface uplift and orographic barrier formation. The intermontane basins of the southern Central Andes contain thick successions of sedimentary material that are commonly interbedded with datable volcanic ashes. We relate variations in the hydrogen isotopic composition of hydrated volcanic glass (delta D-g) of Neogene to Quaternary fills in the semiarid intermontane Humahuaca Basin (Eastern Cordillera, northwest Argentina) to spatiotemporal changes in topography and associated orographic effects. delta D values from volcanic glass in the basin strata (-117 parts per thousand to -98 parts per thousand) show two main trends that accompany observed tectonosedimentary events in the study area. Between 6.0 and 3.5 Ma, delta D-g values decrease by similar to 17 parts per thousand; this is associated with surface uplift in the catchment area. After 3.5 Ma, delta D-g values show abrupt deuterium enrichment, which we associate with (1) the attainment of threshold elevations for blocking moisture transport in the basin-bounding ranges to the east, and (2) the onset of semiarid conditions in the basin. Such orographic barriers throughout the eastern flanks of the Central Andes have impeded moisture transport into the orogen interior; this has likely helped maintain aridity and internal drainage conditions on the adjacent Andean Plateau.