Mixed Signals From the Stable Isotope Composition of Precipitation and Plant Waxes in the Northern Tropical Andes
Mixed Signals From the Stable Isotope Composition of Precipitation and Plant Waxes in the Northern Tropical Andes
复制标题
DOI：
10.1029/2022jg006932
复制
发表时间：
2022-12
期刊：
影响因子：
--
通讯作者：
L. Pérez‐Angel;J. Sepúlveda;C. Montes;Jamila J. Smith;P. Molnar;C. González‐Arango;K. Snell;N. Dildar
中科院分区：
文献类型：
--
作者：
L. Pérez‐Angel;J. Sepúlveda;C. Montes;Jamila J. Smith;P. Molnar;C. González‐Arango;K. Snell;N. Dildar
我们评估了降水和植物蜡的稳定同位素组成作为北方热带安第斯山脉古高度测量和古水文学代表的有效性。本文报道了哥伦比亚东科迪勒拉山脉沿着东西两侧现代土壤中降水的氢（δ 2 Hp）和氧（δ 18 Op）同位素值以及植物蜡（δ 2 Hwax）的氢同位素值。东翼的正C29、正C31和正C33正构烷烃的δ 2 Hp、δ 18 Op以及未加权平均δ 2 Hwax值显示出对海拔的依赖性（R2分别为0.90、0.82和0.65）。与此形成鲜明对比的是，无论是降水还是植物蜡的稳定同位素组成与δ 2 Hwax和δ 2 Hp之间的海拔相关性（R2 0.05）相关。总体而言，东科迪勒拉山脉东侧沿着的δ 2 Hwax值似乎遵循简单瑞利蒸馏过程的趋势，这与南美洲安第斯山脉东侧其他地方的研究一致。δ 2 Hp和δ 18 Op以及δ 2 Hwax都不能提供西翼过去海拔的可靠估计，这可能是由于水汽源混合、蒸发叠加、对比植物群落和/或蒸散差异造成的。因此，δ 2 Hwax仅适用于安第斯山脉东侧的古水文学和古测高重建，而基于东科迪勒拉最高点以西的δ 2 Hp和/或δ 18 Op的解释除了降水量外还需要考虑水分来源的混合。
We evaluate the efficacy of the stable isotope composition of precipitation and plant waxes as proxies for paleoaltimetry and paleohydrology in the northern tropical Andes. We report monthly hydrogen (δ2Hp) and oxygen (δ18Op) isotope values of precipitation for an annual cycle, and hydrogen isotope values of plant waxes (δ2Hwax) obtained from modern soils along the eastern and western flanks of the Eastern Cordillera of Colombia. δ2Hp, δ18Op, as well as the unweighted mean δ2Hwax values of n‐C29, n‐C31, and n‐C33 n‐alkanes in the eastern flank show a dependence on elevation (R2 = 0.90, 0.82, and 0.65, respectively). In stark contrast, the stable isotope compositions of neither precipitation nor plant waxes from the western flank correlate with elevation (R2 0.05) correlation between δ2Hwax and δ2Hp. In general, δ2Hwax values along the eastern flank of the Eastern Cordillera seem to follow the trend of a simple Rayleigh distillation process that is consistent with studies elsewhere on the eastern side of the Andes in South America. Neither δ2Hp nor δ18Op, and therefore δ2Hwax, offer reliable estimates of past elevations in the western flank, due perhaps to water vapor source mixing, evaporation overprint, contrasting plant communities, and/or differences in evapotranspiration. Thus, δ2Hwax is only reliable for paleohydrology and paleoaltimetry reconstructions on the eastern flank of the Andes, whereas interpretations based on δ2Hp and/or δ18Op west of the highest point of the Eastern Cordillera need to consider mixing of moisture sources in addition to precipitation amount.