Organic Molecular Paleohypsometry: A New Approach to Quantifying Paleotopography and Paleorelief
Organic Molecular Paleohypsometry: A New Approach to Quantifying Paleotopography and Paleorelief
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DOI：
10.3389/feart.2021.665324
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发表时间：
2021-09-17
影响因子：
2.9
通讯作者：
Ouimet, William
中科院分区：
文献类型：
--
作者：
Hren, Michael T.;Ouimet, William
稳定同位素古高度测定是量化造山带古海拔历史最常用的方法之一，但这种方法通常仅限于干旱至半干旱气候、具有明显地形雨影的山地系统和陆地盆地。我们提出了一种重建过去地形和地形的新方法，该方法使用有机分子生物标记的流域综合特征来量化河流输出的生物量的高度测量。由于陆地产生的生物分子是在各种全球气候条件下合成的，并且可以保存在陆地和海洋沉积物中，因此河流输送的沉积生物标志物的地球化学可以提供一种方法来研究一系列环境和沉积环境的地形演化，包括那些不太适合传统同位素古测温方法的环境和沉积环境。我们展示了台湾的一个例子，这是一个快速侵蚀的热带山地系统，其特点是生物量产生率高和有机物停留时间短，并讨论了可以影响分子同位素信号产生、传输和整合的关键因素。数据显示，在台湾高地形流域，河流沉积物可以记录整个流域产生的生物量的整合。低海拔河流沉积点的沉积生物标志物 Delta H-2(nC29) 通常与在当地土壤中观察到的 Delta H-2(nC29) 值有所偏移，并且与流域平均海拔产生的有机物的同位素组成一致。我们测试了不同的分子产生和侵蚀函数对河流沉积物中预期的 Delta H-2（nC29）的影响，并表明生物标志物/沉积物的产生和侵蚀的海拔依赖性差异可能仅在流域综合同位素信号中产生适度的差异。将河流生物标记同位素记录与其他全球造山带有机源海拔的定量估计联系起来可能会带来许多挑战，因为许多变量会影响河流系统中的分子产生和整合。我们讨论了影响山地系统中分子生物标志物同位素特征的重要参数，以及采用分子古地势测量方法来量化其他造山系统演化的框架。
Stable isotope paleoaltimetry is one of the most commonly used approaches for quantifying the paleoelevation history of an orogen yet this methodology is often limited to arid to semi-arid climates, mountain systems with a clear orographic rainshadow and terrestrial basins. We present a new approach to reconstructing past topography and relief that uses the catchment-integrated signature of organic molecular biomarkers to quantify the hypsometry of fluvially-exported biomass. Because terrestrially-produced biomolecules are synthesized over the full range of global climate conditions and can be preserved in both terrestrial and marine sediments, the geochemistry of fluvially-transported sedimentary biomarkers can provide a means of interrogating the evolution of topography for a range of environments and depositional settings, including those not well suited for a traditional isotope paleoaltimetry approach. We show an example from Taiwan, a rapidly eroding tropical mountain system that is characterized by high rates of biomass production and short organic residence time and discuss key factors that can influence molecular isotope signal production, transport and integration. Data show that in high relief catchments of Taiwan, river sediments can record integration of biomass produced throughout the catchment. Sedimentary biomarker delta H-2(nC29) in low elevation river deposition sites is generally offset from the delta H-2(nC29) value observed in local soils and consistent with an isotope composition of organics produced at the catchment mean elevation. We test the effect of distinct molecular production and erosion functions on the expected delta H-2(nC29) in river sediments and show that elevation-dependent differences in the production and erosion of biomarkers/sediment may yield only modest differences in the catchment-integrated isotopic signal. Relating fluvial biomarker isotope records to quantitative estimates of organic source elevations in other global orogens will likely pose numerous challenges, with a number of variables that influence molecular production and integration in a river system. We provide a discussion of important parameters that influence molecular biomarker isotope signatures in a mountain system and a framework for employing a molecular paleohypsometry approach to quantifying the evolution of other orogenic systems.