Abstract Alluvial fans are important depositional landforms that offer valuable records of terrestrial sedimentation history if their surfaces can be mapped and dated accurately. Unfortunately, as this often depends on detailed field mapping and intensive absolute dating techniques, it can be a challenging, expensive and time-consuming exercise. In this study, we demonstrate that quantitative information about the ages of alluvial fan surfaces in Owens Valley, California, is recorded by Landsat-8 multispectral satellite imagery. We show that systematic changes in the wavelength-dependent brightness of fan surfaces occur gradually over a timescale of ~100 kyr in this semi-arid setting, and are highly correlated with known deposit ages. Using spectro-radiometry and X-ray diffraction analysis of sediment samples collected in the field, we interpret that surface reflectance evolves primarily in response to the in-situ production of secondary illite and iron oxide by weathering in this landscape. Furthermore, we demonstrate that first-order predictions of absolute fan surface age can be derived from multispectral imagery when an initial age calibration is available. These findings suggest that multispectral imagery, such as Landsat data, can be used (i) for preliminary mapping of alluvial fans prior to detailed field work and before choosing sampling sites for conventional dating techniques, and (ii) to extend age models to un-dated neighbouring surfaces with equivalent physical properties, once an age-brightness calibration has been established.

中文翻译：

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加利福尼亚州欧文斯谷的 Landsat-8 图像记录的冲积扇表面年龄

摘要 冲积扇是重要的沉积地貌，如果能够准确地测绘和测年，可以提供宝贵的陆地沉积历史记录。不幸的是，由于这通常取决于详细的实地测绘和密集的绝对测年技术，因此这可能是一项具有挑战性、成本高昂且耗时的工作。在这项研究中，我们证明了有关加利福尼亚州欧文斯谷冲积扇表面年龄的定量信息是由 Landsat-8 多光谱卫星图像记录的。我们表明，在这种半干旱环境中，扇面波长相关亮度的系统变化在 ~100 kyr 的时间尺度内逐渐发生，并且与已知的沉积年龄高度相关。利用光谱辐射测定法和 X 射线衍射分析现场采集的沉积物样品，我们解释说，表面反射率的演变主要是由于在该景观中风化而产生的次生伊利石和氧化铁的原位产生。此外，我们证明了当初始年龄校准可用时，可以从多光谱图像中推导出绝对扇面年龄的一阶预测。这些发现表明，多光谱图像，例如 Landsat 数据，可用于 (i) 在详细的实地工作之前和在选择常规测年技术的采样点之前对冲积扇进行初步测绘，以及 (ii) 将年龄模型扩展到非一旦建立了年龄亮度校准，则具有等效物理特性的过时相邻表面。