Macropolygon morphology, development, and classification on North Panamint and Eureka playas, Death Valley National Park CA
Macropolygon morphology, development, and classification on North Panamint and Eureka playas, Death Valley National Park CA
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加利福尼亚州死亡谷国家公园北帕纳明特和尤里卡普拉亚的大多边形形态、发育和分类
DOI：
10.1016/j.earscirev.2005.04.011
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发表时间：
2005
影响因子：
12.1
通讯作者：
Ward C. Smith
中科院分区：
文献类型：
--
作者：
P. Messina;P. Stoffer;Ward C. Smith
帕纳明特海滩和尤里卡海滩均位于死亡谷国家公园内，展现出一系列地表特征，包括裂缝、凹坑、土丘和植物覆盖的山脊，代表地形的高低，距海滩表面的起伏可达 2 m。航空照片显示，这些线性线通常会聚形成多边形，长度从几米到近一公里不等。这些特征与典型的普拉亚表面平坦、无植物、干燥的泥土的明亮的中间区域形成鲜明对比。 1999 年（北帕纳明特谷）和 2002 年（尤里卡谷）利用差分 GPS（全球定位系统）对普拉亚特征进行了地面实况测绘。高分辨率数字地图显示，两个普拉亚都具有相似规模和几何形状的大多边形，并且裂缝可以分为两个成因组之一：（1）与海岸平行或普拉亚内部干燥和收缩； (2)构造引起的裂缝。对尤里卡山谷这些特征的早期调查得出的结论是，它们的起源可能与古印第安社区的农业活动有关。尽管每个地点都有丰富的人类文物，但没有证据支持尤里卡普拉亚报告的表面特征起源于人类的推论。我们对 Playas 多边形起源的假设是基于我们目睹 Panamint Playa 山洪暴发后形成过程中的裂缝的偶然经历（1999 年 5 月）；我们的观察揭示了一个悖论，即上普拉亚地壳的饱和导致了一些干燥特征的形成。两年内对同一功能的后续访问是深入了解这些功能的演变和可能的寿命的基础。
Panamint and Eureka playas, both located within Death Valley National Park, exhibit a host of surficial features including fissures, pits, mounds, and plant-covered ridges, representing topographic highs and lows that vary up to 2 m of relief from the playa surface. Aerial photographs reveal that these linear strands often converge to form polygons, ranging in length from several meters to nearly a kilometer. These features stand out in generally dark contrast to the brighter intervening expanse of flat, plant-free, desiccated mud of the typical playa surface. Ground-truth mapping of playa features with differential GPS (Global Positioning System) was conducted in 1999 (North Panamint Valley) and 2002 (Eureka Valley). High-resolution digital maps reveal that both playas possess macropolygons of similar scale and geometry, and that fissures may be categorized into one of two genetic groups: (1) shore-parallel or playa-interior desiccation and shrinkage; and (2) tectonic-induced cracks. Early investigations of these features in Eureka Valley concluded that their origin may have been related to agricultural activity by paleo-Indian communities. Although human artifacts are abundant at each locale, there is no evidence to support the inference that surface features reported on Eureka Playa are anthropogenic in origin. Our assumptions into the genesis of polygons on playas is based on our fortuitous experience of witnessing a fissure in the process of formation on Panamint Playa after a flash flood (May 1999); our observations revealed a paradox that saturation of the upper playa crusts contributes to the establishment of some desiccation features. Follow-up visits to the same feature over 2 yrs' time are a foundation for insight into the evolution and possible longevity of these features.