Near-surface structure of a large linear dune and an associated crossing dune of the northern Namib Sand Sea from Ground Penetrating Radar: Implications for the history of large linear dunes on Earth and Titan

IF 3.1 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Aeolian Research Pub Date : 2022-08-01 DOI:10.1016/j.aeolia.2022.100813
Clayton K. Chandler , Jani Radebaugh , John H. McBride , Thomas H. Morris , Clement Narteau , Karl Arnold , Ralph D. Lorenz , Jason W. Barnes , Alex Hayes , Sébastien Rodriguez , Tammy Rittenour
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引用次数: 2

Abstract

We imaged the near-surface sedimentary structures of a large linear dune, flanking dune forms and an associated crossing linear dune never before studied in the northern Namib Sand Sea using 200-MHz Ground-Penetrating Radar (GPR). The dry, uniform sandy conditions and wavelength used allowed for highly detailed observations of sedimentary structures to depths of ∼ 12 m across a >1km lateral scan. Sedimentary features observed in the main linear dune include scouring and abrupt changes in strata such as trough cross stratification (TCS), onlap, downlap, truncation and avalanche-related bedding, all a result of complex sand transport conditions. Different phases of deposition have produced an opposed succession of strata on each side of the dune. These successions alternate 2-dimensional (2D), or bedform instability mode features with 3-dimensional (3D), or fingering mode features, separated by a clear process boundary. These alternating successions reflect a change in the dominant wind environment in the recent past. The changing winds may feed into the building and overall stability of this dune field and may be a model for conditions in other large linear/longitudinal dune fields. The subsurface structure of an oblique crossing linear dune demonstrates sand transport generally down the dune long axis in the direction predicted from modern, ERA-Interim model as well as paleoclimate model winds. This suggests relatively long-term stability of this intermediate-sized landform and the potential long-term coexistence of large dunes and secondary forms. These studies have implications for the extensive sand seas of Titan, where lack of large secondary forms may indicate a simple wind regime over long time periods.

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来自探地雷达的纳米布沙海北部大型线性沙丘和相关交叉沙丘的近地表结构:对地球和土卫六上大型线性沙丘历史的启示
我们利用200兆赫探地雷达(GPR)对纳米比亚沙海北部一个大型线性沙丘的近地表沉积结构、两侧沙丘形态和相关的交叉线性沙丘进行了成像,这些沙丘以前从未被研究过。使用的干燥、均匀的沙质条件和波长允许在1km横向扫描中高度详细地观察到深度约12 m的沉积结构。在主要线状沙丘中观测到的沉积特征包括冲刷和地层突变,如槽交叉分层(TCS)、上覆、下覆、截断和雪崩相关的层理,这些都是复杂的沙输运条件的结果。不同的沉积阶段在沙丘两侧形成了相反的地层序列。这些序列交替使用二维(2D)或河床不稳定模式特征与三维(3D)或指法模式特征,由一个明确的过程边界分隔。这些交替演替反映了近年来主导风环境的变化。变化的风可能会影响沙丘场的形成和整体稳定性,并可能成为其他大型线性/纵向沙丘场的模型。斜交叉线性沙丘的地下结构表明,沙的输运通常沿着现代、ERA-Interim模式和古气候模式风预测的方向沿着沙丘长轴进行。这表明这种中等大小的地貌具有相对长期的稳定性,大型沙丘和次级地貌可能长期共存。这些研究暗示了土卫六广阔的沙海,那里缺乏大型的次级形式可能表明一个简单的风在很长一段时间内。
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来源期刊
Aeolian Research
Aeolian Research GEOGRAPHY, PHYSICAL-
CiteScore
7.10
自引率
6.10%
发文量
43
审稿时长
>12 weeks
期刊介绍: The scope of Aeolian Research includes the following topics: • Fundamental Aeolian processes, including sand and dust entrainment, transport and deposition of sediment • Modeling and field studies of Aeolian processes • Instrumentation/measurement in the field and lab • Practical applications including environmental impacts and erosion control • Aeolian landforms, geomorphology and paleoenvironments • Dust-atmosphere/cloud interactions.
期刊最新文献
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