Haloturbation in the northern Atacama Desert revealed by a hidden subsurface network of calcium sulphate wedges

IF 2.8 2区 地球科学 Q2 GEOGRAPHY, PHYSICAL Earth Surface Dynamics Pub Date : 2024-04-15 DOI:10.5194/egusphere-2024-592
Aline Zinelabedin, Joel Mohren, Maria Wierzbicka-Wieczorek, Tibor Janos Dunai, Stefan Heinze, Benedikt Ritter
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Abstract

Abstract. While the formation of periglacial wedges and polygonal patterned grounds has been extensively studied and many of the processes involved have been understood, knowledge on the formation of similar post-sedimentary features found in arid to hyperarid environments remains largely rudimentary. Our contribution to fill this gap is the investigation of a network of vertically laminated calcium sulphate-rich wedges in the subsurface of the Aroma fan in the northern Atacama Desert. The subsurface wedges are characterised by high anhydrite contents and hence differ from the wedge and polygon structures of other study sites in the Atacama Desert, which appear to have been predominantly formed by thermal contraction or desiccation processes. By contrast, haloturbation mechanisms are thought to be a main driver of wedge formation at the Aroma fan site. Haloturbation requires moisture input, and hence Aroma fan wedge formation is likely to be associated with meteoric water received from sporadic rain events and episodes of arid climate characterised by slightly wetter conditions than prevailing at present. The polygonal patterned ground is covered by a stratigraphically younger gypsum-dominated surface crust cover. The presence of the surface crust could indicate an environmental change towards drier conditions, which favoured surface accumulation of calcium sulphate and other salts by means of atmospheric deposition. Such a climatic shift could have caused a deceleration of haloturbation and other wedge formation processes in the subsurface, although modern sediment conveyance from the surface towards its interior still appears to occur along cracks within the crust. In order to gain comprehensive insights into the complex mechanisms involved in wedge formation and formation rates, the establishment of a geochronological framework directly obtained from wedge and crust material remains indispensable. The temporal resolution of wedge growth stored within the succession of vertical laminae promises a high potential for the calcium sulphate wedges to be used as palaeoclimate archives, potentially helping to unravel wedge and polygonal patterned ground formation in other water-limited environments, such as Mars.
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隐藏在地表下的硫酸钙楔形网络揭示了阿塔卡马沙漠北部的晕动现象
摘要。尽管人们对围岩楔和多边形图案地层的形成进行了广泛研究,并了解了其中的许多过程,但对干旱到超干旱环境中类似沉积后地貌的形成仍然知之甚少。为填补这一空白,我们对阿塔卡马沙漠北部阿罗玛扇地表下富含硫酸钙的垂直层状楔形网络进行了研究。地表下楔形结构的特点是无水石膏含量高,因此不同于阿塔卡马沙漠其他研究地点的楔形和多边形结构,后者似乎主要是由热收缩或干燥过程形成的。相比之下,人们认为卤扰机制是阿香扇地点楔形结构形成的主要驱动力。晕动作用需要水分的输入,因此阿罗玛扇楔的形成很可能与零星降雨所产生的陨石水以及比目前稍湿的干旱气候有关。多边形图案的地面被地层较年轻的以石膏为主的表壳覆盖。地表结壳的存在可能表明环境条件发生了变化,变得更加干燥,这有利于硫酸钙和其他盐类通过大气沉积作用在地表积累。尽管现代沉积物从地表向地壳内部的输送似乎仍是沿着地壳内部的裂缝进行的,但这种气候转变可能会导致地表下的卤扰动和其他楔形形成过程减速。为了全面了解楔形形成所涉及的复杂机制和形成速度,建立一个直接从楔形和地壳材料中获得的地质年代框架仍然是不可或缺的。储存在垂直层状构造演替中的楔形生长的时间分辨率使硫酸钙楔很有可能被用作古气候档案,从而有可能帮助揭示火星等其他限水环境中的楔形和多边形图案地层的形成。
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来源期刊
Earth Surface Dynamics
Earth Surface Dynamics GEOGRAPHY, PHYSICALGEOSCIENCES, MULTIDISCI-GEOSCIENCES, MULTIDISCIPLINARY
CiteScore
5.40
自引率
5.90%
发文量
56
审稿时长
20 weeks
期刊介绍: Earth Surface Dynamics (ESurf) is an international scientific journal dedicated to the publication and discussion of high-quality research on the physical, chemical, and biological processes shaping Earth''s surface and their interactions on all scales.
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