摘要
随着高分率影像数据的获取,火星大沙波纹进入研究视野。火星大沙波纹是一类间距为米级的风成床面形态,其特殊性反映在形态、格局、流动性及其形成过程等几个方面,然而,受限于探测资料特别是缺乏高分辨率影像资料,对其研究的范围和深度都极其有限,导致这些特殊性被长期忽视,研究者们简单地认为其与地球上常见的沙波纹相类似。遵循地貌学思路,基于已有的有限研究介绍了大沙波纹的形态、组成物质及其形成机制,讨论了其潜在的研究意义。与普通沙波纹相比,火星大沙波纹尺度较大,脊线蜿蜒、尖锐,横截面不对称,背风坡坡度明显大于迎风坡,且背风坡具有明显的滑落或滑塌面;具有较强的移动性,以脊线的纵向延伸为主,侧向移动微弱;大沙波纹脊线具有不同走向,构成网格状格局,能够用来反演较长时段的复杂风况;具有沙波纹、大沙波纹和沙丘3级尺度风成床面形态并存的独特现象;初步探测发现,大沙波纹沉积物组成为分选良好的中细沙。目前关于火星大沙波纹的形成机制有3种假说:沙丘假说、冲击假说和流体拖拽假说,其中流体拖拽假说具有较强的说服力。火星大沙波纹不同于常态沙波纹,其独特性对总体上认识火星风沙地貌、火星环境特征及其演化历史具有重要意义,值得深入研究。
Large Ripples(LRs)on Mars come into the subject of researchers with the acquisition of high resolution image data.LRs are a kind of aeolian bedforms with meter-scale wavelength,and outstanding features of their morphology,bedform patterns,mobility and formation processes.However,due to the limited exploration data,especially the lack of high resolution image data,the research scope and depth are extremely limited,which leads to the long-term neglect of their uniqueness,therefore,researches simply consider them as common sand ripples on Earth.Following the geomorphology law and based on the existing limited research,this paper introduces the morphology,sedimentology and formation mechanism of LRs,and discusses their potential research significance.Compared with ordinary sand ripples,LRs are larger with sinuous and sharp crest lines,asymmetric topographic profiles,the downwind slope angle is much bigger than that of upwind,and slip faces are marked by the presence of grainflows and grainfalls.LRs have strong mobility with obvious longitudinal extension of ridges,and the lateral migration is very small.They have various orientations and network patterns which can be used to inverse the complex wind regimes over a long period of time.Three hierarchical order aeolian bedforms of sand ripples,large ripples,and sand dunes can co-exist.Preliminary explorations show that the sedimentology of LRs is the well sorted fine-to-medium sand.Three formation hypotheses were proposed for LRs:dune hypothesis,impacting hypothesis and fluid-drag hypothesis,with more evidences supporting the fluid-drag hypothesis.LRs are different from normal sand ripples,and their uniqueness is of great significance to comprehend Martian aeolian geomorphology,environmental characteristics,and revolution history,and therefore,they are worth making an intensive study of.
作者
董治宝
吕萍
李超
胡光印
Dong Zhibao;Lü Ping;Li Chao;Hu Guangyin(Planetary Aeolian Research Institute,Shaanxi Normal University,Xi'an 710119,China)
出处
《地球科学进展》
CAS
CSCD
北大核心
2020年第10期1006-1015,共10页
Advances in Earth Science
基金
国家自然科学基金项目“塔里木盆地周围干燥剥蚀山地风化速率研究”(编号:41930641)和“沙丘动力学数值模型时间与空间尺度的确定”(编号:41871011)资助。
关键词
火星风沙地貌
大沙波纹
形态学特征
形成假说
Martian aeolian geomorphology
Large ripples
Morphological characteristics
Formation hypothesis
