(Table 3) Age-related trends of desert pavement properties in the Transantarctic Mountains@en

Compared to mid-latitude deserts, the properties, formation and evolution of desert pavements and the underlying vesicular layer in Antarctica are poorly understood. This study examines the desert pavements and the vesicular layer from seven soil chronosequences in the Transantarctic Mountains that have developed on two contrasting parent materials: sandstone-dolerite and granite-gneiss. The pavement density commonly ranges from 63 to 92% with a median value of 80% and does not vary significantly with time of exposure or parent material composition. The dominant size range of clasts decreases with time of exposure, ranging from 16-64 mm on Holocene and late Quaternary surfaces to 8-16 mm on surfaces of middle Quaternary and older age. The proportion of clasts with ventifaction increases progressively through time from 20% on drifts of Holocene and late Quaternary age to 35% on Miocene-aged drifts. Desert varnish forms rapidly, especially on dolerite clasts, with nearly 100% cover on surfaces of early Quaternary and older age. Macropitting occurs only on clasts that have been exposed since the Miocene. A pavement development index, based on predominant clast-size class, pavement density, and the proportion of clasts with ventifaction, varnish, and pits, readily differentiated pavements according to relative age. From these findings we judge that desert pavements initially form from a surficial concentration of boulders during till deposition followed by a short period of deflation and a longer period of progressive chemical and physical weathering of surface clasts. The vesicular layer that underlies the desert pavement averages 4 cm in thickness and is enriched in silt, which is contributed primarily by weathering rather than eolian deposition. A comparison is made between desert pavement properties in mid-latitude deserts and Antarctic deserts.相较于中纬度沙漠，南极地区荒漠砾幕（desert pavement）及其下伏泡土层（vesicular layer）的特征、形成与演化过程目前研究尚不充分。本研究针对横贯南极山脉（Transantarctic Mountains）的7处土壤年代序列（soil chronosequences）中的荒漠砾幕与下伏泡土层展开分析，这些序列发育于两种截然不同的母质（parent materials）之上：砂岩-辉绿岩与花岗岩-片麻岩。砾幕盖度通常介于63%至92%之间，中位数为80%，且未随暴露时长或母质组成发生显著变化。岩屑（clasts）的优势粒径区间随暴露时长逐渐减小：全新世（Holocene）与晚第四纪（Quaternary）地表的岩屑优势粒径为16~64 mm，中更新世及更老地表的岩屑优势粒径则降至8~16 mm。带有风蚀痕迹（ventifaction）的岩屑占比随时间逐渐升高：全新世与晚第四纪冰碛垅中该占比为20%，中新世（Miocene）冰碛垅中则升至35%。荒漠漆皮（desert varnish）形成速度较快，尤其在辉绿岩岩屑上，早第四纪及更老地表的岩屑几乎全部被荒漠漆皮覆盖。宏观蚀坑（macropitting）仅见于中新世以来暴露的岩屑之上。基于优势粒径区间、砾幕盖度以及带有风蚀痕迹、漆皮与蚀坑的岩屑占比构建的砾幕发育指数，可依据相对年龄对砾幕进行有效区分。基于上述研究结果，我们认为荒漠砾幕最初形成于冰碛物（till）沉积过程中岩块的地表富集阶段，随后经历了短暂的风蚀吹蚀（deflation）过程，以及更长时间的表层岩屑化学与物理风化递进过程。荒漠砾幕下伏的泡土层平均厚度为4 cm，其粉粒富集主要源于风化作用而非风成沉积（eolian deposition）。本研究还对比了中纬度沙漠与南极沙漠的荒漠砾幕特征。