Uncertainties about landscape evolution under cold, nonglacial conditions raise a question fundamental to periglacial geomorphology: what and where are periglacial landscapes? To answer this, with an emphasis on lowland periglacial areas, the present study distinguishes between characteristic and polygenetic periglacial landscapes, and considers how complete is the footprint of periglaciation? Using a conceptual framework of landscape sensitivity and change, the study applies four geological criteria (periglacial persistence, extraglacial regions, ice-rich substrates, and aggradation of sediment and permafrost) through the last 3.5 million years of the late Cenozoic to identify permafrost regions in the Northern Hemisphere. In limited areas of unglaciated permafrost regions are characteristic periglacial landscapes whose morphology has been adjusted essentially to present (i.e., Holocene interglacial) process conditions, namely thermokarst landscapes, and mixed periglacial–alluvial and periglacial–deltaic landscapes. More widespread in past and present permafrost regions are polygenetic periglacial landscapes, which inherit ancient landsurfaces on which periglacial landforms are superimposed to varying degrees, presently or previously. Such landscapes comprise relict accumulation plains and aprons, frost-susceptible and nonfrost-susceptible terrains, cryopediments, and glacial–periglacial landscapes. Periglaciation can produce topographic fingerprints at mesospatial scales (10³–10⁵ m): (1) relict accumulation plains and aprons form where long-term sedimentation buried landsurfaces; and (2) plateaux with convexo–concave hillslopes and inset with valleys, formed by bedrock brecciation, mass wasting, and stream incision in frost-susceptible terrain.

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什么是冰川景观？在哪里？

在寒冷的非冰川条件下景观演变的不确定性提出了冰缘地貌学的一个基本问题：冰缘景观是什么以及在哪里？为了回答这个问题，本研究重点关注低地冰缘地区，区分特征性和多基因冰缘景观，并考虑冰缘的足迹有多完整？该研究使用景观敏感性和变化的概念框架，在晚新生代的最后 350 万年中应用了四个地质标准（冰缘持续性、冰外地区、富含冰的基​​质以及沉积物和永久冻土的积聚），以确定北半球。在未加冰的永久冻土区的有限区域中，有特征性的冰缘景观，其形态基本上已根据当前（即全新世间冰期）过程条件进行了调整，即热岩溶景观，以及冰缘-冲积和冰缘-三角洲混合景观。在过去和现在的永久冻土地区更普遍的是多基因冰缘景观，它继承了古代地表，现在或以前冰缘地貌在这些地表上不同程度地叠加。此类景观包括残积平原和围裙、易霜冻和非易霜冻地形、冰冻地貌和冰川-冰缘景观。冰周作用可以产生中空间尺度的地形指纹（10^{3 –} 10 ⁵ m)：(1) 长期沉积物掩埋地表形成的残余堆积平原和围裙；(2) 易冻地带基岩角砾化、体量消减、溪流切入形成的凹凸不平的山坡和谷地。