Just as glaciers worldwide left a record of past advances and retreats that shifted latitudinally in response to oscillating Quaternary climate changes, so too have cold-climate conditions and permafrost left topographic and sedimentary signatures in former periglacial environments. This review documents widespread occurrence of past permafrost and intense frost action that led to rock fracturing, regolith production, and regolith-mantled slopes in the mid-Atlantic region of the United States during late Pleistocene cold-climate conditions. Strong signatures of thermal contraction cracking and brecciation from frost cracking exist where rocks and sediments are most frost susceptible, as with fissile shales. On sandstone hillslopes, frost weathering produced boulder-rich sediment that episodically flowed slowly down-slope during permafrost thaw, resulting in solifluction lobes and terraces in which colluvium moved cumulatively at least a kilometer. Radiocarbon dating, optically stimulated luminescence age control, and cosmogenic isotope studies constrain some periglacial features to the Last Glacial Maximum but also indicate longer residence times of regolith. ▪ Former permafrost and areas of intensive frost cracking extended over much of the mid-Atlantic region of the eastern United States during late Pleistocene cold glacial periods. ▪ Cold-climate conditions and permafrost left long-lasting topographic and sedimentary records with limited post-depositional erosion in the formerly periglacial mid-Atlantic region. ▪ Prominent relict periglacial landforms include polygon networks and frost wedges that are the result of thermal contraction cracking and brecciated rock formed by segregated ice and frost cracking. ▪ Widespread solifluction landforms are a topographic signature of freezing, thawing, and mass movement of mobile regolith produced by frost cracking, and some were active during the Last Glacial Maximum.

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更新世冰周过程和地貌，美国东部大西洋中部地区


正如世界各地的冰川留下了过去前进和退缩的记录，这些记录因第四纪气候变化的振荡而向纬度移动，寒冷的气候条件和永久冻土在以前的冰期环境中留下了地形和沉积特征。本综述记录了在更新世晚期寒冷气候条件下，美国大西洋中部地区广泛发生的永久冻土和强烈霜冻作用导致岩石破裂、风化层产生和风化层覆盖的斜坡。在岩石和沉积物最易受霜冻影响的地方，存在强烈的热收缩开裂和霜冻开裂角砾岩特征，如裂变页岩。在砂岩山坡上，霜冻风化产生了富含砾石的沉积物，这些沉积物在永久冻土融化期间间歇性地缓慢地向动，导致裂片和阶地，其中崩积层累积移动至少一公里。放射性碳测年、光学刺激发光年龄控制和宇宙同位素研究将一些冰周特征限制在末次冰盛期，但也表明风化层的停留时间更长。▪ 在更新世晚期的冷冰期，前永久冻土和严重冻裂区域延伸到美国东部大西洋中部地区的大部分地区。▪ 寒冷的气候条件和永久冻土在以前的冰期中大西洋中部地区留下了持久的地形和沉积记录，沉积后侵蚀有限。▪ 突出的残余冰周地貌包括热收缩开裂的多边形网络和霜楔，以及由分离冰和霜裂形成的角砾岩。 ▪ 广泛的溶出地貌是冻裂产生的移动风化层冻结、融化和大规模移动的地形特征，有些地貌在末次冰盛期期间很活跃。