Present‐day periglacial microforms in the Lesotho Highlands: Implications for present and past climatic conditions

Patricia M. Hanvey and Margaret E Marker

Permafrost and Periglacial Processes, 1992, vol. 3, issue 4, 353-361

Abstract: A variety of active periglacial microforms have been identified in the vicinity of Tlaeeng Pass (3275 m a.s.l.) in the Lesotho Highlands. These include thufa (both earth and stone‐cored varieties), terracettes, stone polygons and patterned ground. Ground ice within the saturated zone of soil profiles is clearly evident during the winter season, and pebbles perched on needle ice up to 5 cm in length are common. Although possible relict periglacial landforms (such as nivation hollows and protalus ramparts) have been recorded in the area, their identification and, hence, associated climatic inferences is problematic. The presence of active features clearly indicates present‐day periglacial activity, with the variety of forms resulting from diurnal or seasonal freeze‐thaw cycles. Considering a widely accepted global decrease in temperature during the Quaternary, a severity of temperatures greater than what is experienced under present marginal periglacial conditions can be projected for the Lesotho Highlands. However, past moisture regimes are more difficult to project from present‐day features, and this problem is exacerbated by the general paucity of clearly defined diagnostic relict forms. Une variété de microformes périglaciaires actives ont été identifiées au voisinage de Tlaeeng Pass (à 3275 m d'altitude) dans les régions élevées du Lesotho. Il s'agit de thufa (variétés à noyau de terre et à noyau de pierre), de terrassettes, de polygones de pierres et de sols structurés. La présence de glace, lorsque les sols sont saturés en eau, est évidente pendant l'hiver et des cailloux perchés sur des aiguilles de glace plus grandes que 5 cm, ne sont pas rares. Bien que des formes périglaciaires reliques (comme des creux de nivation et des ‘protalus ramparts’) aient été signalées dans la région, leur identification et aussi leur signification paléoclimatique restent problématiques. La présence des phénomènes périglaciaires actifs indique clairement l'action des cycles de gel/dégel diurnes et saisonniers. En considérant la diminution globale de la température pendant le Quaternaire, une plus grande sévérité des conditions périglaciaires peut ětre supposée pour ces

Date: 1992
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Persistent link: https://EconPapers.repec.org/RePEc:wly:perpro:v:3:y:1992:i:4:p:353-361

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