Late holocene ‘mineral palsas’ and associated vegetation patterns: A case study from Lac Hendry, Northern Québec, Canada and significance for european pleistocene thermokarst

• Published in: Quaternary science reviews Vol. 14; no. 2; pp. 179 - 192
• Main Authors: Worsley, Peter, Gurney, Stephen D., Collins, Philip E.E.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1995
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/0277-3791(95)00003-8

Mineral palsas with thin peat covers are described from the continuous to discontinuous permafrost transition zone. They are up to 4 m high and are developed in a clast rich fine grained diamict. Their development post dates the land emergence ca. 4.3 ka BP following isostatic uplift. Morphological and vegetational data suggest a growth and decay cycle from small, emergent, Sphagnum covered mounds to mature palsas with heath and forest taxa and finally arcuate ridges marking the outline of degraded palsas, separated by bogs and open water. It is speculated that long-term ground water supply within a complex talik structure and allied ice segregation through cryosuction are crucial formative processes. Field features diagnostic of these mineral palsas are frost-heaved erratic blocks, surficial sliding of peat blocks, seeps of thawed diamict, and a complex pattern of thermokarst landforms. The palsa fields may be analogues for relict complex thermokarst landforms in parts of western Europe formerly subject to permafrost and previously interpreted as relict pingos.