Phosphate mineral occurrences in Lake Baïkal sediments : Paleo-environment or diagenesis record ?

Poster (2003)

Des traces de glace de ségrégation dans la grotte de Remouchamps (Belgique) : conséquences en ce qui concerne la sédimentation et la paléoclimatologie

in Annales de la Société Géologique de Belgique (1988), 111

In countries with a modern temperate climate, the extent of former permafrost is generally estimated from the observation of ice wedge casts, remnants of pingos and palsas, and periglacial involutions ... [more ▼]

In countries with a modern temperate climate, the extent of former permafrost is generally estimated from the observation of ice wedge casts, remnants of pingos and palsas, and periglacial involutions. These features give no indication at all about the depth of permafrost and are ineffective in identifying the limits of former permafrost. A new tool for this research may be found in caves. We already know that speleothems did not grow -- or grew little — during the colder periods of the last glaciation, probably because of the impervious nature of the frozen ground. The discovery, in the Remouchamps Cave, of the marks of segregation ice in loose fills proves that the temperature did fall below 0°C. Only one cycle of freeze/thaw would have been sufficient to create these marks wich have been preserved because there was indeed little biological activity in this environment. The temperature in such caves is generally very close to the mean annual temperature outside the caves. This evidence will thus be useful for tracing the southern limit of the permafrost in Europe. When the permafrost thawed, the melting of the ice caused mass movements in the cave sediments. The ice had blocked some passages and water levels rose to abnormally high levels, depositing sediments at these levels. [less ▲]