Concept and global context of the glacial landforms from the Bølling–Allerød Interstadial

The Bølling–Allerød concept comes from palaeobotanical studies determined by pollen levels which indicate a warm and humid climate, when forest expanded progressively throughout Europe replacing tundra steppe. Records of the Greenland ice cores show an increase of about 10°C in a few decades and records from alkenones and planktic foraminifera in the ocean sediments that show an increase of 4°C–10°C. The Bølling–Allerød (B-A) is considered in this book as the chronostratigraphic period between 14.6 and 12.9 ka, although the environmental changes over this interval are in fact not entirely synchronous. The B-A is a complex and variable period in its evolution and distribution, interspersed with cold events, usually so short that they are outside the range of certainty of dating methods. The B-A is a period dominated by glacial retreat, both in the areas that were dominated by ice sheets and in the alpine areas, although glacial retreat was already well underway when B-A began. The B-A was a period of great importance in the shaping of European glacial landscapes, either because glacial landforms lost their ice cover, or because these landforms were partially transformed by melting processes, mainly in regions previously covered by the ice sheets, or by paraglacial processes in the case of mountain cirques.