ESTABLISHING A MULTI-PROXY APPROACH TO ALPINE BLOCKFIELD EVOLUTION IN SOUTH-CENTRAL NORWAY
Blockfields in high latitude mountain areas are a wide spread proxy for glaciation history. Their origin is debated since decades, especially in south-central Norway, where glaciation had a major global climate implication. Some authors explain old blockfield features by protection of cold-based ice, others claim they persisted as nunataks during the LGM (~20 kyr BP), or were formed during the Holocene. Former publications have failed to clearly disentangle these theories mostly due to methodological shortcomings. In order to clarify the age and origin of alpine blockfields we established a multi-method approach to combining lichenometry, stratigraphy, granulometry, and geochemistry (XRD, XRF). Our lichenometric results indicate landscape stability for at least ~12.5 kyr BP. The frequent climatic shifts are evident in our profiles by various soil properties. On the basis of geochemical analyses we were able to identify a long-term weathering history and in situ blockfield formation. We assume that the influence of cold-based ice in the glaciation history is overestimated and argue against the preservation by cold-based ice during recent glaciations. The blockfields most likely represent an ice-free location since the Eemian (~130 kyr BP). Thus, our study challenges the general assumption that the Scandinavian Peninsula was entirely ice covered during the last glaciations.