Falko Turner

Potential of palaeosols, sediments and archaeological features to reconstruct Late Glacial fire regimes in northern Central Europe – case study Grabow site and overview

Late Glacial fires in Northern Germany are well known from different geoarchives such as palaeosols, (limnic) sediments and archaeological sites. This has evoked the question if the fire regime during the Allerod and Younger Dryas was driven exclusively by natural agents (temperature, precipitation, vegetation pattern) or was – at least to some extent – a result of anthropogenic burning. We contribute to this question by examining on-site and off-site archives in the Jeetzel valley at the Late Palaeolithic site Grabow 15 (N-Germany). The spatial analysis of the charcoal distribution and biomarkers (“black carbon”) in an on-site test area enabled a detailed reconstruction of human burning activities during the early Allerod. A determination of the charred wood taxa allowed a reconstruction of the local vegetation pattern during the time of human occupation. The evidence of man-made fire was compared to the general occurrence of charcoal particles in two palaeochannels that provided archives for palynological and sedimentological analysis for the time span from the Allerod to the early Holocene. Based on the reconstructed local vegetation patterns, human occupation phases and water levels we conclude that human presence during the early Allerod must have increased the input of charcoal and biomarkers into the local sediments. During the Younger Dryas no human contribution to the local charcoal influx was detected. We concluded that future studies must considerate the very local impact of man-made fires in much greater detail.

Long-term glacier melt fluctuations over the past 2500 yr in monsoonal High Asia revealed by radiocarbon-dated lacustrine pollen concentrates

Long-term records of glacier mass changes are important for improving our understanding of glacier dynamics and for predicting the response of glaciers to future climate change. In contrast to moraine sequences that only record isolated stages of glacier status, proglacial lake sediments may record long-term continuous glacier activities. The melt of old glacier ice releases old pollen that may affect the radiocarbon ages of pollen in proglacial lake sediments. We define the offset between the calibrated pollen 14 C ages and the sediment depositional age as the “old pollen effect” (OPE). In small catchments dominated by glaciers, the OPE may record variations in glacier melt intensity and extent, even though complex processes (e.g., modern pollen flux to a glacier or a proglacial lake, glacier flow velocities) may also impact the OPE. Using the sediments of a small proglacial lake on the southern Tibetan Plateau, we found that over the past 2.5 k.y., a weakened OPE occurred during three historical cool periods that coincided with regional glacier advances defined by moraine ages. Thus, we interpret the OPE as a new indicator of glacier melt intensity and its fluctuations. Our reconstructed glacier variability agrees well with glacier fluctuations in the European Alps and the global average temperature record, suggesting that hemispheric-scale temperature variations and/or mid-latitude Westerlies may have controlled the late Holocene glacier variability in monsoonal High Asia. We also show that the 20 th century glacier melt intensity has exceeded that of two historical warm periods and is unprecedented over the past 2.5 k.y. This implies that current anthropogenic warming poses a serious threat to the survival of glaciers in monsoonal High Asia.

Beaver (Castor fiber) Activity in an Archaeological Context: A Mid-Holocene Beaver Burrow Feature and a Late-Holocene Ecofact at the Late Palaeolithic Grabow Site, Northern Germany

ABSTRACT Bioturbation and intrusive ecofacts are major concerns for the analysis of archaeological sites in wetland environments. Post-sedimentary influence of beavers (Castor fiber) is described for a well dated Late Palaeolithic archaeological record situated in a floodplain in Northern Germany. An extensive burrow system was documented and analysed according to its spatial dimensions and sedimentological properties; it was interpreted to be the result of beaver activity. Palynological analyses proved a Mid-Holocene origin of the infill material and helped in understanding the history of site formation. In addition, a pointed piece of wood was examined and identified as ecofact, which had been gnawed by a small rodent, possibly Arvicola amphibius (water vole). Our study thus illustrates the potential complexity of post-sedimentary site-alteration, describes the sub-surface morphology of a burrow system in a wetland context and documents risks for erroneous archaeological interpretation.