Luminescence Dating of Sediments Associated with Norse Agriculture from Søndre Igaliku, Greenland

Abstract

This study supports a new investigation into the chronology, and the palaeoenvironmental context and consequences, of Viking settlement in Greenland (section 2). Optically stimulated luminescence (OSL) age determinations have been made for a series of sediments associated with Norse agricultural activity around the farm and church site of Søndre Igaliku, Eastern Settlement (section 3). The geomorphological and archaeological significance of the age determinations has been reviewed in the light of the luminescence results and the samples’ depositional contexts, to constrain the deposition/formation dates of the sampled sediments (section 6).
 
 A total of 5 age determinations were made (section 5.3). Dose rate determinations were made using thick source beta counting, high-resolution gamma spectrometry, field gamma spectrometry, measured water contents and calculated cosmic dose rates (sections 4.2.1, 5.1). Equivalent dose determinations were made (sections 4.2.2, 5.2) using the OSL signals from sand sized grains of quartz separated from each sample. Dose rates ranged from 3.1 to 3.7 mGy/a, De values ranged from 2.2 to 3.2 Gy. Age estimates for these samples ranged from 0.66 to 0.94 ka, the average being 0.82 ka ± 0.11 (section 5.3). Uncertainties on the age estimates were commonly 10 % at one
 standard error.
 
 The OSL results indicate formation of soils with anthropogenic input from the 11th through into the 14th Centuries AD at Søndre Igaliku, i.e. covering the expected range of Norse settlement in the region (section 6.3). These appear to have subsequently been buried by material dating to the 12th Century, possibly reworked from coastally eroded homefields associated with the same settlement. Consideration of mechanisms for redeposition in the light of the OSL results indicates that the reworking hypothesis should be testable using soil micromorphological analysis of the microbanded layers (6 to 4). Comparison of the OSL results with 14C results on charcoal from the same sediments indicates that marine reservoir effects and wood-age may combine to produce a residual of c. 100-200 years in calibrated radiocarbon dates (section 6.3).