Journal of Archaeology in the Low Countries 2-2 (November 2010)Bart Vanmontfort; Marijn Van Gils; Etienne Paulissen; Jan Bastiaens; Marc De Bie; Els Meirsman: Human occupation of the Late and Early Post-Glacial environments in the Liereman Landscape (Campine, Belgium)

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4.2 Chronology

Optical dating results combined with field evidence (Derese et al. in press) show that the upper 1.5 m aeolian sand sequence was deposited from the final phase of the Late Pleniglacial up to the Younger Dryas. A more detailed chronology is based on five AMS radiocarbon dates: one sample of uncharred seeds from the very top of the peat in pit B and four samples from charcoal, two in the lower and two in the upper bleached horizon in pit C (table 1 and fig. 9). The end of the peat growth is AMS dated on uncharred seeds at 11,000 ± 60 BP (Poz-28168), or 13,065-13,010 (5.1%) and 12,985-12,672 (90.3%) cal BP according to IntCal09 (Reimer et al. 2009). As no charred seeds were recovered from the bleached horizons, charred wood remains were dated instead. Radiocarbon dating of a sample containing different charcoal fragments implicitly risks producing a mean age of several fire events. This is especially true for samples, which have been radiocarbon dated by the conventional method, needing significantly higher amounts of carbon and thus more charcoal pieces. Therefore single small charcoal fragments have been submitted for AMS dating. Fragments of small branches were selected, as evidenced by their form and growth rings, in order to largely eliminate old wood effect.


Sample number	Locus	Context	Material	Remarks	Conventional Age	2 Sigma Calibration in Cal BP	1 Sigma Calibration in Cal BP
Poz-28168	Korhaan pit B	top peat layer	uncharred seads		11000 ± 60 BP	13084 (95,4%) 12688	12965 (68,2%) 12735
Poz-28515	Korhaan pit C	upper bleached layer	one single charcoal piece		10480 ± 60 BP	12581 (88,9%) 12204	12558 (59,8%) 12380
						12197 (6,5%) 12140	12263 (8,4%) 12223
Poz-28516	Korhaan pit C	upper bleached layer	one single charcoal piece	0,8mg Carbon	10880 ± 60 BP	1290 (95,4%) 12610	12835 (68,2%) 12655
Poz-28517	Korhaan pit C	lower bleached layer	one single charcoal piece		11010 ± 50 BP	13085 (95,4%) 12699	13049 (3,5%) 13,033
							12967 (64,7%) 12752
Poz-28518	Korhaan pit C	lower bleached layer	one single charcoal piece	0,4mg Carbon	11240 ± 120 BP	13358 (95,4%) 12797	13276 (58,5%) 13058
							13023 (9,7%) 12970
Weigthed mean age samples 28516, 28517 and 28518					10983 ± 37 BP	13065 (5,1%) 13010	12925 (68,2%) 12742
						12985 (90,3% 12672

Table 1 Details of the 14C age determinations. All ages have been calibrated with IntCal09 ( Reimer et al. 2009 ) – Oxcal v4.1.5 ( Bronk Ramsey 2009 ).

Fig. 9 Calibrated calendar age probability distribution for the samples from the bleached horizons in pit C. UBH: upper bleached horizon, LBH: lower bleached horizon, WM: weighted mean. All ages have been calibrated with IntCal09 ( ) in Oxcal v.4.1.5 ( ).

For three charcoal pieces (Poz-28516, Poz-28517 and Poz-28518) the possibility that they represent different fire events cannot be excluded on the level of a single standard deviation, but on the 95% confidence level all three dates overlap. The question arises whether or not the four charcoal dates belong to the same normal distribution. As a result of the calculation and for a 1% probability, Poz-28515 is significantly different from the other three samples (Poz-28516, Poz-28517, and Poz-28518), which, although originating from both the upper and lower bleached horizons, may belong to the same normal distribution. The weighted mean of these samples is 10,983 ± 37 BP or 13,065-13,010 (85.1%) and 12,985-12,672 (90.3%) cal BP (fig. 9).