Analysis of a Multi-Millennial Fire Record in a Bog Margin, Pointe-Escuminac, Eastern New Brunswick, Canada.

English Abstract:

The Pointe-Escuminac raised bog is located on the eastern shore of New Brunswick and is affected by coastal erosion which created a peat cliff. The bog margins display several distinct layers of thin charred bands in the peat. We selected three profiles on the southwest section of the cliff to assess fire intervals from these charred layers. The first one is 170 cm thick and has 25 charred layers; we radiocarbon dated six samples at various depth from this profile, the bottom layer being aged at 4780 yrs BP (uncalibrated). The second profile is at an eight meter distance from the first (towards the center of the bog), is 210 cm thick, has 19 charred layers and seven radiocarbon dates with the bottom peat aged at 5090 yrs BP. The third profile is 58 m from the first and is 320 cm thick. The bottom layer could not be dated, but the lowermost of the four radiocarbon dated samples is 5350 yrs BP at a depth of roughly 265 cm. We found 22 charred layers between that point and the topmost peat. Comparison between the three profiles suggests a total of 27 distinct charred layers with an average time interval of 175 radiocarbon years varying between 60 and 630 years. Five alternating periods of longer (330, 340 yrs) and shorter (110, 160 and 160 yrs) mean fire intervals are detected. Comparison with vegetation content of peat strata suggest they are not related to local vegetation changes. It is more likely that the variations in fire intervals were caused by external factors such as climate conditions or regional vegetation changes. Another study discussing micro-charcoal content in a peat profile from a bog located 70 km from Pointe-Escuminac further supports a regional signal and the possibility to use bog margins as suitable long-term regional fire records.