#1INSTITUTE OF GEOGRAPHY Russian Academy of Sciences Founded in 1918 Soil Record of the Holocene Paleofires at the North of European Russia (Arkhangelsk Region) 01 02 03 04 05 06 07 08 09 10 16 17 E 20 CC ④ BY Nikita Mergelov, Dmitry Petrov, Andrey Dolgikh, Elya Zazovskaya Soil Geography and Evolution Department Institute of Geography, Russian Academy of Sciences, Moscow EGU 2020 Assembly Sharing Geoscience Online May 05, 2020#2Study area: Pinega, Arkhangelsk Region, Russia key sites area Arkhangelsk Pinega 0 1500 3 000 km 0 200 400 m 64.747°N 43.387°E#3Study area: karst landscapes with Pinus sylvestris forest Regular matrix of closed karst sinkholes Carbonate and sulfate rocks covered by sandy/sandy loam glacial deposits Subsidence sinkholes: 400-1000 per km² Ø = 1-10 m day surface A = 1-5 m Arkhangelsk Pinega 0 1 500 3 000 km#401 02 03 04 05 06 07 08 09 Pyrogenic archives in sinkhole traps 01 02 01 03 04 05 06 07 08 09 10 E 02 central part of large sinkhole, archive depth 250 cm central part of small sinkhole, archive depth 130 cm gentle slope of large sinkhole charcoal accumulation zone charcoal transportation/accumulation zone 5-20 m distance between zones Dominant processes controlling the completeness of the charcoal record cycles of deposition erosion-deposition / uprooting 01 02 03 04 05 06 07 08 09 10 mesoscale elevation between sinkholes 16 charcoal depletion zone Study objective: to evaluate the series of buried Podzols in karst sinkholes as local-scale archives of the forest paleofires erosion/uprooting#5Results MACROCHARCOAL SUMMARY Pin01-18 3 complementary pyrogenic archives in sinkholes of various size: probability distributions and medians (+) in a set of 34 14C determinations (macrocharcoal) OxCal v4.3.2 Bronk Ramsey (2017); r:5 IntCal13 atmospheric curve (Reimer et al 2013) Probability density + +++ #+ + sinkhole depth 250 cm Stacked archives ++# 0.06 Summed probability 0.04 0.02 n=34 + +++ cal BP 10000 # 8000 +#++ ++ Pin03-18 +++ sinkhole depth 130 cm Pin02-18 sinkhole depth 110 cm 6000 4000 ++++ +++ #++ 2000 #+#+++ #++ 0#6Results MACROCHARCOAL SUMMARY No. of observations Distances between 20 ranges (cal BP, 95,4% probability) for each 14C determination in a row of consecutive pyrogenic events (macrocharcoal data) 15 I cal BP 10 5 0 12000 10000 8000 6000 4000 2000 0 800 > 200 cal yr BP between 2σ ranges 1 600 13 10 m 4 400 200 1-200 cal yr BP between 20 ranges Distance between 20 ranges (cal BP) N 0 -200 Imposed 20 ranges -400 I # I I Reliability of distinguishing individual fires (depends on mitigating uncertainty caused by the "inbuilt age" in 14C age of charcoal)#7• Conclusion Subsidence sinkholes in the karst landscapes (north of Arkhangelsk region, Russia) contain well-preserved soil record of the local pyrogenic events throughout the most part of the Holocene, as well as the data on stages of soil formation during this period The maximum temporal "depth" of archives estimated upon the study of 3 sinkholes is 10,261±40 cal BP. Since this time, the paleofire record encompasses every millennium except for 5000-4000 cal BP 8 out of 34 14C determinations in a consecutive row demonstrate distances of more than 200 cal BP between 2σ ranges (95,4% probability) of neighbor-determinations. Thus, these 14C dates reliably distinguish individual paleofires at a threshold of "charcoal inbuilt age" common to the tree species in the Holocene history of the region Soil formation at the inter-pyrogenic stages maintained a uniform direction for at least 10,000 yrs and profiles of Podzols were regularly replicated In situ record of paleofires in numerous pyrogenic-soil archives located in a regular grid of sinkholes complements the ex situ sedimentary charcoal record in lakes and bogs