G04_P03

Multiple radiocarbon dating of POC, DOC, DIC, and plant remains in ground ice of Siberian permafrost

Minami M¹, Sato R¹, Iwahana G², Hiyama T¹

¹Nagoya University, Nagoya, Japan, ²University of Alaska Fairbanks, Fairbanks, USA

For understanding paleoclimate changes and hydrological environmental changes preserved in ground ice, it is important to determine the chronology of the ice formation. To examine which carbon fraction in ground ice shows the most true formation age, we performed multiple ¹⁴C dating of some carbon fractions in ground ice: particulate organic carbon (POC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and plant remains. The ground ice samples used are permafrost outcrops collected at Syrdakh and Churapcha, near the city of Yakutsk, Russia. The thawing samples were filtered through a 0.7-μm quartz filter, and the filtrate was ultrafiltered through a 10,000 MWCO (Molecular Weight Cut-Off) followed by a 3,000 MWCO (Vivaspin Turbo, Sartorius). The ¹⁴C ages of POC in the ground ice samples were 40−27 kyr BP, which is about 10,000 years older than the plant age of 24−22 kyr BP, while the ¹⁴C ages of DOC varied with molecular size: 28−19 kyr BP for the 0.7 μm−10,000 MW and 10,000−3,000 MW fractions, and a younger age of 18−12 kyr BP for the <3000 MW, which is similar to ¹⁴C ages for DIC.

We will discuss the result of the multiple ¹⁴C dating to determine which carbon fraction in the ground ice is most suitable for accurate dating of the ice formation.