G05_P05

Species-definite AMS ¹⁴C dating, ²¹⁰Pb and ¹³⁷Cs dating on a peat core from Jinchuan Mire, NE China

Misra S¹,  Kashyap S¹, Chou C¹, Chang T¹, Li H¹

¹National Taiwan University, Taipei, Taiwan

AMS ¹⁴C, ²¹⁰Pb and ¹³⁷Cs dating have been done on a 92-cm peat core from Jinchuan Mire in NE China, showing sedimentation rates ranging from 0.066 to 0.54 cm/year over the last 1050 years. Carex lehmanii (a plant of the genus Sedge in the Cyperaceae family) has been chosen for AMS ¹⁴C dating. A total of 110 AMS ¹⁴C dates on Carex from 85 horizons were yielded, in which 16 samples were treated by ABA treatment. The high resolution ¹⁴C dates show significantly variations throughout the core, indicating serious old carbon influence. The comparisons among the ¹⁴C, ²¹⁰Pb and ¹³⁷Cs dating results show mobilization problem of ²¹⁰Pb and ¹³⁷Cs. The detailed dating results exhibit that peat accumulation was 0.102, 0.54 (human impact) and 0.066 cm/yr during periods of 2018~1964, 1964~1950 and 1950~900 CE, respectively. Furthermore, the ABA treated Carex is generally older than the non-ABA treated Carex in the same depth, except samples below 85 cm depth, implying that old carbon influence between 85 and 92 cm was negligible. The decomposition of the peat plants in deeper layers which is related to plant species and climatic conditions and groundwater table which is related to climatic conditions and drilling sites may cause the variation of old carbon (in the dissolved CO₂ uptaken by Carex) influence on the Carex ¹⁴C ages. The Carex AMS ¹⁴C dates will help us not only to refine the previous age model of JCA but also to understand hydro-climatic information recorded by JCA core sediments.