Abstract: Detailed investigations were carried out on the upper undisturbed sediments from Erlongwan maar lake, NE China, which are better annually laminated sediments (varve). Varve couple appears as darkand lightcoloured layers. Based on varve dating of large thin sections under microscope, 36 varve couples, with 4％~7％ discrepancy , 1.1~2 mm varve thickness and 1.53 mm/a rate of sedimentation were found in the upper part of the core (0~5.5 cm), and 5.5 cm correlates to the year of 1965. However, Radiometric dating shows that the highest ¹³⁷Cs activity appears at 5.5 cm depth , assumed to correlate to the 1963 maximum of emission due to the nuclear bomb testing. ¹³⁷Cs activities increase quickly from 6.5 cm to 5.5 cm (from 4.67±0.29 dpm/g to 12.06±0.47 dpm/g ).In addition , By calculating of ²¹⁰Pb_ex (CIC) , 5.5 cm depth corresponds with the 1962. As a result, ²¹⁰Pb_ex (CIC) and ¹³⁷Cs dating show a good agreement with the varve dating. Varve dating is exact and varve sediments can offer an effective means of acquiring highquality palaeoenvironmental records.

Key words: Erlongwan maar lake, varve dating, ¹³⁷Cs and ²¹⁰Pb Dating