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DILEMMA OF DATING ON LACUSTRINE DEPOSITS IN AN HYPERARID INLAND BASIN OF NW CHINA
Abstract
Conventional and accelerator mass spectrometry (AMS) radiocarbon, TL, OSL, and IRSL dating results on
samples from the cores D100 and I70 from Ejina Basin, one of the most important inland basins in arid-hyperarid NW China,
show that it is difficult to determine the ages of sediments at different depths. AMS ages of core D100 samples demonstrate
that the sediments at depths from 10 to 90 m were formed between 14 to 30 kyr BP. The inverted ages from both the D100
and I70 cores imply that there was a strong reworking of the sediments during and after deposition processes. The inverted
ages also indicate drastic fluctuations of groundwater bearing soluble organic matters, which might be related to neotectonic
activities and climate changes during the period. Consequently, it is impossible to establish an accurate and reliable chronology
for the cores based only on these dates. All AMS ages, if they are reliable and acceptable, indicate a high deposition rate
(5~8 mm/yr), and since all TL, OSL, and IRSL ages are much older than those given by AMS, it makes these methods questionable
for determining the ages of lacustrine-fluvial-alluvial deposits.
samples from the cores D100 and I70 from Ejina Basin, one of the most important inland basins in arid-hyperarid NW China,
show that it is difficult to determine the ages of sediments at different depths. AMS ages of core D100 samples demonstrate
that the sediments at depths from 10 to 90 m were formed between 14 to 30 kyr BP. The inverted ages from both the D100
and I70 cores imply that there was a strong reworking of the sediments during and after deposition processes. The inverted
ages also indicate drastic fluctuations of groundwater bearing soluble organic matters, which might be related to neotectonic
activities and climate changes during the period. Consequently, it is impossible to establish an accurate and reliable chronology
for the cores based only on these dates. All AMS ages, if they are reliable and acceptable, indicate a high deposition rate
(5~8 mm/yr), and since all TL, OSL, and IRSL ages are much older than those given by AMS, it makes these methods questionable
for determining the ages of lacustrine-fluvial-alluvial deposits.