QUARTZ OSL AND K-FELDSPAR post-IR IRSL DATING OF SAND ACCUMULATION IN THE LOWER LIAO PLAIN (LIAONING, NE CHINA)

The timing of the formation of extensively distributed sand dunes in the Bohai coastal area and its forcing factors are poorly understood. In this study, the chronology of a well-preserved sand dune located in Panjin Forest Park (PJ) in the Lower Liao Plain (LLP) is investigated using quartz optically stimulated luminescence (OSL) and K-feldspar postinfrared (IR) infrared stimulated luminescence (IRSL) (pIRIR) dating. For the pIRIR measurements, the combination of preheating at 180 degrees C and pIRIR stimulation at 150 degrees C (pIRIR150) is exploited. The quartz results show that the sand dune accumulated from c. 120 a (1890 AD) to c. 70 a (1940 AD) before present, and the underlying sandy soil sediments deposited from c. 5.0 ka to c. 0.13 ka as marsh sediment after the sea level highstand since the mid-Holocene. From the evidence in historical coastline records, the PJ sand dune is an inland sand dune and not a coastal sand dune. Based on further information of climate and temperature change after the Little Ice Age (LIA) and human activity in northeastern China, we conclude that the PJ sand dune accumulation was very likely impacted by the immigrants and land reclamation at the end of Qing dynasty. The fading corrected IR50 ages, the apparent and fading corrected pIRIR150 ages are consistent with quartz ages for two sandy soil samples but overestimate those for six sand samples. The overestimation of the feldspar ages is derived from the residual signal which has not been bleached before burial. The offset obtained from the difference between the quartz OSL and the feldspar pIRIR150 ages are similar to 20-160 a (predicted residual dose: similar to 0.08-0.60 Gy), whereas the measured residual dose after bleaching 4 h in a solar simulator yielded age overestimation of similar to 10-40 a (similar to 0.05-0.16 Gy). The age discrepancy calculated from the predicted residual was larger than those obtained from the laboratory measured residuals. We conclude that the pIRIR150 of aeolian sediment is applicable for samples older than similar to 1000 years where the effect of the residual dose become negligible.