GRAIN-SIZE DISTRIBUTION AND GENESIS OF LOESS IN THE QINGZHOU AREA, SHANDONG

Loess deposits with varying thicknesses are widely distributed on intermontane valleys and piedmont zones on the northern side of the central Shandong mountainous region.A systematic grain-size analysis was performed along the Fujiazhuang loess section of the Qingzhou area.The analytic results of the samples were correlated with those of the samples taken from Quaternary loess-paleosol of the Loess Plateau, modern dust fallouts in Beijing and fluvial deposits.The results show that the grain-size distribution of the Qingzhou loess is very similar to that of modern dust fallouts in Beijing and loess of the Loess Plateau but notably different from that of the fluvial samples.In the whole loess-paleosol sequence, the grain-size variation of the Qingzhou loess is consistent with the typical eolian loess and paleosol of the Loess Plateau.The loess is coarse in size, while the paleosol is fine in size.The above-mentioned results provide evidence for the eolian origin of the Qingzhou loess in the sedimentological context.The grain-size distribution of the Qingzhou loess combined with the previous studies indicates that the main provenances of the Qingzhou loess are the marine strata exposed in the flood plain of the Yellow River and Laizhou Bay north of the sedimentary region and less commonly distal silt and dust carried by high-layer circulation from northwest inland.