The loess of the Chinese Loess Plateau (CLP) potentially provide an important source of information about history of continental aridity, uplift of the Tibetan Plateau, global atmospheric circulation and are closely related to the evolution of the polar ice sheets (e.g. Pye, 1995; Ding
To the east of the CLP, loess sediments widely distributed in Central Shandong Mountains (CSM) are significant terrestrial palaeoclimatic archives in the semi-humid region of eastern China. It is also sensitive records of East Asian monsoon changes for situating in a key region connected to the Eurasian Plate and the Pacific Ocean. However, compared with the detailed work on the loess sediments from the CLP, loess sediments in CSM region have not been well investigated. In recent years, the relatively unified understanding of the loess sedimentation on CSM mainly focused on its genesis and provenance: (1) the loess of CSM was characterized by typical aeolian based on the field stratigraphic characteristics and grain size analysis (Liu
Rapid developments in OSL dating have proved to be very successful for the signal of dating loess bleached by sunlight before sedimentation (e.g. Buylaert
In this study, 20 samples were taken from a 7.5 m loess-palaeosol sequence in CSM region. The objective of this study is two-fold; first, to establish a firm and high-resolution chronology of HS loess using quartz OSL and K-feldspar post-IR IRSL dating over the last interglacial period, which provides a relatively detailed and long-term chronological basis for palaeoenvironmental researches in the study region. The second aim is to investigate the potential of the pIRIR200IR290 protocol in CSM loess dating during 10–75 ka. The quartz OSL and feldspar pIR200IR290 ages are compared with the loess-palaeosol stratigraphy to determine the applicability of the method for the loess sediments in this semi-humid region.
CSM region is located in the lower reaches of the Yellow River (
Fig. 1
(a) Location of the study region of the Central Shandong Mountains. (b) Location of the sampled loess section (HS) in the Central Shandong Mountains.

The new Heishan (HS) loess section (36°10.05′N, 116°20.63′E) sampled from the south bank of lower reaches of Yellow River is in the southwest of CSM (
Fig. 2
The lithology of the studied loess section and the positions of luminescence dating samples.

Twenty samples were collected using light-tight steel tubes (diameter 5 cm, length 20 cm) from a freshly prepared vertical section. The tubes were fully filled with sediments to prevent mixing during transportation. The tubes were then wrapped with aluminium foil at both ends to prevent light exposure and moisture loss for OSL measurement.
Samples were opened under subdued red light conditions, and the outer 3–4 cm layers at the ends of each tube were removed for water content and dose rate analysis. The remaining material at the middle part of the tube was then pretreated using the standard procedures, including treatment with 10% hydrochloric acid (HCl) and 10% hydrogen peroxide (H2O2) to remove carbonates and organic matter, respectively. After wet sieving, grains in the range of 63–90 μm were extracted. This coarse fraction was treated with 10% hydrofluoric acid (HF) for 20 min, to remove coatings and the outer alpha-irradiated layer, and then rinsed in 10% HCl for 20 min to remove precipitated fluorides. Subsequently, the remaining grains were separated by heavy liquid to extract quartz grains (2.58 < ρ < 2.70 g/cm−3) and K-feldspar grains (ρ < 2.58 g/cm−3). Quartz extracts were etched in 40% HF for 1 h and rinsed for 1h in 10% HCl. The purity of quartz was checked by IR depletion ratio method (Duller, 2003) and 110°C TL peak (Li
Quartz and K-feldspar measurements were performed on a Risø TL/OSL-DA-20 reader (Bøtter-Jensen
For quartz OSL, a standard single-aliquot regenerative dose (SAR) protocol (Murray and Wintle, 2000, 2003) was applied for luminescence measurements. The thermal treatment was set as preheat at 260°C and cut-heat at 220°C with blue stimulation at 125°C. The measurement of preheat temperature is described in Section 4. The single aliquot quartz OSL signals were derived from the summation of the initial 0.64 s of stimulation, less an early background of the following 0.64 s of stimulation to minimize a contribution from medium and slow components (Ballarini
For K-feldspar, the SAR pIRIR290 protocol (Thiel
The environmental dose rate was determined from the U and Th concentrations and K contents, measured by neutron activation analysis (NAA) method in the Chinese Atomic Energy Institute. Calculation of the cosmic ray contribution was assessed according to Prescott and Hutton (1994). Measured water content from the HS section varied between 10% and 17%. Based on the water content from previous CSM loess researches (Peng
Summary of the burial depth, radionuclide concentrations, calculated dose rate, quartz and feldspar De values and luminescence ages. The water content is assumed to be 15 ± 5%. A residual dose of 6.2 ± 0.4 Gy was subtracted from the measured feldspar pIRIR290 De values. (n) represents the number of aliquots contributing to the De, 1 represents quartz and 2 is feldspar. Uncertainties represent one standard error.
HS-1 | 1.1 | 2.16 ± 0.04 | 11.80 ± 0.03 | 2.13 ± 0.03 | 3.20 ± 0.05 | 3.65 ± 0.09 | 26.9 ± 1.2 | 42.9 ± 1.0 | 36.7 ± 1.1 | 121/102 | 8.5 ± 0.4 | 10.1 ± 0.3 |
HS-2 | 1.5 | 2.31 ± 0.04 | 11.60 ± 0.03 | 2.09 ± 0.03 | 3.14 ± 0.05 | 3.62 ± 0.09 | 24.3 ± 1.2 | 44.4 ± 1.0 | 38.2 ± 1.1 | 101/92 | 7.8 ± 0.4 | 10.5 ± 0.4 |
HS-3 | 2.1 | 2.20 ± 0.04 | 11.00 ± 0.03 | 2.13 ± 0.03 | 3.10 ± 0.05 | 3.58 ± 0.09 | 28.4 ± 0.9 | 40.0 ± 0.8 | 33.8 ± 0.9 | 101/92 | 9.2 ± 0.3 | 9.4 ± 0.4 |
HS-4 | 2.5 | 2.42 ± 0.04 | 12.10 ± 0.03 | 2.14 ± 0.03 | 3.22 ± 0.05 | 3.70 ± 0.09 | 35.1 ± 1.9 | 48.0 ± 0.8 | 41.8 ± 0.9 | 151/102 | 10.9 ± 0.6 | 11.3 ± 0.4 |
HS-5 | 2.6 | 1.96 ± 0.04 | 11.10 ± 0.03 | 1.97 ± 0.03 | 2.91 ± 0.10 | 3.39 ± 0.13 | 35.4 ± 0.9 | 47.1 ± 1.0 | 40.9 ± 1.1 | 131/92 | 12.2 ± 0.6 | 12.1 ± 0.5 |
HS-6 | 2.7 | 2.04 ± 0.04 | 11.50 ± 0.03 | 1.95 ± 0.03 | 2.93 ± 0.05 | 3.41 ± 0.09 | 43.9 ± 1.4 | 44.2 ± 1.5 | 38.0 ± 1.6 | 121/92 | 15.0 ± 0.6 | 11.1 ± 0.6 |
HS-7 | 2.8 | 2.17 ± 0.04 | 12.10 ± 0.03 | 2.01 ± 0.03 | 3.10 ± 0.10 | 3.53 ± 0.13 | 51.9 ± 1.6 | 68.3 ± 1.1 | 62.1 ± 1.1 | 121/92 | 17.0 ± 0.8 | 17.6 ± 0.8 |
HS-8 | 2.9 | 2.40 ± 0.04 | 12.10 ± 0.03 | 2.18 ± 0.03 | 3.24 ± 0.05 | 3.72 ± 0.09 | 55.5 ± 2.6 | 77.1 ± 1.5 | 70.9 ± 1.6 | 121/102 | 17.1 ± 0.9 | 19.1 ± 0.6 |
HS-9 | 3.1 | 2.07 ± 0.04 | 12.10 ± 0.03 | 2.02 ± 0.03 | 3.03 ± 0.11 | 3.51 ± 0.13 | 48.9 ± 1.4 | 81.4 ± 1.5 | 75.2 ± 1.5 | 121/102 | 16.1 ± 0.8 | 21.4 ± 0.9 |
HS-10 | 3.3 | 2.01 ± 0.04 | 11.90 ± 0.03 | 1.86 ± 0.03 | 2.86 ± 0.11 | 3.34 ± 0.13 | 97.1 ± 4.8 | 108.1 ± 1.3 | 101.9 ± 1.4 | 121/102 | 33.9 ± 2.1 | 30.5 ± 1.3 |
HS-11 | 3.7 | 2.31 ± 0.04 | 12.30 ± 0.03 | 2.09 ± 0.03 | 3.18 ± 0.12 | 3.63 ± 0.09 | 95.5 ± 5.7 | 115.7 ± 1.9 | 109.5 ± 1.9 | 101/92 | 30.4 ± 1.9 | 30.2 ± 0.9 |
HS-12 | 4.2 | 2.45 ± 0.04 | 11.70 ± 0.03 | 1.73 ± 0.03 | 2.82 ± 0.05 | 3.30 ± 0.09 | 88.4 ± 2.4 | 101.1 ± 1.8 | 94.9 ± 1.8 | 101/92 | 31.4 ± 1.0 | 28.8 ± 0.9 |
HS-13 | 4.6 | 2.44 ± 0.04 | 11.10 ± 0.03 | 1.99 ± 0.03 | 3.00 ± 0.05 | 3.48 ± 0.09 | 96.2 ± 1.9 | 107.7 ± 1.0 | 101.5 ± 1.1 | 101/92 | 32.1 ± 0.8 | 29.2 ± 0.8 |
HS-14 | 5.1 | 2.95 ± 0.04 | 11.00 ± 0.03 | 1.95 ± 0.03 | 3.06 ± 0.05 | 3.55 ± 0.09 | 99.6 ± 2.1 | 116.8 ± 1.7 | 110.6 ± 1.7 | 151/92 | 32.6 ± 0.9 | 31.2 ± 0.9 |
HS-15 | 5.5 | 2.54 ± 0.04 | 12.20 ± 0.03 | 1.97 ± 0.03 | 3.06 ± 0.05 | 3.55 ± 0.09 | 103.1 ± 2.0 | 128.4 ± 1.6 | 122.2 ± 1.6 | 121/92 | 33.7 ± 0.9 | 34.5 ± 1.0 |
HS-16 | 5.6 | 2.32 ± 0.04 | 11.20 ± 0.03 | 1.70 ± 0.03 | 2.72 ± 0.10 | 3.20 ± 0.12 | 111.3 ± 3.0 | 137.1 ± 0.9 | 130.9 ± 0.9 | 161/92 | 41.0 ± 1.9 | 40.9 ± 1.6 |
HS-17 | 6.3 | 2.21 ± 0.04 | 8.99 ± 0.03 | 1.93 ± 0.03 | 2.75 ± 0.05 | 3.23 ± 0.08 | 146.3 ± 6.6 | 152.3 ± 2.4 | 146.1 ± 2.5 | 121/92 | 53.2 ± 2.6 | 45.3 ± 1.4 |
HS-18 | 6.7 | 2.17 ± 0.04 | 10.70 ± 0.03 | 1.79 ± 0.03 | 2.72 ± 0.05 | 3.20 ± 0.08 | 167.6 ± 5.6 | 168.0 ± 2.4 | 161.8 ± 2.4 | 121/92 | 61.6 ± 2.3 | 50.5 ± 1.5 |
HS-19 | 7.1 | 2.22 ± 0.04 | 10.80 ± 0.03 | 1.67 ± 0.03 | 2.63 ± 0.05 | 3.11 ± 0.08 | 163.3 ± 9.1 | 208.7 ± 4.3 | 202.5 ± 4.3 | 101/92 | 62.0 ± 3.6 | 65.0 ± 2.2 |
HS-20 | 7.5 | 2.23 ± 0.04 | 11.10 ± 0.03 | 1.69 ± 0.03 | 2.67 ± 0.05 | 3.15 ± 0.08 | 178.0 ± 9.9 | 242.9 ± 3.1 | 236.7 ± 3.1 | 121/92 | 66.7 ± 3.9 | 75.2 ± 2.2 |
To select appropriate preheat temperatures for quartz De determination, preheat temperature plateau tests were used to assess the De dependence on preheat temperature for representative samples HS-4 and HS-16 (
Fig. 3
Coarse-grain quartz luminescence characteristics. (a) Representative small aliquot dose-response curve (preheat 260°C for 10 s, cut heat 220°C) for sample HS-14 showing recycling and recuperation (open symbols) and the interpolation of the sensitivity-corrected natural signal onto the dose response curve. Inset shows the natural decay curve. (b) Preheat plateau tests of samples HS-4 and HS-16. Three aliquots were measured at each temperature, and error bars represent one standard error. The dashed line is drawn at the average De over the 200–300°C interval.

Typical dose-response curve and decay curve of quartz are shown in
Representative decay curves and dose-response curves for the coarse-grained K-feldspar of sample HS-19 are shown in
Fig. 4
Coarse-grain K-feldspar luminescence characteristics. Representative natural decay curve (a) and dose-response curve (b) of pIR200IR290 signal for sample HS-19. (c) Dependence of De on prior IR stimulation temperatures for the upper (HS-3) and lower sample (HS-20) of the HS section. Three aliquots were measured at each temperature, and error bars represent one standard error. The dash-dot line is drawn at the average De over the 50–260°C interval. (d) The pIRIR290 dose residuals after ten days bleach under natural sunlight were plotted against the corresponding equivalent doses.

To check the stability of the pIR200IR290 dating, dose recovery tests were performed. Six aliquots of each sample were bleached for 16 h with a Hönle UVACUBE400 solar simulator before they were given a laboratory β dose close to their natural doses (e.g. Qiu and Zhou, 2015, E
The post-IR IRSL techniques may overestimate the De values due to thermal transfer during high-temperature heat treatment (Buylaert
The resulting pIR200IR290 De and ages are summarized in
Quartz OSL ages for all samples are plotted against K-feldspar pIRIR290 ages in
Fig. 5
Comparison between quartz OSL and K-feldspar pIR200IR290 ages.

As demonstrated in
Fig. 6
Quartz OSL and K-feldspar post-IR IRSL ages of HS loess section.

The dust source of HS loess section in the CSM region might be proximal and most likely from the fluvial deposits (Peng
The sedimentation rate of the HS section is shown in
The rapid sedimentation rate during 34–30 ka was also similar with the lake sediments records (An
We applied high-resolution luminescence dating, using both quartz OSL and K-feldspar pIRIR290 on a loess sequence in the CSM, eastern China. The quartz signal is sensitive, fast component dominated, saturates approximately ∼150 Gy. For K-feldspar pIRIR290, first IR stimulation plateau tests indicated that the determined De does not have any obvious dependence on first IR stimulation temperature between 50°C and 260°C, and the dose recovery is satisfactory. In addition, K-feldspar pIRIR290 signals are far from saturation and show an agreement with the expected stratigraphy (8∼75 ka). Especially, the K-feldspar Post-IR IRSL dating method is the first application of the Loess dating in CSM region, implying that the experimental method has a large potential in the study of the older loess here.
Based on our results, a hiatus of ∼13 ka between ∼30 and ∼17 ka can be interpreted as deflation, which indicates that it is an erosion area during 30–17 ka. This loess sequence provides a relatively long-term chronological basis of palaeoclimatic researches in this semi-humid region since the last glacial period.
Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Summary of the burial depth, radionuclide concentrations, calculated dose rate, quartz and feldspar De values and luminescence ages. The water content is assumed to be 15 ± 5%. A residual dose of 6.2 ± 0.4 Gy was subtracted from the measured feldspar pIRIR290 De values. (n) represents the number of aliquots contributing to the De, 1 represents quartz and 2 is feldspar. Uncertainties represent one standard error.
HS-1 | 1.1 | 2.16 ± 0.04 | 11.80 ± 0.03 | 2.13 ± 0.03 | 3.20 ± 0.05 | 3.65 ± 0.09 | 26.9 ± 1.2 | 42.9 ± 1.0 | 36.7 ± 1.1 | 121/102 | 8.5 ± 0.4 | 10.1 ± 0.3 |
HS-2 | 1.5 | 2.31 ± 0.04 | 11.60 ± 0.03 | 2.09 ± 0.03 | 3.14 ± 0.05 | 3.62 ± 0.09 | 24.3 ± 1.2 | 44.4 ± 1.0 | 38.2 ± 1.1 | 101/92 | 7.8 ± 0.4 | 10.5 ± 0.4 |
HS-3 | 2.1 | 2.20 ± 0.04 | 11.00 ± 0.03 | 2.13 ± 0.03 | 3.10 ± 0.05 | 3.58 ± 0.09 | 28.4 ± 0.9 | 40.0 ± 0.8 | 33.8 ± 0.9 | 101/92 | 9.2 ± 0.3 | 9.4 ± 0.4 |
HS-4 | 2.5 | 2.42 ± 0.04 | 12.10 ± 0.03 | 2.14 ± 0.03 | 3.22 ± 0.05 | 3.70 ± 0.09 | 35.1 ± 1.9 | 48.0 ± 0.8 | 41.8 ± 0.9 | 151/102 | 10.9 ± 0.6 | 11.3 ± 0.4 |
HS-5 | 2.6 | 1.96 ± 0.04 | 11.10 ± 0.03 | 1.97 ± 0.03 | 2.91 ± 0.10 | 3.39 ± 0.13 | 35.4 ± 0.9 | 47.1 ± 1.0 | 40.9 ± 1.1 | 131/92 | 12.2 ± 0.6 | 12.1 ± 0.5 |
HS-6 | 2.7 | 2.04 ± 0.04 | 11.50 ± 0.03 | 1.95 ± 0.03 | 2.93 ± 0.05 | 3.41 ± 0.09 | 43.9 ± 1.4 | 44.2 ± 1.5 | 38.0 ± 1.6 | 121/92 | 15.0 ± 0.6 | 11.1 ± 0.6 |
HS-7 | 2.8 | 2.17 ± 0.04 | 12.10 ± 0.03 | 2.01 ± 0.03 | 3.10 ± 0.10 | 3.53 ± 0.13 | 51.9 ± 1.6 | 68.3 ± 1.1 | 62.1 ± 1.1 | 121/92 | 17.0 ± 0.8 | 17.6 ± 0.8 |
HS-8 | 2.9 | 2.40 ± 0.04 | 12.10 ± 0.03 | 2.18 ± 0.03 | 3.24 ± 0.05 | 3.72 ± 0.09 | 55.5 ± 2.6 | 77.1 ± 1.5 | 70.9 ± 1.6 | 121/102 | 17.1 ± 0.9 | 19.1 ± 0.6 |
HS-9 | 3.1 | 2.07 ± 0.04 | 12.10 ± 0.03 | 2.02 ± 0.03 | 3.03 ± 0.11 | 3.51 ± 0.13 | 48.9 ± 1.4 | 81.4 ± 1.5 | 75.2 ± 1.5 | 121/102 | 16.1 ± 0.8 | 21.4 ± 0.9 |
HS-10 | 3.3 | 2.01 ± 0.04 | 11.90 ± 0.03 | 1.86 ± 0.03 | 2.86 ± 0.11 | 3.34 ± 0.13 | 97.1 ± 4.8 | 108.1 ± 1.3 | 101.9 ± 1.4 | 121/102 | 33.9 ± 2.1 | 30.5 ± 1.3 |
HS-11 | 3.7 | 2.31 ± 0.04 | 12.30 ± 0.03 | 2.09 ± 0.03 | 3.18 ± 0.12 | 3.63 ± 0.09 | 95.5 ± 5.7 | 115.7 ± 1.9 | 109.5 ± 1.9 | 101/92 | 30.4 ± 1.9 | 30.2 ± 0.9 |
HS-12 | 4.2 | 2.45 ± 0.04 | 11.70 ± 0.03 | 1.73 ± 0.03 | 2.82 ± 0.05 | 3.30 ± 0.09 | 88.4 ± 2.4 | 101.1 ± 1.8 | 94.9 ± 1.8 | 101/92 | 31.4 ± 1.0 | 28.8 ± 0.9 |
HS-13 | 4.6 | 2.44 ± 0.04 | 11.10 ± 0.03 | 1.99 ± 0.03 | 3.00 ± 0.05 | 3.48 ± 0.09 | 96.2 ± 1.9 | 107.7 ± 1.0 | 101.5 ± 1.1 | 101/92 | 32.1 ± 0.8 | 29.2 ± 0.8 |
HS-14 | 5.1 | 2.95 ± 0.04 | 11.00 ± 0.03 | 1.95 ± 0.03 | 3.06 ± 0.05 | 3.55 ± 0.09 | 99.6 ± 2.1 | 116.8 ± 1.7 | 110.6 ± 1.7 | 151/92 | 32.6 ± 0.9 | 31.2 ± 0.9 |
HS-15 | 5.5 | 2.54 ± 0.04 | 12.20 ± 0.03 | 1.97 ± 0.03 | 3.06 ± 0.05 | 3.55 ± 0.09 | 103.1 ± 2.0 | 128.4 ± 1.6 | 122.2 ± 1.6 | 121/92 | 33.7 ± 0.9 | 34.5 ± 1.0 |
HS-16 | 5.6 | 2.32 ± 0.04 | 11.20 ± 0.03 | 1.70 ± 0.03 | 2.72 ± 0.10 | 3.20 ± 0.12 | 111.3 ± 3.0 | 137.1 ± 0.9 | 130.9 ± 0.9 | 161/92 | 41.0 ± 1.9 | 40.9 ± 1.6 |
HS-17 | 6.3 | 2.21 ± 0.04 | 8.99 ± 0.03 | 1.93 ± 0.03 | 2.75 ± 0.05 | 3.23 ± 0.08 | 146.3 ± 6.6 | 152.3 ± 2.4 | 146.1 ± 2.5 | 121/92 | 53.2 ± 2.6 | 45.3 ± 1.4 |
HS-18 | 6.7 | 2.17 ± 0.04 | 10.70 ± 0.03 | 1.79 ± 0.03 | 2.72 ± 0.05 | 3.20 ± 0.08 | 167.6 ± 5.6 | 168.0 ± 2.4 | 161.8 ± 2.4 | 121/92 | 61.6 ± 2.3 | 50.5 ± 1.5 |
HS-19 | 7.1 | 2.22 ± 0.04 | 10.80 ± 0.03 | 1.67 ± 0.03 | 2.63 ± 0.05 | 3.11 ± 0.08 | 163.3 ± 9.1 | 208.7 ± 4.3 | 202.5 ± 4.3 | 101/92 | 62.0 ± 3.6 | 65.0 ± 2.2 |
HS-20 | 7.5 | 2.23 ± 0.04 | 11.10 ± 0.03 | 1.69 ± 0.03 | 2.67 ± 0.05 | 3.15 ± 0.08 | 178.0 ± 9.9 | 242.9 ± 3.1 | 236.7 ± 3.1 | 121/92 | 66.7 ± 3.9 | 75.2 ± 2.2 |