Testing polymineral post-IR IRSL and quartz SAR-OSL protocols on Middle to Late Pleistocene loess at Batajnica, Serbia

Abstract

The loess-palaeosol sequence of Batajnica (Vojvodina region, Serbia) is considered as one of the most complete and thickest terrestrial palaeoclimate archives for the Middle and Late Pleistocene. In order to achieve a numerical chronology for this profile, four sets of ages were obtained on 18 individual samples. Equivalent doses were determined using the SAR protocol on fine (4-11 μm) and coarse (63-90 μm) quartz fractions, as well as on polymineral fine grains by using two elevated temperature infrared stimulation methods, pIRIR ₂₉₀ and pIRIR ₂₂₅. We show that the upper age limit of coarse quartz OSL and polymineral pIRIR ₂₉₀ and pIRIR ₂₂₅ techniques is restricted to the Last Glacial/Interglacial cycle due to the field saturation of the natural signals. Luminescence ages on coarse quartz, pIRIR ₂₂₅ and pIRIR ₂₉₀ polymineral fine grains are in general agreement. Fine quartz ages are systematically lower than the coarse quartz and pIRIR ages, the degree of underestimation increasing with age. Comparison between natural and laboratory dose response curves indicate the age range over which each protocol provides reliable ages. For fine and coarse quartz, the natural and laboratory dose response curves overlap up to ~150 and ~250 Gy, respectively, suggesting that the SAR protocol provides reliable ages up to c. 50 ka on fine quartz and c. 100 ka on coarse quartz. Using the pIRIR ₂₂₅ and pIRIR ₂₉₀ protocols, equivalent doses up to ~400 Gy can be determined, beyond which in the case of the former the natural dose response curve slightly overestimates the laboratory dose response curve. Our results suggest that the choice of the mineral and luminescence technique to be used for dating loess sediments should take into consideration the reported limited reliability.

Figure 1

The study area integrated in the map of loess distribution after Haase et al. (2007). SRTM data provided by U.S. Geological Survey. The star represents the investigated loess site, while loess sites mentioned in this paper are marked by solid circles (Mircea‐Voda, Romania (Timar‐Gabor et al. 2011; Vasiliniuc et al. 2012); Stari Slankamen, Serbia (Murray et al. 2014); Crvenka, Serbia (Stevens et al. 2011); Stratzing, Austria (Thiel et al. 2011a)).

Figure 2

Stratigraphy and magnetic susceptibility of the Batajnica site (Marković et al. 2009) and its correlation to the astronomically tuned magnetic susceptibility record from the Titel/Stari Slankamen composite record (Basarin et al. 2014) and benthic oxygen isotope stack (Lisiecki & Raymo 2005). Palaeosols are marked from S0 to S5. Dashed lines indicate loess–palaeosol transitions at the Batajnica site and corresponding ages at the Titel/Stari Slankamen composite record and benthic oxygen isotope stack. On the stratigraphical column, the two tephra layers identified in the L2 loess layer are represented with dashed lines.

Figure 3

Dose recovery test results for (A) fine (open squares) and coarse (open circles) quartz, (B) polymineral fine grains on pIRIR ₂₉₀ (open diamonds) and pIRIR ₂₂₅ (open triangles). The given irradiation doses were chosen to match the equivalent dose of each sample. The solid line indicates the ideal 1:1 dose recovery ratio while the dashed lines bracket a 10% variation from unity.

Figure 4

Dependence of measured pIRIR ₂₉₀ equivalent dose on the size of test dose for samples BAT‐1.9 (open symbols) and BAT‐1.12A (filled symbols). The expected equivalent doses for sample BAT‐1.12A, taken from Table S2, are highlighted with grey. Solid lines are used to indicate the expected values while error ranges are given by dashed lines.

Figure 5

Quartz OSL and polymineral pIRIR ₂₂₅ and pIRIR ₂₉₀ ages for the uppermost loess–palaeosol alternation at the Batajnica site. Note the doublet samples collected at 12 m depth: open symbols indicate sample BAT‐1.12A while filled symbols represent sample BAT‐1.12B.

Figure 6

Luminescence ages plotted against expected ages for samples BAT‐1.0, BAT‐1.11, BAT‐1.12A and BAT‐1.12B (filled symbols). The expected ages are derived from the correlation between loess–palaeosol boundaries and benthic isotope stack (Fig. 2, Table S2).

Figure 7

A. Laboratory dose response curves constructed for 4–11 μm and 63–90 μm quartz, 4–11 μm polymineral grains measured with pIRIR ₂₂₅ and pIRIR ₂₉₀ protocols on sample BAT‐1.19A (>300 ka). All growth curves were fitted with the sum of two saturating exponential functions. Each datapoint represents an average of three measurements. Horizontal lines indicate the average natural sensitivity‐corrected luminescence signals (L_nat/T_nat). The average L_nat/T_nat obtained on all aliquots measured, including D_e measurements, is interpolated on the growth curve. The percentage indicated for each interpolation represents the ratio between the L_nat/T_nat and the L_x/T_x measured for the 5000 Gy regenerative dose. B. pIRIR ₂₉₀ laboratory dose response curves constructed on sample BAT‐1.19A with different test doses: 17 Gy (0.9% D_e), 200 Gy (11% D_e), 400 Gy (22% D_e) and 800 Gy (44% D_e). Three aliquots were measured for each test dose. All growth curves were fitted with the sum of two saturating exponential functions (I = I ₀ + a·(1 − exp(−D/D ₀₁)) + c·(1 − exp(−D/D ₀₂)). The corrected luminescence signals have been normalized to the sum of the amplitude of the exponential functions obtained by fitting (a + c).

Figure 8

Average of natural sensitivity‐corrected luminescence signals emitted by (A) 4–11 μm and (B) 63–90 μm quartz, 4–11 μm polymineral grains measured with (C) pIRIR ₂₂₅ and (D) pIRIR ₂₉₀ protocols, plotted as function of expected equivalent doses for the samples collected from the loess–palaeosol boundaries (BAT‐1.0, BAT‐1.11, BAT‐1.12A, BAT‐1.12B, BAT‐1.16, BAT‐1.17, BAT‐1.19A). The expected equivalent doses are derived from the magnetic susceptibility data correlated to the benthic oxygen stack (Lisiecki & Raymo 2005). The average laboratory dose response is presented for comparison. Data are fitted by the sum of two saturating exponential functions. Note the small vertical uncertainties on the corrected natural light levels.

Figure 9

Ratios of the sensitivity‐corrected natural signals to the sensitivity‐corrected luminescence signals induced by a 5000 Gy dose calculated for (A) quartz and (B) polymineral fine grain samples collected from below the Last Interglacial palaeosol. The threshold of saturation is given by dashed lines and it is set at 0.85. Please note that the laboratory signal emitted by fine quartz continues to grow to doses higher than 5000 Gy (Fig. 7A).