SAR-OSL dating of different grain-sized quartz from a sedimentary section in southern Romania interbedding the Campanian Ignimbrite/Y5 ash layer

Abstract

The SAR-OSL protocol was applied on quartz of different grain sizes (4–11 μm, 63–90 μm, 90–125 μm and respectively 125–180 μm) extracted from aeolian deposits embedding the Campanian Ignimbrite/Y5 (40Ar/39Ar dated elsewhere to 39.28 ± 0.11 ka) ash layer at the site of Caciulatesti on the Jiu valley, southwestern Romania. An analysis of the OSL dose response in the high dose region (5 kGy) was performed and the response is well represented by a sum of two saturating exponential functions. The saturation characteristics of the fine-grained (4–11 μm) quartz were found to be much higher than the saturation characteristic doses of the coarser material (63–90–125–180 μm). The equivalent doses have been determined by interpolating on the region of the dose response growth curves where the first exponential component was not fully saturated. Optical ages ranging from 38.5 ± 2.8 ka (4–11 μm) to 44.6 ± 3.8 ka (90–125 μm) were obtained for the underlying sand layer, whereas for the overlying loess, 36.2 ± 3.3 ka (125–180 μm) to 44.4 ± 3.4 ka (4–11 μm) values were found. The luminescence ages yielded by each grain-size fraction analyzed are consistent within errors limits. The weighted average ages obtained on the two samples confirm chronologically (alongside volcanic glass chemical data) the correlation of this ash layer with the Campanian Ignimbrite/Y5 tephra. These new chronological results establish the value of this ash layer as one the most important stratigraphic markers for the terrestrial deposits of the Lower Danube region during Marine Isotope Stage 3.