Magnetostratigraphy of the Key Loess-Palaesol Sequence at Roxolany (Western Black Sea Region)

Abstract

Roxolany Section (46° 10′N; 30° 27′E) is one of the most representative outcrops within Western Black Sea Lowland. Its 55-m thick loess-palaesol sequence was stratified by palaeomagnetic, palaeopedological, thermoluminescence and other methods, but the results are different. Thus in palaeomagnetic studies of Roxolany the Matuyama–Brunhes (M/B) boundary was placed in the diverse stratigraphic horizons. The authors of (Tretyak et al. Int geol nauk 50, 1987) found a number of zones of normal, reversed and anomalous polarity, but attributed the whole 55-m loess-soil sequence to the Brunhes chron of normal polarity. Later, based on the results of the complex investigation of this section and taking into account the palaeomagnetic data from other outcrops in this region, the position of the M/B boundary was drawn in the loess located below the PK₆ soil at a depth of ~34 m (Tsatskin et al. in Palaeogeogr Palaeoclimatol Palaeoecol 143:111–133, 1998), which corresponds to the Tyasmyn horizon according the stratification cited in (Bogucki et al. in Loess-covering of the North Black Sea Region. KARTPOL, Lublin, pp. 47–58, 2013). Our new palaeomagnetic investigations were carried out in a few laboratories with detailed measurements of specimens from duplicated outcrops after full AF and thermal demagnetization. We identified that the M/B boundary in the Roxolany section is located at a depth of 46.6 m at the contact between the buried soils of the Lubny and Martonosha horizons, which generally agrees with the present-day notions about the Quaternary stratigraphy of the south of Ukraine (Bakhmutov and Hlavatskyi in Geofiz Zhurn 4(38):59–74, 2016).