Preliminary results of dating for the Lower Paleolitic sites of Ukraine (Medzhibozh 1 and Medzhibozh A, Khmelnitskii region) by electron spin resonance method

Abstract

In the West of Ukraine, the Medzhibozh site complex includes two multi-layered open-air Lower Paleolithic sites sitting at 49°35′ N 27°42′ E, 270 m amsl. In Medzhibozh I’s lower alluvial cycle, Layer 16a yielded Paleolithic artefacts, mainly choppers, chopping tools, and flakes with little secondary modification, associated with likely fireplaces and bones with cutmarks left by early hominids inhabiting an ancient shoreline. Ursus deningeri, Stephanorhinus kirchbergensis , and other Middle Pleistocene fossils, as well as microtheriofauna, pollen, paleopedology data suggest that Layers 13—16 must predate 200 ka, but only one TL date has been done here. About 500 m away from Medzhibozh I, Medzhibozh A’s six archaeological layers were intercalated with sterile gravels, with analogous stone products, fauna, hearth relics . Since ESR can date mammalian enamel up to 2—4 Ma with 2—5 % precision, three cervid teeth from Layer 16a at Medzhibozh I and one from the Layer 1 in Medzhibozh A were dated by standard and isochron ESR. Sediment samples were analyzed by NAA to measure volumetrically averaged sedimentary dose rates. Using geological criteria, a ramped box model calculated time-averaged cosmic dose rates were determined. From Medzhibozh A, AT29’s standard LU age of 379±27 ka agreed best with ages estimated from the faunal analyses, but the isochron showed diffusional secondary U uptake, suggesting the age could be older. At Medzhibozh I, all teeth had >100 ppm U in their dentine, but enamel U ranged from 2,8 to 11,8 ppm. AT41’s isochron, which did not show secondary U uptake, suggested that the U uptake rate, p ~4 was the best uptake rate, yielding an age of 373±17 ka, which correlates with late Marine Isotope Stage (MIS) 11. Meanwhile, AT44’s age likely dates at 399±11 ka with p =4, and AT45’s at 396±13 ka with p =6, both of which correlate with mid MIS 11. Their isochrons suggested secondary diffusional U uptake had affected both teeth. All isochron analyses suggest that one secondary uptake event may have affected the entire site, likely due to immersion in U-rich water. If correct, AT29’s age makes Medzhibozh A’s hearths the oldest in the Ukraine, but more teeth from all the layers must be ESR dated and tested with coupled ESR— 230 Th/ 234 U to confirm the ages and p ’s.