Natural radioactivity studies in a paleontology site and paleoclimate interpretation of the last 8 Mya

摘要

Fossil bones and sediments from different horizons of the Upper Miocene paleontological site of Platania, Drama Greece were studied using U-238, U-233, Th-232 series and K-40 measurements obtained by gamma-spectroscopy. Additionally, SEM and XRF analysis was applied to bone and sediment samples while a lithological analysis of the sediments was also carried out. The Ra-226/-U-238 ratios in the fossilization layers are attributed to the U-238 depletion from the sediment and its incorporation into the fossils. The Ra-226/Pa-231 ratio indicates that the absorption of the isotopes started long before 4.2 Ma ago. The Th-232/K-40 profile demonstrate two distinct geological substrates, the lower corresponding to the Upper Miocene whereas the upper to the Upper Pleistocene-Holocene. Among them mediates a Mn-rich layer associated with the "Zanclean flood" during Pliocene. One layer above the "Glacial maximum event" during the Early Pleistocene was recorded. The natural radioactive sedimentary profile obtained reproduces the paleo-climatic conditions in Southeast Europe, which could be useful for the future.