A preliminary study on ESR dating of sediments from Curitiba Basin, Brazil

Sediment samples from a 17 m thick profile composed of clay, arkosic sand and calcrete have been dated by means of ESR spectrometry. The ESR signals of the clay sample are mainly from the feldspar. The E' signal is sensitive to γ-radiation and thus it provides a reliable accumulated absorbed dose (AD) value for dating purposes. The tentative result gives the age of 200 ka for the clay samples from the lower part of the profile, 150-190 ka for the calcrete samples from the lower profile, and 120-130 ka for the clay samples from the upper part of the profile. The ESR ages are considered an order of magnitude younger than the geological age (∼ 1.8 Ma), estimated from geomorphological evidence. An inferred explanation for the underestimation in ESR ages is presented. (author)