Optical dating of K-feldspar grains from Middle Pleistocene lacustrine sediment at Marathousa 1 (Greece)

Post-infrared infrared stimulated luminescence (pIRIR) measurements are reported for multiple aliquots of po-tassium-rich feldspar grains from sedimentary deposits at Marathousa 1 and Choremi Mine in the MegalopolisBasin in southern Greece. Ages were obtained for 9 samples from the deposits that over- and underlie as well asinclude the archaeological and palaeontological deposits at Marathousa 1. These sediments are sandwichedbetween lignite seams II and III and thought to represent sediment deposition during a single glacial period. Asingle age was obtained for a sample from Choremi mine. The equivalent dose estimates are based on a newlydeveloped method presented elsewhere, and environmental dose rate determinations followed standard pro-cedures. A specific focus of this paper is the determination of a representative estimate of time-averaged palaeo-water content of the organic and sand-rich deposits and the impact of porosity and compaction on these esti-mates. Ages are presented using two water content scenarios. Thesefinal ages have relatively large uncertainties,making it difficult to accurately assign deposition to a single oxygen isotope stage (OIS). Taking uncertainty intoaccount, sediment deposition at Marathousa 1 occur sometime during OIS 12 and 11 and at Choremi mineduring MIS 8. When combined with other proxy information, these results support the interpretation that thepeat deposits (represented by lignite seams II and III) were deposited during warm interglacial periods, and thatthe intervening clastic materials were deposited during glacial periods. In this case, the ages are best interpretedas supporting deposition of sediments during MIS12. This is consistent with one of the proposed age models, butyounger than the other.