2 Documenta Praehistorica XLVIII (2021) Introduction Tell Yunatsite (42°13’56”N; 24°15’45”E), also known as Ploskata mogila (the ‘Flat mound’), is situated in Southern Bulgaria, in the western part of the Upper Thracian Plain (Fig. 1). The diameter is 110 x 100m at its base and the height is 12m above the modern- day surface. The tell developed on a low terrace on the ancient bank of the Topolnitsa River near to its confluence with the Maritsa River 1 . It is located in a fertile plain bounded by mountains – the Rhodope Mountains to the south, Rila and Ihtimanska Sredna Gora Mountains to the west, and Sashtinska Sredna Gora Mountain to the north (Fig. 2). The first excavations of the site were carried out by Vasil Mikov in 1939. Systematic archaeological exca- vations of the tell’s eastern section began in 1976 Chronological modelling of the Chalcolithic settlement layers at Tell Yunatsite, Southern Bulgaria Yavor Boyadzhiev 1 , Kamen Boyadzhiev 1 , Lennart Brandtstätter 2 , Raiko Krauß 2 1 National Archaeological Institute with Museum, Bulgarian Academy of Sciences, Sofia, BG yavordb@abv.bg< kamen.boyadzhiev@naim.bg 2 Institute of Prehistory, Early History and Medieval Archaeology, Tübingen University, Tübingen, DE lennart.brandtstaetter@uni-tuebingen.de< raiko.krauss@uni-tuebingen.de ABSTRACT – This article publishes a new series of radiocarbon dates from Tell Yunatsite, Southern Bulgaria. Context-based excavations undertaken over a large surface area, as well as a small test trench, provided a long stratigraphic sequence (11 ‘building levels’) covering a large part of the Chal- colithic period in Thrace (5 th millennium BCE). Bayesian statistics and Gaussian Monte Carlo Wiggle Matching were employed to achieve a fine chronology for the multilayered tell. Implications and problems on the application of the calibration curve for the Late and Final Chalcolithic in Bulgaria are also discussed. IZVLE∞EK – V ≠lanku predstavljamo novo serijo radiokarbonskih datumov s tela Yunatsite v ju∫ni Bolgariji.S pomo≠jo v kontekste usmerjenih velikih izkopnih povr∏in in manj∏ih testnih sond smo pre- poznali dolgo startigrafsko sekvenco (11 ‘gradbenih nivojev’), ki pokriva velik del halkolitskega ob- dobja v Trakiji (peto tiso≠letje pred na∏im ∏tetjem). Za natan≠no kronologijo ve≠slojnega tela sta bili uporabljeni Bayesova statistika in Gaussovo Monte Carlo usklajevanje krivulje. Poleg tega smo ana- lizirali tudi posledice in probleme uporabe kalibracijske krivulje pri datiranju poznega in kon≠nega halkolitika v Bolgariji. KEY WORDS – radiocarbon dating; chronology; stratigraphy; Chalcolithic; Gaussian Monte Carlo Wiggle Matching; Bayesian statistic KLJU∞NE BESEDE – radiokarbonsko datiranje; kronologija; stratigrafija; halkolitik; Gaussovo Monte Carlo usklajevanje krivulje; Bayesova statistika Kronolo[ko modeliranje halkolitskih naselbinskih plasti na telu Yunatsite, jug Bolgarije DOI> 10.4312\dp.48.5 1 The course of the Topolnitsa River has changed through time and in the 20 th century AD it was rectified with dikes.