Abstract: The Nevşehir - Acıgöl maar is one of the eruption centers of Quaternary volcanism in central Anatolia. The Maar - lake fill contains clastic, chemical and organic deposits, including high - calorific peats formed in late Holocene. The main (host) sediments ofthe infill are tuffaceous sandy mudstones. The other accesory fades, controlled mainly by climate, are peats and plant - bearingmudstones, brecciated mudstones, limestones and also travertines originated by thermal waters at the top of the succession. According to the C.I4 dating of the peats, they formed ca. 2000 yrs BP; their calorific values are 2300 to 3165 kCallkg. These values arevery high, considering the yoimgness of the peats. It is thought tliat the lake was primarily dependent on climate; and deposition wasfurtlier controlled by the hydroihermal system. The associated heat flow played an important role in sedimentation by creating amicro - climatic niche, where late - Quaternary (cold regional climate) vegetation could flourish and form substantial peat deposits.The heat flow through the groudwater and clastic sediments was crucial to the high maturation of the peat deposits.