The sediments of the supposed Ries-ejecta-dammed "Rezat-Altmtihl Lake" (Georgensgmtind Formation) are fluviatile deposits and show no evidence of а relation with the Ries event. Accordingly, it is not а mid-Miocene lake dammed up Ьу the Ries impact ejecta. • А volcanic ash layer in the deeper part of the lacustrine succession of the Ries basin, detected for the first time, proves а deep bowl-shaped geometry of the crater fill and а significant crater floor subsidence. А correlation of basin margin carbonates with certain sections of the central basin fill is now comprehensiЬle. • The saline high-alkaline Ries crater lake apparently went through а temporary sulphate-poor phase with methanogenesis, as а result of а shift from sulphate-rich groundwater inflow to sulphate-poorer inflows, with gradual reduction of the sulphate content Ьу sulphate-reducing bacteria. • The Ries crater basin forms а model example for the general chemical and hydrological development of hydrologically closed impact crater lakes of medium size: At first, groundwater inflows from the basement and suevite dominate, later groundwater inflows via fractured megaЬlocks. Only after that, weathering solutions from the primary ejecta cover play а greater role. Finally, very late in the basin development the hydrological catchment area expands, with surface inflows also from outside the crater. • The cooling history of the crater floor with corresponding effects on sedimentation and organism communities in the early Ries crater lake remains to Ье investigated.