This study stresses how zircon-grain length versus age correlation significantly can improve provenance interpretations. Hence, taking sedimentary sorting effects into account, we present a detrital-zircon provenance study for continental deposits of the Central European, Lower Triassic Buntsandstein Group in Germany. The Buntsandstein Group was deposited in an extended intracontinental sag basin of Pangea under arid climate conditions. It included several intrabasinal tectonic swells, some of which have been assumed topographic highs acting as detrital source areas. This study of the Lower and Middle Buntsandstein subgroups in Central Germany indicates that particularly the Massif Central and the Bohemian Massif contributed to the basin fill of the central part of the Central European Basin. The Rhenish Massif, an assumed highland, was submerged. This interpretation is based on > 1000 zircon grains from 12 sandstone beds. The unbroken grains in seven of the zircon separates have mean lengths of 190–220 μm and five are composed 100–140 μm long grains in average. All have a main population of 340–320 Ma Carboniferous ages, representative of granitic, probably zircon-rich, rocks from the Variscan Orogen of the Massif Central and the Bohemian Massif. This first-cycle detritus was mixed with recycled, abraded zircon grains from Ediacaran to Palaeozoic metasedimentary units feeding the basin with 610–460 Ma (Ediacaran to Ordovician) and 2 Ga age grains, as is typical for Gondwana-derived material. The Ediacaran to Ordovician age population is common only in five samples with mean grain lengths of 100–140 μm. Grains of such ages mainly are < 130 μm in the east, but equally common in all grain sizes in western sandstone beds. A western group was fed from the Massif Central and an eastern group derived from the Bohemian Massif. However, abrasion, age-population variations for pre-Variscan grains, and dominating wind directions indicate that two different fluvial systems delivered the Bohemian material and that this was combined with aeolian and alongshore lacustrine transport from the south and west. We conclude that interpretation of detrital zircon ages preferably are separately for different size classes, because zircon studies performed on broad grain-size intervals without considering possible size-age correlations may disguise sorting effects that potentially can lead to a misleading source-area interpretation.