A Deltaic Swamp Forest: Coastal Wetland Vegetation During the Climax of the Carnian Pluvial Episode

Abstract Thewell-knownpaleobiota of the Fossil -Lagerstätte fromthesurroundingsof Lunz-am-See in Lower Austria were deposited during the early–middle Carnian, within a period commonly referred to as the worldwide Late Triassic Carnian Pluvial Episode (CPE). If vegetation thrives during environmental circumstances that change to wetter and moister conditions with time, the expectation is that the plants will develop or evolve certain adaptations to such conditions, for example to compete for sunlight or cope with heavy rain. Adaptations to wet conditions may be evident on macroscopic scale, but may also remain hidden. The latter can be reflected in characters that are visible only on micro-scale, i.e. on cellular level. Most plantfossils from the Carnian (Upper Triassic) Lunz Formation yield excellently preserved cuticles. An adaptation of this presumed coastalvegetation to moister or wetter conditions, reflecting the influences of their coastal exposition, has repeatedly been emphasized. The environmental conditions that affected the ecosystem are re-evaluated here synoptically based on the composition of the vegetation and the different adaptations of the individual plant species on the macro- and microscopic level. The plant-bearing beds of the Lunz Formation are interpreted as the result of a short-term sea-level lowstand and a meandering river delta system. That system transported terrestrial material from the northeast into a brackish marsh area close to the coast, during the otherwise prevailing marine sedimentation in the Alpine Triassic. The vegetation—if considered as a whole and incorporating all aspects—indicates a humid, moist and swampy, deltaic or near-coastalenvironment, with autochthonously embedded plantfossils.