A contribution to the middle Oligocene paleogeography of central Europe: New evidence from fission track ages of the southern Rhine-Graben

Zircon and apatite fission-track (FT) ages of marine well-sorted sandstone layers of late Rupelian age in the southern Rhine-Graben (Meletta beds) pro ve an Alpine origin. The FT ages and the heavy mineral spectra suggest that Austroalpine basement rock was the main source. Transport of medium-sized sand contradicts the existence of a marine trough in front of the Swiss sec tor of the Alpine are during this time. It rather indicates a shallow marin e environment in the central section of the Swiss Molasse basin.