Extensive aeromagnetic surveys in the eastern Weddell Sea, the Lazarev- and Riiser-Larsen Sea carried out during the last six years by the Alfred-Wegener-Institute are the basis of a well constrained model for the early break-up of Gondwanaland.Despite intensive geophysical and geological research that has been conducted in the last two decades in the Weddell Sea and adjacent areas, timing and geometry of the initial stages of the Mesozoic break-up between Africa, Antarctica and South America is still a matter of controversy debate. The new aeromagnetic database, comprising 90000 km of closely spaced (~10 km) flight lines, resulted in a detailed magnetic anomaly grid for this region. For the western part of the grid where clear coast parallel seafloor spreading anomalies exist, synthetic anomaly sequences could be calculated. This, together with another model for the Riiser-Larsen-Sea led to a new model for the early development of this region.It shows, that the first ocean floor off Dronning Maud Land has been created in late Jurassic times (M14N) by a rift, the Weddell Rift, propagating from the south western Weddell Sea to the east along the east coast of East-Antarctica. Some 10 - 15 Ma earlier the first seafloor in the Riiser-Larsen Sea has been created by an almost coast parallel spreading centre. The diverging spreading directions and velocities between the eastern Weddell Sea and the Riiser-Larsen-Sea put West-Gondwana, comprising South America and Africa, under constant tension since the initial phase of rifting and finally led to the opening of the South Atlantic Ocean at chron M9N.Starting with this age model for the eastern Weddell Sea the new aeromagnetic compilation was put together with published data from the USAC (U.S.-Argentina-Chile) Project, the National Geophysical Data Center (NGDC, Boulder,Colorado) and Russian aeromagnetic data (Golynsky et al. 1998) for an integrated interpretation and validation of the new and existing seafloor spreading anomaly picks.We present the new aeromagnetic database, the resulting geodynamic model and the verification of the data and model with respect to existing data and models.References:Golynsky, A.V., Aleshkova, N.D., Kamenv, E.N., Kurinin, R.G., Masolov, V.N. (1998). Magnetic Anomaly Imprints of the Major Tectonic Provinces in the Weddell Sea Region. Abschlußbericht zum Forschungsprojekt BMFT 03F08GUS9, Teilprojekt 4, Alfred-Wegener-Institut, Bremerhaven.