A global survey of Seasat derived geoid anomalies across fracture zones (FZ) has been conducted to characterize the behaviour of the geoid slope with age of plate in response to lithospheric cooling. We present new results for the geoid slope versus age along six FZ of the Atlantic ocean (Gibbs, Pico, Doldrums, Romanche, Ascension and Agulhas-Falkland FZ). Including results of a previous study on Pacific FZ (Mendocino, Murray, Clarion and Unditsey FZ), we confirm that the geoid slope does not vary with age as conductive cooling models predict and show that its complex behaviour is a worldwide phenomenum. Two trends are clearly shown up by the data: (1) a sharp initial decrease of the geoid slope at very young ages, (2) a subsequent increase which typically starts at ages around 30--40 Ma and culminates at ~60 Ma. In a few cases, the rise of the geoid slope occurs later, beyond 80 Ma. According to the recent models developed by Robinson, Parsons and Driscoll, these trends may result from small scale convection induced by the horizontal thermal gradients underneath the FZ, instabilities developing in a sublithospheric low viscosity layer whose properties vary with age. ¿ American Geophysical Union 1988