Seismic anomalies in the chalk and superimposed folding in the Tertiary formations of the southeastern Paris Basin

The high-resolution seismic survey of the eastern Paris Basin shows steep d isharmonic reflectors within the chalk related to diagenetic structures and coming with important thickness variations of the chalk and the overlaying Tertiary. These structures are related to dissolution/recrystallisation ph enomena within the chalk that also led to deformation of the Tertiary forma tions during its deposition. The interpretation of these intra-chalk dishar monies needs to take into account lateral velocity variations within the ch alk to avoid to "generate" wrong dome structures on the seismic profiles.