X. Le Pichon, N. Lybéris and F. Alvarez write: In our discussion of the subsidence history of the North Aegean trough (Le Pichon et al. 1984), we proposed a crustal model within the framework of the homogeneous stretching model. We showed that this model satisfactorily accounted for the data available but pointed out that 'this does not prove that the model is correct'. Thus, an alternative view is certainly welcome provided it also accounts for the existing data but we claim it does not.
An important point concerns the amount of crustal thinning. We pointed out that the gravity surveys indicated that subsidence had occurred under a state of isostatic equilibrium because the free air anomalies were close to zero outside of the North Aegean trough and did not exceed –10 to –20 mgal over the trough itself. We interpreted the 50 to 60 mgal highs on the sides of the troughs as side effects of a deep compensating mass. This was especially clear on profile A of fig. 2 and fig. 12 which we fitted in our model.
Figure 1 shows the gravity profile modelled by Brooks & Kiriakidis (1986) along a different N-S line which ends near the Chalkidiki peninsula. To discuss the solution proposed, by them we have recomputed the same profile showing the gravity contribution of the different layers they have chosen, using the densities proposed by them. We note that, instead of considering the shoulder highs as side effects of a deep compensating mass, Brooks