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A study on central Baikal rift flank uplift and topography questioned the applicability of the flexural cantilever model to the rift and other rift basins. The analysis, however, failed to consider many observed faults and employ a model that would represent the real upper crustal geological feature and process. The study committed an error in readily discounting the flexural cantilever model in rift basin modeling and failed to indicate the model's capacity to incorporate upper crustal fault geometries.

The post-Cretaceous subsidence history of the Voring Basin, part of the Atlantic passive margin offshore mid-Norway, has been investigated. Extension and [Beta]-factors related to rifting and continental break-up during the Palaeocene have been quantified using both forward and reverse basin-modelling techniques. In the preferred geological model it is assumed that rifting occurred in the Voring Basin during the Palaeocene (prior to break-up), following an earlier rift event during the Late Jurassic. During Palaeocene rifting the basin may have been dynamically uplifted by the Iceland mantle plume. In the east of the basin there was no Palaeocene extension. Subsidence analysis shows that in the centre of the basin forward and reverse models converge to predict a modest Palaeocene stretching factor ([Beta]) of c. 1.15. In the west of the basin, closest to the Atlantic margin, forward models of upper-crustal faulting also predict a [Beta] of c. 1.15, but reverse (backstripped) models of subsidence predict a [Beta] of up to 1.75. We suggest that lower-crustal and mantle-lithosphere thinning close to the margin were greater than the extension accommodated by upper-crustal faulting and that some lower-crustal/mantle-lithosphere stretching associated with continental separation was partitioned below the Voring Basin, up to 150 km landwards of the margin. Keywords: Norway, Atlantic Ocean, Palaeocene, models, rifting.

Seismic data made available by the UK OGA (Oil & Gas Authority) has been used to constrain a model of crustal structure and heat-flow history for the UK Rockall Basin. Top basement/base sediment has been interpreted around the full extent of the seismic dataset. This has produced a model for the thickness of the sediment fill within the basin which is thicker than previous published estimates. The new sediment-thickness model has been incorporated into a 3D backstripping study, producing maps of subsidence and thinning factor. Analysis of backstripped subsidence shows the thinning factor reaching peak values of c. 0.8-0.85 (β factor >5) in the south-central axial area, reducing in magnitude northwards to c. 0.7. The new sediment-thickness model has also been incorporated into a 3D gravity-inversion study, mapping Moho depth, crustal thickness and thinning/stretching factor. The results show crustal-basement thickness reduced to c. 6 km, thinning factor c. 0.8, in the south-central area, while it spans the range c. 6-10 km further north. The results are compatible with previous seismic refraction work in both the UK and Irish sectors of the Rockall Basin.We believe that the extension which created the basin was non-magmatic and that the axial region is underlain by highly-thinned continental crust. The results from the gravity inversion have been used to make predictions about the top-basement heat-flow history. Heat flow in the basin centre is predicted to have been initially high, reducing with time, associated with cooling of the transient synrift heat-flow anomaly. On the basin flanks heat flow was less variable over time, its magnitude controlled primarily by constant radiogenic heat input from the basement, rather than by the transient geotherm anomaly. There remain considerable uncertainties associated with our interpretation and analysis. These uncertainties have been addressed with sensitivity analyses. A regional gravity-inversion model, using the new sediment-thickness data spliced into regional public-domain information, shows that structural and stretching continuity can be mapped at the crustal scale along the full length of the UK/Irish Rockall Basin, contrary to conclusions from some previous studies. [ABSTRACT FROM AUTHOR]

Opinion. Comments on the work of Peter van der Beek related to the use of quantitative basin-modeling technique in the study of the central Baikal Rift in Russia. Arguments of the authors; Objectivity and soundness of van der Beek's findings; Response of van der Beek to the criticism.