[1] A general understanding of rifted margins, which form by thinning of the continental lithosphere, exists. Nevertheless, the exact form of thinning is unclear. This debate has been stimulated by acquisition of dense seismic wide-angle and deep reflection surveys from Atlantic Ocean margins. A central issue concerns the way in which thinning changes with depth. We have tackled this issue by developing a generalized inverse model. This model attempts to fit subsidence and crustal thinning observations by varying strain rate as a function of time and space. Depth-dependent thinning is permitted but we do not prescribe its existence or form. Here, the algorithm is applied to six margins, including two of the most contentious conjugate margins: Newfoundland-Iberia and Brazil-Angola. Calculated strain rate histories predict thinning estimates which broadly match estimates inferred from normal faulting. The Eastern Indian and Beaufort Sea margins formed by largely uniform lithospheric thinning. In contrast, the Newfoundland-Iberian conjugate margins formed by a pattern of strongly depth-dependent strain rate. To account for the paucity of syn-rift decompression melting of the underlying asthenosphere, the lithospheric mantle close to oceanic-continent transition must thin more slowly than the overlying crust. This form of depth dependency is not common. For example, the BrazilAngolan conjugate margin could have formed by uniform lithospheric thinning provided thick layers of salt were deposited in a preexisting 400 m deep topographic depression. Depth-dependent thinning is not required to account for rapid subsidence of presalt strata.

It is likely that the Iceland mantle plume generated transient uplift across the North Atlantic region when it initiated in earliest Cenozoic time. However, transient uplift recorded in sedimentary basins fringing the region can be overprinted by the effects of permanent uplift. Identifying and quantifying transient uplift can only be achieved in areas which have a well‐constrained stratigraphic record and across which the relative importance of permanent and transient uplift varies (e.g., the Moray Firth Basin, North Sea). By analyzing the subsidence of 50 boreholes from the Moray Firth Basin (MFB), residual vertical motions unrelated to rifting have been isolated. Transient uplift of 180–425 m occurred during Paleocene times. The western MFB has also been affected by permanent Cenozoic uplift, with denudation decreasing from 1.3 ± 0.1 km in the west of the basin to zero denudation east of 1°W. Dynamic support above the Iceland Plume led to transient uplift of the entire MFB in early Paleocene times, peaking in latest Paleocene times. In early Eocene times the effect of the plume waned, and subsidence occurred. Paleocene permanent uplift of the NW British Isles is generally accepted to have been due to magmatic underplating of the crust emplaced during the British Tertiary Igneous Province (61–58.5 Ma). The cause of Neogene uplift events is poorly understood, but it could also be associated with the Iceland Plume.

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[1] Accurate measurement of the temporal and spatial variation of uplift and denudation would improve our understanding of the way in which mountain building and mantle convection modify the Earth's surface. Here, we show that inverse modeling of stacking velocity data from seismic reflection data sets is a potentially useful tool for obtaining spatially resolved denudation estimates along and across continental shelves. Unlike many techniques for measuring denudation, our approach is not restricted to outcrop or borehole locations, although it is important to calibrate results with other measurements of denudation. We have inverted 2200 stacking velocity analyses from a dense network of two-dimensional seismic reflection lines which surround the British Isles. This region was chosen because there is a well-known signal of Cenozoic uplift and denudation which is big enough to be detectable using our approach. Despite simplified assumptions about the way in which porosity varies with depth, our offshore denudation estimates are consistent with outcrop patterns and accord with published denudation measurements. Furthermore, stacking velocity estimates agree with measurements obtained by analyzing sonic velocity logs from selected boreholes. A region encompassing the British Isles has evidently undergone variable amounts of denudation during Cenozoic times. However, significant denudation (>1.5 km) is concentrated in discrete areas, such as off NW Scotland and parts of the Irish Sea. The magnitude of denudation changes significantly over short ($10 km) distances, implying that differential uplift and erosion have been important factors in creating the present-day denudation pattern.