Crustal Structure, Subsidence and Uplift History, and Thermal and Mechanical Evolution of the Iberia-Newfoundland Conjugate Margin

We have used new compilations of gravity anomaly, bathymetry and sediment thickness data, together with Process-Oriented Gravity Modelling (POGM) techniques, to estimate the effective elastic thickness (Te) of the lithosphere at the West Iberia-Newfoundland conjugate margin. Results suggest that Te generally decreases from 15-40 km over relatively unstretched continental crust onshore to ≤ 10 km over stretched continental crust. The sensitivity of the method decreases over transitional type crust where the basement relief is low. Despite this, there is evidence that the long-term flexural properties of the lithosphere change along-strike the West Iberian Margin (WIM), and that some correlation exists between parameters such as Te and the Variscan structure. The Newfoundland margin, in contrast, is less segmented along-strike. The stretching factors (β) recovered from POGM have been used to compute the thermal structure, the subsidence and uplift history, the palaeowater depths, and the crustal and upper mantle structure of the WIM. Comparisons with the β derived from 1-D Airy backstripping of commercial wells, where the palaeobathymetry is well constrained, suggest that a 0.5-1 km thickness of sediments has been eroded from the shelf and onshore basins during the Upper Jurassic-Early Cretaceous sedimentary hiatus. Based on the thermal structure of the margin we calculate an independent estimative of Te,, which depends on realistic rheological parameters and strain rates for the WIM. We found that the POGM-derived Te is lower than the rheological Te suggesting that other processes such as those associated with magmatic intrusion, thermal blanketing, increased curvature and yielding may act to weaken it.