Final Rifting Evolution from Deep Magma-Poor Rifted Margins: Insights from the Iberia-Newfoundland Rifted Margins

Gwenn Peron-Pinvidic¹, Gianreto Manatscha¹, and Patrick Unternehr^2
1EOST-CGS, Strasbourg, France
²TOTAL, Paris - La Defense, France

In classical rifting models, the transition from rifting to seafloor spreading was suggested to represent a sharp spatial and temporal limit, referred to as ocean-continent boundary and breakup unconformity in the sedimentary sequence. This concept is at present scrutinized by observations from the Iberia-Newfoundland rifted margins.

Our work aims to examine the morphotectonic evolution of the distal domains of these margins in order to constrain the final rifting and continental break-up history. We mapped the architecture of basement structures and dated sedimentary units and used drilling results from ODP legs from the conjugate Iberia-Newfoundland margins. Our results show evidence for a complex overall migration and localization of deformation into the area of final breakup that is linked with a change in the mode of deformation. These observations strongly underline that classical indicators used to determining location and age of breakup can not be used as stand alone criteria (such as breakup unconformity, magnetic anomalies, composition of rocks, occurrence of high-angle faults and sedimentary wedges). Recurrence of distributed tectonic extension and magmatic activity even after onset of localized seafloor spreading suggest that continental breakup is a transitional and complex process that can occur, in magma-poor environments, over 10s of millions of years and result in hundreds of km of crust that is neither oceanic nor continental. Although our study is limited to the Iberia-Newfoundland rift system, comparisons with other margins (e.g. Angola-Gabon) suggest that the described evolution is probably more common and applicable for a large number of rifted margins. These new results have major implications for plate kinematic reconstructions and ask to rethink the terminology, the processes, and the concepts that are used to describe continental breakup.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery