Tectonic Inheritance and the Atlantic Ocean

Chris Parry

It is now becoming more widely accepted that continental plates are not necessarily large rigid bodies but instead are composed of a number of deformable micro-plates. A number of important papers have been published recently on this subject for the North and South Atlantic region and global plate reconstructions, which include Giraud et al., 2010, Moulin et al. 2010 and Torsvik et al., 2010, Osmundsen and Redfield, 2011, Gerlings et al., 2012, Peron-Pinvidic et al, 2012 (a) and (b) and Sutra and Manatschal, 2012 and references therein. Lister et al., 1986, described upper plate and lower plate passive margins, separated by a detachment fault, which give rise to asymmetric conjugate margins after final continental break up. Transfer faults offset marginal features and can cause the upper/lower plate polarity to change along the strike of the margin. These zones of long-lived crustal weakness can be subsequently reactivated during later tectonic episodes, the concept of “tectonic inheritance” associated with Wilson cycles, the opening and subsequent closure of an ocean. The Eastern Seaboard of the North American Continent has experienced at least two complete Wilson cycles. The Proterozoic Grenville Orogeny closure of an ocean formed the Rodinia supercontinent, which was subsequently broken up with the opening of the Iapetus Ocean in the Cambro-Ordovician. Basement related zones of weakness (failed rift arms) in the Appalachian Range form the location of the fractures zones for the opening of the Iapetus Ocean and also influence the Siluro-Devonian Caledonian Orogeny deformation (recesses and salients) during the subsequent ocean closure, forming the Pangaea supercontinent. These same zones of crustal weakness are reactivated once again during the breakup of Pangaea, influenced the location of the fracture zones in the Mesozoic opening of the Atlantic Ocean (Thomas, 2006) and are currently still active (Bailey, 2004). Using the Southern and Central Atlantic Oceans as analogues, the integration of gravity, magnetic and seismic data has been used to construct a simple symmetrical spreading model for the opening of the Norwegian – Greenland Sea between Iceland and the Fram Strait. Continued reactivation of the various fracture zones gives rise to inversion structures and complex compressive and transpressive/transtensional features, which are recognized throughout the conjugate North Atlantic continental shelves, the Faroe Islands and the Jan Mayen Micro-Continent.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013