Plate kinematics of the central Atlantic

Abstract

Opening of the central Atlantic Ocean basin during the past 200 Ma separated North America from Africa and created a classic example of plate tectonic divergent motion and associated geologic features (LePichon, 1968; Morgan, 1968). The entire history of relative motion of these two plates is preserved in the fabric of sea-floor spreading (SFS) recorded by magnetic lineation and fracture zone (FZ) patterns (Fig. 1) (Vine and Matthews, 1963; Heezen and Tharp, 1965) on both flanks of the Mid-Atlantic Ridge. Age calibration of the SFS magnetic anomaly pattern (Cox, 1973; Harland and others, 1982; Kent and Gradstein, this volume) enables us to treat SFS lineations as isochrons of sea-floor crustal ages. FZs mark the path of spreading center offsets (transform faults) through time, providing an approximate flowline trace of the motions that separated the North American and African plates. Reconstruction poles of rotation and stage poles of motion can be determined from the SFS lineation and FZ data sets (Bullard and others, 1965; McKenzie and Parker, 1967; McKenzie and Sclater, 1971; Harrison, 1972). The kinematic history described by these poles provides a framework for examining major tectonic events, anomalous plate behavior, geologic phenomena, paleooceanographic events, etc. (e.g., Vogt and others, 1969; Tarling and Runcorn, 1973; Dewey and others, 1973; Vail and others, 1977; Sclater and others, 1977; Pitman, 1978; Rona and Richardson, 1978; Schwan, 1980; Kerr and Fergusson, 1981;