A New Starting point for the history of South and Equatorial Atlantic Oceans

Abstract

The attempts to obtain the pre-opening fit (and to evaluate its age) and the early evolution of an ocean are strongly dependent to the hypothesis made for the location of the first typical oceanic crust and often require an assessment of the rigidity of the surrounding plates (for the South Atlantic Ocean, see Pindley & Dewey, 1982 ; Curie, 1984 ; Unternehr et al. 1988 ; Nurnberg & Muller, 1991 ; Lawver et al., 1999 ; Macdonald et al., 2003, for the Central Atlantic – Olivet, 1984, Olivet et al., 1996, Sahabi et al., 2004, etc.). Moreover, as in South Atlantic Ocean, this work could be complicated by the lack of well-defined magnetic anomalies that could mark the early history. Nevertheless, the consequences induced by a prebreak-up kinematic reconstruction are tremendous on the genesis of the continental passives margins that marked the breakup area (age, timing, constraints on movements) and on the timing of the first evolution of the ocean (Sahabi et al., 2004). Several authors have already addressed the problem of the pre-opening reconstruction in the South Atlantic Ocean, in the past. Nevertheless, the more recent entire reconstructions of the break-up history (Nurnberg & Muller, 1991; Eagles, 2006) present numerous unexplained misfits (gaps, overlaps and misalignments) that invalidated the fit. We present here a new reconstruction based on magnetic data, satellite altimetry and oceanic and continental geological constraints. This reconstruction is the canvas in which the problem of the continental margins genesis should be addressed.