Print this pageSyn-Rift Sedimentation and Timing of Continental Break-Up of Santos and Campos Basins, Brazil
Continental break-up of the Santos and Campos margin evolved relatively rapidly during the late Barremian-early Aptian. Over approximately 15 m.y., upwards of 4-5 km of syn-rift sediment and 3-4 km of salt were deposited in the rift system. The Campos margin is relatively narrow, whereas the Santos margin is very wide. This difference may be due to possible exhumation of the lower crust and/or mantle in Santos Basin in response to significant hyper-extension of the crust.
Rift activity in SE Brazil varies both temporally and geographically across the margin. In Santos, rift activity shifted from inboard to outboard and propagated to the northeast. After extrusion of the Parana Basalt, rift activity decreased in Santos and shifted its focus to the Central Atlantic. In offshore central Brazil, rifting rapidly developed in the Espirito Santo region and propagated southward through Campos basin. Meanwhile, reactivation of the Santos rift system led to eventual linked-up with the Campos rift system outboard of the Cabo Frio High, by about 116 m.y., to complete the break-up of the South Atlantic.
The mechanism for rifting changed as the margin evolved. Initially, accommodation space was caused by brittle faulting of the upper crust, as shown by expansion of large half-grabens in the lower units of the syn-rift. Subsequently, as crustal properties become more ductile, accommodation space was created by passive sag, as shown by the decreased fault activity of the upper syn-rift units. Overall, the lower units are restricted into isolated half-grabens, whereas the upper units tend to coalesce into more widespread lake systems. Seismic facies correlation and EOD mapping suggest areas of broad lake center facies that potentially hold rich Barremian source rock that are adjacent to, or interbedded with, thick lake margin settings that potentially contain reservoir rocks. Tectonic reconstructions indicate that the southern Santos basin, including the Outer Basin High, was adjacent to Africa during the latest stages of rifting.
AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil