Evolution of the Margins Around Continental Break Up: Insights from the South Atlantic Margins
Patrick Unternehr1, Gwenn Peron-Pinvidic2, and Gianreto Manatschal2
1New Business, Total, Paris la Défense 6, France
2CGS-EOST, Strasbourg, France
Research into the formation of deep passive continental margins is incontestably undergoing a paradigm shift. For the last 15 years, Petroleum Exploration has been developed largely on Deep Offshore areas mainly on turbiditic plays related to post rift deposits and major oil fields have been discovered in several basins .Now, the main evolution for the Industry is to explore further (in bathymetry) and deeper (in burial) looking for new plays as ‘synrift ‘in Ultra Deep Offshore. The large industrial seismic effort really improved the knowledge of these margins and allowed very unexpected observations relating to synrift models. Some of these observations are the discovery of hyperextended crust (and exhumed continental mantle?) devoid of significant normal faulting directly overlain by shallow marine or continental sediments (sag) .Analogs from ancient hyperextended margins exposed in the Alps help to identify lithologies and structures similar to those drilled by the DSDP program along the Iberia-Newfoundland margins or those supposedly comprising the pre-salt sag basins of the South Atlantic.
In this presentation we show a few examples on South Atlantic margins which address some key problems:
How to make a sag basin (without any apparent normal faults) in a shallow environment during the syn oceanization phase (‘synrift’)?
What is the mechanism which thins the lithosphere?
What is the meaning of the ‘Break up unconformity ‘and how this geometrical surface is used and extrapolated when we do not have any well controls?
What is the meaning of ‘synrift/postrift’ related to oceanization?
What is the thermal history and the effect on the maturity of Source Rocks?
The understanding of the mechanisms which explain these observations is a key to making the best predictions in the deep distal parts of these prolific petroleum margins.
AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery