--> The Evolution of the Atlantic Margin of Iberia as Recorded in the Lusitanian Basin (Portugal), Reis, Rui P.; Pimentel, Nuno; Garcia, António, #90100 (2009)

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The Evolution of the Atlantic Margin of Iberia as Recorded in the Lusitanian Basin (Portugal)

Reis, Rui P.1
 Pimentel, Nuno2
 Garcia, António3

1Earth Sciences, University of Coimbra, Coimbra, Portugal.
2
Geology,
University of Lisbon, Lisbon, Portugal.
3
Federal
University of Sergipe, Aracaju, Brazil.

The Lusitanian Basin (LB) is located at the western façade of
Europe, facing the Atlantic Ocean but close to the Mediterranean Sea. It is a peri-atlantic basin originated in a tethyan realm, sharing with both oceans, some of its controls and tectono-sedimentary features. This work aims to present a stratigraphic chart of the LB with the major events of its evolution. The lithostratigraphy of the LB is based on published works, with revisions and formalization for some intervals. A unified chart is presented, integrating those data with recent studies developed within the scope of Project Atlantis (supported by PETROBRAS and developed by brazilian and portuguese universities - UFS/UC/UL).

Besides lithostratigraphy, other aspects of the LB, are presented. The evolution of the basin present three 1st order geodynamic rifting cycles, separated by large-scale regional unconformities. Fourteen 2nd order T-R sequences are established, controlled by sea level changes and tectonic phases. Magmatic and diapiric events underline critical moments, namely in relation with geodynamic changes and the main extensional or compressional episodes. The following regional geodynamic framework and evolution results from the analysis of the sedimentary infilling:

- a Late Triasic to Late Jurassic rifting, dictated mainly by the Pangea break-up and tethyan influence in western European plate; two phases may be defined, the first one (Upper Triassic) mainly continental with an evaporitic event, the second one (Lower and Middle Jurassic) deep ramp to carbonate shelf, both marked at its bases by magmatic intrusions;

- a Upper Jurassic to Lower Cretaceous rifting, driven by the alignment of the basin with the Central Atlantic opening; the basin has been re-oriented and new depocenters developed; intense subsidence triggered diapiric geometries;

- Lower to Upper Cretaceous drift, initiated by the North Atlantic Ocean spreading, begun and ended with magmatism; the break-up unconformity is diachronous, jumping in three steps towards North; diapirism has been intensified and reached extrusion;

- Upper Cretaceous and Cenozoic inversion of the basin with uplift and erosion, resulting from the collision between the Iberian and African plates.
Petroleum system elements, identifiable and active in the LB, may also be integrated in this framework. Source-rocks, reservoirs, maturation and traps, show interesting relations with the stages of the basin’s Mesozoic and Cenozoic evolution.

AAPG Search and Discover Article #90100©2009 AAPG International Conference and Exhibition 15-18 November 2009, Rio de Janeiro, Brazil