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A Comparative Approach to the Petroleum Systems of Peri-Atlantic Basins with a Tethyan Influence - the Example of the Lusitanian Basin (Portugal)

Pimentel, Nuno 1; Pena dos Reis, Rui 2
1 Geology Center, Lisbon University, Lisboa, Portugal.
2 Geosciences Center, Coimbra University, Coimbra, Portugal.

The Lusitanian Basin (LB) is a located in the western façade of Iberia, representing today a passive margin of the North Atlantic Cretaceous opening. However, its evolution has been more complex and started much earlier, with the Triassic and Jurassic crustal stretching of this region, in which the spreading and closure of the Tethys, as well as the opening of the Central Atlantic, played also important roles.

The Lusitanian Basin’s evolution may be divided into 4 main geodynamic steps: i) a first west-tethyean rifting; ii) a second atlantic-oriented rifting; iii) a three-stepped north-atlantic break-up ; iv) the tectonic inversion of the basin and uplift of most of the areas. To understand the petroleum systems of this basin, a regional geodynamic approach must therefore be used, by integrating the lithostratigraphic and petroleum system elements into a broader palaeogeographic framework.

To document this approach, we present a comparative analysis with other basins which were close to the LB during its Mesozoic evolution and shared many of its geodynamic controls and events: the Algarve Basin (SW Iberia), the Essaouira Basin (W Morocco), the Atlas Basin (NE Morocco) and the Jeanne D’Arc Basin (NE America). The analysis of the lithostratigraphic charts, paleogeographic reconstructions and tectonic events of these basins, supports important correlations related with the opening of the Central and North Atlantic, as well as the spreading of the Alpine Tethys and detachment of Iberia from Africa and later from Eurasia.

Petroleum systems of these basins may also be compared, showing interesting similar elements distribution, both in its characteristics and timings. In the atlantic-related basins, source rocks, reservoirs and seals were generated in broadly similar contexts and timings. The tethyean-related basins present a different post-Middle Jurassic evolution, implying different intensities and timings of maturation and migration. Local differences may be related to local factors such as the intensity of inversion and salt tectonics.

This work is a contribution to Project Atlantis - “Geological model for the Jurassic Riftings of the Lusitanian Basin (Portugal)” - financed by Petrobras (Brazil) and developed by the Universities of Coimbra, Lisbon (Portugal) and Sergipe (Brazil).

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009