BAIRD, ALASTAIR, and CHRIS CLAYTON, Kingston University, Kingston upon Thames, Surrey KT1 2EE, UK

Abstract: The Hydrocarbon Systems of the Atlas Mountains of Northern Tunisia

Within the Atlas mountains of northern Tunisia, hydrocarbons are produced from the tilted footwall blocks of some of the post-orogenic grabens which dissect the Atlas mountains. The pre- and syn-orogenic basins of the Atlas mountains contain mature source rock horizons, numerous potential reservoir and cap rocks and active oil seeps. However, oil exploration in these settings region has proved unsuccessful, primarily because inappropriate models of basin and structural evolution have been used.

In most published analyses of the Tunisian Atlas, the Triassic rocks of the Mejerda zone are assumed to have risen diapirically to their present structural level. Some authors have observed that the "diapirs" are sheared and lie within the thrustbelt whilst others argue that they occupy the foreland. Only in the last decade has it been clearly established that the Atlas thrustbelt extends several tens of km SE of the Mejerda zone. More significantly, neither diapirism, nor thrusting, nor any combination of both, can simply explain the structural geometries, sedimentary thicknesses and facies variations in the thrustbelt.

The stratigraphical, sedimentological structural and geophysical evidence is summarised to refute ideas of diapirism and to establish the subsidence history, geometry and polyphase deformation of Mesozoic to Tertiary basins within the Atlas mountains. Subsidence histories, vitrinite analyses, maturity modelling and the spatial distribution of Pb-Zn mineralisation are integrated to establish a rigorous model for the hydrocarbon system in the Tunisian Atlas which links the timing and migration pathways of fluid flow to the structural evolution. 

AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England