THE TALARA FORE-ARC BASIN, NW PERU - DEPOSITIONAL MODELS OF OIL-PRODUCING CENOZOIC CLASTIC SYSTEMS

The Talara Basin is an unusual forearc basin in as much as it displays many features which are not characteristic of such a tectonic context. These features apparently result from the basin's location at the intersection of the Amazonas Aulacogen, the Andean orogenic belt, and the subduction zone of the Peru-Chile Trench. The history of the Talara forearc basin is dominated by extensional rather than compressional tectonic activity, which reached a peak after the Eocene in association with low-angle gravity slides. This tectonism began with a prolonged synsedimentary phase. which, during the Paleocene-Eocene, generated a complex system of horsts and grabens bounded by major high-angle normal faults trending NE-SW and NW-SE. Closely related to repeated phases of uplift and erosion in the eastern Andean source areas. this structural pattern controlled unusually thick and coarse clastic sedimentation during the Paleocene-Eocene: a thickness of about 22,000 ft has been preserved, from which volcanics are essentially absent. The depositional environments were a series of interfering, transverse and longitudinal, deltaic and submarine fan systems, all of which contain distal portions in which organic-rich marine shales were deposited. Given these conditions, it is not surprising that the Talara Basin has produced to date more than a billion (10(9)) barrels of oil. Although oil is produced from these depositional systems both on- and offshore, the latter environment has been barely explored near the present-day coastline, and is believed to have enormous potential for future development.