Fernando Zúñiga-Rivero¹, Hugh Hay-Roe¹, Allen Lowrie²

(1) BPZ & Associates, Inc, Houston, TX
(2) CONSULTANT, Picayune, MS

ABSTRACT: A New View of the Sechura Basin, NW Peru: Stratigraphic and Tectonic Relationships

The Sechura Basin lies SE of the Talara Basin, NW Perú. Eocene producing horizons yield natural gas. Modern seismic and sequence stratigraphic analysis suggest relationships between tectonics and submarine fan deposition. These fans originate at the tectonic zone separating the two basins. Thrust faults, with secondary normal faults, characterize the tectonics.

The Paleozoic basin floor was peneplained with fault-induced offsets of less than 50 m. Offsetting faults extend subsurface-ward.

Four sedimentary units of Mesozoic through Tertiary age suggest a deepening, then a shallowing of the northern Sechura Basin. The deepest Mesozoic unit was deposited in less than 200m water depth and consists of equal thickness fans, which extend from the tectonic zone. The second unit of thick individual fans, extending to the NW and characterized by large submarine canyons, thins rapidly to the SE. The fans' reflector character suggests high-energy environments including sands. The third unit of Paleogene age extends farther to the NW than the two deeper units. Greater lateral extent indicates underlying tectonic quiescence with maximum water depths possibly equivalent to upper slope. The sedimentary source is northwestward of previous sources. Mid-section thinning suggests a by-pass zone, as sediments descended from the NW to the SE. The concave-upward, thickened, down-dip fan is deposition site of reservoir-grade debris. The shallowest interpretable unit is onlapping toward the NW onto underlying sequences. Shallowing continued until reaching regional emergence in Miocene time. This unit is thin and flat-lying.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado