Seismic stratigraphy of an accommodation-zone margin rift-lake delta, Lake Malawi, Africa

The Ruhuhu River enters Lake Malawi adjacent to an accommodation zone, a major linkage region between two adjacent half-graben basins that switch dip-polarity along the axis of the Malawi Rift. A large drainage basin developed because of the drop in elevation of the rift shoulder at the accommodation zone. Single-channel digital seismic reflection data indicate that the Ruhuhu River delta's offshore depositional slopes are steep (2-7°), and that subsurface reflections show a strongly divergent stratal character. Sets of prograding clinoforms are observed at various stratigraphic levels and are interpreted as sand-prone lowstand delta lobes. These prograding packages are 20-50 m thick, and typically cover an area of c. 10 km ². Such accommodation zone delta margins are considered prospective areas for hydrocarbon exploration because of their enhanced structural closure, high input of coarse clastic material for reservoir facies and close proximity to organic-rich deep-water shales.