Regional Stratigraphy of the Pletmos Basin

The Pletmos Basin, which is a sub-basin of the greater Outeniqua Basin, is located off the south coast of South Africa and is bounded by the Bredasdorp Basin to the west, the Gamtoos Basin to the east and the Southern Outeniqua Basin to the south. The area of interest is approximately 28 500km2 in extent.

The approach applied in the analysis for this study was based on five selected seismic transects which were interpreted using seismic stratigraphy. These interpretations were incorporated along with composite logs analysis for their respective wells to provide the framework in understanding how the Pletmos Basin evolved sedimentologically.

A widely accepted nomenclature established by Brown et al (1995) was utilised to fully understand the framework of this interpretation. The sequence boundaries focused on 1At1 (Early Valanginian), 6At1 (Late hauterivian), 9At1 (Mid Barremian), 13At1 (Early Aptian), 15At1 (Late Cenomanian), 17At1 (Early Campanian) and 22At1 (Late Maastrichtian).

Concepts (analysis) of sequence stratigraphy applied for this study was based on work from various authors including Emery and Myers (1996), Catuneanu (2002), Catuneanu (2006) and Catuneanu et al. (2009) among others. Varying stratal terminations were identified and categorised as either onlap, downlap, offlap, toplap and truncation as a way to establish various system tracts. These system tracts are linkages of contemporaneous depositional environments. From this, an evolutional relationship can be established between structural and stratigraphic development.