American Oil and Gas Reporter - June 2014 - 62

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62 THE AMERICAN OIL & GAS REPORTER

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The strength of the Agulhas Current can be at its highest near the coast at the 1,000meter water depth mark in this snapshot of surface speed (in cubic meters per second)
in an ocean model.

the survey will be completed as scheduled.
Tectonic History
Seismic acquisition-for either hydrocarbon exploration or field production
efforts-helps explorationists explore new
frontier basins, particularly as petroleum
resources become more difficult to find.
The eastern coast of South Africa is one
of the frontier areas garnering increased
international interest.
With no exploration wells drilled, the
insights gained through seismic acquisition
are giving geoscientists a new understanding of the subsurface geology and
prospectivity of this area. With very little
published data on this margin, predictions
about the petroleum system in frontier
areas must evolve from using analogue
basins and regional geological knowledge
afforded by published literature.
The tectonic history of the margin can
be broken simply into a Permian to Carboniferous Gondwanan compressive phase,
and a Late Jurassic to Early Cretaceous
Gondwanan breakup phase. Gondwana
(the more southerly of two major land
masses that existed 510 million to 180
million years ago) was under major compressive stress during the Permian to Carboniferous, and saw all analogue basins
tightly packed into one another as part of
one land mass.
Northward, subduction of oceanic crust
from the south formed two major thrust
fronts and created the Cape Fold Belt
and Karoo Foreland Basin. The Karoo
Foreland Basin subsequently would develop to be the key onshore basin for hydrocarbon development across onshore
South Africa.

The breakup of Gondwana began in
the Late Jurassic to Early Cretaceous. In
the area of interest for this survey, Gondwana was broken into three major sections:
Africa, South America and Antarctica;
and into two smaller microplates: the
Maurice Ewing Bank and the Falkland
Islands. This rifting phase formed the
offshore margin of South Africa, with
the Outeniqua Basin to the west, the East
Coast of South Africa (where this new
dataset was acquired), and the Tugela
Cone to the northeast (Figure 1).
Geological Analogues
Additionally, explorationists can use
geological analogues from the conjugate
margin. Plate reconstructions indicate
that Falkland and Maurice Ewing Bank
both originated from the South African
margin, drifting westward as the South
Atlantic formed over the past 180 million
years. With discoveries such as Sea Lion
in the North Falklands basin, experts conjecture that there may be a similar play
story offshore South Africa.
Along the southeast margin, where
there has been little exploration, there is
also sparse geological knowledge. There
is a strong possibility that transtensional
tectonics, such as those seen across the
Transform Margin (for example, offshore
Ivory Coast, Ghana, Togo, Benin, and
Nigeria) could be at play.
In the Transform Margin, instead of
simple rifting, there has been transtension
and wrenching, forming normal fault patterns oblique to the coastline. This transtension formed as the African and South
American plate rifted from one another.
A similar wrench-like rifting can be expected in the South African margin where

American Oil and Gas Reporter - June 2014

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