Pleistocene Estuary Of The Orange River

Palaeochannels are widely distributed along the inner<br>and middle shelf of the west coast of Southern Africa, but<br>of particular interest is a set of channels off the southern<br>Namibian coast (Fig 1). This article describes the mapping<br>of these channels using seismic records, and offers a model<br>for their formation.<br>Two types of seismic data are presented - one using<br>Boomer (Marine Diamond Corporation) and the other using a<br>lower frequency airgun (Geological Survey of South Africa).<br>The Boomer penetrated 20 metres or more into the inshore<br>sediment wedge and its records often show details within the<br>Cretaceous and Tertiary bedrock (Fig 2). The airgun<br>generally achieved better penetration into bedrock but at<br>the expense of resolution. For both surveys, Decca Navigator<br>was used for position fixing (Foster 1973; Birch 1979).