Seismic Geomorphology of Submarine Channels Using Spectral Decomposition Techniques Offshore Angola- West Africa

Abstract

The use of advanced spectral decomposition techniques and Red-Green-Blue (RGB)
blending of 3D seismic data from the transitional slope domain offshore Angola
have provided high resolution imaging of both structural and stratigraphic elements
with great insight into the spatio-temporal distribution of these elements. The
depositional and structural elements observed include sand/mud-filled channels,
sand-rich splays and faults including sub-seismic scale faults. The splays are usually
expressed as bright lobate features (characterized by high amplitude seismic
reflectors) that are up to 10 km wide and 15 km long and deposited at the distal
parts of the turbidite channel systems within unconfined mini-basins. Earlier splay-
deposits are often eroded by subsequent channels cutting through them, with the
products of such erosion deposited as splays within the next mini-basin further
downslope. These eroding channels, once abandoned, are filled with mud – which
are characterized by low amplitude and negative differential compaction in seismic
section. The channels and consequently, the depositional elements appeared to be
controlled by the time-integrated movement of salt – which also creates the mini-
basins. Analysis shows that channels are mostly confined upslope, flowing through
salt walls or salt-cored highs and are mostly erosive but on getting to unconfined
intra-slope mini-basins, these channels spread through the process of avulsion to
deposit splays. In essence, this study has greatly improved our understanding of the
geometry and architecture of depositional elements within the study area, and can
aid in exploration efforts in deepwater settings such as offshore Angola.