The economic importance of contourites
A. R. Viana, W. Almeida, Jr, M. C. V. Nunes, E. M. Bulhões, 2007. "The economic importance of contourites", Economic and Palaeoceanographic Significance of Contourite Deposits, A. R. Viana, M. Rebesco
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The importance of contour currents in shaping and building continental margins has long been accepted. Their economic implications and the stratigraphic framework in which they are developed remain largely unknown. Data retrieved from sidescan sonar images, seismic profiles and their attribute maps, as well as sea-floor coring, boreholes and the few known outcrops around the world, suggest that bottom currents can locally develop large deposits of relatively coarse-grained sediments. Accumulation of coarse-grained deposits under the influence of bottom currents requires sediment availability, a geologically persistent strong circulation regime and a favourable physiographic setting both for enhancing the currents and for hosting the sediments. The hydrocarbon exploration of oceanic depositional systems demands a better understanding of the role of bottom currents and their implications for petroleum systems such as reservoir and sealing rocks. Such understanding implies additional alternatives for the definition of exploration targets and prospect risk reduction. Correlating seismic anomalies from 3D mapping with core and well logging data reveals the depositional geometry and sedimentological characteristics of coarse-grained contourites. Fine-grained drifts can locally and regionally develop large and thick accumulations, which have an important seal potential for trapping hydrocarbon.
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There has lately been a growth in the number and level of studies of contourite deposits. Most recent studies of contourites have two major lines of interest. One, propelled by the oil industry's continuous move into increasingly deep waters, concerns their economic significance. The other involves the stratigraphic/palaeoceanographic record of ocean circulation changes imprinted on contourite deposits that can be a key to understanding better the climate-ocean connection. The application of many different theoretical, experimental and empirical resources provided by geophysics, sedimentology, geochemistry, petrology, scale modeling and field geology are used in the 16 papers of this volume, proposing answers to those two main aspects. The papers are subdivided into two major categories (economic interest and stratigraphic/palaeoceanographic significance), with case studies ranging from well-documented drifts to new examples of modern and fossil series, involving a large diversity of geographic and physiographic scenarios worldwide.