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Michele Rebesco, OGS (Italy)
Angelo Camerlenghi, Icrea, c/o GRC Geociencies Marines, Univ. Barcelona (Spain)
All Authors, Book Contourites (Netherlands)
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Contourites are sediments deposited or substantially reworked by bottom currents. The study of contourites is crucial for three main fields of fundamental and applied research:
(1) palaeoclimatology and paleoceanography, since these fairly continuous and relatively high-resolution sediments hold the key for priceless information on the variability in circulation pattern, current velocity, oceanographic history and basin interconnectivity;
(2) hydrocarbon exploration, since accumulation of source rocks may be favoured by weak bottom currents, whereas "clean" deep-sea sands may be formed by robust flows;
(3) submarine slope instability, since low-permeability fine-grained contourites facilitate the formation of overpressurized gliding planes when fresh contourites with a high pore-water content becomes rapidly loaded, or when their rigid biosiliceous microfabric collapses due to diagenetic conditions.
Despite their significance, contourites are poorly known by the majority of non-specialists. Notwithstanding the growing interest and the intensified research in contourites, a reference book on contourites was missing. The authors of this abstract are the editors of the book CONTOURITES, for the series "Developments in Sedimentology", to be published by Elsevier at the end of 2008.
This book addresses all aspects of the knowledge related to contourites and provides an authoritative and comprehensive coverage of the subject. It can serve as a standard reference work for non-specialists who are seeking an authoritative source of information about contourites.
Through the contributions of all authors of the book CONTOURITES, the editors gained an up-to-date multidisciplinary perspective of the bottom currents and sedimentary processes controlling the large scale geometry/morphology and interior attributes of these kind of sediments. A number of case histories in the different domains of the continental margins detail the research. Among the open questions there is the need for a more stringent terminology and the divergence of opinions about depositional structures.
Traction structures are considered a distinctive aspect of these sediments on the assumption that they are deposited by long-lasting bottom current, by contrast with the episodic, decelerating, gravity-driven currents. And in fact migrating bedforms of variable scale decorate the seafloor beneath the path of present bottom currents. However, conspicuous evidence from deep sea sedimentary cores demonstrates that pervasive bioturbatiuon, which likely obliterated pre-existing sedimentary structures, is the dominant aspect of recent sediments from contouritic drifts. Laminations in recent fine-grained contourites from Antarctic margins and of cross-stratifications in ancient corse-grained carbonatic contourites from Spain suggest that sedimentary structures may be preserved in environmental conditions of suppressed primary productivity and rapid deposition from high-speed flows.
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