Chapter 10 Traction Structures in Contourites

Abstract

Publisher Summary This chapter reviews the traction structures in contourites that are formed in deep marine systems under the influence of oceanic bottom currents. Some general and theoretical constraints on the range of likely processes forming primary sedimentary structures in contourites are established. Each sedimentary structure is documented and analyzed under the constraints and the main controversial points are discussed. Traction structures are inherent to sediments generated or influenced by water flows. Contouritic deposits are developed in close association with bottom currents and show a noticeable variety of bedforms and structures; their study is essential for understanding the patterns of oceanic palaeocirculation. The controversy of traction-structures is also discussed. The proposed sediment structures are, (1) current ripples and cross-lamination, (2) lenticular and flaser bedding, (3) horizontal, subhorizontal, and sinusoidal lamination, (4) large -scale cross-bedding, (5) erosional structures, and (6) grading. The wide spectrum of sedimentary structures in contourites reflects the numerous factors that control their formation including current intensity, steadiness of flow, supply of sediment, hydrochemistry, texture, and composition of available sediment. The Faro Drift facies model and the Gulf of Mexico facies model emphasize the role of primary sedimentary structures.