Abstract This work uses seismic records to document and classify contourite features around the Iberian continental margin to determine their implications for depositional systems and petroleum exploration. Contourites include depositional features (separated, sheeted, plastered and confined drifts), erosional features (abraded surfaces, channels, furrows and moats) and mixed features (contourite terraces). Drifts generally show high- to moderate-amplitude reflectors, which are cyclically intercalated with transparent layers. Transparent layers may represent finer-grained deposits, which can serve as seal rocks. High-amplitude reflectors (HARs) are likely to represent sandier layers, which could form hydrocarbon reservoirs. HARs occur on erosive features (moats and channels), and are clearly developed on contourite terraces and overflow features. Most of the contourite features described here are influenced by Mediterranean water masses throughout their Pliocene and Quaternary history. They specifically record Mediterranean Outflow Water, following its exit through the Gibraltar Strait. This work gives a detailed report on the variation of modern contourite deposits, which can help inform ancient contourite reservoir interpretation. Further research correlating 2D and 3D seismic anomalies with core and well-logging data is needed to develop better diagnostic criteria for contourites. This can help to clarify the role of contourites in petroleum systems.

Abstract Sediment mass transport in the Pacific margin of the Antarctic Peninsula is strongly influenced by its peculiar tectonic and sedimentary evolution. Analysis of swath bathymetry and multichannel seismic reflection data shows that this setting reflects the passage from an active to a passive margin, and the transition from river-dominated to glacier-dominated sedimentation. Only contouritic sedimentation persisted throughout the late Neogene on the continental rise, while rapid progradation of steep wedges composed of glacial diamicton occurs on the slope. Gravitational instability and mass-transport processes, which occur on the continental rise, appear to relate to physical properties of contourite sediments deposited in this high-latitude setting. Other than minor erosional gullies on the upper slope, there is no evidence of major incisions such as channels, canyons, or slide scars on a steep continental slope (averages 13°). This situation results from high shear strength of the slope-forming diamicton delivered by grounded ice sheets. Short-run-out mass failures were the main sediment transport process to the slope. Turbidity currents, most likely originated by downslope evolution of mass flows, were able to generate large deep-sea channel systems at the base of the continental slope. On the continental rise, relatively good sorting and a high accumulation rate of sediments forming sediment drifts favored slope failure even on gentle slopes. Coalescent headscarps that form the drift crest were produced by undercutting of steeper flanks of drifts. This process formed the walls of turbidity-current channels, flowing in low-relief areas between drifts. Failure along stratal weak layers on the gentle sides of sediment drifts produced either relatively small, concave slide scars in the margin-proximal drift or long, rectilinear scars in distal locations.

Abstract: Deep-sea finely laminated and barren glacial sediments occur in the sediment drift field offshore the Pacific margin of the Antarctic Peninsula where a weak contour current flows at present to the SW. Atypical sedimentary facies were related to the coexistence and interaction of different sedimentary processes. Three 'end-members' of radiograph facies were defined to represent the sedimentary sequences controlled by a dominant process, as follows. (1) Direct influence of turbidity currents on sedimentation is observed in the area surrounding the Alexander Channel system with silty layers interbedded with laminated mud free of ice-rafted debris (IRD). (2) Distal meltwater turbid flows dominate the more proximal area of the top plateau with structureless and coarser-grained sediments containing IRD. (3) Along the crest of the drift, persistent weak bottom currents control the deposition of fine-grained sediments conveyed into the system through other processes. These laminated sediments contain IRD and are, atypically, not bioturbated, because of unusual, climatically related, environmental conditions of suppressed primary productivity and oxygen-reduced deep waters. These glacial contourites were observed on most of the Antarctic margin with the exception of the areas in which polynyas were maintained during the glacial stages. Glacial contourites can be used as a proxy to define temporal and spatial extension of the Antarctic sea-ice.