Basin-floor fans of the Central Tertiary Basin, Spitsbergen: relationship of basin-floor sand-bodies to prograding clinoforms in a structurally active basin
Jeff P. Crabaugh, Ronald J. Steel, 2004. "Basin-floor fans of the Central Tertiary Basin, Spitsbergen: relationship of basin-floor sand-bodies to prograding clinoforms in a structurally active basin", Confined Turbidite Systems, S. A. Lomas, P. Joseph
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Lower Eocene shelf-slope clinoforms are exposed in 1 × 10 km mountainside outcrops in the Central Tertiary Basin, Spitsbergen. Where clinoforms are sand-prone they include a deepwater sand complex. Submarine fans represent an early, basin-floor aggradational phase of clinoform growth, whereas later growth of the same clinoform involves a phase of shelf-margin accretion. Individual fans, within stacked series, can be distinguished when traced towards the slope, where a thickening wedge of mudstones separates successive fan bodies. The sand-prone parts of basin-floor fans are some 15–60 m thick and extend into the basin by up to 10–12 km. The lower levels of any fan consist of ripple- to parallel-laminated thin-bedded turbidites interbedded with some thick-bedded turbidites. This association changes irregularly upwards to a succession dominated by thick beds that are structureless and parallel-laminated. The thin-bedded facies are interpreted as turbidite sheets that formed as channel-mouth sandy lobes, sandy levees and crevasse splays. The erosively based, thick-bedded facies are interpreted as constructional channel-fill sandstones. The shallow channels fed sheet-complexes both laterally and distally. The apparent short basinward extent and longitudinal palaeocurrents for the youngest fans suggest that downslope sediment transport became longitudinally deflected by anticlinal topography once sediment reached the basin floor.
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This publication reflects a growing appreciation of the extent to which turbidite depositional system development is fundamentally affected by basin-floor topography. In the many turbidite and turbidite hydrocarbon reservoirs, depositional patterns have been moderately to strongly confined by pre-existing slopes; thus ‘submarine fans’ may be far from fan-shaped where constrained by significant bathymetric features. This volume examines aspects of sediment dispersal and accumulation in deep-water systems where sea-floor topography has exerted a decisive control on deposition, and explores the associated controls on hydrocarbon reservoir architecture and heterogeneity.
The papers presented here offer a global perspective, which is wide-ranging in terms of approach as well as location, including contrasting reviews and case studies of outcrop, subsurface, modern and experimental systems. This book will be of use both to academic geologists and to geoscience professionals in industry dealing with characterization and modelling of deep-water clastic reservoirs.