The influence of lateral basinal slopes on turbidite sedimentation in the Annot sandstones of SE France

摘要: ABSTRACT The deep-water deposits of the lower Oligocene Annot Sandstones SE France were deposited in topographically dissected basins. Axially derived turbidites show marked lateral onlap onto underlying marls. original slopes at least 250 m high, and up to 12° prior compaction-induced steepening; they commonly a stepped or undulatory profile. Lateral tracing individual beds away from their position termination down paleoslope reveals characteristic succession microfacies: thin-bedded, nongraded fine sandstones with upper-flow-regime planar lamination pass downslope into medium-bedded, partially graded medium ripple lamination. At base depositional slope, become thick very thick-bed ed, fully (commonly stepwise) coarse mudstones. most likely interpretation transition lower-flow-regime conditions axial trough margin basin involves pulsatory flow conditions. Episodes increased thickness velocity bed forms on higher parts ramps, while periods waning current trough. During accumulation sands, marls differentially compacted, maximum compaction under axis basin, decreasing zero edges basin. This resulted secondary upper surface overlying marl slopes, which may have been important controlling successive sand packages. Successive overstep layers vertical profile that shows same facies as traced beds. resulting sections coarsen thicken upwards over 5-10 m. characteristics thin-bedded cycles be used distinguish between prograding laterally onlapping turbidite Sandstone packages are (30-60 m), sharp based, sandstone rich. equivalent part package confining slope is thinner, asymmetric coarsening upward signature, more mudstone