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TitreSome controls on sedimentary sequences in foreland basins: examples from the Alberta Basin
AuteurCant, D J; Stockmal, G S
SourceTectonic Controls and Signatures in Sedimentary Successions; par Frostick, L E; Steel, R J; International Association of Sedimentologists, Special Publication 1994 p. 49-65,
Séries alt.Commission géologique du Canada, Contributions aux publications extérieures 26191
ÉditeurBlackwell Publishing Ltd.
Documentpublication en série
Mediapapier; en ligne; numérique
Sujetsbiseaux sédimentaires; sedimentation; analyses stratigraphiques; orogénies; talus continental; Bassin d'Alberta
Diffusé2009 04 16
Résumé(Sommaire disponible en anglais seulement)
The stratigraphy and sedimentology of foreland basin clastic wedges is believed to be controlled largely by the spatial and temporal effects of 'time lag' between the initiation of flexure-induced subsidence and the deposition of large amounts of sediment generated from the overthrust belt. The initial accretion of a terrane to an older continental margin, thereby converting the margin to a compressional orogen, should be associated with a relatively large time-lag effect because initial loading by overthrusting takes place on the continental slope, in the absence of significant early subaerial relief across the thrust belt. The large time-lag effect results in a succession grading from deep-water to shallow-water sediments in the early foreland basin.
Clastic wedges resulting from later overthrusting events are generally expected to show considerably reduced time-lag effects, with composite transgressive sequences succeeded by highstand regressive sequences, both composed mainly of non-marine, marginal-marine and shallow-marine sediments of varied lithologies. This reduced time-lag effect may reflect a relatively continuous background supply of orogen-derived sediment readily available to fill accommodation space as it is created. In extreme cases, some clastic wedges may show essentially no time-lag effect, lacking basal transgressive or deep-water sediments.
As well as orogenesis, other factors also condition foreland successions. In the Alberta Basin, the effects of some base-level change events (eustatic?) are more dramatic in cratonward areas where tectonic subsidence rates are lower. Valley-fill and lowstand deposits reflecting base-level drops are more common and easily recognizable toward that side of the basin. The structures and lithologies of the pre-existing shelf/miogeoclinal succession also affect thicknesses and facies of foreland units through their influence on relief of the basal unconformity and synsedimentary salt dissolution.