Submarine channel response to intrabasinal tectonics: The influence of lateral tilt

Abstract

Lateral tilting is a common deformation style in extensional basins; its influence on subaerial channels is, to a degree, understood and may be significant, controlling the style of channel development and the resultant sand-body architecture. Growth faulting and lateral tilting in turbidite channel systems have been demonstrated from three-dimensional seismic data, but the resultant architecture of channels within these settings has not yet been documented. In the Carboniferous of northern England, a sand-rich slope channel, developed within a basin undergoing late-stage extension, underwent progressive and unidirectional migration toward a topographic low on a laterally tilting block. The resultant sandstone body is wedge shaped in cross section and composed dominantly of sigmoidal lateral accretion deposits. The channel returned to an axial course before undergoing lateral migration in the same direction, creating a multistory, multilateral channel sandstone body. The repeated unidirectional migration combined with evidence of syndepositional deformation suggests that active tectonism strongly influenced channel evolution and deposition. A model of submarine channel evolution in extensional basins is presented; in systems where large displacements occur, the channel system may avulse, creating isolated sand ribbons, which are connected updip; where the lateral dip is always more influential than the regional dip, the system may pond in the hanging-wall syncline. The model is compared to a subsurface channel within the Pliocene of the Nile Delta slope, which was influenced by syndepositional fault movement; application of the outcrop-derived model allows some simple architectural interpretations to be made.