The role of salt mobility in the development of supra-salt sedimentary depocentres and structural styles

• Main Author: Banbury, Nicholas John
• Published: University of Edinburgh 2005
• Subjects: 551.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.641273

With the aim of understanding the relative role of salt mobility and other controls on depocentre development in salt basins, results obtained from strategic targeted observations of three different sedimentary basins are presented. These include the Paradox Basin of Utah/Colorado, USA, where sequences which are the stratigraphic response to Pennsylvanian-Triassic mobility of a Pennsylvanian salt sequence are exposed and investigated at the outcrop scale. The other basins are the Sole Pit/Silver Pit Basin (Southern North Sea) and Shearwater area (Central North Sea), both of which are exclusively subsurface examples that have experienced Mesozoic and Tertiary mobility of Upper Permian salt sequences. These later study areas are investigated using high-resolution 3D seismic data which allow the large-scale structural and stratigraphic geometries to be investigated well beyond the outcrop scale. Observations reveal a wide variety of complex depocentre styles with varying controls on their development. Controls include tectonics, differential sedimentation, availability of salt to move and potential of the overburden to flex or be penetrated. Despite this complexity, depocentre morphologies are considered to be predictable based on the concept that salt moves as a response to the pressure state in the salt layer exerted upon it by its overburden. As salt flows down pressure gradients, subsidence resulting from salt mobility is predictably and consequent sediment accumulation increases the load providing an intricate feedback between salt mobility and sedimentation.