Deformation within and adjacent to salt
Three-dimensional seismic data from the Levant Basin, eastern Mediterranean, was used to quantify longitudinal strains in thick, multilayered Messinian evaporites at an early stage of salt tectonics. Gravity-spreading is driven by basin subsidence and tilting of the Levant margin and by progradation of the Nile Cone. Similar styles of shortening in two separate 3D survey areas comprise detachment folds, thrust-ramp folds and conjugate arrays of strike-slip faults. These Pleistocene structures can be explained with a single deformation phase with a tectonic transport direction of NE to ENE, obliquely opposed to the extension updip, which began in the Late Pliocene. Four major detachments within the Messinian are probably halite-rich intervals in the multilayer. Shortening of competent interlayers varies from 1–2% near the base to c. 7% near the top of the Messinian, with a sharp reduction in shortening at the top Messinian and roof to 1–2%. This shortening profile is attributed to asymmetric Poiseuille flow, indicating that salt is flowing downdip faster than the overburden is translating. Physical modelling supports the inferred flow profile, showing that each mobile layer flows faster than adjoining competent layers and that strains in evaporites can be far greater than in the overburden. This is the first published use of seismic data to demonstrate the flow regime within salt on a regional scale.
Figures & Tables
In this timely volume, geoscientists from both industry and academia present a contemporary view of salt at a global scale. The studies examine the influence of salt on synkinematic sedimentation, its role in basin evolution and tectonics, and ultimately in hydrocarbon prospectivity. Recent improvements in seismic reflection, acquisition and processing techniques have led to significant advances in the understanding of salt and sediment interactions, both along the flanks of vertical or overturned salt margins, and in subsalt plays such as offshore Brazil. The book is broadly separated into five major themes covering a variety of geographical and process-linked topics. These are: halokinetic sequence stratigraphy, salt in passive margin settings, Central European salt basins, deformation within and adjacent to salt, and salt in contractional settings and salt glaciers.