Restoration of multiphase salt tectonic deformation using passive strain markers

Journal article

Several salt basins globally have been subject to multi-phase deformation. The geometry of structures formed within a salt sheet during an early phase of deformation can be concealed by overprinting during later deformation phases, impeding an informed investigation into the early drivers for salt flow. The layered Messinian Evaporites in the deep basins of the Eastern Mediterranean have undergone a Late Messinian phase of deformation, punctuated by truncation of the top of the deformation structures, followed by a Late Pliocene-Recent phase of deformation. Seismic reflection data show that the Messinian Evaporites are internally dominated by contraction structures that verge basinward in the Late Pliocene-Recent flow direction, with several apparent detachments. Planform linear trails of fluid escape pipes, documented in the North Levant Basin, that cross-cut the Messinian Evaporites present natural passive markers for the internal flow kinematics of the salt sheet throughout the Late Pliocene-Recent phase of deformation. Using the Couette (simple shear) strain profile implied by the fluid escape pipes, we remove the effects of the Late Pliocene-Recent deformation through cross-section and map restorations. The subsequent geometries are far simpler, with upright folds that are now vertically aligned. Once apparently detached structures are demonstrably connected through the Messinian Evaporites. The vergence of the present day intra-salt folds can be taken as an indicator for the Late Pliocene-Recent flow direction and distinct deformation geometries that connect at various levels through the salt sequence once retro-deformed can assist when interpreting the salt flow profile. The retro-deformation is essential for how intra-Messinian deformation and its drivers are interpreted going forward. Furthermore, simple shear deformation results in erroneous apparent percentage shortening calculations as line length is not conserved, obscuring the strain from the pre-Pliocene deformational phase. The methodology employed here has important implications for all salt basins that have undergone multi-phase deformation.

Authors: Kirkham, CK; Cartwright, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Wiley
• Journal: Basin Research
• Volume: 33
• Issue: 4
• Pages: 2453-2473
• Publication date: 2021-05-15
• Acceptance date: 2021-03-16
• DOI: 10.1111/bre.12564
• EISSN: 1365-2117
• ISSN: 0950-091X
• Language: English
• Keywords: FFR