Zhiyuan Ge

The impact of abrupt and progressive margin tilting upon passive margin salt basins

Zhiyuan Ge¹, Michael Warsitzka^{2, 3}, Matthias Rosenau³ and Rob L. Gawthorpe¹

¹ Department of Earth Science, University of Bergen, Allégaten 41, 5007 Bergen, Norway

² Institute of Geophysics of the Czech Academy of Sciences, Boční II/1401, 141 31 Prague 4, Czech Republic

³ German Research Centre for Geosciences (GFZ), 14473 Potsdam, Germany

Abstract

Gravitational failure drives thin-skinned salt tectonics in passive margin salt basins where upslope extension is linked to downslope contraction. As one of the main driving mechanisms, the impact of margin tilting is crucial for the structural and kinematic evolution of supra-salt cover deformation. However, the influences of tilting rate on thin-skinned salt tectonics is poorly understood as most modelling studies, either numerical or experimental, use abrupt tilting method. In this study, using a new analogue modelling method enabling progressive tilting monitored with high‐resolution DIC (digital image correlation) system, we investigate how abrupt and progressive margin tilting control the thin-skinned salt tectonic evolution. The results show that abrupt margin tilting allows the extensional structures to develop with largest coverage from very beginning. Afterwards, the extension starts to retreat towards upslope along with the contraction migrating toward the upslope. In contrast, progressive tilting leads to gradual initiation of extension as tilting increases. Extensional structures first occur in the most upslope tip of the basin and gradually migrate downward. The contraction diffuses in a wide area in the downslope first and then localizes on a few, large extensional structures, similar to that of abrupt tilting. Moreover, the pre-kinematic layer thickness have limited influences on the kinematic variation associated with different tilting scenarios. By demonstrating the temporal and spatial variations associated with abrupt and progressive tilting, we suggest that progressive tilting, which is more like to happen in nature, leads to progressive and diachronous development of extensional structures. This contrasts to current models largely based on studies with abrupt tilting where extension structures tend to occur simultaneously.