Contribution of gravity gliding in salt-bearing rift basins – a new experimental setup for simulating salt tectonics under the influence of sub-salt extension and tilting

Michael Warsitzka,Fabian Jähne-Klingberg,Piotr Krzywiec,Prokop Závada

doi:10.5194/se-12-1987-2021

Abstract

Abstract. Basin-scale salt flow and the evolution of salt structures in rift basins is mainly driven by sub- and supra-salt faulting and sedimentary loading. Crustal extension is often accompanied and followed by thermal subsidence leading to tilting of the graben flanks, which might induce an additional basinward-directed driver for salt tectonics. We designed a new experimental analogue apparatus capable of integrating the processes of sub-salt graben extension and tilting of the flanks, such that the overlapping effects on the deformation of a viscous substratum and the brittle overburden can be simulated. The presented experimental study was performed to demonstrate the main functionality of the experimental procedure and setup, demonstrating the main differences in structural evolution between conditions of pure extension, pure tilting, and extension combined with tilting. Digital image correlation of top-view stereoscopic images was applied to reveal the 3D displacement and strain patterns. The results of these experiments suggest that in salt basins affected by sub-salt extension and flank inclination, the salt flow and downward movement of overburden affects the entire flanks of the basin. Supra-salt extension occurring close to the graben centre is overprinted by the downward movement; i.e. the amount of extension is reduced or extensional faults zones are shortened. At the basin margins, thin-skinned extensional faults developed as a result of gravity gliding. A comparison with natural examples reveals that such fault zones can also be observed at the margins of many salt-bearing rift basins indicating that gravity gliding played a role in these basins.

Highlights

Salt layers in sedimentary basins play a key role in the structural and sedimentary evolution
A comparison with natural examples reveals that such fault zones can be observed at the margins of many salt-bearing rift basins indicating that gravity gliding played a role in these basins
We suggest that the occurrence of basin-margin extensional fault zones and reduced supra-salt extension or even shortening close to the basal normal faults are diagnostic indicators of syn-extensional gravity gliding in natural rift basins, since such deformation structures are characteristic of gravity-driven salt tectonics in passive margin basins (Fig. 1a) (e.g. Brun and Fort, 2011; Quirk et al, 2012)

Summary

Introduction

Salt layers in sedimentary basins play a key role in the structural and sedimentary evolution. Driving processes of salt flow are well explained for saltbearing passive margin basins, e.g. the Lower Congo Basin, Western Mediterranean, and the Santos Basin (Fort et al, 2004; Quirk et al, 2012; Jackson et al, 2015; Mianaekere and Adam, 2020), where both driving factors mostly act in the same seaward direction (Fig. 1a) Scaled laboratory experiments focusing on passive margin salt tectonics reveal that seaward-directed tilting of the basin floor and/or sediment progradation typically cause the formation of a downdip compressional and an updip extensional domain (Fig. 1a) Warsitzka et al.: Contribution of gravity gliding on salt tectonics in rift basins

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Discussion

Conclusion