Progressive tilting of salt-bearing continental margins controls thin-skinned deformation

Abstract

As a primary driving force, margin tilting is crucial for gravity-driven thin-skinned salt tectonics. We investigated how instant versus progressive margin tilting mechanisms influence salt tectonics using an analogue modeling setup where tilting rate could be controlled. Instant tilting resulted in initially high deformation rates, triggering widely distributed upslope extension and downslope contraction. Later, both the extensional and contractional domains migrated upslope as early extensional structures were successively deactivated, while deformation rates decreased exponentially. In contrast, progressive tilting led to downslope migration of the extensional domain by sequentially formed, long-lived normal faults. Contraction localized on a few, long-lived thrusts before migrating upslope. We attribute the distinct structural evolution of thin-skinned deformation, especially in the extensional domain, in the two tilting scenarios mainly to mechanical coupling between the brittle overburden and underlying viscous material. The coupling effect in turn is largely controlled by the deformation rate. By demonstrating the spatiotemporal variations of structural style and kinematic evolution associated with instant versus progressive tilting, we suggest that such variation is identifiable in nature and therefore can provide a new way to analyze margin tilting histories.

Initiating Salt Tectonics by Tilting: Viscous Coupling Between a Tilted Salt Layer and Overlying Brittle Sediment

“…Salt topography flattens and the velocity of the sediments and strain rate on all faults decays (Figures 11 and 12). This result is also found in analogue experiments (Ge, Warsitzka, et al., 2019) and is further expected when sediments accumulate and the overburden thickens and strengthens (Figure 4). In the Levant margin, the tilt angles are larger in the North (Cartwright & Jackson, 2008), which means that faulting there is expected to intensify (e.g., Figure 4a vs.…”

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

“…Late Triassic-Early Jurassic 1500 300 3000 5 80 Vejbaek (1990); Geil (1991); Petersen et al (1992); Clausen and Pedersen (1999) The apparatus consists of a central, vertically moving graben structure bounded by two bendable metal plates. The latter can be moved laterally and their outer edges can be uplifted.…”

“…The south Viking Graben and the Egersund Basin (northern North Sea) are salt-bearing half grabens in which the hanging wall graben centre was rotated during rifting (Geil, 1991;Thomas and Coward, 1996;Jackson and Larsen, 2009;Tvedt et al, 2013;Stewart, 2014;Jackson and Lewis, 2016). At the upslope edges of the rotated grabens, thin-skinned extensional growth faults (Fig.…”

“…Downward gravity gliding is often inferred from the occurrence of a domain of thin-skinned extensional structures at the upslope basin margin (e.g. Penge et al, 1999;Geil, 1991;Stewart and Coward, 1995;Best, 1996;Withjack and Callaway, 2000;Thieme and Rockenbauch, 2001;Mohr et al, 2005;Jackson and Larsen, 2009;Tvedt et al, 2013;Vackiner et al, 2013;Labaume and Teixell, 2020). For instance, in many rift basins in the central and southern North Sea, such as the Central Graben, the southern Viking Graben, and the Sole Pit Basin (e.g.…”

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

“…1a) (e.g. Jackson and Cramez, 1989;Mauduit et al, 1997;Brun and Mauduit, 2009;Brun and Fort, 2011;Ge et al, 2019). The initiation of gravity gliding and spreading depends on the angle of the basin slope and of the top surface (e.g.…”