17 18 Minibasins are important features in salt-bearing basins and they are mostly found in salt-detached 19 continental slopes where the sedimentary cover undergoes seaward translation. One question which is 20 relevant to understand the structural evolution of salt-detached slopes is how fast can the sedimentary 21 cover and the minibasins translate. The aim of this study is three-fold: 1) to compare minibasin downslope 22 translation velocity with salt translation velocity; 2) to understand

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... hat controls minibasin translation 23 velocity and 3) to understand how minibasins translating at different velocities can kinematically interact 24 and modify strain patterns around them. To address these questions, we present a 2D numerical modeling 25 study consisting of three simulation series. In the first series, we model a simple scenario where, as a result 26 of gravity, a constant-thickness salt layer moves downslope on an inclined plane. In the second series, we 27 use the same model geometry as in the first (i.e. constant thickness salt layer over an inclined plane), but 28 we add a single, isolated minibasin at the updip portion of the slope. Different minibasin thicknesses, 29 widths and densities are then tested, replicating how in natural salt basins, minibasin size (thickness and 30 width) and fill (density as a proxy of lithology) vary as a function of their maturity, their structural position, 31 and/or the overall regional geological setting in which they form and evolve. Finally, in the third series, we 32 add three minibasins in the updip portion of the slope, and we assess how they interact as they translate 33 downslope. In addition to parameters that control salt velocity on a slope, minibasin thickness is the main 34 factor controlling minibasin velocity in the numerical models. Thicker minibasins translate slower than 35 thinner minibasins. Findings from our numerical modelling approach have direct and significant 36 implications for understanding minibasins behavior, kinematics and strain patterns on natural salt-37 detached slopes. 38 39 3 1. Introduction 40 Minibasins are important features of many salt-bearing basins and can form in different settings 41 (i.e. marine and continental). Most minibasins, however, are found in salt-detached continental slopes, 42 where linked kinematic systems can form (e.g. Jackson and Hudec, 2017). One characteristic of salt-43 bearing slopes is the seaward translation of the supra-salt sedimentary cover. A question inherent to salt-44 detached linked systems is how fast can the supra-salt sedimentary cover translate at present-day or over 45 geological time. In order to understand how fast supra-salt sedimentary cover, including minibasins, can 46 translate on salt-bearing slopes, we first must understand why and how fast salt can actually flow in such 47 settings. 48 Over geological time scales, salt behaves as a fluid of very high viscosity. As a result, on salt-49 bearing continental slopes, salt moves down the slope due to gravity. On slopes, two main mechanisms 50 drive salt flow: gravity spreading (deformation and collapse of a rock mass by its own weight) and gravity 51 gliding (downslope translation of the rock mass over an inclined detachment) (e.g. De Jong and Scholten, 52 1973; Ramberg 1981; Brun and Merle, 1985). Distinguishing between these mechansims on natural 53 examples of continental slopes is difficult, given it is likely that both processes contribute to the 54 downslope flow of salt and the overlying sedimentary cover (e.g. Schulz-Ela, 2001; Rowan, 2004; Brun and 55 Fort, 2011, 2012; Peel, 2014). In any case, as salt flows down the slope, the capping sedimentary cover on 56 top also gets translated. One of the main outcomes of this style of salt-related deformation is the 57 partitioning of continental slopes into three different domains: an up-dip extensional domain and a down-58 dip contractional domain, separated by a translational domain (Figure 1a) . 59 So, gravity causes salt to flow down a slope, but how fast does it move? Direct observation of salt 60 flow is restricted to areas where salt is exposed at the Earth's surface, such as in Iran, where aerial 61 extrusions from salt diapirs form salt glaciers (e.g. Lees, 1927; Kent, 1958; Wenkert, 1979) . These well-62 exposed salt structures enable direct measurements of salt flow at observational time scales (days to 63 years) by means of different methods (i.e. satellite-based observations, alidade surveys), yielding values 64 of 10-400 cm/yr (Wenkert, 1979; Talbot and Rogers, 1980; Talbot and Javis, 1984; Talbot et al., 2000). 65 However, subaerial salt flow responds to complex dissolution-precipitation processes that change the 66 rheology of the salt, and that makes extrapolation of short-term salt flow rates not applicable to salt flow 67 over geological time scales (10 3 -10 6 years) (e.g. Urai et al., 1984). In addition, the salt extrusion on the 68 Zagros are driven by tectonic shortening which impacts the extrusion rate. Thus, our understanding of the 69 rate of salt flow in the geological record is poor. When salt is buried under sediments, as it is the case in 70 salt-detached slopes, salt flow has to be estimated by indirect observations. For example, in the northern 71 Gulf of Mexico salt canopy, estimates of salt advance velocities over geological times rely on well-data-72 contrained age and seismic based observations of the cutoffs of the stratigraphic sequence over which 73 the salt was advancing as it moved downslope (e.g. Tauvers, 1993). Advance rates of salt sheets using 74 structural restorations of geological sections constructed from seismic interpretations provide long-term 75 strain rates that range between 0.1-2 cm/year (e.g. Diegel et al., 1995, Peel et al., 1995 Schuster et al., 76 1995; Jackson and Hudec, 2017 and references therein). These values are 2-3 orders of magnitude slower 77 than the ones measured for subaerial salt glaciers. 78 Constraining how fast salt moves at geological time-scales (thousands to millions of years) is thus 79 challenging and has many uncertainties. Constraining the translation velocity of the sedimentary cover 80 that overlies salt in the translational domain of a continental slope is even more challenging and uncertain. 81 Compared to the updip extensional and the downdip compressional domains, clear indicators of 82 displacement magnitudes (e.g. fault cutoffs) are usually absent in the translational domain (e.g. Jackson 83 and Hudec, 2005). This is even more true if instead of a continuous cover, the domain is populated with 84 minibasins that are only partially interconnected, as is the case of minibasin provinces located in 85 continental slopes (e.g. Northern Gulf of Mexico; Figure 1b). It is not unusual for velocity estimates of the 86 sedimentary cover in the translational domains, to be inferred from observations of salt-detached ramp 87 syncline basins and rafted minibasins (e.g. Jackson and Hudec, 2005; Evans and Jackson, 2019; Pichel et 88 al., 2019; Jackson et al., 2010; Fiduk et al., 2014; Pilcher et al., 2014). Translation rate estimates of 89 sedimentary cover based on reconstructed cross-sections provide velocities in the ranges of 0.1-1 cm/year 90 (e.g. rafted minibasin in the Gulf of Mexico; Jackson et al., 2010). However, minibasin translation velocities 91 may not remain constant through time, and it is presumed that minibasin translation rates will 92 dramatically decrease as they are close to welding at their base (e.g. Wagner and Jackson 2011). 93 Furthermore, the downslope transation of minibasins can be obstructed by base-salt relief or friction 94 associated with primary welding, processes that result in locally complex strain patterns on the slope (e.g. 95 Duffy et al., 2020) (Figure 1c) . 96 One question that has not been explicitly addressed before is, how different the velocity of 97 downslope-flowing salt is from the velocities of overlying minibasins. More specifically, do minibasins 98 move faster or slower than the surrounding salt? How do minibasin thickness, geometry and density affect 99 how fast they translate before they are close to welding? Understanding why and how salt and minibasins 100 move at different velocities is relevant for understanding the evolution of salt-detached slopes. 101 Duffy, O.B., Dooley, T.P., Hudec, M.R., Fernandez, N., Jackson, C.A.L., Soto, J.I. 20XX. Structural 533 evolution of salt-influenced fold-and-thrust belts: principles in salt basins containing isolated minibasins. 534