Detachment fold duplexes within gravity-driven fold and thrust systems

Fold duplexes transfer displacement from a lower to an upper bounding detachment system via trains of folds with broadly parallel geometries. While they have been previously recognised in orogenic systems where are considered be kinematically equivalent imbricating thrust ramps, we here describe the first example gravity-driven fold and (FATS) developed within late-Pleistocene mass transport deposits (MTDs) that formed around Dead Sea Basin. The recognition this study basal detachments bound FATS, together later ramps imbricate folded sequence, indicates duplex model is applicable case. Truncation synclinal hinges, trapping roof stratigraphy cores initiation buckling precedes detachments, which then propagated along boundaries FATS create duplex. Downslope-verging folds, by subsequently cut greatest recorded branch detachment. As increases ramp angles generally reduce, allows thrusts continue move accrue larger displacements. Sequential flattening overstep sequences may apparent ‘back-steepening’ up slope what superficially resembles ‘pseudo-piggyback’ sequences. Flattening achieved through tightening, rotation expulsion wet sediment fluid footwall synclines consequence loading overlying sheets. We speculate expelled fluids pond directly beneath detrital-rich units act as baffles locally increase pressures thereby facilitating further movement establish new model, whereby vergence structures above depends on relative rates translation, slower downslope translation generating upslope verging ‘sub-active’ roof, while more rapid ‘super-active’ creates folds. observation such patterns minor still largely correspond position underlying only limited occurred between FATS. This suggests must transferred upwards shortly after were created, ‘fixing’ spatial correlation. older ‘lock up’, migrates develop pristine ‘easy-slip’ laminations at higher stratigraphic levels, thickening deforming towards free surface. creation these development local principal differences observed settings those surficial