Interplay of downbuilding and gliding in salt-bearing rifted margins: insights from analogue modelling and natural case studiesInterplay of downbuilding and gliding in salt-bearing rifted margins: insights from analogue modelling and natural case studies

Abstract

Our analogue modelling programme simulates a thermally subsiding rifted margin with a regional late syn-rift to early post-rift salt basin. End-member models included i) pure downbuilding in a confined salt basin and ii) dominant gliding on a tilted opened toe margin. The spectrum between these was completed by modelling different amounts of downbuilding vs. dominant gliding. Our results provide structural geometries and tectono-stratigraphic architectures for salt structures related to those end-member processes, as well as when these occur simultaneously. Downbuilding is represented by vertical aggradation of syn-kinematic strata, the erosional truncation of megaflaps, and syn-kinematic debris sourced from salt and pre-kinematic strata. Dominant gliding is represented by salt-detached extension and related diapirism, resulting on the progressive increase in line-lengths of younger stratigraphic units. The transition from downbuilding to dominant gliding is represented by diapir shoulders, and widening of sedimentary depocenters towards flanking salt structures undergoing collapse and salt-detached extension, as well as the truncation of stratigraphy by younger, laterally expanding depocenters. Our modelling results favours the interpretation of an early downbuilding component, followed by gliding for both the South Gabon rifted margin and the Cotiella basin involved in the South-Central Pyrenees fold-and-thrust belt.