Interplay of downbuilding and gliding in salt-bearing rifted margins: Insights from analogue modeling and natural case studies

Abstract

Our analogue modeling program simulates a thermally subsiding rifted margin with a regional late synrift to early postrift salt basin. End member models include (1) pure downbuilding in a confined salt basin and (2) dominant gliding on a tilted opened toe margin. The spectrum between these was completed by modeling different amounts of downbuilding versus 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 synkinematic strata, the erosional truncation of megaflaps, and synkinematic debris sourced from salt and prekinematic strata. Dominant gliding is represented by salt-detached extension and related diapirism, resulting in the progressive increase in line lengths of younger stratigraphic units. The transition from downbuilding to dominant gliding is represented by diapir shoulders and the widening of sedimentary depocenters toward flanking salt structures undergoing collapse and salt-detached extension, as well as the truncation of stratigraphy by younger, laterally expanding depocenters. Our modeling results favor the interpretation of an early downbuilding component, followed by gliding for both the South Gabon rifted margin and the Cotiella Basin involved in the southcentral Pyrenees fold-thrust belt.