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Abstract

The Southern Tail-End Graben, Danish Central Graben, is characterized by a lateral variation in the thickness and mobility of pre-rift Zechstein Supergroup evaporites, allowing investigation of how supra-basement evaporite variability influences rift structural style and tectono-stratigraphy. The study area is divided into two structural domains based on interpretations of the depositional thickness and mobility of the Zechstein Supergroup. Within each domain, we examine the overall basin morphology and the structural styles in the pre-Zechstein and supra-Zechstein (cover) units. Furthermore, integration of two-way travel-time (TWT)-structure and -thickness maps allows fault activity and evaporite migration maps to be generated for pre- and syn-rift stratal units within the two domains, permitting constraints to be placed on: (i) the timing of activity on pre-Zechstein and cover faults and (ii) the onset, duration and migration direction of mobile evaporites. The northern domain is interpreted to be free from evaporite-influence, and has developed in a manner typical of brittle-only, basement-involved rifts. Syn-rift basins display classical half-graben geometries bounded by thick-skinned faults. In contrast, the southern domain is interpreted to be evaporite-influenced, and cover structure reflects a southward increase in the thickness and mobility of the Zechstein Supergroup evaporites. Fault-related and evaporite-related folding is prominent in the southern domain, together with variable degrees of decoupling of sub-Zechstein and cover fault and fold systems. The addition of mobile evaporites to the rift results in: (i) complex and spatially variable modes of tectono-stratigraphic evolution; (ii) syn-rift stratal geometries which are condensed above evaporite swells and over-thickened in areas of withdrawal; (iii) compartmentalized syn-rift depocentres; and (iv) masking of rift-related megasequence boundaries. Through demonstrating these deviations from the characteristics of rifts free from evaporite influence, we highlight the first order control evaporites may exert upon rift structural style and the distribution and thicknesses of syn-rift units.