HALOKINETIC SEQUENCES

Halokinetic sequences are ubiquitous in strata adjacent to salt diapirs and record the dynamic interaction of rising salt and accumulating sediments. The sequences consist of relatively conformable successions of growth strata genetically influenced by near-surface or extrusive salt movement and are locally bounded at the top and base by angular unconformities that become disconformable to conformable with increasing distance from the diapir. They differ from traditional depositional sequences in scale and mechanism of formation. Halokinetic sequences are discordant only within a few km of a diapir, whereas depositional sequences are traceable across a sedimentary basin. Halokinetic sequences form due to temporal variations in bathymetric relief over the diapir, whereas depositional sequences form as accommodation rate varies relative to regional sediment accumulation rate. Angular unconformities form when net diapiric rise rate exceeds local sediment accumulation rate, allowing diapiric inflation at the surface to generate steep, unstable slopes upon which subjacent growth strata are either truncated by attendant slope failure or erosion. Increasing local sediment accumulation rate relative to net diapiric rise rate results in diapir onlap and overlap, which suppress diapiric surface topography and erosion. The angular unconformities are modified during halokinesis by flexural slip along the unconformable surface during diapir-related drape folding. Halokinetic sequences, known from both outcrop and seismic datasets, display differences in stratal and structural character that reflect differences in salt-body rise rate relative to adjacent sediment-accumulation rate.