96-6 Salt moving during its deposition: How does it affect evaporite sedimentation?

Session: Twenty-Seven Years of Advances in Understanding Salt-Sediment Interaction: A Legacy of Katherine A. Giles

Presenting Author:

Authors:

Abstract:

Salt tectonics synchronous with salt deposition have been identified in several offshore locations around the world, including the North Sea, the Red Sea, the Mediterranean Sea, and the Santos basin in Brazil. In most cases, a basal halite-rich unit exhibits mobility and moves during the deposition of an upper Layered Evaporite Sequence (LES) composed of alternations of halite, anhydrite/gypsum and K-Mg salts (carnallite, tachyhydrite, bischofite, etc.). During salt tectonics processes, diapirism generally induces thickness and facies variations in the post-salt sediments. It is a matter of curiosity whether salt tectonics occurring during salt deposition can induce such variations during the deposition of a LES. The Santos basin, located in the South Atlantic Ocean, is a suitable location for the study of salt tectonics synchronous with salt deposition. This is due to the superior quality of seismic imaging within the Aptian-Albian evaporites and the presence of numerous wells that traverse the entire salt formation. In this contribution we leverage the well database and seismic images within the evaporites to elucidate how the early movement of the basal halite-rich unit has impacted the sedimentation of evaporites within the overlying LES. The results suggest that salt tectonics synchronous with salt deposition have influenced the structure and the sedimentation of the LES. Salt withdrawal basins, as typically observed in post-salt sediments, formed in the LES and isolated depocenters where the confined conditions permitted high salinity rates, particularly in the uppermost part of the LES. This led to the formation of local K-Mg salt depocenters, into which resedimentation of evaporites is likely. The findings of this study pave the way for a new understanding of salt tectonics processes, their role in evaporites sedimentation, and the distribution of K-Mg salts in evaporitic basins. These findings may have significant implications for underground energy and waste storage in salt caverns, as well as for potash ore deposits.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5622

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.