Facies distribution along the salt diapirs of the Cotiella mini-basins (Southern Pyrenees, Spain)

Most of the studies focusing on salt-tectonics are limited concerning high-resolution facies variations (seismic resolution/outcrop conditions) and reservoir distribution in salt diapir-flanking strata (few wells). As a consequence, many questions remain unsolved, such as the relation between the type of halokinetic sequences and the facies distribution, the interplay between sedimentary environments and the local halokinetic context. The aim of this study is to better understand spatial and temporal facies distribution and resulting sedimentary stacking pattern along the Cotiella mini-basins salt structures (Spanish Pyrenees).

Our approach is dedicated to detailed field mapping, sedimentological description of the stratigraphic succession as well as the investigation of the facies partitioning and depositional systems along within these exceptionally well exposed group of MBs. There, syn-halokinetic strata deposited during the Middle Coniacian to Early Santonian post-rift succession. Preliminary results show that:

• The Cotiella mini-basin is characterized by a megaflap involving a 130° salt-controlled growth-strata. The Armeña mini-basin corresponds to a salt-expulsion roll-over characterized by a 80° salt-controlled growth-strata. Armeña formed mostly before Cotiella.
• Depositional environments correspond to type-ramp mixed siliciclastic-carbonate platform. The sedimentological succession is composed by a parasequence stack characterized by proximal quartz-rich facies located mainly along the salt-weld and evolving laterally to more distal marine environments. Quartz are partly derived from the erosion of the salt-diapir, which correspond to the Keuper evaporitic facies containing authigenic quartz.
• The stratigraphic successions of the Armena and Cotiella mini-basins is subdivided into 4 depositional sequences (S1a, S1b, S2, S3) but present specific thicknesses and facies partitioning, that suggest a strong control from the salt. These 4 sequences reveal the evolution from early to late stages of the rising salt-diapir.

Ultimately, and by integrating other mini-basins (i.e. mini-basins from the Sivas basin un Turkey), this study will help to better predict reservoir-facies and pinch-out locations along salt diapir-flanking strata.