Dissolution of halite within the Middle Miocene (Badenian) laminated gypsum of southern Poland

Abstract

Breccias formed by early diagenetic dissolution of halite occur within the laminated Middle Miocene (Badenian) gypsum of southern Poland. The solution-collapse origin of the breccias is proved by the flat basal contact, the uneven top surface or their gradual transition into the overlying strata, the traces of halite within the breccias or in the adjacent strata, and the common micro scale effects of collapse over the dissolved halite crystals. The dissolution took place within soft, water saturated and not fully consolidated, laminated gypsum, and led not only to the brecciation but to the complicated soft-sediment deformations as well. The dissolution produced the residual thin-grained gypsum or clay deposits within the halite-bearing horizons and, in many cases, the zone of the collapse breccias above. The most characteristic collapse breccias are composed of fragments or blocks of the laminated gypsum, practically without any matrix or cement. The horizontal flow or creep of slurry residual gypsum could take place directly on the sea bottom.