Resedimentation of basin centre sulphate deposits: Middle Miocene Badenian of Carpathian Foredeep, southern Poland

Abstract

Abstract The Middle Badenian anhydrite sections in the central part of the Carpathian Foredeep consist mainly of interbedded laminated anhydrite and anhydrite breccia. These facies display features characteristic of redeposited sediments such as distortions due to slumping, erosional boundaries, and graded-bedded laminae. Lamination in laminated anhydrite is rarely regular and often accompanied by disruptions. The predominance of clasts of laminated anhydrite combined with the observed brecciation of laminated anhydrite indicates that a short distance for transport and even in situ reworking were common. A high degree of convolution indicates that some reworked sediments were unconsolidated when they moved, but in many cases they were probably at least partly lithified. This is evidenced by the anhydrite breccia consisting of clasts of laminated anhydrite as well as the brecciation in situ. The resedimentation processes have not been related to regional bathymetrical differences as indicated by minor differences along seismic profiles. A great deal of redeposition within the basin centre of the Middle Badenian evaporite basin combined with the in situ brecciation suggests that the triggering mechanism for redeposition could be earthquakes. They generated mass flows and eventually turbidites, so that earlier deposited grains could be redeposited. This implies that in other evaporite basins the laminar facies might be at least partly related to redeposition and not necessarily to changes of surface brine concentration as usually supposed.