Sedimentology (1992) 39,235-249 zyxwvutsrq Earthquake-inducedresedimentationin the Badenian (middle Miocene) gypsum of southern Poland TADEUSZ MAREK PERYT* zyxwvu and ALICJA KASPRZYKt *Panstwowy Instytut Geologiczny, ul. Rakowiecka 4.00-975 Warsaw, Poland fPanstwowy Instytut Geologiczny-Oddzial Swietokrzyski, ul. Zgoda 21,25-953 Kielce, Poland ABSTRACT In the Badenian (middle Miocene) basin of the Carpathian foreland of southern Poland, gypsum breccias occur associated with laminated gypsum deposits. These breccias consist of large clasts of gypsum, carbonates, mads and clay chips of variable size embedded in a gypsarenitic matrix. Constituent gypsum grains and clasts commonly appear to be mechanically abraded and chemically corroded crystals or fragments of selenitic, laminated and alabastrine gypsum. Gypsorudites are commonly accompanied by laminated gypsarenites and gypsolutites which show graded bedding; a vertical sequence of graded gypsum beds showing Bouma sequences may be recognized in borehole sections. Microfolding is common within the folded laminated gypsum, and is closely associated with expressions of extensional strain. Both are accompanied by pervasive microfaulting, suggesting a semi-coherent downslope mass movement. The stratiform geometry of the breccias, together with the intensity of slumping relatively independent of the palaeoslope, suggest earthquake shocks as the initial, main cause. Gypsum deposits form a constant, laterally extensive sequence of different lithofacies. The occurrence of the same lithologies and shallowing-up cycles over a wide area reflects thrusting of the Carpathians over the Carpathian foredeep. Local tectonism has also played a significant role. The tectonic framework favoured activation of dip-slip faults promoting shallow-focus earthquakes. These in turn resulted in the resedimentation of gypsum by slumps, debris flows and turbidites. A similar basinward resedimentation of clastic material by gravity flows initiated by fault-induced earthquakes could be of great importance in the foreland geological setting, and may explain some phenomena observed in other evaporite formations from different geological settings, especially of rift type. INTRODUCTION Resedimentation of sulphate deposits, including for- mation of turbidites, is well established (e.g. Parea zyxwvu & Ricci Lucchi, 1972; Ricci Lucchi, 1973; Meier, 1975, 1977; Catalan0 et al., 1976; Schreiber et al., 1976; Schlager & Bolz, 1977; Dabrio et al., 1982; Orti Cab0 et al., 1988), although disputed by some authors (e.g. Langbein, 1987). The concept of mechanical rework- ing (cannibalism) of evaporites is commonly applied (e.g. Vai & Ricci Lucchi, 1977; Schreiber, 1978), but the assumption of widespread reworking is poorly documented except in cases of mass and turbidite flow deposits (e.g. in the Zechstein of Central Europe- Meier, 1975; Schlager & Bolz, 1977; Paul, 1987; Orti Cab0 et al., 1988; Peryt & Antonowicz, 1990; and in the Messinian of Sicily-Catalan0 et al., 1976; Schreiber et al., 1976). This is especially true of laminated gypsum units, where disturbances are commonly recorded but have been interpreted as forming by recrystallization (e.g. Kwiatkowski, 1972; Langbein, 1987). In the Badenian (middle Miocene) deposits of the Carpathian foreland in southern Poland (Fig. I), gypsum breccias have long been known to occur associated with laminated gypsum deposits (e.g. Pawlowski, 1970; Kwiatkowski, 1972; Osmolski, 1972; Wala, 1979, 1980; Kubica, 1983). Mechanisms responsible for breccia formation were not considered in detail, but most workers have related breccias to 235