OVERTURNED GEOPETAL STRUCTURES FORMED BY SOLUTION OF SULFATES, TRIASSIC (RHAETIAN) PORTORO LIMESTONE, PORTOVENERE AREA (LA SPEZIA), LIGURIA, ITALY

The Triassic Portoro limestone of NW Italy contains four kinds of feat ures that indicate the former presence of sulphates: (1) isolated sing le crystals now pseudomorphed by calcite; (2) nodules encrusted with l arge pseudomorphs on their surfaces; (3) single elliptical nodules (gn occhi); and (4) large amoeba-shaped masses (PAM's). All of these featu res show varying amounts of internal geopetal sediment accumulated dur ing solution of the sulphate minerals. This sediment, now in the tops of the features, plays an important role in deciphering the complex st ructural geology by documenting tectonic overturning. The sulphates ap pear to be late diagenetic features, and their later dissolution was a consequence of fracturing during structural deformation.