SALT WEATHERING AND FORMATION OF HONEYCOMBS AND TAFONI ON OUTCROPS OF BEACHES IN NITEROI (RIO DE JANEIRO, BRAZIL)

Coastal outcrops of granites and gneisses on the beaches of Niteroi (RJ) present morphologies related to salt weathering, such as pits and pans, and the more organized forms such as honeycomb and tafoni, on the surface of the rocks. This paper presents a description of these landforms on the beaches of Niteroi, particularly at Itacoatiara, where better examples are found. SEM, IC and AAS analysis carried on 12 samples collected from the outcrop at Itacoatiara, identified halite, gypsum, sylvite, bischofite, mirabilite, thenardite and kieserite. Wet/dry cycles and its frequency generate salt crystalization and dissolution which promotes rock disintegration giving rise to these observed cavernous morphologies. Geological characteristics such as exfoliation planes, lithological contacts, composition and textures, among others, play an important role on the type of morphology developed during salt weathering processes.