Petrografia de beachrock em zona costa afora adjacente ao litoral norte do Rio Grande do Norte, Brasil

Abstract

Petrographic analysis was carried out in a submerged rock-body on the north shelf of Rio Grande do Norte state. It is 18 km far from the actual coastline and it is named Urca do Minhoto. Quartz, bioclasts, feldspar and rock-fragments are the most important framework grains. Calcium carbonate cement occurs in three distinct types: micritic porefiling and equant spar, both of them filling the pore space, and isopachous prismatic rims, precipitated on the grain border. Grain-size varies from very-fine sand to granules. The grain packing suggests a shallow cementation environment (eodiagenesis).

Genesis of submerged sandstones in Paraná State continental shelf, Southern Brazil, based on cementation patterns, ages and stable isotopes

“…Branner, 1904;Chaves and Sial, 1998;Manso et al, 2003;Guerra and Sial, 2003;Vieira et al, 2007;Morais et al, 2009) or submerged on continental shelf (e.g. Cabral Neto et al, 2010). From Northeastern to Southeastern regions these are also identified outcropping on the intertidal zone (Fúlfaro and Amaral, 1970;Suguio et al, 1985, Mansur et al, 2011 and submerged on the continental shelf (Muehe and Carvalho, 1993).…”