Authigenic Mg-clay assemblages in the Barra Velha Formation (Upper Cretaceous) from Santos Basin (Brazil): The role of syngenetic and diagenetic process

Paleoenvironmental Implications of Authigenic Magnesian Clay Formation Sequences in the Barra Velha Formation (Santos Basin, Brazil)

“…A total of 75 samples have been collected from well P1 located in the Santos Outer High structure of the Santos Basin (Figure 1). Fifty-seven of those samples were mineralogically characterized by Netto [2], and 18 more samples were collected, and its characterization allowed the establishment of two mineralogical sequences. The samples comprise core, core plugs and side wall cores from Barra Velha Fm.…”

“…The Barra Velha Fm is separated into lower and upper by the Intra-Alagoas Unconformity. The Barra Velha Fm was deposited during the Alagoas Local Stage, which is correlated to the Ostracod Biozone 011 [21] (modified from Netto et al [2]).…”

“…In recent years there has been a resurgence on the topic of magnesian clay minerals, both in their genetic aspects and applications. These minerals give rise to deposits of economic interest in various parts of the world with a wide variety of industrial and technological applications [1][2][3]. To the above mentioned, we must add the prominence that some of these magnesian clay minerals, mainly kerolite and magnesian smectite, have acquired in the elaboration of models explaining their role in the origin of the huge oil deposits associated with the pre-salt in an extensive area of the Brazilian coast [2,4].…”

“…These minerals give rise to deposits of economic interest in various parts of the world with a wide variety of industrial and technological applications [1][2][3]. To the above mentioned, we must add the prominence that some of these magnesian clay minerals, mainly kerolite and magnesian smectite, have acquired in the elaboration of models explaining their role in the origin of the huge oil deposits associated with the pre-salt in an extensive area of the Brazilian coast [2,4]. Although kerolite is not listed as valid specie in the IMA list of minerals, its name is widely used to describe the nanocrystalline, stacking-disordered talc, with a slightly enlarged layer spacing and significant water content [5,6].…”

“…For years, many researchers have studied the pre-salt carbonates, especially in the Santos Basin, proposing models about the evolution of the basin and the sedimentary processes that originate these globally unique carbonate formations. The Santos Basin is located southeast of the Brazilian continental margin, between parallels 23º and 28º south, covering 350,000 km 2 , up to a bathymetric depth of 3000 m. It includes the coastline of Rio de Janeiro, São Paulo, Paraná and Florianópolis states. It is bounded to the north by the Cabo Frio High and to the south by the Florianópolis High [7].…”