Shallow seismic reflectors and upper Quaternary sea levei changes in the Ubatuba region, São Paulo State, Southeastern Brazil

Abstract

The relationship between shallow seismic Wlits and Quaternary sea level changes in Southeastern Brazil is based on boomer profiles and core data ftom the Ubatuba region, northern São Paulo coast. In Flamengo and Palmas bays, the intecpretation of seismic lines revealed the occurrence of four sedimentary units, separated by regionally correlated reflectors. The upper two Wlits correspond to Late Pleistocene and Holocene deposits. The lowermost sedimentary units were correlated to the older Quaternary transgressive events. These deposits, which have not yet been described for this area, can presently be fOWld on the Rio Grande do Sul coastal plain. In the Boqueirão Strait, two erosional events in the sedimentary strata have been associated with the Cananéia (maximum at 120,000 yr. B.P.) and Santos (maximum at 5,100 yr. B.P.) sea-level rise events.

Analysis of Benthic Foraminifera Biofacies in cores of the Continental Shelf - RJ, Brazil

“…Os intervalos arenosos superiores do testemunho podem estar relacionados às variações climáticas regionais, que promoveram períodos de chuvas torrenciais intensificando a deposição de sedimentos mais grossos, devido ao aumento do aporte sedimentar continental, ou ainda por correntes marinhas mais efetivas que ocorreram na área de estudo (Mahiques & Souza, 1999).…”

Seismic Investigation in the Bertioga Coastal Plain, Brazil

“…A few papers can be mentioned presenting offshore shallow seismic studies, such as: Tessler & Souza (1998), Mahiques & Souza (1999), Paolo & Mahiques (2008).…”

Echo Character and Sedimentary Processes on the Continental Shelf of the São Paulo State

“…These coastlines variations were responsible for differences in the sedimentation regimes due to changes in oceanic circulation patterns. After the Last Glacial Maximum (LGM) (20,000 years BP), the influence of coastal waters in the transport and deposition of sediments has decayed and the Brazil Current and its eddies have changed their geographical position (Mahiques et al, 1999(Mahiques et al, , 2002.…”

“…The continental shelf of São Paulo is characterized by the existence of two sectors (southwestern and northeastern), which exhibit distinct sedimentological and geomorphological characteristics. The São Sebastião Island (SSI) marks the boundary between those sectors (Mahiques et al, 1999).…”

“…In the southwestern sector, the coastline orientation and the isobaths pattern parallel to the coast induce a more effective wave action on the inner shelf, largely preventing mud sedimentation. In the northeastern sector, the complex coastline physiography and the occurrence of many islands in the inner shelf favor mud deposition, as wave activity is diminished in this sheltered environment (Figure 4) (Mahiques and Souza, 1999;Mahiques et al, 2007;Mahiques et al, 2008). The most important source of recent sediments to the southwestern Atlantic shelf is the La Plata River plume, whose sedimentary influence can be recognized up to 25°S (Mahiques et al, 2008).…”