Beachrock de Jaconé, Maricá e Saquarema - RJ: importância para a história da ciência e para o conhecimento geológico

Abstract

Revista Brasileira de Geociências 41(2): 290-303, junho de 2011Arquivo digital disponível on-line no site www.sbgeo.org.br 290Beachrock de Jaconé, Maricá e Saquarema -RJ: importância para a história da ciência e para o conhecimento geológico Abstract The beachrock Jaconé, Maricá and Saquarema -RJ: importance to the history of science and to the geological knowledge. The Caminhos de Darwin Project aims to redeem the episodes experienced byCharles Darwin in the state of Rio de Janeiro and that they have had part in his scientifi c training aboard the Beagle. In the geological approach of this project, the outcrops described by Darwin in the State of Rio de Janeiro are being described with purposes of geoconservation. The beachrock of Jaconé was identifi ed by the naturalist, at then 23 years old, on April 9, 1832. Over the years, archaeological researches conducted in the region discovered pebbles of beachrock in the middens of Beirada and Moa. This fact demonstrates that this rock was already known by prehistoric men for over 4000 years BP. The present study aimed to assess these outcrops as geological heritage and, at the same time, update the knowledge about its geology. Three lithofacies were identifi ed and two of them were analyzed petrographically. The age of the shells was calculated at 8198-7827 cal BP by the radiocarbon method. The occurrence is constituted as a geological heritage of the following typologies: geomorphological, sedimentary, paleoenvironmental, petrological, and archaeological and, also, contextualized in the science history. It has international signifi cance and scientifi c, cultural, educational and ecological value.

Rochas De Praia "Beachrocks" Da Ilha Do Cabo Frio - Litoral Do Estado Do Rio De Janeiro - Sudeste Brasileiro: Gênese E Geocronologia

“…Os resultados aqui obtidos apresentados apontam para semelhanças, em termos de composição, estudos sobre os "beachrocks" em outras praias da costa do Estado do Rio de Janeiro e do nordeste do Brasil (Silva et al, 2014, Mansur et al, 2011, Vieira et al, 2005. No entanto a variedade de bioclasto é bastante diferente, ou seja, na área estudada, o percentual de bioclastos é de 40 a 90% constituído principalmente por rodophytas e bivalves.…”

“…Registram-se também outras ocorrências de "beachrocks" no litoral do Estado do Rio de Janeiro nas praias da Barra da Tijuca no município do Rio de Janeiro, praia de Itaipuaçu em Maricá (Silva et al, 2014) e na praia de Jaconé, no município de Saquarema (Mansur et al, 2011). Apresentam cimentação composta por franja prismática de calcita magnesiana, indicando condições de litifi cação similares às dos "beachrocks" da Ilha do Cabo Frio.…”

Holocene Paleo-Sea Level in Southeastern Brazil: An Approach Based on Vermetids Shells

“…) did not shown the altitudes of these samples in their work and Castro et al (2014) did not present the station used for GPS positioning, making impossible to know the distance between that station and the study area. Carmo (2014) correlated the age found by Mansur et al (2011) and height of that cement, with the sea level change curve proposed by Dias (2009), noting that the height of the sea level in that time would be 1.4 to 1.9 m above the current level, disagreeing with the height presented by Castro et al (op. cit. ), -0.5 m, wherein the trend line of the curve would be higher.…”

“…In this study, the authors present two samples dated by Mansur et al (2011), one related to the carbonate cement from Jaconé (Saquarema-RJ) beach rock and the other to shell fragments of the same deposit, having heights of 0.0 m and 0.5 m, respectively. However, Mansur et al (op.…”

“…Castro et al (2014) constructed a curve representing the sea level changes on the shore of the Rio de Janeiro state by using geological and biological data. Twenty-nine data were presented in this study, 17 from Dias (2009), 4 from Castro and Suguio (2011), 1 from Cunha et al (2012) and 2 from Mansur et al (2011), out of which only 14 data were used to establish the curve and it was not explained which criteria were used in selecting such data (Fig. 4.C).…”