Process Control in The Geneses and Evolution of A Lagoon-Barrier System inside of The Patos Lagoon, South of Brazil

Abstract

The origin and geological evolution of a complex of a beach ridgeplain in the Feitoria lagoon-barrier, located on the western margin of the southern cell Patos lagoon, Brazil was influenced by the interactions between the alocyclic (climate change and relative sea level) and autocyclic (sediment supply, waves, longshore drift and storm surges) forcing. The study of this regressive beach ridgeplain included the analysis of orthophotos; topographic detail (PRO-XRS Trimble ®-postprocessed); and shallow geophysical data with Ground Penetrating Radar (GPR), 150, 200 and 400 MHz antennae, combined with facies analysis and radiocarbon dating (AMS) and Optically Stimulated Luminescence (OSL) from shallow borehole samples. The analysis of orthophotos allowed for the definition of at least nine morphologically distinct series of progradation, marked by truncations of progressive orientation changes. The integration of topographically corrected GPR data, sedimentary records, and geochronological data determined the beginning of the progradation occurred at 7.2 kaBP. At the beginning of progradation, the low tide terrace was at the height of 1.9m (EGM96) Above the Sea Current Level (ASCL). The swash zone was in the 2.5m, and the crest reached 4.3m ASCL. Currently, the low tide terrace quota is-0.4m, the swash zone to 0.3m and the crest reaches 2.1m ASCL. Among other factors, the fall of the lagoon base levels was associated with sea level fall during the Holocene regression. However, crest construction control is dependent on the lagoon base level oscillation, which in turn is controlled by the precipitation regime and storms surges. Moreover, these results suggest that the orientation of the ridges was controlled by changes in the internal lagoon hydrodynamics, due to the progressive narrowing of the lagoon connection with the open ocean.

Padrões De Empilhamento Estratigráfico E Seus Reflexos Na Morfologia Da Barreira Costeira Holocênica No Litoral Médio Do Rio Grande Do Sul, Brasil

“…A aplicação desta ferramenta é potencializada quando utilizada em conjunto com outros produtos de Sensoriamento Remoto em ambiente de Sistemas de Informações Geográfi cas (SIG). Barboza et al (2009Barboza et al ( , 2013Barboza et al ( , 2018 utilizaram o Georadar para avaliar os registros em subsuperfície de trechos da barreira holocênica ao longo da Bacia de Pelotas e defi nir seu padrão de empilhamento; Dillenburg et al (2011) compararam radarfácies de Georadar com litofácies de testemunhos sedimentares para determinar os limites entre diferentes depósitos costeiros; Lima et al (2013) aplicaram o Georadar para caracterizar o modelo evo-lutivo da barreira holocênica no extremo sul do RS (Hermenegildo); , Biancini da Silva et al (2014), e Leal et al (2016) analisaram registros de paleocanais fl uviais na região sul de Santa Catarina (SC); Rosa et al (2017) utilizaram o Georadar para analisar as escalas espaciais e temporais dos depósitos quaternários e propor um arcabouço estratigráfi co hierarquizado para a Bacia de Pelotas; Bitencourt et al (2016), Dillenburg et al (2017) e Manzolli et al (2018) utilizaram o Georadar para inferir o arcabouço sedimentar e o padrão de truncamentos de cordões litorâneos regressivos; Barboza et al (2018) apresentam a relação diácrona entre o máximo transgressivo e o máximo eustático do nível do mar no Holoceno. Recentemente, Leandro et al (2019) integraram dados de sondagens com análise de traço de Georadar para determinar o contato entre depósitos de ambientes deposicionais costeiros.…”