Paleoenvironmental evolution of the coastal plain of Southern Brazil: palynological data from a Holocene core in Santa Catarina State

Anais da Academia Brasileira de Ciências (2017) 89(4): 2581-2595 (Annals of the Brazilian Academy of Sciences) Printed version ISSN 0001-3765 / Online version ISSN 1678-2690 http://dx.doi.org/10.1590/0001-3765201720160895 www.scielo.br/aabc | www.fb.com/aabcjournal Paleoenvironmental evolution of the coastal plain of Southern Brazil: palynological data from a Holocene core in Santa Catarina State LIDIA A. KUHN1, PAULO A. SOUZA1, RODRIGO R. CANCELLI1, WAGNER G. SILVA1,2 and RENATO B. MACEDO1 1 Programa de Pós-Graduação em Geociências, Universidade Federal do Rio Grande do Sul/UFRGS, Instituto de Geociências, Departamento de Paleontologia e Estratigrafia, Laboratório de Palinologia Marleni Marques Toigo, Av. Bento Gonçalves, 9500, 91540-000 Porto Alegre, RS, Brazil 2 Instituto Federal de Educação, Ciência e Tecnologia do Rio Grande do Sul/IFRS, Campus Osório, Rua Santos Dumont, 2127, 95520-000 Osório, RS, Brazil Manuscript received on December 20, 2016; accepted for publication on February 7, 2017 ABSTRACT This paper presents a paleoenvironmental reconstruction from palynological analyses of a sedimentary core of Holocene age, drilled at municipality of Garopaba (Santa Catarina), Southern Brazil. A total of 46 samples was collected for palynological analyses in the 450 cm-long core PCSC-3, as also three samples for radiocarbon dating and granulometric analyses. The palynological content includes 84 taxa related to pollen grains of angiosperms (38) and gimnosperm (3), spores of pteridophyta (16) and bryophyta (2), spores of fungi (8), algae (3), acritarchs (3), dinoflagellate cysts (2) and microforaminiferal linings (1). Three specimens of acritarchs are described and illustrated in detail. Three palynological phases were defined based on changes in assemblages: Phase I, Phase II and Phase III. The Phase I is characterized as a lagoonal paleoenvironment with marine influence from the beginning of the sedimentation (5390 cal yr BP), based on occurrences of acritarchs, dinoflagellate cysts and microforaminiferal linings. The Phase II (3032 yr BP until 858 cal yr BP) also is characterized by a lagoonal paleoenvironment, however, presented decrease in percentage of marine elements and increase in freshwater algae record, suggesting less marine influence in the lagoonal body. In Phase III (last 856 years), underwater sedimentation prevailed, under swamp-like conditions. Key words: coastal plain, environmental evolution, Holocene, palynology, Santa Catarina. INTRODUCTION The paleoclimatic variations and the sea level oscillations modelled the coastal areas worldwide in the Quaternary, resulting in significant sedimentary changes on the Southern Coastal Plain of Brazil. The sedimentary deposits formed during this time Correspondence to: Lidia Aumond Kuhn E-mail: span comprise coastal plain important records on the evolution of Southern of Brazil, providing data set for local and regional analysis of the geological and vegetational history. In recent years, the Coastal Plain of Santa Catarina has shown an intense human occupation, resulting in negative impacts on the natural scenery, especialy near the coastline (Strohaecker 2008). An Acad Bras Cienc (2017) 89 (4) 2582 LIDIA A. KUHN et al. Several palynological studies in Southern and southeastern Brazil based on palynomorph analysis have demonstrated the coastal environmental changes in response to Holocene sea-level variation (de Oliveira et al. 2005). However, little is known about the paleoenvironmental history of Santa Catarina Coastal Plain (e.g., Slompo 1997, Behling and Negrelle 2001, Amaral et al. 2012), when compared to nearby areas, especially Rio Grande do Sul (see summary in Bauermann et al. 2009) and Rio de Janeiro States (e.g., Luz et al. 2006, Freitas and Carvalho 2012, Souza et al. 2016). Palynological data constitute an important tool for paleoclimatical, paleoecological and paleoenvironmental analysis because microfossil assemblages present high potential of preservation. Microfossils are generaly abundant in pelitic deposits, and are distributed in a wide variety of habits and habitats, within marine and transitional to continental basins. Thus, the record of certain marine palynomorphs and the analysis of their frequency and relative abundance in comparison with continental palynomorphs are commonly used as proxies for the delimitation of transgressive and regressive sea level events. This has been done for Brazilian (e.g., Cordeiro and Lorscheitter 1994, Behling and Negrelle 2001, de Oliveira et al. 2005, Meyer et al. 2005a, b), Southern South American (e.g., Vilanova et al. 2006, Borremei and Quattrocchio 2007, Quattrocchio et al. 2008, Mourelle et al. 2015) and other continents (e.g., de Vernal and Giroux 1991, de Vernal 2009, Mudie et al. 2011, Richards et al. 2014), in most cases integrated with other tools of analysis, such as the sedimentology and geochronological calibration. This study presents the results of a palynological analysis performed from the 450 cmlong core PCSC-3 collected in the Coastal Plain of Santa Catarina. A paleoenvironmental model is proposed for the last 5390 cal yr BP, based on the palynological associations, mainly taxa of An Acad Bras Cienc (2017) 89 (4) spore-pollen, algae cysts, dinoflagellate cysts, microforaminiferal linings and acritarchs. STUDY AREA This study was performed on a peat deposit (PCSC3) located in Garopaba (coordinates 28°02’11.95”S; 48°37’41.73”W), Santa Catarina State, Southern Brazil, about 70 km from the state capital and ca. 2 km from the Atlantic Ocean coastline (Figure 1). The Coastal Plain of Santa Catarina has two main geological units: the Basement (Precambrian, Paleozoic and Mesozoic units) to the west, and the Pelotas and Santos sedimentary marginal basins (Cretaceous to Quaternary) to the east. The municipality of Garopaba is in the onshore portion of the Pelotas Basin. The basement is composed of Precambrian rocks of the Catarinense Shield, and Paleozoic and Mesozoic sedimentary rocks, including Jurassic/Cretaceous magmatic rocks of the Serra Geral Formation (Diehl and Horn Filho 1996) of the Paraná Basin. The marginal sedimentary deposits comprise continental systems, corresponding to colluvial deposits, alluvial and fluvial fans, in the higher portions. The coastal system has the barrier-lagoon system, and comprises Pleistocene and Holocene deposits associated with the relative sea level variations developed during the Quaternary (Horn Filho 2003). The climate of Santa Catarina State, similar to the entire Southern Brazil, is influenced by the South Atlantic Anticyclone and the Polar Migratory Anticyclone. The South Atlantic Anticyclone produces the tropical warm and humid air masses, which predominate during spring and summer, while the Polar Migratory Anticyclone is more active during the autumn and winter, producing the Atlantic polar mass, which is characterized by low temperatures (Nimer 1990). The climate of Coastal Plain o (...truncated)