Evidence for a transgressive barrier within a regressive strandplain system: Implications for complex coastal response to environmental change

Abstract

Clastic, depositional strandplain systems have the potential to record changes in the primary drivers of coastal evolution: climate, sea‐level, and the frequency of major meteorological and oceanographic events. This study seeks to use one such record from a southern Brazilian strandplain to highlight the potentially‐complex nature of coastal sedimentological response to small changes in these drivers. Following a 2 to 4 m highstand at ca 5·8 ka in southern Brazil, falling sea‐level reworked shelf sediment onshore, forcing coastal progradation, smoothing the irregular coastline and forming the 5 km wide Pinheira Strandplain, composed of ca 500 successive beach and dune ridges. Sediment cores, grab samples and >11 km of ground‐penetrating radar profiles reveal that the strandplain sequence is composed of well‐sorted, fine to very‐fine quartz sand. Since the mid‐Holocene highstand, the shoreline prograded at a rate of ca 1 to 2 m yr−1 through the deposition of a 4 to 6 m thick shoreface unit; a 1 to 3 m thick foreshore unit containing ubiquitous ridge and runnel facies; and an uppermost beach and foredune unit. However, the discovery of a linear, 100 m wide barrier ridge with associated washover units, a 3 to 4 m deep lagoon and 250 m wide tidal inlet within the strandplain sequence reveals a period of shoreline transgression at 3·3 to 2·8 ka during the otherwise regressive developmental history of the plain. The protected nature of Pinheira largely buffered it from changes in precipitation patterns, wave energy and fluvial sediment supply during the time of its formation. However, multiple lines of evidence indicate that a change in the rate of relative sea‐level fall, probably due to either steric or ice‐volume effects, may have affected this coastline. Thus, whereas these other potential drivers cannot be fully discounted, this study provides insights into the complexity of decadal‐scale to millennial‐scale coastal response to likely variability in sea‐level change rates.

Central Santa Catarina coastal dunefields chronology and their relation to relative sea level and climatic changes

“…The clayey and silty sands are mostly found at south from Pinheira in small bays and lowlands around the estuarine and lagoon systems. In Pinheira strandplain, the Holocene terrace clearly corresponds to a strandplain, as evidenced by the sets of foredune ridges (Hesp et al 2009, Barboza et al 2009, Dillenburg et al 2014, Hein et al 2014.…”

Caracterização geológica, geomorfológica e evolutiva holocênica do litoral sul de Jaguaruna, SC, Brasil

“…Destacam-se os trabalhos de Barboza et al (2009Barboza et al ( , 2014a, Fornari (2010), Tanaka (2010), Biancini da Silva (2011, 2016 Biancini da , Dillenburg et al (2011, Hein et al (2013), , e Leal et al (2016).…”

Shallow gas seismic structures: forms and distribution on Santa Catarina Island, Southern Brazil

“…More recently, the eustatic sea-level rise following the last glacial maximum resulted in a highstand approximately 5.8 ka ago, encroaching in some locations upon Pleistocene highstand barriers (HORN FILHO et al, 1997;CARUSO JR et al, 2000, DOMINGUEZ, 2009). Since then the sea level has fallen 2 to 4 m (SUGUIU et al, 1985;LESSA, 1997;ANGULO et al, 2006;HESP et al, 2009;MCBRIDE et al, 2013;HEIN et al, 2013HEIN et al, , 2014 as a consequence of global isostasy, as demonstrated by MITROVICA and MILNE (2002).…”

“…This part of the coast is characterized by the high relief of the nearby Serra do Mar range, with a series of grabens and horsts parallel to the current coastline that were created by the Tertiary collapse (58 M yr BP) of a large Cretaceous plateau (ZALÁN; OLIVEIRA, 2005), giving rise, over the course of 30 million years, to Large-scale sea-level fluctuations throughout the Quaternary resulted in the deposition of a series of transgressive barriers and regressive barrier-strandplain systems, thus straightening the bedrock-dominated shoreline (DOMINGUEZ, 2009;KLEIN et al, 2010;MCBRIDE et al, 2013;HEIN et al 2013HEIN et al , 2014. Two Quaternary barriers, dating from the Oxygen Isotopic Stage (OIS) 5e and mid-Holocene highstands (SUGUIO et al, 1985;VILLWOCK et al, 1986;MARTINS et al, 1988) have been identified on the central coast of Santa Catarina where the Serra do Mar mountain range abuts the modern coast (HORN FILHO et al, 1997;CARUSO JR et al, 2000;MCBRIDE et al, 2013;HESP et al, 2009;HEIN et al, 2013HEIN et al, , 2014.…”