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This paper discusses a model of coastal barrier progradation where the development of a prograded plain was a product of the successive formation of foredune ridges followed by their burial by transgressive sand sheets and dunefields. The results are based on direct lithological data from drill holes and geomorphological analyses, indirect geophysical data (GPR), and 14C and OSL dating. Barrier progradation started at 6.69 ka (OSL) or 7.2 ka (14C), under sea-level rise. At around 5.0 ka (OSL), or thereabouts, a forced regression condition started to operate, when sea-level started to fall after it reached a maximum of 2.34 ± 0.8 m. During barrier progradation sets of foredunes were formed, and at least some of them were buried by sands of transgressive dunefields (TDF), which later evolved to transgressive sand sheets (TSS). A total of 11+ phases of TSS and a modern phase of TDF were formed in a time span of 6.69 ka (OSL) or 7.2 ka (14C), corresponding to one phase formed at each 560 or 600 yrs. Two models of possible development of the surface of Curumim barrier are proposed. • Arare record of aforedune plain buried by transgressive sandsheets formation. • The cyclic formation of transgressive dunefieldsand transgressive sand sheets. • The foredune/beach contact as a proxy of sea-level position. • Distinct contributions of normal and forced regressionon barrier progradation. • Possibletransformation of a transgressive dunefield in a transgressive sand sheet. [ABSTRACT FROM AUTHOR]

In this paper, a reinterpretation of the older 14C ages of the Pleistocene substrate of the Holocene barrier-lagoon system of three coastal localities in southern Brazil is presented (Hermenegildo, Cassino, and Curumim). Sedimentological, geochronological, palynological, and diatom analyses of a sedimentary deposit formed in an estuarine/shallow marine environment are examined. This sedimentary deposit is presently found between 22 and 25 m depth below sea level in the Pinheira coastal plain. Results from all studied sites indicate that the deposit was formed under a former sea level of Marine Isotopic Stage 3 (MIS 3) that may have oscillated in the study region between 5 and 23 m depth below present sea level, from 36.2 to 47.7 ka. These results are reinforced by studies of nearby sites, including southeast Brazil. The Pleistocene substrate of the Holocene lagoonal-barrier system, at depths lower than 5 m below sea level, seems to correspond to sedimentary deposits of the Pleistocene barrier formed during MIS 5, while at depths greater than 5 m below sea level, they might correspond to sedimentary deposits that were formed during the relative high sea levels of MIS 3. [ABSTRACT FROM AUTHOR]

This paper presents the geological and morphological evolution of the prograded Cassino barrier during the middle and late Holocene. A special focus is given on the presentation and discussion of records of environmental changes that occurred during barrier progradation. The results demonstrated that variable rates of progradation were produced by environmental changes that affected the coastal sediment budget, such as changes in the wave climate. The total progradation of 18 km recorded for the Cassino barrier is probably the highest extension of progradation registered for a ridge plain associated with a coastal barrier. Sea-level changes during barrier progradation were accessed by the high difference between the degree of compaction of the foredune and backshore/foreshore deposits detected by the drilling system applied in this study and were confirmed by the limit of those deposits, which were also revealed by GPR records. During most of the time of barrier progradation, an overall sea-level fall of approximately 2 ± 1 m occurred. Six sets of relict foredune ridges were identified, and the limits between them were well marked by ridge truncations and the formation of transgressive dune sheets (TDS). Optically stimulated luminescence ages show that the TDS were formed under the driest climate conditions, with age periods very close to 3.8, 3.5, 1.9, 1.5, 0.22 and 0.09 ka ago, interspersed with ages of known wetter conditions in southern Brazil. The modern phases of TDS formation, with ages varying from 0.25 to 0.22 ka ago, were coincident with the time period of the younger pulse of the Little Ice Age (LIA), which was characterized by arid and cold conditions in southern South America. A comparison with prograded barriers located 350 to 600 km to the north suggests the existence of teleconnections, with phases of TDS and parabolic dunes that formed with a time interval of approximately 405 to 583 years. [ABSTRACT FROM AUTHOR]

The presentation of Fig. 1 was incorrect. [ABSTRACT FROM AUTHOR]

The trace element content of zircon grains from Holocene beach sands from the Rio Grande do Sul state in southern Brazil was investigated in order to discuss their probable primary source. Zircon grains from 10 samples were separated and analysed by laser ablation inductively coupled plasma mass spectrometer (LA ICP-MS) for rare earth elements (REE), niobium (Nb), uranium (U), thorium (Th), yttrium (Y), hafnium (Hf), and tantalum (Ta) and by microprobe and scanning electron microscopy (SEM) for silicon (Si), zirconium (Zr), and phosphorus (P). The results obtained are similar to those suggested by the zircon classification developed by BELOUSOVA et al. (2002, Igneous zircon: trace element composition as an indicator on source rock type. Contributions to Mineralogy and Petrology, 143, 602-622), nevertheless, additional information and a more detailed characterisation of zircon sources were yielded. The probable geotectonic setting and geochemical affinity of zircon igneous sources were predicted mainly based on thorium/uranium (Th/U), yttrium/holmium (Y/Ho), and niobium/tantalum (Nb/Ta) ratios; lanthanum (La) and niobium (Nb) contents; and REE patterns of zircons. The statistical groups identified by multivariate analysis were an additional useful tool for identifying compositional groups of zircons. Zircon grains from the studied sediments are probably derived from an association of subalkaline to alkaline granitic rocks with their mafic counterparts and metamorphic rocks of amphibolite to granulite facies. The metamorphic sources were more important in the southern sector of the studied coastal segment, whilst in the northern sector zircons from A-type granites are more abundant. The so-called Pelotas Batholith, situated in the eastern part of the Sul-rio-grandense Shield, which is composed mainly of a postcollisional granitic association of Neoproterozoic age and Paleo to Neoproterozoic high-grademetamorphic sequences, is proposed as the probable source of the studied zircons. The compositional variations of zircons from the southern to the northern sector are coherent with the hypothesis that the studied sediments came from relatively near continental source areas, probably transported by several small streams and rivers during phases of sea-level low stands. The chemical composition of zircons, particularly trace element contents and ratios, can be a powerful tool for determining the primary sources of detrital zircons. [ABSTRACT FROM AUTHOR]

The evolution and behavior of coastal barriers are controlled by several allogenic and autogenic factors. Some of these may be more deterministic than others. In this study, the GEOMBEST morphostratigraphic model is used to evaluate the degree of influence of both the substrate slope and the long-term sedimentary budget on the evolution of an extensive lagoon-barrier system during the mid-late Holocene in the middle littoral of Rio Grande do Sul state (Southern Brazil). Along this coastal stretch there is a coexistence of barriers with regressive, transgressive and stationery morphological behavior over >200 km. The modern configuration of the Holocene system (shoreline position and the lagoon-barrier width) was reproduced through the variability of two factors: the substrate slope (which defines the horizontal and vertical distance that the barrier will translate and rotate) and the sedimentary budget (which controls the evolution of the barrier when sea level oscillates slowly). The substrate slope of the middle littoral, between 0.021° and 0.149°, determined the cross-shore position of the shoreline, and the exogenous input or removal of sediment (estimated between −8 to +4.5 m3/m/a) allowed establishing the type of barrier behavior in the last millennia. Thus, the substrate slope exerts both direct and indirect control on coastal evolution. According to sensitivity analysis, a small decrease in the slope of the substrate, on the order of 0.001°, can increase the resulting barrier translation by >150 m, considering a 1-m rise in sea level over a 100-year interval. • Modeling large-scale evolution of Holocene coastal barriers, showing the importance of substrate slope and sediment budget • The substrate slope exerts a major control on barrier evolution and shoreline position, even with a very slight change • The long-term sedimentary budget can define the barrier system width, even with a sea level drop [ABSTRACT FROM AUTHOR]

Dillenburg, S.R.; Barboza, E.G.; Rosa, M.L.C.C.; Caron, F., and Bitencourt, V.B., 2020. Changes in the littoral drift of the Uruguayan coast during the Holocene and its influence in the continuing erosion in southern Brazil. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 453–457. Coconut Creek (Florida), ISSN 0749-0208. In northern Uruguay and southern Brazil, a littoral drift system dominates from southwest to northeast. This littoral drift is a consequence of higher wave-energy, generated in southern latitudes and that has been operating on a long-term scale, playing an important role not only in the evolution of coastal barriers of this region during the Holocene but also in coastal erosion that presently occurs in some parts of this coast. From La Coronilla to Cabo Santa Marta, which is a coastal sector 750 km - along the coast is gently undulating, showing gentle projections located to the south of gentle reentrances, that are dominated by transgressive/stationary and regressive barriers, respectively. In general, the regressive barriers have been developed by sediments brought into the reentrances by long-shore currents. The main source of these sediments had been the transgressive/stationary barriers that occur along the coastal projections. This differentiation of barrier behavior started at around 6-5 ka, at the end of the Postglacial Marine Transgression (PMT), when all rivers were drowned, finishing the delivery of new coarse sediments to the coast. Also, at this time the large rock promontories of the Uruguayan coast were formed and started to retain sediments of the littoral drift system, triggering a long-term coastal erosion in the southernmost coastal projection. Regarding erosion that is occurring in this stretch of coast the important issue to be considered in future coastal planning is that erosion will continue to operate in the long-term but will also be (and certainly has been already) amplified by sea-level rise in the next centuries as projected by the Intergovernmental Panel on Climate Change (IPCC). [ABSTRACT FROM AUTHOR]

This paper investigates the existence of statistical correlations and relationships between geological and oceanographic parameters along a coastal barrier system in southern Brazil. The existence of few statistical studies on coastal barriers motivated the use of multivariate statistical techniques that take environmental parameters such as coastal morphological-sedimentary features and their morphometric measurements into account. The Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) were used to assess the spatial variations of fourteen parameters driving the current and past behavior of this coastal barrier system at fourteen locations. Through the application of HCA, these locations were divided into four groups (Groups 1, 2, 3, and 4). The HCA results were analyzed using PCA. The first (PC 1) and the second (PC 2) principal components together explained at least 76.4% of the variability of all four groups. The most important geological and oceanographic parameters that were correlated to PC 1 and PC 2 were different in each group. In general, the shoreface slope and shoreface dimensions were common to all groups as PC 1 -correlated parameters, being the most important ones regarding data variability. In addition, for the progradational (Groups 1 and 4), retrogradational (Group 2) and aggradational barriers (Group 3) PCA indicated that shoreline orientation (wave exposure) and beach type are secondary, but relevant factors controlling the past and current behavior of coastal barriers in southern Brazil. • Spatial variation of coastal parameters involved in the evolutionary behavior of beaches and coastal barriers • Statistical analysis of driving forces controlling the evolution of coastal barriers • Shoreface dimensions and substrate slope were the most important drivers on barrier evolution in southern Brazil [ABSTRACT FROM AUTHOR]

The pedogenic carbonates found in Pleistocene units of the coastal Brazilian Pampa, informally designated as 'Caliche Cordão', include rhizocretions, soft masses and isolated or coalescent nodules, either isolated within the sediment or forming discrete horizons, the most developed horizons (Ca-01 and Ca-02) stretching for hundreds of meters along the banks of Chuy Creek. Petrographic analyses show micritic (Alpha-type) matrix in most samples, with few signs of recrystallization as circumgranular spar rims or cracked sand grains. Stable carbon (δ13C) and oxygen (δ18O) isotope values in samples from the lower horizon Ca-01 exhibit small variation and indicate C3-dominated plant assemblages and carbonate precipitation from relatively 18O-enriched water, whereas the δ13C and δ18O in samples from the upper horizon (Ca-02) exhibit wider variation, higher proportion of C4 plants and precipitation from 18O-depleted water in some samples. The δ18O variations can be explained by variable degrees of evaporative enrichment, or to relative contributions of 18O-depleted (tropical) or 18O-enriched (subtropical) rainfall, based on the similarity with estimates from fossils of mastodons. Nodules from other sites are similar, but larger isotopic variations indicate carbonate precipitation at distinct times and environmental conditions, and a few exhibit partial recrystallization as larger spar calcite crystals. Luminescence ages of ∼74.7 and ∼71.3 ka of quartz grains in two nodules from Ca-01 indicate precipitation during MIS 4, whereas ages of ∼52 ka from Ca-02, and ≥30 ka in nodules from the shores of Mirim Lagoon indicate carbonate formation between MIS 3 and MIS 2. The probable source of carbonate was calcium released from eolian-sourced silty dust produced by Andean glaciers and transported from loess deposits in Argentina during cold and dry intervals of the last glacial, when arid/semiarid environments expanded from Patagonia across the Pampas up to southern Brazil. The variations of δ13C in calcretes formed between MIS 4 and 2 point to changes in plant assemblages that could have contributed for the local extinction of the mammalian megafauna. • Pleistocene calcretes indicate dry paleoenvironments in the coastal Brazilian Pampa. • The carbonates include nodules and rhizocretions developed in Pleistocene sediments. • OSL ages indicate calcrete formation during the last glacial stage (MIS 4 to MIS2). • The calcretes record changes in the relative proportions of C3 and C4 plants. • Calcretes formed from highly evaporated water or 18O-enriched subtropical rainfall. [ABSTRACT FROM AUTHOR]

Abstract: Transgressive dunefields are present along the entire stretch of the Rio Grande do Sul (RS) coast, from Rondinha to Mostardas. These dunefields change their morphology and size along the coast and through time. The aim of this paper is to describe the spatial and temporal variations of the dunefields and analyze the main agents that control these variations. The dunefields at the northern littoral are narrow (1300 to 1400m wide) due to the local higher precipitation, lower wind drift potential (DP) and smaller sand supply. Southwards, the dunefields increase their width (reaching 6900m), as the precipitation decreases and the wind DP and the sand supply increase in the area. The RS dunefields have changed through time. Since 1948, the dunefields have experienced increases in the deflation area, in the vegetation cover and in the moist areas. These processes of dunefield stabilization are probably the result of the historical increase in precipitation and decrease in wind DP. As the northern dunefields are smaller, they have less sand, thus they were more susceptible to stabilization processes. In the southern dunefields, the larger amount of sand and the ongoing coastline erosion have retarded the stabilization processes. [Copyright &y& Elsevier]

The coastal plain of southern Brazil documents several environmental changes mainly related to sea-level fluctuation and climatic variations during the Quaternary. Comprehensive studies have been carried out, of local and regional scope, in order to improve the knowledge about the geological evolution of this portion of the South American. In this paper we present the results of stable isotope, palynological and palynofaciological analysis of the PSC-03 core (7744 cal yr BP – Modern) was performed to provide the sedimentary evolution of the Santa Catarina coastal plain. Palynological and palynofacies analyses revealed abundant and diversified palynological associations, including terrestrial palynomorphs (spores, pollen grains, fungi, and freshwater algae), marine elements (dinoflagellate cysts and foraminiferal linings), besides abundant phytoclasts and amorphous organic matter. Based on the combined analysis of δ13C isotopes (−20.7 ‰ to −29.6 ‰) and the C/N ratio (15.5–68) of the selected samples, we deduce that the organic matter is derived from marine phytoplankton and terrestrial C 3 plants. The integrated approach of palynofacies and stable isotopes (δ13C and C/N) analyses revealed three distinct intervals, which characterize the environmental evolution of this portion of the coastal plain. The Interval I (7744 to 2844 cal yr BP) is related to a marginal marine environment, followed by the Interval II (2857 to 2276 cal yr BP), which indicates shallow water conditions, with wetland or soggy soils, while the Interval III (2124 cal yr BP to Modern) shows a subaerial scenario, strongly influenced by arboreal forms of the Atlantic Forest. Comparisons with other sites in southeastern South America were carried out, especially from Uruguay and Argentina, showing similarities in the palynological succession, as response to broader climatic conditions. • Stable isotopes (δ13C and C/N) and palynofacies analyses are used for understanding coastal evolution of southern Brazil. • Three paleoenvironmental phases are identified within the last 7744 cal years BP. • The marine influence is evidenced between 7744 and 2884 cal years BP. • Major development of the Atlantic Forest in the area from 2124 cal years BP onwards. [ABSTRACT FROM AUTHOR]

The coastal plain of the state of Rio Grande do Sul, in southern Brazil, includes four barrier-lagoon depositional systems formed by successive Quaternary sea-level highstands that were correlated to marine isotope stages (MIS) 11, 9, 5 and 1, despite the scarcity of absolute ages. This study describes a sea-level highstand older than MIS 5, based on the stratigraphy, ages and fossils of the shallow marine facies found in coastal barrier (Barrier II). This facies outcrops along the banks of Chuí Creek, it is composed of fine, well-sorted quartz sand and contains ichnofossils Ophiomorpha nodosa and Rosselia sp., and molluscan shells. The sedimentary record indicates coastal aggradation followed by sea-level fall and progradation of the coastline. Thermoluminescence (TL) and electron spin resonance (ESR) ages from sediments and fossil shells point to an age of ∼220 ka for the end of this marine transgression, thus correlating it to MIS 7 (substage 7e). Altimetric data point to a maximum amplitude of about 10 meters above present-day mean sea-level, but tectonic processes may be involved. Paleoceanographic conditions at the time of the highstand and correlations with other deposits in the Brazilian coasts are also discussed.