Geomorfologia e estrutura superficial da paisagem de zonas costeiras rochosas: um estudo de caso na Ilha do Cardoso (Litoral Sul de São Paulo)

Com o intuito de contribuir para o conhecimento da geomorfologia litorânea de zonas costeiras rochosas, o presente estudo objetivou caracterizar a estrutura superficial da paisagem das escarpas litorâneas da Ilha do Cardoso (litoral sul de São Paulo). A metodologia consistiu na integração entre trabalhos, mapeamentos e descrições geológicas e geomorfológicas macroscópicas de campo, análises laboratoriais (petrografia) de amostras das unidades litológicas locais e análises de imagens aéreas e orbitais. Com relação a registros da estrutura superficial ligados predominantemente a configurações geomorfológicas e de níveis de base locais distintos das atuais, foram delimitados seis níveis de aplainamento em meio as serranias da Ilha, correlacionados com a geomorfologia litorânea descrita em estudos anteriores. Com relação a registros da estrutura superficial com maiores contribuições de processos atuais e subatuais, foram identificados e caracterizados feições morfológicas de detalhe e depósitos de blocos rochosos de fundos de vales fluviais serranos e de escarpas serranas sob influência direta do mar (costões rochosos). Efetuou-se a caracterização granulométrica, textural e litológica dos referidos registros, bem como ponderou-se sua contextualização na compartimentação da paisagem e na caracterização morfométrica, morfodinâmica, litológica e climática das Serranias da Ilha do Cardoso. Elencou-se que a diversidade da estrutura superficial rochosa local teria contribuição de nove distintos padrões de combinações entre depósitos, formas de relevo, unidades litológicas e processos exógenos, parte deles com sua génese tendo influência de variações climáticas inter-anuais locais e consequentes modificações sazonais na drenagem e escoamento superficial, e uma segunda parte ligada a distintas combinações entre as variações espaciais da caracterização mineralógica das unidades litológicas e dos fatores morfodinâmicos predominantes presentes na linha de costa da Ilha (segmentos expostos a processos lagunares versus segmentos expostos a processos de mar aberto). Geomorphology and surface structure of rocky coastal zones: study case on the Cardoso Island (south coast of São Paulo State, Brazil) A B S T R A C TIn order to contribute to the knowledge of coastal geomorphology of rocky coastal areas, the present study aimed to characterize the surface structure of the coastal escarpments of Ilha do Cardoso (south coast of São Paulo). The methodology consisted of integrating macroscopic geological and geomorphological mapping and field descriptions, characterizing patterns of precipitation and breaking waves in the area, laboratory analysis (petrography) of samples from local lithological units and analysis of aerial and orbital images. There were characterized nine distinct patterns of combinations between deposits, forms of detailed relief, lithological units and exogenous processes. The occurrences of such patterns of surface structure were contextualized amid the characterization of geomorphological compartmentation, precipitation patterns, the prevailing conditions of agitation of the waters surrounding the island, and the mapping and petrographic characterization of local lithological units. Thus, it was pointed out that the genesis of the island's surface structure patterns would have a contribution of overlaps between local inter-annual climatic variations and consequent seasonal changes in drainage and surface runoff, and to different combinations between the spatial variations of the mineralogical characterization of the lithological units and the predominant morphodynamic conditions present on the island (segments exposed predominantly to lagoon processes versus segments exposed to open sea processes versus segments exposed to fluvial action and runoff). The different lithological units of local hard rocks linked to different petrographic characterizations when exposed to the same morphodynamic conditions linked to the action of coastal waters result in features of detail relief and deposits quite different from each other in terms of degree of preservation and inclinations of the rocky platforms, as well as the dimensions and degrees of roundness of the rock fragments deposits. It was interpreted that such heterogeneities would have a contribution of different successibility of the different compositions and mineralogical arrangements of each local hard rock lithological units to the weathering patterns linked to each of the three sets of predominant morphodynamic processes operating in this coastal segmentKeywords: planning levels, coastal rocky cliffs, valley floor deposits, coastal geomorphology, rocky coasts

Beach-face slope dataset for Australia

Sandy beaches are unique environments composed of unconsolidated sediments that are constantly reshaped by the action of waves, tides, currents, and winds. The most seaward region of the dry beach, referred to as the beach face, is the primary interface between land and ocean and is of fundamental importance to coastal processes, including the dissipation and reflection of wave energy at the coast, and the exchange of sediment between the land and sea. The slope of the beach-face is a critical parameter in coastal geomorphology and coastal engineering, necessary to calculate the total elevation and excursion of wave run-up at the shoreline. However, datasets of the beach-face slope remain unavailable along most of the world’s coastlines. This study presents a new dataset of beach-face slopes for the Australian coastline derived from a novel remote sensing technique. The dataset covers 13,200 km of sandy coast and provides an estimate of the beach-face slope at every 100 m alongshore, accompanied by an easy to apply measure of the confidence of each slope estimate. The dataset offers a unique view of large-scale spatial variability in beach-face slope and addresses the growing need for this information to predict coastal hazards around Australia. The beach-face slope dataset and relevant metadata are available at https://doi.org/10.5281/zenodo.5606217 (Vos et al., 2021)

A Comparison of Microplastic in Fish From Australia and Fiji

Awareness surrounding plastic pollution has increased significantly in the past decade, leading to concerns on potential adverse effects on biota, including the consumption of microplastic by fish. Globally, plastic has been found in many species of fish, but little research has been undertaken in the southern hemisphere. We assessed the abundance and type of plastic in fish captured and sold for human consumption in Australia and Fiji. Fish (goatfish, sea mullet, paddletail, and common coral trout) had their gastrointestinal tracts dissected and microplastic quantified under a microscope. Plastic polymer types were confirmed using μ-FTIR. In Australia, plastic was found in 61.6% of fish gastrointestinal tracts, while in Fiji, 35.3% of fish had plastic. Fish from Australia had almost double the amount of plastic on average than fish caught in Fiji, with 1.58 (± 0.23) pieces per fish in Australia compared to 0.86 (± 0.14) in fish caught in Fiji. The types of plastic differed between countries, with fibers comprising 83.6% of microplastic pieces in fish from Australia whereas 50% of microplastic found in fish from Fiji was film. Polyolefin was the most abundant polymer type in both fibers from Australia and film from Fiji. We hypothesize variations in abundance and plastic type are a reflection of the population density and coastal geomorphology, but may also be a result of legislation and waste management strategies in the two countries. This work adds evidence to the pervasive presence of plastic in fish gastrointestinal tracts, reinforcing the urgent need for efficient plastic waste management, but also a better understanding of the impacts of microplastic on marine biota.

The oceanography of Cuchlaine A.M. King

C.A.M. King, the noted British coastal geomorphologist, authored two books in a three-year period. Beaches and Coasts in 1959 was a major contribution to coastal geomorphology, whereas Oceanography for Geographers represents King’s attempt to show the importance of the oceans to all of geography. Their approaches and pedagogy differ, but their lessons remain relevant today.