Antônio Vicente Ferreira Júnior, Bárbara Carla Ehrhardt Paes, M. M. Vieira, A. Sial, V. Neumann
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引用次数: 5
Abstract
This work aims to understand beachrock formation during Holocene through petrology, geochemistry and dating of a core located 5,43m deep in relation to present-day sea-level in the Piedade Beach in Jaboatao dos Guararapes- PE. The core is located 143 meters distant from the coast line towards mainland. Four lithofacies have been identified, taking into account differences in texture and sedimentary structures. The framework grain size ranges from medium to very coarse sand, indicating variations in depositional energy. Petrographic data indicate that the beachrocks have values of 64.23% to 70.69% of framework composed of quartz grains. Carbonate cement (represents 13.5%) consisting of high magnesium calcite surrounding grains as isopachous fringe (4.15% to 11.95%), micritic cement (0.60% to 6.42%) and equant cement (0.26% to 7.01%), indicates marine environment precipitation. The results of the isotopic composition of carbon and oxygen present valuesof 3.09‰ to 3.89‰, with an average of 3.63‰ to δ 13 C PDB and of -0.91‰ to 0.96‰, with an average of 0.54‰ to δ 18 O PDB, suggesting that the cement is formed in a shallow marine environment with freshwater influence. The values obtained in paleotemperature vary from 21oC to 30oC, with an average of 23oC, with little variation indicating precipitation in a shallow water environment. In the study area, the beachrocks are indicators of sea level and the results suggest that between 7.509 years B.P. and 5982 years B.P. there was a marine transgression process, with sea level 9.18 m lower than the current sea level.
期刊介绍:
Quaternary and Environmental Geosciences (QEG) is for the publication of unpublished works in the areas of quaternary and environmental geosciences. QEG aims to publish high quality works on all Quaternary areas and environmental geosciences, from laboratory techniques to synthesis works. It aims to publish works from areas as diverse as climate variability and change, paleovegetation, paleoclimate and paleoenvironments, coastal geology and geomorphology, sea level variations, neotectonics, continental morphogenetic processes and products, sediment and soil geochemistry, geological hazards and paleoenvironment. , relationships between natural and anthropic geological processes, among others. We emphasize interest in interdisciplinary work. We discourage the publication of works that are not clearly linked with the Quaternary or the Environmental Geosciences. The main criterion for acceptance of the papers is their quality, originality, significance and interest to a broad regional to international community.