文章基本信息

标题：Diagenesis of Holocene Beachrock in Northeastern Brazil: Petrology, Isotopic Evidence and Age
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作者：Antonio Vicente Ferreira Junior ; Bárbara Carla Ehrhardt Paes ; Marcela Marques Vieira 等
期刊名称：Quaternary and Environmental Geosciences
印刷版ISSN：2176-6142
出版年度：2018
卷号：9
期号：2
DOI：10.5380/abequa.v9i2.53011
语种：English
出版社：UFPR
其他摘要：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.
其他关键词：Cement;Holocene;Sealevel