Padrões sedimentares de estratigrafia rasa em uma planície lagunar, Costa Oeste do Ceará, Brasi

Abstract

In this study, an analysis ofthe sedimentary patterns ofshallow stratigraphy was carried out in a lagoon plain close to the locations ofPorto dos Barcos and Guajiru in the municipality ofItarema. west coast ofthe Ceará State. In this region, the presence of mangroves and coastal barriers (spit and islands) stands out. Two sedimentary cores (T1 and T2) were collected using tubes of 50 nun in diameter and 1 meter in length. Subsequently, macroscopic identification ofthe sedimentary facies ofthe cores was earned out according to color, grain size, and presence of organic fragments. In the laboratory, granulometric analysis and quantification of calcium carbonate and organic matter contents were performed. From the integration ofthe data, columnar profiles ofthe cores were elaborated. The coloration identified in the cores varied between shades of black, gray, and green, in addition to some shades ofwhite and blue in the core T2. The presence ofvegetal fragments was verified along the entire length ofthe cores, and fragments ofshells and roots were observed in some fractions of the cores. The grain size of the cores showed a predominance of the sand fr action to about other granulometric classes, presenting some facies with a significant presence of mud fraction, mainly in the T2 core. The content of calcium carbonate in the sediments varied fiom 0.90% to 26.84% and of organic matter between 1.06% and 13.2%. It is concluded that the sedimentary dynamics in the T2 area are greaterthan in the T1 area and the granulometry showed a bimodal pattern ofsandy and sandymuddy sedimentary facies. Calcium carbonate was more associated with shell fragments and with coarser grain size irr the core T2. while the core T1 showed no correlation between calcium carbonate and grain size. Organic matter showed a meaningful relationship with finer particle size sediments.