Caracterização sedimentológica quaternária do talude continental do Município de Luís Correia, Piauí

Abstract

Despite the importance and the various works carried out in the Brazilian continental margin, and specifically on the continental shelf, there are still few works in the continental slope, particularly in the slope of Piauí. Therefore, the present dissertation reflects the knowledge gap on the continental slope of Piauí and its purpose is its sedimentological characterization. The study was carried out through the testimonies SIS 720 and ANP 1286, located on the continental slope of the Piauí coast, which are about 91 and 105 km off the coastline, forming the western portion of the Ceará Basin, sub-basin of Piauí-Camocim. From the cartographic survey, bibliographical survey, field activities and laboratory analyzes, the sedimentological characterization of the region was performed. The testimony SIS 720 consists of bioclastic sediment, silt fraction, classified as calcareous vasa. This sediment is composed mostly of whole carapaces of organisms such as planktonic and benthic foraminifera, with less minerals such as quartz, potassium feldspar, kaolinite and ilite. The testimony ANP 1286 is composed of bioclastic, biosiliciclastic and silicibioclastic sediments, both of silt fraction, composed of different proportions of foraminifera carapaces, kaolinite and quartz. These different classifications are due to the strong variation of the calcium carbonate contents in the testimony, marking changes in the sedimentation. The high content of CaCO3 present in the region is given by the large amount of shells of organisms, indicating an environment where little dissolution of carbonate occurs. The minerals present are the result of the alteration of granitic rocks and mark the influence of terrigenous sediments in the region, it is suggested that these have reached the slope by means of gravitational flows. The presence of kaolinite marks the humid tropical climate, where accentuated processes of hydrolysis occur. The predominance of the sediment of the silt fraction indicates a low energy environment with slow deposition of these sediments. The lower continental slope of Piauí is marked by the strong influence of pelagic sediments, high CaCO3 contents, with a lower contribution of terrigenous sediments, quartz, feldspars and clay minerals, thus being the environment created by the joint action of continental and marine processes. It is hoped that this study will provide support for a better understanding of this depositional environment.