Estudos geoquímicos dos platôs marginais dos Estados do Ceará e Rio Grande do Norte (Brasil)

Abstract

This paper deals with the concen­tration of phosphorus, nitrogen, organic carbon, irou, titan, calcium, agnesium and organic matter in sediments of the marginal plateaux of the states of Ceará and Rio Grande do Norte, considering the origin, deposition and migration of these elements. The samples were collected on board of NOc. Almirante Câmera of the Bra­zilian Navy during the "Platôs Margi­nais Cruise", legs 3 and 4. lt has been observed that the carbo­nates are stemmed from the calcareous algae based on the relation Ca/Mg. Li­monite occurs concentrated in the clayey sediments of yellow color. The relation C/N grows from the top towards the bottom of the cores. The phospho­rite deposits have no correlation with the organic matter of the sediments, and are originated by precipitation and as consequente of the replacement of cal­cium by phosphorus. Titanium generally occurs associated with clayey sediments with great amount of shell fragments.