Análise da distribuição estratigráfica de microfósseis de parede orgânica com base em dados de um furo do graben de metangula (Niassa)

Abstract

The Metangula Graben, located northwest of Niassa Province, is one of the sedimentary basins of the Karoo Supergroup, whose structure suggests a complete graben. It occupies approximately 50 km in width, is oriented in the NE-SW direction, and is filled with a set of sediments belonging to the SGK, which rest on Precambrian igneous and metamorphic rocks.

With the aim of analyzing the stratigraphic distribution of organic-walled microfossils, a petrographic and microscopic description of the core sample from borehole JOG16N-5 was carried out at the southeastern end of the Metangula Graben, at a depth of 210 meters, along the K4 Formation. Approximately 11 organoleptic slides were described, identifying about 57 genera and 87 species, grouped into three biozones and eight subgroups: Monosaccharides, non-stretched bisaccharides, stretched bisaccharides, plicates, colpates, monoletes, and triletes.

From the qualitative and quantitative analysis carried out, it was found that of these subgroups, 78% of the relative abundance of species belong to the spore class and 22% to non-stretched and stretched bisaccharide pollen grains. Additionally, based on these studies, new palynomorph associations were identified, with emphasis on the genera Striatopodocarpites, Protohaploxypinus, Cycadopites, and Guttulapollenites, which allowed for the correlation and dating of sedimentary sequences from the K4 Formation of the Metangula Graben from the Lower Permian to the Middle Permian.

This data will allow for a greater understanding of the geology and diversity of palynomorphs that occur in the Metangula Graben. Based on these palynomorph assemblages, the sediments from borehole JOG16N-5 were dated as Lower Permian, from the assemblages of Potonieisporites, Vittatina, Lueckisporites, Densosporites, Emphanisporites and Lundbladispora, and Middle Permian, from the assemblages of Potonieisporites, Protohaploxypinus, Klausipollenites, Densosporites, Lundbladispora, Schopfites, Striatopodocarpidites, Parasaccites, Circulina, Lundbladispora simplex, Dictyotriletes, Sulcatisporites.(TRADUÇÃO NOSSA)