Palinoestratigrafia da formação Manacapuru em Presidente Figueiredo (AM), Lochkoviano da bacia do Amazonas

Abstract

This study presents the chronostratigraphic positioning, as well as paleoenvironmental and paleoclimatic considerations, obtained from the analysis of sedimentary deposits of the Manacapuru Formation, located on the left margin of kilometer 99 of the BR-174 highway (in the Manaus–Boa Vista direction), in the region of Presidente Figueiredo, state of Amazonas, Brazil. A total of five palynological slides (the most fertile) were analyzed, resulting in relatively abundant and diverse palynomorph assemblages, composed of 43 taxa: 22 chitinozoan species (Ancyrochitina ex gr. A. ancyrea, A. ex gr. A. gutnica, A. fragilis, Angochitina elongata, A. echinata, A. aff. mourai, A. sp. B, Angochitina? sp., Cingulochitina ervensis, C. serrata, Eisenackitina cf. bohemica, Fungochitina kosovensis, Lagenochitina navicula, Linochitina sp. A, Plectochitina carminae, Pterochitina megavelata, P. perivelata, Ramochitina bjornsundquisti, R. sp., Saharochitina gomphos, S. sp. A, Sphaerochitina acanthifera, S. sphaerocephala, Vinnalochitina corinnae), 13 acritarchs (Baltisphaeridium gueltaense, Crassiangulina tesselita, Diexallophasis denticulata, Domasia rochesterensis, Estiastra sp., Goniosphaeridium canningia, Leiosphaeridia sp., Micrhystridium stellatum, Neoveryhachium carminae, Orthosphaeridium insculptum, Salopidium granuliferum, Tasmanites minutus, Veryhachium trispinosum), and 7 miospores (Archaeozonotriletes chulus, Brevitriletes delicatus, Brochotriletes foveolatus, Calamospora hartungiana, Cymbosporites dittonensis, Horriditriletes sp., Punctatisporites subtritus). Biostratigraphic marker taxa from previously proposed palynological zonations were identified, mainly among chitinozoans and miospores. The association of these palynomorphs allowed the sedimentary packages of the Manacapuru Formation in the Presidente Figueiredo region to be positioned within the Early Lochkovian. Based on the assemblage composition, a neritic marine paleoenvironment with continental input was interpreted. Furthermore, the presence of Neoveryhachium carminae suggests cold climatic conditions, associated with high paleolatitudes for the Presidente Figueiredo region (AM).