Paleoenvironmental characterization from the carbonate microfacies of the Itaituba Formation (lower Pensilvaniano of the Amazonas Basin), in the municipality of Itaituba (PA).

Abstract

Aiming at the interpretation and inference of the paleoenvironments of two carbonate succession belonging to the Itaituba Formation (Pennsylvanian of the Amazonas Basin), which appears on the banks of the Tapajós River, SW of the state of Pará, petrographic studies focused at the characterization and identification of sedimentary microfacies were performed from the analysis of 50 thin sections. The petrographic analysis was developed according to the standard methodology for studies of this nature, essentially involving the classification of carbonate rocks, the characterization and individualization of microfacies. As a result of these analyzes, nine microfacies were identified: Mudstone with evaporites (Me), Wackestone with terrígenos (Wt), Wackestone with autigenic quartz and fitoclasts (Wqf), Wackestone with brachiopods and crinoids (Wbc), Packstone with brachiopods (Pb), Grainstone (Gb), Grainstone with fusulinids (Gf), Grainstone with binders (Ga) and Boundstone with intraclasts (Bi). From these microfacies, four microbiofacies, based on the bioclastic trends and analysis, and five associations of non-skeletal grains, based on the meaning of these grains. From this, five associations of microfacies (AMF) representative of different depositional systems were interpreted: AMF-01) sabkha, AMF-02) tidal plain, AMF-03) lagoon, AMF-04) tidal channels and AMF-05) bioclastic bars. These associations of microfacies indicate a depositional carbonaceous platform model in ramp, with the development of a shallow marine depositional system, dominated by carbonate sedimentation, influenced by tide, under the dominant regime of semiarid climatic and temperature of the water mass varying from temperate to hot.