Caracterização da matéria orgânica particulada dos últimos 10 mil anos a partir de um testemunho do Parque Estadual do Rio Doce, MG, Brasil: implicações paleoambientais

This paper presents the results of a palynofacies study from a Holocene core of a Lake (Lc2), State Park of Doce River, MG, Brazil. The analysis of palynofacies was carried out on 17 samples of a core of 90 cm (Lc2-01), dated at 80 cm depth in 10,191 cal. years BP, 65 cm in 9,640 cal. years BP, 35 cm in 7,905 cal. years BP and 10 cm 102 cal. years BP. The core Lc2-01 shows an increased level of silt/clay upwards, supporting the idea that the depositional process involved low energy. The identification of the organic components yielded three distinct palynofacies. The Palynofacies 1 (Pf1) is composed of cuticles, corresponding to a fluvio-lacustrine environment; Palynofacies 2 (Pf2) dominant elements are phytoclasts (opaque and nonopaque), representing woody components and Palynofacies 3 (Pf3) is composed of a predominance of amorphous organic matter and palynomorphs (spores, pollen grains and freshwater algae). The stratigraphic distribution of the palynofacies, allowed the identification of three phases in core Lc2-01. Phase 1 (10,375-9,351 cal. years BP) has a predominance of Pf2, suggesting a fluvio lacustrine environment of high energy and even at 9,351 cal. years BP the Doce river bed was not closed. From 9,351-7,905 cal. years BP (phase 2) there was a continuing increase in Pf2 and a severe elevation of Pf1, indicating the beginning of the closing of the valleys of the old Doce river bed. The phase (7,905-102 cal. years BP), demonstrates an abrupt rise of Pf3, suggesting anoxic-dioxic compatible with shallow lacustrine environment or paludal water.