Registro paleoambiental em cabeceira de drenagem inscrita no remanescente de superfície aplainada VIII (A.R.I.E. do Buriti - SW PR)

Abstract

This study identifies paleoenvironmental records in the remaining at planed surface VIII, in Pato Branco (SW PR), more precisely in conservation area (A.R.I.E. do Buriti) by analysis of palynomorphs in a bog, characterization of the surface formations and the 14C dating method. Throughout the testimony of 130 cm, 37 different taxa were identified, which were separated into five ecological categories (trees, shrubs, ground herbs, algae and fern spores). The dating estimated suggests that the base of the bog was formed approximately 13,700 years BP, a period related to the Last Glacial Maximum (LGM). At that time the head of drainage would not have a connection to the piped drainage waterway of Independence river, local base level. According to the data obtained, we can affirm that in the region of the study area during the transition from the Pleistocene / Holocene to the present, there are no records of savannah, only grassland areas in the Pleistocene, inferred by the presence of ground herbs, especially Borreria and Asteraceae found in 12,700 years BP 14C (estimated) and total absence of algae and pollen grains of tree species, suggesting drier hydrological regime. Occasionally, high precipitation phenomeno occurred on the slopes and promoted the degradation of soil horizons in the upper slope (nose), promoting the deposition of colluvial layers until the new water regime, wetter, allowing the establishment of a herbaceous vegetation accompanied by ferns, mainly in the lower areas. In about 10,600 years BP 14C (est.), maintenance of high humidity is established and high precipitation caused the water table surface in the hollow constantly accelerating the hidromorfization paleohorizonte A humic, and developing in the rainy seasons, a small pond in the central axis of the headboard. Fact evidenced by the presence of algae and a significant expansion of Araucaria angustifolia, which requires an annual rainfall exceeding 1,400 mm.yr-1, without a dry season. The predominant vegetation is replaced by the Araucaria Forest and Atlantic Rain Forest composed of genres trees, ground herbs and ferns. The maximum expansion of the Araucaria Forest is logged about 6,880 years BP 14C (est.), face the increase of all taxa recorded, mainly from Araucaria. The presence of algae was more pronounced, again suggesting the occurrence of a blade of water conserved by an abundant and regular rainfall. In the years that followed, probably to 1,060 years BP 14C (est.), a reduction of vegetation as a general rule, changing only in the present with the planting of araucaria after the creation of A.R.I.E. do Buriti. Sometime in this period, the hollow head of the drainage began to develop perennial drainage channels, allowing efficient drainage at the head of drainage, reducing moisture levels in the bog