Registros polínicos para o Holoceno tardio da região da Campanha (Rio Grande do Sul, Brasil) e seu significado na história dos paleoambientes da Savana Estépica Parque

Abstract

POLLEN RECORDS FOR LATE HOLOCENE IN THE CAMPANHA REGION (RIO GRANDE DO SUL, BRAZIL) AND THEIR SIGNIFICANCE IN THE HISTORY OF THE PALEOENVIRONMENTS IN THE SAVANA ESTEPICA PARQUE. This paper presents palynological results from an outcropping section located in the Brazilian side of the Quarai river (30°16'27.9S/57°26'33.6W), south of the Barra do Quarai city, westernmost portion of the Rio Grande Sul State, as well as from 15 surface samples collected in the 'Parque do Espinilho' (PESP), in order to obtain current pollen spectrum. A total of 81 types of palynomorphs (pollen and non pollen) was identifi ed in the ten fertile samples from the outcropping section and 114 taxa from surface samples. Pollen diagrams were performed in order to identify current pollen spectrum and reconstruct the vegetational history of the Savana Estepica Parque during the late Holocene in this region, supported by radiocarbonic datings and granulometry analysis. Results indicate that between 3,380 ± 25 and 2,350 ± 25 14 C yr BP, area was composed by a fl oodplain covered with grasses that formed bodies of water with little depth enabling the development of algae colonies. Between 2,328 and 2,262 yr BP (interpolated age) occurred a decrease in humidity and the temperature rise, as suggested by the disappearance of algae and the bryophytes increasing. Between 2,130 (interpolated age) and 1,940 ± 20 14 C yr BP was recorded an increasing of the humidity, refl ected by the high diversity of arboreal taxa, with expansion of the Mata Ciliar. Granulometrical data corroborate palynological results. Pollen spectra of surface samples refl ected the different current vegetation types of the PESP.