Late-Pleistocene and mid-Holocene environmental changes in highland valley head areas of Santa Catarina state, Southern Brazil

Low resolution of the continental sedimentary record is a common source of skepticism about the application of geomorphology and seclimentology to Quaternary studies. In spite of this, when supported by independent proxy data, geomorphology and seclimentology may favor palaeo-hydrologic interpretation. This paper associates geornorphologic, stratigraphic, sedimentologic, isotopic, palynologic and geochronologic data. The research was conducted in valley head sites in southern Brazilian highlands, under mild subtropical climate. The results point to environmental changes, the ages of which coincide to Marine Isotopic Stages (MIS) 5b, 3, 2 and 1. Although late-Pleistocene temperatures and precipitation were lower than those of today, the study valley heads seem to have sustained locally wetter environments, which fed shallow soil-water saturated zones. These saturated zones are believed to have expanded during transitions between stadia] and interstadial states, contributing to hillslope erosion and sedimentation regardless of the sign of the climatic change. The interior organization of holocenic slope-wash deposits suggests that the mid-Holocene climate was drier than today's and was under the influence of seasonally contrasting precipitation regimes. The predominance of overland flow-related sedimentary records suggests that an excess of precipitation over evaporation influenced local palaeo-hydrology. This paiaeo-hydrologic condition seems to have been recurrent and also explains the alternating periods of pedogenesis and sedimentation. (D 2008 Elsevier Ltd. All rights reserved.