Paleoclimate of the late Pleistocene and Holocene at Lagoa Dourada, Paraná State, southern Brazil

Abstract

A 12 m deep core from the sediments of Lagoa Dourada, Paraná State, southern Brazil, was analyzed about its diatoms, extractable inorganic cations (Ca ++, Mg ++, K +), available phosphorus, organic matter, water contents and sedimentology. Studies of the lake sequence, with a basal date of 11,110±110 yr BP, provide a history of climatic changes divided into nine zones. Zone A1 (prior to 11,000 yr BP) contains diatom taxa suggesting dry environments. Zone B1 (around 11,000 yr BP) indicates very humid climatic conditions synchronous with reduced temperatures. Around 8,710±150 yr BP, the core does not contain diatoms, and the convergence of some paleoclimatic indicators suggests that a drier paleoclimate is represented. Zone A2 and B2 have planktonic diatom spectra that suggest progressive high humidity. A marked decline in moisture levels is expressed in Zone C, as suggested by an increase in only one dominant periphytic taxon. The following periods (Zones D1, D2 and D3) were characterized by several water level oscillations, with short and intensive dry events and longer intervening humid periods. Zone E establishes the present diatom and climatic pattern of Lagoa Dourada. Cultural disturbances could be indicated by the high K + levels detected on the core top, which are probably due to the agricultural boom in the catchment area.