TITLE:
Holocene Environmental Climatic Changes Based on Palynofacies and Organic Geochemical Analyses from an Inland Pond at Altitude in Southern Brazil
AUTHORS:
Gabrielli Teresa Gadens-Marcon, Margot Guerra-Sommer, João Graciano Mendonça-Filho, Joalice de Oliveira Mendonça, Marcelo de Araújo Carvalho, Léo Afraneo Hartmann
KEYWORDS:
Organic Matter (OM); Total Organic Carbon (TOC); Total Sulfur (TS); Paleoclimatic Change; Rainfall Influence
JOURNAL NAME:
American Journal of Climate Change,
Vol.3 No.1,
March
21,
2014
ABSTRACT: This
paper focuses on the interpretations in the analyses of palynofacies and
organic geochemistry carried out on a sedimentary profile covering 9542 cal yr
BP from a pond located at the mining district from Ametista do Sul,
southernmost Brazil. The hydrological isolation renders this pond, located on a
hilltop, highly sensitive to climatic change because the water entering in the
system is subsidized exclusively by the rainfall. The main goal of this study
is to establish relationships between the sedimentary organic record and
climatic fluctuations in the Holocene, trying to correlate the alterations in
the particulate organic matter with regional climatic changes or perhaps even
events on a global scale. Fluctuations in water depth are inferred from the
frequency of the autochthonous elements (algae), which predominate in the basal
intervals, but tend to decrease progressively toward the top, when begining to
alternate periods of high and low frequency with the parautochthonous (spores)
and allochthonous (pollen grains) elements, due to changes in the patterns of
moisture. Pseudoschizaea seems to
have a closer relationship with the spores than with all other algae and can
serve as a biological marker of transitional intervals or have some role in the
successional process of vegetation. The variety of spores of ferns and pollen
grains on the topmost interval indicates increased vegetal diversity, and is
probably related to the process of successional evolution of the area. An increased
rainfall event detected between 8.6 to 7.4 ka yr BP can be responsible for the
beginning of the process of water accumulation in the gossan and sedimentation
of the pond and can be related with the “Bond Events”. The saturation level of the pond, in
turn, remained relatively constant until 6.8 ka yr BP, when changes in the
patterns of moisture make the
environment drier and
resulted in an intermittent pattern of water depth, currently existing on the site.