Palynological analysis of the outer parts of camelid coprolites: implications for vegetation reconstruction

Abstract

The aim of this study was to analyze pollen from the outer parts of camelid coprolites and contemporaneous sediments to evaluate the potential of coprolites for the reconstruction of the vegetation history of Patagonia during the Holocene. The pollen composition of camelid coprolites coming from archeological layers between 10,920 yrs. cal BP and 2823 yrs. cal BP found in the sites Cerro Casa de Piedra 5 and 7 (Perito Moreno National Park, Santa Cruz, Argentina) were analyzed. Coprolites were divided into outer and inner subsamples. Outer subsample pollen extraction was performed through acetolysis and determination and counting under optical microscope. Morisita-Horn index and Wilcoxon test were performed to evaluate similarities between pollen spectra of outer subsamples of coprolites and contemporaneous sediments. The dominant pollen types were: Nothofagus (Nothofagaceae), Empetrum (Ericaceae), Asteraceae subf. Asteroideae, Nassauvia (Asteraceae subf. Mutisioideae), Poaceae and Caryophyllaceae. The similarities found between outer subsamples of coprolites and contemporaneous sediments reflected the dominant pollen types of the vegetation and forest development, whereas significant differences could be attributed to coprolite pollen spectra that may be biased by season of coprolite deposition, selectivity of the diet and/or higher temporal resolution. Also, the presence of pollen types in outer subsamples of coprolites absent in sediments could give information for paleoenvironmental reconstructions by enriching information of the past flora. This study demonstrates that coprolites can be a valuable tool for paleoenvironmental reconstructions in arid and semiarid areas where depositional environments that support pollen preservation are typically rare.