Palynofacies analysis of late cenozoic sediments from the undulating pampa (Argentina): First results

Abstract

A palynofacies analysis of a loessial profile (Late Cenozoic) in the surroundings of Castelar (Buenos Aires, Argentina) was carried out. Integrated analysis of sedimentology, palynofacies, pH and TOC, allowed detection of palaeoenvironmental and palaeoclimatic fluctuations during the period under analysis. Middle Pleistocene (<780 ka): palynofacies type A (loess), palaeoenvironments moderately oxidizing, evidenced by a predominance of finely divided organic matter (not fluorescent), abundance of opaque phytoclasts and a small amount and diversity of palynomorphs. Palynofacies type B (laminar calcrete), locally moist and regionally semiarid palaeoenvironments associated with the development of the herbaceous psammophytic steppe. The evidence of biological and chemical oxidation, both in phytoclast and amorphous organic matter, suggest an alternation of anaerobic and aerobic environments. Late Pleistocene (24,098 cal yr BP): palynofacies type C (loess and lightly edaphized loess), oxidizing palaeoenvironments represented by darkened amorphous organic matter and abundant opaque phytoclasts. The considerable proportion of Myrtaceae was correlated with the input of sediments from the NE of the country. Late Holocene (2,582 cal yr BP): palynofacies type D (modern soil) locally moist and regionally sub-moist palaeoenvironments associated with the presence of the psammophytic herbaceous steppe, with high proportions of water plants pollen, Bryophyta, fungi and algae spores. The predominance of partially gellified and darkened translucent phytoclasts is in accordance with the pedogenic process. © 2010 by the Sociedade Brasileira de Paleontologia.