The establishment of vegetation after late pleistocene deglaciation in the Paramo de Miranda, Venezuelan Andes

Abstract

Palynological analyses of samples from a fluvioglacial terrace at 3920 m elevation, in the periglacial belt of the Paramo de Miranda, has shown that, before 11,500 to about 11,120 yr B.P., the very few plants growing in the region belonged to the Gramineae, the Compositae (mainly to Coespeletia) and Montia. The climate was colder than at present. During the early Holocene the concentration of pollen and spores in sediments increased and new pollen types from paramo plants were incorporated. Pollen of the Caryophyllaceae (mainly Arenaria), of Gentiana, Valeriana, Geranium and a few genera of Compositae reached the site. Long-distance pollen, derived from the cloud forest increased and Podocarpus pollen was more abundant than at present. These results suggest that temperatures increased at the beginning of the Holocene, the vegetation attaining a density similar to that of the present, although with fewer species. From 5470 to 2500 yr B.P. pollen and spore concentrations fluctuated and other types, including Rhizocephalum and Isoetes, followed by Draba, Plantago and certain other genera of the Composite were now present in the sediments. From ca 3000 yr B.P. onwards the composition of the pollen assemblages was the same as at present. Two cold phases were detected, one from earlier than 11,500 to 11,120 yr B.P. and another from 6000 to 5250 yr B.P. A warm phase from ca 2690 to 2500 yr B.P. probably represented a rise of about 1.2°C above the modern average temperature. In general terms, the climatic oscillations detected at Miranda are in accordance with those in other parts of South America.