Preliminary palynological analysis of a Holocene peat bog from Apakará-tepui (Chimantá massif, Venezuelan Guayana)

Preliminary palynological analysis of a Holocene peat bog from Apakará-tepui (Chimantá Massif, Venezuelan Guayana).- This paper reports the preliminary palynological results, at a millennial scale, of a Holocene peat bog sequence, since around 8.0 cal kyr BP to the present, obtained in the summit of the Apakará-tepui (2170 m elevation), in the Chimantá massif, located in the neotropical Venezuelan Guayana. The early Holocene was characterized by a vegetation different to the present, in which trees and shrubs dominated and Myrica (Myricaceae) was the main element of the gallery forests around a permanent water body, as indicated by the continuous presence of Isoëtes (Isoëtaceae) in high percentages. Around the middle Holocene (5.3 cal kyr BP), a shift towards more herbaceous and non-flooded communities occurred, and the present day vegetation established. This has been interpreted as a shift from warmer and wetter climates to cooler and drier conditions. The first phase, from 8.0 to 5.3 cal kyr BP, falls within a warming phase widely documented worldwide, known as the Holocene Thermal Maximum. The millennial trends shown here will be refined with further studies at centennial to decadal time scales. These results support the hypothesis that the best sites to detect paleoenvironmental changes in the summits of the tabular Guayana mountains are close to altitudinal ecotones