EVIDENCE OF EARLY DEGLACIATION AND REGIONAL CLIMATE SYNCHRONY FROM A PERUVIAN CLOUD FOREST

New data from a long paleoecological sequence from the cloud forest in Peru provide evidence of climate change broadly synchronous with Antarctic patterns.

An 8.8-m sediment core was collected from Lake Consuelo (13º57’S, 68º59’W) at 1360 m elevation on the Eastern flank of the Peruvian Andes, immediately east and downslope of Lake Titicaca. Lake Consuelo provides a high resolution record of climate and vegetation change that spans the last 43.5 K cal BP. Fourteen radiocarbon ages provided the time control for the record. The resolution of the pollen analyses was conducted at c. 400-year intervals. Fossil pollen, charcoal, loss on ignition, and density, provide proxy measures on which paleoecological analyses are based.

The abundance of moist-forest elements during the LGM (25-20 K cal BP) demonstrates humidity in the basin, consistent with wet conditions observed in the Altiplano during the LGM. Bayesian analyses of modern plant distributions were used to generate probability models of co-occurrence of selected taxa across a range of temperatures. When applied to the fossil pollen data for the most common pollen taxa in the record, these statistics provided paleotemperature estimates suggesting an LGM cooling of c. 7ºC relative to today. A steady warming trend characterizes the period between 19 and 11 K cal BP. This chronology is consistent with the deglaciational patterns documented from the Altiplano and Antarctica. Finally, changes in the pollen record and a stratigraphic discontinuity between 8 and 3 K cal BP correspond with the timing of the mid-Holocene dry event of the Altpilano.

This research contributes to the understanding of the Quaternary climate and vegetation history of the tropical Andes during the Late Pleistocene, suggesting a strong continental concordance between the Altiplano, Andean flank, and Amazon lowlands, and a hemispheric linkage to Antarctic climate change.