THE EL-ABRA STADIAL IN THE EASTERN CORDILLERA OF COLOMBIA (SOUTH-AMERICA)

The El Abra stadial is a climatic cooling event defined in the Eastern Cordillera of Colombia, which corresponds both in timing and intensit y to the Younger Dryas climatic oscillation of the northern North Atla ntic region. The stadial was preceded by the relatively warm Guantiva interstadial and followed by the warm Holocene. Colder climatic condit ions during the El Abra stadial caused a 400 m lowering of the upper A ndean forest limit below its altitudinal location during the preceding Guantiva interstadial. Translated in temperature change, this represe nts a drop in mean annual temperature of approximately 2 to 3-degrees- C. The lowering of the upper forest limit and inferred temperature cha nge for the El Abra stadial, compared to Late Holocene conditions, are in the order of 600 m and 4-degrees-C, respectively. The transition o f the Guantiva interstadial to the El Abra stadial has been radiocarbo n dated at 11,210 +/- 90 BP and 10,820 +/- 60 BP. Climatic warming may have started shortly after 10,380 +/- 90 BP, and near present-day tem peratures were reached at least as early as 8920 +/- 100 BP. Maximum c ooling was probably attained between 10,800 BP arid 10,300 BP. Further (AMS) radiocarbon dating is planned to establish more exactly the tim ing of the El Abra stadial. A glacial advance of El Abra age, the Boca toma stade, has been recognized in the highest part of the Colombian E astern Cordillera, the Sierra Nevada del Cocuy. During this advance, g laciers extended some 700 m lower than at present. A climatic cooling event of El Abra age, associated with shifts of the upper Andean fores t limit and glacial advances, has also been recognized in other parts of Andean Colombia, including the Central Cordillera and the Sierra Ne vada de Santa Marta.