DATACIÓN POR FOTOLUMINISCENCIA DE LA STONELINE Y OTRAS FORMACIONES SUPERFICIALES DEL LLANO DE OVEJAS, CORDILLERA CENTRAL, ANTIOQUIA
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Universidad Industrial de Santander
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En este trabajo se presentan las primeras dataciones obtenidas en Colombia mediante la aplicación del método de datación de fotoluminiscencia el cual permite datar el último momento en que un material estuvo expuesto a la luz y tiene un rango de aplicación que en condiciones óptimas va de 6 a 800 000 años, lo cual le confere gran importancia para el estudio de depósitos del Cuaternario superior.
La zona de estudio comprende el Llano de Ovejas que constituye uno de los altiplanos de la cordillera Central. Las da-taciones se realizaron en las formaciones superfciales del Llano de Ovejas con énfasis en la stoneline, un horizonte de acumulación de clastos con carácter regional. Además se realizaron algunas dataciones de depósitos aluviales y coluviales infrayacentes a la stoneline.
Las primeras edades obtenidas en el país por el método de fotoluminiscencia son las edades de la stoneline que incluyen 30 900 ± 4 500, 24 100 ± 3 800 y 18 900 ± 2 300 años para los horizontes FSO 07-2, FSO 16-2A y FSO 19-2 respectivamente. Estas edades se enmarcan dentro del Último Máximo Glacial, p
Palabras clave: superfcies de erosión, fotoluminiscencia, stoneline, Llano de Ovejas, estratigrafía, métodos de datación.
This work marks the fst application of Photoluminescence (OSL- Optical Stimulated Luminescence) in Colombia. Photo-luminescence method allows the determination of the age of burial of materials with a range from 6 to 800 000 years under optimal conditions; the method is really important for the study of diverse quaternary deposits. Detailed feld work, aerial photo analysis and stratigraphic study of the study area were completed with emphasis on the stoneline, a regional horizon of clastic accumulation. The aim of this work was to achieve a better understanding of the paleoenvironmental conditions when the surface formations of the area were originated, as well as the evolution of the highlands and uplift of the Central Cordillera. The frst ages obtained in Colombia by photoluminescence correspond to the stoneline: 30 900 ± 4 500, 24 100 ± 3 800 and 18 900 ± 2 300 years for the horizons FSO 07-2, FSO 16-2A and FSO 19-2 respectively. These ages belong to the Last Pleniglacial, erosive period of dry and cold conditions with intermittent rain and scarce vegetation. Deposits below the stoneline where dated in 53 400 ± 5 900, 66 700 ± 14 000 and 36 000 ± 4 900 years at the horizons FSO 06-3, FSO 16-3 and FSO 19-3 respectively, which indicates they were formed during the humid period from 60 000 to 28 000 years BP. Key words: erosion surfaces, photoluminescence, stoneline, Llano de Ovejas, stratigraphy, dating methods, Central Cordillera
This work marks the fst application of Photoluminescence (OSL- Optical Stimulated Luminescence) in Colombia. Photo-luminescence method allows the determination of the age of burial of materials with a range from 6 to 800 000 years under optimal conditions; the method is really important for the study of diverse quaternary deposits. Detailed feld work, aerial photo analysis and stratigraphic study of the study area were completed with emphasis on the stoneline, a regional horizon of clastic accumulation. The aim of this work was to achieve a better understanding of the paleoenvironmental conditions when the surface formations of the area were originated, as well as the evolution of the highlands and uplift of the Central Cordillera. The frst ages obtained in Colombia by photoluminescence correspond to the stoneline: 30 900 ± 4 500, 24 100 ± 3 800 and 18 900 ± 2 300 years for the horizons FSO 07-2, FSO 16-2A and FSO 19-2 respectively. These ages belong to the Last Pleniglacial, erosive period of dry and cold conditions with intermittent rain and scarce vegetation. Deposits below the stoneline where dated in 53 400 ± 5 900, 66 700 ± 14 000 and 36 000 ± 4 900 years at the horizons FSO 06-3, FSO 16-3 and FSO 19-3 respectively, which indicates they were formed during the humid period from 60 000 to 28 000 years BP. Key words: erosion surfaces, photoluminescence, stoneline, Llano de Ovejas, stratigraphy, dating methods, Central Cordillera