U-Pb zircon age of the Yacoraite Formation and its significance to the Cretaceous-Tertiary boundary in the Salta basin, Argentina

Abstract

Se obtuvieron dos edades U-Pb de circón procedentes de dos capas de ceniza de la Formación Yacoraite (Subgrupo Balbuena, Grupo Salta, Cretácico-Eoceno) de la cuenca de Salta, noroeste de la Argentina. La Formación Yacoraite no posee hasta ahora dataciones radimétricas por lo que estos datos resultan significativos para ajustar la cronología de su base y techo. Las edades fueron obtenidas mediante LA-MC-ICP-MS (laser ablation multi-collector inductively coupled plasma mass spectrometry) e indican 71.9 ± 0.4 Ma y 68.4 ± 0.7 Ma, respectivamente. Los nuevos datos permiten ajustar la historia evolutiva de la cuenca de Salta en un momento decisivo, coincidente con el inicio de la etapa de postrift. Y también conjeturar las probables correlaciones regionales, así como la posición del pasaje K-T en la subcuenca de Metán, una de las más representativas de esta extensa cuenca cretácicoterciaria inserta en los Andes Centrales.

Two U-Pb zircon ages were obtained from two layers of ash in the Yacoraite Formation (Balbuena Subgroup, Salta Group, Cretaceous-Eocene) of the Salta basin in northwest Argentina. The Yacoraite Formation had not yet been radiometrically dated, so this information is significant for adjusting the chronology of its base and top. The ages were obtained by means of LA-MCICP-MS (laser ablation multi-collector inductively coupled plasma mass spectrometry) and indicate 71.9 ± 0.4 Ma and 68.4 ± 0.7 Ma, respectively. The new information allows the adjustment of the evolutionary history of the Salta basin at a decisive moment, coinciding with the beginning of the postrift stage. It also allows conjectures to be made regarding probable regional correlations, as well as the position of the K-T boundary in the Metán subbasin, one of the most representative of this extensive Cretaceous-Tertiary basin located in the Central Andes.