LA SECUENCIA VOLCANICLASTICA DE ARANZAZU: REGISTRO DEL IMPACTO DEL VOLCANISMO EN UN SISTEMA FLUVIAL NEOGENO EN LA PARTE MEDIA DE LA CORDILLERA CENTRAL, COLOMBIA
Cargando...
Fecha
Título de la revista
ISSN de la revista
Título del volumen
Editor
Universidad Industrial de Santander
Resumen
Descripción
En los alrededores del municipio de Aranzazu (Caldas), se realizó el análisis estratigráfco y petrográfco de la Secuencia Volcanoclástica de Aranzazu (SVA) del Plioceno tardío - Pleistoceno temprano (?). La depositación ocurrió en las partes proximales a un cinturón volcánico calco-alcalino de la parte media de la cordillera Central. Para el estudio de las secuencias volcaniclásticas se propone una clasifcación de depósitos volcaniclásticos, donde los lahares son defnidos como depósitos volcaniclásticos re-sedimentados y diferenciándolos de los depósitos volcaniclásticos primarios y de los epiclásticos. Y se actualiza la caracterización sedimentodológica y reológica de los depósitos asociados a los eventos laháricos.
La estratigrafía de la SVA se basó en la identifcación de litofacies que defnen los elementos arquitecturales para periodos sin- eruptivos e inter-eruptivos que enmarcan toda la secuencia. El miembro inferior es la agradación sucesiva de lahares sin-eruptivos (elementos SV y SB) que formaron depósitos de fujos de escombros e hiperconcentrados. Los miembros medio y superior muestran el dominio de periodos inter-eruptivos (elemento FF) sobre los sin-eruptivos (elementos SV y SB), cuando se afanzaba el sistema fuvial y se establecían las condiciones propicias para el desarrollo de los peats que luego formarían las capas de carbón que caracterizan estos miembros.
Palabras Claves: depósitos volcaniclásticos, lahares, agradación, volcanismo explosivo, períodos sin-eruptivos e inter-eruptivos.
The volcaniclastic sequence of Aranzazu (VSA, late Pliocene - early Pleistocene?) was sourced from the northernmost sector of the Machín - Cerro Bravo volcanic complex. The volcaniclastic accumulations filled the pre-existing fault-bend depressions in the surroundings of Aranzazu town (Caldas department, Colombia). A new classification of volcaniclastic deposits is proposed, in which the lahars are defined as volcaniclastic resedimented deposits, and differentiated from the primary volcaniclastic and epiclastic deposits. The updating the sedimentology and rheology of the deposits related with the laharic events is aimed. The VSA stratigraphy is based on the lithofacies identification and the definition of the architectural elements for syn- and inter-eruptive periods. The VSA lower member corresponds to the successive aggradation of syneruptive lahars (SV and SB elements) resulted from re-sedimentation of pumice-rich pyroclastic deposits and transported as debris and hyperconcentrated stream/flood flows. The VSA middle and upper members defined by coal contents were formed during the dominion of inter-eruptive (FF element) over the syn-eruptive (SV and SB elements) periods. They were formed during the reestablishment of the fluvial condition after the syn-eruptive laharic activity. Once the fluvial deposition was strengthened, the necessary conditions for the peat formation were propitious and the coal-bearing bedsets were developed. Keywords: volcaniclastic deposits, lahars, aggradation, explosive volcanism, syn-eruptive and inter-eruptive periods.
The volcaniclastic sequence of Aranzazu (VSA, late Pliocene - early Pleistocene?) was sourced from the northernmost sector of the Machín - Cerro Bravo volcanic complex. The volcaniclastic accumulations filled the pre-existing fault-bend depressions in the surroundings of Aranzazu town (Caldas department, Colombia). A new classification of volcaniclastic deposits is proposed, in which the lahars are defined as volcaniclastic resedimented deposits, and differentiated from the primary volcaniclastic and epiclastic deposits. The updating the sedimentology and rheology of the deposits related with the laharic events is aimed. The VSA stratigraphy is based on the lithofacies identification and the definition of the architectural elements for syn- and inter-eruptive periods. The VSA lower member corresponds to the successive aggradation of syneruptive lahars (SV and SB elements) resulted from re-sedimentation of pumice-rich pyroclastic deposits and transported as debris and hyperconcentrated stream/flood flows. The VSA middle and upper members defined by coal contents were formed during the dominion of inter-eruptive (FF element) over the syn-eruptive (SV and SB elements) periods. They were formed during the reestablishment of the fluvial condition after the syn-eruptive laharic activity. Once the fluvial deposition was strengthened, the necessary conditions for the peat formation were propitious and the coal-bearing bedsets were developed. Keywords: volcaniclastic deposits, lahars, aggradation, explosive volcanism, syn-eruptive and inter-eruptive periods.