CICLICIDAD EN LA FORMACIÓN CERREJÓN
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Universidad Industrial de Santander
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El patrón de sedimentación de la Formación Cerrejón es característicamente repetitivo y monótono. Presenta un espesor estratigráfico de aproximadamente 1000 m y una longitud en rumbo de al menos 30 km a lo largo del Valle del Cesar - Ranchería. Esta monotonía ha sido utilizada para definir ocho asociaciones de litofacies y tres secuencias típicas con las que es posible describir la totalidad de esta unidad. El arreglo vertical de dichas asociaciones de litofacies permite establecer los patrones de apilamiento, pero no el mecanismo generador de la repetición y arreglo vertical de estos ciclos. Este estudio pretende reconocer patrones de ciclicidad y así establecer las posibles relaciones causales de estos ciclos, para lo cual se utilizó modelamiento sintético como primera aproximación. Los resultados de este modelamiento sugieren que con subsidencia tectónica, tasas de sedimentación constantes y una variación rítmica en el nivel de base puede reproducirse el patrón progradacional puntuado de la Formación Cerrejón. Únicamente subsidencia tectónica o termal, compactación diferencial, o fenómenos autocíclicos podrían difícilmente generar el patrón observado en tal extensión regional.
Palabras clave: Patrones ciclo, monotonía, modelamiento sintético, subsidencia tectónica
The Cerrejon Formation exhibits a stacking pattern characteristically repetitive and monotonous. It has a stratigraphic thickness of about 1000 m and a strike-length of at least 30 km through Cesar - Ranchería Valley. This monotony has been used to define eight lithofacies assemblages, and three typical sequences that describe the entire unit. The vertical arrangement of these lithofacies assemblages allows the recognition of stacking patterns, but not the mechanisms that generated the repetition and the vertical arrangement of these patterns. This study aims to identify cyclicity in the record and to establish a possible causal relationship for these patterns. To do this, forward modeling was used and preliminarily indicates that the punctuated progradational pattern observed in the Cerrejón Formation can be simulated keeping constant tectonic subsidence, sedimentation rates, and forcing a base level oscillation. Only tectonic or thermal subsidence, differential compaction or autocyclic phenomena could not easily generate the observed pattern on such regional extension. Key words: Cycle patterns, monotony, forward modelling, tectonic subsidence.
The Cerrejon Formation exhibits a stacking pattern characteristically repetitive and monotonous. It has a stratigraphic thickness of about 1000 m and a strike-length of at least 30 km through Cesar - Ranchería Valley. This monotony has been used to define eight lithofacies assemblages, and three typical sequences that describe the entire unit. The vertical arrangement of these lithofacies assemblages allows the recognition of stacking patterns, but not the mechanisms that generated the repetition and the vertical arrangement of these patterns. This study aims to identify cyclicity in the record and to establish a possible causal relationship for these patterns. To do this, forward modeling was used and preliminarily indicates that the punctuated progradational pattern observed in the Cerrejón Formation can be simulated keeping constant tectonic subsidence, sedimentation rates, and forcing a base level oscillation. Only tectonic or thermal subsidence, differential compaction or autocyclic phenomena could not easily generate the observed pattern on such regional extension. Key words: Cycle patterns, monotony, forward modelling, tectonic subsidence.