BIOSTRATIGRAPHY AND PALEOENVIRONMENTAL INFERENCES OF THE FORAMINIFERAL ASSEMBLAGES IN THE CRETACEOUS FORMATIONS LA LUNA-COLÓN (CATATUMBO BASIN, COLOMBIA)
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Universidad Industrial de Santander
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El estudio micropaleontológico (foraminíferos) de un núcleo de perforación y la integración con información previa en otros pozos de la Cuenca del Catatumbo, permitió la caracterización bioestratigráfica y paleoambiental del contacto entre las formaciones La Luna y Colón. Para la parte superior de la Formación La Luna (Coniaciano-Campaniano) las asociaciones de foraminíferos presentaron una baja diversidad, siendo constituidas por una alta proporción de foraminíferos infaunales y planctónicos biseriales, los cuales sugieren condiciones de mar abierto con una baja oxigenación y alta productividad superficial. Para la Formación La Luna, taxones como Bolivinoides spp. (Bolivina explicata), Anomalina redmondi, Praebulimina spp., y Heterohelix spp. fueron encontrados. En contraste, para la parte más inferior de la Formación Colón, las asociaciones de foraminíferos fueron diversas, principalmente compuestas por foraminíferos bentónicos epifaunales y planctónicos no quillados que sugieren condiciones de moderada a buena oxigenación en un entorno de plataforma interna. Taxones como Globotruncana spp., Rugoglobigerina spp., Siphogenerinoides spp., Anomalina spp., Pullenia cretacea, Praebulimina petroleana y Haplophragmoides excavata se consideraron como diagnósticos de la parte inferior de la Formación Colón (Miembro Socuy), con una edad Campaniano tardío-Maastrichtiano.
Este contraste en las asociaciones de foraminíferos y los paleoambientes interpretados ha sido observado en todos los pozos estudiados en la Cuenca del Catatumbo, lo que concuerda con estudios previos que sugieren un contacto discordante entre las dos unidades.
The micropaleontological survey (foraminifers) of a stratigraphic core and its integration with previous data from other wells in the Catatumbo Basin provided the biostratigraphic and paleoenvironmental characterization of the contact between La Luna and Colon formations. For the upper part of La Luna Formation (Coniacian-Santonian) the foraminiferal assemblages were less diversified, with a high proportion of infaunal foraminifera and biserial plancktonics, suggesting an oxygen-depleted open marine environment probably related with higher surface productivity. Taxa such as Bolivinoides spp. (Bolivina explicata), Anomalina redmondi, Praebulimina spp., and Heterohelix spp. were found in this unit. In contrast, for the lowermost Colon Formation, the foraminiferal assemblages were diverse, mainly composed by epifaunal benthic foraminifera and non-keeled plancktonics suggesting well to moderate oxygenated conditions in an inner shelf setting. Taxa such as Globotruncana spp., Rugoglobigerina spp., Siphogenerinoides spp., Anomalina spp., Pullenia cretacea, Praebulimina petroleana and Haplophragmoides excavata were considered as diagnostic of the lower Colon Formation (Socuy Member), with a late Campanian-Maastrichtian age. This turnover in the foraminiferal assemblages and the interpreted paleoenvironments have been observed in all the studied wells in the Catatumbo Basin, agreeing with previous studies that suggest a discordant contact between these two units.
The micropaleontological survey (foraminifers) of a stratigraphic core and its integration with previous data from other wells in the Catatumbo Basin provided the biostratigraphic and paleoenvironmental characterization of the contact between La Luna and Colon formations. For the upper part of La Luna Formation (Coniacian-Santonian) the foraminiferal assemblages were less diversified, with a high proportion of infaunal foraminifera and biserial plancktonics, suggesting an oxygen-depleted open marine environment probably related with higher surface productivity. Taxa such as Bolivinoides spp. (Bolivina explicata), Anomalina redmondi, Praebulimina spp., and Heterohelix spp. were found in this unit. In contrast, for the lowermost Colon Formation, the foraminiferal assemblages were diverse, mainly composed by epifaunal benthic foraminifera and non-keeled plancktonics suggesting well to moderate oxygenated conditions in an inner shelf setting. Taxa such as Globotruncana spp., Rugoglobigerina spp., Siphogenerinoides spp., Anomalina spp., Pullenia cretacea, Praebulimina petroleana and Haplophragmoides excavata were considered as diagnostic of the lower Colon Formation (Socuy Member), with a late Campanian-Maastrichtian age. This turnover in the foraminiferal assemblages and the interpreted paleoenvironments have been observed in all the studied wells in the Catatumbo Basin, agreeing with previous studies that suggest a discordant contact between these two units.
Keywords
Upper Cretaceous, Catatumbo Basin, foraminifers, La Luna-Colón formations, paleoenvironments, Cretácico Superior, Cuenca del Catatumbo, foraminíferos, formaciones La Luna-Colón, paleoambientes