Bioestratigrafía e inferencias paleoambientales de las asociaciones de foraminíferos en las formaciones Cretácicas La Luna-Colón (Cuenca Del Catatumbo, Colombia)

Abstract

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.