Lower Cretaceous Benthic Foraminifers and Ostracods of the Middle Magdalena Basin, Colombia: Biostratigraphic and Paleoenvironmental Inferences

In recent years, there has been an increasing interest in understanding the biostratigraphic framework and depositional environments of the Lower Cretaceous Rosablanca Formation (Middle Magdalena). In order to contribute to this, a micropaleontological study was conducted in two wells that drilled strata of the Rosablanca Formation. Despite the moderate recovery of microfossils, the lower part of the Rosablanca Formation contains several ostracod genera of the families Cytherideidae, Cytheridae, Brachycytheridae, and Cyprididae. This study provides the first evidence of Early Cretaceous ostracods in Colombia. In contrast, the upper part of the Rosablanca Formation contains the benthic foraminifera genera Lenticulina and Choffatella, along with fragments of the Rotaliina and Textulariina suborders. A transitional to normal marine environment is suggested based on the ecologic preferences of the genera Fabanella, Schuleridea, and Perissocytheridea. The Valanginian to Barremian age for the Rosablanca Formation was corroborated with benthic foraminifera, in concordance with previous studies based on macrofossil assemblages.