Agglutinated foraminifera and sequence stratigraphy from the Chipaque Formation (Upper Cretaceous) of El Crucero section, Colombia, South America

摘要

Agglutinated foraminifera from a section of the Chipaque Formation (Cenomanian-Campanian) in the Eastern Cordillera of Colombia are reported. The foraminiferal assemblage is dominated by species of the genera Ammobaculites and Haplophragmoides. The stratigraphic ranges of Ammobaculites colombianus, Haplophragmoides walteri, and Haplophragmoides rugosus are extended from a previously known Coniacian-Maastrichtian to a Cenomanian-Maastrichtian distribution, according to their appearance in the Chipaque Formation. Similarly, the range of Saccamina globosa (Cenomanian-Turonian) is extended to the Maastrichtian. The predominance of agglutinated foraminifera in the section is ascribed to undersaturation of calcium carbonate in the water column over the inner to outer shelf, due to the influx of terrigenous material. The array of parasequences composed of mudstone-sandstone couplets indicate landward and basinward coastline migrations that correspond to third order depositional sequences.