Stratigraphic distribution of ammonoids and other macrofossils from the upper Albian-lower Cenomanian interval in Putumayo, Colombia, northern South America: new data for mid-Cretaceous basin correlation

Despite the rich paleontological heritage of Colombia, in the equatorial Neotropics, the Putumayo is one of the least explored regions in terms of its fossil record, largely due to its considerable ground cover, thick vegetation, rock weathering, geographic remoteness, and overall inaccessibility to well-exposed outcrops. This precludes detailed comparisons with neighboring basins, and thus the generation of more comprehensive biostratigraphic correlations for western northern South America and other paleobiogeographic regions such as the Mediterranean Tethys, northern Africa, and the Western Interior Basin. Here, we report 70 occurrences of mid-Cretaceous macrofossils (e.g., ammonoids, bivalves, decapod crustaceans, fish remains), from the middle Albian of the uppermost Caballos Formation and the upper Albian-lower Cenomanian of the lower Villeta Formation, collected in-situ from a stratigraphic section cropping out on the Mocoa-San Francisco road in the Department of Putumayo, Colombia. Among the ammonoid taxa recovered are several morphotypes assignable to Oxytropidoceras, Elobiceras, Metoicoceras, Idiohamites, Hamites, Hysteroceras, Schloenbachia, and isolated aptychi. The occurrence of the ammonoids Schloenbachia and Oxytropidoceras suggest interconnection of the Putumayo Basin with the Upper Magdalena Valley in Colombia and the Oriente Basin in Ecuador during the mid-Cretaceous, which, together with the rest of the ammonoid assemblage, provide biostratigraphic data to define the Albian-Cenomanian boundary in the basin. ### Competing Interest Statement The authors have declared no competing interest.