In the Alto El Español sector, in the municipality of Amalfi, ammonite and gastropod fossils (Fig. 1, locality 26) from the Hauterivian-Albian are found in the Amalfi Sediments unit (Feininger et al., 1972).

The sedimentary sequence in this area extends in an elongated strip from north to south, approximately 7 kilometers long and less than 800 meters wide. The sedimentary bodies, which are several hundred meters thick, are in contact with the Antioquia Batholith. The predominant rock in this unit is a clayey shale, and the sediments are vertically deposited.

In this fossil-bearing locality, Cretaceous strata unconformably overlie metamorphic rocks, represented by sericitic schists with andalusite. This indicates that in this part of the Cordillera, the metamorphic rocks predate the Early Cretaceous.

Geological Evidence: The unconformity between the Cretaceous strata and the underlying metamorphic rocks is important evidence of the region's tectonic history. This relationship suggests a series of complex geological events, including the deformation and metamorphism of the rocks prior to the deposition of the Cretaceous sediments.

Paleontological Significance : The ammonite and gastropod fossils found at this site are crucial for the study of regional paleontology and geology. These fossils allow scientists to reconstruct the Hauterivian-Albian marine environment and better understand the evolution of marine life during that period.

Regional Context: The presence of clayey shales and the verticality of the sediments indicate specific depositional conditions and an active tectonic history in the region. These aspects contribute to the overall understanding of the geological evolution of the Central Cordillera of Colombia.