Cenozoic Evolution of the Panama Isthmus. the Panama Geology Project

In 2007 the Panama Canal Authority received the green light to start excavations along the Canal area to open new access channels to new and existing locks and to widen and deepen existing navigational channels. These works afford an outstanding opportunity to collect fresh samples along the working areas and study the geology of the isthmus from a set of brand new outcrops. Additional to the surface outcrops, hundreds of geotechnical cored-boreholes, both existing and from future drilling, will be re-examined and re-interpreted. An integrated approach combining detailed structural mapping, geochronology, geochemistry, palynology and paleomagnetism is being implemented to better understand the geology of the isthmus. The Project's main goals include the generation of a structural transect across the isthmus, the discrimination of the tectonic setting of major volcanic events, dating of these events, as well as establishing a palynological framework of the sedimentary units and systematic macro-fossil collection along the transect. Paleomagnetic data collected throughout the isthmus (Darien, Canal zone and Azuero) will help understand the deformation mechanisms involved in the formation of the presently curved land bridge between the Americas so that several competing hypothesis can be tested (oroclinal bending, northwest-trending left-lateral shear, or a volcanic arc progressively accreted to the South American margin). Prelimary data collected along these profiles show clear cross-cutting relationships between volcanic assemblages (Bas Obispo, Panama, Caimito, Caraba, Las Cascadas, Pedro Miguel Formations), and the sedimentary sequences of the Culebra and Cucaracha Formations. Thsese units contain the record of the the growth of the Central American arc over the Caribbean Large Igneous Province (CLIP) since the Late Cretaceous (90 Ma), and the interactions with the Pacific plates and the South American margin.