We correlate seismic map units identified on industry seismic lines in the Gulf of Chiriquí, southwestern Panama, with onland igneous rocks and sedimentary formations described in this chapter. We propose six principal stages in the stratigraphic development of southwestern Panama based on our results and the results of previous workers in Costa Rica, westernmost Panama, and the western Colombian basin. The first stage in southwestern Panama is represented by basaltic basement rocks of Jurassic?-Late Cretaceous age interbedded with Upper Cretaceous pelagic sedimentary rocks. Following previous workers and data presented here, we suggest that these rocks formed in an intraoceanic, oceanic...