The southern part of Central America, together with the adjacent area to the south, including the Pacific side of Colombia (Fig. 1), contains characteristic stratigraphic and structural features that are quite different from those described from northern Central America. This contrast was first noticed by the early investigators of Central America (Vaughn, 1918; Woodring, 1928; Schuchert, 1935; Sapper, 1937) who divided this area into two distinctive geological provinces: a northern one comprising Guatemala, Honduras, and northern Nicaragua, and a southern province comprising southern Nicaragua, Costa Rica, and PanamÃ¡. Schuchert (1935) referred to this southern province as the Isthmian Link, which was later termed the South Central America Orogen (Dengo, 1962a; Lloyd, 1963). Another definition of the northern boundary of the Isthmian Link or South Central America Orogen places most of southern Nicaragua in the northern Central America Province (Nuclear Central America in Schuchert's terminology, later subdivided into the Maya and Chortis blocks by Dengo, 1969).
The area covered in this chapter is one of the most complex of the entire Caribbean region and is characterized by complicated structural patterns, and by stratigraphy developed within narrow and elongate restricted basins (Plate 5B). The region has been the subject of many divergent interpretations as to its tectonic history because it has sustained the interaction of four crustal plates. A clear understanding of the geology of the area is essential in reconstructing a meaningful geological history of the Caribbean and its relationship to the South American and Pacific regions.