. Bulletins of American paleontology. 24 Bulletin 357. Text-figure 7.—Schematic geologic cross section of the Panama Canal Basin from the Bohio Peninsula to the Caribbean coast west of Tore Point. also substantially reduced the number of marine con- nections between the Pacific and Caribbean. The third tectonic influence on southern Central America was the convergence of the South American and Caribbean plates (Text-fig. 1), which increasingly compressed the southern Caribbean Plate margin throughout the Neogene (Silver et al., 1990; Kellogg and Vega, 1995; Mann and Kolarsky, 1995). This up- l
. Bulletins of American paleontology. 24 Bulletin 357. Text-figure 7.—Schematic geologic cross section of the Panama Canal Basin from the Bohio Peninsula to the Caribbean coast west of Tore Point. also substantially reduced the number of marine con- nections between the Pacific and Caribbean. The third tectonic influence on southern Central America was the convergence of the South American and Caribbean plates (Text-fig. 1), which increasingly compressed the southern Caribbean Plate margin throughout the Neogene (Silver et al., 1990; Kellogg and Vega, 1995; Mann and Kolarsky, 1995). This up- lifted eastern Panama and the outer Andes of north- western Colombia and, at about 3 Ma (Keigwin, 1982), finally severed all marine connections between the Pacific and Caribbean. LITHOSTRATIGRAPHY The Panama Canal Basin The Panama Canal Basin (Text-fig. 2) is located at the junction of the Chorotega and Choco terranes (Dengo, 1985; Escalante, 1990), which is manifested by a major contrast in gravity (Case, 1974) and a series of north-south basement faults (de Boer et al, 1988; Mann and Corrigan, 1990; Mann and Kolarsky, 1995). The stratigraphy of the complex series of laterally varying Cenozoic deposits across the Panama Canal Basin is well known because many were excellently exposed during the construction of the Panama Canal. Reviews of the Cenozoic sequence were given by Woodring (1957, 1970, 1977, 1982) and Escalante (1990). In this chapter, I am concerned only with the Neogene Gatun and Chagres formations. These two formations crop out only at the northern end of the Panama Canal Basin, along the Caribbean coast, im- mediately to the west and east of Colon (Map 1), and their stratigraphic relations are shown in Text-figure 7. Collins et al. (1996) provided strong evidence to suggest that the southern Central American archipel- ago was an almost complete ecological barrier between the Pacific and the Caribbean, at the time of the de- position of the Gatun Formation (Late M
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