. Bulletins of American paleontology. 42 Bulletin 357 11°. 7°- Pacific Ocean Text-figure \.—Map of Panama and Costa Rica sliowmg general location of investigation. A, region in Bocas del Toro Basin that was examined in this study and is enlarged in Text-figure 2A; B, region in Limon Basin that was examined in this study and is enlarged in Text-figure 2B. nannofossil zonation of Martini (1971), and second- arily upon that of Bukry (1973, 1975, 1978) and Oka- da and Bukry (1980). There was considerable variation in the abundance and preservation of the calcareous nannofossil assemblages, but the
. Bulletins of American paleontology. 42 Bulletin 357 11°. 7°- Pacific Ocean Text-figure \.—Map of Panama and Costa Rica sliowmg general location of investigation. A, region in Bocas del Toro Basin that was examined in this study and is enlarged in Text-figure 2A; B, region in Limon Basin that was examined in this study and is enlarged in Text-figure 2B. nannofossil zonation of Martini (1971), and second- arily upon that of Bukry (1973, 1975, 1978) and Oka- da and Bukry (1980). There was considerable variation in the abundance and preservation of the calcareous nannofossil assemblages, but they generally were sparse with fair preservation. Most sections contained at least a few barren samples, and some sections had more than half of the samples barren of calcareous nannofossils. However, there were sufficient numbers of specimens, diversity of taxa, and preservational state to allow dating of almost all samples that did contain calcareous nannofossils. Because of the poor preservation in some of the samples, specimens could be identified only to the proper genus (, Discoaster sp., Sphenolithus sp.). Table 1 is a list of calcareous nannofossil species that can be used to date sediments of Miocene, Plio- cene, and Pleistocene age throughout the world. Not all of these species are present in the study area. Zonal markers for the standard Martini zonation are indicated with an *, and a # indicates a zonal marker for the Bukry zonation. The remaining species have been found to be biostratigraphically useful by various au- thors. Placement of these additional first appearance datums (FAD's) and last appearance datums (LAD's) within a particular calcareous nannofossil zone is gen- erally accurate, but the relative positions of FAD's and LAD's to each other within an individual zone are much less accurate. Subdivision of Zone NN 19 is from Gartner (1977). Zone NN 19a is used to denote Gartner's Cyclococcolithina macintyrei Zone, Zone NN 19b is his Helicopontosphaera
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