The calcareous nannofossil assemblages recovered from Site 677A range in age from latest Miocene (NN11) to latest Pleistocene. The consistently high sediment-accumulation rate (mean of 48 m/m.y.) coupled with little dissolution of carbonate has ensured that generally rich, well-preserved coccolith assemblages occur at this site. Exceptions are the Pliocene/Pleistocene boundary sediments, which show evidence of dissolution, and upper Miocene basement sediments, which show evidence of diagenetic overgrowths.The apparent paradox of the occurrence of large numbers of the cool-water species Coccolithus pelagicus together with subtropical and tropical nannofossil species is thought to represent increased seasonality in the degree of upwelling in the Panama Basin. Seasonal upwelling was particularly intense during the late Miocene, when common C. pelagicus occurred with Thalassionema diatoms. Populations of C. pelagicus probably bloomed during a winter period of upwelling that was associated with a shallow thermocline and depressed surface-water temperatures.

species abundance: A = abundant (>10 %), C = common (1.0-10 %), F = few (0.1-1.0 %) , R = rare (<0.1 %), - = not observed

Supplement to: Houghton, Simon D (1989): Late Neogene calcareous nannofossil biostratigraphy and paleoceanography of ODP Hole 677A, Panama Basin. In: Becker, K; Sakai, H; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 111, 277-285