Quaternary planktonic foraminiferal assemblage zones of the northeast Gulf of Mexico, Colombia Basin (Caribbean Sea), and tropical Atlantic Ocean: Graphic correlation of microfossil and oxygen isotope datums

Sediments of Ocean Drilling Program's hole 625B (northeast Gulf of Mexico) represent a virtually continuous record of Pleistocene paleoceanographic development associated with the Florida Loop Current. Utilizing relative abundances of the Globorotalia menardii complex and G. inflata , supplemented by left‐ and right‐coiling varieties of G. truncatulinoides , we have subdivided the prezone W Pleistocene of core 625B into 17 subzones, resulting in an average duration of approximately 100,000 years per unit. This is substantially better resolution than for the Ericson and Wollin [1968] zones alone (average duration ∼300,000 years per unit). The subzones recognized in core 625B can be recognized in Eureka core E67‐135 (northeast Gulf of Mexico) and extended to cores 502B (Colombia Basin, Caribbean Sea) and V16‐205 (tropical Atlantic). Subzonal boundaries are largely coeval between sites based on graphic correlation of paleomagnetic, biostratigraphic, and oxygen isotope datums. The subzonation reveals relatively abrupt changes in sediment accumulation rate which probably decrease the signal to noise ratio in spectral analysis and tuning of oxygen isotope curves. In some cases, accumulation rate changes correspond to core breaks. Abundances of Globorotalia inflata and G. truncatulinoides are damped in the tropical cores (V16‐205 and 502B) but amplified in the subtropical Gulf of Mexico (625B), an observation which is consistent with previously published biogeographic models.