NEOGENE PLANKTONIC FORAMINIFERAL BIOSTRATIGRAPHY OF THE NORTHEASTERN GULF-OF-MEXICO

We have evaluated the planktonic foraminiferal biostratigraphy of seve ral Gulf of Mexico Eureka boreholes, emphasizing the Miocene depositio nal history of the northeastern region (De Soto Canyon). The E68-136 b orehole (De Soto Canyon; 1826', 557m present depth) provides the most continuous Miocene record, although deposition was punctuated by sever al short (<2.0 m.y.) hiatuses. The E66-73 borehole (De Soto Canyon; 28 02', 854m present depth) provides an uppermost lower to upper Miocene and upper Pleistocene record. E68-151 (north of the Florida Escarpment ; 4340', 1323m present depth) provides a discontinuous record of lower , upper middle, and upper upper Miocene sediments. By integrating plan ktonic foraminiferal biostratigraphy with nannoplankton biostratigraph y and Sr-isotope stratigraphy, we were able to estimate the ages of th e hiatuses associated with six distinct unconformities at E68-136 (23. 7-23.2 Ma; 18.0-16.5 Ma; 16.3-15.2 Ma; 14.1-13.6 Ma; -10.4-9.5 Ma, 5.0 -1.9 Ma), three at E66-73 (approximately 11.5-10.8 Ma. 10.3-9.2 Ma, 6. 5-1.7 Ma), and two at E68-151A (19.0-12.6 Ma, 12.5-6.9 Ma). We correla te these unconformities with previously reported unconformities from o ther deep-sea locations, although their causes (i.e., whether related to sea-level or deep-water changes) remain uncertain. We relate a dist inct Pliocene unconformity to intensification of the Loop Current asso ciated with the closure of the Isthmus of Panama.